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A consistent picture of the proton release mechanism of oNBA in water by ultrafast spectroscopy and ab initio molecular dynamics


Donten, M L; Hamm, P; VandeVondele, J (2011). A consistent picture of the proton release mechanism of oNBA in water by ultrafast spectroscopy and ab initio molecular dynamics. Journal of Physical Chemistry. B, 115(5):1075-1083.

Abstract

With a combination of transient pump-probe IR spectroscopy and ab initio molecular dynamics, the controversial
pico- and nanosecond steps of the o-nitrobenzaldehyde
(oNBA) photoreaction have been investigated in aqueous solution. In this way, the measured reaction kinetics
have been complemented with an atomistic picture of the
reactive events as obtained with unbiased simulations in
explicit solvent. Our results allow for a detailed description of the oNBA proton photorelease, a process of fundamental importance and relevant to the use of oNBA as a proton cage in many experiments. In a first step, a stable ketene intermediate is formed on a subpicosecond time scale. This intermediate reacts in a solvent assisted way with an OH transfer to produce nitrosobenzoic acid with a characteristic time of 7 ps. Finally, in permitting pH conditions, this product molecule dissociates a carboxyl proton with a 21 ns time constant. The particular combination of theory and experiment employed in this work appears to be sufficiently general and powerful to find widespread application in the study of ultrafast reactive systems.

With a combination of transient pump-probe IR spectroscopy and ab initio molecular dynamics, the controversial
pico- and nanosecond steps of the o-nitrobenzaldehyde
(oNBA) photoreaction have been investigated in aqueous solution. In this way, the measured reaction kinetics
have been complemented with an atomistic picture of the
reactive events as obtained with unbiased simulations in
explicit solvent. Our results allow for a detailed description of the oNBA proton photorelease, a process of fundamental importance and relevant to the use of oNBA as a proton cage in many experiments. In a first step, a stable ketene intermediate is formed on a subpicosecond time scale. This intermediate reacts in a solvent assisted way with an OH transfer to produce nitrosobenzoic acid with a characteristic time of 7 ps. Finally, in permitting pH conditions, this product molecule dissociates a carboxyl proton with a 21 ns time constant. The particular combination of theory and experiment employed in this work appears to be sufficiently general and powerful to find widespread application in the study of ultrafast reactive systems.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2011
Deposited On:09 Sep 2011 12:33
Last Modified:05 Apr 2016 14:56
Publisher:American Chemical Society
ISSN:1520-5207
Funders:Swiss National Science Foundation (SNF)
Additional Information:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry. B, copyright © American Chemical Society after peer review and technical editing by the publisher.
Publisher DOI:10.1021/jp109053r
Official URL:http://pubs.acs.org/doi/abs/10.1021/jp109053r
PubMed ID:21222460
Permanent URL: http://doi.org/10.5167/uzh-48414

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