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| 2. |
- Chaudhuri, Subhajyoti, et al.
(författare)
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Electron Transfer Assisted by Vibronic Coupling from Multiple Modes
- 2017
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 13:12, s. 6000-6009
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the effect of vibronic coupling on electron transfer (ET) rates is a challenge common to a wide range of applications, from electrochemical synthesis and catalysis to biochemical reactions and solar energy conversion. The Marcus-Jortner-Levich (MJL) theory offers a model of ET rates based on a simple analytic expression with a few adjustable parameters. However, the MJL equation in conjunction with density functional theory (DFT) has yet to be established as a predictive first-principles methodology. A framework is presented for calculating transfer rates modulated by molecular vibrations, that circumvents the steep computational cost which has previously necessitated approximations such as condensing the vibrational manifold into a single empirical frequency. Our DFT MJL approach provides robust and accurate predictions of ET rates spanning over 4 orders of magnitude in the 10(6)-10(10) s(-1) range. We evaluate the full MJL equation with a Monte Carlo sampling of the entire active space of thermally accessible vibrational modes, while using no empirical parameters. The contribution to the rate of individual modes is illustrated, providing insight into the interplay between vibrational degrees of freedom and changes in electronic state. The reported findings are valuable for understanding ET rates modulated by multiple vibrational modes, relevant to a broad range of systems within the chemical sciences.
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| 3. |
- Hedström, Svante, et al.
(författare)
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Thousandfold Enhancement of Photoreduction Lifetime in Re(bpy)(CO)(3) via Spin-Dependent Electron Transfer from a Perylenediimide Radical Anion Donor
- 2017
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 139:46, s. 16466-16469
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Tidskriftsartikel (refereegranskat)abstract
- Spin-dependent intramolecular electron transfer is revealed in the Re-I(CO)(3)(py)(bpy-Ph)perylenediimide radical anion (Re-I-bpy-PDI-(.)) dyad, a prototype model system for artificial photosynthesis. Quantum chemical calculations and ultrafast transient absorption spectroscopy experiments demonstrate that selective photoexcitation of Re-I-bpy results in electron transfer from PD-(.) to Re-I-bpy, forming two distinct charge-shifted states. One is an overall doublet whose return to the ground state is spin-allowed. The other, high spin quartet state, persists for 67 ns due to spin-forbidden back-electron transfer, constituting a more than thousandfold lifetime improvement compared to the low-spin state. Exploiting this spin dependency holds promise for artificial photosynthetic systems requiring long-lived reduced states to perform multi-electron chemistry.
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| 4. |
- La Porte, Nathan T., et al.
(författare)
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Photoexcited radical anion super-reductants for solar fuels catalysis
- 2018
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Ingår i: Coordination chemistry reviews. - : Elsevier BV. - 0010-8545 .- 1873-3840. ; 361, s. 98-119
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Forskningsöversikt (refereegranskat)abstract
- The catalytic transformation of carbon dioxide into fuels is one of the most important reactions for creating a sustainable, carbon-neutral energy economy. Given that the sun is the only plausible energy source that can accommodate the increased global energy demand without contributing to catastrophic climate change, it makes sense to use solar energy to drive this reaction, ideally using the largest possible portion of the solar spectrum. Over the past several years, we have explored the use of reduced rylenediimide chromophores, which absorb wavelengths ranging into the near-infrared, as strongly reducing photosensitizers capable of photosensitizing Re(diimine)(CO)(3)L metal centers towards the binding and reduction of CO2. We have explored the effects of varying the binding geometry, donor-acceptor redox potentials, and excitation wavelength on the kinetics of electron transfer from the reduced rylenediimide to the metal center. So far, we have achieved charge-separated lifetimes in electrocatalytically active complexes of 25 ns when illuminated with near-infrared light, and >250 ns when illuminated with blue light.
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| 5. |
- Li, Xichen, et al.
(författare)
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Theoretical EXAFS studies of a model of the oxygen-evolving complex of photosystem II obtained with the quantum cluster approach
- 2013
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Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 113:4, s. 474-478
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen-evolving complex (OEC) of photosystem II is the only natural system that can form O2 from water and sunlight and it consists of a Mn4Ca cluster. In a series of publications, Siegbahn has developed a model of the OEC with the quantum mechanical (QM) cluster approach that is compatible with available crystal structures, able to form O2 with a reasonable energetic barrier, and has a significantly lower energy than alternative models. In this investigation, we present a method to restrain a QM geometry optimization toward experimental polarized extended X-ray absorption fine structure (EXAFS) data. With this method, we show that the cluster model is compatible with the EXAFS data and we obtain a refined cluster model that is an optimum compromise between QM and polarized EXAFS data.
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