期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 116, 期 6, 页码 1532-1541出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp209636a
关键词
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资金
- National Science Foundation [PIRE-0730072, CHE-1049580]
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1049580] Funding Source: National Science Foundation
The gas phase structures of cationized histidine (His), including complexes with Li+, Na+, Rb+, and Cs+, are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by a free electron laser, in conjunction with quantum chemical 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) (Li+, Na+, and K+ complexes) and B3LYP/HW*/6-311+G(d,p) (Rb+ and Cs+ complexes) levels of theory, where HW* indicates that the Hay-Wadt effective core potential with additional polarization functions was used on the metals. Single point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set. On the basis of these experiments and calculations, the only conformation that reproduces the IRMPD action spectra for the complexes of the smaller alkali metal cations, Li+(His) and Na+(His), is a charge-solvated, tridentate structure where the metal cation binds to the backbone carbonyl oxygen, backbone amino nitrogen, and nitrogen atom of the imidazole side chain, [CO, N alpha,N-1], in agreement with the predicted ground states of these complexes. Spectra of the larger alkali metal cation complexes, K+(His), Rb+(His), and Cs+(His), have very similar spectral features that are considerably more complex than the IRMPD spectra of Li+(His) and Na+(His). For these complexes, the bidentate [CO,N-1] conformer in:which the metal cation binds to the backbone carbonyl oxygen and nitrogen atom of the imidazole side chain is a dominant contributor, although features associated with the tridentate [CO,N-alpha,N-1] conformer remain, and those for the [COOH] conformer are also clearly present. Theoretical results for Rb+(His) and Cs+(His) indicate that both [CO,N-1] and [COOH] conformers are low-energy structures, with different levels of theory predicting different ground conformers.
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