Synthesis, Characterization and Bioactivity Study of Bidentate NS Schiff Base of S-Benzyl Dithiocarbazate and its Zn(II) and Pd(II) Complexes

The bis-chelated four coordinate complexes (ML2, L = deprotonated ligand) of Zn(II) and Pd(II) ionswere synthesized, derived from a new bidentate NS Schiff base called S-benzyl-β-N-(4-hydroxy-3-nitrophenyl)methylene dithiocarbazate (HL) which is the condensation product of S-benzyldithiocarbazate (SBDTC) with 4-hydroxy-3-nitrobenzaldehyde. The synthesized ligand and complexeswere characterized using conventional techniques like NMR, UV-visible, IR, mass spectroscopictechniques, magnetic susceptibility measurement and molar conductance. A single crystal X-raycrystallography data approved the proposed crystal structure of the ligand. Both in solid and solutionphase, the ligand continues to exist in its thione tautomeric form. The chelates were formed by thereaction of ligand with the metal ions through the ligand azomethine nitrogen atom and the deprotonatedthiolate sulfur anion. Magnetic susceptibility and electronic spectroscopic data suggested to have atetrahedral geometry for ZnL2 complex whereas a square planar structure for PdL2 complex. Theanalgesic and anti-inflammatory bioactivity were assayed on both the ligand and its complexes by tailflick and carrageenan induced paw edema test. The ligand at the dose of 10 mg/kg, produced a significant(***p < 0.001) increase in pain threshold in tail flick methods when compared to control but in case ofcomplexes, it showed moderate activity. At the same dose, the ligand and complexes significantly(***p < 0.001) reduced paw edema when compared to the control. Altogether, these results suggestthat ligand and its complexes could be used as a potent anti-inflammatory agent.