Time-Resolved Electron Paramagnetic Resonance Study of Rhodium(III) Corrole Excited States

Photoexcited states of three Rh(III) 5,10,15-tris(pentafluorophenyl)corroles coordinated by different axial ligands; namely, triphenylphosphine P(C6H5)3 group (1), pyridine C6H5N group (2), and two pyridine groups (3) were studied by X- and Q-band time-resolved electron paramagnetic resonance (TREPR) in frozen toluene and liquid crystal E-7. Transient mutations were utilized to identify multiplicity of the detected paramagnetic species. The spectra of 1 and 2 were assigned to triplet (3ππ*) states, while contributions of triplet (3dd and charge transfer 3CT) and quintet (5dd) states were revealed in the spectrum of 3. The results are interpreted in terms of a peculiar nature of transition metal complexes with the unfilled d-shell, where close lying electronic states of different multiplicities may be mixed through configurational, spin−orbit, and vibronic coupling. From the EPR spectra, the spin−orbit coupling constant was estimated to be about 25 cm−1. It is shown that different axial ligation of complex...