Synthesis, crystal structure, redox behavior and comprehensive studies on DNA binding and cleavage properties of transition metal complexes of a fluoro substituted thiosemicarbazone derived from ethyl pyruvate

Air and moisture stable coordination compounds of late first row transition metals, viz. Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), with a newly designed ligand, ethyl 2-(2-(4-fluorophenylcarbamothioyl)hydrazono)propanoate (LH), were prepared and fully characterized using various spectro-analytical techniques. The title compound acts as a tritopic, monobasic chelating ligand with S, N and O as the donor sites and is preferably found in the thiol form in all the complexes studied. The single crystal X-ray structure of the ligand (LH) was determined at 100 K and it was shown to be monoclinic, space group C2/c, with two molecules of LH and one molecule of water in the asymmetric unit giving an overall hemi-hydrate stoichiometry. All the metal complexes were found to be octahedral in nature with a 1:2 metal–ligand stoichiometry except for [Cu(L)Cl·H2O] which has a square pyramidal geometry with a 1:1 metal–ligand ratio. A quasi reversible cyclic voltammogram was obtained for the Cu(II) complex and was assigned to the Cu(II)/Cu(III) couple, whereas Ni(II) exhibited an irreversible anodic peak. Binding and cleavage properties of all the compounds to Escherichia coli DNA were comprehensively investigated by electronic absorption spectroscopy, viscosity, electrochemistry and gel electrophoresis measurements. They are found to be competent binding agents, offering coupled products at room temperature after incubation. Moreover the results of agarose gel electrophoreses showed that [Co(L)2] and [Ni(L)2] in the series have high binding and cleavage affinity towards DNA.

Ethyl 2-(2-(4-fluorophenylcarbamothioyl)hydrazono)propanoate (LH) acts as a tritopic, monobasic chelating ligand with S, N and O donor sites. The single crystal X-ray structure of the ligand (LH) was determined at 100 K and was shown to be monoclinic, space group C2/c, with two molecules of LH and one water molecule in the asymmetric unit, giving an overall hemi-hydrate stoichiometry. Binding and cleavage properties of all the compounds to Escherichia coli DNA were comprehensively investigated by spectroscopic methods and gel electrophoresis measurements.Figure optionsDownload as PowerPoint slideHighlights
► The ligand acts as a tritopic, monobasic chelate with S, N and O as the donor sites.
► The crystal structure shows the overall hemi-hydrate stoichiometry for the ligand.
► The cobalt and nickel complexes have high binding/cleavage affinity towards Escherichia coli DNA.