Photocatalysis of Perfluorinated Oligo(p-Phenylene)s

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Abstract
Perfluorination of oligo(p-phenylene)s (OPP-n), biphenyl(OPP-2) to p-quaterphenyl (OPP-4), induces various changes in the spectral and physical characteristics of OPP-n; a hypsochromic shift of their absorption spectra, a decrease in their fluorescence quantum yields, an increase in their fluorescence lifetimes, and a positive shift of their oxidation potentials. The resulting perfluorinated oligo(p-phenylene)s (F-OPP-n, n = 3 and 4) shows photocatalytic activities for the photoreduction of water and for the photooxidation of benzene to phenol. Irradiation of an aqueous methanol solution of F-OPP-3 with triethylamine as an electron donor, and noble metal colloid as an electron mediator at λ > 290 nm, leads to H2 evolution, although photodefluorination through F-OPP-3−• inevitably occurs to an appreciable extent. A similar irradiation of an aqueous acetonitrile solution with O2 and benzene induces the oxidation of benzene and water, yielding almost equal quantities of phenol and H2O2 without any accompanying degradation of F-OPP-3.