Insight on thermal behaviour of new complexes of Ni(II), Cu(II) and Zn(II) with a bismacrocyclic ligand developed as biologically active species

A multi-component reaction involving metal ion, amines and formaldehyde has been used for a series of decaaza bismacrocyclic complexes M 2 L(CH 3 COO) 4 ·nH 2 O [( 1 ) M: Ni, n = 2.5; ( 2 ) M:Cu, n = 1; ( 3 ) M:Zn, n = 10; L:1,3-bis( N , N -1,3,6,9,12-pentaazacyclotridecane)-benzene] preparation. Elemental analyses, ESI-MS, IR, UV–Vis–NIR, NMR and EPR spectra, magnetic susceptibility at room temperature, molar conductivities, as well as thermogravimetric analysis, provided data concerning complexes features. The macrocyclic ligand behaves as bischelate, resulting in either a square planar or an octahedral stereochemistry. The in vitro screening of the antimicrobial activity was performed against both reference and clinical isolates multi-drug-resistant strains. The overall antimicrobial potency of complexes was enhanced in comparison with the free ligand, against both planktonic and biofilm-embedded pathogenic strains. Complexes exhibit no cytotoxicity on the HCT 8 tumour cells. Thermogravimetric curves (TG, DTG and DTA) evidenced in air processes as water elimination, acetate into carbonate transformation as well as oxidative degradation of the bismacrocyclic ligand. The powder X-ray diffraction data indicate MO (M: Ni, Cu, Zn) as final product.