Effect of solvent on excited-state intramolecular proton transfer in benzotriazole photostabilizers

Abstract

The absorption and fluorescence characteristics of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole and its sulfonated analogue sodium 2-(2′-hydroxy-5′-methylphenyl)benzotriazolesulfonate have been studied in a range of solvents. The ground-state conformations contributing to absorption in these solutions have been resolved and characterized. Excited-state intramolecular proton transfer (ESIPT) is found to be strongly dependent on the hydrogen-bonding properties of the solvent. ESIPT is effectively prevented in those molecules which are hydrogen bonded to aprotic solvents whereas in protic hydrogen-bonding solvents at room temperature the results suggest that ESIPT may occur via an encounter comp..