Effect of addition of calix[n]arenes on photooxygenation of 4,5-diphenylimidazolones

Rates of dye sensitized photo-oxygenation of 4,5-diphenylimidazolones increase markedly on addition of calix[n]arenes. The effect of addition of calix[6]arenes is more pronounced than that of calix[4]- and calix[8]arenes and it varies with the size of the alkyl group (octyl > hexyl > t-butyl > methyl > H) in the same calixarene series.