Anionic water host lattice

Fig. 21.7. Section of the framework anionic-water host lattice formed by linking almost planar (H20)4F groups in (CH3)4N+(F-4H20)-. The water molecules are three-coordinated with an almost planar configuration [436]...

Fig. 21.8. A channel-type anionic-water host lattice formed from vertex-linked (H20)4C1 tetrahedra in the structure of (C2H5)4N+ -(H20)4C1. The (H20)4 homodromic quadrilaterals are almost planar. The water molecules are three-coordinated donating two and accepting one hydrogen bond. The protons appear to be ordered [790]...

Fig. 21.9. A channel-type anionic-water host lattice formed by edge-sharing (H20)4F- tetrahedra with bridging water molecules in the structure of 4 (C2Hj)4N+(F 11H20). In this structure, six waters are three-coordinated and five are only two-coordinated, i.e., are donors only [438]...

Fig. 21.12. The anionic-water host lattice in [n(C4H9)3S]+[F 23H20]-, showing half the large 45548610 polyhedral void that accommodates two anions. The other half is related by the center of symmetry at (0,1,0) sharing the dotted edges. The F anion was not distinguished from the oxygen in this X-ray analysis. It may be disordered over the water lattice. The top figure is the central part of the bottom figure [796]...

In the higher hydrates of the quaternary ammonium salts, the cations are the guest species and the water and anions form the anionic host lattice. In the recently discovered strong add hydrates such as HC104 6H20 [767], the anions are the guests in a cationic water lattice. 

The results of our studies on urea/thiourea/selenourea-anion inclusion compounds have demonstrated that the classical urea or thiourea hydrogen-bonded host lattice can be modified in interesting ways by the incorporation of various anionic moieties, with or without cocrystallized water or other uncharged molecules, and that novel host frameworks bearing different urea, thiourea, or selenourea/guest molar ratios are generated by variation in size of the hydrophobic, pseudo-spherical R4N guest species. The stoichiometric formulas of 46 inclusion compounds and their structural details are listed in Table 10. For convenient description of stoichiometric ratios, the letters u, a, and c are used to denote the urea/thiourea/se-lenourea molecule, the anion, and the cocrystallized neutral molecule, respectively. 

It is noted that the types of host lattices formed are dependent on the stoichiometric ratio of urea derivatives to anions and cocrystallized solvent molecules (water in most cases) or neutral molecules as additional host components. 

In the urea-boric acid-carbonate host lattice (1.11, Figure 39) the boric acid molecules link the carbonate anions and urea molecules to form a double ribbon, and are further connected to water molecules located between adjacent double ribbons to form a hydrogen-bonded planar layer, and three independent urea molecules and a 6303(011)2 fragment of the pentaborate ion are linked by hydrogen bonds to form an infinite twisted ribbon in one urea-pentaborate complex (1.12, Figure 40). Two-dimensional infinite layers of interconnected urea molecules, pentaborate ions, and neutral B(OH)3 molecules generate the host lattice of another urea-pentaborate complex (1.13, Figure 16). 

Finally the structure of the tosylate ciyptate of R3Bp demonstrates the size exclusion expected of the large cation (Fig. 11). Even so, it is not devoid of interaction with the cationic host, in the lattice at least, as each anion exhibits one moderately short H-bond contact to one of the NH1 functions of the cryptate. These direct H-bond contacts are often supported by indirect water-mediated links of shorter dimensions, acting as part of branched hydrate chains which run through the less hydrophobic section of the lattice. 

V=9.267(1) nm, Z=4, Ri=0.0S3 and Rw=0,058. The complex is composed of copper cations, nitrate anions, 1,10-phenanthroline, protocatechuic acid and lattice water molecules. The structure of H3PCA, N03 and waters comprises packing of three-dimensional network by hydrogen bonds with cavities. The complex can be considered as a model of host/guest supermolecule. The three-dimensional hydrogen-bonding network is the host species. The Cu(phen)3 cations, guest species, occupy the cavities of the host. 

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