Persistent Room‐Temperature Phosphorescent Triazole Derivatives with High Quantum Yields and Long Lifetimes

Abstract Pure organic persistent room‐temperature phosphorescence (p‐RTP) materials have attracted rapidly growing attention due to their unique photophysical properties and wide potential practical applications. However, most of the reported pure organic p‐RTP materials have low quantum yields and short lifetimes, and many p‐RTP compounds contain large π‐conjugated structures, which are difficult and complex to synthesize. Herein, a series of triazole derivatives with efficient p‐RTP emissions is reported. 2H‐1,2,3‐triazole‐4,5‐dicarboxylic acid (TDAc) is first found to exhibit green RTP under 312 nm excitation. Then, a series of ionized products of TDAc and their isomers with red‐shifted RTP emissions are further obtained by ionization of TDAc. Among them, the sodium 2H‐1,2,3‐triazole‐4‐carboxy‐5‐carboxylate can emit RTP with an ultra‐long phosphorescence lifetime (3.25 s) and high photoluminescence (PL) and p‐RTP quantum yields of 31.3% and 14.2%, respectively, as well as mechanorochromic behavior. Experimental results and theoretical calculations prove that strong intra‐/intermolecular interactions including hydrogen bonding and ionic bonding promote the overlap of molecular orbitals to form effective through‐space conjugation (TSC) and greatly stabilize the conformations, thus achieving efficient p‐RTP emissions. This work provides a simple and efficient strategy for designing p‐RTP compounds with high quantum yields.