Photon Factory Activity Report 2004 #22 Part B (2005)
Chemistry

10B/2004G082

EXAFS Characterization for Immobilized Metal Ion-Containing Ionic Liquid
Takehiko SASAKI1, Chongmin ZHONG2, Mizuki TADA2, Yasuhiro IWASAWA*2
Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The
University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
2
Department of Chemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyoku, Tokyo 113-0033, Japan.
1

Introduction
Design and preparation of a new class of immobilized
single-reaction-site catalysts derived from structurally
well-defined metal ion-containing ionic liquids may
provide an opportunity to exploit new catalytic materials
with good performance from fundamental interests aswell as practical aspects of an environmental-friendly
system. Ionic liquids or molten salts composed of entirely
ions have received much attention as their versatilefunctionalities and can be regarded as new key precursor
materials for catalysts. Imidazolium ions commonly used
as cationic moiety are 1-ethyl-3-methylimidazolium(Emim) and 1-butyl-3-methylimidazolium (Bmim). We
have synthesized a series of metal ion-containing Bmim
salts for catalytic applications. We also synthesized a newionic liquid molecule, 1-methyl-3-(trimethoxysilylpropyl)
imidazolium chloride that allows us to prepare
immobilized metal ion-containing ionic liquids [1].
The aim of the present study is to characterize the2+
newly prepared immobilized Cu ion containing ionic2+
liquid (Imm-Cu -IL) by EXAFS in comparison with themeasurement for BmimCuCl4 for which X-ray single
crystal structure analysis was already performed in order
to find the local structure around Cu ion.

measurements were also performed for BmimCuCl4, in
which Cu is coordinated by four Cl atoms with thedistance of 0.226 nm in a distorted Td symmetry as foundby XRD analysis. Therefore, fitting was performed with2
the coordination number fixed at 4 and S0 was fitted to be
0.83 ± 0.03. This value was used to fit the data for Imm2+
Cu -IL as summarized in Table 1. These analyses led us
2+
to conclude that Cu atom in Imm-Cu -IL has the same
local structure as that for crystalline BmimCuCl4.

Experimental
The preparation of Imm-Cu2+-IL on silica support(Aerosil 300) is described in the reference [1]. Cu-K edge
EXAFS spectra were measured at BL-10B station ofKEK-IMSS-PF. The energy and current of electrons inthe storage ring were 2.5 GeV and 250 - 400 mA,respectively. Ionization chambers filled with pure N2 andAr/N2 (50:50) mixed gas were used to monitor theincident and transmitted X-rays, respectively. The
EXAFS spectra were analyzed with the UWXAFS
package. The curve-fitting analysis was carried out using
the FEFFIT program in the R-space. The fitting
parameters were coordination numbers (CN), interatomicdistances (R), Debye-Waller factors (σ), amplitude factor2(S0 ), and a correction-of-edge energy (∆E0). The phaseshifts and backscattering amplitudes were calculated by
the FEFF8 code.

Table 1 Curve-Fitting results of the Fourier-transformed
EXAFS data (Cu-Cl shell) for [Bmim]2CuCl4 and ImmCu2+-IL measured at room temperature

Fig. 1 k3-weighted Cu K-edge EXAFS Fourier transforms
and curve fitting results for Imm-Cu2+-IL.
Two solid curves and dotted curves represent the absolutevalues (thick) and imaginary parts (thin) of the observed
data (solid) and the fitted spectra (dotted), respectively.

Sample[Bmim]2CuCl42+bImm-Cu -ILaCN

Distance /-1
10 nm

DW/
-5
210 nmRf(%)

4.0 (fix)
3.9±0.6

2.256±0.002
2.25±0.01

5.56±0.3
10.4±20.25
3.36

a k=3.0 - 12.0 Å-1, R=1.0 - 3.0 Å, ∆E0=-0.1 ±0.4 eV. S02
was fitted to be 0.83 ± 0.03.
2-1b k=3.0 - 11.0Å , R=1.0 - 3.0 Å, ∆E0=-3 ±2 eV. S0 was
fixed at 0.83.
References[1] T. Sasaki, C. Zhong, M. Tada, and Y. Iwasawa, Chem.
Commun., 2506, (2005).
* iwasawa@chem.s.u-tokyo.ac.jp

Results and Discussion
Fig. 1 shows the k3-weighted Cu K-edge EXAFS
2+Fourier transforms and curve fitting results for Imm-Cu IL, where the single Cu-Cl shell appears. EXAFS

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