S-Benzyl-b-N-(benzoyl) dithiocarbazate (SBNBODTC) a new disubstituted dithio-carbazate oxygen-sulfur (OS) donor ligand derived from reaction of S-benzyl dithiocarbazate with benzoyl chloride, formed bischelated complexes of general formula [M(OS)2] where M is Cu2+, Ni2+, Cd2+, Co2+ or Pb2+ and OS is a uninegative bidentate ligand. The ligand and its metal complexes have been characterized by a variety of physico-chemical techniques. Sbenzyl-b-N-(benzoyl) dithiocarbazate crystallized with Z0 = 2 in its thione form in cis-cis conformation, with the N-N bond adopting a cis geometry with respect to C@S, while the Sbenzyl group adopts a cis geometry with respect to the thione sulfur atom across the C-S bond.SBNBODTC, Cu(OS)2, Ni(OS)2 and Pb(OS)2 display marked cytotoxicity against HL-60 (human myeloid leukemia)while Cd(OS)2 and Co(OS)2 are moderately cytotoxic. The compounds showed moderate but selective activity towards targeted pathogens.

A tridentate nitrogen-sulfur Schiff base, 3-methylbenzyl 2-(6-methylpyridin-2-ylmethylene)hydrazine carbodithioate (6mpyS3M), was synthesized by condensation of 6-methylpyridine-2-aldehyde with S-3-methylbenzyldithiocarbazate. It crystallized in space group P 2 1 /n. It displayed intermolecular N-HÁÁÁN hydrogen bonding between the a-nitrogen and the pyridyl nitrogen. The thione sulfur is in a trans position with respect to the 6-methylpyridine fragment across the C-N bond but adopts a cis position with the 3-methylbenzyl fragment through the C-S bond. Octahedral complexes containing two 6mpyS3M ligands were prepared with Cu(II), Ni(II), Zn(II) and Cd(II). 6mpyS3M and its metal complexes were assayed against selected microbes and two breast cancer cell lines. 6mpyS3M was strongly active against both cancer cell lines. Its metal complexes showed high selectivity with Cu(II), Ni(II) and Zn(II) complexes strongly active against only one of the cancer cell lines, whereas the Cd(II) complex was strongly active only against the other. Only Cu(II) and Cd(II) complexes were active against some of the bacteria.

Mixed-ligand complexes of general formula, [Cu(NNS)(sac)] (NNS′ = S-benzyl-β-N-(2acetylpyrid-2-yl)methylenedithiocarbazate, NNS″ = S-benzyl-β-N-(2-benzoylpyrid-2yl)methylenedithiocarbazate and NNS = S-benzyl-β-N-(6-methylpyrid-2-yl)methylenedithiocarbazate, sac = the saccharinate anion) have been synthesized by reacting [Cu(sac)2(H2O)4] • 2H2O with the appropriate ligands in ethanol and characterized by various physico-chemical techniques. Magnetic and spectral evidence indicate that the complexes are four-coordinate in which the Schiff bases coordinate as NNS ligands and the sac-anion coordinates as a unidentate N-donor ligand. An X-ray crystallographic structural analysis of [Cu(NNS′)(sac)] shows that the complex has a distorted square-planar geometry with the Schiff base coordinated to the copper (II) ion as a uninegatively charged tridentate chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulphur atom while the fourth coordination position is occupied by the N-bonded saccharinate anion. The complexes have been evaluated for their biological activities against selected pathogens and cancer cell lines. They display weak activity against the pathogenic bacteria and fungi. The complexes were highly active against the leukemic cell line (HL-60) but only [Cu(NNS′)(sac)] was found to exhibit strong cytotoxicity against the ovarian cancer cell line (Caov-3). All complexes were inactive against the breast cancer cell line (MCF-7).

Schiff bases were prepared from S-benzyldithiocarbazate with 5-fluro-, 5-chloro-and 5bromoisatin. All are potential tridentate nitrogen, oxygen, sulfur donors. They were found to be selectively active against MCF-7 cell line (Human non-metastatic mammary gland adenocarcinoma cell line). The bromide and fluoride compounds were the most active with IC50 values of 6.40 μM (2.6 μg/mL) and 9.26 μM (3.2 μg/mL) respectively while the chloride derivative was weakly active with an IC50 value of 38.69 μM (14.0 μg/mL). The cytotoxic activity of the halo substituted isatins against the breast cancer cell lines tested is in the order of Br > F > Cl. Planarity of the isatin ring in the Schiff bases can be arranged in the following order SB5FISA > SB5ClISA > SB5BrISA while the perpendicularity of the benzyl ring towards the dithiocarbazate plane can be ordered as follows, SB5FISA > SB5BrISA > SB5ClISA.

Copper(II) complex of S-methyldithiocarbazate with isatin has been prepared and screened for their cytotoxic activities against MCF-7 (Human non-metastatic mammary gland adenocarcinoma cell line) and MDA-MB-231 (Human metastatic mammary gland adenocarcinoma cell line). The compound crystallized in an orthorhombic crystal system with a space group C 2cb and was found to be selectively active against MCF-7 cell line (Human non-metastatic mammary gland adenocarcinoma cell line with an IC50 value 0.45 μg/mL. The crystal structure of this centrosymmetric Cu(SMISA)2 complex (SMISA = Schiff base formed by condensation reaction of S-methyldithiocarbazate with isatin) showed that the copper atom has a distorted square-planar geometry with the Schiff base coordinated to the metal ion as a uninegatively charged bidentate ligand through the azomethine nitrogen and thiolate sulfur.