Photoresponsive triazole-based donor–acceptor molecules: color change and heat/air-stable diradicals

Abstract

Photoinduced generation of stable radicals is important for photochromism, photoswitching and other applications, but was limited only to a few systems. An unprecedented series of triazole-based donor–acceptor organic molecules were found to form heat/air-stable triplet diradicals in the solid state and show a clear color change through photoinduced intramolecular charge separation, which was confirmed by electron spin resonance studies, ultrafast laser flash photolysis analyses and density functional theoretical calculations. In these molecules, electron-withdrawing substituents were more beneficial to the photoinduced charge separation than electron-donating ones. Moreover, a high molecular dipole moment was more conducive to photoinduced charge separation in the presence of an electron-withdrawing substituent.