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

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 pi-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. Persistent room-temperature phosphorescence of 2H-1,2,3-triazole-4,5-dicarboxylic acid (TDAc) and its ionized derivatives is reported for the first time. Sodium 2H-1,2,3-triazole-4-carboxy-5-carboxylate (TDA-2Na) exhibits a surprisingly ultra-long phosphorescence lifetime of 3.25 s and a quantum yield of 31.3%.image