Coordination and Supramolecular Self-Assemblies of Alkali and Alkaline Earth Metal Ions to Cucurbit[5]uril in the Presence of Nitrophenol

In the present study, the coordination and supramolecular self-assemblies of a series of alkali and alkaline earth metal ions to cucurbit[5]uril in the presence of nitrophenol are introduced. The experimental results have proven that the presence of nitrophenol and the ionic radiuses of the metal ions influence greatly the coordination and supramolecular self-assemblies of these metal ions to Q[5] molecule. Compared to in the absence of p-nitrophenol, the presence of p-nitrophenol seems to frustrate the formation of the K-Q[5] coordination polymer, while the presence of p-nitrophenol induces the formation of Rb- and Cs-Q[5] coordination polymers. Basically, one-dimensional supramolecular chains are constructed of alkaline earth metal ions and Q[5] molecules alternating; the sizes of their ionic radiuses influence the interaction modes in the chain. The formation of the Ca-Q[5] polymer results in the partial coordination of Ca cations to the portals of adjacent Q[5] molecules due to the smaller ionic radius. The formation of the Sr-Q[5] supramolecular chain results in the threading of the Sr-Q[5] molecular bowl through hydrogen bonding, while the formation of the Ba-Q[5] polymer results in the threading of the Ba-Q[5] molecular bowl through direct coordination.