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  - Ravat, Prince
T1  - Carbo[n]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs
JF  - Chemistry – A European Journal
N2  - The most important stereodynamic feature of carbo[n]helicenes is the interconversion of their enantiomers. The Gibbs activation energy (ΔG≠(T)) of this process, which determines the rate of enantiomerization, dictates the configurational stability of [n]helicenes. High values of ΔG≠(T) are required for applications of functional chiral molecules incorporating [n]helicenes or helicene substructures. This minireview provides an overview of the mechanism, recent developments, and factors affecting the enantiomerization of [n]helicenes, which will accelerate the design process of configurationally stable functional chiral molecules based on helicene substructures. Additionally, this minireview addresses the misconception and irregularities in the recent literature on how the terms “racemization” and “enantiomerization” are used as well as how the activation parameters are calculated for [n]helicenes and related compounds.
KW  - [n]helicenes
KW  - configurational stability
KW  - enantiomerization
KW  - Gibbs activation energy
KW  - racemization
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225871
VL  - 27
IS  - 12
SP  - 3957
EP  - 3967
ER  - 
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  - INPR
A1  - Saal, Fridolin
A1  - Swain, Asim
A1  - Schmiedel, Alexander
A1  - Holzapfel, Marco
A1  - Lambert, Christoph
A1  - Ravat, Prince
T1  - Push-Pull [7]Helicene Diimide: Excited-State Charge Transfer and Solvatochromic Circularly Polarised Luminescence
N2  - In this communication we describe a helically chiral push-pull molecule named 9,10-dimethoxy-[7]helicene diimide, displaying fluorescence (FL) and circularly polarised luminescence (CPL) over nearly the entire visible spectrum dependent on solvent polarity. The synthesised molecule exhibits an unusual solvent polarity dependence of FL quantum yield and nonradiative rate constant, as well as remarkable gabs and glum values along with high configurational stability.
KW  - Helicene diimide
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-345207
UR  - https://doi.org/10.1039/D3CC04470J
ET  - submitted version
ER  -