The nature of metal complexes of heterocyclic thiosemicarbazones reported in the literature through 1989 have been reviewed with an emphasis on variations in stoichiometry and stereochemistry. A brief introduction is followed by a survey of the biological activity of the uncomplexed thiosemicarbazones. Next is a section on the chemical nature of thiosemicarbazones including a discussion of preparative methods, modes of coordination and isomerism. This is followed by a discussion of structural information and biological activity of the iron(III), iron(II), copper(II), cobalt(III), cobalt(II) and nickel(II) complexes of heterocyclic thiosemicarbazones. Short sections on the biological activity of other chelating thiosemicarbazones and metal complexes are also included.

Structural and physical correlations in the biological properties of transition metal heterocyclic thiosemicarbazone and S -alkyldithiocarbazate complexes

New Schiff base ligand L derived from the condensation reaction of 2-amino-3-formylchromone with (R)-2-amino-2-phenylethanol was synthesized and characterized which involves combination element of ammine functionality and naturally occurring heterocyclic chromone, 4H-benzopyran-4-one. Subsequently, their complexes 1 and 2 with Cu(NO 3 ) 2 and Zn(NO 3 ) 2 , respectively were prepared. The DNA binding studies of the ligand L and complexes 1 and 2 with CT-DNA as compared to classical anticancer drug cisplatin were carried out by employing different optical methods viz, UV–vis, fluorescence, circular dichroism and viscosity measurements. Furthermore, the absorption studies, 1 H and 31 P with mononucleotides were also monitored to examine the base specific interactions of the transition metal complexes which revealed a higher propensity of copper(II) complex 1 for 5′-GMP while for zinc(II) complex 2 towards 5′-TMP involving groove binding mechanism of the complexes towards DNA. The complex 1 exhibits a remarkable DNA cleavage activity with pBR322 DNA in presence of different activators and cleavage reaction involves various oxygen species suggesting the involvement of active oxygen species for the DNA scission.

Synthesis of new chiral heterocyclic Schiff base modulated Cu(II)/Zn(II) complexes: their comparative binding studies with CT-DNA, mononucleotides and cleavage activity.

Coordination chemistry and bioactivity of Ni2+, Cu2+, Cd2+ and Zn2+ complexes containing bidentate Schiff bases derived from S-benzyldithiocarbazate and the X-ray crystal structure of bis[S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazato]cadmium(II)

Crystal structure and spectroscopic studies on metal complexes containing ns donor ligands derived from S-benzyldithiocarbazate andp-dimethylaminobenzaldehyde

Several new complexes of a tridentate ONS Schiff base derived from the condensation of S-benzyldithiocarbazate with salicylaldehyde have been characterised by elemental analyses, molar conductivity measurements and by i.r. and electronic spectra. The Schiff base (HONSH) behaves as a dinegatively charged ligand coordinating through the thiolo sulphur, the azomethine nitrogen and the hydroxyl oxygen. It forms mono-ligand complexes: [M(ONS)X], [M=NiII, CuII, CrIII, SbIII, ZnII, ZrIV or UVI with X = H2O, Cl]. The ligand produced a bis-chelated complex of composition [Th(ONS)2] with ThIV. Square-planar structures are proposed for the NiII and CuII complexes. Antimicrobial tests indicate that the Schiff base and five of the metal complexes of CuII, NiII, UVI, ZnII and SbIII are strongly active against bacteria. NiII and SbIII complexes were the most effective against Pseudomonas aeruginosa (gram negative), while the CuII complex proved to be best against Bacillus cereus (gram positive bacteria). Antifungal activities were also noted with the Schiff base and the UVI complex. These compounds showed positive results against Candida albicans fungi, however, none of them 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 μg cm−3) while the copper, uranium and thorium complexes are moderately active (CD50 = 6.9–9.5 μg cm−3). The nickel, zirconium and chromium complexes were found to be inactive.

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

Metal complexes of sulphur and nitrogen-containing ligands: Complexes of s-benzyldithiocarbazate and a schiff base formed by its condensation with pyridine-2-carboxaldehyde

M.T.H. Tarafdar

Papers

Metal complexes of sulphur and nitrogen-containing ligands: Complexes of s-benzyldithiocarbazate and a schiff base formed by its condensation with pyridine-2-carboxaldehyde