Assembly of Dimeric and Tetrameric Complexes of Polyoxomolybdobisphosphonates Built from [(Mo3O8){O3PC(O)(CH2-3-C5NH5)PO3}]2– Subunits

Two hybrid organic–inorganic organobisphosphonate polyoxomolybdates, Na4H2[(Mo3O8)2(O){O3PC(O)(CH2-3-C5NH5)PO3}2]·12H2O (1) and Na8[(Mo3O8){O3PC(O)(CH2-3-C5NH5)PO3}]4·30H2O (2), have been successfully synthesized and structurally characterized. Compounds 1 and 2 are prepared in aqueous solution by one-pot reaction of 1-hydroxo-2-(3-pyridyl) ethylidenebisphosphonate (risedronic acid) with molybdate. Structural analysis reveals that the two polyanions are composed of the same building blocks and can be described as a dimeric and tetrameric assembly of [(Mo3O8){O3PC(O)(CH2-3-C5NH5)PO3}]2– subunits, respectively. Elemental analysis, IR spectra, thermogravimetric analysis, and luminescence properties of the compounds have been studied in the solid state. The compounds are also characterized in the solution by multinuclear 31P NMR spectrometry, which evidences a subtle equilibrium between some species, and the results indicate that 1 presents two conformers of these hexanuclear polyanions in solution, whereas 2...