Electrochemical synthesis and structural characterization of Co(II), Ni(II) and Cu(II) complexes of N,N-bis(4,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine

Abstract

The electrochemical oxidation of anodic metal (cobalt, nickel or copper) in a cell containing an acetonitrile solution of the ligand N,N-bis(4,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine (H₂L) affords complexes [Co₂L₂]·H₂O (1), [Ni₃L₃] (2) and [Cu₂L₂] 3H₂O (4). On using nickel as the anode and the addition to the solution electrolytic phase of the amount of water necessary to saturate the solution, the electrolytic process gave rise to the new compound [Ni₂L₂(H₂O)_1.5]·CH₃CN (3). Compounds 1 and 4 are dimeric and the metal atoms are pentacoordinated. Compound 3 also consists of dimeric neutral molecules with the nickel atoms in both penta- and hexacoordinated environments. The crystal structure of 2 shows the presence of a trimeric compound in which the nickel atoms are hexacoordinated. Electronic, IR and FAB spectra of the complexes are discussed and related to the structural information. The magnetic behavior of 1–4 denotes the occurrence of intramolecular antiferromagnetic interactions. The values obtained for the coupling constant J are −4.2 cm⁻¹, −5.3 cm⁻¹, −30 cm⁻¹ and −4.7 cm⁻¹ for 1, 2, 3 and 4, respectively. These values are in full agreement with the structural characteristics of the compounds. The catalytic activity of the complexes towards the decomposition of hydrogen peroxide (catalase activity) was also studied.