Host/guest relation

Kaplan, L., Sousa, L. R., Hoffman, D. H., and Cram, D. J. (1974) Total optical resolution of amino esters by designed host-guest relations in molecular complexation, J. Am. Chem. Soc. 96, 7100-7101. 

Fig. 2. Classification/nomenclature of host—guest type inclusion compounds, definitions and relations (/) coordinative interaction, (2) lattice barrier interaction, (J) monomolecular shielding interaction (I) coordination-type inclusion compound (inclusion complex), (II) lattice-type inclusion compound (multimolecular/extramolecular inclusion compound, clathrate), (III) cavitate-type inclusion compound (monomolecular/intramolecular inclusion...

In this chapter we discuss host-guest complexes of arenediazonium salts with crown ethers and related compounds. Transition metal complexes of arenediazonium ions are treated together with those of dinitrogen and of diazoalkanes in our second book (Zollinger, 1995, Sec. 10.1). 

Another related host-guest complex has been constructed from citric acid, boric acid, and a strontium salt in a 2 1 1 stoichiometry. In this complex the strontium cation is surrounded by four water molecules, two monodentate carboxyl groups and one oxygen atom of the BO4 unit [161]. 

Combining features typical of both complexes and clathrates (coordinatoclathrate) should provide new possibilities of host-guest control2). They are indicated by the relations specified in Fig. 8, e.g. chemoselectivity or selectivity for functional groups on the one hand, caused by the complex part, and on the other hand constitutional selectivity or selectivity for molecular size and expanse due to the clathrate branche of the diagrammatic family tree of a coordinatoclathrate shown in Fig. 8. 

Examination of the steric relations in these complexes (cf. Fig. 30) suggests that the more voluminous branched alcohols cannot follow the same principle. Indeed, in the 2-butanol and also in the t-butanol inclusion compound, a different ring system is built (Fig. 17b and type I in Fig. 19). While the short-chain alcohols form twelve-membered H-bond loops, the branched butyl alcohols are embedded into a ten-membered asymmetric loop. The stoichiometry of the asymmetric unit also changes from 1 2 (host guest) ratio to 1 1. The so-built ring system of homodromic H-bonds still contains a mirror-related pair of hosts 1, but comprises only one guest molecule. 

The 1987 Nobel Prize in Chemistry was awarded to Charles J. Pedersen, Donald J. Cram, and Jean-Marie Lehn for their work on crown ethers and related compounds (host-guest chemisty). 

Host-guest complexation involving crowns and related polyether... 

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