Small Figure-Eight Luminophores: Double-Twisted Tethered Cyclic Binaphthyls Boost Circularly Polarized Luminescence
Yuki Nojima, Dr. Masashi Hasegawa, Nobuyuki Hara, Prof. Dr. Yoshitane Imai, Prof. Dr. Yasuhiro Mazaki
Chemistry A European Journal Volume27, Issue19 April 1, 2021 Pages 5923-5929
Double-twisted cyclic binaphthyls, in which two naphthalenes are tethered by -O(CH2)nO- linkage (n=1–3), have been synthesized. X-ray analyses and DFT calculations revealed a tightly constrained stereogenic figure-eight geometry. Tethering of two naphthalenes by short linkage forces a small dihedral angle, and the cyclic binaphthyls with short tether (n=1, 2) exhibit remarkable boosting of the glum value (1.0–1.6×10−2) in circularly polarized luminescence (CPL) and unusual glum/gabs ratios (0.93–1.3). These experimental high |glum| values are in accord with the results of excited state TD-DFT calculations, which show transannular interactions and that consequent extensive delocalization occurs throughout the figure-eight π-core. As a result, the present figure-eight luminophore promote the elongation of the magnetic transition dipole moment that results in significant increases in glum values.
Circularly Polarized Luminescence