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Lecture Erik T.J. Nibbering


19 May 2005 FWN-Building 5118.-152, Nijenborgh 4, 9747 AG, Groningen
Speaker: Dr. Erik T.J. Nibbering
Affiliation: Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin
Title: Sequential proton transfer through water bridges in acid-base reactions
Date: Thu May 19, 2005
Start: 15.00
Location: FWN-Building 5118.-152
Host: J. Knoester
Telephone: +31 50 363 4369


Aqueous proton transfer is one of the most fundamental chemical reactions. For instance, water mediates the transfer of a proton in membrane protein proton channels. These proton channels function by a sequential hopping of protons through proton wires consisting of amino acid side groups and water molecules. A sequential proton transfer is also at the heart of the von Grotthuss mechanism of anomalous high proton mobility in water. Water is considered to play a key role in aqueous acid-base neutralization reactions, where a proton is exchanged between an acid and a base, forming the conjugated base and conjugated acid respectively. Theoretical considerations have shown that water facilitates an efficient charge separation when the proton leaves the acid.

In this work we show compelling experimental evidence that water in addition functions as a bridge between an acid and a base, by both providing and stabilizing the proton transfer pathway. For optical triggering the proton transfer reaction we use a photoacid [1,2]. In particular we detect the transient behaviour of the IR-active marker mode of the hydrated proton to be correlated with the transient reactant and product bands. The hydrated proton in our acid-base neutralization experiment turns out to be similar to the Eigen cation  and not the Zundel cation  for solvated protons in water.

[1] M. Rini, B. Magnes, E. Pines, E. T. J. Nibbering, Science 301, 349 (2003).
[2] M. Rini, D. Pines, B. Z. Magnes, E. Pines, E. T. J. Nibbering, J. Chem. Phys. 121, 9593 (2004)

Last modified:22 October 2012 2.30 p.m.