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4 ?, thus appears to be the weakest hydrogen bond in the structure. As shown in Fig. 6 ?, Fourier maps (F obs) phased on the refined structure reveal no partially occupied H-atom sites in the tetramer rings at any temperatures, at least down to the level of the background noise (around 5% of the nuclear scattering density due to a H atom); the Ow6 and Ow9 molecules are thus orientationally ordered and remain so throughout cooling and warming. Figure 6 Fourier maps, F obs, phased on the refined structure at Duvelisib ic50 each temperature and visualized in a slice through the water tetramer defined by Ow6 and Ow9 (the panel at the top depicts the corresponding local atomic structure). Peaks �C bright spots ... One hitherto unidentified aspect of the structure of these highly hydrated inorganic salts is the occurrence of extended water polymer networks. In MgSeO4��9H2O the water tetramer described above is merely the centre of a larger structure, a centrosymmetric dodecamer, (H2O)12, comprised of Ow2, PRDX4 Ow5, Ow6, Ow7, Ow8 and Ow9 (Fig. 7 ? a). The aforementioned tetramer is extended by a pair of pentagonal rings with apical chains folded back upon the structure in such a way as to form a pseudo-pentagonal sigmoidal profile (Fig. 7 ? b), the ��missing�� edge of the open pentagon being supplied by the edge of the Mg(H2O)6 octahedron. Figure 7 (a) The hydrogen-bonded dodecamer of water molecules viewed obliquely and (b) perpendicular to the central tetramer unit illustrating the pentagonal sigmoidal folding of the structure and its relationship to the adjacent Mg(H2O)6 octahedra. The position of the neutral dodecamer cluster in relation to its surrounding ionic polyhedra and the remaining three water monomers is shown in Fig. 8 ?. Figure 8 The broader context of the neutral dodecamer��s relationship to the ionic polyhedra and to particular planes that were identified previously as common forms in the macroscopic morphology of the crystals. Similar pentagonal motifs occur in the polymeric water frameworks of all related hydrates with one or more free interstitial water molecule (Fig. 9 ?). In MgSeO4��7H2O there is an infinite chain Bleomycin in vitro of open-sided pentagons with decorated corners extending along the crystal��s c-axis, whereas in MgSeO4��11H2O there is a hexadecamer, (H2O)16, composed of closed pentagonal rings, which has short side-chains extending along the c-axis of the crystal. Figure 9 Polymeric water structures found in this and related hydrate structures revealing the propensity of these chains or clusters to adopt pentagonal motifs. The observation of dodecamer and hexadecamer water clusters in crystal structures is not unique (see Song & Ma, 2007 ?; Wang et al., 2010 ?; Li et al., 2012 ?; Ghosh & Bharadwaj, 2004 ?; Jin et al., 2008 ?); indeed there is a dodecamer structure very similar to that described here in copper citrate phenanthroline hexahydrate (Fu et al., 2010 ?).