Complexes of a tridentate ONS Schiff base. Synthesis and biological properties

Several new complexes of a tridentate ONS Schiff base derived from the cond ensation of S-benzyldithiocarbazate with salicylaldehyde have been characte rised by elemental analyses, molar conductivity measurements and by i.r. an d electronic spectra. The Schiff base (HONSH) behaves as a dinegatively cha rged ligand coordinating through the thiolo sulphur, the azomethine nitroge n and the hydroxyl oxygen. It forms mono-ligand complexes: [M(ONS)X], [M = Ni-II, Cu-II, Cr-III, Sb-III, Zn-II, Zr-IV or U-VI with X = H2O, Cl]. The l igand produced a bis-chelated complex of composition [Th(ONS)(2)] with Th-I V. Square-planar structures are proposed for the Ni-II and Cu-II complexes. Antimicrobial tests indicate that the Schiff base and five of the metal co mplexes of Cu-II, Ni-II, U-VI, Zn-II and Sb-III are strongly active against bacteria. Ni-II and Sb-III complexes were the most effective against Pseud omonas aeruginosa (gram negative), while the Cu-II complex proved to be bes t against Bacillus cereus (gram positive bacteria). Antifungal activities w ere also noted with the Schiff base and the U-VI complex. These compounds s howed positive results against Candida albicans fungi, however, none of the m were effective against Aspergillus ochraceous fungi. The Schiff base and its zinc and antimony complexes are strongly active against leukemic cells (CD50 = 2.3-4.3 mu g cm(-3)) while the copper, uranium and thorium complexe s are moderately active (CD50 = 6.9-9.5 mu g cm(-3)). The nickel, zirconium and chromium complexes were found to be inactive.