Two-dimensional hydrogen-bonded

Stimulated by these observations, Odelius et al. [73] performed molecular dynamic (MD) simulations of water adsorption at the surface of muscovite mica. They found that at monolayer coverage, water forms a fully connected two-dimensional hydrogen-bonded network in epitaxy with the mica lattice, which is stable at room temperature. A model of the calculated structure is shown in Figure 26. The icelike monolayer (actually a warped molecular bilayer) corresponds to what we have called phase-I. The model is in line with the observed hexagonal shape of the boundaries between phase-I and phase-II. Another result of the MD simulations is that no free OH bonds stick out of the surface and that on average the dipole moment of the water molecules points downward toward the surface, giving a ferroelectric character to the water bilayer. 

Fig. 32a and b. Schematic illustration of intermolecular arrangements in the crystalline complexes of host 25 (taken from Ref.25>) a the two-dimensional hydrogen bonding pattern parallel to the ab plane (the shaded area represents the 1,1-diphenylcyclohexane framework) b the van der Waals type packing of the hydrogen bonded layers along the c axis (R represents the cyclohexyl ends of the host species)... 

V. A. Russell, M. D. Ward, Two-dimensional hydrogen-bonded assemblies the influence of sterics and competitive hydrogen bonding on the structures of guanidinium arenesulfonate networks , J. Mater. Chem 1997, 71123-1133. 

V. A. RusseU, C. C., Evans, W. Li, M. D. Ward, "Nanopor-ous molecular sandwiches pillared two-dimensional hydrogen bonded networks with adjustable porosity , Science 1997,276,575-579. 

II Open systems in two dimensions in which chains are linked to usually six other chains forming a two-dimensional hydrogen-bonded framework. The only known example of this type is fi polyglycine. 

H. Koyano, P. Bissel, K. Yoshihara, K. Ariga, T. Kumitake, Effect of Melamine-Amphiphile Structure on the Extent of Two-Dimensional Hydrogen-Bonded Networks Incorporating Barbituric Acid , Chem. Eur. J., 3,1077 (1997)... 

Polyamino acids can be considered as models for conformational studies, providing an atomistic description of the secondary structural motifs typically found in proteins [30-39]. Two-dimensional hydrogen-bonded layers and columns in the structures of crystalline amino acids can mimic S-sheets and helices in proteins and amyloids [40 5], and can be compared with two-dimensional crystalline layers at interfaces [46-58]. Nano-porous structures of small peptides can mimic cavities in proteins [24, 59-63]. One can also prepare crystals in which selected functional groups and side chains are located with respect to each other in the same way, as at recognition sites of substrate-receptor complexes, and use the systems to simulate the mutual adaptation of components of the complex responsible for recognition. 

Among extended polymeric structures, two-dimensional hydrogen-bonded frameworks are enormously popular, and the resulting assemblies resemble practically crinkled tapes (153,154) and infinite sheets (155-158). Smith and co-workers have structurally characterized a... 

The dimer synthon formed by the carboxyl group has been used to assemble a variety of supermolecules due to its bidentate character which increases the strength of the interaction. For example, terephthalic acid (8) [39] and iso-phthalic acid (9) [40] form one dimensional tapes. Trimesic acid (2) with its threefold molecular symmetry forms a two dimensional hydrogen bonded sheet [41] and adamantane-l,3,5,7-tetracarboxylic acid (10) with its tetrahedrally disposed carboxy functionality forms a diamondoid network (Fig. 9) [42]. 

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