CIDEP Study of the Photoreduction of Benzophenone with Aromatic Amines-in Micellar Solutions

Abstract

The reactions between photoexcited benzophenone and several aromatic amines were studied by a time-resolved ESR technique in different kind of micellar solutions (SDS, CTAB and Brij 35) at room temperature. The systems of benzophenone(BP)/N, N-dimethylaniline and BP/N, N-diethylaniline showed the formation of an emissively spin-polarized benzophenone anion radical in all micellar solutions. The systems including N-methyl- and N-ethylanilines showed mainly the benzophenone ketyl radical with emissive spin-polarization in SDS and CTAB micellar solutions, and the benzophenone anion radical in Brij 35. The systems including aniline yielded an emissively spin-polarized aniline N-centered radical in all the micelles. All the emissive spin-polarization observed is explained by the triplet mechanism of CIDEP. These experimental results lead to the conclusion that such micellar environments and/or interfaces promote a function of charge separation and prohibit a back charge transfer of a transient charge transfer complex or a radical-ion pair formed immediately after photolysis, when amines have low ionization potentials.