Group 10 metal complexes of dithiocarbamates derived from primary anilines: Synthesis, characterization, computational and antimicrobial studies

Dithiocarbamate ligands obtained from primary amines, namely N-phenylaniline, 4-methylaniline and 4-ethylaniline, and represented as L¹, L² and L³ respectively, have been used to prepare some Ni(II), Pd(II) and Pt(II) complexes. The complexes were characterized by NMR, FTIR spectroscopy and elemental analysis. The spectroscopic data showed that the ligands were chelated to the metal ions in a bidentate mode. The complexes [Pt(L¹)₂], [Pt(L³)₂], and [Pd(L¹)₂] were further characterized by single crystal X-ray analysis and distorted square planar geometries were confirmed in all cases. The magnetic susceptibility measurements of the nickel complexes suggest a square planar geometry for the diamagnetic compounds. Thermal decomposition studies of the complexes gave their respective metal sulfides as residues. Geometry optimization and harmonic frequency calculations of the ligands and the complexes were carried out using density functional theory (DFT). Molecular electrostatic potential energy calculations were used to support the coordination through the dithio-sulfur groups of the three dithiocarbamate ligands. Non-covalent interaction (NCI) theory analysis was used to reveal the different intra and intermolecular interactions in the hydrogen bonded structures of the platinum and palladium complexes. Antimicrobial screening, conducted using selected microbes, showed that the complexes gave moderate to very active antimicrobial activities against Gram negative (Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa), Gram positive (Bacillus cereus and Staphylococcus aureus) and fungi (Candida albicans and Aspergillus flavus) organisms at a concentration of at 50 μg/mL. However, the [Pt(L³)₂] complex gave the best antimicrobial properties with an inhibitory zone range of 8–26 mm.