Photochemistry of Pyrazolotriazole Azomethine Dyes

Abstract

Singlet and triplet state properties of pyrazolotriazole azomethine dyes have been examined using absorption, fluorescence, and flash photolysis techniques. Second derivative absorption spectroscopy and emission polarization studies suggest that the visible absorption band of these compounds is a single electronic transition and that the structure seen in non-polar solvents is vibronic. Room temperature emission is very weak, with quantum yields of ca. 1x 10^-4 Triplet state energies of ca. 100-118 kJ mol^-1 have been obtained from energy transfer studies and a lower limit of 10 ns has been estimated for the triplet state lifetime.