Visible Light Driven Bromide Oxidation and Ligand Substitution Photochemistry of a Ru Diimine Complex
Abstract
We report the complex [Ru(deeb)(bpz)2]2+ (RuBPZ2+, deeb = 4,4'-diethylester-2,2'-bipyridine, bpz = 2,2'-bipyrazine) forms a single ion pair with bromide, [RuBPZ2+, Br–]+, with Keq = 8400 ± 200 M–1 in acetone. The RuBPZ2+ displayed photoluminescence (PL) at room temperature with a lifetime of 1.75 μs. The addition of bromide to a RuBPZ2+ acetone solution led to significant PL quenching and Stern–Volmer plots showed upward curvature. Time-resolved PL measurements identified two excited state quenching pathways, static and dynamic, which were operative toward [RuBPZ2+, Br–]+ and free RuBPZ2+, respectively. The single ion-pair [RuBPZ2+, Br–]+* had a lifetime of 45 ± 5 ns, consistent with an electron transfer rate constant, ket = (2.2 ± 0.3) × 107 s–1. In contrast, RuBPZ2+* was dynamically quenched by bromide with a quenching rate constant, kq = (8.1 ± 0.1) × 1010 M–1 s–1. Nanosecond transient absorption revealed that both the static and dynamic pathways yielded RuBPZ+ and Br2•– products that underwent recombination to regenerate the ground state with a second-order rate constant, kcr = (2.3 ± 0.5) × 1010 M–1 s–1. Kinetic analysis revealed that RuBPZ+ was a primary photoproduct, while Br2•– was secondary product formed by the reaction of a Br• with Br–, k = (1.1more »
- Authors:
-
- Univ. of North Carolina, Chapel Hill, NC (United States)
- Publication Date:
- Research Org.:
- Energy Frontier Research Centers (EFRC) (United States). Center for Solar Fuels (UNC EFRC)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1470297
- Grant/Contract Number:
- SC0001011
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Journal of the American Chemical Society
- Additional Journal Information:
- Journal Volume: 140; Journal Issue: 16; Related Information: UNC partners with University of North Carolina (lead); Duke University; University of Florida; Georgia Institute of Technology; University; North Carolina Central University; Research Triangle Institute; Journal ID: ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; catalysis (homogeneous); catalysis (heterogeneous); solar (photovoltaic); solar (fuels); photosynthesis (natural and artificial); hydrogen and fuel cells; electrodes - solar; charge transport; materials and chemistry by design; synthesis (novel materials); synthesis (self-assembly)
Citation Formats
Li, Guocan, Brady, Matthew D., and Meyer, Gerald J. Visible Light Driven Bromide Oxidation and Ligand Substitution Photochemistry of a Ru Diimine Complex. United States: N. p., 2018.
Web. doi:10.1021/jacs.8b00944.
Li, Guocan, Brady, Matthew D., & Meyer, Gerald J. Visible Light Driven Bromide Oxidation and Ligand Substitution Photochemistry of a Ru Diimine Complex. United States. doi:10.1021/jacs.8b00944.
Li, Guocan, Brady, Matthew D., and Meyer, Gerald J. Thu .
"Visible Light Driven Bromide Oxidation and Ligand Substitution Photochemistry of a Ru Diimine Complex". United States. doi:10.1021/jacs.8b00944. https://www.osti.gov/servlets/purl/1470297.
@article{osti_1470297,
title = {Visible Light Driven Bromide Oxidation and Ligand Substitution Photochemistry of a Ru Diimine Complex},
author = {Li, Guocan and Brady, Matthew D. and Meyer, Gerald J.},
abstractNote = {We report the complex [Ru(deeb)(bpz)2]2+ (RuBPZ2+, deeb = 4,4'-diethylester-2,2'-bipyridine, bpz = 2,2'-bipyrazine) forms a single ion pair with bromide, [RuBPZ2+, Br–]+, with Keq = 8400 ± 200 M–1 in acetone. The RuBPZ2+ displayed photoluminescence (PL) at room temperature with a lifetime of 1.75 μs. The addition of bromide to a RuBPZ2+ acetone solution led to significant PL quenching and Stern–Volmer plots showed upward curvature. Time-resolved PL measurements identified two excited state quenching pathways, static and dynamic, which were operative toward [RuBPZ2+, Br–]+ and free RuBPZ2+, respectively. The single ion-pair [RuBPZ2+, Br–]+* had a lifetime of 45 ± 5 ns, consistent with an electron transfer rate constant, ket = (2.2 ± 0.3) × 107 s–1. In contrast, RuBPZ2+* was dynamically quenched by bromide with a quenching rate constant, kq = (8.1 ± 0.1) × 1010 M–1 s–1. Nanosecond transient absorption revealed that both the static and dynamic pathways yielded RuBPZ+ and Br2•– products that underwent recombination to regenerate the ground state with a second-order rate constant, kcr = (2.3 ± 0.5) × 1010 M–1 s–1. Kinetic analysis revealed that RuBPZ+ was a primary photoproduct, while Br2•– was secondary product formed by the reaction of a Br• with Br–, k = (1.1 ± 0.2) × 1010 M–1 s–1. Marcus theory afforded an estimate of the formal reduction potential for E0(Br•/–) in acetone, 1.42 V vs NHE. A 1H NMR analysis indicated that the ion-paired bromide was preferentially situated close to the RuII center. Prolonged steady state photolysis of RuBPZ2+ and bromide yielded two ligand-substituted photoproducts, cis- and trans-Ru(deeb)(bpz)Br2. Finally, a photochemical intermediate, proposed to be [Ru(deeb)(bpz)(κ1-bpz)(Br)]+, was found to absorb a second photon to yield cis- and trans-Ru(deeb)(bpz)Br2 photoproducts.},
doi = {10.1021/jacs.8b00944},
journal = {Journal of the American Chemical Society},
number = 16,
volume = 140,
place = {United States},
year = {2018},
month = {3}
}
Web of Science
Works referencing / citing this record:
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