Self-assembled transition metal dithiocarbamates of pyridine-3-carboxamide: synthesis, spectral characterization, thermal and biological studies

Abstract

A novel bidentate dithiocarbamate ligand (ndtc) derived from pyridine-3-carboxamide, (nicotinamide) by the insertion reaction of carbon disulfide and its subsequent self-assembled first row transition metal complexes having the formula M(ndtc)₂ [where M = Co(II), Ni(II), Cu(II), and Zn(II) ions] was synthesized and characterized using various spectral techniques. The facile reaction between the transition metal halide and ndtc in a 1 : 2 molar ratio yielded the aforesaid complexes in high yields. The formation of a single product was confirmed by thin layer chromatography. CHNS, IR, NMR spectra (¹H and ¹³C), TGA/DTA, XRD, UV-visible spectra, magnetic moment, and conductivity measurements were performed to ascertain the proposed structure of the synthesized complexes. On the basis of the abovementioned studies, the complexes were found to possess an octahedral arrangement, except for the Cu(II) ion, which was found to have a square-planar structure. The dithiocarbamate moiety was found to coordinate in a bidentate symmetrical fashion with the metal ions in all the complexes. The complexes were screened against a variety of human cancer cell lines such as human hepatocellular carcinoma (Hep3B), human breast adenocarcinoma (MCF7), and normal cells (PBMC). The complexes displayed moderate to good cytotoxicity on these cancer cell lines. However, Cu(ndtc)₂ was found to be most potent on MCF7, with an IC₅₀ value, 3.56 ± 1.1500, while Zn(ndtc)₂ was the most potent against liver and cervical cancer cell lines, with IC₅₀ values, 2.32 ± 1.5000 and 3.58 ± 1.6100 in micro-molar concentrations, respectively. The antioxidant potential of the ndtc and its metal complexes was determined using DPPH, and Cu(ndtc)₂ was found to be most efficient. Moreover, molecular docking simulations were also performed for the ndtc and its complexes, which confirmed the findings of the cytotoxicity.