Zinc(II) and cadmium(II) complexes with rigid 3,3′,5,5′- tetra(1H-imidazol-1-yl)-1,1′-biphenyl and varied carboxylate ligands

Article abstract of DOI:10.1021/cg300220q

Six new coordination polymers [Zn(L)_0.5(CO₃)] ?H₂O (1), [Zn(L)_0.5(DC)]?H₂O (2), [Cd(L)_0.5(DC)] (3), [Cd(L)_0.5(PBEA)]?H₂O (4), [Cd₂(L)(MBEA)₂]?4H₂O (5), and [Zn(L)_0.5(MBEA)]?2H₂O (6) with different structures and topologies were successfully synthesized by hydrothermal reactions of zinc(II)/cadmium(II) salts with rigid ligand 3,3′,5,5′-tetra(1H- imidazol-1-yl)-1,1′-biphenyl (L) and auxiliary multicarboxylic acids of 1,3,5-tri(4-carboxyphenyl)benzene (H₃BTB), 1,4-benzenediacrylic acid (H₂DC), 1,4-benzenediacetic acid (H₂PBEA), and 1,3-benzenediacetic acid (H₂MBEA), respectively. Carbonate anion, rather than the carboxylate anion of H₃BTB, is incorporated in 1. Complexes 1 and 5 are (4,4)- and (4,6)-connected binodal two-dimensional (2D) networks with a point (Schlaefli) symbol of (4.6⁴.8) ₂(4².6⁴) and (3².4 ².5²)(3⁴.4⁴.5⁴.6 ³), respectively. Complex 2 is a self-penetrating three-dimensional (3D) framework with a point (Schlaefli) symbol of (6².8 ⁴)(6⁴.8²)₂, while 3 shows a (3,4,5)-connected trinodal 3D framework with a point (Schlaefli) symbol of (4.6³.8⁶)₂(4².8⁴)(6 ³)₂. The 3-fold interpenetrating net of 4 is a subnet of sta with a point (Schlaefli) symbol of (4.6⁴.8) ₂(4².6².8²), while the net of 6 is vested in nbo set net with a point (Schlaefli) symbol of (6 ⁴)(8²). The results show that the auxiliary ligands and metal centers play important roles in the formation of complexes with diverse structures. Furthermore, the thermal stability, photoluminescence, and sorption properties of the complexes were investigated.

Full text of DOI:10.1021/cg300220q

Article
pubs.acs.org/crystal
Zinc(II) and Cadmium(II) Complexes with Rigid
3,3′,5,5′-Tetra(1H-imidazol-1-yl)-1,1′-biphenyl and
Varied Carboxylate Ligands
Li Luo, Peng Wang, Guan-Cheng Xu, Qing Liu, Kai Chen, Yi Lu, Yue Zhao, and Wei-Yin Sun*
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering,
Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, China
S
* Supporting Information
ABSTRACT: Six new coordination polymers [Zn(L)0.5(CO3)]·H2O (1), [Zn-
(L)0.5(DC)]·H2O (2), [Cd(L)0.5(DC)] (3), [Cd(L)0.5(PBEA)]·H2O (4), [Cd2(L)-
(MBEA)2]·4H2O (5), and [Zn(L)0.5(MBEA)]·2H2O (6) with different structures
and topologies were successfully synthesized by hydrothermal reactions of zinc(II)/
cadmium(II) salts with rigid ligand 3,3′,5,5′-tetra(1H-imidazol-1-yl)-1,1′-biphenyl (L)
and auxiliary multicarboxylic acids of 1,3,5-tri(4-carboxyphenyl)benzene (H3BTB),
1,4-benzenediacrylic acid (H2DC), 1,4-benzenediacetic acid (H2PBEA), and 1,3-
benzenediacetic acid (H2MBEA), respectively. Carbonate anion, rather than the
carboxylate anion of H3BTB, is incorporated in 1. Complexes 1 and 5 are (4,4)- and
(4,6)-connected binodal two-dimensional (2D) networks with a point (Schlafli)
̈
symbol of (4.64.8)2(42.64) and (32.42.52)(34.44.54.63), respectively. Complex 2 is a self-penetrating three-dimensional (3D)
framework with a point (Schlafli) symbol of (62.84)(64.82) , while 3 shows a (3,4,5)-connected trinodal 3D framework with a
̈
2
point (Schlafli) symbol of (4.63.86) (42.84)(63) . The 3-fold interpenetrating net of 4 is a subnet of sta with a point (Schlafli)
̈
̈
2
2
symbol of (4.64.8) (42.62.82), while the net of 6 is vested in nbo set net with a point (Schlafli) symbol of (64)(82). The results
show that the auxiliary ligands and metal centers play important roles in the formation of complexes with diverse structures.
Furthermore, the thermal stability, photoluminescence, and sorption properties of the complexes were investigated.
̈
2
combined with multicarboxylate ligands and successfully
obtained complexes with diverse structures and topologies
as well as specific properties.2d,9c,18
As a continuation of our previous works, a new rigid tetra-
dentate ligand 3,3′,5,5′-tetra(1H-imidazol-1-yl)-1,1′-biphenyl
(L, Scheme 1) was designed, which has more coordination
INTRODUCTION
■
The construction of coordination polymers with novel
structures and topologies has attracted great attention of
chemists not only owing to their undisputed array of structures
such as bowl, cage, helix, self-penetrating/interpenetrating
frameworks, etc., but also because of their potential applications
in gas storage/separation, optics, and so on.1−8 According to the
previously reported studies, tetradentate ligand with nitrogen
donors, for example, 1,2,4,5-tetrakis(imidazol-1-ylmethyl)-
benzene, 4,4′,6,6′-tetrakis(4-pyridyl)bimesityl, and 3,3′,5,5′-
tetrakis(3-pyridyl)-1,1′-biphenyl have been demonstrated to be
powerful building blocks in the assembly of metal−organic
frameworks (MOFs) with novel structures and topologies of
corundum, diamond, PtS, etc.9−11 On the other hand, many
outstanding research studies have been carried out using
carboxylate ligands such as terephthalic acid, 1,3,5-benzene-
tricarboxylic acid, 1,4-benzenediacrylic acid, 1,4-benzenediacetic
acid, and 1,3-benzenediacetic acid to build MOFs with diverse
structures and interesting properties.12−16 Moreover, the
carboxylate ligands have enriched coordination modes. On the
basis of the advantage of nitrogen donor and carboxylate ligands,
the strategy using mixed carboxylate and nitrogen donor ligands
has came into play in the construction of MOFs.17−19 Until now,
much research based on mixed imidazole-containing ligand and
multicarboxylate has been carried out. In our previous studies, we
adopted 1,4-di(1H-imidazol-4-yl)benzene, 1,3,5-tris(1-imidazolyl)-
benzene, and 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene
Scheme 1. Schematic Drawing for the Ligand L
sites and conjugated aromatic groups. We used the combina-
tion of L with 1,3,5-tri(4-carboxyphenyl)benzene (H3BTB),
1,4-benzenediacrylic acid (H2DC), 1,4-benzenediacetic acid
(H2PBEA), 1,3-benzenediacetic acid (H2MBEA), and ZnII/CdII
salts to construct novel coordination polymers. We here intend
to compare the diversities of the structures by changing the
Received: February 15, 2012
Revised: March 30, 2012
Published: April 2, 2012
© 2012 American Chemical Society
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Article
49.57; H, 3.54; N, 10.48%. IR (KBr pellet, cm−1): 1608 (s), 1557 (s),
1511 (s), 1395 (s), 1288 (w), 1257 (m), 1112 (w), 1066 (m), 936
(m), 864 (w), 760 (w).
structure and flexibility of the carboxylate ligands under similar
experimental conditions. Herein, we report the syntheses,
crystal structures, and properties of six new ZnII/CdII coordina-
tion polymers, namely, [Zn(L)0.5(CO3)]·H2O (1), [Zn(L)0.5-
(DC)]·H2O (2), [Cd(L)0.5(DC)] (3), [Cd(L)0.5(PBEA)]·H2O
(4), [Cd2(L)(MBEA)2]·4H2O (5), [Zn(L)0.5(MBEA)]·2H2O (6).
Preparation of [Cd2(L)(MBEA)2]·4H2O (5). Complex 5 was
obtained by the same procedure used for preparation of 4 except that
H2PBEA (9.7 mg, 0.05 mmol) was replaced by H2MBEA (9.7 mg,
0.05 mmol). Yellow block crystals of 5 were obtained in 80% yield.
Anal. Calcd for C44H42N8O12Cd2: C, 48.06; H, 3.85; N, 10.19%.
Found: C, 47.93; H, 3.83; N, 10.16%. IR (KBr pellet, cm−1): 1611 (s),
1565 (s), 1507 (s), 1389 (s), 1321 (m), 1274 (w), 1249 (w), 1114
(w), 1084 (m), 1009 (w), 926 (w), 864 (w), 765 (m), 719 (m).
Preparation of [Zn(L)0.5(MBEA)]·2H2O (6). Complex 6 was
obtained by the same procedure used for preparation of 5 except that
the metal salt was replaced by ZnSO4·7H2O (14.4 mg, 0.05 mmol).
Yellow crystals of 6 were obtained in 86% yield. Anal. Calcd for
C22H21N4O6Zn: C, 52.55; H, 4.21; N, 11.14%. Found: C, 52.42; H,
4.19; N, 11.11%. IR (KBr pellet, cm−1): 1639 (s), 1611 (s), 1580 (s),
1525 (m), 1507 (m), 1367 (s), 1321 (m), 1274 (m), 1122 (w), 1086
(m), 1073 (m), 1020 (w), 946 (w), 839 (w), 760 (w), 719 (m).
Crystallography. The crystallographic data collections for 1−6
were carried out on a Bruker Smart Apex CCD area detector diffracto-
meter with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å)
at 20(2) °C using ω-scan technique. The diffraction data were
integrated by using the SAINT program,22 which was also used for the
intensity corrections for the Lorentz and polarization effects.
Semiempirical absorption corrections were applied using SADABS
program.23 The structures were solved by direct methods, and all of
the non-hydrogen atoms were refined anisotropically on F2 by the full-
matrix least-squares technique using the SHELXL-97 crystallographic
software package.24 The hydrogen atoms except those of water
molecules were generated geometrically and refined isotropically using
the riding model. The hydrogen atoms of free water molecules in the
complexes were not found. Atoms C2, C3, C4, C5, and C6 in 2 are
disordered into two positions with site occupancies of 0.459(7) and
0.541(7), respectively. The C10, C11, C21, and C22 in 3 are disordered
into two positions with site occupancies of 0.473(10) and 0.527(10),
respectively, while the C24 and C25 also have two disordered positions
with site occupancies of 0.490(6) and 0.510(6), respectively. Atoms O3
and O4 in 4 are also disordered into two positions, each with a site
occupancy of 0.50. The details of the crystal parameters, data collection,
and refinements for the complexes are summarized in Table 1, and
selected bond lengths and angles are listed in Table 2.
EXPERIMENTAL SECTION
■
All commercially available chemicals and solvents are of reagent grade
and were used as received without further purification. Elemental
analyses for C, H, and N were performed on a Perkin-Elmer 240C
elemental analyzer at the analysis center of Nanjing University.
Thermogravimetric analyses (TGA) were performed on a simultaneous
SDT 2960 thermal analyzer under nitrogen with a heating rate of 10 °C
min−1. Fourier transform infrared (FT-IR) spectra were recorded in the
range of 400−4000 cm−1 on a Bruker Vector22 FT-IR spectropho-
tometer using KBr pellets. Powder X-ray diffraction (PXRD) patterns
were obtained on a Shimadzu XRD-6000 X-ray diffractometer with Cu
Kα (λ = 1.5418 Å) radiation at room temperature. The luminescence
spectra for the powdered solid samples were measured on an Aminco
Bowman Series 2 spectrofluorometer with a xenon arc lamp as the light
source. In the measurements of emission and excitation spectra, the
pass width is 5 nm, and all the measurements were carried out under
the same experimental conditions. Sorption experiments were carried
out on a Belsorp-max volumetric gas sorption instrument. The bulk
samples of 1 and 6 for sorption experiments were obtained by heating
the fresh complexes at 190 and 180 °C, respectively, for 10 h under
high vacuum to remove the free water molecules.
Synthesis of Ligand L. The compound L was prepared in 75%
yield by using 3,3′,5,5′-tetrabromo-1,1′-biphenyl (5.64 g, 12.0 mmol),20
imidazole (6.54 g, 96.0 mmol), K2CO3 (8.84 g, 64.0 mmol), and
anhydrous CuSO4 (64.0 mg, 0.40 mmol) following the previously
reported procedures used for synthesis of 1,3,5-tris(7-azaindol-1-yl)-
benzene.21 1HNMR [(CD3)2SO]: δ = 8.58 (s, 4H), 8.16 (s, 4H), 8.07
(s, 6H), 7.20 ppm (s, 4H). Anal. Calcd for C24H18N8: C, 68.89; H,
4.34; N, 26.78%. Found: C, 68.72; H, 4.22; N, 26.69%.
Preparation of [Zn(L)0.5(CO3)]·H2O (1). A mixture of L (10.5 mg,
0.025 mmol), ZnSO4·7H2O (14.4 mg, 0.05 mmol), H3BTB (13.1 mg,
0.03 mmol), and NaHCO3 (8.4 mg, 0.1 mmol) in 8 mL of H2O
was sealed into Teflon-lined stainless steel container and heated at
180 °C for 3 days. After the mixture was cooled to room temperature,
yellow block crystals were obtained in 65% yield. Anal. Calcd for
C13H11N4O4Zn: C, 44.28; H, 3.14; N, 15.89%. Found: C, 44.17; H,
3.06; N, 15.84%. IR (KBr pellet, cm−1): 1618 (s), 1520 (s), 1483 (s),
1401 (s), 1244 (m), 1112 (m), 1067 (s), 966 (w), 876 (w), 845 (m),
758 (m).
Preparation of [Zn(L)0.5(DC)]·H2O (2). A mixture of (10.5 mg,
0.025 mmol), ZnSO4·7H2O (14.4 mg, 0.05 mmol), H2DC (10.9 mg,
0.05 mmol), and NaOH (4.0 mg, 0.1 mmol) in 8 mL of H2O was
sealed into Teflon-lined stainless steel container and heated at 180 °C
for 3 days. After the mixture was cooled to room temperature, yellow
crystals of 2 were obtained in 85% yield. Anal. Calcd for
C24H19N4O5Zn: C, 56.65; H, 3.76; N, 11.01%. Found: C, 56.50; H,
3.69; N, 10.96%. IR (KBr pellet, cm−1): 1641 (s), 1600(s), 1513 (m),
1354 (s), 1245 (w), 1120 (w), 1072 (m), 970(w), 946 (w), 854 (w),
756 (w).
Preparation of [Cd(L)0.5(DC)] (3). Complex 3 was obtained by the
same procedure used for preparation of 2 except that ZnSO4·7H2O
(14.4 mg, 0.05 mmol) was replaced by CdSO4·8/3H2O (12.9 mg,
0.05 mmol). Yellow crystals of 3 were obtained in 87% yield. Anal.
Calcd for C24H17N4O4Cd: C, 53.60; H, 3.19; N, 10.42%. Found: C,
53.45; H, 3.16; N, 10.38%. IR (KBr pellet, cm−1): 1639 (w), 1606 (m),
1560 (s), 1501 (m), 1425 (w), 1392 (m), 1310 (w), 1109(w), 1070
(m), 970 (m), 841 (w), 717 (m).
RESULTS AND DISCUSSION
■
Crystal Structure of [Zn(L)0.5(CO3)]·H2O (1). The results
of single crystal X-ray diffraction analysis revealed that the
asymmetric unit of 1 consists of half a molecule of
[Zn(L)0.5(CO3)]·H2O, in which the ZnII atom is on the
specific position with half occupancy. It is noteworthy that the
auxiliary carboxylate ligand of H3BTB was not incorporated in
1, and instead the carbonate anion was found in 1. As shown
in Figure 1a, the central ZnII atom is four-coordinated with
distorted tetrahedral coordination geometry by two O atoms
(O1, O2B) from two different CO32− anions and two N atoms
(N2, N2G) from two different L ligands, with Zn1−O bond
distances of 1.939(4) and 1.955(4) Å and Zn1−N one of
2.025 Å (Table 2). Each L ligand connects four ZnII atoms, and
each CO32− anion adopts the μ2-η1:η1:η0 coordination mode to
link two ZnII atoms. If the connections of L ligands are ignored,
the CO3 anions link the ZnII atoms to form an infinite one-
2−
dimensional (1D) chain, and then the chains are further linked
together by L ligands to form a two-dimensional (2D) network
(Figure 1b). And the 2D layers of 1 are packing in an -ABAB-
sequence along the a axis (Figure 1c).
To further understand the structure of 1, topological analysis
by reducing multidimensional structure to simple node-and-
linker net was performed. On the basis of the simplification
Preparation of [Cd(L)0.5(PBEA)]·H2O (4). Complex 4 was
prepared by the same procedure used for preparation of 3 except
that H2DC (10.9 mg, 0.05 mmol) was replaced by H2PBEA (9.7 mg,
0.05 mmol). Colorless crystals of 4 were obtained in 60% yield. Anal.
Calcd for C22H19N4O5Cd: C, 49.69; H, 3.60; N, 10.53%. Found: C,
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Article
two O atoms (O2, O3) from two different DC2− ligands. The
Zn−N bond lengths are 1.985(2) and 2.020(2) Å, and the ones
of Zn−O are 1.939(2) and 1.943(2) Å, respectively. The bond
angles around the ZnII atom are in the range of 96.5(1)−
123.3(1)° (Table 2). There are two different kinds of DC2−
ligands with the same μ2-bridge coordination mode (type I,
Scheme 2), in which each carboxylate group is in μ1-η1:η0-
monodentate fashion. Each L ligand connects four ZnII atoms
using its four imidazole groups to give a 2D (4,4) net if the
connections of the DC2− ligands are ignored (Figure 2b). Four
ZnII atoms and four L ligands form a grid, with the Zn···Zn edge
distances of 10.21 Å for Zn1A···Zn1B, 11.09 Å for Zn1B···Zn1C
and Zn1D···Zn1A, 12.96 Å for Zn1C···Zn1D. The 2D layers are
further linked together by one of the two DC2− ligands to form
a 3-fold interpenetrating three-dimensional (3D) framework
(Figure 2c). Interestingly, such 3-fold interpenetrating 3D net is
connected by the other kinds of DC2− ligands to form the final
self-interpenetrating 3D structure.
Table 1. Crystal Data and Refinement Results for Complexes
1−6
compound
1
2
3
empirical formula
formula weight
crystal system
space group
a /Å
C13H11N4O4Zn
352.63
C24H19N4O5Zn
508.79
C24H17N4O4Cd
537.82
orthorhombic
Pnnm
monoclinic
C2/c
monoclinic
C2/c
17.647(2)
5.2995(7)
13.9680(18)
90.00
20.742(3)
19.431(3)
12.3964(17)
107.989(7)
4752.0(12)
8
26.6249(10)
6.7018(3)
23.2725(9)
105.0980(10)
4009.3(3)
8
b /Å
c /Å
β /°
V (Å3)
1306.3(3)
4
Z
Dc (g cm−3
)
1.793
1.420
1.782
μ (mm−1
)
1.906
1.075
1.132
F(000)
716
2080
2152
reflections
collected
6017
11794
10836
The topological analysis was carried out to get insight into the
structure of 2; each ZnII atom links two DC2− ligands and two L
ligands, meanwhile each L and DC2− ligand connects four and
two ZnII atoms, respectively. Thus, the ZnII atom and L ligand
can be regarded as 4-connectors, and the DC2− ligand can be
viewed as 2-connector. According to the simplification principle,
the resulting structure of complex 2 is a (4, 4)-connected binodal
3D net with stoichiometry (4-c)(4-c)2, as shown in Figure 2d.
Topological analysis by the TOPOS program23 suggests that the
independent
1212
4206
3611
reflections
goodness-of-fit on 1.063
1.037
1.063
F2
a
R1 [I > 2σ (I)]
wR2 [I > 2σ (I)]
compound
0.0385
0.1128
4
0.0464
0.1370
5
0.0279
0.0763
6
b
empirical
formula
C22H19N4O5Cd
C44H42N8O12Cd2
C22H21N4O6Zn
formula weight
crystal system
space group
a (Å)
531.81
monoclinic
C2/c
1099.59
monoclinic
C2/c
502.80
point (Schlafli) symbol of the net is (62.84)(64.82) , which is a
̈
monoclinic
P21/c
2
new topology. As highlighted in Figure 2d, there are six-
membered shortest circuits catenated to each other, which can be
seen more clearly from Figure 2e. Thus, 2 is another example of
the self-penetrating coordination polymer.27
10.997(3)
30.043(8)
14.553(4)
109.807(4)
4523(2)
8
42.542(5)
13.6415(15)
15.2419(16)
99.301(2)
8729.1(16)
8
6.761(5)
16.856(5)
18.782(5)
95.091(5)
2132.0(18)
4
b (Å)
c (Å)
Crystal Structure of [Cd(L)0.5(DC)] (3). Considering the
structure of coordination polymers can be influenced by various
factors including the metal centers,28 we brought in another kind
of d10 metal center of CdII and a new complex 3 was obtained.
The asymmetric unit of 3 consists of one CdII atom, half of L
and one DC2− ligands. As illustrated in Figure 3a, Cd1 is six-
coordinated with distorted octahedral coordination geometry
by two N atoms (N12, N22E) from two different L ligands and
four O atoms (O1B, O2, O3H, and O4H) from three different
DC2−. The Cd1−O bond distances are in the range of
2.259(2)−2.497(3) Å, and the Cd1−N ones are 2.259(2) and
2.272(2) Å. The bond angles around the CdII atom are in the
range of 54.8(1)−167.3(1)° (Table 2).
β (°)
V (Å3)
Z
Dc (g cm−3
)
1.556
1.661
1.566
μ (mm−1
)
1.005
1.048
1.201
F(000)
2120
4368
1036
reflections
collected
11178
23791
11896
independent
reflections
3956
8490
3782
goodness-of-fit
1.084
0.0848
1.128
1.035
on F2
a
R1 [I > 2σ(I)]
wR2 [I > 2σ(I)]
0.0607
0.1787
0.0364
0.1067
b
0.2360
The two carboxylate groups of each DC2− ligand in 3 exhibit
two kinds of coordination modes which are different from those
in 2, one in a μ1-η1:η1 chelating mode and the other one in a
μ2-η1:η1 bridging fashion (type II, Scheme 2); thus each DC2−
ligand is a μ3-bridge. If the connections of L ligand are
neglected, the DC2− ligands link CdII atoms to form a 2D
network (Figure 3b). Then four different layers are connected
by L ligands to generate the final 3D framework structure of 3,
as illustrated in Figure 3c. Similar topological analysis was
carried out to analyze the structure of 3. As mentioned above,
each DC2− and L ligand links three and four CdII atoms, and
accordingly the DC2− and L ligands can be viewed as 3- and
4-connected nodes, respectively. For each CdII atom, it connects
three DC2− ligands and two L ligands; hence, it can be treated
as 5-connector. On the basis of the simplification principle,
the overall structure of 3 is a (3,4,5)-connected trinodal net
with stoichiometry (3-c)2(4-c)(5-c)2, as shown in Figure 3d.
a
b
R1 = Σ||Fo| − |Fc||/Σ|Fo|. wR2 = |Σw(|Fo|2 − |Fc|2)|/Σ|w(Fo)2|1/2
,
where w = 1/[σ2(Fo ) + (aP)2 + bP]. P = (Fo + 2Fc2)/3.
2
2
principle,25 each L ligand connects four ZnII atoms and each
CO3 anion connects two ZnII atoms, while the ZnII atom
2−
2−
links two L ligands and two CO3 anions; thus they can be
regarded as a 4-, 2-, and 4-connector, respectively. Hence,
the overall structure of 1 is a (4, 4)-connected binodal 2D net
with stoichiometry of (4-c)(4-c)2, as shown in Figure 1d. The
topological analysis by TOPOS program26 suggests that the
point (Schlafli) symbol of the net is (4.64.8) (42.64) and the
̈
2
topological type is 4,4L28.
Crystal Structure of [Zn(L)0.5(DC)]·H2O (2). When H2DC,
instead of H3BTB, was used in the reaction, complex 2 was
obtained. As shown in Figure 2a, each ZnII atom with distorted
tetrahedral coordination geometry is surrounded by two N
atoms (N1, N4) of imidazole groups provided by two L and
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Article
a
Table 2. Selected Bond Distances (Å) and Angles (deg) for Complexes 1−6
1
4
Zn(1)−O(1)
Zn(1)−N(12)
1.939(4)
2.025(3)
Zn(1)−O(2)#1
1.955(4)
105.8(1)
120.8(2)
N(22)#1−Cd(2)−O
124.8(3)
52.1(3)
79.8(3)
175.8(4)
N(22)−Cd(2)−O
97.3(3)
131.8(3)
52.1(3)
(1)
(2)
O(1)−Cd(2)−O(2)
O(1)#1−Cd(2)−O
O(1)−Zn(1)−O(2)
106.0(2)
O(1)−Zn(1)−N
(12)#2
N(12)−Zn(1)−N
(12)#2
(2)
#1
N(22)−Cd(2)−O
(2)#1
O(2)−Cd(2)−O(2)
#1
O(1)#1−Cd(2)−O
(2)#1
O(2)#1−Zn(1)−N
108.7(1)
(12)
2
3
Zn(1)−O(3)
Zn(1)−N(1)
O(3)−Zn(1)−O(2)
O(2)−Zn(1)−N(1)
O(2)−Zn(1)−N(4)
1.939(2)
Zn(1)−O(2)
Zn(1)−N(4)
O(3)−Zn(1)−N(1)
O(3)−Zn(1)−N(4)
N(1)−Zn(1)−N(4)
1.943(2)
2.020(2)
118.3(1)
5
1.985(2)
96.5(1)
Cd(1)−N(32)#1
Cd(1)−O(3)
Cd(1)−O(6)#2
Cd(1)−O(4)
Cd(2)−N(42)
Cd(2)−O(1)#5
Cd(2)−O(1)#3
2.270(6) Cd(1)−N(22)
2.279(6) Cd(1)−O(5)
2.379(6) Cd(1)−O(5)#2
2.625(6) Cd(2)−N(12)#3
2.319(6) Cd(2)−O(7)#4
2.336(5) Cd(2)−O(2)#3
2.527(6) Cd(2)−O(8)#4
2.270(6)
2.351(5)
2.475(6)
2.265(6)
2.332(5)
2.350(6)
2.542(5)
94.8(2)
123.3(1)
112.6(1)
104.3(1)
101.0(1)
Cd(1)−O(3)#1
Cd(1)−O(1)#3
Cd(1)−O(2)
2.259(2) Cd(1)−N(22)#2
2.290(2) Cd(1)−N(12)
2.304(2) Cd(1)−O(4)#1
2.272(2)
2.298(2)
2.497(3)
83.13(8)
N(32)#1−Cd(1)−N
172.1(2)
N(32)#1−Cd(1)−O
O(3)#1−Cd(1)−N
112.4(1)
O(3)#1−Cd(1)−O
(22)
(3)
(22)#2
(1)#3
N(22)−Cd(1)−O
87.8(3)
140.5(2)
52.2(2)
N(22)−Cd(1)−O(5)
86.8(2)
75.2(2)
85.6(2)
N(22)#2−Cd(1)−O
(1)#3
96.73(7)
96.5(1)
98.42(8)
54.8(1)
O(3)#1−Cd(1)−N
145.9(1)
84.24(8)
87.74(9)
167.3(1)
(3)
(12)
O(3)−Cd(1)−O(5)
O(5)−Cd(1)−O(5)
#2
N(22)−Cd(1)−O(4)
O(1)#3−Cd(1)−N
O(3)#1−Cd(1)−O
(12)
(2)
O(6)#2−Cd(1)−O
(5)#2
O(3)−Cd(1)−O(4)
N(22)#2−Cd(1)−O
N(12)−Cd(1)−O(2)
(2)
52.6(2)
O(5)−Cd(1)−O(4)
N(12)#3−Cd(2)−O
(7)#4
N(42)−Cd(2)−O(2)
#3
O(1)#5−Cd(2)−O
(2)#3
O(2)#3−Cd(2)−O
(1)#3
O(1)#5−Cd(2)−O
(8)#4
88.0(2)
94.1(2)
O(3)#1−Cd(1)−O
(4)#1
N(22)#2−Cd(1)−O
(4)#1
N(12)#3−Cd(2)−N
171.8(2)
(42)
4
N(42)−Cd(2)−O
(1)#5
O(7)#4−Cd(2)−O
(2)#3
O(1)#5−Cd(2)−O
(1)#3
O(7)#4−Cd(2)−O
(8)#4
86.7(2)
91.9(2)
69.9(2)
53.5(2)
94.9(3)
120.3(2)
50.4(2)
94.7(2)
Cd(1)−O(3)
Cd(1)-O(3′)
Cd(1)−O(4)
Cd(2)−O(1)
2.24(2)
2.31(2)
2.47(2)
Cd(1)−N(12)
Cd(1)-O(4′)
Cd(2)−N(22)
2.285(7)
2.34(2)
2.270(6)
2.496(8)
117.6(6)
2.274(7) Cd(2)−O(2)
82(1)
O(3)−Cd(1)−O(3)
O(3)−Cd(1)−N
#1
(12)
O(3)#1−Cd(1)−N
125.7(5)
36.1(7)
53.8(6)
102.1(5)
94.6(4)
N(12)−Cd(1)−N
(12)#1
N(12)−Cd(1)−O
(4′)
92.5(4)
145.9(6)
126.7(6)
77.4(4)
6
(12)
Zn(1)−O(1)
Zn(1)−N(12)
1.957(2) Zn(1)−O(4)#1
2.007(2) Zn(1)−N(22)#2
104.94(9)
114.95(8)
95.73(8)
1.980(2)
2.033(2)
O(3)−Cd(1)−O(4′)
O(3)−Cd(1)−O(4)
O(3)#1−Cd(1)−O
O(1)−Zn(1)−O(4)
O(1)−Zn(1)−N(12) 122.04(9)
(4)
#1
N(12)−Cd(1)−O
N(12)#1-Cd(1)−O
O(4)#1−Zn(1)−N
O(1)−Zn(1)−N(22) 116.10(9)
#2
N(12)−Zn(1)−N
(22)#2
(4)
(4)
(12)
N(22)−Cd(2)−N
N(22)−Cd(2)−O
114.6(3)
O(4)#1−Zn(1)−N
(22)#2
100.29(9)
(22)#1
(1)
a
Symmetry transformations used to generate equivalent atoms: #1 x, y + 1, z; #2 x, y, −z + 1 for 1; #1 x + 1/2, y + 1/2, z; #2 x, −y + 2, z − 1/2; #3
x, y + 1, z for 3; #1 −x + 2, y, −z + 1/2 for 4; #1 x, y − 1, z; #2 −x, y,−-z + 1/2; #3 x, y + 1, z; #4 −x, y + 1, −z + 1/2; #5 −x + 1/2, −y + 3/2, −z +
1 for 5; #1 x, −y + 1/2, z − 1/2; #2 −x + 1, y + 1/2, −z + 3/2 for 6.
The point (Schlafli) symbol of the net is (4.63.86) (42.84)(63) ,
which is a new topology.
is 2.270(6) Å and the Cd2−O ones are 2.274(7) and
2.496(8) Å (Table 2). The coordination angles around Cd2
extend from 52.1(3)−175.8(4)°, while the ones around Cd1
are in the range of 36.1(7)−145.9(6)° (Table 2). There are two
different kinds of PBEA2− ligands in 4 with the same
coordination mode (type III, Scheme 2).
̈
2
2
Crystal Structure of [Cd(L)0.5(PBEA)]·H2O (4). When the
flexible acid of H2PBEA, instead of the semirigid one of H2DC,
was used in the reaction with the other experimental conditions
unchanged as those for the synthesis of 3, complex 4 with
different structure was obtained. As depicted in Figure 4a, there
are two crystallographically different CdII atoms in the
asymmetric unit of 4. The Cd1 is six-coordinated by four O
atoms (O3, O4, O3A, and O4A) from two different PBEA2−,
and two N atoms (N12, N12A) from two different L ligands.
The Cd1−N bond length is 2.285(7) Å and the Cd1−O ones
are in the range of 2.24(2)−2.47(2) Å (Table 2). The Cd2 has
a similar coordination environment with that of Cd1. Each Cd2
is also six-coordinated by four O atoms (O1, O2, O1A, and
O2A) from two different PBEA2− and two N atoms (N22,
N22A) from two different L ligands. The Cd2−N bond length
If the connections through the one kind of PBEA2‑ are
ignored, the L and another kind of PBEA2− ligand links CdII
atoms to form a 2D network in the ac plane as shown in
Figure 4b. The adjacent 2D layers are connected by the above
ignored PBEA2− ligands along the b axis to give rise to the final
3D framework of 4 (Figure 4c). As described above, one L
ligand connects four CdII atoms and each CdII atom links two L
and two PBEA2− ligands, while each of the PBEA2− ligand joins
two CdII atoms; thus L, CdII, and PBEA2− can be treated as 4-,
4-, 2-connectors, respectively. According to the simplification
rule, the resulting structure of 4 is a (4,4)-connected binodal
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net with the point (Schlafli) symbol of (4.64.8) (42.62.82),
̈
2
which is a subnet of the sta net. It is noticed that there are large
channels in 4 which can be seen clearly from the space-filling
diagram (Figure 4d). Because of its large vacancy, it is apt to
form an interpenetrating framework,29 and accordingly, the
final structure of 4 is a 3-fold interpenetrating framework as
illustrated in Figure 4e.
Crystal Structure of [Cd2(L)(MBEA)2]·4H2O (5). To
further investigate the effect of carboxylate ligand on the
structural diversity of the complexes,2d,30 a flexible acid of
H2MBEA, instead of the H2PBEA, was used in the preparation
and complex 5 with different structure was successfully
obtained. Figure 5a shows the coordination environments of
two independent CdII atoms with the atom numbering scheme.
Cd1 atom is seven-coordinated with distorted pentagonal
bipyramid coordination geometry by five O atoms (O3, O4,
O5, O5D, and O6D) from three different MBEA2− and two N
atoms (N22, N32A) from two different L ligands. It is notable
that the Cd1−O4 distance of 2.625(6) Å is long indicating the
weak interactions between them as observed in the previously
reported CdII complexes.31 The Cd1−N bond lengths are both
2.270(6) Å and the Cd1−O ones are in the range of 2.279(6)−
2.625(6) Å. The bond angles around Cd1 atom vary from
52.2(2) to 172.1(2)° (Table 2). The Cd2 has a similar
coordination environment and geometry with Cd1. The Cd2−
O bond lengths extend from 2.332(5) to 2.542(5) Å, and the
Cd2−N bond lengths are 2.265(6) and 2.319(6) Å, respectively
(Table 2). In the asymmetric unit of 5, there are two different
MBEA2− ligands with the same coordination mode (type IV,
Scheme 2). One of the two carboxylate groups is chelating
mode, and the other one is in μ2-η2:η1 chelating/bridging mode
in which the O1 and O5 atoms act as a bridge to connect two
CdII atoms (Cd2 and Cd2, Cd1 and Cd1) with Cd···Cd
distances of 3.89 and 3.99 Å, respectively.
If the connections through the MBEA2− ligands are ignored,
the L ligand links CdII atoms using its imidazole groups to form
an infinite hinged chain structure (Figure 5b). Then the
adjacent chains are further connected by the MBEA2− ligands
to generate a 2D network (Figure 5c). If the binuclear Cd2O2
motif is viewed as the node, it links four L and two Cd2O2 via
four MBEA2− ligands, and thus it is treated as 6-connected
node (Figure S1, Supporting Information). The L and MBEA2−
ligands connect four Cd2O2 and two Cd2O2 motifs, and
accordingly they can be regarded as 4- and 2-connected nodes,
respectively. Thus the simplified overall structure of 5 is (4, 6)-
connected binodal net with stoichiometry (4-c)(6-c), as shown
in Figure 5d. The point (Schlafli) symbol for the net is
̈
(32.42.52)(34.44.54.63) calculated by the TOPOS program, and
the topological type is 4,6L26.
Crystal Structure of [Zn(L)0.5(MBEA)]·2H2O (6). When
ZnSO4·7H2O, instead of CdSO4·8/3H2O, was used in the
synthesis under the same reaction conditions as those for the
preparation of 5, complex 6 was obtained. As illustrated in
Figure 6a, the asymmetric unit of 6 consists of one ZnII atom,
half of L, one MBEA2− ligand, and two free water molecules.
The ZnII atom is four coordinated with distorted tetrahedral
coordination geometry by two N atoms (N12, N22B) from two
different L and two O atoms (O2, O4A) from two different
MBEA2− ligands. The Zn−O bond lengths are 1.957(2) and
1.980(2) Å, and the ones of Zn−N are 2.007(2) and 2.033(2) Å.
The bond angles around ZnII atom range from 95.73(8) to
122.04(9)° (Table 2). In 6, the coordination mode of MBEA2−
ligand is different from that in 5, which is μ2-bridging fashion
Figure 1. (a) The coordination environment of ZnII in 1 with the
ellipsoids drawn at the 30% probability level. The hydrogen atoms and
water molecule are omitted for clarity. Symmetry code: B x, 1 + y, z; C
−x, 2 − y, z; D −x, 2 − y, −z; F x, y, −z; G x, y, 1 − z. (b) 2D layer
structure of 1. (c) The packing diagram of 1 along the a axis in an
-ABAB- sequence. (d) Schematic representation of the (4,4)-
connected binodal 2D network of 1 with (4.64.8)2(42.64) topology
(turquoise ball: Zn1; blue ball: the center of the L ligand).
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Figure 2. (a) Coordination environment of ZnII in 2 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and free water
molecule are omitted for clarity. Symmetry code: A 2 − x, y, 0.5 − z; B 2 − x, −y, 1 − z; C 0.5 + x, 0.5 + y, z; F 1.5 − x, 0.5 + y, 0.5 − z; G 1.5 − x,
0.5 − y, 2 − z. (b) 2D network of 2 constructed by ZnII atoms and L ligands. (c) The 3-fold interpenetrating 3D framework of 2 formed from 2D
networks pillared by DC2− ligands. (d) Schematic representation of the (4, 4)-connected binodal self-penetrating 3D framework of 2 with two self-
penetrated 6-membered shortest circuits highlighted (pink ball: the center of the L ligand; turquoise ball: Zn1; green stick: the normal DC2− ligand;
red stick: the disordered DC2− ligand). (e) View of the self-penetration of two 6-membered circuits in 2.
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Scheme 2. Coordination Modes of Multicarboxylate Ligands
in Complexes 2−6
with each carboxylate group in μ1-η1:η0-monodentate mode
(type V, Scheme 2). Each L ligand links four ZnII atoms to
generate an infinite 2D network (Figure 6b). Then the adjacent
layers are further linked together by MBEA2− ligands to form a
3D architecture (Figure 6c). From a topological view, each
2-connected bridging MBEA2− ligand can be regarded as a
linear linker. Each L ligand connects four ZnII atoms and can be
treated as a 4-connector. Each ZnII atom can be regarded as
4-connected node since it links two L and two MBEA2− ligands.
Therefore, the overall structure of 6 is a 4-connected uninodal
3D net with stoichiometry (4-c)(4-c)2, as shown in Figure 6d.
The point (Schlafli) symbol for the net is (64)(82) calculated by
̈
the TOPOS program,25 which has been referred by O’Keeffe
and Wells to the nbo notation.26
Comparison the Structures of the Complexes 1−6. Six
new ZnII/CdII complexes were successfully synthesized by
using L and multidentate carboxylate ligands. And among these
complexes, the auxiliary carboxylate ligands are completely
deprotonated, which was confirmed by the IR spectral data
(see Experimental Section) as well as the crystal structures as
described above. It is known that multicarboxylate ligands are
good candidates for the construction of MOFs with specific
structure and topology due to their varied coordination modes.
The different structures and topologies of the complexes 1, 2,
and 6 with the same metal center of ZnII and L ligand as well as
3, 4, and 5 with the same CdII and L ligand indicate that the
multicarboxylate ligands have great influence on the structures
of the complexes due to their different structures, flexibility, and
coordination modes (Scheme 2). The auxiliary ligands except
for H3BTB used for preparation of 1 participate in the
formation of the complexes. The dicarboxylate groups of DC2−,
PBEA2−, MBEA2− in 2−6 act as μ2, μ3, μ2, μ3, and μ2-bridging
ligands. And the carboxylate groups present different
coordination modes in 2−6, namely, μ1-η1:η0-monodentate in
2, μ1-η1:η1-chelate and μ2-η1:η1-bridge in 3, μ1-η1:η1-chelate in
4, μ1-η1:η1-chelate and μ2-η2:η1-chelate/bridge in 5, and μ1-
η1:η0-monodentate in 6. In addition, complexes 1−6 show 2D
and 3D structures with different topologies. In brief, the
different modes of the carboxylate groups lead to the formation
of the complexes with varied structures, and at the same time,
make it difficult to predict the structures of the resulting
complexes. On the other hand, during the syntheses of
complexes 2 and 3 as well as 5 and 6, the same auxiliary
ligands and L ligand were used. However the obtained structures
are distinct, which could be ascribed to the different nature of
the metal ions such as ion radius, coordination number, and
geometry. In 2, each ZnII atom is four-coordinated, while in 3
each CdII atom is six-coordinated. Similarly, in 5, the CdII atoms
are seven-coordinated, while in 6 each ZnII is four-coordinated.
Figure 3. (a) Coordination environment of CdII in 3 with the
ellipsoids drawn at the 30% probability level. The hydrogen atoms are
omitted for clarity. Symmetry code: B x,1 + y, z; C 1 − x, y, 1.5 − z; E
x, 2 − y, −0.5 + z; H 0.5 + x, 0.5 + y, z. (b) The layer structure of 3
constructed by CdII atoms and DC2− ligands. (c) 3D framework of 3:
blue represented the L ligands,and the rest colors for different 2D
layers. (d) Schematic representation of the 3D net of 3 with
(4.63.86)2(42.84)(63)2 topology (teal: Cd1 atom; red: the center of
DC2−; blue: the center of L).
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Figure 4. (a) Coordination environment of CdII atoms in 4 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and free
water molecules are omitted for clarity. Symmetry code: A 2 − x, y, 0.5 − z; B 2 − x, 1 − y, 1 − z; C 1 − x, y, 0.5 − z; D 1.5 − x, −0.5 − y, −z.
(b) 2D layer structure of 4 constructed by CdII atoms, PBEA2− and L ligands in the ac plane. (c) 3D framework of 4:
different colors for different layers. (d) The space-filling diagram of 4. (e) Schematic representation of the (4, 4)-connected binodal 3D 3-fold
interpenetrating sta net of 4 with (4.64.8)2(42.62.82) topology (yellow ball: the center of L ligand; teal ball: Cd2; turquoise ball: Cd1; different colors
stick: independent 3D net).
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under N2 atmosphere to examine the thermal stability of the
coordination polymers and the results are shown in Figure S2,
Supporting Information. Complex 1 shows a weight loss of
5.28% before 215 °C corresponding to the release of free water
molecules (calcd 5.10%), and the decomposition of the residue
was observed at 425 °C. For 2, a weight loss of 3.62% was
observed in the temperature range of 40−180 °C, which
corresponds to the liberation of the free water molecules (calcd
3.62%), and further weight loss was observed at about 396 °C,
owing to the collapse of the framework of 2. No obvious
weight loss was found for 3 before the decomposition of the
framework occurred at about 395 °C, which is in good
agreement with the result of its crystal structure. Complex 4
shows the weight loss of 3.48% between 54 and 230 °C,
which is attributed to the release of the free water molecules
(calcd 3.38%); the residue begins to decompose at 415 °C.
For 5 and 6, weight losses of 6.32% and 7.08% were
observed in the temperature range of ca. 40−180 °C, which
correspond to the liberation of the free water molecules
(calcd 6.55% for 5 and 7.16% for 6), respectively, and further
weight losses were observed at about 300 and 335 °C,
respectively, owing to the collapse of the frameworks of
5 and 6.
The pure phase of the synthesized complexes 1−6 was
confirmed by powder X-ray diffraction (PXRD) measurements
and the results are shown in Figure S3, Supporting Information.
And each PXRD pattern of the as-synthesized sample is very
consistent with the simulated one.
Sorption Property. The results of structural analyses show
that there are water molecules in the complexes except 3
without solvent molecules. Thus further TGA and PXRD
measurements were carried out to ascertain the thermal stability
of the complexes for sorption property investigation, and it was
found that the water molecules in 1 and 6 can be removed
completely by heating to give dehydrated samples of 1′ and 6′,
respectively without destroying the structure (Figures S2b and
S3, Supporting Information). For complex 1, the PXRD pattern
of the dehydrated sample 1′ is consistent with the one of the
as-synthesized one. While in the case of complex 6, the PXRD
pattern of the dehydrated sample 6′ is different from that of the
as-synthesized one. Fortunately, the PXRD pattern of the
rehydrated sample matches well with the as-synthesized one,
indicating that the water molecule can induce the trans-
formation of the framework. As shown in Figure 7, the
sorption curves of N2 at 77 K for samples 1′ and 6′ suggest
only surface adsorption.32 However, the H2O vapor sorption
of 1′ and 6′ was observed. The final values of 73.056 cm3 g−1
(60.34 mg g−1) for 1′ and 100.21 cm3 g−1 (80.56 mg g−1) for
6′ at P = 0.99 atm correspond to 1.09 and 2.09 H2O
molecules per formula unit for 1 and 6, respectively, which
are close to the one and two molecules in 1 and 6 indicated
by crystallographic analysis. The large hysteresis and
incomplete desorption imply the strong adsorbate−adsorbent
interactions.33
Figure 5. (a) Coordination environment of CdII in 5 with the
ellipsoids drawn at the 30% probability level. The hydrogen atoms and
free water molecules are omitted for clarity. Symmetry code: A x, −1 +
y, z; B x, 1 + y, z; D −x, y, 0.5 − z; E −x, 1 + y, 0.5 − z; F 0.5 − x, 1.5
− y, 1 − z. (b) Hinged chain structure of 5 constructed by CdII atoms
and L ligands. (c) 2D network of 5 formed from hinged chains linked
by MBEA2− ligands (different colors for different chains and red for
the MBEA2− ligands). (d) Schematic representation of the (4, 6)-
connected binodal 2D network of 5 with (32.42.52)(34.44.54.63)
topology (balls: Cd2O2 units; blue stick: L ligand; red stick:
MBEA2− ligand).
Photoluminescence Properties of the Complexes. The
inorganic−organic hybrid coordination polymers, especially
with d10 metal centers, have been well investigated for fluo-
rescence properties owing to their ability to adjust the emis-
sion of the substances.34 Therefore, we carried out an
investigation on the luminescence properties of the
complexes in view of their potential applications as photo-
active materials. The photoluminescence properties of 1−6
ligands were studied in the solid state in the room temperature
The results of this work provide further evidence to confirm that
the auxiliary carboxylate ligands are versatile in construction of
MOFs.
Thermal Stability and PXRD of the Complexes. The
thermogravimetric analyses (TGA) of 1−6 were carried out
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Figure 6. (a) Coordination environment of ZnII atom in 6 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and free water
molecules are omitted for clarity. Symmetry code: A x, 0.5 − y, −0.5 + z; B 1 − x, 0.5 + y, 1.5 − z; C −x, −y, 1 − z. (b) 2D layer structure of 6
constructed by ZnII atoms and L ligands. (c) 3D framework of 6 formed from layers connected by the MBEA2− ligands (different colors for different
layers; red stick: the MBEA2− ligand). (d) Schematic representation of the 4-connected uninodal 3D nbo net of 6 with (64)(82) topology (turquoise
ball: Zn1; blue ball: the center of the L ligand).
under the same experimental conditions, and the emission
spectra are exhibited in Figure 8, while the emission spectra of
the auxiliary ligands are given in Figure S4, Supporting
Information. Intense emission bands were observed at
430 nm (λex = 360 nm) for L, 409 nm (λex = 383 nm) for
H2DC, 454 nm (λex = 365 nm) for H2PBEA, and 434 nm (λex =
375 nm) for H2MBEA. Emission bands were observed at
433 nm (λex = 353 nm) for 1, 437 nm (λex = 373 nm) for 2, 454 nm
(λex = 380 nm) for 3, 417 nm (λex = 330 nm) for 4, 427 nm
(λex = 355 nm) for 5, and 430 nm (λex = 362 nm) for 6,
respectively. Such photoluminescence emissions may be owing
to the intraligand transition of the ligands as a result of their
close similarity.35 The red- or blue-shift of the emission
maximum between the complex and the ligand was considered
to originate from the influence of the coordination of the ligand
to the metal centers.36
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present study also demonstrates that the mixed ligands are
powerful for construction of MOFs with diverse structures.
ASSOCIATED CONTENT
* Supporting Information
■
S
X-ray crystallographic file in CIF format, 6-connected node
(Figure S1), TGA (Figure S2), PXRD (Figure S3), emission of
the auxiliary ligands (Figure S4). This information is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Fax: 86 25 8331 4502. Tel: 86 25 8359 3485. E-mail: sunwy@
nju.edu.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was financially supported by the National Natural
Science Foundation of China (Grant Nos. 91122001 and
21021062) and the National Basic Research Program of China
(Grant No. 2010CB923303).
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