Construction and solvent recognition of cucurbit[5]uril-alkali metal and alkali-earth metal supramolecular self-assembly induced by 2,7-naphthalene disulfonic acid

By introducing 2,7-naphthalene disulfonic acid (H2NDA) as a structure-directed agent, four new Q[5]- based supramolecular self-assemblies, namely [K-2(H2O)(4)(Q[5])](2,7-NDA) center dot 4H(2)O (1), [Rb-2(H2O)5(Q[5])](2,7-NDA)center dot 3H(2)O (2), [Mg(H2O)4(Q[5])](2,7-NDA)center dot 8H(2)O (3), and [Ca(H2O)(4)(Q[5])](2,7-NDA)center dot 10H(2)O (4), were prepared under hydrothermal conditions. Single crystal X-ray diffraction results show that the self-assemblies 1 and 2 have the same structure. The coordination of the Q[5] molecule with metal ions forms a"molecular capsule"structure in 1 and 2, while the coordination of Q[5] and Mg2+ in 3 forms a 1:1 simple complex structure. In 4, Q[5] and Ca2+ can directly coordinate to form a 1D Q[5] -Ca(2+)coordination polymer chain structure. The 2,7-NDA2- anions in these structures balance the system charge, and through their outer-surface interactions with Q[5], promote its final construction into a 3D supramolecular structure. In addition, we also studied the fluorescence sensing properties of self-assembly 4, which could be used as quenching fluorescence probes for the organic solvents acetone and DMF. CCDC: 2246647, 1; 2246648, 2; 2246649, 3; 2246650, 4.