SPECTROSCOPIC AND ELECTROCHEMICAL STUDIES OF NI-II, CU-II, PD-II AND VOII COMPLEXES WITH NAPHTHOQUINONIC LIGANDS

The electron transfer complexes of general type [M(L(1))(2)], [M(L(2)) (2)] and [M(L(3))(2)] with M = Ni-II, Cu-II, Pd-II and VOII ions have been investigated using 2-hydroxy-3-methylmercaptan-1,4-naphthoquinone (HL(1)), 2-amino-3-methylmercaptan-1,4-naphthoquinone (HL(2)) and 2,3 -diamino-1,4-naphthoquinone (HL(3)) as ligands. Polarographic results confirmed that some the these neutral compounds underwent reversible o r quasi-reversible one-electron reduction processes, and the reduction potentials for the [M(L(1))(2)] and [M(L(3))(2)] complexes were lower than those of the corresponding [M(L(2))(2)] complexes. EPR spectra o f the prepared compounds, except the [Pd(L(2))(2)] complex, show that they are paramagnetic and some of them behave as free radicals stabili zed through the cation. An attempt to correlate spectroscopic and redo x parameters has been made. Copyright (C) 1996 Elsevier Science Ltd