Small Caged Molecules synthesis

Cryptophanes are related to hemicarcerands - they are composed of smaller and shallower cavitand bowls, such as cyclotriveratrylene (CTV) molecules that have been used for both anion and neutral molecule recognition (Section 2.5.2). The first cryptophane was synthesised in 1981 via a self-directed synthesis. This small cage is named, chronologically, cryptophane-A (2.126) (Figure 2.31). Space-filling models of cryptophane-A show a closed surface container, with... 

In small pore zeolites with cage structure, e. g., faujasites, dye molecules encapsulated by in situ synthesis or crystallization inclusion are stable against extraction.1 2 However, these methods fail for MCM-41 due to the channel structure and the wider pore diameter (3 nm) of the host material. Covalent bonding of guests is necessary to obtain diffusion stability. Therefore, anchoring of organic molecules with catalytic functions into MCM-41 by covalent bonding was recently reported by Brunei et al.3... 

The hollow interior of dodecahedrane and other organic cage compounds described in section 4.9 is much too small to envelop atoms, ions, or molecules. Tight closed-shell macromolecules have been obtained from vesicles by several research groups, by polymerization of amphiphiles possessing double or triple bonds within the membrane or at the head groups. Smaller, but well-defined, closed-shell containers have been obtained by two other methods described below, namely by directed synthesis and by formation of closed-shell all-carbon molecules in graphite vapor. 

One example for a challenging yet unrealized synthesis goal is the introduction of a window into the fullerene framework large enough to allow atoms, ions or small molecules to enter the cage followed by a cluster closure reaction. Such a reaction sequence would provide an elegant access to endohedral fullerenes. 

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