Three new vic‐dioxime ligands: Synthesis, characterization, spectroscopy, and redox properties of their mononuclear nickel(II) complexes

Abstract

AbstractNickel(II) complexes with three new vic‐dioxime reagents, N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)phenylglyoxime (L1H2), N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L2H2) and N,N′‐bis(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L3H2), have been prepared. Mononuclear nickel(II) complexes with a metal/ligand ratio of 1:2 were prepared using Ni(II) salt. All these nickel(II) complexes are nonelectrolytes as shown by their molar conductivities (ΛM) in DMF solution at 10−3 M concentration. The ligands are soluble in common solvents such as DMSO, DMF, CHCl3, and C2H5OH. The ligands and their Ni(II) complexes were characterized by elemental analyses, FT‐IR, UV‐visible, 1H NMR, 13C NMR, magnetic susceptibility measurements, cyclic voltammetry, and molar conductivities (ΛM). The cyclic voltammetric measurements show that [Ni(L1H)2] and [Ni(L2H)2] complexes exhibit almost similar electrochemical behavior, with two reduction and two oxidation processes based on either metals or oxime moities, while [Ni(L3H)2⋅2H2O] complex displays irreversible, with one reduction and one oxidation processes based on oxime moity. This main difference could be attributed to the highly polarized [Ni(L3H)2⋅2H2O] complex that has four carboxylate groups attached to piperidine on the oxime moieties. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:657–663, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20357