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ID 45934
file
creator
Hirai, Kenta
NDC
Chemistry
abstract
Ultraviolet photodissociation (UVPD) spectra of calix[4]arene (C4A) complexes with alkali metal ions, M+•C4A (M = Na, K, Rb, and Cs), are measured in the 34000–37000 cm–1 region under cold (~10 K) conditions in the gas phase. The Na+•C4A and K+•C4A complexes show several sharp vibronic bands, while the UVPD spectra of the Rb+•C4A and Cs+•C4A complexes exhibit only broad features. The UVPD spectra are assigned with the aid of quantum chemical calculations. Most of the features in the UVPD spectra can be attributed to cone isomers, which are the most stable for all the M+•C4A complexes. In all the cone isomers, the M+ ion is encapsulated inside the cavity of C4A, and the structure is distorted to C2 symmetry from that of bare C4A (C4 symmetry). The cone isomers show a big difference in the electronic structure between the K+ and Rb+ complexes. The Rb+ and Cs+ complexes have an electronic structure similar to that of bare C4A. In the Na+ and K+ complexes, a pair of two benzene rings facing to each other has a short distance between them (< 6 Å). This results in substantial overlap of π clouds between them, and an electronic transition is localized on this pair. Only this localized electronic transition of the Na+ and K+ complexes shows sharp band features in the UVPD spectra. In the Na+•C4A complex, the UVPD spectroscopic result suggests the coexistence of other isomers having a partial cone and 1,3-alternate form. The energetics for isomerization reactions of C4A and Na+•C4A is examined theoretically. Estimated potential barriers between the stable conformers are less than 75 kJ/mol for Na+•C4A, suggesting that conformational conversion can occur at room temperature, before the Na+•C4A complex enters the cold ion trap. The existence of multiple conformations for Na+•C4A is attributed to higher stability of these conformers, both kinetically and thermodynamically, compared to the case of bare C4A and the other M+•C4A
complexes.
description
This work was supported by JSPS KAKENHI Grant Number 16H04098.
journal title
Physical Chemistry Chemical Physics
volume
Volume 19
issue
Issue 20
start page
12857
end page
12867
date of issued
2017-05-28
publisher
Royal Society of Chemistry
issn
1463-9076
1463-9084
publisher doi
pubmed id
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
Copyright (c) the Owner Societies 2017
This is the accepted manuscript of the article is available at https://doi.org/10.1039/C7CP01580A
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
department
Graduate School of Science