Organic organized assemblies

Fig. 29. Molecular recognition of an organized assembly at the air—water interface (184).

A number of studies have focused on D-A systems in which D and A are either embedded in a rigid matrix [103-110] or separated by a rigid spacer with covalent bonds [111-118], Miller etal. [114, 115] gave the first experimental evidence for the bell-shape energy gap dependence in charge shift type ET reactions [114,115], Many studies have been reported on the photoinduced ET across the interfaces of some organized assemblies such as surfactant micelles [4] and vesicles [5], wherein some particular D and A species are expected to be separated by a phase boundary. However, owing to the dynamic nature of such interfacial systems, D and A are not always statically fixed at specific locations. 

O. A. El Seoud, Reversed micelles and water-in-oil microemulsions, in W. L. Hinze (ed.) Organized Assemblies in Chemical Analysis, Vol. 1, Wiley, New York, NY 1994, 1. 

The fluorescence polarization technique is a very powerful tool for studying the fluidity and orientational order of organized assemblies (see Chapter 8) aqueous micelles, reverse micelles and microemulsions, lipid bilayers, synthetic non-ionic vesicles, liquid crystals. This technique is also very useful for probing the segmental mobility of polymers and antibody molecules. Information on the orientation of chains in solid polymers can also be obtained. 

The action of organized assemblies is discussed and the mode of interaction of organic and inorganic solutes with the assemblies indicated. 

Figure 1. Various organized assemblies formed from a simple surfactant molecule in mixtures of...

Organized assemblies are useful to promote specialized features of a reaction, e.g., proximity effects, surface energy effects, or reactant organization. These features are useful in energy storage. As more is learned about these systems and their participation in reactions, it may be possible to obtain precise information on the effects of microscopic geometric arrangements of reactants on the subsequent course of reaction. Many assemblies are known many others are available but have not been studied as yet. 

General Discussion—Effect of Organized Assemblies on Chemical Reactions... 

As we have seen, an area of major importance and of considerable interest is that of substitution reactions of metal complexes in aqueous, nonaqueous and organized assemblies (particularly micellar systems). The accumulation of a great deal of data on substitution in nickel(II) and cobalt(II) in solution (9) has failed to shake the dissociative mechanism for substitution and for these the statement "The mechanisms of formation reactions of solvated metal cations have also been settled, the majority taking place by the Eigen-Wilkins interchange mechanism or by understandable variants of it" (10) seems appropriate. Required, however, are more data for substitution in the other... 

Mechanistic Studies of Thermal and Photoinduced Atropisomerization of Substituted Tetraphenyl Porphyrins in Solution and Organized Assemblies... 

Note This is number 48 in the series Photochemical Reactions in Organized Assemblies. 

Although more work is needed to clearly correlate the type of solubilization site occupied by different porphyrins with their reactivity in such sites towards atropisomerization, it is clear that different sites exist and that these sites show quite different reactivity in both thermal and photochemical processes. Preliminary studies have shown that related behavior probably occurs in other organized assemblies formed by dispersion of surfactant molecules in... 

Figure 2.3 Representation of organized assemblies (a) bilayers, (b) cylindrical micelles, and (c) lamellar structure.

Here, we are most interested in the interaction of these organized assemblies with another molecule, that is, molecular recognition. We will broadly classify these interactions into nonspecific and specific ones. In addition to the chemical interaction between the molecules, there has been a significant amount of work on achieving amphiphilic block copolymer assemblies that respond to physical stimuli, for example, temperature. We will not discuss this in any detail, except when relevant to the focused topic of chemical recognition. 

Paleos CM, Tsiourvas D. Molecular recognition of organized assemblies via hydrogen bonding in aqueous media. Adv Mater 1997 9 695-710. 

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