Synthesis, Spectral Characterization and Electrochemical Properties of New vic-dioxime Complexes Bearing Carboxylate

Three new vic-dioxime ligands, [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)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF2+-capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L1·BF2)2] and [Co(L2·BF2)2]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (ΛM) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., 1H- and 13C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the substituents attached on the oxime moieties of the complexes.