title: Dynamics of Radical Ion Pairs following Photoinduced Electron Transfer in Solvents with Low and Intermediate Polarities.
abstract: Fluorescence quenching of p-xylene, naphthalene, or pyrene by fumaronitrile in apolar solvents and in solvents of intermediate polarities leads to weakly fluorescent radical ion pairs. This emission is assigned to ion pairs in close contact on the basis of their solvent polarity dependence, kinetics, and thermodynamics. The temperature-dependence of the intensity and fluorescence emission maxima of ion pairs in methyl acetate reveals that they have decay channels competitive with their thermal equilibration. The results presented in this work are consistent with the direct formation of contact ion pairs in weakly polar solvents and in solvents of intermediate polarities as the result of bimolecular photoinduced electron transfer reactions between aromatic hydrocarbons and nitriles. The implications of these findings in free-energy relationships of electron transfer reactions are discussed.
authors.affiliation: Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Kamila K
authors.initials: KK
authors.lastname: Mentel
authors.affiliation: Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Rui M D
authors.initials: RM
authors.lastname: Nunes
authors.affiliation: Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Serpa
authors.affiliation: Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Luis G
authors.initials: LG
authors.lastname: Arnaut
mesh_terms: D004579:Electron Transport; D005453:Fluorescence; D005609:Free Radicals / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D055668:Photochemical Processes; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D005609:Free Radicals; D007477:Ions; D012997:Solvents