Berlin 2015 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 57: Poster - Diffusion

DY 57.5: Poster

Donnerstag, 19. März 2015, 16:00–18:00, Poster A

Excited State Proton Transfer in Aqueous Media: Ab-Initio Molecular Dynamics Simulation of Photoacids — •Gül Bekcioglu, Felix Hoffmann, and Daniel Sebastiani — Martin-Luther-Universität Halle-Wittenberg, Institut für Chemie - Theoretische Chemie

Photoacids are molecules which undergo a decrease in pKa value upon photoexcitation.[1,2] Since their acidity can be controlled in a very defined manner they are important model system for the investigation of proton transport in aqueous media. However, many details of the proton transfer from the photoacid to water remain elusive, for example, the structure and stability of the contact ion pair between the photoacid and the hydrated proton. A particular drastic drop in pKa value is exhibited by the "super" photoacid N-methyl-6-hydroxyquinolinium (HMQ). [3] Here, we present a microscopic study of the role water plays in mediating excited state proton transfer of HMQ in aqueous solution. The central question addressed here is the determination of elementary steps that lead to a full dissociation of the proton. In this regard, we computed IR spectra from Wannier center calculations to elucidate spectroscopic fingerprints of specific intermediates during the acid dissociation. [3]

[1] G. Bekcioglu, C. Allolio, M. Ekimova, E. T. J. Nibbering, and D. Sebastiani, Phys. Chem. Chem. Phys.,16, 13047-13051, (2014)

[2] G. Bekcioglu, C. Allolio, and D. Sebastiani, Phys. Chem. Chem. Phys., Submitted, (2014)

[3] G. Bekcioglu, F. Hoffmann, and D. Sebastiani, in preparation.