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Published July 2017 | Published + Supplemental Material
Journal Article Open

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

Abstract

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.

Additional Information

© 2017 The Authors. All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). (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.

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Supplemental Material - .listing

Supplemental Material - Fe_bpy_2_CN_2.SOM.final.pdf

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Created:
August 19, 2023
Modified:
October 18, 2023