title: Dual electron transfer pathways from 4,4'-dimethoxybenzophenone ketyl radical in the excited state to parent molecule in the ground state.
abstract: Dual intermolecular electron transfer (ELT) pathways from 4,4'-dimethoxybenzophenone (1) ketyl radical (1H*) in the excited state [1H*(D1)] to the ground-state 4,4'-dimethoxybenzophenone [1(S0)] were found in 2-methyltetrahydrofuran (MTHF) by observing bis(4-methoxyphenyl)methanol cation (1H+) and 4,4'-dimethoxybenzophenone radical anion (1*-) during nanosecond-picosecond two-color two-laser flash photolysis. ELT pathway I involved the two-photon ionization of 1H* following the injection of electron to the solvent. The solvated electron was quickly trapped by 1(S0) to produce 1*-. ELT pathway II was a self-quenching-like ELT from 1H*(D1) to 1(S0) to give 1H+ and 1*-. From the fluorescence quenching of 1H*(D1), the ELT rate constant was determined to be 1.0 x 10(10) M(-1) s(-1), which is close to the diffusion-controlled rate constant of MTHF. The self-quenching-like ELT mechanism was discussed on the basis of Marcus' ELT theory.
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Xichen
authors.initials: X
authors.lastname: Cai
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D001577:Benzophenones / Q000737:chemistry*; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D007700:Kinetics; D007834:Lasers; D015394:Molecular Structure; D010782:Photolysis; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: C521191:4,4'-dimethoxybenzophenone; D001577:Benzophenones; D005609:Free Radicals; D007659:Ketones; D012997:Solvents