| 1. |
- 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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| 2. |
- 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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