UV and IR Spectroscopic Studies of Cold Alkali Metal Ion-Crown Ether Complexes in the Gas Phase

Journal of the American Chemical Society Volume 133 Issue 31 Page 12256-12263 published_at 2011-08-10
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Title ( eng )
UV and IR Spectroscopic Studies of Cold Alkali Metal Ion-Crown Ether Complexes in the Gas Phase
Creator
Boyarkin Oleg V.
Kusaka Ryoji
Rizzo Thomas R.
Source Title
Journal of the American Chemical Society
Volume 133
Issue 31
Start Page 12256
End Page 12263
Abstract
We report UV photodissociation (UVPD) and IR-UV double-resonance spectra of dibenzo-18-crown-6 (DB18C6) complexes with alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) in a cold, 22-pole ion trap. All the complexes show a number of vibronically resolved UV bands in the 36000-38000 cm-1 region. The Li+ and Na+ complexes each exhibit two stable conformations in the cold ion trap (as verified by IR-UV double-resonance), whereas the K+, Rb+, and Cs+ complexes exist in a single conformation. We analyze the structure of the conformers with the aid of density functional theory (DFT) calculations. In the Li+ and Na+ complexes, DB18C6 distorts the ether ring to fit the cavity size to the small diameter of Li+ and Na+. In the complexes with K+, Rb+, and Cs+, DB18C6 adopts a boat-type (C2v) open conformation. The K+ ion is captured in the cavity of the open conformer thanks to the optimum matching between the cavity size and the ion diameter. The Rb+ and Cs+ ions sit on top of the ether ring, because they are too large to enter the cavity of the open conformer. According to time-dependent DFT calculations, complexes that are highly distorted to hold metal ions open the ether ring upon S1-S0 excitation, and this is confirmed by extensive low-frequency progressions in the UVPD spectra.
Descriptions
This is a preprint of an article published by American Chemical Society in Journal of the American Chemical Society, 2011, available online: http://pubs.acs.org/doi/abs/10.1021/ja2046205.
This work is supported by Grant-in-Aids (Grant No. 21350016) for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan and the Swiss National Science foundation through grant 200020_130579.
NDC
Chemistry [ 430 ]
Language
eng
Resource Type journal article
Publisher
American Chemical Society
Date of Issued 2011-08-10
Rights
Copyright (c) 2011 American Chemical Society
Publish Type Author’s Original
Access Rights open access
Source Identifier
[ISSN] 0002-7863
[DOI] 10.1021/ja2046205
[DOI] http://dx.doi.org/10.1021/ja2046205 isVersionOf
[PMID] 21728334