Host framework

Among three-dimensional framework hosts forming intercalation compounds, zeolites (see Section 1.5) have attracted considerable attention because of their technical importance (Derouane, 1982 Dyer, 1984). Intracrystalline voids in anhydrous zeolites provide a strongly polar environment that can be filled with polar or ionic species to increase the crystal energy. Treatment of zeolites (e.g. Na-Y zeolite) with vapours of sodium results in the formation of a red product consisting of Na intercalated into the zeolite cavities (Thomas, 1983). The locations of these clusters inside the zeolites are not yet known, but they seem to be buried within the rather inaccessible cavities inside zeolites, with the result that ordinary solvents do not reach them. Such intercalation of ionic species in zeolites may have implications in nuclear-waste treatment and storage. 

The brief overview of intercalation chemistry presented above shows that the subject encompasses a fascinating variety of solid state reactions between two- or three-dimensional host materials and guest atoms and molecules. Not all host material that 

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Figure 1.19. Le Typical shape of a head-tail molecule acting as an injector-, acceptor-, or Simply as a stopcock. The positive charge is desirable but not necessary for anionic framework hosts. Reactive groups may help to fix the stopcock. Middle Fluorescent molecules that already have been inserted in zeolite L could be modified with an inert head. Right Examples of molecules that could be used as stopcocks with a fluorescent head.

A number of clay-like 2D layered and zeolite-like 3D framework host structures have been materialized using isopolycyanocadmate as the linkage unit. The 2D layered and the 3D framed hosts accommodate a variety of organic guest molecules and onium cations of different geometrical characters. 

Caulfield T (2004). Biotechnology Patents, Public Trust and Patent Pools The Need for Governance Health Biotechnology and Intellectual Property A New Framework. Hosted at the European University Institute, Florence, Italy. 

Fig. 5 Typical examples of (a-c) self-assembling inclusion hosts (d-f) interlocked and interwoven systems and (g-j) solid state inclusion hosts (a) tennis ball dimer (b) metallamacrocycle (c) ladder-structured metal array (d) catenane (e) rotaxane (f) helicate (g) network lattice host (exemplary host molecule) (h) coorclinatoclathrate host (exemplary hosts) (i) curved framework host molecule and (j) aukward-shape host molecule.

Nishikiori, S. Ratcliffe. C.I. Ripmeester. J.A. Crystal structure of Cd5(CN)io(H20)4 4C6HnOH studied by x-ray diffraction and solid-state Cd NMR. A new type of cristobalite-like framework host with a site interaction with cyclohexanol by hydrogen bonding. J. Am. Chem. Soc. 1992. 114. 8590-8595. 

The Na -ion electrolyte for a Na-S battery needs to consist of a framework host with mobile Na" ions in the interstitial space, but it must also have the bottom of the conduction band of the host above the Ep of elemental Sodium. These criteria are... 

Normally in porous carbon materials, active ensembles are bonded or incorporated on the support, which is usually constituted by frameworks not totally connected among them. This causes a decrease of electrical conductivity, with consequent energy dissipation (cut bridges Fig. 9a) [104-107]. The interconnection among various frameworks hosting active ensemble is cmcial to have a good overall current density, or electron percolation, and to exploit each active ensemble as a generator of electricity. 

Flexible molecular framework hosts, with high stability and regularity of the pores, are of fundamental importance, and have many potential applications in gas storage, purification, and catalysis. In this context, inorganic frameworks [Rh2(02CPh) (Rpyrazine)] (68a, Figure 9.27, Rj = R2 = H Rj =H, R2 = Me Ri = Rj = Me) have been investigated by Takamizawa et al., as hosts to accommodate gas molecules of various sizes and properties, such as Hj, O, CO2, CH, N2, NO, Xe, Ar, as well as... 

The above approach for sodalite structure analogues is currently being extended to other periodic 3-d open framework hosts. Some specific goals (in addition to those noted previously) include ... 

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