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Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
Recent years have seen the development of new iron-centered N-heterocyclic carbene (NHC) complexes for solar energy applications. Compared to typical ligand systems, the NHC ligands provide Fe complexes with longer-lived metal-to-ligand charge transfer (MLCT) states. This increased lifetime is ascri...
Autores principales: | , , , , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Royal Society of Chemistry
2017
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868308/ https://www.ncbi.nlm.nih.gov/pubmed/29629111 http://dx.doi.org/10.1039/c7sc02815f |
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author | Leshchev, Denis Harlang, Tobias C. B. Fredin, Lisa A. Khakhulin, Dmitry Liu, Yizhu Biasin, Elisa Laursen, Mads G. Newby, Gemma E. Haldrup, Kristoffer Nielsen, Martin M. Wärnmark, Kenneth Sundström, Villy Persson, Petter Kjær, Kasper S. Wulff, Michael |
author_facet | Leshchev, Denis Harlang, Tobias C. B. Fredin, Lisa A. Khakhulin, Dmitry Liu, Yizhu Biasin, Elisa Laursen, Mads G. Newby, Gemma E. Haldrup, Kristoffer Nielsen, Martin M. Wärnmark, Kenneth Sundström, Villy Persson, Petter Kjær, Kasper S. Wulff, Michael |
author_sort | Leshchev, Denis |
collection | PubMed |
description | Recent years have seen the development of new iron-centered N-heterocyclic carbene (NHC) complexes for solar energy applications. Compared to typical ligand systems, the NHC ligands provide Fe complexes with longer-lived metal-to-ligand charge transfer (MLCT) states. This increased lifetime is ascribed to strong ligand field splitting provided by the NHC ligands that raises the energy levels of the metal centered (MC) states and therefore reduces the deactivation efficiency of MLCT states. Among currently known NHC systems, [Fe(btbip)(2)](2+) (btbip = 2,6-bis(3-tert-butyl-imidazol-1-ylidene)pyridine) is a unique complex as it exhibits a short-lived MC state with a lifetime on the scale of a few hundreds of picoseconds. Hence, this complex allows for a detailed investigation, using 100 ps X-ray pulses from a synchrotron, of strong ligand field effects on the intermediate MC state in an NHC complex. Here, we use time-resolved wide angle X-ray scattering (TRWAXS) aided by density functional theory (DFT) to investigate the molecular structure, energetics and lifetime of the high-energy MC state in the Fe–NHC complex [Fe(btbip)(2)](2+) after excitation to the MLCT manifold. We identify it as a 260 ps metal-centered quintet ((5)MC) state, and we refine the molecular structure of the excited-state complex verifying the DFT results. Using information about the hydrodynamic state of the solvent, we also determine, for the first time, the energy of the (5)MC state as 0.75 ± 0.15 eV. Our results demonstrate that due to the increased ligand field strength caused by NHC ligands, upon transition from the ground state to the (5)MC state, the metal to ligand bonds extend by unusually large values: by 0.29 Å in the axial and 0.21 Å in the equatorial direction. These results imply that the transition in the photochemical properties from typical Fe complexes to novel NHC compounds is manifested not only in the destabilization of the MC states, but also in structural distortion of these states. |
format | Online Article Text |
id | pubmed-5868308 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2017 |
publisher | Royal Society of Chemistry |
record_format | MEDLINE/PubMed |
spelling | pubmed-58683082018-04-06 Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering Leshchev, Denis Harlang, Tobias C. B. Fredin, Lisa A. Khakhulin, Dmitry Liu, Yizhu Biasin, Elisa Laursen, Mads G. Newby, Gemma E. Haldrup, Kristoffer Nielsen, Martin M. Wärnmark, Kenneth Sundström, Villy Persson, Petter Kjær, Kasper S. Wulff, Michael Chem Sci Chemistry Recent years have seen the development of new iron-centered N-heterocyclic carbene (NHC) complexes for solar energy applications. Compared to typical ligand systems, the NHC ligands provide Fe complexes with longer-lived metal-to-ligand charge transfer (MLCT) states. This increased lifetime is ascribed to strong ligand field splitting provided by the NHC ligands that raises the energy levels of the metal centered (MC) states and therefore reduces the deactivation efficiency of MLCT states. Among currently known NHC systems, [Fe(btbip)(2)](2+) (btbip = 2,6-bis(3-tert-butyl-imidazol-1-ylidene)pyridine) is a unique complex as it exhibits a short-lived MC state with a lifetime on the scale of a few hundreds of picoseconds. Hence, this complex allows for a detailed investigation, using 100 ps X-ray pulses from a synchrotron, of strong ligand field effects on the intermediate MC state in an NHC complex. Here, we use time-resolved wide angle X-ray scattering (TRWAXS) aided by density functional theory (DFT) to investigate the molecular structure, energetics and lifetime of the high-energy MC state in the Fe–NHC complex [Fe(btbip)(2)](2+) after excitation to the MLCT manifold. We identify it as a 260 ps metal-centered quintet ((5)MC) state, and we refine the molecular structure of the excited-state complex verifying the DFT results. Using information about the hydrodynamic state of the solvent, we also determine, for the first time, the energy of the (5)MC state as 0.75 ± 0.15 eV. Our results demonstrate that due to the increased ligand field strength caused by NHC ligands, upon transition from the ground state to the (5)MC state, the metal to ligand bonds extend by unusually large values: by 0.29 Å in the axial and 0.21 Å in the equatorial direction. These results imply that the transition in the photochemical properties from typical Fe complexes to novel NHC compounds is manifested not only in the destabilization of the MC states, but also in structural distortion of these states. Royal Society of Chemistry 2017-10-31 /pmc/articles/PMC5868308/ /pubmed/29629111 http://dx.doi.org/10.1039/c7sc02815f Text en This journal is © The Royal Society of Chemistry 2018 http://creativecommons.org/licenses/by-nc/3.0/ This article is freely available. This article is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported Licence (CC BY-NC 3.0) |
spellingShingle | Chemistry Leshchev, Denis Harlang, Tobias C. B. Fredin, Lisa A. Khakhulin, Dmitry Liu, Yizhu Biasin, Elisa Laursen, Mads G. Newby, Gemma E. Haldrup, Kristoffer Nielsen, Martin M. Wärnmark, Kenneth Sundström, Villy Persson, Petter Kjær, Kasper S. Wulff, Michael Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering |
title | Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
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title_full | Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
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title_fullStr | Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
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title_full_unstemmed | Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
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title_short | Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering
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title_sort | tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved x-ray scattering |
topic | Chemistry |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868308/ https://www.ncbi.nlm.nih.gov/pubmed/29629111 http://dx.doi.org/10.1039/c7sc02815f |
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