On the Phosphorescence of Benzologues of Furan, Thiophene, Selenophene, and Tellurophene: A Systematic Study of the Intra-annular Internal Heavy-atom Effect

Abstract

Phosphorescence in ethanol and n-pentane at 77 K of the benzologues 1 -8 of furan, thiophene, selenophene and tellurophene has been investigated. The rate constants of both the radiative (kPT) and non-radiative (kGT) deactivation of the lowest triplet state correlate linearly with [formula omitted] where & ckdenotes the Hückel AO coefficients in the HOMO of the carbon atoms bound to the hetero-atom and ξ is the spin-orbit coupling constant of the hetero-atom present. - The linear correlation observed between kPTand kGTis an example for the Orlandi-Siebrand rule. - The influence of an external heavy-atom perturber (methyl iodide) on phosphorescence lifetimes and the vibrational structure of phosphorescence spectra is the more efficient the less efficient is the internal perturbation caused by the intra-annular heavy-atom. © 1989, Verlag der Zeitschrift für Naturforschung. All rights reserved.