Achieving Single-Component Phosphorescent Dual Emission via Molecular Conformation Regulation

Subtle
changes in molecular conformation can significantly influence
the frontier orbital distribution and energy level arrangement. By
the construction of molecules with distinct stable conformations,
dual-emission is achieved through their differentiated triplet energy
levels. However, a long-standing challenge in this field lies in balancing
the relationships among these conformational states, overcoming rapid
energy exchange, and mutual quenching between them. Herein, we designed
two crystal materials with room-temperature phosphorescence (RTP)
dual emission properties in a single-component system through substituent
engineering: 1,2-bis­(4-methylphenyl)­ethanedione (p-BJ) and 1,2-bis­(4-methoxyphenyl)­ethanedione
(p-BOX). These crystals exhibit different substitution sites on their
benzene rings, effectively modulating intermolecular steric hindrance.
As steric hindrance diminishes, intramolecular interactions weaken,
enabling the excited-state conformations of p-BJ and p-BOX crystals
to relax into more planar structures under an external force. This
conformational transformation ultimately induces the RTP dual emission
in p-BJ and p-BOX. This work provides a new approach for achieving
single-component dual emission by regulating the excited-state conformation.