Erlangen 2018 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Posters 1: Ultrafast Spectroscopy

MO 13.6: Poster

Tuesday, March 6, 2018, 16:15–18:15, Orangerie

Quantum Chemical Study of a Super-Photoacid — •Niklas Suelzner and Christof Hättig — Arbeitsgruppe Quantenchemie, Ruhr-Universität Bochum, 44780 Bochum

Photoacidity, i.e. the increase of acidity upon photo-excitation, is a common feature of aromatic alcohols. Depending on the ring’s substituents, the strength of a photoacid may vary significantly which, in turn, initiated the discussion of different mechanism for excited-state proton transfer (ESPT). Frequently mentioned molecular origins of photoacidity include intramolecular charge redistribution (charge transfer), hydrogen bonding and solvent interactions.

Accompanying the experimental work on hydroxypyrene-tris(hexafluoropropanylsulfonate), we performed a detailed quantum chemical study on this super-photoacid using the wavefunction-based methods ADC(2) and CC2 together with the solvation model COSMO for the treatment of bulk solvation effects. We aimed at gaining insights into the electronic structure and the structural changes occurring upon electronic excitation. The protonated and deprotonated forms were treated separately and in addition, a water complex was investigated. Our results clearly indicate a contribution of charge redistribution in the first excited-state as well as hydrogen bonding to solvent molecules, in accordance with the experimental electronic spectra.