Photoinduced electron transfer from (alkoxyphenyl)triphenylporphyrins to interface water of aerosol dioctyl- and cetyltrimethylammonium bromide/alcohol reverse micelles at 77 K

Photoinduced electron transfer from (alkoxyphenyl)triphenylporphyrins (C[sub n]OPTPP) to the interface water of anionic aerosol dioctyl- (AOT) and cationic cetytrimethylammonium bromide/alcohol (CTAB/ROH) reverse micelles at 77 K produces paramagnetic (alkoxyphenyl)triphenylporphyrin cation radical (C[sub n]OPTPP[sup +]). The photoproduced radicals are identified and quantitated with electron spin resonance by measuring the g factor, hyperfine splitting, and the doubly integrated spectrum. The photoproduced radical yields are correlated with the deuterium modulation depth of C[sub n]OPTPP[sup +] by electron spin-echo modulation (ESEM), which measures changes in the interaction distance of the porphyrin cation headgroup with water (D[sub 2]O) at the reverse micelle interface as a function of the C[sub n] alkyl chain length. The location of the porphyrin cation headgroup relative to interface water (D[sub 2]O) is controlled by the alkyl chain length of C[sub n]OPTPP, the cosurfactant alcohol and the headgroup charge of the surfactant forming the reverse micelle. A longer alkyl chain decreases the photoyield because of increased hydrophobic interaction between C[sub n]OPTPP and the surfactant alkyl chains of the reverse micelles which [open quotes]pulls[close quotes] the porphyrin moiety more into the alkane region of the reverse micelles. 34 refs., 7 figs.