Two new Schiff base copper(II) complexes, [CuL 1 (tmen)] (1) and [Cu 2 L 2 2 (tmen)] (2) {where, H 2 L 1 = N-(salicylidene)-L-valine, H 2 L 2 = N-(3,5-dichlorosalicylidene)-L-valine and tmen = N,N,N ,Ntetramethylethylene-1,2-diamine} have been synthesized and characterized by molar conductance, elemental analyses, VSM-RT, UV-Vis, FTIR, EPR, and CD spectra. Both the complexes were structurally characterized by single crystal XRD. The crystal structure of complex 1 displays a distorted square pyramidal geometry in which Schiff base is coordinated to the Cu(II) ion via ONO-donor in the axial mode, whereas, the chelating diamine displays axial and equatorial mode of binding via NN-donor atoms. The crystal structure of the complex 2 reveals a syn-anti mode of carboxylate bridged dinuclear complex, in which, the coordination geometry around Cu(1) is square pyramid and distorted square planar around Cu(2). The target complexes were screened for in vitro antidiabetic activity. Both the complexes showed good inhibitory activity for α-amylase and α-glucosidase.

A series of four new Schiff base transition metal complexes [Co(II), Ni(II), Cu(II) and Zn(II)] derived from N-(salicylidene)- L-alanine and N,N,N',N'-tetramethylethylene-1,2-diamine (tmen) were designed, synthesized and tested for larvicidal activity against Culex quinquefasciatus, the southern house mosquito, which is the primary vector of St. Louis encephalitis virus and West Nile virus. All the complexes were characterized by physicochemical and spectral studies such as UV-Visible, FTIR, and EPR. The X-ray crystallographic analysis of Ni(II) complex revealed that, Ni(II) cation is surrounded by nitrogen and oxygen atoms from the Schiff base ligand, the oxygen atom of a water molecule, and two nitrogen atoms from tmen. Intermolecular hydrogen bonding stabilizes the Ni(II) complex. Results indicated that all the complexes exhibited higher mosquito larvicidal activity against C. quinquefasciatus.

A pentacoordinated mononuclear copper(II) complex, namely, bis(2,2′-bipyridine)sulphatecopper(II) urea trisolvate dihydrate, has been synthesised and characterised by molar conductance and UV-Vis and FTIR spectra. The structure of the complex was unambiguously confirmed by single crystal XRD. The complex crystallizes in monoclinic system, space groupC2/c, with the valuesa = 20.155(4),b = 20.858(4), andc = 14.425(3) Å;α = 90.00°,β = 96.51°, andγ = 90.00°;V = 6025(2) Å3andZ = 8. The Cu(II) ion is coordinated to four nitrogen atoms of two bidentate 2,2′-bipyridine ligands (bipy) and by one oxygen atom of the sulphate group and displays distorted trigonal bipyramidal geometry. The crystal packing is stabilized by inter- and intramolecular hydrogen bonding. The Cu(II) complex was screened for antimicrobial activity againstStaphylococcus aureus,Escherichia coli,Klebsiella pneumonia,Aspergillus niger,Aspergillus flavus, andCandida albicans. Larvicidal activity of the synthesized copper(II) complex was carried out against larvae ofCulex quinquefasciatusandAnopheles subpictus.

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