Synthesis, characterization, antimicrobial evaluation and QSAR studies of organotin(IV) complexes of Schiff base ligands of 2-amino-6-substituted benzothiazole derivatives

A series of organotin(IV) complexes of type R2SnLCl [R = Ph, Bu, Et, Me] were prepared by reaction of diorganotindichloride(IV) with Schiff base ligands, L-1 = (1-[(6-ethoxy-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol), L-2 = (1-[(6-nitro-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol), L-3 = (1-[(6-methoxy-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol) and L-4 = (1-[(6-methyl-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol) obtained from 2-amino-6-substituted benzothiazole derivatives with 2-hydroxy-1-naphthaldehyde in 1:1 molar ratio. These organotin(IV) complexes were characterized by various spectroscopic techniques (H-1, C-13 and Sn-119 NMR, FT-IR), and physical techniques (X-ray powder diffraction analysis and elemental analysis). The coordination of the prepared complexes has been planned as pentacoordinated around the central tin atom during which ligands coordinated to tin atom in bidentate manner acted as N, O donor system. The ligands and their complexes were screened for antibacterial and antifungal activities against Gram-positive bacteria Bacillus cereus (MTCC 10072), Staphylococcus aureus (NCIM 2901), Gram-negative bacteria Escherichia coli (MTCC 732), Pseudomonas aeruginosa (MTCC 424) and fungi Aspergillus niger (MTCC 9933) and Aspergillus flavus (ATCC 76801). The output of QSAR analysis indicated that topological parameters (molecular connectivity indices) were responsible for controlling the antimicrobial activity of the synthesized compounds.