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The formation of 3D fused 10-membered “bracelet” frameworks derived from the alkyl-substituted curcurbit[5]urils (SQ[5]s), 1,2,4-hexamethylcucurbit[5]uril (1,2,4-HMeQ[5]), and pentacyclopentanocucurbit[5]uril (PCyHQ[5]) and K+ ions is described. These remarkable catenated structures feature trigonal-planar branching units involving three SQ[5]s connected via their bound K+ ions in a triangular manner in which the coordination of each K+ ion to the five portal carbonyl oxygen atoms of one SQ[5] as well as to a bridging portal carbonyl oxygen from an adjacent SQ[5] draws the edges of three portals into close proximity. The corresponding offset angle at each junction provides the basis for the 3D assembly of the observed fused 10-membered SQ[5] bracelet frameworks.

Four molecular capsules based on three methyl-substituted cucurbit[5]urils, which are α,β,δ-hexamethyl cucurbit[5]uril (α,β,δ-HMeQ[5]), decamethylcucurbit[5]uril (Me10Q[5]) and a pentamethylcucurbit[5]uril constructed of a monomethyl-glycouril (PMeQ[5]), were synthesized and structurally characterized by single crystal X-ray diffractions. They are {[α,β,δ-HMeQ[5]@Cl][Sr(H2O)2]2}3+3·Cl−·13(H2O) (1), {[α,β,δ-HMeQ[5]@(NO3)][Sr(NO3)(H2O)]2}+[NO3]−HNO3·4(H2O) (2), {[Me10Q[5]@(NO3)][Sr(NO3)(H2O)]2}+(NO3)−8(H2O) (3) and {[PMeQ[5]@Cl][Sr(H2O)2]2}3+3·Cl−·22(H2O) (4). In the crystal structure of these compounds, molecular capsules included a Cl− or a NO 3 - anion and lidded with strontium cations were observed.

We introduce an approach for the synthesis of networks based on the coordination of alkyl-substituted cucurbit[5]uril (SQ[5]), dimethylcucurbit[5]uril (DMeQ[5]), 1,3-dicyclohexanocucurbit[5]uril (1,3-DCyHQ[5]), 1,2,4-tricyclohexanocucurbit[5]uril (1,2,4-TriCyHQ[5]), 1,2,3-cyclohexanocucurbit[5]uril (1,2,3-TriCyHQ[5]), and pentacyclopentanocucurbit[5]uril (PCyPQ[5]) with K+ ions in the absence of a structure inducer. These novel SQ[5]-K+-based networks feature trigonal-planar branches constructed from three SQ[5]s and K+ ions in a triangular manner, in which the coordination of each K+ ion to the five portal carbonyl oxygen atoms of one SQ[5] as well as to a bridging portal carbonyl oxygen from an adjacent SQ[5] draws the edges of three portals into close proximity. Thus, a 3-K+-cation junction is formed at each portal of the S[5] and there are four 3-K+-cation junctions in which one or two coordinated water molecule(s) are shared by the three K+ cations in the trigonal-planar branch. Detailed inspection of the relationship of the planes at the 3-K+ junction has revealed that the dihedral angles between the junction plane and the center junction plane have a strong influence on the supramolecular assembly of SQ[5] with K+ ions into 2D-networks or 3D-frameworks. Moreover, these dihedral angles determine the structural conformation of the SQ[5]-K+-based networks and the superimposition of 2D-networks in the compounds.