OPTICALLY DETECTED MAGNETIC-RESONANCE SPECTROSCOPY OF RHODIUM(III) MIXED-CHELATE COMPLEXES

An optically detected magnetic resonance study of the lowest ''cited s tate of [Rh(thpy) (phpy) (bpy)]+, doped into a single Crystal Of [Rh(P hPy)2(bpy)]PF6, is reported. Here, thpy-=2,2'-thienylpyridine, phpy-=2 -phenylpyridine and bpy=2,2'-bipyridine. In emission, the dopant molec ule gives rise to two zero-phonon lines, at 519.9 and 517.9 nm, respec tively. The two zero-phonon lines are characteristic of the two struct urally inequivalent forms of the dopant complex in the crystal lattice . From zero- and low-field ODMR data it is concluded that the lowest e xcited state in each of the two complex conformations is a phosphoresc ent triplet state. The fine structure splittings and the orientation o f the fine structure tensor main axes of the triplet states of the two complex conformations are found to be different. It is argued that fo r both conformations the lowest excited state is a thpy--localized 3pi pi state.