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ID 46471
file
creator
Soga, Kazuki
Hirai, Kenta
Kida, Motoki
Morishima, Fumiya
subject
calix[4]arene
alkali metal
ion trap
electrospray
ultraviolet
conformation
NDC
Chemistry
abstract
The cooling of ionic species in the gas phase greatly simplifies the UV spectrum, which is of special importance to study the electronic and geometric structures of large systems, such as bio-related molecules and host-guest complexes. Many efforts have been devoted to achieving the ion cooling with a cold quadrupole Paul ion trap (QIT), but one problem was insufficient cooling of ions (up to ~30 K) in the QIT. In this study, we construct a mass spectrometer for ultraviolet photodissociation (UVPD) spectroscopy of gas-phase cold ions. The instrument consists of an electrospray ion source, a QIT cooled with a He cryostat, and a time-of-flight mass spectrometer. Giving a great care for the cooling condition, we can achieve ~10 K for the vibrational temperature of ions in the QIT, which is estimated from UVPD spectra of the benzo-18-crown-6 (B18C6) complex with potassium ion, K+•B18C6. Using this setup, we measure a UVPD spectrum of cold calix[4]arene (C4A) complex with potassium ion, K+•C4A. The spectrum shows a very weak band and a strong one at 36018 and 36156 cm–1, respectively, accompanied by many sharp vibronic bands in the 36000–36600 cm–1 region. In the geometry optimization of the K+•C4A complex, we obtain three stable isomers: one endo and two exo forms. On the basis of the total energy and UV spectral patterns predicted by density functional theory calculations, we attribute the structure of the K+•C4A complex to the endo isomer (C2 symmetry), in which the K+ ion is located inside the cup of C4A. The vibronic bands of K+•C4A at 36018 and 36156 cm–1 are assigned to the S1(A)–S0(A) and S2(B)–S0(A) transitions of the endo isomer, respectively.
description
This work is partly supported by the Japan Society for the Promotion of Science (JSPS) through the program “Strategic Young Researcher Overseas Visits Program for Accelerating Brain Circulation”.
journal title
Journal of Physical Chemistry A
volume
Volume 119
issue
Issue 31
start page
8512
end page
8518
date of issued
2015-08-06
publisher
American Chemical Society
issn
1089-5639
1520-5215
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
Copyright (c) 2015 American Chemical Society
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry A, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpca.5b05328.
relation url
department
Graduate School of Science