Synthesis of Blue Fluorescent Benzotriazoles Incorporating 2-(2-Hydroxyphenyl)-2H-Benzotriazole Derivatives and their Optical Properties and Photostability

Abstract

To gain insight into the improvement of photostability for blue fluorescent benzotriazole derivatives, we synthesized dyad molecules consisting of various derivatives and UV absorbers 2-(2-hydroxyphenyl)-2 H -benzotriazole components (2HPBTA) linked by an ester bond. The dyad molecules showed blue fluorescence, but their fluorescence quantum yields were lower than those of blue fluorescent benzotriazole derivatives without 2HPBTA. The quantum chemical calculations predicted that the excited state intramolecular proton transfer (ESIPT) is thermodynamically allowed for the dyad molecules and is a factor that inhibits radiative deactivation. The polymer films containing dyad molecules showed blue fluorescence, but their fluorescence intensities were decreased after continuous UV irradiation. This result suggested that the 2HPBTA components linked by an ester bond do not affect the photostability of the dyad molecules. On the other hand, the substituents on the benzene ring of blue fluorescent benzotriazole components significantly affected the fluorescence intensities of the dyad molecules.