Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy

Nils Huse*, Tae Kyu Kim, Lindsey Jamula, James K. McCusker, Frank M. F. de Groot, Robert W. Schoenlein

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Solution-phase photoinduced low-spin to high-spin conversion in the Fe-II polypyridyl complex [Fe(tren(py)(3))](2+) (where tren(py)3 is tris(2-pyridylmethyliminoethyl)amine) has been studied via picosecond soft X-ray spectroscopy. Following (1)A(1) -> (MLCT)-M-1 (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L-2- and L-3-edges were observed concomitant with formation of the transient high-spin T-5(2) state. Charge-transfer multiplet calculations coupled with data acquired on low-spin and high-spin model complexes revealed a reduction in ligand field splitting of similar to 1 eV in the high-spin state relative to the singlet ground state. A significant reduction in orbital overlap between the central Fe-3d and the ligand N-2p orbitals was directly observed, consistent with the expected ca. 0.2 angstrom increase in Fe-N bond length upon formation of the high-spin state. The overall occupancy of the Fe-3d orbitals remains constant upon spin crossover, suggesting that the reduction in a-donation is compensated by significant attenuation of pi-back-bonding in the metal ligand interactions. These results demonstrate the feasibility and unique potential of time-resolved soft X-ray absorption spectroscopy to study ultrafast reactions in the liquid phase by directly probing the valence orbitals of first-row metals as well as lighter elements during the course of photochemical transformations.

Original languageEnglish
Pages (from-to)6809-6816
Number of pages8
JournalJournal of the American Chemical Society
Volume132
Issue number19
DOIs
Publication statusPublished - 19 May 2010

Funding

This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, the Chemical Sciences, Geosciences, and Biosciences Division under the Department of Energy Contract No. DE-AC02-05CH11231 (N.H. and R.W.S) and Grant No. DE-FG02-01ER15282 (J.K.M.), as well as Grant No. R-01-2008-000-20717-0 of the Basic Research Program of the Korea Science and Engineering Foundation, Republic of Korea (T.K.K.) and Grant No. 700.56.443 of the Netherlands National Science Foundation (NWO) VICI program (F.d.G.).

Keywords

  • ABSORPTION-SPECTROSCOPY
  • L-EDGE
  • MULTIPLET CALCULATIONS
  • CHARGE-TRANSFER
  • CRYSTAL-FIELD
  • LIQUID WATER
  • DYNAMICS
  • BAND
  • IRON
  • FE

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