Azo-phenolate vs. carboxylate: (N, O)-Sn bonding advantage in stability and antibacterial activity of Dimethyltin(IV) explored via DFT and molecular docking

Abstract

This study presents investigations on a dimethyltin(IV) complex of 4-(2,4-dihydroxy-phenylazo)-benzoic acid. The primary focus is on the comparative stability of its azo-phenolate (N, O)-Sn and carboxylate (COO)-Sn bonded structural isomers. Analytical techniques, including multinuclear NMR, FT-IR, and DFT, identify the 5-membered (N, O)-Sn 4-coordinate distorted tetrahedral structure as the most stable isomer in solution. The complex demonstrates broad-spectrum activity across both Gram-negative and Gram-positive bacteria with inhibition zones of 8 mm (K. pneumoniae), 14 mm (V. cholerae), 19.3 mm (S. aureus), and 10.7 mm (S. pneumoniae). In comparison, standard antibiotics – Gentamycin and Vancomycin- are inactive against Gram-positive and Gram-negative bacteria, respectively. Molecular docking analyses reveal that the complex effectively binds to the active sites of bacterial enzymes Hibernation-Promoting Factor and Autolysin E. This leads to the disruption of bacterial survival under stress. Overall, this research establishes the stability and antibacterial potential of (N, O)-Sn complexes—an area not previously investigated.