Bright Fluorescent p‐Phenylene‐bridged Triarylmethyl Highly Stable Diradical

Abstract Two 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−(Hex 2 Ph)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.