Crystal structures of host–guest complexes of meta-tricyclohexyl cucurbit[6]uril with small organic molecules

Three host–guest complexes, {acetone@m-TriCyHQ[6]}19H2O (1), {acetone@m-TriCyHQ[6]}{app}+Cl−12H2O (2), and {55dmbpy@m-TriCyHQ[6]}+ Cl−17H2O (3) were prepared with meta-tricyclohexyl cucurbit[6]uril (m-TriCyHQ[6]) and acetone, 3-amino-5-phenylpyrazole(app), and 5,5′-dimethyl-2,2′dipyridyl(55dmbpy), respectively. Their crystal structures along with that of {m-TriCyHQ[6]}22H2O (4) were characterized by single-crystal X-ray diffractions. The crystal structures of these host–guest complexes revealed that the host m-TriCyHQ[6] had a strong selectivity for different guest molecules, which were readily included in the cavity of m-TriCyHQ[6]. Small organic compounds, such as acetone and dioxane, showed a relatively strong tendency to interact only with the cavity of m-TriCyHQ[6]. However, guest 3-amino-5-phenylpyrazole hydrochloride preferred to interact with the portals of m-TriCyHQ[6] and guest 5,5′-dimethyl-2,2′-dipyridyl showed strong interactions with both the cavity and portals of m-TriCyHQ[6]. Basically, these guests form inclusion host–guest complexes with m-TriCyHQ[6], which were stabilized by the hydrophobic interactions in the cavity and the hydrophilic interactions at the portals.