Molecular sheet

With dielectric permeability for the region of crystal lattice vibrations of InSe (e1 = 6.8) and GaSe crystals (e1 = 6.2) [17] it is not difficult to show that appearance of a crystal layer between two H2 molecular sheets lead to screening of their interaction. It results in increase of parameter Ch2 in a matrix of a layered crystal, which becomes practically conterminous with parameter CGaSe and C rlSc in the given crystals. 

Fig. 2 (a) Three-dimensional structure of the 2 1 TCA-BP co-crystal containing toluene, 2, in the channels, (b) Stacking arrangement of molecular sheets perpendicular to the channels. 

Henderson, K.W., Kennedy, A.R., McKeown, A.E., and Strachan, D., Lithiated a-cyanophosphonates. Self-assembly of two-dimensional molecular sheets composed of interconnected twenty-four membered rings, J. Chem. Soc., Dalton Trans., 4348, 2000. 

Fig. 24 Depiction of the different hydrogen bonding patterns which hold molecular sheets together in the a- and (l-polymorphs of nitrofurantoin. Hydrogen bonds are shown by dotted lines (37).

Within the molecular sheets the interbond angles are almost exactly 90°, suggesting that simple pz orbitals are involved in the covalent bonding. The forces between the sheets are primarily van der Waals bonds, but, as in the selenium structure, there is no doubt that these forces also have an appreciable component of metallic character which increases with increasing atomic number, as is shown by the progressive... 

The resulting molecular sheets stack vertically to form channels incorporating solvent molecules and counter anions the intersheet distances depend on the extent of coplanarity of the in-sheet aromatic moieties and are 4.68, 6.30,... 

The molecular sheets can remarkably also be linked by covalent bonds. An alkane- or arenesulfonate anion (RSOj) 54 and the guanidinium cation 55 form an interesting inorganic 2D net 56, in which the organic moieties Rs are sticking out of the sheet (Fig. 14). The sheets are intercalatively layered in an R-depen-dent manner (57 for the top view) [62]. A simple use of an alkane- or arenedi-sulfonate 58-62 (Fig. 14) results in covalent linkage of the neighbouring sheets (63) [30]. 

As discussed earlier briefly, semicrystalline or amorphous nanotubes can be obtained from 3D compounds and metals by depositing a precursor on a nanotube template intermediately, and subsequently removing the template by calcination. If the template molecules are not removed and they are able to effectively passivate the dangling bonds of the compound, a perfectly crystalline nanotube composite can be obtained. However, after high-temperature calcination, the organic scaffold is removed and the inorganic oxide remains. Because a nanotube is the rolled-up structure of a 2D-molecular sheet, there is no way that all the chemical bonds of the 3D-inorganic compound will be fuUy satisfied on the nanotube inner and outer surfaces. Furthermore, the number of molecules increases with the diameter, and hence a full commensuration between the various molecular layers is not possible. Therefore, nanotubes of 3D... 

Undoubtedly, the development of reliable and robust synthetic routes leading to the creation of periodic covalent molecular sheets would raise unique structural,... 

Some other experiments by the Marburg group should be mentioned here . They might be named molecular sheet experiments. Here, mono-molecular layers of two different dyestuffs, one the donor and the other the acceptor, were separated by multiple layers of an inert surface-active material, 50 to several 100 A thick. The transfer efficiency from one side of that sandwich to the other was found to decrease with the inverse 4th power of the distance. For two-dimensional layers this corresponds to a / -distance dependence of the elementary transfer process. It must be mentioned, however, that the experimental Rq values are essentially higher than calculated. This might result from the mutual interaction between the close-lying dyestuff molecules in their individual layers. 

This review vdU cover recent progress in the areas of terpyridine-based suprametaUomolecular macrocycles, 3D structures, supramolecular interconversions, hierarchical self-assembly toward materials, and monolayer, molecular sheet structures. 

E.L. Tae, K.E. Lee, J.S. Jeong, K.B. Yoon, Synthesis of diamond-shape titanate molecular sheets with different sizes and realization of quantum confinement effect during dimensionality rednction from two to zero, J. Am. Chem. Soc. 130 (2008) 6534—6543. 

Fig. 2.5 a Depiction of the tetragonal packing in fluorobenzene via C-H- F-C and interactions (ref code PACFAQ crystallizes in [64]. b Formation of a molecular sheet... 

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