Bright Fluorescent p‐Phenylene‐bridged Triarylmethyl Highly Stable Diradical

Abstract

AbstractTwo units of highly stable luminescent triarylmethyl radical, (3,5‐dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl radical (PyBTM), were bridged by p‐phenylene linker. The photoluminescence quantum yield (PLQY) of PyBTM−PhPyBTM was at most 0.4 % in various organic solvents. Adding two mesityl groups on the terminals did not improve the PLQY. In the MesPyBTM−PhPyBTM−Mes, the mesityl group did not worked as an electron donor unlike the previously reported monoradical MesPyBTM. However, adding two n‐hexyl groups on the bridging p‐phenylene did greatly improve it, and the PLQY of the PyBTM−(Hex2Ph)PyBTM was 7 % in dichloromethane and acetone, and 12 % in poly(methyl methacrylate) (PMMA) film. Twisting p‐phenylene linker by hexyl groups hindered the π‐conjugation and suppressed the non‐radiative decay of the excited state.