A series of complexes [M₂L₂Cl₂(OH₂) _n ]·mH₂O (M: Co, n = 0, m = 1; M: Ni, n = 2, m = 0; M: Cu, n = 0, m = 0; M: Zn, n = 0, m = 1; HL·H₂O: 2-[(E)-1H-1,2,4-triazol-3-ylimino)methyl]phenol) were synthesised and characterised. The features of complexes have been assigned from microanalytical, thermal, IR, UV–Vis-NIR, EPR spectroscopy as well as magnetic data at room temperature. The electrochemical behaviour of the complexes was also investigated by cyclic voltammetry. The simultaneous TG/DTA experiments of these in flowing air atmosphere evidenced the occurrence of water or chloride as well as oxidative degradation of the Schiff base. The final product of decomposition was the most stable metal oxide as powder X-ray diffraction indicates. The complexes exhibited an improved antibacterial activity in comparison with the ligand towards both planktonic as well as biofilm embedded cells. The Cu(II) and Zn(II) complexes exhibited an inhibitory effect on the tumor cell lines growth, as revealed by the increased G2 phase and percentage of apoptotic/necrotic cells.