Diorganotin(IV) complexes of Schiff bases derived from salicylaldehyde and 2-amino-6-substituted benzothiazoles: synthesis, spectral studies, in vitro antimicrobial evaluation and QSAR studies

In the present work, Schiff base ligands (1-4) were prepared by condensation of 2-amino-6-substituted-benzothiazole and salicyaldehyde in a 1:1 molar ratio and were further treated with diorganotindichloride R'2SnCl2 leading to a series of organotin(IV) complexes (5-20) of type R'2SnL1-4Cl [R' = Ph, Bu, Et, Me]. The prepared Schiff base ligands and the organotin(IV) complexes were characterized by various spectroscopic techniques (H-1, C-13, Sn-119 NMR, FT-IR) and physical techniques. All the synthesized compounds were evaluated for in vitro antibacterial and antifungal activity against two Gram positive bacterial strains B. cereus, S. aureus, two Gram negative bacterial strains E. coli, P. aeruginosa and two fungal strains A. niger and A. flavus by serial dilution method. The spectral data revealed that the complexes were pentacoordinated with bidentate ligands coordinated through oxygen and nitrogen. The results of antimicrobial activity revealed that the synthesized complexes were more toxic towards Gram positive bacterial strains as compared to Gram negative bacterial strains. From the results of QSAR analysis, it was indicated that the antimicrobial activity of the synthesized compounds were controlled by topological parameters (molecular connectivity indices).