Synthesis and characterization of new coordination polymers generated from bent bis(cyanophenyl)oxadiazole ligands and Ag(I) salts

Article abstract of DOI:10.1021/ic050218s

Two new bent bis(cyanophenyl)oxadiazole ligands, 2,5-bis(4-cyanophenyl)-1, 3,4-oxadiazole (L7) and 2,5-bis(3-cyanophenyl)-1,3,4-oxadiazole (L8), were synthesized. The coordination chemistry of these ligands with various Ag(I) salts has been investigated. Seven new coordination polymers, namely, {[Ag(L7)(H₂O)]ClO₄}_n (1) (triclinic, P1, a = 9.342(4) A, b = 9.889(4) A, c = 10.512(4) A, α = 68.978(6)°, β = 78.217(6)°, γ = 81.851(7)°, Z = 2), {[Ag(L7)]SO₃CF₃}_n (2) (monoclinic, P2 ₁/n, a = 7.559(2) A, b = 23.739(6) A, c = 10.426(3) A, β = 108.071(4)°, Z = 4), {[Ag(L8)]BF₄·0. 5(C₆H₆)·H₂O}_n(3) (triclinic, P1, a = 7.498(3) A, b = 10.649(4) A, c = 13.673(5) A, α = 98.602(5)°, β = 100.004(5)°, γ = 110.232(5)°, Z = 2), {[Ag(L8)SbF₆]·H₂O}_n (4) (triclinic, P1, a = 8.2621(9) A, b = 10.6127(12) A, c = 13.3685(15) A, α = 98.012(2)°, β = 106.259(2)°, γ = 112.362(2)°, Z = 2), {[Ag₂(L8)₂(SO₃CF₃)]·H ₂O}_n (5) (triclinic, P1, a = 10.713(4) A, b = 13.449(5) A, c = 15.423(5) A, α = 65.908(5)°, β = 74.231(5)°, γ = 83.255(5)°, Z = 2), {[Ag₂(L8)(C ₆H₆)(ClO₄)]·ClO₄} _n (6) (monoclinic, P2₁/n, a = 6.9681(17) A, b = 20.627(5) A, c = 17.437(4) A, β = 95.880(4)°, Z = 4), and {[Ag₂(L₈)(H₂PO₄)₂]} _n (7) (triclinic, P1, a = 7.956(2) A, b = 9.938(3) A, c = 14.242(4) A, α = 106.191(4)°, β = 97.322(4)°, γ = 107.392(4)°, Z = 1), were obtained by the combination of L7 and L8 with Ag(I) salts in a benzene/methylene chloride mixed-solvent system and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. In addition, the luminescence and electrical conductance properties of compounds 1-6 and the host-guest chemistry of compound 3 were investigated.

Full text of DOI:10.1021/ic050218s

Inorg. Chem. 2005, 44, 4679−4692
Synthesis and Characterization of New Coordination Polymers
Generated from Bent Bis(Cyanophenyl)oxadiazole Ligands and Ag(I)
Salts
Yu-Bin Dong,* Hai-Ying Wang, Jian-Ping Ma, Da-Zhong Shen, and Ru-Qi Huang
College of Chemistry, Chemical Engineering and Materials Science, and Shandong Key Lab of
Chemical Functional Materials, Shandong Normal UniVersity, Jinan 250014,
People’s Republic of China
Received February 10, 2005
Two new bent bis(cyanophenyl)oxadiazole ligands, 2,5-bis(4-cyanophenyl)-1,3,4-oxadiazole (L7) and 2,5-bis(3-
cyanophenyl)-1,3,4-oxadiazole (L8), were synthesized. The coordination chemistry of these ligands with various
Ag(I) salts has been investigated. Seven new coordination polymers, namely,
P1, a 9.342(4) Å, b 9.889(4) Å, c 10.512(4) Å, R ) 68.978(6) â ) 78.217(6)
2), [Ag(L7)]SO3CF3 (2) (monoclinic, P21/n, a 23.739(6) Å, c
108.071(4) 7.498(3) Å, b
13.673(5) Å, R ) 98.602(5) [Ag(L8)SbF6] H2O
â ) 106.259(2)
13.449(5) Å, c
[Ag2(L8)(C6H6)(ClO4)] ClO4 (6) (monoclinic, P21/n, a
17.437(4) Å, â ) 95.880(4) , Z 4), and
9.938(3) Å, c 14.242(4) Å, R ) 106.191(4) â ) 97.322(4)
1), were obtained by the combination of L7 and L8 with Ag(I) salts in a benzene/methylene chloride mixed-
solvent system and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction.
{[Ag(L7)(H2O)]ClO4} (1) (triclinic,
n
h
)
)
)
°
)
, a
2),
,
°
,
)
γ ) 81.851(7)
10.426(3) Å, â )
10.649(4) Å, c
(4) (triclinic, P1
°, Z )
{
}
4),
)
}
7.559(2) Å, b
n(3) (triclinic, P1
γ )110.232(5) , Z
13.3685(15) Å, R ) 98.012(2)
(5) (triclinic, P1, a 10.713(4) Å, b
2),
n
°
, Z
)
{
[Ag(L8)]BF4
â ) 100.004(5)
10.6127(12) Å, c
[Ag2(L8)2(SO3CF3)] H2O
â ) 74.231(5)
6.9681(17) Å, b 20.627(5) Å, c
P1, a 7.956(2) Å, b
‚
0.5(C6H6)
‚
°
H2O
,
h
)
)
{
)
)
°
,
°
‚
}
h
,
n
a
Z
)
)
8.2621(9) Å, b
2),
)
)
°
,
°, γ ) 112.362(2)°
,
{
°
‚
}
h
)
{
)
) 15.423(5) Å, R )
n
65.908(5)
,
°
,
γ ) 83.255(5)
°
, Z
)
‚
}
)
n
)
)
°
)
{
[Ag2(L8)(H2PO4)2]
}
n
(7) (triclinic,
h
)
)
)
°
,
°, γ ) 107.392(4)°, Z
)
In addition, the luminescence and electrical conductance properties of compounds 1−6 and the host−guest chemistry
of compound 3 were investigated.
Introduction
optics, gas separation, magnetic properties, and molecular
recognition.4 In general, primary control over the type and
topology of the product generated from the self-assembly
of inorganic metal codes and organic spacers can be achieved
by the functionality of the ligand5 and metal coordination
Within the field now called “inorganic/organic coordina-
tion polymers”, efforts to use transition metal ions and
organic spacers simultaneously have recently been extremely
fruitful.1-3 During the past decades, a number of these
compounds, with interesting polymeric motifs, have been
successfully designed and synthesized. Some of them exhibit
encouraging potential for application in catalysis, nonlinear
(2) Yaghi, O. M.; Li, G.; Li, H. Nature 1995, 378, 703. (b) Yaghi, O.
M.; Li, H. J. Am. Chem. Soc. 1995, 117, 10401. (c) Yaghi, O. M.; Li,
H.; Groy, T. L. J. Am. Chem. Soc. 1996, 118, 9096. (d) Fujita, M.;
Oka, H.; Yamaguchi, K.; Ogura, K. Nature 1995, 378, 469. (e) Fujita,
M.; Kwon, Y. J.; Sasaki, O.; Yamaguchi, K.; Ogura, K. J. Am. Chem.
Soc. 1995, 117, 7287. (f) Losier, P.; Zaworotko, M. J. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 2779. (g) Power, K. N.; Hennigar, T. L.;
Zaworotko, M. J. Chem. Commun. 1998, 595.
(3) Heintz, R. A.; Zhao, H.; Ouyang, X.; Grandinetti, G.; Cowen, J.;
Dunbar, K. R. Inorg. Chem. 1999, 38, 144. (b) Mayr, A.; Guo, J.
Inorg. Chem. 1999, 38, 921. (c) Su, C.-Y.; Goforth, A. M.; Smith, M.
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3576. (d) Mao, L. F.; Mayr, A. Inorg. Chem. 1996, 35, 3183. (e) Choi,
H. J.; Suh, M. P. J. Am. Chem. Soc. 1998, 120, 10622. (f) Sharma, C.
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* To whom correspondence should be addressed. E-mail: yubindong@
sdnu.edu.cn.
(1) Zaworotko, M. J.; Moulton, B. Chem. ReV. 2001, 101, 2619. (b)
Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; Keeffe,
M. O.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319. (c) Constable,
E. C. Prog. Inorg. Chem. 1994, 42, 67. (d) Hirsch, K. A.; Wilson, S.
R.; Moore, J. S. Inorg. Chem. 1997, 36, 2960. (e) Dunbar, K. R.;
Heintz, K. R. Prog. Inorg. Chem. 1996, 283. (f) Whiteford, J. A.;
Rachlin, E. M.; Stang, P. J. Angew. Chem., Int. Ed. Engl. 1996, 35,
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Nature 1995, 374, 792.
10.1021/ic050218s CCC: $30.25
Published on Web 06/01/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 13, 2005 4679

Dong et al.
Scheme 1. Bent Organic Ligands Used in the Construction of
Coordination Polymers and Supramolecular Complexes
geometry preference. For example, the combination of a
linear rigid ligand, such as 4,4′-bipyridine or its derivatives,
and a tetrahedral metal node will generate a diamondoid
motif. In addition, the topology of the polymeric complexes
can also be modified by the inorganic counterion,6 solvent
system,6 and metal salt-to-ligand ratio,7 which is demon-
strated well by many previous studies. It is well-known that
the rigid linear ligands have been the main theme in the
chemistry of coordination polymers and have proven to be
among the most important types of organic ligands for the
design and construction of coordination polymers exhibiting
remarkable polymeric structural motifs.8 However, until now,
little attention has been paid to the organic-inorganic
coordination polymers or supramolecular complexes gener-
ated from bent organic ligands. Compared to rigid linear
organic ligands, the bent rigid organic spacers do not
propagate the metal coordination code legibly into the
metal-organic architectures which makes it more difficult
to forecast the coordination network topologies. Thus, the
coordination chemistry of complexes based on bent organic
ligands is more attractive.
Our research group has investigated the construction of
coordination polymers and supramolecular complexes with
the bent organic ligands. As shown in Scheme 1, in this
project, five-membered oxadiazole and triazole heteroatom
cyclic rings were chosen as the bridge, pyridyl, and ami-
nophenyl groups of the terminal coordination sites (L1-
L6).9 As a result of the specific geometry of five-membered
heterocycle-bridging ligands and the coordination preferences
of the transition metals, various new types of coordination
polymers, some with open channels and interesting lumi-
nescent properties, have been obtained. This encourages us
to continue this project and expand the symmetric five-
membered heterocycle-bridging bipyridine and biphenyl-
amine types of ligands to include symmetric five-membered
heterocycle-bridged bibenzonitrile ligands L7 and L8 (Scheme
2). Herein, we wish to report seven new Ag(I)-containing
coordination polymers with novel polymeric motifs, namely,
{[Ag(L7)(H2O)]ClO4}n (1), {[Ag(L7)]SO3CF3}n (2), {[Ag-
(L8)]BF4‚0.5(C6H6)‚H2O}n (3), {[Ag(L8)SbF6]‚H2O}n (4),
{[Ag2(L8)2(SO3CF3)]‚H2O}n (5), {[Ag2(L8)(C6H6)(ClO4)]‚
ClO4}n (6), and {[Ag2(L8)(H2PO4)2]}n (7), generated from
L7 and L8 (Scheme 2) and various Ag(I) salts in solution.
(4) Kobel, W.; Hanack, M. Inorg. Chem. 1986, 25, 103. (b) Kato, R.;
Kobayashi, H.; Kobayashi, A. J. Am. Chem. Soc. 1989, 111, 5224.
(c) Sinzger, K.; Hu¨nig, S.; Jopp, M.; Bauer, D.; Bietsch, W.; von
Schu¨tz, J. U.; Wolf, H. C.; Kremer, R. K.; Metzenthin, T.; Bau, R.;
Khan, S. I.; Lindaum, A.; Lengauer, C. L.; Tillmanns, E. J. Am. Chem.
Soc. 1993, 115, 7696. (d) Erk, P.; Gross, H.-J.; Hu¨nig, U. L.; Meixner,
H.; Werner, H.-P.; von Schu¨tz, J. U.; Wolf, H. C. Angew. Chem., Int.
Ed. Engl. 1989, 28, 1245. (e) Jung, O.; Pierpont, C. G. J. Am. Chem.
Soc. 1994, 116, 2229. (f) Patoux, C.; Loudret, C.; Launay, L. P.;
Joachim, C.; Gourdon, A. Inorg. Chem. 1997, 36, 5037. (g) Dybtsev,
D. N.; Chun, H.; Yoon, S. H.; Kim, D.; Kim, K. J. Am. Chem. Soc.
2004, 126, 32. (h) Maji, T. K.; Uemura, K.; Chang, H.-C.; Matsuda,
R.; Kitagawa, S. J. Am. Chem. Soc. 2004, 126, 3269.
(5) Kuroda-Sowa, T.; Horrino, T.; Yamamoto, M.; Ohno, Y.; Maekawa,
M.; Munakata, M. Inorg. Chem. 1997, 36, 6382. (b) Munakata, M.;
Wu, L. P.; Kuroda-Sowa, T. Bull. Chem. Soc. Jpn. 1997, 70, 1727.
(c) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.;
Moriwaki, K.; Kitagawa, S. Inorg. Chem. 1997, 36, 5416. (d) Hennigar,
T. L.; MacQuarrie, D. C.; Losier, P.; Rogers, R. D.; Zaworotko, M. J.
Angew. Chem., Int. Ed. Engl. 1997, 36, 972.
Experimental Section
Materials and Methods. AgSO3CF3, AgClO4, AgPF6, AgBF4,
AgSbF6, and AgH2PO4 (Acros) were used as obtained without
further purification. Infrared (IR) samples were prepared as KBr
(6) Lu, J.; Paliwala, T.; Lim, S. C.; Yu, C.; Niu, T.; Jacobson, A. J. Inorg.
Chem. 1997, 36, 923. (b) Munakata, M.; Ning, G. L.; Kuroda-Sowa,
T.; Maekawa, M.; Suenaga, Y.; Harino, T. Inorg. Chem. 1998, 37,
5651. (c) Power, K. N.; Hennigar, T. L.; Zaworotko, M. J. New J.
Chem. 1998, 22, 177. (d) Jung, O. S.; Park, S. H.; Kim, K. M.; Jang,
H. G. Inorg. Chem. 1998, 37, 5781.
(7) Gable, R. W.; Hoskins, B. F.; Robson, R. J. Chem. Soc., Chem.
Commun. 1990, 1677. (b) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura,
K. J. Am. Chem. Soc. 1994, 116, 1151. (c) Robson, R.; Abrahams, B.
F.; Batten, S. R.; Gable, R. W.; Hoskins, B. F.; Liu, J. In Supramo-
lecular Architecture; Bein, T., Ed.; ACS Symposium Series 449;
American Chemical Society: Washington, DC, 1992; Chapter 19. (d)
Carlucci, L.; Ciani, G.; Proserpio, D. M.; Sironi, A. J. Chem. Soc.,
Chem. Commun. 1994, 2755.
(8) Hagrman, P. J.; Hagrman, D.; Zubieta, J. Angew. Chem., Int. Ed. 1999,
38, 2638. (b) Blake, A. J.; Champness, N. R.; Hubberstey, P.; Li, W.-
S.; Withersby, M. A.; Schro¨der, M. Coord. Chem. ReV. 1999, 183,
117. (c) Batten, S.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460.
(d) Barnett, S. A.; Champness, N. R. Coord. Chem. ReV. 2003, 246,
145.
(9) (a) Dong, Y.-B.; Ma, J.-P.; Smith, M. D.; Huang, R.-Q.; Tang, B.;
Chen, D.; zur Loye, H.-C. Solid State Sci. 2002, 4, 1313. (b) Dong,
Y.-B.; Ma, J.-P.; Huang, R.-Q.; Smith, M. D.; zur Loye, H.-C. Inorg.
Chem. 2003, 42, 294. (c) Dong, Y.-B.; Ma, J.-P.; Smith, M. D.; Huang,
R.-Q.; Tang, B.; Guo, D.-S.; Wang, J.-S.; zur Loye, H.-C. Solid State
Sci. 2003, 5, 601. (d) Dong, Y.-B.; Ma, J.-P.; Smith, M. D.; Huang,
R.-Q.; Wang, J.-S.; zur Loye, H.-C. Solid State Sci. 2003, 5, 1177.
(e) Dong, Y.-B.; Cheng, J.-Y.; Wang, H.-Y.; Huang, R.-Q.; Tang, B.;
Smith, M. D.; zur Loye, H.-C. Chem. Mater. 2003, 15, 2593. (f) Dong,
Y.-B.; Ma, J.-P.; Huang, R.-Q.; Liang, F.-Z.; Smith, M. D. J. Chem.
Soc., Dalton Trans. 2003, 9, 1472. (g) Dong, Y.-B.; Cheng, J.-Y.;
Huang, R.-Q.; Tang, B.; Smith, M. D.; zur Loye, H.-C. Inorg. Chem.
2003, 42, 5699. (h) Cheng, J.-Y.; Dong, Y.-B.; Ma, J.-P.; Huang, R.-
Q.; Smith, M. D. Inorg. Chem. Commun. 2005, 8, 6. (i) Dong, Y.-B.;
Cheng, J.-Y.; Huang, R.-Q.; Smith, M. D. Inorg. Chim. Acta 2005,
385, 901. (j) Dong, Y.-B.; Cheng, J.-Y.; Ma, J.-P.; Huang R.-Q.; Smith,
M. D. Crystal Growth & Design 2005, 5, 585. (k) Dong, Y.-B.; Wang,
H.-Y.; Ma, J.-P.; Huang, R.-Q.; Smith, M. D. Cryst. Growth Des. 2005,
359, 891.
4680 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
Scheme 2. Synthesis of Ligands L7 and L8
pellets, and the spectra were obtained in the 400-4000 cm-1 range
using a Perkin-Elmer 1600 FTIR spectrometer. Elemental analyses
were performed on a Perkin-Elmer Model 2400 analyzer. 1H NMR
data were collected using an AM-300 spectrometer. Chemical shifts
are reported in δ relative to TMS. All fluorescence measurements
were carried out on a Cary Eclipse spectrofluorimeter (Varian,
Australia) equipped with a xenon lamp and quartz carrier at room
temperature. Thermogravimetric analyses were carried out using a
TA instrument SDT 2960 simultaneous DTA-TGA under flowing
nitrogen at a heating rate of 10 °C/min. XRD patterns were obtained
on a Rigaku D/Max-rB X-ray powder diffraction (XRD) apparatus
with Cu KR radiation (λ)1.5405 & Aring). Electrical conductivity
was performed on an Agilent Technologies model 4294A-ATO-
20150 instrument. Caution! Two of the crystallization procedures
inVolVe AgClO4 which is a strong oxidizer.
Preparation of L7 and L8. An aqueous solution of NaNO2 (1.50
g, 22 mmol) was added to a solution of L5 (1.26 g, 5 mmol) in
concentrated hydrochloric acid (25 mL) at 0 °C. The mixture was
stirred for 1 h at room temperature. The diazonium salt solution,
washed with 10% aqueous NaHCO3, was added to an aqueous
solution of K2Cu2(CN)4, generated from the reaction of CuSO4‚
5H2O (2.6 g, 1.04 mmol), NaHSO3 (0.56 g, 5.4 mmol) and KCN
(2.64 g, 41 mmol). The mixture was stirred at room temperature
overnight, and then the temperature was gradually increased to 80
°C; then, the mixture was stirred for 0.5 h. The mixture was allowed
to cool to room temperature, and the product was collected by
vacuum filtration and dried in air. The product was purified by
column chromatrography on silica gel using CH2Cl2 as an eluent
to produce L7 (0.35 g) as a light yellow solid (26% yield). 1H NMR
(DMSO): δ 8.35-8.33 (d, 4H, C6H4), 8.13-8.10 (d, 4H, C6H4).
IR (KBr): 2230 (s), 1653 (s), 1572 (s), 1539 (s), 1485 (s), 1411
(s), 1312 (s), 1274 (m), 1098 (s), 1060 (s), 1014 (s), 960 (s), 863
(s), 742 (s), 700 (s), 586 (s), 547 (s) cm-1. Anal. Calcd for
C16H8N4O (L7): C, 70.59; H, 2.94; N, 20.59. Found: C, 70.41;
H, 2.80; N, 20.34. UV-vis spectrum (in CH3CN at room temper-
ature): λmax 297 nm.
L8 was prepared following the procedure described for L7 except
L6 was used instead of L5 to produce L8 in a 28% yield as a light
1
pink crystalline solid. H NMR (DMSO): δ 8.67 (s, 2H, C6H4),
8.50-8.48 (d, 2H, C6H4), 8.14-8.12 (d, 2H, C6H4), 7.88-7.83 (t,
2H, C6H4). IR (KBr): 2234 (s), 1612 (s), 1548 (s), 1487 (s), 1408
(s), 1295 (s), 1187 (m), 1081 (s), 986 (m), 916 (m), 832 (s), 736
(s), 678 (s), 582 (s), 459 (m) cm-1. Anal. Calcd for C16H8N4O
(L7): C, 70.59; H, 2.94; N, 20.59. Found: C, 70.46; H, 2.82; N,
20.39. UV-vis spectrum (in CH3CN at room temperature): λmax
234 nm, 279 nm.
Preparation of {[Ag(L7)(H2O)]ClO4}n (1). A solution of
AgClO4 (12 mg, 0.052 mmol) in benzene (10 mL) was layered
onto a solution of L7 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL).
The solutions were left at room temperature for about 2 days, and
colorless crystals were obtained. Yield: 54%. IR (KBr): 3463 (br),
2232 (s), 1650 (m), 1543 (s), 1490 (s), 1401 (s), 1274 (s), 1117
Inorganic Chemistry, Vol. 44, No. 13, 2005 4681

Dong et al.
Table 1. Crystallographic Data for L7 and 1-3
L7
1
2
3
empirical formula
fw
cryst syst
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C16H8N4O
272.26
orthorhombic
6.563(3)
12.744(5)
15.905(6)
90
90
90
1330.3(9)
Pbcn
4
1.359
0.090
298(2)
6400
0.0329, 0.0866
C16H10AgClN4O6
497.60
C17H8AgF3N4O4S
529.20
C19H13AgBF4N4O2
524.01
triclinic
9.342(4)
9.889(4)
10.512(4)
68.978(6)
78.217(6)
81.851(7)
884.8(6)
P1h
monoclinic
7.559(2)
23.739(6)
10.426(3)
90
108.071(4)
90
1778.7(8)
P21/n
triclinic
7.498(3)
10.649(4)
13.673(5)
98.602(5)
100.004(5)
110.232(5)
982.5(6)
P1h
space group
Z
2
4
2
F
calcd (g/cm3)
1.868
1.334
293(2)
3208
1.976
1.317
293(2)
3867
1.771
1.088
293(2)
3760
µ(Mo KR) (mm-1
)
temp (K)
no. of observations (I > 3σ)
Final R indices [I > 2σI]
0.0512, 0.1379
0.0740, 0.1760
0.0590, 0.1527
a
R and Rw
a R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
.
2
2
2
(vs), 1084 (vs), 858 (m), 746 (w), 672 (w), 626 (m), 551 (m) cm-1
.
Preparation of {[Ag2(L8)(C6H6)(ClO4)]‚ClO4}n (6). A solution
of AgClO4 (12 mg, 0.052 mmol) in benzene (10 mL) was layered
onto a solution of L8 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL).
The solutions were left at room temperature for about 2 days, and
colorless crystals were obtained. Yield: 61%. IR (KBr): 3449 (br),
2234 (s), 1613 (m), 1549 (s), 1487 (s), 1410 (m), 1297 (m), 1144
(vs), 1114 (vs), 1084 (vs), 915 (m), 807 (m), 736 (s), 679 (s), 628
(m), 582 (m), 455 (m) cm-1. Anal. Calcd for C22H14Ag2Cl2N4O9
(5): C, 34.51; H, 1.83; N, 7.32. Found: C, 34.43; H, 1.68; N, 7.55.
UV-vis spectrum (in CH3CN at room temperature): λmax 233 nm,
279 nm.
Preparation of {[Ag2(L8)(H2PO4)2]}n (7). A solution of AgH2-
PO4 (0.047 mmol) in benzene (10 mL) was layered onto a solution
of L8 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL). The solutions
were left at room temperature for about 4 days, and red crystals
were obtained. Yield: 34%. IR (KBr): 3442 (br), 3075 (s), 2923
(m), 2233 (s), 1611 (s), 1548 (s), 1487 (s), 1407 (s), 1297 (s), 1143
(s), 1081 (s), 983 (s), 915 (s), 832 (m), 804 (s), 736 (s), 678 (s),
582 (m), 507 (m), 454 (m) cm-1. Anal. Calcd for C16H12Ag2N4O9P2
(7): C, 28.15; H, 1.76; N, 8.21. Found: C, 27.98; H, 1.67; N, 8.16.
Single-Crystal Structure Determination. Suitable single crys-
tals of compounds L1 and 1-7 were selected and mounted in air
onto thin glass fibers. X-ray intensity data were measured at 150
K on a Bruker SMART APEX CCD-based diffractometer (Mo KR
radiation, λ ) 0.71073 Å). The raw frame data for L1 and 1-7
were integrated into SHELX format reflection files and corrected
for Lorentz and polarization effects using SAINT.10 Corrections
for incident and diffracted beam absorption effects were applied
using SADABS.10 None of the crystals showed evidence of crystal
decay during data collection. All structures were solved by a
combination of direct methods and difference Fourier syntheses
and refined against F2 by the full-matrix least-squares technique.
Crystal data, data collection parameters, and refinement statistics
for L7 and 1-7 are listed in Tables 1-2. Relevant interatomic
bond distances and bond angles for 1-7 are given in Tables 3-9.
Anal. Calcd for C16H10AgClN4O6 (1): C, 38.59; H, 2.01; N, 11.25.
Found: C, 38.41; H, 2.21; N, 11.17. UV-vis spectrum (in
CH3CN at room temperature): λmax 297 nm.
Preparation of {[Ag(L7)]SO3CF3}n (2). A solution of AgSO3-
CF3 (12 mg, 0.047 mmol) in benzene (10 mL) was layered onto a
solution of L7 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL). The
solutions were left at room temperature for about 2 days, and
colorless crystals were obtained. Yield: 63%. IR (KBr): 3421 (br),
2231 (s), 1621 (s), 1542 (s), 1489 (s), 1401 (m), 1265 (vs), 1176
(s), 1037 (s), 856 (m), 835 (m), 742 (m), 644 (s), 547 (s), 516 (m)
cm-1. Anal. Calcd for C17H8AgF3N4O4S (2): C, 38.55; H, 1.51;
N, 10.58. Found: C, 38.39; H, 1.48; N, 10.23. UV-vis spectrum
(in CH3CN at room temperature): λmax 297 nm.
Preparation of {[Ag(L8)]BF4‚0.5(C6H6)‚H2O}n(3). A solution
of AgBF4 (10 mg, 0.051 mmol) in benzene (10 mL) was layered
onto a solution of L8 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL).
The solutions were left at room temperature for about 3 days, and
pink crystals were obtained. Yield: 62%. IR (KBr): 3444 (br),
2235 (s), 1648 (s), 1543 (s), 1522 (m), 1490 (s), 1401 (s), 1082
(s), 1032 (s), 807 (m), 738 (m), 676 (s) cm-1. Anal. Calcd for
C19H13AgBF4N4O2 (3): C, 43.51; H, 2.48; N, 10.69. Found: C,
43.32; H, 2.28; N, 10.53. UV-vis spectrum (in CH3CN at room
temperature): λmax 234 nm, 279 nm.
Preparation of {[Ag(L8)SbF6]‚H2O}n (4). A solution of AgSbF6
(17 mg, 0.049 mmol) in benzene (10 mL) was layered onto a
solution of L8 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL). The
solutions were left at room temperature for about 4 days, and
colorless crystals were obtained. Yield: 50%. IR (KBr): 3416 (br),
2235 (m), 1619 (s), 1550 (s), 1485 (s), 1402 (s), 1292 (s), 1167
(m), 1091 (m), 915 (m), 809 (m), 741 (s), 632 (m), 477 (s) cm-1
.
Anal. Calcd for C16H10AgF6N4O2Sb (4): C, 30.29; H, 1.58; N, 8.83.
Found: C, 30.17; H, 1.48; N, 8.59. UV-vis spectrum (in CH3CN
at room temperature): λmax 233 nm, 278 nm.
Preparation of {[Ag2(L8)2(SO3CF3)]‚H2O}n (5). A solution of
AgSO3CF3 (12 mg, 0.047 mmol) in benzene (10 mL) was layered
onto a solution of L8 (9.0 mg, 0.033 mmol) in CH2Cl2 (10 mL).
The solutions were left at room temperature for about 2 days, and
red crystals were obtained. Yield: 64%. IR (KBr): 3421 (br), 2248
(s), 1611 (s), 1550 (s), 1474 (m), 1401 (s), 1260 (vs), 1156 (s),
Results and Discussion
Synthesis and Structural Analysis of Ligands L7-L8.
L7 and L8 were synthesized by classical Sandmeyer reaction
in a relatively low yield. They can be considered to be new
members of the five-membered heterocycle-bridging organic
1029 (s), 915 (s), 809 (s), 739 (m), 682 (s), 571 (m), 517 (m) cm-1
.
Anal. Calcd for C34H18Ag2F6N8O9S2 (5): C, 37.90; H, 1.67; N,
10.40. Found: C, 37.79; H, 1.45; N, 10.47. UV-vis spectrum (in
CH3CN at room temperature): λmax 233 nm, 277 nm.
(10) Bruker Analytical X-ray Systems, Inc.: Madison, WI, 1998.
4682 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
Table 2. Crystallographic Data for 4-7
4
5
6
7
empirical formula
fw
cryst syst
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C16H10AgF6N4O2Sb
633.90
C34H18Ag2F6N8O9S2
1076.42
triclinic
C22H14Ag2Cl2N4O9
765.01
C16H12Ag2N4O9P2
681.98
triclinic
triclinic
8.2621(9)
10.6127(12)
13.3685(15)
98.012(2)
106.259(2)
112.362(2)
999.97(19)
P1h
monoclinic
6.9681(17)
20.627(5)
17.437(4)
90
95.880(4)
90
2493.1(11)
P21/n
10.713(4)
13.449(5)
15.423(5)
65.908(5)
74.231(5)
83.255(5)
1952.2(12)
P1h
7.956(2)
9.938(3)
14.242(4)
106.191(4)
97.322(4)
107.392(4)
1004.3(5)
P21/n
space group
Z
2
2
4
2
F
calcd (g/cm3)
2.105
2.405
298(2)
1.831
1.203
293(2)
2.308
1.846
293(2)
2.255
2.171
293(2)
µ(Mo KR) (mm-1
)
temp (K)
no. of observations (I > 3σ)
3637
0.0478, 0.1254
7113
0.0540, 0.1270
4630
0.0646, 0.1183
3482
0.0775, 0.1648
final R indices [I > 2σI]
a
R and Rw
a R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
Table 3. Interatomic Distances (Å) and Bond Angles (deg) for 1a
.
2
2
2
Table 6. Interatomic Distances (Å) and Bond Angles (deg) for 4a
Ag(1)-N(3)#1
Ag(1)-N(2)
2.261(4)
2.329(4)
Ag(1)-N(1)#2
Ag(1)-O(6)
2.320(4)
2.458(5)
Ag(1)-N(2)
Ag(1)-N(4)#2
2.277(4)
2.341(6)
Ag(1)-N(1)#1
Ag(1)-N(3)#3
2.299(4)
2.344(6)
N(3)#1-Ag(1)-N(1)#2 112.11(15) N(3)#1-Ag(1)-N(2) 114.51(15)
N(2)-Ag(1)-N(1)#1
121.21(15) N(2)-Ag(1)-N(4)#2
117.5(2)
102.5(2)
N(4)#2-Ag(1)-N(3)#3 96.2(2)
N(1)#2-Ag(1)-N(2)
N(1)#2-Ag(1)-O(6)
N(2)-N(1)-Ag(1)#2
127.88(12) N(3)#1-Ag(1)-O(6) 120.4(2)
91.31(18) N(2)-Ag(1)-O(6) 84.62(18)
119.7(2) C(8)-N(1)-Ag(1)#2 133.6(3)
N(1)#1-Ag(1)-N(4)#2 103.0(2)
N(1)#1-Ag(1)-N(3)#3 114.0(2)
N(2)-Ag(1)-N(3)#3
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 2, -y + 1, -z; #2 -x + 1, -y, -z; #3 x, y - 1, z; #4 x, y + 1, z.
a Symmetry transformations used to generate equivalent atoms: #1 x +
1, y - 1, z; #2 -x + 1, -y, -z + 1; #3 x - 1, y + 1, z.
Table 7. Interatomic Distances (Å) and Bond Angles (deg) for 5a
Table 4. Interatomic Distances (Å) and Bond Angles (deg) for 2a
Ag(1)-N(2)
Ag(1)-N(5)
Ag(2)-N(3)
Ag(2)-N(4)
2.275(4)
2.328(4)
2.240(4)
2.293(4)
Ag(1)-N(8)#1
Ag(1)-N(1)#2
Ag(2)-N(7)#3
Ag(2)-N(6)#4
2.288(5)
2.421(6)
2.259(5)
2.447(5)
Ag(1)-N(2)#1
Ag(1)-N(4)#2
2.319(5)
2.380(6)
Ag(1)-N(3)
Ag(1)-O(2)
2.333(5)
2.523(6)
N(2)#1-Ag(1)-N(3) 128.06(16) N(2)#1-Ag(1)-N(4)#2 116.85(19)
N(3)-Ag(1)-N(4)#2 112.60(19) N(2)#1-Ag(1)-O(2)
107.9(2)
85.3(2)
168.3(5)
N(2)-Ag(1)-N(8)#1
N(8)#1-Ag(1)-N(5)
127.09(17) N(2)-Ag(1)-N(5)
120.01(13)
N(3)-Ag(1)-O(2)
N(2)-N(3)-Ag(1)
90.7(2)
N(4)#2-Ag(1)-O(2)
C(4)-N(4)-Ag(1)#3
102.25(17) N(2)-Ag(1)-N(1)#2 100.92(16)
116.8(3)
N(8)#1-Ag(1)-N(1)#2 93.1(2)
N(5)-Ag(1)-N(1)#2 108.89(17)
N(3)-Ag(2)-N(7)#3
N(7)#3-Ag(2)-N(4)
123.31(17) N(3)-Ag(2)-N(4)
120.91(14)
96.53(16)
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 2, -y + 2, -z + 1; #2 x + 1/2, -y + 3/2, z + 1/2; #3 x - 1/2, -y +
3/2, z - 1/2.
108.57(16) N(3)-Ag(2)-N(6)#4
N(7)#3-Ag(2)-N(6)#4 96.46(19) N(4)-Ag(2)-N(6)#4 104.27(17)
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 1, -y, -z + 1; #2 x + 1, y, z; #3 x - 1, y, z; #4 -x, -y, -z.
Table 5. Interatomic Distances (Å) and Bond Angles (deg) for 3a
Ag(1)-N(3)
2.256(4)
2.394(6)
2.433(6)
Ag(1)-N(2)#1
Ag(1)-N(1)#3
2.263(4)
2.433(6)
Table 8. Interatomic Distances (Å) and Bond Angles (deg) for 6a
Ag(1)-N(4)#2
N(1)-Ag(1)#4
Ag(1)-N(3)#1
Ag(2)-N(4)#2
Ag(2)-C(17)
2.193(7)
2.303(7)
2.562(8)
Ag(1)-N(2)
Ag(2)-N(1)
Ag(2)-C(18)
2.280(6)
2.348(6)
2.646(9)
N(3)-Ag(1)-N(2)#1
N(2)#1-Ag(1)-N(4)#2 100.42(17) N(3)-Ag(1)-N(1)#3
N(2)#1-Ag(1)-N(1)#3 120.71(19) N(4)#2-Ag(1)-N(1)#3 88.6(2)
N(3)-N(2)-Ag(1)#1 117.7(3) N(2)-N(3)-Ag(1) 118.4(3)
123.85(15) N(3)-Ag(1)-N(4)#2
119.84(18)
99.12(18)
N(3)#1-Ag(1)-N(2)
N(4)#2-Ag(2)-C(17)
N(4)#2-Ag(2)-C(18)
C(17)-Ag(2)-C(18)
146.0(2)
106.6(3)
102.9(3)
30.3(3)
N(4)#2-Ag(2)-N(1)
N(1)-Ag(2)-C(17)
N(1)-Ag(2)-C(18)
N(1)-N(2)-Ag(1)
119.5(3)
98.2(3)
123.3(3)
117.8(4)
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 1, -y + 1, -z + 1; #2 -x + 1, -y, -z + 1; #3 x - 1, y - 1, z; #4 x
+ 1, y + 1, z; #5 -x + 2, -y + 1, -z + 1.
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 1/2, y + 1/2, -z + 3/2; #2 -x + 1/2, y - 1/2, -z + 3/2.
ligands. Their structures have been fully characterized by
infrared spectroscopy, elemental analysis, and 1H NMR. The
solid molecular structure of L7 was determined using single-
crystal X-ray diffraction to further confirm the structure of
the new ligands. As shown in Figure 1, the ligand is a bent
shape, which is similar to the shape of the known organic
ligands L1-L6. Two terminal benzonitrile groups and the
bridging oxadiazole moiety lie in the same plane and are
linked together at the para position by the five-membered
oxadiazole ring. The separation between the two terminal N
donors is 14.76 Å, which is longer than the corresponding
distances found in L1 (10.21 Å) and L3 (12.21 Å). L7 and
L8 are soluble in common polar organic solvents, such as
CH2Cl2, CHCl3, THF, CH3OH, and C2H5OH, which facili-
tates the solution reaction between the ligands and inorganic
metal salts. In addition, they give us the ability to modify
L7 and L8 to new organic spacers with different coordination
functional groups by some functional group transformation
reactions related to -CN.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4683

Dong et al.
Table 9. Interatomic Distances (Å) and Bond Angles (deg) for 7a
within the normal range for a N-containing heterocyclic
Ag(I) complexes.9 Two Ag(1) atoms are bridged by four
Noxadiazole atoms into a {Ag2N4} dinuclear core with a short
Ag‚‚‚Ag contact of 3.45 Å, which is identical to the sum of
the van der Waals radii of two silver atoms (3.44 Å). In 1,
the ligand itself is not planar, and the three rings are slightly
twisted. The uncoordinated ClO4- counterion is located near
the Ag(I) center and hydrogen bonded to the coordinated
water molecule through an O-H‚‚‚O bonding interaction (dO‚
Ag(1)-N(4)
Ag(1)-O(9)
Ag(2)-N(2)#1
Ag(2)-O(2)
Ag(2)-Ag(2)#1
2.277(10)
2.371(8)
2.253(7)
2.407(12)
3.356(2)
Ag(1)-N(3)#1
Ag(1)-O(9)#2
Ag(2)-N(1)
2.284(10)
2.472(8)
2.265(7)
2.464(9)
Ag(2)-O(6)#3
N(4)-Ag(1)-N(3)#1
N(3)#1-Ag(1)-O(9)
109.2(4)
100.5(3)
N(4)-Ag(1)-O(9)
N(4)-Ag(1)-O(9)#2
O(9)-Ag(1)-O(9)#2
N(2)#1-Ag(2)-O(2)
141.2(3)
100.5(3)
76.8(3)
N(3)#1-Ag(1)-O(9)#2 130.8(3)
N(2)#1-Ag(2)-N(1)
N(1)-Ag(2)-O(2)
N(1)-Ag(2)-O(6)#3
N(2)#1-Ag(2)-Ag(2)#1 64.01(19) N(1)-Ag(2)-Ag(2)#1
O(2)-Ag(2)-Ag(2)#1 141.8(4)
128.5(3)
106.6(4)
105.5(3)
115.0(4)
N(2)#1-Ag(2)-O(6)#3 107.9(3)
O(2)-Ag(2)-O(6)#3
83.6(4)
64.60(19)
‚‚ ) 2.26(2) Å, dO‚‚‚O ) 2.942(11) Å, and O-H‚‚‚O )
H
140(3)°).
O(6)#3-Ag(2)-Ag(2)#1 134.4(3)
In the solid state, the {Ag2(L7)2} dinuclear moieties are
linked together in a hand-in-hand fashion through one of two
terminal benzonitrile groups on L7 to form a one-dimensional
chain (Figure 3). In addition, hydrogen-bonding interactions
are present in 1. The one-dimensional polymer chains of 1
are linked into a two-dimensional sheet containing a square-
like cavity via interchain hydrogen-bonding interactions. The
weak hydrogen bonding system involves N(4) of the
uncoordinated -CN group and H(4) on the L7 ligand of the
neighboring chain (Figure 3). The corresponding N‚‚‚H and
N‚‚‚C distances are 2.52(4) and 3.36(4) Å, respectively. The
uncoordinated guest water molecules are located in the
square-like cavities. The existence and structural importance
of the weak C-H‚‚‚X hydrogen bonding interactions are now
well-established11 and are observed in many compounds,
such as the N‚‚‚H-C interaction in 1,3,5-tricyanobenzene-
hexamethylbenzene.12 These hydrogen bonds, although weak,
contribute significantly to the alignment of the molecules of
1 in the crystalline state.
a Symmetry transformations used to generate equivalent atoms: #1 -x
+ 1, -y + 2, -z + 2; #2 -x + 2, -y + 1, -z + 1; #3 -x + 1, -y + 1,
-z + 1.
Figure 1. Molecular structure of L7.
Structural Analysis of {[Ag(L7)(H2O)]ClO4}n (1). Crys-
tallization of L7 with AgClO4 in a CH2Cl2/C6H6 mixed-
solvent system at room temperature produced the infinite
one-dimensional chain structure in a 54% yield. Single-
crystal analysis revealed that there is one kind of crystal-
lographic Ag(I) center in 1. Compound 1 is air stable, and
the TGA trace shows that the framework of 1 is stable up to
285 °C. As shown in Figure 2, it has a distorted tetrahedral
coordination sphere consisting of two Noxadiazole (dAg(1)-N(1)
) 2.320(4) Å and dAg(1)-N(2) ) 2.329(4) Å), one Nbenzonitrile
(dAg(1)-N(3) ) 2.261(4) Å) from three L7 ligands, and one O
donor (dAg(1)-O(6) ) 2.458(5) Å) from a coordinated water
molecule. It is worthwhile to point out that only one terminal
-CN group on L7 involves the Ag(I) coordination sphere.
Thus, ligand L7 acts as a tridentate ligand toward the Ag(I)
ion herein. All of the Ag-N bond distances found in 1 are
Structural Analysis of {[Ag(L7)]SO3CF3}n (2). The more
strongly coordinated SO3CF3- anion was used instead of the
-
more weakly coordinated ClO4 anion to investigate the
effect of the counterion on the long range order of the
Ag(1)-L7 coordination polymer. Crystallization of L7 with
AgClO4 in a CH2Cl2/C6H6 mixed-solvent system at room
temperature produced the infinite noninterpenetrating three-
dimensional polymeric compound 2 in a 63% yield. Com-
pound 2 is air stable, and TGA shows that compound 2 is
stable up to 275 °C. As shown in Figure 4, there is one kind
Figure 2. ORTEP figure of 1 showing the atom labeling and 50% thermal ellipsoids.
4684 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
coordination sites to bind the Ag(1) atom). Although different
metal-to-ligand ratios were tried, compounds 1 and 2 were
the only products isolated. different templating effects and
coordination behaviors from the counterions might explain
why compounds 1 and 2 pass from a one-dimensional chain
to a three-dimensional framework.
Structural Analysis of {[Ag(L8)]BF4‚0.5(C6H6)‚H2O}n
(3). The reason that ligand L8 was used was to control the
supramolecular motifs through 3,3′-bibenzonitrile-type ligands.
It is well-known that the relative orientations of the nitrogen
donors and the different bridging space may result in unusual
building blocks, which can lead to the construction of
supramolecular motifs that have not been achieved using
normal rigid linear organic ligands. Our previous studies
demonstrated that the five-membered 1,3,4-oxadiazole-
bridged 3,3′-bipyridine and 3,3′-biphenylamine ligands could
bind metal ions with a cis or trans conformation and result
in a versatile framework topology, sometimes even affecting
the formation of the polymer versus the molecule.9
Figure 3. (a) One-dimensional chain and (b) two-dimensional H-bonded
network in 1 (One set of the hydrogen bonds is labeled). Ag(I)‚‚‚Ag(I)
interactions and hydrogen bonds are shown as dotted lines.
The L8 ligand reacted with AgBF4 in CH2Cl2/C6H6 at
room temperature to produce the polymeric compound 3 as
pink crystals with a novel noninterpenetrating three-
dimensional network in a 62% yield. Thermogravimetric
analysis shows that the benzene guest molecules are lost at
170-190 °C and that the framework is stable up to ∼270
°C. As shown in Figure 6, the Ag(I) center lies in a distorted
of crystallographic Ag(1) center in 2. It adopts a distorted
tetrahedral coordination sphere that consists of one Otriflate
two Noxadiazole, and one Nbenzonitrile from three tridentate L7
ligands. The corresponding Ag(I)-Otriflate, Ag(I)-Noxadiazole
,
,
and Ag(I)-Nbenzonitrile bonding distances are 2.523(6),
2.333(5), 2.380(6), and 2.319(5) Å, respectively. The Ag(I)
and L7 connectivity has -Ag-N-N-Ag-N-N- group-
ings, which are the same as those observed in compound 1.
The Ag‚‚‚Ag distance (3.44 Å) is the same as the sum of
the van der Waals radii of two silver atoms. The Ag2(L7)2
unit is introduced into a two-dimensional net instead of one-
dimensional chain, which is different from 1. This two-
dimensional net is undulating and exhibits a Chinese
tetrahedral coordination sphere which consists of two Noxa
-
diazole and two Nbenzonitrile donors from four L8 ligands. The
Ag-Nbenzonitrile and Ag-Noxadiazole bond distances range from
2.394(6) to 2.433(6) Å and from 2.256(4) to 2.263(4) Å,
respectively. It is worth pointing out that the coordination
behavior of L8 is different from that of L7 in 1 and 2. The
ligand L8 herein acts as a tetradentate spacer instead of a
tridentate spacer toward the Ag(1) ion. An {Ag2N4} six-
membered ring the same as that found in compounds 1 and
2 has been found in 3. The corresponding Ag‚‚‚Ag contact
is 3.52(4) Å, which is slightly longer that those of 1 and 2.
Four {Ag2N4} units are connected by tetradentate L8 ligands
to form a molecular cage in which a guest benzene molecule
is located and fixed by the π-π interactions between
-
housetop fashion (Figure 5). Coordinated SO3CF3 coun-
terions are located between the layers and, furthermore, link
the two-dimensional layers into a three-dimensional network
through somewhat long Ag(I)-Otriflate bonds (Figure 5).
The common feature of compounds 1 and 2 is the
possession of a {Ag2(L7)2} molecular sub-building block.
In compounds 1 and 2, L7 exhibits similar coordination
behavior (i.e., uses only one of the two terminal -CN
Figure 4. ORTEP figure of 2 showing the atom labeling and 50% thermal ellipsoids.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4685

Dong et al.
the one of the most common motifs in nature,14 synthetic
noninterpenetrating networks with honeycomb-like cross
sections are still unusual because two-dimensional nets are
always inclined to stack in an -ABAB- or -ABCABC-
stacking sequence, such as the stacking fashion observed in
compound [Ag(TCB)(CF3SO3)] (TCB ) 1, 3,5-tricyano-
benzene);14b,15 therefore, the assembly of honeycomb-like
channels is challenging.
Structural Analysis of {[Ag(L8)SbF6]‚H2O}n (4). Crys-
tallization of L8 with AgSbF6 in the same mixed-solvent
system at room temperature produced polymeric compound
4 as colorless crystals with a novel noninterpenetrating two-
dimensional network in a 49% yield. TGA shows that the
framework of 4 is stable up to ∼280 °C. Single-crystal X-ray
analysis shows that the local coordination geometry of the
Ag(I) center in compound 4 is similar to that of compound
3. The Ag-N bond lengths lie in the range of 2.277(4)-
2.344(6) Å, which are comparable to the corresponding bond
distances in compound 3. The same {Ag2N4} connectivity
as that of compounds 1-3 has been found in 4 with an
Ag‚‚‚Ag contact of 3.65 Å. Single-crystal X-ray analysis
revealed that compounds 3 and 4 are isostructural; however,
for compounds 3-4, there is an interesting change in the
unit cell parameters upon the increase of the counterion size
-
from BF4- to SbF6 . The cell volume increases as expected,
but it does so in an anisotropic way. The shorter a axis
expands, while the long b and c axes contract. In the solid
state, compound 4 adopts the same noninterpenetrating two-
dimensional network as that found in compound 3. Honey-
comb-like channels contain distorted SbF6- counterions and
water molecules; however, no benzene solvent molecules
have been found. The corresponding channel dimensions are
almost identical with those in 3 (Figure 9).
Figure 5. (a) Single two-dimensional wavelike network, (b) triflate-Ag-
(I) linkage, and (c) three-dimensional framework in 2.
oxadiazole and benzene (Figure 7).13 The longest and shortest
Ag‚‚‚Ag distances in the cage are 7.5 and 16.5 Å. The
accessible void volume of the channels in one unit cell is
122.1 Å3, which is estimated to be 12.4% of the total volume
(982.5 Å3).
In the solid state, compound 3 exhibits a novel noninter-
penetrating cationic two-dimensional network which is
parallel to the crystallographic ab plane. The crystal packing
of 3 is shown in Figure 8. All of the two-dimensional nets
stack exactly together along the crystallographic c axis to
generate honeycomb-like channels. Inside the channels,
Structural Analysis of {[Ag2(L8)2(SO3CF3)]‚H2O}n (5).
The L8 ligand reacted with AgSO3CF3 in the same mixed-
solvent system at room temperature to produce the polymeric
compound 5 as red crystals with a noninterpenetrating two-
dimensional network in a 64% yield. TGA shows that the
guest water molecules were lost at 120-130 °C and that
the framework of 5 is stable up to ∼300 °C. The X-ray
structure of 5 shows that there are two independent crystal-
lographic Ag(I) centers in 5 and both lie in a distorted
tetrahedral coordination sphere which is similar to that of
-
uncoordinated BF4 counterions, water, and benzene mol-
ecules stack neatly upon each other to form a guest column
(Figure 8). In the column, the distance between two adjacent
benzene planes is 13.67 Å. Although the hexagon represents
Figure 6. ORTEP figure of 3 showing the atom labeling and 50% thermal ellipsoids.
4686 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
Figure 7. (a) Side and (b) top views of the molecular cage containing the
benzene molecule. The benzene guest molecule is marked in yellow.
compound 3. This distorted tetrahedral coordination environ-
ment consists of two Noxadiazole and two Nbenzonitrile donors from
four L8 ligands. The Ag-N bond lengths lie in the range of
2.240-2.447 Å, which are comparable to those of the
corresponding bonds found in 4. The same {Ag2N4} con-
nectivity as that in compounds 1-4 has been found in 5 with
an Ag‚‚‚Ag distance of 3.61 Å. Here, the ligand again acts
as a tetradentate spacer toward these two independent Ag(I)
ions. In the solid state, Ag(I) atoms are linked to each other
by L8 ligands via the {Ag2N4} moiety into a noninterpen-
etrating honeycomb-like net, which is similar to that found
in 3 and 4. It is worthy to point out that the two-dimensional
layers repeat in an -ABAB- stacking sequence instead of
the stacking fashion observed in 3 and 4. This difference
may be caused by the different templating effect of the
-
Figure 8. (a) Two sets of two-dimensional nets (view down the
crystallographic a axis), (b) a view of 3 perpendicular to the channels, and
(c) the packing diagram of the triflate anions, benzene, and water guest
molecules in 3 (view down the crystallographic [110] direction).
SO3CF3 counterion (Figure 10). In the single cage, the
shortest and longest Ag‚‚‚Ag distances are 8.61 and 15.82
Å, respectively.
Structural Analysis of {[Ag2(L8)(C6H6)(ClO4)]‚ClO4}n
(6). Compound 6 was obtained as colorless crystals by
combination of the L8 ligand with AgClO4 in a CH2Cl2/
C6H6 mixed-solvent system at room temperature in a 60%
yield. The framework of 6 is stable up to ∼260 °C. The
X-ray structure of 6 shows that there are two independent
Ag(I) centers present the asymmetric unit (Figure 11). The
first kind of Ag(1) atom is coordinated by one Nbenzonitrile
(Ag(1)-N(3)#1 ) 2.193(7) Å) and one Noxadiazole (Ag(1)-
N(2) ) 2.280(6) Å) donors from two L8 ligands and one O
-
donor (O(6)) from one ClO4 anion in the equatorial plane
with the other two perchlorate O donors (Ag(1)-O(3) )
2.694(6) Å and Ag(1)-O(5) ) 2.825(6) Å) in the axial
positions, thus forming the distorted trigonal bipyramidal
geometry of {AgN2O3}. The second Ag(2) center lies in a
{AgN2O2π} coordination environment which is composed
of two N donors from the benzonitrile (Ag(2)-N(4)#2 )
2.303(7) Å) and oxadiazole (Ag(2)-N(1) ) 2.348(6) Å)
moieties of two individual L8 ligands, two weakly coordi-
(11) Desiraju, G. R. Acc. Chem. Res. 1996, 29, 441.
(12) Reddy, D. S.; Goud, B. S.; Panneerselvam, K.; Desiraju, G. R. J. Chem.
Soc. Commun. 1993, 663.
(13) Chen, C.-L.; Su, C.-Y.; Cai, Y.-P.; Zhang, H.-X.; Xu, A.-W.; Kang,
B.-S.; zur Loye, H.-C. Inorg. Chem. 2003, 42, 3738.
(14) Choi, H. J.; Suh, M. P. J. Am. Chem. Soc. 1998, 120, 10622. (b)
Gardner, G. B.; Venkataraman, D.; Moore, J. S.; Lee, S. Nature 1995,
374, 792. (c) Abrahams, B. F.; Hoskins, B. F.; Liu, J.; Robson, R. J.
Am. Chem. Soc. 1991, 113, 3045. (d) Abrahams, B. F.; Hoskins, B.
F.; Robson, R. J. Chem. Soc., Chem. Commun. 1990, 60.
(15) Pshirer, N. G.; Ciurtin, D. M.; Smith, M. D.; Bunz, U. H. F.; zur
Loye, H.-C. Angew. Chem., Int. Ed. 2002, 41, 583.
-
nated O donors from a bidentate ClO4 counterion with
somewhat long Ag-O distances at 2.819(6) and 2.795(6)
Å, respectively, and a π donor from a coordinated benzene
solvent molecule. The Ag(2)-C(17) and Ag(2)-C(18) bond
Inorganic Chemistry, Vol. 44, No. 13, 2005 4687

Dong et al.
In the solid state, Ag(1) and Ag(2) atoms are linked
together by the tetradentate L8 ligands into a undulating one-
dimensional chain extended along the crystallographic b axis
(Figure 12). It is worth pointing out that compound 6 contains
the {Ag2N2O} moiety instead of the {Ag2N4} cluster core
that is commonly observed in oxadiazole-bridging
ligands-Ag(I) coordination polymers. The corresponding
Ag(1)‚‚‚Ag(2) distance in the {Ag2N2O} moiety contact is
3.66 Å, which is slightly longer that those of 1-5. As shown
in Figure 13, these one-dimensional chains are connected to
each other by {AgClO4} linkages along the crystallographic
a axis to form a two-dimensional porous network, in which
coordinated benzene molecules are located. Thermogravi-
metric analysis indicates that these coordinated benzene
molecules are lost in the temperature range of 140-180 °C.
Structural Analysis of {[Ag2(L8)(H2PO4)2]}n (7). The
more strongly coordinating H2PO4- anion was used instead
of the weakly coordinating counterions to investigate the
effect of the counterion on the long range order of the Ag-
(I)-L8 coordination polymer. Compound 7 was synthesized
by the combination of L8 and AgH2PO4 in a CH2Cl2/C6H6
mixed-solvent system which produced red crystals in a 34%
yield. An ORTEP drawing of 7 with the atom numbering
scheme is shown in Figure 14. There are two different
Ag(I) centers in 7. They reside in a distorted tetrahedral
coordination sphere. For Ag(1), its coordination environment
consists of two Nbenzonitrile from two L8 ligands and two O
Figure 9. (a) Molecular cage and (b) two-dimensional net in 4. No benzene
guest molecules are found in the honeycomb-like channels.
-
donors from two H2PO4 anions. The Ag(1)-N distances
are 2.277(10) and 2.284(10) Å, while the Ag(1)-O distances
are 2.371(8) and 2.472(8) Å. The Ag(2) center is connected
-
to two Noxadiazole donors and two O donors from two H2PO4 .
The Ag(2)-N bond lengths are 2.265(7) and 2.253(7) Å,
while the Ag(2)-O bond lengths are 2.407(12) and
2.464(9) Å. As shown in Figure 15, two L8 ligands arrange
in a face-to-face fashion to coordinate four Ag(I) ions from
opposite directions, generating a tetranuclear {Ag4(L8)2}
plane, in which the shortest and longest Ag(I)‚‚‚Ag(I)
distances are 3.356(2) and 15.82(2) Å. Two tetranuclear
-
planes are further linked by bidentate coordinated H2PO4
counterions through two Ag(1)-H2PO4-Ag(2) linkages into
a cagelike sub-building block which is filled with two
-
monodentrate H2PO4 anions. These cagelike sub-building
blocks are bound together by four {Ag2O2} fragments into
a novel two-dimensional net extended in the crystallographic
ac plane (Figure 16). In the net, all of the {Ag4(L8)2} planes
are exactly parallel and vertical to the two-dimensional net.
Ligand L8 adopts a trans conformation to bind Ag(I)
centers in compounds 3-7, which is different than the
coordination behavior of its analogues L2, L4, and L6. Our
previous study shows that L2, L4, and L6 could adopt either
a cis or trans conformation to link the metal atoms into
coordination polymers or suporamolecular complexes.9 For
example, the combination of L2 with M(II) (M ) Cu and
Zn) in a CH3CN/CH2Cl2 solution generated the dimeric
macrocycles [Zn(cis-L2)(H2O)3(NO3)]2(NO3)2 and {[Cu(cis-
L2)(CH3CN)(NO3)]2. Compounds 1-7 are insoluble in
common organic solvents because of their polymeric nature.
They are soluble in CH3CN and slightly soluble in DMSO
Figure 10. (a) Two-dimensional net in 5 stacking together in an -ABAB-
fashion and (b) the packing diagram of the triflate anions in 5.
distances are 2.562(8) and 2.646(9) Å, respectively, while
the remaining Ag-C contact distances are greater than 2.80
Å, which is beyond the limits (2.47-2.80 Å) commonly
observed in Ag(I)-aromatic complexes.16
(16) Griffith, E. A. H.; Amma, E. L. J. Am. Chem. Soc. 1974, 96, 5407.
(b) Rodesiler, P. F.; Amma, E. L. Inorg. Chem. 1972, 11, 388.
4688 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
Figure 11. Ag(1) and Ag(2) coordination environments in 6 with 50% probability displacement ellipsoids.
Figure 12. The undulating one-dimensional chain in 6.
types of electroluminescent materials, especially for d10 or
d10-d10 systems18 and oxadiazole-containing complexes.19
We have been exploring the luminescent properties of L1-
L6 and organic-inorganic coordination polymers and su-
pramolecular complexes in the solid state. The results
indicate that the emission colors of organic spacers L1-L6
were affected by their incorporation into metal-containing
coordination compounds. The luminescent properties of L7
and L8 and polymeric compounds 1-6 were investigated
in CH3CN and the solid state. The fluorescence spectra of
L7 and L8 and 1-6 are summarized in Table 10. As
indicated in Figure 17, in CH3CN, L7 and L8 each present
two maxima at 350 and 364 nm for L7 and 342 and 347 nm
for L8. In the solid state, L7 and L8 each exhibit one
emission maximum at 385 and 399 nm, respectively. In the
solid state, the emission colors of the free ligands were
slightly affected by their incorporation into the Ag-containing
polymeric compounds 1-6, as evidenced by the small shift
in the emission. We thus believe that the luminescence of
1-6 originate from ligand-centered n-π* or π-π* process.18g
In CH3CN, almost no difference has been found between
ligand and the complex’s emission colors. This implies that
the polymeric complexes disaggregate into oligomers or
starting materials in acetonitrile.
Figure 13. (a) {AgClO4} linkage in 6 and (b) the two-dimensional
framework containing coordinated benzene molecules marked in yellow.
and DMF. In CH3CN, all complexes were dissolved to
dissociate into oligomers or the starting materials, which were
identified by the UV-vis spectra (Experimental Section).
Luminescent Properties of L7 and L8 and 1-6.
Inorganic-organic hybrid coordination polymers have been
investigated for fluorescence properties and for potential
applications as luminescent materials, such as light-emitting
diodes (LEDs).17 Because of the higher thermal stability of
inorganic-organic coordination polymers and the ability to
affect the emission wavelength of organic materials, syn-
theses of inorganic-organic coordination polymers by the
judicious choice of conjugated organic spacers and transition
metal centers can be an efficient method for obtaining new
(18) Harvey, P. D.; Gray, H. B. J. Am. Chem. Soc. 1988, 110, 2145. (b)
Catalano, V. J.; Kar, H. M.; Bennett, B. L. Inorg. Chem. 2000, 39,
121. (c) Tong, M.-L.; Chen, X.-M.; Ye, B.-H.; Ji, L.-N. Angew. Chem.,
Int. Ed. 1999, 38, 2237. (d) Burini, A.; Bravi, R.; Fackler, J. P., Jr.;
Galassi, R.; Grant, T. A.; Omary, M. A.; Pietroni, B. R.; Staples, R.
J. Inorg. Chem. 2000, 39, 3158. (e) Seward, C.; Jia, W.-L.; Wang,
R.-Y.; Enright, G. D.; Wang, S.-N. Angew. Chem., Int. Ed. 2004, 43,
2933. (f) Yam, V. W.-W.; Lo, K. K.-W. Chem. Soc. ReV. 1999, 28,
323. (g) Wu, C.-D.; Ngo, H. L.; Lin, W. Chem. Commun. 2004, 1588.
(19) Hu, N.-X.; Esteghamatian, M.; Xie, S.; Popovic, Z.; Hor, A.-M.; Ong,
B.; Wang, S.-N. AdV. Mater. 1999, 11, 1460. (b) de Silva, A. S.; de
Silva, M. A. A.; Carvalho, C. E. M.; Antunes, O. A. C.; Herrera, J.
O. M.; Brinn, I. M.; Mangrich, A. S. Inorg. Chim. Acta 1999, 292, 1.
(c) Wang, J.; Wang, R.; Yang, J.; Zheng, Z.; Carducci, M. D.; Cayou,
T.; Peyghambarian, N.; Jabbour, G. E. J. Am. Chem. Soc. 2001, 123,
6179.
(17) Ciurtin, D. M.; Pschirer, N. G.; Smith, M. D.; Bunz, U. H. F.; zur
Loye, H.-C. Chem. Mater. 2001, 13, 2743. (b) Cariati, E.; Bu, X.;
Ford, P. C. Chem. Mater. 2000, 12, 3385. (c) Wu¨rthner, F.; Sautter,
A. Chem. Commun. 2000, 445.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4689

Dong et al.
Figure 14. Ag(I) coordination environments in 7. Displacement ellipsoids drawn at the 50% probability level.
Table 10. Luminescent Properties of L7 and L8 and 1-6 in the Solid
State and CH3CN
solid state
CH3CN
solid state
CH3CN
(λex/λem
)
(λex/λem
)
(λex/λem
)
(λex/λem)
L7
L8
1
224/399
208/385
204/386
210/393
296/350, 364
297/342, 347
299/348, 363
297/349, 364
3
4
5
6
204/383
206/373
204/375
295/330, 345
298/345
284/332, 346
296/347
-
Figure 15. {Ag4(L8)2} planar moiety linked by H2PO4 into cagelike
sub-building block.
2
206/378, 388
of the included guest molecule, often undergo phase transi-
tions to other more dense structures.21 Primary guest sorption
experiments were performed on 3 with benzene to explore
the reversible adsorption and readsorption of 3 in solution.
The experimental results show that 3 exhibits a clear affinity
for the benzene molecule and can reversibly desorb and
reabsorb this guest molecule at room temperature. The
desolvated sample was prepared by heating the as-synthe-
1
sized crystals of 3. The H NMR spectra and TGA trace
show that all benzene guest molecules could be removed at
∼190 °C (Figure 18). The X-ray powder diffraction (XRD)
pattern of a thermally desolvated sample of 3 was compared
with that of an as-synthesized solvent-containing sample of
3 in Figure 19. The XRD pattern after heating shows that
the shapes and intensities of some reflections are slightly
changed relative to that of the original sample. This means
that guest loss does not result in symmetry change or cavity
volume collapse. When the desolvated solids are immersed
in benzene for 24 h at room temperature, an XRD pattern
nearly identical to that obtained for the original crystals is
regenerated indicating that the benzene molecules were re-
Figure 16. Perspective view of two-dimensional layer in 7.
Host-Guest Chemistry of Compound 3. The most
important factor in seeking and developing new molecular-
based porous materials is that the frameworks of such
materials are stable even after removal of the guest mol-
ecules.20 As we know, many porous systems, upon removal
Figure 17. Photoinduced ex- and emission spectra of L7 (left) and L8 (right) in CH3CN.
4690 Inorganic Chemistry, Vol. 44, No. 13, 2005

New Bent Bis(cyanophenyl)oxadiazole Ligands
Figure 19. X-ray powder diffraction patterns of 3. (a) The original crystals
of 3, (b) 3 heated to 190 °C and (c) sample obtained by immersing (b) in
benzene for 24 h at room temperature and then dried at room temperature
for 2 days.
Table 11. Electrical Conductivity of Compounds 1-6
L
(µm)
G
(ns)
B
r
Fa
ꢀrb
(µs) (×10-5 Ω-1 cm-1
)
(×102 Ω m) (×102)
1
2
3
4
5
6
26.33 170.76 6.03
128.01 128.21 5.74
2.87
10.47
1.39
6.79
3.92
5.04
3.48
0.955
7.19
1.47
2.55
1.98
3.64
16.83
7.17
8.42
18.30
6.66
54.41
61.02 174.43 6.02
150.08 40.94 5.33
47.01 168.03 6.19
40.01 5.76
a Resistivity (F) of 1-6 was obtained depending on the formula S/LG
(S ) πr2, L ) length of the single crystals). b Dielectric constant (ꢀr) of
1-6 was obtained depending on the formula BL/2πfs.
possibility of a dissolution-recrystallization mechanism to
explain the solvent reabsorption is unlikely.
Electrical Conductivity. Synthesis of single-component
molecular coordination complexes by the judicious choice
of organic spacers and metal centers can be an efficient
method for obtaining new types of conductive materials,22
for example, [M(dimt)2]2-type molecular complexes (M )
Ni(II), Pd(II), Pt(II), Cu(II), and so on; dimt ) 4,5-
dimercapto-1,3-dithiole-2-thione).23 Some of these complexes
have been confirmed to be semiconductors or superconduc-
tors. Up to now, a number of molecular-based transition
metal complexes with interesting electrical conductivity have
been reported. However, the study of conductive properties
on polymeric coordination complexes has received consider-
ably less attention. The electrical conductive experiments
were performed on compounds 1-6 in the solid state to
explore the electrical conductive properties of these new
polymeric complexes. The conductivity measurements of
1-6 were performed on single crystals at a direction on bc
plane using an Agilent Technologies instrument (4294A-
ATO-20150) with a scan range of 5(0.1) MHz. The primary
result indicates that compounds 1-6 behave as typical
semiconductors with a resistivity (F) value lying in the range
of 9.55 × 10-7.19 × 102 Ωm (Table 11). The dielectric
Figure 18. 1H NMR spectra of 3 in DMSO-d6. (a) 1H NMR spectrum of
original sample of 3 recorded at room temperature. (b) The solid sample of
3 was heated to 120 °C, then dissolved in DMSO-d6, and the spectrum was
recorded at ambient temperature. (c) The solid sample of 3 was heated to
180 °C, then dissolved in DMSO-d6, and the spectrum was recorded at
ambient temperature. (d) The solid sample of 3 was heated to 190 °C, then
dissolved in DMSO-d6, and the spectrum was recorded at ambient
temperature. (e) Complex 3 immersed in benzene for 24 h and then dried
at room temperature for 2 days. (f) TGA trace of compound 3.
incorporated into the framework under these mild conditions.
After the sample was taken out of the benzene, it was dried
at room temperature for 48 h before recording the 1H NMR.
1
The H NMR confirmed the re-uptake of benzene to the
extent of 93%. Because 3 is insoluble in benzene, the
(20) Gardner, G. B.; Kiang, Y.-H.; Lee, S.; Asgaonkar, A.; Venkataraman,
D. J. Am. Chem. Soc. 1996, 118, 6946. (b) Kepert, C. J.; Prior, T. J.;
Rosseinsky, M. J. J. Am. Chem. Soc. 2000, 122, 5158. (c) Su, C.-Y.;
Smith, M. D.; zur Loye, H.-C. Angew. Chem., Int. Ed. 2003, 42, 4085.
(21) Abrahams, B. F.; Hoskins, B. F.; Michail, D. M.; Robson, R. Nature
1994, 369, 727. (b) Wang, X.; Smard, M.; Wuest, J. D. J. Am. Chem.
Soc. 1994, 116, 12119. (c) Venkataraman, D.; Lee, S.; Zhang, J.;
Moore, J. S. Nature 1994, 371, 591. (d) Hoskins, B. F.; Robson, R. J.
Am. Chem. Soc. 1990, 112, 1546.
(22) Kobayashi, A.; Tanaka, H.; Kobayashi, H. J. Mater. Chem. 2001, 11,
2078. (b) Zheng, S.-L.; Zhang, J.-P.; Wang, W.-T.; Chen, X.-M. J.
Am. Chem. Soc. 2003, 125, 6882.
(23) Bousseau, M.; Valade, L.; Legros, J.-P.; Cassoux, P.; Garbauskas, M.;
Interrante, V. J. Am. Chem. Soc. 1986, 108, 1908.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4691

Dong et al.
constants (ꢀr) of 1-6 were obtained in the range of 3.64 ×
102-18.30 × 102.
preparing new symmetric and unsymmetric oxadiazole-
containing ligands of this type containing different coordina-
tion functional groups and having different orientations of
the terminal coordination sites. We anticipate that this new
type of organic ligand will result in a variety of new
coordination polymers with novel polymeric patterns and
interesting chemical and physical properties.
Conclusions
This study demonstrates that the bent oxadiazole-bridging
benzonitrile organic ligands, 2,5-bis(4-cyanophenyl)-1,3,4-
oxadiazole (L7) and 2,5-bis(3-cyanophenyl)-1,3,4-oxadiazole
(L8), are capable of coordinating metal centers with both
Npyridyl and Ntriazole donors generating novel coordination
polymers. Seven new polymeric compounds, 1-7, were
synthesized from solution reactions of L7 and L8 with
various Ag(I) salts. The relative orientation of the nitrogen
donors on the cyanophenyl groups and the five-membered
oxadiazole spacing in L7 and L8 resulted in unusual building
blocks leading to the construction of polymeric motifs, which
have not been obtained using normal linear rigid bidentate
organic ligands. We are currently extending this research by
Acknowledgment. We are grateful for financial support
from the National Natural Science Foundation of China
(20371030 and 20174023), and the Shangdong Natural
Science Foundation (Z2004B01).
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
IC050218S
4692 Inorganic Chemistry, Vol. 44, No. 13, 2005