Coordination diversity of new mononuclear ONS hydrazone with transition metals: Synthesis, characterization, molecular modeling and antimicrobial studies

The mononuclear hydrazone ligand, H2L, a condensation product of 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one with 2-hydroxy-1-naphthaldehyde and its metal chelates of Cu(II), Ni(II), Co(II), Zn(II), Cd(II), VO(IV) and UO2(VI) ions were synthesized and characterized using elemental analyses, spectral, magnetic and molar conductance studies as well as thermal gravimetric analysis (TGA). The physico-chemical studies support that the ligand acts as mono- or dibasic tridentate ONS donor toward metal ions forming a mononuclear square planar, tetrahedral, square pyramidal and octahedral geometrical arrangements except UO2(VI) complex in which the metal ion is octa-coordinated. The ligand field parameters, Dq, B and β values, in the case of the cobalt and nickel complexes are calculated. The kinetics of the thermal decomposition for some metal complexes studied and their thermodynamic parameters were reported. Structural parameters of the ligand and its metal chelates have been calculated and correlated with the experimental data. The ligand and its metal chelates were screened for their antimicrobial activity against Staphylococcus aureus and Bacillus subtilis as Gram-positive bacteria, Escherichia coli and Salmonella typhimurium as Gram-negative bacteria and Candida albicans as fungus strain.