Hydrothermal syntheses, crystal structures, and properties of a novel class of 3,3′,4,4′-benzophenone-tetracarboxylate (BPTC) polymers

Article abstract of DOI:10.1021/ic0491074

Three novel BPTC complexes, (H₂BPTC)(4,4′-H ₂bpy)H₂O (1), [Cd₂Cu(HBPTC)₂(μ ₂-4,4′-bpy)₂(4,4′-bpy)₂(H ₂O)₂]_n (2), and [Co₃(HBPTC) ₂(μ₂-4,4′-bpy)₃(H₂O) ₄]_n·2nH₂O (3) (BPTC = 3,3′,4,4′-benzophenone-tetracarboxylate and bpy = bipyridine), were hydrothermally synthesized. Complex 1, which is obtained as a coproduct during the syntheses of complexes 2 and 3, features a 2-D layered strong hydrogen bonding network with 2-fold interpenetration. Complex 2 has an unusual 2-D double-layered motif, which is linked together by Cu atoms in a face-to-face manner. It exhibits nanosized channels filled by 4,4′-bpy ligands. Three six-coordinated Co atoms in 3 are interlinked by HBPTC ligands to form a 2-D grid structure, which is further sustained by rigid 4,4′-bpy ligands into a 3-D open framework similar to CdSO₄ with the BPTC moieties situated in the tunnels. The thermal stabilities of complexes 1-3 were examined. The photoluminescence properties of complexes 1-2 and temperature-dependent magnetic susceptibility for 3 were also studied.

Full text of DOI:10.1021/ic0491074

Inorg. Chem. 2004, 43, 8085−8091
Hydrothermal Syntheses, Crystal Structures, and Properties of a Novel
Class of 3,3 ,4,4 -Benzophenone-tetracarboxylate (BPTC) Polymers
′
′
Jian Zhang, Zhao-Ji Li, Yao Kang, Jian-Kai Cheng, and Yuan-Gen Yao*
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, The Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China
Received July 8, 2004
Three novel BPTC complexes, (H2BPTC)(4,4
′
-H2bpy)H2O (1), [Cd2Cu(HBPTC)2(µ2-4,4′-bpy)2(4,4′-bpy)2(H2O)2]n (2),
and [Co3(HBPTC)2( 2-4,4 -bpy)3(H2O)4]n 2nH2O (3) (BPTC
µ
′
‚
)
3,3 ,4,4 -benzophenone-tetracarboxylate and bpy )
′
′
bipyridine), were hydrothermally synthesized. Complex 1, which is obtained as a coproduct during the syntheses
of complexes 2 and 3, features a 2-D layered strong hydrogen bonding network with 2-fold interpenetration. Complex
2 has an unusual 2-D double-layered motif, which is linked together by Cu atoms in a face-to-face manner. It
exhibits nanosized channels filled by 4,4
HBPTC ligands to form a 2-D grid structure, which is further sustained by rigid 4,4
framework similar to CdSO4 with the BPTC moieties situated in the tunnels. The thermal stabilities of complexes
3 were examined. The photoluminescence properties of complexes 1 2 and temperature-dependent magnetic
susceptibility for 3 were also studied.
′
-bpy ligands. Three six-coordinated Co atoms in 3 are interlinked by
′
-bpy ligands into a 3-D open
1−
−
Chart 1
Introduction
Crystal engineering has grown into a subject that attracts
intense attention because controlling the molecular organiza-
tion in the solid state can lead to materials with novel
structure and promising properties.1 Many efforts in this field
have focused on the predictable assembly of organic mo-
lecular solids and metal coordination compounds (coordina-
tion).2 In this context, there have been major advances with
organic-inorganic hybrid systems, and a lot of infinite one-,
two-, and three-dimensional metal-organic hybrid com-
pounds synthesized from various metal-ligand building
blocks have been reported. In general, structural motifs of
these hybrid compounds are closely related to the geometry
and the number of coordination sites provided by organic
ligands.3 As an important family of multidentate O-donor
ligands, organic aromatic polycarboxylate ligands, such as
1,2-benzenedicarboxylate, 1,3,5-benzenetricarboxylate, and
1,2,4,5-benzenetetracarboxylate, have been extensively em-
ployed in the preparation of such metal-organic complexes
in possession of multidimensional networks and interesting
properties.4 In this aspect, the 3,3′,4,4′-benzophenonetetra-
carboxylate (BPTC) ligand (Chart 1), which has nine
potential donor oxygen atoms, is a quite versatile ligand for
the construction of novel metal-organic hybrid compounds
* To whom correspondence should be addressed. E-mail: yyg@
fjirsm.ac.cn.
(1) (a) Braga, D. Chem. Commun. 2003, 2751. (b) Braga, D.; Desiraju,
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4, 500. (c) Desiraju, G. R. Crystal Engineering: The Design of Organic
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10.1021/ic0491074 CCC: $27.50
Published on Web 11/17/2004
© 2004 American Chemical Society
Inorganic Chemistry, Vol. 43, No. 25, 2004 8085

Zhang et al.
Table 1. Crystallographic Data for the Three Complexes
1
2
3
empirical formula
temp (K)
cryst color
cryst size (mm3)
fw
cryst syst
space group
a (Å)
C27H20N2O10
293(2)
yellow
C74H50Cd2-CuN8O20
293(2)
blue
C64H50Co3-N6O24
293(2)
red
0.30 × 0.12 ×0.11
0.20 × 0.15 ×0.08
0.55 × 0.15 ×0.07
1463.89
monoclinic
P2/c
11.32(2)
11.410(5)
22.795(18)
90
532.45
1657.54
monoclinic
P21/c
11.9357(12)
13.5389(13)
14.4089(16)
90
96.835(2)
90
2311.9(4)
4
triclinic
P1h
7.52480(10)
10.8479(3)
20.2178(5)
79.0110(10)
87.8000(10)
80.9930(10)
1600.04(6)
1
b (Å)
c (Å)
R (deg)
â (deg)
92.951(14)
90
2940(6)
γ (deg)
V (Å3)
Z
2
density (calcd)
1.530
0.119
1.720
1.077
1.654
0.932
abs coeff (mm-1
)
F(000)
1104
833
1498
reflns collections
indep reflns
obsd reflns
7098
8118
22242
6723[R(int) ) 0.0390]
5870
4055[R(int) ) 0.0471]
2266
5479[R(int) ) 0.0266]
4601
params
364
1.085
481
1.042
450
1.058
GOF on F2
R1, wR2 [I > 2σ(I)]
R1,wR2 (all data)
largest difference
peak and hole (e Å-3
0.0788, 0.1599
0.1545, 0.2064
0.272, -0.272
0.0454, 0.1111
0.0621, 0.1355
0.623, -0.915
0.0501, 0.1118
0.0608, 0.1225
0.705, -0.500
)
TCSPC system. Thermogravimetric measurements were carried out
on preweighed samples in a nitrogen stream using a Netzsch
STA449C apparatus with a heating rate of 15 °C/min. Variable-
temperature magnetic susceptibilities in the temperature range
5-300 K were performed on a model CF-1 superconducting
extracting sample magnetometer with the powdered sample kept
in the capsule for weighing. All data were corrected for diamag-
netism of the ligands estimated from Pascal’s constants.
owing to its quadrupole carboxyl dentate arms. However, to
the best of our knowledge, BPTC transition metal complexes
have not been studied so far. With the aim of understanding
the coordination chemistry of BPTC and preparing new
materials with interesting structural topology and excellent
physical properties, we have recently engaged in the research
of this kind of polymer complex. We also notice that the
introduction of N-containing auxiliary ligands, such as 4,4′-
bipyridine, pyrazine, etc., into the {M-BPTC} (M )
transition metal) system may lead to new structural evolution
and fine-tune the structural motif of these metal-organic
hybrid compounds.5 Herein we report three interesting
polymeric complexes with mixed organic ligands, (H2BPTC)-
(4,4′-H2bpy)H2O (1), [Cd2Cu(HBPTC)2(µ2-4,4′-bpy)2(4,4′-
bpy)2(H2O)2]n (2), and [Co3(HBPTC)2(µ2-4,4′-bpy)3(H2O)4]n‚
2nH2O (3). Our results demonstrate that the BPTC ligand
can form new building blocks in various coordination modes
with metals. These building blocks finally aggregate to
generate intriguing supramolecular architectures with aux-
iliary ligands.
Syntheses of (H2BPTC)(4,4′-H2bpy)H2O (1) and [Cd2Cu-
(HBPTC)2(µ2-4,4′-bpy)2(4,4′-bpy)2(H2O)2]n (2). A mixture of
CdCO3 (0.17 g, 1.0 mmol) and Cu(NO3)2‚3H2O (0.12 g, 0.5 mmol)
with 3,3′4,4′-benzophenone-tetracarboxylic dianhydride (0.16 g, 0.5
mmol) and 4,4′-bpy (0.08 g, 0.5 mmol) in molar ratio 2:1:1:1 and
10 mL of H2O was placed in a Parr Teflon-lined stainless steel
vessel (25 cm3), and then the vessel was sealed and heated to 160
°C. The temperature was hold for 3 days, and then the reactant
mixture was cooled at a rate of 0.5 °Cmin-1 to lead to the formations
of yellow crystals of 1 (yield: 53% based on 4,4′-bpy) and blue
crystals of 2 (yield: 30% based on 4,4′-bpy) in one pot. Anal. Calcd
for complex 1, C27H20N2O10: C, 60.91; H, 3.79; N, 5.26. Found:
C, 60.85; H, 3.66; N, 5.30%. IR (solid KBr pellet, v/cm-1) for
complex 1: 3437 (m), 3101 (m), 1718(m), 1651 (vs), 1497 (m),
1401 (s), 1233 (s), 1066 (m), 1008 (w), 813 (m). Anal. Calcd for
complex 2, C74H48Cd2CuN8O20: C, 53.56; H, 3.04; N, 6.75.
Experimental Section
Found: C, 53.60; H, 3.11; N, 6.67%. IR (solid KBr pellet, v/cm-1
)
All the syntheses were performed in poly(tetrafluoroethylene)-
lined stainless steel autoclaves under autogenous pressure. Reagents
were purchased commercially and were used without further
purification. Elemental analyses of C, N, and H were performed
on an EA1110 CHNS-0 CE elemental analyzer. IR (KBr pellet)
spectra were recorded on a Nicolet Magna 750FT-IR spectrometer.
And fluorescent data were collected on an Edinburgh FLS920
for complex 2: 3434 (s), 3152 (s), 1604(s) 1579 (m), 1489 (w),
1401 (vs), 1297 (w), 1073 (w), 1008 (w), 810 (m), 630 (w).
Synthesis of [Co3(HBPTC)2(µ2-4,4′-bpy)3(H2O)4]n‚2nH2O (3).
Complex 3 was synthesized in an analogous procedure to 2 except
that 0.294 g (1 mmol) of Co(NO3)2‚6H2O was used instead of
CdCO3 and Cu(NO3)2‚3H2O. The reactant mixture was cooled to
lead to the formation of yellow crystals of 1 (yield: 58% based on
4,4′-bpy) and red crystals of 3 (yield: 25% based on 4,4′-bpy) in
one pot. Anal. Calcd for C64H50Co3N6O24: C, 52.51; H, 3.44; N,
5.74. Found: C, 52.54; H, 3.41; N, 5.79%. IR (solid KBr pellet,
v/cm-1): 3385 (s), 3134 (vs), 1649 (m), 1607 (m), 1574 (m), 1489
(5) (a) Biradha, K.; Seward, C.; Zaworotko, M. J. Angew. Chem., Int.
Ed. 1999, 38, 492. (b) Lightfoot, P.; Snedden, A. J. Chem. Soc., Dalton
Trans. 1999, 3549. (c) Pan, L.; Liu, H. M.; Lei, X. G.; Huang, X. Y.;
Olson, D. H.; Turro, N. J.; Li, J. Angew. Chem., Int. Ed. 2003, 42,
542. (d) Kitaura, R.; Seki, K.; Akiyama, G.; Kitagawa, S. Angew.
Chem., Int. Ed. 2003, 42, 428.
8086 Inorganic Chemistry, Vol. 43, No. 25, 2004

Properties of a NoWel Class of BPTC Polymers
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) of 2
and 3
Complex 2a
Cd(1)-O(1)#1
Cd(1)-N(3)
Cd(1)-O(2′)#2
Cd(1)-OW1
Cd(1)-O(3)
2.265(4)
2.306(4)
2.307(4)
2.315(4)
2.381(4)
Cd(1)-N(1)
Cu(1)-O(4)
Cu(1)-O(3)
Cu(1)-N(2)#4
2.388(4)
1.972(3)
2.683(4)
1.987(4)
O(1)#1-Cd(1)-N(3)
N(3)-Cd(1)-O(2′)#2
O(1)#1-Cd(1)-OW1
N(3)-Cd(1)-OW1
99.52(15) OW1-Cd(1)-O(3)
96.54(15)
Figure 1. View of 1 with 30% probability displacement ellipsoids. H atoms
are shown as small spheres of arbitrary radii.
85.72(15) O(1)#1-Cd(1)-N(1) 166.08(15)
88.22(15) N(3)-Cd(1)-N(1) 91.71(16)
172.03(16) O(2′)#2-Cd(1)-N(1) 96.15(15)
Table 3. Hydrogen-Bonding Geometry (Å, deg) of Complex 1
O(2′)#2-Cd(1)-OW1 91.99(16) OW1-Cd(1)-N(1)
80.92(16)
86.71(14)
87.81(15)
92.19(15)
O(1)#1-Cd(1)-O(3)
N(3)-Cd(1)-O(3)
O(2′)#2-Cd(1)-O(3) 171.34(13) O(4)-Cu(1)-N(2)#5
85.90(14) O(3)-Cd(1)-N(1)
86.03(14) O(4)-Cu(1)-N(2)#4
D-H‚‚‚A
D-H
0.86
0.84(5)
0.86
0.83(5)
0.84 (2)
0.84 (7)
H‚‚‚A
D‚‚‚A
D-H‚‚‚A
N1-H1B‚‚‚O3′
1.85
1.89(3)
1.72
1.70(2)
2.37 (5)
2.24 (9)
2.680(6)
2.709(6)
2.580 (5)
2.524(5)
3.147 (7)
2.803 (6)
161.4
162(6)
176.6
170(6)
153 (10)
125 (9)
O1-H1A‚‚‚O3′ia
N2-H2B‚‚‚O3iv
O1′-H1′A‚‚‚O4ii
OW1-HW1B‚‚‚O4
OW1-HW1A‚‚‚O2iii
Complex 3b
Co(1)-O(2W)
Co(1)-O(7)
Co(1)-N(3)
Co(1)-N(2)#2
Co(2)-O(6)
Co(2)-O(8)
2.076(3)
2.115(3)
2.123(4)
2.173(3)
2.082(3)
2.108(4)
Co(2)-N(4)#2
Co(2)-N(5)
Co(3)-O(3W)
Co(3)-O(5)
Co(3)-N(1)
2.155(3)
2.166(4)
2.063(2)
2.104(2)
2.120(5)
a Symmetry codes: (i) 1 - x, 1 - y, -z; (ii) 1 + x, 1/2 - y, 1/2 + z; (iii)
1
1
1
3
x, /2 - y, /2 + z; (iv) 1 + x, /2 - y, /2 + z.
O(2W)-Co(1)-O(7)
O(2W)-Co(1)-N(3)
O(7)-Co(1)-N(3)
90.94(15) O(8)-Co(2)-N(4)#2
92.09(6)
87.97(6)
87.91(6)
tional ligands, hydrothermal synthesis has been proven to
be a powerful method. In such a relatively low temperature
and under the autogenous pressure, problems of ligand
solubility and reactivity are minimized, and appropriate
O-donor and N-donor ligands can be selected by the metal
centers for efficient molecular building during the crystal-
lization process.8 The complexes 1-3 reported here were
simply synthesized under hydrothermal reaction conditions.
Interestingly, during both the syntheses of complexes 2 and
3, we obtained complex 1 as a coproduct with high yield.
The formation of complex 1 may arise from the following
aspects: (1) It is understandable that 3,3′4,4′-benzophenone-
tetracarboxylic dianhydride can easily been hydrolyzed to
H4BPTC. H4BPTC in the synthetic system acts not only as
a necessary coordination ligand, but also a pH adjuster of
the reaction mixture. (2) 4,4′-Bpy plays an important role in
the formation of 1, probably through acting as a reaction
template and deprotonation reagent. When a more stable
ligand, pyrazine or 4,4′-trimethylenedipyridine, was used
instead of 4,4′-bpy in the same reaction, we did not obtain
the corresponding coproducts similar to complex 1.
(H2BPTC)(4,4′-H2bpy)H2O (1). Complex 1 features a 2-D
layered hydrogen bonding network with 2-fold interpenetra-
tion. As shown in Figure 1, the asymmetric unit contains
one H2BPTC anion, one 4,4′-H2bpy cation, and one free H2O
molecule. The structure is based on a strong and distinctive
pattern of hydrogen bonding interactions (Table 3). Figure
2 shows a 2-D layered hydrogen bonding network and how
H2BPTC units and 4,4′-H2bpy units are connected to each
other through hydrogen bonds. Each H2BPTC unit links two
4,4′-H2bpy species through N-H‚‚‚O hydrogen bonds
(N1‚‚‚O3′ ) 2.680 (6) Å and N2‚‚‚O3ii ) 2.580 (5) Å) and
two other H2BPTC units through O-H‚‚‚O hydrogen bonds
(O1′‚‚‚O4iii ) 2.524(5) Å). These short distances indicate
89.52(7)
95.19(6)
O(6)-Co(2)-N(5)
O(8)-Co(2)-N(5)
O(2W)-Co(1)-N(2)#2 90.48(7)
N(4)#2-Co(2)-N(5) 180.000(1)
O(3W)-Co(3)-O(5)
O(7)-Co(1)-N(2)#2
O(6)-Co(2)-O(8)
O(6)-Co(2)-N(4)#2
84.81(6)
91.77(11) O(3W)-Co(3)-N(1)
92.03(6) O(5)-Co(3)-N(1)
89.22(11)
90.48(9)
89.52(9)
a Symmetry transformations used to generate equivalent atoms: #1 x -
1, y, z; #2 x - 1, y - 1, z; #3 -x, -y, -z; #4 x - 1, y + 1, z; #5 -x +
1, -y - 1, -z. b Symmetry transformations used to generate equivalent
1
atoms: #1 -x, y, -z + /2; #2 x, y - 1, z.
(w), 1401 (vs), 1300 (w), 1246 (m), 1162 (m), 1130 (m), 1093
(m), 814 (m), 631 (w).
X-ray Structure Analyses. X-ray intensities of complexes 1-3
were collected on a Siemens Smart CCD diffractometer equipped
with graphite monochromated Mo KR radiation (λ ) 0.71073 Å)
at 293(2) K. Empirical absorption corrections were applied to the
data using the SADABS program.6 The structures were solved by
the direct method and refined by the full-matrix least-squares on
F2 using the SHELXTL-97 program.7 All of the non-hydrogen
atoms were refined anisotropically. The H atoms bonded to C atoms
and N atoms were positioned geometrically and refined using a
riding model [C-H 0.93 Å and Uiso(H) ) 1.2Ueq(C); N-H 0.86 Å
and Uiso(H) ) 1.2Ueq(N)]. The H atoms bonded to O atoms were
located from difference maps and refined isotropically with the
O-H distances fixed at 0.82 Å [Uiso(H) ) 1.5Ueq(O)]. The structure
for 1 has not gotten a satisfying reliability factor (R ) 0.0788),
probably as a result of the presence of pure organic ligands.
Crystallographic data and other pertinent information for 1-3 are
summarized in Table 1. Selected bond lengths and bond angles
are listed in Table 2. More details on the crystallographic studies
as well as atomic displacement parameters are given as Supporting
Information as a CIF file.
Results and Discussion
Synthesis and General Characterization. To design new
organic-inorganic hybrid compounds with the multifunc-
(8) (a) Feng, S. H.; Xu, R. R. Acc. Chem. Res. 2001, 34, 239. (b) Hagrman,
P. J.; Zubieta, J. Inorg. Chem. 2000, 39, 5218. (c) Hammond, R. P.;
Chesnut, D. J.; Zubieta, J. J. Solid State Chem. 2001, 158, 55. (d)
Tao, J.; Zhang, X. M.; Tong, M. L.; Chen, X. M. J. Chem. Soc., Dalton
Trans. 2001, 770.
(6) Sheldrick, G. M. SADABS; University of Go¨ttingen: Go¨ttingen,
Germany, 1996.
(7) SHELXTL (version 5.05); Siemens Analytical X-ray Instruments
Inc.: Madison, WI, 1994.
Inorganic Chemistry, Vol. 43, No. 25, 2004 8087

Zhang et al.
Figure 2. 2-D hydrogen bonding network with a 50-membered large ring A in 1. The hydrogen bonding interactions are represented by dashed lines.
Figure 3. Packing structure along c-axis of 1 displaying 2-fold interpenetration. Two 2-D frameworks (red and blue) interpenetrate each other through the
large ring A. The hydrogen bonding interactions are represented by dashed lines.
very strong H-bonding interactions. The two phenyl rings
from the same H2BPTC unit twist by 50.55° from each other,
and the torsion angles between COO- group and phenyl ring
range from 7.75° to 70.15°. The severely twisted H2BPTC
unit finally results in the wavelike 2-D layer network (Figure
2). There is a 50-membered large ring A in the 2D layer,
which is composed of four H2BPTC and two 4,4′-H2bpy
units. The dimension of the ring A is approximately 6.34 ×
22.87 Å2. The void space in the single framework is so large
that two 2-D frameworks interpenetrate each other through
the large ring as shown in Figure 3. The structure of 1 agrees
with the prediction that crystal structures with such large
cavities are always stabilized either by inclusion of suitable
Figure 4. ORTEP drawing of 2 with 30% probability displacement
ellipsoids. H atoms and water moleculars were omitted for clarity.
guests or by interpenetrating lattices. As shown in Figure 3,
the adjacent interpenetrated 2D layers are further linked to
molecule. Each CdII center has a slightly distorted {CdN2O4}
octahedral coordination sphere and is defined by one nitrogen
donor (N1) of a µ2-4,4′-bpy ligand and one oxygen donor
(O1f) of a BPTC ligand in the axial positions. The equatorial
positions are occupied by one nitrogen donor of 4,4′-bpy
ligand, two oxygen donors from two individual BPTC
ligands, and one oxygen from the H2O molecule. Cd-O bond
lengths fall in the range 2.265(4)-2.381(4) Å, and Cd-N
bond lengths are 2.388, 2.306 Å, respectively. These values
are within the normal experimental limitation (Table 2). The
each other by relatively weaker O-H‚‚‚O and Ow-H‚‚‚O
hydrogen bonds (d(O1-O3′i) ) 2.709(6) Å, d(Ow1-O4)
) 3.147(7) Å, and d(Ow1-O2iii) ) 2.803(6) Å) to complete
the final 3D architecture.
[Cd2Cu(HBPTC)2(µ2-4,4′-bpy)2(4,4′-bpy)2(H2O)2]n (2).
Complex 2 features an unusual two-dimensional double-
layered motif with Cu atoms acting as the junctures between
the two layers. As shown in Figure 4, the asymmetric unit
contains one Cd2+ cation, Cu2+ cation with an occupancy of
0.5, one HBPTC anion, two 4,4′-bpy molecules, and one H2O
8088 Inorganic Chemistry, Vol. 43, No. 25, 2004

Properties of a NoWel Class of BPTC Polymers
Figure 5. View of Cd atoms interlinked by BPTC ligands to generate a
2-D grid network parallel to (001) in 2.
CuII center also has a slightly distorted {CuN2O4} octahedral
coordination sphere, with two nitrogen donors of µ2-4,4′-
bpy ligand in the apical positions (Cu-N ) 1.987(4) Å),
and four oxygen donors from two carboxylate groups in the
equatorial positions (Cu-O ) 1.972(3)-2.683(4) Å). These
four carboxylate groups on the BPTC anion display different
functionality: one group bidentately bridging two different
metal centers (CdII and CuII) in anti-syn fashion and two
groups monotonically coordinating to two Cd atoms in the
syn fashion, and the left one does not participate in
coordination. The two phenyl rings from the same BPTC
unit twist by 79.84° from each other, and the torsion angles
between the COO- group and phenyl ring range from 7.72°
to 80.23°. There are two crystallographically independent
4,4′-bpy ligands in their own coordination modes in 2: one
acts as a bidentate bridging ligand binding Cd and Cu
simultaneously at the two N ends, the other one acts as a
unidentate ligand binding one Cd atom at its one N end while
the other N end is involved in hydrogen bond with the
uncoordinated carboxylate group of HBPTC ligand (O3′‚‚‚
N4i ) 2.638(6) Å [symmetry code: (i) 2 - x, 1 - y, -z]).
As shown in Figure 5, the Cd atoms are interlinked by
HBPTC ligands to generate a 2-D layer parallel to (001),
which is composed practically of a 32-membered ring. The
Cd‚‚‚Cd distance separations in the layer are 7.525 and
14.137 Å, respectively, and the Cd‚‚‚Cu distance separated
by the bridging carboxylate group is 4.614 Å.
Figure 6. (Top) Molecular double-layered motif displaying nanosized
channel filled by 4,4′-bpy bridging ligand in 2. (Bottom) Space-filling
representation of the 1-D nanosized channels with 4,4′-bpy ligands omitted.
Figure 7. ORTEP drawing of 3 with 30% probability displacement
ellipsoids. H atoms and solvent water molecular were omitted for clarity.
[Co3(HBPTC)2(4,4′-bpy)3(H2O)4]n‚2nH2O (3). Complex
3 features a pillared layer architecture in which the Co(II)
ions are integrated by HBPTC ligands into a 2-D wavelike
layer network; the layers are further pillared by 4,4′-bpy
ligands into a 3-D structure similar to CdSO4. As shown in
Figure 7, there are three unique Co(II) atoms in the
asymmetric unit. Both Co(1) and Co(3) centers are located
on a 2-fold axis and are octahedrally coordinated by two
It is interesting to notice that coplanar Cu atoms integrated
the adjacent two layers mentioned above in a face-to-face
manner into a novel double-layered motif exhibiting large
channels (Figure 6) with the approximate dimension 11.46
× 13.47 Å2. A crystallographic C2 symmetry passes through
the center of the channel. µ2-4,4′-Bpy ligands act not only
as µ2 bridging ligands to support the 2-D framework, but
also as guest molecules to fill effectively the nanosized
channel (Figure 6). Although several types of double-layered
architectures have been fabricated by the assembly of
T-shaped9,10 or rectangular11 building blocks, this type of
molecular double-layered motif is, to the best of our
knowledge, unprecedented. The adjacent 2-D bilayers are
further linked each other by the O-H‚‚‚N hydrogen bonds
to complete the final 3D architecture (Figure S1).
(9) (a) Power, K. N.; Hennigar, T. L.; Zaworotko, M. J. New J. Chem.
1998, 22, 177. (b) Dai, J.-C.; Wu, X.-T.; Fu, Z.-Y.; Cui, C.-P.; Hu,
S.-M.; Du, W.-X.; Wu, L.-M.; Zhang, H.-H.; Sun, R.-Q. Inorg Chem.
2002, 41, 1391. (c) Fu, Z.-Y.; Wu, X.-T.; Dai, J.-C.; Hu, S.-M.; Du,
W.-X. New J. Chem. 2002, 26, 978. (d) Kepert, C. J.; Rosseinsky, M.
J. Chem. Commun. 1999, 375. (e) Rujiwatra, A.; Kepert, C. J.;
Rosseinsky, M. J. Chem. Commun.1999, 2307. (f) Kitagawa, S.;
Kondo, M. Bull. Chem. Soc. Jpn. 1998, 71, 1739. (g) Kondo, M.;
Yoshitomi, T.; Seki, K.; Matsuzaka, H.; Kitagawa, S. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1725.
(10) Zaworotko, M. J. Chem. Commun. 2001, 1.
(11) Fu, Z.-Y.; Wu, X.-T.; Dai, J.-C.; Wu, L.-M.; Cui, C.-P.; Hu, S.-M.
Chem. Commun. 2001, 1856.
Inorganic Chemistry, Vol. 43, No. 25, 2004 8089

Zhang et al.
Table 4. Hydrogen-Bonding Geometry (Å, deg) of Complex 3
D-H‚‚‚A
D-H
H‚‚‚A
D‚‚‚A
D-H‚‚‚A
O1-H1O‚‚‚O4
0.839(19)
0.85(4)
0.86(4)
0.797(19)
0.823(19)
0.81(4)
1.57(2)
1.95(2)
2.04(2)
1.92(2)
1.96(2)
2.01(2)
1.94(2)
2.388(4)
2.779(5)
2.880(4)
2.713(4)
2.771(4)
2.804(4)
2.741(5)
164(6)
165(5)
166(5)
177(4)
168(4)
167(4)
171(4)
O1W-H1WA‚‚‚O6
O1W-H1WB‚‚‚O3ia
O2W-H2WB‚‚‚O1W
O2W-H2WA‚‚‚O2ii
O3W-H3WB‚‚‚O9iii
O3W-H3WA‚‚‚O3i
0.808(19)
1
1
a Symmetry codes: (i) -x, 1 + y, /2 - z; (ii) -x, y, /2 - z; (iii) 1 -
1
x, 1 + y, /2 - z.
Figure 9. Topology of the structure of complex 3 showing 2-D layers
being pillared by rigid 4,4′-bpy ligands.
ligands to form a 3-D open framework exhibiting large tunnel
propagating infinitely along the a-axis. The tunnel has a
diameter of 11.410 × 12.003 Å3 based on the Co‚‚‚Co
distance (between the strutted 4,4′-bipyridine ligand) and the
separation between neighboring 4,4′-bipyridine ligands.
BPTC ligands are just inside the tunnels. The neighboring
4,4′-bipyridine ligands orient almost perpendicularly to each
other so that the side C-H bonds of one 4,4′-bipyridine are
directed to the pyridyl plane of the other. The 3-D structural
topology of complex 3 is similar to that of CdSO4 (Figure
S9).
According to the above structural description of our
example compounds, the BPTC ligand exhibits two kinds
of bridging modes as shown in Chart 2. In complex 2, the
BPTC ligand bridges three symmetry-related Cd atoms while
simultaneously chaleting to a Cu atom, leaving one carboxyl-
ate group uncoordinated (Chart 2a). In complex 3, two
adjacent carboxylate groups at one side of the BPTC ligand
bridge three different Co atoms while the other two carboxyl-
ate groups at the other side are left free (Chart 2b). The
assignment of IR spectra of these three complexes revealed
its characteristic bands of the asymmetric vibrations between
1718 and 1489 cm-1 and the symmetric vibrations at 1401
cm-1 (Figure S2).
Thermogravimetric Analyses. To study the stability of
the polymers, thermogravimetric analyses (TGA) of com-
plexes 1-3 were performed. The TGA diagrams of 1 indicate
three main steps of weight losses and support the structural
result that there exists a strong hydrogen-bonding network
in 1 (Figure S3). The weight loss begins at 126 °C and is
completed at 208 °C. The observed weight loss of 3.48% is
corresponding to the loss of the crystallization water
molecules (calcd 3.38%). The second weight loss occurs in
the range 208-292 °C, which can be attributed to the
elimination of bpy (calcd 29.32%).14 The third step is
attributed to the further decomposition of BPTC ligands. The
Figure 8. View of the whole Co atoms interlinked by HBPTC ligand to
generate a 2D grid layer parallel to (010) in 3. The coplanar 4,4′-bpy ligands
link the symmetric relative Co(3) atoms to form a linear chain.
oxygen donors from two carboxylate ligands, as well as two
nitrogen donors from 4,4′-bpy ligands and two aqua ligands.
The Co(2) atom, occupying a position of the 2-fold sym-
metry, is also in an octahedral environment coordinated by
four oxygen donors of four carboxylate groups from two
individual HBPTC ligands and two nitrogen donors from
4,4′-bpy ligands. The Co-N distances range between
2.120(5) and 2.173(3) Å, and the Co-O bonds range between
2.063(2) and 2.115(3) Å. These distances are comparable to
those reported values.12,13 It is notable that only two
carboxylate groups on one side of the HBPTC ligand
participate in coordination and both of them are coordinated
to Co2 atom. These uncoordinated carboxylate oxygen atoms
are involved in hydrogen bonding with aqua ligands and
interstitial water molecules (Table 4), increasing the structural
stability of the complex. Each coordinated carboxylate group
bidentately bridges two Co atoms in syn-anti fashion, and
the torsion angles between the COO- group and phenyl ring
are 78.41° (3 site) and 34.41°(4 site), respectively. All Co
atoms are interlinked by the HBPTC ligand to generate a
2-D layer parallel to (010) (Figure 8). The resulting layer is
composed practically of 7- and 30-membered rings. The Co‚
‚‚Co separations in this layer are 5.677 (Co2-Co1) and 6.001
(Co2-Co3) Å, respectively. Two symmetric relative Co3
atoms are linked together by coplanar 4,4′-bipyridine,
forming a linear chain. As shown in Figure 9, the resulting
wavelike layers are strutted by the rigid 4,4′-bipyridine
(12) Kuhlman, R.; Schimek, G. L.; Kolis, J. W. Inorg. Chem. 1999, 38,
194.
(13) Lu, J. Y.; Lawandy, M. A.; Li, J.; Yuen, T.; Lin, C. L. Inorg. Chem.
1999, 38, 2695.
(14) Song, J. L.; Zhao, H. H.; Mao, J. G.; Dunbar, K. R. Chem. Mater.
2004, 16, 1884.
8090 Inorganic Chemistry, Vol. 43, No. 25, 2004

Properties of a NoWel Class of BPTC Polymers
Chart 2
TGA diagrams of 2 indicate two main steps of weight losses
(Figure S4). The weight loss begins at 215 °C and is
completed at 323 °C. The observed weight loss of 39.71%
is corresponding to the loss of the water molecules and bpy
ligands (calcd 39.83%). The second step is attributed to the
decomposition of the BPTC ligands. The TGA diagrams of
3 indicate three main steps of weight losses (Figure S5). The
weight loss begins at 81 °C and is completed at 180 °C.
The observed weight loss of 2.48% is corresponding to the
loss of the two crystallization water molecules (calcd 2.46%).
The second weight loss begins at 190 °C and is completed
at 285 °C. The observed weight loss of 37.09% is corre-
sponding to the loss of the four coordinated water molecules
and 4,4′-bpy ligands (calcd 36.94%). The third step is
attributed to the further decomposition of BPTC ligands.
Photoluminescent Properties. The emission spectra of
complexes 1 and 2 in the solid state at room temperature
are investigated. It can be observed that an emission occurs
at 609 nm (Figure S7, λex ) 518 nm) for 1, which is larger
than that of free ligand (3,3′4,4′-benzophenone-tetra-
carboxylic dianhydride) by a factor of ca. 52 nm, probably
due to the H-bonding and the enhanced rigidity of 1,
compared to the free ligand. We tentatively assign it to the
intraligand (π-π*) fluoresence since a weak similar emission
with λmax at 557 nm is also observed for the free ligand
(Figure S6). The blue fluorescent emission of 1 suggests that
it may be used as a new blue-light emitting material. It can
also be observed that the intense emissions occurring at 571
nm (Figure S8, λex ) 460 nm) for 2. Interestingly, a clear
blue shift of emission occurs in 2, compared with 1.
Compared to the spectrum of the free ligand, the emission
spectrum of complex 2 is neither metal-to-ligand charge
transfer (MLCT) nor ligand-to-metal charge transfer (LMCT)
in nature. It can be attributed to an intraligand emission state.
Magnetic Property. The temperature-dependent magnetic
susceptibility of 3 was measured from 2 to 300 K (Figure
S10). The ømT product for this compound is 8.5 cm3‚mol-1
at room temperature and slowly decreases on cooling to a
value of 8.4 cm3‚mol-1 at 110 K. However, the curve drops
gradually below 110 K, indicating that an antiferromagnetic
interaction exists in 3 at lower temperatures. The inverse
susceptibility plot as a function of temperature is linear
(above 10 K), closely following the Curie-Weiss law with
a Curie constant, C ) 8.81 cm3‚mol-1‚K, and a Weiss
constant, θ ) -6.8 K. The negative θ indicates that there
exist predominantly antiferromagnetic interactions in 3.
According to the crystal structure of 3, it could be presumed
that the superexchange interactions between Co(II) ions
through the bridging carboxylate groups are weak, which
may lead to such magnetic behavior.
Conclusion
Three novel complexes with different architectures, (H2-
BPTC)(4,4′-H2bpy)H2O (1), [Cd2Cu(HBPTC)2(µ2-4,4′-bpy)2-
(4,4′-bpy)2(H2O)2]n (2), and [Co3(HBPTC)2(µ2-4,4′-bpy)3-
(H2O)4]n‚2nH2O (3), were constructed from H4BPTC ligand
in the presence of auxiliary 4,4′-bpy ligand. Structural
determinations of these complexes in this work have
demonstrated that the BPTC ligand has the unique ability to
form strong hydrogen bonding network and exhibits remark-
able versatility to chelate metals in different coordination
modes, forming different interesting topological frameworks.
4,4′-Bpy ligand plays a important role acting as a reaction
template and deprotonation reagent. This work also reveals
a novel type of 2-fold interpenetrating composite hydrogen
bonding network, a new molecular double-layered architec-
ture, and a pillared layer architecture similar to CdSO4
topology.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China under Project
20173063, the State Key Basic Research and Development
Plan of China (001CB108906), and the NSF of Fujian
Province (E0020001).
Supporting Information Available: X-ray crystallographic files
in CIF format, figures of IR, TGA curves, photoluminescent spectra.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC0491074
Inorganic Chemistry, Vol. 43, No. 25, 2004 8091