Manipulating P States of Organophosphine Polymers to Enhance Multi-Channel Synergetic Room-Temperature Phosphorescence

According to El-Sayed's rule, nπ* component would facilitate intersystem crossing (ISC) and room-temperature phosphorescence (RTP) of organic molecules. However, purposeful molecular design still faces big challenge due to insufficient understanding of inherent effect of nπ* states on RTP. Herein, phosphorus-containing groups of triphenylphosphine, triphenylphosphine oxide, and tetraphenylphosphonium bromide are introduced in polyacrylamide matrix, corresponding to PAM-TPP, PAM-TPPO, and PAM-TPP⁺. It shows that phosphorus ("P") states determine excited-state compositions of these polymers and, more importantly, result in different RTP processes. p-π conjugation between P atom and phenyls in PAM-TPP integrates ISC acceleration and triplet convergence to stabilize triplet states (T_n*). In contrast, P = O localized nπ* state of PAM-TPPO competes with ππ* states of phenyls, while PAM-TPP⁺ has pure ππ* states. In contrast to RTP-free PAM-TPPO and PAM-TPP⁺, with RTP dependent on ¹ππ* excitation, PAM-TPP achieves the best RTP performance, including the longest lifetime beyond 250 ms, the highest efficiency reaching 10.8%, and the limited excitation dependence, owing to its more than fourfold larger ISC rate constants reaching 10^-7 s^-1 and doubled RTP proportions. This work clarifies the importance of nπ*-ππ* synergy for developing high-performance RTP materials.