Synthesis, spectroscopic investigation and biological activity of metal(II) complexes with N2O4ligands

Abstract

A new series of Mn(II), Ni(II), Co(II) and Cu(II) complexes derived from diacetylmonoxime and 2-, 4- and 6-aminobenzoic acids have been prepared and characterised by elemental and thermal analyses (DTA, DTG and TG) as well as 1H and 13C NMR, IR, UV-Vis., Mass and ESR spectra, magnetic susceptibility and conductance measurements. The IR spectral data show that the ligands behave as mono- or di-basic, bis-, tri-, or tetradentate-chelates towards the metal ion. The stability of the complexes is achieved via intra- and inter-molecular hydrogen bonding of the OHgroup with the oximato-oxygen atom or oxygen atom of a carboxylic group, giving polymeric networks in the solid state. Molar conductances in DMF solution indicate that the complexes are non-electrolytes. The ESR spectra of solid complexes [Co (HL 1)2].2H2O (4), [Mn(HL 1) 2].H2O(5),[Mn(HL2)2(H 2O)2].H2O (10), [Cu2(HL 3)2(OAc)2 (H2O)4] (12) and[(Mn)3(L3)2(OAc)2(H 2O)6].4H2O (15) at room temperature and 77 K, are isotropic, however, the copper(II) complexes [Cu(HL1)(OAc)(H 2O)2}2] (2) and [Cu(HL2)2 (H2O)2].H2O (7) are non-axial and axial (dx2-y2) respectively with covalent bond character. The metal complexes exhibit greater inhibitory effects than tetracycline (bacteria) and amphotricen (fungi).