@article{HagspielArrowsmithFantuzzietal.2021,
author = {Hagspiel, Stephan and Arrowsmith, Merle and Fantuzzi, Felipe and Vargas, Alfredo and Rempel, Anna and Hermann, Alexander and Br{\"u}ckner, Tobias and Braunschweig, Holger},
title = {Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {12},
doi = {10.1002/anie.202015508},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256432},
pages = {6446-6450},
year = {2021},
abstract = {Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.},
language = {en}
}
@article{MerzDietzVonhausenetal.2020,
author = {Merz, Julia and Dietz, Maximilian and Vonhausen, Yvonne and W{\"o}ber, Frederik and Friedrich, Alexandra and Sieh, Daniel and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Holzapfel, Marco and Lambert, Christoph and Marder, Todd B.},
title = {Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives},
series = {Chemistry - A European Journal},
volume = {26},
journal = {Chemistry - A European Journal},
number = {2},
doi = {10.1002/chem.201904219},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-207486},
pages = {438-453},
year = {2020},
abstract = {We synthesized new pyrene derivatives with strong bis(para -methoxyphenyl)amine donors at the 2,7-positions and n -azaacene acceptors at the K-region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7-substituted pyrenes but not for K-region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin-Day class-II and delocalized Robin-Day class-III species.},
language = {en}
}
@phdthesis{Kelch2018,
author = {Kelch, Hauke},
title = {Synthese und Reaktivit{\"a}t neuer Bor-haltiger Heterocyclen UND Element-Element-Bindungsaktivierungen durch vicinale Biscarbenoide},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-153951},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2018},
abstract = {Teil 1: Synthese und Reaktivit{\"a}t neuer Bor-haltiger Heterocyclen Im Rahmen der vorliegenden Arbeit wurden Versuche unternommen, neue Borolverbindungen auf Basis des 2,3,4,5-Tetrakis(pinakolboryl)buta-1,3-diendiyl-R{\"u}ckgrates mit unterschiedlichen Substituenten am Borzentrum darzustellen. Des Weiteren wurde ein neues Borolsystem auf Basis des Tetraphenylbutadien-Ger{\"u}stes synthetisiert, das die elektronenziehende Perfluorphenylgruppe als Bor-st{\"a}ndigen Substituenten tr{\"a}gt. Durch experimentelle Gegen{\"u}berstellung der strukturellen und spektroskopischen Parameter konnte - unterst{\"u}tzt durch quantenchemische Berechnungen - der Einfluss der R{\"u}ckgratsubstitution eingehend untersucht werden. Teil 2: Element-Element-Bindungsaktivierungen durch vicinale Biscarbenoide Im Rahmen der vorliegenden Arbeit wurde das vicinale Biscarbenoid Bis(piperidyl)acetylen eingesetzt um die Reaktivit{\"a}t dieser Verbindungsklasse gegen{\"u}ber Lewis-sauren Hauptgruppenelementverbindungen aufzukl{\"a}ren.},
subject = {Borheterocyclen},
language = {de}
}
@article{HorrerKrahfussLubitzetal.2020,
author = {Horrer, G{\"u}nther and Krahfuß, Mirjam J. and Lubitz, Katharina and Krummenacher, Ivo and Braunschweig, Holger and Radius, Udo},
title = {N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Complexes of Titanium(IV) and Titanium(III)},
series = {European Journal of Inorganic Chemistry},
volume = {2020},
journal = {European Journal of Inorganic Chemistry},
number = {3},
doi = {10.1002/ejic.201901207},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208725},
pages = {281-291},
year = {2020},
abstract = {The reaction of one and two equivalents of the N -heterocyclic carbene IMes [IMes = 1,3-bis(2,4,6-trimethyl-phenyl)imidazolin-2-ylidene] or the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) [cAAC\(^{Me}\) = 1-(2,6-diisopropyl-phenyl)-3,3,5,5-tetra-methylpyrrolidin-2-ylidene] with [TiCl\(_{4}\)] in n -hexane results in the formation of mono- and bis-carbene complexes [TiCl\(_{4}\)(IMes)] 1 , [TiCl\(_{4}\)(IMes)2] 2 , [TiCl\(_{4}\)(cAAC\(^{Me}\))] 3 , and [TiCl\(_{4}\)(cAAC\(^{Me}\))\(_{2}\)] 4 , respectively. For comparison, the titanium(IV) NHC complex [TiCl\(_{4}\)(Ii Pr\(^{Me}\))] 5 (Ii Pr\(^{Me}\) = 1,3-diisopropyl-4,5-dimethyl-imidazolin-2-ylidene) has been synthesized and structurally characterized. The reaction of [TiCl\(_{4}\)(IMes)] 1 with PMe\(_{3}\) affords the mixed substituted complex [TiCl\(_{4}\)(IMes)(PMe\(_{3}\))] 6 . The reactions of [TiCl\(_{3}\)(THF)\(_{3}\)] with two equivalents of the carbenes IMes and cAAC\(^{Me}\) in n -hexane lead to the clean formation of the titanium(III) complexes [TiCl\(_{3}\)(IMes)\(_{2}\)] 7 and [TiCl\(_{3}\)(cAAC\(^{Me}\))\(_{2}\)] 8 . Compounds 1 -8 have been completely characterized by elemental analysis, IR and multinuclear NMR spectroscopy and for 2 -5 , 7 and 8 by X-ray diffraction. Magnetometry in solution, EPR and UV/Vis spectroscopy and DFT calculations performed on 7 and 8 are indicative of a predominantly metal-centered d\(^{1}\)-radical in both cases.},
language = {en}
}
@article{RienschSwobodaLiketal.2021,
author = {Riensch, Nicolas Alexander and Swoboda, Lukas and Lik, Artur and Krummenacher, Ivo and Braunschweig, Holger and Helten, Holger},
title = {Conjugated Bis(triarylboranes) with Disconnected Conjugation},
series = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie},
volume = {647},
journal = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie},
number = {5},
doi = {10.1002/zaac.202000476},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258020},
pages = {421-424},
year = {2021},
abstract = {A series of methylene-bridged bis(triarylboranes) has been synthesized via two complementary routes using metal-free catalytic Si/B exchange condensation under mild conditions. The title compounds comprise two borane moieties that show effective internal π-conjugation involving the respective boron centers and the adjacent hetaryl groups. Conjugation between both borane units, however, is disrupted by the aliphatic linker. Cyclic voltammetry revealed minimal electronic communication between the boron centers, as evidenced by two closely spaced reduction processes. The UV-vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which is attributed to the methylene bridge. A further red-shift results upon introduction of methyl or SiMe\(_3\) groups at the terminal thiophene rings.},
language = {en}
}
@article{HeRauchFriedrichetal.2021,
author = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Krebs, Johannes and Krummenacher, Ivo and Bertermann, R{\"u}diger and Nitsch, J{\"o}rn and Braunschweig, Holger and Finze, Maik and Marder, Todd B.},
title = {Phenylpyridyl-fused boroles: a unique coordination mode and weak B-N coordination-induced dual fluorescence},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {9},
doi = {10.1002/anie.202013692},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256423},
pages = {4833-4840},
year = {2021},
abstract = {Phenylpyridyl-fused boroles [TipPBB1]\(_4\) and TipPBB2 were synthesized and their properties investigated. [TipPBB1]\(_4\) forms a tetramer in both the solid state and solution. TipPBB2 contains a 4-coordinate boron atom in the solid state but dissociates to give a 3-coordinate boron species in solution. TipPBB2 shows interesting temperature-dependent dual fluorescence in solution because of the equilibrium between 3- and 4-coordinate boron species due to weak N⋅⋅⋅B intermolecular coordination.},
language = {en}
}
@article{ZapfRadiusFinze2021,
author = {Zapf, Ludwig and Radius, Udo and Finze, Maik},
title = {1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion - a ditopic dianionic N-heterocyclic carbene ligand},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {33},
doi = {10.1002/anie.202105529},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256498},
pages = {17974-17980},
year = {2021},
abstract = {The 1,3-bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)\(_3\)-pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H\(_5\)O\(_2\)\(^+\) salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N-heterocyclic carbene (NHC), 1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)\(_4\)] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ-donor and π-acceptor ability, make NHC 3 a unique and promising ligand and building block.},
language = {en}
}
@article{HanftLichtenberg2020,
author = {Hanft, Anna and Lichtenberg, Crispin},
title = {Dimerization of 2-[(2-((2-aminophenyl)thio)phenyl)amino]-cyclohepta-2,4,6-trien-1-one through hydrogen bonding, C\(_{19}\)H\(_{16}\)N\(_2\)OS},
series = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
volume = {235},
journal = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
number = {4},
doi = {10.1515/ncrs-2020-0124},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229482},
pages = {963-966},
year = {2020},
abstract = {C\(_{19}\)H\(_{16}\)N\(_2\)OS, triclinic, P (1) over bar (no. 2), a= 8.1510(3) angstrom, b = 8.8021(3) angstrom, c =11.3953(5) angstrom, alpha =72.546(2)degrees, beta=84.568(2)degrees, gamma =80.760(2)degrees, V =768.86(5) angstrom(3), Z =2, R\(_{gt}\)(F) = 0.0491, WR\(_{ref}\)(F-2) = 0.1494, T =100 K.},
language = {en}
}
@article{WuNitschMarder2021,
author = {Wu, Zhu and Nitsch, J{\"o}rn and Marder, Todd B.},
title = {Persistent room-temperature phosphorence from purely organic molecules and multi-component systems},
series = {Advanced Optical Materials},
volume = {9},
journal = {Advanced Optical Materials},
number = {20},
doi = {doi.org/10.1002/adom.202100411},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256415},
year = {2021},
abstract = {Recently, luminophores showing efficient room-temperature phosphorescence (RTP) have gained tremendous interest due to their numerous applications. However, most phosphors are derived from transition metal complexes because of their intrinsic fast intersystem crossing (ISC) induced by strong spin-orbit coupling (SOC) constants of the heavy metal. Metal-free RTP materials are rare and have become a promising field because they are inexpensive and environmentally friendly. This review summarizes organic molecular materials with long triplet lifetimes at room temperature from the perspective of whether they stem from a molecular or multi-component system. Among purely organic phosphors, heteroatoms are usually introduced into the backbone in order to boost the singlet-triplet ISC rate constant. In multi-component systems, useful strategies such as host-guest, polymer matrix, copolymerization, and supramolecular assembly provide a rigid matrix to restrict nonradiative pathways thus realizing ultralong RTP.},
language = {en}
}
@phdthesis{Stangl2018,
author = {Stangl, Johannes Maria},
title = {Quantitative Feuchtesensorik mit lumineszierenden Ln-MOFs und Polymer-MOF-Matrix-Membranen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173190},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2018},
abstract = {In der vorliegenden Arbeit werden die Sensorikeigenschaften der lumineszierenden metallorganischen Ger{\"u}stverbindungen (metal-organic frameworks, MOFs) ■(3@∞)[Ba0.98Eu0.02(Im)2] (1), ■(3@∞)[Sr0.90Eu0.10(Im)2] (2), ■(3@∞)[Tb(Im)3] (3), ■(2@∞)[Tb2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (4) und ■(2@∞)[Eu2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (5), sowohl in Form der Bulksubstanzen als auch in Form von mixed-matrix membranes (MMMs) gegen{\"u}ber den Analyten Wasser, Methanol, Ethanol und Isopropanol untersucht und mittels kinetischer Betrachtungen quantitativ beschrieben. Hierf{\"u}r wurde ein Versuchsaufbau konstruiert, der den Anforderungen einer quantitativen Erfassung der Sensorikeigenschaften gen{\"u}gt und einflussgebende externe und interne Parameter, wie die Konzentration des Analyten, Temperatur, Druck, Probenmenge und Probenoberfl{\"a}che standardisiert, um eine m{\"o}glichst genaue Erfassung der auftretenden Ver{\"a}nderung der Lumineszenzintensit{\"a}t zu erm{\"o}glichen. Zus{\"a}tzlich wurde eine mathematische Betrachtung genutzt, um die Ergebnisse der Experimente zu interpretieren und in einen Gesamtkontext zu setzen. F{\"u}r jedes der f{\"u}nf Modellsysteme wurde je eine Messreihe gegen ein breites Spektrum an relativen Feuchten (Wasser als Analyt) bei 25 °C durchgef{\"u}hrt. Der in allen F{\"a}llen auftretende Lumineszenzverlust ließ sich jeweils mittels einer Exponentialfunktion beschreiben und zur Bestimmung der konzentrationsabh{\"a}ngigen Reaktionskonstanten sowie der Halbwertszeiten nutzen. Die gewonnenen Informationen wurden verwendet, um die Reaktionskonstanten und die Schwellenwerte der Sensorik der jeweiligen Systeme zu bestimmten. In weiteren Versuchsreihen wurde der Messaufbau genutzt und der Einfluss der Alkohole Methanol, Ethanol und Isopropanol auf die Lumineszenz der MOFs ■(3@∞)[Ba0.98Eu0.02(Im)2] (1), ■(2@∞)[Tb2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (4) und ■(2@∞)[Eu2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (5) bei verschie-denen Konzentrationen in der Gasphase und bei unterschiedlichen Temperaturen untersucht, quantitativ bestimmt und gem{\"a}ß der vorangegangen Messreihen f{\"u}r Feuchte beschrieben. Zus{\"a}tzlich wurde die Ver{\"a}nderung des Lumineszenzmusters der MOFs ■(2@∞)[Tb2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (4) und ■(2@∞)[Eu2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (5) untersucht. Die M{\"o}glichkeiten der Prozessierung von ■(3@∞)[Ba0.98Eu0.02(Im)2] (1), und ■(2@∞)[Tb2Cl6(4,4'-bipy)3]•2(4,4'-bipy) (4) wurden im Hinblick auf eine praktische Anwendung im Bereich der Sensorik hin untersucht. Hierf{\"u}r wurden die jeweiligen Bulksubstanzen via Dropcoating in die drei Polymere Polystyrol (PS), Polyvinychlorid (PVC) und Polymethylpenten (TPX) eingebettet. Die so dargestellten MMMs wurden auf ihre Sensorikeigenschaften hin untersucht und der Lumineszenzverlust wurde quantitativ beschrieben. Des Weiteren wurde die korrespondierende Bulksubstanz, in Bezug auf die (konzentrationsabh{\"a}ngigen) Reaktionskonstanten und Halbwertszeiten, mit den MMMs verglichen. Im Rahmen einer Kooperation mit der Arbeitsgruppe von Prof. Dr. Janiak der Heinrich-Heine-Universit{\"a}t D{\"u}sseldorf wurden die MOFs ■(3@∞)[Ba0.98Eu0.02(Im)2] (1) und ■(3@∞)[Sr0.90Eu0.10(Im)2] (2) in Polysulfon (PSF) eingebettet und ebenfalls auf ihre F{\"a}higkeit zur Feuchtesensorik hin untersucht. Im Rahmen der vorliegenden Arbeit war es erstmals m{\"o}glich, die Sensoreigenschaften der genutzten MOFs und CPs (1 - 5) quantitativ zu erfassen und mathematisch zu beschreiben. Ebenso konnte das entwickelte Sensorikkonzept erfolgreich auf die Erfassung von verschiedenen Alkoholen in der Gasphase {\"u}bertragen werden (f{\"u}r System 1, 4 und 5). Anschließend war es m{\"o}glich, die genutzten Modellsysteme 1, 2 und 4 unter dem Erhalt der Lumineszenzeigenschaft in verschiedene Polymere einzubetten und deren Eigenschaften zur Feuchtesensorik ebenfalls quantitativ zu erfassen und mathematisch zu beschreiben. Im letzten Abschnitt der Arbeit wurden die beiden por{\"o}sen ZIFs (zeolitic imidazolate frameworks) Na-Rho-ZMOF (6) und Zn(nmIm)2 (7) mit einer Terbiumnitratl{\"o}sung behandelt, um durch die F{\"u}llung der Kavit{\"a}ten die Lumineszenzeigenschaft der Terbiumionen in das ZIF zu implementieren. Der Grad und die Qualit{\"a}t der Bef{\"u}llung wurden anschließend analytisch auf Lumineszenzeigenschaften hin untersucht. Hierbei konnte die Bef{\"u}llung von Na-Rho-ZMOF (6) erfolgreich nachgewiesen werden, w{\"a}hrend es bei Zn(nmIm)2 (7) nicht zu einer Bef{\"u}llung des Porensystems kam.},
language = {de}
}
@phdthesis{Kuehn2022,
author = {Kuehn, Laura},
title = {Earth-Abundant Metal-Catalyzed and Transition Metal-Free Borylation of Aryl Halides},
doi = {10.25972/OPUS-21149},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-211499},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {The present work focusses on the borylation of aryl halides. The first chapter presents a detailed review about previously reported nickel-catalyzed borylation reactions. The second chapter of the thesis describes, the borylation reaction of C-Cl bonds in aryl chlorides mediated by an NHC-stabilized nickel catalyst. The cyclohexyl substituted NHC Cy2Im was used to synthesize novel Cy2Im-stabilized nickel complexes [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1, [Ni(Cy2Im)2(η2-C2H4)] 2, and [Ni(Cy2Im)2(η2-COE)] 3. An optimized procedure was developed using 5 mol\% of the Ni-catalyst, 1.5 equivalents of the boron reagent B2pin2, and 1.5 equivalents of NaOAc as the base in methylcyclohexane at 100 °C. With these optimized conditions, it was shown that a variety of aryl chlorides, containing either electron-withdrawing or -donating groups, were converted to the corresponding aryl boronic esters in yields up to 99\% (88\% isolated) yield. Mechanistic investigations revealed that the C-Cl oxidative addition product [Ni(Cy2Im)2(Cl)(4-F3C-C6H4)] 11, which has been synthesized and isolated separately, also catalyzes the reaction. Thus, rapid oxidative addition of the C-Cl bond of the aryl chloride to [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1 to yield trans-[Ni(Cy2Im)2(Cl)(Ar)] represents the first step in the catalytic cycle. The rate limiting step in this catalytic cycle is the transmetalation of boron to nickel forming trans-[Ni(Cy2Im)2(Bpin)(Ar)], which was not possible to isolate. The boryl transfer reagent is assumed to be the anionic adduct Na[B2pin2(OAc)]. A final reductive elimination step gives the desired borylated product Ar-Bpin and regenerates [Ni(Cy2Im)2]. In the next chapter the first effective C-Cl bond borylation of aryl chlorides using NHC-stabilized Cu(I)-complexes of the type [Cu(NHC)(Cl)] was developed. The known complexes [Cu(iPr2Im)(Cl)] 15, [Cu(Me2ImMe)(Cl)] 16, and [Cu(Cy2Im)(Cl)] 17, bearing the small alkyl substituted NHCs, were synthesized in good yields by the reaction of copper(I) chloride with the corresponding free NHC at low temperature (-78 °C) in THF. A range of catalysts, bases, solvents, and boron sources were screened to determine the scope and limitations of this reaction. [Cu(Cy2Im)(Cl)] 17 revealed a significantly higher catalytic activity than [Cu(iPr2Im)(Cl)] 15. KOtBu turned out to be the only efficient base for this borylation reaction. Besides methylcyclohexane, toluene was the only solvent that gave the borylated product in moderate yields of 53\%. It was shown that a variety of electron-rich and electron-poor aryl chlorides can be converted to the corresponding aryl boronic esters in isolated yields of up to 80\%. A mechanism was proposed, in which a Cu-boryl complex [Cu(L)(Bpin)] is formed in the initial step. This is followed by C-B bond formation via σ-bond metathesis with the aryl chloride forming the aryl boronic ester and [Cu(L)(Cl)]. The latter reacts with KOtBu to give [Cu(L)(OtBu)], which regenerates the copper boryl complex by reaction with B2pin2. Chapter 4 describes studies directed towards the transition metal-free borylation of aryl halides using Lewis base adducts of diborane(4) compounds. A variety of novel pyridine and NHC adducts of boron compounds were synthesized. Adducts of the type pyridine·B2cat2 18-19 and NHC·B2(OR)4 20-23 were examined for their ability to transfer a boryl moiety to an aryl iodide. However, only Me2ImMe∙B2pin2 20 was found to be effective. The stoichiometric reaction of 20 with different substituted aryl iodides and bromides in benzene, at elevated temperatures, gave the desired aryl boronic esters in good yields. Interestingly, depending on the reaction temperature, C-C coupling between the aryl halide and the solvent (benzene), was detected leading to a side product which, together with observed hydrodehalogenation of the aryl halide, provided indications that the reaction might be radical in nature. When the boryl transfer reaction based on Me2ImMe∙B2pin2 20 was followed by EPR spectroscopy, a signal (though very weak and ill-defined) was detected, which is suggestive of a mechanism involving a boron-based radical. In addition, the boronium cation [(Me2ImMe)2∙Bpin]+ 37 with iodide as the counterion was isolated from the reaction residue, indicating the fate of the second boryl moiety. A preliminary mechanism for the boryl transfer from 20 to aryl iodides was proposed, which involves an NHC-Bpin˙ radical as the key intermediate. Me2ImMe-Bpin˙ is formed by homolytic B-B bond cleavage of the bis-NHC adduct (Me2ImMe)2∙B2pin2, which is formed in situ in small amounts under the reaction conditions. Me2ImMe-Bpin˙ reacts with the aryl iodide to give the aryl boronic ester with recovery of aromaticity. In the same step, from the second equivalent of NHC-Bpin˙, an NHC-stabilized iodo-Bpin adduct is formed as an intermediate, which is further coordinated by another NHC, yielding [(Me2ImMe)2∙Bpin]+I- 37.},
subject = {NHC-Nickel-Catalyst},
language = {en}
}
@article{NeitzBessiKachleretal.2022,
author = {Neitz, Hermann and Bessi, Irene and Kachler, Valentin and Michel, Manuela and H{\"o}bartner, Claudia},
title = {Tailored tolane-perfluorotolane assembly as supramolecular base pair replacement in DNA},
series = {Angewandte Chemie International Edition},
volume = {62},
journal = {Angewandte Chemie International Edition},
number = {1},
doi = {10.1002/anie.202214456},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312575},
year = {2022},
abstract = {Arene-fluoroarene interactions offer outstanding possibilities for engineering of supramolecular systems, including nucleic acids. Here, we implement the tolane-perfluorotolane interaction as base pair replacement in DNA. Tolane (THH) and perfluorotolane (TFF) moieties were connected to acyclic backbone units, comprising glycol nucleic acid (GNA) or butyl nucleic acid (BuNA) building blocks, that were incorporated via phosphoramidite chemistry at opposite positions in a DNA duplex. Thermodynamic analyses by UV thermal melting revealed a compelling stabilization by THH/TFF heteropairs only when connected to the BuNA backbone, but not with the shorter GNA linker. Detailed NMR studies confirmed the preference of the BuNA backbone for enhanced polar π-stacking. This work defines how orthogonal supramolecular interactions can be tailored by small constitutional changes in the DNA backbone, and it inspires future studies of arene-fluoroarene-programmed assembly of DNA.},
language = {en}
}
@phdthesis{Feizy2019,
author = {Feizy, Nilab},
title = {iClick-Reaktionen von Palladium(II)azid- und Platin(II)azid-Komplexen mit tridentaten N,N,N-Chelatliganden und elektronenarmen Alkinen},
doi = {10.25972/OPUS-17893},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178938},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2019},
abstract = {Katalysatorfreie [3+2]-Cycloadditionen von Aziden mit Alkinen werden in der bioorthogonalen Chemie h{\"a}ufig verwendet und haben großes Potential zur milden Synthese von Biokonjugaten. W{\"a}hrend solche Reaktionen in der Ligandenperipherie von Metallkomplexen h{\"a}ufiger angewendet werden ist, sind solche Reaktionen direkt in der inneren Koordinationssph{\"a}re von Metallzentren bisher nur wenig erforscht. Die neue Beispiele daf{\"u}r sind die Synthese und Untersuchungen der Kinetik und Reaktivit{\"a}t einer Reihe von Rhodium(III)azid-Halbsandwichkomplexen der allgemeinen Formel [Rh(Cp*)(N3)(bpyR,R)]+ oder von isoelektronische und isostrukturelle Molybd{\"a}n(II)azid- und Wolfram(II)azid-Komplexe mit verschiedenen elektronenarme Alkine. Das Ziel der vorliegenden Arbeit waren daher iClick-Reaktionen (engl. inorganic click, „iClick") von Palladium(II)azid- und Platin(II)azid-Komplexen der allgemeinen Formel [M(N3)(L)]+ und [M(N3)(L)] mit elektronenarmen Alkinen Dimethylacetylendicarboxylat (DMAD) und 4,4,4-Trifluorobut-2-ins{\"a}ureethylester. Als Liganden kamen die N,N,N-Chelatoren 1,3-Bis(arylimino)isoindolin (HL1-4) die sich nur im Bezug auf die Position der Methylgruppen in den Pyridinringen unterscheiden, 6',6"-Dimethyl-2',2:6,2"-terpyridin (L5) und 2,6-Bis(3-pyridazinyl)pyridin (L6) zum Einsatz. Die Reaktionen von L1-L4 mit [MCl2(cod)] (M = Pd, Pt) liefert neutrale Komplexe [MCl(L1-3)] und f{\"u}r L5 einfach geladene [MCl(L5)]+. Das koordinierte Chlorid wurde dann mit Natriumazid substituiert. Im abschließenden Teil der Arbeit wurde die zwei Alkinen in iClick-Reaktion verwendet um Palladium(II)- und Platin-Triazolat-Komplexe zu synthetisieren. F{\"u}r die resultierenden Triazolat-Komplexe wurde eine N2-koordinierten des Triazolat-Liganden durch R{\"o}ntgenstrukturanalyse f{\"u}r baii-Triazolat-Komplexe best{\"a}tigt. Besonderes Merkmal dieser Verbindungen ist, dass der Triazolat-Ligand aus Platzmangel senkrecht zum 1,3-Bis(arylimino)isoindolin-Ligand steht. In verwandten Terpyridin-Komplexen sind der mono- und tridentate Ligand dagegen coplanar. Mit 1,3-Bis(6-methyl-2-pyridylimino)isoindolin als Ligand konnten man keine Metall-Komplexe hergestellt werden, da die zus{\"a}tzlichen Methylgruppem in 6',6"-Positionen aus sterische Gr{\"u}nden eine Reaktion mit [MCl2(cod)] verhindern. Auch der in drei Stufen synthetisierte Ligand 6',6"-Dimethyl-2',2:6,2"-terpyridin der im Vergleich zu Terpyridin zwei zus{\"a}tzliche Methylgruppen in 6',6"-Position besitzen reagiert nur mit [PdCl2(cod)] nicht aber mit [PtCl2(cod)], da der Ionenradius von Pt(II) gr{\"o}ßer als der von Pd(II) ist. Die hergestellte Chlorid-, Azid- und Triazolat-Komplexe mit L5 als N,N,N-Chelator waren nur in DMSO L{\"o}slich. Darin zersetzt es sich jedoch teilweise wieder in den freien Liganden. Die zus{\"a}tzlichen Methylgruppem in 6',6"-Positionen verhindern aus sterische Gr{\"u}nden die Chlorid-, Azid- und Triazolat-Komplexe stabil zu bleiben. Ligand L6 konnte nur in sehr niedrige Ausbeute isoliert werden, da in der letzten Stufe bzw. bei Stille-Kupplung zwischen 2,6-Bis(trimethylstannyl)pyridin und 3-Iodopyridazin die Homokupplungsprodukte von 3-Iodopyridazin entsteht, sodass die nicht getrennt werden konnten. Aufgrund der niedrigen Ausbeute wurden dann mit L6 keine Metall-Komplexe hergestellt. Die Kinetik der iClick-Reaktion ist ein entscheidender Faktor, wenn diese f{\"u}r die Markierung von Bio(makro)molek{\"u}len eingesetzt werden soll, da die Markierungsreaktion schneller als der interessierende biologische Prozess ablaufen muss. Daher wurden mit IR- und UV/Vis-Spektroskopie die Geschwindigkeitskonstanten pseudoerster Ordnung f{\"u}r die iClick-Reaktion der verschiedenen baii-Palladium(II)azid- und baii-Platin(II)azid-Komplexe mit Dimethylacetylendicarboxylat (DMAD) und 4,4,4-Trifluorobut-2-ins{\"a}ureethylester bestimmt. Hier sollte insbesondere der Einfluss der zus{\"a}tzlichen Methylgruppen in 4',4"- bzw. 5',5"-Positionen am 1,3-Bis(arylimino)isoindolin-Liganden sowie die Variation des Metallzentrums und Alkins auf die Geschwindigkeit der iClick-Reaktionen untersucht werden. Mit IR-Spektroskopie wurden Geschwindigkeitskonstanten um (2.8-4.9)⋅10-4 s-1 an Alkinen erhalten. Die Einf{\"u}hrung elektronenschiebender Methylgruppen in 4',4"- bzw. 5',5"-Positionen am 1,3-Bis(arylimino)isoindolin-Liganden f{\"u}hrt zu einer Erh{\"o}hung der Geschwindigkeitskonstant einem Faktor von 1.3 bzw. 1.2 gegen{\"u}ber 1,3-Bis(2-pyridylimino)isoindolin. Die iClick-Reaktion mit Platin als Metall ist 1.3-mal schneller als mit Palladium. Elektronenarme Alkine wie 4,4,4-Trifluorobut-2-ins{\"a}ureethylester f{\"u}hren im Vergleich zu Dimethylacetylendicarboxylat (DMAD) zu einer 1.8-fachen Erh{\"o}hung der Reaktionsgeschwindigkeit. Mit UV/Vis-Spektroskopie wurden niedrigere Geschwindigkeitskonstanten um 8.9·10-6 - 3.3·10-5 s-1 nur f{\"u}r die iClick-Reaktion der 1,3-Bis(arylimino)isoindolinplatin(II)azid-Komplexe mit Dimethylacetylendicarboxylat (DMAD) und 4,4,4-Trifluorobut-2-ins{\"a}ureethylester bestimmt, weil die Spektralen Unterschiede zwischen Azid-Vorstufe und Triazolat-Produkt mit Palladium als Metallzentren zu gering sind. Auch hier konnte die Erh{\"o}hung der Geschwindigkeitskonstanten durch Verwendung elektronen{\"a}rmerer Alkine best{\"a}tigt werden. Hier sollte die iClick-Reaktion in Zukunft f{\"u}r gr{\"o}ßere Auswahlm{\"o}glichkeiten an Chelatoren optimiert und außerdem die Geschwindigkeitskonstanten der Bildung von iClick-Produkten mit anderen Methoden untersucht werden, bevor biologische Tests durchgef{\"u}hrt werden.},
subject = {Alkine},
language = {de}
}
@phdthesis{Duda2021,
author = {Duda, Katharina},
title = {Synthesen und Eigenschaften von Dicarba-closo-dodecaboran-Derivaten und ersten gemischten Fluorohydridoborat-Anionen},
doi = {10.25972/OPUS-18103},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-181038},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {Ein wesentliches Ziel dieser Arbeit war die Durchf{\"u}hrung von regioselektiven Deborierungsreaktionen von 1,7-Dicarba-closo-dodecaboranen sowie die Herstellung von polyfunktionalisierten meta-Carboran-Derivaten. Die synthetisierten {nido-7,9-C2B9}- und {closo-1,7-C2B10}-Derivate und ausgew{\"a}hlte ortho-Carboran-Derivate wurden nach erfolgter Kumada-artiger Kreuzkupplungsreaktion bzgl. ihrer Koordinationschemie untersucht. Die ethinylfunktionalisierten Borcluster wurden als Edukte f{\"u}r die Herstellung von Gold(I)-Komplexen genutzt. Weitere Ziele dieser Arbeit waren außerdem die Synthese und umfassende Charakterisierung des gemischten Fluorohydridoborat-Anions [BHF3]- und der carboranylsubstituierten Borat-Anionen [1-HF2B-closo-1,2-C2B10H11]- und [1-HF2B-9,12-I2-closo-1,2-C2B10H9]- sowie die Untersuchung hinsichtlich ihrer Folgechemie.},
subject = {Carborane},
language = {de}
}
@article{KrebsHaehnelKrummenacheretal.2021,
author = {Krebs, Johannes and Haehnel, Martin and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Finze, Maik and Ji, Lei and Marder, Todd B.},
title = {Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {31},
doi = {10.1002/chem.202100938},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256841},
pages = {8159-8167},
year = {2021},
abstract = {Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.-}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.-}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.},
language = {en}
}
@phdthesis{Boshuis2022,
author = {Boshuis, Tim},
title = {Konzeption eines praxisorientierten Seminarkonzepts im Biologie/Chemiestudium zur Erfassung und F{\"o}rderung der Reflexionsf{\"a}higkeit von Lehramtsstudierenden},
doi = {10.25972/OPUS-25897},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258973},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {Um Kompetenzen von angehenden Lehrkr{\"a}ften zu f{\"o}rdern, werden Praxisphasen in das Lehramtsstudium integriert. Damit diese Phasen m{\"o}glichst effektiv sein k{\"o}nnen, m{\"u}ssen sie Studierenden die M{\"o}glichkeit bieten, Unterrichtsinhalte zu reflektieren. Dabei k{\"o}nnten Lehr-Lern-Labor-Seminare eine M{\"o}glichkeit sein, durch Praxisn{\"a}he und der komplexit{\"a}tsreduzierten Lehr-Lern-Umgebung, die systematische Reflexion konkreter unterrichtlicher Inhalte zu f{\"o}rdern. In der vorliegenden Arbeit wird deshalb dargestellt, inwiefern solche Seminare zur Vermittlung eines Reflexionsschemas eingesetzt werden k{\"o}nnen. Mit Hilfe einer strukturierenden Inhaltsanalyse wird untersucht, welche Komponenten der didaktischen Rekonstruktion von den Studierenden wahrgenommen werden und inwiefern sie in der Lage sind, ein Reflexionsschema in diesen Bereichen einzusetzen. Da das Handeln im Unterricht stark durch Pers{\"o}nlichkeitsmerkmale beeinflusst wird, wird ebenfalls {\"u}berpr{\"u}ft, ob {\"U}berzeugungen, Kognitionsbed{\"u}rfnis und Praxiserfahrung die Anwendung eines Reflexionsschemas beeinflussen. Durch die Ergebnisse dieser Arbeit war es m{\"o}glich, ein Reflexionsschema zu validieren, dass es Studierenden erm{\"o}glicht, selbstst{\"a}ndig und fachunabh{\"a}ngig Unterrichtsinhalte zu reflektieren.},
subject = {Lehr-Lern-Labor},
language = {de}
}
@phdthesis{Riensch2021,
author = {Riensch, Nicolas Alexander},
title = {Silicon/Boron Exchange Routes to Novel Inorganic-Organic Hybrid Molecules, Oligomers, Polymers and Macrocycles},
doi = {10.25972/OPUS-23865},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238657},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {Industrially used semiconducting materials, building blocks of modern electronics and computer industry, are mostly based on inorganic, crystalline solids, which have the drawback of relatively high production costs. As an alternative, organic pi-conjugated systems show enhanced flexibility and processability as well as the opportunity to obtain light-weight materials. They have emerged as attractive candidates, especially since elements beyond hydrogen and carbon can be used to create pi-conjugated frameworks. In recent years, pi-conjugated oligomers and polymers with tricoordinate boron centers incorporated into the main chain of such organic polymers have attracted considerable attention as the interaction of the vacant p orbital on boron with an adjacent pi system of the chain leads to extended conjugated materials. These materials show intriguing optical and electronic properties and potential applications in organic electronics and optoelectronics (OLEDs, OFETs, photovoltaics) or as sensory materials. In this thesis, a catalytic Si/B exchange reaction protocol is used as a facile and highly effective B-C bond formation method to synthesize organoboron molecules, oligomers, polymers and macrocycles. This reaction is applied to synthesize a series of thienyl- and furylborane based materials. Special focus is on furylborane based materials, which, in general, have been only scarcely explored so far. This is mainly due to synthetic challenges since furan decomposes readily in the presence of light and oxygen. Our mild and highly selective reaction protocol in combination with sufficient kinetic protection of the boron centers gives access to a series of extended organoboranes featuring furylborane units in the main chain. Furthermore, kinetically stabilized furylboranes are established as highly robust and versatile building blocks for pi conjugated materials. The obtained materials reveal remarkable luminescence properties. The scope of potential starting materials was investigated by a catalyst screening, demonstrating that the Si/B exchange reaction can also be performed for less reactive aryldichloroboranes. Furthermore, borazine-based hybrid cyclomatrix microspheres have been synthesized via a Si/B exchange condensation reaction under precipitation polymerization conditions. Finally, synthetic routes to tetrabora- and diboraporphyrinogens were attempted in a multi-step reaction procedure. In the case for tetraboraporphyrinogens, the final macrocyclization reaction under pseudo high-dilution conditions afforded a mixture of macrocycles with different ring sizes. UV-vis and fluorescence spectroscopic analysis indicated significant differences in comparison to their linear congeners.},
subject = {Bororganische Verbindungen},
language = {en}
}
@phdthesis{Zottnick2018,
author = {Zottnick, Sven Holger},
title = {Lumineszierende Lanthanid-Koordinationsverbindungen auf Basis von Cyano- und Spiroborat Salzen und ionischen Fl{\"u}ssigkeiten},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157945},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2018},
abstract = {Im Rahmen dieser Arbeit konnten, ausgehend von Borat-haltigen Salzen und ionischen Fl{\"u}ssigkeiten (ILs) sowie Lanthanid-haltigen Precursoren, 30 neue Komplexe und Koordinationspolymere dargestellt werden. Dazu wurden vielf{\"a}ltige Synthesestrategien verfolgt und angewendet, unter anderem Salzmetathesen in L{\"o}sung, Solvothermalsynthesen und Ionothermalsynthesen. Ein Hauptaugenmerk bei der Synthese der Zielverbindungen lag auf deren Eigenschaften, wobei insbesondere die Photolumineszenzeigenschaften der erhaltenen Koordinationsverbindungen untersucht wurden. Als Borat-haltige Liganden wurden sowohl Cyanoborate als auch Oxoborate hinsichtlich ihrer Eignung zum Aufbau neuer Koordinationspolymere untersucht. Als Cyanoborat-haltige Edukte wurden dabei S{\"a}uren und ionische Fl{\"u}ssigkeiten mit Dicyano-, Tricyano- und Tetracyanoborat- Anionen eingesetzt, die durch die unterschiedliche Zahl an Cyanogruppen zu vielf{\"a}ltigen Koordinationsverbindungen f{\"u}hren k{\"o}nnen. Mittels Ionothermalsynthese konnten die Verbindungen 1∞[Ln(NO3)2{B(CN)4}(H2O)4] (Ln = La, Eu) sowie [EMIm]1∞[LaNO3{B(CN)4}3(H2O)3] dargestellt werden, wobei es zu einer Transformation der ionischen Fl{\"u}ssigkeit [EMIm][B(CN)4] in ein Koordinationspolymer kommt, in dem sowohl Kation als auch Anion der IL beteiligt sind. Dabei ist es bemerkenswerterweise durch die Reaktionstemperatur m{\"o}glich zu steuern, welches Produkt sich letztlich bildet. Ebenfalls durch Ionothermalsynthese gelang die Synthese von Einkristallen der Verbindung 3∞[La{C2F5B(CN)3}3], durch deren Kenntnis die Verbindungen 3∞[Ln{C2F5B(CN)3}3](Ln = Eu, Ho) als isotype Strukturen identifiziert und hinsichtlich ihrer Lumineszenzeigenschaften charakterisiert werden konnten. Durch Umsetzungen der Lanthanidchloride mit der S{\"a}ure H[BH2(CN)2] in Solvothermalsynthesen in Pyridin (py) konnten eindimensionale Koordinationspolymere [H(py)2]1∞[LnCl2{BH2(CN)2}2(py)2]·0.5py (Ln = Ce, Pr) erhalten werden. Unter vergleichbaren Synthesebedingungen aber im L{\"o}sungsmittel MeCN beobachtet man hingegen die Bildung von Raumnetzen der Zusammensetzung 3∞[Ln2{BH2(CN)2}9]·[Ln(CH3CN)9] (Ln = Ce, Eu, Tb). Die dreidimensionalen Koordinationspolymere 3∞[Ln{BH(CN)3}3] (Ln = Eu, Tb) wurden ebenfalls in MeCN synthetisiert, allerdings ausgehend von der S{\"a}ure [H3O][BH(CN)3]. Die erw{\"a}hnten Verbindungen zeigen f{\"u}r die spektroskopisch relevanten Vertreter charakteristische Lumineszenz auf Basis von 5d-4f- respektive 4f-4f-{\"U}berg{\"a}ngen, die {\"u}berwiegend auf der direkten Anregung der jeweiligen Lanthanidionen beruht. Mit dem Bis-salicylatoborat-Anion (= BSB-) gelang ausgehend von Na[BSB] und LnCl3 unter solvothermalen Bedingungen in Pyridin die Synthese der eindimensionalen, strangartigen Koordinationspolymere 1∞[Ln(BSB)3(py)2] (Ln = Y, La - Nd, Sm) und der zweidimensionalen, schichtartigen Verbindungen 2∞[Ln(BSB)3(py)] (Ln = Sm, Eu, Tb - Er). Einblicke {\"u}ber den Mechanismus der Bildung der genannten Verbindungen konnten durch den Komplex [ErCl2(py)4BSB] gewonnen werden, der eine sukzessive Substitution der Chlorid-Liganden nachweist. Die Verbindungen mit dem [BSB]--Anion zeigen Photolumineszenz, die auf unterschiedliche Prozesse zur{\"u}ckgef{\"u}hrt werden kann. So weist 1∞[Y(BSB)3(py)2] Fluoreszenz auf, die von den [BSB]--Anionen herr{\"u}hrt, w{\"a}hrend 1∞[Ln(BSB)3(py)2] (Ln = Ce, Nd, Sm) sowie 2∞[Ln(BSB)3(py)] (Ln = Sm, Tb, Dy) Lumineszenz auf Basis von 5d-4f- und 4f-4f-{\"U}berg{\"a}ngen zeigen, die durch einen Antenneneffekt der koordinierenden [BSB]--Anionen vergleichsweise intensiv beobachtet werden k{\"o}nnen. Eine Sonderstellung nehmen hier die Verbindungen 2∞[Ln(BSB)3(py)] (Ln = Eu, Ho) ein. W{\"a}hrend mit Eu3+ {\"u}berwiegend direkte Anregung festgestellt werden kann, treten f{\"u}r Ho3+ Reabsorptionsprozesse auf. Durch Kombination unterschiedlicher Gehalte an Eu3+- bzw. Tb3+-Ionen in den eindimensionalen Koordinationspolymeren 1∞[EuxTb1-x(BSB)3(py)2] (x = 0.75, 0.50, 0.25) k{\"o}nnen zudem Mischfarben der Lumineszenz erzeugt werden. Mit dem Komplex [B2O(C2O4)2(dmf)2] (dmf = Dimethylformamid) und dem Koordinationspolymer 1∞[Tb{o-C6H4(CO2)2}(H2O)6][PHB]2 (PHB- = Phthalatoborat) konnte zudem die Sonderstellung des [BSB]--Anions deutlich gemacht werden, da es als einziges untersuchtes Spiroborat-Anion vollst{\"a}ndig in Zielverbindungen eingebaut werden konnte, w{\"a}hrend vergleichbare Spiroborat-Anionen wie das [PHB]--Anion in Gegenwart Lewis-acider Verbindungen hingegen die Abspaltung funktioneller Gruppen zeigten. Insgesamt konnten in dieser Arbeit somit zahlreiche neue, lumineszierende Koordinationspolymere mit Cyano- und Oxoboraten erfolgreich dargestellt werden.},
subject = {Photolumineszenz},
language = {de}
}
@phdthesis{Stauch2019,
author = {Stauch, Claudia},
title = {Synthese und Charakterisierung nanostrukturierter Mikropartikel mit einstellbarem Zerfallsverhalten als Additive f{\"u}r Elastomerkomposite},
doi = {10.25972/OPUS-17615},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-176154},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2019},
abstract = {Die vorliegende Arbeit befasst sich mit der Synthese und Charakterisierung von nanostrukturierten Mikropartikelpulvern mit einstellbarem Zerfalls- und Dispergierungsverhalten und deren Anwendung als verst{\"a}rkender F{\"u}llstoff sowie deren Eignung f{\"u}r Sensoranwendungen. Sie ist in drei Teilbereiche gegliedert: Der erste Teil beschreibt die Synthese der nanostrukturierten Mikropartikelpulvern durch Spr{\"u}htrocknung von kolloidalen oxidischen (silicatischen und eisenoxidischen) Nanopartikeln. Es wird ausgef{\"u}hrt, wie durch Variation der Art und Gr{\"o}ße der Prim{\"a}rpartikel und deren mengenanteiligen Kombination Mikropartikel unterschiedlichster nanostruktureller Maserung und Auspr{\"a}gung erhalten wurden. Das Spektrum dieser Partikel reichte von homogen verteilten Strukturen bis hin zu Kern-Satellit-Struktur, von kontrollierter Aggregierung bis hin zur vollst{\"a}ndigen Dispergierbarkeit. Im zweiten Teil der Arbeit wurden die Partikel im Hinblick auf ihre Eignung und Verwendung als F{\"u}llstoffe f{\"u}r Elastomer-Matrices untersucht. Im Fokus stand die Verst{\"a}rkungswirkung und die Korrelation mit dem Dispergierverhalten in PDMS. Im dritten Teil der Arbeit wurde das Syntheseprinzip der Herstellung nanostrukturierter Mikropartikel auf Hydroxid-basierte Systeme wie LDHs erweitert. Teil I: Von Silica-NP zu nanostrukturierten Mikropartikeln mit einstellbarem Zerfallsverhalten Um nanostrukturierte Mikropartikel mit einem integrierten Zerfallsverhalten zu erzeugen, wurden zun{\"a}chst kolloidale Silica-NP mit einer Gr{\"o}ße von 20 nm abgestuft mit unterschiedlichen Mengen (0, 1/10, 1/5, 1/3, 1/2, 2/3, 1) eines hydrophobierend wirkenden Silans (Triethoxyoctylsilan, OCTEO) modifiziert. Neben den beiden Extremen der vollst{\"a}ndigen und unmodifizierten Varianten (1 und 0) wurden teilweise modifizierte Zwischenstufen erhalten, indem die Silanmenge auf 2/3, 1/2, 1/3, 1/5 und 1/10 im Vergleich zu den vollmodifizierten Silica-NP verringert wurde. Die modifizierten Nanopartikel zeigten beim Dispergieren in verschiedenen Fl{\"u}ssigkeiten (Wasser, Toluol) eindeutige und graduell klar differenzierbare Unterschiede in Abh{\"a}ngigkeit vom Bedeckungsgrad der Partikeloberfl{\"a}che mit dem Silan. Wie erwartet nahm das hydrophobe Verhalten der Nanopartikel mit zunehmendem Bedeckungs- und damit Modifizierungsgrad zu und die Nanopartikel waren in unpolaren Fl{\"u}ssigkeiten wie Toluol gut dispergierbar, w{\"a}hrend sie in polaren Fl{\"u}ssigkeiten wie Wasser zur Agglomeration und Sedimentation neigten. In einem n{\"a}chsten Schritt wurden die zu unterschiedlichen Graden mit OCTEO modifizierten kolloidalen Silica-NP mittels Spr{\"u}htrocknung in mikroskalige Pulver {\"u}berf{\"u}hrt. Die nanostrukturierten Mikropartikelpulver wurden mit verschiedenen Analysemethoden wie REM-Aufnahmen, BET-, FTIR- und TG-Messungen untersucht, und die Eigenschaften der gebildeten Partikel charakterisiert. Die nanostrukturierten Mikropartikel zeigten auf den REM-Aufnahmen abh{\"a}ngig vom Modifizierungsgrad der Nanopartikel ein sehr unterschiedliches Aussehen. W{\"a}hrend die Mikropartikel aus vollst{\"a}ndig modifizierten Nanopartikeln eine eher raue Oberfl{\"a}che besaßen, hatten die aus unmodifizierten Nanopartiklen gebildeten eine sehr glatte, kompakt erscheinende Oberfl{\"a}che, was als Hinweis auf eine Kondensation und eine damit verbundene Aggregation der Nanopartikel gewertet wurde. Da sich diese Hypothese anhand der Aufnahmen aber nicht beweisen ließ, wurden in einer n{\"a}chsten weiterf{\"u}hrenden Testreihe Nano-Indenter-Experimente unter dem REM mit den aus voll- und unmodifizierten Nanopartikeln aufgebauten Mikropartikeln durchgef{\"u}hrt. Die Ergebnisse best{\"a}tigten den ersten Eindruck der REM-Aufnahmen insofern, als das sich die sehr kompakt wirkenden unmodifizierten Partikel nicht mit einer Wolfram-Spitze eindr{\"u}cken ließen und damit die Hypothese mechanisch stabiler Aggregate untermauerten. Ganz anders verhielten sich die vollmodifizierten Partikel, die mithilfe der Wolfram-Spitze so eingedr{\"u}ckt werden konnten, dass die Nanopartikel aus dem Mikropartikelverbund herausgel{\"o}st wurden und teilweise vereinzelt vorlagen. Hier handelte es sich mit hoher Wahrscheinlichkeit um Agglomerate, die unter der Einwirkung einer Scherkraft wieder vereinzelt werden konnten. Da es mit mikroskopischen Verfahren wie REM nicht m{\"o}glich war, unmittelbare Aussagen bez{\"u}glich der Wechselwirkung der Nanopartikel im Mikropartikel zu treffen, wurden zun{\"a}chst die Oberfl{\"a}cheneigenschaften mittels BET-, FTIR- und TG-Messungen untersucht. Im Hinblick auf die sp{\"a}tere Anwendung war es sehr wichtig, die Oberfl{\"a}cheneigenschaften der Mikropartikel m{\"o}glichst umfassend zu charakterisieren, da diese entscheidend zur Dispergierbarkeit der Partikel in einem Matrixsystem beitragen. Mithilfe der FTIR- und TG-Messungen konnte die Anwesenheit und Menge von Silan auf der Partikeloberfl{\"a}che bestimmt werden. Es zeigte sich ein klarer Trend f{\"u}r die zu verschiedenen Graden mit OCTEO modifizierten Silica-NP. Mit zunehmender Silanmenge nahm sowohl die Intensit{\"a}t der FTIR-Bande f{\"u}r die CH2- und CH3-Streckschwingung als auch der Masseverlust zu. Im Gegensatz zu diesen Messungen zeigte sich bei den BET-Messungen kein klarer Trend in Abh{\"a}ngigkeit vom Bedeckungsgrad der Silica-NP. Die h{\"o}chsten Werte f{\"u}r die spezifische Oberfl{\"a}che hatten Mikropartikel, die aus 1/5- und 1/3-modifizierten Silica-NP bestanden. Eine schl{\"u}ssige Erkl{\"a}rung wird darin gesehen, dass durch die Alkylgruppen auf der Oberfl{\"a}che ein Kondensieren der Silica-NP weitestgehend verhindert wurde und gleichzeitig noch gen{\"u}gend Mikroporen vorhanden blieben, die mit den Stickstoffmolek{\"u}len wechselwirken konnten. Neben den Standard-Analysemethoden wurden Dispergierbarkeitsuntersuchungen durchgef{\"u}hrt sowie die Hansen-Dispergierbarkeitsparameter (HDP) und die ET (30)-Werte mit dem Reichardt-Farbstoff bestimmt. Anhand der Dispergierbarkeitsuntersuchungen konnten erste qualitative Aussagen getroffen werden, ob es sich um hydrophile oder hydrophobe Partikel handelt. Diese ersten Ergebnisse und Trends konnten anschließend mit den HDP und dem RD quantitativ untermauert werden. Die Polarit{\"a}t der Mikropartikel, die aus zu unterschiedlichen Graden mit OCTEO modifizierten Silica-NP aufgebaut waren, nahm mit zunehmender Oberfl{\"a}chenbedeckung ab. Dieser Trend korrelierte mit den aus den FTIR- und TG-Messungen erhaltenen Werten. Da es mit den Silica-basierten Mikropartikeln nicht m{\"o}glich war, unmittelbare Aussagen zum Agglomerations- bzw. Aggregationsgrad der Nanopartikel im Mikropartikel zu treffen, wurde das Prinzip der Agglomerations/Aggregationssteuerung {\"u}ber Oberfl{\"a}chenmodifikation auf magnetische Nanopartikel {\"u}bertragen und so ein Modell geschaffen, das die Wechselwirkung auf nanopartikul{\"a}rer Ebene sichtbar und messbar macht. Diese Informationen zum Agglomerationsgrad der Nanopartikel lieferten wertvolle Hinweise im Hinblick auf die Dispergierbarkeit der Partikel in einer Matrix: Handelte es sich bei den Partikeln um lose Agglomerate, k{\"o}nnten diese zum Beispiel in einem Elastomer wieder auf Prim{\"a}rpartikelgr{\"o}ße dispergiert werden, w{\"a}hrend Aggregate nur in undefinierte Sekund{\"a}rstrukturen zerfallen. Gleichzeitig wurde mit dieser System{\"u}bertragung die Frage beantwortet, ob es sich bei den teilmodifizierten Partikeln um eine Mischung aus voll- und unmodifizierten Partikeln handelte oder ob das Silan statistisch {\"u}ber die komplette Oberfl{\"a}che verteilt war. Wie auch schon beim Silica-System wurden die Nanopartikel zun{\"a}chst abgestuft mit OCTEO modifiziert (0, 1/10, 1/3, 1/2, 2/3, 1) und anschließend spr{\"u}hgetrocknet. Aufgrund ihrer magnetischen Eigenschaften konnten die Eisenoxid-Partikel mittels ZFC- und FC-Messungen untersucht werden. Diese spezielle Analysemethode erlaubte es, Aussagen {\"u}ber den Grad der magnetischen Wechselwirkung der Partikel zu treffen und somit indirekt auch {\"u}ber den Grad der Agglomeration/ Aggregation der Nanopartikel im Mikropartikel. Es zeigten sich klare Unterschiede in den Werten f{\"u}r die Blocking-Temperatur (TB) zwischen den voll- und unmodifizierten Partikeln. TB ist die Temperatur, ab welcher die Magnetisierungsrichtung der Partikel aufgrund der thermischen Energie frei fluktuieren kann. Die vollmodifizierten Partikeln hatten einen sehr niedrigen Wert f{\"u}r TB, was auf eine schwache Dipol-Dipol- Wechselwirkung zwischen den einzelnen Eisenoxid-NP schließen ließ, w{\"a}hrend die unmodifizierten Eisenoxid-Partikel einen hohen TB-Wert hatten, woraus zu schließen war, dass es sich um Aggregate mit einem sehr geringen Partikel-Partikel-Abstand handelte und einer deshalb h{\"o}heren Wechselwirkung. Die Werte der teilmodifizierten Partikel folgten dem Trend, dass mit zunehmender Silan-Bedeckung der TB-Wert abnahm. Um die Frage der Silan-Verteilung zu beantworten, wurde zus{\"a}tzlich ein Mischsystem aus voll- und unmodifizierten Eisenoxid-NP verspr{\"u}ht. Sollte es sich bei den teilmodifizierten Partikeln (als Beispiel 1/2) nicht um eine statistische Verteilung der Octylgruppen auf der Oberfl{\"a}che handeln, m{\"u}ssten die beiden Messungen {\"U}bereinstimmungen aufweisen. Dies war allerdings nicht der Fall, was mithilfe der ZFC- und FC-Messungen gezeigt werden konnte. Der TB-Wert des Mischsystems lag zwischen dem der voll- und zu 2/3-modifizierten Partikel, w{\"a}hrend der Tir-Wert dem der unmodifizierten Partikel entsprach. Die Breite der Aufspaltung zwischen TB undTir konnte als breite Partikelverteilung (Mischung aus Agglomeraten und Aggregaten) interpretiert werden. Im Hinblick auf die Anwendung als F{\"u}llstoff wurden die Mikropartikel in eine PDMS-Matrix eingearbeitet und erneut ZFC- und FC-Messungen durchgef{\"u}hrt, wobei die gleichen Trends wie bei den reinen nanostrukturierten Mikropartikeln erhalten wurden. Das bedeutete, dass sich die vollmodifizierten Eisenoxid-NP gut im Elastomer verteilt hatten und somit eine nur sehr geringe Dipol-Dipol-Wechselwirkung vorhanden war. Mit dem entwickelten System der nanostrukturierten Mikropartikel l{\"a}sst sich der Agglomerations- bzw. Aggregationsgrad der Nanopartikel mehr oder weniger gezielt einstellen, und es k{\"o}nnen zus{\"a}tzlich Voraussagen {\"u}ber die Redispergierbarkeit des Partikelpulvers in einer geeigneten Matrix gemacht werden. Basierend auf den gewonnen Erkenntnissen, die zum Verst{\"a}ndnis der nanostrukturierten Mikropartikel beitrugen, wurden in einem n{\"a}chsten Schritt gezielt komplexe Strukturen aufgebaut. F{\"u}r eine gezielte Strukturierung von Nanopartikeln in Kern-Satellit-Partikel wurde zun{\"a}chst große 100 nm Silica-NP mit einem PCE funktionalisiert und anschließend mit kleinen und großen unmodifizierten Silica-NP verspr{\"u}ht. Wurden die geeigneten Verh{\"a}ltnisse (70:20:10; 100 nm Mel : 100 nm blank : 20 nm blank) der Partikel zueinander gew{\"a}hlt, konnten Kern-Satellit-Strukturen auf der Mikropartikeloberfl{\"a}che erzeugt werden. Beim Dispergieren der Mikropartikel in einer Fl{\"u}ssigkeit und in einem Elastomer (PDMS) konnten vereinzelte Kern-Satellit-Strukturen erhalten werden. Um zu best{\"a}tigen, dass es sich bei den dispergierten Kern-Satellit-Partikeln nicht um durch Trocknungseffekte entstandene Strukturen handelte, wurden in-situ-Fl{\"u}ssigkeitszellen- TEM-Aufnahmen gemacht. Die Aufnahmen konnten zeigen, dass sich die Kern-Satellit- Partikel in Abh{\"a}ngigkeit zueinander bewegen und nicht jeder Nanopartikel f{\"u}r sich, was auf eine Bindung der Partikel untereinander hindeutete. Neben den Silica-basierten Kern-Satellit-Partikeln konnten auch welche erzeugt werden, deren Satellit-Partikel aus Eisenoxid bestanden. Mit diesem System ist es m{\"o}glich, multifunktionelle Partikel mit verschiedensten Eigenschaften und Strukturen herzustellen. Teil II: Anwendungspotential nanostrukturierter Mikropartikel Im zweiten Teil der Arbeit wurde zun{\"a}chst die Anwendung der nanostrukturierten Mikropartikel als F{\"u}llstoff in IR und PDMS untersucht. Daf{\"u}r wurde ein weiteres Silan, Si69TM, zur abgestuften Modifizierung der Silica-NP eingesetzt. Es handelt sich um ein multifunktionelles Silan, welches sowohl an die Partikeloberfl{\"a}che als auch an das Elastomer binden kann. Bei den mechanischen Untersuchungen der IR-Silica-Komposite zeigte sich, dass das Silan einen entscheidenden Einfluss auf die Verst{\"a}rkung bei kleinen Deformationen hatte. W{\"a}hrend bei dem monofunktionellen Silan (OCTEO) eine direkte Korrelation zwischen Bedeckungsgrad und mechanischer Verst{\"a}rkung (G') bei gleichbleibendem F{\"u}llstoffgehalt beobachtet werden konnte, hatte der Bedeckungsgrad beim multifunktionellen Silan (Si69TM) keinen Einfluss. Anders als bei kleinen Deformationen zeigte sich bei großen Deformationen ein gegenteiliges Bild. Die Verschleißrate der IR-Silica-Komposite nahm bei beiden Silantypen mit zunehmendem Modifizierungsgrad ab, wobei die mit Si69TM modifizierten Partikel-Komposite wesentlich best{\"a}ndiger gegen Verschleiß waren als die mit OCTEO modifizierten Partikel-Komposite, was auf die zus{\"a}tzliche Matrixanbindung des Si69TM zur{\"u}ckzuf{\"u}hren war. Wurden die IR-Silica- Komposite mit den PDMS-Silica-Kompositen verglichen, konnten keine {\"u}bereinstimmenden Trends gefunden werden. Im PDMS-System war die mechanische Verst{\"a}rkung f{\"u}r Mikropartikel aus 2/3 mit OCTEO modifizierten Silica-NP maximal. Diese Unterschiede k{\"o}nnten sowohl auf die unterschiedliche Einarbeitung als auch auf die sehr unterschiedlichen Matrices zur{\"u}ckgef{\"u}hrt werden. Als weitere Anwendung wurden die nanostrukturierten Mikropartikel als Schersensoren f{\"u}r den 3D-Druck untersucht. Hierf{\"u}r wurden die Silica-NP mit einem PCE modifiziert und anschließend spr{\"u}hgetrocknet. Um die entstandenen Mikropartikel vollst{\"a}ndig in einer Matrix zu dispergieren, waren hohe Scherkr{\"a}fte und lange Scherzeiten erforderlich, was eine m{\"o}gliche Anwendung als Schersensor nur schwer realisierbar macht. Teil III: Erweiterung des Ansatzes zur Herstellung nanostrukturierter Mikropartikel auf Hydroxid-basierte Systeme Im dritten Teil dieser Arbeit wurde das System zur Modifizierung von oxidischen Silicaund Eisenoxid-Partikeln auf ein hydroxidisches Systeme {\"u}bertragen. Hierf{\"u}r wurden mittels F{\"a}llungsprozess LDH-Partikel hergestellt, die anschließend mit OCTEO modifiziert und abschließend spr{\"u}hgetrocknet wurden. In gleicher Weise wie bei den Mikropartikeln aus Silica-NP nahm der hydrophobe Charakter der LDH-Mikropartikel mit zunehmendem Modifizierungsgrad der Ausgangspartikel zu, was sich anhand von Untersuchungen zur Dispergierbarkeit in Fl{\"u}ssigkeiten unterschiedlicher Polarit{\"a}t zeigte. Zudem ließen sich die aus vollmodifizierten LDHs aufgebauten Mikropartikel in einer PDMS-Matrix wieder in vereinzelte Partikel dispergieren. Die Verst{\"a}rkung der Komposite war f{\"u}r die teilmodifizierten Partikel (2/3) maximal, da es sich hier, wie auch bei den anderen Partikelsystemen (Silica und Eisenoxid), um eine Mischung aus vereinzelten LDHs und kleineren Aggregate handelte, was aufgrund der starken F{\"u}llstoff-F{\"u}llstoff-Wechselwirkung zu einer mechanischen Verst{\"a}rkung bei kleinen Deformationen/Dehnungen f{\"u}hrte. Die Eigenschaften der Polymer-Partikel-Komposite ließen sich {\"u}ber den Modifizierungsgrad der Prim{\"a}rpartikel einstellen. Dies konnte f{\"u}r alle drei Partikelsysteme (Silica, Eisenoxid und LDH) beobachtet werden. Ausblick In der vorliegenden Arbeit konnte die Synthese von verschiedenen nanostrukturierten Mikropartikeln und deren einstellbaren Zerfall gezeigt werden. Um den Zerfall der Mikropartikel noch gezielter einstellen zu k{\"o}nnen, sollte in weiterf{\"u}hrenden Arbeiten vor allem die Modifizierung der Nanopartikel noch eingehender untersucht werden. Mithilfe der magnetischen Messungen konnte zwar zwischen einer Mischung aus un- und vollmodifizierten Partikel im Vergleich zu teilmodifizierten Partikel unterschieden werden, es konnten jedoch keine konkreten Aussagen zur Verteilung der Silanmolek{\"u}le auf der Partikeloberfl{\"a}che getroffen werden. Hierf{\"u}r sollten weitere Charakterisierungsmethoden hinzugezogen werden, die die Modifizierung auf molekularer Ebene analysieren. Zus{\"a}tzlich sollte die Verteilung/Anordnung der teilmodifizierten Nanopartikel im Mikropartikel untersucht werden. Gerade f{\"u}r Nanopartikel mit einem geringen Modifizierungsgrad (1/10, 1/5 und 1/3) sind verschiedene Anordnungen m{\"o}glich. Die Nanopartikel k{\"o}nnen sich w{\"a}hrend der Spr{\"u}htrocknung so anordnen, dass sich die Alkylketten entweder nach außen oder in die Mitte des Mikropartikels orientieren/ausrichten. Die Anordnung der Nanopartikel hat einen großen Einfluss auf die Polarit{\"a}t der entstehenden Mikropartikel- pulver. Dar{\"u}ber hinaus hat sie einen Einfluss auf die Aggregation der Nanopartikel untereinander und somit auf die Bildung von komplexen Unterstrukturen wie zum Beispiel Kern-Satellit-Partikel. Neben der Modifizierung der Nanopartikel sollte die Herstellung der komplexen Strukturen/Suprapartikel weiter optimiert werden. Mit einem detaillierten Verst{\"a}ndnis der physikalischen Prozesse w{\"a}hrend der Spr{\"u}htrocknung k{\"o}nnte die Anzahl der Satelliten auf den Kernpartikel kontrollierter eingestellt werden. Grunds{\"a}tzlich kann das hier entwickelte System der nanostrukturierten Mikropartikel mit einstellbarem Zerfallsverhalten an eine Vielzahl von Anwendungen angepasst werden. Da das System f{\"u}r zahlreiche Partikeltypen (Silica-, Eisenoxid-NP und LDH) geeignet ist, k{\"o}nnten verschiedene Partikel ko-verspr{\"u}ht und so Suprapartikel mit ganz neuen Funktionalit{\"a}ten und Eigenschaften erzeugt werden. Diese k{\"o}nnen als verst{\"a}rkende F{\"u}llstoffe in Elastomere oder zur Stabilisierung von Dispersionen eingesetzt werden. Mischpartikel aus Silica- und Eisenoxid-Partikel h{\"a}tten zum Beispiel den Vorteil, dass sie eine Dispersion stabilisieren und gleichzeitig wieder magnetisch abgetrennt werden k{\"o}nnen. Diese Mischpartikel k{\"o}nnten auch als F{\"u}llstoffe in komplexe Kunststoffbauteile eingearbeitet werden, in denen sie zum einen als mechanisch verst{\"a}rkender F{\"u}llstoff wirken und gleichzeitig durch induktive Erw{\"a}rmung das Bauteil vernetzt. Beim induktiven Erw{\"a}rmen handelt es sich um eine schonende Methode Bauteile gezielt zu vernetzen, indem die W{\"a}rme im Bauteil selbst, {\"u}ber magnetische Verluste der Magnetpartikel in einem magnetischen Wechselfeld, erzeugt wird und nicht {\"u}ber seine Oberfl{\"a}che eingebracht werden muss. Eine weitere interessante Anwendung f{\"u}r Mischpartikel ist die als magnetooptisch aktiver Marker oder Tracer in der medizinischen Diagnostik. Aufgrund von Quenching-Effekten (Ausl{\"o}schungseffekte) ist es schwierig magnetische Nanopartikel mit einer Farbigkeit oder Fluoreszenz auszustatten.[385] Mischt man jedoch die magnetischen Nanopartikel mit einem weiteren Partikelsystem wie zum Beispiel Silica-NP oder LDHs, k{\"o}nnen magnetooptische Eigenschaften erhalten werden},
subject = {Mikropartikel},
language = {de}
}
@article{TenderaHelmKrahfussetal.2021,
author = {Tendera, Lukas and Helm, Moritz and Krahfuss, Mirjam and Kuntze-Fechner, Maximilian W. and Radius, Udo},
title = {Case Study of N-\(^{i}\)Pr versus N-Mes Substituted NHC Ligands in Nickel Chemistry: The Coordination and Cyclotrimerization of Alkynes at [Ni(NHC)\(_{2}\)]},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {71},
doi = {10.1002/chem.202103093},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257137},
pages = {17849-17861},
year = {2021},
abstract = {A case study on the effect of the employment of two different NHC ligands in complexes [Ni(NHC)\(_{2}\)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\) 1\(^{Me}\), Mes\(_{2}\)Im 2) and their behavior towards alkynes is reported. The reaction of a mixture of [Ni\(_{2}\)(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{4}\)(μ-(η\(^{2}\) : η\(^{2}\))-COD)] B/ [Ni(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{2}\)(η\(^{4}\)-COD)] B' or [Ni(Mes\(_{2}\)Im)\(_{2}\)] 2, respectively, with alkynes afforded complexes [Ni(NHC)\(_{2}\)(η\(^{2}\)-alkyne)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\): alkyne=MeC≡CMe 3, H\(_{7}\)C\(_{3}\)C≡CC\(_{3}\)H\(_{7}\) 4, PhC≡CPh 5, MeOOCC≡CCOOMe 6, Me\(_{3}\)SiC≡CSiMe\(_{3}\) 7, PhC≡CMe 8, HC≡CC\(_{3}\)H\(_{7}\) 9, HC≡CPh 10, HC≡C(p-Tol) 11, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 12, HC≡CCOOMe 13; NHC=Mes\(_{2}\)Im: alkyne=MeC≡CMe 14, MeOOCC≡CCOOMe 15, PhC≡CMe 16, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 17, HC≡CCOOMe 18). Unusual rearrangement products 11 a and 12 a were identified for the complexes of the terminal alkynes HC≡C(p-Tol) and HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)), 11 and 12, which were formed by addition of a C-H bond of one of the NHC N-\(^{i}\)Pr methyl groups to the C≡C triple bond of the coordinated alkyne. Complex 2 catalyzes the cyclotrimerization of 2-butyne, 4-octyne, diphenylacetylene, dimethyl acetylendicarboxylate, 1-pentyne, phenylacetylene and methyl propiolate at ambient conditions, whereas 1\(^{Me}\) is not a good catalyst. The reaction of 2 with 2-butyne was monitored in some detail, which led to a mechanistic proposal for the cyclotrimerization at [Ni(NHC)\(_{2}\)]. DFT calculations reveal that the differences between 1\(^{Me}\) and 2 for alkyne cyclotrimerization lie in the energy profile of the initiation steps, which is very shallow for 2, and each step is associated with only a moderate energy change. The higher stability of 3 compared to 14 is attributed to a better electron transfer from the NHC to the metal to the alkyne ligand for the N-alkyl substituted NHC, to enhanced Ni-alkyne backbonding due to a smaller C\(_{NHC}\)-Ni-C\(_{NHC}\) bite angle, and to less steric repulsion of the smaller NHC \(^{i}\)Pr\(_{2}\)Im\(^{Me}\).},
language = {en}
}
@phdthesis{Rauch2020,
author = {Rauch, Florian},
title = {1,3-Bis(trifluoromethyl)benzene: A Versatile Building Block for the Synthesis of New Boron-Containing Conjugated Systems},
doi = {10.25972/OPUS-21147},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-211478},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Chapter 1 Thermally activated delayed fluorescence (TADF) materials provide a strategy to improve external quantum efficiencies of organic light emitting diodes (OLEDs). Because of spin-statistics, 25\% singlet and 75\% triplet excitons are generated in an electronic device. Conventional organic emitters cannot harvest the triplet excitons, due to low spin orbit coupling, and exhibit low external quantum efficiencies. TADF materials have to be designed in such a way, that the energy gap between the lowest singlet and triplet states (ΔES-T) is sufficiently small to allow reverse intersystem crossing (rISC) in organic systems. An established structure property relationship for the generation of TADF materials is the spatial separation of HOMO and LUMO via an orthogonal arrangement of donor and acceptor in donor-π-acceptor (D-π-A) compounds. This is achieved by increasing the steric bulk of the π-bridge. However, this is not always the most efficient method and electronic parameters have to be considered. In a combined experimental and theoretical study, a computational protocol to predict the excited states in D-π-A compounds containing the B(FXyl)2 (FXyl = 2,6-bis(trifluoromethyl)phenyl) acceptor group for the design of new TADF emitters is presented. To this end, the effect of different donor and π-bridge moieties on the energy gaps between local and charge-transfer singlet and triplet states was examined. To prove the computationally aided design concept, the D-π-B(FXyl)2 compounds Cbz-π (1), Cbz-Meπ (2), Phox-Meπ (3), Phox-MeOπ (4), and MeO₃Ph-FMeπ (5) were synthesized and fully characterized. The photophysical properties of these compounds in various solvents, polymeric film and in a frozen matrix were investigated in detail and show excellent agreement with the computationally obtained data (Figure 5.1). A simple structure-property relationship based on the molecular fragment orbitals of the donor and the π-bridge which minimize the relevant singlet-triplet gaps to achieve efficient TADF emitters is presented. Chapter 2 Three-coordinate boron is widely used as an acceptor in conjugated materials. In recent years the employment of trifluoromethylated aryls was shown to improve the acceptor properties of such boranes. Astonishingly, the use of ortho-trifluoromethylated aryls in boron containing systems also improves the stability of those systems in regard to their inherent reactivity towards nucleophiles. Borafluorenes are stronger acceptors than their non-annulated triarylborane derivatives. In previous studies, the effect of trifluoromethylated aryls as the exo-aryl moieties in borafluorenes, as well as the effect of fluorination on the backbone, were examined. As the latter suffers from a very low stability, systems using trifluoromethyl groups, both on the exo-aryl as well as the borafluorene backbone were designed in order to maximize both the stability as well as the acceptor strength. Three different perfluoroalkylated borafluorenes were prepared and their electronic and photophysical properties were investigated. The systems have four trifluoromethyl moieties on the borafluorene moiety as well as two trifluoromethyl groups at the ortho positions of their exo-aryl moieties. They differ with regard to the para-substituents on their exo-aryl moieties, being a proton (FXylFBf), a trifluoromethyl group (FMesFBf) or a dimethylamino group (p NMe2-FXylFBf), respectively. Furthermore, an acetonitrile adduct of FMesFBf was obtained and characterized. All derivatives exhibit extraordinarily low reduction potentials, comparable to those of perylenediimides. The most electron deficient derivative FMesFBf was also chemically reduced and its radical anion isolated and characterized. Furthermore, the photophysical properties of all compounds were investigated. All compounds exhibit weakly allowed lowest energy absorptions and very long fluorescent lifetimes of ca. 250 ns up to 1.6 μs; however, the underlying mechanisms differ. The donor substituted derivative p-NMe2-FXylFBf exhibits thermally activated delayed fluorescence from a charge transfer (CT) state, while the FMesFBf and FXylFBf borafluorenes exhibit only weakly allowed locally excited (LE) transitions due to their symmetry and low transition dipole moments, as suggested by DFT and TD-DFT calculations. Chapter 3 Conjugated dendrimers find wide application in various fields, such as charge transport/storage or emitter materials in organic solar cells or OLEDs. Previous studies on boron containing conjugated dendrimers are scarce and mostly employ a convergent synthesis approach, lacking a simple, generally applicable synthetic access. A new divergent approach was designed and conjugated triarylborane dendrimers were synthesized up to the 2nd generation. The synthetic strategy consists of three steps: 1) functionalization, via iridium catalyzed C-H borylation; 2) activation, via fluorination of the generated boronate ester with K[HF2] or [N(nBu)4][HF2]; and 3) expansion, via reaction of the trifluoroborate salts with aryl Grignard reagents. The concept was also shown to be viable for a convergent approach. All but one of the conjugated borane dendrimers exhibit multiple, distinct and reversible reduction potentials, making them potentially interesting materials for applications in molecular accumulators (Figure 5.7). Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. The conjugation does not further increase upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane sub-units, suggesting a potential application as photonic antennas. Chapter 4 A surprisingly high electronically-driven regioselectivity for the iridium-catalyzed C-H borylation using [Ir(COD)OMe]2 (COD = 1,5-cyclooctadiene) as the precatalytic species, bis(pinacolato)diboron (B2pin2) as the boron source and 4,4'-ditertbutyl-2,2'-bipyridin (dtbpy) as the ligand of D-π-A systems with diphenylamino (1) or carbazolyl (2) moieties as the donor, bis(2,6-bis(trifluoromethyl)phenyl)boryl (B(FXyl)2) as the acceptor, and 1,4-phenylene as the π-bridge was observed. Under these conditions, borylation was observed only at the sterically least encumbered para-positions of the acceptor groups. As boronate esters are versatile building blocks for organic synthesis (C-C coupling, functional group transformations), the C-H borylation represents a simple potential method for post-functionalization by which electronic or other properties of D-π-A systems can be fine-tuned for specific applications. The photophysical and electrochemical properties of the borylated (1-(Bpin)2) and unborylated (1) diphenylamino-substituted D-π-A systems were investigated. Interestingly, the borylated derivative exhibits coordination of THF to the boronate ester moieties, influencing the photophysical properties and exemplifying the non-innocence of boronate esters.},
subject = {Triarylborane},
language = {en}
}
@phdthesis{Peng2020,
author = {Peng, Kun},
title = {iClick reactions as a modular access to palladium(II) and platinum(II) triazolato complexes: Trends in kinetics and biological activity},
doi = {10.25972/OPUS-21161},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-211613},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {In the context of this work, important trends in the influence of the metal center, coligand, and alkyne reaction partner on the iClick reaction of square-planar palladium(II) and platinum(II) complexes with a N^N^N, C^N^N, or S^N^N coordination sphere and a number of internal as well as terminal alkynes were elaborated. Preliminary bioactivity studies on a human cancer cell line gave low micromolar EC50 values, for the most promising compound comparable to cisplatin serving as a reference drug. The further application of the iClick reaction to bioconjugation will be explored in future work.},
subject = {Click-Chemie},
language = {en}
}
@article{LiuMingZhangetal.2019,
author = {Liu, Xiaocui and Ming, Wenbo and Zhang, Yixiao and Friedrich, Alexandra and Marder, Todd B.},
title = {Copper-Catalyzed Triboration: Straightforward, Atom-Economical Synthesis of 1,1,1-Triborylalkanes from Terminal Alkynes and HBpin},
series = {Angewandte Chemie International Edition},
volume = {58},
journal = {Angewandte Chemie International Edition},
number = {52},
doi = {10.1002/anie.201909376},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206185},
pages = {18923-18927},
year = {2019},
abstract = {A convenient and efficient one-step synthesis of 1,1,1-triborylalkanes was achieved via sequential dehydrogenative borylation and double hydroborations of terminal alkynes with HBpin (HBpin=pinacolborane) catalyzed by inexpensive and readily available Cu(OAc)\(_2\). This process proceeds under mild conditions, furnishing 1,1,1-tris(boronates) with wide substrate scope, excellent selectivity, and good functional-group tolerance, and is applicable to gram-scale synthesis without loss of yield. The 1,1,1-triborylalkanes can be used in the preparation of α-vinylboronates and borylated cyclic compounds, which are valuable but previously rare compounds. Different alkyl groups can be introduced stepwise via base-mediated deborylative alkylation to produce racemic tertiary alkyl boronates, which can be readily transformed into useful tertiary alcohols.},
language = {en}
}
@phdthesis{He2020,
author = {He, Jiang},
title = {Studies of N-heterocyclic olefins as donors in triarylboranes and electron-poor phenylpyridyl-fused boroles},
doi = {10.25972/OPUS-21717},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217175},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Chapter 1 N-Heterocyclic olefins (NHOs), relatives of N-heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π-electron donating ability, NHOs were attached to triarylborane π-acceptors (A) giving donor(D)-π-A compounds 1-3. In addition, an enamine π-donor analogue (4) was synthesized for comparison. UV-visible absorption studies show a larger red shift for the NHO-containing boranes than for the enamine analogue, a relative of a CAAC. The red shifted absorption of NHO-containing boranes indicate smaller energy gaps of NHO-containing boranes than CAAC-containing boranes. Solvent-dependent emission studies indicate that 1-4 have moderate intramolecular charge transfer (ICT) behavior. Electrochemical investigations reveal that the NHO-containing boranes have extremely low reversible oxidation potentials (e.g., for 3, E1/2ox = -0.40 V vs. Fc/Fc+ in THF) which indicate the electron rich property of NHOs. Furthermore, TD-DFT calculations were carried out on these four D-π-A boranes. The results show that the LUMOs of 1-4 only show a small difference, but the HOMOs of 1-3 are much more destabilized than that of the enamine-containing 4, which is in agreement with the electrochemical investigations and confirms the stronger donating ability of NHOs. Chapter 2 Since the beginning of this century, the chemistry of (hetero)arene-fused boroles has attracted increasing interest. (Hetero)arene-fused boroles exhibit strong Lewis acidity, distinct fluorescence properties, strong electron accepting abilities, etc. However, their chemistry been only very briefly reviewed either as part of reviews on "free" boroles or on boron-doped polycyclic aromatic hydrocarbons (PAHs). In this chapter, we addressed the chemistry of (hetero)arene-fused boroles from fundamentals to their widely varying applications. It includes: 1) Synthetic methodology Both historical and recently developed strategies for the synthesis of fused boroles. 2) Stabilities A comparison of different kinetic protection strategies. 3) 9-Borafluorenes with a fluorinated backbone Application as Lewis acids, forming ion pairs with Cp2Zr(CH3)2 and applied as activators for polymerization, activators of H2, and other related applications. 4) Donor-acceptor 9-borafluorenes Applications as F- "turn on" sensors, potential applications as electron accepting units for organic (opto)electronics, bipolar transporting materials, TADF materials, and different functionalization strategies. 5) Heteroarene-fused boroles Enhanced antiaromaticity, unique coordination mode and their interesting properties. 6) Intramolecular dative bonding in 9-borafluorenes Bond-cleavage-induced intramolecular charge transfer (BICT), BICT-induced large Stoke shifts and dual emissions, application as a ratiometric sensor. 7) 9-Borafluorene-based main chain polymers Application in polymer chemistry and their distinct properties, e.g., as a sensor for gaseous NH3. 8) Electrochemistry A comparison of electron-accepting ability of different functionalized fused boroles through electrochemical studies. 9) Chemical reduction of fused boroles Stable radical anions and dianions of fused boroles and their properties. 10) Three-coordinate borafluorenium cations Cationic 9-borafluorenes and their interesting properties, e.g., in THF, reversible thermal colour switching properties. Finally, a conclusion and outlook regarding the chemistry, properties and applications, and suggestions for areas which require further study was provided. Chapter 3 Interested in fusing electron-poor arene onto boroles, two electron-poor phenylpyridyl-fused boroles, [TipPBB1]4 and TipPBB2 were prepared. [TipPBB1]4 is a white solid adopting a unique coordination mode, which forming a tetramer with a cavity in both the solid state and solution (1H DOSY). The boron center of TipPBB2 is 4-coordinate in the solid state, evidenced by a solid-state 11B{1H} RSHE/MAS NMR study, but the system dissociates in solution, leading to 3-coordinate borole species. [TipPBB1]4 exhibits two reduction processes which are attributed to the phenylpyridyl cores. TipPBB2 also exhibits two reduction processes with the first half-reduction potential of E1/2red = -1.94 V. The electron accepting ability of TipPBB2 is largely enhanced and comparable to that of FMesBf. This enhanced electron accepting ability is attributed to the electron withdrawing property of the pyridyl group. TipPBB2 exhibits concentration- and temperature-dependent dual fluorescence in solution. With the temperature is lowered, the emission intensity decreases (Figure 6.4, left). We suggested that the dual fluorescence is caused by an equilibrium between 3-coordinate TipPBB2 and a weak intermolecular adduct of TipPBB2 via a B-N bond. This hypothesis was further supported by lifetime measurements at different concentrations, low temperature excitation spectra low temperature 1H NMR spectra and lifetime measurements upon addition of DMAP to a solution of TipPBB2 to simulate the 4-coordiante TipPBB2 species. Interestingly, the ratio of the relative percentages of the two lifetimes shows a linear relationship with temperature; thus, TipPBB2 could serve as a fluorescent thermometer. Furthermore, theoretical studies were carried out on TipPBB2, and two models, ((BMe3)TipPBB1(NMe3) and (BMe3)TipPBB2(NMe3)), which utilize a BMe3 group as the Lewis acid coordinated to pyridine and an NMe3 group as the Lewis base coordinated to the boron center of the borole, were used to simulate the [TipPBB1]4 and intermolecular 4-coordinate TipPBB2, respectively. Theoretical studies indicate that the HOMO of TipPBB2 is located at the Tip group, which is in contrast to its borafluorene derivatives for which the HOMOs are located on the borafluorene cores. Chapter 4 Two derivatives of phenylpyridyl-fused boroles were prepared via functionalization of the pyridyl groups in two different directions, namely an electron-rich dihydropyridine moiety (compound 10) and an electron-deficient N-methylpyridinium cation (compound 11). Both compounds were fully characterized. The 11B NMR signal of compound 10 was observed at 58.8 ppm in CDCl3, which suggests strong conjugation between the boron atom and dihydropyridine moiety. Compound 11 shows a reversible coordination to THF which was confirmed by NMR studies. Compared to other 2,4,6-triisopropylphenyl protected 9-borafluorenes which only coordinate to CH3CN or DMF, the coordination of the weaker and bulkier THF to compound 11 indicates an extremely electron-deficient boron center in compound 11. The electron-rich property of the dihydropyridine moiety of compound 10 was confirmed by its oxidation potential (Epc = +0.37 V). Due to the strong conjugation of the dihydropyridine moiety with the boron atom, the reduction potential of compound 10 shifts cathodically and is more negative than -2.5 V. Compound 11 exhibits three reduction processes with the first reversible reduction potential at Ered1/2 = -1.23 V, which is significantly anodically shifted compared to that of its precursor (TipPBB2) or its framework 1-methyl-2-phenylpyridin-1-ium triflate (12). This significantly anodically shifted reduction potential confirms an extremely electron-deficient property of compound 11. Photophysical studies indicate that the lowest energy transition of compound 10 is more likely a locally-excited (LE) transition and compound 11 exhibits a polarized ground state. Furthermore, we performed theoretical studies for both compounds. The electron cloud distribution of the HOMO of compound 10 supports the strong conjugation between the boron atom and the dihydropyridine moiety in the ground state. An extremely low LUMO energy was determined by theoretical studies which confirmed the extremely electron-deficient property of compound 11. Chapter 5 Inspired by the enhancement of electron accepting ability with increasing numbers of electron withdrawing groups at boron, we tried to study the properties of a bis(pyridyl)arylboranes. In our attempt to synthesize a bis(pyridyl)arylborane, we obtained a bis(2-pyridyl)methoxyborate Li+ complex which is as a dimer both in solution and the solid state. In the solid state, compound [16]2 is a dimer containing two bis(2-pyridyl)methoxyborate which are linked by two lithium cations. Each lithium cation coordinates to one methoxy group and two pyridyl groups, one from each of the two bis(2-pyridyl)methoxyborate anions. The parameters of [16]2 were compared with other bis(2-pyridyl)methoxyborate stabilized Pt(IV) complex, bis(2-pyridyl)hydroxylborate stabilized Ru(II) complex and the dimer of EtAl(OMe)(2-pyridyl)2Li. To confirm the coordination mode in solution, 1H DOSY spectroscopy was carried out in CD2Cl2. The van der Waals radius obtained by 1H DOSY nicely matches with the result from the solid state and thus proves the dimer of 16 is persistent in solution. Finally, different Lewis acids (e.g., TMSCl, BF3•Et2O, AlCl3, HCl) were used to attempt to detach the methoxy group of [16]2. However, we observed either decomposition or selective cleavage of the Tip group, or no reaction at all, rather than cleavage of the methoxy group from boron.},
subject = {Triarylborane},
language = {en}
}
@phdthesis{Gernert2021,
author = {Gernert, Markus Stefan},
title = {Lumineszenzverhalten von Kupfer(I)- und Zink(II)-verbindungen mit N-heterozyklischen Carbenen als π-Chromophorliganden},
doi = {10.25972/OPUS-23109},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231099},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {Zu Beginn dieser Arbeit galten Kupfer(I)-emitter als vielversprechende Alternativen zu den bis dato f{\"u}hrenden Iridium(III)-emittern, waren dabei aber nur sehr selten tats{\"a}chlich kompetitiv. Die oftmals verwendenten chelatisierenden Diimin- bzw. Phosphanliganden als π-Chromophorligand erm{\"o}glichten bei diesen Kupfer(I)-emittern die Nutzung von TADF als Emissionsmechanismus, womit in seltenen F{\"a}llen strahlenden Ratenkonstanten von kr > 105 s-1 erreicht wurden. Diese Werte konnten allerdings nicht f{\"u}r den gesamten sichtbaren Spektralbereich erzielt werden, was auf eingeschr{\"a}nkte Modifikationsm{\"o}glichkeiten sowie unvollst{\"a}ndige Struktur-Eigenschafts-Beziehungen zur{\"u}ckgef{\"u}hrt werden kann. Erkl{\"a}rtes Ziel dieser Arbeit war es folglich, die Modifikationsm{\"o}glichkeiten von Kupfer(I)-emittern deutlich zu vergr{\"o}ßern. Hierbei wurde besonderes Augenmerk auf die Verwendung von Carbenen als monodentaten π-Chromophorliganden gelegt. Ausgehend von MeCAAC bzw. verschiedenen CAArCs konnte eine Bandbreite von Kupfer(I)- sowie Zink(II)-verbindungen synthetisiert sowie charakterisiert werden. Die durchgef{\"u}hrten Photolumineszenzstudien zeigen eindrucksvoll die Chromophoreigenschaften der verwendeten Carbene auf, werden doch Quantenausbeuten bis nahezu 1 sowie strahlende Ratenkonstanten von bis zu 9·105 s-1 erreicht. Es gelang somit also, Kupfer(I)-carbenverbindungen als vielversprechende Emitterklasse zu etablieren. In einem zweiten Bereich wurden anschließend erste Versuche unternommen, die gewonnen Erkenntnisse auf das Feld der Zink(II)-carbenverbindungen zu {\"u}bertragen. Dabei konnten wichtige Erkenntnisse hinsichtlich Struktur und Stabilit{\"a}t Zink(II)-MeCAAC-verbindungen erhalten werden.},
subject = {Photolumineszenz},
language = {de}
}
@phdthesis{Crumbach2021,
author = {Crumbach, Merian},
title = {Modifying the Optoelectronic Properties of Polycyclic Aromatic Hydrocarbons and Linear Oligomers by Doping with Boron and Further Heteroatoms},
doi = {10.25972/OPUS-24284},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242845},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {Der Austausch ausgew{\"a}hlter CC-Einheiten durch ihre isoelektronischen und isosteren BN-Einheiten in π-konjugierten organischen Verbindungen (BN/CC-Isosterie), insbesondere in polyzyklischen aromatischen Kohlenwasserstoffen (PAKs), hat sich als erfolgreiche Strategie zur Herstellung neuartiger organisch-anorganischer Hybridmaterialien erwiesen, die strukturelle {\"A}hnlichkeiten mit ihren reinen Kohlenstoff Analoga aufweisen, aber in vielen F{\"a}llen mit ver{\"a}nderten faszinierenden Eigenschaften und Funktionen. In den ersten beiden Kapiteln werden die Synthese und Eigenschaften von neuartigen BNB-dotierten Phenalenylen, Dithienoazadiborepinen und Dithienooxadiborepinen vorgestellt. Die optoelektronischen Eigenschaften dieser neuen Bauelemente k{\"o}nnen durch Variation der eingebauten Ar- (Mes, Tip, FMes) und R-Gruppen (H, Me, i-Pr, t-Bu, Ph) effektiv eingestellt werden. Theoretische Untersuchungen, einschließlich NICS (Nucleus Independent Chemical Shift) Scans und AICD (Anisotropy of the Induced Current Density)-Berechnungen, wurden durchgef{\"u}hrt und geben Einblick in ihren aromatischen oder antiaromatischen Charakter. Der Einbau von BP-Einheiten, welche mit BN und CC valenz-isoelektronisch sind, in unges{\"a}ttigte organische Verbindungen ist dagegen bisher kaum untersucht worden, obwohl das Potenzial der resultierenden BCP-Hybridmaterialien f{\"u}r elektronische Anwendungen erst k{\"u}rzlich erkannt wurde. Konjugierte Hauptkettenpolymere mit BP-Fragmenten im R{\"u}ckgrat sind bisher unbekannt. Die ersten molekularen Modellverbindungen f{\"u}r ein BP-Analogon des konjugierten Polymers Poly(p-phenylen-vinylen) (PPV) werden in Kapitel 3 vorgestellt. Theoretische Untersuchungen ergaben, dass die Mes*-Gruppe das Phosphor-zentrum vollst{\"a}ndig planarisiert, wodurch der B=P-Doppelbindungscharakter verst{\"a}rkt und eine Konjugation {\"u}ber die BP-Einheit erm{\"o}glicht wird. Es wurden verschiedene synthetische Ans{\"a}tze zu diesen molekularen Modellverbindungen untersucht und eine erfolgreiche synthetische Strategie gefunden.},
subject = {Aromatizit{\"a}t},
language = {en}
}
@phdthesis{Fritze2021,
author = {Fritze, Lars},
title = {Ways to Novel Inorganic-Organic Hybrid Materials Applying New B-C Bond Formation Strategies},
doi = {10.25972/OPUS-24217},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242173},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {π-Conjugated oligomers and polymers with tricoordinate boron centers incorporated into the main chain have attracted considerable attention as the interaction of the vacant p orbital on boron with an adjacent π system of the chain leads to conjugated materials with intriguing optical and electronic properties. This enables applicability in organic electronics and optoelectronics (OLEDs, OFETs, photovoltaics) or as sensory materials. The potential of our B-C coupling protocol using metal-free catalytic Si/B exchange condensation is demonstrated by the synthesis of a series of π-conjugated monodisperse (het)aryl oligoboranes. Variation of the (het)aryl moieties allowed for tunability of the optoelectronic properties of the materials. Additionally, catalytic C-C cross-coupling strategies were applied to synthesize oligofuryl-based mono- and bisboranes, as well as polymers. These studies led to very robust and highly emissive compounds (f up to 97 \%), which allow for tuning of their emission color from blue to orange. Furthermore, this work includes investigations of reaction routes to a kinetically stabilized tetraoxaporphyrinogen. Being a key aspect of this work, a full investigation of the mechanism of the catalytic Si/B exchange was carried out. Additionally, this work presents the use of borenium cations to perform B-C coupling via intermolecular electrophilic borylation. Similar to the Si/B exchange, this route is capable of giving access to diaryl(bromo)boranes.},
subject = {Konjugierte Polymere},
language = {en}
}
@phdthesis{Berger2022,
author = {Berger, Sarina Maria},
title = {Influence of Charge and Its Distribution on Biological Applications of Bis-Triarylboranes and Preliminary Investigations on H\(_2\)O\(_2\)-Cleavable Aryl Boronate Esters},
doi = {10.25972/OPUS-24314},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-243147},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {This dissertation describes the synthesis of an unsymmetrically-substituted triarylborane. This term describes a three-coordinate boron atom that is bound to three different aromatic systems, namely 2,6-dimethylphenyl, mesityl, and 4-(N,N-dimethylamino)-2,6-dimethylphenyl. It is also demonstrated that the amine functionality can be converted with methyl triflate into an ammonium moiety. The investigation of photophysical and electrochemical properties of this compound in comparison with the non-aminated and di-aminated analogues of the triarylborane is described besides other investigations of e. g. singlet oxygen sensitization, rotational barriers, and fundamental DFT calculations. Based on these investigations, selectively mono-, bis- and tris-dimethylamino- and trimethylammonium-substituted bis-triarylborane bithiophene chromophores were synthesized and their photophysical, and electrochemical properties were investigated together with the water solubility and singlet oxygen sensitizing efficiency of the cationic compounds Cat1+, Cat2+, Cat(i)2+, and Cat3+. Comparing these properties with the results obtained for the mono-triarylboranes reveals a large influence of the bridging unit on the investigated properties of the bis-triarylboranes. In addition, the interaction of the cationic bis-triarylboranes with different polynucleotides were investigated in buffered solutions as well as the ability of these selectively charged compounds to enter and localize within organelles of human lung carcinoma and normal lung cells. All these investigations demonstrate that the number of charges and their distribution influences the interactions and staining properties as well as most of the other properties investigated. In addition, preliminary investigations on H2O2-cleavable boronate esters in the presence of stochiometric amounts of H2O2 are described for three different aryl boronate esters.},
subject = {Triarylborane},
language = {en}
}
@article{ArrowsmithEndresHeinzetal.2021,
author = {Arrowsmith, Merle and Endres, Sara and Heinz, Myron and Nestler, Vincent and Holthausen, Max C. and Braunschweig, Holger},
title = {Probing the Boundaries between Lewis-Basic and Redox Behavior of a Parent Borylene},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {70},
doi = {10.1002/chem.202103256},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257154},
pages = {17660-17668},
year = {2021},
abstract = {The parent borylene (CAAC)(Me\(_{3}\)P)BH, 1 (CAAC=cyclic alkyl(amino)carbene), acts both as a Lewis base and one-electron reducing agent towards group 13 trichlorides (ECl\(_{3}\), E=B, Al, Ga, In), yielding the adducts 1-ECl\(_{3}\) and increasing proportions of the radical cation [1]\(^{•+}\) for the heavier group 13 analogues. With boron trihalides (BX\(_{3}\), X=F, Cl, Br, I) 1 undergoes sequential adduct formation and halide abstraction reactions to yield borylboronium cations and shows an increasing tendency towards redox processes for the heavier halides. Calculations confirm that 1 acts as a strong Lewis base towards EX3 and show a marked increase in the B-E bond dissociation energies down both group 13 and the halide group.},
language = {en}
}
@phdthesis{Sorg2020,
author = {Sorg, Jens Rudolf},
title = {Koordinationspolymere auf Antimon- und Bismut-Basis mit aromatischen Stickstoff-Donor Liganden - Einblick in Strukturen und Lumineszenz},
doi = {10.25972/OPUS-21107},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-211074},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Im Rahmen dieser Arbeit konnten die Strukturen von 32 neuen Koordinationspolymeren (CPs) und acht neuen Komplexen auf Basis von Antimon- \bzw Bismuthalogeniden und N-Donor Liganden aufgekl{\"a}rt werden. Davon konnten 26 CPs vollst{\"a}ndig mittels diffraktometrischer, spektroskopischer und thermischer Analysetechniken charakterisiert werden. Das Hauptaugenmerk dieser Arbeit lag dabei auf den strukturellen Eigenschaften sowie den Photolumineszenzeigenschaften der antimon- \bzw bismuthaltigen Koordinationspolymere. F{\"u}r die Synthese der Koordinationsverbindungen wurden die Bis- \bzw Trispyridyle 4,4'-Bipyridin (\textit{4-bipy}), 1,2-Bis(4-pyridyl)ethylen (\textit{4-bpe}), 1,2-Bis(4-pyridyl)ethan (\textit{4-bpa}) und 2,4,6-Tris(4-pyridyl)triazin (\textit{4-tpt}), die aromatischen Nitrile 4-Cyanopyridin (\textit{4-cypy}) und 2,4,6-Tris(4-cyanophenyl)triazin (\textit{4-tcpt}) sowie die Heteroaromaten Pyrazin (\textit{pyz}) und Thiazol (\textit{thz}) zusammen mit SbX\$_3\$ und BiX\$_3\$ (X: Cl, Br, I) eingesetzt. Die Reagenzien wurden unter unterschiedlichen Synthesebedingungen miteinander zur Reaktion gebracht, um die Koordination der organische Liganden zu realisieren. Auf diese Weise konnte eine F{\"u}lle an Strukturen beobachtet werden, die sich von Komplexen {\"u}ber eindimensionale Str{\"a}nge und zweidimensionale Schichten bis hin zu dreidimensionalen Netzwerken erstreckt. Als bevorzugte Koordinationsumgebung wurde sowohl f{\"u}r Bi\$^{3+}\$, als auch f{\"u}r Sb\$^{3+}\$ verzerrte Oktaeder beobachtet. F{\"u}r Antimon konnten dar{\"u}ber hinaus quadratisch pyramidale und tetraedrische Koordination mit stereochemisch aktiven freien Elektronenpaaren beobachtet werden, w{\"a}hrend vergleichbare Bismutverbindungen oktaedrische Koordination aufweisen. Dies verdeutlicht die st{\"a}rkere Neigung des freien Elektronenpaares von Sb\$^{3+}\$ {\"u}ber sterische Wechselwirkungen mit den Liganden in Interaktion zu treten, verglichen mit jenem von Bi\$^{3+}\$. Die Bispyridyl Liganden \textit{4-bipy}, \textit{4-bpe} und \textit{4-bpa} formen mit den Antimon(III)- und Bismut(III)halogeniden die sublimierbaren, doppelstr{\"a}ngigen CPs \$^{\ 1}_\infty\$[E\$_2\$X\$_6\$(\textit{L})\$_2\$] (E: Sb, Bi; X: Cl, Br, I; L: \textit{4-bipy}, \textit{4-bpe}, \textit{4-bpa}; \textbf{1}-\textbf{6}, \textbf{8}-\textbf{15}) sowie \$^{\ 1}_\infty\$[SbCl\$_3\$(\textit{4-bipy})] (\textbf{7}). In den CPs \textbf{1}-\textbf{6}, \textbf{8}-\textbf{15} erfolgt die Verkn{\"u}pfung der E\$^{3+}\$-Kationen nicht nur {\"u}ber die organischen Liganden, sondern auch {\"u}ber die Halogenidoliganden. Eine {\"a}hnliche Art der Verkn{\"u}pfung tritt in den CPs \$^{\ 3}_\infty[\$Bi\$_2\$Br\$_6\$(\textit{4-tcpt})] (\textbf{26}) und \$^{\ 2}_\infty[\$Bi\$_2\$Br\$_6\$(\textit{pyz})] (\textbf{32}) auf, w{\"a}hrend in \$^{\ 1}_\infty[\$BiX\$_3\$(\textit{4-cypy})\$_2\$] (X: Cl, Br; \textbf{16}, \textbf{17}) die Verkn{\"u}pfung sogar ausschließlich {\"u}ber die Halogenidoliganden erfolgt. Umsetzungen der Halogenide mit \textit{4-tpt} f{\"u}hren zur Ausbildung verschiedener Koordinationspolymere. W{\"a}hrend mit den Iodiden sowohl die CPs \$^{\ 1}_\infty[\$EI\$_3\$(\textit{4-tpt})] (E: Sb, Bi; \textbf{22}, \textbf{23}), als auch \$^{\ 2}_\infty[\$E\$_4\$I\$_{12}\$(\textit{4-tpt})\$_2\$] (E: Sb, Bi; \textbf{24}, \textbf{25}) zug{\"a}nglich sind, reagieren die Chloride und Bromide zu \$^{\ 2}_\infty[\$EX\$_3\$(\textit{4-tpt})] (E: Sb , Bi; X: Cl, Br; \textbf{18}-\textbf{21}). Aus dem CP \$^{\ 1}_\infty[\$SbCl\$_3\$(\textit{pyz})] (\textbf{29}), das quadratische \{SbCl\$_3\$N\$_2\$\}-Pyramiden enth{\"a}lt, kann durch Erhitzen das h{\"o}her vernetzte \$^{\ 3}_\infty[\$Sb\$_2\$Cl\$_6\$(\textit{pyz})\$_3\$] (\textbf{30}) mit oktaedrischer Sb\$^{3+}\$-Koordination in einer Kondensationsreaktion dargestellt werden. Eine verwandte Struktur wurde auch f{\"u}r die iodidhaltige Verbindung \$^{\ 3}_\infty[\$Sb\$_2\$Cl\$_6\$(\textit{pyz})\$_3\$] (\textbf{31}) beobachtet werden. Die Untersuchung der Lumineszenzeigenschaften der synthetisierten Koordinationspolymere ergab, dass die breitbandigen Anregungsprozesse in den Sb- und Bi-CPs durch metal-to-ligand charge-transfer (MLCT) Prozesse hervorgerufen werden. F{\"u}r die Emission stellen ligand-to-metal charge-transfer (LMCT) {\"U}berg{\"a}nge von ligandzentrierten Zust{\"a}nde in die elektronischen Grundzust{\"a}nde an den anorganischen Koordinationseinheiten und inter-valence charge-transfer (IVCT) Prozesse in E\$^{3+}\$-Paaren die bedeutendsten Prozesse dar. Dar{\"u}ber hinaus konnte in einigen CPs aber auch ligandbasierte Fluoreszenz \bzw Phosphoreszenz beobachtet werden. Die Intensit{\"a}t der Lumineszenz ist erheblich von den enthaltenen Halogenidoliganden abh{\"a}ngig (Cl>Br>I), weshalb f{\"u}r iodidhaltige Verbindungen keine Lumineszenz beobachtet werden konnte. Dar{\"u}ber hinaus wurden vier lanthanoidhaltige Koordinationspolymere der Zusammensetzung \$\beta\$-\$^{\ 1}_\infty[\$Bi\$_{2-x}\$Ln\$_x\$Cl\$_6\$(\textit{4-bipy})\$_2\$] (Ln: Ce, Eu, Tb, Eu/Tb; \textbf{41:Ln}) hergestellt. Dadurch konnte die hervorragende Eignung bismutbasierter Koordinationspolymere als Wirtsverbindungen f{\"u}r Ln\$^{3+}\$-Kationen nachgewiesen werden. In diesen Verbindungen f{\"u}hrt die Anregung des Wirtsgitters {\"u}ber einen Energietransfer zu den charakteristischen Eu\$^{3+}\$- und Tb\$^{3+}\$-Emissionen. Die Anwesenheit von Ce\$^{3+}\$ f{\"u}hrt hingegen zu einer deutlichen Intensit{\"a}tssteigerung der Lumineszenz der Wirtsverbindung. Somit sind auf diese Weise effiziente Phosphore mit variablen Lumineszenzfarben zug{\"a}nglich. Insgesamt konnten im Rahmen dieser Arbeit zahlreiche neue Sb- und Bi-basierte Koordinationsverbindungen mit N-Donor Liganden dargestellt werden und neue Erkenntnisse {\"u}ber ihre strukturellen Eigenschaften und Photolumineszenzeigenschaften erhalten werden.},
subject = {Photolumineszenz},
language = {de}
}
@phdthesis{Liu2020,
author = {Liu, Xiaocui},
title = {Catalytic Triboration and Diboration of Terminal Alkynes},
doi = {10.25972/OPUS-19253},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192537},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Chapter two reports the catalytic triboration of terminal alkynes with B2pin2 using readily available Cu(OAc)2 and PnBu3. Various 1,1,2-triborylalkenes, a class of compounds which have been demonstrated to be potential Matrix Metalloproteinase-2 (MMP-2) inhibitors, are obtained directly in moderate to good yields. The process features mild reaction conditions, broad substrate scope, and good functional group tolerance were observed. This Cu-catalyzed reaction can be conducted on a gram scale to produce the corresponding 1,1,2-triborylalkenes in modest yields. The utility of these products is demonstrated by further transformation of the C-B bonds to prepare gem-dihaloborylalkenes (F, Cl, Br), monohalodiborylalkenes (Cl, Br), and trans-diaryldiborylalkenes, which serve as important synthons and have previously been challenging to prepare. A convenient and efficient one step synthesis of 1,1,1-triborylalkanes was achieved via sequential dehydrogenative borylation and double hydroboration of terminal alkynes with HBpin (HBpin = pinacolborane) catalyzed by inexpensive and readily available Cu(OAc)2. This protocol proceeded under mild conditions, furnishing 1,1,1-tris(boronates) with wide substrate scope, excellent selectivity and good functional group tolerance, and is applicable to gram-scale synthesis without loss of yield. The 1,1,1-triborylalkanes can be used in the preparation of α-vinylboronates and borylated cyclic compounds, which are valuable but previously rare compounds. Different alkyl groups can be introduced stepwise via base-mediated deborylative alkylation to produce racemic tertiary alkyl boronates, which can be readily transformed into useful tertiary alcohols. Chapter 4 reported a NaOtBu-catalyzed mixed 1,1-diboration of terminal alkynes with an unsymmetrical diboron reagent BpinBdan. This Br{\o}nsted base-catalyzed reaction proceeds in a regio- and stereoselective fashion affording 1,1-diborylalkenes with two different boryl moieties in moderate to high yields, and is applicable to gram-scale synthesis without loss of yield or selectivity. Hydrogen bonding between the Bdan group and tBuOH is proposed to be responsible for the observed stereoselectivity. The mixed 1,1-diborylalkenes can be utilized in stereoselective Suzuki-Miyaura cross-coupling reactions.},
subject = {Borylierung},
language = {en}
}
@article{BrosgeLorenzHeltenetal.2019,
author = {Brosge, Felix and Lorenz, Thomas and Helten, Holger and Bolm, Carsten},
title = {BN- and BO-Doped Inorganic-Organic Hybrid Polymers with Sulfoximine Core Units},
series = {Chemistry - A European Journal},
volume = {25},
journal = {Chemistry - A European Journal},
number = {55},
doi = {10.1002/chem.201903289},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206194},
pages = {12708-12711},
year = {2019},
abstract = {While polysulfones constitute a class of well-established, highly valuable applied materials, knowledge about polymers based on the related sulfoximine group is very limited. We have employed functionalized diaryl sulfoximines and a p -phenylene bisborane as building blocks for unprecedented BN- and BO-doped alternating inorganic-organic hybrid copolymers. While the former were accessed by a facile silicon/boron exchange protocol, the synthesis of polymers with main-chain B-O linkages was achieved by salt elimination.},
language = {en}
}
@phdthesis{Saalfrank2020,
author = {Saalfrank, Christian},
title = {Lewis-Basen stabilisierte, aromatische Verbindungen des Bors : Darstellung und Reaktivit{\"a}t},
doi = {10.25972/OPUS-21057},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-210578},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Die vorliegende Arbeit befasst sich mit der Darstellung und Untersuchung cyclischer konjugierter Systeme des Bors. Hierbei wurden die zentralen Ringeinheiten der organischen Analoga mit zwei Boratomen in 1,4-Position substituiert. 1 Darstellung und Eigenschaften des CyCAAC-stabilisierten 1,4 Diborabenzols (87) Die Darstellung eines weiteren Vertreters des basenstabilisierten 1,4-Diborabenzols orientierte sich an vorangegangen Arbeiten der Gruppe um Braunschweig auf diesem Gebiet. Das Cyclohexyl-CAAC koordinierte Diboracumulen (85) wurde unter einer gereinigten Acetylen-atmosph{\"a}re mit einem Druck von etwa 1 bar ger{\"u}hrt. Quantenchemische Rechnungen ergaben einen NICS(0)-Wert von -2.6483 des [B2C4]-Rings (vgl. NICS(0)Benzol: -8.1723; B3LYP/Def2SVP Niveau) und best{\"a}tigten zus{\"a}tzlich die Bildung eines Ringstroms bzw. eines aromatischen Systems. Umsetzungen des Diborabenzols 87 mit den Alkalimetallen Lithium und Natrium wurden durchgef{\"u}hrt und die entsprechenden dianionischen Verbindungen 88 und 89 erhalten. Unter gleichen Reaktionsbedingungen wurden im Falle des Kaliums Einkristalle erhalten deren r{\"o}ntgenkristallographische Untersuchung den Konnektivit{\"a}tsbeweis f{\"u}r das Monoanion 90 liefern. 2 Synthese und Umsetzungen CAAC-stabilisierter 9,10 Diboraanthracene Die Darstellung des 9,10-(Dibromo)diboraanthracens 63 entlehnt sich der Literatur und findet durch eine Abfolge von Salzmetathesereaktionen zwischen o(Bistrimethylsilyl)benzol (65) und Bortribromid statt. Nach der Koordination der CAAC-Liganden an 63 wurde die schrittweise reduktive Abstraktion der Bromatome m{\"o}glich. Die Einelektronreduktionen von 92 und 93 lieferten nicht, wie erwartet, neutrale gemischtvalente Systeme. R{\"o}ntgenkristallographische Untersuchungen an geeigneten Einkristallen der Verbindung 99 zeigten, dass sich eine salzartige Struktur bildete. Bei der Reduktion von 93 wurden beide Bromidreste abgespalten und das Diboraanthracenfragment liegt als Radikalkation vor. Die zweifache Reduktion der Verbindungen 92 und 93 liefert ebenfalls Produkte, die keine 11B-NMR-Resonanz zeigen. Dieser Umstand spricht erneut f{\"u}r die Generierung offenschaliger Systeme. Die R{\"o}ntgenstrukturanalyse geeigneter Einkristalle der beiden erhaltenen Produkte 103 und 104 zeigte, dass die neutrale Diboraanthracenspezies gebildet wurde (Schema 58). ESR-Experimente bei tiefen Temperaturen lieferten Einsicht {\"u}ber den elektronischen Grundzustand der beiden Verbindungen 103 und 104. Die beiden Verbindungen liegen, unter den gew{\"a}hlten Bedingungen, im open shell-Singulett-grundzustand vor. Es ergeben sich Singulett-Triplett-Abst{\"a}nde ΔES→T = 0.43 kJ/mol (4.46 meV) f{\"u}r 103 bzw. ΔES→T = 2.3 kJ/mol (23.8 meV) f{\"u}r 104. Die Reduktion von 92 mit einem {\"U}berschuss von Lithium l{\"a}sst die Darstellung des dianionischen Diborataanthracens 110 zu. Unter photochemischen Bedingungen bildet 103 eine zwitterionische Spiroverbindung 113, durch die Insertion eines Boratoms in den Pyrrolidinring des koordinierten CAAC-Liganden. Weiterhin sind 103 und 104 geeignete Ausgangsmaterialien zur Aktivierung kleiner Molek{\"u}le unter milden Bedingungen. Die Umsetzung der MeCAAC-Spezies 103 mit elementarem Schwefel liefert Verbindung 128, bei der eine S3-Br{\"u}cke zwischen den Boratomen insertiert wird. Im Falle des CyCAAC-Diboraanthracens 104 konnte die Koordination eines CO-Molek{\"u}ls an die Boratome (140) nachgewiesen werden. Zus{\"a}tzlich konnten, durch die Darstellung des Halbsandwichkomplexes 149, erste Einsichten in die Verwendung des Diboraanthracens (104) als Ligand in der {\"U}bergangsmetallchemie gewonnen werden (Schema 60). Der Halbsandwichkomplex [η6-(9,10-(CyCAAC)2DBA)Cr(CO)3] (149) wurde durch die Zugabe von 104 zu [(MeCN)3Cr(CO)3] dargestellt und das zugeh{\"o}rige IR-Spektrum der Verbindung 149 identifiziert 104 als starken Elektronendonorliganden.},
subject = {Diradikal},
language = {de}
}
@article{FranzsicoFantuzziCardozoetal.2021,
author = {Franzsico, Marcos A. S. and Fantuzzi, Felipe and Cardozo, Thiago M. and Esteves, Pierre M. and Engels, Bernd and Oliveira, Ricardo R.},
title = {Taming the Antiferromagnetic Beast: Computational Design of Ultrashort Mn-Mn Bonds Stabilized by N-Heterocyclic Carbenes},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {47},
doi = {10.1002/chem.202101116},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256874},
pages = {12126-12136},
year = {2021},
abstract = {The development of complexes featuring low-valent, multiply bonded metal centers is an exciting field with several potential applications. In this work, we describe the design principles and extensive computational investigation of new organometallic platforms featuring the elusive manganese-manganese bond stabilized by experimentally realized N-heterocyclic carbenes (NHCs). By using DFT computations benchmarked against multireference calculations, as well as MO- and VB-based bonding analyses, we could disentangle the various electronic and structural effects contributing to the thermodynamic and kinetic stability, as well as the experimental feasibility, of the systems. In particular, we explored the nature of the metal-carbene interaction and the role of the ancillary η\(^{6}\) coordination to the generation of Mn\(_{2}\) systems featuring ultrashort metal-metal bonds, closed-shell singlet multiplicities, and positive adiabatic singlet-triplet gaps. Our analysis identifies two distinct classes of viable synthetic targets, whose electrostructural properties are thoroughly investigated.},
language = {en}
}
@article{BruecknerFantuzziStennettetal.2021,
author = {Br{\"u}ckner, Tobias and Fantuzzi, Felipe and Stennett, Tom E. and Krummenacher, Ivo and Dewhurst, Rian D. and Engels, Bernd and Braunschweig, Holger},
title = {Isolation of neutral, mono-, and dicationic B\(_2\)P\(_2\) rings by diphosphorus addition to a boron-boron triple bond},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {24},
doi = {10.1002/anie.202102218},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256451},
pages = {13661-13665},
year = {2021},
abstract = {The NHC-stabilised diboryne (B\(_2\)(SIDep)\(_2\); SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B\(_2\)P\(_2\) heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B\(_2\)P\(_2\) rings, with their diradicaloid, planar-ring isomers lying close in energy.},
language = {en}
}
@article{MuessigLisinetskayaDewhurstetal.2020,
author = {Muessig, Jonas H. and Lisinetskaya, Polina and Dewhurst, Rian D. and Bertermann, R{\"u}diger and Thaler, Melanie and Mitric, Roland and Braunschweig, Holger},
title = {Dibortetraiodid (B\(_2\)I\(_4\)) ist im Festk{\"o}rper ein Polymer aus sp3-hybridisiertem Bor},
series = {Angewandte Chemie},
volume = {132},
journal = {Angewandte Chemie},
number = {14},
doi = {10.1002/ange.201913590},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219653},
pages = {5574-5579},
year = {2020},
abstract = {Anhand der ersten Festk{\"o}rperstrukturen von Dibortetraiodid (B\(_2\)I\(_4\)) wird gezeigt, dass dieses nicht, wie lange angenommen, analog zu den leichteren Dibortetrahalogeniden B\(_2\)F\(_4\), B\(_2\)Cl\(_4\) und B\(_2\)Br\(_4\) in allen Aggregatzust{\"a}nden in Form diskreter Molek{\"u}le mit planaren, dreifach koordinierten Boratomen vorliegt. R{\"o}ntgenstrukturanalysen, Festk{\"o}rper-NMR- und IR-Messungen zeigen, dass B\(_2\)I\(_4\) im Festk{\"o}rper in zwei polymeren Konformeren vorkommt, die tetraedrisch koordinierte Boratome enthalten. Anhand von DFT-Rechnungen werden die IR-Spektren in L{\"o}sung und im Festk{\"o}rper simuliert und mit den experimentellen Daten verglichen.},
language = {de}
}
@article{MuessigLisinetskayaDewhurstetal.2020,
author = {Muessig, Jonas H. and Lisinetskaya, Polina and Dewhurst, Rian D. and Bertermann, R{\"u}diger and Thaler, Melanie and Mitric, Roland and Braunschweig, Holger},
title = {Tetraiododiborane(4) (B\(_2\)I\(_4\)) is a Polymer based on sp\(^3\) Boron in the Solid State},
series = {Angewandte Chemie International Edition},
volume = {59},
journal = {Angewandte Chemie International Edition},
doi = {10.1002/anie.201913590},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-209428},
pages = {5531-5535},
year = {2020},
abstract = {Herein we present the first solid-state structures of tetraiododiborane(4) (B\(_2\)I\(_4\)), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\), and B\(_2\)Br\(_4\). Single-crystal X-ray diffraction, solid-state NMR, and IR measurements indicate that B\(_2\)I\(_4\) in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid-state structures, and these are compared with the experimental spectra.},
language = {en}
}
@article{SchneiderTanzerKrauelDeutschetal.2021,
author = {Schneider, Leon N. and Tanzer Krauel, Eva-Maria and Deutsch, Carl and Urbahns, Klaus and Bischof, Tobias and Maibom, Kristina A. M. and Landmann, Johannes and Keppner, Fabian and Kerpen, Christoph and Hailmann, Michael and Zapf, Ludwig and Knuplez, Tanja and Bertermann, R{\"u}diger and Ignat'ev, Nikolai V. and Finze, Maik},
title = {Stable and Storable N(CF\(_{3}\))\(_{2}\) Transfer Reagents},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {42},
doi = {10.1002/chem.202101436},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256890},
pages = {10973-10978},
year = {2021},
abstract = {Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF\(_{3}\))\(_{2}\) group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of Cu\(^{I}\) and Ag\(^{I}\) bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine.},
language = {en}
}
@article{LiuMingZhangetal.2019,
author = {Liu, Xiaocui and Ming, Wenbo and Zhang, Yixiao and Friedrich, Alexandra and Marder, Todd B.},
title = {Kupferkatalysierte Triborierung: Einfache, atom{\"o}konomische Synthese von 1,1,1-Triborylalkanen aus terminalen Alkinen und HBpin},
series = {Angewandte Chemie},
volume = {131},
journal = {Angewandte Chemie},
number = {52},
doi = {10.1002/ange.201909376},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212189},
pages = {19099-19103},
year = {2019},
abstract = {Eine effiziente, einstufige Synthese von 1,1,1-Trialkylalkanen durch die sequenzielle, dehydrierende Borylierung und zweifache Hydroborierung von terminalen Alkinen mit Pinakolboran (HBpin) wurde unter Verwendung des kosteng{\"u}nstigen und einfach zug{\"a}nglichen Kupfersalzes Cu(OAc)2 als Katalysator realisiert. Das Verfahren zeichnet sich durch ein breites Substratspektrum, eine außerordentliche Selektivit{\"a}t und eine hohe Toleranz gegen{\"u}ber funktionellen Gruppen aus. Zudem kann die Reaktion ohne Ausbeuteverlust im Gramm-Maßstab durchgef{\"u}hrt werden. Die somit erhaltenen 1,1,1-Trialkylalkane k{\"o}nnen Anwendungen in der Herstellung von synthetisch wertvollen und bislang schwer zug{\"a}nglichen α-Vinylboronaten und zyklischen Boryl-Verbindungen finden. Verschiedene Alkylgruppen k{\"o}nnen stufenweise {\"u}ber eine basenvermittelte deborylierende Alkylierung eingef{\"u}hrt werden, um racemische, terti{\"a}re Alkylboronate herzustellen, die einfach in n{\"u}tzliche terti{\"a}re Alkohole umgewandelt werden k{\"o}nnen.},
language = {de}
}
@article{CzernetzkiArrowsmithFantuzzietal.2021,
author = {Czernetzki, Corinna and Arrowsmith, Merle and Fantuzzi, Felipe and G{\"a}rtner, Annalena and Tr{\"o}ster, Tobias and Krummenacher, Ivo and Schorr, Fabian and Braunschweig, Holger},
title = {A neutral beryllium(I) radical},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {38},
doi = {10.1002/anie.202108405},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256529},
pages = {20776-20780},
year = {2021},
abstract = {The reduction of a cyclic alkyl(amino)carbene (CAAC)-stabilized organoberyllium chloride yields the first neutral beryllium radical, which was characterized by EPR, IR, UV/Vis spectroscopy and X-ray crystallography. DFT calculations show significant spin density at beryllium and confirm donor-acceptor bonding between an alkylberyllium radical fragment and a neutral CAAC ligand.},
language = {en}
}
@phdthesis{Huang2022,
author = {Huang, Mingming},
title = {C-S Bond Borylation and Diborylation of Alkyl Halides, Tosylates, and Alcohols},
doi = {10.25972/OPUS-25718},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257186},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {Alkylboronates play an important role in synthetic chemistry, materials science and drug discovery. They are easy to handle due to their good air and moisture stability, and can be readily employed to form carbon-carbon and carbon-heteroatom bonds and can be converted to various functional groups under mild reaction conditions. Compared with conventional groups, such as aryl (pseudo)halides or alcohols, organosulfur compounds represent an alternative and complimentary substitute in coupling reactions. The construction of C-B bond from C-SO bond of aryl sulfoxide is presented in Chapter 2. The selective cleavage of either alkyl(C)-sulfonyl or aryl(C)-sulfonyl bonds of an aryl alkyl sulfone via Cu-free or Cu-mediated processes generates the corresponding boronate esters, which are presented in Chapter 3 and Chapter 4. 1,2-Bis(boronate esters) are emerging as important synthetic intermediates for preparing 1,2-difunctional compounds. In addition, the boryl moieties in different environments in a 1,2-bis(boronate ester) can be differentiated and converted selectively, allowing the synthesis of a wide variety of complex molecules. A direct and selective diboration of C-X and C-O bonds for the preparation of 1,2-bis(boronate esters) is presented in Chapter 5.},
language = {en}
}
@article{CuiDietzHaerterichetal.2021,
author = {Cui, Jingjing and Dietz, Maximilian and H{\"a}rterich, Marcel and Fantuzzi, Felipe and Lu, Wei and Dewhurst, Rian D. and Braunschweig, Holger},
title = {Diphosphino-Functionalized 1,8-Naphthyridines: a Multifaceted Ligand Platform for Boranes and Diboranes},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {63},
doi = {10.1002/chem.202102721},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256994},
pages = {15751-15756},
year = {2021},
abstract = {A 1,8-naphthyridine diphosphine (NDP) reacts with boron-containing Lewis acids to generate complexes featuring a number of different naphthyridine bonding modes. When exposed to diborane B\(_{2}\)Br\(_{4}\), NDP underwent self-deprotonation to afford [NDP-B\(_{2}\)Br\(_{3}\)]Br, an unsymmetrical diborane comprised of four fused rings. The reaction of two equivalents of monoborane BBr\(_{3}\) and NDP in a non-polar solvent provided the simple phosphine-borane adduct [NDP(BBr\(_{3}\))\(_{2}\)], which then underwent intramolecular halide abstraction to furnish the salt [NDP-BBr\(_{2}\)][BBr\(_{4}\)], featuring a different coordination mode from that of [NDP-B\(_{2}\)Br\(_{3}\)]Br. Direct deprotonation of NDP by KHMDS or PhCH2K generates mono- and dipotassium reagents, respectively. The monopotassium reagent reacts with one or half an equivalent of B\(_{2}\)(NMe\(_{2}\))\(_{2}\)Cl\(_{2}\) to afford NDP-based diboranes with three or four amino substituents.},
language = {en}
}
@phdthesis{Wu2022,
author = {Wu, Zhu},
title = {Room Temperature Phosphorescence (RTP): Experimental And Theoretical Studies on Boron-Containing Materials},
doi = {10.25972/OPUS-26084},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260844},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {Persistent room temperature phosphorescent (RTP) luminophores have gained remarkable interest recently for a number of applications in security printing, OLEDs, optical storage, time-gated biological imaging and oxygen sensors. We report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. We also have prepared 3 isomeric (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. At last, we checked the RTP properties from the boric acid. We found that the pure boric acid does not show RTP in the solid state.},
language = {en}
}
@phdthesis{Budiman2020,
author = {Budiman, Yudha Prawira},
title = {Applications of Fluorinated Aryl Boronates in Organic Synthesis},
doi = {10.25972/OPUS-21757},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217579},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {Fluorinated compounds are an important motif, particularly in pharmaceuticals, as one-third of the top performing drugs have fluorine in their structures. Fluorinated biaryls also have numerous applications in areas such as material science, agriculture, crystal engineering, supramolecular chemistry, etc. Thus, the development of new synthetic routes to fluorinated chemical compounds is an important area of current research. One promising method is the borylation of suitable precursors to generate fluorinated aryl boronates as versatile building blocks for organic synthesis. Chapter 1 In this chapter, the latest developments in the synthesis, stability issues, and applications of fluorinated aryl boronates in organic synthesis are reviewed. The catalytic synthesis of fluorinated aryl boronates using different methods, such as C-H, C-F, and C-X (X = Cl, Br, I, OTf) borylations are discussed. Further studies covering instability issues of the fluorinated boronate derivatives, which are accelerated by ortho-fluorine, have been reported, and the applications of these substrates, therefore, need special treatment. Numerous groups have reported methods to employ highly fluorinated aryl boronates that anticipate the protodeboronation issue; thus, polyfluorinated aryl boronates, especially those containing ortho-fluorine substituents, can be converted into chloride, bromide, iodide, phenol, carboxylic acid, nitro, cyano, methyl esters, and aldehyde analogues. These substrates can be applied in many cross-coupling reactions, such as the Suzuki-Miyaura reaction with aryl halides, the Chan-Evans-Lam C-N reaction with aryl amines or nitrosoarenes, C-C(O) reactions with N-(aryl-carbonyloxy)phthalamides or thiol esters (Liebskind-Srogl cross-coupling), and oxidative coupling reactions with terminal alkynes. Furthermore, the difficult reductive elimination from the highly stable complex [PdL2(2,6-C6F2+nH3-n)2] was the next challenge to be targeted in the homocoupling of 2,6-di-fluoro aryl pinacol boronates, and it has been solved by conducting the reaction in arene solvents that reduce the energy barrier in this step as long as no coordinating solvent or ancillary ligand is employed. Chapter 2 In this chapter, phenanthroline-ligated copper complexes proved to be efficient catalysts for the Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters (ArF-Bpin) with aryl iodides or bromides. This newly developed method is an attractive alternative to the traditional methods as copper is an Earth-abundant metal, less toxic, and cheaper compared to the traditional methods which commonly required palladium catalysts, and silver oxide that is also often required in stoichiometric amounts. A combination of 10 mol\% copper iodide and 10 mol\% phenanthroline, with CsF as a base, in DMF, at 130 ˚C, for 18 hours is efficient to cross-couple fluorinated aryl pinacol boronates with aryl iodides to generate cross-coupled products in good to excellent yields. This method is also viable for polyfluorophenyl borate salts such as pentafluorophenyl-BF3K. Notably, employing aryl bromides instead of aryl iodides for the coupling with fluorinated aryl-Bpin compounds is also possible; however, increased amounts of CuI/phenanthroline catalyst is necessary, in a mixture of DMF and toluene (1:1). A diverse range of π···π stacking interactions is observed in the cross-coupling products partly perfluorinated biaryl crystals. They range from arene-perfluoroarene interactions (2-(perfluorophenyl)naphthalene and 2,3,4-trifluorobiphenyl) to arene-arene (9-perfluorophenyl)anthracene) and perfluoroarene-perfluoroarene (2,3,4,5,6-pentafluoro-2'methylbiphenyl) interactions. Chapter 3 In this chapter, the efficient Pd-catalyzed homocoupling reaction of aryl pinacol pinacol boronates (ArF-Bpin) that contain two ortho-fluorines is presented. The reaction must be conducted in a "noncoordinating" solvent such as toluene, benzene, or m-xylene and, notably, stronger coordinating solvents or ancillary ligands have to be avoided. Thus, the Pd center becomes more electron deficient and the reductive elimination becomes more favorable. The Pd-catalyzed homocoupling reaction of di-ortho-fluorinated aryl boronate derivatives is difficult in strongly coordinating solvents or in the presence of strong ancillary ligands, as the reaction stops at the [PdL2(2,6-C6F2+nH3-n)2] stage after the transmetalations without the reductive elimination taking place. It is known that the rate of reductive elimination of Ar-Ar from [ML2(Ar)(Ar)] complexes containing group-10 metals decreases in the order Arrich-Arpoor > Arrich-Arrich > Arpoor-Arpoor. Furthermore, reductive elimination of the most electron-poor diaryls, such as C6F5-C6F5, from [PdL2(C6F5)2] complexes is difficult and has been a challenge for 50 years, due to their high stability as the Pd-Caryl bond is strong. Thus, the Pd-catalyzed homocoupling of perfluoro phenyl boronates is found to be rather difficult. Further investigation showed that stoichiometric reactions of C6F5Bpin, 2,4,6-trifluorophenyl-Bpin, or 2,6-difluorophenyl-Bpin with palladium acetate in MeCN stops at the double transmetalation step, as demonstrated by the isolation of cis-[Pd(MeCN)2(C6F5)2], cis-[Pd(MeCN)2(2,4,6-C6F3H2)2], and cis-[Pd(MeCN)2(2,6-C6F2H3)2] in quantitative yields. Thus, it can be concluded that the reductive elimination from diaryl-palladium complexes containing two ortho-fluorines in both aryl rings, is difficult even in a weakly coordinating solvent such as MeCN. Therefore, even less coordinating solvents are needed to make the Pd center more electron deficient. Reactions using "noncoordinating" arene solvents such as toluene, benzene, or m-xylene were conducted and found to be effective for the catalytic homocoupling of 2,6-C6F2+nH3-nBpin. The scope of the reactions was expanded. Using toluene as the solvent, the palladium-catalyzed homocoupling of ArF-Bpin derivatives containing one, two or no ortho-fluorines gave the coupled products in excellent yields without any difficulties. DFT calculations at the B3LYP-D3/def2-TZVP/6-311+g(2d,p)/IEFPCM // B3LYP-D3/SDD/6-31g**/IEFPCM level of theory predicted an exergonic process and lower barrier (< 21 kcal/mol) for the reductive elimination of Pd(C6F5)2 complexes bearing arene ligands, compared to stronger coordinating solvents (acetonitrile, THF, SMe2, and PMe3), which have high barriers ( > 33.7 kcal/mol). Reductive elimination from [Pd(ηn-Ar)(C6F5)2] complexes have low barriers due to: (i) ring slippage of the arene ligand as a hapticity change from η6 in the reactant to ηn (n ≤ 3) in the transition state and the product, which led to less σ-repulsion; and (ii) more favorable π-back-bonding from Pd(ArF)2 to the arene fragment in the transition state. Chapter 4 In this chapter, the efficient Pd-catalyzed C-Cl borylation of aryl chlorides containing two ortho-fluorines is presented. The reactions are conducted under base-free conditions to prevent the decomposition of the di-ortho-fluorinated aryl boronates, which are unstable in the presence of base. A combination of Pd(dba)2 (dba = dibenzylideneacetone) with SPhos (2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl) as a ligand is efficient to catalyze the C-Cl borylation of aryl chlorides containing two ortho-fluorine substituents without base, and the products were isolated in excellent yields. The substrate scope can be expanded to aryl chloride containing one or no ortho-fluorines and the borylated products were isolated in good to very good yield. This method provides a nice alternative to traditional methodologies using lithium or Grignard reagents.},
subject = {Homogene Katalyse},
language = {en}
}
@phdthesis{Lorenz2021,
author = {Lorenz, Thomas},
title = {Conjugated Polymers with BN Units in the Main Chain},
doi = {10.25972/OPUS-21923},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219230},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {In recent years PI-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons have attracted a lot of interest due to their great potential in organic electronics. However, there are only few known examples of conjugated polymers with BN units in their main chain. Within this work silazane cleavage with silicon-boron (Si/B) exchange for the synthesis of a novel class of inorganic-organic hybrid polymers is demonstrated. These polymers consist of alternating NBN and para-phenylene units in the main chain. Photophysical studies and TD-DFT calculations for the polymer and molecular model systems were carried out, revealing a low extent of PI-conjugation across the NBN units. The new polymers can be used as macromolecular polyligands by a cross-linking reaction with a ZrIV compound. In the next chapter the synthesis and characterization of the first poly(p-phenylene iminoborane) is presented. This novel inorganic-organic hybrid polymer can be described as a BN analogue of the well-known poly(p-phenylene vinylene) (PPV) and is also accessible using the previously described Si/B exchange as synthetic strategy. Photophysical investigations and TD-DFT calculations on the polymer and corresponding model oligomers provide clear evidence for PI-conjugation across the B=N units and extension of the conjugation path with increasing chain length. Furthermore, a possible application of Si/B exchange for the synthesis of polysulfoximines was explored. Herein, diaryl sulfoximines and a p-phenylene bisborane serve as building blocks for new BN- and BO-doped alternating inorganic-organic hybrid copolymers. While the BN-linked polymers were accessible by a facile silicon/boron exchange protocol, the synthesis of polymers with B-O linkages in the main chain is achieved by salt elimination. In the last chapter the concept of Si/B exchange was investigated for the synthesis of BP-linked oligomers. Herein oligomers with sterically less demanding substituents (substituents: 2,4,6-trimethylphenyl or 2,4,6-tri-iso-propylphenyl) at the phosphorus are accessible using Si/B exchange, but the oligomer with Mes* (2,4,6-tri-tert-butylphenyl) as substituent needed a salt elimination pathway to give the desired product. Experimental data and theoretical investigations indicate, that the P-substituent has a high influence on the geometry of the phosphorus center and therefore on the possible conjugation over the BP units.},
subject = {Polyphenylenvinylenanaloga},
language = {en}
}
@phdthesis{Krahfuss2020,
author = {Krahfuß, Mirjam Julia},
title = {N-Heterocyclic Silylenes as ambiphilic Reagents in Main Group Chemistry and as Ligands in Transition Metal Chemistry},
doi = {10.25972/OPUS-21724},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217246},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2020},
abstract = {This thesis reports on the applications of a particular N-heterocyclic silylene, Dipp2NHSi (1), as an ambiphilic reagent in main group chemistry and as a ligand in transition metal chemistry. One focus of the work lies in the evaluation of the differences in the reactivity of N-heterocyclic silylenes in main group element and transition metal chemistry in comparison with the in these areas nowadays ubiquitous N-heterocyclic carbenes. The first chapter gives an insight into the reactivity of Dipp2NHSi with respect to different types of main group element compounds. Silylene 1 was reacted with group 13 compounds. Adduct formation was observed with AlI3, Al(C6F5)3 and B(C6F5)3 which led to isolation of Dipp2NHSi·AlI3 (2), Dipp2NHSi·Al(C6F5)3 (3) and Dipp2NHSi·B(C6F5)3 (4). Furthermore, the reactivity of Dipp2NHSi (1) with respect to different elementhalide bonds was investigated. The reaction with elemental bromine and iodine leads to the dihalosilanes Dipp2NHSiBr2 (5) and Dipp2NHSiI2 (6). Utilizing methyl iodide, benzyl chloride and benzyl bromide, the insertion products Dipp2NHSi(I)(Me) (10), Dipp2NHSi(Cl)(benzyl) (11) and Dipp2NHSi(Br)(benzyl) (12) are obtained. Thus, insertion is preferred to reductive coupling with formation of RH2C-CH2R (R = H, Ph) and the corresponding dihalosilane. The reaction of 1 with Me3SnCl leads to the diazabutene {(Me3Sn)N(Dipp)CH}2 (9). The reaction of 1 with Ph2SnCl2 gives exclusively Dipp2NHSiCl2 (8) and cyclic polystannanes (Ph2Sn)n. The reactivity of 1 towards selected 1,3-dipolar compounds was also examined and Dipp2NHSi was reacted with azides of different size. The reaction with adamantyl azide led to the formation of the tetrazoline 13. For the reaction with the sterically less demanding trimethylsilyl azide the azido silane Dipp2NHSi(N(SiMe3)2)(N3) (14) and the degradation product 14* was isolated. The cyclosilamine 15 was formed from the reaction of 1 with 2,6-(diphenyl)phenyl azide. The bonding situation and ligation properties of Dipp2NHSi in transition metal complexes was assessed in the second part of the thesis by means of theoretical calculations and experimental investigations. Calculations on the main electronic features of Me2Im/Me2NHSi and Dipp2NHSi/Dipp2Im revealed significant differences in the frontier orbital region of these compounds, which affect the ligation properties of NHSis in general. It was demonstrated that NHSis show significantly different behaviour concerning their coordination chemistry. In particular, one energetically low lying π-acceptor orbital seems to determine the coordination chemistry of these ligands. To provide experimental support for these calculations, the silylene complexes [M(CO)5(Dipp2NHSi)] (M = Cr 16, Mo 17, W 18) were synthesized from Dipp2NHSi and [M(CO)6] (M = Cr, Mo, W) and the tungsten NHSi complex 18 was compared to the NHC complexes [W(CO)5(iPr2Im)] (19), [W(CO)5(iPr2ImMe)] (20) and [W(CO)5(Me2ImMe)] (21). The bonding of Me2Im and Me2NHSi (= L) to transition metal complexes has been assessed with DFT calculations for the model systems [Ni(L)], [Ni(CO)3(L)], and [W(CO)5(L)]. These studies revealed some common features in the difference between M-NHSi and M-NHC bonding which largely affect the bonding situation in transition metal complexes. NHSis show a propensity for bridging two metal atoms which was demonstrated on three different examples. Dipp2NHSi reacts with [Ni(CO)4] to form the dinuclear silylene-bridged complex [{Ni(CO)2(μ-Dipp2NHSi)}2] (22) upon CO elimination. The reduction of [Ni(η5-C5H5)2] with lithium naphthalenide in the presence of Dipp2NHSi yielded the NHSi-bridged Ni(I) dimer [{(η5 C5H5)Ni(µ-Dipp2NHSi)}2] (23). The dimeric half-sandwich complex [{(η5-C5H5)Fe(CO)2}2] led upon reaction with Dipp2NHSi to the formation of the dinuclear, NHSi-bridged complex [{(η5-C5H5)Fe(CO)}2(µ-CO)(µ-Dipp2NHSi)] (24). The insertion of Dipp2NHSi into metal halide bonds was investigated in a series of manganese complexes [Mn(CO)5(X)] (X = Cl, Br, I). The reaction of Dipp2NHSi with [Mn(CO)5(I)] led to substitution of two carbonyl ligands with Dipp2NHSi (1) to afford the tricarbonyl complex [Mn(CO)3(Dipp2NHSi)2(I)] (25). In 25, the iodide ligand is aligned in the {Mn(CO)3} plane, located between both NHSi silicon atoms. Treatment of [Mn(CO)5(Br)] with two equivalents of Dipp2NHSi afforded the complex [Mn(CO)3(Dipp2NHSi)2(Br)] (26), in which the bromide ligand is distorted towards one of the NHSi ligands. The reaction of the silylene ligand with [Mn(CO)5(Cl)] at room temperature afforded a mixture of two products, [Mn(CO)3(Dipp2NHSi)2(Cl)] (27*) and the insertion product [Mn(CO)4(Dipp2NHSi)(Dipp2NHSi-Cl)] (27). Complete transfer of a halide to the silylene was achieved for the reaction of Dipp2NHSi with [(η5-C5H5)Ni(PPh3)(Cl)] to yield [Ni(PPh3)(η5-C5H5)(Dipp2NHSi-Cl)] (28). Similarly, the reaction with [(η5-C5H5)Fe(CO)2(I)] led to the formation of [(η5 C5H5)Fe(CO)2(Dipp2NHSi-I)] (29).},
subject = {Silandiylverbindungen},
language = {en}
}
@article{HuangWuKrebsetal.2021,
author = {Huang, Mingming and Wu, Zhu and Krebs, Johannes and Friedrich, Alexandra and Luo, Xiaoling and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
title = {Ni-Catalyzed Borylation of Aryl Sulfoxides},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {31},
doi = {10.1002/chem.202100342},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256778},
pages = {8149-8158},
year = {2021},
abstract = {A nickel/N-heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B\(_{2}\)(neop)\(_{2}\) (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron-deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni-catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4-(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans-[Ni(ICy)\(_{2}\)(4-CF\(_{3}\)-C\(_{6}\)H\(_{4}\)){(SO)-4-MeO-C\(_{6}\)H\(_{4}\)}] 4. For complex 5, the isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I is in equilibrium with the S-bonded isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(SOC\(_{6}\)H\(_{5}\))] 5, as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2-TZVP-level of theory) and connected via a transition state trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(η\(^{2}\)-{SO}-C\(_{6}\)H\(_{5}\))], which lies only 10.8 kcal/mol above 5.},
language = {en}
}
@article{LiuKoleBudimanetal.2021,
author = {Liu, Zhiqiang and Kole, Goutam Kumar and Budiman, Yudha P. and Tian, Ya-Ming and Friedrich, Alexandra and Luo, Xiaoling and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
title = {Transition metal catalyst-free, base-promoted 1,2-additions of polyfluorophenylboronates to aldehydes and ketones},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {30},
doi = {10.1002/anie.202103686},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256487},
pages = {16529-16538},
year = {2021},
abstract = {A novel protocol for the transition metal-free 1,2-addition of polyfluoroaryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K\(^+\) in the carbonate base are critical. The distinguishing features of this procedure include the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H⋅⋅⋅O and O-H⋅⋅⋅N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroaryl carbinols have also been addressed.},
language = {en}
}
@article{HagspielFantuzziDewhurstetal.2021,
author = {Hagspiel, Stephan and Fantuzzi, Felipe and Dewhurst, Rian D. and G{\"a}rtner, Annalena and Lindl, Felix and Lamprecht, Anna and Braunschweig, Holger},
title = {Adducts of the parent boraphosphaketene H\(_2\)BPCO and their decarbonylative insertion chemistry},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
number = {24},
doi = {10.1002/anie.202103521},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256470},
pages = {13666-13670},
year = {2021},
abstract = {The first examples of Lewis base adducts of the parent boraphosphaketene (H\(_2\)B-PCO) and their cyclodimers are prepared. One of these adducts is shown to undergo mild decarbonylation and phosphinidene insertion into a B-C bond of a borole, forming very rare examples of 1,2-phosphaborinines, B/P isosteres of benzene. The strong donor properties of these 1,2-phosphaborinines are confirmed by the synthesis of their π complexes with the Group 6 metals.},
language = {en}
}
@phdthesis{GamachegebRupp2021,
author = {Gamache [geb. Rupp], Mira Theresa},
title = {Ligand Design for Ru(II) Photosensitizers in Photocatalytic Hydrogen Evolution},
doi = {10.25972/OPUS-24676},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246766},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2021},
abstract = {This thesis investigates different ligand designs for Ru(II) complexes and the activity of the complexes as photosensitizer (PS) in photocatalytic hydrogen evolution. The catalytic system typically contains a catalyst, a sacrificial electron donor (SED) and a PS, which needs to exhibit strong absorption and luminescence, as well as reversible redox behavior. Electron-withdrawing pyridine substituents on the terpyridine metal ion receptor result in an increase of excited-state lifetime and quantum yield (Φ = 74*10-5; τ = 3.8 ns) and lead to complex III-C1 exhibiting activity as PS. While the turn-over frequency (TOFmax) and turn-over number (TON) are relatively low (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS-1), the catalytic system is long-lived, losing only 20\% of its activity over the course of 12 days. Interestingly, the heteroleptic design in III-C1 proves to be beneficial for the performance as PS, despite III-C1 having comparable photophysical and electrochemical properties as the homoleptic complex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). Reductive quenching of the excited PS by the SED is identified as rate-limiting step in both cases. Hence, the ligands are designed to be more electron-accepting either via N-methylation of the peripheral pyridine substituents or introduction of a pyrimidine ring in the metal ion receptor, leading to increased excited-state lifetimes (τ = 9-40 ns) and luminescence quantum yields (Φ = 40-400*10-5). However, the more electron-accepting character of the ligands also results in anodically shifted reduction potentials, leading to a lack of driving force for the electron transfer from the reduced PS to the catalyst. Hence, this electron transfer step is found to be a limiting factor to the overall performance of the PS. While higher TOFmax in hydrogen evolution experiments are observed for pyrimidine-containing PS (TOFmax = 300-715 mmolH2 molPS-1 min-1), the longevity for these systems is reduced with half-life times of 2-6 h. Expansion of the pyrimidine-containing ligands to dinuclear complexes yields a stronger absorptivity (ε = 100-135*103 L mol-1 cm-1), increased luminescence (τ = 90-125 ns, Φ = 210-350*10-5) and can also result in higher TOFmax given sufficient driving force for electron transfer to the catalyst (TOFmax = 1500 mmolH2 molPS-1 min-1). When comparing complexes with similar driving forces, stronger luminescence is reflected in a higher TOFmax. Besides thermodynamic considerations, kinetic effects and electron transfer efficiency are assumed to impact the observed activity in hydrogen evolution. In summary, this work shows that targeted ligand design can make the previously disregarded group of Ru(II) complexes with tridentate ligands attractive candidates for use as PS in photocatalytic hydrogen evolution.},
subject = {Fotokatalyse},
language = {en}
}
@phdthesis{Schmidt2022,
author = {Schmidt, Uwe},
title = {Sandwich- und Halbsandwich-substituierte Diborene - Synthese, Eigenschaften und Reaktivit{\"a}t},
doi = {10.25972/OPUS-23460},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234601},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2022},
abstract = {Innerhalb der vorliegenden Arbeit ist es gelungen, durch das Einf{\"u}hren von Cymantrenylresten neue Diborene darzustellen, welche Halbsandwich-Substituenten tragen und somit das Substitutionsmuster von basenstabilisierten Diborenen um eine weitere Verbindungsklasse zu erweitern. Neben Cymantrenylresten gelang es auch, Ferrocenylreste als weitere Substituenten in entsprechende Diborensysteme einzuf{\"u}hren. {\"U}ber die Darstellung neuer Diborensysteme hinaus, waren Reaktivit{\"a}tsstudien am Diboraferrocenophan 29 ebenso ein wesentlicher Bestandteil der vorliegenden Arbeit. Es konnte gezeigt werden, dass 29 mit kleinen Lewis-Basen, Element-Wasserstoff-Verbindungen und Hydrierungsreagenzien zur Reaktion gebracht werden kann.},
subject = {Diborene},
language = {de}
}
@article{TinajeroTrejoRanaNageletal.2016,
author = {Tinajero-Trejo, Mariana and Rana, Namrata and Nagel, Christoph and Jesse, Helen E. and Smith, Thomas W. and Wareham, Lauren K. and Hippler, Michael and Schatzschneider, Ulrich and Poole, Robert K.},
title = {Antimicrobial Activity of the Manganese Photoactivated Carbon Monoxide-Releasing Molecule [Mn(CO)\(_3\)(tpa-kappa\(^3\)N)]\(^+\) Against a Pathogenic Escherichia coli that Causes Urinary Infections},
series = {Antioxidants \& Redox Signaling},
volume = {24},
journal = {Antioxidants \& Redox Signaling},
number = {14},
doi = {10.1089/ars.2015.6484},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188910},
pages = {765-780},
year = {2016},
abstract = {Aims: We set out to investigate the antibacterial activity of a new Mn-based photoactivated carbon monoxide-releasing molecule (PhotoCORM, [Mn(CO)\(_3\)(tpa-kappa\(^3\)N)]\(^+\)) against an antibiotic-resistant uropathogenic strain (EC958) of Escherichia coli. Results: Activated PhotoCORM inhibits growth and decreases viability of E. coli EC958, but non-illuminated carbon monoxide-releasing molecule (CORM) is without effect. NADH-supported respiration rates are significantly decreased by activated PhotoCORM, mimicking the effect of dissolved CO gas. CO from the PhotoCORM binds to intracellular targets, namely respiratory oxidases in strain EC958 and a bacterial globin heterologously expressed in strain K-12. However, unlike previously characterized CORMs, the PhotoCORM is not significantly accumulated in cells, as deduced from the cellular manganese content. Activated PhotoCORM reacts avidly with hydrogen peroxide producing hydroxyl radicals; the observed peroxide-enhanced toxicity of the PhotoCORM is ameliorated by thiourea. The PhotoCORM also potentiates the effect of the antibiotic, doxycycline. Innovation: The present work investigates for the first time the antimicrobial activity of a light-activated PhotoCORM against an antibiotic-resistant pathogen. A comprehensive study of the effects of the PhotoCORM and its derivative molecules upon illumination is performed and mechanisms of toxicity of the activated PhotoCORM are investigated. Conclusion: The PhotoCORM allows a site-specific and time-controlled release of CO in bacterial cultures and has the potential to provide much needed information on the generality of CORM activities in biology. Understanding the mechanism(s) of activated PhotoCORM toxicity will be key in exploring the potential of this and similar compounds as antimicrobial agents, perhaps in combinatorial therapies with other agents.},
language = {en}
}
@article{ChenMengLiaoetal.2021,
author = {Chen, Xing and Meng, Guoyun and Liao, Guanming and Rauch, Florian and He, Jiang and Friedrich, Alexandra and Marder, Todd B. and Wang, Nan and Chen, Pangkuan and Wang, Suning and Yin, Xiaodong},
title = {Highly Emissive 9-Borafluorene Derivatives: Synthesis, Photophysical Properties and Device Fabrication},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {20},
doi = {10.1002/chem.202005185},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256738},
pages = {6274-6282},
year = {2021},
abstract = {A series of 9-borafluorene derivatives, functionalised with electron-donating groups, have been prepared. Some of these 9-borafluorene compounds exhibit strong yellowish emission in solution and in the solid state with relatively high quantum yields (up to 73.6 \% for FMesB-Cz as a neat film). The results suggest that the highly twisted donor groups suppress charge transfer, but the intrinsic photophysical properties of the 9-borafluorene systems remain. The new compounds showed enhanced stability towards the atmosphere, and exhibited excellent thermal stability, revealing their potential for application in materials science. Organic light-emitting diode (OLED) devices were fabricated with two of the highly emissive compounds, and they exhibited strong yellow-greenish electroluminescence, with a maximum luminance intensity of >22 000 cd m\(^{-2}\). These are the first two examples of 9-borafluorene derivatives being used as light-emitting materials in OLED devices, and they have enabled us to achieve a balance between maintaining their intrinsic properties while improving their stability.},
language = {en}
}
@article{MatlerArrowsmithSchorretal.2021,
author = {Matler, Alexander and Arrowsmith, Merle and Schorr, Fabian and Hermann, Alexander and Hofmann, Alexander and Lenczyk, Carsten and Braunschweig, Holger},
title = {Reactivity of Terminal Iron Borylenes and Bis(borylenes) with Carbodiimides: Cycloaddition, Metathesis, Insertion and C-H Activation Pathways},
series = {European Journal of Inorganic Chemistry},
volume = {2021},
journal = {European Journal of Inorganic Chemistry},
number = {45},
doi = {10.1002/ejic.202100629},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257397},
pages = {4619-4631},
year = {2021},
abstract = {The reactions of carbodiimides with the iron arylborylene complex [Fe=BDur(CO)\(_{3}\)(PMe\(_{3}\))] (Dur=2,3,5,6-Me\(_{4}\)C\(_{6}\)H) and the iron bis(borylene) complex [Fe{=BDur}{=BN(SiMe\(_{3}\))\(_{2}\)}(CO)\(_{3}\)] yield a wide variety of temperature-dependent products, including known FeBNC and novel FeBNB metallacycles, complexes of N-heterocyclic boracarbene and spiro-boracarbene ligands and a unique 1,3,2,4-diazadiborolyl pianostool complex, characterized by NMR spectroscopy and X-ray crystallography. The product distributions can be rationalized by considering sequences of cycloaddition, metathesis, insertion, and C-H activation pathways mainly governed by sterics.},
language = {en}
}
@article{PhilippKrahfussRadackietal.2021,
author = {Philipp, Michael S. M. and Krahfuss, Mirjam J. and Radacki, Krzysztof and Radius, Udo},
title = {N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Adducts of Antimony(III)},
series = {European Journal of Inorganic Chemistry},
volume = {2021},
journal = {European Journal of Inorganic Chemistry},
number = {38},
doi = {10.1002/ejic.202100632},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257408},
pages = {4007-4019},
year = {2021},
abstract = {A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with antimony(III) chlorides of the general formula SbCl\(_{2}\)R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me\(_{2}\)Im\(^{Me}\) (1,3,4,5-tetra-methyl-imidazolin-2-ylidene), iPr\(_{2}\)Im\(^{Me}\) (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Mes\(_{2}\)Im, Dipp\(_{2}\)Im (R\(_{2}\)Im=1,3-di-organyl-imidazolin-2-ylidene; Mes=2,4,6-trimethylphenyl, Dipp=2,6-di-isopropylphenyl) and cAAC\(^{Me}\) with antimony(III) compounds SbCl\(_{2}\)R (R=Cl (1), Ph (2) and Mes (3)) yields the adducts NHC ⋅ SbCl\(_{2}\)R (R=Cl (4), Ph (5) and Mes (6); NHC=Me\(_{2}\)Im\(^{Me}\) (a), iPr\(_{2}\)Im\(^{Me}\) (b), Dipp\(_{2}\)Im (c) and Mes\(_{2}\)Im (d)) and cAAC\(^{Me}\) ⋅ SbCl\(_{2}\)R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp\(_{2}\)Im) ⋅ SbCl\(_{2}\)Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated \(^{a}\)NHC-adduct \(^{a}\)Dipp\(_{2}\)Im ⋅ SbCl\(_{2}\)Ar (Ar=Mes (7) and Ph (8)) (\(^{"a"}\) denotes "abnormal" coordination mode of the NHC) in high yields. One of the chloride substituents at antimony of 7 can be abstracted by GaCl3 or Ag[BF\(_{4}\)] to obtain the imidazolium salts [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][BF\(_{4}\)] (9) and [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][GaCl\(_{4}\)] (10).},
language = {en}
}
@article{KoleMerzAmaretal.2021,
author = {Kole, Goutam Kumar and Merz, Julia and Amar, Anissa and Fontaine, Bruno and Boucekkine, Abdou and Nitsch, J{\"o}rn and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Košćak, Marta and Braunschweig, Holger and Piantanida, Ivo and Halet, Jean-Fran{\c{c}}ois and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.},
title = {2- and 2,7-substituted para-N-methylpyridinium pyrenes: syntheses, molecular and electronic structures, photophysical, electrochemical, and spectroelectrochemical properties and binding to double-stranded (ds) DNA},
series = {Chemistry - A European Journal},
volume = {27},
journal = {Chemistry - A European Journal},
number = {8},
doi = {10.1002/chem.202004748},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256642},
pages = {2837-2853},
year = {2021},
abstract = {Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm\(^{-1}\). The N-methylpyridinium compounds have a single reduction at ca. -1.5 V vs. Fc/Fc\(^+\) in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.},
language = {en}
}
@article{BudimanFriedrichRadiusetal.2019,
author = {Budiman, Yudha P. and Friedrich, Alexandra and Radius, Udo and Marder, Todd B.},
title = {Copper-catalysed Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters with aryl iodides and bromides and fluoroarene-arene π-stacking interactions in the products},
series = {ChemCatChem},
volume = {11},
journal = {ChemCatChem},
number = {21},
doi = {10.1002/cctc.201901220},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204839},
pages = {5387-5396},
year = {2019},
abstract = {A combination of copper iodide and phenanthroline as the ligand is an efficient catalyst for Suzuki-Miyaura cross-coupling of highly fluorinated boronate esters (aryl-Bpin) with aryl iodides and bromides to generate fluorinated biaryls in good to excellent yields. This method represents a nice alternative to traditional cross-coupling methods which require palladium catalysts and stoichiometric amounts of silver oxide. We note that π⋅⋅⋅π stacking interactions dominate the molecular packing in the partly fluorinated biaryl crystals investigated herein. They are present either between the arene and perfluoroarene, or solely between arenes or perfluoroarenes, respectively.},
language = {en}
}
@article{GraebGeidel2019,
author = {Gr{\"a}b, Patrick and Geidel, Ekkehard},
title = {Spectroscopic studies of food colorings},
series = {World Journal of Chemical Education},
volume = {7},
journal = {World Journal of Chemical Education},
number = {2},
doi = {10.12691/wjce-7-2-13},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201908},
pages = {136-144},
year = {2019},
abstract = {In chemical education, it is often a challenge to understand the basic principles of spectroscopic techniques due to missing connections to the real world. Therefore, the present contribution offers context-based applications of UV/Vis spectroscopy for analytics of food colorings with which learners can improve their skills regarding this method. The spectroscopic determination of food colorings seems to be a promising approach due to the long tradition and omnipresence of dyes in supermarket products. The therefor-required spectral data for commonly used dyes are provided for educational usage. Qualitative and quantitative analytics of food colorings in four different lemonades and chocolate beans have been used to introduce learners to important analytical techniques like sample preparation or elimination of confounding factors. These analytics also display the limitations of the method in the visible range of light in the case of tartrazine and curcumin. By applying Lambert-Beer-Bouguer's Law in different variations, typical calculations of concentrations can be studied in quantitative analyses. The studied food samples demonstrate the different usage of food colorings depending on the country of sale. Finally, a 3D-printable low-cost photometer suitable for the discussed quantitative analytics in educational contexts is presented.},
language = {en}
}
@article{LorkowskiKrahfussKubickietal.2019,
author = {Lorkowski, Jan and Krahfuss, Mirjam and Kubicki, Maciej and Radius, Udo and Pietraszuk, Cezary},
title = {Intramolecular ring expansion reaction (RER) and intermolecular coordination of in situ generated Cyclic (Amino)(Aryl)Carbenes (cAArCs)},
series = {Chemistry - A European Journal},
volume = {25},
journal = {Chemistry - A European Journal},
number = {48},
doi = {10.1002/chem.201902630},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204847},
pages = {11365-11374},
year = {2019},
abstract = {Cyclic (amino)(aryl)carbenes (cAArCs) based on the isoindoline core were successfully generated in situ by α-elimination of 3-alkoxyisoindolines at high temperatures or by deprotonation of isoindol-2-ium chlorides with sodium or copper(I) acetates at low temperatures. 3-Alkoxy-isoindolines 2 a ,b-OR (R=Me, Et, i Pr) have been prepared in high yields by the addition of a solution of 2-aryl-1,1-diphenylisoindol-2-ium triflate (1 a ,b-OTf ; a : aryl=Dipp=2,6-diisopropylphenyl; b : Mesityl-, Mes=2,4,6-trimethylphenyl) to the corresponding alcohol (ROH) with NEt3 at room temperature. Furthermore, the reaction of 2 a ,b-OMe in diethyl ether with a tenfold excess of hydrochloric acid led to the isolation of the isoindol-2-ium chlorides 1 a ,b-Cl in high yields. The thermally generated cAArC reacts with sulfur to form the thioamide 3 a . Without any additional trapping reagent, in situ generation of 1,1-diphenylisoidolin-3-ylidenes does not lead to the isolation of these compounds, but to the reaction products of the insertion of the carbene carbon atom into an ortho C-H bond of a phenyl substituent, followed by ring-expansion reaction; namely, anthracene derivatives 9-N(H)aryl-10-Ph-C14H8 4 a ,b (a : Dipp; b : Mes). These compounds are conveniently synthesized by deprotonation of the isoindol-2-ium chlorides with sodium acetate in high yields. Deprotonation of 1 a-Cl with copper(I) acetate at low temperatures afforded a mixture of 4 a and the corresponding cAArC copper(I) chloride 5 a , and allowed the isolation and structural characterization of the first example of a cAArC copper complex of general formula [(cAArC)CuCl].},
language = {en}
}
@article{BanGriesbeckTomićetal.2020,
author = {Ban, Željka and Griesbeck, Stefanie and Tomić, Sanja and Nitsch, J{\"o}rn and Marder, Todd B. and Piantanida, Ivo},
title = {A Quadrupolar Bis-Triarylborane Chromophore as a Fluorimetric and Chirooptic Probe for Simultaneous and Selective Sensing of DNA, RNA and Proteins},
series = {Chemistry - A European Journal},
volume = {26},
journal = {Chemistry - A European Journal},
number = {10},
doi = {10.1002/chem.201903936},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208154},
pages = {2195-2203},
year = {2020},
abstract = {A water-soluble tetracationic quadrupolar bis-triarylborane chromophore showed strong binding to ds-DNA, ds-RNA, ss-RNA, as well as to the naturally most abundant protein, BSA. The novel dye can distinguish between DNA/RNA and BSA by fluorescence emission separated by Δv =3600 cm\(^{-1}\), allowing for the simultaneous quantification of DNA/RNA and protein (BSA) in a mixture. The applicability of such fluorimetric differentiation in vitro was demonstrated, strongly supporting a protein-like target as a dominant binding site of 1 in cells. Moreover, our dye also bound strongly to ss-RNA, with the unusual rod-like structure of the dye, decorated by four positive charges at its termini and having a hydrophobic core, acting as a spindle for wrapping A, C and U ss-RNAs, but not poly G, the latter preserving its secondary structure. To the best of our knowledge, such unmatched, multifaceted binding activity of a small molecule toward DNA, RNA, and proteins and the selectivity of its fluorimetric and chirooptic response makes the quadrupolar bis-triarylborane a novel chromophore/fluorophore moiety for biochemical applications.},
language = {en}
}
@article{BelaidiRauchZhangetal.2019,
author = {Belaidi, Houmam and Rauch, Florian and Zhang, Zuolun and Latouche, Camille and Boucekkine, Abdou and Marder, Todd B. and Halet, Jean-Francois},
title = {Insights into the optical properties of triarylboranes with strongly electron-accepting bis(fluoromesityl)boryl groups: when theory meets experiment},
series = {ChemPhotoChem},
volume = {4},
journal = {ChemPhotoChem},
number = {3},
doi = {10.1002/cptc.201900256},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-205600},
pages = {173-180},
year = {2019},
abstract = {The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4-D-C\(_6\)H\(_4\)-B(Ar)\(_2\) (D=\(^t\)Bu or NPh\(_2\); Ar=mesityl (Mes) or 2,4,6-tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state-of-the-art DFT and TD-DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4-\(^t\)Bu-C\(_6\)H\(_4\)-B(Fmes)\(_2\) 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert-butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.},
language = {en}
}
@article{LiuMingFriedrichetal.2020,
author = {Liu, Xiaocui and Ming, Wenbo and Friedrich, Alexandra and Kerner, Florian and Marder, Todd B.},
title = {Copper-Catalyzed Triboration of Terminal Alkynes Using B\(_2\)pin\(_2\): Efficient Synthesis of 1,1,2-Triborylalkenes},
series = {Angewandte Chemie International Edition},
volume = {59},
journal = {Angewandte Chemie International Edition},
number = {1},
doi = {10.1002/anie.201908466},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206694},
pages = {304-309},
year = {2020},
abstract = {We report herein the catalytic triboration of terminal alkynes with B\(_2\)pin\(_2\) (bis(pinacolato)diboron) using readily available Cu(OAc)\(_2\) and P\(^n\)Bu\(_3\). Various 1,1,2-triborylalkenes, a class of compounds that have been demonstrated to be potential matrix metalloproteinase (MMP-2) inhibitors, were obtained directly in moderate to good yields. The process features mild reaction conditions, a broad substrate scope, and good functional group tolerance. This copper-catalyzed reaction can be conducted on a gram scale to produce the corresponding 1,1,2-triborylalkenes in modest yields. The utility of these products was demonstrated by further transformations of the C-B bonds to prepare gem -dihaloborylalkenes (F, Cl, Br), monohaloborylalkenes (Cl, Br), and trans -diaryldiborylalkenes, which serve as important synthons and have previously been challenging to prepare.},
language = {en}
}
@article{BelangerChabotBraunschweig2019,
author = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger},
title = {Hexahalogendiborat-Dianionen: Eine neue Klasse bin{\"a}rer Borhalogenide},
series = {Angewandte Chemie},
volume = {131},
journal = {Angewandte Chemie},
number = {40},
doi = {10.1002/ange.201906666},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212605},
pages = {14408-14412},
year = {2019},
abstract = {Die elektronenpr{\"a}zisen bin{\"a}ren Borsubhalogenide [B\(_2\)X\(_6\)]\(^{2-}\) (X=F, Br, I) wurden synthetisiert und strukturell im Festk{\"o}rper untersucht. Zudem konnte die vermutete Existenz von [B\(_2\)Cl\(_6\)]\(^{2-}\) mittels R{\"o}ntgendiffraktometrie nachgewiesen werden. Diese Dianionen sind isoelektronisch zu den Hexahalogeniden des Ethans und k{\"o}nnen als Homologe des Tetrahalogenborat-Anions BX\(_4\)\(^-\) betrachtet werden. Dar{\"u}ber hinaus geh{\"o}ren sie zu den seltenen Beispielen von elektronenpr{\"a}zisen bin{\"a}ren Borverbindungen (B\(_2\)X\(_4\), BX\(_3\), [BX\(_4\)]\(^-\)).},
language = {de}
}
@article{TenderaSchaubKrahfussetal.2020,
author = {Tendera, Lukas and Schaub, Thomas and Krahfuss, Mirjam J. and Kuntze-Fechner, Maximilian W. and Radius, Udo},
title = {Large vs. Small NHC Ligands in Nickel(0) Complexes: The Coordination of Olefins, Ketones and Aldehydes at [Ni(NHC)\(_{2}\)]},
series = {European Journal of Inorganic Chemistry},
volume = {2020},
journal = {European Journal of Inorganic Chemistry},
number = {33},
doi = {10.1002/ejic.202000493},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216058},
pages = {3194 -- 3207},
year = {2020},
abstract = {Investigations concerning the reactivity of Ni(0) complexes [Ni(NHC)\(_{2}\)] of NHCs (N-heterocyclic carbene) of different steric demand, Mes\(_{2}\)Im (= 1,3-dimesitylimidazoline-2-ylidene) and iPr\(_{2}\)Im (= 1,3-diisopropyl-imidazoline-2-ylidene), with olefins, ketones and aldehydes are reported. The reaction of [Ni(Mes\(_{2}\)Im)\(_{2}\)] 1 with ethylene or methyl acrylate afforded the complexes [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-C\(_{2}\)H\(_{4}\))] 3 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-(C,C)-H\(_{2}\)C=CHCOOMe)] 4, as it was previously reported for [Ni\(_{2}\)(iPr\(_{2}\)Im)\(_{4}\)(µ-(η\(^{2}\):η\(^{2}\))-COD)] 2 as a source for [Ni(iPr\(_{2}\)Im)\(_{2}\)]. In contrast to 2, complex 1 does not react with sterically more demanding olefins such as tetramethylethylene, 1,1-diphenylethylene and cyclohexene. The reaction of [Ni(NHC)\(_{2}\)] with more π-acidic ketones or aldehydes led to formation of complexes with side-on η\(^{2}\)-(C,O)-coordinating ligands: [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH\(^{t}\)Bu)] 5, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 6, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CMePh)] 7, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 8, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 9, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(OMe)(CF\(_{3}\)))] 10 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 11, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(CH(CH\(_{3}\))\(_{2}\)))] 12, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-NMe\(_{2}\)-C\(_{6}\)H\(_{4}\)))] 13, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-OMe-C\(_{6}\)H\(_{4}\)))] 14, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 15 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 16. The reaction of 1 and 2 with these simple aldehydes and ketones does not lead to a significantly different outcome, but NHC ligand rotation is hindered for the Mes\(_{2}\)Im complexes 3, 4 and 11-16 according to NMR spectroscopy. The solid-state structures of 3, 4, 11 and 12 reveal significantly larger C\(_{NHC}\)-Ni-C\(_{NHC}\) angles in the Mes\(_{2}\)Im complexes compared to the iPr\(_{2}\)Im complexes. As electron transfer in d\(^{8}\)- (or d\(^{10}\)-) ML\(_{2}\) complexes to π-acidic ligands depends on the L-M-L bite angle, the different NHCs lead thus to a different degree of electron transfer and activation of the olefin, aldehyde or ketone ligand, i.e., [Ni(iPr\(_{2}\)Im)\(_{2}\)] is the better donor to these π-acidic ligands. Furthermore, we identified two different side products from the reaction of 1 with benzaldehyde, trans-[Ni(Mes\(_{2}\)Im)\(_{2}\)H(OOCPh)] 17 and [Ni\(_{2}\)(Mes\(_{2}\)Im)\(_{2}\)(µ\(_{2}\)-CO)(µ\(_{2}\)-η\(^{2}\)-C,O-PhCOCOPh)] 18, which indicate that radical intermediates and electron transfer processes might be of importance in the reaction of 1 with aldehydes and ketones.},
language = {en}
}
@article{KrahfussRadius2021,
author = {Krahfuss, Mirjam J. and Radius, Udo},
title = {N-Heterocyclic Silylene Main Group Element Chemistry: Adduct Formation, Insertion into E-X Bonds and Cyclization of Organoazides},
series = {European Journal of Inorganic Chemistry},
volume = {2021},
journal = {European Journal of Inorganic Chemistry},
number = {6},
doi = {10.1002/ejic.202000942},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224507},
pages = {548 -- 561},
year = {2021},
abstract = {Investigations concerning the reactivity of the N-heterocyclic silylene Dipp\(_{2}\)NHSi (1, 1,3-bis(2,6-diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene) towards selected alanes and boranes, elemental halides X\(_{2}\) (X=Br, I), selected halide containing substrates such as tin chlorides and halocarbons, as well as organoazides are presented. The NHSi adducts Dipp\(_{2}\)NHSi⋅AlI\(_{3}\) (2), Dipp\(_{2}\)NHSi⋅Al(C\(_{6}\)F\(_{5}\))\(_{3}\) (3), and Dipp\(_{2}\)NHSi⋅B(C\(_{6}\)F\(_{5}\))\(_{3}\) (4) were formed by the reaction of Dipp\(_{2}\)NHSi with the corresponding Lewis acids AlI\(_{3}\), Al(C\(_{6}\)F\(_{6}\))\(_{3}\) and B(C\(_{6}\)F\(_{5}\))\(_{3}\). Adducts 3 and 4 were tested with respect to their ability to activate small organic molecules, but no frustrated Lewis pair reactivity was observed. Reactions of Dipp\(_{2}\)NHSi with Br\(_{2}\), I\(_{2}\), Ph\(_{2}\)SnCl\(_{2}\) and Me\(_{3}\)SnCl led to formation of Dipp\(_{2}\)NHSiBr\(_{2}\) (5), Dipp\(_{2}\)NHSiI\(_{2}\) (6), Dipp\(_{2}\)NHSiCl\(_{2}\) (7) and {(Me\(_{3}\)Sn)N(Dipp)CH}\(_{2}\) (8), respectively. The reaction with the halocarbons methyl iodide, benzyl chloride, and benzyl bromide afforded the insertion products Dipp\(_{2}\)NHSi(I)(CH\(_{3}\)) (9), Dipp\(_{2}\)NHSi(Cl)(CH\(_{2}\)Ph) (10) and Dipp\(_{2}\)NHSi(Br)(CH\(_{2}\)Ph) (11). Reaction of Dipp\(_{2}\)NHSi with the organoazides Ad-N\(_{3}\) (Ad=adamantyl) and TMS-N\(_{3}\) (TMS=trimethylsilyl) led to the formation of 1-Dipp\(_{2}\)NHSi-2,5-bis(adamantyl)-tetrazoline (12) and bis(trimethylsilyl)amido azido silane (13), respectively. For 2,6-(diphenyl)phenyl-N\(_{3}\) C-H activation occurs and a cyclosilamine 14 was isolated.},
language = {en}
}
@article{HockWernerRiethmannetal.2020,
author = {Hock, Andreas and Werner, Luis and Riethmann, Melanie and Radius, Udo},
title = {Bis-NHC Aluminium and Gallium Dihydride Cations [(NHC)\(_{2}\)EH\(_{2}\)]\(^{+}\) (E = Al, Ga)},
series = {European Journal of Inorganic Chemistry},
volume = {2020},
journal = {European Journal of Inorganic Chemistry},
number = {42},
doi = {10.1002/ejic.202000720},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217928},
pages = {4015 -- 4023},
year = {2020},
abstract = {The NHC alane and gallane adducts (NHC)·AlH\(_{2}\)I (NHC = Me\(_{2}\)Im\(^{Me}\) 7, iPr\(_{2}\)Im 8, iPr\(_{2}\)Im\(^{Me}\) 9) and (NHC)·GaH\(_{2}\)I (NHC = Me\(_{2}\)Im\(^{Me}\) 10, iPr\(_{2}\)Im\(^{Me}\) 11, Dipp\(_{2}\)Im 12; R\(_{2}\)Im = 1,3-di-organyl-imidazolin-2-ylidene; Dipp = 2,6-diisopropylphenyl; iPr = isopropyl; Me\(_{2}\)Im\(^{Me}\) = 1,3,4,5-tetra-methyl-imidazolin-2-ylidene) were prepared either by the simple yet efficient reaction of the NHC adduct (NHC)·AlH\(_{3}\) with elemental iodine or by the treatment of (NHC)·GaH\(_{3}\) with an excess of methyl iodide at room temperature. The reaction of one equivalent of the group 13 NHC complexes with an additional equivalent of the corresponding NHC afforded cationic aluminium and gallium hydrides [(NHC)\(_{2}\)·AlH\(_{2}\)]\(^{+}\)I- (NHC = Me\(_{2}\)Im\(^{Me}\) 13, iPr\(_{2}\)Im 14, iPr\(_{2}\)Im\(^{Me}\) 15) and [(NHC)\(_{2}\)·GaH\(_{2}\)]\(^{+}\)I- (NHC = Me\(_{2}\)Im\(^{Me}\) 16, iPr\(_{2}\)Im\(^{Me}\) 17) and the normal and abnormal NHC coordinated compound [(Dipp\(_{2}\)Im)·GaH\(_{2}\)(aDipp\(_{2}\)Im)]+I- 18. Compounds 7-18 were isolated and characterized by means of elemental analysis, IR and multinuclear NMR spectroscopy and by X-ray diffraction of the compounds 7, 9, 10, 15, 16 and 18.},
language = {en}
}
@article{MansourSteigerNageletal.2019,
author = {Mansour, Ahmed M. and Steiger, Christoph and Nagel, Christoph and Schatzschneider, Ulrich},
title = {Wavelength-dependent control of the CO release kinetics of manganese(I) tricarbonyl PhotoCORMs with benzimidazole coligands},
series = {European Journal of Inorganic Chemistry},
volume = {2019},
journal = {European Journal of Inorganic Chemistry},
number = {42},
doi = {10.1002/ejic.201900894},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218362},
pages = {4572-4581},
year = {2019},
abstract = {A series of photoactivatable CO-releasing molecules (PhotoCORMs) was prepared from manganese pentacarbonyl bromide and 1H-benzimidazol-2-ylmethyl-(N-phenyl)amine ligands (L) bearing different electron-donating and electron-withdrawing groups R = H, 4-CH\(_3\), 4-OCH\(_3\), 4-Cl, 4-NO\(_2\), 2-, 3-, and 4-COOCH\(_3\) on the phenyl substituent to give octahedral manganese(I) complexes of the general formula [MnBr(CO)\(_3\)(L)]. Aerated DMSO solutions of the compounds are stable in the dark for 16 h with no CO release. However, the compounds rapidly release CO upon illumination at 412-525 nm, depending on the substitution pattern. Its influence on the photophysical and photochemical properties was systematically explored using UV/Vis spectroscopy and CO release measurements with a commercial gas sensor system. In the nitro-substituted compound, the electronically excited state switched from benzimidazole- to phenyl-centered, leading to a markedly different photochemical behavior of this visible-light activated PhotoCORM.},
language = {en}
}
@article{LiuMingFriedrichetal.2020,
author = {Liu, Xiaocui and Ming, Wenbo and Friedrich, Alexandra and Marder, Todd B.},
title = {Kupfer-katalysierte Triborierung terminaler Alkine mit B2pin2: Effiziente Synthese von 1,1,2-Triborylalkenen},
series = {Angewandte Chemie},
volume = {132},
journal = {Angewandte Chemie},
number = {1},
doi = {10.1002/ange.201908466},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219699},
pages = {311-316},
year = {2020},
abstract = {Wir berichten {\"u}ber die katalytische Triborierung terminaler Alkine mit B\(_2\)pin\(_2\) (Bis-(pinakolato)-dibor) unter Verwendung von einfach zug{\"a}nglichem Cu(OAc)\(_2\) und P\(^n\)Bu\(_3\). Verschiedene 1,1,2-Triborylalkene, eine Verbindungsklasse mit potentieller Funktion als Matrix-Metallo-Proteinase(MMP-2)-Inhibitor, werden direkt in m{\"a}ßigen bis guten Ausbeuten erhalten. Das Verfahren zeichnet sich durch milde Reaktionsbedingungen, ein breites Substratspektrum und eine gute Vertr{\"a}glichkeit gegen{\"u}ber funktionellen Gruppen aus. Diese Cu-katalysierte Reaktion kann im Gramm-Maßstab durchgef{\"u}hrt werden und liefert die entsprechenden 1,1,2-Triborylalkene in m{\"a}ßigen Ausbeuten. Die Verwendung solcher Verbindungen wird anhand weiterer Transformationen der C-B-Bindungen zur Darstellung eines geminalen Dihalogenborylalkens (F, Cl, Br), eines Monohalogendiborylalkens (Cl, Br) und eines trans-Diaryldiborylalkens demonstriert, welche bedeutende Synthesebausteine darstellen und bisher nur schwer zug{\"a}nglich waren.},
language = {de}
}
@article{LenczykRoyNitschetal.2019,
author = {Lenczyk, Carsten and Roy, Dipak Kumar and Nitsch, J{\"o}rn and Radacki, Krzysztof and Rauch, Florian and Dewhurst, Rian D. and Bickelhaupt, F. Matthias and Marder, Todd B. and Braunschweig, Holger},
title = {Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes},
series = {Chemistry - A European Journal},
volume = {25},
journal = {Chemistry - A European Journal},
number = {59},
issn = {1521-3765},
doi = {10.1002/chem.201902890},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219537},
pages = {13566-13571},
year = {2019},
abstract = {The steric and electronic properties of aryl substituents in monoaryl borohydrides (Li[ArBH\(_3\)]) and dihydroboranes were systematically varied and their reactions with [Ru(PCy\(_3\))\(_2\)HCl(H\(_2\))] (Cy: cyclohexyl) were studied, resulting in bis(σ)-borane or terminal borylene complexes of ruthenium. These variations allowed for the investigation of the factors involved in the activation of dihydroboranes in the synthesis of terminal borylene complexes. The complexes were studied by multinuclear NMR spectroscopy, mass spectrometry, X-ray diffraction analysis, and density functional theory (DFT) calculations. The experimental and computational results suggest that the ortho-substitution of the aryl groups is necessary for the formation of terminal borylene complexes.},
language = {en}
}
@article{SchmidtWernerArrowsmithetal.2020,
author = {Schmidt, Uwe and Werner, Luis and Arrowsmith, Merle and Deissenberger, Andrea and Hermann, Alexander and Hofmann, Alexander and Ullrich, Stefan and Mattock, James D. and Vargas, Alfredo and Braunschweig, Holger},
title = {Trans-selektive Dihydroborierung eines cis-Diborens durch Insertion: Synthese eines linearen sp\(^3\)-sp\(^2\)-sp\(^3\)-Triborans und anschließende Kationisierung},
series = {Angewandte Chemie},
volume = {132},
journal = {Angewandte Chemie},
number = {1},
doi = {10.1002/ange.201911645},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219713},
pages = {333-337},
year = {2020},
abstract = {Die Reaktion zwischen Aryl- und Amino(dihydro)boranen und Dibora[2]ferrocenophan 1 f{\"u}hrt zur Bildung von 1,3-trans-Dihydrotriboranen durch formale Hydrierung und Insertion eines Borylens in die B=B Doppelbindung. Die Aryltriboran-Derivate unterliegen einer reversiblen Photoisomerisierung zugunsten eines cis-1,2-μ-H-3-Hydrotriborans, w{\"a}hrend eine Hydridabstraktion zu kationischen Triboranen f{\"u}hrt, welche die ersten doppelt basenstabilisierten B\(_3\)H\(_4\)\(^+\)-Analoga darstellen.},
language = {de}
}
@article{Belanger‐ChabotBraunschweig2019,
author = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger},
title = {Hexahalodiborate Dianions: A New Family of Binary Boron Halides},
series = {Angewandte Chemie International Edition},
volume = {58},
journal = {Angewandte Chemie International Edition},
number = {40},
doi = {10.1002/anie.201906666},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219688},
pages = {14270-14274},
year = {2019},
abstract = {The electron-precise binary boron subhalide species [B\(_2\)X\(_6\)]\(^{2-}\) X=F, Br, I) were synthesized and their structures confirmed by X-ray crystallography. The existence of the previously claimed [B\(_2\)Cl\(_6\)]\(^{2-}\), which had been questioned, was also confirmed by X-ray crystallography. The dianions are isoelectronic to hexahaloethanes, are subhalide analogues of the well-known tetrahaloborate anions (BX\(_4\)\(^-\)), and are rare examples of molecular electron-precise binary boron species beyond B\(_2\)X\(_4\), BX\(_3\), and [BX\(_4\)]\(^-\).},
language = {en}
}
@article{SchmidtWernerArrowsmithetal.2020,
author = {Schmidt, Uwe and Werner, Luis and Arrowsmith, Merle and Deissenberger, Andrea and Hermann, Alexander and Hofmann, Alexander and Ullrich, Stefan and Mattock, James D. and Vargas, Alfredo and Braunschweig, Holger},
title = {trans-Selective Insertional Dihydroboration of a cis-Diborene: Synthesis of Linear sp\(^3\)-sp\(^2\)-sp\(^3\)-Triboranes and Subsequent Cationization},
series = {Angewandte Chemie International Edition},
volume = {59},
journal = {Angewandte Chemie International Edition},
number = {1},
doi = {10.1002/anie.201911645},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208090},
pages = {325-329},
year = {2020},
abstract = {The reaction of aryl- and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3-trans -dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis -1,2-μ-H-3-hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3H4\(^+\) analogues.},
language = {en}
}
@article{OberdorfHanftRamleretal.2021,
author = {Oberdorf, Kai and Hanft, Anna and Ramler, Jacqueline and Krummenacher, Ivo and Bickelhaupt, Matthias and Poater, Jordi and Lichtenberg, Crispin},
title = {Bismuth Amides Mediate Facile and Highly Selective Pn-Pn Radical-Coupling Reactions (Pn=N, P, As)},
series = {Angewandte Chemie, International Edition},
volume = {60},
journal = {Angewandte Chemie, International Edition},
number = {12},
doi = {10.1002/anie.202015514},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236582},
pages = {6441-6445},
year = {2021},
abstract = {The controlled release of well-defined radical species under mild conditions for subsequent use in selective reactions is an important and challenging task in synthetic chemistry. We show here that simple bismuth amide species [Bi(NAr\(_2\))\(_3\)] readily release aminyl radicals [NAr\(_2\)]. at ambient temperature in solution. These reactions yield the corresponding hydrazines, Ar\(_2\)N-NAr\(_2\), as a result of highly selective N-N coupling. The exploitation of facile homolytic Bi-Pn bond cleavage for Pn-Pn bond formation was extended to higher homologues of the pnictogens (Pn=N-As): homoleptic bismuth amides mediate the highly selective dehydrocoupling of HPnR\(_2\) to give R\(_2\)Pn-PnR\(_2\). Analyses by NMR and EPR spectroscopy, single-crystal X-ray diffraction, and DFT calculations reveal low Bi-N homolytic bond-dissociation energies, suggest radical coupling in the coordination sphere of bismuth, and reveal electronic and steric parameters as effective tools to control these reactions.},
language = {en}
}
@article{HermannFantuzziArrowsmithetal.2020,
author = {Hermann, Alexander and Fantuzzi, Felipe and Arrowsmith, Merle and Zorn, Theresa and Krummenacher, Ivo and Ritschel, Benedikt and Radacki, Krzysztof and Engels, Bernd and Braunschweig, Holger},
title = {Oxidation, Coordination, and Nickel-Mediated Deconstruction of a Highly Electron-Rich Diboron Analogue of 1,3,5-Hexatriene},
series = {Angewandte Chemie, International Edition},
volume = {59},
journal = {Angewandte Chemie, International Edition},
number = {36},
doi = {10.1002/anie.202006131},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240652},
pages = {15717-15725},
year = {2020},
abstract = {The reductive coupling of an N-heterocyclic carbene (NHC) stabilized (dibromo)vinylborane yields a 1,2-divinyl- diborene, which, although isoelectronic to a 1,3,5-triene, displays no extended p conjugation because of twisting of the C\(_2\)B\(_2\)C\(_2\) chain. While this divinyldiborene coordinates to copper(I) and platinum(0) in an η\(^2\)-B\(_2\) and η\(^4\)-C\(_2\)B\(_2\) fashion, respectively, it undergoes a complex rearrangement to an η\(^4\)-1,3-diborete upon complexation with nickel(0).},
language = {en}
}
@article{BruecknerHessStennettetal.2021,
author = {Br{\"u}ckner, Tobias and Heß, Merlin and Stennett, Tom E. and Rempel, Anna and Braunschweig, Holger},
title = {Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond},
series = {Angewandte Chemie, International Edition},
volume = {60},
journal = {Angewandte Chemie, International Edition},
number = {2},
doi = {10.1002/anie.202012101},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240669},
pages = {736-741},
year = {2021},
abstract = {An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit.},
language = {en}
}
@article{WirthensohnFinze2020,
author = {Wirthensohn, Raphael and Finze, Maik},
title = {The crystal structure of trimethylsulfonium tris(trifluoromethylsulfonyl)methanide, C\(_7\)H\(_9\)F\(_9\)O\(_6\)S\(_4\)},
series = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
volume = {236},
journal = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
number = {2},
doi = {10.1515/ncrs-2020-0612},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231358},
pages = {417-419},
year = {2020},
abstract = {C\(_7\)H\(_9\)F\(_9\)O\(_6\)S\(_4\), orthorhombic, P2\(_1\)2\(_1\)2\(_1\) (no. 19), a = 8.80180(10) {\AA}, b= 10.96580(10) {\AA}, c = 16.91360(10) {\AA},V= 1632.48(3) {\AA}\(^3\), Z= 4, R\(_{gt}\)(F) = 0.0222, wR\(_{ref}\)(F\(^2\)) = 0.0604, T = 100 K.},
language = {en}
}
@article{EmmertHessGraebetal.2020,
author = {Emmert, Marcel and Heß, Konrad and Gr{\"a}b, Patrick and Geidel, Ekkehard},
title = {Experiments to Introduce Students into the Temperature Dependence of the Reaction Rate},
series = {World Journal of Chemical Education},
volume = {8},
journal = {World Journal of Chemical Education},
number = {2},
doi = {10.12691/wjce-8-2-5},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229993},
pages = {92-99},
year = {2020},
abstract = {It is a challenge in chemical education to understand basic principles of chemical reaction kinetics on an experimental basis because of the relatively extensive experimental setup and the often time-consuming measurement series. This contribution offers an introduction into the field of the temperature dependence of reaction rate with easy-to-use experiments. Data logging systems have been used to get sufficient data-sets to evaluate different measurements in reaction kinetics. Several experiments were designed for practical courses in chemistry, which allow students to derive the simple van't Hoff rule on the one hand. On the other hand, the Arrhenius equation can only be derived on the basis of experimental data with the help of information from collision theory and Maxwell-Boltzmann distribution.},
language = {en}
}
@article{FergerBergerRauchetal.2021,
author = {Ferger, Matthias and Berger, Sarina M. and Rauch, Florian and Sch{\"o}nitz, Markus and R{\"u}he, Jessica and Krebs, Johannes and Friedrich, Alexandra and Marder, Todd B.},
title = {Synthesis of Highly Functionalizable Symmetrically and Unsymmetrically Substituted Triarylboranes from Bench-Stable Boron Precursors},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {35},
doi = {10.1002/chem.202100632},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256827},
pages = {9094-9101},
year = {2021},
abstract = {A novel and convenient methodology for the one-pot synthesis of sterically congested triarylboranes by using bench-stable aryltrifluoroborates as the boron source is reported. This procedure gives systematic access to symmetrically and unsymmetrically substituted triarylboranes of the types BAr\(_{2}\)Ar' and BArAr'Ar'', respectively. Three unsymmetrically substituted triarylboranes as well as their iridium-catalyzed C-H borylation products are reported. These borylated triarylboranes contain one to three positions that can subsequently be orthogonally functionalized in follow-up reactions, such as Suzuki-Miyaura cross-couplings or Sonogashira couplings.},
language = {en}
}
@article{RamlerFantuzziGeistetal.2021,
author = {Ramler, Jaqueline and Fantuzzi, Felipe and Geist, Felix and Hanft, Anna and Braunschweig, Holger and Engels, Bernd and Lichtenberg, Crispin},
title = {The dimethylbismuth cation: entry into dative Bi-Bi bonding and unconventional methyl exchange},
series = {Angewandte Chemie International Edition},
volume = {60},
journal = {Angewandte Chemie International Edition},
doi = {10.1002/anie.202109545},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256543},
pages = {24388-24394},
year = {2021},
abstract = {The dimethyl bismuth cation, [BiMe\(_2\)(SbF\(_6\))], has been isolated and characterized. Reaction with BiMe\(_3\) allows access to the first compound featuring Bi→Bi donor-acceptor bonding. In solution, dynamic behavior with methyl exchange via an unusual S\(_E\)2 mechanism is observed, underlining the unique properties of bismuth species as soft Lewis acids with the ability to undergo reversible Bi-C bond cleavage.},
language = {en}
}
@article{SchorrSchopperRienschetal.2021,
author = {Schorr, Fabian and Schopper, Nils and Riensch, Nicolas and Fantuzzi, Felipe and Neder, Marco and Dewhurst, Rian D. and Thiess, Thorsten and Br{\"u}ckner, Tobias and Hammond, Kai and Helten, Holger and Finze, Maik and Braunschweig, Holger},
title = {Controlled Synthesis of Oligomers Containing Main-Chain B(sp\(^{2}\))-B(sp\(^{2}\)) Bonds},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {64},
doi = {10.1002/chem.202103366},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257274},
pages = {16043-16048},
year = {2021},
abstract = {A number of novel alkynyl-functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl-appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well-characterized macromolecular species with B-B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size-exclusion chromatography techniques.},
language = {en}
}
@article{BergerRueheSchwarzmannetal.2021,
author = {Berger, Sarina M. and R{\"u}he, Jessica and Schwarzmann, Johannes and Phillipps, Alexandra and Richard, Ann-Katrin and Ferger, Matthias and Krummenacher, Ivo and Tumir, Lidija-Marija and Ban, Željka and Crnolatac, Ivo and Majhen, Dragomira and Barišić, Ivan and Piantanida, Ivo and Schleier, Domenik and Griesbeck, Stefanie and Friedrich, Alexandra and Braunschweig, Holger and Marder, Todd B.},
title = {Bithiophene-Cored, mono-, bis-, and tris-(Trimethylammonium)-Substituted, bis-Triarylborane Chromophores: Effect of the Number and Position of Charges on Cell Imaging and DNA/RNA Sensing},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {56},
doi = {10.1002/chem.202102308},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256963},
pages = {14057-14072},
year = {2021},
abstract = {The synthesis, photophysical, and electrochemical properties of selectively mono-, bis- and tris-dimethylamino- and trimethylammonium-substituted bis-triarylborane bithiophene chromophores are presented along with the water solubility and singlet oxygen sensitizing efficiency of the cationic compounds Cat\(^{1+}\), Cat\(^{2+}\), Cat(i)\(^{2+}\), and Cat\(^{3+}\). Comparison with the mono-triarylboranes reveals the large influence of the bridging unit on the properties of the bis-triarylboranes, especially those of the cationic compounds. Based on these preliminary investigations, the interactions of Cat\(^{1+}\), Cat\(^{2+}\), Cat(i)\(^{2+}\), and Cat\(^{3+}\) with DNA, RNA, and DNApore were investigated in buffered solutions. The same compounds were investigated for their ability to enter and localize within organelles of human lung carcinoma (A549) and normal lung (WI38) cells showing that not only the number of charges but also their distribution over the chromophore influences interactions and staining properties.},
language = {en}
}
@article{HanftRottschaeferWieprechtetal.2021,
author = {Hanft, Anna and Rottsch{\"a}fer, Dennis and Wieprecht, Nele and Geist, Felix and Radacki, Krzysztof and Lichtenberg, Crispin},
title = {Aminotroponiminates: Impact of the NO\(_{2}\) Functional Group on Coordination, Isomerisation, and Backbone Substitution},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {57},
doi = {10.1002/chem.202102324},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256988},
pages = {14250-14262},
year = {2021},
abstract = {Aminotroponiminate (ATI) ligands are a versatile class of redox-active and potentially cooperative ligands with a rich coordination chemistry that have consequently found a wide range of applications in synthesis and catalysis. While backbone substitution of these ligands has been investigated in some detail, the impact of electron-withdrawing groups on the coordination chemistry and reactivity of ATIs has been little investigated. We report here Li, Na, and K salts of an ATI ligand with a nitro-substituent in the backbone. It is demonstrated that the NO2 group actively contributes to the coordination chemistry of these complexes, effectively competing with the N,N-binding pocket as a coordination site. This results in an unprecedented E/Z isomerisation of an ATI imino group and culminates in the isolation of the first "naked" (i. e., without directional bonding to a metal atom) ATI anion. Reactions of sodium ATIs with silver(I) and tritylium salts gave the first N,N-coordinated silver ATI complexes and unprecedented backbone substitution reactions. Analytical techniques applied in this work include multinuclear (VT-)NMR spectroscopy, single-crystal X-ray diffraction analysis, and DFT calculations.},
language = {en}
}
@article{HuangHuKrummenacheretal.2022,
author = {Huang, Mingming and Hu, Jiefeng and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
title = {Base-Mediated Radical Borylation of Alkyl Sulfones},
series = {Chemistry—A European Journal},
volume = {28},
journal = {Chemistry—A European Journal},
number = {3},
doi = {10.1002/chem.202103866},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257281},
pages = {e202103866},
year = {2022},
abstract = {A practical and direct method was developed for the production of versatile alkyl boronate esters via transition metal-free borylation of primary and secondary alkyl sulfones. The key to the success of the strategy is the use of bis(neopentyl glycolato) diboron (B\(_{2}\)neop\(_{2}\)), with a stoichiometric amount of base as a promoter. The practicality and industrial potential of this protocol are highlighted by its wide functional group tolerance, the late-stage modification of complex compounds, no need for further transesterification, and operational simplicity. Radical clock, radical trap experiments, and EPR studies were conducted which show that the borylation process involves radical intermediates.},
language = {en}
}
@article{ZapfFinze2021,
author = {Zapf, Ludwig and Finze, Maik},
title = {The crystal structure of poly[(μ \(_3\)-imidazolato-κ \(^3\) N:N:N′)(tetrahydrofuran- κ \(^1\) O)lithium(I)], C\(_7\)H\(_{11}\)LiN\(_2\)O},
series = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
volume = {236},
journal = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures},
number = {5},
doi = {10.1515/ncrs-2021-0192},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260745},
pages = {1007-1009},
year = {2021},
abstract = {C\(_7\)H\(_{11}\)LiN\(_2\)O, monoclinic, P2\(_1\)/c (no. 14), a = 8.9067(1) angstrom, b = 8.6975(1) angstrom, c = 10.2398(1) angstrom, beta = 101.900(3)degrees, V = 770.491(15) angstrom(3), Z = 4, R-gt (F) = 0.0338, wR(ref) (F\(^2\)) = 0.0925, T = 100 K.},
language = {en}
}
@phdthesis{Wirthensohn2023,
author = {Wirthensohn, Raphael Sebastian},
title = {Metallvermittelte Perfluoralkylierungen und die elektrochemische Fluorierung zu Perfluoralkylverbindungen},
doi = {10.25972/OPUS-28664},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286640},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Diese Arbeit besch{\"a}ftigt sich mit der Synthese und Charakterisierung von mehrfach perfluoralkylierten Verbindungen. Das erste Kapitel behandelt die Kupfer-vermittelte mehrfache Pentafluorethylierung von aromatischen Systemen, sowie die Untersuchung deren Folgechemie. Dabei wurden iodierte Aryl-Derivate mit dem Kupferorganyl CuC2F5 umgesetzt. Mit dieser Methode konnten symmetrisch und unsymmetrisch pentafluorethylierte Anilin- und Phenol-Derivate dargestellt werden. Die Anilin-Derivate wurden zu den entsprechenden Diazoniumsalzen umgesetzt, welche zun{\"a}chst vollst{\"a}ndig charakterisiert und anschließend deren Folgechemie untersucht wurde. Das zweite Kapitel behandelt die Darstellung von Bis(trifluormethyl)sulfon durch elektrochemische Fluorierung mittels des Simons-Prozesses. Dabei wurde der Umsatz der Reaktion durch Verwendung der teilfluorierten Verbindung (Trifluormethyl)methylsulfon als Startmaterial optimiert.},
subject = {Perfluoralkylierung},
language = {de}
}
@phdthesis{Zapf2023,
author = {Zapf, Ludwig},
title = {Novel Borane- and Phosphorane- Functionalized Anionic Carbene Ligands},
doi = {10.25972/OPUS-32078},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320781},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {N-heterocyclic carbenes (NHC) are utilized for the stabilization of reactive compounds, for the activation of strong bonds, and as ligands in transition metal chemistry. In contrast to neutral NHCs, few examples of anionic or even dianionic NHCs are known. One approach for the synthesis of anionic carbenes is the deprotonation of neutral or anionic precursors, bearing Lewis acids instead of alkyl or aryl substituents. Following this strategy, novel anionic and dianionic NHCs, featuring weakly coordinating fluorinated borane and phosphorane substituents or coordinating tricyanoborane substituents were synthesized within the scope of this thesis. These carbenes possess unprecedented stabilities compared to related species. Furthermore, their electronic and steric properties can be directly adjusted by the type of Lewis acid attached. Their potential as ligands with highly shielding weakly coordinating substituents next to the carbene coordination center was demonstrated by the syntheses of the respective NHC selenium adducts and NHC gold(I) complexes. In contrast anionic NHCs with coordinating tricyanoborane moieties have an outstanding potential as ditopic ligands with coordination being possible at the carbene center and via the cyano groups. Their beneficial ligand properties were demonstrated by the syntheses of the respective NHC selenium adducts and NHC nickeltricarbonyl complexes. The combination of electronic properties, the large buried volume, the negative charge, the possibility to act as ditopic or ligands with weakly coordinating groups, and the ease of accessibility render borane- and phosphorane functionalized NHCs unique novel ligands. A further project of this PhD thesis deals with the steric properties of Lewis acids. Therefore, an easy-to-apply model was designed to quantify the steric demand of Lewis acids. Using the results of this evaluation, a second model was developed which judges the steric repulsion in Lewis acid/base adduct formation for arbitrary sets of acids and bases.},
subject = {Komplexe},
language = {en}
}
@article{LuisHorrerPhilippetal.2021,
author = {Luis, Werner and Horrer, G{\"u}nther and Philipp, Michael and Lubitz, Katharina and Kuntze-Fechner, Maximilian W. and Radius, Udo},
title = {A General Synthetic Route to NHC-Phosphinidenes: NHC-mediated Dehydrogenation of Primary Phosphines},
series = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie},
volume = {647},
journal = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie},
number = {8},
doi = {10.1002/zaac.202000405},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258016},
pages = {881-895},
year = {2021},
abstract = {The dehydrocoupling of primary phosphines with N-heterocyclic carbenes (NHCs) to yield NHC-phosphinidenes is reported. The reaction of two equivalents of the NHCs Me\(_2\)Im (1,3-dimethylimidazolin-2-ylidene), Me\(_4\)Im (1,3,4,5-tetramethylimidazolin-2-ylidene), iPr\(_2\)Im (1,3-di-iso-propylimidazolin-2-ylidene) and Mes\(_2\)Im (2,4,6-trimethylphenylimidazolin-2-ylidene) with PhPH\(_2\) and MesPH\(_2\) led to the NHC stabilized phosphinidenes (NHC)PAr: (iPr\(_2\)Im)PPh (1), (Mes\(_2\)Im)PPh (2), (Me\(_4\)Im)PPh (3), (Mes\(_2\)Im)PMes (4), (Me\(_2\)Im)PMes (5), (Me\(_4\)Im)PMes (6) and (iPr\(_2\)Im)PMes (7). The reaction of tBuPH\(_2\) with two equivalents of the NHCs afforded the corresponding NHC stabilized parent phosphinidenes (NHC)PH: (iPr\(_2\)Im)PH (8), (Mes\(_2\)Im)PH (9) and (Me\(_4\)Im)PH (10). Reaction of 1 with oxygen and sulfur led to isolation of iPr\(_2\)Im-P(O)\(_2\)Ph (11) and iPr\(_2\)Im-P(S)\(_2\)Ph (12), whereas the reaction with elemental selenium and tellurium gave (NHC)PPh cleavage with formation of (iPr\(_2\)Im)Se (13), iPr\(_2\)ImTe (14) and different cyclo-oligophosphines. Furthermore, the complexes [{(iPr\(_2\)Im)PPh}W(CO)\(_5\)] (15), [Co(CO)\(_2\)(NO){(iPr\(_2\)Im)PPh}] (16) and [(η\(^5\)-C\(_5\)Me\(_2\))Co(η\(^2\)-C\(_2\)H\(_4\)){(iPr\(_2\)Im)PPh}] (17) have been prepared starting from 1 and a suitable transition metal complex precursor. The complexes 16 and 17 decompose in solution upon heating to ca. 80 °C to yield the NHC complexes [Co(iPr\(_2\)Im)(CO)\(_2\)(NO)] and [(η\(^5\)-C\(_5\)Me\(_5\))Co(iPr\(_2\)Im)(η\(^2\)-C\(_2\)H\(_4\))] with formation of cyclo-oligophosphines. The reaction of 1 with [Ni(COD)\(_2\)] afforded the diphosphene complex [Ni(iPr\(_2\)Im)\(_2\)(trans-PhP=PPh)] 18.},
language = {en}
}
@article{LindlGuoKrummenacheretal.2021,
author = {Lindl, Felix and Guo, Xueying and Krummenacher, Ivo and Rauch, Florian and Rempel, Anna and Paprocki, Valerie and Dellermann, Theresa and Stennett, Tom E. and Lamprecht, Anna and Br{\"u}ckner, Tobias and Radacki, Krzysztof and B{\´e}langer-Chabot, Guillaume and Marder, Todd B. and Lin, Zhenyang and Braunschweig, Holger},
title = {Rethinking Borole Cycloaddition Reactivity},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {43},
doi = {10.1002/chem.202101290},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256888},
pages = {11226-11233},
year = {2021},
abstract = {Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature. Herein, we question the long-established mechanistic picture of pericyclic rearrangements by demonstrating that seven-membered borepins (i. e., heptaphenylborepin and two derivatives substituted with a thienyl and chloride substituent on boron) exist in a dynamic equilibrium with the corresponding bicyclic boranorbornadienes, the direct Diels-Alder products, but are not isolable products from the reactions. Heating gradually converts the isomeric mixtures into fluorescent tricyclic boracyclohexenes, the most stable isomers in the series. Results from mechanistic DFT calculations reveal that the tricyclic compounds derive from the boranorbornadienes and not the borepins, which were previously believed to be intermediates in purely pericyclic processes.},
language = {en}
}
@article{HessKrummenacherDellermannetal.2021,
author = {Heß, Merlin and Krummenacher, Ivo and Dellermann, Theresa and Braunschweig, Holger},
title = {Rhodium-Mediated Stoichiometric Synthesis of Mono-, Bi-, and Bis-1,2-Azaborinines: 1-Rhoda-3,2-azaboroles as Reactive Precursors},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {37},
doi = {10.1002/chem.202100795},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256830},
pages = {9503-9507},
year = {2021},
abstract = {A series of highly substituted 1,2-azaborinines, including a phenylene-bridged bis-1,2-azaborinine, was synthesized from the reaction of 1,2-azaborete rhodium complexes with variously substituted alkynes. 1-Rhoda-3,2-azaborole complexes, which are accessible by phosphine addition to the corresponding 1,2-azaborete complexes, were also found to be suitable precursors for the synthesis of 1,2-azaborinines and readily reacted with alkynyl-substituted 1,2-azaborinines to generate new regioisomers of bi-1,2-azaborinines, which feature directly connected aromatic rings. Their molecular structures, which can be viewed as boron-nitrogen isosteres of biphenyls, show nearly perpendicular 1,2-azaborinine rings. The new method using rhodacycles instead of 1,2-azaborete complexes as precursors is shown to be more effective, allowing the synthesis of a wider range of 1,2-azaborinines.},
language = {en}
}
@article{GaertnerMarekArrowsmithetal.2021,
author = {G{\"a}rtner, Annalena and Marek, Matth{\"a}us and Arrowsmith, Merle and Auerhammer, Dominic and Radacki, Krzysztof and Prieschl, Dominic and Dewhurst, Rian D. and Braunschweig, Holger},
title = {Boron- versus Nitrogen-Centered Nucleophilic Reactivity of (Cyano)hydroboryl Anions: Synthesis of Cyano(hydro)organoboranes and 2-Aza-1,4-diborabutatrienes},
series = {Chemistry—A European Journal},
volume = {27},
journal = {Chemistry—A European Journal},
number = {37},
doi = {10.1002/chem.202101025},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256853},
pages = {9694-9699},
year = {2021},
abstract = {Cyclic alkyl(amino)carbene-stabilized (cyano)hydroboryl anions were synthesized by deprotonation of (cyano)dihydroborane precursors. While they display boron-centered nucleophilic reactivity towards organohalides, generating fully unsymmetrically substituted cyano(hydro)organoboranes, they show cyano-nitrogen-centered nucleophilic reactivity towards haloboranes, resulting in the formation of hitherto unknown linear 2-aza-1,4-diborabutatrienes.},
language = {en}
}
@article{BrammerBlankeKellneretal.2022,
author = {Brammer, Jan C. and Blanke, Gerd and Kellner, Claudia and Hoffmann, Alexander and Herres-Pawlis, Sonja and Schatzschneider, Ulrich},
title = {TUCAN: A molecular identifier and descriptor applicable to the whole periodic table from hydrogen to oganesson},
series = {Journal of Cheminformatics},
volume = {14},
journal = {Journal of Cheminformatics},
number = {1},
issn = {1758-2946},
doi = {10.1186/s13321-022-00640-5},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-299730},
year = {2022},
abstract = {TUCAN is a canonical serialization format that is independent of domain-specific concepts of structure and bonding. The atomic number is the only chemical feature that is used to derive the TUCAN format. Other than that, the format is solely based on the molecular topology. Validation is reported on a manually curated test set of molecules as well as a library of non-chemical graphs. The serialization procedure generates a canonical "tuple-style" output which is bidirectional, allowing the TUCAN string to serve as both identifier and descriptor. Use of the Python NetworkX graph library facilitated a compact and easily extensible implementation.},
language = {en}
}
@article{FoehrenbacherZehKrahfussetal.2021,
author = {F{\"o}hrenbacher, Steffen A. and Zeh, Vivien and Krahfuss, Mirjam J. and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo},
title = {Tris(pentafluoroethyl)difluorophosphorane and N-Heterocyclic Carbenes: Adduct Formation and Frustrated Lewis Pair Reactivity},
series = {European Journal of Inorganic Chemistry},
volume = {2021},
journal = {European Journal of Inorganic Chemistry},
number = {20},
doi = {10.1002/ejic.202100183},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257386},
pages = {1941-1960},
year = {2021},
abstract = {The synthesis and characterization of Lewis acid/base adducts between tris(pentafluoroethyl)difluorophosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and selected N-heterocyclic carbenes (NHCs) R\(_{2}\)Im (1,3-di-organyl-imidazolin-2-ylidene) and phosphines are reported. For NHCs with small alkyl substituents at nitrogen (R=Me, nPr, iPr) the adducts NHC ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (2 a-h) were isolated. The reaction with the sterically more demanding NHCs Dipp\(_{2}\)Im (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolin-2-ylidene) (1 i) and tBu\(_{2}\)Im (1,3-di-tert-butyl-imidazolin-2-ylidene) (1 j) afforded the aNHC adducts 3 i and 3 j (a denotes "abnormal" NHC coordination via a backbone carbon atom). The use of tBuMeIm (1-tert-butyl-3-methyl-imidazolin-2-ylidene) (1 m) led to partial decomposition of the NHC and formation of the salt [tBuMeIm-H][MeIm ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)] (4 m). The phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) forms adducts with PMe\(_{3}\) but does not react with PPh\(_{3}\) or PCy\(_{3}\). The mer-cis isomer of literature-known Me\(_{3}\)P ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (5 a) was structurally characterized. Mixtures of the phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and the sterically encumbered NHCs tBu\(_{2}\)Im, Dipp\(_{2}\)Im, and Dipp\(_{2}\)Im\(^{H2}\) (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolidin-2-ylidene) (1 k) showed properties of FLPs (Frustrated Lewis Pairs) as these mixtures were able to open the ring of THF (tetrahydrofuran) to yield NHC-(CH\(_{2}\))\(_{4}\)O-PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) 6 i-k. Furthermore, the deprotonation of the weak C-H acids CH\(_{3}\)CN, acetone, and ethyl acetate was achieved, which led to the formation of the corresponding imidazolium salts and the phosphates [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CN)]\(^{-}\) (7), [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(OC(=CH\(_{2}\))CH\(_{3}\))]\(^{-}\) (8) and [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CO\(_{2}\)Et)]\(^{-}\) (9).},
language = {en}
}
@article{LuJayaramanFantuzzietal.2022,
author = {Lu, Wei and Jayaraman, Arumugam and Fantuzzi, Felipe and Dewhurst, Rian D. and H{\"a}rterich, Marcel and Dietz, Maximilian and Hagspiel, Stephan and Krummenbacher, Ivo and Hammond, Kai and Cui, Jingjing and Braunschweig, Holger},
title = {An unsymmetrical, cyclic diborene based on a chelating CAAC ligand and its small-molecule activation and rearrangement chemistry},
series = {Angewandte Chemie International Edition},
volume = {61},
journal = {Angewandte Chemie International Edition},
number = {3},
doi = {10.1002/anie.202113947},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256576},
year = {2022},
abstract = {A one-pot synthesis of a CAAC-stabilized, unsymmetrical, cyclic diborene was achieved via consecutive two-electron reduction steps from an adduct of CAAC and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\). Theoretical studies revealed that this diborene has a considerably smaller HOMO-LUMO gap than those of reported NHC- and phosphine-supported diborenes. Complexation of the diborene with [AuCl(PCy\(_3\))] afforded two diborene-Au\(^I\) π complexes, while reaction with DurBH\(_2\), P\(_4\) and a terminal acetylene led to the cleavage of B-H, P-P, and C-C π bonds, respectively. Thermal rearrangement of the diborene gave an electron-rich cyclic alkylideneborane, which readily coordinated to Ag\(^I\) via its B=C double bond.},
language = {en}
}
@phdthesis{Ramler2023,
author = {Ramler, Jacqueline},
title = {Versatile Use of Neutral and Cationic Diorgano Bismuth Compounds: Ligation of Transition Metals, Lewis Acidity, Low Valent Species and Catalysis},
doi = {10.25972/OPUS-24054},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240547},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {In der vorliegenden Arbeit wurden Diorganobismut-Spezies hinsichtlich ihrer Eigenschaften als Liganden in {\"U}bergangsmetallkomplexen, ihrer Lewis-Azidit{\"a}t, ihrer Eignung als Katalysatoren und die Generierung niedervalenter Spezies untersucht.},
subject = {Bismut},
language = {en}
}
@phdthesis{Tendera2023,
author = {Tendera, Lukas},
title = {NHC-ligated Nickel(0)-Complexes: Bond Activation, Redox Behavior and Catalysis},
doi = {10.25972/OPUS-29065},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-290654},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {This thesis describes the synthesis and reactivity of bis-NHC ligated nickel(0)-complexes and their application in catalytic cyclization and borylation reactions of alkynes. The focus of the presented work lies on the investigation of the electronic and steric impact of different NHC ligands on the reactivity and catalytic activity of [Ni(NHC)2] complexes. Since d10 ML2 complexes play a decisive role for numerous catalytic reactions, such as the Suzuki-Miyaura cross-coupling, the first chapter provides an overview about the general properties of NHCs and the chemistry of NHC-ligated nickel complexes, their synthesis, characterization, reactivity, and application in catalysis.},
subject = {{\"U}bergangsmetallkomplexe},
language = {en}
}
@phdthesis{Fuchs2023,
author = {Fuchs, Sonja},
title = {Synthese und Reaktivit{\"a}t von anellierten Borolen und Diboramakrocyclen},
doi = {10.25972/OPUS-28946},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-289460},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Diese Arbeit besch{\"a}ftigt sich mit der Synthese neuer anellierter Borole und Boramakrocyclen, so wie deren Reaktivit{\"a}ten und Eigenschaften.},
subject = {Borole},
language = {de}
}
@phdthesis{Nees2023,
author = {Nees, Samuel},
title = {Synthese und Reaktivit{\"a}t von niedervalenten Aluminium-Phosphor-Verbindungen},
doi = {10.25972/OPUS-29284},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-292848},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Die vorliegende Arbeit besch{\"a}ftigt sich mit der Darstellung und Reaktivit{\"a}t von Cp substituierten Aluminium(I)-Verbindungen. Außerdem konnten die ersten Vertreter f{\"u}r planare Cyclopenten-4-yl-Kationen dargestellt werden. Die Reaktivit{\"a}t von Cp3tAl(I), [AlCp*]4 und DipNacNacAl wurde gegen{\"u}ber Cyclotriphosphiranen untersucht. In Abh{\"a}ngigkeit vom sterischen Anspruch der Substituenten am Phosphor- und Aluminiumatom wurden hierbei verschiedenartige AlP-Ringsysteme erhalten. Desweiteren wurden Phospha-Wittig-Reagenzien als Phosphinidenquelle f{\"u}r die Umsetzung mit Aluminium(I)-Spezies getestet, wobei verschiedene 3- und 4 gliedrige Strukturmotive erhalten werden konnten. Bei Erh{\"o}hung der Sterik am Phospha-Wittig-Reagenz zu einem DipTer-Substituenten konnte im Fall der Umsetzung mit [AlCp*]4 der ersten Vertreter eines Phosphaalumens dagestellt werden. In ersten Reaktivit{\"a}tsstudien mit unges{\"a}ttigten Substraten konnten f{\"u}r Doppelbindungssysteme charakteristische Additionsreaktionen nachgewiesen werden.},
subject = {Niedervalente Verbindungen},
language = {de}
}
@phdthesis{Keppner2023,
author = {Keppner, Fabian},
title = {closo-Borcluster-oberfl{\"a}chenmodifizierte Chromatographiematerialien -sowie- Trialkylammonium-Salze von polyhalogenierten und nicht-halogenierten 1-Amino-carba-closo-dodecaboraten},
doi = {10.25972/OPUS-20576},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-205763},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Auf Grund der hohen Affinit{\"a}t von closo-Borclustern zu Proteinen, stellen mit closo-Borclustern modifizierte Chromatographiematerialien m{\"o}gliche neuartige Chromatographiematerialien in der biologischen und pharmazeutischen Chemie dar. Im Zuge dieser Arbeit sollen Synthesen von Amin- und Allyl-funktionalisierten closo-Borclustern (Dicarba-closo-dodecaborane, Carba-closo-dodecaborat-, closo-Dodecaborat- und closo-Decaborat-Anionen) entwickelt werden, die sich f{\"u}r eine anschließende Oberfl{\"a}chenmodifikation eignen. Als Vergleichsverbindung mit einem organischen Grundger{\"u}st dienen Amantadin und Allyl-funktionalisierte Adamantan-Derivate. Diese Verbindungen sollen auf die Oberfl{\"a}che von Materialien aufgebracht und diese anschließend charakterisiert werden. Besonders die Untersuchung bez{\"u}glich ihrer F{\"a}higkeit der dynamischen Bindungskapazit{\"a}t gegen{\"u}ber Bovin-Albumin-Serum Fraktion V ist ein Schwerpunkt dieser Arbeit. Hierbei wird vor allem der Vergleich zu dem k{\"a}uflich erwerblichen CaptoTM Blue gezogen. Der zweite Teil dieser Arbeit besch{\"a}ftigt sich mit der Synthese von Trialkylammonium-Salzen von halogenierten und nicht halogenierten 1-Amino-carba-closo-dodecaborat-Anionen. Hierbei steht vor allem die Untersuchung der Wechselwirkung zwischen den verschiedenen Kationen und dem Anion im Fokus. Zu diesem Zweck wurden Synthesen hinf{\"u}hrend zu den jeweiligen Salzen entwickelt und die erhaltenen Produkte umfassend charakterisiert.},
subject = {Chromatographie},
language = {de}
}
@phdthesis{Rang2023,
author = {Rang, Maximilian},
title = {Metall{\"a}hnliche Reaktivit{\"a}t \(in\) \(situ\) erzeugter Borylene},
doi = {10.25972/OPUS-24046},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240465},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Einfach Lewis-Basen stabilisierte Borylene wurden durch Reduktion in situ hergestellt und in Gegenwart von Kohlenstoffmonoxid oder Distickstoff umgesetzt. Die entstandenen Verbindungen wurden mittels NMR-, ESR-, UV/Vis- und IR-Spektroskopie sowie Einkristallr{\"o}ntgenstrukturanalyse charakterisiert. Im Zuge dessen konnten f{\"u}r die erhaltenen Spezies Eigenschaften ermittelt werden, die denen analoger {\"U}bergangsmetallkomplexe {\"a}hneln. Ferner konnten die zugrundeliegenden mechanistischen Vorg{\"a}nge der Reaktionen durch gezielte Variation der Reaktionsparameter aufgekl{\"a}rt werden. Zudem wurden Redoxverhalten und Reaktivit{\"a}ten der isolierten Produkte in weiterf{\"u}hrenden Studien n{\"a}her untersucht.},
subject = {Bor},
language = {de}
}
@phdthesis{Preitschopf2023,
author = {Preitschopf, Tobias},
title = {Disentangling the Formation of PAHs in Extreme Environments by IR/UV Double Resonance Spectroscopy},
doi = {10.25972/OPUS-32279},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-322791},
school = {Universit{\"a}t W{\"u}rzburg},
year = {2023},
abstract = {Polycyclic Aromatic Hydrocarbons (PAHs) are considered as key building blocks in the formation of carbonaceous particles such as soot. In our immediate surroundings, they are mainly generated in incomplete combustion processes and are further considered as carriers of the Unidentified Infrared Bands which are detected in a wide variety of astrophysical envelopes in the interstellar medium. Currently, astrochemical as well as combustion related models favour small resonance stabilized radicals (RSR) as major contributors to PAHs in sequential reactions. Therefore, we generated two RSR under well-defined conditions to investigate their contribution to PAH formation in a pyrolysis microreactor. The various reaction products were identified by IR/UV ion dip spectroscopy which combines the mass-selectivity of UV light with the structural sensitivity of IR radiation. Finally, we investigated the intermolecular interactions in azaphenanthrene dimers in combination with high-level theoretical calculations and found a preferential formation of pi-stacked van der Waals cluster in a molecular jet expansion.},
subject = {Infrarotspektroskopie},
language = {en}
}