RESONANCE RAMAN AND TIME-RESOLVED RESONANCE RAMAN EVIDENCE FOR ENHANCED LOCALIZATION IN THE (3)MLCT STATES OF RUTHENIUM(II) COMPLEXES WITH THE INHERENTLY ASYMMETRIC LIGAND 2-(2-PYRIDYL)PYRAZINE

The resonance Raman (RR) and time-resolved resonance Raman (TR3) spectra of ruthenium(II) complexes containing the inherently asymmetric 2-(2-pyridyl)pyrazine (pypz) and its selectively deuteriated analogue are reported. The spectrum of the ground-state species is interpretable in terms of vibrationally isolated fragments with the exception of several modes which involve the interring and adjacent bonds. More importantly, the TR3 spectra of the (triplet) metal-to-ligand-charge-transfer state are shown to be consistent with the presence of a coordinated pypz in which the electronic charge is polarized toward the pyrazine fragment. A detailed discussion of the spectral analysis which leads to this conclusion is provided, and the potential implication of the effect for the design of practical devices is discussed.