Synthesis and characterization of tetraprolinium silicotungstic acid tetra-hydrate, a new organic-inorganic hybrid based on polyoxometallates

A new solvated polyoxometallate bearing an amino acid, (I), has been prepared for the first time by the reaction of 0.16 mmol alpha-H4SiW12O40.15H(2)O with 0.78 mmol of L-proline in hydrochloric acid at pH 3. The structure of (I) was substantially characterized by some physical approaches, such as elemental analysis, infrared spectroscopy, and H-1-NMR. Our findings proved that (I) could be formulated as [L-C5H10NO2]4[SiW12O40].4H(2)O. It is believed that the electrostatic attractions and hydrogen bonding between tungstosilisic acid and the prolinium cation affected the structure of (I). It is evident that the polyoxometallates moieties were arranged in good order to form large holes in the structural backbone. These cavities were occupied by the prolinium cations and water molecules. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.