A series of La(III) and Th(IV) complexes have been synthesized by template condensation of ortho-phthalaldehyde, bis-(4-amino-5-mercapto-1,2,4-triazole-3-yl)alkanes and La(NO3)3 .6H2O /Th(NO3)4. 5H2O in ethanol. These complexes were characterized by elemental analyses, magnetic susceptibility, molar conductance, spectral (IR, UV-Vis, 1H NMR FAB-mass), and thermal studies. Elemental analyses suggest 1:1 stoichiometry. Spectroscopic study indicates that the coordination occurs through nitrogen of azomethine group and bridging bidentate nitrates. All the Schiff bases and their La (III) and Th (IV) complexes have been screened for their antibacterial (Escherichia coli, Staphylococus aureus, Salmonella typhi, Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and Cladosporium) by the minimum inhibitory concentration method. The DNA cleavage study was done by Agarose gel electrophoresis.