Intramolecular energy transfer in a rhodium(III) metalloorganic bichromophore system. Photochemical and photoluminescence studies

Article abstract of DOI:10.1021/ic50220a031

Reported are the photochemical, photoluminescence, and spectral studies of a series of pentaammine(organonitrilo)rhodium(III) compounds, Rh(NH₃)₅(N≡C-R)³⁺ (where R is a phenyl, benzyl, or 2-phenylethyl group or a substituted derivative). The absorption spectroscopy exhibits features attributable to both ππ* and ligand field transitions. The luminescence spectra, however, exhibit only ligand field (LF) emissions regardless of whether the ππ* or LF states are initially populated. The luminescence lifetimes at 77 K are also characteristic of LF states. Irradiation of the ππ* or LF bands in aqueous solutions leads to photosubstitution of the organonitrile ligand with the quantum yields being somewhat smaller for λ_irr = 254 nm (ππ*) than 313 nm (LF) in most cases. The results are discussed in terms of the efficiency of interconfigurational energy transfer between ππ* and LF states.