title: Characterizing the Solvated Structure of Photoexcited [Os(terpy)₂](2+) with X-ray Transient Absorption Spectroscopy and DFT Calculations.
abstract: Characterizing the geometric and electronic structures of individual photoexcited dye molecules in solution is an important step towards understanding the interfacial properties of photo-active electrodes. The broad family of "red sensitizers" based on osmium(II) polypyridyl compounds often undergoes small photo-induced structural changes which are challenging to characterize. In this work, X-ray transient absorption spectroscopy with picosecond temporal resolution is employed to determine the geometric and electronic structures of the photoexcited triplet state of [Os(terpy)₂](2+) (terpy: 2,2':6',2″-terpyridine) solvated in methanol. From the EXAFS analysis, the structural changes can be characterized by a slight overall expansion of the first coordination shell [OsN₆]. DFT calculations supports the XTA results. They also provide additional information about the nature of the molecular orbitals that contribute to the optical spectrum (with TD-DFT) and the near-edge region of the X-ray spectra.
authors.affiliation: X-ray Sciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA. xyzhang@aps.anl.gov.
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark. papai@kemi.dtu.dk.|Wigner Research Centre for Physics, Hungarian Academy of Sciences, "Lendület" (Momentum) Femtosecond Spectroscopy Research Group, P.O. Box 49, Budapest H-1525, Hungary. papai@kemi.dtu.dk.
authors.forename: Mátyás
authors.initials: M
authors.lastname: Pápai
authors.affiliation: Department of Chemistry, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark. klaus.moller@kemi.dtu.dk.
authors.forename: Klaus B
authors.initials: KB
authors.lastname: Møller
authors.affiliation: School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China. zjx1980@126.com.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Deutsches Elecktronen Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany. secanton2012@gmail.com.|IFG Structural Dynamics of (Bio)Chemical Systems, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen D-37077, Germany. secanton2012@gmail.com.
authors.forename: Sophie E
authors.initials: SE
authors.lastname: Canton
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D004566:Electrodes; D046911:Macromolecular Substances / Q000737:chemistry*; D015394:Molecular Structure; D017892:Osmium Compounds / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D004396:Coloring Agents; D046911:Macromolecular Substances; D017892:Osmium Compounds; D012996:Solutions
keywords: X-ray transient absorption spectroscopy; excited-state; osmium polypyridyl complex