Synthesis, characterization, thermal, computational and biological activity studies of new potential bioactive diorganotin (IV) nitrosubstitutedhydroxamates-A comparative study

The new diorganotin (IV) complexes of composition [Me2SnCl(3,5-(NO2)(2)C6H2(OH)CONHO)] (I) and [n-Bu2SnCl(3,5-(NO2)(2)C6H2(OH)CONHO)] (II) have been synthesized by the reactions of Me2SnCl2 and n-Bu2SnCl2 with potassium 3,5-dinitrosalicylhydroxamate [3,5-(NO2)(2)C6H2(OH)CONHOK]- a ligand of biological significance bearing -NO2 and -OH substituents presumed to yield complexes with efficient bioactivity. The complexes have been characterized by elemental analyses, IR, H-1, C-13 and Sn-119 NMR and mass spectrometry in order to study the ligational behavior and probale geometry around tin as the ligand might show different bonding modes and geometry in complexes. The geometries of (I) and (II) have been computed using B3LYP/6-31 + G(d,p) set by DFT method and the vibrational frequencies, H-1 and C-13 NMR spectra compared with the experimental data. A comparison of computed bond lengths (C=O, C-N, and N-O) of (I) and (II) with that of free ligand, the Sn-O bond lengths, bond angles coupled with Sn-119 NMR and IR spectral data have suggested coordination through carbonyl and hydroxamic oxygens (O, O coordination) displaying five-coordinate distorted trigonal-bipyramidal geometry around tin. The thermal behavior of (I) and (II) has been studied by thermogravimetric techniques (TGA, DTG, DTA) and various kinetic parameters have been calculated. The electrochemical behavior of ligand, (I) and (II) studied by cyclic voltammetric technique has shown ligand centered redection. The HOMO-LUMO energies and orbitals, global reactivity descriptors, various thermodynamic parameters and dipole moment (mu) have been computed to determin the molecular properties of complexes. The in vitro antimicrobial activity assay against bacteria and fungi by MIC method has indicated higher potency of (I) than (II). The in vitro cytotoxicity on human muscle rhabdomyosarcoma (RD) by MTT method and the antioxidant potential by DPPH free radical scavenging showed higher inhibitory effect of complexes than ligand.