Thermally triggered solid-state single-crystal-to-single-crystal structural transformation accompanies property changes

Article abstract of DOI:10.1002/chem.201405984

The 1D complex [(CuL_0.5H₂O)·H₂O]n (1) (H₄ L = 2,2′-bipyridine-3,3′ ,6,6′-tetracarboxylic acid) undergoes an irreversible thermally triggered single-crystal-to-single-crystal (SCSC) transformation to produce the 3D anhydrous complex [CuL_0.5]_n (2). This SCSC structural transformation was confirmed by single-crystal X-ray diffraction analysis, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) patterns, variable-temperature powder X-ray diffraction (VT-PXRD) patterns, and IR spectroscopy. Structural analyses reveal that in complex 2, though the initial 1D chain is still retained as in complex 1, accompanied with the Cu-bound H2O removed and new O(carboxyl)-Cu bond forming, the coordination geometries around the CuII ions vary from a distorted trigonal bipyramid to a distorted square pyramid. With the drastic structural transition, significant property changes are observed. Magnetic analyses show prominent changes from antiferromagnetism to weak ferromagnetism due to the new formed Cu1-O-C-O-Cu4 bridge. The catalytic results demonstrate that, even though both solid-state materials present high catalytic activity for the synthesis of 2-imidazolines derivatives and can be reused, the activation temperature of complex 1 is higher than that of complex 2. In addition, a possible pathway for the SCSC structural transformations is proposed.

Full text of DOI:10.1002/chem.201405984

DOI: 10.1002/chem.201405984
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&
Crystal Engineering
Thermally Triggered Solid-State Single-Crystal-to-Single-Crystal
Structural Transformation Accompanies Property Changes
Quan-Quan Li, Chun-Yan Ren, Yang-Yang Huang, Jian-Li Li, Ping Liu,* Bin Liu, Yang Liu, and
Yao-Yu Wang[a]
Abstract: The 1D complex [(CuL0.5H2O)·H2O]n (1) (H4L=2,2’-
bipyridine-3,3’,6,6’-tetracarboxylic acid) undergoes an irrever-
sible thermally triggered single-crystal-to-single-crystal
(SCSC) transformation to produce the 3D anhydrous com-
plex [CuL0.5]n (2). This SCSC structural transformation was
confirmed by single-crystal X-ray diffraction analysis, ther-
mogravimetric (TG) analysis, powder X-ray diffraction (PXRD)
patterns, variable-temperature powder X-ray diffraction (VT–
PXRD) patterns, and IR spectroscopy. Structural analyses
reveal that in complex 2, though the initial 1D chain is still
retained as in complex 1, accompanied with the Cu-bound
H2O removed and new O(carboxyl)ꢀCu bond forming, the
coordination geometries around the CuII ions vary from a dis-
torted trigonal bipyramid to a distorted square pyramid.
With the drastic structural transition, significant property
changes are observed. Magnetic analyses show prominent
changes from antiferromagnetism to weak ferromagnetism
due to the new formed Cu1-O-C-O-Cu4 bridge. The catalytic
results demonstrate that, even though both solid-state ma-
terials present high catalytic activity for the synthesis of 2-
imidazolines derivatives and can be reused, the activation
temperature of complex 1 is higher than that of complex 2.
In addition, a possible pathway for the SCSC structural trans-
formations is proposed.
Introduction
is difficult to harvest intact single crystals for further tests after
employing multiple artifices (for example exchange of metal
centers, chemical reactions, light, or heat, etc.),[4] besides, most
of the reported examples focus only on the structure re-
search.[5] So far, further research of the solid-state SCSC trans-
formation, especially for the properties and the relationship
between the structures and properties, is imperative and chal-
lenging.
Solid-state single-crystal-to-single-crystal (SCSC) transforma-
tions of coordination polymers (CPs) have recently turned to
be an appealing and promising research field in molecular ma-
terials.[1] Such transformation processes usually involve the co-
ordination and/or covalent bond breakage and formation,
which not only lead to drastic structural rearrangement accom-
panied by changes of the coordination geometry, the coordi-
nation number, the dimensionality, etc. but also often result in
dramatic property changes such as color, magnetism, lumines-
cence, chirality, gas adsorption/selection, etc.[2] Especially,
sometimes the resulting multifunctional materials cannot be
directly obtained by traditional synthetic routes.[3] More impor-
tantly, the procedure of SCSC transformations can provide de-
tailed structural information for better understanding of the
mechanism of the transformation, and give insights into the
relationship between the structures and properties.[4] However,
such CPs SCSC transformations are relatively scarce because it
Imidazolines and their derivatives, as an important class of
bioactive molecules, are widely used in the fields of drugs and
pharmaceuticals.[6] The development of efficient catalyst sys-
tems for the synthesis of imidazolines and their derivatives has
recently attracted considerable attention. However, the proce-
dures for the construction of imidazoline generally suffer from
low product yields, poor functional-group tolerance, or expen-
sive catalysts.[7] So all the time, the major challenge of this cat-
alytic reaction is to look for new efficient and low-cost cata-
lysts. More recently, studies exhibit that a carboxylate CuII com-
plex appears to be an efficient Lewis acid catalyst for the syn-
thesis of imidazoline.[8] In addition, though the application of
CuII CPs in the catalytic synthesis of 2-imidazolines still remains
an underexplored area, it is a proven and promising way to
use the crystalline CPs as an attractive heterogeneous catalyst
due to their tunable structure, single-site active species as well
as their easy separation and recycling.[9] So by considering CPs
containing the transition metal CuII and polycarboxylic aromat-
ic compounds, there is a logical interest in studying their cata-
lytic properties in this sector. Furthermore, when the materials
before and after SCSC transformation are simultaneously used
as catalysts, analysis and compare of their catalytic activity
[a] Q.-Q. Li,+ C.-Y. Ren,+ Y.-Y. Huang, Prof. Dr. J.-L. Li, Prof. Dr. P. Liu,
Prof. Dr. B. Liu, Y. Liu, Prof. Dr. Y.-Y. Wang
College of Chemistry & Materials Science
Key Laboratory of Synthetic and
Natural Functional Molecule Chemistry
of the Ministry of Education, Shaanxi Key Laboratory of
Physico-Inorganic Chemistry
Northwest University, Xi’an 710069 (P.R. China)
E-mail: liuping@nwu.edu.cn
[+] These authors contributed equally to this work.
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405984.
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based on the detailed single-crystal structural characterization
have become possible. For the above reasons, it is quite neces-
sary to test the catalytic performances of the obtained CuII
CPs.
Discussion
Synthesis and dehydration of complex 1
Therefore, the main purposes of the present work are to
study the solid-state SCSC structural transformation and the
properties, particularly for the catalytic and magnetic proper-
ties, of the materials before and after SCSC transformation.
Based on the ligand 2,2’-bipyridine-3,3’,6,6’-tetracarboxylic acid
(H4L) (Figure 1a), we report herein a typical SCSC “polymeri-
Complex 1 was synthesized by reacting cheap Cu(NO3)2·3(H2O)
with the ligand H4L in 63% yield, which is much higher than
the previously reported 10%.[10] The improved yield and the
cheaper reactants have allowed obtaining enough quantity of
material for the catalytic tests. When heating at 2008C for 4 h
in dry air, single crystals remain single, whereas 1D complex
1 is dehydrated to produce 3D complex 2 with a color chang-
ing from blue-green to blackish-green (Figure S1 in the Sup-
porting Information). It is worthy to mention that complex 2
has never been reaped by reactions in solution, which confirms
that solid-state reactions can provide access to molecules oth-
erwise difficult or impossible to be obtained from solution re-
actions.
However, such dehydration process is irreversible. When
complex 2 is soaked into water, it cannot revert to the parent
complex 1 and could stabilize in water at room temperature at
least two weeks. This is not unexpected, as complex 2 exhibits
a dense and compact structure. Further water/moisture stabili-
ty tests of complexes 1 and 2 in air (10 days) and in boiling
water (6 h) also reveal that both frameworks are maintained.
Their high stabilities toward humidity and even boiling water
are confirmed by powder X-Ray diffraction (PXRD) methods
(see Figure S2 in the Supporting Information).
Figure 1. a) Chemical structure of the ligand 2,2’-bipyridine-3,3’,6,6’-tetracar-
boxylic acid. b) Change of the coordination modes of the ligand L4ꢀ during
the SCSC transformation. The ligand L4ꢀ in complex 1 adopts m4-coordina-
tion mode and bridges four Cu atoms, whereas in complex 2 it takes a m6-
coordination mode and bridges two more Cu atoms. Hydrogen atoms are
omitted for the sake of clarity.
Crystal structures of complexes 1 and 2
zation” reaction, transforming a 1D antiferromagnetic complex
[(CuL0.5H2O)·H2O]n (1) to a 3D weak ferromagnetic complex
[CuL0.5]n (2), which is driven by heat treatment to remove the
lattice H2O and the Cu-bound H2O sequentially. A possible
pathway for the SCSC structural transformations is proposed.
As in both complexes 1 and 2 there exist coordinatively unsa-
turated CuII centers, which may have their potential applica-
tions in catalysis, the catalytic function of these two obtained
Cu products were studied. The results demonstrate that both
CPs show excellent catalytic activity for the synthesis of 2-imi-
dazolines, although the activation temperature of complex 1 is
higher than that of complex 2, due to the different coordina-
tion environment of the active metallic CuII centers. To the
best of our knowledge, this is the first representation that the
catalytic activities of CPs, especially for the materials before
and after SCSC transformation, are simultaneously tested for
the synthesis of 2-imidazolines. The catalysts 1 and 2 remain
relatively stable, which is proven by the powder X-ray diffrac-
tion (PXRD) analyses and by IR spectroscopy of the reused and
recovered powders. This fact also accords with the conclusion
that this SCSC transformation is a solid-state reaction and has
never happened in solution. This work also shows the great
potential of developing CuII CPs as highly efficient, stable, recy-
clable, and reusable heterogeneous catalysts for the catalytic
synthesis of 2-imidazolines.
For the sake of understanding this solid-state SCSC transforma-
tion, a detailed crystal structure analysis of complexes 1 and 2
is necessary. X-ray single-crystal structure analysis demon-
strates that both of them crystallize in the monoclinic system
within the space group C/2c (Table S1 in the Supporting Infor-
mation). As shown in Figure 2a, complex 1 contains one
unique CuII ion, one half L4ꢀ ligand, one coordinated H2O mole-
cule, and one lattice H2O molecule in the asymmetric unit.
Each CuII atom is pentacoordinated showing a distorted trigo-
nal-bipyramidal geometry with t=0.95 (O5 from a terminal
H2O ligand and N1 from one L4ꢀ ligand are arranged at the
axial positions).[11] Each L4ꢀ ligand connects four contiguous
CuII centers with m4-coordination mode to form a ribbon-like
1D chain (Figures 1b and 2b). The intrachain Cu···Cu distances
are 5.571 and 5.410 ꢁ for Cu1···Cu2 and Cu1···Cu3, respectively,
whereas the interchain Cu1···Cu4 distance is 7.540 ꢁ and the
Cu3-Cu1-Cu4 angle is 111.08 (Figure S3a in the Supporting In-
formation). In the packing motif for complex 1, as shown in
Figure 2c, water molecules hold the adjacent chains together
through four kinds of hydrogen-bonding interactions (i.e., O5ꢀ
H5A···O3, O5ꢀH5B···O6, O6ꢀH6A···O1, and O6ꢀH6B···O4) to a 3D
supramolecular framework.
The powder X-ray diffraction analysis reveals that the as-syn-
thesized complex 1 is consistent with the simulated patterns
from the corresponding single-crystal structure, demonstrating
the phase purities (Figure S5 in the Supporting Information).
Thermal analysis shows that a weight loss of 13.5% in the
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decompose gradually at 2908C (Figure S6 in the Supporting In-
formation).
To determine whether single crystallinity is retained during
the dehydration process, the dehydrated crystalline phase 2 is
determined by single-crystal X-ray diffraction analysis. Structur-
al analysis reveals that the 1D complex 1 undergoes thermally
driven SCSC transformation to produce the 3D anhydrous
complex 2 [CuL0.5]n. In complex 2, the asymmetric unit contains
one unique CuII ion and one half L4ꢀ ligand (Figure 3). Different
Figure 3. Local coordination environment of the CuII ion in complex 2. Sym-
metry codes: A: ꢀx, y, 0.5ꢀz; B: x, ꢀy, ꢀ0.5+z; C: 0.5+x, 0.5+y, z.
to complex 1, the pentacoordinated CuII atom in complex 2
shows a distorted square-pyramidal geometry with t=0.37.[11]
The basal positions of the square pyramid are occupied by the
O1, O3A, O4C, and N1 atoms, whereas the O2B atom locates in
the apical position. For complex 2, the initial 1D chain is still
retained as in complex 1, although the coordination water
molecule in complex 1 is substituted by the uncoordinated
carboxylic oxygen atom (O4), which is similar to the previously
described work.[12] To visualize the “dehydrated” chain in the
SCSC transformation process, as shown as in Figure 4b, the
Figure 2. a) Local coordination environment of the CuII ion in complex 1.
Symmetry codes: A: 2ꢀx, 2ꢀy, 2ꢀz; B: x, y, 1+z. b) 1D chain of complex
1 along the c axis. c) 3D supramolecular structure of complex 1, which is
constructed by holding the adjacent chains together through four kinds of
hydrogen-bonding interactions (i.e., O5ꢀH5A···O3, O5ꢀH5B···O6, O6ꢀ
H6A···O1, and O6ꢀH6B···O4).
Figure 4. Structural transformation from complex 1 to two the different pos-
ited products 2’ and 2. The hydrated and dehydrated {Cu4L2} unit in complex
1 (a) and complex 2 (b), respectively, and the eight potentially free coordina-
tion sites of each dehydrated {Cu4L2} unit along four propagation directions
(c) and (d) are shown.
range of 80–1408C is in good agreement with the release of
the coordinated H2O molecules and lattice H2O molecules
(calcd 13.6%), and then the framework of complex 1 begins to
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Cu-bound water molecules from the 1D chain are omitted.
Each dehydrated {Cu4L2} unit has eight potentially free coordi-
nation sites including four unsaturated CuII centers and four
free O4 atoms and can act as a tetra-bridging ligand (one un-
saturated CuII center and one O4 atom as one conjugate pair
being bond to one neighboring “dehydrated” 1D chain). There-
fore, each “dehydrated” chain can connect four adjacent
chains forming four pairs of new O(carboxyl)ꢀCu coordination
bonds along four propagation directions. It was found that
there exist two possible arrangements, as shown in Figures 4c
and 4d, to form the different deduced products 2’ or 2
(Figure 4). In fact, the neighborhood 1D chains move along the
a axis to form a denser and more compact production 2. That
is to say, this 1D-to-3D SCSC structural transformation is trig-
gered by the entropically favored loss of water molecules, and
the main driving force for this transformation is due to the loss
of water molecules and the formation of a thermally stable,
dense, and compact crystalline 3D network. The topological
analysis indicates that the 3D architecture of complex 2 is a di-
nodal (3,6)-connected net with the point symbol
(42.6)2(44.62.88.10) (Figure S7 in the Supporting Information).
Compared with complex 1, it was found that some signifi-
cant structural changes occur after this SCSC transformation.
Firstly, accompanied by the Cu-bound and lattice water losing,
a new O(carboxyl)ꢀCu bond forms with a normal CuꢀO bond
length 1.964 ꢁ, and the Cu3-Cu1-Cu4 angle is reduced to
104.88 (Figure S3c in the Supporting Information). Secondly,
the coordination geometries around the CuII ions vary from
a distorted trigonal bipyramid to a distorted square pyramid.
The O2B atom from the adjacent L4ꢀ ligand is located in the
apical position with a longer Cu1ꢀO2B distance (2.230 ꢁ) due
b (90.0688), a (14.387 ꢁ), and V (1264.1(2) ꢁ3) of complex 2 are
smaller than that of complex 1 (108.9788, 19.884 ꢁ, and
1606(2) ꢁ3, respectively), which implies that the structure is
compacted by the interchain distances shortened and the
chains slipped during the transformations (Table S1 in the Sup-
porting Information). Actually, as shown in Figures 5 and S9 in
the Supporting Information, the adjacent 1D chains will move
closer together along a axis but farther apart along the b and
c axis in complex 2. Thus, the distances between the interchain
Cu atoms planes, the Cu1···Cu4 distance, and the Cu3-Cu1-Cu4
angle are indeed reduced from 4.209 ꢁ, 7.540 ꢁ, and 111.08 to
1.839 ꢁ, 4.872 ꢁ, and 104.88, respectively (Figures 5 and S3 in
the Supporting Information).
SCSC structural transformation analyzed by various tech-
niques
The SCSC structural transformation is also confirmed by ther-
mogravimetric (TG) analysis, PXRD patterns, variable-tempera-
ture PXRD patterns, and IR spectroscopy. Comparison of the IR
spectra of complexes 1 and 2 also reveals that complex 2 has
been almost completely dehydrated, for the observed strong
band in the range n˜ =3500–3320 cmꢀ1 in the spectrum of
complex 1, which is attributed to the OꢀH stretching vibra-
tions of H2O molecules, is nearly invisible in the spectrum of
complex 2 (Figure S10 in the Supporting Information).[13] The
existing extremely weak band for complex 2 is attributable to
the moisture in the air. Furthermore, the different frequency
numbers and shapes in the range of n˜ =1343–1373 and 1554–
1610 cmꢀ1, which are assigned to the ns(COOꢀ) and nas(COOꢀ)
modes, respectively, indicate the different coordination modes
to the Jahn–Teller effect. Thirdly, due to the new O(carboxyl)ꢀ of the carboxylic groups.[13] Actually, the carboxylic group in
Cu bond formed, the L4ꢀ ligand adopts a m6-coordination
mode and bridges two more Cu atoms in complex 2 (Fig-
ure 1b). Fourthly, for dragging the neighboring unsaturated
CuII centers and uncoordinated carboxylic O atoms closely to
forming new coordination bonds, the dihedral angles are
changed, containing the reduced dihedral angles (a–d) and
the increased dihedral angles (a–b, a–g, and b–g) (Figure S8 in
the Supporting Information). Fifthly, the cell parameters
complex 2 coordinates to the Cu center in a bidentate mode,
whereas in complex 1 there is the coexistence of both uni-
and bidentate coordinating carboxylic groups.
In addition, the PXRD patterns of complex 2 are consistent
with its simulated patterns but significant different to that of
complex 1 (Figure S11 in the Supporting Information), clearly
indicating that the structural transformation occurs. Compared
with complex 1, the main diffraction peaks at approximately
9.4 and 18.88 shift to about 12.2 and 24.78, respectively, which
correspond to the reflection of the (200) and (400) plane for
complexes 1 and 2 respectively. These reflection shifts also in-
dicate that the framework transforms from an open one to
a closed one, which is consistent with the results of single-crys-
tal X-ray diffraction studies. To track the process of the phase
transformation in solid states, VT-XRD was carried out. As
shown in Figure S12a in the Supporting Information, the re-
sults demonstrate that there are no obvious changes from
room temperature to 1008C, the XRPD patterns at 1508C are
very similar to the simulated one of complex 2, and the SCSC
transformation from complex 1 to complex 2 is almost com-
plete at 2008C. At 1108C, the peak at 148 is split and then
upon further heating, one of the split peaks at 168 appears
more prominently and the peak at 98 disappeared, which is in-
dicative for the formation of an intermediate. Unexpected,
though the framework of complex 2 destroys beyond 3508C,
Figure 5. The SCSC structural transformation from complex 1 to complex 2
with the removal of H2O molecules. The distances between the two inter-
chain Cu atom planes for complex 1 (a) and complex 2 (b) are given.
Dashed lines denote hydrogen bonds.
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the VT-PXRD result shows that some new diffraction peaks
appear in the range of 30–508. Thus, it is imperative to note
here that the crystallinity of the compound is still kept. These
diffraction peaks are in accord with the mixture of CuO and
Cu2O, indicating that the mixture of CuO and Cu2O is formed
after the decomposition of complex 2 (Figure S13 in the Sup-
porting Information).[14]
Similar behaviors are observed in the TG analysis results.
Complex 1 is heated at different temperatures ranging from 50
to 1558C for 4 h under air conditions, and then these samples
are analyzed by TG (Figure S12b in the Supporting Informa-
tion). The TG analysis of complex 2 exhibits no weight loss
until 2908C, proving that there is no molecular water in com-
plex 2 (Figures S6 and S12b in the Supporting Information).
The curves at 50–808C are nearly identical to that of complex
1, and the curve at 1558C exhibits nearly inexistence of water
molecules, which is close to that of complex 2. The curves at
90–1258C show partial water loss, providing a further evidence
for the existence of a potential intermediate during the dehy-
dration process. However, unfortunately our attempt by the
single-crystal X-ray diffraction method to characterize the inter-
mediate, which is obtained after “gently” heating the single
crystal of compound 1 at 90, 105, 115, and 1258C for 4 h
either in air or under vacuum, was unsuccessful.
The proposed SCSC structural transformation pathway
It is well known that the solid-state reaction occurs depending
on the fact that the reactive functional groups are already
close and aligned in the correct orientation. Owing to the
maintaining of single crystallinity after this structural transfor-
mation, a detailed analysis of the substitutable coordination
site of coordinated water molecules and the motile 1D chain
are possible. So the details of this SCSC transformation path-
way may be inferred.
Figure 6. a) The distances of Cu1···O4, Cu2···O4, O5(Cu1)···O4, and
O5(Cu2)···O4 as well as the coordination environment of the water molecule
between the chains in complex 1. b) The simulated semi-dehydrated “inter-
mediate” state during the SCSC transformation.
Meanwhile, the new possibly OꢀH···O hydrogen bonding
would be formed between uncoordinated O4 atom as hydro-
gen-bond acceptor and the Cu1-bound water as hydrogen-
bond donor, then ultimately the reactive functional group O4
is closer to the Cu1 center and is in the preferred orientation
(Figure 6b). The weak hydrogen-bonding interactions may play
an important role in bringing the reactive functional groups
closer together and in the correct orientations.
Based on the above-discussed structural analysis, it is known
that compound 2 is formed by the Cu-bound water losing and
new O4(carboxyl)ꢀCu bond formation. To get a deeper under-
standing of the coordination of the O4 atom with Cu, further
observation is needed. As shown in Figure 6a, it was found
that there are two potential coordination sites, that is, Cu2 or
Cu1, around the O4 atom. When selecting the potential coordi-
nation sites Cu2 or Cu1 to coordinate with the O4 atom, re-
spectively, different products 2’ or 2 will form (Figure 4). Thus,
it is meaning that the O4 atom coordinates with Cu1, though
Cu2 is closer to the substituent site O4 (Cu1···O4, 5.451 ꢁ;
Cu2···O4, 5.107 ꢁ). However, it was found that the O5(Cu1)···O4
distance (3.783 ꢁ) is shorter than the O5(Cu2)···O4 (3.807 ꢁ) dis-
tance (Figure 6a). Then the intermolecular hydrogen-bond in-
teractions between the carboxylate carbonyl groups, the free
molecular water, and the coordinated water molecules attract
our attention. Examples have been reported that lattice water
and coordination water can be removed stepwise in the dehy-
dration processes.[15] If the lattice water is removed firstly, it is
reasonable to expect that the hemi-dehydration intermediate,
that is, {CuL0.5H2O}, would be formed, which is also indicated
by the results of the TG analysis and the VT-PXRD patterns.
On the basis of above-presented analysis and assumption,
we could propose a possible pathway involving three steps in
the structural transformations (Figure 7). From the microscopic
point of view, in the first step, the removal of the lattice water
forms the “intermediate” state. The unsaturated carboxylic
oxygen atom O4 moves and turns to appropriate location and
direction to form hydrogen bonding with the coordinated
water molecules of the adjacent chain, accompanied by the
chains compaction and slip. In the next step, under higher
temperature, the removal of the Cu-bound H2O leaves the Cu
center unsaturated and activated. In the last step, the unsatu-
rated carboxylic O atoms (O4) further move and compensate
the vacancy of the activated Cu center to form a stable frame-
work. The initial 1D chain is retained throughout the dehydra-
tion process. We have outlined the possible pathways based
on both the assumed intermediate and the observation of the
initial and final structures of complexes 1 and 2 when taking
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Figure 7. Three distinct steps in the structural transformations. 1) The first
step is the removal of the lattice water molecules to form the “intermediate”
state. 2) The second step is the removal of the Cu-bound H2O leaving the
Cu unsaturated and activated. 3) In the last step the unsaturated carboxylic
O atoms (O4) further move and compensate the vacancy of the activated Cu
for a stable framework.
Figure 8. cmT and cm versus T plots for complexes 1 (a) and 2 (b). The solid
ꢀ1
lines denote the theoretical curves with the best-fit parameters. Inset cm
versus T plots and Curie–Weiss fitting line.
the dynamics of the H2O removal into consideration. The
mechanistic pathways outlined here provide us a reasonable
insight that is necessary to make better control of the desired
structures.
The magnetic data of complexes 1 and 2 were fitted by
using the magnetic chain model given in Equation (1).
Ng2b2SðS þ 1Þ 1 þ u
c ¼
Magnetic properties
3kT
1 ꢀ u
Variable-temperature magnetic susceptibilities of complexes
1 and 2 have been measured in an applied magnetic field (H=
1000 Oe) in the temperature range of 1.8–300 K. As shown in
Figure 8, at 300 K, the cmT values per Cu for complexes 1 and
2 are 0.46 and 0.44 cm3 Kmolꢀ1, respectively, larger than the
value expected for one independent CuII ion (S=1/2, g=2.0).
For complex 1, upon cooling, the cmT value shows a gradual
decrease to 0.45 cm3 Kꢀ1 molꢀ1 at 20 K, followed by a rapid de-
cline to 0.19 cm3 Kꢀ1 molꢀ1 at 1.8 K. The susceptibility data fit
the Curie–Weiss law (cm =C/(Tꢀq)) well, giving Curie (C) and
Weiss (q) constants of 0.47 cm3 Kmolꢀ1 and ꢀ1.78 K, respective-
ly, with R=4.98ꢂ10ꢀ4. The behavior of the cmT value and the
negative q value indicate a weak antiferromagnetic exchange
between the neighboring Cu centers. Different with complex
1, as the temperature is lowered, the cmT value of complex 2
increases slowly, reaching a maximum of 0.46 cm3 Kꢀ1 molꢀ1 at
25.0 K and then quickly decreases to 0.22 cm3 Kꢀ1 molꢀ1 at
2.0 K. The susceptibility data fit the Curie–Weiss law well,
giving Curie and Weiss constants of 0.42 cm3 Kꢀ1 molꢀ1 and
0.69 K, respectively, with R=6.17ꢂ10ꢀ4. The behavior of the
cmT value and the positive q value indicate a weak ferromag-
netic exchange between the Cu centers.
ꢀ
ꢁ
ꢀ
ꢁ
ð1Þ
JSðS þ 1Þ
kT
u ¼ coth
ꢀ
kT
JSðS þ 1Þ
The best-fit parameters obtained are g=2.22, J=
ꢀ0.45 cmꢀ1, zJ=ꢀ0.069 cmꢀ1, and R=1ꢂ10ꢀ5 for complex 1,
and g=2.15, J=0.08 cmꢀ1, zJ=ꢀ0.32 cmꢀ1, and R=8ꢂ10ꢀ5
for complex 2. The g values for complexes 1 and 2 are consis-
tent with the g values obtained by the variable-temperature
EPR analysis (Figure S14 in the Supporting Information). Here,
R is calculated from S[(cmT)obsꢀ(cmT)calcd]2/S[(cmT)obs
2
]
and the
other parameters in Equation (1) have their usual meaning.
The resulting different magnetism might be ascribed to the
drastic structural variance from the 1D complex 1 to the 3D
complex 2. Structural analysis demonstrates that, for complex
1, the neighboring Cu2+ ions are connected to each other by
carboxyl groups in anti conformation to forming a ribbon-like
1D chain and the atoms of Cu1-O-C-O-Cu2 are arranged in an
approximate horizontal orientation. The Cu1···Cu2 distance is
5.571 ꢁ and the torsion angle Cu1-O-C-O-Cu2 is 172.68. Where-
as for complex 2, although the Cu1-O-C-O-Cu2 is still kept, the
new Cu1-O-C-O-Cu4 is created and the atoms of the Cu1-O-C-
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O-Cu4 are located in an obvious non-planar orientation with
a short Cu1···Cu4 distance (4.872 ꢁ) and an extra distortional
(Cu1-O-C-O-Cu4 torsion angle is 157.98). In addition, in com-
plex 2 the Cu1···Cu2 distance is 5.610 ꢁ and the torsion angle
Cu1-O-C-O-Cu2 is 174.928. From the magnetic point of view,
the new formed Cu1-O-C-O-Cu4 with short Cu1···Cu4 separa-
tion and the obvious non-co-planarity of the atoms might be
the predominant factor for the ferromagnetic interactions of
complex 2.[16]
bly due to the different coordination environment of the metal
CuII ions (a distorted trigonal-bipyramidal geometry in complex
1 and a distorted square-pyramidal geometry in complex 2). In
order to further verify the catalytic performance of complexes
1 and 2 in this system, various aromatic and heteroaromatic ni-
triles were reacted with EDA to obtain the corresponding 2-
substituted imidazolines under the optimized reaction condi-
tions. As shown in Table 1, reactions catalyzed by both com-
Table 1. Preparation of 2-imidazolines catalyzed by compounds 1 and
2.[a]
Catalytic property study
Although large amounts of CP structures have been reported,
their huge potential in heterogeneous catalysis is still not fully
appreciated and far less explored. As observed in the struc-
tures 1 and 2, all CuII atoms are pentacoordinated and can be
used as unsaturated metal centers providing vacant coordina-
tion sites/Lewis acid sites, as well as implying their potential
applications in catalysis. In addition, the water stability and
bulk synthetic technique of complexes 1 and 2 also make
them possible to test their catalytic ability as Lewis acid cata-
lysts. To evaluate the catalytic function of both complexes, the
catalyzed reaction of 2-cyanopyridine with ethylendiamine
(EDA) was performed.
Entry Nitrile
Product
Catalyst Yield[b] [%]
1
2
3
4
5
6
7
8
1a
1b
1c
1d
3a
3b
3c
3d
1
2
1
2
1
2
1
2
97
91
1a
1b
1c
1d
3a
3b
3c
3d
100
100
100
100
91
The catalytic reactions were carried out by mixing a heteroar-
omatic nitrile, ethylenediamine, and the copper catalysts either
in solvent or in neat and stirring the mixture for 4 h. The ob-
tained results are summarized in Tables S4 in the Supporting
Information and 1. In order to identify the optimal reaction
conditions for the reaction, different solvents and reaction
temperatures were screened firstly in the presence of 1 mol%
catalyst. The data demonstrate that although the reaction at
room temperature is negligible (Table S4 in the Supporting In-
formation, entries 1–6), the conversion increases with the tem-
perature. The catalysts 1 and 2 show superior activity under
solvent-free reaction conditions at 1008C (under the boiling
point of EDA, i.e., 1168C) (Table S4 in the Supporting Informa-
tion, entries 21 and 22). Variation of the concentration of the
catalyst was investigated under the above-selected reaction
conditions in the presence of 0.2, 0.5, and 1.5 mol% catalyst
(Table S4 in the Supporting Information, entries 27–32). The
optimal conditions are: complex 1 or 2 as the catalyst
(0.5 mmol%), solvent free, and 1008C. The catalytic activities of
complexes 1 and 2 are comparable or higher than that of the
reported discrete CuII complex catalysts, because the reaction
temperature and the catalyst concentrations of complexes
1 and 2 are lower.[17]
82
9
1e
1 f
3e
3 f
1
89
10
11
12
1e
1 f
3e
3 f
2
1
2
92
79
72
[a] For details see the Experimental Section in the Supporting Informa-
tion. [b] Yield determined by GC-MS by using an internal standard.
plexes 1 and 2 show excellent or good conversions. For com-
parison, a blank experiment in the absence of catalysts was
performed to prove that no reaction occurs even at stirring
under optimal conditions for a longer reaction time (10 h). Fur-
thermore, the shutdown of the reaction by either removing
the catalysts or adding cupric nitrate/cupric sulfate verifies the
heterogeneous catalysis by complexes 1 and 2.
In addition, it was found that at relatively low temperatures
such as 40 and 708C, the yield of compound 3a catalyzed by
complex 1 is much lower than that received by using complex
2 as catalyst (408C: 18% (1) vs. 51% (2); 708C: 47% (1) vs.
67% (2)), whereas at 1008C, complexes 1 and 2 exhibit im-
proved and comparable reaction activities for the synthesis of
compound 3a in excellent yield (97% for complex 1 and 91%
for complex 2) (Table S4 in the Supporting Information, en-
tries 21 and 22). These results indicate that the activation tem-
perature of complex 1 is higher than that of complex 2, proba-
After the reactions were finished, the catalysts (i.e., com-
plexes 1 and 2) can be easily recovered by filtration, washed
with ethanol, and dried at room temperature. The recovered
powders were collected and characterized by PXRD analyses
and IR spectroscopy. The PXRD patterns of the recovered cata-
lysts 1 and 2 were found to well match those of the as-synthe-
sized complexes 1 and 2 (as shown in Figure S15 in the Sup-
porting Information), indicating that complexes 1 and 2 are
stable in the catalytic process. Furthermore, direct comparisons
of the IR resonances show that no deviations were observed
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and the catalyst was removed by filtration. The solvent of the fil-
trate was removed under reduced pressure and the residue was
purified by silica gel chromatography to give the pure product
(EtOAc/MeOH, 3:1). The characterization data for the products are
given in the Supporting Information.
between the fresh and recovered catalysts (Figure S16 in the
Supporting Information), which further proves that the original
structure is maintained. Taken together, these data suggest
that the catalysts 1 and 2 remain structurally stable after the
reaction. Moreover, reuse experiments based on complexes
1 and 2 were carried out three times under the conditions de-
scribed above. Almost no catalytic activity loss was observed
in the repeated tests for both complexes 1 and 2.
Reuse experiments were carried out for the reaction of 2-cyanopyr-
idine with EDA under the optimal conditions. Once the reaction
was completed, the catalyst was recovered by centrifugation,
washed with ethanol, and dried at room temperature. The recov-
ered powder was placed in a vial to repeat the reaction under the
same conditions twice. Every time the recovered powder was char-
acterized by PXRD and IR spectroscopy.
Conclusion
At elevated temperature, the CuII complex 1 undergoes a 1D-
to-3D solid-state SCSC structural transformations to form com-
plex 2 by losing both lattice and coordinated H2O molecules
and by forming new O(carboxyl)ꢀCu coordination bonds. This
transformation exhibits structural changes, such as the sliding
of the 1D chains, the conformation of the L4ꢀ ligand, the coor-
dination environment of the metal CuII ions changed from
In addition, a blank experiment was performed by the reaction of
2-cyanopyridine with EDA under otherwise identical reaction con-
ditions described above to probe the role of the catalysts. No for-
mation of compound 3a was observed even for stirring under
reflux conditions for a longer reaction time (10 h).
X-ray crystallographic measurements
Diffraction data were collected with
a MoKa radiation (l=
a
distorted trigonal-bipyramidal geometry to a distorted
0.71073 ꢁ) at 296(2) K on a Bruker-AXS SMART CCD area detector
diffractometer. The single-crystal crystallographic data for com-
plexes 1 and 2 were received by using a Bruker SMART APEX II
CCD diffractometer equipped with a graphite-monochromated
MoKa radiation (l=0.71073 ꢁ) by using f/w scan technique at
room temperature. The structure was determined by direct meth-
ods and refined by the full-matrix least-squares techniques on F2
with the SHELXS-97 crystallographic program package.[18] Aniso-
tropic thermal parameters were applied to all non-hydrogen
atoms. All the hydrogen atoms were generated geometrically ideal
positions and refined isotropically. CCDC 958426 (1) and 958427 (2)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
square-pyramidal. Furthermore, a relevant structure–function
correlation has been established among the structure of 1/2
and its magnetic and catalytic properties. Magnetic analyses
show that the new formed Cu-O-C-O-Cu array might be the
predominant factor for the significant magnetic changes from
antiferromagnetic to weak ferromagnetic. Both of these two
CuII polymers materials present highly effective, recyclable, re-
usable, and selective catalytic activity for the synthesis of 2-imi-
dazolines and its derivatives, though the activation tempera-
ture of complex 1 is higher than that of complex 2.
Experimental Section
Synthesis
Crystal data for [(CuL0.5H2O)·H2O]n: C7H6CuNO6; M=263.67; blue-
green block; 0.3ꢂ0.25ꢂ0.22 mm3; monoclinic; space group
C2/c (no. 15); a=19.884(2), b=8.133(6), c=10.500(8) ꢁ; b=
108.978(1)8; V=1606(2) ꢁ3; Z=8, 1calcd =2.181 gcmꢀ3; F000 =1056;
Bruker SMART APEX II CCD diffractometer; synchrotron radiation,
l=0.71073 ꢁ; T=296(2) K; 2qmax =51.988; 4177 reflections collect-
ed; 1568 unique (Rint =0.0250); final GooF=1.172; R1 =0.0395;
wR2 =0.1284; R indices based on 1361 reflections with I>2s(I) (re-
finement on F2); 136 parameters; 0 restraints; lp and absorption
Synthesis of [(CuL0.5H2O)·H2O]n (1): Cu(NO3)2·3(H2O) (0.10 mmol,
0.024 g) and the ligand H4L (0.05 mmol, 0.017 g) were added in
H2O (10 mL), the pH was adjusted to 7.0 with 1m KOH. Then the
mixture was transferred to a Teflon-lined stainless steel container
and kept at 1058C for 72 h. After cooling to room temperature, the
blue-green block-shaped crystals of compound 1 were isolated by
washing with distilled water and they were dried in vacuum. The
yield was about 62.6% based on H4L. IR (KBr): n˜ =3390.54 (s),
3120.96 (s), 1607.91 (vs), 1563.37 (m), 1449.70 (w), 1373.00 (s),
1253.61 (w), 1153.39 (w), 1079.99 (w), 843.86 (m), 782.94 cmꢀ1 (w);
elemental analysis calcd % for C7H6CuNO6: C 31.89, H 2.29, N 5.31;
found: C 31.83, H 2.32, N 5.28.
corrections applied; m=2.730 mmꢀ1
.
Crystal data for [CuL0.5]n: C7H2CuNO4; M=227.64; blackish green
block; 0.3ꢂ0.25ꢂ0.22 mm3; monoclinic; space group C2/c (no. 15);
a=14.387(7), b=8.358(7), c=10.512(7) ꢁ; b=90.068(2)8; V=
1264.1(2) ꢁ3; Z=8, 1calcd =2.392 gcmꢀ3; F000 =896; Bruker SMART
APEX II CCD diffractometer; synchrotron radiation, l=0.71073 ꢁ;
T=296(2) K; 2qmax =50.208; 2588 reflections collected; 1100
unique (Rint =0.0871); final GooF=1.092; R1 =0.0622; wR2 =0.1483;
R indices based on 741 reflections with I>2s(I) (refinement on F2);
118 parameters; 0 restraints; lp and absorption corrections applied;
Synthesis of [CuL0.5]n (2): When heating a sample of complex 1 at
2008C for 4 h in dry air, the blackish green block-shaped crystals of
complex 2 were obtained. IR (KBr): n˜ =3390.51 (w), 3120.98 (w),
1609.93 (s), 1554.39 (m), 1433.75 (w), 1343.01 (m), 1235.65 (w),
1156.57 (w), 1056.79 (w), 843.55 (m), 781.46 cmꢀ1 (w); elemental
analysis calcd (%) for C7H2CuNO4: C 36.93, H 0.89, N 6.15; found: C
36.98, H 0.92, N 6.17.
m=3.425 mmꢀ1
.
Catalysis studies
Acknowledgements
A mixture of nitrile (4 mmol), ethylenediamine, and Cu catalyst was
stirred 4 h. The progress of the reaction was monitored by TLC
(EtOAc/MeOH 3:1). After completion of the reaction, the mixture
was cooled to room temperature, then CH2Cl2 (10 mL) was added,
This work was supported by the National Natural Science
Foundation of China (No. 21143010, 21371142, 20931005, and
91022004), the Natural Science Foundation of Shaanxi Province
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[7] a) S. L. You, J. W. Kelly, Org. Lett. 2004, 6, 1681–1683; b) H. Salgado-
Zamora, E. Campos, R. Jimenez, H. Ceevantes, Heterocycles 1998, 47,
1043–1049.
[8] J. Zhang, X. Wang, M. P. Yang, K. R. Wan, B. Yin, Y. X. Wang, J. L. Li, Z. Shi,
Tetrahedron Lett. 2011, 52, 1578–1582.
[9] a) A. Dikhtiarenko, S. A. Khainakov, I. de Pedro, J. A. Blanco, J. R. Garcꢃa,
J. Gimeno, Inorg. Chem. 2013, 52, 3933–3941; b) N. Mizuno, M. Misono,
Chem. Rev. 1998, 98, 199–217; c) M. Yoon, R. Srirambalaji, K. Kim, Chem.
Rev. 2012, 112, 1196–1231; d) G. Kumar, R. Gupta, Inorg. Chem. 2013,
52, 10773–10787.
of China (No. 2012JQ2007), the Natural Scientific Research
Foundation of Shaanxi Provincial Education Office of China
(No. 2010JS116 and 2010JK875) and Xi’an Committee of Sci-
ence and Technology of China (No. CXY1429(6) and
CXY1434(7)). We thank Prof. W. W. Zuo for their dedication to
this work.
Keywords: catalysis
· coordination polymers · magnetic
´
[10] A. Kochel, M. Hołynska, Inorg. Chim. Acta 2013, 408, 193–198.
properties · single-crystal-to-single-crystal
[11] A. W. Addison, T. N. Rao, J. Reedijk, J. Vanrijn, G. C. Verschoor, J. Chem.
Soc. Dalton Trans. 1984, 1349–1356.
[12] D. L. Reger, A. Leitner, M. D. Smith, Inorg. Chem. 2013, 52, 10041–
10051.
[1] a) J. J. Vittal, Coord. Chem. Rev. 2007, 251, 1781–1795; b) G. J. Halder,
C. J. Kepert, Aust. J. Chem. 2006, 59, 597–604; c) H. L. Wang, W. Cao, T.
Liu, C. Y. Duan, J. Z. Jiang, Chem. Eur. J. 2013, 19, 2266–2270; d) Y. C.
Ou, D. S. Zhi, W. T. Liu, Z. P. Ni, M. L. Tong, Chem. Eur. J. 2012, 18, 7357–
7361; e) M. Du, C. P. Li, J. M. Wu, J. H. Guo, G. C. Wang, Chem. Commun.
2011, 47, 8088–8090.
[2] a) D. Armentano, G. D. Munno, T. F. Mastropietro, M. Julve, F. Lloret, J.
Am. Chem. Soc. 2005, 127, 10778–10779; b) X. N. Cheng, W. X. Zhang,
Y. Y. Lin, Y. Z. Zheng, X. M. Chen, Adv. Mater. 2007, 19, 1494–1498;
c) G. C. Lv, P. Wang, Q. Liu, J. Fan, K. Chen, W. Y. Sun, Chem. Commun.
2012, 48, 10249–10251; d) Y. Q. Lan, H. L. Jiang, S. L. Li, Q. Xu, Inorg.
Chem. 2012, 51, 7484–7491; e) M. H. Xie, X. L. Yang, C. D. Wu, Chem.
Eur. J. 2011, 17, 11424–11427; f) L. X. Shi, W. F. Zhao, X. Xu, J. Tang, C. D.
Wu, Inorg. Chem. 2011, 50, 12387–12389; g) A. Aslani, A. Morsali, Chem.
Commun. 2008, 3402–3404.
[3] a) Y. J. Zhang, T. Liu, S. Kanegawa, O. Sato, J. Am. Chem. Soc. 2009, 131,
7942–7943; b) M. Wriedt, A. A. Yakovenko, G. J. Halder, A. V. Prosvirin,
K. R. Dunbar, H. C. Zhou, J. Am. Chem. Soc. 2013, 135, 4040–4050.
[4] a) S. M. Neville, G. J. Halder, K. W. Chapman, M. B. Duriska, P. D. Southon,
J. D. Cashion, J. F. Letard, B. Moubaraki, K. S. Murray, C. J. Kepert, J. Am.
Chem. Soc. 2008, 130, 2869–2876; b) J. Campo, L. R. Falvello, I. Mayoral,
F. Palacio, T. Soler, M. Tomas, J. Am. Chem. Soc. 2008, 130, 2932–2933;
c) D. Sarma, S. Natarajan, Cryst. Growth Des. 2011, 11, 5415–5423;
d) K. D. Demadis, M. Papadaki, M. A. G. Aranda, A. Cabeza, P. Olivera-
Pastor, Y. Sanakis, Cryst. Growth Des. 2010, 10, 357–364.
[13] a) D. Deya, S. Roya, R. N. D. Purkayastha, R. Pallepogu, P. McArdle, J. Mol.
Struct. 2013, 1053, 127–133; b) T. Premkumar, S. Govindarajan, J. Therm.
Anal. Calorim. 2005, 79, 685–689; c) E. G. Bakalbassis, J. Mrozinski, C. A.
Tsipis, Inorg. Chem. 1986, 25, 3684–3690; d) Y. B. Huang, T. F. Liu, J. X.
Lin, J. Lꢄ, Z. J. Lin, R. Cao, Inorg. Chem. 2011, 50, 2191–2198.
[14] a) Z. G. Guo, M. V. Reddy, B. M. Goh, A. K. P. San, Q. L. Bao, K. P. Loh, RSC
Adv. 2013, 3, 19051–19056; b) H. Thakuria, G. Das, Polyhedron 2007, 26,
149–153; c) N. N. Sheno, A. Morsali, S. W. Joo, Mater. Lett. 2014, 117,
31–33; d) R. B. Wu, X. K. Qian, F. Yu, H. Liu, K. Zhou, J. Wei, Y. Z. Huang,
J. Mater. Chem. A 2013, 1, 11126–11129; e) F. Millange, R. E. Osta, M. E.
Medina, R. I. Walton, CrystEngComm 2011, 13, 103–108.
[15] a) X. Y. Wang, M. Scancella, S. C. Sevov, Chem. Mater. 2007, 19, 4506–
4513; b) D. Sarma, V. Srivastava, S. Natarajan, Dalton Trans. 2012, 41,
4135–4145.
[16] a) R. Baldomꢅ, M. Monfort, J. Ribas, X. Solans, M. A. Maestro, Inorg.
Chem. 2006, 45, 8144–8155; b) R. Carballo, B. Covelo, M. S. E. Fallah, J.
Ribas, E. M. Vꢅzquez-Lꢆpez, Cryst. Growth Des. 2007, 7, 1069–1077;
c) S. K. Dey, B. Bag, K. M. A. Malik, M. S. E. Fallah, J. Ribas, S. Mitra, Inorg.
Chem. 2003, 42, 4029–4035.
[17] a) H. X. Li, Z. G. Ren, D. Liu, Y. Chen, J. P. Lang, Z. P. Cheng, X. L. Zhu, B. F.
Abrahams, Chem. Commun. 2010, 46, 8430–8432; b) J. H. Fu, H. J. Li,
Y. J. Mu, H. W. Hou, Y. T. Fan, Chem. Commun. 2011, 47, 5271–5273;
c) M. Panera, J. Dꢃez, I. Merino, E. Rubio, M. P. Gamasa, Inorg. Chem.
2009, 48, 11147–11160.
[18] G. M. Sheldrick, SHELXS-97, Program for X-ray Crystal Structure Solution,
University of Gçttingen (Germany), 1997.
[5] a) Q. X. Yao, J. L. Sun, K. Li, J. Su, M. V. Peskov, X. D. Zou, Dalton Trans.
2012, 41, 3953–3955; b) G. Mahmoudi, A. Morsali, Cryst. Growth Des.
2008, 8, 391–394; c) A. S. R. Chesman, D. R. Turner, G. B. Deacon, S. R.
Batten, Chem. Commun. 2010, 46, 4899–4901.
Received: November 6, 2014
[6] A. O. Dolinkin, M. S. Chernov’yants, Pharm. Chem. J. 2010, 44, 99–106.
Published online on && &&, 0000
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FULL PAPER
SCSC: A 1D Cu complex undergoes an
irreversible thermally triggered single-
crystal-to-single-crystal (SCSC) transfor-
mation to produce the 3D anhydrous
complex (see figure). With the drastic
structural transition, significant magnet-
ic changes from antiferromagnetism to
weak ferromagnetism occur. Both mate-
rials present high catalytic activity for
the synthesis of 2-imidazolines.
&
Crystal Engineering
Q.-Q. Li, C.-Y. Ren, Y.-Y. Huang, J.-L. Li,
P. Liu,* B. Liu, Y. Liu, Y.-Y. Wang
&& – &&
Thermally Triggered Solid-State
Single-Crystal-to-Single-Crystal
Structural Transformation
Accompanies Property Changes
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Chem. Eur. J. 2015, 21, 1 – 10
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10
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!