Synthesis, X-ray crystal structure and vibrational spectroscopy of the acidic pyrophosphate KMg0.5H2P2O7·H2O |
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Authors: | M Harcharras A Ennaciri AGG Moliterni V Bertolasi |
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Institution: | a Laboratory of Spectroscopy, Department of Chemistry, Faculty of Sciences, University Ibn Tofail; B.P.133, 14000 Kenitra, Moroccob Dipartimento Geomineralogico, Istituto di Cristallografia (IC-CNR), Via Orabona 4, 70125 Bari, Italyc Istituto di Metodologie Inorganiche e dei Plasmi (IMIP-CNR), Area della ricerca di Roma-Montelibretti, Via Salaria Km 29,300, C.P. 10-00016 Monterotondo Stazione Roma, Roma, Italyd Dipartimento di Chimica and Centro di Strutturistica Diffrattometrica, Università di Ferrara, Via Borsari 46, 44100 Ferrara, Italy |
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Abstract: | The hydrated potassium hemimagnesium dihydrogen pyrophosphate KMg0.5H2P2O7·H2O was synthesized. It crystallizes in the triclinic system, space group (n. 2), Z=2, with the following unit-cell parameters: a=6.8565(2) Å, b=7.3621(3) Å, c=7.6202(3) Å, α=81.044(2)°, β=72.248(2)°, γ=83.314(3)°, V=360.90(2) Å3. The structure was obtained by single-crystal X-ray diffractometry, and a full-matrix least-squares refinement based on F2 gave a final R index of =0.0368 (wR=0.0975), utilizing 1446 observed reflections with I>2σ(I). The crystal packing consists in a three-dimensional network made by layers parallel to ab plane of PO4 double tetrahedra and MgO6 octahedra, linked by hydrogen bonds, while K atoms form complex coordination within cavities between tetrahedra and octahedra. The dihydro-pyrophosphate anion (H2P2O7)2− shows bent eclipsed conformation and the Mg2+ ion lies on inversion center. No coincidences observed between most of infrared and Raman spectral bands confirmed the centrosymmetric structure of the title compound; the vibrational spectra point to a bent POP bridge angle. |
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Keywords: | Pyrophosphate X-ray single-crystal diffractometry Ci symmetry Hydrogen bond Raman spectroscopy Infrared spectroscopy |
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