A Twisted Phosphor: Breaking T_1 Energy Conservation in Dopant-Matrix Organic Phosphorescence Systems

摘要

In the exciton model of organic compounds proposed by Kasha, energylevels of T_1 states are insensitive to microenvironment because of negligiblysmall transition dipole moments of T_1 states. This phenomenon of T_1 energyconservation holds true in most organic systems. Here a serendipitousfinding of a twisted organic phosphor that breaks T_1 energy conservationin dopant-matrix phosphorescence systems is reported. Specifically, thetwisted phosphor exhibits distinct phosphorescence colors and T_1 energylevels when doped into different organic matrices under ambient conditions.Time-dependent density functional theory calculations reveal that, whenthe twisted phosphor is in its freely rotating form, the increase of twistedangle leads to the increase of its T_1 energy level. After being planarized byalkyl cyclization, the phosphor shows the recovery of T_1 energy conservation.Owing to its sensitive T_1 level, the twisted phosphor functions as label-freeand visual probe for direct observation of polymer phase separation.