Spectroscopic Studies of Ruthenium(II) Complexes. Assignment of the Luminescence

Absorption and emission spectra of nine ${\text{(4d)}}^6$ ruthenium(II) complexes dissolved in rigid glasses are reported. Tris(bipyridine), tris($o$ ‐phenanthroline), bis(tripyridine), and a series of cis‐substituted bis(bipyridine) complexes of ruthenium(II) were synthesized. The cis substituents were cyanide, ethylenediamine, pyridine, oxalate, and chloride chosen for their order in the spectrochemical series. On the basis of the structures of the emission spectra, their energy relationships with charge‐transfer absorption bands, and the lack of correlation between the energies of emission and predictions from crystal‐field theory, it is proposed that the intense luminescence observed from all the complexes under excitation by ultraviolet light is charge transfer in nature.