Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MO: Fachverband Molekülphysik

MO 21: Photochemistry

MO 21.2: Vortrag

Freitag, 21. März 2014, 10:45–11:00, BEBEL HS213

Solvent Dependence of Excited-State Proton Transfer from Pyranine-derived Photoacids — •Christian Spies¹, Björn Finkler¹, Dina Pines², Ehud Pines², Dan Huppert³, and Gregor Jung¹ — ¹Biophysical Chemistry, Saarland University, Saarbrücken, Germany — ²Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel — ³Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Israel

The transfer of a proton to a base is one of the most fundamental chemical reactions. Especially, photoexcitation of aromatic alcohols, leading to an enhanced acidity, served as paradigm for this kind of reaction. One of the most widely used photoacids is hydroxypyrene-trisulfonate (HPTS) and its even more acidic sulfonamide derivative (HPTA). Recently, we synthesized a new series of strong photoacids based on HPTS and HPTA, with high photostability and pKa* values ranging from -0.7 to -4. In this contribution we study the solvent dependence of these photoacids. A differential solvatochromism approach enables us to identify a charge transfer as the most distinct feature for the strong solvatochromism and photoacidity of these molecules. The excited-state proton transfer rate (kPT) of these photoacids is measured in more detail by time-resolved spectroscopy. Different solvents in which proton transfer takes place such as water, methanol and ethanol are investigated. The results are quantitatively explained by adiabatic and non-adiabatic proton transfer formalism and analyzed in terms of Marcus free energy correlations.