Chemistry, kinds supramolecular

Most chemical reactions and spectroscopic work are carried out in solution. However, recent investigations have shown great potential for solid-state chemistry. First, supramolecular systems consisting of more than one kind of molecule exhibit characteristics that are different from those of the individual molecules. We have recently reported inverted supramolecular chirality of bis(zinc octae-thylporphyrin), an enantiopure monoamine system in solution and in the solid phase [3]. Secondly, solid-state reactions occur more frequently than previously envisaged [4-7], and they may give products in high yield that are unobtainable by reaction in solution. They are kind to the environment because of their solvent-free nature and hence are currently attracting attention from the industrial sector as well. Compared with thermal or chemical reactions, photochemistry is particularly... 

Calixarenes, which are macrocyclic compounds, are one of the best building blocks to design molecular hosts in supramolecular chemistry [158]. Synthesis of calix[4]arenes, which have been adamantylated, has been reported [105, 109]. In calix[4]arenes, adamantane or its ester/carboxylic acid derivatives were introduced as substituents (Fig. 29). The purpose of this synthesis was to learn how to employ the flexible chemistry of adamantane in order to construct different kinds of molecular hosts. The X-ray structure analysis of p-(l-adamantyl)thiacalix[4]arene [109] demonstrated that it contained four CHCI3 molecules, one of which was located inside the host molecule cavity, and the host molecule assumed the cone-like conformational shape (Fig. 30). 

When supramolecular chemistry emerged at the forefront of science, it embodied colloid chemistry as one of its facets. A semantic boundary exists between supramolecular chemistry and colloids, as the former involves design logistics a priori in addition to preselected synthetic strategies. The simplest kind of colloidal... 

The book is a candidate to become a reference book for future years. The multidisciplinary approach, with chapters reserved to biological, materials, and supramolecular chemistry, presents the book as an important source of information not only for chemists but also for physicists, biochemists, and other researchers, who in some way deal with chalcogen compounds. I hope the book may induce some curiosity in the reader and attract him towards this kind of chemistry. 

In recent years, supramolecular chemistry has produced a number of systems which have been shown to be able to effectively catalyze a Diels-Alder reaction. Most systems selectively afforded only one diastereomer because of a pre-organized orientation of the reactants. These systems include cyclodextrines, of which applications in Diels-Alder chemistry have recently been reviewed89. Some other kinds of non-Lewis acid catalyzed Diels-Alder reactions, including catalysis by proteins and ultrasound, have been discussed by Pindur and colleagues90. 

The previous chapter discussed covalent and ionic bonds. These are strong chemical bonds formed when atoms share electrons, in the case of covalent bonds, or transfer electrons, as in ionic bonds. A large portion of chemistry textbooks are devoted to these chemical bonds, and rightfully so, considering their importance in the formation of many of the compounds and materials that people use. But there are other kinds of bonds, generally referred to as noncovalent bonds, that are weaker and often temporary, breaking and forming repeatedly. These bonds play a vital role in certain materials and are the primary mechanisms involved in supramolecular chemistry. 

We saw in Figure 1.2c that supramolecular chemistry is not just about solid state or solution host-guest chemistry but increasingly emphasises self-assembly and the construction of multi-nanometre scale devices and ultimately materials based on nanometre-scale components (a nanometre is 10 9 of a metre). Strict supramolecular self-assembly (Chapter 10) involves the spontaneous formation of a multi-component aggregate under thermodynamically controlled conditions based on information encoded within the individual building blocks (referred to as tectons ) themselves. The aggregate might comprise only one kind of molecule (as in the multiple copies of the same protein that comprise... 

In this chapter we focus on supramolecular chemical reactivity. In particular this means predominantly the role supramolecular chemistry plays in accelerating or understanding chemical reactions. There are close parallels between artificial, abiotic supramolecular reactivity and biochemistry, for example in the study of enzymes, Nature s catalysts - described in Section 2.6. Synthetic catalysts can both model natural ones and allow the design of new, different kinds of reactions. Supramolecular catalysis sits somewhere between chemical catalysis (transition metal and organocatalysis) and biology. Some considerations within various kinds of catalysis are summed up in the chart shown in Figure 12.1. 

Supramolecular chemistry allows novel kinds of polymer linkages such as the mechanical links found in polycatenanes and polyrotaxanes. 

The aim of this book is to provide the reader with an overview of interfacial supramolecular chemistry. Supramolecular assemblies of the kind considered in this text are truly interfacial, not only because they separate solid- and solution-phase components but also because they represent the junctions where biology, chemistry, physics and engineering meet. In true interfacial supramolecular systems, individual moieties, e.g. the supporting surface and an adsorbed luminophore, interact co-operatively to produce a new function or property. In addition, these two- and three-dimensional structures remain an important step in the evolution of structure from discrete molecules, to interacting assemblies, and finally to solids. In this last chapter, the future of interfacial assemblies will be briefly considered. This discussion will focus on the possibility of integrating such assemblies into practical devices and the identification of the important scientific challenges. 

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