| Autor: |
Armentrout PB; Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, United States., Boles GC; Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, United States., Ghiassee M; Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, United States., Berden G; Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, NL-6525 ED Nijmegen, The Netherlands., Oomens J; Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, NL-6525 ED Nijmegen, The Netherlands.; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands. |
| Abstrakt: |
Sodiated complexes of the aliphatic amino acids, Gly, Ala, Val, Leu, and Ile, were examined with infrared multiple-photon dissociation action spectroscopy utilizing light from a free-electron laser. To identify structures, the experimental spectra were compared to linear spectra calculated at the B3LYP/6-311+G(d,p) level of theory. Relative energetics of all complexes were calculated at B3LYP, B3P86, MP2(full), B3LYP-GD3BJ, and M06-2X levels using a 6-311+G(2d,2p) basis set. Spectral comparison for all complexes indicates that the dominant conformation, [N, CO], binds to the amino nitrogen and carbonyl oxygen. For all complexes except Gly, contributions are observed from [CO 2 - ] structures, where the sodium cation binds to both oxygens of the carboxylate group in the zwitterionic form of the amino acid. The semiquantitative distribution between these two structures appears to be best-predicted by the B3LYP and MP2(full) levels of theory, with predictions from the other three levels inconsistent with the experiment. |
