Investigating the antimicrobial potential of diorganotin(IV) complexes incorporating hydrazone ligands: Synthesis, structural elucidation, X-ray crystallography, DFT, and antimicrobial activity

Sixteen diorganotin(IV) complexes having the general formula R2SnL1-4, (where R = Me, Et, Bu, and Ph) have been synthesized from hydrazone ligands, which were obtained by the condensation reaction of 4-(benzyloxy)-2hydroxybenzaldehyde with hydrazide derivatives. The synthesized compounds were fully characterized by several spectroscopic and physicochemical techniques, like elemental analysis, FT-IR, (1H, 13C, and 119Sn) NMR, mass spectrometry, UV-Vis. and TGA. The obtained spectroscopic data revealed that hydrazone ligand bound to the tin atom in a tridentate fashion via phenolic O, imine N, and enolic O donor atoms and forms a pentacoordinated environment which was further confirmed by the X-ray crystallography diffraction analysis of complex 4. Complex 4 crystallizes in triclinic cell with space group P-1 and exhibits a distorted trigonal bipyramidal geometry. The equilibrium geometry of selected compounds was estimated using density functional theory (DFT) calculations implemented at B3LYP/LanL2DZ theory level to get insight into geometric and electronic structures using Gaussian 9 software package. Furthermore, the synthesized compounds were tested for their in vitro antimicrobial activity against four bacterial and two fungal strains. The results demonstrated that diorganotin(IV) complexes displayed better activity as compared to the hydrazone ligands. The best results are shown by complexes 4, 8, 12 and 16 with MIC values in the range of 0.0048-0.0050 mu mol/mL, respectively against B. subtilis and C albicans strains, further suggesting their greater lipophilicity which may have a substantial impact on facilitating microbial cell penetration.