Low-Temperature Single-Crystal Raman and Neutron-Diffraction Study of the Hydrogenous Ammonium Copper(II) Tutton Salt and the Deuterated Analogue in the Metastable State

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• 作者：Christopher Dobe ; Graham Carver ; Hans-Beat Bü ; rgi ; Philip L. W. Tregenna-Piggott ; Garry J. McIntyre ; Maria A. Augustyniak-Jablokow ; and Mark J. Riley
• 刊名：Inorganic Chemistry
• 出版年：2003
• 出版时间：December 15, 2003
• 年：2003
• 卷：42
• 期：25
• 页码：8524 - 8533
• 全文大小：161K
• 年卷期：v.42,no.25(December 15, 2003)
• ISSN：1520-510X

文摘

Low-temperature (15 K) single-crystal neutron-diffraction structures and Raman spectra of the salts (NX₄)₂[Cu(OX₂)₆](SO₄)₂, where X = H or D, are reported. This study is concerned with the origin of the structural phasechange that is known to occur upon deuteration. Data for the deuterated salt were measured in the metastablestate, achieved by application of 500 bar of hydrostatic pressure at ~303 K followed by cooling to 281 K and thesubsequent release of pressure. This allows for the direct comparison between the hydrogenous and deuteratedsalts, in the same modification, at ambient pressure and low temperature. The Raman spectra provide no intimationof any significant change in the intermolecular bonding. Furthermore, structural differences are few, the largestbeing for the long Cu-O bond, which is 2.2834(5) and 2.2802(4) Å for the hydrogenous and the deuterated salts,respectively. Calorimetric data for the deuterated salt are also presented, providing an estimate of 0.17(2) kJ/molfor the enthalpy difference between the two structural forms at 295.8(5) K. The structural data suggest that substitutionof hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions that result in a slightly reducedforce field about the copper(II) center. The small structural differences suggest different relative stabilities for thehydrogenous and deuterated salts, which may be sufficient to stabilize the hydrogenous salt in the anomalousstructural form.