Hydrogen bond coordination number

No obvious separation of molecules into network vs interstitial types suggests itself. This fact is consistent with the single-peak character of the hydrogen-bond coordination number distributions exhibited in Fig. 19. It also seems to diminish the validity of the interstitial models that have been proposed to explain liquid water. 

According to these authors all gas hydrates crystallize in either of two cubic structures (I and II) in which the hydrated molecules are situated in cavities formed by a framework of water molecules linked together by hydrogen bonds. The numbers and sizes of the cavities differ for the two structures, but in both the water molecules are tetrahedrally coordinated as in ordinary ice. Apparently gas hydrates are clathrate compounds. 

While cation-dipole interactions dominate in the recognition of inorganic cations, anion-dipole interactions have been rarely taken advantage of in the design of ionophores for ISEs. Instead, a number of different interaction types have been used to develop ionophores for anions. These include hydrogen bonds, coordination to metal centers, and covalent bonds. 

Consequently, we can split the total coordination number (equation 13), into hydrogen bonding coordination. 

Another way to tackle the problem of defining the CVs is to renounce general-purpose CVs (e.g., number of hydrogen bonds, coordination of water, gyration radius in a typical folding problem) and to deduce them directly from the behavior of the system during the simulations. 

Element Electronegativity Covalent radius, pm Usual coordination number Bond with hydrogen Bond length, pm Bond energy, kj/mot ... 

The coordination chemistry of the large, electropositive Ln ions is complicated, especially in solution, by ill-defined stereochemistries and uncertain coordination numbers. This is well illustrated by the aquo ions themselves.These are known for all the lanthanides, providing the solutions are moderately acidic to prevent hydrolysis, with hydration numbers probably about 8 or 9 but with reported values depending on the methods used to measure them. It is likely that the primary hydration number decreases as the cationic radius falls across the series. However, confusion arises because the polarization of the H2O molecules attached directly to the cation facilitates hydrogen bonding to other H2O molecules. As this tendency will be the greater, the smaller the cation, it is quite reasonable that the secondary hydration number increases across the series. 

First, the hydrogen bond is a bond by hydrogen between two atoms the coordination number of hydrogen does not exceed two.7 The positive hydrogen ion is a bare proton, with no electron shell about it. This vanishingly small cation would attract one anion (which we idealize here as a rigid sphere of finite radius—see Chap. 13) to the equilibrium intemuclear distance equal to the anion radius, and could then similarly attract a second anion, as shown in Figure 12-1, to form... 

Open chain polyamine ligands have been widely studied. Often the coordination of zinc is compared with other first row transition metals and factors, such as behavior across a pH range, studied. The protonation patterns and stability constants are of particular interest. Octahedral zinc tris(ethylenediamine) structures have been characterized by X-ray diffraction with a number of different counter anions.94 The X-ray structure of zinc tris(ethylenediamine) with fluoride counter ions reveals extensive hydrogen bonding.95... 

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