TY - JOUR A1 - Zhang, Fangyuan A1 - Radacki, Krzysztof A1 - Braunschweig, Holger A1 - Lambert, Christoph A1 - Ravat, Prince T1 - Zinc-[7]helicenocyanine and its discrete π-stacked homochiral Dimer JF - Angewandte Chemie International Edition N2 - In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×10\(^6\) M\(^{−1}\) and 3.42×107 M\(^{−1}\) in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn\(^{-7}\)HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state. KW - organic chemistry KW - supramolecular assembly KW - chirality KW - helicenes KW - homochiral dimer KW - phthalocyanines Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256534 VL - 60 ER - TY - JOUR A1 - Zhang, Fangyuan A1 - Michail, Evripidis A1 - Saal, Fridolin A1 - Krause, Ana-Maria A1 - Ravat, Prince T1 - Stereospecific Synthesis and Photophysical Properties of Propeller-Shaped C\(_{90}\)H\(_{48}\) PAH JF - Chemistry - A European Journal N2 - Herein, we have synthesized an enantiomerically pure propeller‐shaped PAH, C\(_{90}\)H\(_{48}\), possessing three [7]helicene and three [5]helicene subunits. This compound can be obtained in gram quantities in a straightforward manner. The photophysical and chiroptical properties were investigated using UV/Vis absorption and emission, optical rotation and circular dichroism spectroscopy, supported by DFT calculations. The nonlinear optical properties were investigated by two‐photon absorption measurements using linearly and circularly polarized light. The extremely twisted structure and packing of the homochiral compound were investigated by single‐crystal X‐ray diffraction analysis. KW - chirality KW - enantiomers KW - helicenes KW - polycyclic aromatic hydrocarbons KW - stereospecific sythesis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208682 VL - 25 IS - 71 ER - TY - JOUR A1 - Full, Julian A1 - Panchal, Santosh P. A1 - Götz, Julian A1 - Krause, Ana‐Maria A1 - Nowak‐Król, Agnieszka T1 - Modular Synthesis of Organoboron Helically Chiral Compounds: Cutouts from Extended Helices JF - Angewandte Chemie International Edition N2 - Two types of helically chiral compounds bearing one and two boron atoms were synthesized by a modular approach. Formation of the helical scaffolds was executed by the introduction of boron to flexible biaryl and triaryl derived from small achiral building blocks. All‐ortho‐fused azabora[7]helicenes feature exceptional configurational stability, blue or green fluorescence with quantum yields (Φ\(_{fl}\)) of 18–24 % in solution, green or yellow solid‐state emission (Φ\(_{fl}\) up to 23 %), and strong chiroptical response with large dissymmetry factors of up to 1.12×10\(^{-2}\). Azabora[9]helicenes consisting of angularly and linearly fused rings are blue emitters exhibiting Φ\(_{fl}\) of up to 47 % in CH\(_{2}\)Cl\(_{2}\) and 25 % in the solid state. As revealed by the DFT calculations, their P–M interconversion pathway is more complex than that of H1. Single‐crystal X‐ray analysis shows clear differences in the packing arrangement of methyl and phenyl derivatives. These molecules are proposed as primary structures of extended helices. KW - chirality KW - circular dichroism KW - fluorescence KW - helicene KW - organoboron Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225775 VL - 60 IS - 8 SP - 4350 EP - 4357 ER - TY - THES A1 - Safont Sempere, Marina Montserrat T1 - Chiral self-sorting of atropo-enantiomeric perylene bisimide dyes T1 - Chirale Self-sortierung von Atropo-enantiomerische Perilene Bisimide Farbstofe N2 - This thesis included the synthesis of conformationally stable chiral perylene bisimide (PBI) dyes, the study of their optical properties in solution and their chiral self-sorting behaviour in nonpolar solvents in which dimerization via pi-pi-stacking takes place. Furthermore, the influence of PBI core chirality on the properties of these dyes in the condensed state has been also studied. We have demonstrated and quantified the prevalence of chiral self-recognition over self-discrimination in pi-stacking dimerization of PBIs. It has been shown that this self-recognition event is compromised by the increasing flexibility of the structures related to the size of the OEG bridging units. Moreover, the inherent chirality of these PBIs has been proven to strongly influence their condensed state properties, for which large differences between the pure enantiomers and the racemates were revealed, as well as between the different bridged macrocyclic PBIs. N2 - Das Ziel der vorliegenden Arbeit war die Synthese von konformationsstabilen chiralen Perylenbisimidfarbstoffen (PBI), die Bestimmung ihrer optischen Eigenschaften in Lösung und ihrer chiralen Selbstsortierung in unpolaren Lösungsmitteln, in denen Dimerisierung durch pi-pi-Stapelung stattfindet. Des Weiteren wurde noch der Einfluss der PBI Kernchiralität auf die flüssigkristallinen Eigenschaften untersucht. Zusammenfassend konnte im Rahmen dieser Arbeit die Bevorzugung der chiralen Selbst-Erkennung gegenüber der Selbst-Diskriminierung in pi-gestapelten dimerisierten PBIs quantifiziert und bewiesen werden. Eine erhöhte Flexibilität der Moleküle durch Verlängerung der OEG Brückeneinheiten verringert jedoch die Qualität dieses Selbsterkennungsvorgangs. Des Weiteren hat die Chiralität dieser PBIs einem sehr starken Einfluss auf die Eigenschaften der kondensierten Materie, in welcher große Unterschiede für reine Enantiomere und das Racemat sowie zwischen PBIs mit unterschiedlichen Brückeneinheiten gefunden wurden. KW - Farbstoff KW - Selbstorganisation KW - Chiralität KW - Atropisomerie KW - Self-Sortierung KW - pi-pi Wechselwirkungen KW - Aggregation KW - self-sorting KW - chirality KW - pi-pi- stacking Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-55359 ER - TY - JOUR A1 - Renner, Rebecca A1 - Mahlmeister, Bernhard A1 - Anhalt, Olga A1 - Stolte, Matthias A1 - Würthner, Frank T1 - Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area JF - Chemistry - A European Journal N2 - A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol\(^{−1}\) for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol\(^{−1}\). The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy. KW - Suzuki coupling KW - perylenebisimide dyes KW - circular polarized luminescence KW - chirality Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-249070 VL - 27 IS - 46 SP - 11997 EP - 12006 ER -