Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy

Matthew S. Kelley, Megan L. Shelby, Michael W. Mara, Kristoffer Haldrup, Dugan Hayes, Ryan G. Hadt, Xiaoyi Zhang, Andrew B. Stickrath, Romain Ruppert, Jean Pierre Sauvage, Diling Zhu, Henrik T. Lemke, Matthieu Chollet, George C Schatz, Lin X. Chen

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Ultrafast structural dynamics of the metal to ligand charge transfer (MLCT) states of two copper bis-phenanthroline complexes were captured by using x-ray transient absorption (XTA) spectroscopy at the Linac Coherent Light Source and further described by theoretical calculations. These complexes have the general formula [Cu(I)(R)2]+, where R =2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline disulfonic acid disodium salt (dpps). [Cu(I)(dmp)2]+ has methyl groups at the 2,9 positions of phenanthroline (phen) and adopts a pseudo-tetrahedral geometry. In contrast, [Cu(I)(dpps)2]+ possesses two bulky phenyl-sulfonate groups attached to each phen ligand that force the molecule to adopt a flattened tetrahedral geometry in the ground state. Previously, optical transient absorption (OTA) and synchrotron based XTA experiments with 100 ps time resolution have been employed to study the relationship between structural distortions and excited state relaxation pathways in the two complexes. However, the dynamics of the MLCT transition during the first few picoseconds after excitation in these complexes remained unclear because of limitations in element specificity in OTA and in the time resolution of synchrotron sources in XTA. In this experiment, the local coordination geometry and oxidation state of copper were probed with a temporal resolution of ∼300 fs. Unexpectedly, the depletion of the Cu(I) signal due to the MLCT transition was found to be non-impulsive in the case of [Cu(I)(dpps)2]+ with a time constant of 0.6 ps, while the Cu(I) depletion in [Cu(I)(dmp)2]+ was instantaneous within the 300 fs instrument response time. The slower Cu(I) depletion kinetics in [Cu(I)(dpps)2]+, previously unobserved in femtosecond OTA experiments, is likely due to intramolecular motions on the sub-picosecond time scale that could alter the localization of the transferred electron in the phen ligands.

Original languageEnglish
Article number154006
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume50
Issue number15
DOIs
Publication statusPublished - Jul 12 2017

Fingerprint

absorption spectroscopy
copper
ligands
depletion
charge transfer
x rays
synchrotrons
geometry
metals
dynamic structural analysis
coherent light
sulfonates
temporal resolution
time constant
excitation
light sources
salts
oxidation
acids
ground state

Keywords

  • copper diimine complex
  • excited state structural dynamics
  • MLCT state
  • ultrafast Jahn-Teller distortion
  • ultrafast x-ray transient absorption
  • x-ray free electron laser

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics

Cite this

Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy. / Kelley, Matthew S.; Shelby, Megan L.; Mara, Michael W.; Haldrup, Kristoffer; Hayes, Dugan; Hadt, Ryan G.; Zhang, Xiaoyi; Stickrath, Andrew B.; Ruppert, Romain; Sauvage, Jean Pierre; Zhu, Diling; Lemke, Henrik T.; Chollet, Matthieu; Schatz, George C; Chen, Lin X.

In: Journal of Physics B: Atomic, Molecular and Optical Physics, Vol. 50, No. 15, 154006, 12.07.2017.

Research output: Contribution to journalArticle

Kelley, MS, Shelby, ML, Mara, MW, Haldrup, K, Hayes, D, Hadt, RG, Zhang, X, Stickrath, AB, Ruppert, R, Sauvage, JP, Zhu, D, Lemke, HT, Chollet, M, Schatz, GC & Chen, LX 2017, 'Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 50, no. 15, 154006. https://doi.org/10.1088/1361-6455/aa7b97
Kelley, Matthew S. ; Shelby, Megan L. ; Mara, Michael W. ; Haldrup, Kristoffer ; Hayes, Dugan ; Hadt, Ryan G. ; Zhang, Xiaoyi ; Stickrath, Andrew B. ; Ruppert, Romain ; Sauvage, Jean Pierre ; Zhu, Diling ; Lemke, Henrik T. ; Chollet, Matthieu ; Schatz, George C ; Chen, Lin X. / Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy. In: Journal of Physics B: Atomic, Molecular and Optical Physics. 2017 ; Vol. 50, No. 15.
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abstract = "Ultrafast structural dynamics of the metal to ligand charge transfer (MLCT) states of two copper bis-phenanthroline complexes were captured by using x-ray transient absorption (XTA) spectroscopy at the Linac Coherent Light Source and further described by theoretical calculations. These complexes have the general formula [Cu(I)(R)2]+, where R =2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline disulfonic acid disodium salt (dpps). [Cu(I)(dmp)2]+ has methyl groups at the 2,9 positions of phenanthroline (phen) and adopts a pseudo-tetrahedral geometry. In contrast, [Cu(I)(dpps)2]+ possesses two bulky phenyl-sulfonate groups attached to each phen ligand that force the molecule to adopt a flattened tetrahedral geometry in the ground state. Previously, optical transient absorption (OTA) and synchrotron based XTA experiments with 100 ps time resolution have been employed to study the relationship between structural distortions and excited state relaxation pathways in the two complexes. However, the dynamics of the MLCT transition during the first few picoseconds after excitation in these complexes remained unclear because of limitations in element specificity in OTA and in the time resolution of synchrotron sources in XTA. In this experiment, the local coordination geometry and oxidation state of copper were probed with a temporal resolution of ∼300 fs. Unexpectedly, the depletion of the Cu(I) signal due to the MLCT transition was found to be non-impulsive in the case of [Cu(I)(dpps)2]+ with a time constant of 0.6 ps, while the Cu(I) depletion in [Cu(I)(dmp)2]+ was instantaneous within the 300 fs instrument response time. The slower Cu(I) depletion kinetics in [Cu(I)(dpps)2]+, previously unobserved in femtosecond OTA experiments, is likely due to intramolecular motions on the sub-picosecond time scale that could alter the localization of the transferred electron in the phen ligands.",
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T1 - Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy

AU - Kelley, Matthew S.

AU - Shelby, Megan L.

AU - Mara, Michael W.

AU - Haldrup, Kristoffer

AU - Hayes, Dugan

AU - Hadt, Ryan G.

AU - Zhang, Xiaoyi

AU - Stickrath, Andrew B.

AU - Ruppert, Romain

AU - Sauvage, Jean Pierre

AU - Zhu, Diling

AU - Lemke, Henrik T.

AU - Chollet, Matthieu

AU - Schatz, George C

AU - Chen, Lin X.

PY - 2017/7/12

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N2 - Ultrafast structural dynamics of the metal to ligand charge transfer (MLCT) states of two copper bis-phenanthroline complexes were captured by using x-ray transient absorption (XTA) spectroscopy at the Linac Coherent Light Source and further described by theoretical calculations. These complexes have the general formula [Cu(I)(R)2]+, where R =2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline disulfonic acid disodium salt (dpps). [Cu(I)(dmp)2]+ has methyl groups at the 2,9 positions of phenanthroline (phen) and adopts a pseudo-tetrahedral geometry. In contrast, [Cu(I)(dpps)2]+ possesses two bulky phenyl-sulfonate groups attached to each phen ligand that force the molecule to adopt a flattened tetrahedral geometry in the ground state. Previously, optical transient absorption (OTA) and synchrotron based XTA experiments with 100 ps time resolution have been employed to study the relationship between structural distortions and excited state relaxation pathways in the two complexes. However, the dynamics of the MLCT transition during the first few picoseconds after excitation in these complexes remained unclear because of limitations in element specificity in OTA and in the time resolution of synchrotron sources in XTA. In this experiment, the local coordination geometry and oxidation state of copper were probed with a temporal resolution of ∼300 fs. Unexpectedly, the depletion of the Cu(I) signal due to the MLCT transition was found to be non-impulsive in the case of [Cu(I)(dpps)2]+ with a time constant of 0.6 ps, while the Cu(I) depletion in [Cu(I)(dmp)2]+ was instantaneous within the 300 fs instrument response time. The slower Cu(I) depletion kinetics in [Cu(I)(dpps)2]+, previously unobserved in femtosecond OTA experiments, is likely due to intramolecular motions on the sub-picosecond time scale that could alter the localization of the transferred electron in the phen ligands.

AB - Ultrafast structural dynamics of the metal to ligand charge transfer (MLCT) states of two copper bis-phenanthroline complexes were captured by using x-ray transient absorption (XTA) spectroscopy at the Linac Coherent Light Source and further described by theoretical calculations. These complexes have the general formula [Cu(I)(R)2]+, where R =2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline disulfonic acid disodium salt (dpps). [Cu(I)(dmp)2]+ has methyl groups at the 2,9 positions of phenanthroline (phen) and adopts a pseudo-tetrahedral geometry. In contrast, [Cu(I)(dpps)2]+ possesses two bulky phenyl-sulfonate groups attached to each phen ligand that force the molecule to adopt a flattened tetrahedral geometry in the ground state. Previously, optical transient absorption (OTA) and synchrotron based XTA experiments with 100 ps time resolution have been employed to study the relationship between structural distortions and excited state relaxation pathways in the two complexes. However, the dynamics of the MLCT transition during the first few picoseconds after excitation in these complexes remained unclear because of limitations in element specificity in OTA and in the time resolution of synchrotron sources in XTA. In this experiment, the local coordination geometry and oxidation state of copper were probed with a temporal resolution of ∼300 fs. Unexpectedly, the depletion of the Cu(I) signal due to the MLCT transition was found to be non-impulsive in the case of [Cu(I)(dpps)2]+ with a time constant of 0.6 ps, while the Cu(I) depletion in [Cu(I)(dmp)2]+ was instantaneous within the 300 fs instrument response time. The slower Cu(I) depletion kinetics in [Cu(I)(dpps)2]+, previously unobserved in femtosecond OTA experiments, is likely due to intramolecular motions on the sub-picosecond time scale that could alter the localization of the transferred electron in the phen ligands.

KW - copper diimine complex

KW - excited state structural dynamics

KW - MLCT state

KW - ultrafast Jahn-Teller distortion

KW - ultrafast x-ray transient absorption

KW - x-ray free electron laser

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