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Coordination complexes of Co(II), Ni(II), Cu(II) and Zn(II) with Schiff base derived from syringaldehyde and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine have been synthesized. These complexes have been characterized by elemental analysis, magnetic moment, spectroscopic (IR, Electronic, 1 H NMR, ESR) and thermogravimetric analysis. Magnetic and spectral data suggest octahedral geometry for Co(II), Ni(II) and Zn(II) complexes and square planar for Cu(II) complexes. The presence of coordinated water in metal complexes was confirmed by thermal and IR data. The Schiff base and its metal complexes have been screened for antibacterial (Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, Staphylococcus aureus) and antifungal activities (Aspergillus niger, A. flavus). A comparison is made between activities of complexes with Schiff base and with the standard antibiotics.

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A series of cobalt, nickel, copper, and zinc complexes of bidentate Schiff bases derived from the condensation reaction of 4-amino-5-mercapto-3-methyl/ethyl-1,2,4-triazole with 2,4-dichlorobenzaldehyde were synthesized and tested as antimicrobial agents. The synthesized Schiff bases and their metal complexes were characterized with the aid of elemental analyses, magnetic moment measurements, spectroscopic and thermogravimetric techniques. The presence of coordinated water in metal complexes was supported by infrared and thermal gravimetric studies. A square planar geometry was suggested for Cu(II) and octahedral geometry proposed for Co(II), Ni(II), and Zn(II) complexes. The Schiff bases and their metal complexes have been screened for antibacterial (Pseudomonas aeruginosa, Bacillus subtilis) and antifungal activities (Aspergillus niger, A. flavus). The metal complexes exhibited significantly enhanced antibacterial and antifungal activity as compared to their simple Schiff bases.

The Schiff bases HL1-3 have been prepared by the reaction of 5-bromothiophene-2-carboxaldehyde with 4-amino-5-mercapto-3-methyl/propyl/isopropyl-s-triazole, respectively. Organosilicon(IV) and organotin(IV) complexes of formulae (CH3)2MCl(L1-3), (CH3)2M(L1-3)2 were synthesized from the reaction of (CH3)2MCl2 and the Schiff bases in 1 : 1 and 1 : 2 molar ratio, where M = Si and Sn. The synthesized Schiff bases and their metal complexes have been characterized with the aid of various physicochemical techniques like elemental analyses, molar conductance, UV, IR, 1H, 13C, 29Si, and 119Sn NMR spectroscopy. Based on these studies, the trigonal bipyramidal and octahedral geometries have been proposed for these complexes. The ligands and their metal complexes have been screened in vitro against some bacteria and fungi.