Journal ArticleDOI
Competing Pathways in the photo-Proton-Coupled Electron Transfer Reduction of fac-[Re(bpy)(CO)3(4,4′-bpy]+* by Hydroquinone
David J. Stewart,M. Kyle Brennaman,Stephanie E. Bettis,Li Wang,Robert A. Binstead,John M. Papanikolas,Thomas J. Meyer +6 more
TLDR
In this article, the metal-to-ligand charge transfer (MLCT) excited state of fac-[ReI(bpy)(CO)3(4,4′-bpy)]+ is reductively quenched by 1,4-hydroquinone (H2Q) in CH3CN at 23 ± 2 °C by competing pathways to give a common electronproton-transfer intermediate.Abstract:
The emitting metal-to-ligand charge transfer (MLCT) excited state of fac-[ReI(bpy)(CO)3(4,4′-bpy)]+ (1) (bpy is 2,2′-bipyridine, 4,4′-bpy is 4,4′-bipyridine), [ReII(bpy–•)(CO)3(4,4′-bpy)]+*, is reductively quenched by 1,4-hydroquinone (H2Q) in CH3CN at 23 ± 2 °C by competing pathways to give a common electron–proton-transfer intermediate. In one pathway, electron transfer (ET) quenching occurs to give ReI(bpy–•)(CO)3(4,4′-bpy)]0 with k = (1.8 ± 0.2) × 109 M–1 s–1, followed by proton transfer from H2Q to give [ReI(bpy)(CO)3(4,4′-bpyH•)]+. Protonation triggers intramolecular bpy•– → 4,4′-bpyH+ electron transfer. In the second pathway, preassociation occurs between the ground state and H2Q at high concentrations. Subsequent Re → bpy MLCT excitation of the adduct is followed by electron–proton transfer from H2Q in concert with intramolecular bpy•– → 4,4′-bpyH+ electron transfer to give [ReI(bpy)(CO)3(4,4′-bpyH•)]+ with k = (1.0 ± 0.4) × 109 s–1 in 3:1 CH3CN/H2O.read more
Citations
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Journal ArticleDOI
Proton-coupled electron transfer with photoexcited metal complexes.
TL;DR: Recent studies of excited-state PCET with d(6) metal complexes with central question whether concerted proton-electron transfer (CPET) can compete kinetically with sequential electron and proton transfer steps are described.
Journal ArticleDOI
Proton-coupled electron transfer with photoexcited ruthenium(II), rhenium(I), and iridium(III) complexes
TL;DR: The field of excited-state proton-coupled electron transfer (PCET) with d6 metal complexes is reviewed in this paper, which aims to illustrate the usefulness of such complexes for mechanistic studies of excitedstate PCET.
Journal ArticleDOI
Kinetic Isotope Effects in Reductive Excited-State Quenching of Ru(2,2’-Bipyrazine)32+ by Phenols
TL;DR: In this article, electron transfer 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.
Journal ArticleDOI
Proton-coupled electron transfer between 4-cyanophenol and photoexcited rhenium(I) complexes with different protonatable sites.
TL;DR: This study aimed to explore how a difference in electronic excited-state structure affects the rates and the reaction mechanism for photoinduced proton-coupled electron transfer (PCET) between 4-cyanophenol and the two rhenium(I) complexes.
Journal ArticleDOI
Inverse kinetic isotope effect in the excited-state relaxation of a Ru(II)-aquo complex: revealing the impact of hydrogen-bond dynamics on nonradiative decay.
TL;DR: Data indicate control of excited-state lifetime via a pre-equilibrium between the (3)MLCT state that initiates H-bond dynamics with the solvent and the ( 3)MC state that serves as the principal pathway for nonradiative decay.
References
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Integrating proton coupled electron transfer (PCET) and excited states
Christopher J. Gagliardi,Brittany C. Westlake,Caleb A. Kent,Jared J. Paul,John M. Papanikolas,Thomas J. Meyer +5 more
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Journal ArticleDOI
Halide-Dependent Change of the Lowest-Excited-State Character from MLCT to XLCT for the Complexes Re(X)(CO)3(α-diimine) (X = Cl, Br, I; α-diimine = bpy, iPr-PyCa, iPr-DAB) Studied by Resonance Raman, Time-Resolved Absorption, and Emission Spectroscopy
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Journal ArticleDOI
Ionization constants and spectral characteristics of some semiquinone radicals in aqueous solution
P. S. Rao,E. Hayon +1 more
Journal ArticleDOI
Excited-state quenching by proton-coupled electron transfer
Javier J. Concepcion,M. Kyle Brennaman,Jeremy R. Deyton,Natalia V. Lebedeva,Malcolm D. E. Forbes,John M. Papanikolas,Thomas J. Meyer +6 more
TL;DR: The protonated, reduced complex [Ru(bpy)2(bpzH•)]2+ functions as a H-atom reductant toward quinone or benzaldehyde with potential implications for net photochemistry and energy conversion.
Journal ArticleDOI
The role of free energy change in coupled electron-proton transfer.
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