Inclusion compounds in perhydrotriphenylene. Part I. The crystal structure of perhydrotriphenylene and of some inclusion compounds

Abstract

The equatorial isomer of perhydrotriphenylene (PHTP) gives rise to a wide variety of inclusion compounds with different kinds of molecules, ranging from those with a nearly spherical (e.g., CCl₄) or planar shape (benzene) to linear molecules and macromolecules. All the investigated adducts have a channel-like structure, with the PHTP molecules arranged in infinite stacks whose axes are parallel to the threefold axis of the molecules. The structures of three different adducts are described: (a) one with a n-hydrocarbon, n-heptane (which is isomorphous with those containing n-ethers, n-carboxylic acids, n-esters, and also iso-octane and CCl₄); (b) that with CHCl₃; (c) that with cyclohexane. In case (a) no coherence is observed between the rows of included molecules and the host structure, but in (b) and (c) the presence of simple molecular ratios between the host and guest compounds leads to formation of more complex structures. In the (b) adduct two kinds of non-equivalent included molecules are present; the (c) structure results from the packing of parallel PHTP molecules arranged along helices with a small radius (0·40 Å) and nine residues in two pitches, with rows of regularly spaced cyclohexane molecules. Other different crystal structures have been observed: with dioxan; with benzene, or toluene, or bromoform; and with some substituted polybuta-1,4-dienes. The structural results on two different modifications of pure PHTP showing different stability at room temperature, are also reported.