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

Abstract

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, <br /> 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.