Synthesis, Spectroscopic Investigation and Biological Activity of Metal(ll) Complexes with N2O4 Ligands

Abstract

A new series of Mn(II), Ni(II), Co(II) and Cu(ll) 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 OH-group 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 (HL1)21.2H2O (4), [Mn(HL1)2].H2O (5), [Mn(HL2)2(H2O)2].H2O (10), [Cu2(HL3)2(OAc)2(H2O)4] (12) and [(Mn)3 (L3)2(OAc)2(H2O)6].4H2O (15) at room temperature and 77 K, are isotropic, however, the copper(ll) complexes [Cu(HL1)(OAc)(H2O)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).