Synthesis, characterization, molecular modeling and eukaryotic DNA degradation of 1-(3,4-dihydroxybenzylidene)thiosemicarbazide complexes

A new chelating agent, 1-(3,4-dihydroxybenzylidene)thiosemicarbazide, H3BTS, has been introduced for complexation with AsO2+, SbO+, VO2+, Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Bi(III) ions. The isolated chelates are characterized by partial elemental analyses, magnetic moments, spectra (IR, UV–Vis, ESR) and thermal studies. The molecular parameters of the ligand and its metal complexes have been calculated. The protonation constants of H3BTS (10.35, 9.45 and 8.35) and the stepwise stability constants of its complexes are calculated; Fe(III)–H3BTS system was found the most stable while Cr(III)–H3BTS was the lowest. The ligand coordinates as tribasic with Fe(III), Ni(II) and SbO+, dibasic with VO2+, Cu(II), Co(II), Bi(III), AsO2+ and Cr(III) and monobasic with Zn(II) ions. Copper(II) and chromium(III) complexes measured anomalous magnetic moments while Co(II), Ni(II) and Fe(III) complexes have normal values. The ligand field parameters were calculated for [Cr2(HL)(OAc)2(OH)2(H2O)] and [Co(HL)(H2O)2] and their values were found in the range reported for a tetrahedral structure. The ESR spectra of the Cu(II) and VO2+ complexes support the binuclear structure. The end product in the thermal decomposition of some complexes are the metals (Bi, As and/or Sb). [(VO)2(HL)(SO4)]2H2O, [Cr2(HL)(OAc)2(OH)2(H2O)] and [Co(HL)(H2O)2] are found active for the degradation of the DNA of eukaryotic subject completely.