Photodimerization and complexation dynamics of coumarins in the presence of cucurbit[8]urils.

Coumarin derivatives with non-polar substituents at the 6 or 7 position undergoes photodimerization in the presence of CB[8] in water to give the syn dimer as the major product. It is postulated that these neutral coumarins form dynamic complexes in the presence of CB[8] and the product selectivity is reflective of the type of complex, available volume in the CB[8] cavity and relative rate of photodimerization inside and outside the CB[8] cavity.