Interaction of Prolin, Leucine and methylurea with inorganic cluster [(PO4)M12O36].nH2O; (M = Mo, W)

Three new inorganic-organic hybrid materials based on heteropolyoxometalates, [L-C6H14NO2]3[(PO4)Mo12O36].3H2O (1), [L-C5H10NO2]3[(PO4)W12O36].H2O (2), and [C2H7N2O]3[(PO4)W12O36]. 4H2O (3), where C6H14NO2, C5H10NO2, and C2H7N2O are protonated L-leucine, L-proline, and methylurea, respectively, have been synthesized and structurally characterized by some physico-chemical methods. Elemental analyses, IR, Raman, mass, UV, and 1H NMR spectroscopies of the title hybrid materials indicate that there are van der Waals interactions between O atoms of the heteropolyoxometalates and water molecules, as well as the N and O atoms of the amino acids and methyl urea moieties. The molecular structures of synthesized hybrid materials contain discrete entities of L-leucinium, L-prolinium or methyluronium and water molecules that surround every [(PO4)M12O36]3- anion, over the extended crystalline network. The observed bands in Raman spectra of 2 and 3 demonstrate that [(PO4)W12O36]3- anion retains its “Keggin structure”. Between pH =7 and pH =4 the characteristic bands of the Keggin anion [(PO4)M12O36]3−(M = Mo, W) appear at 210 and 260 nm in the UV spectra, respectively.