Impact of substituents on the crystal structures and anti-leishmanial activity of new homoleptic Bi(iii) dithiocarbamates??

New Journal of Chemistry Pub Date: 2019-10-04 DOI: 10.1039/C9NJ04477A

Abstract

Six new functionalised homoleptic Bi(III) dithiocarbamate complexes, [Bi(L1–L6)3] (L1 = (N-4-nitrobenzyl-N-furfuryl)dithiocarbamate 1, L2 = (N-4-chlorobenzyl-N-3-methylpyridyl)dithiocarbamate 2, L3 = (N-4-bromobenzyl-N-3-methylpyridyl)dithiocarbamate 3, L4 = (N-4-dimethylaminobenzyl-N-3-methylpyridyl)dithiocarbamate 4, L5 = (1-(2-pyridyl)piperazine)dithiocarbamate 5 and L6 = (N-4-methoxybenzyl-N-benzyl)dithiocarbamate 6), have been prepared and characterised by elemental analyses, powder X-ray diffraction (PXRD) and (IR, UV-Vis, 1H and 13C{1H} NMR) spectroscopy. The structures of the six complexes have been revealed in the solid state by X-ray crystallography and assessed by DFT calculations. Complexes 1 and (2, 5 and 6) are similarly dimeric in which the three dithiocarbamate ligands are bound to the seven and eight-coordinate Bi(III) centre, respectively, in asymmetric S,S-bidentate and μ2,κ2 S,S-chelating/chelating-bridging modes. By contrast, complex 4 is monomeric with a six-co-ordinate metal atom while complex 3 forms a polymeric structure with the metal in a seven-coordinate environment. The specific geometries of all compounds are distorted by the stereochemical lone pair. In these complexes, supramolecular structures have been sustained by non-covalent C–H?N, C–H?O, C–H?Cl, C–H?Br, C–H?π, C–H?π (BiCS2, chelate) and H?H interactions. The anti-leishmanial activities of the complexes have been tested; 5 and 6 showed potential anti-promastigote activity with IC50 values of 7.16 and 7.44 μM, and anti-amastigote activity with IC50 values of 8.40 and 9.70 μM, respectively. Cytotoxicity assays for complexes 1–6 showed toxicity on promastigotes but lower toxicity against the RAW 264.7 cell line at different concentrations.

Graphical abstract: Impact of substituents on the crystal structures and anti-leishmanial activity of new homoleptic Bi(iii) dithiocarbamates
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