Heteropolymolybdate–amino acid complexes: synthesis, characterization and biological activity

Three Keggin-type polyoxometalates functionalized by amino acids, (C5H13N2O2)2(H3O)PMo12O40·8H2O 1, (C5H14N2O2)2SiMo12O40·12H2O 2 and (C5H14N2O2)2GeMo12O40·12H2O 3, were synthesized and characterized by elemental analysis, IR and 1H NMR spectra and single-crystal X-ray diffraction. The X-ray crystallographic study showed that the structures of the three compounds involved N–H···O and O–H···O hydrogen bonds among the protonated ornithine cations, water molecules and the heteropolyanion cluster, and thus represent a model interaction between polyoxometalates and proteins. These complexes display inhibitory actions to the human cancer cells Hela and PC-3 m in vitro.