Intermolecular voids

At one extreme of the inclusion compounds variety are complexes, usually classified as solvates, in which molecules of the solvent are enclosed within intermolecular voids of the crystal to fill empty space or to complete a coordination sphere around a functional moiety. Quite often, it is difficult to control such a co-crystallization... 

Figure 4. Schematic representations of possible modes of controlling permeability through an oriented membrane by host-guest complexation. (a) Control of permeability through intermolecular voids, (b) Control of permeability through intramolecular channels (reprinted with permission from Anal. Chem. 1993, 65,928. Copyright 1993 American Chemical Society).

Cuest-induced Changes in Membrane Permeability. As mentioned earlier, guest-induced changes in membrane permeability may be effected by oriented membranes through the intermolecular voids between or the intramolecular channels within the membrane molecules (see Figure 4a and Figure 4b, respectively). 

Guest-induced changes in permeability through intermolecular voids between membrane molecules has also been applied by other groups for chemical sensing of various analytes. Sensing of Ca " or urea ° by electrodes coated with... 

Of the 7.57 water molecules per asymmetric unit, four are fully ordered and one, W(5), shows two positions at 0.64 and 0.36 occupation. These water molecules are located in intermolecular voids, and the remaining 2.57 waters are statistically distributed over four sites in the a-cyclodextrin cavity (see Fig. 18.6 b). Associated with this disorder in the a-cyclodextrin cavity is a round shape of the macrocycle, where in contrast to the other two a-cyclodextrin hydrate forms, all six intramolecular interglucose 0(2) 0(3 ) hydrogen bonds are formed. Because hydrogen atoms attached to the disordered water molecules in the 7.57 hydrate could... 

Classification of composites by the phase inclusion size bears a philosophical aspect how small should a component in the matrix be not to make the term composite material so universal as to include in fact all materials Interatomic distances in molecules and crystals are of 1.5 10 m dimensionality, distances between iterative elements of the crystalline structure are 10 —10 m, while the size of the smallest intermolecular voids in polymers is 10 m. Note that mean nanoparticle size (plastic pigments are 10-8-10 m in size, the diameter of monocrystalline fibers or whiskers is 10 —10 m, glass microspheres are 10 —10 m) is commensurate with parameters of monolithic simple materials. This means that in the totality of engineering materials, nanocomposites occupy a place at the boundary between composite and simple materials. 

The monolayers are not perfectly ordered intermolecular voids are present and, therefore, no efficient inhibition of electron transfer across such layers was seen, as reported by Kaifer et al. [36]. There have been several approaches to the provision of anchoring groups of thiol, sulfide, and disulfide functionalities with which CyDs would be deposited on the gold surface as a better ordered monolayer. In the case of j5-CyD, full substitution of the seven primary hydroxyl groups by thiol- or sulfide-containing groups results in submonolayers with relatively large defect sites [36]. 

Membrane technologists are well aware that the most permeable glassy polymers are those which possess a very high free volume, where the term free volume refers to the intermolecular voids within a material [1], Scientists who work with molecular sieves, such as zeolites, commonly use the term microporous material to describe those materials which contain pores or channels less than 2nm in width, a definition that arises in the context of gas adsorption studies [2],... 

Solutions of salts in water represent typical insertion structures where ions occupy intermolecular voids, being oriented by the positive or negative charges to the corresponding poles in a dipole of the H2O molecule. Samoylov [90], having analyzed the XRD data and using an original thermochemical method to estimate the coordination of ions in water solutions, has found, that in diluted solutions the ions replace a molecule of water each and thus acquire Nc 4. In concentrated solutions, ions coordinate water molecules around them the structures resemble those of crystalline... 

The oxidation and reduction peaks in the absence of analyte showed that there was substantial background permeability for the membranes. This can have two possible origins (i) microscopic imperfections such as pinholes, and (ii) permeation of the hydroquinone into intermolecular voids and complexing with the C[4]RA itself. A further notable feature is the substantial shift of the reduction peak to more negative values, more pronounced in the case of the chloroform than in the case of the acetone. A shift of the redox peaks positions has also been reported in [5]. 

I. 922(5) to 1.944(7) A and the bond angle is 110.8°. A toluene molecule is guested in the intramolecular apolar cavity of each macrocycle, whereas two other molecules occupy intermolecular voids of the crystal lattice. These two molecules are rather disordered and this causes probably problems in the final refinement of the crystal structure. 

Channel Mimetic Sensing Membranes Based on the Control of Permeability through Intermolecular Voids... 

Interesting results have been obtained on the control of permeability through intermolecular voids. However, considering the high efficiency and selectivity of permeation through biological ion channels based on a discrete molecular entity with a well-defined channel structure, it would be quite significant for the development of... 

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