Copper(II) and ruthenium(II)/(III) Schiff base complexes

Metal complexes of general formula [Cu(L)](ClO4)(2), [Ru(L)(PPh3)(2)]Cl-2 a nd [Ru(L)(PPh3)Cl]Cl-2[L = 1,4-di- (o-benzylidiminophenoxy/benzylidiminophe nylthio)butane] containing N2O2 or N2S2 donor atoms have been prepared and characterised by spectral, magnetic and cyclic voltammetric studies. The rh ombic nature of the e.s.r. spectra of the Ru-III complexes indicates an asy mmetry in the electronic environment around the Ru atom. e.s.r. spectra of the Cu-II complexes show a typical four-line spectrum with approximate tetr ahedral distortion. The observed low A(parallel to) values in the Cu-II com plexes, of the order of 132-160 x 10(-4) cm(-1), indicates a tetrahedrally distorted square planar structure. The influence of modified ligands is reflected in the metal-centered redox potentials. Cu-II complexes having the N2S2 chromophore, in MeCN on a glass y carbon electrode, undergo quasi-reversible reduction in the 540-680 mV ra nge. A depression in E-1/2 values for the open chain N2S2 chromophoric macr ocyclic Cu-II complexes, compared to electronically similar cyclic tetraden tate Cu-II analogues, is due to the increased stabilization of the Cu-I sta te by added flexibility provided through the open chain donor sites.