jz300714t_si_001.pdf (1.46 MB)
Monitoring Intramolecular Proton Transfer with Two-Dimensional Infrared Spectroscopy: A Computational Prediction
journal contribution
posted on 2015-12-16, 21:33 authored by Z. L. Terranova, S. A. CorcelliProton transfer processes are ubiquitous and play a vital
role
in a broad range of chemical and biochemical phenomena. The ability
of two-dimensional infrared (2D IR) spectroscopy with a carbon–deuterium
(C–D) reporter to monitor the kinetics of proton transfer in
the model compound malonaldehyde was demonstrated computationally.
One of the two carbonyl/enol carbon atoms in malonaldehyde was labeled
with a C–D bond. The C–D stretch vibrational frequency
provides ∼150 cm–1 of sensitivity to the
two tautomers of malonaldehyde. Mixed quantum mechanics/molecular
mechanics simulations employing the self-consistent-charge density
functional tight binding (SCC-DFTB) method were used to compute 2D
IR line shapes for the C–D stretch of labeled malonaldehyde
in aqueous solution. The 2D IR spectra reveal cross peaks from the
chemical exchange of the proton. The kinetics for the growth of the
cross-peaks (and the decay of the diagonal peaks) precisely match
the proton transfer rate observed in the SCC-DFTB simulations.