Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 16: POSTER: Computational Physics, Complex Systems

CPP 16.28: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Solvation and Solvation Dynamics of Hydrogen Bonding Dyes Solvation and Solvation Dynamics of Hydrogen Bonding Dyes — •Dzmitry Starukhin¹, Frank Cichos², and Christian von Borczyskowski¹ — ¹Institut für Physik 122501, TU Chemnitz, 09107 Chemnitz — ²Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz

Hydrogen bonding is a key element of many biological macromolecules to ensure function and structure. To study hydrogen bonding effects in relation to solvent dynamics, we employ a resorufin dye, which is sensitive to solute-solvent hydrogen bonds. We show that the dye emission wavelength in different solvents is not governed by dielectric effects such as dipolar solvation but rather completely determined by hydrogen bonds. Steady state spectroscopy of the dye in protic solvents shows, that ground and excited state of the dye possess the same number of hydrogen bonds, but at different positions of the molecule. This results in two spectroscopically distinguishable forms of the molecule, which exchange upon photoexcitation. Due to the exchange the fluorescence decay of the dye studied by time correlated single photon counting shows mainly two different timescales. One very fast component is due to a braking and making of hydrogen bonds and is accompanied by a structural relaxation of the solvent. The structural relaxation shows time constants which are close to the typical time constants found in dipolar solvation dynamics measurements. These experimental findings are further supported by quantum chemical calculations as well as molecular dynamics simulations.