Issue 37, 2022

Infrared multiple-photon dissociation spectroscopy of cationized glycine: effects of alkali metal cation size on gas-phase conformation

Abstract

The gas-phase structures of cationized glycine (Gly), including complexes with Li+, Na+, K+, Rb+, and Cs+, are examined using infrared multiple-photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. To identify the structures present in the experimental studies, measured IRMPD spectra are compared to spectra calculated at B3LYP/6-311+G(d,p) for the Li+, Na+, and K+ complexes and at B3LYP/def2TZVP for the Rb+ and Cs+ complexes. Single-point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set for Li+, Na+, K+ and the def2TZVPP basis set for Rb+ and Cs+. The Li+ and Na+ complexes are identified as metal cation coordination to the amino nitrogen and carbonyl oxygen, [N,CO]-tt, although Na+(Gly) may have contributions from additional structures. The heavier metal cations coordinate to either the carbonyl oxygen, [CO]-cc, or the carbonyl oxygen and hydroxy oxygen, [CO,OH]-cc, with the former apparently preferred for Rb+ and Cs+ and the latter for K+. These two structures reside in a double-well potential and different levels of theory predict very different relative stabilities. Some experimental evidence is provided that MP2(full) theory provides the most accurate relative energies.

Graphical abstract: Infrared multiple-photon dissociation spectroscopy of cationized glycine: effects of alkali metal cation size on gas-phase conformation

Supplementary files

Article information

Article type
Paper
Submitted
28 Jul 2022
Accepted
14 Sep 2022
First published
14 Sep 2022

Phys. Chem. Chem. Phys., 2022,24, 22950-22959

Author version available

Infrared multiple-photon dissociation spectroscopy of cationized glycine: effects of alkali metal cation size on gas-phase conformation

P. B. Armentrout, B. C. Stevenson, M. Ghiassee, G. C. Boles, G. Berden and J. Oomens, Phys. Chem. Chem. Phys., 2022, 24, 22950 DOI: 10.1039/D2CP03469G

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