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

Abstract

Three supramolecular architectures, namely, (C₄₀H₄₄O₁₂)·(H₃O)₄⁴⁺·(CuCl₄)₂⁴⁻·8H₂O (1), [(C₄₀H₄₄O₁₂)(CuCl₂)₂(H₂O)₄]·10H₂O (2), (C₄₀H₄₄O₁₂)·14H₂O (3), have been successfully synthesized through the reaction of symmetrical α,α′,δ,δ′-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⋯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.