Infrared and resonance Raman spectroscopic characterization of electronically conducting ruthenium(II) co-ordination polymers

Abstract

Resonance Raman spectra are presented for a series of ruthenium(II) co-ordination polymers [{Ru(L–L)_xCl₂(dmso)_{4 – 2x}}_n][L–L = pyrazine (pyz), p-phenylenediamine (ppd) or 1,4-diisocyanobenzene (dib); dmso = dimethyl sulphoxide; x= 1 or 2], obtained from the reaction between [RuCl₂(dmso)₄] and L–L in toluene. When an excess of ligand is used samples of formula [{Ru(L–L)₃Cl₂(dmso)}_n] are isolated. There is intensity enhancement of the bands assigned to totally symmetric vibrations of the bridging ligand, resulting from the uniquely strong metal-to-ligand charge transfer bands of the Ru^II complexes. While pyz and ppd are N-donors, with Ru–N stretching bands at 274 and 280 cm^–1 respectively, the more unusual bidentate ligand dib is a C-donor with a Ru–C stretching band at 186 cm^–1. The mode of co-ordination is apparent from the IR and Raman spectra: when x is close to 1 the polymers contain bridging ligands but when x= 3, the polymers contain terminal ligands. Structures involving one-dimensional chains and two-dimensional grids with bridging L–L are proposed.