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41.
Juan Tolosa Dr. Chris Kub Uwe H. F. Bunz Prof. 《Angewandte Chemie (International ed. in English)》2009,48(25):4610-4612
Out on a limb : Sonogashira coupling of a suitable AB2 monomer containing two iodine and one alkyne group forms a hyperbranched conjugated polymer that is studded with iodine end groups (see picture: I purple). These iodine groups are a perfect handle for convenient, efficient, and high‐yielding post‐functionalization to access hyperbranched, fluorescent poly(phenyleneethynylene)s.
42.
Gard MN Zucchero AJ Kuzmanich G Oelsner C Guldi D Dreuw A Bunz UH Garcia-Garibay MA 《Organic letters》2012,14(4):1000-1003
Steady-state and time-resolved polarized spectroscopy studies reveal that electronic excitation to the third excited state of 1,4-distyryl-2,5-bis(arylethynyl)benzene cruciforms results in fluorescence emission that is shifted an angle of ca. 60°. This result is consistent with quantum chemical calculations of the lowest electronic excited states and their transition dipole moments. The shift originates from the disjointed nature of the occupied molecular orbitals being localized on the different branches of the cruciforms. 相似文献
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44.
Dipl. Chem. Benjamin D. Lindner Dipl. Chem. Jens U. Engelhart Michaela Märken Olena Tverskoy Dr. Anthony L. Appleton Dr. Frank Rominger Dr. Kenneth I. Hardcastle Prof. Markus Enders Prof. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4627-4633
A series of functionalized diaza‐ and tetraazatetracenes was synthesized, either by condensation of an aromatic diamine with an ortho‐quinone/diethyloxalate followed by chlorination with POCl3 to give diazatetracenes or by palladium‐catalyzed coupling of a phenylenediamine with various 2,3‐dichloroquinoxalines to give tetraazatetracenes (after oxidation with MnO2). Representative examples included halogenated and nitrated derivatives. The optical properties of these azatetracenes were discussed with respect to their molecular structures and substitution patterns. The diazatetracenes and tetraazatetracenes formed two different groups that had significantly different electronic structures and properties. Furthermore, 1,2,3,4‐tetrafluoro‐6,11‐bis((triisopropylsilyl)ethynyl)benzo[b]phenazine was synthesized, which is the first reported fluorinated diazatetracene. Single‐crystal X‐ray analysis of this compound is reported. 相似文献
45.
Daniel Canseco‐Gonzalez Dr. Andrzej Gniewek Michal Szulmanowicz Dr. Helge Müller‐Bunz Prof. Dr. Anna M. Trzeciak Prof. Dr. Martin Albrecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):6055-6062
A series of PEPPSI‐type palladium(II) complexes was synthesized that contain 3‐chloropyridine as an easily removable ligand and a triazolylidene as a strongly donating mesoionic spectator ligand. Catalytic tests in Suzuki–Miyaura cross‐coupling reactions revealed the activity of these complexes towards aryl bromides and aryl chlorides at moderate temperatures (50 °C). However, the impact of steric shielding was the inverse of that observed with related normal Nheterocyclic carbenes (imidazol‐2‐ylidenes) and sterically congested mesityl substituents induced lower activity than small alkyl groups. Mechanistic investigations, including mercury poisoning experiments, TEM analyses, and ESI mass spectrometry, provide evidence for ligand dissociation and the formation of nanoparticles as a catalyst resting state. These heterogeneous particles provide a reservoir for soluble palladium atoms or clusters as operationally homogeneous catalysts for the arylation of aryl halides. Clearly, the substitution of a normal N‐heterocyclic carbene for a more basic triazolylidene ligand in the precatalyst has a profound impact on the mode of action of the catalytic system. 相似文献
46.
Dr. Matthias Müller M. Sc. Steffen Maier Olena Tverskoy Dr. Frank Rominger Dr. Jan Freudenberg Prof. Uwe H. F. Bunz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(5):1982-1985
In combination with bulky substituents at the core, fourfold benzannulation at the cata-positions stabilizes a nonacene sufficiently to allow its isolation and characterization by 1H NMR and X-ray analysis. The four benzo units blueshift the absorption spectrum in comparison to a solely linear nonacene, but significantly increase the stability in the solid state. 相似文献
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48.
Ritesh Haldar Mariana Kozlowska Michael Ganschow Samrat Ghosh Marius Jakoby Hongye Chen Farhad Ghalami Weiwei Xie Shahriar Heidrich Yusuke Tsutsui Jan Freudenberg Shu Seki Ian A. Howard Bryce S. Richards Uwe H. F. Bunz Marcus Elstner Wolfgang Wenzel Christof Wll 《Chemical science》2021,12(12):4477
Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the density of defects. We have employed a new type of crystalline assembly strategy to engineer the arrangement of the OSC pentacene in a structure not realized as crystals to date. Our approach is based on metal–organic frameworks (MOFs), in which suitably substituted pentacenes act as ditopic linkers and assemble into highly ordered π-stacks with long-range order. Layer-by-layer fabrication of the MOF yields arrays of electronically coupled pentacene chains, running parallel to the substrate surface. Detailed photophysical studies reveal strong, anisotropic inter-pentacene electronic coupling, leading to efficient charge delocalization. Despite a high degree of structural order and pronounced dispersion of the 1D-bands for the static arrangement, our experimental results demonstrate hopping-like charge transport with an activation energy of 64 meV dominating the band transport over a wide range of temperatures. A thorough combined quantum mechanical and molecular dynamics investigation identifies frustrated localized rotations of the pentacene cores as the reason for the breakdown of band transport and paves the way for a crystal engineering strategy of molecular OSCs that independently varies the arrangement of the molecular cores and their vibrational degrees of freedom.Pentacene assembled into 1D arrays using a metal–organic framework (MOF) approach. This cofacial packing motif, which is not present in pentacene bulk, shows an interesting interplay of band-like and hopping-type transport. 相似文献
49.
Hao Zhang Eugen A. Kotlear Soh Kushida Steffen Maier Dr. Frank Rominger Dr. Jan Freudenberg Prof. Dr. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8137-8143
Two linear 1,4-distyrylbenzenes and five star-shaped 1,3,5-tristyrylbenzene derivatives ( L2a and L2b , Y0–Y3 and YNBu ) were synthesized and spectroscopically characterized. The photophysical properties, optical response to acid and metal ions were investigated. Upon backbone extension of linear distyrylbenzenes or the introduction of dibutylanilines, the electronic spectra are redshifted. Incorporation of electron-deficient pyridyl units does not significantly affect the optical properties. Variation of the number of pyridine rings and substitution pattern tune the fluorescence response to acids and metal ions. The novel arenes discriminate Al3+, Mn2+, Fe3+, Fe2+, Cd2+, Ag+ and Hg2+. 相似文献
50.
Vibe B. Jakobsen Elzbieta Trzop Laurence C. Gavin Emiel Dobbelaar Shalinee Chikara Xiaxin Ding Kane Esien Helge Müller‐Bunz Solveig Felton Vivien S. Zapf Eric Collet Michael A. Carpenter Grace G. Morgan 《Angewandte Chemie (International ed. in English)》2020,59(32):13305-13312
Domain wall motion is detected for the first time during the transition to a ferroelastic and spin state ordered phase of a spin crossover complex. Single‐crystal X‐ray diffraction and resonant ultrasound spectroscopy (RUS) revealed two distinct symmetry‐breaking phase transitions in the mononuclear Mn3+ compound [Mn(3,5‐diBr‐sal2(323))]BPh4, 1. The first at 250 K, involves the space group change Cc→Pc and is thermodynamically continuous, while the second, Pc→P1 at 85 K, is discontinuous and related to spin crossover and spin state ordering. Stress‐induced domain wall mobility was interpreted on the basis of a steep increase in acoustic loss immediately below the the Pc‐P1 transition 相似文献