Static and dynamic phenomena in the quenching of phenanthrene triplets by conjugated dienes in anionic micelles

Abstract

The photochemistry of phenanthrene in sodium dodecyl sulfate micelles in the presence of conjugated dienes having from five to eight carbon atoms has been examined using laser flash photolysis techniques. The effect of the addition of the diene quenchers on the intensity of the T–T absorptions immediately after singlet decay reflects largely the distribution of the quenchers and can be used to determine micellar properties, e.g. the aggregation number. The effect of quenchers on the lifetime of triplet phenanthrene is largely controlled by the rate constants for quencher entry and exit from the micelles. Typical rates of entry are in the 1–2 × 109 M−1 s−1 range, while the exit rates are strongly dependent on the number of carbon atoms and are different for open and cyclic molecules; for example the exit rate constants are 1.3 × 105 and 3.5 × 105 s−1 for 1,3-octadiene and 1,3-cyclooctadiene, respectively.