Spectator ligand effects on the vibrational spectra of heteroleptic complexes of ruthenium with bipyrazine

Resonance Raman (RR) and transient resonance Raman (TR 2 ) spectra were acquired for a series of heteroleptic complexes of ruthenium, i.e. RuL 2 (bpz) 2+ , where bpz is 2,2′‐bipyrazine and L is 2,2′‐bipyridine (bpy) or an alkylated 2,2′‐bipyridine [i.e. diazafluorene (daf) or 4,4′‐dimethyl‐5,5′‐diethyl‐2,2′‐bipyridine (dmdeb)]. Resonance Raman spectra acquired at different excitation wavelengths for the ground‐state complexes reveal selective enhancement of modes associated with the coordinated bpz or the spectator ligands, as expected. The TR 2 spectra, acquired with excitation at 355 nm, confirm selective population of a bpz‐localized 3 MLCT excited state for each complex. Both the ground‐state RR spectra and the excited state TR 2 data indicate that only slight shifts are observed in a few modes as the donor strengths of the spectator ligands are varied. Such data for a systematically manipulated set of complexes, acquired here for the first time, imply that both the RR and TR 2 spectral parameters are reliably characteristic for a given ligand, varying only slightly as the nature of other ligands in the complex is changed. Copyright © 2004 John Wiley & Sons, Ltd.