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Photoinduced energy and electron transfer

Spectroscopic investigations of ultrafast photoinduced energy and electron transfer in transition metal complexes present a central focus of our work. In particular, we are interested in the interplay between molecular structure, photoinduced dynamics and the function of the complexes. Currently, we are focussing on detailing the light-induced reaction steps in molecular photocatalysts, highly luminescent Ru, Os and Fe terpyridine complexes, terpyridine-based coordination polymers and complexes potentially used in dye-sensitized solar cells.

This work is financially supported by the Thüringer Ministerium für Bildung, Wissenschaft und Kultur via the ProExzellenz Initiative (project PhotoMIC).

  1. Maria Wächtler, Stephan Kupfer, Julien Guthmuller, Jürgen Popp, Leticia González and Benjamin Dietzek,
    Influence of Multiple Protonation on the Initial Excitation in a Black Dye.
    Journal of Physical Chemistry C, 115(48), 24004-24012 (2011).
  2. Ronald Siebert, Christoph Hunger, Julien Guthmuller, Florian Schlütter, Andreas Winter, Ulrich S. Schubert, Leticia González, Benjamin Dietzek and Jürgen Popp,
    Direct Observation of Temperature-Dependent Excited-State Equilibrium in Dinuclear Ruthenium Terpyridine Complexes Bearing Electron-Poor Bridging Ligands.
    Journal of Physical Chemistry C, 115(25), 12677-12688 (2011).
  3. Christian Kuhnt, Michael Karnahl, Michael Schmitt, Sven Rau, Benjamin Dietzek and Jürgen Popp,
    Excited-state annihilation in a homodinuclear ruthenium complex.
    Chemical Communications, 47(13), 3820-3821 (2011).
  4. Ronald Siebert, Andreas Winter, Ulrich S. Schubert, Benjamin Dietzek and Jürgen Popp,
    The molecular mechanism of dual emission in terpyridine transition metal complexes - ultrafast investigations of photoinduced dynamics.
    Physical Chemistry Chemical Physics, 13(4), 1606-1617 (2011).
  5. Stefanie Tschierlei, Martin Presselt, Christian Kuhnt, Arkady Yartsev, Torbjörn Pascher, Villy Sundström, Michael Karnahl, Matthias Schwalbe, Bernhard Schäfer, Sven Rau, Michael Schmitt, Benjamin Dietzek and Jürgen Popp,
    Photophysics of the intramolecular hydrogen evolving photocatalyst Ru-tpphz-Pd.
    Chemistry - A European Journal, 15(31), 7678-7688 (2009).

Photoinduced dynamics in Protochlorophyllide a

Within this project, the mechanistic interplay between protein structure of the protochlorophyllide-NADPH-oxidoreductase and its function will be investigated on an ultrafast timescale (on the time scale of picoseconds, i.e., 10-12 s). This is done by combining mutagenesis studies of the catalytic reaction center with various spectroscopic tools such as femtosecond time-resolved differential absorption (in the UV/Visultraviolet/&zwnj and mid-IRinfrared spectral range) and picosecond time-resolved luminescence measurements on the substrate protochlorophyllide a. This combination of techniques enables the assessment of individual protein sites, which are critical for the ultrafast photoresponse of the enzyme, and the determination of the relevant reaction coordinates on an ultrafast time-scale.

This work is supported by the German Science Foundation (DFG) via the Jena School of Microbial Communication.

  1. Robert Hanf, Sonja Fey, Benjamin Dietzek, Michael Schmitt, Christiane Reinbothe, Steffen Reinbothe, Gudrun Hermann and Jürgen Popp,
    Protein-Induced Excited-State Dynamics of Protochlorophyllide.
    Journal of Physical Chemistry A, 115(27), 7873-7881 (2011).
  2. Miriam Colindres-Rojas, Matthias M.N. Wolf, Ruth Groß, Sonja Seidel, Benjamin Dietzek, Michael Schmitt, Jürgen Popp, Gudrun Hermann and Rolf Diller,
    Excited-State Dynamics of Protochlorophyllide Revealed by Subpicosecond Infrared Spectroscopy.
    Biophysical Journal, 100(1), 260-267 (2011).
  3. Benjamin Dietzek, Stefanie Tschierlei, Robert Hanf, Sonja Seidel, Arkady Yartsev, Michael Schmitt, Gudrun Hermann and Jürgen Popp,
    Dynamics of charge separation in the excited-state chemistry of protochlorophyllide.
    Chemical Physics Letters, 492(1-3), 157-163 (2010).
  4. Benjamin Dietzek, Stefanie Tschierlei, Gudrun Hermann, Arkady Yartsev, Torbjörn Pascher, Villy Sundström, Michael Schmitt and Jürgen Popp,
    Protochlorophyllide a: A Comprehensive Photophysical Picture.
    ChemPhysChem, 10(1), 144 (2009).

Femtosecond time-resolved transient chirality

Chirality is ubiquitous in nature. However, it is extremely difficult to access the small photoinduced chirality changes in small molecules. We have established an experimental setup for investigating transient chirality changes with sub-200-fs temporal resolution in the UVultraviolet spectral range. First experiments dealt with the photophysics of 7-dehydrocholesterol and could resolve ambiguities in the interpretation of the photophysical data obtained from transient absorption spectroscopy.

This work is financially supported by the German Science Foundation (DFG).

  1. Julia Meyer-Ilse, Denis Akimov and Benjamin Dietzek,
    Ultrafast Circular Dichroism Study of the Ring Opening of 7-Dehydrocholesterol.
    Journal of Physical Chemistry Letters, 3(2), 182-185 (2012).

Nanoparticle-Molecule-Interfaces

Nanoparticle-molecule interfaces play a central role in e.g. opto-electronic devices such as dye-sensitized solar cells or in heterogeneous catalysis. Our research interest lies in the construction of well defined nanoparticle-molecule interfaces both on metals and semiconductors and the spectroscopic characterization of photoinduced processes in such systems. In particular, we are interested in the interfacial charge-transfer processes and their correlation with the geometrical and electronic structure of the molecules at the interface.

This work is financially supported by the Bundesministerium für Bildung und Forschung via the program Spitzenforschung und Innovation in den Neuen Ländern (project Phona).