Cage-like molecules

The broad, featureless nature of the Si NMR signal is likely due to one of three phenomena that are well-known to cause such effects in NMR spectroscopy a multiplicity of chemical and physical environments about the silicon atoms restricted segmental motion in polycyclic or cage-like molecules or ne broadening due to ySi magnetic interactions with the numerous N quadrupoles. 

Buckyballs are cage-like molecules of fullerenes. They are robust and can carry radioactive drugs to targets. Research is directed at using these buckyballs as delivery systems for the treatment of cancer. 

Irradiation of 2,6-dimethylpyran-4-one (357) in ethanol or benzene or in the solid state yields the cage-like molecule (358) from which the pyran-4-one is regenerated by hydrochloric acid (63JA1208). When the photodimerization is conducted in water but in the absence of air, a small amount of 4,5-dimethylfuran-2-aldehyde is also formed (63JA2956). Pyran-4-one is photoisomerized to pyran-2-one (359) the intermediates postulated resemble those suggested in the irradiation of pyrylium salts (Section 2.23.2.1) (79JA7521). 

Figure 2.9 The formation of a flillerene cage. The tendency toward minimizing the number of unsaturated bonding sites causes the generation of five-membered rings and thus an increasing curvature and final closure of the stmcture to be a cage-like molecule.

To gain five electrons, boron builds unique closo or cage-like molecules. One class of neutral B-H ionic species called boranes serves as a good example of what could be possible with other organometallic compounds that form cagelike molecules. 

Under controlled conditions of hydrolysis, the cage-like molecules of P40]q will disintegrate by rupture of successive P-O-P linkages to form a variety of products. The main process entails the rupture of two P-O-P linkages to give cyclic tetrametaphosphoric acid as indicated in (4.49). 

Phosphorus forms a number of cage-like molecules based on arrangements (6.928) which have (ideally at least) C3v symmetry and threefold symmetry axes. The first of these (6.928a) and its sulphide, is made according to scheme (6.929). 

Cryptophanes are cage-like molecules where two C3-symmetric CTV fragments have been covalently joined... 

The high regiospecificity of the template encapsulation reaction should be noted. Eleven molecules (three en, six HCHO, and two NH3 or two CH5NO2) participate in the formation of the chelate rings of the final macrocyclic product. In the absence of a matrix a cage-like molecule is believed to be formed in 0.1% yield at best [10], Moreover, if a chiral octahedral (Table 4-1) ethane-1,2-diamine... 

Due to the remarkable ability of carbon to exist in different hybridization states, carbon-based materials display an unusually rich variety. Diamond, graphene, cage-like molecules and perhaps most notably carbon nanotubes are examples of the large selection of possibilities. 

The reducing agent approaches from outer side of the cage-like molecule. 

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