A novel series of complexes ML(ClO4)·nH2O (M: Co, Ni, Cu, Zn; HL: 2-[(E)-(1H-1,2,4-triazol-3-ylimino)methyl]phenol) have been synthesized and characterized as mononuclear species. The features of complexes have been assigned from microanalytical, FAB-MS, IR, UV–Vis-NIR, EPR and magnetic data. The IR spectra indicate the chelate behaviour of Schiff base and the perchlorate presence either as free ion or as ligand. Electronic and magnetic data are consistent with hexa-coordination of Co(II) and Ni(II) and penta-coordination for Cu(II) ions in complexes. The simultaneous TG-DSC/MS measurements evidenced processes as water (hydration or coordination) elimination, perchlorate decomposition as well as Schiff base both fragmentation and oxidative degradation. The in vitro screening of the antimicrobial behaviour on Gram-positive and Gram-negative bacteria, as well as on fungal strains, indicates a good activity for Cu(II) and Zn(II) complexes against both planktonic or adherent cells. Moreover, Cu(II) complex also exhibited a promising antiproliferative activity on HT 29 cell line.