Vibrational behavior of transition metal cupferronato complexes. Raman andSERS studies on nickel(II) cupferronato complexes

Raman and surface enhanced Raman scattering (SERS) spectra of the cupferron [PhN2O2]NH4 and new NiL(2)A(n) complexes, with L = PhN2O2-, n = 1, A = o-p henanthroline, o,o'-bipyridine and n = 2, A = H2O, o-NH2Py, o-C6H4(NH2)(2) have been recorded and discussed. Vibrational analysis of the neutral ligan d and newly prepared nickel(II) cupferronato complexes suggests electron de localization through the coordinated N-nitroso-N-hydroxylaminato (ONNO) uni t and the bidentate coordination of the anionic ligand to the metal center through the oxygen atoms. A Raman band of the new nickel(II) complexes was found at about 1300 cm(-1). The NiL(2)A(n), complexes with n=1, A=o-phenant hroline, o,o'-bipyridine and n = 2, A = H2O were found to adsorb on differe nt Ag SERS substrates. The best SERS spectra were recorded on the nanometer Ag colloid particles. The SERS bands associated to the chemical interactio n between the ONNO unit and Ag colloidal particles were observed. o-Phenant hroline and o,o'-bipyridine ring vibrational modes were assigned in the SER S spectra of the corresponding complexes. SERS spectra of the title compoun ds bring additional arguments for the bidentate coordination of the ONNO gr oup. (C) 2000 Elsevier Science B.V. All rights reserved.