The photophysical and photochemical behavior of azobenzene (AB) incorporated into solvent-swollen acid form Nafion (Nafion-H+) membranes were examined. In water-swollen Nafion-H+ membrane AB exhibits strong fluorescence at room temperature, which has never been observed in isotropic solvents. Photolysis of AB adsorbed in water-swollen Nafion-H+ results in its cyclization to give benzo[c]cinnoline (BC) and benzidine (BZ) in quantitative yield. The product distribution is very dependent upon the number of AB molecules in each water cluster of the Nafion membrane (occupancy number). In the case of the occupancy number greater than 2, BC and BZ are formed equimolarly, while when only one AB molecule exists in each water cluster, BC is exclusively produced. The AB molecules incorporated into methanol-swollen Nafion-H+ membrane do not emit fluorescence and only undergo cis − trans isomerization when they are photoirradiated. These observations suggest that in water-swollen Nafion-H+ AB molecules are solublized in the fluorocarbon/water interface, and the protons of the Nafion-H+ participate in the photochemical and photophysical processes of AB. On the other hand, in methanol-swollen Nafion-H+ membrane AB molecules are located in the methanol pools, and their photochemical and photophysical behaviors are not intervened by the Nafion protons.

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 derived from superoxide radical anion is detected. In contrast, incorporating both the substrate and the sensitizer within the water-swollen Nafion membranes leads to the possibility of situating the two dissimilar molecules near one another within the restricted space of the Nafion cluster. Thus, the electron transfer from the alkenes to the singlet excited state of DCA is enhanced, and the efficiency of the intersystem crossing from 1DCA* to 3DCA* is reduced. The photosensitized oxidation in this case only gives products derived from the electron-transfer pathway, and no singlet oxygen mediated product is observed.

The photocycloaddition of five 9-substituted anthracenes [AnCH(2)N(+)(CH(3))(3)Br(-) (1), AnCH(2)COO(-)Na(+) (2), AnCH(2)OH (3), AnCOCH(3) (4), and AnCH(3) (5), An = 9-anthryl] incorporated within Nafion membranes has been investigated. While irradiation of the above compounds in homogeneous solutions, and 5 in Nafion also, mainly gave rise to their head-to-tail (h-t) photocyclomers, photoirradiation of the samples of 1-4 incorporated within Nafion membranes almost exclusively resulted in the head-to-head (h-h) photocyclomers. Furthermore, the h-h photocyclomers are significantly more stable in Nafion membranes than in homogeneous solutions. These observations can be explained in terms of the preorientation of the substrate molecules in the inverse micelle-like clusters of Nafion.