Supramolecular stabilization

Steroid-Based Anion Conzplexation Agents, p. 1365 Supramolecular Chemistry Definition, p. 1401 Supramolecular Stabilization, p. 1453 Surfactants, Part I Fundamentals, p. 1458 Surfactants, Part 11 Applications, p. 1470 van der Waals Forces, p. 1550 Weak Hydrogen Bonds, p. 1576... 

Isostmcturality of Inclusion Compounds, p. 767 Supramolecular Stabilization, p. 1453 X-Ray Crystallography, p. 1586... 

Supramolecular stabilization means stabilization of certain chemical species, their different forms, and assemblies in a particular supramolecular environment. Supramolecular stabilization is responsible for the existence of "energetically unfavorable" conformations, different spatial isomers, unexpected oligomers, "unstable" molecules. highly reactive radicals, elements in unusual oxidation states, certain ionic species, and so on, in supramolecular phases. Such species decompose, change, or equilibrate with alternative forms once they are brought out of their "stabilizing" environment. The best-known chemical reaction based strictly on supramolecular stabilization is the so-called "blue reaction." where iodine reversibly polymerizes in the presence of starch. 

Supramolecular stabilization provides an excellent opportunity to store highly reactive species or to obtain species not available by traditional methods in high concentration. The phenomenon plays an important role in stabilizing drugs and may be useful in the creation of new methods of separation and purification, the design of new functional and smart materials, and the development of new approaches to chemical and biological research. 

First described in the literature in 1814, the blue reaction of iodine with starch is the best-known example of a polymerization process induced by supramolecular stabilization. Structural studies indicate that amylose (the linear fraction of starch) forms a helix with six glucose residues per turn to include guest iodine molecules. Inside this helix, iodine molecules form a polymeric chain with a periodicity of 3.1 A, which is much shorter than the nonbonded distance between iodine atoms (4.3 A) but greater than the single I-I bond distance (2.7 A). The amylose-iodine reaction is widely used in analytical chemistry and was utilized for the solubilization and purification of carbon nanotubes. 

In a broader sense, supramolecular stabilization is responsible for the regular arrangement of species in supramolecular stmctures. The following examples show some of the applications of the phenomenon. 

Supramolecular stabilization is an important concept that needs to be introduced when considering the influence of the supramolecular environment on the structures and stabilities of chemical species. The kinetic component of the phenomenon is responsible for increasing or decreasing the lifetime of chemical species included in host structures. The thermodynamic component of the phenomenon explains the existence of unusual, or one of many possible, chemical entities in supramolecular solids. Our current understanding of these phenomena allows a number of experimental facts to be explained and makes qualitative predictions possible in some cases. Further development of these concepts to more quantitative levels will allow improved predictions and the purposeful design of desired species stabilized in supramolecular environments. 

This Study further demonstrates that an elusive species such as the 3-thioallophanate anion can be generated in situ and stabilized in a crystalline inclusion compound through hydrogen-bonding interactions with neighboring molecules, and here thiourea functions as a supramolecular stabilizing agent. 

Qiau NTT, Guegan J-P, Menuel S, Guerrero M, Hapiot F, Monflier E, Philippot K, Denicourt-Nowicki A, Roucoux A. p-Cyclodextrins grafted with chiral amino acids a promising supramolecular stabilizer of nanr rarticles for asymmetric hydrogenation Appl Cat A... 

This paper served as a sample study for the latter work with the supramolecular stabilization of Schiff base tautomers, where it was shown that these postulates can be successfully applied even to monocomponent molecular solids [67]. The Schiffbase X, synthesized by the condensation of 2-amino-3-hydroxypyridine and... 

Fig. 7. Formation of a supramolecular aggregate composed of a compound containing nine melamine rings (the three-layered nonamelamine derivative A) and nine molecules of neohexylisocyanurate (B). Of the 16 possible conformers that can result, two are shown The first has the nine molecules of B arranged in three rosettes of three molecules each, stacked atop each other in the second, the rosettes are staggered with respect to each other such that the rosettes in the first and third layers of A are aligned with each other, but not with the rosette in the second layer. The supramolecular assembly is stabilized...

In this context it is interesting to note that archaea, which possess S-layers as exclusive cell wall components outside the cytoplasmic membrane (Fig. 14), exist under extreme environmental conditions (e.g., high temperatures, hydrostatic pressure, and salt concentrations, low pH values). Thus, it is obvious one should study the effect of proteinaceous S-layer lattices on the fluidity, integrity, structure, and stability of lipid membranes. This section focuses on the generation and characterization of composite structures that mimic the supramolecular assembly of archaeal cell envelope structures composed of a cytoplasmic membrane and a closely associated S-layer. In this biomimetic structure, either a tetraether... 

Another important area of future development concerns copying the supramolecular principle of cell envelopes of archaea, which have evolved in the most extreme and hostile ecosystems. This biomimetic approach is expected to lead to new technologies for stabilizing fnnctional lipid membranes and their nse at the mesoscopic and macroscopic scales [200]. Along the same line, liposomes coated with S-layer lattices resemble archaeal cell envelopes or virns envelopes. Since liposomes have a broad application potential, particu-... 

In this review, CPOs constructed by covalent bonds are mainly focused on however, stable coordination bonds comparable to the stability of the covalent bonds have potential for future enhanced molecular design of novel CPOs. One representative is the bond between pyridine-type nitrogen and metal, which is widely used in supramolecular chemistry, that is, the cyclic supramolecular formation reaction between pyridine-substituted porphyrin and metal salts (Fig. 6d) [27,28]. Palladium salts are frequently used as the metal salts. From the viewpoint of the hard and soft acid and base theory (HSAB), this N-Pd coordination bond is a well-balanced combination, because the bonds between nitrogen and other group X metals, N-Ni and Ni-Pt coordination bonds, are too weak and too strong to obtain the desired CPOs, respectively. For the former, the supramolecular architectures tend to dissociate into pieces in the solution state, and for the latter. 

Socaciu, C. et al.. Carotenoid-rich fractions in sea buckthorn berry oleosomes separation, characterisation and stability in colloid supramolecular structures, in Proceedings of 4th International Congress on Pigments in Food, Hohenheim, Germany, Carle, R. et al., Eds., Shaker Verlag, Aachen, 2006, 203. 

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