@article{GriesbeckMichailRauchetal.2019,
  author    = {Griesbeck, Stefanie and Michail, Evripidis and Rauch, Florian and Ogasawara, Hiroaki and Wang, Chenguang and Sato, Yoshikatsu and Edkins, Robert M. and Zhang, Zuolun and Taki, Masayasu and Lambert, Christoph and Yamaguchi, Shigehiro and Marder, Todd B.},
  title     = {The Effect of Branching on the One- and Two-Photon Absorption, Cell Viability, and Localization of Cationic Triarylborane Chromophores with Dipolar versus Octupolar Charge Distributions for Cellular Imaging},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {57},
  doi       = {10.1002/chem.201902461},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212887},
  pages     = {13164 -- 13175},
  year      = {2019},
  abstract  = {Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two-photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two-photon excited fluorescence (TPEF) live-cell imaging.},
  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-212496},
  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, iPr) 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{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{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{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{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{LenczykRoyOberdorfetal.2019,
  author    = {Lenczyk, Carsten and Roy, Dipak Kumar and Oberdorf, Kai and Nitsch, J{\"o}rn and Dewhurst, Rian D. and Radacki, Krzysztof and Halet, Jean-Fran{\c{c}}ois and Marder, Todd B. and Bickelhaupt, Matthias and Braunschweig, Holger},
  title     = {Toward Transition-Metal-Templated Construction of Arylated B\(_{4}\) Chains by Dihydroborane Dehydrocoupling},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {72},
  doi       = {10.1002/chem.201904772},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214324},
  pages     = {16544-16549},
  year      = {2019},
  abstract  = {The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH\(_{2}\)] (Dur=2,3,5,6-Me\(_{4}\)C\(_{6}\)H) and [(Me\(_{3}\)Si)\(_{2}\)NBH\(_{2}\)] led to the formation of bridging borylene complexes of the form [(Cp\(^{*}\)RuH)\(_{2}\)BR] (Cp\(^{*}\)=C\(_{5}\)Me\(_{5}\); 1 a: R=Dur; 1 b: R=N(SiMe\(_{3}\))\(_{2}\)) through oxidative addition of the B-H bonds with concomitant hydrogen liberation. Employing the more electron-deficient dihydroborane [3,5-(CF\(_{3}\))\(_{2}\)-C\(_{6}\)H\(_{3}\)BH\(_{2}\)] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)\(_{4}\)[(Cp\(^{*}\)Ru)\(_{2}\)B\(_{4}\)H\(_{5}\)(3,5-(CF\(_{3}\))\(_{2}\)C\(_{6}\)H\(_{3}\))\(_{4}\)] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido-[1,2(Cp\(^{*}\)Ru)\(_{2}\)(μ-H)B\(_{4}\)H\(_{9}\)] (I) indicates that there appear to be no classical σ-bonds between the boron atoms in complex I, whereas in the case of 4 the B\(_{4}\) chain better resembles a network of three B-B σ bonds, the central bond being significantly weaker than the other two.},
  language  = {en}
}
@article{HattoriMichailSchmiedeletal.2019,
  author    = {Hattori, Yohei and Michail, Evripidis and Schmiedel, Alexander and Moos, Michael and Holzapfel, Marco and Krummenacher, Ivo and Braunschweig, Holger and M{\"u}ller, Ulrich and Pflaum, Jens and Lambert, Christoph},
  title     = {Luminescent Mono-, Di-, and Tri-radicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {68},
  doi       = {10.1002/chem.201903007},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208162},
  pages     = {15463-15471},
  year      = {2019},
  abstract  = {Up to three polychlorinated pyridyldiphenylmethyl radicals bridged by a triphenylamine carrying electron withdrawing (CN), neutral (Me), or donating (OMe) groups were synthesized and analogous radicals bridged by tris(2,6-dimethylphenyl)borane were prepared for comparison. All compounds were as stable as common closed-shell organic compounds and showed significant fluorescence upon excitation. Electronic, magnetic, absorption, and emission properties were examined in detail, and experimental results were interpreted using DFT calculations. Oxidation potentials, absorption and emission energies could be tuned depending on the electron density of the bridges. The triphenylamine bridges mediated intramolecular weak antiferromagnetic interactions between the radical spins, and the energy difference between the high spin and low spin states was determined by temperature dependent ESR spectroscopy and DFT calculations. The fluorescent properties of all radicals were examined in detail and revealed no difference for high and low spin states which facilitates application of these dyes in two-photon absorption spectroscopy and OLED devices.},
  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}
}
@article{GriesbeckMichailRauchetal.2019,
  author    = {Griesbeck, Stefanie and Michail, Evripidis and Rauch, Florian and Ogasawara, Hiroaki and Wang, Chenguang and Sato, Yoshikatsu and Edkins, Robert M. and Zhang, Zuolun and Taki, Masayasu and Lambert, Christoph and Yamaguchi, Shigehiro and Marder, Todd B.},
  title     = {The Effect of Branching on One- and Two-Photon Absorption, Cell Viability and Localization of Cationic Triarylborane Chromophores with Dipolar versus Octupolar Charge Distributions for Cellular Imaging},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {57},
  doi       = {10.1002/chem.201902461},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204829},
  pages     = {13164-13175},
  year      = {2019},
  abstract  = {Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two-photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two-photon excited fluorescence (TPEF) live-cell imaging.},
  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}
}
@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{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{ThiessMellerupBraunschweig2019,
  author    = {Thiess, Torsten and Mellerup, Soren K. and Braunschweig, Holger},
  title     = {B-B Cleavage and Ring-Expansion of a 1,4,2,3-Diazadiborinine with N-Heterocyclic Carbenes},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {59},
  doi       = {10.1002/chem.201903259},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206173},
  pages     = {13572-13578},
  year      = {2019},
  abstract  = {A 1,4,2,3-diazadiborinine derivative was found to form Lewis adducts with strong two-electron donors such as N-heterocyclic and cyclic (alkyl)(amino)carbenes. Depending on the donor, some of these Lewis pairs are thermally unstable, converting to sole B,N-embedded products upon gentle heating. The products of these reactions, which have been fully characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction, were identified as B,N-heterocycles with fused 1,5,2,4-diazadiborepine and 1,4,2-diazaborinine rings. Computational modelling of the reaction mechanism provides insight into the formation of these unique structures, suggesting that a series of B-H, C-N, and B-B bond activation steps are responsible for these "intercalation" reactions between the 1,4,2,3-diazadiborinine and NHCs.},
  language  = {en}
}
@article{HeRauchFriedrichetal.2019,
  author    = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Sieh, Daniel and Ribbeck, Tatjana and Krummenacher, Ivo and Braunschweig, Holger and Finze, Maik and Marder, Todd B.},
  title     = {N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis, Optical and Electronic Properties of D-π-A Compounds},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  doi       = {10.1002/chem.201903118},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204690},
  pages     = {13777-13784},
  year      = {2019},
  abstract  = {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 cyclic (alkyl)(amino) carbenes (CAACs). 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, \(E^{ox}_{1/2}\) =-0.40 V vs. ferrocene/ferrocenium, Fc/Fc\(^+\), in THF). Time-dependent (TD) DFT calculations show that the HOMOs of 1-3 are much more destabilized than that of the enamine-containing 4, which confirms the stronger donating ability of NHOs.},
  language  = {en}
}
@article{MuellerLuettigMalyetal.2019,
  author    = {Mueller, Stefan and L{\"u}ttig, Julian and Mal{\´y}, Pavel and Ji, Lei and Han, Jie and Moos, Michael and Marder, Todd B. and Bunz, Uwe H. F. and Dreuw, Andreas and Lambert, Christoph and Brixner, Tobias},
  title     = {Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-12602-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202529},
  pages     = {4735},
  year      = {2019},
  abstract  = {Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.},
  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}
}
@unpublished{BruecknerStennettHessetal.2019,
  author    = {Br{\"u}ckner, Tobias and Stennett, Tom E. and Heß, Merlin and Braunschweig, Holger},
  title     = {Single and Double Hydroboration of B-B Triple Bonds and Conver- gent Routes to a Cationic Tetraborane},
  series = {Journal of the American Chemical Society},
  journal   = {Journal of the American Chemical Society},
  doi       = {10.1021/jacs.9b07991},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188632},
  year      = {2019},
  abstract  = {A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H- from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B2 moiety. Spectroscopic and crystallographic data and DFT calculations support a 'protonated diborene' structure for this compound, which can also be accessed via direct protonation of the corresponding diborene.},
  language  = {en}
}
@article{BruecknerDewhurstDellermannetal.2019,
  author    = {Br{\"u}ckner, Tobias and Dewhurst, Rian D. and Dellermann, Theresa and M{\"u}ller, Marcel and Braunschweig, Holger},
  title     = {Mild synthesis of diboryldiborenes by diboration of B-B triple bonds},
  series = {Chemical Science},
  volume    = {10},
  journal   = {Chemical Science},
  doi       = {10.1039/C9SC02544H},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-186306},
  pages     = {7375-7378},
  year      = {2019},
  abstract  = {A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B-B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents.},
  language  = {en}
}
@unpublished{LegarePranckeviciusBraunschweig2019,
  author    = {L{\´e}gar{\´e}, Marc-Andr{\´e} and Pranckevicius, Conor and Braunschweig, Holger},
  title     = {Metallomimetic Chemistry of Boron},
  series = {Chemical Reviews},
  journal   = {Chemical Reviews},
  doi       = {10.1021/acs.chemrev.8b00561},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-186317},
  year      = {2019},
  abstract  = {The study of main-group molecules that behave and react similarly to transition-metal (TM) complexes has attracted significant interest in recent decades. Most notably, the attractive idea of replacing the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of TM complexes that arises from combinations of empty and filled d orbitals and that seem ideally suited to bind and activate many substrates. In this review, we look at boron, an element that despite its nonmetal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in interelement cooperative systems, diboron molecules, and hypovalent complexes the fifth element can acquire a truly metallomimetic character. As we discuss, this character is powerfully demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2.},
  language  = {en}
}
@unpublished{EnglertStoyArrowsmithetal.2019,
  author    = {Englert, Lukas and Stoy, Andreas and Arrowsmith, Merle and M{\"u}ssig, Jonas H. and Thaler, Melanie and Deißenberger, Andrea and H{\"a}fner, Alena and B{\"o}hnke, Julian and Hupp, Florian and Seufert, Jens and Mies, Jan and Damme, Alexander and Dellermann, Theresa and Hammond, Kai and Kupfer, Thomas and Radacki, Krzysztof and Thiess, Torsten and Braunschweig, Holger},
  title     = {Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity},
  series = {Chemistry - A European Journal},
  journal   = {Chemistry - A European Journal},
  doi       = {10.1002/chem.201901437},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184888},
  year      = {2019},
  abstract  = {A series of 22 new bis(phosphine), bis(carbene) and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X = Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X = Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopic, (C,H,N)- elemental and, for 20 of these compounds, X-ray crystallographic analysis, revealing an unexpected variation in the bonding motifs. Besides the classical B2X4L2 diborane(6) adducts, some of the more sterically demanding carbene ligands induce a halide displacement leading to the first halide-bridged monocationic diboron species, [B2X3L2]A (A = BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed.},
  language  = {en}
}
@unpublished{BruecknerArrowsmithHessetal.2019,
  author    = {Br{\"u}ckner, Tobias and Arrowsmith, Merle and Heß, Merlin and Hammond, Kai and M{\"u}ller, Marcel and Braunschweig, Holger},
  title     = {Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne},
  series = {Chemical Communications},
  journal   = {Chemical Communications},
  doi       = {10.1039/C9CC02657F},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184899},
  year      = {2019},
  abstract  = {The addition of alkynes to a staturated N-heterocyclic carbene (NHC)-supported diboryne results in spontaneous cycloaddition, with complete B≡B and C≡C triple bond cleavage, NHC ring- expansion and activation of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles.},
  language  = {en}
}
@unpublished{ArrowsmithDoemlingSchmidtetal.2019,
  author    = {Arrowsmith, Merle and D{\"o}mling, Michael and Schmidt, Uwe and Werner, Luis and Castro, Abril C. and Jim{\´e}nez-Halla, J. Oscar C. and M{\"u}ssig, Jonas and Prieschl, Dominic and Braunschweig, Holger},
  title     = {Spontaneous trans-Selective Transfer Hydrogenation of Apolar B=B Double Bonds},
  series = {Angewandte Chemie, International Edition},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201902656},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184874},
  year      = {2019},
  abstract  = {The transfer hydrogenation of NHC-supported diborenes with dimethylamine borane proceeds with high selectivity for the trans-1,2-dihydrodiboranes(6). DFT calculations suggest a stepwise proton-first-hydride-second reaction mechanism via an intermediate μ-hydrodiboronium dimethylaminoborate ion pair.},
  language  = {en}
}
@article{RamlerPoaterHirschetal.2019,
  author    = {Ramler, Jacqueline and Poater, Jordi and Hirsch, Florian and Ritschel, Benedikt and Fischer, Ingo and Bickelhaupt, F. Matthias and Lichtenberg, Crispin},
  title     = {Carbon monoxide insertion at a heavy p-block element: unprecedented formation of a cationic bismuth carbamoyl},
  series = {Chemical Science},
  volume    = {10},
  journal   = {Chemical Science},
  doi       = {10.1039/C9SC00278B},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-181627},
  pages     = {4169 - 4176},
  year      = {2019},
  abstract  = {Major advances in the chemistry of 5th and 6th row heavy p-block element compounds have recently uncovered intriguing reactivity patterns towards small molecules such as H\(_2\), CO\(_2\), and ethylene. However, well-defined, homogeneous insertion reactions with carbon monoxide, one of the benchmark substrates in this field, have not been reported to date. We demonstrate here, that a cationic bismuth amide undergoes facile insertion of CO into the Bi-N bond under mild conditions. This approach grants direct access to the first cationic bismuth carbamoyl species. Its characterization by NMR, IR, and UV/vis spectroscopy, elemental analysis, single-crystal X-ray analysis, cyclic voltammetry, and DFT calculations revealed intriguing properties, such as a reversible electron transfer at the bismuth center and an absorption feature at 353 nm ascribed to a transition involving σ- and π-type orbitals of the bismuth-carbamoyl functionality. A combined experimental and theoretical approach provided insight into the mechanism of CO insertion. The substrate scope could be extended to isonitriles.},
  language  = {en}
}
@unpublished{StennettBissingerGriesbecketal.2019,
  author    = {Stennett, Tom E. and Bissinger, Philipp and Griesbeck, Stefanie and Ullrich, Stefan and Krummenacher, Ivo and Auth, Michael and Sperlich, Andreas and Stolte, Matthias and Radacki, Krzysztof and Yao, Chang-Jiang and W{\"u}rthner, Frank and Steffen, Andreas and Marder, Todd B. and Braunschweig, Holger},
  title     = {Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units},
  series = {Angewandte Chemie, International Edition},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201900889},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180391},
  year      = {2019},
  abstract  = {In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts.},
  language  = {en}
}
@unpublished{MuessigThalerDewhurstetal.2019,
  author    = {Muessig, Jonas H. and Thaler, Melanie and Dewhurst, Rian D. and Paprocki, Valerie and Seufert, Jens and Mattock, James D. and Vargas, Alfredo and Braunschweig, Holger},
  title     = {Phosphine-Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds},
  series = {Angewandte Chemie, International Edition},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201814230},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178608},
  year      = {2019},
  abstract  = {The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange.},
  language  = {en}
}
@phdthesis{Rieger2019,
  author    = {Rieger, Max},
  title     = {Preconcentration with Metal-Organic Frameworks as adsorbents for airborne Explosives and Hazardous Materials - A study using inverse gas chromatography},
  doi       = {10.25972/OPUS-17775},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177750},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Sensitivity and selectivity remain the central technical requirement for analytical devices, detectors and sensors. Especially in the gas phase, concentrations of threat substances can be very low (e.g. explosives) or have severe effects on health even at low concentrations (e.g. benzene) while it contains many potential interferents. Preconcentration, facilitated by active or passive sampling of air by an adsorbent, followed by thermal desorption, results in these substances being released in a smaller volume, effectively increasing their concentration. Traditionally, a wide range of adsorbents, such as active carbons or porous polymers, are used for preconcentration. However, many adsorbents either show chemical reactions due to active surfaces, serious water retention or high background emission due to thermal instability. Metal-organic frameworks (MOFs) are a hybrid substance class, composed inorganic and organic building blocks, being a special case of coordination polymers containing pores. They can be tailored for specific applications such as gas storage, separation, catalysis, sensors or drug delivery. This thesis is focused on investigating MOFs for their use in thermal preconcentration for airborne detection systems. A pre-screening method for MOF-adsorbate interactions was developed and applied, namely inverse gas chromatography (iGC). Using this pulse chromatographic method, the interaction of MOFs and molecules from the class of explosives and volatile organic compounds was studied at different temperatures and compared to thermal desorption results. In the first part, it is shown that archetype MOFs (HKUST-1, MIL-53 and Fe-BTC) outperformed the state-of-the-art polymeric adsorbent Tenax® TA in nitromethane preconcentration for a 1000 (later 1) ppm nitromethane source. For HKUST-1, a factor of more than 2000 per g of adsorbent was achieved, about 100 times higher than for Tenax. Thereby, a nitromethane concentration of 1 ppb could be increased to 2 ppm. High enrichment is addressed to the specific interaction of the nitro group as by iGC, which was determined by comparing nitromethane's free enthalpy of adsorption with the respective saturated alkane. Also, HKUST-1 shows a similar mode of sorption (enthalpy-entropy compensation) for nitro and saturated alkanes. In the second part, benzene of 1 ppm of concentration was enriched with a similar setup, using 2nd generation MOFs, primarily UiO-66 and UiO-67, under dry and humid (50 \%rH) conditions using constant sampling times. Not any MOF within the study did surpass the polymeric Tenax in benzene preconcentration. This is most certainly due to low sampling times - while Tenax may be highly saturated after 600 s, MOFs are not. For regular UiO-66, four differently synthesized samples showed a strongly varying behavior for dry and humid enrichment which cannot be completely explained. iGC investigations with regular alkanes and BTEX compounds revealed that confinement factors and dispersive surface energy were different for all UiO-66 samples. Using physicochemical parameters from iGC, no unified hypothesis explaining all variances could be developed. Altogether, it was shown that MOFs can replace or add to state-of-the-art adsorbents for the enrichment of specific analytes with preconcentration being a universal sensitivity-boosting concept for detectors and sensors. Especially with iGC as a powerful screening tool, most suitable MOFs for the respective target analyte can be evaluated. iGC can be used for determining "single point" retention volumes, which translate into partition coefficients for a specific MOF × analyte × temperature combination.},
  subject      = {Metallorganisches Netzwerk},
  language  = {en}
}