Resonance Raman spectra of d6 metal-diimine complexes reflect changes in metal-ligand interaction and character of electronic transition

This article reports the results of a comparative resonance Raman (rR) study of low-valent d(6) transition-metal a-diimine complexes. The oc-diimine ligand used is N,N'-diisopropyl-1,4-diaza-1,3-butadiene (Pr-i-DAB) which has a relatively simple structure and hence only a few vibrations. This simplifies the assignment of the vibrational spectra of complexes of this ligand. With the help of DFT calculations of the frontier orbitals and vibrational frequencies of (model) complexes, the rR bands are assigned unambiguously. Their frequencies and intensities are discussed in terms of the electronic structures of the complexes. Comparison of the rR data demonstrates how these spectra can be used to establish changes in the metal-ligand interaction and in the character of the charge transfer transitions of these complexes. (C) 2001 Elsevier Science B.V. All rights reserved.