Vibronic-spin-orbit interactions in heterocyclic analogues of fluorene with the N and O heteroatoms

Abstract

The transition dipole moments P 0 s for the transitions from the electronic triplet state 3 B 2(ππ*) to vibrational sublevels of the vibrational out-of-plane modes n of the carbazole and dibenzofuran molecules are calculated. The values of the radiative deactivation rate constant k rad s of the triplet sublevels T s are determined along with the components k SO s and k VSO s of this constant, which depend on the intramolecular spin-orbit (SO) and vibronic-spin-orbit (VSO) interaction. It is ascertained that k rad z > k rad y . For different structural units of the molecules (the heteroatom and the carbon atoms of the dibenzene fragment), the effect of the SO coupling on the constant k VSO∼Σs, n (P 0 s )2 is studied. A competition between the effects on k VSO from the SO coupling in the carbon atoms and in the light N and O heteroatoms is revealed. This competition accounts for the weak influence of the heteroatom on this component of the rate constant k rad in these molecules. It is ascertained that the intensity distribution among the vibronic lines in the phosphorescence spectra of carbazole and dibenzofuran I 0n ∼Σs (P 0 s )2 is different due to the substantially different influence of the N and O heteroatoms on the deactivation of the triplet sublevel T y .