Thermal, spectral, magnetic and antimicrobial behaviour of new Ni(II), Cu(II) and Zn(II) complexes with a hexaazamacrocyclic ligand

New species of type MLCl₂·nH₂O (M:Ni, n = 6; M:Cu, n = 1.5 and M:Zn, n = 1; L: 1,8-bis(3′-ketopyridil)-1,3,6,8,10,13-hexaazacyclotetradecane, ligand resulted by 1,2-diaminoethane, nicotinamide and formaldehyde template condensation) were synthesised. The compounds were characterised by chemical analysis, ESI–MS, IR, NMR, UV–Vis-NIR and EPR spectroscopy as well as magnetic data at room temperature. The modifications in the IR and NMR spectra are in accordance with the condensation process. Electronic spectra indicate that Ni(II) adopts an octahedral stereochemistry while the surrounding of Cu(II) is square-pyramidal. The proposed stereochemistry was furthermore confirmed by magnetic moments and EPR spectrum at room temperature. The water is eliminated in one or two steps, respectively, while the oxidative degradation of the ligand and chloride decomposition occur in two steps. The final residues consist of the most stable metallic oxides as X-ray powder diffraction indicates. The newly synthesised compounds were evaluated for their antimicrobial effect against different bacterial and fungal strains.