title: Hofmeister effects on electron-transfer reactions of 1-pyrenesulfonic acid radical cation with nucleophilic anions in Nafion membranes.
abstract: The electron-transfer reaction from nucleophilic anions such as SCN(-), N(3)(-), I(-), and Br(-) to the 1-pyrenesulfonic acid radical cation (Py(*+)SA(-)) generated via a resonant two-photon ionization process in the Nafion membranes was investigated with transient absorption measurements. The apparent quenching rates observed in the Nafion membrane (k(q)(Nf)) were almost 2-4 orders smaller than those observed in the bulk solutions (k(q)(bulk)). The attenuation factor (AF), which is defined as log(k(q)(Nf)/k(q)(bulk)), decreased in the order SCN(-) > N(3)(-) > I(-) > Br(-). This interesting behavior was interpreted in terms of the anionic Hofmeister effects. The effects of hydrophobic organic cations such as tetrabutylammonium ion (Bu(4)N(+)) and tetraethylammonium ion (Et(4)N(+)) exchanged into the Nafion membranes were also examined.
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tachikawa
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Ramaraj
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D000838:Anions; D002412:Cations; D002627:Chemistry, Physical / Q000379:methods*; D004579:Electron Transport; D004583:Electrons; D005609:Free Radicals; D007700:Kinetics; D008566:Membranes / Q000737:chemistry; D017785:Photons; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013451:Sulfonic Acids / Q000737:chemistry*; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D000838:Anions; D002412:Cations; D005609:Free Radicals; D000644:Quaternary Ammonium Compounds; D013451:Sulfonic Acids; C009405:tetrabutylammonium