Synthesis, spectral, DFT, intrinsic constant of DNA binding and antioxidant activity of vanadyl (IV)2+ complexes of a symmetrical bisthiosemicarbazides

Abstract

A new series of complexes were prepared by reacting vanadyl (II) sulphate with three multidentate bisthiosemicarbazides, TSCs in search for synthesizing a series of vanadyl complexes to be good candidates for utilization as anti-diabetic drugs. The TSCs 1(H4DDAT), 3 (H4DDET) and 5 (H4DDPT) were characterized by partial elemental analyses, 2DNMR, mass, FTIR and UV–vis. Spectra. The complexes were characterized by elemental analyses (C, H, N, S, M), spectral (FTIR, UV–vis., mass, ESR and XRD), magnetic susceptibility and molar conductivity measurements and assigned the formulae: [(VO)(H4DDAT) (H2O) (OH)]. H2O (2), [(VO)(H4DDET)(SO4)(H2O)].1·5H2O (4) and [(VO)(H4DDPT)(H2O)(SO4)2].2H2O (6). TSC`s were found to bind metal ion in keto or enol/thiol forms as neutral, monobasic or dibasic tridentate and / or hexadentate selective chelate as proved by the data of FTIR and NMR (heteronuclear single quantum coherence (HSQCNMR), correlated spectroscopy (COSY-NMR). UV–vis. and EPR data suggested a square pyramidal arrangement for complex (2) and an octahedral geometry for complexes (4) and (6), respectively. The anisotropic Lande splitting factor evaluated from EPR spectra for the complexes gave values; g|| < g⊥ < ge =2 0.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The thermal stability and nature of solvent molecules nature were studied by TGA and DrTGA. XRD data complex (2) suggested a triclinic complex (2); a cubic structure for complex (4) and a monoclinic for complex (6). Molecular modeling evaluated by DFT theory suggested oxygen atoms, N of NH or S of CS groups as donor atoms of TSc moiety and the geometry, Mullikan population, Mullikan charge and HOMO–LUMO gap were computed. Moreover, all compounds were screened for antioxidant activity such as SOD-like activity, scavenging of hydroxyl radicals as well as DNA binding ability.