Electronic, infrared, and resonance-Raman spectroscopic study of pyridine complexes of ruthenium-(II) and -(III)

Abstract

The electronic, i.r., Raman, and resonance-Raman spectra of the complexes [Ru^II(NH₃)₅L][PF₆]₃(L = 4-cyano-1-methylpyridinium or 1-methyl-4,4′-bipyridinium) and [Ru^III(NH₃)₅L]Cl₃(L = 4-dimethylaminopyridine) have been studied. Excitation within the contour of the strong (εca. 15 000 dm³ mol^–1 cm^–1) band at 545–640 nm in the electronic spectra of the ruthenium(II) complexes leads to resonance enhancement of many a₁ bands (all with depolarisation ratio ⅓) of the pyridine ring in each case. The resonant transition is thus deduced to be a z-polarised, pyridine (π*)â†� Ru (d_π) transition, in agreement with a previous conclusion. The most plausible assignment for the resonant transition is b₂(π*)â†�b₂(d_yz).