Anion concentration control in the self-assembly of symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6] uril-based tubular architectures

Three supramolecular architectures, namely, (C40H44O12)center dot(H3O)(4)(4+)(CuCl4)(2)(4)-center dot 8H(2)O (1), [(C40H44O12)(CuCl2)(2)(H2O)(4)]center dot 10H(2)O (2), (C40H44O12)center dot 14H(2)O (3), have been successfully synthesized through the reaction of symmetrical alpha, alpha', delta, delta'-tetramethyl-cucurbit[6] uril (TMeQ[6]) with CuCl2 at different chloride anion concentration conditions. In the structure of compound 1, which is formed in 6.0 M hydrochloric acid solution, tetrahedral [CuCl4](2-)dianions and TMeQ[6] macrocycles are linked into a 1D tubular structure through hydrogen bonding, C-H center dot center dot center dot Cl contacts, and ion-dipole interactions. The compound 2 is isolated in 3.0 M hydrochloric acid solution, in which Cu2+ ions were found to be directly coordinated to the carbonyl oxygens of TMeQ[6] macrocycles and generated a tubular coordination polymer. A further decrease of chloride anion concentration to 1.0 M leads to compound 3, in which no Cu2+ was located and TMeQ[6] macrocycles are packed into a 3D supramolecular assembly containing numerous 1D tubular channels.