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Title: Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp) 2] 2+

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 5T 2/ 3T 1 crossing 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 5T 2 state 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 5T 2 state and suggest a high anisotropy of the primary coordination sphere around the metal center in the excited 5T 2 state, in stark contrast to the nearly perfect octahedral symmetry that characterizes the low-spin 1A 1 ground state structure. This study illustrates how the application of time-resolvedmore » 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.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2];  [3];  [3];  [2];  [2];  [2];  [4];  [5];  [5];  [6];  [6]; ORCiD logo [7];  [6]; ORCiD logo [6];  [8];  [9]; ORCiD logo [9];  [10] more »;  [11];  [5];  [12]; ORCiD logo [9]; ORCiD logo [13]; ORCiD logo [6];  [2]; ORCiD logo [3] « less
  1. European X-ray Free-Electron Laser (XFEL), Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Hamburg (Germany)
  2. European X-ray Free-Electron Laser (XFEL), Hamburg (Germany)
  3. Michigan State Univ., East Lansing, MI (United States). Dept. of Chemistry
  4. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Div.
  6. Hungarian Academy Sciences, Budapest (Hungary). Wigner Research Centre for Physics
  7. Hungarian Academy Sciences, Budapest (Hungary). Wigner Research Centre for Physics; Technical Univ. of Denmark (Denmark). Dept. of Chemistry
  8. Korea Research Inst. of Standards and Science, Daejeon (Korea). Center for Analytical Chemistry, Division of Chemical and Medical Metrology
  9. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
  10. Department of Chemistry and Chemistry Institute of Functional Materials, Pusan National University, Busan 46241, Republic of Korea
  11. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Ultrafast X-ray Science Lab.
  12. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Div.; The Univ. of Chicago, Chicago IL (United States). Dept. of Physics and The James Franck Inst.
  13. Max Planck Institute for , 22761 Hamburg, Germany; Max Planck Inst. for the Structure and Dynamics of Matter, Heidelberg (Germany); Univ. of Hamburg (Germany). Center for Free-Electron Laser Science
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); European XFEL; German Research Foundation (DFG); Hamburg Centre for Ultrafast Imaging; National Science Centre (Poland); Hungarian Academy of Sciences; European Regional Development Fund (ERDF); US Army Research Office (ARO); European Union (EU)
OSTI Identifier:
1560644
Alternate Identifier(s):
OSTI ID: 1574390
Grant/Contract Number:  
AC02-76SF00515; 609405; FG02-01ER15282.; LP2013-59; W911NF-15-1-0124; VEKOP-2.3.2-16-2017-00015; 2016/22/E/ST4/00543; SFB 925; NKFIH FK 124460; AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 14; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Fe-based photophysics; ligand-field excited states; ultrafast x-ray absorption and emission spectroscopy

Citation Formats

Britz, Alexander, Gawelda, Wojciech, Assefa, Tadesse A., Jamula, Lindsey L., Yarranton, Jonathan T., Galler, Andreas, Khakhulin, Dmitry, Diez, Michael, Harder, Manuel, Doumy, Gilles, March, Anne Marie, Bajnóczi, Éva, Németh, Zoltán, Pápai, Mátyás, Rozsályi, Emese, Sárosiné Szemes, Dorottya, Cho, Hana, Mukherjee, Sriparna, Liu, Chang, Kim, Tae Kyu, Schoenlein, Robert W., Southworth, Stephen H., Young, Linda, Jakubikova, Elena, Huse, Nils, Vankó, György, Bressler, Christian, and McCusker, James K. Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp) 2]2+. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b01063.
Britz, Alexander, Gawelda, Wojciech, Assefa, Tadesse A., Jamula, Lindsey L., Yarranton, Jonathan T., Galler, Andreas, Khakhulin, Dmitry, Diez, Michael, Harder, Manuel, Doumy, Gilles, March, Anne Marie, Bajnóczi, Éva, Németh, Zoltán, Pápai, Mátyás, Rozsályi, Emese, Sárosiné Szemes, Dorottya, Cho, Hana, Mukherjee, Sriparna, Liu, Chang, Kim, Tae Kyu, Schoenlein, Robert W., Southworth, Stephen H., Young, Linda, Jakubikova, Elena, Huse, Nils, Vankó, György, Bressler, Christian, & McCusker, James K. Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp) 2]2+. United States. doi:10.1021/acs.inorgchem.9b01063.
Britz, Alexander, Gawelda, Wojciech, Assefa, Tadesse A., Jamula, Lindsey L., Yarranton, Jonathan T., Galler, Andreas, Khakhulin, Dmitry, Diez, Michael, Harder, Manuel, Doumy, Gilles, March, Anne Marie, Bajnóczi, Éva, Németh, Zoltán, Pápai, Mátyás, Rozsályi, Emese, Sárosiné Szemes, Dorottya, Cho, Hana, Mukherjee, Sriparna, Liu, Chang, Kim, Tae Kyu, Schoenlein, Robert W., Southworth, Stephen H., Young, Linda, Jakubikova, Elena, Huse, Nils, Vankó, György, Bressler, Christian, and McCusker, James K. Wed . "Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp) 2]2+". United States. doi:10.1021/acs.inorgchem.9b01063. https://www.osti.gov/servlets/purl/1560644.
@article{osti_1560644,
title = {Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp) 2]2+},
author = {Britz, Alexander and Gawelda, Wojciech and Assefa, Tadesse A. and Jamula, Lindsey L. and Yarranton, Jonathan T. and Galler, Andreas and Khakhulin, Dmitry and Diez, Michael and Harder, Manuel and Doumy, Gilles and March, Anne Marie and Bajnóczi, Éva and Németh, Zoltán and Pápai, Mátyás and Rozsályi, Emese and Sárosiné Szemes, Dorottya and Cho, Hana and Mukherjee, Sriparna and Liu, Chang and Kim, Tae Kyu and Schoenlein, Robert W. and Southworth, Stephen H. and Young, Linda and Jakubikova, Elena and Huse, Nils and Vankó, György and Bressler, Christian and McCusker, James K.},
abstractNote = {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 5T2/3T1 crossing 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 5T2 state 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 5T2 state and suggest a high anisotropy of the primary coordination sphere around the metal center in the excited 5T2 state, in stark contrast to the nearly perfect octahedral symmetry that characterizes the low-spin 1A1 ground 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.},
doi = {10.1021/acs.inorgchem.9b01063},
journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 14,
volume = 58,
place = {United States},
year = {2019},
month = {6}
}

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