Exploring the antimicrobial, antioxidant efficacies and computational studies of tridentate ligands derived from xanthene Schiff base and their mononuclear diorganotin(IV) complexes

In response to the growing need for new therapeutic agents, we have synthesized twelve new diorganotin(IV) complexes derived from xanthene derivatives through multistep reactions and structurally characterized using various spectral techniques, including, NMR, HRMS, FTIR, single crystal X-RD etc. The crystal structure of complex 7 reveals the ligand is bound to the diphenyltin(IV) moiety in a tridentate ONO manner, producing a square pyramidal geometry. The in-vitro antimicrobial efficacy of the synthesized compounds was screened using numerous strains via the serial dilution method. Xanthene derived diorganotin(IV) complexes were found to be more active than Schiff base ligands. Complexes 7 (MIC range = 0.0047–0.0098 µmol/mL), 14 (MIC range = 0.0045–0.0091 µmol/mL), and 15 (MIC range = 0.0043–0.0086 µmol/mL) exhibited comparable activity with reference drug towards microbial strains. Antimicrobial activity for diorganotin(IV) complexes follows the order as diphenyltin > dibutyltin > diethyltin > dimethyltin. Further, antioxidant potency was assessed via the DPPH assay using ascorbic acid as a reference. Results indicated that the incorporation of metal moiety and presence of hydroxyl group, led to comparable antioxidant activity in all synthesized complexes. Complex 11 (IC₅₀ = 3.1 µM) exhibited higher activity. Additionally, variable quantum parameters and optimized geometry of ligand 3 and its corresponding complexes 12–15 were figured out by DFT.