p-Hydroxybenzoic acid-assisted homochiral 1D-helical coordination polymers from calcium cations and cucurbit[5]uril

A homochiral 1D-helical coordination polymer has been assembled from calcium ions (Ca2+) and cucurbit[5]uril (Q[5]) in the presence of p-hydroxybenzoic acid (Hyb) as an organic structure inducer. This result shows that a homochiral 1D-helical coordination polymer can be obtained from Q[5] with not only heavy lanthanides but also other metal ions, such as calcium dications in the present case, and that p-hydroxybenzoic acid (Hyb) can serve as an organic structure inducer in place of the previously used hydroquinone (Hyq). Control experiments by X-ray diffraction analysis have shown that Q[5] coordinates with the calcium cations to form a linear coordination polymer in the absence of Hyb, while a mixture of Q[5] and Hyb, without a metal salt under the same synthetic conditions, produces Q[5]-based linear supramolecular chains linked by hydrogen-bonding networks, which lie in a Hyb-based net.