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) spect ra 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 i n terms of vibrationally isolated fragments with the exception of seve ral modes which involve the interring and adjacent bonds. More importa ntly, the TR3 spectra of the (triplet) metal-to-ligand-charge-transfer state are shown to be consistent with the presence of a coordinated p ypz in which the electronic charge is polarized toward the pyrazine fr agment. A detailed discussion of the spectral analysis which leads to this conclusion is provided, and the potential implication of the effe ct for the design of practical devices is discussed.