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

Research output: Contribution to journalArticle

116 Citations (Scopus)

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 1A11MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L2- and L3-edges were observed concomitant with formation of the transient high-spin 5T2 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 ∼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 Å 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 δ-donation is compensated by significant attenuation of φ-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 - 2010 May 19

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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