Syntheses, structures, and photochemical properties of six new metal-organic frameworks based on aromatic dicarboxylate acids and V-shaped imidazole ligands

Article abstract of DOI:10.1021/cg1008208

Solvothermal reactions of 4,4′-bis(imidazol-1-yl)diphenyl ether (BIDPE) with deprotonated 1,4-benzenedicarboxylic acid (H₂bdc) in the presence of cadmium, zinc, cobalt, nickel, and manganese salts in H ₂O or H₂O/DMF yielde

Full text of DOI:10.1021/cg1008208

DOI: 10.1021/cg1008208
Syntheses, Structures, and Photochemical Properties of
Six New Metal-Organic Frameworks Based on Aromatic
Dicarboxylate Acids and V-Shaped Imidazole Ligands
2010, Vol. 10
4135–4142
Jin-Song Hu,† Yong-Jia Shang,‡ Xiao-Qiang Yao,† Ling Qin,† Yi-Zhi Li,† Zi-Jian Guo,†
He-Gen Zheng,*,†,§ and Zi-Ling Xue*,
†State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering,
Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093,
‡P. R. China, Key Laboratory of Functional Molecular Solids, Ministry of Education,
Anhui Key Laboratory of Molecule-Based Materials, College of Chemistry and Materials Science,
Anhui Normal University, Wuhu 241000, P. R. China, §State Key Laboratory of Structural Chemistry,
Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002,
P. R. China, and Department of Chemistry, The University of Tennessee, Knoxville,
Tennessee 37996-1600
Received June 18, 2010; Revised Manuscript Received July 29, 2010
ABSTRACT: Solvothermal reactions of 4,40-bis(imidazol-1-yl)diphenyl ether (BIDPE) with deprotonated 1,4-benzenedicar-
boxylic acid (H2bdc) in the presence of cadmium, zinc, cobalt, nickel, and manganese salts in H2O or H2O/DMF yielded six new
complexes, namely, {[Co(BIDPE)(bdc)]2 (H2O)2(DMF)}n (1), {[Cd(BIDPE)(bdc)]4 (H2O)4(DMF)2}n (2), {[Zn(BIDPE)(bdc)]2
3
3
3
(H2O)2(DMF)}n (3), [Cd3(BIDPE)2(bdc)3]n (4), and [Ni(BIDPE)(bdc)(H2O)2]n (5), and [Mn(bdc)(BIDPE)(H2O)]n (6). These
complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complexes 1 and 3
reveal a 2-fold interpenetrating three-dimensional (3D) framework constructed from BIDPE and H2bdc with Co and Zn salts;
complexes 2 and 4 have the same staring materials but possess different 3D frameworks and are prepared from BIDPE and
H2bdc under different reaction conditions. In complexes 5 and 6, BIDPE and H2bdc link Ni and Mn centers, respectively, to
generate 2D f 2D interlocked sheets. The thermal stabilities and photochemical properties of these new complexes have also
been studied.
Introduction
ligand, 4,40-bis(imidazol-1-yl) diphenyl ether (BIDPE), which
may be regarded as a half-flexible ligand. To test the ability of
this ligand to give new architectures and topologies, we have
selected this new ligand, H2bdc ligand (Scheme 1), and diffe-
rent bivalent metal salts, to prepare solvothermally six new
coordination polymers with intriguing structures, namely, {[Co-
(BIDPE)(bdc)]2 (H2O)2(DMF)}n (1), {[Cd(BIDPE)(bdc)]4
Crystal engineering of coordination polymers has attracted
great attention due to their novel architectures and potential
applications in photochemical areas,1 molecular magnetism,2
heterogeneous catalysis,3 and molecular sorption.4 However,
many factors, such as organic ligands,5 solvent systems,6 metal
ions,7 and counterions,8 have been found to greatly influence
the structures in the self-assembly process, and they may play
a key role in predicting the construction of molecular archi-
tectures. Systematic studies of diversified conditions lead-
ing to different structures in the formation of coordination
polymers are thus important and of intense interest.
Recently, a large number of mixed-ligand metal-organic
frameworks (MOFs) have been reported,9 most of which contain
N-containing ligands introduced into metal-polycarboxylate
systems. The combination of different ligands may result in
greater tunability of structural frameworks than that present
with single ligands. Hence, a mixed-ligand is undoubtedly a
good choice for the construction of new polymeric structures.
Imidazole ligands have been used in the synthesis of unique
MOFs which possess excellent coordination ability and allow
free rotation of the imidazole ring to meet the requirement
of coordination geometries of metal ions. Until now, a great
number of ingenious MOFs have been synthesized designed
based on imidazole ligands.10 Syntheses of new imidazole
ligands are still a long-standing fascination of chemists, and
we have designed and synthesized a new V-shape imidazole
3
3
(H2O)4(DMF)2}n (2), {[Zn(BIDPE)(bdc)]2 (H2O)2(DMF)}n
3
(3), [Cd3(BIDPE)2(bdc)3]n (4), [Ni(BIDPE)(bdc)(H2O)2]n (5),
and [Mn(bdc)(BIDPE)(H2O)]n (6). All compounds were char-
acterized by elemental analysis, IR spectra, and X-ray crystal-
lography. The crystal structures, topological analyses, and ther-
mal properties of these compounds are presented. In addition,
the photochemical properties of these complexes are discussed
in detail.
Experimental Section
Materials and Measurements. The reagents and solvents employed
were commercially available and used as received. IR absorption spec-
tra of the complexes were recorded in the range of 400-4000 cm-1 on a
Nicolet (Impact 410) spectrometer with KBr pellets (5 mg of sample
in 500 mg of KBr). C, H, and N analyses were carried out with a
Perkin-Elmer 240C elemental analyzer. Powder X-ray diffraction
(PXRD) measurements were performed on a Bruker D8 Advance
˚
X-ray diffractometer using Cu KR radiation (λ=1.5418 A), in which
the X-ray tube was operated at 40 kV and 40 mA. NMR spectra were
recorded on a Bruker NMR 500 DRX spectrometer. Solid-state
UV-vis diffuse reflectance spectra were obtained at room temperature
using a Shimadzu UV-3600 double monochromator spectrophot-
ometer, and BaSO4 was used as a 100% reflectance standard for all
materials. Luminescent spectra were recorded with a SHIMAZU
VF-320 X-ray fluorescence spectrophotometer at room temperature.
*To whom correspondence should be addressed. E-mail: zhenghg@
nju.edu.cn (H.-G.Z.); xue@ion.chem.utk.edu (Z.-L.X.). Fax: 86-25-83314502.
r
2010 American Chemical Society
Published on Web 08/16/2010
pubs.acs.org/crystal

4136 Crystal Growth & Design, Vol. 10, No. 9, 2010
Hu et al.
The as-synthesized samples were characterized by thermogravimetric
analysis (TGA) on a Perkin-Elmer thermogravimetric analyzer Pyris
1 TGA up to 1023 K using a heating rate of 10 K min-1 under N2
atmosphere.
Calcd for C110H98O28N18Cd4: C, 51.43; H, 3.81; N, 9.82. Found: C,
51.35; H, 3.85; N, 9.83. IR (KBr, cm-1): 3456(w), 3115(w), 1554(s),
1518(s), 1383(s), 1240(s), 1123(m), 1067(s), 1015(w), 964(w), 930(w),
855(m), 824(s), 745(s), 653(m), 531(m).
Synthesis of 4,40-Bis(imidazol-1-yl)diphenyl Ether (BIDPE). A
mixture of Cu2O (0.07 g, 0.5 mmol), 4,40-dibromodiphenyl ether
(3.24 g, 10 mmol), imidazole (2.72 g, 4.0 mmol), and K2CO3 (5.52 g,
4.0 mmol) in anhydrous DMF (30 mL) in a 100-mL two-necked
round-bottom flask under N2 was stirred at 150 °C for 48 h. The
reaction mixture was filtered, and then the filtrate was added into
200 mL of H2O. The deposit was filtered and washed with water and
dried in vacuum to afford the product in 80%. 1H NMR: (CDCl3,
500 Hz) δ7.39 (d, J=9.0 Hz, 4H), 7.21 (s, 2H), 7.26 (s, 2H), 7.38 (d, J=
9.0 Hz, 4H), 7.82 (s, 2H) ppm (Supporting Information, Figure S1).
MS (EI): m/z=303 (Mþ). Anal. Calcd for C18H14N4O: C, 71.51; H,
4.67; N, 18.53. Found: C, 71.48; H, 4.55; N, 18.66. IR (KBr, cm-1):
3122(w), 3108(w), 1510(s), 1304(m), 1234(s), 1170(m), 1108(m), 1061(s),
961(m), 910(m), 869(m), 829(s), 762(m), 657(s), 520(m). Melting
point: 150-151 °C.
Synthesis of {[Zn(BIDPE)(bdc)]2 (H2O)2(DMF)}n (3). Com-
pound 3 was prepared in a process similar to that for compound 1.
Zn(NO3)2 6H2O (29.7 mg, 0.1 mmol), H2bdc (16.6 mg, 0.1 mmol),
and BIDPE (30.2 mg, 0.1 mmol) were dissolved in 12 mL of DMF/
H2O (3:1, v/v). Colorless-plank crystals of 3 were obtained in 65%
yield based on BIDPE. Anal. Calcd for C54H44O13N9Zn2: C, 56.02;
H, 3.83; N, 10.89. Found: C, 55.98; H, 3.87; N, 10.91. IR (KBr, cm-1):
3416(w), 3139(w), 1593(s), 1519(s), 1396(m), 1351(s), 1239(s), 1172(w),
1122(s), 1066(s), 1013(w), 829(s), 750(s), 653(m), 529(m).
Synthesis of [Cd3(bdc)3(BIDPE)2]n (4). Compounds 4 and 2 have
the same stoichiometric ratios of staring materials, but the reaction
conditions are different. The materials were dissolved in 10 mL of
distilled water. The pH value of the solution was adjusted to 7.0 by
addition of 1 M NaOH solution. The final mixture was sealed in a
15 mL Parr Teflon-lined stainless-steel vessel and heated at 140 °C
for 3 days. After the reaction system was cooled to room tempera-
ture, colorless block crystals of 4 were obtained (yield: 53% based
on BIDPE). Calcd for C60H40O14N8Cd3: C, 50.25; H, 2.81; N, 7.81.
Found: C, 50.21; H, 2.84; N 7.86. IR (KBr, cm-1): 3358(m), 3133(m),
3072 (w), 1719(w), 1542(s), 1514(m), 1378(s), 1304(w), 1230(s), 1120(s),
1058(s), 1016(w), 933(w), 866(s), 751(s), 650(m).
3
3
Synthesis of {[Co(BIDPE)(bdc)]2 (H2O)2(DMF)}n (1). A mixture
3
of Co(NO3)2 6H2O (29.1 mg, 0.1 mmol), H2bdc (16.6 mg, 0.1 mmol),
3
and BIDPE (30.2 mg, 0.1 mmol) in 12 mL of DMF/H2O (3:1, v/v)
was placed in a Parr Teflon-lined stainless steel vessel (15 mL) under
autogenous pressure and heated at 90 °C for 3 days. Purple crystals
were obtained, and crystals were filtered off, washed with mother
liquid, and dried under ambient conditions to give 1 in 66% yield
based on BIDPE. Anal. Calcd for C54H44O13N9Co2: C, 56.65; H,
3.87; N, 11.01. Found: C, 56.62; H, 3.85; N, 11.04. IR (KBr, cm-1):
3439(w), 3415(w), 2361(w), 1649(m), 1613(m), 1578(s), 1518(s),
1384(s), 1307(w), 1237(s), 1175(w), 1122(m), 1067(s), 1013(w), 964(w),
835(m), 751(s), 653 (m), 528(m).
Synthesis of [Ni(bdc)(BIDPE)(H2O)2]n (5). Compound 5 was
prepared by a process similar to that yielding compound 1 by using
Ni(NO3)2 4H2O (25.4 mg, 0.1 mmol), H2bdc (16.6 mg, 0.1 mmol),
3
and BIDPE (30.2 mg, 0.1 mmol) in 8 mL of DMF and H2O (1:1, v/
v). Green crystals were obtained (yield: 56% based on BIDPE).
Anal. Calcd for C26H22O7N4Ni: C, 55.65, H; 3.95; N, 9.98. Found:
C, 55.62; H, 3.97; N, 10.04. IR (KBr, cm-1): 3441(w), 3127(w),
1552(s), 1515(s), 1377(s), 1272(w), 1244(s), 1169(w), 1132(w),
1211(s), 1104(w), 1060(s), 1039(m), 971(w), 898(s), 880(s), 829(s),
783(s), 718(s), 666 (m), 570(m), 540 (s).
Synthesis of {[Cd(BIDPE)(bdc)]4 (H2O)4(DMF)2}n (2). A mix-
ture of Cd(NO3)2 4H2O (30.1 mg, 0.1 mmol), H2bdc (16.6 mg, 0.1
3
3
mmol), and BIDPE (30.2 mg, 0.1 mmol) was dissolved in 12 mL of
DMF/H2O (3:1, v/v). The final mixture was placed in a Parr Teflon-
lined stainless steel vessel (15 mL) under autogenous pressure and
heated at 90 °C for 3 days. The large quantities of colorless-plank
crystals of 2 were obtained in 76% yield based on BIDPE. Anal.
Synthesis of [Mn(bdc)(BIDPE)(H2O)]n (6). Compound 6 was
prepared in a manner similar to that used for compound 1 by using
MnCl2 4H2O (19.7 mg, 0.1 mmol), H2bdc (16.6 mg, 0.1 mmol), and
3
BIDPE (30.2 mg, 0.1 mmol) in 10 mL of DMF and H2O (1:4, v/v).
Colorless crystals were obtained (yield: 56% based on BIDPE).
Anal. Calcd for C26H20N4O6Mn: C, 57.89; H 3.74; N, 10.39. Found:
C, 57.93; H, 3.81; N, 10.41. IR (KBr, cm-1): 3421(w), 3133(w),
1669(s),1568(w), 1518(s), 1380(m), 1304(m), 1240(s), 1173(m),1119(m),
1060(s), 1011(w), 960(w), 927(w), 838(s), 731(s), 654(s), 527 (s).
X-ray Crystallography. Single crystals of 1-6 were prepared by
the methods described in the synthetic procedures. X-ray crystal-
lographic data of 1-6 were collected at room temperature using
epoxy-coated crystals mounted on glass fiber. All measurements
Scheme 1. Two N-Containing and Dicarboxylate Ligands
Table 1. Crystallographic Data and Structure Refinement Details for Complexes 1-6
1
2
3
4
5
6
formula
C54H44O13N9Co2 C110H97O28N18Cd4 C54H44O13N9Zn2 C60H40O14N8Cd3 C26H22O7N4Ni C26H20N4O6Mn
formula weight
crystal system
space group
1140.8
tetragonal
I41/acd
18.4905(17)
18.4905(17)
61.775(8)
90.00
90.00
90.00
21121(4)
16
1.435
2569.66
tetragonal
I41/acd
18.903(3)
18.903(3)
62.293(9)
90.00
90.00
90.00
22258(6)
8
1.533
1157.76
tetragonal
I41/acd
18.3863(17)
18.3863(17)
61.935(12)
90.00
90.00
90.00
20937(5)
16
1.469
1434.20
monoclinic
P21/n
9.961(2)
17.750(4)
15.444(4)
90.00
92.662(5)
90.00
2727.8(11)
2
1.746
561.17
monoclinic
P21/n
6.3784(9)
17.552(3)
22.179(3)
90.00
93.715(3)
90.00
2477.9(6)
4
1.504
539.40
monoclinic
P21/c
12.1170(16)
18.247(2)
21.183(3)
90.00
97.541(3)
90.00
4643.1(11)
8
1.543
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
Dc (g cm-3
)
μ(Mo KR) (mm-1
F(000)
)
0.702
0.838
10400
4856
0.078
0.991
1.237
1424
4790
0.0678
0.838
1160
4841
0.0641
0.621
2216
8710
0.0692
9360.0
4614
0.0825
9520.0
4611
0.1171
tot, uniq data
R(int)
observed data [I>2σ(I)]
[I>2σ(I)]
3209
0.0754, 0.1657
1.082
3713
0.0627, 0.1853
1.120
2118
0.0635, 0.1588
1.009
3507
0.0477, 0.1346
1.084
2884
0.0518, 0.0929
0.855
5102
0.0566, 0.0979
0.952
R1, wR2 [I>2σ(I)]
S
min and max. resd dens
-0.413, 0.646
-1.407, 1.761
-1.119, 0.665
-2.19, 2.23
-0.342, 0.383
-0.348, 0.411
-3
-3
˚
˚
(e A ) (e A
)
3
3

Article
Crystal Growth & Design, Vol. 10, No. 9, 2010 4137
Figure 1. (a) Coordination environment of the Co(II) ion in 1. The hydrogen atoms are omitted for clarity. Symmetry codes: (#1) 0.5 þ x, 1 - y,
z. (b) Views of the 1D wavelike chain with a helical channel of BIDPE ligands and Co ions. (c) Views of the 1D zigzag chain of bdc2- and Co
ions. (d) Views of 1D helical channels. (e) Perspective of 3D framework in 1 along the a axis. (f) Illustration of solvents position. (g) Schematic
representation of a single 3D framework of compound 1. (h) 2-fold interpenetrating framework in 1.
were made on a Bruker Apex Smart CCD diffractometer with
˚
BIDPE and bdc2- anions with Co(II), Cd(II), or Zn(II) salts,
which are further connected into a 3D network. Hence, only
the crystal structure of compound 1 is described in detail
here. Compound 1 crystallizes in the tetragonal space group
I41/acd. The asymmetric unit of 1 contains an independent
Co(II) cation, one bdc2- anion, one BIDPE ligand, one free
water, and half a disordered DMF molecule. As shown in
Figure 1a, carboxylate groups of bdc2- adopt two coordina-
tion modes: one carboxylate group adopts a monodentate
coordination mode, whereas another carboxylate group
coordinates to the same Co center by adopting a chelating
coordination mode (Scheme 2a). The Co(II) center is five
coordinated by three carboxylic O atoms from two H2bdc
ligands and two nitrogen atoms from two BIDPE ligands to
graphite-monochromated Mo KR radiation (λ = 0.71073 A). The
structures of 1-6 were solved by direct methods, and the non-
hydrogen atoms were located from the trial structure and then
refined anisotropically with SHELXTL using a full-matrix least-
squares procedure based on F2 values.11 The hydrogen atom posi-
tions were fixed geometrically at calculated distances and allowed to
ride on the parent atoms. The relevant crystallographic data are
presented in Table 1, while the selected bond lengths and angles are
given in Supporting Information Table S1.
Results and Discussion
Crystal Structure of {[Co(BIDPE)(bdc)]2 (H2O)2(DMF)}n
3
(1). X-ray analysis reveals that compounds 1, 2, and 3 are
isostructural. These compounds are self-assembled from the

4138 Crystal Growth & Design, Vol. 10, No. 9, 2010
Hu et al.
Scheme 2. Crystallographically Established Coordination
Modes of Carboxylic Groups in Compounds 1-6
nitrogen atoms from two BIDPE ligands. The carboxylate
groups of the bdc2- ligand adopt unidentate coordination
modes (Scheme 2c). The bond angles and lengths are listed in
Table S1.
Crystal Structure of [Cd3(BIDPE)2(bdc)3]n (4). The crystal
structure of 4 was solved in the space group P2(1)/n. The
asymmetric unit of 4 contains two crystallographically in-
dependent cadmium ions (Cd1 and Cd2), of which Cd2 (1.0,
0.0, 0.5) is localized on a special position, one and a half
bdc2- anions, and one BIDPE ligand. As shown in Figure 2a,
the carboxylate groups of bdc2- adopt three different co-
ordination modes, in which one bonding carboxylate group
is chelating in a bidentate mode, one is bridging bidentate,
and the other is in the chelating-bridging tridentate mode
(Scheme 2d and e). The Cd(II) atoms are bridged by carboxy-
late ligands to form a linear trinuclear cluster unit Cd(1)
Cd(2) Cd(1) with the Cd(1) Cd(2) distance of 3.946(3) A.
3 3 3
˚
3 3 3
3 3 3
The Cd(2) center is six-coordinated to form an octahedral
geometry by four O (O2, O33, O2#1, O33#1) atoms from
H2bdc ligands in an equatorial position and two N(N3,
N3#1) atoms from BIDPE in an axial position. The four
O atoms are almost in a plane, the Cd-O lengths are in the
form a distorted trigonal bipyramidal geometry. The Co-O
˚
lengths are in the range of 1.989(4)-2.387(4) A, and the Cd-N
˚
lengths are 2.036(4)-2.0575(4) A, which are all similar to
those values found in other Co(II) complexes.
˚
˚
The neighboring Co(II) ions are linked by BIDPE ligands
to form an infinitely wavelike 1D helical chain along the
range 2.326(5)-2.348(4) A, andtheCd-N length is 2.280(5) A.
Cd(1) is also six-coordinated and resides in a distorted octa-
hedral coordination environment: five O atoms from three
H2bdc ligands and one N atom from the BIDPE ligand.
˚
a axis (Figure 1b): the Co Co distance is 18.103 A, and the
3 3 3
N-Co-N angle is 101.18(18)°. Similarly, the neighboring
Co(II) ions are connected by bdc2- to form an infinitely 1D
zigzag chain along the c axis (Figure 1c). The Co Co
˚
The Cd-O lengths are in the range 2.256(5)-2.754(5) A, and
the Cd-N length is 2.281(6) A, which are all similar to those
˚
3 3 3
˚
distance is 10.879 A, and the dihedral angle of two carboxylic
found in other Cd(II) complexes.
Each trinuclear Cd cluster coordinates to six bdc2- anions
to form a 3D brick wall framework containing rectangle chan-
nels along the a axis with 44-remember rings (Figure 2b). The
acids is 84.147(2)°. An interesting feature in this complex is
that left-handed and right-handed 1D helical channels exist
alternately running along the c axis (-BIDPE-Co-BIDPE-
2
2-
2
˚
˚
Co-), and the size is 8.395ꢀ8.395 A (Figure 1d). The bdc
size is about 17.750ꢀ9.987 A . The rectangle channels were
links these 1D helical chains to form a 3D framework com-
posed of helical chains of opposite handness (Figure 1e). The
framework contains three kinds of channels, A, B, and C;
channel C is small and water molecules filled it in, while
channel A is large and water and DMF molecules filled it in,
and medium sized channel B is occupied by DMF, with all
these slovents making the framework more stable (Figure 1f).
A better insight into the nature of this intricate framework
can be achieved by the application of a topological approach,
reducing multidimensional structures to a simple node and
connection nets. The Co(II) ions can be regarded as 4-con-
nected nodes, and all crystallographical independent BIDPE
ligands act as linkers. Therefore, the whole structure can thus
be symbolized as a {86} topology (Figure 1g). Structures
containing 3D four-connected nets are reported, such as
well-known diamond (66), NbO (64 82-a and 64 82-b net),
filled by coordinated BIDPE ligands, which link trinuclear
Cd clusters through N coordination to form a 3D network
(Figure 2c). To reduce multidimensional structures to simple
node and connection nets, the trinuclear Cd cluster can be
regarded as 10-connected nodes, all crystallographically
independent BIDPE, and the bdc2- ligands linkers. There-
fore, the whole structure can thus be symbolized as a {441 64}
3
topology (Figure 2d).
Crystal Structure of [Ni(bdc)(BIDPE)(H2O)2]n (5). Com-
pound 5 is self-assembled from the BIDPE ligand as V-shaped
linker motifs and bdc2- anions as linking rods that are fur-
ther connected and interpenetrated to give a 2D f 2D network.
Single crystal X-ray analysis reveals compound 5 crystallized
in the monoclinic crystal system, space group P21/n. The
asymmetric unit of 5 contains one Ni(II) cation, one BIDPE
ligand, one bdc2- anion, and two coordinated water mole-
cules. As shown in Figure 3a, the coordination environment
around the Ni(II) cation can be described as a slightly dis-
torted octahedron geometry of two unidentate carboxylic
oxygen atoms (O2, O5#2) and two coordinated water O atoms
(O3, O4) at the equatorial position with the other two coordi-
nated N atoms (N1, N3#3) at the axial positions. The Ni-O
3
3
and PtS (42 84 net). While a four-connected {86} net is not
3
specifically identified by Wells,12 related reports have existed.13
Because of the spacious nature of a single network, it allows
another identical network to penetrate it, leading to a 2-fold
interpenetrated structure (Figure 1h).
Compounds 1, 2, and 3 are isostructural, but the coordi-
nation environments of Cd(II) in 2 (Supporting Information,
Figure S2) and Zn(II) in 3 (Supporting Information, Figure S3)
were changed. Cd(II) ions are in an octahedral coordination
environment of four carboxylic O atoms from two H2bdc
ligands and two nitrogen atoms from two BIDPE ligands,
with the carboxylate groups of the bdc2- ligand adopting
chelating bidentate coordination modes (Scheme 2b), while
Zn(II) ions are in a tetrahedral coordination environment of
two carboxylic O atoms from two H2bdc ligands and two
˚
distances are in the range 2.047(2)-2.122(2) A, and the
˚
Ni-N distances are 2.032(3)-2.039(3) A.
The neighboring Ni(II) ions are linked by the BIDPE
ligands and bdc2- anions to form an infinitely wavelike 2D
sheet. In this sheet, the BIDPE ligands arranged in an oppo-
site construction to form distorted tetragon grids about 9.375ꢀ
2
˚
7.517 A large (Figure 3b). Of particular interest, the most
striking feature of complex 5 is that a pair of identical 2D
single nets interlocked with each other (Figure 3c). As shown

Article
Crystal Growth & Design, Vol. 10, No. 9, 2010 4139
Figure 2. (a) Coordination environment of the Cd(II) ion in 4. Hydrogen atoms are omitted for clarity. Symmetry codes: (#1) 2 - x, -y, 1 - z.
(b) Views of the 3D brick wall framework by bdc2- and Cd anions along the a axis. (c) Views of the 3D framework of 4 along the a axis.
(d) Schematic representation of a single 3D framework of compound 4.
˚
˚
in Figure 3d, the channels of each network are threaded by
one bdc-Ni-bdc rod of another network, and vice versa.
Crystal Structure of [Mn(bdc)(BIDPE)(H2O)]n (6). We
have tried to use Mn(NO3)2, but the crystal was not very
well ordered and cannot fix the structure; when Mn(NO3)2
was replaced by MnCl2, better crystals were obtained. The
crystal structure of 6 was solved in the space group P21/c. As
depicted in Figure 4a, compound 6 consists of two parts with
two types of coordination environments around the Mn(II)
ions. The two Mn(II) ions all have distorted octahedron
geometry with three carboxylic O atoms from bdc2- anions
and one coordinated water O atom at the equatorial plane
and two N atoms from two BIDPE ligands at the axial
position. The Mn-O distances are in the range 2.087(4)-
2.340(4) A, and the Mn-N distances are 2.233(5)-2.253(4) A.
Similar to the case for compound 5, the neighboring Mn(II)
ions are linked by BIDPE ligands and bdc2- anions to form
two infinitely wavelike 2D sheets (Figure 4b), in which every
two BIDPE ligands and bdc2- anions link four Mn atoms
to form distorted tetragon grids about 10.622 ꢀ 9.788 and
2
˚
10.592ꢀ9.022 A . The most striking feature of complex 6 is
that these two different 2D sheets interlocked each other
(Figure 4c). Further inspection shows that the coordinated
water molecules and carboxylate groups from another sheet
are actually contacting each other by strong H-bonding
˚
(O O distances range from 2.616 to 2.790 A). Obviously,
3 3 3
these H-bonded interactions are also available for increasing
the stability of the whole crystal structure of 6 (Figure 4d).

4140 Crystal Growth & Design, Vol. 10, No. 9, 2010
Hu et al.
Figure 3. (a) Coordination environment of the Ni(II) ion in 5. The hydrogen atoms are omitted for clarity. Symmetry codes: (#1) 0.5 þ x,
0.5 - y, 0.5 þ z. (b) Views of 2D sheet. (c) Views of interlocked framework in 5. (d) Schematic representation of interlocked 2D framework
of compound 5.
Configuration of BIDPE. To the best of our knowledge,
flexible ligands freely rotate to meet the requirement of
coordination geometries of metal ions in the assembly pro-
cess. In this paper, the V-shaped BIDPE ligand also has some
characteristics of flexible ligands. It can slightly change the
angle to meet the requirement of coordination. The angles
can be assessed by comparing the N Ocore N angle defi-
480 to 580 nm and of complex 5 from 580 to 620 nm and from
350 to 390 nm are assigned as d-d transitions, while lower
energy bands from 310 to 350 nm are assigned as metal-to-
ligand charge-transfer (MLCT) transitions.14
Thermal Analysis and XRD Results. To characterize the
complexes more fully in terms of thermal stability, their
thermal behaviors were studied by TGA (Supporting Infor-
mation, Figure S6). For complex 1, a rapid weight loss of the
lattice water molecules of 3.15% (calcd 3.25%) was observed
from 30 to 110 °C. The second weight loss of 5.11% (calcd
5.07%) from 110 to 280 °C is attributed to the loss of DMF
molecules. The structure decomposed at 390 °C. For com-
plex 2, a rapid weight loss of 4.15% (calcd 4.20%) is observed
from 25 to 135 °C, which is attributed to the loss of the lattice
water, while the second weight loss of 5.59% (calcd 5.68%)
from 140 to 290 °C is attributed to the loss of DMF mole-
cules, and then the structure decomposed from 360 °C. The
TGA curve of 3 shows a weight loss of 5.25% from 20 to 240 °C
from the loss of lattice water and DMF molecules, and the
framework collapsed at 390 °C. The anhydrous compound 4
begins to decompose at 353 °C. In the case of 5, a weight loss
is observed from 20 to 165 °C, which is attributed to the
release of the coordinated water with a weight loss of 6.41%
(calcd 6.42%). The network collapsed at 330 °C. TGA of 6
shows a 3.33% (calcd 3.38%) weight loss between 100 and
245 °C due to loss of coordinated water molecules. The
framework collapsed at 320 °C. To confirm whether the
crystal structures are truly representative of the bulk mate-
rials, PXRD experiments were carried out for 1-6. The
PXRD experimental and computer-simulated patterns of
the corresponding complexes are shown in the Supporting
3 3 3
3 3 3
ned by the central oxygen atom and the coordinated nitrogen
atoms of the imidazole groups. In order to illuminate the
influence of the angles, six compounds are list in Table 2.
Photochemical Properties. Luminescent compounds are of
great interest due to their various applications in chemical
sensors and photochemistry. The luminescent properties of
free ligands BIDPE, and H2bdc, with complexes 2, 3, and 4
have been investigated in the solid state at room temperature,
as depicted in the Supporting Information (Figure S4). An
intense emission of the free H2bdc and BIDPE ligands was
observed with wavelength from 370 to 410 nm (λmax = 390
and 395 nm), which could be attributed to the π*-π transi-
tions. Complexes 2, 3, and 4 exhibit emission characteristics
similar to those of the free H2bdc and BIDPE ligands. The
emission peaks at 420 nm (λex =360 nm) in 2, 425 nm (λex =
354 nm) in 3, and 440 nm (λex=350 nm) in 4 show a small red
shift compared with that of the H2bdc and BIDPE ligands,
which is probably due to enhanced conjugation in the ligands
upon metal coordination. In addition, the UV-vis absorp-
tion spectra of compounds 1-6 were carried out in crystal-
line state at room temperature (BIDPE and H2bdc in solid
state) (Figure S5). BIDPE and H2bdc show intense absorp-
tion peaks at 220-320 nm, which can be ascribed to π-π*
transitions of the ligands. Energy bands of complex 1 from

Article
Crystal Growth & Design, Vol. 10, No. 9, 2010 4141
Figure 4. (a) Coordination environment of the Mn(II) ion in 6. Hydrogen atoms are omitted for clarity. (#1) x, 0.5 - y, -0.5 þ z; (#2) 1 þ x,
0.5 - y, 0.5 þ z; (#3) x, 0.5 - y, 0.5 þ z. (b) Views of interlocked framework in 6. (c) Schematic representation of 2-fold interlocked 2D frame-
work of compound 6. (d) O-H O interaction between two sheets.
3 3 3
Table 2. Different Angles of BIDPE Ligand
complexes constructed by BIDPE ligand with more auxiliary
ligands and metal ions.
compound
N
Ocore
N
conditions
dimensions
3 3 3
3 3 3
1
2
3
4
5
6
138.819(8)°
137.088(7)°
133.982(9)°
115.952(9)°
118.836(5)°
114.077(5)°,
DMF/H2O (3/1), 90 °C
DMF/H2O (3/1), 90 °C
DMF/H2O (3/1), 90 °C
H2O, 140 °C
DMF/H2O (1/1), 90 °C
DMF/H2O (1/4), 90 °C
3D
3D
3D
3D
2D
2D
Acknowledgment. This work was supported by grants from
the Natural Science Foundation of China (Nos. 20971065;
20872001; 20721002), the National Basic Research Program
of China (2010CB923303; 2007CB925103), and the U.S. Nati-
onal Science Foundation (CHE-0516928 to Z.-L.X.).
116.128(6)°
Supporting Information Available: Crystallographic data in CIF
format, selected bond lengths and angles, and patterns of photo-
chemistry, TGA, and PXRD in PDF format. This information is
available free of charge via the Internet at http://pubs.acs.org.
Information (Figures S7-S12); they show that the bulk
synthesized materials and the measured single crystals are
the same. XRPD patterns of different temperatures can
prove that their structures are retained, though the solvents
are lost. When the temperatures continue rising, the peaks of
XRPD will become weak, but the structure is still retained
until the structure decomposes (Figures S13-S17).
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In summary, six new complexes have been synthesized by
the self-assembly of BIDPE, H2bdc ligands, and various metal
ions under solvothermal conditions. The results show that the
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Compounds1, 2, and3have similar3Dframeworks. Complex
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