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MO: Molekülphysik

MO 15: Molecular Clusters II

MO 15.3: Talk

Monday, March 13, 2006, 17:00–17:15, H10

Spectroscopic Characterization of Proton Wires: IR Spectra of Microsolvated Protonated Ethanol Chains — •Otto Dopfer and Nicola Solca — Institut für Physikalische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

Proton transfer, proton transport, and proton pumps are fundamental chemical and biological phenomena. Detailed understanding of these processes at the molecular level requires knowledge of the potential energy surface describing the proton wire. Mass spectrometric, spectroscopic, and quantum chemical characterization of proton-bound complexes under isolated or controlled microsolvation conditions provide the most direct access to this potential, yielding valuable informaton on the mobility of excess protons in solution. The present work reports IR photodissociation spectra [1] of size-selected protonated ethanol complexes of the type (EtOH)mH+-Ln, with L=Ar and N2, m=1-4, and n=0-5. The IR spectra provide detailed information on the degree of delocalization of the excess proton along the ethanol chain as a function of the length of the chain (m), the type of solvent (L), and the degree of solvation (n) [2,3]. Significantly, the symmetry of the proton bridge (Zundel or Eigen type) is found to depend sensitively on the symmetry of the microsolvation environment. Moreover, the acidity of the terminal OH groups decreases with the length of the chain. Density functional calculations support the interpretation derived from the spectroscopic data.

[1] O. Dopfer, Int. Rev. Phys. Chem. 22, 437 (2003). [2] N. Solca and O. Dopfer, J. Am. Chem. Soc. 126, 9520 (2004). [3] N. Solca and O. Dopfer, J. Phys. Chem. A 109, 6147 (2005).