Supramolecular diorganotin(IV) complexes of N′-(2-hydroxynaphthalen-1-yl)methylene)formohydrazide: Synthesis, spectroscopic characterization, X-ray structure, antibacterial screening, cytotoxicity and docking study

Abstract

Three organotin(IV) complexes [Me2SnL(1), Ph2SnL(2), tert-Bu2SnL(3)] have been synthesized by the reaction of a novel ligand N'-(2-hydroxynaphthalen-1-yl)methylene)formohydrazide (H2L) with dialkyltin(IV) dichlorides [R2SnCl2 (R = Me, Ph, tert-Bu) in presence of Et3N. The ligand and complexes have been characterized by elemental analysis, mass spectrometry, FT-IR, 1H, 13C and 119Sn NMR spectroscopic techniques. The spectroscopic data suggests coordination of ligand to the diorganotin(IV) moieties via oxygen nitrogen donor sites and five coordinated tin centers. The molecular structures of ligand (H2L) and complexes (1, 3) were also confirmed by single crystal X-ray analysis. The solid state structure of ligand showed it to be in the amido form whereas the single crystal X-ray analysis of complexes revealed the dibasic tridentate nature of ligand and monometallic nature of complexes. In both the complexes (1, 3) the Sn atom is in a distorted five-coordinate square pyramidal geometry with trigonality index(τ) 0.33 and 0.41, respectively. Packing diagrams reveal the important role of H…H, CH…π and O…H interactions in generating the supramolecular assembly. The antibacterial potential of all the compounds was investigated against two gram-positive bacteria (Bacillus subtilis, Stephlococcus aureus) and four gram-negative bacterial strains (Escherichia coli, Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi), using imipenem as the standard drug. Complex 2 exhibited highest activity against Bacillus subtilis and highest cytotoxicity against brine shrimp nauplii with LD50 1.01 μg/mL. Molecular Docking investigations revealed the best target protein, the positive impact of diphenyltin(IV) moiety on the compound-protein binding and the important role of hydrogen bonding, pi-pi and hydrophobic forces in such type of interaction.