Exploring the Microbial Inhibition Ability of Newly Synthesized Diorganotin(IV) Complexes of Hydrazone Ligands: Structural Elucidation, Crystal Structure, and DFT Studies

In our work, we have successfully synthesized twelve diorganotin(IV) complexes (4-15) from different hydrazone ligands and diorganotin(IV) dichlorides. The complexes have a general formula [R2SnL1-3], where R = Et, Me, Bu, and Ph groups. The hydrazone ligands (1-3) were synthesized through a condensation reaction involving 3-ethoxysalicylaldehyde with different benzhydrazide derivatives. All the synthesized hydrazone ligands and their complexes underwent screening by employing numerous spectroscopic and physicochemical techniques, such as molar conductance measurements, mass spectrometry, (1H, 119Sn, and 13C) NMR, SEM-EDAX, and FT-IR. Spectroscopic analysis revealed that the hydrazone ligands were attached to tin atoms in a tridentate fashion via ONO donor atoms, suggesting a pentacoordinated geometry for the complexes. Furthermore, the X-ray crystallography analysis for Complex 6 revealed the distorted square pyramidal geometry around the tin atom. Moreover, a DFT study was also carried out for Ligand 3 and its complexes (12-15) by employing B3LYP/LanL2DZ theory level (Gaussian 9 software package) to obtain the optimized geometry and global reactivity descriptors, structural behavior, and their efficacy against different microbes. To assess the biological efficacy of synthesized compounds, an in vitro antimicrobial assay was conducted against different fungal (Aspergillus niger and Candida albicans) and bacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa) strains. The results of the antimicrobial assay demonstrated that Complexes 7, 11, and 15 depicted better results against E. coli strain and C. albicans strain, implying that the higher lipophilic character of these complexes facilitates their easy passage through the cell membrane of microbes. Furthermore, an ADMET study was carried out to evaluate the toxicity score of synthesized compounds. Diorganotin(IV) complexes were prepared from newly synthesized hydrazone ligands, and both were characterized by different spectroscopic and physicochemical techniques. DFT calculations were performed to study the equilibrium geometry of selected compounds employing the B3LYP/LanL2DZ theory level. Furthermore, the in vitro antimicrobial efficacy of all the synthesized compounds was evaluated.image