Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature.

Abstract

Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non‐radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p‐bromophenyl)‐bis(2,6‐dimethylphenyl)boranes. Among the 3 isomers ( o ‐, m ‐ and p ‐BrTAB) synthesized, the ortho‐one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o ‐BrTAB, the short lifetime component is ascribed to the T1 M state of the monomer which emits the higher energy phosphorescence. The long‐lived, lower energy phosphorescence emission is attributed to the T1 A state of an aggregate, with multiple intermolecular interactions existing in crystalline o ‐BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.