Supramolecular mechanisms

In keeping with the basic tenet of supramolecular chemistry, that it is chemistry beyond the molecule , any therapy that claims to work through a supramolecular mechanism must involve multiple target specific interactions. Furthermore the nature of the interactions should be non-covalent. 

Valkova L., Borovkov N., Koifman O., Kutepov A., Berzina T., Fontana M., Rella R., and Valli L., Sorption of amines by the Langmuir-Blodgett films of soluble cobalt phthalocyanines Evidence for the supramolecular mechanisms. Biosens. Bioelectron., 20, 1177-1184, 2004. 

The theory of polymer fibres durability, derived by Jurkov s ther-mal-fluctuational theory assumes the origin of deformation and fracture processes in the atomic-molecular and supramolecular mechanism. Its peculiar importance resides in the fact that this theory explains the role played by the chains orientation during the occurrence of deformation and fracture. On can conclude that the increase of fibres resistance and, therefore, durability can be... 

The scheme of the peroxides activation and decomposition in the presence of quaternary onium salt is proposed. It is substantiated by kinetic methods as well as by molecular modeling methods. It has been shown that peroxides decomposition in the presence of tetraethylammonium bromide proceeded according to supramolecular mechanism. Cyclohexanone peroxides in the presence of Et4NBr effectively initiate the radical chain cumene oxidation. 

Key words oxycycloalkylperoxides, quaternary ammonium salts, catalysis, supramolecular mechanism, initiation efficiency, molecular modeling... 

Chapter 7 is devoted to important physicochemical —basically mechanistic — aspects of the direct enantioseparations, carried out by using either CSP or mobile phase. In such cases, the diversity of the involved separation mechanisms is much greater than the most of other chromatographic modes (and, particularly, when compared with the relatively simple physicochemical rules governing adsorption or partition liquid chromatography). Thus, the author of this chapter discusses enantioseparation in terms of the solute-chiral selector complexation constants, stoichiometry and selectivity of complexation, the nature of the binding sites on the stationary phase surface, and, finally, the supramolecular mechanisms of complexation. 

The mechanism of recognition of most supramolecular entities (such as abiotic receptors) is the formation of several hydrogen bonds. Since heterocyclic tautomers possess both strong HBA and HBD properties (see Sections III,G, V,D,2, and VI,G), they are often used for this purpose. For instance, the hydrogen bond network formed by 5,5 -linked bis(2-pyridones) has been used by Dickert to obtain sensors (96BBG1312). 

It hag been shown that transition of a backbone carbon from the sp to sp state is promoted by tensile stresses and inhibited by compressive strains (10,44). The acceleration of the process of ozone oxidation of the polymers under load is not associated with the changes in supramolecular structure or segmental mobility of the chain. The probably reason of this effect is a decreasing of the activation energy for hydrogen abstraction (44). The mechanism of initial stages of the reaction of ozone with PP can be represented as ... 

Supramolecular chemistry takes into consideration the weak and reversible non-covalent interactions between molecules, which include H-bond-ing, metal coordination, hydrophobic forces, van der Waals forces, n—n interactions, and covers different research fields, for example, molecular recognition, host-guest chemistry, mechanically interlocked and nanochemistry. 

Despite the vast number of reported syntheses, crystal structures, properties and applications of monomeric Pcs, it is still difficult to clarify clearly the synthetic mechanisms of Pcs in various conditions, to predict fully the supramolecular structures of Pcs in the solid state (except for a very few types of simple Pcs), and to elucidate completely the correlation between molecular structure and properties. The large-scale preparation and separation of some novel Pcs with interestingly properties is still very hard. On the basis of the great potential applications of Pcs in high-tech fields, exploitation of multi-functional Pc materials needs to be strengthened in the future. There is still plenty of room for further investigation of Pc chemistry. 

Trzaska and co-workers showed a similar propeller mechanism for the formation of helical columns from disclike metallomesogens (29-31).34 These metallomesogens also have C3 symmetry and 30 and 31 are provided with chiral side chains. In the hexagonal columnar mesophase these chiral side chains induce a Cotton effect in the chromophore of the helically arranged core. Heating the mesophase to the isotropic liquid results in the disappearance of the Cotton effect because of the loss of helical order. This effect illustrates the need for the molecules to be positionally ordered in order for the side-chain chirality to be transferred to the supramolecular column. 

Currently the main interest in template reactions lies in their key role in the controlled synthesis or the self-assembly of a variety of supramole-cular entities (449). One needs a combination of intuition, conjecture, and serendipity (450) a recent example of successfully combining serendipity and rational design is provided by the silver(I)-promoted assembly of one-dimensional stranded chains (451). One also needs an understanding of mechanism in order to optimize the selection and design of building blocks and templates for the generation of yet more sophisticated supramolecular structures references cited in this present review contain at least some kinetic or mechanistic information or speculation. Template routes to interlocked molecular structures have been reviewed (452), while a discussion of switching by transition metal contains a little about the kinetics and mechanisms of this aspect of template... 

First, the use of higher dimensional robust networks (such as the two-dimensional GS network) simplifies crystal engineering because is reduces crystal design to the last remaining dimension. The use of two-dimensional supramolecular modules, in particular, provides an easily conceptualized mechanism for topological adaptation (in the case of GS networks the arrangement of the pillars). 

The mechanical movements taking place in this supramolecular system, in which a free molecule can be driven electrochemically to associate with either of two different receptors, opens the way to futuristic applications in the field of molecular-level signal processors.161 One can conceive second generation systems wherein the electrochemically driven... 

Impressive, highly ordered centimetre-sized fibres are obtained whose synergistic growth mechanism based on the kinetic cross-coupling of a dynamical supramolecular self-assembly and a stabilizing silica mineralization may well be the basis of the synthetic paths used by Nature to obtain its materials with well-defined multiscale architectures in biological systems. 

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