TY - JOUR
T1 - Solvent control of charge transfer excited state relaxation pathways in [Fe(2,2′-bipyridine)(CN)4]2-
AU - Kjær, Kasper S.
AU - Kunnus, Kristjan
AU - Harlang, Tobias C.B.
AU - Van Driel, Tim B.
AU - Ledbetter, Kathryn
AU - Hartsock, Robert W.
AU - Reinhard, Marco E.
AU - Koroidov, Sergey
AU - Li, Lin
AU - Laursen, Mads G.
AU - Biasin, Elisa
AU - Hansen, Frederik B.
AU - Vester, Peter
AU - Christensen, Morten
AU - Haldrup, Kristoffer
AU - Nielsen, Martin M.
AU - Chabera, Pavel
AU - Liu, Yizhu
AU - Tatsuno, Hideyuki
AU - Timm, Cornelia
AU - Uhlig, Jens
AU - Sundstöm, Villy
AU - Németh, Zoltán
AU - Szemes, Dorottya Sárosiné
AU - Bajnóczi, Éva
AU - Vankó, György
AU - Alonso-Mori, Roberto
AU - Glownia, James M.
AU - Nelson, Silke
AU - Sikorski, Marcin
AU - Sokaras, Dimosthenis
AU - Lemke, Henrik T.
AU - Canton, Sophie E.
AU - Wärnmark, Kenneth
AU - Persson, Petter
AU - Cordones, Amy A.
AU - Gaffney, Kelly J.
PY - 2018
Y1 - 2018
N2 - The excited state dynamics of solvated [Fe(bpy)(CN)4]2-, where bpy = 2,2′-bipyridine, show significant sensitivity to the solvent Lewis acidity. Using a combination of optical absorption and X-ray emission transient spectroscopies, we have previously shown that the metal to ligand charge transfer (MLCT) excited state of [Fe(bpy)(CN)4]2- has a 19 picosecond lifetime and no discernable contribution from metal centered (MC) states in weak Lewis acid solvents, such as dimethyl sulfoxide and acetonitrile.1,2 In the present work, we use the same combination of spectroscopic techniques to measure the MLCT excited state relaxation dynamics of [Fe(bpy)(CN)4]2- in water, a strong Lewis acid solvent. The charge-transfer excited state is now found to decay in less than 100 femtoseconds, forming a quasi-stable metal centered excited state with a 13 picosecond lifetime. We find that this MC excited state has triplet (3MC) character, unlike other reported six-coordinate Fe(ii)-centered coordination compounds, which form MC quintet (5MC) states. The solvent dependent changes in excited state non-radiative relaxation for [Fe(bpy)(CN)4]2- allows us to infer the influence of the solvent on the electronic structure of the complex. Furthermore, the robust characterization of the dynamics and optical spectral signatures of the isolated 3MC intermediate provides a strong foundation for identifying 3MC intermediates in the electronic excited state relaxation mechanisms of similar Fe-centered systems being developed for solar applications.
AB - The excited state dynamics of solvated [Fe(bpy)(CN)4]2-, where bpy = 2,2′-bipyridine, show significant sensitivity to the solvent Lewis acidity. Using a combination of optical absorption and X-ray emission transient spectroscopies, we have previously shown that the metal to ligand charge transfer (MLCT) excited state of [Fe(bpy)(CN)4]2- has a 19 picosecond lifetime and no discernable contribution from metal centered (MC) states in weak Lewis acid solvents, such as dimethyl sulfoxide and acetonitrile.1,2 In the present work, we use the same combination of spectroscopic techniques to measure the MLCT excited state relaxation dynamics of [Fe(bpy)(CN)4]2- in water, a strong Lewis acid solvent. The charge-transfer excited state is now found to decay in less than 100 femtoseconds, forming a quasi-stable metal centered excited state with a 13 picosecond lifetime. We find that this MC excited state has triplet (3MC) character, unlike other reported six-coordinate Fe(ii)-centered coordination compounds, which form MC quintet (5MC) states. The solvent dependent changes in excited state non-radiative relaxation for [Fe(bpy)(CN)4]2- allows us to infer the influence of the solvent on the electronic structure of the complex. Furthermore, the robust characterization of the dynamics and optical spectral signatures of the isolated 3MC intermediate provides a strong foundation for identifying 3MC intermediates in the electronic excited state relaxation mechanisms of similar Fe-centered systems being developed for solar applications.
UR - https://www.scopus.com/pages/publications/85041855594
U2 - 10.1039/c7cp07838b
DO - 10.1039/c7cp07838b
M3 - Article
C2 - 29364300
AN - SCOPUS:85041855594
SN - 1463-9076
VL - 20
SP - 4238
EP - 4249
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 6
ER -