title: Butterfly Deformation Modes in a Photoexcited Pyrazolate-Bridged Pt Complex Measured by Time-Resolved X-Ray Scattering in Solution.
abstract: Pyrazolate-bridged dinuclear Pt(II) complexes represent a series of molecules with tunable absorption and emission properties that can be directly modulated by structural factors, such as the Pt-Pt distance. However, direct experimental information regarding the structure of the emissive triplet excited state has remained scarce. Using time-resolved wide-angle X-ray scattering (WAXS), the excited triplet state molecular structure of [Pt(ppy)(μ-t-Bu2pz)]2 (ppy = 2-phenylpyridine; t-Bu2pz = 3,5-di-tert-butylpyrazolate), complex 1, was obtained in a dilute (0.5 mM) toluene solution utilizing the monochromatic X-ray pulses at Beamline 11IDD of the Advanced Photon Source. The excited-state structural analysis of 1 was performed based on the results from both transient WAXS measurements and density functional theory calculations to shed light on the primary structural changes in its triplet metal-metal-to-ligand charge-transfer (MMLCT) state, in particular, the Pt-Pt distance and ligand rotation. We found a pronounced Pt-Pt distance contraction accompanied by rotational motions of ppy ligands toward one another in the MMLCT state of 1. Our results suggest that the contraction is larger than what has previously been reported, but they are in good agreement with recent theoretical efforts and suggest the ppy moieties as targets for rational synthesis aimed at tuning the excited-state structure and properties.
authors: Physics Department, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark.
authors: Kristoffer
authors: K
authors: Haldrup
authors: Physics Department, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark.
authors: Asmus O
authors: AO
authors: Dohn
authors: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors: Megan L
authors: ML
authors: Shelby
authors: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors: Michael W
authors: MW
authors: Mara
authors: Andrew B
authors: AB
authors: Stickrath
authors: Michael R
authors: MR
authors: Harpham
authors: Jier
authors: J
authors: Huang
authors: Xiaoyi
authors: X
authors: Zhang
authors: Physics Department, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark.
authors: Klaus B
authors: KB
authors: Møller
authors: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors: Arnab
authors: A
authors: Chakraborty
authors: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors: Felix N
authors: FN
authors: Castellano
authors: David M
authors: DM
authors: Tiede
authors: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors: Lin X
authors: LX
authors: Chen