Cyclodextrins with Multiple Pyrenyl Groups: An Approach to Organic Molecules Exhibiting Bright Excimer Circularly Polarized Luminescence
Hajime Shigemitsu, Kosei Kawakami, Yuuya Nagata, Rikuo Kajiwara, Shintaro Yamada, Tadashi Mori, Toshiyuki Kida
Abstract
Abstract We report a simple and effective approach to organic molecules exhibiting bright circularly polarized luminescence (CPL) by combining a chiral cyclic molecular scaffold and multiple excimer‐enabling moieties. An α‐cyclodextrin ( CyD ) scaffold was modified with six pyrenyl groups to obtain pyrene–cyclodextrins ( PCD s) in a one‐step synthesis from commercially available compounds. The PCDs exhibited high molar extinction coefficients (ϵ≈10 5 M −1 cm −1 ), polarized emission with a good dissymmetry factor (|g lum |≈10 −2 ), and quantum yield (Φ f ≈0.5). Owing to the excellent photophysical properties of the PCDs, the circularly polarized luminescence brightness (B CPL ) reached 340 M −1 cm −1 . Photophysical and chiroptical studies of the PCD s with only five pyrene units and with linkers of various lengths connecting the CyD with the pyrene units revealed that the formation of a pyrene excimer in a spatially crowded environment is crucial for CPL anisotropy. This study paves the way for the development of bright CPL organic molecules.