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Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp)2]2+
- Source :
- Inorganic Chemistry; July 2019, Vol. 58 Issue: 14 p9341-9350, 10p
- Publication Year :
- 2019
-
Abstract
- We have employed a range of ultrafast X-ray spectroscopies in an effort to characterize the lowest energy excited state of [Fe(dcpp)2]2+(where dcpp is 2,6-(dicarboxypyridyl)pyridine). This compound exhibits an unusually short excited-state lifetime for a low-spin Fe(II) polypyridyl complex of 270 ps in a room-temperature fluid solution, raising questions as to whether the ligand-field strength of dcpp had pushed this system beyond the 5T2/3T1crossing point and stabilizing the latter as the lowest energy excited state. Kα and Kβ X-ray emission spectroscopies have been used to unambiguously determine the quintet spin multiplicity of the long-lived excited state, thereby establishing the 5T2state as the lowest energy excited state of this compound. Geometric changes associated with the photoinduced ligand-field state conversion have also been monitored with extended X-ray absorption fine structure. The data show the typical average Fe-ligand bond length elongation of ∼0.18 Å for a 5T2state and suggest a high anisotropy of the primary coordination sphere around the metal center in the excited 5T2state, in stark contrast to the nearly perfect octahedral symmetry that characterizes the low-spin 1A1ground state structure. This study illustrates how the application of time-resolved X-ray techniques can provide insights into the electronic structures of molecules—in particular, transition metal complexes—that are difficult if not impossible to obtain by other means.
Details
- Language :
- English
- ISSN :
- 00201669 and 1520510X
- Volume :
- 58
- Issue :
- 14
- Database :
- Supplemental Index
- Journal :
- Inorganic Chemistry
- Publication Type :
- Periodical
- Accession number :
- ejs50464832
- Full Text :
- https://doi.org/10.1021/acs.inorgchem.9b01063