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Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2'-bipyridine)_2(CN)_2]

Kjær, Kasper S. and Zhang, Wenkai and Alonso-Mori, Roberto and Bergmann, Uwe and Chollet, Matthieu and Hadt, Ryan G. and Hartsock, Robert W. and Harlang, Tobias and Kroll, Thomas and Kubiček, Katharina and Lemke, Henrik T. and Liang, Huiyang W. and Liu, Yizhu and Nielsen, Martin M. and Robinson, Joseph S. and Solomon, Edward I. and Sokaras, Dimosthenis and van Driel, Tim B. and Weng, Tsu-Chien and Zhu, Diling and Persson, Petter and Wärnmark, Kenneth and Sundström, Villy and Gaffney, Kelly J. (2017) Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2'-bipyridine)_2(CN)_2]. Structural Dynamics, 4 (4). Art. No. 044030. ISSN 2329-7778. PMCID PMC5461172. doi:10.1063/1.4985017.

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We have used femtosecond resolution UV-visible and Kβ x-ray emission spectroscopy to characterize the electronic excited state dynamics of [Fe(bpy)_2(CN)_2], where bpy=2,2'-bipyridine, initiated by metal-to-ligand charge transfer (MLCT) excitation. The excited-state absorption in the transient UV-visible spectra, associated with the 2,2'-bipyridine radical anion, provides a robust marker for the MLCT excited state, while the transient Kβ x-ray emission spectra provide a clear measure of intermediate and high spin metal-centered excited states. From these measurements, we conclude that the MLCT state of [Fe(bpy)_2(CN)_2] undergoes ultrafast spin crossover to a metal-centered quintet excited state through a short lived metal-centered triplet transient species. These measurements of [Fe(bpy)_2(CN)_2] complement prior measurement performed on [Fe(bpy)_3]^(2+) and [Fe(bpy)_4(CN)]^(2-) in dimethylsulfoxide solution and help complete the chemical series [Fe(bpy)_N(CN)_(6-2N)]^(2N-4), where N = 1-3. The measurements confirm that simple ligand modifications can significantly change the relaxation pathways and excited state lifetimes and support the further investigation of light harvesting and photocatalytic applications of 3 transition metal complexes.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle Information
Bergmann, Uwe0000-0001-5639-166X
Hadt, Ryan G.0000-0001-6026-1358
Solomon, Edward I.0000-0003-0291-3199
Persson, Petter0000-0001-7600-3230
Wärnmark, Kenneth0000-0002-9022-3165
Alternate Title:Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2'-bipyridine)2(CN)2]
Additional Information:© 2017 The Authors. All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license ( (Received 18 April 2017; accepted 21 May 2017; published online 6 June 2017) Experiments were carried out at LCLS and SSRL, the National User Facilities operated for DOE, OBES by the Stanford University. W.Z., R.W.H., H.W.L., and K.J.G. acknowledge the support from the AMOS program within the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. E.I.S. acknowledges the support from the NIH GM040392. R.G.H. acknowledges the Gerhard Casper Stanford Graduate Fellowship and the Achievements Rewards for College Scientists (ARCS) Foundation. T.K. acknowledges the German Research Foundation (DFG), Grant No. KR3611/2–1. K.S.K., M.M.N., and T.B.v.D. acknowledge the support from the Danish National Research Foundation and from DANSCATT. K.S.K. gratefully acknowledge the support of the Carlsberg Foundation and the Danish Council for Independent Research. Y.L., T.H., K.W., P.P., and V.S. acknowledge the support from the Crafoord Foundation, the Swedish Research Council (VR), the Knut and Alice Wallenberg (KAW) Foundation, the European Research Council (ERC, 226136-VISCHEM) and the Swedish Energy Agency. K.K. acknowledges the financial support from the Volkswagen Foundation (Volkswagen Stiftung) under the Peter Paul Ewald fellowship program (Az.: I/85832 and 87008) and from the German Research Foundation (Deutsche Forschungsgemeinschaft (DFG)] within the SFB755 “Nanoscale Photonic Imaging,” Project No. B03.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Stanford UniversityUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)KR3611/2-1
Danish Research FoundationUNSPECIFIED
Carlsberg FoundationUNSPECIFIED
Danish Council for Independent ResearchUNSPECIFIED
Crafoord FoundationUNSPECIFIED
Swedish Research CouncilUNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
European Research Council (ERC)226136-VISCHEM
Swedish Energy AgencyUNSPECIFIED
Volkswagen StiftungI/85832
Volkswagen StiftungI/87008
Deutsche Forschungsgemeinschaft (DFG)SFB755
Issue or Number:4
PubMed Central ID:PMC5461172
Record Number:CaltechAUTHORS:20180612-100432522
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86998
Deposited By: George Porter
Deposited On:12 Jun 2018 17:43
Last Modified:15 Nov 2021 20:44

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