Complex formation reactions of gallium(III) and iron(III/II) with l-proline-thiosemicarbazone hybrids: A comparative study

Two gallium(III) complexes with l-proline-thiosemicarbazone hybrids have been synthesised and comprehensively characterised. Reaction of iron(III) with the terminally dimethylated l-proline-thiosemicarbazone hybrid led to an oxidative cyclisation of the ligand and isolation of an iron(III) complex. The cytotoxicity of the new compounds was studied on three human cancer and one normal cell line, revealing no or low activity. The complexation reactions with iron(II), iron(III) and gallium(III) were studied in solution by using different methods. The low stability of the gallium(III) complexes at physiological pH and the low iron(II) binding affinity of the ligand precursors most probably contributes to the low antiproliferative activity of the studied substances.