Comparison of the quenching of excited states by 5-DOXYL and 12-DOXYL-stearates in micellar solution

The relative reactivity of the nitroxides tetramethylpiperidin-N-oxide, 5-DOXYL-stearic acid and 12-DOXYL-stearic acid in the quenching of excited states in sodium dodecyl sulfate micelles has been examined. 12-DOXYL-stearic acid is a better quencher in the case of very hydrophobic sensitizers, such as pyrene singlets or phenanthrene (singlet or triplet states). The converse is true for the hydrophilic xanthone triplet or excited Ru(bipy)32+. The results support the idea of preferential solubilization in different regions of the micelle and provide a method for probing this preference.