Synthesis, properties and crystal structure of some polyoxometallates containing the tris(hydroxymethyl)aminomethane cation

Polyoxometallates [(CH2OH)3CNH3]3PMo12O40·5H2O, [(CH2OH)3CNH3]3PW12O40·11H2O, [(CH2OH)3CNH3]2H2SiW12O40·10H2O, [(CH2OH)3CNH3]4GeW12O40·9H2O, [C4H12NO3]4SiMo12O40·5H2O, [(CH2OH)3CNH3]2H4P2W18O62·3H2O and [(CH2OH)3CNH3]3H3As2W18O62·4H2O have been synthesized for the first time, purified, and structurally characterized by means of elemental analyses, IR spectrum, electronic spectrum, cyclic voltammogram, 31P NMR and X-ray diffraction. The crystal structure of [(CH2OH)3CNH3]4PMo12O40·5H2O has been determined by X-ray diffraction. Hydrogen bonding between (CH2OH)3CNH2 and PMo12O40 3− was inferred from heavy atom distances. The solid reflectance electronic spectra and IR spectra indicate that there is interaction between the H3PMo12O40 and the organic substrate. The complexes have photosensitivity under irradiation of sunlight to result in charge transfer by oxidation of (CH2OH)3CNH2 and the reduction of the polyoxometallates. We also found that [(CH2OH)3CNH3]3PMo12O40·5H2O and [(CH2OH)3CNH3]3 PW12O40·11H2O exhibited substantial catalytic activity toward the electro-reduction of bromate and nitrite, respectively.