Distinct structures of coordination polymers incorporating flexible triazole-based ligand: Topological diversities, crystal structures and property studies

Article abstract of DOI:10.1039/c0dt00894j

Six new coordination polymers, namely {[Zn(btec)_0.5(btmb)] ·2H₂O}_n (1), {[Co(btec)_0.5(btmb)(H ₂O)]·3H₂O}_n (2), {[Cu(btec) _0.5(btmb)]·H₂O}_n (3), {[Cu ₄(btc)₄(btmb)₄]·H₂O} _n (4), {[Co₃(bta)₂(btmb)₂] ·2H₂O}_n (5), [Co(Hbta)(btmb)]_n (6) (H₄btec = 1,2,4,5-benzenetetracarboxylate, H₃btc = 1,3,5-benzenetricarboxylate, H₃bta = 1,2,4-benzenetricarboxylate and btmb = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been successfully synthesized under hydrothermal conditions. All these complexes were structurally determined by single-crystal X-ray diffraction, elemental analysis, IR, TGA and XRD. Crystal structural analysis reveals that 1 is the first example of an unusual 3D framework with (8⁶) topology containing a 2D molecular fabric structure. Complex 2 exhibits a 3D NbO network with (6 ⁴·8²) topology. In 3, Cu(ii) ions are coordinated by anti-conformational btmb ligands to form left- and right-handed double helices, which are further bridged by the 4-connected btec^4- anions to give a 3D porous network. Complex 4 presents a rare 3D gra network structure with (6³)(6⁹·8) topology. 5 and 6 were obtained through controllable pH values of solution, 5 features a scarce binodal (3,8)-connected tfz-d framework with the trinuclear Co(ii) clusters acting as nodes, whereas 6 has an extended 2D 4⁴ grid-like layer and the adjacent 2D layers are interconnected by strong hydrogen bonding interactions into a 3D supramolecular framework. The structural diversities indicate that distinct organic acid ligands, the nature of metal ions and the pH value play crucial roles in modulating the formation of the resulting coordination complexes and the connectivity of the ultimate topological nets. Moreover, magnetic susceptibility measurement of 5 indicates the presence of weak ferromagnetic interactions between the Co(ii) ions bridged by carboxylate groups.

Full text of DOI:10.1039/c0dt00894j

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2011, 40, 793
www.rsc.org/dalton
PAPER
Distinct structures of coordination polymers incorporating flexible
triazole-based ligand: topological diversities, crystal structures and property
studies†
Chen Ren, Lei Hou, Bin Liu, Guo-Ping Yang, Yao-Yu Wang* and Qi-Zhen Shi
Received 22nd July 2010, Accepted 6th October 2010
DOI: 10.1039/c0dt00894j
Six new coordination polymers, namely {[Zn(btec)0.5(btmb)]·2H2O}n (1),
{[Co(btec)0.5(btmb)(H2O)]·3H2O}n (2), {[Cu(btec)0.5(btmb)]·H2O}n (3), {[Cu4(btc)4(btmb)4]·H2O}n (4),
{[Co3(bta)2(btmb)2]·2H2O}n (5), [Co(Hbta)(btmb)]n (6) (H4btec = 1,2,4,5-benzenetetracarboxylate,
H3btc = 1,3,5-benzenetricarboxylate, H3bta = 1,2,4-benzenetricarboxylate and btmb =
4,4¢-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been successfully synthesized under hydrothermal
conditions. All these complexes were structurally determined by single-crystal X-ray diffraction,
elemental analysis, IR, TGA and XRD. Crystal structural analysis reveals that 1 is the first example of
an unusual 3D framework with (86) topology containing a 2D molecular fabric structure. Complex 2
exhibits a 3D NbO network with (64·82) topology. In 3, Cu(II) ions are coordinated by
anti-conformational btmb ligands to form left- and right-handed double helices, which are further
bridged by the 4-connected btec4- anions to give a 3D porous network. Complex 4 presents a rare 3D
gra network structure with (63)(69·8) topology. 5 and 6 were obtained through controllable pH values of
solution, 5 features a scarce binodal (3,8)-connected tfz-d framework with the trinuclear Co(II) clusters
acting as nodes, whereas 6 has an extended 2D 44 grid-like layer and the adjacent 2D layers are
interconnected by strong hydrogen bonding interactions into a 3D supramolecular framework. The
structural diversities indicate that distinct organic acid ligands, the nature of metal ions and the pH
value play crucial roles in modulating the formation of the resulting coordination complexes and the
connectivity of the ultimate topological nets. Moreover, magnetic susceptibility measurement of 5
indicates the presence of weak ferromagnetic interactions between the Co(II) ions bridged by
carboxylate groups.
value of the solution etc.3–4 In this field, organic ligands act
Introduction
as bridging linkers, which are of utmost importance because
The design and synthesis of functional metal–organic frameworks
they greatly influence the overall framework of the coordination
(MOFs) by the self-assembly of organic ligands with appropriate
polymers in the self-assembly process. The partially or completely
functional groups and metal ions acting as connecting nodes
deprotonated forms of aromatic polycarboxylate ligands can
has attracted considerable interest, because of their intriguing
adopt diverse binding modes and geometrical configurations
variety of topologies and potential applications.1–2 Up to now,
to provide unique multidimensional structures and fascinating
topologies. Some examples are 1,4-benzenedicarboxylate,5 1,3,5-
benzenetricarboxylate,6 1,2,4-benzenetricarboxylate7 and 1,2,4,5-
benzenetetracarboxylate,8 which have been extensively employed
in the construction of interesting coordination polymers. The
introduction of additional N-donor ligands to such synthetic
systems can modify the structures and physical properties of the
final materials. In this regard, flexible bis-imidazole or triazole
ligands are good candidates for N-bridging ligands, which exhibit
special abilities to formulate new coordination polymers with
beautiful architectures and interesting properties.9–10
the numerous studies devoted to the preparation of coordi-
nation polymers have been influenced by many factors, such
as the metal-to-ligand molar ratio, the coordination geome-
try of the metal ions, the reaction temperature and the pH
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of
the Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic
Chemistry, College of Chemistry and Materials Science, Northwest Univer-
sity, Xi’an 710069, P.R. China. E-mail: wyaoyu@nwu.edu.cn; Fax: +86-29-
88303798
† Electronic supplementary information (ESI) available: Selected bond
distances and angles (Table S1), TG and XRD patterns for complexes 1–6.
Additional crystallographic figures. CCDC reference numbers 785345–
785350. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c0dt00894j
The flexible 1,2,4-triazole-containing 4,4¢-bis(1,2,4-triazol-1-
ylmethyl)biphenyl (btmb) ligand is also a good candidate, because
the 1,2,4-triazole group exhibits strong coordination capacity
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 793
©

View Article Online
and can provide more potential coordination sites, acting as a
bridging ligand to produce targeted coordination polymers with
fascinating architectures and multifunctional molecule materials.11
In addition, two triazole groups can twist freely around two –
CH2– groups with different angles, to meet the requirement of the
coordination geometries of the metal ions. So far, the coordination
polymers constructed from the mixed flexible btmb and aromatic
polycarboxylate ligands have rarely been investigated.11
On the basis of the aforementioned points, with the
aim of further understanding the coordination chemistry of
btmb and the influence of differently symmetrical polycar-
boxylate ligands on the formation of coordination polymers,
herein, the simultaneous hydrothermal reaction of aromatic
organic acids and long conformational bis-triazole ligand with
metal ions affords six novel coordination polymers. These
are {[Zn(btec)0.5(btmb)]·2H2O}n (1), {[Co(btec)0.5(btmb)(H2O)]·
3H2O}n (2), {[Cu(btec)0.5(btmb)]·H2O}n (3), {[Cu4(btc)4(btmb)4]·
H2O}n (4), {[Co3(bta)2(btmb)2]·2H2O}n (5), [Co(Hbta)(btmb)]n
(6) (H4btec = 1,2,4,5-benzenetetracarboxylate, H3btc = 1,3,5-
benzenetricarboxylate and H3bta = 1,2,4-benzenetricarboxylate).
The thermal stabilities of these coordination complexes were
discussed. Moreover, the photoluminescence property of 1 and
magnetic property of 5 have also been investigated in detail.
Elemental analysis (%) calcd for C23H21ZnN6O6: C 50.89, H 3.90,
N 15.48. Found: C 50.73, H 3.83, N 15.86. IR (cm-1): 357 m, 3126
m, 3100 m, 1669 s, 1594 s, 1544 w, 1496 w, 1382 s, 1272 m, 1129 s,
1074 w, 997 s, 832 m, 810 m, 754 s, 671 w, 640 m, 553 m.
Synthesis of {[Co(btec)0.5(btmb)(H2O)]·3H2O}n (2). The
preparation of
2
was similar to that of 1, except
Co(CH3COO)2·4H2O (0.0249 g, 0.1 mmol) was used instead of
Zn(NO3)2·6H2O. The pH value was then adjusted to 6.0 with 1 M
NaOH solution. Pink crystals of 2 were collected in 68% yield
(based on Co). Elemental analysis (%) calcd for C23H25CoN6O8:
C 48.26, H 4.40, N 14.68. Found: C 48.29, H 4.53, N 14.59. IR
(cm-1): 3423 m, 3116 w, 2930 w, 1634 m, 1566 s, 1521 w, 1489 w,
1433 m, 1374 s, 1278 m, 1132 m, 1011 m, 986 w, 866 w, 811 m, 756
m, 676 m, 645 w, 581 w, 521 w.
Synthesis of {[Cu(btec)0.5(btmb)]·H2O}n (3). The preparation
of 3 was similar to that of 1, except Cu(NO3)2·4H2O (0.0332 g,
0.1 mmol) was used instead of Zn(NO3)2·6H2O. The pH value was
then adjusted to 5.5 with 1 M NaOH solution. Blue crystals of
3 were collected in 42% yield (based on Cu). Elemental analysis
(%) calcd for C23H19CuN6O5: C 52.82, H 3.66, N 16.07. Found: C
52.57, H 3.97, N 15.93. IR (cm-1): 3440 s, 3128 m, 2926 w, 1629 m,
1584 s, 1540 m, 1486 m, 1363 s, 1285 m, 1206 w, 1124 s, 1043 w,
1002 m, 921 w, 891 w, 809 m, 752 m, 695 m, 599 w.
Synthesis of {[Cu4(btc)4(btmb)4]·H2O}n (4). The preparation
of 4 was similar to that of 3, except H3btc (0.0210 g, 0.1 mmol)
was used instead of H4btec. Only the pH value was then adjusted
to 5.5 with 1 M NaOH solution. Blue crystals of 4 were collected
in 40% yield (based on Cu). Elemental analysis (%) calcd for
C108H76Cu4N24O25: C 54.82, H 3.32, N 14.20. Found: C 54.39,
H 3.14, N 14.35. IR (cm-1): 3423 m, 3131 w, 3034 w, 1677 s, 1617
s, 1575 m, 1531 m, 1423 m, 1341 s, 1291 w, 1245 w, 1181 w, 1129
m, 1002 w, 841 w, 752 m, 720 m, 694 w, 628 w, 525 w.
Experimental
Materials and physical measurements
The 4,4¢-bis(1,2,4-triazol-1-ylmethyl)biphenyl (btmb) ligand was
synthesized according to the literature methods.10d,11 All other
starting materials were purchased from commercial sources, with-
out further purification and used as received. Elemental analyses
were recorded on a Perkin–Elmer model 240 C instrument. Mass
spectra were determined with AXIMA-CFRTMplus MALDI-
TOF Mass Spectrometer mode. IR spectra were recorded with
a Perkin–Elmer Spectrum One spectrometer in the region 4000–
400 cm-1 using KBr pellets. Thermal analyses were performed on
a NETZSCH STA 449 C microanalyzer with a heating rate of
10 ◦C min-1 under a N2 atmosphere. The X-ray powder diffraction
(XRD) data were recorded on a Rigaku RU200 diffractometer at
Synthesis of {[Co3(bta)2(btmb)2]·2H2O}n (5). The preparation
of 5 was similar to that of 2, except H3bta (0.0210 g, 0.1 mmol) was
used instead of H4btec. The pH value was then adjusted to 6.5 with
1 M NaOH solution. Pink crystals of 5 were collected in 70% yield
(based on Co). Elemental analysis (%) calcd for C54H42Co3N12O14:
C 51.48, H 3.36, N 13.34. Found: C 51.39, H 3.34, N 13.04. IR
(cm-1): 3441 s, 3158 w, 3117 m, 1593 s, 1544 m, 1486 w, 1396 s,
1369 w, 1323 m, 1238 w, 1181 w, 1122 m, 1063 m, 1021 w, 813 m,
781 w, 675 w, 540 w.
˚
60 KV, 300 mA and Cu-Ka radiation (l = 1.5406 A), with a scan
speed of 2◦ C min-1 and a step size of 0.02◦ in 2q. Luminescence
spectra for the solid samples were investigated with a Hitachi F-
4500 fluorescence spectrophotometer at room temperature. The
magnetic susceptibility of the microcrystalline sample restrained
in parafilm was measured on a Quantum Design MPMS-XL7
SQUID magnetometer with an applied field of 1 kOe. Diamagnetic
correction was estimated from Pascal’s constants.
Synthesis of [Co(Hbta)(btmb)]n (6). The preparation of 6 was
similar to that of 2, except H3bta (0.0210 g, 0.1 mmol) was used
instead of H4btec. The pH value was adjusted to 5.0 with 1 M
NaOH solution and pink crystals of 6 were collected in 30% yield
(based on Co). Elemental analysis (%) calcd for C27H20CoN6O6:
C 55.58, H 3.46, N 14.40. Found: C 55.39, H 3.69, N 14.34. IR
(cm-1): 3378 s, 3109 w,1567 s, 1435 w, 1379 s, 1277 w, 1182 w, 1128
m, 1076 w, 1017 m, 885 w, 851 w, 769 w, 756 m, 673 w, 642 w, 550
m, 501 w.
Preparation of complexes 1–6
Synthesis of {[Zn(btec)0.5(btmb)]·2H2O}n (1). The mixture of
Zn(NO3)2·6H2O (0.0297 g, 0.1 mmol), H4btec (0.0254 g, 0.1 mmol)
and btmb (0.0316 g, 0.1 mmol) was dissolved in 12 mL of distilled
water. The pH value was then adjusted to 6.0 with 1 M NaOH
solution and the resulting mixture was transferred and sealed in a
25 mL Teflon-lined stainless steel vessel. This was then he◦ated at
X-Ray crystallography
Single crystal X-ray diffraction analyses of the six complexes were
carried out on a Bruker SMART APEX II CCD diffractometer
equipped with a graphite monochromated Mo-Ka radiation (l =
◦
150 C for 3 days and cooled to room temperature at 10 C h-1.
˚
Colourless crystals of 1 were collected in 51% yield (based on Zn).
0.71073 A) by using f/w scan technique at room temperature.
794 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Table 1 Crystal data and structure refinements for complexes 1–6a
Complexes
1
2
3
4
5
6
Formula
C23H21ZnN6O6
542.83
Monoclinic
C23H25CoN6O8
572.42
Monoclinic
C23H19CuN6O5
522.98
Monoclinic
C108H78Cu4N24O25
2366.11
Monoclinic
C54H42Co3N12O14
1259.79
C27H20CoN6O6
583.42
Orthorhombic
Formula mass
Crystal system
Space group
Triclinic
¯
P21/c
P21/c
C2/c
P21/c
P1
Pnma
˚
a/A
14.967(5)
14.962(5)
10.836(4)
90
15.237(7)
10.469(5)
15.889(7)
90
28.600(4)
11.5539(14)
17.686(2)
90
10.1765(11)
16.4109(18)
17.3490(17)
90
9.301(2)
10.576(3)
14.184(3)
86.683(3)
84.712(4)
77.508(3)
1355.4(6)
1
14.8802(15)
18.6040(19)
9.5356(10)
90
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
92.494(5)
90
2424.4(14)
4
1.487
1.064
91.075(7)
90
2534(2)
4
1.500
0.737
116.123(2)
90
5247.3(11)
8
1.319
0.884
119.258(2)
90
2527.8(4)
1
1.553
0.921
90
90
2639.8(5)
4
1.468
0.704
1196
2.19–25.10
12 615/2429
1.040
3
˚
V/A
Z
Dc/g cm-3
1.543
0.986
643
1.44–25.10
6861/4738
1.046
R1 = 0.0709
wR2 = 0.1913
m/mm-1
F [000]
1116
1184
2128
1208
q/◦
1.36–25.10
11 776/4298
1.033
R1 = 0.0815
wR2 = 0.1734
2.33–25.10
12 342/4486
1.008
R1 = 0.0642
wR2 = 0.1427
1.93–25.10
12 898/4664
1.029
R1 = 0.0755
wR2 = 0.2246
1.83–25.09
12 407/4473
1.037
R1 = 0.0462
wR2 = 0.1137
Reflections/unique collected
Goodness-of-fit on F2
Final Ra indices [I > 2s(I)]
R1 = 0.0597
wR2 = 0.1610
2
a R1 = R(|Fo| - |Fc|)/R|Fo|; wR2 = [Rw(Fo - Fc2)2/Rw(Fo2)2]1/2
.
All structures were solved by direct methods and refined by full-
matrix least-squares fitting on F2 by SHELX-97.12 Absorption
corrections were applied by using multi-scan program SADABS.13
All of the nonhydrogen atoms were refined anisotropically. The
hydrogen atoms of the organic ligands were refined as rigid groups.
In 2, the water hydrogen atoms of O6, O7 and O8 were located
in difference Fourier maps and placed in calculated positions.
Some of hydrogen atoms from the water molecules in complexes
1, 3, 4 and 5 could not be positioned reliably. In complex 3,
the two water O atoms, O5 and O6 were assigned 0.6 and 0.4
occupancies with no hydrogen atoms. Complex 4 has disordered
free water molecule with the occupancy of 0.25. The results of
TG and elemental analyses further confirmed the existence of
water molecules in 3 and 4. During refinement of the structure,
some restraints were applied including distance restraints (DFIX)
and thermal restraints (ISOR) which have been used on some
unreasonable atoms in order to permit acceptable refinement of
these parameters in complexes 1–6.
on the employment of different aromatic polycarboxylate ligands
(H3btc, H3bta and H4btec), because differences in their size, their
coordination ability, the number of carboxylate groups and the
positions of the carboxylate groups may influence the framework
of the final structure in the assembly process. In this study, it should
be emphasized that the introduction of Zn(II), Co(II) and Cu(II)
centre ions gave varied structures and topologies in 1–3. When the
pH value of the solvent was adjusted to 6.5 and 5.0, the H3bta
ligand shows different coordination modes in complexes 5 and 6,
respectively. All the complexes are air stable and insoluble in water
or common organic solvents.
Structural description
{[Zn(btec)0.5(btmb)]·2H2O}n (1)
Single-crystal X-ray structural analysis reveals that 1 presents an
interesting 3D network with a weave structure. The asymmetric
unit is comprised of one Zn(II) ion, half of a btec4- ligand,
two half btmb ligands and two water solvent molecules. The
half btec4- ligand lies about an inversion centre, while the two
half btmb ligands each lie about other independent inversion
centres. As shown in Fig. 1a, each Zn(II) ion is coordinated by
two carboxylic oxygen atoms from two different btec4- anions
The detailed crystallographic data and other pertinent infor-
mation for complexes are summarized in Table 1. Selected bond
lengths and angles are listed in Table S1.† Crystallographic data
(excluding structure factors) for 1–6 have been deposited at the
Cambridge Crystallographic Data Centre with CCDC reference
numbers 785345–785350.
˚
(Zn–O = 1.931(6) and 1.945(6) A) and two nitrogen atoms from
˚
two different btmb ligands (Zn–N = 2.010(8) and 2.007(7) A),
Results and Discussion
displaying a distorted tetrahedral environment, with all the bond
lengths around the metal centres within the normal range.8e Each
btec4- anion adopts a m4 bridging mode to link four Zn atoms
to form a sheet (Scheme 1a), leading to a 2D layer structure
(Fig. 1b).14 These adjacent 2D layers are further extended into
3D framework by anti-conformational btmb ligands. Each btmb
ligand adopts an anti-configuration bridging mode to link the
Zn(II) ions to form a 1D undulating chain with Zn ◊ ◊ ◊ Zn distances
Syntheses
As is well known, the hydrothermal synthesis method has been
demonstrated to be an effective and powerful technique for grow-
ing crystals of coordination polymers with interesting structural
motifs and special properties. The construction of coordination
polymers depends on the combination and careful control of many
factors.3–4 The control of the final product under hydrothermal
reaction conditions is still a great challenge. We focus our attention
˚
of 17.071(9)–18.148(3) A. However, it is fascinating that the
crosslinking of adjacent 1D undulating [Zn(btmb)]n chains via
2-
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 795
©

View Article Online
Fig. 1 (a) The coordination environment of the Zn(II) ions in 1, water molecules have been omitted for clarity. Symmetry code: A = x, 0.5-y, 0.5+z,
B = 2-x, -y, 1-z. (b) The 2D layer structure based on Zn(II) and 4-connected btec4- anions. (c) View of the 2D (1O/1U) molecular fabric structure is
formed by 1D undulating chains. (d) Perspective view of the 3D structure of 1 along the c axis, the red space filling model shows the channels with water
molecules. (e) Schematic description of the 3D framework with (86) topology.
btec4- anions (O5 ◊ ◊ ◊ O4#1 = 2.762(9) A, O6 ◊ ◊ ◊ O5#2 = 2.958(5) A,
˚
˚
˚
O6 ◊ ◊ ◊ O1#3 = 2.855(1) A; #1 x, 1+y, z. #2 1-x, 1-y, -z. #3 -1+x,
0.5-y, -0.5+z), to further stabilize the resulting 3D framework
(Fig. 1d). From the topological point of view, if the Zn(II) ions
and btec4- ligand are viewed as 4-connected nodes and btmb
ligands are considered as linear linkers, the whole framework of
coordination polymer 1 can be topologically considered as a scarce
3D framework with (86) net (Fig. 1e). Notably, this is the first
example of a 3D coordination polymer containing weave structure
with (86) topology.16
{[Co(btec)0.5(btmb)(H2O)]·3H2O}n (2)
The asymmetric unit of 2 contains one Co(II) ion, half of a btec4-
ligand, one btmb ligand and four water molecules. The btec4-
ligand is generated by an inversion centre located in the middle
of the aromatic ring and one of the four water molecules (O5)
is directly bonded to the Co(II) centre. Each Co(II) ion adopts
a distorted octahedral coordination geometry (Fig. 2a), which is
coordinated by two nitrogen atoms from two btmb ligands (Co1–
Scheme 1 The coordination modes of the aromatic carboxylic acids in
complexes 1–6.
weak p ◊ ◊ ◊ p stacking interactions leads to a 2D “one-over/one-
under”(1O/1U) molecular fabric structure (Fig. 1c), which is also
observed in other 1D coordination polymers.15 The weak p ◊ ◊ ◊ p
stacking interactions exist between the two phenyl rings, with a
˚
N1 = 2.098(4) and Co1–N4 = 2.143(4) A), two oxygen atoms from
one chelating carboxylate group (Co1–O1 = 2.189(3), Co1–O2 =
4-
˚
˚
centre-to-centre distance of 4.056(6) A, which stabilizes the crystal
2.173(3) A), one monodentate oxygen atom from a btec ligand
˚
structure. To the best of our knowledge, these so-called fabric
structures, which are interesting networks, are still surprisingly
rare.15
In addition, there exist hydrogen bonding interactions between
the free water molecules and the carboxylic oxygen atoms of the
(Co1–O4 = 2.029(3) A) and one coordinated water molecule (Co1–
˚
O5 = 2.045(4) A). If the btmb ligand is neglected, each completely
deprotonated btec4- anion acts as a m4 bridging ligand, linking four
Co(II) ions to build a 2D layer structure (Scheme 1b, Fig. 2b).14
On the basis of this conductive way, these neighbouring 2D layers
796 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Fig. 2 (a) Perspective drawing of 2 showing the local coordination environment around the Co(II) ion. Symmetry code: A = -1+x, 0.5-y, -0.5+z, B =
-x, -0.5+y, 0.5-z, C = -x, 1-y, 1-z. (b) View of 2D layer structure in 2. (c) Schematic view of the topological framework of 2.
˚
are further connected together by btmb ligands to generate a 3D
framework (Figure S1a†).
2.000(5) A). However, the bond lengths of Cu1–O2 and Cu1–
O5 are obviously longer than the normal range of the Cu–O
bond, these are suggested to be non-negligible weak interactions
between the metal centre and the oxygen atoms.19 These weak
interactions may play an important role in fixing the metal centres
in a definite coordination geometry in 3. Similarly to 2 (Scheme
1b), the four carboxylic groups of the fully deprotonated btec4-
ligand exhibit two kinds of coordination modes. The btec4- ligand
links copper ions to generate a 2D layer structure (Fig. 3b). More
interestingly, Cu(II) ions are bridged by the anti-conformational
btmb ligand to produce two kinds of 1D double helical chains
Water clusters (H2O)n play an important role in crystallizing
and stabilizing the conformation of the native crystal polymers,
due to their ability to form hydrogen bonds with the host
structure.17 Interestingly, guest water molecules in 2 assemble
themselves to form a water trimer, (H2O)3, through hydrogen
˚
bonding interactions with distances of 2.833(7) A (O7 ◊ ◊ ◊ O6) and
˚
2.929(2) A (O6 ◊ ◊ ◊ O8), which is connected by O3 to give an infinite
1D chain (Figure S1b†). The bond angles of (O3 ◊ ◊ ◊ O7 ◊ ◊ ◊ O6),
(O7 ◊ ◊ ◊ O6 ◊ ◊ ◊ O8), (O6 ◊ ◊ ◊ O8 ◊ ◊ ◊ O3) and (O8 ◊ ◊ ◊ O3 ◊ ◊ ◊ O7) are
139.46◦, 98.09◦, 116.87◦ and 115.74◦, respectively. More notice-
ably, these intermolecular hydrogen bonding interactions further
stabilize and strengthen the overall structure of complex 2.
From the topological view, the btec4- anions and Co(II) centre
can be considered as 4-connected nodes, the btmb ligand is
simplified as a linker between the metal centres and the structure
of 2 can be described as a 3D NbO network with (64·82) topology
(Fig. 2c).18
˚
(left- and right-handed) with a pitch of 23.10(7) A (Fig. 3c). Two
examples of double helical chains constructed with flexible btmb
and bimb ligands have been reported previously (bimb = 4,4¢-
bis(1-imidazolyl)biphenyl).9a,20 These 1D double helical chains are
further superposed and interlinked by 4-connected btec4- anions,
to generate a 3D porous framework (Fig. 3d). Notably, there exist
weak hydrogen bonding interactions between O4, O5 and O6
˚
(O ◊ ◊ ◊ O = 2.889(0)–3.016(1) A) from the host framework, which
stabilize the whole crystal structure of 3. When removing free
water molecules, the effective free volume of 3 was calculated by
3
{[Cu(btec)0.5(btmb)(H2O)]·H2O}n (3)
˚
PLATON analysis as 24.9% of the crystal volume (1305 A out of
3
21
˚
the 5247 A unit cell volume).
Single-crystal X-ray crystallography reveals that complex 3 rep-
resents a novel 3D porous coordination polymer, consisting of
double helical chains with Cu(II)-btmb units. As shown in Fig.
3a, the half btec4- ligand lies about an inversion centre in the
asymmetric unit, the Cu(II) centre represents a highly distorted
octahedral coordination sphere that is defined by three oxygen
atoms from two distinct btec4- ligands (Cu1–O1 = 1.978(4), Cu1–
In the view of topology, the simplified nodes of the Cu(II) centres
and btec4- anions are the same as in complexes 1 and 2. Hence, the
overall framework for 3 can be regarded as a new 4-connected 3D
network with Schla¨fli symbols (62·84)(64·82)2 (Fig. 3e).
{[Cu4(btc)4(btmb)4]·H2O}n (4)
˚
˚
O2 = 2.626(8) and Cu1–O3 = 1.953(3) A), one oxygen atom from
a water molecule (Cu1–O5 = 2.799(5) A) and two nitrogen atoms
When the symmetric H4btec ligands are replaced by trigonal H3btc
from two different btmb ligands (Cu1–N1 = 1.980(5), Cu1–N4 =
ligands, a different 3D metal–organic framework 4 was obtained.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 797
©

View Article Online
Fig. 3 (a) The coordination environment of the Cu(II) ion in 3, all hydrogen atoms were omitted for clarity. Symmetry code: A = 0.5-x, -0.5+y, 0.5-z,
B = -x, -1+y, 0.5-z, C = 0.5-x, 0.5-y, -z. (b) Schematic view of the 2D layer based on btec4- anions and Cu(II) ions. (c) 1D double (left and right-handed)
helical chains in 3. (d) Schematic representation of the 3D framework and helical rectangular tubes of 3. (e) Schematic view of the topological structure
of 3. The btmb linkers are shown as the two-coloured blue bonds.
The asymmetric unit of 4 consists of one Cu(II) ion and one btc3-
anion in general positions, two half btmb molecules each lying
about independent inversion centres and a quarter of a free water
molecule. Each Cu(II) centre displays an octahedral coordination
geometry with two nitrogen atoms from two independent btmb
In the previous work, one 3D complex [Cu3(btc)2-
(bimb)2(H2O)3]n was hydrothermally synthesized by incorpo-
rating a rigid imidazole-based spacer, bimb and a rigid aro-
matic 1,3,5-benzenetricarboxylate, which exhibits a trinodal 4-
connected framework.4a Btmb is more flexible than the rigid
bimb ligand. It generates the strong spacial tendency because
of showing changeable conformational coordination modes with
metal ions.8d,9 Suitable steric geometry of the second ligands is
also very important for the fabrication of the final coordination
architectures.
˚
ligands (Cu–N = 1.973(3) and 1.980(3) A), four oxygen atoms
from three different btc3- anions (Cu1–O = 1.966(2), 1.972(2),
˚
2.372(2) and 2.732(1) A) (Fig. 4a). The longer Cu1–O3 bond is
˚
2.732(1) A, suggesting a non-negligible weak interaction which
can be regarded as a semi-chelating coordination mode to stabilize
the octahedral geometry of the Cu(II) centre.4a The completely
deprotonated btc3- anion displays bis-chelating and monodentate
coordinated modes (Scheme 1c), in which each btc3- anion can also
be considered as a 3-connected node, to coordinate with Cu(II) ions
to generate a 2D honeycomb network with (6,3) sheets (Fig. 4b).22
These 2D frameworks are further linked by anti-conformational
btmb ligands to form a 3D framework along the a axis (Figure
S2†). Compared with other coordination polymers containing
btmb ligands, a distinct 1D chain was formed by the metal centres
and Z-shaped btmb ligands, without twisting the two phenyl rings
(Fig. 4c).11 In the view of topology, the Cu(II) centre and btc3-
ligand are regarded as 5- and 3-connected nodes and btmb ligand
is considered as a linker, respectively. Therefore, the structure of 4
can be defined as a binodal (3,5)-connected 3D gra network with
Schla¨fli symbols of (63)(69·8) (Fig. 4d). It should be emphasized
that MOFs possessing a binodal (3,5)-connected framework are
relatively rare, so far only a few coordination polymers with gra
nets have been found.23
{[Co3(bta)2(btmb)2]·2H2O}n (5)
Compared with complex 2, in order to investigate the influence
of asymmetrical phenyl polycarboxylic acid on the construction
of coordination polymers, the highly asymmetrical H3bta ligand
was introduced, which leads to a new complex 5. Significantly,
it is interesting that btmb displays an asymmetrical gauche
conformation with the different positions of the nitrogen atoms
in 5 (See ESI†). There are two crystallographically independent
Co(II) ions, both of which show distorted octahedral coordination
geometries. It should be noted that the Co1 atom is in a general
position in the asymmetric unit and the other Co2 atom lies on a
crystallographic inversion centre. Each Co1 centre is coordinated
by four oxygen atoms from three separated bta3- anions (Co1–
O1 = 2.049(4), Co1–O2 = 2.058(4), Co1–O3 = 2.164(4) and Co1–
˚
O5 = 2.064(4) A) and two nitrogen atoms from two btmb ligands
˚
(Co1–N1 = 2.175(6) and Co1–N4 = 2.130(5) A). Co2 is also
798 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Fig. 4 (a) The coordination environment of the Cu(II) ion in 4, all hydrogen atoms were omitted for clarity. Symmetry code: A = -1+x, y, z, B = 0.5-x,
-0.5+y, 1.5-z. (b) View of the 2D layer with (6,3) sheets. (c) 1D chain based on Cu(II) ions and the btmb ligands. (d) Schematic representation of the
(3,5)-connected 3D gra network with Schla¨fli symbols (63)(69·8) in 4.
six-coordinated by four oxygen atoms from three bta3- anions
represents a new example of binodal high-connected MOFs in
coordination chemistry frameworks.
˚
(Co2–O3 = 2.139(4) and Co2–O6 = 2.048(4) A) and two nitrogen
˚
atoms from two btmb ligands (Co2–N5 = 2.150(5) A) (Fig. 5a). As
described in 1–4, 1D chains are formed by bridging btmb ligands
with bis-monodentate coordination mode. However, in the case of
5, the asymmetrical btmb ligand adopts a tridentate coordination
mode, which plays a 3-connected role in bridging Co(II) ions to
generate a ladder-like chain (Fig. 5b). The bta3- anion shows a
m6 coordination mode (Scheme 1d)24 and the Co(II) centres are
interconnected by carboxylate groups to form a 2D layer structure,
containing a trinuclear Co(II) cluster unit (Co1, Co2, Co1a) (Fig.
5c). The Co(II) ◊ ◊ ◊ Co(II) distances are in the range of 3.514(9)–
[Co(Hbta)(btmb)]n (6)
When the hydrothermal reactions of H3bta, btmb and cobalt
salts were carried out at about pH value 5.0, a 2D grid-like
layer structure of complex 6 was obtained. The asymmetric unit
of 6 consists of one Co(II) ion, half of a btmb molecule and
one Hbta2- anion. The Co(II) ion and Hbta2- ligand lie on a
mirror plane with disorder of the carboxylic group and the half
btmb ligand lies about an inversion centre in the asymmetric
unit. As shown in Fig. 6a, the Co(II) ion shows a tetrahedral
geometry, coordinated by two nitrogen atoms from two btmb
˚
4.569(0) A. These 2D layers are then pillared by flexible btmb
spacers in two directions to generate a 3D framework with 1D
water channels (Fig. S3†). After removal of the water molecules,
PLATON analysis indicated that the effective free volume of 5 was
˚
ligands (Co1–N1 = 2.037(5) A) and two oxygen atoms from two
Hbta2- molecules (Co1–O = 1.909(5) and 1.976(4) A). The Co(II)
˚
3
3
˚
˚
12.4% of the crystal volume (168 A out of the 1355 A unit cell
volume).21
ions are bridged by anti-conformational btmb ligands to form a
1D infinite zigzag chain with a Co ◊ ◊ ◊ Co distance of 18.256(0)
˚
On the basis of the simplification principle, if the trinuclear
Co(II) cluster unit is considered as an 8-connected single node, the
bta3- anion can be viewed as a 3-connected node and btmb ligand
can be regarded as a linear linker between the trinuclear Co(II)
clusters. Then the resulting structure of coordination polymer
5 can be classified as a unique binodal (3,8)-connected tfz-d
framework with Schla¨fli symbols (43)2(46·618·84) (Fig. 5d),25 which
A, which is further interconnected through the bis-monodentate
Hbta ligands (Scheme 1e) to generate a 2D undulating network
with (4,4) sheets (Fig. 6b). In addition, the adjacent 2D undulating
layer structures are parallel with each other and are extended by the
strong hydrogen bonding interactions into a 3D supramolecular
architecture (O3 ◊ ◊ ◊ O2 C = 2.495(7) A. Symmetry code: C = 1/2+x,
1/2-y, 1/2-z) (Fig. 6c).
˚
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 799
©

View Article Online
Fig. 5 (a) Coordination environment of the Co(II) ion in 5, all hydrogen atoms were omitted for clarity. Symmetry code: A = 1-x, 2-y, 1-z, B = 1+x, y,
z, C = -1+x, 1+y, 1+z, D = -1+x, y, z, E = -x, 3-y, 1-z, F = -1-x, 3-y, 1-z, G = 1-x, 2-y, -z, H = -2+x, 1+y, 1+z. (b) The 1D ladder-like chain was
formed by btmb ligands and Co(II) ions. (c) View of the 2D network containing trinuclear Co(II) clusters. (d) Schematic view of the topology of 5. Pink
spheres represent trinuclear Co(II) cluster units, red nodes show bta3- anions and btmb bridges are shown as blue linkers.
and 6 were obtained under similar reaction conditions, but at
different pH values, which were adjusted by the addition of 1M
NaOH. In complexes 5 and 6, the H3bta ligand displays m6 and
m2 bridging modes, respectively (Scheme 1d–e), it has been shown
Comparison of the structures of coordination polymers
In the same synthetic conditions, the introduction of symmetrical
and asymmetrical polycarboxylate ligands into the M(II)-btmb
system affords diverse frameworks. In the 3D coordination
that an increase in the pH value results in a higher connectivity
level of the bta3- ligands, which in turn affects the formation
of the high-dimensional reaction products and the topological
networks.
complexes 1–3, the highly symmetrical H4btec ligand exhibits
a m4 bridging mode to link the M(II) centres, to give 2D grid
structures, which are extended into 4-connected topological frame-
works through long flexible bis-triazole ligands. The different
metal centres may be responsible for the structural diversities in
1–3. Compared with the symmetrical H4btec ligands, the unique
three carboxylic groups of the asymmetrical H3bta ligand offer
more complicated coordination modes with the Co(II) ions,
consequently resulting in the formation of a 3D (3,8)-connected
architecture containing trinuclear Co(II) cluster units in 5. Each
fully deprotonated bta3- anion adopts a m5 coordination mode
Thermal stability analyses and X-ray power diffraction
To estimate the thermal stabilities of the six complexes, thermo-
gravimetric analyses (TGA) experiments were carried out from
30 to 850 ◦C (Fig. S4†). The TGA curve of 1 shows that the
first weight loss of 6.18% appeared from 60 to 120 ◦C, this
corresponded to the loss of the two free lattice water molecules
(calculated, 6.04%) and the second weight loss of 20.56% from
280 to 380 ◦C corresponded to the loss of the half btec molecule
(calculated, 20.10%), the framework was then decomposed quickly
resulting in the residue ZnO. For complex 2, the first weight loss
1
1
2
1
1
1
with three carboxylate groups in m2-h :h , m2-h :h and m2-h :h
bridging modes (Scheme 1d), respectively. In 3, the btec4- anion
adopts a m4 coordination mode and further connects the double
helical chains to produce a 3D porous framework. Whereas in 4,
the incorporation of the C3-symmetric H3btc ligand only results
in a (3,5)-connected gra network, the deprotonated btc3- ligand
displays a m3 coordination mode to coordinate with the Cu(II) ions
to generate 2D honeycomb network. Therefore, the comparison
reveals that the steric geometry of the polycarboxylate ligands
has a very significant effect on the formation and modulation
of the final structures and topological nets. Highly asymmetrical
carboxylate ligands possess a variety of coordination modes to
produce unexpected architectures, as well as higher connected
metal–organic frameworks.
◦
of 12.12% at 60–172 C was consistent with the loss of the three
lattice water molecules and the one coordinated water molecule
(calculated, 12.59%). The resulting residue of complex 2 remains
as CoO (calculated: 13.09%, found: 12.89%). For 3, the weight
loss from 40 to 166 ◦C was consistent with the loss of the free
lattice water molecules. The observed weight loss of 3.98% is
in agreement with the calculated 3.45%. At above 250 ◦C, the
framework begins to decompose slowly and the remaining weight
is attributed to the formation of CuO (calculated: 15.21%, found:
15.80%). In complex 4, the first weight loss of is 1.01% in the
temperature range of 60–82 ◦C, which corresponds to loss of the
In addition, the pH value of the solution may also influence
the construction of the resulting frameworks.3a,4b,4c Complexes 5
800 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Fig. 6 (a) The coordination environment of the Co(II) ion in 6, all hydrogen atoms were omitted for clarity. Symmetry code: A = x, 0.5-y, z, B = x, y,
1+z. (b) View of 2D undulating layer network with (4,4) sheets. (c) View of the 3D supramolecular framework is formed by the strong hydrogen bonding
˚
interactions (O3 ◊ ◊ ◊ O2 C = 2.495(7) A. Symmetry code: C = 1/2+x, 1/2-y, 1/2-z).
free water molecule (calculated: 0.76%). The second weight loss
is 32.89% at 130–325 ◦C and the third weight loss is 52.67% in
the temperature range of 326–700 C, all assigned to the loss of
intensity variations in the XRD patterns of 3 were observed, which
may correspond to the loss of guest water molecules. No major
differences are observed in the range 150–200 ◦C, which indicates
that the framework of 3 is still maintained after removing the guest
molecules. As shown in Fig. S5e,† the XRD of 5 was measured
after heating at 100 ◦C, 150 ◦C and 220 ◦C, respectively. The
results indicate that the overall framework of 5 is retained after
the removal of the guest water molecule below 220 ◦C.
◦
organic ligands (calculated: 32.36% for H3btc, 53.48% for btmb).
The remaining weight, 14.02%, indicated that the final product was
CuO (calculated: 13.45%). For complex 5, there is an initial weight
loss in the temperature range 40–130 ◦C, which arises from the
loss of the water molecules (calculated: 2.86%, found: 2.87%). The
second weight loss of 49.59% in the range of 227–441 ◦C may be
assigned to the release of the btmb ligand and then the remaining
weight, 19.00%, indicated that the remaining residue was Co2O3
(calculated: 19.75%). For 6, the whole framework is stable up to
300 ◦C, from which point the composition of the framework begins
to collapse and the remaining weight is attributed to the formation
of CoO (calculated: 12.84%, found: 13.02%).
In order to characterize the phase purity of these complexes,
X-ray power diffraction (XRD) patterns of complexes 1–6 were
performed (Fig. S5†). Although minor differences can be observed
in the positions, intensities and widths of some peaks, this shows
that these complexes were obtained as a single phase. In complex
3, After heating of the original sample at 150 ◦C for 5h, the
guest water molecules were removed (Fig. S5c†). Diffraction
Luminescent properties
Functional coordination polymers, especially those with d10 metals
complexes, have been investigated for their photoluminescent
properties and potential applications.26 As illustrated in Fig. S6,†
the solid-state luminescent properties of complex 1 and the free
btmb ligand were investigated at room temperature. An intense
luminescent emission was observed at 400 nm (lex = 280 nm)
for complex 1 and at 352 nm (lex = 280 nm) for the free
btmb ligand. According to the previous studies, the free 1,2,4,5-
benzenetetracarboxylic acid (H4btec) exhibits one weak emission
band at 342 (lex = 308 nm).14,27 Therefore, the emission of complex
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 801
©

View Article Online
1, with the enhancement of luminescence and red shift, may be
Co(II) with a spin–orbit coupling parameter l in a molecular-field
assigned to the ligand-to-metal charge transfer (LMCT).28
approximation.31
2
7(3−A )2 x 12(A + 2)2
2(11−2A ) x 176(A + 2)2
⎧
⎪
⎫
⎪
⎪
⎨
⎪
⎪
⎬
⎪
+
+
+
exp(−5Ax 2)
5
25A
45
675A
Magnetic properties
⎪
⎪
⎭
⎩
2
(A +5) x 20(A + 2)2
⎧
⎪
⎫
⎪
⎪
⎪
⎨
⎪
+
−
exp(−4Ax)
⎬
3N β2
k (T −q)x
⎪
A magnetic study has been performed on powdered samples of
5 at 1000 Oe in the range of 1.8–300 K. The cM and cMT vs
T plots of 5 are shown in Fig. 7. The cMT value at 300 K
is 9.63 cm3 K mol-1, which is higher than the expected value
(5.64 cm3 K mol-1) of three spin-only Co(II) ions (S = 3/2, g =
2.0), indicating the important orbital contribution arising from
the high-spin octahedral Co(II) centres.29 As T is lowered, cMT
continuously decreases and reaches a local minimum of 6.65 cm3
K mol-1 at about 16 K, before increasing rapidly to a value of
9.89 cm3 K mol-1 down to 1.8 K. The increase of cMT below 16 K
suggests an appreciable ferromagnetic coupling between the Co(II)
ions, which are connected to each other through m2-carboxylate
and m2-carboxylate oxygen bridges.29 The decrease of cMT in the
range of 16–300 K is typical of spin–orbit coupling due to strong
single-ion behaviour of Co(II).4d In order to estimate the strength
of the ferromagnetic exchange interaction between Co(II) ions, the
magnetic data of 5 were fitted using the simple phenomenological
equation.30
9
27A
⎪
⎩
⎪
⎭
3cCo(II)
=
3+ 2exp(−5Ax 2) + exp(−4Ax)
(1)
Where x = l/kT, A is a crystal field parameter, l is the spin–orbit
coupling constant. The best fit gives the parameters A = 1.323, l =
148 cm-1 and q = 5.23 K (Fig. S7a†). The M vs. H at 1.8 K among 0–
70 KOe is given in Fig. S7b,† which further confirms the expected
ferromagnetic coupling between Co(II) centres in complex 5 (M =
7.00 Nb) and the field dependence of the magnetization of 5
shows no hysteresis loop. Further, the AC magnetic susceptibility
of 5 show that the in-phase (c¢) magnetization increases with
decreasing temperature, but no max peak was observed and the
magnetization of out-phase (c¢¢) keeps constant within 0 K–50 K
(Fig. S7c†) and suggests the absence of any magnetic ordering.32
Conclusions
In summary, a series of interesting coordination polymers have
been hydrothermally synthesized by the combination of bis-
triazole and rigid polycarboxylates ligands with metal ions.
Complex 1 is the first example of a 3D framework containing
weave structure with (86) topology. Complex 2 exhibits a 3D NbO
network with (64·82) topology. Complex 3 presents a novel 3D
porous network consisting of double helical chains. Complex
4 shows a 3D gra network structure with (63)(69·8) topology,
while complex 5 exhibits the rare (3,8)-connected tfz-d framework
based on trinuclear Co(II) cluster units. Complex 6 has an
undulating 2D 44 grid-like layer. Comparing the structures of
these complexes, it is indicated that the distinct symmetry of
organic acid anions, the nature of the metal ions and the pH
value play crucial roles in modulating the formation of the final
structures and topological nets. This work will not only deepen
our systemic understanding of the structural functionality of the
conformational flexibility of the btmb ligand but also provide new
perspectives for generating metal–organic frameworks to enrich
the field of crystal engineering. It is anticipated that more metal–
organic frameworks containing conformational btmb ligands and
carboxylate anions with intriguing structures and topologies as
well as interesting physical properties will be synthesized.
cT = A exp(-E1/kT) + B exp(-E2/kT)
Fig. 7 cMT and cM plots for 5.
The least-squares analysis (R = 8 ¥ 10-4), shown as solid lines in
Fig. 7, led to parameters A = 1.38 cm3 mol-1 K, E1/k = 65 K,
B = 2.08 cm3 mol-1 K and E2/k = -0.84 K per Co(II). Here,
A+B equals the Curie constant, and E1 and E2 represent the
“activation energies” corresponding to the spin–orbit coupling
and the magnetic exchange interaction. The Curie constant value
found for A+B = 3.46 cm3 mol-1 K, which agrees with that obtained
from the Curie–Weiss law in the high temperature range and the
value for E1/k is consistent with those given in the literature for
both the effects of spin–orbit coupling and site distortion (E1/k of
the order of 100 K). The value E2/k = -0.84 K, corresponding
to spin coupling between two Co(II) ions, shows the distinct
ferromagnetic exchange mediated between Co(II) ions through m2-
O and O–C–O bridges.
Acknowledgements
We gratefully acknowledge financial support of this work by
the National Natural Science Foundation of China (Grant No.
20771090), State Key Program of National Natural Science
of China (Grant No. 20931005), Natural Science Foundation
of Shaanxi Province (Grant No. 2009JZ001) and Specialized
Research Found for the Doctoral Program of Higher Education
(Grant No. 20096101110005).
References
1 (a) R. E. Morris and P. S. Wheatley, Angew. Chem., Int. Ed., 2008, 47,
4966; (b) S. S. Kaye, A. Dailly, O. M. Yaghi and J. R. Long, J. Am.
Chem. Soc., 2007, 129, 14176; (c) M. Latroche, S. Surble´, C. Serre, C.
In order to estimate the spin–orbit coupling strength, the exper-
imental data were fitted in eqn (1) by considering a mononuclear
802 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Mellot-Draznieks, P. L. Llewellyn, J.-H. Lee, J.-S. Chang, S. H. Jhung
and G. Fe´rey, Angew. Chem., Int. Ed., 2006, 45, 8227; (d) A. Corma,
Chem. Rev., 1997, 97, 2373; (e) F. Schu¨th and W. Schmidt, Adv. Mater.,
2002, 14, 629; (f) A. Stein, Adv. Mater., 2003, 15, 763.
10 (a) Y. Q. Lan, S. L. Li, J. S. Qin, D. Y. Du, X. L. Wang, Z. M. Su and Q.
Fu, Inorg. Chem., 2008, 47, 10600; (b) J. D. Lin, C. C. Jia, Z. H. Li and
S. W. Du, Inorg. Chem. Commun., 2009, 12, 558; (c) B. F. Hoskins, R.
Robson and D. A. Slizys, Angew. Chem., Int. Ed. Engl., 1997, 36, 2336;
(d) X. R. Meng, Y. L. Song, H. W. Hou, H. Y. Han, B. Xiao, Y. T. Fan
and Y. Zhu, Inorg. Chem., 2004, 43, 3528; (e) B. L. Li, Y. F. Peng, B. Z.
Li and Y. Zhang, Chem. Commun., 2005, 2333; (f) C. Qin, X. L. Wang,
L. Yuan and E. B. Wang, Cryst. Growth Des., 2008, 8, 2093; (g) C. Qin,
X. L. Wang, E. B. Wang and Z. M. Su, Inorg. Chem., 2008, 47, 5555.
11 (a) X. L. Wang, C. Qin, E. B. Wang and Z. M. Su, Chem. Commun.,
2007, 4245; (b) T. J. Ni, M. Shao, S. R. Zhu, Y. M. Zhao, F. F. Xing and
M. X. Li, Cryst. Growth Des., 2010, 10, 943; (c) X. J. Shi, X. Wang, L.
K. Li, H. W. Hou and Y. T. Fan, Cryst. Growth Des., 2010, 10, 2490;
(d) Y. J. Mu, Y. J. Song, C. Wang, H. W. Hou and Y. T. Fan, Inorg.
Chim. Acta, 2010, DOI: 10.1016/j.ica.2010.09.001.
2 (a) J. L. C. Rowsell and O. M. Yaghi, Microporous Mesoporous Mater.,
2004, 73, 3; (b) M. P. Suh, Y. E. Cheon and E. Y. Lee, Coord. Chem. Rev.,
2008, 252, 1007; (c) W. Lin, O. R. Evans, R. G. Xiong and Z. Wang,
J. Am. Chem. Soc., 1998, 120, 13272; (d) J. Pang, E. J. P. Marcotte, C.
Seward, R. S. Brown and S. N. Wang, Angew. Chem., Int. Ed., 2001,
40, 4042; (e) K. Inoue, H. Imai, P. S. Ghalsasi, K. Kikuchi, M. Ohba,
H. Okawa and J. V. Yakhmi, Angew. Chem., Int. Ed., 2001, 40, 4242.
3 (a) H. Wang, Y. Y. Wang, G. P. Yang, C. J. Wang, G. L. Wen, Q. Z. Shi
and S. R. Batten, CrystEngComm, 2008, 10, 1583; (b) M. Munakata, L.
P. Wu, T. Kuroda–Sowa, M. Maekawa, K. Moriwaki and S. Kitagawa,
Inorg. Chem., 1997, 36, 5416; (c) Y. Suenaga, S. G. Yan, L. P. Wu,
I. Ino, T. Kuroda–Sowa, M. Maekawa and M. Munakata, J. Chem.
Soc., Dalton Trans., 1998, 1121; (d) L. Carlucci, G. Ciani, D. W. V.
Gudenberg, D. M. Proserpio and A. Sironi, Chem. Commun., 1997,
631; (e) X. L. Wang, C. Qin, E. B. Wang and Z. M. Su, Chem.–Eur. J.,
2006, 12, 2680.
4 (a) A. Y. Robin and K. M. Fromm, Coord. Chem. Rev., 2006, 250, 2127;
(b) L. F. Ma, L. Y. Wang, D. H. Lu, S. R. Batten and J. G. Wang,
Cryst. Growth Des., 2009, 9, 1741; (c) W. H. Zhang, Y. Y. Wang, E. K.
Lermontova, G. P. Yang, B. Liu, J. C. Jin, Z. Dong and Q. Z. Shi, Cryst.
Growth Des., 2010, 10, 76; (d) Y. Y. Liu, J. F. Ma, J. Yang and Z. M. Su,
Inorg. Chem., 2007, 46, 3027; (e) J. Q. Liu, Y. N. Zhang, Y. Y. Wang, J.
C. Jin, E. Kh. Lermontova and Q. Z. Shi, Dalton Trans., 2009, 5365.
5 (a) Q. X. Yao, Z. F. Ju, X. H. Jin and J. Zhang, Inorg. Chem., 2009, 48,
1266; (b) J. H. Cavka, S. Jakobsen, U. Olsbye, N. Guillou, C. Lamberti,
S. Bordiga and K. P. Lillerud, J. Am. Chem. Soc., 2008, 130, 13850;
(c) L. Zhang, Z. J. Li, Q. P. Lin, Y. Y. Qin, J. Zhang, P. X. Yin, J. K.
Cheng and Y. G. Yao, Inorg. Chem., 2009, 48, 6517; (d) B. Chen, X.
Zhao, A. Putkham, K. Hong, E. B. Lobkovsky, E. J. Hurtado, A. J.
Fletcher and K. M. Thomas, J. Am. Chem. Soc., 2008, 130, 6411; (e) P.
Horcajada, C. Serre, G. Maurin, N. Ramsahye, A. F. Balas, M. Vallet-
Reg´ı, M. Sebban, F. Taulelle and G. Fe´rey, J. Am. Chem. Soc., 2008,
130, 6774; (f) X. L. Wang, C. Qin, Y. Q. Lan, K. Z. Shao, Z. M. Su and
E. B. Wang, Chem. Commun., 2009, 410.
6 (a) L. L. Wen, F. Wang, J. Feng, K. L. Lv, C. G. Wang and D. F. Li,
Cryst. Growth Des., 2009, 9, 3581; (b) C. D. Ene, A. M. Madalan, C.
Maxim, B. Jurca, N. Avarvari and M. Andruh, J. Am. Chem. Soc.,
2009, 131, 4586; (c) B. L. Chen, L. B. Wang, F. Zapata, G. D. Qian
and E. B. Lobkovsky, J. Am. Chem. Soc., 2008, 130, 6718; (d) S. T.
Zheng, J. Zhang and G. Y. Yang, Angew. Chem., Int. Ed., 2008, 47,
3909; (e) S. S. Y. Chui, S. M. F. Lo, J. P. H. Charmant, A. G. Orpen and
L. D. Williams, Science, 1999, 283, 1148; (f) R. E. Melendez, C. V. K.
Sharma, M. J. Zaworkotko, C. Bauer and R. D. Togers, Angew. Chem.,
Int. Ed. Engl., 1996, 35, 2213.
7 (a) J. Yao, Z. D. Lu, Y. Z. Li, J. G. Lin, X. Y. Duan, S. Gao, Q. J. Meng
and C. S. Lu, CrystEngComm, 2008, 10, 1379; (b) P. Mahata, M. Prabu
and S. Natarajan, Inorg. Chem., 2008, 47, 8451; (c) C. Qin, X. L. Wang,
E. B. Wang, C. W. Hu and L. Xu, Inorg. Chem. Commun., 2004, 7, 788;
(d) Y. Yan, C. D. Wu and C. Z. Lu, Z. Anorg. Allg. Chem., 2003, 629,
1991; (e) Y. Yan, C. D. Wu, X. He, Y. Q. Sun and C. Z. Lu, Cryst.
Growth Des., 2005, 5, 821; (f) C. Qin, X. L. Wang, Y. G. Li, E. B. Wang,
Z. M. Su, L. Xu and R. Cle´rac, Dalton Trans., 2005, 2609; (g) L. Wang,
M. Yang, Z. Shi, Y. Chen and S. H. Feng, J. Solid State Chem., 2005,
178, 3359.
12 G. M. Sheldrick, SHELXL–97, University of Go¨ttingen, Germany,
1997.
13 G. M. Sheldrick, SADABS 2.05,University of Go¨ttingen, Germany,
2002.
14 J. D. Lin, J. W. Cheng and S. W. Du, Cryst. Growth Des., 2008, 8, 3345.
15 (a) Y. H. Li, C. Y. Su, A. M. Goforth, K. D. Shimizu, K. D. Gray,
M. D. Smith and H. C. Zur Loye, Chem. Commun., 2003, 1630; (b) P.
M. V. Calcar, M. M. Olmstead and A. L. Balch, J. Chem. Soc., Chem.
Commun., 1995, 1773; (c) A. M. P. Peedikakkal and J. J. Vittal, Cryst.
Growth Des., 2008, 8, 375; (d) L. Carlucci, G. Ciani, A. Gramaccioli,
D. M. Proserpio and S. Rizzato, CrystEngComm, 2000, 154; (e) P. M.
V. Calcar, M. M. Olmstead and A. L. Balch, Inorg. Chem., 1997, 36,
5231.
16 (a) J. F. Ma, J. Yang, G. L. Zheng, L. Li and J. F. Liu, Inorg. Chem.,
2003, 42, 7531; (b) M. L. Tong, X. M. Chen and S. R. Batten, J. Am.
Chem. Soc., 2003, 125, 16170.
17 (a) J. M. Ugald, I. Alkorta and J. Elguero, Angew. Chem., Int. Ed., 2000,
39, 717; (b) R. Ludwig, Angew. Chem., Int. Ed., 2001, 40, 1808; (c) D. S.
Li, Y. Y. Wang, X. J. Luan, P. Liu, C. H. Zhou, H. R. Ma and Q. Z. Shi,
Eur. J. Inorg. Chem., 2005, 2678; (d) F. N. Keutsch, J. D. Cruzan and
R. J. Saykally, Chem. Rev., 2003, 103, 2533; (e) S. Pal, N. B. Sankaran
and A. Samanta, Angew. Chem., Int. Ed., 2003, 42, 1741; (f) S. L. Li, Y.
Q. Lan, J. C. Ma, J. F. Ma and Z. M. Su, Cryst. Growth Des., 2010, 10,
1161.
18 (a) L. Carlucci, N. Cozzi, G. Ciani, M. Moret, D. M. Proserpio and
S. Rizzato, Chem. Commun., 2002, 1354; (b) X. Lin, I. Telepeni, A. J.
Blake, A. Dailly, C. M. Brown, J. M. Simmons, M. Zoppi, G. S. Walker,
K. M. Thomas, T. J. Mays, P. Hubberstey, N. R. Champness and M.
Schro¨der, J. Am. Chem. Soc., 2009, 131, 2159.
19 (a) W. Bidell, V. Shklover and H. Berke, Inorg. Chem., 1992, 31, 5561;
(b) M. S. Wang, G. C. Guo, M. L. Fu, L. Xu, L. Z. Cai and J. S. Huang,
Dalton Trans., 2005, 2899; (c) F. He, M. L. Tong, X. L. Yu and X. M.
Chen, Inorg. Chem., 2005, 44, 559; (d) Y. Wang, X. Q. Zhao, W. Shi, P.
Cheng, D. Z. Liao and S. P. Yan, Cryst. Growth Des., 2009, 9, 2137.
20 S. L. Li, Y. Q. Lan, J. S. Qin, J. F. Ma, J. Liu and J. Yang, Cryst. Growth
Des., 2009, 9, 4142.
21 A. L. J. Spek, J. Appl. Crystallogr., 2003, 36, 7.
22 (a) S. R. Batten, B. F. Hoskins, B. Moubaraki, K. S. Murray and R.
Robson, Chem. Commun., 2000, 1095; (b) W. X. Chen, S. T. Wu, L. S.
Long, R. B. Huang and L. S. Zheng, Cryst. Growth Des., 2007, 7, 1171;
(c) L. P. Zhang, J. Yang, J. F. Ma, Z. F. Jia, Y. P. Xie and G. H. Wei,
CrystEngComm, 2008, 10, 1410.
23 (a) I. A. Baburin, V. A. Blatov, L. Carlucci, G. Ciani and D. M.
Proserpio, Cryst. Growth Des., 2008, 8, 519; (b) L. Hou, J. P. Zhang
and X. M. Chen, Cryst. Growth Des., 2009, 9, 2415; (c) M. O’Keeffe,
M. A. Peskov, S. J. Ramsden and O. M. Yaghi, Acc. Chem. Res., 2008,
41, 1782; (d) R. Heck, J. Bacsa, J. E. Warren, M. J. Rosseinsky and
D. Bradshaw, CrystEngComm, 2008, 10, 1687; (e) D. Kong, J. Zon, J.
McBee and A. Clearfield, Inorg. Chem., 2006, 45, 977.
8 (a) J. Y. Wu, M. T. Ding, Y. S. Wen, Y. H. Liu and K. L. Lu, Chem.–
Eur. J., 2009, 15, 3604; (b) A. C. McKinlay, B. Xiao, D. S. Wragg, P. S.
Wheatley, I. L. Megson and R. E. Morris, J. Am. Chem. Soc., 2008, 130,
10440; (c) O. Fabelo, J. Pasa´n, F. Lloret, M. Julve and C. Ruiz-Pe´rez,
Inorg. Chem., 2008, 47, 3568; (d) O. Fabelo, J. Pasa´n, L. Can˜adillas-
Delgado, F. S. Delgado, F. Lloret, M. Julve and C. Ruiz-Pe´rez, Inorg.
Chem., 2008, 47, 8053; (e) S. H. Huang, C. H. Lin, W. C. Wu and S. L.
Wang, Angew. Chem., Int. Ed., 2009, 48, 6124.
24 Z. L. Lu, W. Chen, J. Q. Xu, L. J. Zhang, C. L. Pan and T. G. Wang,
Inorg. Chem. Commun., 2003, 6, 244.
9 (a) B. F. Hoskins, R. Robson and D. A. Slizys, J. Am. Chem. Soc., 1997,
119, 2952; (b) J. Yang, J. F. Ma, S. R. Batten and Z. M. Su, Chem.
Commun., 2008, 2233; (c) L. L. Wen, D. B. Dang, C. Y. Duan, Y. Z. Li,
Z. F. Tian and Q. J. Meng, Inorg. Chem., 2005, 44, 7161; (d) L. Carlucci,
G. Ciani and D. M. Proserpio, Chem. Commun., 2004, 380; (e) J. Yang,
J. F. Ma, Y. Y. Liu, J. C. Ma and S. R. Batten, Cryst. Growth Des., 2008,
8, 519; (f) Y. Qi, F. Luo, Y. X. Che and J. M. Zheng, Cryst. Growth Des.,
2008, 8, 606; (g) J. Fan, G. T. Yee, G. Wang and B. E. Hanson, Inorg.
Chem., 2006, 45, 599.
25 (a) G. H. Wang, Y. Q. Lei, N. Wang, R. L. He, H. Q. Jia, N. H. Hu
and J. W. Xu, Cryst. Growth Des., 2010, 10, 534; (b) S. J. Garibay, J.
R. Stork, Z. Q. Wang, S. M. Cohen and S. G. Telfer, Chem. Commun.,
2007, 4881; (c) M. O’Keeffe, M. A. Peskov, S. J. Ramsden and O. M.
Yaghi, Acc. Chem. Res., 2008, 41, 1782; (d) G. J. Xu, Y. H. Zhao, K. Z.
Shao, Y. Q. Lan, X. L. Wang, Z. M. Su and L. K. Yan, CrystEngComm,
2009, 11, 1842.
26 (a) Q. Wu, M. Esteghamatian, N. X. Hu, Z. D. Popovic, G. Enright, Y.
Tao, M. D’Iorio and S. Wang, Chem. Mater., 2000, 12, 79; (b) G. De.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 793–804 | 803
©

View Article Online
Santis, L. Fabbrizzi, M. Licchelli, A. Poggi and A. Taglietti, Angew.
Chem., Int. Ed. Engl., 1996, 35, 202; (c) U. H. F. Buna, Chem. Rev.,
2000, 100, 1605; (d) G. Yu, S. Yin, Y. Liu, Z. Shuai and D. Zhu, J. Am.
Chem. Soc., 2003, 125, 14816; (e) W. Chen, J. Y. Wang, C. Chen, Q.
Yue, H. M. Yuan, J. S. Chen and S. N. Wang, Inorg. Chem., 2003, 42,
944.
2010, 49, 6436; (d) O. Kahn, Molecular Magnetism, VCH Publishers,
New York, 1993; (e) J. S. Miller, M. Drillon, Magnetism: Molecules to
Materials I–V, Wiley–VCH, Weinheim, Germany, 2001; (f) V. Laget,
C. Hornick, P. Rabu, M. Drillon and R. Ziessel, Coord. Chem. Rev.,
1998, 178, 1533.
30 (a) J. M. Rueff, N. Masciocchi, P. Rabu, A. Sironi and A. Skoulios,
Eur. J. Inorg. Chem., 2001, 2843; (b) P. Rabu, J. M. Rueff, Z. L. Huang,
S. Angelov, J. Souletie and M. Drillon, Polyhedron, 2001, 20, 1677;
(c) J. M. Rueff, N. Masciocchi, P. Rabu, A. Sironi and A. Skoulios,
Chem.–Eur. J., 2002, 8, 1813.
27 Y. Hou, S. T. Wang, E. H. Shen, E. B. Wang, D. R. Xiao, Y. G. Li, L.
Xu and C. W. Hu, Inorg. Chim. Acta, 2004, 357, 3155.
28 S. L. Zheng, J. P. Zhang, X. M. Chen, Z. L. Huang, Z. Y. Lin and W.
T. Wong, Chem.–Eur. J., 2003, 9, 3888.
29 (a) P. Lama, A. Aijaz, E. C. San˜udo and P. K. Bharadwaj, Cryst. Growth
Des., 2010, 10, 283; (b) L. F. Ma, Y. Y. Wang, L. Y. Wang, D. H. Lu,
S. R. Batten and J. G. Wang, Cryst. Growth Des., 2009, 9, 2036; (c) M.
H. Zeng, Y. L. Zhou, M. C. Wu, H. L. Sun and M. Du, Inorg. Chem.,
31 J. W. Raebiger, J. L. Manson, R. D. Sommer, U. Geiser, A. L. Rheingold
and J. S. Miller, Inorg. Chem., 2001, 40, 2578.
32 F. Luo, Y. X. Che and J. M. Zheng, Cryst. Growth Des., 2009, 9,
1066.
804 | Dalton Trans., 2011, 40, 793–804
This journal is
The Royal Society of Chemistry 2011
©