Hydrocarbon cage molecules

All other homoatomic Pn cluster anions are cage molecules with localized two-center-two-electron bonds. The cyclic [PnJ anion has been characterized by NMR spectroscopy for Pn = P [210], and structures are known for Pn = P, As, Sb, Bi (Table 2). A planar [Ps] anion has only been detected in solution by P NMR spectroscopy [210]. Envelop-shaped five- and six-membered rings are found for [Pns] and [Pe]", whereas [Asg]" deviates only slightly from planarity and has a chair conformation. The aromaticity of the planar anions [P4] and [Pe]" is distinct from that of regular 671-aromatic hydrocarbons and has been described... 

Another saturated, polycyclic hydrocarbon for which a heat of formation is available is hexa-cyclo[7,2, l,0 ,0 ,0 ]dodecane, the cage molecule shown in Fig. 15. From combustion data< the value has been obtained A (c) = + 12 06 0 27 kcal/mole, and taking a somewhat arbitrary heat of sublimation of 12 kcal/... 

An obvious approach to render these rigid-rod polymers colorless is to synthetically alter their molecular structures so as to disrupt their conjugation systems. This modification is, of course, predicated on imposing little or no adverse effects on the other important properties of the polymers, for example, environmental survivability. Cage-like, aliphatic hydrocarbon molecules, such as adamantane, diamantane, cubane, etc., are thermally stable, and non-chromophoric due to the lack of 7t-electrons. Some of these cage molecules can be synthesized as difiinctionalized monomers that also satisfy the all-para molecular geometry requirement of rigid-rod macromolecules. 

It has been suggested that free polycyllc aromatic hydrocarbon (PAH) molecules can account for unidentified Interstellar emission features In the infrared (8) and for the diffuse Interstellar absorption bands In the visible (9), Also, the possibility of the Interstellar and circumstellar presence of hollow, cage-llke polycarbon molecules with spheroidal shells of hexagonal, graphlte-like sheets of carbon atoms has... 

Hydrophobic interactions of this kind have been assumed to originate because the attempt to dissolve the hydrocarbon component causes the development of cage structures of hydrogen-bonded water molecules around the non-polar solute. This increase in the regularity of the solvent would result in an overall reduction in entropy of the system, and therefore is not favoured. Hydrophobic effects of this kind are significant in solutions of all water-soluble polymers except poly(acrylic acid) and poly(acrylamide), where large heats of solution of the polar groups swamp the effect. 

The problem of accessibility in microporous solids is extreme in zero-dimensional zeolite structures such as clathrasils, that is, zeolite-related materials consisting of window-connected cages. The pore openings in these caged structures are restricted to six-membered rings of [Si04] units at most, which corresponds to pore diameters of approximately 0.2 nm [58]. These pores are too small for the removal of templates and, afterward, are impenetrable to typical sorptive molecules for characterization such as N2 and Ar or reactants such as hydrocarbons. Therefore, the intrinsic... 

Diamondoids can also be seen as cage-like saturated hydrocarbon molecules that possess a rigid carbon framework of diamond-like sp -bonded carbon atoms. Lower-order... 

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