Optoacoustic Effect in the Study of the [2 + 2] Photocycloaddition Reaction of a Styryl Dye in a 2 : 1 Inclusion Complex with Cucurbit[8]uril

The magnitude of the optoacoustic effect in aqueous solutions of the styryl dye 4-[(E)-2-(3,4-dimethoxyphenyl)ethenyl]-l-ethylpyridinium perchlorate in the presence of 0.5 equiv cucurbit[8]uril (CB[8]) has been found to depend on the [2 + 2] photocycloaddition reaction, which effectively occurs in the CB[8] cavity and serves as an additional nonradiative channel for pump energy conversion in the 418-nm region. Moreover, the fraction of excitation energy converted to heat is three times lower in the presence of CB[8] than for solutions of the free dye.