One-Dimensional Coordination Polymers of Lanthanide Cations to Cucurbit[7]uril Built Using a Range of Tetrachloride Transition-Metal Dianion Structure Inducers

A number of linear coordination polymers have been assembled from lanthanide cations (Ln) and cucurbit[7]uril (Q[7]) in the presence of [CuCl4]or [CoCl4] anions acting as inorganic structure inducers in HCl solution. X-ray diffraction analysis has revealed that they form three groups of isomorphous structures. Generally, the complexes of Q[7] with light lanthanide cations (those with atomic number below that of neodymium (Nd)) are in one group. The other two groups, in which the lanthanide cation has atomic number greater than that of europium (Eu), seem to follow no obvious rule. For example, the complexes of Q[7] with Eu and Gdcations are in the second group in the presence of [CuCl4] anions, while they are in the third group in the presence of [CoCl4] anions. However, whatever group a given complex belongs to, they all show a common honeycomb-patterned supramolecular assembly, in which [CuCl4]or [CoCl4] anions OPEN ACCESS Polymers 2013, 5 419 form a honeycomb structure. The Ln cations then coordinate to neighboring Q[7] molecules to form 1D coordination polymers that are inserted into the channels of the honeycomb framework, such that each individual coordination polymer is surrounded by [CuCl4]or [CoCl4] anions.