Cucurbit7uril

Cucurbit[7]uril, commonly abbreviated CB7, is a synthetic macrocyclic molecule in the cucurbituril family. It is composed of seven glycoluril units linked by methylene bridges, forming a rigid, barrel-shaped cavity. The outer surface is hydrophilic, while the interior cavity is hydrophobic. The portals at each end are lined with carbonyl groups, which gives the molecule a polar character and facilitates water solubility as well as selective binding of guest molecules.

In aqueous solution CB7 acts as a host for a range of neutral and charged guests, with a preference for hydrophobic, positively charged, or protonated species. Binding is driven by a combination of hydrophobic effects within the cavity and electrostatic interactions at the carbonyl-lined portals. Complexation often results in 1:1 host–guest stoichiometry and can significantly alter the solubility, stability, or reactivity of the guest.

Synthesis of CB7 involves condensations of glycoluril derivatives with formaldehyde under acidic conditions, followed by purification to isolate the seven-unit macrocycle from mixtures of cucurbit[n]urils. CB7, like other cucurbiturils, is widely used in supramolecular chemistry as a tool to study host–guest interactions and to modulate properties of guest molecules in water. Its applications span sensing, catalysis, drug formulation, and the development of responsive materials.