Crystalline host-guest systems

Supramolecular structures obtained via self-assembly processes may be named as another future topic, which just starts an increasingly rapid development.294 By some examples it was already demonstrated how molecular chirality may by translated into supramolecular chirality in such self-assembled structures and this may lead not only to new, improved host-guest systems but also eventually to new materials in a more general sense. Liquid-crystalline systems or materials for nonlinear optics may be mentioned just as two examples. 

Kato T, Hirota N, Fujishima A, Frechet JMJ. 1996. Supramolecular hydrogen bonded liquid crystalline pol5mer complexes. Design of side chain pol5uners and a host guest system by noncovalent interaction. J Pol5un Sci, Part A 34(1) 57 62. 

Already, more than 25 years ago, Toda et al. reported the mechanochemical preparation of crystalline host-guest inclusion compounds and of charge-transfer (CT) systems. CT systems have also been studied by Kuroda et al., who were able to obtain multicomponent systems based on racemic bis-)8-naphtol, benzoquinone, and anthracene the cocrystal formation could be easily followed by the change in color of the solid mixtures. Importantly, this material was not accessible from conventional solution crystallization procedures and required structure determination from X-ray powder diffraction. ... 

Gies H, Marler B (1996) Crystalline microporous silicas as host-guest systems. In Mac-Nicol DD, Toda F, Bishop R (eds) Supramolecular chemistry, vol 6. Elsevier Science, Oxford, Chap 26,851 pp... 

Another example of a side-chain supra-raolecular polymer is prepared from poly(4-vinylpyridine) and H-bonding side chains [32-35]. In this case, mesogenic side-chain groups are directly attached to the polymer backbone and liquid-crystalline polymers such as 19 are formed by the noncovalent interaction [33]. This molecular design has been used to incorporate functional molecules into liquid-crystalline, host-guest polymeric systems [32]. 

Materials for cathodes and anodes (insertion electrodes) for rechargeable lithium batteries are called intercalation compounds and constimte a special class of electroactive material [122]. The intercalation refers to the reversible insertion of mobile guest species into a crystalline host lattice, which contains an interconnected system of empty lattice sites of appropriate size, while the structural integrity of the host lattice is formally conserved [122]. 

The field of supramolecular chemistry is concerned with a large number of systems ranging from simple host-guest complexes to more complicated solution assemblies, as well as two-dimensional (organized monolayers) and three-dimensional assemblies (crystalline solids). Nonco-valent interactions play an important role in the kinetic assembly and thermodynamic stabilization of all these systems and constitute their most distinctive feature. Electron-transfer reactions can obviously be affected by supramolecular structures, but the reverse is also true. It is possible to alter the structure and the thermodynamic stability of supramolecular assemblies using electrochemical (redox) conversions. In other words, electron-transfer reactions can be utilized to exert some degree of control on supramolecular aggregates. Provided in this article is an overview of the interplay between supramolecular structure and electron-transfer reactions. 

C SPs. The assembly belongs to the class of clathrates (inclusion compounds) that have interest for separation processes. Single chains are confined in small channels (diameter — 6 A) for a wide variety of crystalline adducts. These systems suggests that smoothed-out effects assist rhe formation of host-guest polymeric assemblies in addition to localized interactions. The nonlocalized effects may arise from the suppression of... 

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