Micelles vectorial

Photosensitized vectorial electron transfer from the (morpholine)ethenesulfonate anion (MES ) to 1,5-anthraquinone disulfonate (AQDS ) mediated by dibutyl (BTDB) or diethyl (BTDE) esters of 2,l,3-benzothiadiazole-4,7-dicarboxylic acid solubilized in CTAB micelles has also been reported [73], The proposed mechanism of BTD-mediated electron transfer is shown in Figure 7, where reductive quenching of photoexcited BTD by interfacially adsorbed MES is followed by electron transfer from reduced BTD to the AQDS , recycling the sensitizer. 

SDS micelles have also been used as a basis for light-induced charge separation processes. A hydrophobic, photooxidizable dye (e.g., a zinc porphyrinate) was, for example, dissolved in an anionic SDS micelle with copper(II) counterions. Upon excitation with visible light an electron was transferred first and very fast to the copper(II) coating, which then was reoxidized by anionic ferricyanide in the bulk water phase. The reduced ferrocyanide ion formed did not react with the oxidized porphyrin, because the anionic micelles and reductant repelled each other and the ferrocyanide was highly diluted by ferricyanide (Fig. 2.5.5). The energy of sunlight has thus initiated a simple vectorial reaction in a primitive membranous system. 

The viologen reduction by EDTA in reverse micelles in the presence of Ru(bpy)3 is another example of vectorial photoinduced electron transfer [106], The accumulation of photoproducts is associated with the catalytic cycles depicted in Fig. 10(b). The oxidative quenching of the ruthenium complex occurs at the micelle outer boundary, while the regeneration of the dye takes place by the oxidation of EDTA in the inner core of the micelle. The reduction of the final product 4-dimethylaminoazobenzene is further mediated by the acceptor 1-benzylnicotinamide (BNA ). In Fig. 10(c), the photocatalytic reduction of methyl benzoylformate (MBF) by thiosulfate is described in the presence of the porphyrin ZnTPPS and the mediator quinolinium-3-carboxiamide (DCA ) [107]. This sequence of reactions occurs only in micelles such as those formed by hexadecyl-trimethylammonium bromide, which contain in the interior the ultimate donor acceptor. Finder illumination, ZnTPPS photoreduces DCA to DCQ, which is subsequently extracted into the micelle core. Within the microenvironment, DCA is regenerated via reduction of MBF, while the oxidized porphyrin is reduced by thiosulfate outside the micelle. 

---