The effect of the nonplanarity of heterocyclic analogues of fluorene with the phosphorus atom on spin-orbit interactions

Abstract

The transition dipole moments P00S for the transitions from the sublevels s=z,y, and x of the triplet electronic states 3A″, which are caused by intramolecular spin-orbit (SO) interactions, are calculated. The calculation is carried out for molecules of heterocyclic analogues of fluorene containing phosphorus and nitrogen (namely, the groups P-H, P-C6H5, and N-H). The influence that the planar and nonplanar models of the molecules, as well as the substituents −C6H5 and −H at the heteroatom (HA), exert on the values of (P00S)2 and on the directions of the corresponding vectors is considered. The values of the component \(k_{SO^ \sim } \sum _s (P_{00}^s )^2 \) of the radiative deactivation rate constant of the T1 state are calculated. It is ascertained that, in the series of molecules with HA = N, O, P, and S, both the calculated values of kSO and those experimentally determined from an analysis of the intensity distribution in fine-structure phosphorescence spectra vary little, whereas the constant of the SO coupling in the heteroatom ςHA increases substantially along this series. The reason for the weak influence of ςHA on values of kSO—common for both planar and nonplanar molecules—is found.