Hannover 2020 – scientific programme
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MO: Fachverband Molekülphysik
MO 8: MO Poster 2
MO 8.7: Poster
Tuesday, March 10, 2020, 17:00–19:00, Empore Lichthof
Reaction pathways of a chiral salicylimine studied by ultrafast spectroscopy and vibrational circular dichroism — •Kevin Artmann1, Corina Pollok2, Christian Merten2, and Patrick Nuernberger1 — 1Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93040 Regensburg — 2Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44780 Bochum
Due to its prominent reaction mechanism and its simple molecular structure, salicylimines were intensively investigated in the past. Upon excitation, an excited-state intramolecular proton transfer (ESIPT) leads to the formation of a keto conformer. In addition, the ESIPT competes with a torsional angle rotation that produces a twisted enol conformer. It has been therefore suggested that the excitation wavelength can influence the population of the different conformers, but there is still no experimental evidence available. In this study, we combine the results from ultrafast transient absorption spectroscopy and matrix-isolation vibrational circular dichroism spectroscopy (MI-VCD) to elucidate the influence of the excitation energy and of the solvent on the reaction mechanism. Besides unraveling the characteristic time scales of the different reaction pathways, it is demonstrated that a higher excitation energy correlates with a lower population of the keto conformer. A higher excitation energy is needed to excite molecules that are already twisted before excitation, therefore the rotational pathway is preferred. Furthermore, we show that the concentration of the keto conformer increases if a solvent with a larger dielectric constant is used.