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Issue 9, 2008
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Mid-IR spectra of different conformers of phenylalanine in the gas phase

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Abstract

The experimental mid- and far-IR spectra of six conformers of phenylalanine in the gas phase are presented. The experimental spectra are compared to spectra calculated at the B3LYP and at the MP2 level. The differences between B3LYP and MP2 IR spectra are found to be small. The agreement between experiment and theory is generally found to be very good, however strong discrepancies exist when –NH2 out-of-plane vibrations are involved. The relative energies of the minima as well as of some transition states connecting the minima are explored at the CCSD(T) level. Most transition states are found to be less than 2000 cm−1 above the lowest energy structure. A simple model to describe the observed conformer abundances based on quasi-equilibria near the barriers is presented and it appears to describe the experimental observation reasonably well. In addition, the vibrations of one of the conformers are investigated using the correlation-corrected vibrational self-consistent field method.

Graphical abstract: Mid-IR spectra of different conformers of phenylalanine in the gas phase

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Publication details

The article was received on 29 Aug 2007, accepted on 13 Nov 2007 and first published on 29 Nov 2007


Article type: Paper
DOI: 10.1039/B713274C
Phys. Chem. Chem. Phys., 2008,10, 1248-1256

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    Mid-IR spectra of different conformers of phenylalanine in the gas phase

    G. von Helden, I. Compagnon, M. N. Blom, M. Frankowski, U. Erlekam, J. Oomens, B. Brauer, R. B. Gerber and G. Meijer, Phys. Chem. Chem. Phys., 2008, 10, 1248
    DOI: 10.1039/B713274C

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