Thermal, spectral, magnetic and biologic characterization of new Ni(II), Cu(II) and Zn(II) complexes with a hexaazamacrocyclic ligand bearing ketopyridine moieties

Abstract

New species of type MLCl2·nH2O (M:Ni, n = 4.5; M:Cu, n = 0 and M:Zn, n = 0; L: (4,5-11,12)-bisphenylen-1,3,6,8,10,13-hexaazacyclotetradecan-bis(pyrid-3-yl)methanone resulted by 1,2-phenylendiamine, nicotinamide and formaldehyde template condensation) were synthesised. The complex features have been assigned from microanalytical, IR, UV–Vis, 1H NMR and EPR spectra as well as magnetic data at room temperature. Simultaneous TG/DTA and TG/DSC/EGA measurements were performed in order to evidence the thermal decomposition pattern and the nature of the gaseous products formed in each step. Processes as water and chloride elimination as well as fragmentation and oxidative degradation of the organic ligand were observed during the thermal decomposition. The final product of decomposition was metal(II) oxide. The obtained complexes exhibited an improved antimicrobial activity in comparison with the ligand, both on planktonic and biofilm embedded cells, as well as a low cytotoxicity. The microbicidal and anti-biofilm activity of the complex (3) against the Gram-negative strains recommend it for the development of new antimicrobial solutions for these emerging multidrug-resistant bacteria causing life-threatening infectious diseases often untreatable with the existing antimicrobial agents. The assay on HEp-2 cells indicates a low cytotoxicity for all complexes. The plethysmometry assays indicate an anti-inflammatory activity for Cu(II) complex.