Impact of Optical Purity on the Light Harvesting Property in Supramolecular Nanofibers

J. Phys. Chem. Lett. 2018, 9, 16, 4516-4521
DOI: 10.1021/acs.jpclett.8b02015

Ramarani Sethy^a, Rémi Métivier*^b, Arnaud Brosseau^b, Tsuyoshi Kawai*^a and Takuya Nakashima*^a
a Graduate School of Science and Technology, Division of Materials Science, Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192, Japan
^b PPSM, ENS Cachan, CNRS, Université Paris-Saclay, 94235 Cachan, France

Abstract
Supramolecular ordering and orientation of chromophores are tremendously accomplished in photosynthetic light harvesting complexes, which are crucial for long-range transfer of collected solar energy. We herein demonstrate the importance of optical purity on the organization of chromophoric chiral molecules for efficient energy migration. Enantiomeric bichromophoric compounds, which self-assemble into nanofibers capable of chiral recognition, were mixed to form supramolecular coassemblies with variable enantiopurity. The chiral molecules self-assembled into extended fibers regardless of enantiopurity, while their morphology was dependent on the enantiomeric excess. The optical purity of assemblies also had an effect on the emission efficiency; the nanofibers with higher enantiomeric excess afforded a larger emission quantum yield. The presence of an opposite enantiomer is considered to deteriorate the chiral molecular packing suitable for directional growth of the nanofiber, efficient exciton migration, and chiral guest recognition.