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

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journal contribution
posted on 2013-06-05, 00:00 authored by Lu Yang, Zhen Zhou, Pengtao Ma, Jingping Wang, Jingyang Niu
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 is metastable, which might gradually decompose into one isomer of the dimer units. The photochromic property of 1 is determined under ultraviolet (UV) irradiation of 365 nm, and the sample develops a reddish coloration.

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