Synthesis, crystal structures and properties of new homoleptic Ni(II)/Pd(II) β-oxodithioester chelates

Abstract Six new cis -chelate complexes, [M(L) 2 ] (L = methyl-3-hydroxy-3-(furyl)-2-propenedithioate L1, M = Ni(II) 1 , Pd(II) 4 ; methyl-3-hydroxy-3-(thiophenyl )-2-propenedithioate L2, M = Ni(II) 2 , Pd(II) 5 and methyl-3-hydroxy-3-(phenyl)-2-propenedithioate L3, M = Ni(II) 3 , Pd(II) 6 have been prepared and characterized by elemental analyses, spectroscopy (IR, UV–Vis., 1 H and 13 C{ 1 H} NMR). The structures of 2 – 6 have been revealed by X-ray crystallography. In all the crystal structures, the metal has four-coordinate slightly distorted square planar geometry with a cis -configuration of the ligands. Anti-leishmanial properties of the complexes have been studied; 2, 3 and 6 showed potential anti-promastigote and anti-amastigote activities with IC 50 values of 1.70 ± 0.50, 1.62 ± 0.19, 9.20 ± 2.16 μg/mL and IC 50 2.50 ± 0.10, 2.05 ± 0.40, 12.84 ± 3.46 μg/mL respectively. Cytotoxicity assays on these complexes showed toxicity on the promastigotes but less toxicity against RAW 264.7 cell lines at different concentrations. Palladium complexes 4 , 5 and 6 show luminescent characteristics in CH 2 Cl 2 solution at room temperature. Complexes 1 – 6 are weakly conducting (σ rt  = 10 −4 -10 −6  S cm −1 , E a  = 0.19–1.13 eV) but show semiconducting behavior in the solid phase.