Synthesis, characterisation and anti-diabetic activities of triorganotin(IV) azo-carboxylates derived from amino benzoic acids and resorcinol: Crystal structure and topological study of a 48 membered macrocyclic-tetrameric trimethyltin(IV) complex

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Triorganotin(IV) complexes of azo-carboxylic acids derived from amino benzoic acids and resorcinol were synthesized by the reaction of 2/4-(2,4-dihydroxy-phenylazo)-benzoic acids with appropriate triorganotin(IV) chlorides [R=Me (1 and 3), Ph (2 and 4) and Bu (5)] in presence of triethylamine. The characterisation of the complexes was accomplished by elemental analyses, UV, IR and multinuclear (1H, 13C and 119Sn) NMR spectroscopy. Structure of compound 3 was established by X-ray crystal structure analysis. X-ray crystal structure of 3 revealed that the compound exhibits a 48 membered macrocyclic-tetrameric structure with trigonal bipyramidal geometry around the tin atoms in which the three methyl groups occupy the equatorial positions while the apical positions are being occupied by the oxygen atom of carboxylate group of one ligand and the phenoxide oxygen atom of another ligand. The coordination network in 3 has also been analysed from the topological viewpoint. All the complexes display a sharp singlet 119Sn resonance in the range specified for the four coordinate structures suggesting that complexes have tetrahedral structures in solution. The five coordinate structure of the complexes in solid state dissociated into monomeric species with four coordinate structures in solution. Anti-diabetic activities of the complexes were studied and the results showed that the compounds 2, 3 and 4 exhibited effective activity even higher than the standard compound.