Microwave-assisted post-synthesis modification of layered simple hydroxides

Article abstract of DOI:10.1039/c3nj01231j

A new method to functionalize layered simple hydroxides by post-synthesis modification is described. A layered cobalt hydroxide was modified with a molecule bearing a free amino group. We show here that it is possible to post-functionalize the metal hydroxide layers by performing in situ microwave assisted reactions with the free amino group, constituting a new appealing strategy for functionalization of layered solids. The obtained compounds are characterized by ancillary techniques and their magnetic properties were investigated, which show that the inorganic magnetic layers are not deeply affected by the post-functionalization process.

Full text of DOI:10.1039/c3nj01231j

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Microwave-assisted post-synthesis modification
of layered simple hydroxides†
O. Palamarciuc,abc E. Delahaye,ab P. Rabuab and G. Rogez*ab
Cite this: New J. Chem., 2014,
38, 2016
A new method to functionalize layered simple hydroxides by post-synthesis modification is described.
A layered cobalt hydroxide was modified with a molecule bearing a free amino group. We show here
that it is possible to post-functionalize the metal hydroxide layers by performing in situ microwave
assisted reactions with the free amino group, constituting a new appealing strategy for functionalization
of layered solids. The obtained compounds are characterized by ancillary techniques and their magnetic
properties were investigated, which show that the inorganic magnetic layers are not deeply affected by
the post-functionalization process.
Received (in Montpellier, France)
7th October 2013,
Accepted 20th November 2013
DOI: 10.1039/c3nj01231j
www.rsc.org/njc
fact that they proceed by anion-exchange reaction, especially
effective in aqueous medium at basic pH (typically around pH = 8).
Introduction
Since the discovery of the outstanding electronic properties of The pre-intercalation strategy allows for partial stabilization of
the graphene derivatives,1 the research into functional nano- species sensitive to hydrolysis, by creating a hydrophobic
materials has been increasingly concerned with the conception environment in-between the inorganic layers.15 But the ion-
of new multifunctional nanosheet-based systems,2,3 with inten- exchange reaction still requires the use of water, even when pre-
sification of research in the field of layered materials.4,5 Among intercalation is used. This severely limits the type of molecules
the possible chemical routes, the hybrid organic–inorganic that can be considered to be grafted in the interlamellar space.
approach is particularly well suited to promote multifunction- To overcome this difficulty, one solution is to synthesize in situ
ality within a single material. It is indeed possible to control the (in the interlamellar space) the desired molecules from a pre-
assembly at the nanoscale level of two components, each grafted functional precursor. Thus, only the first stage (grafting
bearing its own properties.6–8 In that way, each sub-network the precursor) requires the use of insertion-grafting conditions
exhibits its own properties or contributes synergistically to new by anion exchange. The following reactions may appeal to a
physical phenomena and novel applications.9,10
much larger panel of conditions, including the use of non-
Transition metal layered simple hydroxides (LSH), of general aqueous solvents. Confinement of the reaction space may also
formula MII2(OH)3(X)ꢀmH2O (M = Co, Cu, Ni and X is an easily have specific effects on the synthesis.
substitutable anion, nitrate or acetate for instance), are very
The post-synthesis modification strategy has been widely
well adapted to grafting reactions of various organic molecules. developed for Metal Organic Frameworks20–27 or for meso-
We and others have recently obtained hybrid compounds based porous silicates.28,29 Yet, to our knowledge it has seldom been
on LSH functionalized with (oligo)thiophenes,11,12 azo dyes,13 used in layered materials. One noticeable example concerns the
diarylethene,14 or complexes of transition metals.15–19 We have controlled 2D growth of Prussian blue analogues in the inter-
notably developed a pre-intercalation procedure which enables lamellar space of Layered Double Hydroxides (LDH).30,31 In this
the insertion–grafting of large molecules due to the pre- example, a Prussian blue analogue is synthesized in a two-step
swelling of the layered host.13 However, a major drawback of reaction. Hexacyanometalate is first inserted in the interlamellar
the functionalization reactions of layered hydroxides lies in the space of LDH, then a M(II) salt is reacted with the hybrid, and
the in situ reaction leads to the formation of a Prussian blue
analogue in-between the inorganic layers. Another example deals
a
´
Institut de Physique et Chimie des Materiaux de Strasbourg, UMR 7504
with confined synthesis of pyridinic and pyrrolic nitrogen-doped
graphene in layered montmorillonite.32 Yet, stricto-sensu, these
examples are not really representative of a post-synthesis modi-
fication. According to Cohen,22 post-synthesis modification can
be broadly defined as ‘‘a chemical derivatization of MOFs after
their formation’’; in a more strict sense, it may refer only to
those modifications involving covalent bonds22 or dative bonds25
´
CNRS - Universite de Strasbourg, and Labex NIE, 23 rue du Loess, BP 43,
67034 Strasbourg cedex 2, France. E-mail: rogez@unistra.fr
b Fondation icFRC International Center for Frontier Research in Chemistry,
´
8, allee Gaspard Monge, F-67000 Strasbourg, France
c State University of Moldova, Mateevici 60, Chisinau MD-2009,
Republic of Moldova
† Electronic supplementary information (ESI) available: SEM images of all
compounds. See DOI: 10.1039/c3nj01231j
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with the framework or deprotection.25 (In the present proposed
extension of definition ‘‘MOFs’’ may be replaced by ‘‘hybrid
solids’’.)
We report in this article the post-synthesis modification of a
Co LSH, functionalized with p-amino-benzoic acid. We show
that the amine groups react in situ with various aldehydes
(aliphatic and aromatic) to form imines (azomethine groups).
Interestingly, conventional activation (heating) is inefficient in
the present case, whereas microwave irradiation enables the
in situ reaction. This technique constitutes a new appealing
strategy for functionalization of layered structures.
Results and discussion
Scheme 1 Post-synthesis modification strategy.
We investigated the functionalization of layered cobalt hydroxide
acetate, Co2(OH)3(OAc)ꢀH2O, the structure of which is presented
in Fig. 1.
ethanol as solvent (20 mL in a sealed microwave tube of 30 mL),
0.5 moles of 1, 3 equivalents of aldehyde and 30 W microwave
irradiation for 10 min. Under these conditions the pressure in
the microwave tube reached typically 9 bar and the temperature
increased up to 140 1C. Microwave activation has proved to be
particularly useful to accelerate reactions, to increase the yields
and the purity of compounds under milder reaction conditions
and to obtain products which cannot be obtained otherwise.
It has essentially been used in organic chemistry,37 but also in
coordination chemistry38–40 and in materials chemistry.41,42
It has also been used for the post-functionalization of nano-
particles43 or of MOFs,25,44–47 but to the best of our knowledge
it is the first time microwave heating is used for the internal
post-synthesis modification of layered hybrid solids which are
stable in a reduced range of pH.
It is worth noting here that it has not been necessary to preli-
minarily dehydrate the starting compound (4-NH2–BzAc)CCo (1)
even though it contains 2.4 water molecules per formula unit.
It was neither necessary to remove water which forms during
the reaction, contrary to what is usually done to displace the
equilibrium of reactions which produce water as a by-product
(using molecular sieves for instance, or Dean–Stark apparatus).
The water molecules which form remain within the product,
as attested by elemental analysis, and are probably engaged in
H-bonding with the inorganic hydroxy network.
The general strategy we have followed is schematized in
Scheme 1. We have chosen the in situ formation of various alkyl
or aryl imino-benzoates as a model reaction to validate the
concept of post-functionalization in layered metal hydroxides.
In the first step, a layered Co hydroxide was functionalized
with p-amino-benzoic acid providing (4-NH2–BzAc)CCo (1) by
classical anion exchange. The initial pH has to be carefully set
at 8 ꢁ 0.2. Larger values lead to low crystallinity and to Co-oxide
impurities, whereas lower values lead to a mixture of unidenti-
fied non-lamellar phases. The use of ethanol along with water
(ethanol–water = 1/4 (v : v)) is also crucial, as ethanol may serve
as an antioxidant.
The second step deals with the post-functionalization itself.
Compound 1 is made to react with aldehydes, which likely
condense with the free amino groups to give imines, sketched
in Scheme 1, and water. Yet, all attempts to perform this
reaction using classical heating (up to 80 1C), in dry solvents
(alcohols, toluene, and chloroform) led to the recovery of the
starting material. In order to overcome this difficulty, the reactions
were then performed using microwave activation under auto-
geneous pressure. The best conditions were found to be: absolute
Two kinds of aldehyde have been chosen to react with the amino
group of the pre-grafted amino-benzoate: aliphatic aldehydes,
with various alkyl chain lengths (butanal, pentanal, hexanal and
dodecanal) and one aromatic aldehyde (4-cyanobenzaldehyde),
bearing a cyano group to serve as an IR marker.
In addition, the imine LH formed from the condensation of
4-aminobenzoic acid with 4-cyanobenzaldehyde was isolated
and further grafted into the interlamellar space of Co2(OH)3-
(OAc)ꢀH2O by ‘‘classical’’ ion exchange. This compound, denoted
6ae, served for comparison with the compound obtained by in situ
reaction, denoted 6is. Notably, it has not been possible to insert
the other preformed imine ligands by ion-exchange. The yields
of the post-synthesis modification reactions are all around 80%.
The yield of 6ae is notably lower, around 60%. This underlines
%
Fig. 1 Structure of Co2(OH)3(OAc)ꢀH2O (R3m, a = 0.313 nm, c = 1.27 nm,
a-Co(OH)2 polytype).33–36 Pink and purple polyhedra hold for Co(II) ions in
octahedral and tetrahedral sites respectively.
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Fig. 2 Powder X-ray diffraction patterns for compounds 1–5, 6is, 6ae and
the starting compound Co2(OH)3(OAc)ꢀH2O (black).
Fig. 3 Correlation between the interlamellar distance of the hybrid com-
pounds and the size of the molecule inserted or synthesized in situ. Color
stands for the family of compounds (black for the starting compound 1, red
for the compounds with aliphatic chains 2–5, and green for the com-
pounds with the cyanobenzyl group 6is and 6ae).
the relative efficiency of the microwave assisted post-synthetic
modification with respect to functionalization by ion exchange.
Interestingly, despite the reversible character of the imine
formation reaction, it has not been possible to hydrolyze the
imine formed within the interlamellar space (while keeping the
integrity of the inorganic host), regardless of the activation
used (classical or microwave).
suggesting a lower crystallinity. Thus in situ post-synthesis
modification leads to the same material as direct ion exchange.
Even though it is not possible to claim from elemental analysis
that only the in situ formation of imine took place, the results of
the elemental analysis confirm the presence of additional organic
moieties with respect to the starting compound 1. The post-
synthesis modification procedure induces a small loss of the
grafted ligand: with respect to the general formula Co2(OH)4ꢂx(L)x,
x = 0.65 for 1, whereas x is slightly smaller for 2–5 and for 6is,
ranging from 0.43 to 0.53. For 6ae x is of the same order of
magnitude as for 1 (x = 0.62). This observation underlines that
despite post-synthesis modification is supposed to let the inorganic
matrix untouched, the mechanism is most probably more compli-
cated. The inorganic network probably readjusts its structure to
adapt the layers to the new molecular area of the organic compo-
nents. In the case of compounds obtained by in situ reaction, this
rearrangement leads to partial leaching of amino-benzoate
molecules. Therefore, compounds 6ae and 6is, although of
similar structure, are slightly different in composition.
Unfortunately, the attempts to characterize the functionalization
of the samples by means of solid state 13C NMR spectroscopy were
unsuccessful. This is likely due to a broadening of the signal caused
by the slowly relaxing paramagnetic CoII ions. Nevertheless, the
compounds were further characterized by infrared spectroscopy
(Fig. 4). Principal characteristic bands are collected in Table 2.
The first noticeable feature is that in all hybrid compounds
1–5, 6is and 6ae, the position of the carboxylate vibration bands
hardly changes. The asymmetric band corresponding to the
asymmetric vibration mode is around 1540 cmꢂ1 whereas the
one corresponding to the symmetric vibration mode is around
1390 cmꢂ1. For comparison, these bands are located at 1682 cmꢂ1
and 1429 cmꢂ1, respectively, for the free ligand LH. The
position of the bands as well as the value of Dn = nas ꢂ ns
indicates that the carboxylate is coordinated to the inorganic
layers, in a unidentate mode.49–52
The products were first characterized by powder X-ray diffrac-
tion (Fig. 2).
The XRD pattern of all compounds shows intense 00l diffraction
peaks at low angle which evidences their lamellar structure. For 1,
6ae and 6is, up to four harmonics are visible, whereas for com-
pounds 2–5, only two harmonics are visible, which underlines their
lower crystallinity. In the high angle region, all XRD patterns exhibit
similar asymmetrical peaks at 2y = 331 (Cu Ka1 = 0.1540598 nm)
corresponding to in-plane diffraction lines. The asymmetry
suggests turbostratic disorder. The interlamellar distances for
all compounds are collected in Table 1.
The important feature is that the interlamellar distance increases
gradually when the size of the aldehyde increases. For small alkyl
chains (compounds 2, 3 and 4), the variation of the interlamellar
spacing is linear with the number of carbon atoms of the alkyl
chain. For the long alkyl chain (compound 5) a discontinuity occurs
(with respect to the other aliphatic compounds) which is likely
due to a change in the interdigitation of the molecules. Fig. 3
shows a clear correlation between the size of the molecule48
which is supposed to form in the interlamellar space and the
interlamellar distance of the hybrid compounds, which constitute
further evidence for the in situ reaction.
The XRD patterns of 6is and 6ae are similar, but the XRD
pattern of 6ae reveals slightly broader peaks, especially at 331,
Table 1 Interlamellar spacing of the hybrid compounds 1–5, 6is and 6ae
Interlamellar
distance (nm)
Compound
Inserted molecule
Co2(OH)3(OAc)ꢀH2O
OAc
4-NH2–BzAc
1.27
1.56
1.88
1.90
1.92
2.81
2.07
2.07
1
2
3
4
5
6is
6ae
AcBz–NQCH–C3H7
AcBz–NQCH–C4H9
AcBz–NQCH–C5H11
AcBz–NQCH–C11H23
AcBz–NQCH–Bz–CN
AcBz–NQCH–Bz–CN
In 1, the bending vibration of the free amine groups is
visible at 1610 cmꢂ1 whereas their stretching vibration at
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Fig. 5 SEM images of compounds 1 (left) and 4 (right).
Fig. 4 FTIR spectra of compounds 1–5, 6is, 6ae and of the imine LH.
higher energy is masked by the stretching vibration of the water
molecules.
The similarity between the spectra of 6is and 6ae confirms
that the two compounds are indeed identical as evidenced from
elemental analysis and X-ray diffraction.
Several features confirm that additional organic moieties are
present in the hybrid compounds. The CH2 and CH3 vibrations
are clearly identified in the 2850–3000 cmꢂ1 region for com-
pounds 2–5. In addition, the intensity of these bands increases
with the length of the alkyl chain of the aldehyde used. For
6ae and 6is, the cyanide vibration band is clearly visible at
Fig. 6 wT = f (T) under 0.5 T for compounds 1 (red), 2 (dark blue), 3 (light
green), 4 (brown), 5 (dark green), 6is (light blue) and 6ae (purple).
2235 cmꢂ1 indicating the presence of the cyanobenzene moiety. with the lamellar character of their structure. No particular
Finally indications concerning the effectiveness of the in situ difference in shape, size or morphology was noticed whether
formation of the imine functions in the hybrid compounds 2–5 the compounds were obtained by post-synthesis modification
and 6is are given by the disappearance of the NH2 bending or by anion exchange.
vibration at 1610 cmꢂ1, the absence of the characteristic vibra-
tion of the aldehyde group at 1700 cmꢂ1 and the appearance in The Curie constants, determined from the fit of 1/w = f(T) to the
all compounds of the imine vibration band around 1600 cmꢂ1 Curie–Weiss law, are all within the range 5.69–6.27 emu K molꢂ1
The magnetic behaviors of all compounds are much alike (Fig. 6).
.
,
The SEM images of compounds 1 and 4 are shown in Fig. 5 in agreement with the presence of a mixture of tetrahedral and
and are representative of all hybrid compounds reported here octahedral high-spin Co(II) ions.53 Upon cooling, the wT pro-
(see Fig. S1, ESI†). They are obtained as thin platelets, in agreement ducts of all compounds decrease slowly down to a minimum
Table 2 Characteristic infrared absorption bands
Compound
n(CRN) (cmꢂ1
)
d(NH2) (cmꢂ1
)
n(CQN) (cmꢂ1
)
n
as(OAc) (cmꢂ1
)
ns(OAc) (cmꢂ1
)
Dn (cmꢂ1
)
Co2(OH)3(OAc)ꢀH2O
/
/
/
/
/
/
/
/
/
1568
1528
1539
1541
1539
1543
1546
1543
1682
1403
1393
1386
1387
1385
1386
1385
1391
1429
165
135
153
154
154
157
161
152
253
1
1610
2
3
4
5
6is
6ae
LH
/
/
/
/
/
/
/
1606
1603
1605
1603
1593
1594
1592
2235
2235
2222
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Fig. 8 M = f (H) at 1.8 K for compounds 1 (red), 2 (dark blue), 3 (light green),
4 (brown), 5 (dark green), 6is (light blue) and 6ae (purple) (full lines are just
guides for the eye). Inset: zoom of the ꢂ1/+1 T region.
Fig. 7 In-phase susceptibility (w0, bottom, open circles) and out-of-phase
susceptibility (w00, top, open squares) for compounds 1 (red), 2 (dark blue),
3 (light green), 4 (brown), 5 (dark green), 6is (light blue) and 6ae (purple)
(full lines are just guides for the eye).
than the ones of compounds 2–5 (14.9 K, 16.7 K, 13.2 K and
13.0 K respectively). This feature is reminiscent of what has been
described in the case of layered Ni(II) organophosphonates.54
In this family, the magnetic behaviour of the compounds func-
tionalized with long alkyl chain organophosphonates is much
different than that of compounds functionalized with short alkyl
chain organophosphonates, or with aromatic organophosphonates.
This has been ascribed to the chemical pressure induced by the
long alkyl chains onto the magnetic layers.54–56 The resulting
distorsions may cause some changes in the in-plane superexchange
pathways and in the size of the 2D correlation domains.57 More-
over, different magnetic dimensionalities (2D to 3D) were pointed
out, highlighting the possible role of interlamellar p–p interactions
in the interlayer coupling. In the present series of compounds,
p-stacking interactions (in the case of 1, 6is, and 6ae) or
H-bonding interactions (in the case of 1) may be responsible
for the slightly different coupling mechanism between the
layers and hence of different ordering temperature.
around 100 K. This behaviour is attributed to spin–orbit
coupling for high-spin Co(II) ions in octahedral sites, and/or
to antiferromagnetic interactions between the spin carriers.
Below this minimum, the wT products diverge, up to a field
dependent maximum (around 20 K here under 0.5 T), which is
due to the saturation effect.
This peculiar behaviour is attributed to the occurrence of a
long range ferromagnetic-type ordering. The ordering tempera-
tures are further determined from the maximum of the in-phase
susceptibility, around 15 K for compounds 2–5, and around 20 K
for compounds 1, 6is and 6ae (Fig. 7, and Table 3).
The ferromagnetic-type behaviour is confirmed by the occur-
rence of out of phase signals. Accordingly, the low temperature
magnetization vs. field curves (Fig. 8) show the presence of
hysteresis loops, with coercive fields around 0.25 T (Table 3).
The low value of the moments at high fields, much lower than
expected for the total alignment of the moments (4–6 mB for two
Co(II) ions), supports a ferrimagnetic ordering.18,53
The resemblance between the magnetic behaviours of all
compounds underlines that the post-synthesis modification
does not deeply alter the magnetic properties of the parent
compound 1. Yet two tendencies can be distinguished. The
ordering temperatures of compounds 1, 6is and 6ae (21.0 K,
19.8 K and 21.0 K respectively) are indeed significantly larger
Conclusions
We have shown here that in addition to classical ion-exchange
reactions, the functionalization of layered simple hydroxides can
also proceed via post-synthesis modification. Post-synthesis
modification allows functionalizing LSH in non-aqueous solvent,
which is a major advantage. Indeed, LSH may be unstable in
water at too low or too high pH. Moreover, the molecules to
functionalize the LSH with may be unstable under the condi-
tions of classical ion-exchange. Therefore synthesizing them
in situ is an interesting strategy to overcome this difficulty.
In this paper we validate the feasibility of such procedure in the
case of layered simple hydroxides. We underline the advantage of
microwave activation, since classical thermal activation is ineffi-
cient in the present case. To the best of our knowledge, it is the
first time microwave activation is used to perform post-synthesis
Table 3 Magnetic characteristics of compounds 1–5, 6is and 6ae
C (emu K molꢂ1
)
TN (K)
m0Hc (T)
M(7 T) (mB)
1
2
3
4
5
6is
6ae
6.29
6.27
6.11
5.87
6.20
6.45
5.69
21.0
14.9
16.7
13.2
13.0
19.8
21.0
0.50
0.32
0.36
0.22
0.23
0.33
0.39
2.1
2.5
2.3
2.2
2.6
2.5
2.2
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modification of layered solids. We are currently working to
extend this strategy to the in situ synthesis of other molecules,
in order to bring new properties to layered magnetic materials, 17.47; H, 3.29; N, 2.62; calcd: Co, 38.45; C, 17.83; H, 3.96; N, 2.97.
such as luminescence for instance. This strategy may further be IR (KBr pellet, cmꢂ1): 3385 (s), 1610 (s), 1528 (s), 1512 (s), 1393 (s),
applied to the functionalization of other kinds of layered 1177 (m) 852 (w), 789 (m), 635 (w), 501 (w).
materials (clays, LDH, layered oxalates, etc.). It thus opens up
Anal. for Co2(OH)3.35(4-NH2–BzAc)0.65ꢀ2.4 H2O: Co2C4.55H7.25
-
N
0.65O4.65ꢀ2.4 H2O (M = 306.55 g molꢂ1) found (%): Co, 37.92; C,
Q
(AcBz–N CH–C3H7)CCo (2)
very promising perspectives for the introduction of new func-
tionalities in layered materials, unattainable with the classical 1 (153 mg, 0.5 mmol), butyraldehyde (butanal) (108 mg, 1.5 mmol)
functionalization processes.
and 20 mL of absolute ethanol were introduced in a 30 mL sealed
microwave vessel. The mixture was placed under the microwave
irradiation (30 W) for 10 min. The dark green powder was
collected by filtration, washed with ethanol and dried under
vacuum. Yield: 80%.
Experimental
Chemicals were of reagent grade (Alfa-Aesar and Aldrich (cobalt
acetate)) and were used without further purification. Microwave
syntheses were performed using a microwave synthesis reactor
Monowave 300 (Anton Paar). Elemental analyses for C, H, N,
and Co were carried out at the Service Central d’Analyse of the
CNRS (USR-59). The powder XRD patterns were collected using
a Bruker D8 diffractometer (Cu Ka1 = 0.1540598 nm) equipped
with a SolX detector with energy discrimination. The SEM
images were obtained using a JEOL 6700F (scanning electron
microscope (SEM) equipped with a field emission gun, operat-
ing at 3 kV in the SEI mode). FT-IR spectra were collected on a
Digilab FTS 3000 computer-driven instrument (0.1 mm thick
powder samples in KBr). Solution 1H NMR spectra were
recorded using a Bruker AVANCE 300 (300 MHz) spectrometer.
The internal references of the spectrum correspond to the peak
of the non-deuterated solvent. The magnetic studies were carried
out using a SQUID magnetometer (Quantum Design Squid-VSM)
covering the temperature and field ranges 2–300 K, ꢁ7 T.
ac susceptibility measurements were performed in a 0.20 mT
alternative field (95 Hz). Magnetization measurements at
different fields at room temperature confirm the absence of
ferromagnetic impurities.
Anal. for Co2(OH)3.47(AcBz–NQCH–C3H7)0.53ꢀ2.8 H2O: Co2C5.83
-
H
9.83N0.53O4.53ꢀ2.8 H2O (M = 328.13 g molꢂ1) found (%): Co, 35.99;
C, 21.26; H, 3.73; N, 2.04; calcd: Co, 35.92; C, 21.34; H, 4.73;
N, 2.26. IR (KBr pellet, cmꢂ1): 3426 (s), 2962 (m), 2928 (m),
2873 (w), 1606 (s), 1539 (s), 1386 (s), 1178 (m) 849 (w), 788 (m),
622 (w), 509 (w).
(AcBz–N = CH–C4H9)CCo (3)
1 (153 mg, 0.5 mmol), valeraldehyde (pentanal) (129 mg, 1.5 mmol)
and 20 mL of absolute ethanol were introduced in a 30 mL sealed
microwave vessel. The mixture was placed under the microwave
irradiation (30 W) for 10 min. The dark green powder was collected
by filtration, washed with ethanol and dried under vacuum.
Yield: 80%.
Anal. for Co2(OH)3.53(AcBz–NQCH–C4H9)0.47ꢀ2.9 H2O: Co2C5.64
-
H
10.11N0.47O4.47ꢀ2.9 H2O (M = 326.13 g molꢂ1) found (%): Co, 36.17;
C, 20.76; H, 3.23; N, 1.74; calcd: Co, 36.13; C, 20.77; H, 4.92;
N, 2.02. IR (KBr pellet, cmꢂ1): 3426 (s), 2958 (m), 2930 (m), 2868 (w),
1603 (s), 1541 (s), 1387 (s), 1179 (m) 1056 (w), 786 (m).
Q
(AcBz–N CH–C5H11)CCo (4)
1 (153 mg, 0.5 mmol), hexanal (150 mg, 1.5 mmol) and 20 mL of
absolute ethanol were introduced in a 30 mL sealed microwave
vessel. The mixture was placed under microwave irradiation (30 W)
for 10 min. The dark green powder was collected by filtration,
washed with ethanol and dried under vacuum. Yield: 80%.
Co2(OH)3(OAc)ꢀH2O was prepared as previously described.14,58,59
LH
The imine ligand was synthesized by mixing 4-aminobenzoic acid
(1.37 g, 10 mmol) and 4-cyanobenzaldehyde (1.31 g, 10 mmol) in
60 mL of absolute ethanol. After refluxing for 2 h, the reaction
was cooled to 5 1C using an ice bath. The light yellow compound
was collected by filtration, washed with cold absolute ethanol and
dried under vacuum. Yield: 65%.
Anal. for Co2(OH)3.57(AcBz–NQCH–C5H11)0.43ꢀ2.3 H2O: Co2C5.59
-
H
10.45N0.43O4.43ꢀ2.3 H2O (M = 313.87 g molꢂ1) found (%): Co, 37.29;
C, 21.32; H, 3.83; N, 1.95; calcd: Co, 37.55; C, 21.39; H, 4.83; N, 1.92.
IR (KBr pellet, cmꢂ1): 3425 (s), 2927 (m), 2858 (w), 1605 (s), 1539 (s),
1385 (s), 1179 (m), 789 (m), 618 (w), 507 (w).
1H NMR (300 MHz, [D6]DMSO): d = 12.92 (1H, s), 8.73 (1H, s),
8.10 (2H, d, J = 8.3 Hz), 7.99 (4H, d, J = 8.3 Hz), 7.35 (2H, d,
J = 8.3 Hz) ppm.
Q
(AcBz–N CH–C11H23)CCo (5)
1 (153 mg, 0.5 mmol), dodecanal (276 mg, 1.5 mmol) and 20 mL
of absolute ethanol were introduced in a 30 mL sealed micro-
wave vessel. The mixture was placed under microwave irradia-
(4-NH2–BzAc)CCo (1)
4-Aminobenzoic acid (4-NH2–BzAc) (822 mg, 6 mmol) was tion (30 W) for 10 min. The dark green powder was collected
dissolved in water (160 mL) and the pH was adjusted to 8 using by filtration, washed with ethanol and dried under vacuum.
NaOH (0.2 mol Lꢂ1). At this stage, Co2(OH)3(OAc)ꢀH2O (496 mg, Yield: 80%.
2 mmol) was added along with 40 mL of ethanol. The mixture
was stirred under argon at room temperature for 48 h. The dark
green powder was collected by filtration, washed with water and 28.86; C, 28.35; H, 4.97; N, 1.86; calcd: Co, 28.95; C, 28.59; H,
Anal. for Co2(OH)3.49(AcBz–NQCH–C11H23)0.51ꢀ4.2 H2O: Co2C9.69
-
H
12.67N0.51O4.51ꢀ4.2 H2O (M = 407.12 g molꢂ1) found (%): Co,
ethanol, and dried under vacuum. Yield: 85%.
6.48; N, 1.75. IR (KBr pellet, cmꢂ1): 3426 (s), 2925 (s), 2854 (s),
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Paper
5 M. Nagarathinam, K. Saravanan, E. J. H. Phua, M. V. Reddy,
B. V. R. Chowdari and J. J. Vittal, Angew. Chem., Int. Ed.,
2012, 51, 5866–5870.
1603 (s), 1543 (s), 1386 (s), 1179 (m), 1098 (w), 1060 (w), 847 (w),
786 (m), 591 (w).
Q
(AcBz–N CH–Bz–CN)CCo (6is)
´
6 Functional Hybrid Materials, ed. P. Gomez-Romero and
C. Sanchez, Wiley-VCH, Weinheim, 2004.
7 Chem. Soc. Rev., 2011, 40, Themed issue on Hybrid Materials.
8 J. Mater. Chem., 2005, 15, Themed issue on Functional
hybrid materials.
9 M. Li and S. Mann, Angew. Chem., Int. Ed., 2008, 47,
9476–9479.
1 (153 mg, 0.5 mmol), 4-cyanobenzaldehyde (0.197 g, 1.5 mmol)
and 20 mL of absolute ethanol were introduced in a 30 mL
sealed microwave vessel. The mixture was placed under micro-
wave irradiation (30 W) for 10 min. The dark green powder was
collected by filtration, washed with ethanol and dried under
vacuum. Yield: 80%.
10 C. Train, R. Gheorghe, V. Krstic, L.-M. Chamoreau, N. S.
Ovanesyan, G. L. J. A. Rikken, M. Gruselle and M. Verdaguer,
Nat. Mater., 2008, 7, 729–734.
11 A. Demessence, G. Rogez and P. Rabu, Chem. Mater., 2006,
18, 3005–3015.
Anal. for Co2(OH)3.51(AcBz–NQCH–Bz–CN)0.49ꢀ3.0 H2O: Co2C7.35
-
H
7.92N0.98O4.49ꢀ4.2 H2O (M = 353.73 g molꢂ1) found (%): Co, 33.26;
C, 25.04; H, 3.02; N, 3.65; calcd: Co, 33.32; C, 24.96; H, 3.97; N, 3.88.
IR (KBr pellet, cmꢂ1): 3432 (s), 2235 (m), 1593 (s), 1546 (s), 1385 (s),
1171 (m), 787 (w), 613 (w), 557 (w).
12 A. Demessence, A. Yassar, G. Rogez, L. Miozzo, S. De Brion
and P. Rabu, J. Mater. Chem., 2010, 20, 9401–9414.
13 E. Delahaye, S. Eyele-Mezui, J.-F. Bardeau, C. Leuvrey,
L. Mager, P. Rabu and G. Rogez, J. Mater. Chem., 2009, 19,
6106–6115.
14 H. Shimizu, M. Okubo, A. Nakamoto, M. Enomoto and
N. Kojima, Inorg. Chem., 2006, 45, 10240–10247.
15 E. Delahaye, S. Eyele-Mezui, M. Diop, C. Leuvrey, P. Rabu
and G. Rogez, Dalton Trans., 2010, 39, 10577–10580.
16 E. Delahaye, S. Eyele-Mezui, M. Diop, C. Leuvrey, D. Foix,
D. Gonbeau, P. Rabu and G. Rogez, Eur. J. Inorg. Chem.,
2012, 2731–2740.
Q
(AcBz–N CH–Bz–CN)CCo (6ae)
LH (750 mg, 3 mmol) was dissolved in 50 mL of water and
the pH was adjusted to 8 using 0.2 M NaOH. At this stage
Co2(OH)3(OAc)ꢀH2O (248 mg, 1 mmol) was added along with
20 mL of ethanol. The mixture was stirred under argon at room
temperature for 48 h. The dark green powder was collected
by filtration, washed with ethanol and dried under vacuum.
Yield: 60%.
Anal. for Co2(OH)3.38(AcBz–NQCH–Bz–CN)0.62ꢀ1.0 H2O: Co2C9.30
-
H
8.96N1.24O4.62ꢀ1.0 H2O (M = 347.89 g molꢂ1) found (%): Co, 33.77;
C, 32.28; H, 3.24; N, 4.68; calcd: Co, 33.88; C, 32.11; H, 3.18; N, 4.99.
IR (KBr pellet, cmꢂ1): 3430 (s), 2235 (m), 1594 (s), 1543 (s), 1391 (s),
1170 (m), 1100 (w), 787 (w), 605 (w), 557 (m).
17 S. Eyele-Mezui, E. Delahaye, G. Rogez and P. Rabu, Eur.
J. Inorg. Chem., 2012, 5225–5238.
18 G. Rogez, C. Massobrio, P. Rabu and M. Drillon, Chem. Soc.
Rev., 2011, 40, 1031–1058.
Acknowledgements
19 R. Bourzami, S. Eyele-Mezui, E. Delahaye, M. Drillon, P. Rabu,
N. Parizel, S. Choua, P. Turek and G. Rogez, submitted.
20 B. F. Hoskins and R. Robson, J. Am. Chem. Soc., 1990, 112,
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´
The authors thank the CNRS, the Universite de Strasbourg and
the Agence Nationale de la Recherche (ANR contract no. 2010-
BLAN-913-01 (C-BLUE)). The European COST action MP1202
(HINT) is also gratefully acknowledged. The International Centre
for Frontier Research in Chemistry (icFRC) is acknowledged for
a post-doc grant. The authors thank A. Derory, C. Leuvrey and
D. Burger for technical assistance, Dr J. Fouchet and Pr L. Douce
for their help with the microwave oven.
23 S. M. Cohen, Chem. Sci., 2010, 1, 32–36.
24 K. K. Tanabe and S. M. Cohen, Chem. Soc. Rev., 2011, 40,
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25 S. M. Cohen, Chem. Rev., 2012, 112, 970–1000.
26 R. M. Abdelhameed, L. D. Carlos, A. M. S. Silva and J. Rocha,
Chem. Commun., 2013, 49, 5019–5021.
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