SAMOP 2021 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 6: Ultrafast
MO 6.1: Vortrag
Donnerstag, 23. September 2021, 14:00–14:15, H2
Ultrafast Spectroscopy of Excited States of Novel Ru and Cu Photosensitizers — •Miguel Andre Argüello Cordero1, Pit Jean Boden2, Martin Rentschler4, Patrick Di Martino-Fumo2, Wolfgang Frey3, Yingya Yang4, Markus Gerhards2, Michael Karnahl4, Stefan Lochbrunner1, and Stefanie Tschierlei4 — 1Institute for Physics, University of Rostock — 2Chemistry Department, TU Kaiserslauter — 3Institute of Organic Chemistry, University of Stuttgart — 4Institute of Physical and Theoretical Chemistry, TU Braunschweig
Newly synthesized Ru based photosensitizers with an extended π-system were found to exhibit long lived excited states with lifetimes of 1.7 and 24.7 µs after optical excitation. The applied biipo ligand coordinates via a phenanthroline moiety, which is extended with a naphthalimide unit. In order to replace the rare noble metal, a Cu based analogion was developed. Nanosecond transient absorption (TA) measurements revealed, that in the Cu complex, non-emissive excited state are populated which exhibit even much longer lifetimes.
In the present work, we investigate this complex and the plain ligand by femtosecond TA spectroscopy and observe rich intramolecular relaxation dynamics. The shortest lifetime of 0.3 ps can be assigned to a flattening of the geometrical structure of the complex after optical excitation. The second exponential component of 3.3 ps reflects probably ISC to a triplet MLCT-state. However, the associated spectral signatures decay with a time constant of 10 ps. This may point to a transfer of the excited electron from the MLCT-state to a LC-state.