A SURFACE-ENHANCED RAMAN-STUDY OF THE ADSORPTION OF TRIS(2,2-BIPYRIDINE)RUTHENIUM(II) AND SUBSTITUTED ANALOGS ON CHEMICALLY-DEPOSITED SILVER FILMS

The surface enhanced resonance Raman spectroscopy (SERRS) of a series of tris(2,2'-bipyridine)ruthenium(II) complexes on chemically produced silver films is reported. The SERR spectra of [Ru(bipy)3]2+, several tris complexes of Ru(II) containing substituted 2,2'-bipyridine (4,4'-dimethyl-, 4,4'-diphenyl-, 4,4'-diamino- and 4,4'-diethylcarboxylate-2,2'-bipyridine) ligands and the neutral cis-bis complexes [Ru(bipy)2(NCS)2] and [Ru(bipy)2Cl2] show very high band intensities. The large enhancement arises from the combination of the inherent resonance Raman effect and the surface plasmon resonance (due to the rough nature of the silver film). The molecules are not chemisorbed on the silver surface and hence the enhancement occurs solely via the electromagnetic mechanism. The SERR spectra are virtually free of the fluorescence which dominates the corresponding RR spectra thus illustrating the use of SERRS in the vibrational spectroscopy of strongly luminescing species. The SERRS spectra of the substituted 2,2'-bipyridine complexes are discussed.