Structures of supramolecular assemblies formed by substituted cucurbiturils and metal ions

Four supramolecular assemblies based on two partial substituted cucurbituril, α,δ-tetramethylcucurbit[6]uril (TMeQ[6]) and α,δ-dicyclohexanocucurbit[6]uril ((CyH)2Q[6]), with different metal ions were synthesized and structurally characterized by single-crystal X-ray diffractions. They are {[TMeQ[6]@2H2O]·[Zn(H2O)4]}·[ZnCl4]·12H2O (1), {[TMeQ[6]@H2O]·[Sr2Cl2]}·[Cl]2·10H2O (2), {TMeQ[6]·[CaCl]}·[Cl]·17.5H2O (3), {[(CyH)2Q[6]@acetone]·1.5[Ni(H2O)6]}·(NO3)32H2O (4). The crystal structures of these complexes showed that supramolecular chains were formed through different interaction modes. In complex 1, the transition metal ion Zn2+ was coordinated not only with water molecules but also directly with carbonyl oxygens of a portal of TMeQ[6]. The Zinc aqua complexes served as a bridge between TMeQ[6]s in the 1D supramolecular chains. In complex 2, each Sr2+ ion was coordinated directly with two carbonyl oxygen atoms at a portal of two TMeQ[6], and each TMeQ[6] was coordinated with four Sr2+ ions, resulting in the formation of supramolecular chains consisted of alternating metal ions and TMeQ[6]. In complex 3, two TMeQ[6] molecules were coordinated by two Ca2+ ions to form a assembled unit. The assembled units were connected through hydrogen bonds, leading to the formation of supramolecular chains. In complex 4, supramolecular chains consisted of alternating [Ni(H2O)]2+ complex cation and (CyH)2Q[6] were formed through hydrogen bonding.