Synthesis, spectral, thermal, solid state d.c. electrical conductivity and biological studies of Co(II), Ni(II) and Cu(II) complexes with 3-substituted-4-amino (indole-3-aldehydo)-5-mercapto-1,2,4-triazole Schiff bases

A series of cobalt(II), nickel(II) and copper(II) complexes have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazole and indole-3-aldehyde in ethanol. These complexes have been characterized by elemental analyses, magnetic, spectroscopic (IR, UV-Vis, H-NMR, ESR, FAB-mass), thermal, electrochemical (CV) and solid state d.c. electrical conductivity studies. The elemental analyses confirm 1 : 2 stoichiometry of the type ML2·2H2O (M = Co/Ni) and ML2 (M=Cu). The complexes are colored solids and non-electrolytes in DMF and DMSO. Magnetic and spectral data suggest octahedral geometry for Co(II) and Ni(II) complexes and square-planar geometry for Cu(II) complexes. The presence of coordinated water in Co(II) and Ni(II) complexes was confirmed by thermal and IR data of the complexes. The complexes are insoluble in water and common organic solvents and decompose at higher temperature. All these ligands and their complexes have also been screened for antibacterial (Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger and Aspergillus fumigates) by the cup plate method.