Vibronic interaction and triplet state photophysics of phenylisatin and oxindole

Photophysical study of phenylisatin and oxindole triplet states have been m ade at room temperature and in different glasses at 77K. Qualitatively, in all respects the compounds have identical spectroscopic characteristics. Ph osphorescence emission, excitation along with their polarization and lifeti me suggest that a perturbation of the zero-point level of emitting state (( 3)pi pi*) by a close-lying triplet state ((3)n pi*) leads to a number of ne w spectral features. The experimental observations have been interpreted sa tisfactorily in terms of a switch ((3)pi pi* State to (3)n pi*) in the char acter 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. (C ) 1999 Elsevier Science B.V. All rights reserved.