4,4′-Biphenyldisulfonic acid induced coordination polymers of symmetrical tetramethyl cucurbit[6]uril with alkaline-earth metals for detection of antibiotics

Abstract

Three new coordination polymers based on macrocyclic symmetrical tetramethyl cucurbit[6]uril (TMeQ[6]) with formulae {[Ca₂(C₄₀H₄₄N₂₄O₁₂)(H₂O)₁₀](C₁₂H₈O₆S₂)₂}·13H₂O (1), {[Sr(C₄₀H₄₄N₂₄O₁₂)(H₂O)₄](C₁₂H₈O₆S₂)}·13H₂O (2), and {[Ba₂(C₄₀H₄₄N₂₄O₁₂)(C₁₂H₈O₆S₂)](C₁₂H₈O₆S₂)(H₂O)₇}·12H₂O (3) have been obtained by the self-assembly of TMeQ[6] with the corresponding alkaline-earth metal salts in the presence of 4,4′-biphenyldisulfonic acid (H₂BPDS). Single crystal X-ray diffraction analysis of these three coordination polymers reveals that the deprotonated 4,4′-biphenyldisulfonic acid (H₂BPDS²⁻) plays an important role in the self-assembly of these coordination polymers. In complexes 1 and 2, only the TMeQ[6] is involved in coordination with the Ca²⁺ and Sr²⁺ ions. The BPDS²⁻ is involved in “outer-surface interactions” with the TMeQ[6]. Meanwhile, in complex 3, the BPDS²⁻ is also coordinated with the Ba²⁺ ion. These coordination polymers provide a new strategy to design and construct Q[n]-based poly-dimensional coordination polymers, which can be built by one-dimensional Q[n]-metal coordination chains via outer-surface interactions. Furthermore, complex 1 can detect NFX (norfloxacin) molecules with high selectivity.