INFRARED AND RESONANCE RAMAN-SPECTROSCOPIC CHARACTERIZATION OF ELECTRONICALLY CONDUCTING RUTHENIUM(II) COORDINATION POLYMERS

Resonance Raman spectra are presented for a series of ruthenium(II) co-ordination polymers [{Ru(L-L)(x)Cl2(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.