Construction and isomeric transformation of polyoxometalates directed by 1,ω-bis(pyridinium)alkane templates

Article abstract of DOI:10.1039/c1ce05245d

Ten novel inorganic-organic hybrid polyoxometalates, namely, [1,3-bis(pyridinium) propane]₂[α-Mo₈O₂₆] (1), [1,4-bis(pyridinium)butane]₂[1D-Mo₈O₂₆] (2), [1,5-bis(pyridinium)pentane]₂[-Mo₈O₂₆] (3), [1,6-bis(pyridinium)hexane]₂[1D-Mo₈O₂₆] (4), [1,7-bis(pyridinium)heptane]₂[β-Mo₈O ₂₆] (5), [1,8-bis(pyridinium)octane]₂[-Mo ₈O₂₆] (6), [1,9-bis(pyridinium)nonane] ₂[(α + β)-Mo₈O₂₆] (7), [1,10-bis(pyridinium)decane]₂[β-Mo₈O₂₆] (8), [1,11-bis(pyridinium)undecane]₂[β-Mo₈O ₂₆] (9), [1,12-bis(pyridinium)dodecane]₂[γ-Mo ₈O₂₆] (10), (Scheme 1) were synthesized by cation templated self-assembly with octamolybdate anions under hydrothermal reaction conditions. Crystal data analysis revealed that these compounds were all composed of discrete organic cations and polyacid anions [Mo₈O ₂₆]^4- interacting by electrostatic and hydrogen bond interactions. Interestingly in these compounds the anion fraction could take on α-, β-, -, γ-[Mo₈O₂₆]^4- 0D isomers or rare 1D- polymeric frameworks with a simple length modification of the alkane components. Moreover, these polyacid compounds had definite catalytic activities on the oxidation reaction of acetaldehyde to acetic acid and the relationship of structure/catalytic activities were initially demonstrated.

Full text of DOI:10.1039/c1ce05245d

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PAPER
Construction and isomeric transformation of polyoxometalates directed by
1,u-bis(pyridinium)alkane templates†
a
Yun-Yin Niu, Ling-Fang Wang,a Xiao-Rui Lv,a Hai-Juan Du,a Yong-Zhen Qiao,a Hong-Mei Wang,a
*
Li-Sha Song,a Ben-Lai Wu,a Hong-Wei Houa and Seik Weng Ngb
Received 24th February 2011, Accepted 21st April 2011
DOI: 10.1039/c1ce05245d
Ten novel inorganic–organic hybrid polyoxometalates, namely, [1,3-bis(pyridinium) propane]2[a-
Mo8O26] (1), [1,4-bis(pyridinium)butane]2[1D-Mo8O26] (2), [1,5-bis(pyridinium)pentane]2[q-Mo8O26]
(3), [1,6-bis(pyridinium)hexane]2[1D-Mo8O26] (4), [1,7-bis(pyridinium)heptane]2[b-Mo8O26] (5),
[1,8-bis(pyridinium)octane]2[q-Mo8O26] (6), [1,9-bis(pyridinium)nonane]2[(a + b)-Mo8O26] (7),
[1,10-bis(pyridinium)decane]2[b-Mo8O26] (8), [1,11-bis(pyridinium)undecane]2[b-Mo8O26] (9),
[1,12-bis(pyridinium)dodecane]2[g-Mo8O26] (10), (Scheme 1) were synthesized by cation templated
self-assembly with octamolybdate anions under hydrothermal reaction conditions. Crystal data
analysis revealed that these compounds were all composed of discrete organic cations and polyacid
anions [Mo8O26]4ꢀ interacting by electrostatic and hydrogen bond interactions. Interestingly in these
compounds the anion fraction could take on a-, b-, q-, g-[Mo8O26]4ꢀ 0D isomers or rare 1D- polymeric
frameworks with a simple length modification of the alkane components. Moreover, these polyacid
compounds had definite catalytic activities on the oxidation reaction of acetaldehyde to acetic acid and
the relationship of structure/catalytic activities were initially demonstrated.
incorporation of organic and inorganic counterparts into one
structural unit.16
Introduction
The rational design and synthesis of organic–inorganic hybrid
Recently, a great deal of research effort has been paid to the
materials had attracted considerable interest in the last few years
functionalization of POMs by incorporating an organic
not only from a structural point of view, but also due to their
component or transition metal complex,17 and more organic–
potential applications in different areas such as catalysis, medi-
inorganic hybrid materials were successfully prepared by using
cine, sorption, electrical conductivity, magnetism and photo-
POMs as building blocks. Octamolybdates provided an impor-
chemistry.1–7 One synthetic strategy for design of inorganic–
tant branch of polyoxomolybdate chemistry due to their varied
organic hybrid materials was to select suitable inorganic building
structural patterns in the solid state. Up to now, eight isomeric
blocks and organic templates with structure-directing functions.
forms including the a-, b-, g-, d-, 3-, z-, h-, and q- octamolybdates
Polyoxometalates (POMs), as one kind of significant metal oxide
had been prepared in discrete presentations.18–26 In this paper, as
cluster of nanosize and abundant topologies have been employed
a first attempt at the systematic use of 1,u-bis(pyridinium)alkane
as inorganic building blocks for the construction of supramo-
lecular arrays with various organic ligands.8–11 These supramo-
dications (u ¼ 3–12) (Scheme 1) as templated microstructural
tuners to synthesise polyacid species,27 ten octamolybdates
lecular assemblies possessed interesting 1–3 dimensional
supramolecular isomers were created and presented simulta-
structures, and exhibited potential applications in many
neously in the same work. Moreover, it was indicated that these
fields.12–15 Therefore, the functionality of inorganic–organic
polyacid compounds all had definite catalytic activities through
hybrid materials based on POMs could be multiplied by the
the investigation of the oxidation reaction of acetaldehyde to
acetic acid.
aDepartment of Chemistry, Zhengzhou University, Zhengzhou, 450001,
P. R. China. E-mail: mailto:niuyy@zzu.edu.cn
bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur,
Malaysia
† Electronic supplementary information (ESI) available: Selected bond
distances and angles for 1–10, structural figures of 3, 4, 8, 9,
experimental and simulated powder XRD patterns, and the detailed
crystallographic data and structural refinement parameters for 1–10.
CCDC reference numbers 814192–814201. For ESI and
Scheme 1 Schematic representation of the 1,u-bis(pyridinium)alkane
dications (n ¼ 3–12).
crystallographic data in CIF or other electronic format see DOI:
10.1039/c1ce05245d
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Results and discussion
Discussion of synthesis
All this series of compounds were hydrothermally synthesized by
a large number of experiments. Preparation of compounds was
mainly affected by several factors:
(1) pH value. From the perspective of the synthetic experi-
ments, pH played an important role in the formation of the
molybdenum oxygen anions. Compounds 1–3 were obtained at
an initial pH value of 5; while compounds 4–10 were prepared
adjusting with dilute HNO3 to pH 3–3.5. Otherwise only light
yellow powders were obtained at a pH value of 5. This could be
related to the existence of different states of molybdenum oxide
anions at different pH and cation templated conditions. (2)
Temperature. It was shown that the best temperature for the
preparation of these compounds was in the range of 120–160 ꢁC.
Compounds 1 and 2 were obtained at an optimal reaction
temperature of 120 ꢁC, while the optimal range of reaction
temperature for other several compounds was 150–160 ꢁC. At
low heating temperature only some light yellow powders were
obtained, but the organic cations decomposed thermally under
the high temperature and non-crystal product formation
occurred. Thus, the temperature was also a key factor in this
hydrothermal reaction. (3) Organic cations. The organic cations
played a structure directing, template and charge counter-ban-
lancing role in the synthetic process of the compounds. Different
organic cations required different crystallization temperatures
and pH conditions. The shorter the length of the alkyl chain in
1,u-bis(pyridinium) alkanes was, the lower the reaction
temperature required is, and the slightly higher the pH value. (4)
Reaction time. Reaction time affected the formation of the crystal
nucleus, and the crystal size. It was shown that the complete
crystal shape of compound 1 appeared in a reaction period of
3-days, while the complete crystals of other compounds were
obtained in 4 days. No complete crystals of 2–10 except some
powders were obtained in a reaction time of less than 4 days.
In the synthesis process, the octamolybdate product of n ¼ 1
and 2 could not be obtained as the organic cation 1,10-bis(pyr-
idinium)methane broke up into pyridine under hydrothermal
conditions, so that the crystalline product obtained at room
temperature was the pyridinium cation. Meanwhile, the self
assembled reaction of 1,2-bis(pyridinium)ethane cation did not
form a crystal of the hybrid product under the above experi-
mental conditions, with only precipitation being observed.
Fig. 1 a Structure of compound 1 with atomic labeling. Symmetry
codes: #1 ꢀ x + 1,ꢀy + 1, ꢀz + 1. All H atoms were omitted for clarity.
b Packing of compound 1 viewing along the crystallographic [100]
direction. All H atoms were omitted for clarity.
their bonding features, namely, terminal oxygen atoms with Mo–
ꢀ
O distances of 1.689–1.704 A, double bridging oxygen atoms
ꢀ
with Mo–O distances of 1.876–1.928 A, and triple bridging
ꢀ
oxygen atoms with Mo–O distances of 1.778–2.525 A. The Mo–
O average distance of the three sets was 1.697, 1.940, and 2.095
ꢀ
A, respectively. The results indicated that MoO6 octahedron and
MoO4 tetrahedron showed definite distortion. Along the crys-
tallographic a axis, each polyanion [Mo8O26]4ꢀ cluster was sur-
rounded by twin organic cations (Fig. 1b). Along the
crystallographic c axis, polyanions [Mo8O26]4ꢀ cluster and
organic cations showed a parallel array, and mutually filled in
each other’s interspaces, giving rise to form a three-dimensional
supramolecular network by electrostatic interactions and inter-
molecular interactions.
Description of crystal structures
Structure of [1,3-bis(pyridinium)propane]2[a-Mo8O26] (1) with
a-octamolybdate isomer. Single crystal X-ray diffraction analysis
revealed that compound 1 consisted of 1,3-bis(pyridinium)-
propane cations and the polyanion a-[Mo8O26]4–28 held together
by electrostatic interactions (Fig. 1a). The [Mo8O26]4ꢀanion lies
about an inversion centre. In the crystal of compound 1, the alkyl
chain of 1,3-bis(pyridinium)propane dication existed in an anti-
gauche conformation. The polyanion [Mo8O26]4ꢀ is composed of
two centrosymmetric subunits [Mo4O13]2ꢀ. Each subunit con-
sisted of three MoO6 octahedra and one MoO4 tetrahedron by
edge-sharing and corner-sharing. The oxygen atoms within the
[Mo8O26]4ꢀ cluster could be divided into three sets according to
Structures of [1,4-bis(pyridinium)butane]2[1D-Mo8O26] (2), and
[1,6-bis(pyridinium)hexane]2[1D-Mo8O26] (4) with 1D anion chain.
Single crystal X-ray diffraction analysis revealed that compound
2 was composed of independent 1,4-bis(pyridinium)butane
cation and infinite polyanion [Mo8O26]4ꢀ (Fig. 2a). In the crystal,
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Fig. 2 a Structure of compound 2 with atomic labeling. Symmetry codes: #1 x ꢀ 1, y, z #2 ꢀx + 2, ꢀy + 1, ꢀz + 1. All H atoms were omitted for clarity.
4ꢀ
b The supramolecular structure diagram of compound 2 along the crystallographic c axis with ball and stick and polyhedral style. Polyacid [Mo8O26
]
anion represented chain-shape structure in 2. All H atoms were omitted for clarity.
the alkyl chain of 1,4-bis(pyridinium)butane dication existed in
an anti-anti-anti conformation. The [Mo8O26]4ꢀ anion consisted
of a twin-cage structure arranged as two centrosymmetric subsets
of [Mo4O13]2ꢀ. Each subunit contained four MoO6 octahedra,
but the Mo–O distances were unequal. The results showed that
MoO6 octahedron showed definite distortion from the ideal
geometry, which may be related to the introduction of the
organic cation and the changed oxygen atoms sets around the
Mo atoms. The anion [Mo4O13]2ꢀ subunit consisted of four sets
of Mo atoms which were coordinated with different oxygen
atoms: oxygen atoms sets around Mo1 include two terminal
oxygen atoms, two double bridging oxygen atoms, one triple
bridging oxygen atom and one quadruple bridging oxygen atom.
The Mo(1)–O (3), Mo(1)–O(1), Mo(1)–O(4), Mo(1)–O(12)#1,
Mo(1)–O(5) and Mo(1)–O(2) bond distances were 1.701(3), 1.710
Two antisymmetric [Mo4O13]2ꢀ units were linked to form
a dimeric cage structure [Mo8O26]4ꢀ cluster by O12, and then
each of the [Mo8O26]4ꢀ cluster units extended to construct
a scarce one-dimensional catenarian anion structure via two
bridging O9 atoms linking to each other.29a,b The polyanion
catenarian structure exhibited a parallel array along the crys-
tallographic c axis, and organic 1,4-bis(pyridinium)butane
cations were orderly arrayed between layers of the one-dimen-
sional chain. Meanwhile, organic cations and polyanions formed
an organic–inorganic polyacid supramolecular compound by
electrostatic interaction and weak hydrogen bond interaction
(Fig. 2b).
In the crystal of compound 4, the alkyl chain of the 1,6- bis
(pyridinium)hexane dication existed in an anti-anti-gauche-gau-
che-anti conformation. The crystal structure of compound 4 was
similar to that of compound 2, and was composed of an inde-
pendent 1,6- bis(pyridinium)hexane cation and an infinite poly-
anion [Mo8O26]4ꢀ(Fig. S1a–b†). These results suggested that
organic cations of n ¼ 4 and n ¼ 6 have a similar templating
effect on the molybdenum oxide anion although they have
different alkyl chain lengths.
ꢀ
(2), 1.860(2), 1.992(2), 2.249(2), and 2.388(2) A, respectively;
oxygen atom sets around Mo2 were one terminal oxygen atom,
three double bridging oxygen atoms, one triple bridging oxygen
atoms, one quadruple bridging oxygen atom; oxygen atom sets
around Mo3 were two terminal oxygen atoms, two double
bridging oxygen atoms, two triple bridging oxygen atom; oxygen
atom sets around Mo4 were one terminal oxygen atom, one
double bridging oxygen atom, two triple bridging oxygen atoms,
two quadruple bridging oxygen atoms.
It is interesting to show another two examples of [Mo8O26]
isomers induced by di-cationic charged alkyl chain lengths of n ¼
4 {[1,10-(butane-1,4-diyl)bis(imidazolium)]2[d-Mo8O26]}29c and
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n ¼ 6 {[Me3N(CH2)6NMe3] [g-Mo8O26]$2H2O},29d in which the
head groups of the di-cations are different, and the [Mo8O26]
isomers are also different. So both the head groups and the
hydrophobic spacer are important for the template effects.
but the bond distances were slightly different. The opposite Mo–
Mo distances in the compound 3 were 7.213, 6.692, 6.681, and
ꢀ
3.679 A, respectively, while the Mo–Mo distances in the
[Fe(tpyprz)2]2[Mo8O26]$3.7H2O were 7.256, 6.646, 6.509, and
ꢀ
3.669 A, respectively. The results indicated that the cage struc-
Structures of [1,5-bis(pyridinium)pentane]2[q-Mo8O26] (3) and
[1,8-bis(pyridinium)octane]2[q-Mo8O26] (6) with q-octamolybdate
isomer. In the crystal of compound 3, the alkyl chain of the 1,5-
bis(pyridinium)pentane dication existed in an anti-(gauche)2-anti
conformation. Single crystal X-ray diffraction analysis revealed
that compound 3 was made of an organic 1,5-bis(pyridinium)-
pentane cation and a polyacid anion q-[Mo8O26]4ꢀ lying about an
inversion centre,30 as is shown in Fig. 3a. The cluster may be
described as a ring of four [MoO6] octahedra and two [MoO5]
square pyramids in an edge- and corner-sharing arrangement,
capped on either face by tetrahedral {MoO4} subunits in
a corner-sharing mode. The overall structure included 14
terminal-, 8 doubly bridging- and 4 triply bridging-oxo-groups.
Then the coordination environment of the Mo atoms and oxygen
atoms in 3 was same as that in [Fe(tpyprz)2]2[Mo8O26]$3.7H2O,30
ture of compound 3 was bigger and more rounded than
[Fe(tpyprz)2]2[Mo8O26]$3.7H2O. This q-polyacid compound with
four-coordinated environmental Mo atom is rare.
The packing structure diagram of compound 3 is shown in
Fig. 3b. Along the b direction the polyacid [Mo8O26]4ꢀ anions
together with the organic 1,5-bis(pyridinium)pentane cations
exhibit an ABAB repeated mode. Along the crystallographic
b axis, the polyanions [Mo8O26]4ꢀ cluster and the organic cations
show a parallel array, and mutually fill each other’s interspaces,
giving rise to a three-dimensional supramolecular network by
electrostatic interactions and intermolecular interactions.
In the crystal of compound 6, the alkyl chain of the 1,8-bis-
(pyridinium)octane dication existed in an anti-gauche-(anti)2-
gauche-anti-anti conformation. The single crystal X-ray
diffraction analysis revealed that compound 6 was made of an
organic 1,8-bis(pyridinium)octane cation and a polyacid anion
q-[Mo8O26]4ꢀ lying about an inversion centre, as was shown in
Fig. S2a–b.† The overall anion cluster structure was similar to
that of 3, which indicated that organic 1,5-bis(pyridinium)-
pentane and 1,8-bis(pyridinium)octane cations have similar
templating effects on the assembly of the molybdenum oxide
anion. The packing structure diagram of compound 6 is shown in
Fig. S2b.† Polyacid [Mo8O26]4ꢀ anions exhibited a parallel array
in space, and the coupled organic cations showed a tortuous
‘‘back to back’’ shape. Along the crystallographic c axis, organic
1,8-bis(pyridinium)octane cations formed a parallel ‘‘Z-shape’’
chain. Furthermore, polyacid [Mo8O26]4ꢀ anions orderly
arranged between these ‘‘Z-shape’’ chains, giving rise to an
organic–inorganic polyacid supramolecular compound. It is
interesting to compare the packing structure of 6 with that of its
closely related compound [Fe(tpyprz)2]2[Mo8O26]$3.7H2O.30 In
the packing structure of the latter, the [Fe(tpyprz)2]2+ complex
cation also showed a ‘‘Z-shape’’ chain along the b-axis. This
similarity provides further evidence that the [Fe(tpyprz)2]2+
cation possessed an analogous template effect to that of 1,8-bis-
(pyridinium)octane.
Structures of [1,7-bis(pyridinium)heptane]2[b-Mo8O26] (5),
[1,10-bis(pyridinium)decane]2[b-Mo8O26] (8), and [1,11-bis(pyr-
idinium)undecane]2[b-Mo8O26] (9). In the crystal of compound 5,
the alkyl chain of the 1,7-bis(pyridinium)heptane dication existed
in an anti-(anti)3-gauche-gauche conformation. Single crystal
X-ray diffraction analysis revealed that compound 5 was
composed of an independent 1,7-bis(pyridinium)heptane cation
and
a
typical centrosymmetric b-octamolybdate anion
[Mo8O26]4–31 held together by electrostatic interactions (Fig. 4a).
The [Mo8O26]4ꢀ anion lies about an inversion centre. The b-
octamolybdate anion [Mo8O26]4ꢀ included two centrosymmetric
[Mo4O13]2ꢀ interleaving units linked via a bridging oxygen atom.
Each [Mo4O13]2ꢀ unit was made up of four MoO6 edge-sharing
octahedra. The oxygen atoms within the [Mo8O26]4ꢀ cluster
could be divided into four groups according to their bonding
features, namely, terminal oxygen atoms with Mo–O distances of
Fig. 3 a Structure of compound 3 with ball and stick style. Symmetry
codes: #1 ꢀ x, ꢀy, ꢀz. All H atoms were omitted for clarity. b Packing
structure of compound 3 along the crystallographic c axis. All H atoms
were omitted for clarity.
ꢀ
1.691–1.703 A, double bridging oxygen atoms with Mo–O
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Fig. 4 a Structure of compound 5 with ball and stick style. Symmetry codes: #1 ꢀx + 2, ꢀy, ꢀz + 1. All H atoms were omitted for clarity. b Packing
structure of compound 5 with polyhedra ball and stick style along the crystallographic a axis. All H atoms were omitted for clarity.
ꢀ
distances of 1.739(7)–2.277 A, triple bridging oxygen atoms with
ꢀ
Mo–O distances of 1.942(6)–2.356 A, quintuple bridging oxygen
ꢀ
atoms with Mo–O distances of 2.146(6)–2.487(6) A. The Mo–O
Structure of [1,9-bis(pyridinium)nonane]2[(a + b)-Mo8O26] (7).
Single crystal X-ray diffraction analysis revealed that compound
7 was composed of two organic 1,9-bis(pyridinium)nonane
cations and two independent [Mo8O26]4ꢀ anions lying about
inversion centres (Fig. 5a). In the crystal of compound 7, the
alkyl chains of two separate 1,9-bis(pyridinium)nonane dications
existed in an anti-(anti)3-gauche-(anti)2-anti and anti-(anti)2-
gauche-(anti)3-gauche conformations, respectively. The unit cell
consisted of two separate organic cations perpendicularly
crossed between two anions. However, the structures of the two
polyacid [Mo8O26]4ꢀ anions were different. One [Mo8O26]4ꢀ
anion had a typical a-octamolybdate configuration which was
similar to that of compound 1, the other [Mo8O26]4ꢀ anion had
a typical b-octamolybdate configuration which was similar to
that of compound 5. The interesting structure contained anions
of both a- and b-[Mo8O26]4ꢀ configuration, indicating that the
compound was evidently a middle transition type, with the
alkane modification and the template effect of the organic cation
1,9-bis(pyridinium)nonane integrating the effects of 1,3-bis(pyr-
idinium)propane in 1 and 1,7-bis(pyridinium)heptane in 5. It was
shown that the polyacid anion [Mo8O26]4ꢀ took on various
structural frameworks for the rational modification of the
organic components, and compound 7 featured the first mixed
average distance of these four groups was 1.697, 1.940, 2.095,
ꢀ
and 2.327 A, respectively. The result showed that these molyb-
denum oxide polyhedrons were irregular octahedra.
The polyhedral ball and stick packing diagram of 5 viewed
down the a axis is shown in Fig. 4b. The polyacid anions
[Mo8O26]4ꢀ showed a parallel packing arrangement, and the
organic cations which acted as the charge balancing component
and space-filling component filled in the cavities of the anions
cluster, giving rise to an organic–inorganic polyacid supramo-
lecular compound held together by electrostatic interactions and
weak hydrogen bond interactions.
In the crystal of compound 8, the alkyl chain of 1,10-bis(pyr-
idinium)decane dication existed in an anti-(anti)7-anti conformation
(Fig. S3a–b†), and in the crystal of compound 9, the alkyl chain of
the 1,11-bis(pyridinium)undecane dication existed in an anti-(anti)7-
gauche-anti conformation (Fig. S4a–b†). Comparably, in
compounds 5, 8 and 9 the [Mo8O26]4ꢀanion lies about an inversion
centre, and the distances of the Mo–O bond were only slightly
different. These results also indicated that organic cations of n ¼ 7,
10, 11 have asimilartemplateeffecttothe molybdenum oxide anion.
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Fig. 5 a Structure of compound 7 as wireframe style. Symmetry codes: #1 ꢀx + 1, ꢀy, ꢀz + 1 #2 ꢀx, ꢀy + 2, ꢀz. All H atoms were omitted for clarity.
b Packing structure of compound 7 along the crystallographic c axis. All H atoms were omitted for clarity.
type [Mo8O26]4ꢀ polyoxometalate, so the cation-templating effect
played an important role in the preparation of novel organic–
inorganic polyacid supramolecular compounds.
g-[Mo8O26]4ꢀ anion (Fig. 6a).32 The two independent [Mo8O26]4ꢀ
anions lie about inversion centres. The polyacid anion
[Mo8O26]4ꢀ possessed a cage structure consisted of an edge-
sharing arrangement of six [MoO6] octahedra and two [MoO5]
square pyramids. The oxygen atoms within the [Mo8O26]4ꢀ
cluster could be divided into four groups according to their
bonding features, namely, terminal oxygen atoms with Mo–O
ꢀ
distances of 1.639–1.698 A, double bridging oxygen atoms with
ꢀ
Mo–O distances of 1.734–2.377 A, triple bridging oxygen atoms
ꢀ
with Mo–O distances of 1.865–2.453 A, quadruple bridging
ꢀ
oxygen atoms with Mo–O distances of 1.918–2.441 A. The Mo–
Along the crystallographic c axis, the structure of the
[Mo8O26]4ꢀ anion in every layer was homogeneous while the
structure of the [Mo8O26]4ꢀ anion in adjacent layers was
different, then the a- and b-octamolybdate [Mo8O26]4ꢀ anion
configuration exhibited an alternative array. The crystal packing
of the compound suggested that alternating crossed organic
cations filled between parallel layers of anions and formed
parallel layered structures. The packing structure diagram of the
compound is shown in Fig. 5b.
O average distance of the four groups was 1.669, 2.056, 2.159,
ꢀ
and 2.180 A, respectively, and the result shows that the MoO6
Structure of [1,12-bis(pyridinium)dodecane]2[g-Mo8O26] (10).
In the crystal of compound 10, the alkyl chain of the 1,12-bis
(pyridinium)dodecane dication existed in an anti-anti-gauche-
(anti)7-gauche conformation. Single crystal X-ray diffraction
analysis revealed that compound 10 was composed of a organic
octahedra appear slightly distorted.
Along the crystallographic c axis, each polyacid [Mo8O26]4ꢀ
anion exhibited an alternate layered array, and the crooked
organic cation chains with a pyridyl group at either end are
connected end-to-end to each other to form an s-shaped chain.
Then these organic cations chains extended to form a layered
1,12-bis(pyridinium)dodecane cation and
a rare polyacid
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dimensionality with the shortening of the lengths of the alkane
such as u ¼ 2 / 1 although the two octamolybdate products
were not obtained.
IR spectra
In this paper, we used 1,u-bis(pyridinium) alkane cations as
stepwise modification templates and all the anions were
[Mo8O26]4ꢀ; so the IR spectra of the ten compounds were basi-
cally similar. The absorption band at about 3400cmꢀ1 and
3050cmꢀ1 could be assigned to the stretching vibration absorp-
tion peak of C–H of the unsaturated carbon atoms. The vibra-
tion absorption bands of the aromatic ring appeared in the range
of 1650–1400cmꢀ1. The band at about 2000cmꢀ1 and 1150cmꢀ1
corresponded to the stretching vibrations peak of –CH2– and
C–N. The characteristic absorption bands of the polyacid anion
[Mo8O26]4ꢀ appeared in the range 1000–800cmꢀ1. The sharp
absorption bands at 1000–800cmꢀ1 could be assigned to the
stretching vibration of Mo–Ot while in the range 800–550cmꢀ1
could be attributed to the stretching vibration absorption peak of
bridging bonds Mo–Ob-Mo. Slight shifts of some peaks come
from the template effect of different organic cations and distin-
guishable polyacid anion configurations.
TGA
In order to investigate the thermal decomposition behavior of 1–
10, TGA experiments were carried out up to 800 ꢁC in a flowing
air atmosphere. As is shown in Fig. S5–S14,† almost all 10
ꢁ
compounds were thermally stable up to 300 C. The decompo-
sition of 1–6 mainly proceeded in two stages. The first stage took
place at the range of 305.0 ꢁC–353 ꢁC, which probably corre-
sponded to the elimination of 1,u-bis(pyridinium)alkane dica-
tions; the second stage began at the range of 700–740 ꢁC mainly
involved the decomposition of the octamolybdate isomers. The
TGA curve for compounds 7–10 displays three steps of weight
loss. The first and second weight loss began at 290–440 ꢁC,
corresponding to the decomposition of the long organic cations.
Fig. 6 a Structure of compound 10 with ball and stick style. Symmetry
codes: #1 ꢀx, ꢀy + 1, ꢀz. All H atoms were omitted for clarity. b Packing
structure of compound 10 along the crystallographic c axis. All H atoms
were omitted for clarity.
ꢁ
The third stage at about 740 C mainly involved the collapse of
structure viewed down the a axis, and the polyacid [Mo8O26]4ꢀ
anions are orderly arrayed between these organic layers. Mean-
while, organic cations and polyacid anions extended to form
the octamolybdate isomers. Overall, the decomposition temper-
ature of the dications decreased with the growth of the alkane
chain length, while all the octamolybdates disintegrated steadily
at high temperatures.
a
three dimensional organic–inorganic supramolecular
compound via electrostatic interactions and weak intermolecular
hydrogen bonds. The packing structure is shown in Fig. 6b. The
reported g-[Mo8O26]4ꢀ mainly came from transition metal
complex templates,32a–d compound 10 indicated that the
bolaamphiphile cation had an integrated effect from the metal
and ligands and behaved as a type of excellent supramolecular
template.
Catalytic activities of the compounds
Polyoxometalates (POMs) are known to catalyze the probe
reaction for the oxidation of acetaldehyde with H2O2.33 The
catalytic properties of [Mo8O26]4ꢀ have been also studied.34 Thus,
we decided to test the ability of our POMs to act as oxidation
catalysts, and to show preliminary evidence for the effect of
variation of the alkane spacer groups on the catalytic properties.
The catalytic results diagram is shown in Fig. 7. Under the
conditions of the catalysis reactions of these compounds, it was
shown that conversion of acetaldehyde was comparatively steady
after reacting for 2.5 h. After 3h, the conversions of acetaldehyde
were 12.14%, 8.6%, 7.8%, 10.2%, 8.0%, 7.13%, 6.86%, 6.5%,
6.3%, respectively. Under the same experimental conditions, the
title compounds showed an acetic acid formation rate of 40.47,
28.67, 26.00, 26.93, 34.03, 23.77, 22.90, 21.67, 21.00 mmol
It is also interesting to compare the influences of the lengths of
the alkane from the organic cations on the ultimate packing
fashions of these 10 hybrid solids. The cell volumes increase
roughly with the growing of the length of the alkyl chain showing
the cation size effect. However, compounds 2 and 4 have smaller
volumes and compound 7 has a larger one, which are consistent
with the anion numbers in the unit cell, and showed that the
packing fashion of the anions is inevitably under the influence of
that of the cations. This reciprocal template effect from the
(+)/(ꢀ) moieties also presages
a high anion polymeric
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View Article Online
alkane groups of the cation. Thus, detailed studies on the
mechanism of peroxide activation of these POMs are warranted
and are being conducted in our laboratory.
Experimental section
Materials and methods
The dications [Py-(CH2)n-Py]2+ (n ¼ 3–12) were prepared as the
bromide salts by direct alkylation of pyridine with 1,u-dibro-
moalkane. Other chemicals were obtained from commercial
sources and used as received without further purification. The IR
spectrum was recorded on a Shimazu IR435 spectrometer as KBr
disk (4000–400 cmꢀ1). Elemental analyses (C, H, and N) were
carried out on a FLASH EA 1112 elemental analyzer. The purity
of the bulk microcrystalline materials obtained from the
syntheses was checked by Powder X-ray diffraction analyses.
XRPD patterns were recorded using Cu-Ka1 radiation on
a
PAN analytical X’Pert PRO diffractometer. A model
NETZSCHTG209 thermal analyzer was used to record simul-
taneous TG, DTG curves in ꢁa flowing air atmosphere of 20 mL
minꢀ1 at a heating rate of 5 C minꢀ1 in the temperature range
ꢁ
0–850 C using platinum crucibles.
Compound syntheses
[1,3-Bis(pyridinium)propane]2[a-Mo8O26] (1). A mixture of
(NH4)6Mo7O24$4H2O (0.0617 g, 0.05 mmol), [1,3-bis(pyr-
idinium)propane]$2Br (0.0540 g, 0.15 mmol), and H2O (10 mL)
was stirred for 20 min in air until it was homogeneous. The
mixture was sealed in a 23 mL Teflon-lined stainless steel
ꢁ
container, which was heated to 120 C under autogenous pres-
surꢁe for 3 d. After the mixture was cooled to room temperature at
10 C hꢀ1, light yellow green crystals of 1 were obtained, Yield:
54%. Anal. calcd (%) for C26H32Mo8N4O26: C 19.72, H 2.01, N
3.54 found: C 19.61, H 2.36, N 3.55; IR (KBr, cmꢀ1): 3444 (s),
3062 (m), 1632 (s), 1490 (m), 913 (s), 804 (s), 670 (s), 569 (m).
Fig. 7 Conversion versus time plot of catalytic oxidation of acetalde-
hyde with H2O2. (a) Catalytic results with 1, 2, and 3 as catalyst. (b)
Catalytic results with 5, 6, and 7 as catalyst. (c) Catalytic results with 8, 9,
and 10 as catalyst.
[1,4-Bis(pyridinium)butane]2[1D-Mo8O26] (2). Compound 2
was synthesized similarly to compound 1 by using [1,4-bis(pyr-
idinium)butane]$2Br (0.0561 g, 0.15 mmol) instead of [1,3-bis-
(pyridinium)propane]$2Br. Then the mixture was heated to
120 ꢁC under autogenous pressure for 4 d. Light green rod
crystals of 2 were obtained in a 52% yield. Anal. calcd (%) for
C14H18Mo4N2O13: C 20.87, H 2.26, N 3.48 found: C 20.71, H
2.36, N 3.58; IR (KBr, cmꢀ1): 3745 (s),16 30 (s), 1483 (m),
1273 (m),1173 (m), 937 (m), 864 (m), 622 (s), 480 (s).
(g-cat.)ꢀ1 hꢀ1, respectively, while Ni2Al–CO3, i. e. the clay cata-
lyst Ni0.7Al0.3(OH)2$0.15CO3$0.86H2O, has an activity of
8.0 mmol (g-cat.)ꢀ1 hꢀ1 33a
The catalytic activity shows an
.
increase of around 2.62–5.05 times for the title compounds over
Ni2Al–CO3. These POMs may thus be good candidates for
oxidative catalysts in some other organic reactions.
However, the most active catalysts seem to be those that
contained short alkane spacers. The catalytic activities decrease
with the increase of the length of the alkyl chain in the 1,u-bis-
(pyridinium) alkanes. We deduced that long organic cations
chains were probably adverse to the electron transmission in the
oxidation–reduction reaction. These results clearly show differ-
ences in catalytic activity which can be attributed to alkane
spacer groups with varying electron transfer abilities. One
possible scenario is that the short alkane chain and cation size
bring large flexibility and electron transfer abilities in solution,
which facilitates the interaction with the peroxide via hydrogen
bonding35 (among CH2, [Mo8O26]4ꢀ and H2O2), the activation of
H2O2 and the cleavage of the peroxide O–O bond. In short, the
catalytic activities of these POMs seem to be modulated by the
[1,5-Bis(pyridinium)pentane]2[q-Mo8O26] (3). Compound 3 was
synthesized similarly to compound 1 by using [1,5-bis(pyr-
idinium)pentane]$2Br (0.0582 g, 0.15 mmol) instead of [1,3-bis-
(pyridinium)propane]$2Br. Then the mixture was heated to
150 ꢁC under autogenous pressure for 4d. The resulting colorless
crystals of 3 were formed, yield: 58%. Anal. calcd (%) for C15
H20Mo4 N2O13: C 21.98, H 2.45, N 3.42 found: C 21.81, H 2.66,
N 3.74; IR (KBr, cmꢀ1): 3447(s), 1632 (s), 1490 (m), 921 (s),
800 (s), 658 (s), 552 (m).
[1,6-Bis(pyridinium)hexane]2[1D-Mo8O26] (4).
A
mixture
mmol),
of
(NH4)6Mo7O24$4H2O (0.0617 g,0.05
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[1,6-bis(pyridinium)hexane]$2Br (0.0603 g, 0.15 mmol), and H2O
(10 mL) was adjusted with dilute HNO3 to pH 3–3.5. Then, the
mixture was placed in a 23 mL Teflon-lined autoclave and kept
under autogenous pressure at 160 ꢁC for 4 days. After it was
2.83, N 3.30 found: C 24.31, H 2.76, N 3.32; IR (KBr, cmꢀ1): 3448
(s), 3060 (s), 1626 (s), 1484 (s), 1188 (m), 941 (s), 848 (s), 716 (s),
552 (m).
gradually cooled to room temperature at a rate of 10 ꢁC hꢀ1
,
[1,8-Bis(pyridinium)octane]2[q-Mo8O26] (6). Compound 6 was
synthesized similarly to compound 4 by using [1,8-bis(pyr-
idinium)octane]$2Br (0.0430 g, 0.1 mmol) instead of [1,6-bis-
(pyridinium)hexane]$2Br. Colorless crystals of 6 were formed,
yield: 60%. Anal. calcd (%) for C36H52Mo8N4O26: C 25.08, H
3.04, N 3.25 found: C 25.61, H 3.16, N 3.41; IR (KBr, cmꢀ1): 3448
(s), 3062 (s), 2973 (m), 1629 (s), 1485 (s), 1314 (s), 1173 (s), 911 (s),
804 (s), 659 (s), 550 (m).
colorless crystals of 4 were obtained. Yield: 48%. Anal. calcd (%)
for C16H22Mo4N2O13: C 23.03, H 2.65, N 3.36 found: C 23.61, H
2.76, N 3.43; IR (KBr, cmꢀ1): 3454(s), 3057(s), 2928(m), 1629(s),
1484(s), 1165(s), 926(s), 865(s), 761(s), 482(s).
[1,7-Bis(pyridinium)heptane]2[b-Mo8O26] (5). Compound 5 was
synthesized similarly to compound 4 by using [1,7-bis(pyr-
idinium)heptane]$2Br (0.0416 g, 0.1 mmol) instead of [1,6-bis-
(pyridinium)hexane]$2Br. Colorless crystals of 5 were formed,
yield: 50%. Anal. calcd (%) for C34H48Mo8N4O26: C 24.08, H
[1,9-Bis(pyridinium)nonane]2[(a + b)-Mo8O26] (7). Compound
7
was synthesized similarly to compound 4 by using
Table 1 Crystal data and structure refinement details for 1–10
1
2
3
4
5
Formula
C26H32Mo8N4O26
1584.08
Monoclinic
P21/n
10.2659(4)
20.0891(8)
10.3756(4)
90
100.6330(10)
90
2102.99(14)
2
2.502
2.401
1520
13326
4802
0.0211
1.041
0.0254
0.0646
C14H18Mo4N2O13
806.06
Triclinic
P-1
9.6800(6)
10.4525(6)
12.2127(8)
65.7660(10)
79.8680(10)
70.7540(10)
1062.63(11)
2
2.519
2.378
776
5654
3685
0.0143
1.056
0.0222
C15H20Mo4 N2O13
820.09
Monoclinic
P21/n
10.434(2)
20.632(4)
11.583(2)
90
107.98(3)
90
2371.8(8)
4
2.297
2.133
1584
7445
3914
0.0330
1.097
0.0549
0.1358
1.144/ꢀ1.931
C16H22Mo4N2O13
834.12
Triclinic
P-1
9.6722(6)
9.8924(6)
12.7236(8)
105.8290(10)
94.8730(10)
95.7600(10)
1157.28(12)
2
2.394
2.188
808
6766
4463
0.0122
1.037
0.0263
C34H48Mo8N4O26
1696.28
Monoclinic
P21/n
11.2831(7)
18.3289(11)
11.9515(7)
90
90.8730(10)
90
2471.4(3)
2
2.280
2.051
1648
13501
4594
0.0148
1.060
0.0216
0.0600
Formula weight
Cryst. syst.
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
3
ꢀ
Vol/A
Z
Dc/g cmꢀ3
m/mmꢀ1
F(000)
Rflns collected
Unique rflns
Rint
GOF
R1 (I > 2s(I))
a
wR2a (all data)
Drmax/Drmin/e A
0.0656
0.918/ꢀ0.650
0.0635
1.014/ꢀ0.623
ꢀ3
ꢀ
1.556/ꢀ1.630
0.614/ꢀ0.945
6
7
8
9
10
Formula
C36H52Mo8N4O26
1724.34
Monoclinic
P21/n
15.5447(8)
10.1543(5)
16.6922(8)
90
90.0590(10)
90
2634.8(2)
2
2.173
C76H112Mo16N8O52
3504.78
Monoclinic
P21/n
22.684(2)
13.1384(12)
19.4278(17)
90
108.6190(10)
90
5487.0(8)
2
2.121
C40H60Mo8N4O26
1780.44
Monoclinic
P21/n
11.1947(8)
17.5265(13)
14.1876(10)
90
97.3510(10)
90
2760.8(3)
2
2.142
C42H64Mo8N4O26
1808.49
Monoclinic
P21/n
12.5763(8)
13.0193(9)
17.6460(12)
90
99.0140(10)
90
2853.6(3)
2
2.105
C44H68Mo8N4O26
1836.54
Monoclinic
P21/n
12.5475(7)
16.7311(10)
14.5205(8)
90
97.3650(10)
90
3023.2(3)
2
2.018
Formula weight
Cryst. syst.
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
3
ꢀ
Vol/A
Z
Dc/g cmꢀ3
m/mmꢀ1
F(000)
1.926
1680
1.851
3424
1.842
1744
1.783
1776
1.685
1808
Rflns collected
Unique rflns
Rint
14302
4901
0.0173
1.069
0.0254
0.0641
0.971/-0.814
29522
10100
0.0246
1.053
0.0915
0.2427
12.800/-2.107
15100
5137
0.0380
1.050
0.0299
0.0825
0.591/-0.965
15439
5273
0.0175
1.107
0.0211
0.0542
0.327/-0.666
16634
5618
0.0173
1.034
0.0231
0.0567
1.183/-0.673
GOF
R1 (I > 2s(I))
a
wR2a (all data)
Drmax/Drmin/e A
ꢀ3
ꢀ
a
2
2
R1 ¼ kFo| ꢀ |Fck/|Fo|; wR2 ¼ [w(Fo ꢀ Fc )2/w(Fo2)2]1/2
.
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[1,9-bis(pyridinium)nonane]$2Br (0.0444 g, 0.1 mmol) instead of
[1,6-bis(pyridinium)hexane]$2Br. Colorless crystals of 7 were
formed, yield: 54%. Anal. calcd (%) for C76H112Mo16N8O52: C
26.05, H 3.21, N 3.20 found: C 26.21, H 3.56, N 3.30; IR (KBr,
cmꢀ1): 3449 (s), 3064 (s), 2926 (s), 1628 (s), 1484 (s), 1170 (m), 912
(s), 805 (s), 663 (s), 552 (m).
Catalysis oxidation reactions of acetaldehyde to acetic acid
In this article, we selected the oxidation reaction of acetaldehyde
to acetic acid as a model reaction in order to measure the cata-
lytic oxidation activities of these compounds. A mixture of
acetaldehyde (0.05 mol, 5.7 ml, 40%) and H2O2 (0.1 mol, 10 ml,
30%) was placed in a three-neck flask (50 ml) at room tempera-
ꢁ
ture, stirred and heated to 60 C, then the catalyst (0.05 g) that
[1,10-Bis(pyridinium)decane]2[b-Mo8O26] (8). Compound 8
was synthesized similarly to compound 4 by using [1,10-bis-
(pyridinium)decane]$2Br (0.0458 g, 0.1 mmol) instead of [1,6-bis-
(pyridinium)hexane]$2Br. Colorless crystals of 8 were formed,
yield: 58%. Anal. calcd (%) for C40H60Mo8N4O26: C 26.98, H
3.40, N 3.15 found: C 26.61, H 3.56, N 3.32; IR (KBr, cmꢀ1): 3430
(s), 3060 (s), 2926 (m), 1628 (s), 1485 (s), 1168 (s), 946 (s), 844 (s),
714 (s), 556 (m).
was one of the above compounds was added into the mixture and
the reaction was retained in the range 50–60 ꢁC, refluxing for 3 h.
The sampling frequency at the beginning of the reaction was once
every 10 min, then once every 30 min 1 h later. The final solution
was titrated with standard NaOH solution and the conversion
ratio of acetaldehyde was calculated. The formation rate of the
ethanoic acid produced [mmol (g-cat.)ꢀ1 hꢀ1] was taken in order
to assess the catalytic activity.
[1,11-Bis(pyridinium)undecane]2[b-Mo8O26] (9). Compound 9
was obtained similarly to compound 4 by using [1,11-bis(pyr-
idinium)undecane]$2Br (0.0470 g, 0.1 mmol) instead of [1,6-bis-
(pyridinium)hexane]$2Br. Colorless crystals of 9 were formed,
yield: 52%. Anal. calcd (%) for C42H64Mo8N4O26: C 27.88, H
3.56, N 3.10 found: C 27.61, H 3.76, N 3.27; IR (KBr, cmꢀ1): 3444
(s), 3058 (s), 2925 (m), 1630 (s), 1484 (s), 1172 (s), 940 (s), 909 (s),
711 (s), 520 (m).
Conclusion
Aiming at crystal engineering with nanosized POM building
blocks we succeeded in preparing ten novel inorganic–organic
hybrid octamolybdate supramolecular isomers by modification
of 1,u-bis(pyridinium) alkane dications acting as permanent
templates.36 The templates filling in cavities of polyacid anions
not only play the role of charge compensation and direct the
packing motif, more importantly, it also significantly influences
the structure of the POM framework, and some unprecedented
POMs were expected as components of hybrids with cation
templates. In these ten compounds, the octamolybdate anion
[Mo8O26]4ꢀ of compounds 2 and 4 both had a one-dimensional
catenarian structure, while the others were of a different cage
structure. Compound 1 contained the discrete a-[Mo8O26]4ꢀ
clusters, while the octamolybdate anion [Mo8O26]4ꢀ was always
the typical b-[Mo8O26]4ꢀ cluster in compound 5, 8 and 9. In
compound 3 and 6, the octamolybdate anion [Mo8O26]4ꢀ was an
ellipsoid shaped cage structure and belonged to the scarce q-
[Mo8O26]4ꢀ cluster. An interesting structure of polyacid
[Mo8O26]4ꢀ anions in compound 7 contained both the anion
structure of compound 1 and compounds 5, 8, 9, showing that
the compound 7 was a middle transition type. Compound 10
contained the unusual g-[Mo8O26]4ꢀ clusters and looked like
a flat cage structure. Consequently, we demonstrated that these
polyacid [Mo8O26]4ꢀ anions took on various isomeric frame-
works for the fine modification of organic components. There-
fore, cation-templed effects played an important role in the
preparation of novel organic–inorganic polyacid supramolecular
compounds. Moreover, it was indicated that all these polyacid
compounds had definite catalytic activities in some organic
oxidation reactions and the catalytic activities were related to the
length of the alkyl chain in 1,u-bis(pyridinium) alkanes.
[1,12-Bis(pyridinium)dodecane]2[g-Mo8O26] (10). Compound
10 was prepared similarly to compound 4 by using [1,12-bis-
(pyridinium)dodecane]$2Br (0.0486 g, 0.1 mmol) instead of [1,6-
bis(pyridinium)hexane]$2Br. Colorless crystals of 10 were
formed, yield: 54%. Anal. calcd (%) for C44H68Mo8N4O26: C
28.76, H 3.74, N 3.05 found: C 280.61, H 3.86, N 3.47; IR (KBr,
cmꢀ1): 3444 (s), 3060 (s), 2924 (m), 1710 (m), 1631 (s), 1487 (s),
1172 (m), 907 (s), 794 (s), 659 (s).
X-Ray crystallography
Crystallographic data for the ten compounds was collected on
a Bruker APEX-II area-detector diffractometer with Mo-Ka
radiation (l ¼ 0.71073). Absorption corrections were applied by
using SADABS. The structures were solved with direct methods
and refined with full-matrix least-squares techniques on F2 using
the SHELXTL program package. All of the non-hydrogen atoms
were refined anisotropically. The hydrogen atoms were assigned
with common isotropic displacement factors and included in the
final refinement by using geometrical restrains. In 7 the large
ꢀ
residual electron density peak was located close to (1.3 A from)
the Mo atom and was most likely due to imperfect absorption
corrections frequently encountered in heavy-metal atom struc-
tures. Crystal data for 1–10 were summarized in detail in Table 1.
Selected bond lengths and bond angles were put in Table S1.† In
order to confirm the phase purity of the bulk materials, X-ray
powder diffraction (XRPD) experiments were carried out for
compounds 1–10. The experimental PXRD patterns of 1–10
correspond well to the simulated PXRD patterns, indicating that
the bulk phase materials are isomorphous. The difference in
reflection intensities between the simulated and experimental
patterns was due to the variation in the preferred orientation of
the powder sample during collection of the experimental PXRD
data (Fig. S15-S24†).
Acknowledgements
Research efforts in the Niu group are supported by the National
Science Foundation of China (No. 20671083).
References
1 S. I. Stupp and P. V. Braun, Science, 1997, 277, 1242.
5080 | CrystEngComm, 2011, 13, 5071–5081
This journal is ª The Royal Society of Chemistry 2011

View Article Online
2 P. V. Braun, P. Osenar, V. Tohver, S. B. Kennedy and S. I. Stupp, J.
Am. Chem. Soc., 1999, 121, 7302–7309.
24 D. R. Xiao, Y. Hou, E. B. Wang, S. T. Wang, Y. G. Li, L. Xu and
C. W. Hu, Inorg. Chim. Acta, 2004, 357, 2525–2531.
€
€
3 A. Muller, S. Q. N. Shah, H. Bogge and M. Schmidtmann, Nature,
1999, 397, 48–50.
25 R. S. Rarig and J. Zubieta, Inorg. Chim. Acta, 2001, 312, 188–196.
26 J. P. Wang, S. Z. Li, J. W. Zhao and J. Y. Niu, Inorg. Chem.
Commun., 2006, 9, 599–602.
27 Y. Y. Niu, B. L. Wu, X. L. Guo, Y. L. Song, X. C. Liu, H. Y. Zhang,
H. W. Hou, C. Y. Niu and S. W. Ng, Cryst. Growth Des., 2008, 8,
2393–2401.
28 (a) R. S. Rarig Jr., L. Bewley, V. Golub, C. J. O’Connor and
J. Zubieta, Inorg. Chem. Commun., 2003, 6, 539; (b) P. J. Hagrman
and J. Zubieta, Inorg. Chem., 1999, 38, 4480.
4 M. J. Zaworotko, Angew. Chem., Int. Ed., 1998, 37, 1211.
5 (a) M. C. Hong, Cryst. Growth Des., 2007, 7(1), 10–14; (b) C. L. Hill,
Chem. Rev., 1998, 98, 1.
6 A. K. Cheetham, G. Ferey and T. Loiscau, Angew. Chem., Int. Ed.,
1999, 38, 3268–3292.
7 X. L. Wang, C. Qin, E. B. Wang, Y. G. Li, C. W. Hu and L. Xu,
Chem. Commun., 2004, 378–379.
8 (a) M. Sadakane, M. H. Dickman and M. T. Pope, Angew. Chem., Int.
Ed., 2000, 39, 2914; (b) X. M. Zhang, M. L. Tong and X. M. Chen,
Chem. Commun., 2000, 1817–1818.
9 (a) C.-M. Liu, Y.-L. Hou, J. Zhang and S. Gao, Inorg. Chem., 2002,
41, 140–143; (b) C.-D. Wu, C.-Z. Lu, X. Lin, D.-M. Wu, S.-F. Lu,
H.-H. Zhuang and J.-S. Huang, Chem. Commun., 2003, 1284–1285;
(c) J.-R. Li, X.-H. Bu and R.-H. Zhang, Inorg. Chem., 2004, 43,
237–244.
29 (a) P. J. Hagrman, D. Hagrman and J. Zubieta, Angew. Chem., Int.
Ed., 1999, 38, 2638–2684; (b) K. J. Thorn, A. Narducci Sarjeant
and A. J. Norquist, Acta Crystallogr., Sect. E: Struct. Rep. Online,
2005, 61, m1665–m1667; (c) R. Dessapt, D. Kervern, M. Bujoli-
Doeuff, P. Deniard, M. Evain and S. Jobic, Inorg. Chem., 2010, 49,
11309–11316; (d) H. G. Hou and J. L. Yang, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2007, 63, m2194; (e) M. L Niven,
J. J. Cruywagen, J. Bernard and B. Heynes, J. Chem. Soc., Dalton
Trans., 1991, (8), 2007.
30 D. G. Allis, E. Burkholder and J. Zubieta, Polyhedron, 2004, 23, 1145.
31 (a) S. Upreti and A. Ramanan, Cryst. Growth Des., 2005, 5(5), 1837–
1843; (b) T. Duraisamy, A. Ramanan and J. J. Vittal, J. Mater.
Chem., 1999, 9, 763–767.
32 (a) C. D. Wu, C. Z. Lu, S. M. Chen, H. H. Zhuang and J. S. Huang,
Polyhedron, 2003, 22, 3091; (b) J. R. D. DeBord, R. C. Haushalter,
L. M. Meyer, D. J. Rose, P. J. Zapf and J. Zubieta, Inorg. Chim.
Acta, 1997, 256, 165; (c) R. S. Rarig Jr., P. J. Hagrman and
J. Zubieta, Solid State Sci., 2002, 4, 77; (d) X. B. Cui, K. Lii,
Y. Fan, J. Q. Xu, L. Ye, Y. H. Sun, Y. Li, H. H. Yu and Z. H. Yi,
J. Mol. Struct., 2005, 743, 151.
33 (a) C. W. Hu, X. Zhang, L. Xu, B. L. Mu, W. Zu and E. B. Wang,
Appl. Clay Sci., 1998, 13, 495–511; (b) R. Bagtache, K. Abdmeziem,
S. Boutamine, M. Meklati and O. Vittori, Synth. React. Inorg.,
Metal-Org., Nano-Metal Chem., 2009, 39, 467–474; (c) L. Xu,
Y. Q. Sun, E. B. Wang, E. H. Shen, Z. R. Liu, C. W. Hu, Y. Xing,
Y. H. Lin and H. Q. Jia, Inorg. Chem. Commun., 1998, 1, 382–385;
(d) L. Xu, Y. Q. Sun, E. B. Wang, E. H. Shen, Z. R. Liu,
C. W. Hu, Y. Xing, Y. H. Lin and H. Q. Jia, New J. Chem., 1999,
23, 1041–1044; (e) B. Z. Lin, G. H. Han, B. H. Xu, L. Bai,
Y. L. Feng and H. Su, J. Cluster Sci., 2008, 19, 379–390; (f) L. Xu,
Y. Q. Sun, E. B. Wang, E. H. Shen, Z. R. Liu and C. W. Hu,
Transition Met. Chem., 1999, 24, 492–495; (g) L. Xu, Y. Q. Sun,
E. B. Wang, E. H. Shen, Z. R. Liu and C. W. Hu, J. Solid State
Chem., 1999, 146, 533–537.
10 (a) U. Kortz, M. G. Savelieff, F. Y. Abou Ghali, L. M. Khalil,
S. A. Maalouf and D. I. Sinno, Angew. Chem., Int. Ed., 2002, 41,
4070; (b) C. D. Peloux, P. Mialane, A. Dolbecq, J. Marrot and
ꢁ
F. Secheresse, Angew. Chem., Int. Ed., 2002, 41, 2808–2810; (c)
C. Z. Wu, H. H. Lu and J. S. Zhuang, J. Am. Chem. Soc., 2002,
124, 3836–3837.
€
11 (a) A. Muller and C. Serain, Acc. Chem. Res., 2000, 33, 2–10; (b)
D. L. Long and L. Cronin, Chem.–Eur. J., 2006, 12, 3698–3706.
€
€
12 M. Holscher, U. Englert, B. Zibrowius and W. F. Holderich, Angew.
Chem., Int. Ed. Engl., 1995, 33, 2491–2493.
13 (a) E. Coronado, J. R. Gamenez-Saiz, C. J. Gomez-Garcia,
L. R. Falvello and P. Delaes, Inorg. Chem., 1998, 37, 2183–2188; (b)
A. R. Moore, H. Kwen, A. M. Beatty and E. A. Maatta, Chem.
Commun., 2000, 1793–1794.
14 L. Xu, M. Lu, B. B. Xu, Y. G. Wei, Z. H. Peng and D. Powell, Angew.
Chem., Int. Ed., 2002, 41, 4129–4132.
15 Y. G. Li, N. Hao, E. B. Wang, M. Yuan, C. W. Hu, N. H. Hu and
H. Q. Jia, Inorg. Chem., 2003, 42, 2729–2735.
16 (a) C. T. Kressge, M. E. Leonowicz, W. J. Roth, J. C. Vartuni and
J. S. Beck, Nature, 1992, 359, 710; (b) E. Coronado and
C. J. Go’mez-Garcı’a, Chem. Rev., 1998, 98, 273–296.
17 (a) Y. Du, A. L. Rheingold and E. A. Maatta, J. Am. Chem. Soc.,
1992, 114, 346–348; (b) R. Proust, M. Thouvenot, F. Chaussade,
F. Robert and P. Gouzerh, Inorg. Chim. Acta, 1994, 224, 81–95.
18 D. Hagrman, C. Zubieta, R. C. Haushalter and J. Zubieta, Angew.
Chem., Int. Ed. Engl., 1997, 36, 873.
19 D. G. Allis, R. S. Rarig, E. Burkholder and J. Zubieta, J. Mol. Struct.,
2004, 688, 11–31.
20 A. J. Bridgeman, J. Phys. Chem. A, 2002, 106, 12151–12160.
21 D. G. Allis, E. Burkholder and J. Zubieta, Polyhedron, 2004, 23,
1145–1152.
22 C. D. Wu, C. Z. Lu, H. H. Zhuang and J. S. Huang, Inorg. Chem.,
2002, 41, 5636.
23 D. Hagrman, P. J. Zapf and J. Zubieta, Chem. Commun., 1998, (12),
1283.
34 (a) M. L. Guo and H. Z. Li, Green Chem., 2007, 9, 421–423; (b)
C. B. Yang, Q. P. Jin, H. Zhang, J. Liao, J. Zhu, B. Yu and
J. G. Deng, Green Chem., 2009, 11, 1401–1405.
35 (a) C. J. Chang, L. L. Chng and D. G. Nocera, J. Am. Chem. Soc., 2003,
125, 1866–1876; (b) J. D. Soper, S. V. Kryatov, E. V. Rybak-Akimova
and D. G. Nocera, J. Am. Chem. Soc., 2007, 129, 5069–5075; (c)
V. G. Organo, A. S. Filatov, J. S. Quartararo, Z. M. Friedman and
E. V. Rybak-Akimova, Inorg. Chem., 2009, 48, 8456–8468.
36 H. Ralf and V. Fritz, Angew. Chem., Int. Ed. Engl., 1994, 33, 375.
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