Metal complexes of (ML2)X2 type (X = H2O) of Co(II), Mn(II), Fe(II) and Fe(III) (X is NO3 – and H2O) were synthesized using Schiff base, S-benzyl-β-N-(p-dimethylaminophenyl)methylene dithiocarbazate (HL), which was synthesized by the condensation of equimolar concentrations of p-(dimethylamino)benzaldehyde and S-benzyldithiocarbazate. The metal complexes and dithiocarbazate ligands were confirmed by elemental study and spectroscopic techniques such as 1H and 13C NMR, electronic absorption spectroscopy, molar conductance, infrared techniques. The magnetic susceptibility and UV-vis spectral data suggest that the metal complexes (ML2)X2 show octahedral geometry. The bioactivity of ligand and its metal complexes were investigated by the well diffusion method against one fungus (Candida albicans) and three pathogenic bacteria (E. coli and B. cereus and S. aureus). Bioactivity analysis revealed that the (ML2)X2 complex of Fe(II) and Fe(III) shows enhanced antibacterial activity than free ligand. Comparatively, among all metal complexes, the Fe(III) complex shows higher antibacterial activity and moderate antifungal activity.

The regioselective 1,4-addition reactions of copper thiocyanate catalyzed Grignard reagents to the substituted chalcones are reported. The homogeneous solution of dilithium tetrachloromanganate is used to transmetallate magnesium by using manganese. It adds regio-selectively to substituted chalcone derivatives and forms 1,4-addition products with higher yield under nitrogen atmosphere and at a lower temperature. It have been observed that manganese from dilithium tetrachloromanganate reagent replaces magnesium from Grignard reagent and adds regioselectively by 1,4-addition manner utilizing copper thiocyanate as a catalyst. The course of the reaction in the absence of dilithium tetrachloromanganate reagent was also studied and obtained a mixture of 1,2-addition and 1,4-addition products. In presence of dilithium tetrachloromanganate reagent, a good regio-selectivity and higher yield of desired 1,4-addition product were obtained. All the synthesized compounds were also evaluated for their antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli (Gramnegative) and antifungal activity against Aspergillus niger.

The regioselective 1,4-addition of CuSCN catalyzed Grignard reagents to the substituted coumarins are reported. The Li2MnCl4 reagent is used to transmetallate magnesium by manganese. It adds regioselectively to coumarins and forms 1,4-addition products with higher yield under the atmosphere of nitrogen gas and at a lower temperature

The complexes of M(Db-scdtc)2 type [ Cu(Db-scdtc)2, Ni(Db-scdtc)2, and Zn(Db-scdtc)2] were synthesized by reaction of S-p-chlorobenzyl-β-N-(4-dimethylaminophenyl)methylenedithiocarbazate (H-Db-scdtc) and metal acetate salts in which Db-scdtc is anionic form of S-p-chlorobenzyl-β-N-(4-dimethylaminophenyl)methylenedithiocarbazate. The complexes and ligand were characterized by UV-Vis, Infrared spectroscopy, NMR (H1 and C13), elemental analysis and Molar conductance, and Magnetic moment. The Magnetic moment Data suggest that central zinc metal ion in zinc complex forms a four-coordinate tetrahedron with two bidentate Schiff base ligands shows tetrahedral geometry, while copper and nickel complexes exhibited square planar geometry. The biological activity experiment adopted by the well diffusion method. Preliminary studies showed that the dithiocarbazate ligand has a significant inhibitory effect on the proliferation of pathogenic strains compared to the metal complexes. Moreover, in metal complexes Cu2+ complexes showed prominent antibacterial activity against Salmonella typhi and Staphylococcus aureus. In addition, Ni2+ complex exhibited good antifungal activity against Candida albicans.

The general formula M(mAp-sadtc)2 type of metal complexes (where M = Cu2+, Ni2+, Zn2+) were synthesized by reaction of S-allyl-β-N-(1-(4-methoxyphenyl)ethylidene)dithiocarbazate ligand [H-(mAp-sadtc)] with metal(II) acetate salts (M = Ni2+, Cu2+ or Zn2+). The bis-chelated metal complexes were synthesized by subsequent reaction of metal(II) acetate salts and dithiocarbazate ligand in 1:2 proportion, respectively. The metal complexes and dithiocarbazate Schiff base were characterized by available methods like elemental analysis, 1H NMR, UV-Vis spectroscopy, 13C NMR, FT-IR spectroscopy, molar conductance and magnetic moments. Both nitrogen atoms of azomethine moiety (C=N) and deprotonated thiolate sulfur of dithiocarbazate ligand coordinated to the central metal ion formed five-membered rings on chelation. The synthesized dithiocarbazate ligand [H-(mAp-sadtc)] (1) and its bis-chelated M(mAp-sadtc)2 complexes (2-4) were screened for bioactivity against bacterial strains. The antibacterial results show that the metal(II) complexes exhibited significantly prominent antibacterial activity than dithiocarbazate ligand. Among the synthesized bis-chelated metal complexes, Ni-complex exhibited prominent antibacterial and antifungal activity as compared to other metal(II) complexes and ligand.