Hydrothermal syntheses, crystal structures, and characteristics of a series of Cd-btx coordination polymers (btx = 1,4-bis(triazol-1-ylmethyl)benzene)

Article abstract of DOI:10.1021/ic0354670

Four novel cadmium-btx (btx = 1,4-bis(triazol-1-ylmethyl)benzene) coordination polymers [Cd(btx)₂(NO₃)₂]n (1), [Cd(btx)₂Cl₂]n (2), [Cd(btx)(SO₄)(H ₂O)₂]n (3), and [Cd(btx)(S₂O ₇)(H₂O)]n (4) have been prepared by hydrothermal reaction (140 or 180 °C) and characterized. Both 1 and 2 have two-dimensional rhombohedral grid structures, 3 possesses a two-dimensional rectangular grid structure, and 4 displays a three-dimensional framework, which is formed by btx bridging parallel layers. To the author's best knowledge, polymer 4 is the first Cd(II) polymer in which the Cd(II) ion is eight-coordinated in a hexagonal bipyrimidal geometry. In addition, we studied the effects of temperature on the hydrothermal reaction system of btx and CdSO₄ and found that different products can be obtained at different temperatures. Furthermore, polymer 3 possesses a very strong third-order NLO absorptive effect with an α₂ value of 1.15 × 10^-9 m W^-1. Polymers 2-4 display strong fluorescent emissions in the solid state at room temperature. The DTA and TGA results of the four polymers are in agreement with the crystal structures.

Full text of DOI:10.1021/ic0354670

Inorg. Chem. 2004, 43, 3528−3536
Hydrothermal Syntheses, Crystal Structures, and Characteristics of a
Series of Cd−btx Coordination Polymers (btx )
1,4-Bis(triazol-1-ylmethyl)benzene)
,†
Xiangru Meng,† Yinglin Song,‡ Hongwei Hou,* Huayun Han,† Bo Xiao,† Yaoting Fan,† and Yu Zhu†
Department of Chemistry, Zhengzhou UniVersity, Henan 450052, P. R. China, and
Department of Applied Physics, Harbin Institute of Technology, Heilongjiang 150001, P. R. China
Received December 20, 2003
Four novel cadmium−btx (btx ) 1,4-bis(triazol-1-ylmethyl)benzene) coordination polymers [Cd(btx)2(NO ) ] (1),
3 2 n
[Cd(btx)2Cl2]n (2), [Cd(btx)(SO )(H O)2]n (3), and [Cd(btx)(S O )(H O)]n (4) have been prepared by hydrothermal
4
2
2
7
2
reaction (140 or 180 °C) and characterized. Both 1 and 2 have two-dimensional rhombohedral grid structures, 3
possesses a two-dimensional rectangular grid structure, and 4 displays a three-dimensional framework, which is
formed by btx bridging parallel layers. To the author’s best knowledge, polymer 4 is the first Cd(II) polymer in
which the Cd(II) ion is eight-coordinated in a hexagonal bipyrimidal geometry. In addition, we studied the effects
of temperature on the hydrothermal reaction system of btx and CdSO and found that different products can be
4
obtained at different temperatures. Furthermore, polymer 3 possesses a very strong third-order NLO absorptive
-1
effect with an R2 value of 1.15 × 10-9 mW . Polymers 2−4 display strong fluorescent emissions in the solid state
at room temperature. The DTA and TGA results of the four polymers are in agreement with the crystal structures.
Introduction
in crystal engineering. The generation of supramolecular
frameworks rests on various factors.12-17 Hydrothermal
synthesis has been demonstrated to be an effective and
powerful technique for crystal growth of many coordination
polymers and hdrogen-bonded systems.18-26 The vast major-
Although a remarkable variety of polymeric frameworks
with intriguing topologies and interesting electric, magnetic,
catalytic, fluorescence, and optical properties have been
syntheszed over the last 10 years,1-11 rational control in the
construction of polymeric networks remains a great challenge
(12) Munakata, M.; Wu, L. P.; Sowa, T. K.; Maekawa, M.; Moriwaki, K.;
Kitagawa, S. Inorg. Chem. 1997, 36, 5416.
* Author to whom correspondence should be addressed. E-mail:
houhongw@zzu.edu.cn. Tel. and fax: +86-371-7761744.
† Zhengzhou University.
(13) Hong, M. C.; Su, W. P.; Cao, R.; Zhang, W. J.; Lu, J. X. Inorg. Chem.
1999, 38, 600.
(14) Munakata, M.; Wu, L. P.; Sowa, T. K. Bull. Chem. Soc. Jpn. 1997,
70, 1727.
‡ Harbin Institute of Technology.
(1) Hoskins, B. F.; Robson, R.; Slizys, D. A. J. Am. Chem. Soc. 1997,
119, 2952.
(2) Hoskins, B. F.; Robson, R.; Slizys, D. A. Angew. Chem., Int. Ed. Engl.
1997, 36, 2336.
(3) Fu, A. H.; Huang, X. Y.; Li, J.; Yuen, T.; Lin, C. L. Chem.sEur. J.
2002, 8, 2239.
(4) Fujita, M.; Kwon, Y. J. J. Am. Chem. Soc. 1994, 116, 1151.
(5) 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.
(6) Fun, H. K.; Raj, S. S. S.; Xiong, R. G.; Zuo, J. L.; Yu, Z.; You, X. Z.
J. Chem. Soc., Dalton Trans. 1999, 1915.
(15) Carlucci, L.; Ciani, G.; Prosperpio, D. M.; Sironi, A. Inorg. Chem.
1995, 34, 5698.
(16) Kasai, M.; Aoyagi, M.; Fujita, M. J. Am. Chem. Soc. 2000, 122, 2140.
(17) Noro, S. I.; Kondo, M.; Ishii, T.; Kitagaw, S.; Matsuzaka, H. J. Chem.
Soc., Dalton Trans. 1999, 1569.
(18) Yaghi, O. M.; Li, Groy, H.; T. L. J. Am. Chem. Soc. 1996, 118, 9096.
(19) Gutschke, S. O. H.; Molinier, M.; Powell, A. K.; Winpenny, E. P.;
Wood, P. T. J. Chem. Soc., Chem. Commun. 1996, 823.
(20) Feng, P.; Bu, X.; Stucky, G. D. Nature 1997, 338, 735.
(21) Hagrman, D.; Hammond, R. P.; Haushalter, R.; Zubieta, J. Chem.
Mater. 1998, 10, 2091.
(7) Meng, X. R.; Song, Y. L.; Hou, H. W.; Fan, Y. T.; Li, G.; Zhu, Y.
Inorg. Chem. 2003, 42, 1306.
(8) Hou, H. W.; Meng, X. R.; Song, Y. L.; Fan, Y. T.; Zhu, Y.; Lu, H.
J.; Du, C. X.; Shao, W. H. Inorg. Chem. 2002, 41, 4068.
(9) Hou, H. W.; Song, Y. L.; Fan, Y. T.; Zhang, L. P.; Du, C. X.; Zhu,
Y. Inorg. Chim. Acta 2001, 316, 140.
(22) Chesnut, D. J.; Kusnetzow, A.; Birge, R. R.; Zubieta, J. Inorg. Chem.
1999, 38, 2663.
(23) Lu, J. Y.; Cabrera, B. R.; Wang, R. J.; Li, J. Inorg. Chem. 1998, 37,
4480.
(24) Lu, J. Y.; Lawandy, M. A.; Li, J.; Yuen, T.; Lin, C. L. Inorg. Chem.
1999, 38, 2695.
(10) Hou, H. W.; Wei, Y. L.; Fan, Y. T.; Du, C. X.; Zhu, Y.; Song, Y. L.;
Niu, Y. Y.; Xin, X. Q. Inorg. Chim. Acta 2001, 319, 212.
(11) Hou, H. W.; Wei, Y. L.;. Song, Y. L.; Zhu, Y.; Li, L. K.; Fan, Y. T.
J. Mater. Chem. 2002, 12, 838.
(25) Lawandy, M. A.; Huang, X. Y.; Lu, J. Y.; Li, J.; Yuen, T.; Lin, C. L.
Inorg. Chem. 1999, 38, 5410.
(26) Pan, L.; Huang, X. Y.; Li, J.; Wu, Y. G.; Zheng, N. W. Angew. Chem.,
Int. Ed. 2000, 39, 527.
3528 Inorganic Chemistry, Vol. 43, No. 11, 2004
10.1021/ic0354670 CCC: $27.50 © 2004 American Chemical Society
Published on Web 05/05/2004

Cd-btx Coordination Polymers
ity of the reported polymeric networks with fascinating
coordiantion architectures have been carried out on transition
metals and polydentate organic ligands.27-31
order NLO properties and the fluorescence properties of
polymers 1-4 are also investigated. The results show that
polymer 3 possesses a very large third-order NLO absorptive
effect and polymers 2-4 display strong fluorescent emis-
sions.
On the other hand, Cd(II)-containing coordination poly-
mers have attracted considerable recent interest owing to the
ambiability to form bounds with different dornors simulta-
neously, the large radius, various coordination modes, and
special physical properties of Cd(II) ion. To date, researchers
have reported a number of 1-D, 2-D, or 3-D Cd(II)
coordination polymers and explored their potential applica-
tions in catalysis, luminescent materials, NLO materials,
phase transformation, and host-guest chemistry.4-6,32-43 For
instance, Fujita and co-workers have studied the catalytic
activity of {[Cd(bpy)2](NO3)2}n in the procedure of cyanosi-
lylation reactions.4 Several groups have investigated the
fluorescent properties of [Cd(TPT)(py)]n (TPT ) terephtha-
lato),6 [Cd3(tma)2‚13H2O]n (tma ) trimesate, dabco ) 1,4-
diazabicyclo[2,2,2]octanes),5 {Cd(2-PEB)2‚(H2O)}n (2-PEBN
) 4-[2-(2-pyridyl)ethenyl]benzonitrile), {Cd(2-CEQA)(Py)}n
(2-CEQH ) 2-[2-(4-cyanophenyl)ethenyl]-8-quinolinol),38
and so on. Lin et al. have reported the second-order non-
linear optical (NLO) properties of polymers {[Cd(4-
pyridylacrylate)2]‚H2O}n, {Cd[4-(4-pyridyl)benzoate]2‚H2O}n,39
and {[Cd3(µ3-OH)L3(py)6](ClO4)2}n (L ) 4-[2-(4-pyridyl)-
ethenyl]benzoate).40 Our group has investigated the third-
order NLO properties of polymers [Cd(bbbt)2(NCS)2]n (bbbt
) 1,1′-(1,4-butanediyl)bis(1H-benzotriazole))8 and [Cd(N3)2-
(bpfp)]n (bpfp ) N,N′-bis(3-pyridylformyl)piperazine)41 and
found that they exhibit very large NLO absorptive effects
and strong refractive behavior. Our current research involves
constructing new Cd-containing polymeric complexes by the
hydrothermal reaction and further investigating their third-
order NLO properties and fluorescence properties. In this
paper, four novel Cd(II)-btx coordination polymers, [Cd-
(btx)2(NO3)2]n (1), [Cd(btx)2Cl2]n (2), [Cd(btx)(SO4)(H2O)2]n
(3), and [Cd(btx)(S2O7)(H2O)]n (4), are synthesized by the
hydrothermal technique. To our best knowledge, 4 is the first
Cd(II) polymer in which Cd(II) ion is eight-coordinated in
a hexagonal bipyrimidal geometry. Furthermore, the third-
Experimental Section
Materials and General Details. Commercially available solvents
and chemicals were used without further purification. IR spectros-
copy was performed on a PE 1710 spectrophotometer in the 400-
4000 cm-1 regions. Carbon, hydrogen, and nitrogen analyses were
performed with Carlo-Erba 1106 analyzer.
Preparation of the Ligand 1,4-Bis(triazol-1-ylmethyl)benzene
(btx). Triazole (1.38 g, 20 mmol) was dissolved in acetone (30
mL), and then PEG-400 (2 g), anhydrous potassium carbonate (5
g), and potassium iodide (0.5 g) were added to the above solution.
After the solution was stirring for 30 min, R,R′-dichloro-p-oxylene
(1.75 g, 10 mmol) was dropwise added. The mixture was vigorously
stirred and refluxed for 10 h. A white residue was obtained after
filtering and distilling off the filtrate. The crude product was
recrystallized from water to give 1.4 g (60%) of white crystalline
state product, 1,4-bis(triazol-1-ylmethyl)benzene (btx). Mp: 163-
164 °C. Anal. Calcd for C12H12N6: C, 59.99; H, 5.03; N, 34.98.
Found: C, 60.04; H, 5.02; N, 34.62. IR (KBr)/cm-1: 3099 s, 1511
1
s, 1265 s, 1146 s, 1016 s, 769 s. H NMR (D2O): δ 5.300 (4H),
7.165 (4H), 7.897 (2H), 8.389 (2H).
Preparation of Polymer [Cd(btx)2(NO3)2]n (1). A mixture of
Cd(NO3)2‚6H2O (30.85 mg, 0.1 mmol), btx (48.0 mg, 0.2 mmol),
and H2O (6 mL) in a mole ratio of ca. 1:2:3333 was sealed in a 25
mL stainless steel reactor with Teflon liner and directly heated to
140 °C for 3 days and then cooled to room temperature during 6 h.
Colorless single crystals suitable for X-ray diffraction were obtained
in 62% yield. Anal. Calcd for C24H24CdN14O6: C, 40.21; H, 3.37;
N, 27.35. Found: C, 40.36; H, 3.32; N, 27.18. IR (KBr)/cm-1: 3134
s, 1522 s, 1274 s, 1129 s, 1014 s, 775 s.
Preparation of Polymer [Cd(btx)2Cl2]n (2). The procedure was
the same as that for 1, except that CdCl2‚2.5H2O was used instead of
Cd(NO3)2‚6H2O, yield ca. 55%. Anal. Calcd for C24H24CdCl2N12:
C, 43.42; H, 3.64; N, 25.32. Found: C, 43.18; H, 3.67; N, 25.24.
IR (KBr)/cm-1: 3022 s, 1519 s, 1276 s, 1113 s, 1011 s, 767 s.
Preparation of Polymer [Cd(btx)(SO4)(H2O)2]n (3). The
procedure was the same as that for 1, except that 3CdSO4‚8H2O
was used instead of Cd(NO3)2‚6H2O, yield ca. 58%. Anal. Calcd
for C12H16CdN6O6S: C, 29.73; H, 3.33; N, 17.34. Found: C, 29.58;
H, 3.37; N, 17.41. IR (KBr)/cm-1: 3021 s, 1507 s, 1258 s, 1121 s,
1040 s, 753 s.
(27) Turner, A.; Jaffres, P. A.; MacLean, E. J.; Villemin, D.; McKee, V.;
Hix, G. B. J. Chem. Soc., Dalton Trans. 2003, 1314.
(28) Tao, J.; Tong, M. L., Chen, X. M. J. Chem. Soc., Dalton Trans. 2000,
3669.
(29) Finn, R. C.; Zubieta, J.J. Chem. Soc., Dalton Trans. 2000, 1821.
(30) Lai, S. F.; Cheng, C. Y.; Lin, K. J. Chem. Commun. 2001, 1082.
(31) Kim, Y.; Jung, D. Y. Inorg. Chem. 2000, 39, 1470.
(32) Pan, L.; Huang, X. Y.; Li, J. J. Solid State Chem. 2000, 152, 236.
(33) Kongshaug, K. O.; Fjellvåg, H. Solid State Sci. 2002, 4, 443.
(34) Zhang, L. R.; Shi, Z.; Yang, G. Y.; Chen, X. M.; Feng, S. H. J. Chem.
Soc., Dalton Trans. 2000, 275.
(35) Lu, J. Y.; Kohler, E. E. Inorg. Chem. Commun. 2002, 5, 196.
(36) Chen, Z. F.; Zhang, P.; Xiong, R. G.; Liu, D. J.; You, X. Z. Inorg.
Chem. Commun. 2002, 5, 35.
(37) Yuan, R. X.; Xiong, R. G.; Xie, Y. L.; You, X. Z.; Peng, S. M.; Lee,
G. H. Inorg. Chem. Commun. 2001, 4, 384.
(38) Zhang, J.; Xie, Y. R.; Ye, Q.; Xiong, R. G.; Xue, Z. L.; You, X. Z.
Eur. J. Inorg. Chem. 2003, 14, 2572.
(39) Evans, O. R.; Lin, W. B. Chem. Mater. 2001, 13, 2705.
(40) Lin, W. B.; Wang, Z. Y.; Ma, L. J. Am. Chem. Soc. 1999, 121, 11249.
(41) Hou, H. W.; Song, Y. L.; Xu, H.; Wei, Y. L.; Fan, Y. T.; Zhu, Y.; Li,
L. K.; Du, C. X. Macromolecules 2003, 36, 999.
(42) Zheng, C. G.; Xie, Y. L.; Xiong, R. G.; You, X. Z. Inorg. Chem.
Commun. 2001, 4, 405.
Preparation of Polymer [Cd(btx)(S2O7)(H2O)]n (4). An aque-
ous mixture (6 mL) containing btx (48.0 mg, 0.2 mmol) and
3CdSO4‚8H2O (25.6 mg, 0.033 mmol) was placed in a Teflon-
lined stainless steel vessel (25 mL), and the vessel was sealed and
heated to 180 °C for 3 days and then cooled to room temperature
during 8 h. Colorless single crystals suitable for X-ray diffraction
were obtained in ca. 60% yield. Anal. Calcd for C12H14CdN6O8S2:
C, 26.36; H, 2.58; N, 15.37. Found: C, 26.19; H, 2.61; N, 15.26.
IR (KBr)/cm-1: 3087 s, 1518 s, 1279 s, 1139 s, 1014 s, 772 s.
Crystal Structure Determination. A crystal suitable for X-ray
determination was mounted on a glass fiber. All data were collected
at room temperature on a Rigaku RAXIS-IV image plate area
detector with graphite-monochromated Mo KR radiation (λ )
0.710 73 Å). The structures were solved by direct methods and
expanded using Fourier techniques. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included but not
refined. The final cycle of full-matrix least-squares refinement was
(43) Xia, S. Q.; Hu, S. M.; Zhang, J. J.; Wu, X. T.; Dai, J. C.; Fu, Z. Y.;
Du, W. X. Inorg. Chem. Commun. 2004, 7, 271.
Inorganic Chemistry, Vol. 43, No. 11, 2004 3529

Meng et al.
Table 1. Crystal and Structure Refinement Data for Polymers 1-4
param
1
2
3
4
formula
fw
C24H24CdN14O6
716.97
C24H24CdCl2N12
663.85
C24H32Cd2N12O12S2
969.54
C12H14CdN6O8S2
546.81
temp (K)
wavelength (Å)
crystal size (mm)
color
cryst system
space group
a (Å)
293(2)
291(2)
291(2)
291(2)
0.710 73
0.30 × 0.20 × 0.20
colorless
monoclinic
P21/c
8.3343(17)
21.190(4)
8.6625(17)
90
105.91(3)
90
1471.3(5)
2
0.710 73
0.27 × 0.20 × 0.18
colorless
monoclinic
P21/c
7.6765(15)
21.895(4)
8.9479(18)
90
109.23(3)
90
1420.0(5)
2
0.710 73
0.24 × 0.20 × 0.20
colorless
triclinic
0.710 73
0.24 × 0.20 × 0.20
colorless
triclinic
P1h
P1h
12.407(3)
12.805(3)
11.297(2)
89.90(3)
101.75(3)
102.37(3)
1714.8(6)
2
8.5563(17)
12.438(3)
8.5420(17)
8.5420(17)
97.22(3)
88.63(3)
860.8(3)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Dc (g‚cm-3
)
1.618
0.808
1.553
0.995
1.878
1.440
2.110
1.573
abs coeff (mm-1
)
F(000)
724
668
968
544
reflcns collcd/unique
data/restraints/params
goodness-of-fit on F2
R1, wR2
4444/2595
2595/0/206
1.105
956/2226
2226/0/179
1.077
4431/4431
4431/0/476
1.153
2282/2282
2282/0/270
1.375
0.0604, 0.1597
0.0336, 0.0828
0.1078, 0.2777
0.0990, 0.2794
based on observed reflections and variable parameters. All calcula-
tions were performed using the SHELXL-97 crystallographic
software package.44 Table 1 shows crystallographic crystal data and
processing parameters for polymers 1-4. Selected bond lengths
and bond angles are listed in Table 2.
Determination of TGA-DTA. TGA-DTA measurements were
performed by heating the sample from 25 to 800 °C (or 1100 °C)
at a rate of 10 °C min-1 in air on a Perkin-Elmer DTA-7 and TGA-7
differential thermal analyzer.
Nonlinear Optical Measurements. The DMF solution of
polymers 1-4 was placed in the 1 mm quartz cuvette for NLO
measurements. The nonlinear refraction was measured with a
linearly polarized laser light (λ ) 532 nm; pulse widths ) 7 ns)
generated from a Q-switched and frequency-doubled Nd:YAG laser.
The spatial profiles of the optical pulses were nearly Gaussian. The
laser beam was focused with a 25-cm focal-length focusing mirror.
The radius of the beam waist was measured to be 35 ( 5 µm (half-
width at 1/e2 maximum). The interval between the laser pulses was
chosen to be ∼5 s for operational convenience. The incident and
transmitted pulse energies were measured simultaneously by two
Laser Precision detectors (RjP-735 energy probes), which were
linked to a computer by an IEEE interface. The NLO properties of
the samples were manifested by moving the samples along the axis
of the incident beam (z-direction) with respect to the focal point.45
An aperture of 0.5 mm in radius was placed in front of the detector
to assist the measurement of the self-focusing effect.
The generation of supramolecular frameworks rests on
various parameters, such as the coordination environments
of metal centers, position and type of functional groups on
the ligands, the ratio between metal salts and ligands,
templates, solvent system, counterions, temperature, teaction
time, pH value, etc.12-17 Polymers 1-4 are synthesized via
a self-assembly process under midtemperature hydrothermal
conditions. When a mixture of Cd(NO3)2‚6H2O (or CdCl2‚
2.5H2O or 3CdSO4‚8H2O), btx, and H2O in a mole ratio of
ca. 1:2:3333 was heated to 140 °C for 3 days and cooled to
room temperature, fine colorless single crystals of polymer
1, 2, or 3 suitable for X-ray diffraction were obtained from
the reaction mixture. To investigate the effects of temperature
on the synthesis of coordination polymers, the mixtures of
Cd(II) salts and btx were reacted at 180 °C. The results show
that the reactions of Cd(NO3)2‚6H2O or CdCl2‚2.5H2O with
btx in 180 °C afford the same product as that obtained in
140 °C, but the reaction of 3CdSO4‚8H2O with btx at 180
°C generates a new product (polymer 4) which is different
from that formed at 140 °C. This may be explained as
follows: when the temperature is changed from 140 to 180
°C, sulfates can polymerize to pyrosulfates and pyrosulfates
have more coordination sites leading to a new coordination
polymer with a novel network pattern. The formations of
1-4 are shown in Scheme 1.
Determination of Photoluminescent Properties. The lumines-
cent spectra were measured on powder samples at room temperature
using a model F-4500 Hitachi fluorescence spectrophotometer. The
excitation slit was 2.5 nm, the emission slit was 2.5 nm also, and
the response time was 2 s.
In addition, Diez-Barra’s group synthesized a series of
1,2,4-triazol ligands, such as 1,3-bis(triazol-1-ylmethyl)-
benzene, and their related complexes.47-49 In 1,3-bis(triazol-
1-ylmethyl)benzene two triazol groups are in meta positions
and nitrogen atoms are inclined to coordinate to the same
metal ion; in 1,4-bis(triazol-1-ylmethyl)benzene) (btx) two
Results and Discussion
Synthesis. The application of the hydrothermal technique
to synthetic crystal growth has been used for some time.46
(47) Diez-Barra, E.; Guerra, J.; Lopez-Solera, I.; Merino, S.; Rodriguez-
Lopez, J.; Sanchez-Verdu, P.; Tejeda, J. Organometallics 2003, 22,
541.
(48) Diez-Barra, E.; Guerra, J.; Hornillos, V.; Merino, S.; Tejeda, J.
Organometallics 2003, 22, 4610.
(49) Diez-Barra, E.; de la Hoz, A.; Rodriguez-Curiel, R.; Tejeda, J.
Tetrahedron 1997, 53, 2253.
(44) Sheldrick, G. M. SHELXTL-97 Program for Refining Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(45) Sheik-Bahae, M.; Said, A. A.; Van Stryland, E. W. Opt. Lett. 1989,
14, 955.
(46) Feng, S. H.; Xu, R. R. Acc. Chem. Res. 2001, 34, 239.
3530 Inorganic Chemistry, Vol. 43, No. 11, 2004

Cd-btx Coordination Polymers
Table 2. Selected Bond Lengths (Å) and Angles (deg) for Polymers 1-4
Polymer 1a
Cd(1)-N(1)#1
Cd(1)-N(6)#2
2.324(4) Cd(1)-N(1)
2.334(5) Cd(1)-N(6)#3
2.324(4) Cd(1)-O(1)
2.343(7) Cd(1)-O(1)#1
2.343(7)
83.8(3)
81.3(2)
2.334(5) N(6)#2-Cd(1)-O(1)
90.46(17) N(1)#1-Cd(1)-O(1)#1
89.54(17) N(6)#2-Cd(1)-O(1)#1
96.2(3)
98.7(2)
N(6)#3-Cd(1)-O(1)
N(1)-Cd(1)-O(1)#1
N(1)#1-Cd(1)-N(1) 180.000(1) N(1)#1-Cd(1)-(6)#2
N(1)-Cd(1)-N(6)#2
N(1)-Cd(1)-N(6)#3
N(1)#1-Cd(1)-O(1)
89.54(17) N(1)#1-Cd(1)-N(6)#3
83.8(3)
N(6)#3-Cd(1)-O(1)#1 96.2(3)
90.46(17) N(6)#2-Cd(1)-N(6)#3 180.000(1) O(1)-Cd(1)-O(1)#1
180.000(1)
81.3(2)
N(1)-Cd(1)-O(1)
98.7(2)
Polymer 2b
Cd(1)-N(6)#1
Cd(1)-N(1)
2.344(3) Cd(1)-N(6)#2
2.354(3) Cd(1)-N(1)#3
2.344(3) Cd(1)-Cl(1)#3
2.354(3)
2.6477(13) Cd(1)-Cl(1)
2.6477(13)
N(6)#1-Cd(1)-N(6)#2 180.00(16) N(6)#1-Cd(1)-N(1)
86.93(12) N(1)-Cd(1)-Cl(1)#3
93.07(12) N(6)#1-Cd(1)-Cl(1)
180.00(18) N(1)-Cd(1)-Cl(1)
90.96(9)
89.19(8)
89.04(9)
N(1)#3-Cd(1)-l(1)#3 89.04(9)
N(6)#2-Cd(1)-N(1)
N(6)#2-Cd(1)-N(1)#3
N(6)#1-Cd(1)-Cl(1)#3
93.07(12) N(6)#1-Cd(1)-N(1)#3
86.93(12) N(1)-Cd(1)-N(1)#3
N(6)#2-Cd(1)-Cl(1) 90.81(8)
N(1)#3-Cd(1)-Cl(1) 90.96(9)
90.81(8)
N(6)#2-Cd(1)-Cl(1)#3
89.19(8)
Cl(1)#3-Cd(1)-Cl(1) 180.0
Polymer 3c
Cd(1)-O(12)#1
Cd(1)-O(1)
Cd(1)-N(1)
Cd(2)-O(3)
Cd(2)-N(6)#4
Cd(2)-O(2)#4
2.297(8) Cd(1)-O(12)#2
2.301(9) Cd(1)-O(1)#3
2.337(12) Cd(1)-N(1)#3
2.296(8) Cd(2)-O(3)#4
2.305(12) Cd(2)-N(6)
2.343(8) Cd(2)-O(2)
2.297(8) Cd(3)-O(6)
2.301(9) Cd(3)-N(7)
2.337(12) Cd(3)-O(7)#5
2.296(8) Cd(4)-O(9)
2.305(12) Cd(4)-N(12)#2
2.343(8) Cd(4)-O(8)
2.286(8) Cd(3)-O(6)#5
2.286(8)
2.302(12)
2.340(8)
2.283(7)
2.289(13)
2.356(8)
95.6(4)
84.4(4)
180.0(5)
93.1(3)
93.1(3)
86.9(3)
87.1(4)
180.0(4)
87.2(4)
2.302(12) Cd(3)-N(7)#5
2.340(8) Cd(3)-O(7)
2.283(7) Cd(4)-O(9)#2
2.289(13) Cd(4)-N(12)
2.356(8) Cd(4)-O(8)#2
180.00(11) O(6)-Cd(3)-N(7)
O(12)#1-Cd(1)-O(12)#2 180.0(3)
O(12)#1-Cd(1)-O(1)
89.9(3)
O(6)-Cd(3)-O(6)#5
O(6)#5-Cd(3)-N(7)
O(12)#2-Cd(1)-O(1)
O(12)#2-Cd(1)-O(1)#3
O(12)#1-Cd(1)-N(1)
O(1)-Cd(1)-N(1)
90.1(3)
89.9(3)
94.7(4)
96.4(4)
85.3(4)
83.6(4)
O(12)#1-Cd(1)-O(1)#3 90.1(3)
84.4(4)
95.6(4)
86.9(3)
87.1(4)
92.9(4)
92.9(4)
O(6)-Cd(3)-N(7)#5
N(7)-Cd(3)-N(7)#5
O(6)#5-Cd(3)-O(7)#5
O(6)-Cd(3)-O(7)
O(6)#5-Cd(3)-O(7)
N(7)#5-Cd(3)-O(7)
O(1)-Cd(1)-O(1)#3
O(12)#2-Cd(1)-N(1)
O(1)#3-Cd(1)-N(1)
180.000(2) O(6)#5-Cd(3)-N(7)#5
85.3(4)
83.6(4)
O(6)-Cd(3)-O(7)#5
N(7)-Cd(3)-O(7)#5
N(7)#5-Cd(3)-O(7)#5
N(7)-Cd(3)-O(7)
O(12)#1-Cd(1)-N(1)#3
O(1)-Cd(1)-N(1)#3
N(1)-Cd(1)-N(1)#3
O(3)-Cd(2)-N(6)#4
O(3)-Cd(2)-N(6)
O(12)#2-Cd(1)-N(1)#3 94.7(4)
O(1)#3-Cd(1)-N(1)#3
96.4(4)
180.000(2) O(3)-Cd(2)-O(3)#4
180.000(2) O(7)#5-Cd(3)-O(7)
180.000(1) O(9)-Cd(4)-O(9)#2
94.1(4)
85.9(4)
O(3)#4-Cd(2)-N(6)#4
O(3)#4-Cd(2)-N(6)
85.9(4)
94.1(4)
89.0(3)
95.8(4)
91.0(3)
84.2(4)
O(9)-Cd(4)-N(12)#2
O(9)-Cd(4)-N(12)
92.8(4)
87.2(4)
O(9)#2-Cd(4)-(12)#2
O(9)#2-Cd(4)-N(12)
92.8(4)
90.5(3)
89.7(4)
89.5(3)
N(6)#4-Cd(2)-N(6)
O(3)#4-Cd(2)-O(2)#4
N(6)-Cd(2)-O(2)#4
O(3)#4-Cd(2)-O(2)
N(6)-Cd(2)-O(2)
180.000(2) O(3)-Cd(2)-O(2)#4
N(12)#2-Cd(4)-N(12) 180.000(1) O(9)-Cd(4)-O(8)
91.0(3)
84.2(4)
89.0(3)
95.8(4)
N(6)#4-Cd(2)-O(2)#4
O(3)-Cd(2)-O(2)
N(6)#4-Cd(2)-O(2)
O(2)#4-Cd(2)-O(2)
O(9)#2-Cd(4)-O(8)
N(12)-Cd(4)-O(8)
O(9)#2-Cd(4)-O(8)#2
89.5(3)
90.3(4)
90.5(3)
89.7(4)
N(12)#2-Cd(4)-O(8)
O(9)-Cd(4)-O(8)#2
N(12)#2-Cd(4)-O(8)#2 90.3(4)
180.000(2) N(12)-Cd(4)-O(8)#2
O(8)-Cd(4)-O(8)#2
180.000(1)
Polymer 4d
Cd(1)-O(4)
2.307(8)
2.310(9)
2.319(10) Cd(1)-N(1)
2.292(11) Cd(2)-N(6)
180.000(2)
91.2(4)
88.8(4)
85.0(4)
84.2(4)
95.0(4)
95.8(4)
Cd(1)-O(4)#1
Cd(1)-O(5)#1
2.307(8)
2.310(9)
2.319(10) Cd(2)-O(8)
2.292(11)
88.8(4)
91.2(4)
180.000(2)
95.0(4)
95.8(4)
85.0(4)
Cd(2)-O(9)
2.313(12) Cd(2)-O(9)#2
2.435(18) Cd(2)-O(2)#3
2.313(12)
2.435(18)
2.61(3)
Cd(1)-O(5)
Cd(2)-O(2)#1
Cd(1)-N(1)#1
2.61(3)
Cd(2)-O(8)#2
Cd(2)-N(6)#2
O(4)-Cd(1)-O(4)#1
O(4)#1-Cd(1)-O(5)
O(4)#1-Cd(1)-O(5)#1
O(4)-Cd(1)-N(1)#1
O(5)-Cd(1)-N(1)#1
O(4)-Cd(1)-N(1)
O(5)-Cd(1)-N(1)
N(1)#1-Cd(1)-N(1)
N(6)#2-Cd(2)-O(9)
N(6)#2-Cd(2)-O(9)#2
O(9)-Cd(2)-O(9)#2
O(4)-Cd(1)-O(5)
N(6)-Cd(2)-(2)#1
93.6(6)
76.8(8)
86.4(6)
O(9)-Cd(2)-O(2)#1 103.2(8)
O(4)-Cd(1)-O(5)#1
O(5)-Cd(1)-O(5)#1
O(4)#1-Cd(1)-N(1)#1
O(5)#1-Cd(1)-N(1)#1
O(4)#1-Cd(1)-N(1)
O(5)#1-Cd(1)-N(1)
N(6)#2-Cd(2)-N(6)
N(6)-Cd(2)-O(9)
O(9)#2-Cd(2)-O(2)#1
N(6)-Cd(2)-O(2)#3
N(6)#2-Cd(2)-O(2)#3
O(9)-Cd(2)-O(2)#3
93.6(6)
76.8(8)
O(9)#2-Cd(2)-O(2)#3 103.2(8)
O(2)#1-Cd(2)-O(2)#3 180.000(3)
N(6)#2-Cd(2)-O(8)
O(9)-Cd(2)-O(8)
O(2)#1-Cd(2)-O(8)
N(6)#2-Cd(2)-O(8)#2
100.7(6)
75.4(8)
31.8(6)
79.3(6)
N(6)-Cd(2)-O(8)
O(9)#2-Cd(2)-O(8)
O(2)#3-Cd(2)-O(8)
79.3(6)
104.6(8)
148.2(6)
84.2(4)
180.000(3)
91.7(4)
180.000(2)
88.3(4)
91.7(4)
N(6)-Cd(2)-O(8)#2 100.7(6)
O(9)-Cd(2)-O(8)#2 104.6(8)
O(2)#1-Cd(2)-O(8)#2 148.2(6)
O(8)-Cd(2)-O(8)#2 180.000(5)
O(9)#2-Cd(2)-O(8)#2
O(2)#3-Cd(2)-O(8)#2
75.4(8)
31.8(6)
N(6)-Cd(2)-O(9)#2
N(6)#2-Cd(2)-O(2)#1
88.3(4)
86.4(6)
180.0(8)
a Symmetry transformations used to generate equivalent atoms in polymer 1: #1, -x, -y + 1, -z + 1; #2, x - 1, -y + 3/2, z + 1/2; #3, -x + 1, y -
1/2, -z + 1/2. b Symmetry transformations used to generate equivalent atoms in polymer 2: #1, -x + 1, y - 1/2, -z - 1/2; #2, x - 1, -y + 3/2, z + 1/2;
#3, -x, -y + 1, -z. c Symmetry transformations used to generate equivalent atoms in polymer 3: #1, x, y, z - 1; #2, -x + 2, -y - 2, -z; #3, -x + 2,
-y - 2, -z - 1; #4, -x + 4, -y - 3, -z; #5, -x + 4, -y - 3, -z + 1. d Symmetry transformations used to generate equivalent atoms in polymer 4: #1,
-x, -y + 1, -z + 2; #2, -x + 1, -y + 1, -z + 3; #3, x + 1, y, z + 1.
Scheme 1
obvious that the positions of functional groups in the similar
ligands affect the crystal structures of the complexes.
Crystal Structure of [Cd(btx)2(NO3)2]n (1). The X-ray
diffraction shows that all of the Cd(II) atoms and btx ligands
in polymer 1 are equivalent. Figure 1a depicts the coordina-
tion geometry of the Cd(II) center. Each Cd(II) ion binds to
four nitrogen atoms from four equatorial btx and two oxygen
atoms from two axial monodentate nitrate anion leading to
a slightly elongated octahedral geometry. The Cd-N bonds
triazol groups are in para positions and nitrogen atoms
have the same bond length of 2.324(4) Å and are slightly
coordinate to different metal ions simultaneously. It is
shorter than the Cd-O bond length of 2.343(7) Å. N1, N1A,
Inorganic Chemistry, Vol. 43, No. 11, 2004 3531

Meng et al.
Figure 2. (a) Coordination geometry of the Cd(II) center in [Cd(btx)2Cl2]n
(2) with atom numbering, showing 30% thermal ellipsoids. Hydrogen atoms
have been omitted for clarity. (b) Two-dimensional layered structure of
[Cd(btx)2Cl2]n (2) with rhombohedral grid units.
coplanar. Each rhombohedral grid is organized by four btx
ligands acting as the four edges and four Cd(II) ions
representing the four vertexes. The four edges have the same
length of 14.841 Å, the diagonals are 20.786 and 21.190 Å,
and the interior angles are 88.9 and 91.1°, respectively. The
network resembles the rhombohedral grids in [Cd(bbbt)2-
(NCS)2]n (bbbt ) 1,1′-(1,4-butanediyl)bis(1H-benzotriaz-
ole))8 and other Cd(II) coordiantion polymers.50-53
Figure 1. (a) Coordination geometry of the Cd(II) center in [Cd(btx)2-
(NO3)2]n (1) with atom numbering, showing 30% thermal ellipsoids.
Hydrogen atoms have been omitted for clarity. (b) Two-dimensional layered
structure of [Cd(btx)2(NO3)2]n (1) with rhombohedral grid units.
Crystal Structure of [Cd(btx)2Cl2]n (2). The structure
of polymer 2 is made up of two-dimensional rhombohedral
grid layers, similar to that of 1. As illustrated in Figure 2a,
all of the Cd(II) ions and btx are equivalent, respectively.
The N1, N1A, N6B, and N6C atoms are completely coplanar.
N6B, and N6C atoms are completely coplanar. The mean
deviations from planes N1-N2-N3-C1-C2 (1), N4-N5-
N6-C11-C12 (2), C4-C5-C6-C7-C8-C9 (3), and
N4C-N5C-N6C-C11C-C12C (4) are 0.0066, 0.0006,
0.0114, and 0.0006 Å, respectively. The dihedral angles
between planes 1 and 2, 1 and 3, 1 and 4, and 2 and 3 are
57.1, 67.7, 89.3, and 67.5°, respectively.
Each btx ligand binds with two Cd(II) ions forming a two-
dimensional layered structure with rhombohedral grid units
(Figure 1b). In each layer, all Cd(II) ions are completely
(50) Wu, H. P.; Jania, C.; Uehlin, L.; Klu¨fers, P.; Mayer, P. Chem. Commun.
1998, 2637.
(51) Wang, Z. Y.; Xiong, R. G.; Foxman, B. M.; Wilson, S. R.; Lin, W.
B. Inorg. Chem. 1999, 38, 1523.
(52) Fujita, M.; Aoyagi, M.; Ogura, K. Bull. Chem. Jpn. 1998, 71, 1799.
(53) Plater, M. J.; Foreman, M. R. S. J.; Gelbrich, T.; Coles, S. J. J. Chem.
Soc., Dalton Trans. 2000, 3065.
3532 Inorganic Chemistry, Vol. 43, No. 11, 2004

Cd-btx Coordination Polymers
around the four kinds of Cd(II) ions are similar, all of which
are octahedral. Each Cd(II) ion is coordinated by four oxygen
atoms, of which two are from two sulfate anions and two
are from two water molecules, and two nitrogen atoms from
two bidentate btx. In the coordination sphere around each
Cd(II) ion, there is an ideal planarity of the CdO4 unit. Four
Cd(II) ions are linked by btx and sulfate anions forming a
distorted rectangular grid unit. Each grid is constructed from
two btx ligands and two sulfate anion ligands acting as the
four edges and four Cd(II) ions acting as the four vertexes
giving a 36-membered metallocycle. The lengths of the
opposite edges are equal at 15.238 and 5.648 Å, the diagonals
are 15.031 and 17.299 Å, and the interior angles are 78.2
and 101.8°, respectively. In the reported two-dimensional
quadrilateral grid coordination polymers, the grid is usually
formed by four identical metal ions and four identical ligands,
for example, polymers [Cd(NCS)2(L)2]n (L ) 2,2′-bi-1,6-
naphthyridine),50 [Cd(L)2(ClO4)2]n [L ) N,N-2-pyridyl-(4-
pyridylmethyl)amine],51 [Cd(L)2(NO3)2]n [L) bis(4-pyridyl)-
methane],43 [Cd(NO3)2(Py2CH2)2]n, and [Cd2(NO3)4(Py2C3H6)4-
(H2O)]n.53 But in polymer 3, not only the btx ligands but
also the sulfate anions act as bridging ligands, so each grid
contains four Cd(II) ions, two btx ligands, and two sulfate
anions. Polymer 3’s two-dimensional layered structure is
different from those of the reported Cd(II) polymers. It is a
less common Cd(II) two-dimensional polymer with quadri-
lateral grid units.
Figure 3b gives the the two-dimensional layered structure.
Along the c-direction, Cd2 and Cd3 are bridged by sulfate
anions leading to a linear chain ‚‚‚Cd2-S(1)O4-Cd3-
S(1)O4-Cd2-S(1)O4-Cd3‚‚‚, and Cd1 and Cd4 are bridged
by sulfate anions forming another linear chain ‚‚‚Cd1-S(2)-
O4-Cd4-S(2)O4-Cd1-S(2)O4-Cd4‚‚‚. Along the a-direc-
tion, Cd(II) ions are connected by a btx ligand generating
two kinds of linear chains: one is ‚‚‚Cd1-btx-Cd2-btx-
Cd1-btx-Cd2‚‚‚, and the other is ‚‚‚Cd3-btx-Cd4-btx-
Cd3-btx-Cd4‚‚‚. Linear chains along the c-direction and
a-direction are interconnected each other to finish the two-
dimensional layered frameworks.
Crystal Structure of [Cd(btx)(S2O7)(H2O)]n (4). Al-
though the elements in 3 and 4 are completely identical, the
structural determination reveals that 4 is a most remarkable
and unique three-dimensional structure polymer. As depicted
in Figure 4a, there are two distinct Cd(II) ions which have
different coordination environments in the crystallographic
asymmetric unit. Cd1 is coordinated by four oxygen atoms
of pyrosulfate in a ideal square planar geometry and two ni-
trogen atoms from two bidentate btx. The Cd1-O distances
of 2.307(8) and 2.310(9) Å and the Cd1-N distances of
2.292(11) Å are similar to those of polymers 1-3 and other
reported Cd(II) polymers.28,51,53 Cd2 is in a hexagonal
bipyrimidal coordination environment (Figure 4b) and binds
to two nitrogen atoms from two bxt ligands and six oxygen
atoms from four pyrosulfate groups and two water molecules.
As shown in Figure 4c, if we neglect the interactions of
Cd(II) centers with the btx ligands, the structure of 4 has a
two-dimensional layered topology consisting of two kinds
of independent Cd(II) ions and two kinds of independent
Figure 3. (a) Coordination geometry of the four Cd(II) centers in [Cd-
(btx)(SO4)(H2O)2]n (3) with atom numbering, showing 30% thermal
ellipsoids. Hydrogen atoms have been omitted for clarity. (b) Two-
dimensional layered structure of [Cd(btx)(SO4)(H2O)2]n (3) with distorted
rectangular grid units.
The Cd-N bond lengths (2.344(3) and 2.354(3) Å) are
slightly longer than the Cd-N bond lengths of polymer 1,
while the Cd-Cl bond lengths (2.6477(13) Å) are obviously
longer than those of Cd-N bond lengths. The Cd(II) ion is
in an elongated octahedral geometry coordinated by four
nitrogen atoms of four bidentate btx ligands and two chlorine
atoms. The mean deviations from planes N1-N2-N3-C1-
C2 (1), N4B-N5B-N6B-C11B-C12B (2), C4-C5-C6-
C7-C8-C9 (3), and N4-N5-N6-C11-C12 (4) are 0.0020,
0.0016, 0.0054, and 0.0015 Å, respectively. The dihedral
angles between planes 1 and 2, 1 and 3, 1 and 4, and 3 and
4 are 99.3, 72.4, 71.0, and 50.6°, respectively.
As depicted in Figure 2b, the two-dimensional layered
structure is based upon the rhombohedral grid units (Cd(btx)4)
which are formed by four btx ligands and four Cd(II) ions.
In each grid, the edge lengths of 14.880 Å are slightly longer
than those in polymer 1, the diagonals are 20.156 and 21.156
Å, and the interior angles are 85.3 and 94.7°, respectively.
Crystal Structure of [Cd(btx)(SO4)(H2O)2]n (3). Polymer
3 possesses an infinite two-dimensional layered structure with
distorted rectangular grid units which are different from those
of 1 and 2. As shown in Figure 3a, there are two crystallo-
graphically independent btx ligands, two crystallographically
independent bidentate sulfates, and four crystallographically
independent Cd(II) ions. The coordination enviroments
Inorganic Chemistry, Vol. 43, No. 11, 2004 3533

Meng et al.
Figure 4. (a) Coordination geometry of the Cd(II) centers in Cd2(btx)2(S2O7)2(H2O)2]n (4) with atom numbering, showing 30% thermal ellipsoids. Hydrogen
atoms have been omitted for clarity. (b) Polyhedral view of the octahedra of Cd1 (yellow) and dodecahedra of Cd2 (blue) in Cd2(btx)2(S2O7)2(H2O)2]n (4).
(c) Two-dimensional layer in Cd2(btx)2(S2O7)2(H2O)2]n (4), neglecting the interaction of Cd(II) centers with btx ligands. (d) Three-dimensional network of
2-
Cd2(btx)2(S2O7)2(H2O)2]n (4). Adjacent two-dimensional layers are connected by bridging S2O7 anions.
pyrosulfate groups. Along the a-direction, Cd1 atoms are
bridged by (S2)2O7 groups with the Cd1‚‚‚Cd1 distance of
8.556 Å and Cd2 atoms are linked by (S1)2O7 groups with
the Cd2‚‚‚Cd2 distance of 8.556 Å leading to two kinds of
linear chains. Along the c-direction, Cd1 atoms are ligated
by (S1)2O7 groups with the Cd1‚‚‚Cd1 distance of 8.542 Å
and Cd2 atoms are connected by (S2)2O7 groups with the
Cd2‚‚‚Cd2 distance of 8.542 Å forming other two kinds of
linear chains. Linear chains along the a-direction intersect
those along c-direction generating the two-dimensional
frameworks only consisting of Cd(II) ions and pyrosulfate
groups. These two-dimensional layers are stacked parallel
and connected by btx leading to the three-dimensional
framework (Figure 4d).
In the known Cd(II) polymers, the coordination numbers
of Cd(II) ions include 4-7, and the corresponding coordina-
tion geometries are quadrilateral plane, trigonal bipyramid,
octahedron, and pentagonal bipyramid, respectively.4,28,50-53,54
For example, in [Cd(NO3)2(Py2C4H8)(H2O)2]n and [Cd2-
(NO3)4(Py2C3H6)4(H2O)]n,53 the coordination number for the
Cd(II) ion is 6 and the corresponding coordination geometry
is octahedal; in [Cd2(NO3)4(Py2C5H10)3(H2O)]n53 and [Cd(tp)-
(4,4′-bipy)]n,28 the coordination number for Cd(II) ions is 7
and the corresponding coordination geometry is pentagonal
bipyramid. But in 4, one type of Cd(II) ion is eight-
coordinated and its geometry is hexagonal bipyrimid. To the
authors’ best knowledge this kind of coordination geometry
has not previously occurred in the reported Cd(II) polymers.
Due to the difference of reaction temperature, 3 and 4 ex-
hibit completely different crystal structures; 3 shows a two-
dimensional layered structure, and 4 has a three-dimensional
network.
Thermogravimetric Analysis (TGA). The TG-DTA of
polymers 1-4 was determined in the range of 25-800 °C
(or 1100 °C for polymer 2) in air. TG data show that 1 is
stable up to 285 °C and then loses weight from 285 to 618
3534 Inorganic Chemistry, Vol. 43, No. 11, 2004

Cd-btx Coordination Polymers
°C corresponding to the release of btx and the decomposition
of the nitrate anions. Finally a plateau region is observed
from 618 to 800 °C. A brown residue of CdO (obsd 17.13%,
calcd 17.93%) remained. There are two exothermic peaks
(345 and 534 °C) in the DTA curve of 1. The TG data of 2
show that it is also stable up to 215 °C and then keeps losing
weight from 215 to 1077 °C corresponding to the losses of
btx and CdCl2. At 1077 °C, the weight is lost completely.
One endothermic peak (291 °C) and two exothermic peaks
(371, 622 °C) were observed in the DTA curve of 2. The
TG data for 3 show that it began to decompose at 103 °C.
Then there are two weight loss stages in the ranges 103-
151 and 293-543 °C, corresponding to the release of the
crystallized water molecules and btx, respectively. Finally a
plateau region is observed from 543 to 800 °C. A white
residue of CdSO4 (obsd 42.10%, calcd 43.02%) remained.
One endothermic peak (175 °C) and two exothermic peaks
(446, 514 °C) are observed in the DTA curve of 3. In the
DTA curve of 4, there are one endothermic peak (169 °C)
and three exothermic peaks (447, 509, 635 °C). The weight
loss from 109 to 145 °C corresponds to the departure of the
H2O, and the weight loss from 296 to 539 °C corresponds
to the loss of btx. A plateau region is observed from 539 to
800 °C. The remaining white residue is CdS2O7 (obsd
51.46%, calcd 52.74%).
Figure 5. NLO absorption data for 3 in a 3.1 × 10-4 mol‚dm-3 DMF
solution at 532 nm with incident energy of 150 µJ. The data were collected
under an open aperture configuration.
concentration 3.1 × 10-4 mol‚dm-3. In Figure 5, the filled
squares are the experimental data and the solid line is the
theoretical curve from eqs 1 and 2. A reasonably good fit
between the experimental data and the theoretical curve
suggests that the experimentally obtained NLO effects are
effectively third order in nature. The figure clearly illustrate
that the absorption increases as the incident light irradiance
rises since light transmittance (T) is a function of the sample’s
z position. It can be seen from Figure 5 that the normalized
transmittance drops to about 65% for polymer 3 at the focus;
the corresponding third-order NLO absorptive coefficient R2
is calculated to be 1.15 × 10-9 m W-1. It is comparable to
or larger than those of the well-performing coordination
Nonlinear Optical Properties. The third-order NLO
properties of polymers 1-4 were investigated with 532 nm
laser pulses of 7 ns duration by Z-scan experiment in DMF
solution.55,56 The results show that polymer 3 possesses very
strong third-order NLO absorptive effect and weak refractive
behavior, and polymers 1, 2, and 4 display both weak third-
order NLO absorptive and weak refractive behaviors.
polymers such as [Cd(bbbt)2(NCS)2]n (R2 ) 5.0 × 10-9
m
The NLO absorption components were evaluated by
Z-scan experiment under an open aperture configuration. The
NLO absorption data can be well represented by eqs 1 and
2, which describe a third-order NLO process:55
W-1) (bbbt ) 1,1′-(1,4-butanediyl)bis(1H-benzotriazole)),
[HgI2(4,4′-azopyridine)]n (R2 ) 1.3 × 10-11 m W-1), [HgI2-
(bpea)]n (R2 ) 1.1 × 10-11 m W-1) (bpea ) 1,2-bis-
(4-pyridyl)ethane), and [Pb(NCS)2(bpea)]n (R2 ) 1.1 × 10-11
m W-1).8,57-59
2
1
T(Z) )
-+∞∞In[1 + q(Z)]eτ dτ
(1)
∫
Interestingly, polymers 1-3 have the same btx ligand, the
same metal ion, and the similar two-dimensional layered
structure, but they display different NLO properties since
they have different anions. Polymers 3 and 4 contain identical
elements, but they exhibit different NLO effects owing to
their different crystal structures. It is obvious that the third-
order NLO properties of coordination polymers can be altered
through anions or structural manipulation.
Photoluminescent Properties. The emission spectra of
polymers 1-4 in the solid state at room temperature are
shown in Figure 6. Excitation at 238 nm leads to violet-
fluorescent emission bands at 291 nm for 1, 287 nm for 2,
299 nm for 3, and 287 nm for 4 under the same conditions.
The emissions observed in 1-4 are neither MLCT (metal-
to-ligand charge transfer) nor LMCT (ligand-to-metal charge
x
πq(Z)
-R0L
I0
2
∞
q(Z) )
∞R
0
e[-2(r/ω )2-(t/t ) ]
r dr dt
1 - e
0
0
∫ ∫
21 + (Z/Z0)2
0
R0
(2)
Here Z is the distance of the sample from the focal point, R0
and R2 are the linear and nonlinear absorption coefficients,
respectively, L is the sample thickness, I0 is the peak
2
irradiation intensity at focus, Z0 ) πω0 /λ with ω0 being the
spot radius of the laser beam at focus and λ being the
wavelength of the laser, r is the radial coordinate, τ is the
time, and t0 is the pulse width. Figure 5 depicts the NLO
absorptive properties of polymer 3 in a DMF solution of
(54) Fujita, M.; Kwon, Y. J.; Sasaki, O.; Yamaguchi, A.; Lemenovskii, D.
A. J. Am. Chem. Soc. 1995, 117, 7287.
(55) Sheik-Bahae, M.; Said, A. A.; Wei, T. H.; Hagan, D. J.; Van Stryland,
E. W. IEEE J. Quantum Electron. 1990, 26, 760.
(57) Niu, Y. Y.; Song, Y. L.; Chen, T. N.; Xue, Z. L.; Xin, X. Q.
CrystEngComm 2001, 36, 1.
(58) Niu, Y. Y.; Song, Y. L.; Hou, H. W.; Zheng, H. G.; Fun, H. K.; Xin,
X. Q. Chin. J. Inorg. Chem. 2001, 17, 723.
(56) Hou, H. W.; Xin, X. Q.; Liu, J.; Chen, M. Q.; Shi, S. J. Chem. Soc.,
Dalton Trans. 1994, 3211.
(59) Niu, Y. Y.; Hou, H. W.; Li, F.; Song, Y. L.; Zheng, H. G.; Fun, H.
K.; Xin, X. Q. Chin. J. Inorg. Chem. 2001, 17, 533.
Inorganic Chemistry, Vol. 43, No. 11, 2004 3535

Meng et al.
strongest fluorescent intensity; 1 exhibits a quenching of the
fluorescence. These observations suggest that 2 will be an
excellent candidate for solvent-resistant fluorescent material
because it is almost insoluble in most common solvents such
as ethanol, chloroform, ethyl acetate, acetone, acetonitrile,
benzene, and water.
Acknowledgment. The authors thank the National Natu-
ral Science Foundation of China (Grant Nos. 20001006 and
20371042), the Excellent Young Teachers Program In the
Higher Education Institute, and the Innovation Foundation
of Henan Province for financial support.
Figure 6. Solid-state emission spectra of polymers 1 (d), 2 (a), 3 (c), and
4 (b) at room temperature.
Supporting Information Available: Crystallographic data for
polymers 1-4 in CIF format, TGA-DTA data, and an H NMR
spectrum of the ligand btx. This material is available free of charge
via the Internet at http://pubs.acs.org.
transfer) in nature and can tentatively be assigned to the
intraligand fluorescent emission since a similar emission
(when λex ) 238 nm, λem ) 289 nm) is also observed for
btx. A clearly bathochromic shift of emission occurs in 3
compared with 1, 2, and 4. It is obvious that 2 possesses the
1
IC0354670
3536 Inorganic Chemistry, Vol. 43, No. 11, 2004