Unveiling the Impact of Aggregation on Optical Anisotropy of Triazaacephenanthrylene Single Crystals. A Combined Quantum Crystallography and Conceptual Density Functional Theory Approach

Abstract

Triazaacephenanthrylene (TAAP) triclinic single crystals show substantial optical anisotropy of absorption and fluorescence. The maximum effect can be correlated with the direction perpendicular to the plane of chromophores connected in a head-to-tail manner via weak dispersive interactions. This phenomenon is uncommon as usually the existence of postulated π···π interactions between the molecules forming dimers or stacks cause quenching of fluorescence. Herein we present a comprehensive study of inter- and intramolecular interactions in the crystal of TAAP enriched with the investigation of aromaticity. Our results show that intramolecular interactions stabilize the overall conformation of the molecule whereas dispersive forces determine the aggregation between TAAP molecules. In fact, there is no conventional π···π interaction between the molecules in the dimer. Instead, we observed a close contact between the lone pair of the bridgehead N10B atom and π-deficient pyrazine ring from an adjacent molecule. Optical anisotropy in TAAP crystals was directly correlated with the alignment of the molecular transition dipole moments caused by specific molecular self-assembly.

Evolution of microstructures and hydrogen bond interactions within choline amino acid ionic liquid and water mixtures

“…Moreover, as seen from the ESP values, the –OH group is the HB donor of Cho + due to the maximum ESP value. 34 For Lys − and Asp − , the –COO − group (O2 and O3) is the main HB acceptor because of its minimum ESP value. Also, the anion can interact through the α-N2H 2 or R-N3H 2 group, of which the N atom can be the HB acceptor while the –NH 2 moiety can be the HB donor.…”

Current developments and trends in quantum crystallography

“…In the context of structure-property correlation investigations it is also worth mentioning some recent updates on the elucidation of (non-)linear optical properties of molecular crystals, particularly in the areas of optical anisotropy of fluorescent materials (Gryl et al, 2020) and of second harmonic generation (SHG; Wojnarska et al, 2019Wojnarska et al, , 2021. In the first case, the authors considered an organic crystal that exhibit substantial optical anisotropy of both absorption and fluorescence.…”