Ultrafast X-ray scattering offers a structural view of excited-state charge transfer.

Autor:	Yong H; Department of Chemistry, Brown University, Providence, RI 02912., Xu X; Department of Chemistry, Brown University, Providence, RI 02912., Ruddock JM; Department of Chemistry, Brown University, Providence, RI 02912., Stankus B; Department of Chemistry and Biochemistry, Western Connecticut State University, Danbury, CT 06810., Carrascosa AM; Department of Chemistry, Brown University, Providence, RI 02912., Zotev N; EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom.; Center for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom., Bellshaw D; EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom.; Center for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom., Du W; Department of Chemistry, Brown University, Providence, RI 02912., Goff N; Department of Chemistry, Brown University, Providence, RI 02912., Chang Y; Department of Chemistry, Brown University, Providence, RI 02912., Boutet S; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Carbajo S; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Koglin JE; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Liang M; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Robinson JS; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Kirrander A; EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom; adam.kirrander@ed.ac.uk peter_weber@brown.edu.; Center for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom., Minitti MP; Linac Coherent Light Source, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, CA 94025., Weber PM; Department of Chemistry, Brown University, Providence, RI 02912; adam.kirrander@ed.ac.uk peter_weber@brown.edu.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2021 May 11; Vol. 118 (19).
DOI:	10.1073/pnas.2021714118
Abstrakt:	Intramolecular charge transfer and the associated changes in molecular structure in N,N'-dimethylpiperazine are tracked using femtosecond gas-phase X-ray scattering. The molecules are optically excited to the 3p state at 200 nm. Following rapid relaxation to the 3s state, distinct charge-localized and charge-delocalized species related by charge transfer are observed. The experiment determines the molecular structure of the two species, with the redistribution of electron density accounted for by a scattering correction factor. The initially dominant charge-localized state has a weakened carbon-carbon bond and reorients one methyl group compared with the ground state. Subsequent charge transfer to the charge-delocalized state elongates the carbon-carbon bond further, creating an extended 1.634 Å bond, and also reorients the second methyl group. At the same time, the bond lengths between the nitrogen and the ring-carbon atoms contract from an average of 1.505 to 1.465 Å. The experiment determines the overall charge transfer time constant for approaching the equilibrium between charge-localized and charge-delocalized species to 3.0 ps. Competing Interests: The authors declare no competing interest.
Databáze:	MEDLINE
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