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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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 (US)
Article number154006
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Issue number15
StatePublished - Jul 12 2017


  • MLCT state
  • copper diimine complex
  • excited state structural dynamics
  • 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


Dive into the research topics of 'Ultrafast dynamics of two copper bis-phenanthroline complexes measured by x-ray transient absorption spectroscopy'. Together they form a unique fingerprint.

Cite this