Zero-field splittings of the two lowest excited electronic states in crystalline [Ru(bpy)3]X2 with X=PF6, ClO4

Abstract

For the title compounds zero-magnetic field ODMR signals have been observed on the zero-phonon lines which correspond to the two lowest excited states and which result from Ru4d→bpyπ* charge-transfer transitions. The splitting into sublevels are of the order of 0.1 cm−1 and the corresponding electronic states may be classified as doubly degenerate on the basis of the usual resolution of the optical emission spectra. Several microwave resonances are detected and assigned to different sites of the [Ru(bpy)3]2+ chromophores. Small relaxation rates between the sublevels (compared to other excited-state deactivation rates) are found to be important for a description of the spectroscopic properties at low temperatures.