TY - JOUR A1 - Ban, Željka A1 - Karačić, Zrinka A1 - Tomić, Sanja A1 - Amini, Hashem A1 - Marder, Todd B. A1 - Piantanida, Ivo T1 - Triarylborane dyes as a novel non-covalent and non-inhibitive fluorimetric markers for DPP III enzyme JF - Molecules N2 - Novel dyes were prepared by simple “click CuAAC” attachment of a triarylborane–alkyne to the azide side chain of an amino acid yielding triarylborane dye 1 which was conjugated with pyrene (dye 2) forming a triarylborane–pyrene FRET pair. In contrast to previous cationic triarylboranes, the novel neutral dyes interact only with proteins, while their affinity to DNA/RNA is completely abolished. Both the reference triarylborane amino acid and triarylborane–pyrene conjugate bind to BSA and the hDPP III enzyme with high affinities, exhibiting a strong (up to 100-fold) fluorescence increase, whereby the triarylborane–pyrene conjugate additionally retained FRET upon binding to the protein. Furthermore, the triarylborane dyes, upon binding to the hDPP III enzyme, did not impair its enzymatic activity under a wide range of experimental conditions, thus being the first non-covalent fluorimetric markers for hDPP III, also applicable during enzymatic reactions with hDPP III substrates. KW - triarylborane KW - pyrene KW - click CuAAC synthesis KW - DPP III enzyme KW - BSA KW - fluorescence Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-245046 SN - 1420-3049 VL - 26 IS - 16 ER - TY - JOUR A1 - Barak, Arvind A1 - Dhiman, Nishant A1 - Sturm, Floriane A1 - Rauch, Florian A1 - Lakshmanna, Yapamanu Adithya A1 - Findlay, Karen S. A1 - Beeby, Andrew A1 - Marder, Todd B. A1 - Umapathy, Siva T1 - Excited‐State Intramolecular Charge‐Transfer Dynamics in 4‐Dimethylamino‐4′‐cyanodiphenylacetylene: An Ultrafast Raman Loss Spectroscopic Perspective JF - ChemPhotoChem N2 - Photo‐initiated intramolecular charge transfer (ICT) processes play a pivotal role in the excited state reaction dynamics in donor‐bridge‐acceptor systems. The efficacy of such a process can be improved by modifying the extent of π‐conjugation, relative orientation/twists of the donor/acceptor entities and polarity of the environment. Herein, 4‐dimethylamino‐4′‐cyanodiphenylacetylene (DACN‐DPA), a typical donor‐π‐bridge‐acceptor system, was chosen to unravel the role of various internal coordinates that govern the extent of photo‐initiated ICT dynamics. Transient absorption (TA) spectra of DACN‐DPA in n‐hexane exhibit a lifetime of >2 ns indicating the formation of a triplet state while, in acetonitrile, a short time‐constant of ∼2 ps indicates the formation of charge transferred species. Ultrafast Raman loss spectroscopy (URLS) measurements show distinct temporal and spectral dynamics of Raman bands associated with C≡C and C=C stretching vibrations. The appearance of a new band at ∼1492 cm\(^{−1}\) in acetonitrile clearly indicates structural modification during the ultrafast ICT process. Furthermore, these observations are supported by TD‐DFT computations. KW - charge transfer KW - ultrafast Raman loss spectroscopy KW - 4-dimethylamino-4′-cyanodiphenylacetylene KW - transient absorption KW - TD-DFT Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312280 VL - 6 IS - 12 ER - TY - JOUR A1 - Belaidi, Houmam A1 - Rauch, Florian A1 - Zhang, Zuolun A1 - Latouche, Camille A1 - Boucekkine, Abdou A1 - Marder, Todd B. A1 - Halet, Jean-Francois T1 - Insights into the optical properties of triarylboranes with strongly electron-accepting bis(fluoromesityl)boryl groups: when theory meets experiment JF - ChemPhotoChem N2 - 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. KW - boron KW - density functional calculations KW - luminescence KW - phosphorescence KW - photophysics KW - activated delayes flourescence KW - 3-coordinate organoboron compounds KW - light-emitting-diodes KW - phosphorescene spectra KW - molecular structures KW - high efficiency KW - pi-conjugation KW - trivalent boron KW - single photon KW - donor Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-205600 VL - 4 IS - 3 ER - TY - JOUR A1 - Berger, Sarina M. A1 - Ferger, Matthias A1 - Marder, Todd B. T1 - Synthetic Approaches to Triarylboranes from 1885 to 2020 JF - Chemistry – A European Journal N2 - In recent years, research in the fields of optoelectronics, anion sensors and bioimaging agents have been greatly influenced by novel compounds containing triarylborane motifs. Such compounds possess an empty p‐orbital at boron which results in useful optical and electronic properties. Such a diversity of applications was not expected when the first triarylborane was reported in 1885. Synthetic approaches to triarylboranes underwent various changes over the following century, some of which are still used in the present day, such as the generally applicable routes developed by Krause et al. in 1922, or by Grisdale et al. in 1972 at Eastman Kodak. Some other developments were not pursued further after their initial reports, such as the synthesis of two triarylboranes bearing three different aromatic groups by Mikhailov et al. in 1958. This review summarizes the development of synthetic approaches to triarylboranes from their first report nearly 135 years ago to the present. KW - arylmetalate KW - boranes KW - chromophore KW - Lewis acid KW - synthetic methods Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238952 VL - 27 IS - 24 SP - 7043 EP - 7058 ER - TY - JOUR A1 - Berger, Sarina M. A1 - Rühe, Jessica A1 - Schwarzmann, Johannes A1 - Phillipps, Alexandra A1 - Richard, Ann-Katrin A1 - Ferger, Matthias A1 - Krummenacher, Ivo A1 - Tumir, Lidija-Marija A1 - Ban, Željka A1 - Crnolatac, Ivo A1 - Majhen, Dragomira A1 - Barišić, Ivan A1 - Piantanida, Ivo A1 - Schleier, Domenik A1 - Griesbeck, Stefanie A1 - Friedrich, Alexandra A1 - Braunschweig, Holger A1 - Marder, Todd B. T1 - 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 JF - Chemistry—A European Journal N2 - 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. KW - singlet oxygen KW - boron KW - bioimaging KW - luminescence KW - nucleic acid Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256963 VL - 27 IS - 56 ER - TY - JOUR A1 - Budiman, Yudha P. A1 - Lorenzen, Sabine A1 - Liu, Zhiqiang A1 - Radius, Udo A1 - Marder, Todd B. T1 - Base‐Free Pd‐Catalyzed C−Cl Borylation of Fluorinated Aryl Chlorides JF - Chemistry – A European Journal N2 - Catalytic C−X borylation of aryl halides containing two ortho‐fluorines has been found to be challenging, as most previous methods require stoichiometric amounts of base and the polyfluorinated aryl boronates suffer from protodeboronation, which is accelerated by ortho‐fluorine substituents. Herein, we report that 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. This method, conducted under base‐free conditions, is compatible with the resulting di‐ortho‐fluorinated aryl boronate products which are sensitive to base. KW - boronate ester KW - borylation KW - cross-coupling KW - fluoroarene KW - palladium-catalyzed Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225687 VL - 27 IS - 11 SP - 3869 EP - 3874 ER - TY - JOUR A1 - Budiman, Yudha P. A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Fluorinated Aryl Boronates as Building Blocks in Organic Synthesis JF - Advanced Synthesis & Catalysis N2 - Organoboron compounds are well known building blocks for many organic reactions. However, under basic conditions, polyfluorinated aryl boronic acid derivatives suffer from instability issues that are accelerated in compounds containing an ortho‐fluorine group, which result in the formation of the corresponding protodeboronation products. Therefore, a considerable amount of research has focused on novel methodologies to synthesize these valuable compounds while avoiding the protodeboronation issue. This review summarizes the latest developments in the synthesis of fluorinated aryl boronic acid derivatives and their applications in cross‐coupling reactions and other transformations. image KW - homogeneous catalysis KW - boron reagents KW - boronates KW - fluorine KW - fluoroarene Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225908 VL - 363 IS - 9 SP - 2224 EP - 2255 ER - TY - JOUR A1 - Chen, Xing A1 - Meng, Guoyun A1 - Liao, Guanming A1 - Rauch, Florian A1 - He, Jiang A1 - Friedrich, Alexandra A1 - Marder, Todd B. A1 - Wang, Nan A1 - Chen, Pangkuan A1 - Wang, Suning A1 - Yin, Xiaodong T1 - Highly Emissive 9-Borafluorene Derivatives: Synthesis, Photophysical Properties and Device Fabrication JF - Chemistry—A European Journal N2 - 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. KW - boron heterocycles KW - photophysics KW - organic light-emitting diodes KW - luminescence KW - density functional calculations Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256738 VL - 27 IS - 20 ER - TY - JOUR A1 - Ferger, Matthias A1 - Ban, Željka A1 - Krošl, Ivona A1 - Tomić, Sanja A1 - Dietrich, Lena A1 - Lorenzen, Sabine A1 - Rauch, Florian A1 - Sieh, Daniel A1 - Friedrich, Alexandra A1 - Griesbeck, Stefanie A1 - Kenđel, Adriana A1 - Miljanić, Snežana A1 - Piantanida, Ivo A1 - Marder, Todd B. T1 - Bis(phenylethynyl)arene Linkers in Tetracationic Bis-triarylborane Chromophores Control Fluorimetric and Raman Sensing of Various DNAs and RNAs JF - Chemistry-A European Journal N2 - We report four new luminescent tetracationic bis-triarylborane DNA and RNA sensors that show high binding affinities, in several cases even in the nanomolar range. Three of the compounds contain substituted, highly emissive and structurally flexible bis(2,6-dimethylphenyl-4-ethynyl)arene linkers (3: arene=5,5′-2,2′-bithiophene; 4: arene=1,4-benzene; 5: arene=9,10-anthracene) between the two boryl moieties and serve as efficient dual Raman and fluorescence chromophores. The shorter analogue 6 employs 9,10-anthracene as the linker and demonstrates the importance of an adequate linker length with a certain level of flexibility by exhibiting generally lower binding affinities than 3–5. Pronounced aggregation–deaggregation processes are observed in fluorimetric titration experiments with DNA for compounds 3 and 5. Molecular modelling of complexes of 5 with AT-DNA, suggest the minor groove as the dominant binding site for monomeric 5, but demonstrate that dimers of 5 can also be accommodated. Strong SERS responses for 3–5 versus a very weak response for 6, particularly the strong signals from anthracene itself observed for 5 but not for 6, demonstrate the importance of triple bonds for strong Raman activity in molecules of this compound class. The energy of the characteristic stretching vibration of the C≡C bonds is significantly dependent on the aromatic moiety between the triple bonds. The insertion of aromatic moieties between two C≡C bonds thus offers an alternative design for dual Raman and fluorescence chromophores, applicable in multiplex biological Raman imaging. KW - boranes KW - Raman probes KW - molecular modelling KW - fluorescent probes KW - DNA/RNA sensors Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256717 VL - 27 IS - 16 ER - TY - JOUR A1 - Ferger, Matthias A1 - Berger, Sarina M. A1 - Rauch, Florian A1 - Schönitz, Markus A1 - Rühe, Jessica A1 - Krebs, Johannes A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Synthesis of Highly Functionalizable Symmetrically and Unsymmetrically Substituted Triarylboranes from Bench-Stable Boron Precursors JF - Chemistry—A European Journal N2 - 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. KW - synthetic methods KW - boranes KW - borylation KW - chromophore KW - functionalization Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256827 VL - 27 IS - 35 ER - TY - JOUR A1 - Ferger, Matthias A1 - Roger, Chantal A1 - Köster, Eva A1 - Rauch, Florian A1 - Lorenzen, Sabine A1 - Krummenacher, Ivo A1 - Friedrich, Alexandra A1 - Košćak, Marta A1 - Nestić, Davor A1 - Braunschweig, Holger A1 - Lambert, Christoph A1 - Piantanida, Ivo A1 - Marder, Todd B. T1 - Electron‐Rich EDOT Linkers in Tetracationic bis‐Triarylborane Chromophores: Influence on Water Stability, Biomacromolecule Sensing, and Photoinduced Cytotoxicity JF - Chemistry – A European Journal N2 - Three novel tetracationic bis‐triarylboranes with 3,4‐ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red‐shifted absorption and emission compared to their thiophene‐containing analogues, with one of the EDOT‐derivatives emitting in the NIR region. Only the EDOT‐linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3‐methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT‐linked trixylylborane tetracation and its bis‐thiophene analogue revealed efficient photo‐induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds‐DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra‐tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well‐focused visible light. KW - boranes KW - DNA/RNA sensors KW - fluorescent probes KW - singlet oxygen KW - theranostics Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287241 VL - 28 IS - 48 ER - TY - JOUR A1 - Foster, Jonathan A. A1 - Edkins, Robert M. A1 - Cameron, Gary J. A1 - Colgin, Neil A1 - Fucke, Katharina A1 - Ridgeway, Sam A1 - Crawford, Andrew G. A1 - Marder, Todd B. A1 - Beeby, Andrew A1 - Cobb, Steven L. A1 - Steed, Jonathan W. T1 - Blending Gelators to Tune Gel Structure and Probe Anion-Induced Disassembly JF - Chemistry : A European Journal N2 - Blending different low molecular weight gelators (LMWGs) provides a convenient route to tune the properties of a gel and incorporate functionalities such as fluorescence. Blending a series of gelators having a common bis-urea motif, and functionalised with different amino acid-derived end-groups and differing length alkylene spacers is reported. Fluorescent gelators incorporating 1- and 2-pyrenyl moieties provide a probe of the mixed systems alongside structural and morphological data from powder diffraction and electron microscopy. Characterisation of the individual gelators reveals that although the expected α-urea tape motif is preserved, there is considerable variation in the gelation properties, molecular packing, fibre morphology and rheological behaviour. Mixing of the gelators revealed examples in which: 1) the gels formed separate, orthogonal networks maintaining their own packing and morphology, 2) the gels blended together into a single network, either adopting the packing and morphology of one gelator, or 3) a new structure not seen for either of the gelators individually was created. The strong binding of the urea functionalities to anions was exploited as a means of breaking down the gel structure, and the use of fluorescent gel blends provides new insights into anion-mediated gel dissolution. KW - blend KW - co-gels KW - fluorescence KW - orthogonal self-assembly KW - supramolecular chemistry Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-121141 VL - 20 ER - TY - JOUR A1 - Griesbeck, Stefanie A1 - Michail, Evripidis A1 - Rauch, Florian A1 - Ogasawara, Hiroaki A1 - Wang, Chenguang A1 - Sato, Yoshikatsu A1 - Edkins, Robert M. A1 - Zhang, Zuolun A1 - Taki, Masayasu A1 - Lambert, Christoph A1 - Yamaguchi, Shigehiro A1 - Marder, Todd B. T1 - 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 JF - Chemistry – A European Journal N2 - 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. KW - boranes KW - cell imaging KW - fluorescence KW - lysosome KW - two-photon excited fluorescence Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212887 VL - 25 IS - 57 SP - 13164 EP - 13175 ER - TY - JOUR A1 - He, Jiang A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Krebs, Johannes A1 - Krummenacher, Ivo A1 - Bertermann, Rüdiger A1 - Nitsch, Jörn A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - Phenylpyridyl-fused boroles: a unique coordination mode and weak B-N coordination-induced dual fluorescence JF - Angewandte Chemie International Edition N2 - 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. KW - inorganic chemistry KW - weak intermolecular coordination KW - boroles KW - dual fluorescence KW - equilibrium KW - tetramers Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256423 VL - 60 IS - 9 ER - TY - JOUR A1 - Huang, Mingming A1 - Hu, Jiefeng A1 - Krummenacher, Ivo A1 - Friedrich, Alexandra A1 - Braunschweig, Holger A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Base-Mediated Radical Borylation of Alkyl Sulfones JF - Chemistry—A European Journal N2 - 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. KW - boron KW - boronate KW - boronic acid KW - metal-free KW - radical Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257281 VL - 28 IS - 3 ER - TY - JOUR A1 - Huang, Mingming A1 - Hu, Jiefeng A1 - Shi, Shasha A1 - Friedrich, Alexandra A1 - Krebs, Johannes A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols JF - Chemistry-A European Journal N2 - Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program. KW - organic synthesis KW - boronate esters KW - alkyl halides Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318262 VL - 28 IS - 24 ER - TY - JOUR A1 - Huang, Mingming A1 - Wu, Zhu A1 - Krebs, Johannes A1 - Friedrich, Alexandra A1 - Luo, Xiaoling A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Ni-Catalyzed Borylation of Aryl Sulfoxides JF - Chemistry—A European Journal N2 - 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. KW - Boron KW - cross-coupling KW - N-heterocyclic carbenes KW - nickel KW - borylation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256778 VL - 27 IS - 31 ER - TY - JOUR A1 - Ji, Lei A1 - Griesbeck, Stefanie A1 - Marder, Todd B. T1 - Recent developments in and perspectives on three-coordinate boron materials: a bright future JF - Chemical Science N2 - The empty p\(_z\)-orbital of a three-coordinate organoboron compound leads to its electron-deficient properties, which make it an excellent π-acceptor in conjugated organic chromophores. The empty p-orbital in such Lewis acids can be attacked by nucleophiles, so bulky groups are often employed to provide air-stable materials. However, many of these can still bind fluoride and cyanide anions leading to applications as anion-selective sensors. One electron reduction generates radical anions. The π-acceptor strength can be easily tuned by varying the organic substituents. Many of these compounds show strong two-photon absorption (TPA) and two-photon excited fluorescence (TPEF) behaviour, which can be applied for e.g. biological imaging. Furthermore, these chromophores can be used as emitters and electron transporters in OLEDs, and examples have recently been found to exhibit efficient thermally activated delayed fluorescence (TADF). The three-coordinate organoboron unit can also be incorporated into polycyclic aromatic hydrocarbons. Such boron-doped compounds exhibit very interesting properties, distinct from their all-carbon analogues. Significant developments have been made in all of these areas in recent years and new applications are rapidly emerging for this class of boron compounds. KW - anorganic chemistry KW - boron KW - 3-coordinate boron KW - Lewis acids KW - OLED KW - polycyclic aromatic hydrocarbons KW - chromophore Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171912 VL - 8 IS - 2 ER - TY - JOUR A1 - Jos, Swetha A1 - Szwetkowski, Connor A1 - Slebodnick, Carla A1 - Ricker, Robert A1 - Chan, Ka Lok A1 - Chan, Wing Chun A1 - Radius, Udo A1 - Lin, Zhenyang A1 - Marder, Todd B. A1 - Santos, Webster L. T1 - Transition Metal‐Free Regio‐ and Stereo‐Selective trans Hydroboration of 1,3‐Diynes: A Phosphine‐Catalyzed Access to (E)‐1‐Boryl‐1,3‐Enynes JF - Chemistry – A European Journal N2 - We report a transition metal‐free, regio‐ and stereo‐selective, phosphine‐catalyzed method for the trans hydroboration of 1,3‐diynes with pinacolborane that affords (E)‐1‐boryl‐1,3‐enynes. The reaction proceeds with excellent selectivity for boron addition to the external carbon of the 1,3‐diyne framework as unambiguously established by NMR and X‐ray crystallographic studies. The reaction displays a broad substrate scope including unsymmetrical diynes to generate products in high yield (up to 95 %). Experimental and theoretical studies suggest that phosphine attack on the alkyne is a key process in the catalytic cycle. KW - enediyne KW - enyne KW - hydroboration KW - organocatalytic KW - stereoselective Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293784 VL - 28 IS - 63 ER - TY - JOUR A1 - Kole, Goutam Kumar A1 - Košćak, Marta A1 - Amar, Anissa A1 - Majhen, Dragomira A1 - Božinović, Ksenija A1 - Brkljaca, Zlatko A1 - Ferger, Matthias A1 - Michail, Evripidis A1 - Lorenzen, Sabine A1 - Friedrich, Alexandra A1 - Krummenacher, Ivo A1 - Moos, Michael A1 - Braunschweig, Holger A1 - Boucekkine, Abdou A1 - Lambert, Christoph A1 - Halet, Jean‐François A1 - Piantanida, Ivo A1 - Müller‐Buschbaum, Klaus A1 - Marder, Todd B. T1 - Methyl Viologens of Bis‐(4’‐Pyridylethynyl)Arenes – Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology JF - Chemistry – A European Journal N2 - A series of bis‐(4’‐pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis‐N‐methylpyridinium compounds were investigated as a class of π‐extended methyl viologens. Their structures were determined by single crystal X‐ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis‐N‐methylpyridinium compound showed a larger two‐photon absorption cross‐section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds‐DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene‐analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi‐faceted features, in combination with its two‐photon absorption properties, suggest it to be a promising lead compound for development of novel light‐activated theranostic agents. KW - cell imaging KW - DNA/RNA binding KW - methyl viologen KW - singlet oxygen KW - two-photon absorption Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287126 VL - 28 IS - 40 ER - TY - JOUR A1 - Kole, Goutam Kumar A1 - Merz, Julia A1 - Amar, Anissa A1 - Fontaine, Bruno A1 - Boucekkine, Abdou A1 - Nitsch, Jörn A1 - Lorenzen, Sabine A1 - Friedrich, Alexandra A1 - Krummenacher, Ivo A1 - Košćak, Marta A1 - Braunschweig, Holger A1 - Piantanida, Ivo A1 - Halet, Jean-François A1 - Müller-Buschbaum, Klaus A1 - Marder, Todd B. T1 - 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 JF - Chemistry - A European Journal N2 - 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. KW - inorganic chemistry KW - viologens KW - chromophores KW - luminescent KW - pyrenes KW - pyridinium Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256642 VL - 27 IS - 8 ER - TY - JOUR A1 - Košćak, Marta A1 - Pehar, Isabela A1 - Božinović, Ksenija A1 - Kole, Goutam Kumar A1 - Sobočanec, Sandra A1 - Podgorski, Iva I. A1 - Pinterić, Marija A1 - Müller-Buschbaum, Klaus A1 - Majhen, Dragomira A1 - Piantanida, Ivo A1 - Marder, Todd B. T1 - Para-N-methylpyridinium pyrenes: impact of positive charge on ds-DNA/RNA and protein recognition, photo-induced bioactivity, and intracellular localisation JF - Pharmaceutics N2 - The 2- and 2,7- substituted para-N-methylpyridinium pyrene cations show high-affinity intercalation into ds-DNAs, whereas their non-methylated analogues interacted with ds-DNA/RNA only in the protonated form (at pH 5), but not at physiological conditions (pH 7). The fluorescence from non-methylated analogues was strongly dependent on the protonation of the pyridines; consequently, they act as fluorescence ratiometric probes for simultaneous detection of both ds-DNA and BSA at pH 5, relying on the ratio between intensities at 420 nm (BSA specific) and 520 nm (DNA specific), whereby exclusively ds-DNA sensing could be switched-off by adjustment to pH 7. Only methylated, permanently charged pyrenes show photoinduced cleavage of circular DNA, attributed to pyrene-mediated irradiation-induced production of singlet oxygen. Consequently, the moderate toxicity of these cations against human cell lines is strongly increased upon irradiation. Detailed studies revealed increased total ROS production in cells treated by the compounds studied, accompanied by cell swelling and augmentation of cellular complexity. The most photo-active 2-para-N-methylpyridinium pyrene showed significant localization at mitochondria, its photo-bioactivity likely due to mitochondrial DNA damage. Other derivatives were mostly non-selectively distributed between various cytoplasmic organelles, thus being less photoactive. KW - N-methylpyridinium pyrene KW - DNA sensing KW - protein sensing KW - singlet oxygen KW - photodynamic therapy KW - fluorescence KW - theranostics Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-297247 SN - 1999-4923 VL - 14 IS - 11 ER - TY - JOUR A1 - Krebs, Johannes A1 - Haehnel, Martin A1 - Krummenacher, Ivo A1 - Friedrich, Alexandra A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Ji, Lei A1 - Marder, Todd B. T1 - Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion JF - Chemistry—A European Journal N2 - 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. KW - Wade’s rules KW - carborane KW - charge transfer KW - radical KW - threecoordinate boron Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256841 VL - 27 IS - 31 ER - TY - JOUR A1 - Lenczyk, Carsten A1 - Roy, Dipak Kumar A1 - Nitsch, Jörn A1 - Radacki, Krzysztof A1 - Rauch, Florian A1 - Dewhurst, Rian D. A1 - Bickelhaupt, F. Matthias A1 - Marder, Todd B. A1 - Braunschweig, Holger T1 - Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes JF - Chemistry - A European Journal N2 - 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. KW - Arylborylene Complexes KW - Ruthenium KW - Dihydroboranes KW - boranes KW - borohydrides KW - borylenes KW - steric effects KW - sigma boranes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219537 SN - 1521-3765 VL - 25 IS - 59 ER - TY - JOUR A1 - Lenczyk, Carsten A1 - Roy, Dipak Kumar A1 - Oberdorf, Kai A1 - Nitsch, Jörn A1 - Dewhurst, Rian D. A1 - Radacki, Krzysztof A1 - Halet, Jean-François A1 - Marder, Todd B. A1 - Bickelhaupt, Matthias A1 - Braunschweig, Holger T1 - Toward Transition‐Metal‐Templated Construction of Arylated B\(_{4}\) Chains by Dihydroborane Dehydrocoupling JF - Chemistry - A European Journal N2 - 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. KW - transition metal KW - B−H activation KW - boron KW - dehydrocoupling KW - ruthenium Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214324 VL - 25 IS - 72 ER - TY - JOUR A1 - Lindl, Felix A1 - Guo, Xueying A1 - Krummenacher, Ivo A1 - Rauch, Florian A1 - Rempel, Anna A1 - Paprocki, Valerie A1 - Dellermann, Theresa A1 - Stennett, Tom E. A1 - Lamprecht, Anna A1 - Brückner, Tobias A1 - Radacki, Krzysztof A1 - Bélanger-Chabot, Guillaume A1 - Marder, Todd B. A1 - Lin, Zhenyang A1 - Braunschweig, Holger T1 - Rethinking Borole Cycloaddition Reactivity JF - Chemistry—A European Journal N2 - 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. KW - pericyclic reaction KW - Boron KW - computational chemistry KW - isomer KW - isomerization Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256888 VL - 27 IS - 43 ER - TY - JOUR A1 - Liu, Xiaocui A1 - Ming, Wenbo A1 - Friedrich, Alexandra A1 - Kerner, Florian A1 - Marder, Todd B. T1 - Copper-Catalyzed Triboration of Terminal Alkynes Using B\(_2\)pin\(_2\): Efficient Synthesis of 1,1,2-Triborylalkenes JF - Angewandte Chemie International Edition N2 - 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. KW - boronate esters KW - borylation KW - cross-coupling KW - diboration KW - halogenation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206694 VL - 59 IS - 1 ER - TY - JOUR A1 - Liu, Xiaocui A1 - Ming, Wenbo A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Kupfer‐katalysierte Triborierung terminaler Alkine mit B2pin2: Effiziente Synthese von 1,1,2‐Triborylalkenen JF - Angewandte Chemie N2 - Wir berichten über die katalytische Triborierung terminaler Alkine mit B\(_2\)pin\(_2\) (Bis‐(pinakolato)‐dibor) unter Verwendung von einfach zugänglichem 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 mäßigen bis guten Ausbeuten erhalten. Das Verfahren zeichnet sich durch milde Reaktionsbedingungen, ein breites Substratspektrum und eine gute Verträglichkeit gegenüber funktionellen Gruppen aus. Diese Cu‐katalysierte Reaktion kann im Gramm‐Maßstab durchgeführt werden und liefert die entsprechenden 1,1,2‐Triborylalkene in mäßigen 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 zugänglich waren. KW - Boronatester KW - Borylierung KW - Diborierung KW - Halogenierung KW - Kreuzkupplungen Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219699 VL - 132 IS - 1 ER - TY - JOUR A1 - Liu, Xiaocui A1 - Ming, Wenbo A1 - Luo, Xiaoling A1 - Friedrich, Alexandra A1 - Maier, Jan A1 - Radius, Udo A1 - Santos, Webster L. A1 - Marder, Todd B. T1 - Regio‐ and Stereoselective Synthesis of 1,1‐Diborylalkenes via Brønsted Base‐Catalyzed Mixed Diboration of Alkynyl Esters and Amides with BpinBdan JF - European Journal of Organic Chemistry N2 - The NaOtBu‐catalyzed mixed 1,1‐diboration of terminal alkynes using the unsymmetrical diboron reagent BpinBdan (pin = pinacolato; dan = 1,8‐diaminonaphthalene) proceeds in a regio‐ and stereoselective fashion affording moderate to high yields of 1,1‐diborylalkenes bearing orthogonal boron protecting groups. It is applicable to gram‐scale synthesis without loss of yield or selectivity. The mixed 1,1‐diborylalkene products can be utilized in Suzuki–Miyaura cross‐coupling reactions which take place selectivly at the C–B site. DFT calculations suggest the NaOtBu‐catalyzed mixed 1,1‐diboration of alkynes occurs through deprotonation of the terminal alkyne, stepwise addition of BpinBdan to the terminal carbon followed by protonation with tBuOH. Experimentally observed selective formation of (Z)‐diborylalkenes is supported by our theoretical studies. KW - boronate esters KW - borylation KW - cross‐coupling KW - synthesis design KW - structure elucidation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214728 VL - 2020 IS - 13 SP - 1941 EP - 1946 ER - TY - JOUR A1 - Liu, Xiaocui A1 - Ming, Wenbo A1 - Zhang, Yixiao A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Kupferkatalysierte Triborierung: Einfache, atomökonomische Synthese von 1,1,1‐Triborylalkanen aus terminalen Alkinen und HBpin JF - Angewandte Chemie N2 - 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 kostengünstigen und einfach zugänglichen Kupfersalzes Cu(OAc)2 als Katalysator realisiert. Das Verfahren zeichnet sich durch ein breites Substratspektrum, eine außerordentliche Selektivität und eine hohe Toleranz gegenüber funktionellen Gruppen aus. Zudem kann die Reaktion ohne Ausbeuteverlust im Gramm‐Maßstab durchgeführt werden. Die somit erhaltenen 1,1,1‐Trialkylalkane können Anwendungen in der Herstellung von synthetisch wertvollen und bislang schwer zugänglichen α‐Vinylboronaten und zyklischen Boryl‐Verbindungen finden. Verschiedene Alkylgruppen können stufenweise über eine basenvermittelte deborylierende Alkylierung eingeführt werden, um racemische, tertiäre Alkylboronate herzustellen, die einfach in nützliche tertiäre Alkohole umgewandelt werden können. KW - Boronsäure KW - Dehydrierende Borylierung KW - Geminaler Bisboronat KW - Hydroborierung KW - Kreuzkupplung Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212189 VL - 131 IS - 52 ER - TY - JOUR A1 - Liu, Zhiqiang A1 - Budiman, Yudha P. A1 - Tian, Ya‐Ming A1 - Friedrich, Alexandra A1 - Huang, Mingming A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Copper‐Catalyzed Oxidative Cross‐Coupling of Electron‐Deficient Polyfluorophenylboronate Esters with Terminal Alkynes JF - Chemistry – A European Journal N2 - We report herein a mild procedure for the copper‐catalyzed oxidative cross‐coupling of electron‐deficient polyfluorophenylboronate esters with terminal alkynes. This method displays good functional group tolerance and broad substrate scope, generating cross‐coupled alkynyl(fluoro)arene products in moderate to excellent yields. Thus, it represents a simple alternative to the conventional Sonogashira reaction. KW - boronate esters KW - coupling reactions KW - fluorine KW - fluoroarenes KW - Sonogashira reaction Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224362 VL - 26 IS - 71 SP - 17267 EP - 17274 ER - TY - JOUR A1 - Liu, Zhiqiang A1 - Kole, Goutam Kumar A1 - Budiman, Yudha P. A1 - Tian, Ya-Ming A1 - Friedrich, Alexandra A1 - Luo, Xiaoling A1 - Westcott, Stephen A. A1 - Radius, Udo A1 - Marder, Todd B. T1 - Transition metal catalyst-free, base-promoted 1,2-additions of polyfluorophenylboronates to aldehydes and ketones JF - Angewandte Chemie International Edition N2 - 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. KW - inorganic chemistry KW - transition metal-free KW - alcohol KW - 1,2-additionreaction KW - boronateesters KW - fluoroarene Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256487 VL - 60 IS - 30 ER - TY - JOUR A1 - Maier, Jan A1 - Marder, Todd B. T1 - Mechanistic and Kinetic Factors of ortho‐Benzyne Formation in Hexadehydro‐Diels‐Alder (HDDA) Reactions JF - Chemistry – A European Journal N2 - With the rapid development of the hexadehydro‐Diels‐Alder reaction (HDDA) from its first discovery in 1997, the question of whether a concerted or stepwise mechanism better describes the thermally activated formation of ortho‐benzyne from a diyne and a diynophile has been debated. Mechanistic and kinetic investigations were able to show that this is not a black or white situation, as minor changes can tip the balance. For that reason, especially, linked yne‐diynes were studied to examine steric, electronic, and radical‐stabilizing effects of their terminal substituents on the reaction mechanism and kinetics. Furthermore, the influence of the nature of the linker on the HDDA reaction was explored. The more recently discovered photochemical HDDA reaction also gives ortho‐arynes, which display the same reactivity as the thermally generated ones, but their formation might not proceed by the same mechanism. This minireview summarizes the current state of mechanistic understanding of the HDDA reaction. KW - Alkyne KW - Benzyne KW - Cyclization KW - Hexadehydro-Diels-Alder KW - reaction mechanism Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-239006 VL - 27 IS - 30 SP - 7978 EP - 7991 ER - TY - JOUR A1 - Merz, Julia A1 - Dietrich, Lena A1 - Nitsch, Jörn A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Moos, Michael A1 - Mims, David A1 - Lambert, Christoph A1 - Marder, Todd B. T1 - Synthesis, Photophysical and Electronic Properties of Mono‐, Di‐, and Tri‐Amino‐Substituted Ortho‐Perylenes, and Comparison to the Tetra‐Substituted Derivative JF - Chemistry – A European Journal N2 - We synthesized a series of new mono‐, di‐, tri‐ and tetra‐substituted perylene derivatives with strong bis(para‐methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11‐positions. The properties of our new donor‐substituted perylenes were studied in detail to establish a structure‐property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)‐Per possesses one reversible oxidation while (DPA)\(_{4}\)‐Per has four. The mono‐ and di‐substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83. KW - borylation KW - intersystem crossing KW - luminescence KW - polycyclic aromatic hydrocarbon KW - triarylamine Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-217835 VL - 26 IS - 52 SP - 12050 EP - 12059 ER - TY - JOUR A1 - Merz, Viktor A1 - Merz, Julia A1 - Kirchner, Maximilian A1 - Lenhart, Julian A1 - Marder, Todd B. A1 - Krueger, Anke T1 - Pyrene-Based "Turn-Off" Probe with Broad Detection Range for Cu\(^{2+}\), Pb\(^{2+}\) and Hg\(^{2+}\) Ions JF - Chemistry—A European Journal N2 - Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited for the fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra- and intermolecular excimers, which is however limiting the sensitivity range due to masking of e. g. quenching effects by the excimer emission. Herein we report a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This sensor can quantitatively detect Cu\(^{2+}\), Pb\(^{2+}\) and Hg\(^{2+}\) in organic solvents over a broad concentrations range, even in the presence of ubiquitous ions such as Na\(^{+}\), K\(^{+}\), Ca\(^{2+}\) and Mg\(^{2+}\). The strongly emissive sensor's fluorescence with a long lifetime of 165 ns is quenched by a 1 : 1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi-Hildebrand, and a non-linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health-relevant nM range and could be used e. g. for the monitoring of the respective ions in waste streams. KW - probes KW - fluorescence spectroscopy KW - pyrene KW - heavy metals KW - luminescence Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256803 VL - 27 IS - 31 ER - TY - JOUR A1 - Mueller, Stefan A1 - Lüttig, Julian A1 - Malý, Pavel A1 - Ji, Lei A1 - Han, Jie A1 - Moos, Michael A1 - Marder, Todd B. A1 - Bunz, Uwe H. F. A1 - Dreuw, Andreas A1 - Lambert, Christoph A1 - Brixner, Tobias T1 - Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways JF - Nature Communications N2 - 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. KW - Atomic and molecular interactions with photons KW - Optical spectroscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202529 VL - 10 ER - TY - JOUR A1 - Rauch, Florian A1 - Endres, Peter A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Hähnel, Martin A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Ji, Lei A1 - Marder, Todd B. T1 - An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers JF - Chemistry – A European Journal N2 - Using a new divergent approach, 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[HF\(_{2}\)] or [N(nBu\(_{4}\))][HF\(_{2}\)]; 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. Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. However, the conjugation does not increase further upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane subunits, suggesting a potential application as photonic antennas. KW - density functional calculations KW - electron storage KW - luminescence KW - redox KW - triarylborane Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218345 VL - 26 IS - 57 SP - 12951 EP - 12963 ER - TY - JOUR A1 - Rauch, Florian A1 - Fuchs, Sonja A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes JF - Chemistry – A European Journal N2 - Three different perfluoroalkylated borafluorenes (\(^{F}\)Bf) 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 \(^{F}\)Xyl\(^{F}\)Bf, \(^{F}\)Xyl: 2,6‐bis(trifluoromethyl)phenyl), a trifluoromethyl group (\(^{F}\)Mes\(^{F}\)Bf, \(^{F}\)Mes: 2,4,6‐tris(trifluoromethyl)phenyl) or a dimethylamino group (p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf, p‐NMe\(_{2}\)‐\(^{F}\)Xyl: 4‐(dimethylamino)‐2,6‐bis(trifluoromethyl)phenyl), respectively. All derivatives exhibit extraordinarily low reduction potentials, comparable to those of perylenediimides. The most electron‐deficient derivative \(^{F}\)Mes\(^{F}\)Bf was also chemically reduced and its radical anion isolated and characterized. Furthermore, all compounds exhibit very long fluorescent lifetimes of about 250 ns up to 1.6 μs; however, the underlying mechanisms responsible for this differ. The donor‐substituted derivative p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf exhibits thermally activated delayed fluorescence (TADF) from a charge‐transfer (CT) state, whereas the \(^{F}\)Mes\(^{F}\)Bf and FXylFBf borafluorenes exhibit only weakly allowed locally excited (LE) transitions due to their symmetry and low transition‐dipole moments. KW - borafluorenes KW - boron KW - EPR spectroscopy KW - fluorescence KW - heterocycles Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218390 VL - 26 IS - 56 SP - 12794 EP - 12808 ER - TY - INPR A1 - Stennett, Tom E. A1 - Bissinger, Philipp A1 - Griesbeck, Stefanie A1 - Ullrich, Stefan A1 - Krummenacher, Ivo A1 - Auth, Michael A1 - Sperlich, Andreas A1 - Stolte, Matthias A1 - Radacki, Krzysztof A1 - Yao, Chang-Jiang A1 - Würthner, Frank A1 - Steffen, Andreas A1 - Marder, Todd B. A1 - Braunschweig, Holger T1 - Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units T2 - Angewandte Chemie, International Edition N2 - 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. KW - boron KW - near-IR chromophores KW - conjugation KW - low-valent compounds KW - synthesis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180391 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, P. Bissinger, S. Griesbeck, S. Ullrich, I. Krummenacher, M. Auth, A. Sperlich, M. Stolte, K. Radacki, C.-J. Yao, F. Wuerthner, A. Steffen, T. B. Marder, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 6449. , which has been published in final form at https://doi.org/10.1002/anie.201900889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - JOUR A1 - Tumir, Lidija-Marija A1 - Pavlović Saftić, Dijana A1 - Crnolatac, Ivo A1 - Ban, Željka A1 - Maslać, Matea A1 - Griesbeck, Stefanie A1 - Marder, Todd B. A1 - Piantanida, Ivo T1 - The nature of the (oligo/hetero)arene linker connecting two triarylborane cations controls fluorimetric and circular dichroism sensing of various ds-DNAs and ds-RNAs JF - Molecules N2 - A series of tetracationic bis-triarylborane dyes, differing in the aromatic linker connecting two dicationic triarylborane moieties, showed very high submicromolar affinities toward ds-DNA and ds-RNA. The linker strongly influenced the emissive properties of triarylborane cations and controlled the fluorimetric response of dyes. The fluorene-analog shows the most selective fluorescence response between AT-DNA, GC-DNA, and AU-RNA, the pyrene-analog’s emission is non-selectively enhanced by all DNA/RNA, and the dithienyl-diketopyrrolopyrrole analog’s emission is strongly quenched upon DNA/RNA binding. The emission properties of the biphenyl-analog were not applicable, but the compound showed specific induced circular dichroism (ICD) signals only for AT-sequence-containing ds-DNAs, whereas the pyrene-analog ICD signals were specific for AT-DNA with respect to GC-DNA, and also recognized AU-RNA by giving a different ICD pattern from that observed upon interaction with AT-DNA. The fluorene- and dithienyl-diketopyrrolopyrrole analogs were ICD-signal silent. Thus, fine-tuning of the aromatic linker properties connecting two triarylborane dications can be used for the dual sensing (fluorimetric and CD) of various ds-DNA/RNA secondary structures, depending on the steric properties of the DNA/RNA grooves. KW - triarylborane KW - fluorescent probe KW - circular dichroism KW - DNA recognition KW - RNA recognition Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-319322 SN - 1420-3049 VL - 28 IS - 11 ER - TY - JOUR A1 - Wu, Zhu A1 - Dinkelbach, Fabian A1 - Kerner, Florian A1 - Friedrich, Alexandra A1 - Ji, Lei A1 - Stepanenko, Vladimir A1 - Würthner, Frank A1 - Marian, Christel M. A1 - Marder, Todd B. T1 - Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature JF - Chemistry—A European Journal N2 - Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (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. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently. KW - AIE KW - luminescence KW - phosphorescence KW - triarylborane KW - triplet Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318297 VL - 28 IS - 30 ER - TY - JOUR A1 - Wu, Zhu A1 - Nitsch, Jörn A1 - Marder, Todd B. T1 - Persistent room-temperature phosphorence from purely organic molecules and multi-component systems JF - Advanced Optical Materials N2 - 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. KW - inorganic chemistry KW - non-radiative decay KW - polymer matrix KW - intersystem crossing KW - luminescence KW - photophysics Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256415 VL - 9 IS - 20 ER - TY - JOUR A1 - Wu, Zhu A1 - Roldao, Juan Carlos A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Ferger, Matthias A1 - Würthner, Frank A1 - Gierschner, Johannes A1 - Marder, Todd B. T1 - Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP) JF - Angewandte Chemie N2 - Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)\(_{3}\) does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP. KW - boric acid KW - room-temperature phosphorescence (RTP) KW - optical materials Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318308 VL - 61 IS - 15 ER - TY - JOUR A1 - Zhang, Xiaolei A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Copper-Catalyzed Borylation of Acyl Chlorides with an Alkoxy Diboron Reagent: A Facile Route to Acylboron Compounds JF - Chemistry—A European Journal N2 - Herein, the copper-catalyzed borylation of readily available acyl chlorides with bis(pinacolato)diboron, (B\(_{2}\)pin\(_{2}\)) or bis(neopentane glycolato)diboron (B\(_{2}\)neop\(_{2}\)) is reported, which provides stable potassium acyltrifluoroborates (KATs) in good yields from the acylboronate esters. A variety of functional groups are tolerated under the mild reaction conditions (room temperature) and substrates containing different carbon-skeletons, such as aryl, heteroaryl and primary, secondary, tertiary alkyl are applicable. Acyl N-methyliminodiacetic acid (MIDA) boronates can also been accessed by modification of the workup procedures. This process is scalable and also amenable to the late-stage conversion of carboxylic acid-containing drugs into their acylboron analogues, which have been challenging to prepare previously. A catalytic mechanism is proposed based on in situ monitoring of the reaction between p-toluoyl chloride and an NHC-copper(I) boryl complex as well as the isolation of an unusual lithium acylBpinOBpin compound as a key intermediate. KW - boronate KW - catalysis KW - borylation KW - carbonyl KW - copper Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318318 VL - 28 IS - 42 ER -