Remarkable Product Selectivity in Photosensitized Oxidation of Alkenes within Nafion Membranes

Abstract

9,10-Dicyanoanthracene (DCA)-sensitized photooxidation of trans,trans-1,4-diphenyl-1,3-butadiene (DPB), trans-stilbene (TS), and α-pinene (PE) incorporated in Nafion membranes has been investigated. While the oxidation in homogeneous solution yields the products derived from both the energy transfer and the electron transfer pathways, that within Nafion membranes selectively gives either the singlet oxygen mediated or the superoxide radical anion mediated products depending on the status and location of the substrate and sensitizer molecules in the reaction media. Upon incorporating the alkene within the water-swollen Nafion membranes and dissolving DCA in the surrounding CH2Cl2 solution, the sensitizer is isolated from the substrate during the irradiation time and the electron transfer between them is prevented. The singlet oxygen produced in the surrounding solution diffuses into the Nafion clusters and reacts with the alkenes. Thus, only the singlet oxygen oxidation products are obtained and no product...