H-bond network

That is, the H-bonded network provides a natural route for rapid transport. This phenomenon of proton jumping thus occurs with little actual movement of the water molecules themselves. Ice has an electrical conductivity close to that of water because such proton jumps also readily occur even when the water molecules are fixed in a crystal lattice. Such conduction of protons via H-bonded networks has been offered as an explanation for a number of rapid proton transfers of biological significance. 

Tin(II) chlorides are similarly complex (Fig. 10.5). In the gas phase, SnCh forms bent molecules, but the crystalline material (mp 246°, bp 623°) has a layer structure with chains of comer-shared trigonal pyramidal SnClsl groups. The dihydrate also has a 3-coordinated structure with only I of the H2O molecules directly bonded to the Sn (Fig. I0.5c) the neutral aquo complexes are arranged in double layers with the second H2O molecules interleaved between them to form a two-dimensional H-bonded network... 

These hydrates are not ionically dissociated but contain chains of H2O molecules cross-linked by NH3 molecules into a three-dimensional H-bonded network. 

In the solid state sulfamic acid forms a strongly H-bonded network which is best described in terms of zwitterion units +H3NSO3" rather than the more obvious formulation as aminosulfuric acid, H2NS02(0H). The zwitterion has the staggered configuration shown in Fig. 15.50a and the S-N distance is notably longer than in the sulfamate ion or sulfamide. 

Dynamic light-scattering experiments or the analysis of some physicochemical properties have shown that finite amounts of formamide, A-methylformamide, AA-dimethyl-formamide, ethylene glycol, glycerol, acetonitrile, methanol, and 1,2 propanediol can be entrapped within the micellar core of AOT-reversed micelles [33-36], The encapsulation of formamide and A-methylformamide nanoclusters in AOT-reversed micelles involves a significant breakage of the H-bond network characterizing their structure in the pure state. Moreover, from solvation dynamics measurements it was deduced that the intramicellar formamide is nearly completely immobilized [34,35],... 

DMSO and water form a solution with nonideal behavior, meaning that the properties of the solution are not predicted from the properties of the individual components adjusted for the molar ratios of the components. The strong H-bonding interaction between water and DMSO is nonideal and is the primary driver for the very hygroscopic behavior of DMSO. Even short exposure of DMSO to humid air results in significant water uptake. Water and DMSO nonideal behavior results in an increase in viscosity on mixing due to the extensive H-bond network. 

Metal complexes of pteridine have provided 3D H-bonded networks containing H bonding between pteridine ligands and water molecules, and 7r-stacking and H bonding between adjacent pteridine ligands. The complex [ZnL(H20)2].2H20 has been prepared.267... 

This essential absence of longer-range proton order in tetrahedral H-bond networks is the origin of the famous zero-point entropy of ice L. Pauling, J. Am. Chem. Soc. 57 (1935), 2680 and L. Pauling, note 16, pp. 466-468. 

An extensive H-bonding network exists in the vicinity of homocitrate and nearby bridging sulfides. 

Of course, it is impracticable to synthesise nanoscale devices based solely on covalently-linked bridged systems and it is reassuring to learn that ET is also strongly mediated by H-bonded networks and by solvent molecules, thereby opening the way for the construction of photovoltaic supramolecu-lar assemblies. 

A. Berkessel and J. A. Adrio, Dramatic acceleration of olefin epoxidation in fluorinated alcohols Activation of hydrogen peroxide by multiple H bond networks. J. Am. Chem. Soc. 128, 13412 13420 (2006). 

The coupling constants could be used to characterize H-bond networks in the active centers of enzymes and ribozymes. In particular, the proposed low-barrier H-bonds or short strong H-bonds should give rise to very strong coupling values. 

P parameter actually increases with added CO2, which must be a result of changes in the H-bond network between methanol and water because CO2 has a negligibly small and negative fi. However, the most important attribute is that the mixtures basically have high solvent strength even when high proportions of CO2 are added to the mixtures. 

PDB 1M56 R. spharoides D and K pathway entrance aa residues in green. H-bonding network aa residues in blue. Red dashed lines describe proton translocation routes. 

Chirality can be introduced at two possible sites on the basic tripodal structures replacing the tripodal template by a chiral template or modifying each arm with a chiral component, usually as amino acids, between the template and the ligating groups. Incorporation of amino acids inevitably introduced an amide bond known to promote intricate H-bonding networks. The latter can be applied to the various templates described so far. 

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