A new dithiocarbazate ligand, S-2-picolyldithiocarbazate (S2PDTC) was synthesized using 2picolylchloride hydrochloride. Tridentate Schiff bases were prepared by condensation of S-2picolyldithiocarbazate (S2PDTC) with pyridine-2-carboxaldehyde (NNS′), 2-acetylpyrrole (NNS″) and 2-acetylthiophene (NSS), while a bidentate Schiff base (NS) was prepared by condensing the S2PDTC with 2-acetylfuran. Complexes of S2PDTC and its Schiff bases with Ni(II) salts were synthesized and characterized by elemental analyses and various physicochemical techniques. A square-planar structure has been proposed for the diamagnetic [Ni(S2PDTC)2] and [Ni(NNS″) • Cl] complexes while [Ni(NS) • Cl] complex was dimeric. Complexes of [Ni(NNS′)2] and [Ni(NSS)2] were paramagnetic with octahedral stereochemistry. S2PDTC showed activity against bacteria and fungi (inhibitory zones above 15 mm). The NS and NSS Schiff bases showed activity toward a number of the bacteria assayed, while the NS and NSS Schiff bases, and the [Ni(NNS″) • Cl] and [Ni(NS) • Cl] complexes were found to be active only against C. lypolytica (2075). S2PDTC proved moderately active against HT-29 and weakly active toward CEM-SS with CD50 values of 9.5 and 24.0 μg cm−3, respectively, while among its Schiff bases reported herein, only the NNS′ Schiff base showed strong activity toward CEM-SS (Human cell T-lymphoblastic leukemia) and HT-29 (Human colon adenocarcinoma cells) with CD50 values of 2.3 μg cm−3. All of the Ni(II) complexes were inactive against CEM-SS cancer cells.

New bidentate isomeric NS and NS′ Schiff bases were derived from the condensation of Sbenzyldithiocarbazate (SBDTC) with 5-methyl-2-furyldehyde and 2-furyl-methylketone. Reaction of NS ligand with Ni(II), Cu(II), Cd(II) and Zn(II) salts gave solid complexes. Only the Ni(II) complex of the NS′ ligand was isolated. All complexes were characterized by a variety of physico-chemical techniques, viz. elemental analyses, molar conductivity, i.r. and electronic spectral studies. The Schiff bases behaved as uninegatively charged bidentate ligands. Square-planar structures have been proposed for the Cu(II) complex containing the NS Schiff base ligand and the Ni(II) complexes of the bidentate NS and NS′ Schiff base ligands. Single crystal X-ray diffraction study of [Cd(NS)2] showed that the complex was bis chelated with a distorted tetrahedral structure. The antimicrobial properties of the Schiff bases and their metal complexes indicate that the organic compounds are stronger antifungal agents than their complexes with the metals studied. However, the zinc complex of the Schiff base, S-benzyl-β-N-(5-methyl-2-furyl)methylenedithiocarbazate, (NS), was found to be highly active against CEM-SS (Human cell T-lymphoblastic leukemia) with a CD50 value of 2.0 μg cm−3, while [Cd(NS)2] was moderately active with a CD50 value of 4.95 μg cm−3. None of the compounds were found to be active against HT-29 (Human colon adenocarcinoma cells). The bioactivity of a previously reported tridentate NNS Schiff base (SBD1) and its metal complexes with nickel(II) and copper(II) are also discussed.

Coordination chemistry and bioactivity of some metal complexes containing two isomeric bidentate NS schiff bases derived from S-benzyldithiocarbazate and the x-ray crystal structures of S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazate and bis[S-benzyl-β-N-(2-furylmethylketone)dithiocarbazato]cadmium(II).

No abstract

No abstract

A new series of six Schiff bases derived from S-methyldithiocarbazate (SMDTC) and S-benzyldithiocarbazate (SBDTC) with methyl levulinate (SMML, SBML), levulinic acid (SMLA, SBLA), and 4-carboxybenzaldehyde (SM4CB, SB4CB) were reacted with copper(II), producing complexes of general formula ML2 (M = Cu(II), L = ligand). All compounds were characterized using established physicochemical and spectroscopic methods. Crystal structures were determined for three Schiff bases (SMML, SBML, SBLA) and two Cu(II) complexes (Cu(SMML)2 and Cu(SMLA)2). In order to provide more insight into the behavior of the complexes in solution, electron paramagnetic resonance (EPR) and electrochemical experiments were performed. The parent ligands and their respective copper(II) complexes exhibited moderate antibacterial activity against both Gram-negative and Gram-positive bacteria. The most active ligand (SB4CB) and its analogous S-methyl derivative (SM4CB) were conjugated with various vector moieties: polyarginines (R1, R4, R9, and RW9), oligoethylene glycol (OEG), and an efflux pump blocker, phenylalanine-arginine-β-naphthylamide (PAβN). Nonaarginine (R9) derivatives showed the most encouraging synergistic effects upon conjugation and complexation with copper ion including enhanced water solubility, bacteria cell membrane permeability, and bioactivity. These Cu(II)-R9 derivatives display remarkable antibacterial activity against a wide spectrum of bacteria and, in particular, are highly efficacious against Staphylococcus aureus with minimum inhibitory concentration (MIC) values of 0.5-1 μM. This pioneer study clearly indicates that the conjugation of cell-penetrating peptides (CPPs) to dithiocarbazate compounds greatly enhances their therapeutic potential.

A tridentate Schiff base having HNNS donor sequence was prepared by condensing Sbenzyldithiocarbazate (NH2NHCSSCH2Ph) with pyridine-2-carboxaldehyde. Complexes of this ligand, pyCHNNHCSSCH2Ph(HNNS), with Cu(II), Cd(II) and Zn(II) were synthesized and characterized by elemental analyses and various physico-chemical techniques. X-ray crystallographic analysis shows that the Zn(II) complex, [Zn(NNS)2], is six-coordinate and has a distorted octahedral structure with the ligand coordinated to the Zn(II) ion as a uninegatively charged tridentate chelating agent via the pyridine nitrogen, the azomethine nitrogen and the mercaptide sulfur atoms. Distortions from the regular octahedral geometry are attributed to the restricted bite angles of the planar NNS tridentate ligand. The Cu(II) complex, [Cu(NNS)Cl], was paramagnetic with a square-planar stereochemistry while the Cd(II) complex, [Cd(NNS)Br], was diamagnetic and is suggested to have a tetrahedral structure. The Schiff base and its complexes were screened for antimicrobial, cytotoxic and antioxidant activities. Disc diffusion methods were employed for antimicrobial assays against eight pathogenic microorganisms. The Schiff base and the complexes do not display activities against any of the microorganisms. The Schiff base was cytotoxic with a CD50 value of 5.90 μg ml−1 against the T-lymphoblastic leukemic cells while the Cu(II) and Cd(II) complexes were strongly cytotoxic with CD50 values of 2.20 and 2.30 μg ml−1, respectively. The Cu(II) and Cd(II) complexes were also effective against colon cancer cells with CD50 values of 2.60 and 3.10 μg ml−1, respectively. SBDTC showed a higher antioxidant activity than the αtocopherol (vitamin E) and was comparable with butylated hydroxytoluene (BHT), a commercially used synthetic antioxidant.

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.