Photophysical aspects of 6-methylcoumarin–cucurbit[8]uril host–guest complexes

Photophysical measurements of 6-methylcoumarin (1) encapsulated within cucurbit[8]uril (CB[8]) indicate a pronounced red shift in the fluorescence maximum with an increase in the emission quantum yield and fluorescence lifetime. In addition, at 77 K, there is observable phosphorescence upon encapsulation within CB[8]. The photophysical measurements add credibility to our previously proposed dynamic nature of the CB–coumarin complex in solution. The dynamic nature of the CB[8]–coumarin host–guest complex in water is critical to a CB acting as a supramolecular catalytic nanoreaction vessel to facilitate the photodimerization of coumarins leading to syn dimers.