Host–guest inclusion complexes of four partial alkyl-substituted cucurbit[6]urils with some probe guests

Using probe guests, three host–guest inclusion complexes of two new alkyl-substituted cucurbit[6]uril hosts, ortho-tetramethyl cucurbit[6]uril (o-TMeQ[6]) and symmetrical tetracyclohexano cucurbit[6]uril (TCyHQ[6]) have been characterized successfully by single crystal X-ray diffractions. They are {o-TMeQ[6]-5,5′dimethyl-2,2′-bispyridine (DMBPY)+}Cl−21H2O(1), {(o-TMeQ[6])2-1,6-bisbenzoimidazolylhexane (SBH)2+} 2Cl−52H2O (2) and {TCyHQ[6]-dioxane}14H2O (3). Moreover, two similar crystal structure of two inclusion complexes of other two partial substituted cucurbit[6]urils, meta-hexamethyl cucurbit[6]uril (m-HMeQ[6]) and symmetrical dicyclohexano cucurbit[6]uril (p-(CyH)2Q[6]) with HCl salt of DMBPY were also reported. They were {p-(CyH)2Q[6]-DMBPY+}Cl−16H2O (4) and {m-HMeQ[6]-DMBPY+}Cl−15H2O (5). The driving force for the information of the host–guest inclusion complexes can be attributed to not only the cavity interaction (host), but also the hydrogen bonding and ion–dipole interaction between the carbonyl oxygen at the portals of the host and the protonated nitrogen of the guest.