Radiative deactivation of states in molecules with heteroatoms on the C2v axis. Xanthone

Abstract

Abstract For the planar molecules of xanthone and its deuterated derivatives, the dipole moments of transitions T s ( 3 A 1 ( ππ * ))→ S 0 from the triplet sublevels s = z , y to vibrational levels of the out-of-plane B 1 modes, as well as the radiative rate constants k rad s , have been calculated. A predominant deactivation channel for the T z sublevel has been ascertained. The difference between the rate constants ( k rad z ≫ k rad y ) is associated with the different role of unshared electron pairs of the oxygen atoms of the ether and carbonyl groups. The effect of configurational mixing of the 3 A 1 ( ππ * ) and 3 A 2 ( nπ * ) states on the intensity distributions in the fine structure spectrum of the ππ * phosphorescence, related to the T z →S 0 and T y →S 0 transitions, as well as on the rate constants k rad s , is discussed. For the T y →S 0 transition, a similarity between the vibronic–spin–orbit coupling in the molecules of xanthone, dibenzo- p -dioxin and dibenzofurane is considered.