The mechanism and effect of the quenching of aromatic hydrocarbon singlet excited states by conjugated dienes
Strong and rather specific quenching of fluorescence of aromatic hydrocarbons by conjugated dienes has been observed in solution at room temperature, despite the fact that the first excited singlet states of dienes lie considerably higher than those of the aromatic hydrocarbons involved. A study of...
| Summary: | Strong and rather specific quenching of fluorescence of aromatic hydrocarbons by conjugated dienes has been observed in solution at room temperature, despite the fact that the first excited singlet states of dienes lie considerably higher than those of the aromatic hydrocarbons involved. A study of various substituent effects on the quenching rates has been carried out and attempts have been made to ascertain those effects important in determining these rates and the stability of the (presumed) excited complex. A model based on delocalization of excitation energy through virtual states of the diene is proposed and is successful in rationalizing the correlation found between diene singlet state energies and quenching rates. The model will allow qualitative estimation of the effect of diene structure on quenching rates and will predict the susceptibility of various aromatic hydrocarbon singlets to diene quenching.
The quenching has been shown to be noneffective in producing diene excited states or in inducing any appreciable change in the diene or aromatic hydrocarbon. It is concluded, therefore, that dienes quench, by acting as specific catalysts for the nonradiative decay of aromatic hydrocarbon singlets.
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