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Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Intense Circularly Polarized Luminescence Induced by Chiral Supramolecular Assembly: The Importance of Intermolecular
Zheng-Fei Liu1, Xin-Xin Liu1, Han Zhang1
1Key Laboratory of Radiopharmaceuticals, Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China.
Abstract:
Herein we report on circularly polarized luminescence (CPL) emission originating from supramolecular chirality of organic microcrystals with a |glum| value up to 0.11. The microcrystals were prepared from highly emissive difluoroboron β-diketonate (BF2dbk) dyes R-1 or S-1 with chiral binaphthol (BINOL) skeletons. R-1 and S-1 exhibit undetectable CPL signals in solution but manifest intense CPL emission in their chiral microcrystals. The chiral superstructures induced by BINOL skeletons were confirmed by single-crystal XRD analysis. Spectral analysis and theoretical calculations indicate that intermolecular electronic coupling, mediated by the asymmetric stacking in the chiral superstructures, effectively alters excited-state electronic structures and facilitates electron transitions perpendicular to BF2bdk planes. The coupling increases cosθμ,m from 0.05 (monomer) to 0.86 (tetramer) and triggers intense optical activity of BF2bdk. The results demonstrate that optical activity of chromophores within assemblies can be regulated by both orientation and extent of intermolecular electronic couplings.
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