Synthesis, Structural Characterization, and Antimicrobial Activities of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Triazole-based Azodyes

The synthesis and characterization of new transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3-(2-hydroxynaph-1-ylazo)-1,2,4-triazole (HL1) and 3-(2-hydroxy-3-carboxynaph-1-ylazo)-1,2,4-triazole (HL2) have been carried out. Their structures were confirmed by elemental analyses, thermal analyses, spectral and magnetic data. The IR and 1H NMR spectra indicated that HL1 and HL2 coordinated to the metal ions as bidentate monobasic ligands via the hydroxyl O and azo N atoms. The UV-Vis, ESR spectra and magnetic moment data revealed the formation of octahedral complexes [MnL1(AcO)(H2O)3] (1), [CoL1(AcO)(H2O)3]·H2O (2), [MnL2(AcO)(H2O)3] (6) and [CoL2(AcO)(H2O)3] (7), [NiL1(AcO)(H2O)] (3), [ZnL1(AcO)(H2O)]·H2O (5), [NiL2(AcO)(H2O)] (8), [ZnL2(AcO)(H2O)]·10H2O (10) have tetrahedral geometry, whereas [CuL1(AcO)(H2O)2] (4) and [CuL2(AcO)(H2O)2]·5H2O (9) have square pyramidal geometry.. The mass spectra of the complexes under EI-con- ditions showed the highest peaks corresponding to their molecular weights, based on the atomic weights of 55Mn, 59Co, 58Ni, 63Cu and 64Zn isotopes; besides, other peaks containing other isotopes distribution of the metal. Kinetic and thermodynamic parameters of the thermal decomposition stages were computed from the thermal data using Coats-Redfern method. HL2 and complexes 6–10 were found to have moderate antimicrobial activities against Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Salmonella sp bacteria, and antifungal activity against Fusarium oxysporum, Aspergillus niger and Candida albicans. Also, in most cases, metallation increased the activity compared with the free ligand.