OPTICALLY DETECTED MAGNETIC-RESONANCE STUDY OF PHOTO-EXCITED RH-3+-TRISDIIMINE CHELATES

The phosphorescent 3-pi-pi* state of [Rh(phen)n(bPY)3-n](ClO4)3, with n = 0, 2 and 3, has been studied using optically detected magnetic resonance (ODMR) spectroscopy. The zero-field ODMR transitions of [Rh(phen)2(bpy)](ClO4)3 have been obtained and correspond with the zero-field ODMR transitions observed for both [Rh(bpy)3](ClO4)3 and [Rh(phen)3](ClO4)3. Furthermore, from phosphorescence microwave double resonance (PMDR) experiments it is found that the optical excitation is trapped at either a bipyridyl or a phenanthroline ligand molecule in the phosphorescent triplet state. Finally, time-resolved adiabatic fast passage experiments yield the triplet sublevel lifetimes of photo-excited [Rh(phen)2(bPY)](XClO4)3 and their origin is attributed to spin-orbit induced mixing of 3-pi-pi* and 1d-pi* configurations.