Synthesis, characterization, and in vitro antibacterial and cytotoxic study of Co(II), Ni(II), Cu(II), and Zn(II) complexes of N-(4-methoxybenzyl) N-(phenylethyl) dithiocarbamate ligand

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Four new homoleptic complexes of Co(II) [C-1], Ni(II) [C-2], Cu(II) [C-3], and Zn(II) [C-4] derived from N-(4-methoxybenzyl) N-(phenylethyl) dithiocarbamate ligand (KL) with general formula ML2 were synthesized with good yield and characterized by elemental analysis and different spectroscopic techniques like FTIR, 1H and 13C NMR, HRMS, UV–vis and fluorescence spectroscopy. The crystal structure of the complex C-4 was determined by the single crystal X-ray diffraction technique (SC-XRD), which shows a distorted square pyramidal geometry around the Zn(II) ion. Thermogravimetric studies of all four complexes were performed and found that decomposition occurred in three steps and the final product of the thermal decomposition was metal sulfides. The magnetic properties of cobalt, nickel, and copper complexes were analyzed by a vibrating sample magnetometer (VSM) and the hysteresis of magnetization showed the paramagnetic nature of cobalt and copper complexes while the diamagnetic nature of the nickel complex. Electronic spectral studies of the ligand and all four complexes were recorded in methanolic solution and the spectra show the absorption for the ligand at 301 nm and the absorption band for complexes was observed in the range 265-275 nm which is due to intra-ligand charge transfer (ILCT) transitions. Complexes C-1, C-2, and C-3 showed transitions in the range of 325-445 nm due to ligand-to-metal charge transfer (LMCT) transitions. Anti-bacterial studies of all compounds were performed against Bacillus subtilis, Staphylococcus aureus, Clostridium sporogenes, and Escherichia coli and the result showed that complexes C-2 and C-4 have significant anti-bacterial properties. The cytotoxicity study of all compounds against breast cancer cell line MCF-7 shows that complex C-2 has a potential anti-cancerous property with the least IC50 value against normal cell line HEK-293.