Anti-leishmanial study of discrete tetrahedral zinc(ii) β-oxodithioester complexes

Abstract

We have synthesized four new oxygen/sulfur(O^S) chelate complexes, [Zn(L)₂], where L represents different ligands: methyl-3-hydroxy-3-(furyl)-2-propenedithioate (L1, 1), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L2, 2), methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedithioate (L3, 3), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L4, 4). These complexes have been characterized by using IR, multinuclear NMR (¹H, ¹³C{¹H}, and ¹⁹F{¹H}), and UV-vis spectroscopy. The structural characterization of complexes 1, 2, and 4 was further achieved by single crystal X-ray diffraction (SCXRD). The supramolecular structures of these complexes are stabilized by non-covalent C–H⋯π (ZnOSC₃, chelate), C–S⋯π (ZnOSC₃, chelate), π⋯π (ZnOSC₃,), C–H⋯O, C–H⋯F–C and C–H⋯H–C interactions. The luminescence properties of Zn(II) complexes 1–4 were studied at room temperature in the solid phase. The antileishmanial activity was evaluated for all complexes. Complexes 1 and 4 exhibited significant anti-promastigote and anti-amastigote activities, with IC₅₀ values of 2.0 and 1.33 μg mL⁻¹, and 2.79 and 2.02 μg mL⁻¹, respectively. Additionally, cytotoxicity assays demonstrated that these Zn(II) β-oxodithioester complexes were toxic to promastigotes, but showed reduced toxicity towards RAW 264.7 cell lines at varying concentrations. Furthermore, the optical band gap energies of complexes 1–4 were measured and found to exhibit semiconducting behavior.