Host guest species

Materials with uniform pore structures offer a wide range of applications, including catalysis, adsorption, and separation. These materials have the benefit ofboth specific pore systems and intrinsic chemical properties [1-3]. The pores in the materials are able to host guest species and provide a pathway for molecule transportation. The skeletal pore walls provide an active and/or affinity surface to associate with guest molecules. According to the International Union of Pure and Applied Chemistry (IUPAC), porous materials can be classified into three main categories based on the diameters of their pores, that is, microporous, mesoporous, and macroporous... 

Etter, M. C., Urbanczyklipkowska, Z., Jahn, D. A., Frye, J. S., Solid-state structural characterization of 1,3-cyclohex-anedione and of a 6-1 cyclohexanedione-benzene cyclamer, a novel host guest species. J. Am. Chem. Soc. 1986, 108, 5871-5876. 

Chapter 4 by H. Forster is devoted to the potential of and achievements obtained by electron spectroscopy in the field of molecular sieves. This contribution comprises, in a rather detailed manner, the theoretical fimdamentals and principles, the experimental techniques, as well as a wealth of applications and results obtained. Results are, e.g., reported on the characterization of zeolites as hosts, guest species contained in zeolite structures, framework and non-framework cations, and zeoHtic acidity. 

Complexation of the NH4+ cation by a range of cryptands has been well documented. For example, 2.2.2 forms a stable complex with NH4+ in water (log K = 4.5) while this value is less than that for K+ (log K = 5.3) under similar conditions, it is stiU quite respectable. The X-ray structure of this host-guest species (Figure 9) confirms... 

Weber and JoseP have proposed a detailed classification which takes account of host-guest species, the type of molecular interactions, the topology of the structure, and the host to guest ratio. This has enjoyed a measure of success, but there has not been universal acceptance. 

---