Hexakis [60]Fullerene Adduct-Mediated Covalent Assembly of Ruthenium Nanoparticles and Their Catalytic Properties

Article abstract of DOI:10.1002/chem.201701043

The C₆₆(COOH)₁₂ hexa-adduct has been successfully used as a building block to construct carboxylate bridged 3D networks with very homogeneous sub-1.8 nm ruthenium nanoparticles. The obtained nanostructures are active in nitrobenzene selective hydrogenation.

Full text of DOI:10.1002/chem.201701043

A Journal of
Accepted Article
Title: Hexakis [60]Fullerene Adduct-Mediated Covalent Assembly of
Ruthenium Nanoparticles and Their Catalytic Properties
Authors: Philippe Serp, Faqiang Leng, Iann C. Gerber, Pierre Lecante,
Ahmed Bentaleb, Antonio Muñoz, Beatriz M. Illescas, Nazario
Martín, Georgian Melinte, Ovidiu Ersen, Hervé Martinez, and
M. Rosa Axet
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To be cited as: Chem. Eur. J. 10.1002/chem.201701043
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Hexakis [60]Fullerene Adduct-Mediated Covalent Assembly of
Ruthenium Nanoparticles and Their Catalytic Properties
Faqiang Leng,[a],[b] Iann C. Gerber, Pierre Lecante, Ahmed Bentaleb, Antonio Muñoz, Beatriz M.
[c]
[d]
[e]
[f]
[f]
[f],[g]
[h]
[h]
[i]
*[a],[b]
Illescas, Nazario Martín,
and Philippe Serp*[a],[b]
Georgian Melinte, Ovidiu Ersen, Hervé Martinez, M. Rosa Axet
Abstract: The C66(COOH)12 hexa-adduct has been successfully used
as a building block to construct via carboxylate bridges 3D networks
with very homogeneous sub-1.8 nm ruthenium nanoparticles. The
obtained nanostructures are active in nitrobenzene selective
hydrogenation.
covalent interactions between NPs,[1] resulting in assemblies of
poor mechanical stability, which can be detrimental to many
applications. In order to obtain stable assemblies, and particularly
metal NP assemblies, molecular linkers or mediators that can
induce a covalent linking between the NPs have also been
exploited.[1b, 2] The insertion of molecules with a large variety of
size, shape, charge or electronic features allows to tune the metal
interparticle interaction in NP assemblies bringing about novel
functionalities. The properties of the resulting hybrid structures
are not only interesting from a fundamental point of view, but are
currently considered as technologically relevant, since they can
address many cutting-edge applications such as plasmonic,
sensor,[4] or catalysis, where it has been shown that the proximity
of the NPs may affect their catalytic performances and their
stability.[5]
The use of C60 fullerene as a molecular linker is particularly
attractive since: i) it is possible to produce bis-, tris-, tetrakis-,
pentakis-, hexakis- and decakis-substituted C60 adducts,[6] paving
Introduction
The synthesis of nanoparticle (NP) assemblies stabilized by
functional molecules is a common research topic in nanoscience.
The ability to control interparticle distances and positions in NP
assemblies is one of the major challenges for the design and
understanding of functional nanostructures. A combination of self-
and directed-assembly processes, involving interparticle and
externally applied forces, can be applied to produce the desired
nanostructured materials. These processes usually involve non
[3]
the way to 1D, 2D or 3D assemblies of metallic NPs; and ii) the
size of the [60]fullerene adduct is similar to the one of small NPs
[
a]
Dr. F. Leng, Dr. M. Rosa Axet, Pr. Dr. P. Serp
CNRS, LCC (Laboratoire de Chimie de Coordination)
composante ENSIACET, 4 allée Emile Monso, BP 44099, F-31030
Toulouse Cedex 4, France
E-mail: rosa.axet@lcc-toulouse.fr; philippe.serp@ensiacet.fr
Dr. F. Leng, Dr. M. R. Axet, Pr. Dr. P. Serp
Université de Toulouse, UPS, INPT
F-31077 Toulouse Cedex 4, France
Dr. I. C. Gerber
LPCNO, Université de Toulouse, CNRS, INSA, UPS
(
1-1.5 nm). Only few reports in the literature deal with the
assembly of metal NPs by [60]fullerene adducts, all of them with
gold NPs.[7] The assembly of Au NPs by functionalized fullerenes
through electrostatic interactions between negatively charged
groups on Au NPs and positively charged piperazinyl groups on
[b]
[c]
[d]
1-(4-methyl)piperazinyl fullerene leads to 11.5-nm Au NPs
assemblies with edge-to-edge interparticle distance of 1.14 ± 0.20
[7a]
nm.
A new organo-soluble C60 hexa-adduct bearing twelve
135 avenue de Rangueil, F-31077 Toulouse, France
thiocyanate functions has been used as a stabilizing/assembling
agent to assemble homogeneous 3 nm Au NPs into apparently
extended tridimensional networks.[7b] Hexakis-substituted
Dr. P. Lecante
Centre d’élaboration des matériaux et d’études structurales UPR
CNRS 801
2
9 Rue Jeanne-Marvig, BP 4347, 31055 Toulouse, France Toulouse
[
60]fullerene adducts have been recently identified as potential
Cedex 4, France
Dr. A. Bentaleb
Centre de Recherche Paul Pascal - CNRS University of Bordeaux
highly connective linkers for coordination polymer and metal–
organic framework synthesis.[8]
[
e]
f]
1
15 avenue Schweitzer 33600 Pessac, France
Herein, we report the synthesis of Ru@C66(COOH)12
nanostructures, their characterization, and their use as catalysts.
[
Dr. A. Muñoz, Dr. B.M. Illescas, Pr. Dr. N. Martín
Departamento de Química Orgánica, Facultad de Ciencias
Químicas, Universidad Complutense de Madrid, Madrid, Spain
23 rue du Loess BP43, 67034 Strasbourg cedex 2, France
[
g]
h]
Pr. Dr. N. Martín
IMDEA-Nanoscience, Campus de Cantoblanco, Madrid, Spain.
Dr. G. Melinte, Pr. Dr. O. Ersen
Results and Discussion
[
The Ru@C66(COOH)12 nanostructures have been produced at
room temperature from the reductive decomposition of
[Ru(COD)(COT)] (COD= 1,5 cyclooctadiene, COT= 1,3,5-
IPCMS, UMR 7504 Université de Strasbourg – CNRS, 23 rue du
Loess, BP 43, 67034 Strasbourg Cedex 2, France.
Pr. Dr. H. Martinez
IPREM CNRS UMR 5254, Helioparc Pau-Pyrénée, 2 Av du Pdt
Angot, 64053 Pau Cedex, France
[i]
cyclooctatriene) by molecular
H
2
in the presence of
fullerenehexamalonic acid C66(COOH)12 (Scheme 1). The effect
Supporting information for this article is given via a link at the end of
the document.
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of the solvent and the [Ru(COD)(COT)]/C66(COOH)12 ratio on the
structure of the synthesized materials have been investigated.
Ru@C66(COOH)12 samples synthesized in THF, sealed in
Lindemann glass capillaries were also analysed by WAXS. The
diffractograms of Ru@C66(COOH)12 6/1, 12/1 and 30/1 are
detailed in Fig. S4 in the ESI, and the pair-distribution functions
(
PDF) are displayed in Figure 3. The three diffractograms of
Ru@C66(COOH)12 6/1, 12/1 and 30/1 were very similar, and fully
consistent with the presence of metallic hcp Ru.
Scheme 1. Synthesis of C66(COOH)12-mediated covalent assembly of Ru NPs.
The produced nanostructures were characterized in detail using
Transmission Electron Microscopy (TEM) and Electron
Tomography together with Wide-Angle X-ray Scattering (WAXS),
Small Angle X-ray Scattering (SAXS), Solid State NMR (SSNMR),
X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total
Reflection Infrared spectroscopy (ATR-IR).
The effect of the solvent on the nanostructures was studied at a
constant [Ru(COD)(COT)]/C66(COOH)12 ratio of 6/1. The solvents
(
C
THF, methanol and DMF) were chosen according to
66(COOH)12 solubility. Figure 1 shows the TEM images of the
obtained materials. In all cases, objects with irregular shapes
containing Ru NPs were observed. The Ru@C66(COOH)12
nanostructures synthesized in THF and MeOH (Fig. 1a and 1b
and Fig. S1 in the SI) present the smallest Ru NPs, 1.23 ± 0.43
and 1.04 ± 0.30 nm, respectively. In the THF sample, the NPs are
included in assemblies and no free NPs have been detected by
TEM, contrarily to the samples prepared in MeOH and DMF. The
synthesis carried out in DMF afforded less homogeneous and
slightly larger Ru NPs (1.74 ± 0.87 nm, Fig. S1 in the ESI). THF
was chosen as solvent as it produced homogeneous Ru NPs,
which were all included in the assemblies. A series of experiments
using Ru/C66(COOH)12 ratio from 6/1 to 50/1 were carried in THF
out in order to investigate the effect of the Ru/ligand ratio on the
nanostructures synthesised. The mean diameter of the Ru NPs
increased slightly with increasing the Ru content (Table 1, and Fig.
S2 in the ESI), while the nanostructures remained almost
unchanged. The HREM images of Ru@C66(COOH)12
nanostructures 6/1 and 30/1 are depicted in Figure 2. Small Ru
NPs are visible in both samples. The Ru NPs are well crystallized
with crystal parameters corresponding to hexagonal close packed
(
hcp) Ru (Fig. 2b). EDX analyses have confirmed that the
Ru@C66(COOH)12 nanostructures are composed of Ru and C
Fig. S3 in the ESI).
(
Table 1. Mean size diameters of Ru NPs with several Ru/C66(COOH)12 ratio.
a
Ru@C66(COOH)12
Ru loading
%)
Nanoparticles mean
b
(
size (nm)
6
/1
22.6
40.7
52.4
nd
1.23 ± 0.43
1.54 ± 0.45
1.52 ± 0.44
1.78 ± 0.79
12/1
30/1
50/1
a
b
ICP analysis. Mean values of size nanoparticle determined from TEM
micrographs by considering at least 200 particles.
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Figure 1. TEM micrographs of Ru@C66(COOH)12 nanostructures with
Ru/C66(COOH)12 = 6/1 synthesized in different solvents: a) THF; b) MeOH; and
c) DMF. (scale bars 50 nm).
were determined and a pair distribution function was calculated
by using a methodology previously described.[9] The distribution
shows that the NPs do not present a long-range order, but as the
well-defined peak appearing around 2.9 nm shows (Fig. 5d), a
short-range one. This relatively broad peak is assigned to the first
neighbour distance, as shown also in Fig. 5b. The electron
tomography analyses are in a very good agreement with the
SAXS results. XPS analysis of the Ru@C66(COOH)12 systems is
inherently difficult because of the overlap of the C(1s) and Ru(3d)
core levels, and the asymmetric nature of the Ru core level line
shape.
The sharp peak signal at small angles is assigned to C66(COOH)12
since it is very similar to the feature of pure C66(COOH)12. After
corrections and Fourier Transforms, the related PDF functions are
also very similar (Fig. 3). The PDFs indicate that Ru NPs have a
single size distribution and an average diameter close to 1.5 nm,
in agreement with the TEM measurements.
,
SAXS analysis was performed on the Ru@C66(COOH)12 12/1
nanostructure. The scattering intensity profile (Fig. 4) shows a
global increase of the scattering intensity towards small q values,
and is thus coherent with a system constituted of NPs. At higher
-1
q values, around qmax = 0.22Å , we can observe a peak
interpreted as a correlation distance between NPs. From the peak
position, the correlation distance was found to be 2π/qmax = 2.85
nm. This value is considered as an average center to center
distance between NPs in the superstructure and is coherent with
a compact arrangement of the NPs, whose diameter is around 1.5
nm. Taking into account that the Ru NPs mean size diameter in
Ru@C66(COOH)12 12/1 nanostructure is 1.56 nm and the
diameter of the C66(COOH)12 fullerene is 1.48 nm (calculated by
DFT), the theoretical Ru NPs-Ru NPs distance is 3.04 nm, which
correlates well with the distance found by SAXS (2.85 nm).
Figure 3. Pair-distribution functions of Ru@C66(COOH)12 6/1, 12/1 and 30/1
nanostructures.
However, chemical state information may still be obtained from
observing a combination of both the Ru(3d) and the less well-used
Ru(3p) core levels, which presents a lower photoionization cross
section. XPS analyses of Ru@C66(COOH)12 12/1 are detailed in
Table S1 and Fig. S5 in the ESI.The Ru 3d and C1s peaks have
been deconvoluted into 8 peaks: O-C=O (288.5 eV), C66(COOH)12
3
sp -C (286.2 eV), C-C/C-H contamination (285.0 eV),
2
C
66(COOH)12 sp -C (284.4 eV), Ru 3d3/2 (280.5 eV) and Ru 3d5/2
(
(
284.7 eV). O1s binding energy peaks are consistent with O=C-O
533 eV), O=C-O and/or C-OH (531.5 eV), and RuO (531.1 eV).
x
Figure 2. HREM micrographs of Ru@C66(COOH)12 nanostructures: a), b)
Ru/C66(COOH)12 6/1; inset: Fast Fourier Transform (FFT) with the
corresponding orientation of the Ru lattice; and c), d) Ru/C66(COOH)12 30/1.
To confirm the short range order between the ruthenium NPs, we
performed an electron tomography analysis on
aggregate from the Ru@C66(COOH)12 12/1 nanostructure. After
D reconstruction from a tilt series of TEM images (Fig. 5, and
video in SI), the 3D coordinates of all the NPs from the aggregate
a typical
3
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Figure 4. SAXS spectrum of Ru@C66(COOH)12 12/1.
C66(COOH)12 compound in both samples, while the peaks
attributed to the carboxylic groups shifted. The peak visible at δ
45 ppm attributed to the quaternary carbon upfield shifted of 20
ppm appearing at δ 25 ppm, and the peak attributed to the -COOH
is splitted in two, with a downfield shifted to δ 185 ppm (see Figure
5b for CP-MAS13C-NMR), and still a contribution at 168 ppm. The
shift of the peaks attributed to the -COOH moieties points out that
The Ru(3p) energy of 462.5 eV is consistent with the formation of
x
RuO /Ru, and further supported by the Ru(3d) value of 280.5
eV.[ The percentage of C and O found by XPS analyses (74.6%
C, 22.2% O) was similar to the one expected for
Ru/C66(COOH)12 12/1 ratio (70.3% C, 28.8% O). The coexistence
10]
a
of RuO
x
and Ru(0) phases could be due to a coordination of
C66(COOH)12 is coordinating to the Ru NPs thought these
carboxylate ligands from C66(COOH)12 on Ru NPs.[11]
carbonyl moieties, probably in a carboxylate form. Also, the split
of the peak of the carbonyl group indicates that the COOH(1) and
COOH(2) groups do not present the same reactivity, which is
probably related to the different acidity of the two acid functions
of the malonic acid moieties. As infrared spectra can give
supplementary information of the coordination mode of the
fullerene ligands on the Ru NPs the ATR-IR spectra were
recorded for C66(COOH)12 and Ru@C66(COOH)12 6/1, 12/1 and
30/1 samples in the solid state (Fig. S6 in the ESI).
Figure 5. Electron tomography analysis of a representative aggregate from the
Ru@C66(COOH)12 12/1 sample. a) TEM image from the tilt series at 0° tilt. b)
3D model of the reconstructed volume showing the spatial distribution of all
nanoparticles forming the aggregate. c) Typical longitudinal slice extracted from
the reconstruction volume. The inserted image shows the distribution of a few
NPs around a reference one. The repetitive distance is around 2.8 nm. d) Pair
distribution function of the distances between NPs calculated from their 3D
coordinates extracted from electron tomography data. Primary peak shows a
short range order around 2.9 nm.
Solid-State NMR (SSNMR) and infrared spectroscopy, as well as
DFT calculations were performed in order to get insight into the
exact nature of the interaction between the Ru NPs and the
C66(COOH)12 species. In C66(COOH)12, the first carboxylic group,
COOH(1), of the malonic acid functional group behaves as an
almost strong acid, whereas the second COOH(2) group is a weak
acid with pK of about 5.5. Thus, we can anticipate a different
2
coordination of the COOH(1) and COOH(2) groups to the ruthenium
center. 13C-NMR SSNMR spectra of Ru@C66(COOH)12 12/1 and
3
0/1 are displayed in Figure 6 together with the spectrum of the
Figure 6. 13C-NMR spectra of a) SSNMR and b) CP-MAS SSNMR of
C66(COOH)12, Ru@C66(COOH)12 12/1 and Ru@C66(COOH)12 30/1.
functionalized fullerene. The 13C-NMR solid state NMR spectrum
of C66(COOH)12 shows a peak at δ 69 ppm and a broad signal at
1
41-145 ppm attributed to the fullerene cage. In addition, a peak
The C66(COOH)12 ATR-IR spectrum show peaks at 2900, 1700,
-1
visible at δ 45 ppm is attributed to the quaternary carbon of the
malonate moiety and a peak visible at δ 165 ppm to the carbon of
the carbonyl moieties. The 13C-NMR solid state NMR spectra of
Ru@C66(COOH)12 12/1 and 30/1 displayed the same number of
peaks. The peaks at δ 69 ppm and 141-145 ppm attributed to the
fullerene cage; remain unchanged with respect to the
1192, 830, 708, 540 and 524 cm . The intense peaks at 2900
(COOH), 1700 (C=O), and 1192 (C-O) cm-1 are attributed to the -
COOH moiety, while the other peaks are attributed to vibrations
of the fullerene cage. Ru@C66(COOH)12 6/1, 12/1 and 30/1
-
samples gave similar ATR-IR spectra. Peaks at 540 and 524 cm
1
attributed to the fullerene cage remained unchanged, while the
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-1
C=O vibration of the COOH group observed at 1700 cm , present
migration of hydrides on the Ru cluster is spontaneous, resulting
in the free ligand, is absent in the spectra of the Ru nanostructures. in the formation of carboxylate groups, with an energy gain of
Two new peaks at 1555 and 1367 cm-1 were attributed to the C=O
vibrations of a new COO-Ru species, confirming again the
coordination of the fullerene through the carboxylate moieties.
These data are in accordance with published values for Ru-
around 15 kcal/mol per H adsorbed. Globally the formation of this
complex is highly favourable: -149 kcal/mol.
Finally, we performed a preliminary study on the catalytic activity
of the Ru@C66(COOH)12 6/1, 12/1 and 30/1 catalysts for
nitrobenzene (NB) hydrogenation, and we compared their
performances to the ones obtained with a [Ru(COD)(COT)]-
carboxylate complexes.[12]
A
new peak at 1740 cm-1
corresponding to a C=O vibration, suggests that the COOH(1) and
COOH(2) groups have not a similar reactivity. The peak at around
C
66(COOH)12 homogeneous mixture. NB hydrogenation was
1
900 cm-1 could be due the bond vibration of Ru-H species.[13],[14]
studied at 30 bar H
2
and 80°C in ethanol (see ESI for details).[16]
or to partial decarbonylation of the C66(COOH)12 and further CO
adsorption on the Ru particles. In order to get better insights of
the molecular structure of the Ru@C60 hybrids, Density
Functional Theory (DFT) calculations have been performed.
To investigate the coordination modes of the functionalized C60 to
Ru NPs, we have modelled the system using two functionalized
We independently verified that under these experimental
conditions, C66(COOH)12 was not active for this reaction. The
results are presented on Table 2. The only reaction products were
aniline (AN) and N-ethylaniline (AN-Et), which is formed from N-
alkylation of AN due to reaction with the solvent, for all the
catalysts except for Ru@C66(COOH)12 30/1. For this latter
catalyst, in a first step AN is produced, and in a second step AN
is hydrogenated to cyclohexylamine (CA), which can also react
with the solvent to produce N-ethylcyclohexylamine (CA-Et). Such
a stepwise hydrogenation of NB, first to AN and then to CA has
already been reported for Ru@C60 catalysts.[16] The low metal
loaded catalysts (Ru/C60 ratio ≤12) were found to be inactive for
the hydrogenation of the aromatic ring, and AN was produced with
selectivity >80%. An explanation could be that, since complete
conversion of NB is not reached with these samples due to the
low Ru loading, the AN hydrogenation did not proceed. While the
initial activity of the Ru@C66(COOH)12 systems is relatively high
C60 in interaction with a Ru13 cluster. As shown in Figure 7, the
coordination mode implies 3 oxygens with a facet of the cluster
consisting of 3 surface Ru atoms.
-1
(
up to TOF = 89 h ), it decreases to reach a value of
-1
approximately 30 h in all Ru NPs catalysts. In contrast, the
activity of the [Ru(COD)(COT)]-C66(COOH)12 homogeneous
catalyst slightly increases with reaction time with a TOF of 18 h
-1
-1
at 1h to reach 27 h at 4h. This behavior points out that probably
the [Ru(COD)(COT)] complex decomposes during catalysis to
give Ru NPs as it can be easily decomposed in the presence of
Figure 7. Optimized structure of the C66(COOH)12-Ru13-C66(COOH)12 species.
H
2
. Indeed, a black solid was collected after reaction, pointing
towards decomposition reaction of the [Ru(COD)(COT)]
a
This result confirms the different reactivity of the COOH(1) and
COOH(2) groups, and explain the SSNMR and ATR-IR results.
The Ru-O distances are typical of such systems with values
ranging from 1.97 to 2.05 Å, in good agreement with a previous
study on the interaction of Ru NPs with oxidized carbon
nanotubes sidewalls.[15] Interestingly, as in a former study,[15] the
complex during catalysis. However, no metallic NPs have been
observed on this material by TEM; although the formation of small
clusters cannot be excluded (Figure S7 in the ESI) After reaction,
the size of the Ru NPs in Ru@C66(COOH)12 samples was not
significantly changed (Figure S7 in the ESI).
Table 2. Activity and selectivity for the nitrobenzene hydrogenation for the Ru@C66(COOH)12 and [Ru(COD)(COT)]-C66(COOH)12 catalysts.
b
Selectivity
a
b
[
Ru]
TOF
Conversion
(%)
Catalyst
(%)
-
1
(mM)
(h )
AN
89
84
85
90
AN-Et
10
CA
---
---
---
CA-Et
---
[
Ru(COD)(COT)]-C66(COOH)12 12/1
Ru@C66(COOH)12 6/1
0.66
0.37
0.66
0.86
18
89
64
88
16
---
Ru@C66(COOH)12 12/1
62
97
15
---
c
d
d
Ru@C66(COOH)12 30/1
51 (123)
100
10
80
20
Reaction conditions: 5 mg of catalyst, 500 mg (4.06 mmol) of NB, 200 mg (1.1 mmol) of dodecane (internal standard), 30 bar H
2
, 80
a)
b)
°
C, 30 mL EtOH. TOFs calculated after 1 hour reaction for nitrobenzene hydrogenation to aniline. Determined by GC-MS using
c)
the internal standard technique at 60% conversion. Value in parentheses corresponds to the TOF calculated after 1 hour reaction
for aniline hydrogenation to cyclohexylamine. d) Determined by GC-MS at 100% conversion of AN.
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micrographs from different areas of the TEM grid (at least 200 particles).
Other TEM micrographs were acquired with a JEOL 2100F S/TEM
microscope equipped with a FEG operating at 200 kV, a spherical
Conclusions
aberration probe corrector and
Experimental data for tomography were acquired by means of a JEOL
100F transmission electron microscope with a field emission gun
a GATAN Tridiem energy filter.
Hexasubstituted fullerene C66(COOH)12 is able to stabilize small
Ru NPs (1.23-1.78 nm) synthesised under mild reaction
conditions from [Ru(COD)(COT)]. SAXS and electron
tomography analyses show that Ru NPs are organized, displaying
a Ru NPs distance of 2.85 nm in the case of Ru@C66(COOH)12
2
operating at 200 kV. The tilt series of TEM bight field images were
recorded with a 2048 x 2048 pixel cooled CCD detector having a pixel size
of about 0.25 nm and a 1 s exposure time for each record. The angular
interval sampled during the acquisition was between 68 and -70°, with a
tilt increment given by a 1.7°, giving a total of 82 images. The volume
reconstructions were computed using the simultaneous iterative
reconstruction techniques (SIRT) implemented in the Tomo3d.[17]
Visualization and quantitative analysis of the calculated volumes were
carried out using Slicer and ImageJ Software.
12/1 synthesized in THF. TEM analyses together with WAXS
measurements corroborate that the Ru NPs are well crystallized
and display an hcp structure. Furthermore, IR, SSNMR and XPS
point out that the substituted fullerene coordinates to the Ru NPs
via carboxylate groups, which is corroborate by DFT calculations.
The Ru@C66(COOH)12 materials display high selectivity and
activity in nitrobenzene hydrogenation. Finally, it is important to
stress that such a methodology can be apply to a family of
materials that could find applications in many other fields than
catalysis.
DFT Calculations
DFT calculations were carried out using the Vienna ab initio simulation
package VASP.[18] The code uses the full-potential projector augmented
wave (PAW) framework.[19] Exchange-correlation effects have been
approximated using the PBE functional[20] and applied in spin-polarized
calculations. A kinetic-energy cutoff of 400 eV was found to be sufficient
to achieve a total-energy convergence within several meV, considering a
k-point sampling in Gamma-point only calculations for isolated molecules
and complexes, in conjunction with a Gaussian smearing with a width of
0.05 eV. All the atoms were fully relaxed until forces on individual atoms
were smaller than 0.01 eV/Å. Calculation cells for isolated molecules and
Experimental Section
General Methods
3
All operations were carried out under argon atmosphere using standard
Schlenk techniques or in an MBraun glovebox. Solvents were purified by
standard methods or by an MBraun SPS-800 solvent purification system.
complexes were (25x26x27) Å , to avoid spurious interactions between
periodic images. Figures of the different geometries were produced thanks
to the 3D visualization program VESTA.[21]
[
Ru(COD)(COT)] was purchased from Nanomeps Toulouse, fullerene C60
99.5%), diethyl malonate(99%), carbon tetrabromide (CBr 99%), 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU 98%), Amberlite IR-120 hydrogen
form from Sigma-Aldrich, CO and H from Air Liquid. All these reactants
were used as received. The ruthenium content in the products was
measured by inductively coupled plasma optical emission spectroscopy
(
4
SAXS, WAXS and XPS analyses
2
The samples were characterized by small-angle X-ray scattering (SAXS)
on a Nanostar (Bruker Co.), equipped with a Siemens Copper anode (40kV,
35mA). The apparatus is equipped with two crossed Goebel mirrors in
(ICP-OES) performed at the LCC with a Thermo Scientific ICAP 6300
order to select the CuKα wavelength (0.154 nm) and produces a parallel
beam, the final collimation being adjusted with a three-pinhole setup (with
a 300 µm diameter for pinhole-2 setting the beam size). SAXS patterns
were acquired using a 22 × 22 cm 2D gas detector HiStar from Bruker Co.,
positioned at a distance D of the sample. Silver behenate was used as a
instrument. Solid state NMR (MAS-NMR) with and without 1H-13C cross
polarization (CP) were performed at the LCC on a Bruker Avance 400WB
instrument equipped with a 4 mm probe with the sample rotation frequency
being set at 12 kHz, unless otherwise indicated. Measurements were
carried out in a 4 mm ZrO
Bruker Fourier 300 systems using CDCl
2
rotor. Liquid NMR spectra were obtained on
/d-acetone as solvent, TMS as
calibration standard, yielding D = 1.06 m. The scattering wave vector range
used was 0.1–2.0 nm−1. Wide Angle X-ray Scattering measurements were
3
internal standard, with proton and carbon resonances at 300 and 75 MHz,
respectively. ATR-IR spectra were recorded on a Perkin-Elmer GX2000
spectrometer installed in a glovebox, in the range 4000-400 cm−1. GC-MS
analyses were performed in a PerkinElmer Autosystem GC equipped with
an Elite-5MS Capillary Column (30 m × 0.25 mm × 0.25 µm) coupled to a
Turbo Mass mass spectrometer. Hydrogenation reactions were performed
in Top Industry high pressure and temperature stainless steel autoclave
with a controlling system.
performed at CEMES on a diffractometer dedicated to Pair Distribution
Function (PDF) analysis: graphite-monochromatized Molybdenum
radiation (0.07169 nm), solid state detection and low background setup.
Samples were sealed in Lindemann glass capillaries (diameter 1.5mm) to
avoid any oxidation after filling in a glove box. For all samples data were
collected on an extended angular range (129 degrees in 2theta) with
counting times of typically 150s for each of the 457 data points, thus
allowing for PDF analysis. Classic corrections (polarization and absorption
in cylindrical geometry) were applied before reduction and Fourier
transform. The samples were also analyzed by X-ray photoelectron
spectroscopy (XPS) using a VG Escalab MKII spectrophotometer, which
operated with a non monochromatized Mg K source (1253.6 eV).
TEM analyses
TEM and HRTEM analyses were performed at the “Centre de
microcaracterisation Raimond Castaing, UMS 3623, Toulouse” by using a
JEOL JEM 1011 CX-T electron microscope operating at 100 kV with a
point resolution of 4.5 Å and a JEOL JEM 1400 electron microscope
operating at 120 kv. The high resolution analyses were conduct using a
JEOL JEM 2100F equipped with a Field Emission Gun (FEG) operating at
Synthesis of fullerene derivatives
C
T
66(COOH)12 was synthesized by reaction of an excess of NaH with the
-hexa-adducts diethyl malonate fullerene C66(COOEt)12,[22] which was
h
200 kV with a point resolution of 2.3 Å and a JEOL JEM-ARM200F Cold
synthesized by nucleophilic cyclopropanation of fullerene C60 with diethyl
bromo-malonate using a previously described procedure.[23]
FEG operating at 200 kV with a point resolution of >1.9 Å. The particles
size distribution was made through a manual measurement of enlarged
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Chemistry - A European Journal
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OEt OEt
O
Ru@C66(COOH)12 6/1: 100 mg (0.32 mmol) of [Ru(COD)(COT)]; 70.4 mg
(0.053 mmol) of C66(COOH)12 and 150 mL of THF. Yield: 82 mg. Ru: 22.6%
O
EtO
EtO
O
O
O
O
OEt
OEt
Ru@C66(COOH)12 12/1: 113.5 mg (0.36 mmol) of [Ru(COD)(COT)]; 45 mg
0.035 mmol) of C66(COOH)12 and 100 mL of THF. Yield: 69mg. Ru: 40.7%
(
O
O
O
O
Ru@C66(COOH)12 30/1: 282 mg (0.90 mmol) of [Ru(COD)(COT)]; 40 mg
0.033 mmol) of C66(COOH)12 and 90 mL of THF. Yield: 116 mg. Ru: 52.4%.
EtO
EtO
OEt
OEt
(
O
O
OEt OEt
Ru@C66(COOH)12 50/1: 41.7 mg (0.13 mmol) of [Ru(COD)(COT)]; 3.5 mg
0.003 mmol) of C66(COOH)12 and 10 mL of THF. Yield: 5 mg.
(
General procedure for the hydrogenation of nitrobenzene
4
C66(COOEt)12. CBr (22.8g, 69.5 mmol), diethyl malonate (1.104 g, 6.9
mmol) and DBU (2.1 g, 13.8 mmol) were dissolved in dry toluene (500 ml)
and the solution was successively added to a fullerene C60 solution (500
mg, 0.7 mmol). The reaction was allowed to react during 4 days. The
reaction crude was purified by flash chromatography using a toluene/ethyl
acetate mixture. The product was isolated as a yellow solid (580 mg, 49%
Hydrogenation reactions were performed in a Top Industry high pressure
and temperature stainless steel autoclave with a controlling system. In a
typical experiment, the autoclave was purged by three vacuum/argon
cycles. The mixture of
[
[
5
mg of Ru@C66(COOH)12 catalysts (for
Ru(COD)(COT)]-C66(COOH)12 12/1 homogeneous catalyst: 6.2 mg of
Ru(COD)(COT)] and 2.4 mg of C66(COOH)12), dodecane (as internal
yield). 1H-NMR (CDCl
CH -), 1.33 (t, J = 7.11 Hz, 36H, -CH
δ= 164 (C=O), 146 (sp -C C60), 141 (sp -C C60), 69.2 (sp -C C60), 62.9 (-
, 300 MHz, ppm): δ= 4.33 (q, J = 7.14 Hz, 24H, -
3
); 13C-NMR (CDCl
2
3
3
, 75 MHz, ppm):
standard, 200 mg, 1.1 mmol) and nitrobenzene (500 mg, 4.06 mmol) in 30
mL of ethanol was prepared in a glovebox, ultrasonicated for 5 min and
then transferred into a high-pressure autoclave under argon atmosphere.
The autoclave was heated to 80°C and pressurized with 30 bar of H2; the
stirring rate was fixed at 1000 rpm. Samples of the reaction mixture were
taken periodically and then analyzed by GC-MS. Quantitative analysis of
reaction mixtures was performed via GC-MS using calibration solutions of
commercially available products.
2
2
3
2 3
CH -), 45.5 (tert-C), 14.2 (-CH ).
OH OH
O
O
HO
HO
O
O
O
OH
OH
O
O
O
O
Acknowledgements
HO
HO
OH
OH
O
O
O
This work was supported by the Centre National de la Recherche
Scientifique (CNRS), which we gratefully acknowledge. The
authors acknowledge financial support from the program of China
Scholarships Council (CSC) for F. L. grant. I.C. Gerber also
acknowledges the Calcul en Midi-Pyrénées initiative-CALMIP
OH OH
C66(COOH)12. C66(COOEt)12 (200 mg, 0.119 mmol) was dissolved in 50
mL of toluene, and NaH (57.2 mg, 2.38 mmol) was slowly added to the
solution. The resulting mixture was stirred 3h at 75 °C. The reaction
mixture was centrifuged, after the precipitate was washed with toluene
three times (10 ml). Afterwards the crude was dissolved in distilled water
and the solution passed through a resin (Amberlite IR-120 hydrogen form).
The water was evaporated to afford a yellow-brown solid (127 mg, 80%
yield).C13-NMR (d-acetone, 75 MHz, ppm): δ= 164.7 (C=O), 146.3 (sp -C
(
Project p0812) for allocations of computer time and GENCI-
IDRIS and CINES through the project x2016096649. We also
thank the European Research Council (ERC-320441-
Chirallcarbon), and the CAM FOTOCARBON project S20.
2
Keywords: Ru • Fullerenes • C60 • Nanomaterials • Polymers
2
3
C
60), 142.5 (sp -C C60), 70.4 (sp -C C60), 47.7 (tert-C). IR (ATR): ν 2900
COOH), 1700 (C=O), 1192 (C-O), 830, 708, 540 (-C60), 524 (-C60). Anal.
Calcd. for C78 12 (1332 g/mol): C, 70.3; H, 0.01. Found: C, 60; H, 1.8.
(
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vacuum. Pentane was then added to the colloidal suspension to precipitate
the Ru@C66(COOH)12 nanostructures. After filtration under argon with a
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FULL PAPER
We report the synthesis of Ru
F. Leng, I. C. Gerber, P. Lecante, A.
Bentaleb, A. Muñoz, B. M. Illescas, N.
Martín,G. Melinte, O. Ersen, H.
nanoparticle assemblies with a control
of interparticle distances via covalent
bonds with functional molecules.
*
*
Martinez, M. R. Axet and P. Serp
Page No. – Page No.
Hexakis [60]Fullerene Adduct-
Mediated Covalent Assembly of
Ruthenium Nanoparticles and Their
Catalytic Properties
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