A novel of substituted dithiocarbazate derivatives: synthesis, characterisation, and antibacterial activity of S-benzyl-β-N-4-chloro-3-nitrobenzoyl dithiocarbazate (SB3NO) and its Cu(II), Zn(II), Co(II), and Ni(II) complexes

Cu(II), Zn(II), Co(II), and Ni(II) metal complexes have been synthesized using the O, S bidentate ligand S-benzyl-4-chloro-3-nitrodithiocarbazate (SB3NO). SB3NO coordinates with the metal ions according to the general formula of [M(SB3NO)2], where M is Cu2+, Zn2+, Co2+, and Ni2+. Various spectroscopic techniques, such as elemental analysis, FT-IR, NMR, GC-MS, TGA, UV-Vis spectroscopy, molar conductivity measurements, and magnetic susceptibility testing, were used to characterize the ligand and complexes. In a solid state, SB3NO exists in a thione tautomeric form and deprotonated to chelate metal(II) center through the oxygen of carbonyl and ionic sulfur of thiol in liquid, giving rise to either tetrahedral or square planar geometry. Additionally, the in-vitro antibacterial activity of SB3NO and its metal complexes was assessed against pathogenic gram positive and gram-negative bacteria. The test revealed that Zn(SB3NO)₂ exhibited the strongest antibacterial activity against Pseudomonas aeruginosa (ATCC 27853) in the MIC assay (437 μg/ml). This study concludes that incorporating metal ions enhances the antibacterial activity of the free ligand, highlighting their potential as promising metal-based antibacterial agents.