Formation and decay of styrene-amine exciplexes

The formation and decay of the fluorescent exciplexes formed between two styrenes (trans-1-phenylpropene and trans-1-(4-cyanophenyl)propene) and two trialkylamines (triethylamine and diisopropylethylamine) were investigated using steady state and transient fluorescence measurements. The standard exciplex kinetic scheme has been expanded for the first time to include quenching of a reversibly-formed exciplex by ground state amine. Analysis of the data for the four exciplex systems provides examples of the four possible modes of exciplex formation (reversible and irreversible) and decay (quenched and unquenched). An anticipated, an increase in the driving force for exciplex formation leads to a decrease in the rate constant for exciplex dissociation, while an increase in the steric bulk of the amine leads to a decrease in the rate constant for exciplex quenching by ground state amine.