Synthesis of new Cu(II), Ni(II) and Co(II) complexes with a bis-amide ligand functionalized with pyridine moieties: Spectral, magnetic and electrochemical studies

Abstract

Three new copper(II), nickel(II) and cobalt (II) dinuclear complexes with a bis-amide ligand derived from tartaric acid have been prepared and characterized. For this purpose, the ligand ( R, R)-(+)-di- N, N′-methylpyridino-tartramide (dmpt) was synthesized via the classical aminolysis of ( R, R)-(+)-dimethyltartrate with pyridylmethylamine. The molecular structures of the complexes Na[Cu 2(dmptH −3)(CO 3)] · 8H 2O ( 1) and [Ni 2(dmptH −2) 2] · 9.75H 2O ( 2) were elucidated by X-ray diffraction, and the complex [Co 2(dmptH −3)(μ-OH)] · NaClO 4 · 5H 2O ( 3) by XAS. The crystal structure of ( 1) shows that the two metallic centres are in a square planar environment. Each copper(II) is bound to pyridyl and deprotonated amidic nitrogen atoms and to the oxygen atoms of hydroxyl and carbonato groups. In complex ( 2), both nickel atoms are in a distorted octahedral environment with an identical set of donors atoms, N 4O 2, coming from four nitrogen atoms of two pyridylmethylamido moieties and two oxygen donor atoms of alcohol groups. XAS analysis of complex ( 3) allows us to propose a CoN 2O 4 chromophore, with two nitrogen atoms coming from pyridyl and amidic groups and two bridged oxygen atoms from a deprotonated alcohol group and an hydroxyl group; the hexacoordination is achieved by two water molecules. The spectroscopic, electrochemical and magnetic properties of these complexes were investigated.