Molecular inclusion chemistry

The work summarized here fits into the broad subject of molecular inclusion chemistry [1-5]. Cavities in molecules are tailored electronically and geometrically to the chemical purpose at hand. In simple systems, the goal might be selective coordination of metal ions or selective binding of small ligands to previously coordinated metal ions. 

E. Weber, editor. Molecular inclusion and molecular recognition— Clathrates 1, volume 140 of Topics in Current Chemistry. Springer Verlag, Berlin, 1987. 

Molecular inclusion and molecular recognition — clathrates II. (Topics in current chemistry 149)... 

Molecular inclusion and molecular recognition Clathrates I II , Topics in Current Chemistry, Vol. 140 and 149 (Ed. E. Weber), Springer-Verlag, New York, 1987 and 1988. 

Keywords Network structures Molecular hosts Inclusion chemistry... 

We shall now discuss several recognition processes and describe the main properties of the corresponding molecular receptors. Insofar as receptor molecules have cyclic geometries and contain cavities into which the substrate(s) may bind, the chemistry of molecular recognition also covers macrocyclic chemistry and inclusion chemistry. In view of the extensive literature concerning these domains, the reader is referred to specific monographs, reviews or original papers for more information (see Appendix). 

Sometimes the estimation of the electronic structures of polymer chains necessitates the inclusion of long-range interactions and intermolecular interactions in the chemical shift calculations. To do so, it is necessary to use a sophisticated theoretical method which can take account of the characteristics of polymers. In this context, the tight-binding molecular orbital(TB MO) theory from the field of solid state physics is used, in the same sense in which it is employed in the LCAO approximation in molecular quantum chemistry to describe the electronic structures of infinite polymers with a periodical structure -11,36). In a polymer chain with linearly bonded monomer units, the potential energy if an electron varies periodically along the chain. In such a system, the wave function vj/ (k) for electrons at a position r can be obtained from Bloch s theorem as follows(36,37) ... 

The study of pyridinophanes resulted in joint publications on the complexation of water and the encapsulation of halocarbons within pyridino-crown hosts. Additional professional exchanges occurred over the years in which both groups were pursuing mutual synthetic interests in heterocyclic chemistry, stereochemistry, and cyclophanes. Central to those interests was a better understanding of molecular inclusion and recognition phenomena, now more uniquely defined as an aspect of supramolecular chemistry. 

A simple possibility for the synthesis of esters, the reaction of an acid chloride with an alcohol, was used by Schrage and Vogtle [58] for a two-step synthesis of the macrocycle 63 from the alcohol 61 and the acid chloride 62. Compound 63, an example from the field of host/guest chemistry, forms a cavity, as studied with CPK-models, which could include planar, aromatic guests. Crystals obtained from benzene/ -heptane point to a 1 2 stoichiometry of 63 and benzene according to NMR-spectroscopic data. However, whether this is a molecular inclusion complex or just a clathrate is not yet known. 

Zeolite molecular sieves are very attractive candidates for inclusion chemistry in structurally well-defined, nanometer-size chaimel structures. The present review focuses on recent studies addressing the encapsulation of molecular conductors in zeolite host channels. 

Numerous studies have established the wide scope of inclusion chemistry that is possible with inorganic solids. From layered hosts such as FeOCl and nanoporous membranes to zeolite molecular sieves, very different dimensions are accessible for the encapsulation of conjugated, potentially conducting materials. Zeolites are distinct hosts because they offer well-defined, crystalline pore systems at molecular dimensions, with sizes in mesoporous systems now reaching even beyond the molecular scale. 

Accurate determination of the structures of molecular inclusion complexes and molecular assemblies has gained in importance in supramolecular chemistry and recently in crystal engineering. Detailed information about the nature of these weak intermolecular interactions is crucial in order to understand and further develop supramolecular systems and understand crystal growth and the properties of crystalline materials. Particularly accurate structural information can be gained in the solid state by single crystal X-ray crystallography. 

New types of mesoporous molecular sieves (their first synthesis opened a new subfield of molecular sieve chemistry) have been prepared over the last ten years by new synthetic approaches, different from those known for zeolites. The variety of the synthetic procedures described and the differences in the textural properties due to different synthetic procedures, as well as to the high temperature treatment, give evidence that mesoporous molecular sieves of different chemical compositions are very interesting materials not only in materials science. They could be important also for the application as heterogeneous catalysis, support for immobilization of homogeneous catalysts, adsorbents or materials for synthesis of new types of inclusion compounds. 

Herbstein FH (1996) 1,3,5-Benzenetricarboxylicacid (trimesic acid) and some analogues. Lehn J-M, Atwood JL et al. (eds) In Solid state supramolecular chemistry crystal engineering. Pergamon, New York, chap 3. See also Herbstein FH (1987) In Weber E (ed) Molecular inclusion and molecular recognition - clathrates I. Topics in Current Chemistry, vol 140. Springer, Berlin Heidelberg New York, p 107 Etter MC, Frankenbach GM (1989) Chem Mater 1 10... 

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