Characterization of a new hexasodium diphosphopentamolybdate hydrate, Na6[P2Mo5O23]x7H2O, by 23Na MQMAS NMR spectroscopy and X-ray powder diffraction

Tris(ethyl-enediammonium) bis-[(2-amino-ethyl)ammonium] bis-[bis-(μ(5)-hydrogen phosphato)penta-μ(2)-oxido-deca-oxido-penta-molybdenum(VI)] deca-hydrate

The title compound, (C(2)H(10)N(2))(3)(C(2)H(9)N(2))(2)[Mo(5)(HPO(4))(2)O(15)]·10H(2)O, was prepared under hydro-thermal conditions at pH 5.0. The structure contains mono- and diprotonated ethyl-enediamine cations, [Mo(5)O(15)(HPO(4))(2)](4-) anions and uncoord-in-ated water mol-ecules. The [Mo(5)O(15)(HPO(4))(2)](4-) hetero-poly-oxometallate anion is made up of five MoO(6) octa-hedra sharing an edge and forming a ring, which is closed by common corners of the terminal MoO(6) octa-hedron. The ring is topped on both sides by two slightly distorted PO(4) tetra-hedra, sharing three corners with three MoO(6) octa-hedra. The terminal oxygen atoms of the PO(4) units are protonated. Together with the anions, the water mol-ecules and the ethyl-enediammonium cations are involved in N-H⋯O and O-H⋯O hydrogen bonding, forming a three-dimensional supra-molecular network.

Solution structural studies of molybdate-nucleotide polyanions

The complexation of molybdate with the nucleotides adenosine-5'-monophosphate (5'-AMP), adenosine-3'-monophosphate (3'-AMP) and guanosine-5'-monophosphate (5'-GMP) has been investigated by (1)H and (31)P NMR and Mo K-edge X-ray absorption near edge (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Acidification of aqueous solutions containing molybdate and each of the nucleotides resulted in the formation of a single species characterized by (1)H resonances which are deshielded relative to those of free nucleotide. Analysis of the two-component systems indicated a Mo/nucleotide ratio of 2.5:1 for the complexation species. White compounds, characterized as Na(2)[Mo(5)O(15)(HB)(2)] (B=5'-AMP, 5'-GMP), have been isolated from the acidified molybdate/H(2)B solutions. Dissolution in D(2)O replicates the NMR spectra of the solution species observed prior to precipitation. Solution and solid state Mo K-edge XAS and EXAFS spectroscopy of Na(2)[Mo(5)O(15)(HAMP)(2)] and Na(6)[Mo(5)O(15)(PO(4))(2)] provide convincing evidence for the presence of a pentamolybdodiphosphate core in the molybdate-nucleotide complexes in both the solid and solution states.