Vibronic interaction and triplet state photophysics of phenylisatin and oxindole

Abstract

Photophysical study of phenylisatin and oxindole triplet states have been made at room temperature and in different glasses at 77K. Qualitatively, in all respects the compounds have identical spectroscopic characteristics. Phosphorescence emission, excitation along with their polarization and lifetime suggest that a perturbation of the zero-point level of emitting state ( 3ππ*) by a close-lying triplet state ( 3nπ*) leads to a number of new spectral features. The experimental observations have been interpreted satisfactorily in terms of a switch ( 3ππ* state to 3nπ*) in the character of the lowest triplet states (T 1 and T 2) and also a similar switch in the character of the excited singlet states S 1 and S 2 for a change of glass matrix from MCH to ethanol. Invoking of first order and second order spin-orbit coupling explains the phosphorescence emission unambiguously.