%0 Journal Article
%A Bronner, Catherine
%A Wenger, Oliver S.
%D 2015
%T Kinetic Isotope Effects
in Reductive Excited-State
Quenching of Ru(2,2′-bipyrazine)32+ by
Phenols
%U https://acs.figshare.com/articles/journal_contribution/Kinetic_Isotope_Effects_in_Reductive_Excited_State_Quenching_of_Ru_2_2_bipyrazine_sub_3_sub_sup_2_sup_by_Phenols/2017806
%R 10.1021/jz201494n.s001
%2 https://ndownloader.figshare.com/files/3589080
%K PhenolsElectron transfer
%K Possible PCET reaction mechanisms
%K Br
%K emission quenching
%K KIE
%K OCH
%K Kinetic Isotope Effects
%K phenol molecules
%K phenolic proton
%K CH
%K CN
%K nitrogen atom
%K isotope effects
%K CPET
%X Electron transfer (ET) from phenol molecules to a photoexcited
ruthenium(II) complex was investigated as a function of the para-substituent
(R = OCH3, CH3, H, Cl, Br, CN) attached to the
phenols. For phenols with electron-donating substituents (R = OCH3, CH3), the rate-determining excited-state deactivation
process is ordinary ET. For all other phenols, significant kinetic
isotope effects (KIEs) (ranging from 2.91 ± 0.18 for R = Br to
10.18 ± 0.64 for R = CN) are associated with emission quenching,
and this is taken as indirect evidence for transfer of a phenolic
proton to a peripheral nitrogen atom of a 2,2′-bipyrazine ligand
in the course of an overall proton-coupled electron transfer (PCET)
reaction. Possible PCET reaction mechanisms for the various phenol/ruthenium
couples are discussed. While 4-cyanophenol likely reacts via concerted
proton–electron transfer (CPET), a stepwise proton transfer–electron
transfer mechanism cannot be excluded in the case of the phenols with
R = Br, Cl, and H.
%I ACS Publications