Radiationless Transitions in Substituted Benzopyrylium Dyes: Competing Adiabatic Photoreactions Towards Nonradiative Funnels

A wide variety of substituted flavylium salts and bridged derivatives are compared with respect to their fluorescence quantum yields and lifetimes. The dependence of the nonradiative decay rate constant on substitution pattern, on twisting possibility and on solvent polarity could be explained by the formation of non‐fluorescent Twisted Intramolecular Charge Transfer (TICT) states. In some dyes, two different TICT channels compete. Molecules‐in‐molecules (MIM) calculations are used to analyze and predict different TICT formation possibilities.