Three-dimensional metal azide coordination polymers with amino carboxylate coligands: Synthesis, structure, and magnetic properties

Article abstract of DOI:10.1021/ic802026n

The reaction of M(II) ions with azido ligands in the presence of different amino carboxylic acids gave four three-dimensional metal-azido coordination polymers, [Mn(3,5-daba)(N₃)]_n (1), [Cd(3,5-daba)(N ₃)]_n (2;

Full text of DOI:10.1021/ic802026n

4674 Inorg. Chem. 2009, 48,
DOI:10.1021/ic802026n
Three-Dimensional Metal Azide Coordination Polymers with Amino Carboxylate
Coligands: Synthesis, Structure, and Magnetic Properties
Zi-Lu Chen,† Chun-Fang Jiang,† Wei-Hong Yan,† Fu-Pei Liang,*,† and Stuart R. Batten‡
†School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin 541004,
China and ‡School of Chemistry, Monash University, Victoria 3800, Australia
Received October 22, 2008
The reaction of M(II) ions with azido ligands in the presence of different amino carboxylic acids gave four three-
dimensional metal-azido coordination polymers, [Mn(3,5-daba)(N3)]n (1), [Cd(3,5-daba)(N3)]n (2; 3,5-daba = 3,
5-diaminobenzoate), [Mn(4-aba)(N3)]n (3; 4-aba = 4-aminobenzoate), and [Cu2(gly)2(N3)2]n (4; gly = glycinate), which
::
display different topological structures. Polymers 1 and 2 present 4,6-connected 3D networks with different Schlafli
::
symbols. However, 3 and 4 feature an unprecedented trinodal 3,6-connected network with the Schlafli symbol (42.6)
(4.62)(43.66.86) and an unusual 4-connected 3D net with the Lonsdaleite (hexagonal diamond) topology, respectively.
Magnetic susceptibility measurements revealed dominant antiferromagnetic couplings for 1 and 3 and an overall
dominant ferromagnetic coupling for 4, which presents metamagnetic behavior with a magnetic phase transition at a
critical temperature of 6 K and a transition field of ca. 6030 Oe. The results demonstrate that the EE azido and syn-anti
carboxylato bridges in our cases induce an antiferomagnetic interaction, and the anti-anti carboxylato bridge in
4 mediates a ferromagnetic interaction. The magnetic interaction through the EO azido bridge in 3 and 4 has
a dependence on the value of the M-N-M bond angle.
Introduction
via the azido bridge are found to be affected by the linking
modes of the azido ligand. In general, the exchange is
ferromagnetic for the EO mode and antiferromagnetic for
the EE mode.3-5 Other interesting magnetic phenomena
The syntheses and properties of metal-azido complexes
have attracted great research interest for many years due to
their fascinating structural diversities, their importance in
understanding magneto-structural correlations, and their
promising potential applications in functional materials.1 A
variety of metal-azido complexes with discrete or one-, two-,
and three-dimensional structures have been reported, in
which the azido ligand exhibits various coordination modes
ranging from μ-1,1 (end-on, EO) and μ-1,3 (end-to-end, EE)
to μ-1,1,1, μ-1,1,3, μ-1,1,1,1, μ-1,1,3,3, and μ-1,1,1,3,3,3,
depending on the steric and electronic demands of the
coligands.2 The magnetic coupling interactions mediated
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yahoo.com. Tel.: +86(0)773/5845973. Fax: +86(0)773/5832294.
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pubs.acs.org/IC
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Article
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have also been observed in systems with mixed azide bridging
modes.6
simultaneous bridges in metal-azido systems is attractive
since the carboxylates are well-established ligands in the
field of molecular magnetism because of their versatile
bridging modes,15 and such systems featuring mixed azido
and carboxylate bridges are good materials for studying the
mechanism of magnetic exchange interaction mediated by
different superexchange pathways.16 Amino carboxylic acid
ligands feature multiple coordination sites that combine the
characteristics of amine and carboxylic groups and are able
to exhibit different coordination modes depending on the
natureof thereaction system. Therefore, new supramolecular
frameworks might be expected for metal-azido complexes
with amino carboxylic acid coligands. However, as far as
we know, only two diamagnetic Zn(II) and Cd(II) azido
complexes with 4-aminobenzoic acid as a bridging coligand
have been reported,17 while high-dimensional paramagnetic
coordination polymers with both amino carboxylate and
azido bridges have not been reported. Some attempts were
made via the reaction of manganese with amino carboxylic
acid in the presence of NaN3; however, these just led to
the formation of amino carboxylate complexes without azido
ligands present in the final product.18 Herein, we wish to
report the syntheses and structures of four three-dimensional
metal-azido coordination polymers with different amino
carboxylic acids as second bridging ligands, [Mn (3,5-
daba)(N3)]n (1), [Cd(3,5-daba)(N3)]n (2; 3,5-daba = 3,5-
diaminobenzoate), [Mn(4-aba)(N3)]n (3; 4-aba = 4-amino-
benzoate), and [Cu2(gly)2(N3)2]n (4; gly = glycinate), and the
magnetic properties of 1, 3, and 4. Polymer 4 is the first
example of a coordination polymer with a flexible amino acid
as a second bridging ligand in metal-azido complexes, and
3 displays an interesting 3,6-connected topology that has not
been reported previously.
In the field of metal-azido chemistry, the construction
of high-dimensional networks of azido-bridged complexes is
of particular interest because of their novel topology and
potential enhancement of bulk magnetic properties.7 The
common strategies for this purpose reported in the literature
include the further extension of metal-azido assemblies
by introducing a second bridging ligand8 or the use of more
azido ligands by adding a countercation, such as Cs+ or
N(CH3)4+,9 or by employing chelating diamine ligands, such
as ethylenediamine and its derivatives,10 to alter the network
topology. When secondary bridging ligands are used in
constructing high-dimensional metal-azido systems, neutral
organic ligands have been the most popular, while the
use of bridging anionic ligands is relatively rare. Incorpora-
tion of bridging anionic ligands into metal-azido systems is
still a challenge due to the competition of the negative
charged ligand with azide in the self-assembly process.11,12
Recently, several high-dimensional complexes containing
mixed azide and carboxylate bridges have been successfully
synthesized.13,14 The utilization of carboxylate ligands as
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Experimental Section
Materials and General Methods. All chemicals were used
as obtained without further purification. Infrared spectra were
recorded as KBr pellets using a Nicolet 360 FT-IR spectrometer.
Elemental analyses (C, H, and N) were performed on a Vario EL
analyzer. All magnetic measurements including zero-field-
cooled and field-cooled magnetizations (ZFCM and FCM,
respectively), ac susceptibility measurements, and field-depen-
dent magnetization were carried out on a Quantum Design
MPMS-XL SQUID magnetometer. Data were corrected for
the diamagnetic contribution calculated from Pascal constants,
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Bu, X. H. Inorg. Chem. 2007, 46, 7698–7700. (d) Liu, F.-C.; Zeng, Y.-F.;
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Chen et al.
and the diamagnetism of the sample and sample holder were
taken into account.
in Table 1. The selected bond distances and angles for 1-4 are
listed in Table 2.
Caution! Azide complexes are potentially explosive. The ex-
periments were carried out in an isolated room, and experimenters
should be equipped with safeguards. Only a small amount of the
materials should be prepared and handled with great care.
Synthesis of [Mn(3,5-daba)(N3)]n (1). A mixture of 3,
Results and Discussion
Syntheses and Characterization. A few transition-
metal-azido coordination polymers with rigid carboxy-
late-bearing N-containing heterocycles as coligands have
been reported.13,14 Almost all of these compounds were
synthesized by solvothermal methods. Using the same
solvothermal technique, compounds 1-3 were success-
fully prepared in our case. Reaction of MnCl2 with NaN3
and 3,5-diaminobenzoic acid or 4-aminobenzoic acid in a
solvent mixture of ethanol and water in an autoclave at
393 K afforded 1 and 3, respectively, while the reaction of
CdCl2 with NaN3 and 3,5-diaminobenzoic acid under
hydrothermal conditions at a temperature of 373 K gave
rise to 2. The successful syntheses in our work, together
with those reported previously,13,14 indicate that the
solvothermal reactions are an effective way to obtain
azide-based coordination architectures with rigid carbox-
ylate coligands. However, due to the potentially explosive
nature of azide, the reactions must be carried out with
great care. Compound 4, which has a flexible amino
carboxylic acid coligand, was synthesized using a con-
ventional solution method. Reaction of Cu(NO3)2 and
NaN3 in the presence of glycine in H2O-C2H5OH at a pH
of about 6.4 led to the isolation of 4. It was found that
reactions starting from different cupric salts such as
Cu(NO3)2, CuCl2, and Cu(ClO4)2 gave the same synthetic
result, indicating that the anion of the metal salt does not
affect the formation of 4.
5-diaminobenzoic acid (0.0760 g, 0.5 mmol), MnCl2 4H2O
3
(0.0980 g, 0.5 mmol), NaN3 (0.0650 g, 1 mmol), EtOH (3 mL),
and H2O (1 mL) was sealed in a 25 mL Teflon-lined autoclave
and heated at 393 K for 6 days. Then, the autoclave was slowly
cooled to room temperature, giving brown block crystals of 1.
Yield: 38%. Anal. calcd for C7H7MnN5O2: C, 33.89; H, 2.84; N,
28.23. Found: C, 33.56; H, 2.58; N, 28.04%. IR (KBr, cm-1):
3442(w), 3347(m), 3285(m), 3159(w), 2110(vs), 2088(vs), 1576
(s), 1413(s), 1331(w), 1172(w), 1014(m), 975(m), 932(m), 881(m),
783(m), 760(m), 689(w), 537(w).
Synthesis of [Cd(3,5-daba)(N3)]n (2). A mixture of
3,5-diaminobenzoic acid (0.0760 g, 0.5 mmol), CdCl2 2.5H2O
3
(0.1140 g, 0.5 mmol), NaN3 (0.0650 g, 1 mmol), and H2O
(2 mL) was sealed in a 25 mL Teflon-lined autoclave and heated
at 373 K for 3 days. Then, the autoclave was cooled to room
temperature over a period of 24 h. Brown block crystals of
2 were obtained. Yield: 52%. Anal. calcd for C7H7CdN5O2: C,
27.51; H, 2.31; N, 22.92. Found: C, 27.27; H, 2.47; N, 22.63%. IR
(KBr, cm-1): 3337(m), 3313(m), 3262(m), 2042(vs), 1544(s), 1399(s),
1329(w), 1062(m), 969(m), 942(w), 795(m), 772(m), 681(w), 494(w).
Synthesis of [Mn(4-aba)(N3)]n (3). A mixture of 4-amino-
benzoic acid (0.0685 g, 0.5 mmol), MnCl2 4H2O (0.098 g,
3
0.5 mmol), NaN3 (0.0975 g, 1.5 mmol), ethanol (4 mL), and
water (0.5 mL) was placed in a 25-mL Teflon-lined autoclave
and heated at 393 K for 7 days. Then, it was cooled down slowly
to room temperature, giving brown needle crystals of 3 in a yield
of 40%. Anal. calcd for C7H6MnN4O2: C, 36.07; H, 2.59; N,
24.04. Found: C, 36.20; H, 2.47; N, 24.27%. IR (KBr, cm-1):
3412(w), 3336(m), 3265(m), 2078(s), 1608(s), 1551(s), 1516(s),
1398(s), 1241(w), 1179(w), 1099(w), 987(m), 966(m), 860(w),
852(w), 790(m), 703(w), 653(w), 621(m), 548(m).
The characteristic νas stretching vibrations of the
N3- ion in the IR spectra are observed at 2110 and 2088
cm-1 for 1 and 2042 cm-1 for 2, which confirm the EE
-
coordination mode of the N3 ion in 123 and the EO
Synthesis of [Cu2(gly)2(N3)2 ]n (4). A solution of NaN3
(0.0195 g, 0.3 mmol) in 2 mL of ethanol and 1 mL of water was
added slowly into a solution of Cu(NO3)2 3H2O (0.1449 g,
coordination mode of the N3 ion in 2.5 Complex 4
-
exhibits νas stretching vibrations at 2111 and 2056 cm-1
attributed to the EO coordination mode in 4, which is
similar to [Cu2(μ2-1,1-N3)2(NO3)(Me3NCH2CO2)2]n
with a Cu-N-Cu angle of 119.5(2)° and νas stretching
3
0.6 mmol) and gly (0.0450 g, 0.6 mmol) in 10 mL of water.
The pH value of the solution was adjusted to 6.4 by adding
0.1 mol L-1 NaOH. The resulted solution was stirred at room
3
vibrations at 2101 and 2081 cm .
-1 5,24 The strong absorp-
temperature for 2 h and then placed in a refrigerator to give
green crystals after two weeks in a yield of 58%. Anal. calcd for
C4H8Cu2N8O4: C, 13.37; H, 2.24; N, 31.19. Found: C, 13.65; H,
2.15; N, 31.30%. IR (KBr, cm-1): 3352(m), 3284(m), 2111(s),
2056(m), 1617(s), 1428(w), 1379(m), 1299(w), 1106(w), 1041(w),
915(w), 739(w), 594(w).
tion bands at 2078 cm-1 in the IR spectrum of 3 were
-
assigned to the νas stretching vibration of the N3 ion,
much broader than those of 1, 2, and 4, indicating a much
more complicated coordination mode of the N3- ion in 3.
This is consistent with the μ3-1,1,3- coordination mode in
3 revealed by the single-crystal X-ray diffraction analysis.
The strong absorption bands at 1517-1617 and 1379-
1413 cm-1 can be assigned to the antisymmetric stretch-
ing νas (COO-) and symmetric stretching νs (COO-)
vibrations, respectively, which is consistent with the
known complexes.25 The bands belonging to the amino
X-Ray Crystallography. The selected single crystals of 1-4
were put in a sealed tube, and the measurement was per-
formed on a Bruker Smart Apex-II CCD diffractometer using
˚
graphite-monochromated Mo KR radiation (λ = 0.71073 A).
Absorption correction was applied by using the multiscan
program SADABS.19 The structures were solved by direct
methods using SHELXS-9720 and refined by full-matrix least-
squares against F2 using the SHELXL-97 program21 or
groups occur in the range of 3450-3150 cm-1
Crystal Structure of 1. Complex 1 crystallizes in the
orthorhombic space group Pbca with each Mn(II) in
a distorted octahedral geometry completed by two
.
the corresponding programs in the SHELXTL package.22
H
atoms on C and N atoms were placed in calculated positions.
Experimental details for the structure analyses of 1-4 are given
::
(19) Sheldrick, G. M. SADABS, version 2.05; University of Gottingen:
::
(23) Bitschnau, B.; Egger, A.; Escuer, A.; Mautner, F. A.; Sodin, B.;
Vicente, R. Inorg. Chem. 2006, 45, 868–876.
(24) Chow, M. Y.; Zhou, Z. Y.; Mak, T. C. W. Inorg. Chem. 1992, 31,
Gottingen, Germany, 2002.
::
(20) Sheldrick, G. M. SHELXS-97, PC Version; University of Gottingen:
::
Gottingen, Germany, 1997.
::
(21) Sheldrick, G. M. SHELXL-97, PC Version; University of Gottingen:
4900–4902.
::
(25) (a) Maji, T. K.; Sain, S.; Mostafa, G.; Lu, T. H.; Ribas, J.; Monfort,
M.; Chaudhuri, N. R. Inorg. Chem. 2003, 42, 709–716. (b) Mondal, K. C.;
Sengupta, O.; Nethaji, M.; Mukherjee, P. S. Dalton Trans. 2008, 767–775.
Gottingen, Germany, 1997.
(22) Sheldrick, G. M. SHELXTL NT, version 5.1; University of
::
::
Gottingen: Gottingen, Germany, 1997.

Article
Inorg. Chem., Vol. 48, No. 11, 2009
4677
Table 1. Crystal Data and Structure Refinement Parameters for Compounds 1-4
1
2
3
4
formula
fw
T/K
λ (Mo KR) (A)
cryst color
cryst syst
C7H7MnN5O2
248.12
291(2) K
0.71073
brown
orthorhombic
Pbca
12.6897(9)
8.6978(6)
15.9901(11)
90
90
90
1764.9(2)
8
1.868
1.481
1000
1.043
10209/2020
0.0133
0.0242
0.0655
C7H7CdN5O2
305.58
294(2)
0.71073
brown
monoclinic
P21/c
8.3972(13)
16.135(2)
7.0043(11)
90
112.921(2)
90
874.1(2)
4
2.322
2.484
592
1.051
4888/1795
0.0260
0.0232
0.0525
C7H6MnN4O2
233.10
298(2)
0.71073
brown
monoclinic
P21/c
9.211(4)
11.186(5)
8.034(3)
90
102.365(5)
90
808.5(6)
4
1.915
1.607
468
1.085
4002/1422
0.0293
0.0274
0.0583
C4H8Cu2N8O4
359.26
298(2)
0.71073
green
orthorhombic
Pca21
14.049(3)
5.7809(14)
13.021(3)
90
90
90
1057.5(4)
4
2.256
4.046
712
1.060
6255/2280
0.0233
0.0209
0.0505
-0.002(13)
˚
space group
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
Dc, g cm-3
μ, mm-1
F(000)
GOF on F2
reflns (collected/unique)
Rint
R1a (I > 2σ(I))
wR2b (I > 2σ(I))
flack Parameter
P
P
P
P
a R1 =
Fo| - |Fc
/
|Fo|. b wR2 = [ w(F2o - F2c)2/ w(Fo2)2]1/2
.
carboxylato oxygen atoms from two 3,5-daba ligands,
two nitrogen atoms from another two 3,5-daba ligands,
and another two nitrogen atoms from two N3 ions
network is shown in Figure S2 (Supporting Information)
::
and has the Schlafli symbol (4.52.63)(4.59.64.7).
-
Crystal Structure of 2. Complex 2 crystallizes in the
monoclinic space group P21/c. The Cd(II) ion in 2 presents a
distorted octahedral geometry with coordination of two car-
boxlato oxygen atoms from two 3,5-daba ligands, two nitrogen
atoms from another two 3,5-daba ligands, and another two
nitrogen atoms from two N3- ions (Figure 2a), which is similar
to the Mn(II) ion of 1. The Cd-O and Cd-N bond lengths
(Figure 1a). All Mn-O and Mn-N bond lengths fall in
the normal range. The O-Mn-N, O-Mn-O, and N-
Mn-N bond angles range from 80.14(6) to 168.98(7)°.
The N3- ligand in 1 adopts a μ-1,3-bridging mode (EE),
and the 3,5-daba ligand behaves as a μ4,η4- bridge
to connect four Mn(II) ions using its two amino groups
and one syn-anti carboxylato group. The neighboring
Mn(II) ions along the b axis are bridged by μ-1,3-N3- ions
˚
are in a normal range of 2.300(2)-2.412(2) A and 2.364(3)-
˚
2.429(3) A, respectively. The O-Cd-N, O-Cd-O, and
to form a one-dimensional zigzag chain with a Mn Mn
˚
distance of 6.2044(3) A, as revealed in Figure S1 (Sup-
N-Cd-N bond angles range from 76.23(9) to 163.23(9)°.
The 3,5-daba ligand in 2 adopts the same μ4,η4-bridging mode
as that in 1, connecting four Cd(II) ions using its two amino
groups and one syn-anti carboxlato group. This is very
different from the reported 2D Cd(II)-3,5-daba complexes, in
which 3,5-daba acts as tridentate or bidentate ligand.26
Although the 3,5-daba ligands in 1 and 2 present the same
bridging mode, the N3- ligand in 2shows a μ-1,1-bridging mode
(EO) which is different from the μ-1,3-bridging mode (EO) in 1.
Every two adjacent Cd(II) ions in 2 are connected
3 3 3
porting Information). Two neighboring Mn(II) ions from
different 1D chains are bridged by two syn-anti carbox-
˚
ylato groups with a Mn Mn distance of 4.4703(2) A,
3 3 3
resulting in the formation of a two-dimensional network
parallel to the ab plane, highlighted by purple-colored
bonds in Figure 1b. This kind of 2D network is further
stabilized by the coordination of one of the amino groups
of each 3,5-daba ligand to another Mn(II) ion from
another 1D chain within the 2D network. The remain-
ing amino group of each 3,5-daba ligand coordinates
to another Mn(II) ion from another 1D chain in the
neighboring 2D network, leading to the construction
of an overall 3D framework (Figure 1b). Thus, each
μ4,η4-bridging 3,5-daba ligand interacts with four adja-
cent 1D zigzag chains via the coordination of two carbox-
ylato oxygen atoms and two amino groups to four Mn(II)
ions from the four 1D chains.
-
by one μ-1,1-N3 ligand and one syn-anti carboxyla
to group forming a one-dimensional chain parallel to the
c axis (Figure S3, Supporting Information) with a
˚
Cd Cd separation of 3.9118(5) A and a Cd-N-Cd
3 3 3
angle of 108.239(2)°. The further coordination of the two
amino groups of each 3,5-daba ligand in one 1D chain to
two Cd(II) ions from another two adjacent 1D chains
leads to the connection of each 1D chain to six adjacent
chains. Thus, each 3,5-daba ligand in 2 links just three 1D
chains, which are different from that in 1. The propaga-
tion of this kind of connection results in the con-
struction of a 3D metal-organic framework, as shown
in Figure 2b.
As described above, the azide ligand shows a μ-1,
3- bridging mode and connects two Mn(II) ions, while
the 3,5-daba ligand coordinates to four Mn atoms, one
each per oxygen or nitrogen atom. The Mn(II) ion in turn
coordinates to two cis azide ligands and four 3,5-daba
ligands. Thus, from a topological viewpoint, the Mn(II)
ions act as 6-connecting nodes, and the 3,5-daba ligands
act as 4-connecting nodes. The overall 4,6-connected 3D
(26) Ye, Q.; Chen, X.-B.; Song, Y.-M.; Wang, X.-S.; Zhang, J.; Xiong,
R.-G.; Fun, H.-K.; You, X.-Z. Inorg. Chim. Acta 2005, 358,
1258–1262.

4678 Inorg. Chem., Vol. 48, No. 11, 2009
Chen et al.
a
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) for 1-4
1
Mn1-O2A
2.1395(12)
2.1422(11)
111.45(5)
88.69(7)
91.73(6)
86.33(6)
160.04(8)
Mn1-N5B
2.1840(17)
2.2386(18)
97.91(10)
81.44(6)
87.38(5)
168.98(7)
86.39(9)
Mn1-N2C
2.3113(13)
2.3646(13)
166.25(5)
81.56(5)
95.56(7)
80.14(6)
95.17(4)
Mn1-O1
Mn1-N3
Mn1-N1D
O2A-Mn1-O1
O2A-Mn1-N5B
O1-Mn1-N5B
O2A-Mn1-N3
O1-Mn1-N3
N5B-Mn1-N3
O2A-Mn1-N2C
O1-Mn1-N2C
N5B-Mn1-N2C
N3-Mn1-N2C
O2A-Mn1-N1D
O1-Mn1-N1D
N5B-Mn1-N1D
N3-Mn1-N1D
N2C-Mn1-N1D
2
Cd1-O1
2.300(2)
2.364(3)
76.23(9)
90.69(9)
160.88(9)
151.24(9)
96.90(9)
Cd1-N3B
2.399(3)
2.410(3)
87.87(9)
81.93(8)
86.13(9)
78.16(9)
69.66(9)
Cd1-O2B
2.412(2)
2.429(3)
114.78(9)
98.87(9)
99.28(9)
93.78(9)
163.23(9)
Cd1-N1A
Cd1-N2C
Cd1-N3
O1-Cd1-N1A
O1-Cd1-N3B
N1A-Cd1-N3B
O1-Cd1-N2C
N1A-Cd1-N2C
N3B-Cd1-N2C
O1-Cd1-O2B
N1A-Cd1-O2B
N3B-Cd1-O2B
N2C-Cd1-O2B
O1-Cd1-N3
N1A-Cd1-N3
N3B-Cd1-N3
N2C-Cd1-N3
O2B-Cd1-N3
3
Mn1-O1
2.097(2)
2.109(2)
94.99(9)
165.19(8)
89.12(9)
96.67(8)
91.90(8)
Mn1-N2B
2.255(2)
2.259(2)
97.41(8)
86.70(9)
177.94(9)
88.95(9)
89.06(9)
Mn1-N1D
2.314(2)
2.346(2)
85.60(8)
92.03(8)
80.03(8)
175.27(8)
86.93(8)
Mn1-O2A
Mn1-N4C
Mn1-N2
O1-Mn1-O2A
O1-Mn1-N2B
O2A-Mn1-N2B
O1-Mn1-N4C
O2A-Mn1-N4C
N2B-Mn1-N4C
O1-Mn1-N1D
O2A-Mn1-N1D
N2B-Mn1-N1D
N4C-Mn1-N1D
O1-Mn1-N2
O2A-Mn1-N2
N2B-Mn1-N2
N4C-Mn1-N2
N1D-Mn1-N2
4
Cu1-O1
1.959(2)
1.988(2)
1.998(3)
2.016(2)
84.76(9)
83.89(9)
167.43(10)
166.25(8)
94.19(10)
95.55(10)
86.14(10)
Cu1-O4A
2.321(2)
1.9663(19)
1.966(3)
104.62(9)
101.96(10)
89.02(8)
83.73(10)
86.71(8)
166.70(14)
175.89(9)
95.46(11)
Cu2-N3
2.001(2)
2.020(2)
2.328(2)
93.43(10)
97.23(8)
92.24(14)
98.12(9)
86.81(8)
117.29(10)
116.85(11)
Cu1-N6
Cu2-O3
Cu2-N6B
Cu1-N1
Cu1-N3
Cu2-N2
Cu2-O2C
O1-Cu1-O4A
N6-Cu1-O4A
N3-Cu1-O4A
O3-Cu2-N2
O3-Cu2-N3
N2-Cu2-N3
O3-Cu2-N6B
N2-Cu2-N6B
N3-Cu2-N6B
O3-Cu2-O2C
N2-Cu2-O2C
N3-Cu2-O2C
N6B-Cu2-O2C
Cu2-N3-Cu1
Cu1-N6-Cu2D
O1-Cu1-N6
O1-Cu1-N1
N6-Cu1-N1
O1-Cu1-N3
N6-Cu1-N3
N1-Cu1-N3
N1-Cu1-O4A
a Symmetry codes. For 1: (A) -x + 1, -y + 1, -z + 1; (B) -x + 1/2, y + 1/2, z; (C) -x + 3/2, y - 1/2, z; (D) x - 1/2, y, -z + 3/2; (E) x + 1/2, y, -z +
3/2; (F) -x + 3/2, y + 1/2, z; (G) -x + 1/2, y - 1/2, z. For 2: (A) -x, y - 1/2, -z + 3/2; (B) x, -y + 3/2, z - 1/2; (C) x - 1, -y + 3/2, z - 1/2. For 3:
(A) x, -y + 1.5, z + 0.5; (B) -x + 1, -y + 2, -z + 1; (C) -x + 1, y - 0.5, -z + 0.5; (D) x - 1, y, z. For 4: (A) x-1/2, -y + 2, z; (B) x, y - 1, z; (C) -x +
1, -y + 2.
The structure analysis reveals that the structure of 2 is
similar to that of 1 in that it contains one unique metal
ion, one unique N3 anion, and one unique 3,5-daba
ligand. However, while the bridging azide again bridges
two metals, this time it shows the shorter μ-1,1-bridging
mode. As before, the 3,5-daba ligand connects four
metals, and the metals coordinate to two cis azide ligands
and four 3,5-daba ligands. Thus, a 3D 4,6-connected
network is again formed (Figure S4, Supporting Informa-
respectively, which are comparable to those in 1 and
the reported cases.27 The O-Mn-N, O-Mn-O, and
N-Mn-N bond angles of 3 range from 80.03(8)
to 177.94(9)°. The 4-aba ligand of 3 acts as a μ3,η3-bridge
to connect three Mn(II) ions using its amino group and
-
-
the syn-anti carboxylato group. The N3 ligand in 3
adopts a μ3-1,1,3-bridging mode connecting three Mn(II)
ions together, which is different from the μ-1,3 and
μ-1,1 bridging modes in 1 and 2.
tion); however, the topology is different from that seen in
Two Mn(II) ions of 3 are bridged by two N3- ligands in
a μ-1,1-bridging mode generating a dinuclear building
::
1. The Schlafli symbol is (3.42.53)(32.42.54.65.72).
˚
block with a Mn Mn distance of 3.5244(11) A. Each
dinuclear building block provides the two nitrogen atoms
Crystal Structure of 3. As shown in Figure 3a, the
asymmetric unit of 3 consists of one unique Mn(II) ion,
one unique 4-aba, and one unique N3 ion. The Mn(II)
3 3 3
-
at the other end of the two N3- ligands to coordinate to
ion of 3 is six-coordinated in a distorted octahedral
geometry by two carboxylato oxygen atoms from two
4-aba ligands, one amino group from another 4-aba
ligand, and three nitrogen atoms from three N3 ions.
The Mn-O and Mn-N bond lengths of 3 are in the
ranges of 2.097(2)-2.109(2) and 2.255(2)-2.346(2),
(27) (a) Chen, Z.; Ma, Y.; Liang, F.; Zhou, Z. J. Organomet. Chem. 2008,
693, 646–654. (b) Durot, S.; Policar, C.; Pelosi, G.; Bisceglie, F.; Mallah, T.;
Mahy, J. P. Inorg. Chem. 2003, 42, 8072–8080. (c) Yao, Y. L.; Che, Y. X.;
Zheng, J. M. Cryst. Growth Des. 2008, 8, 2299–2306. (d) Ma, C. B.; Chen, C.
N.; Liu, Q. T.; Chen, F.; Liao, D. Z.; Li, L. C.; Sun, L. C. Eur. J. Inorg. Chem.
2003, 2872–2879.
-

Article
Inorg. Chem., Vol. 48, No. 11, 2009
4679
Figure 2. (a) A view of the coordination environment of the Cd(II) ion
and the binding fashions of 3,5-daba and N3- ligands in 2 with displace-
ment ellipsoids drawn at the 30% probability level. Symmetry codes:
(A) -x, y - 1/2, -z + 3/2; (B) x, -y + 3/2, z - 1/2; (C) x - 1, -y + 3/2, z
- 1/2; (D) x, -y + 3/2, z + 1/2; (E) -x, y + 1/2, -z + 3/2; (F) x + 1, -y
+ 3/2, z + 1/2; (G) -1 + x, y, z, (H) x + 1, y, z, (I) -x, 1 - y, 1 - z, (J) -1
- x, 1 - y, 1 - z. (b) A view of the 3D metal-organic framework of 2.
Hydrogen atoms are omitted for clarity.
Figure 1. (a) A view of the coordination environment of the Mn(II) ion
and the binding fashions of 3,5-daba and N3 ligands in 1 with dis-
-
placement ellipsoids drawn at the 30% probability level. Symmetry
codes: (A) -x + 1, -y + 1, -z + 1; (B) -x + 1/2, y + 1/2, z; (C) -x
+ 3/2, y - 1/2, z; (D) x - 1/2, y, -z + 3/2; (E) x + 1/2, y, -z + 3/2; (F) -
x + 3/2, y + 1/2, z; (G) -x + 1/2, y - 1/2, z. (b) A view of the 3D
framework of 1 showing a 2D network highlighted by purple-colored
bonds. Hydrogen atoms are omitted for clarity.
knowledge, this 3,6-connected net has not been re-
::
ported.28 It has the Schlafli symbol (42.6)(4.62)(43.66.86).
two Mn(II) ions from another two dinuclear building blocks,
Crystal Structure of 4. The structure of 4 contains two
unique Cu atoms, two unique azide anions, and two
unique gly ligands in one asymmetric unit, as revealed in
Figure 5a. Chemically, however, each pair shows the
same coordination environment. Each Cu(II) ion coor-
dinates to one gly ligand, which chelates via its nitrogen
atom and one oxygen atom, coordinates to another gly
ligand in a monodentate fashion via one oxygen atom,
and coordinates to two nitrogen atoms from two μ-1,1
bridging azide anions, forming a distorted square-pyr-
˚
with Mn Mn distances of 4.8793(15) and 5.9164(12) A.Thus,
3 3 3
the N3- ligands display a 3-connecting μ3-1,1,3-bridging mode
and join the metal atoms into 2D (4.82) sheets parallel to the
bc plane (Figure 3b) with the 4-aminophenyl groups aligned on
both sides of the 2D plane alternatively. These sheets
are reinforced by syn-anti carboxylate bridges from the
4-aba ligands via connecting the nearest two Mn(II) ions from
two adjacent dinuclear building blocks. Ultimately, the
4-aba ligands connect the 2D sheets into a 3D network through
the coordination of the amino groups to the Mn(II) ions from
adjacent 2D sheets, and vice versa, as shown in Figure S5
(Supporting Information).
-
amidal geometry. Both the N3 and gly ligands of 4 in
turn connect pairs of Cu(II) ions via μ-1,1- and μ2,
η3-bridging coordination modes, respectively. Cu(II)
-
ions are bridged by μ-1,1-bridging N3 to form one-
dimensional zigzag chains along the b axis (Figure 5b)
Topologically, the structure is composed of 3-con-
necting azide anions, 3-connecting 4-aba ligands, and
6-connecting Mn atoms. The complicated trinodal
3,6-connected network is shown in Figure 4 and
Figure S6 (Supporting Information). To the best of our
(28) Du, M.; Zhang, Z.-H.; Tang, L.-F.; Wang, X.-G.; Zhao, X.-J.;
Batten, S. R. Chem.;Eur. J. 2007, 13, 2578–2586.

4680 Inorg. Chem., Vol. 48, No. 11, 2009
Chen et al.
Figure 4. The overall network topologyof3, viewedside-on tothelayers
shown in Figure 3b. Orange spheres represent the Mn nodes. Blue spheres
represent the azide anions, and red spheres represent the 4-aba ligands.
anti-anti-COO--Cu- running along the c axis and -
Cu-EO-N3--Cu- running along the b axis.
Topologically, the Cu(II) ions in the 3D framework of
4 act as 4-connecting nodes, while the ligands all act as
simple bridges between the metal atoms. The 4-connected
3D net formed is shown in Figure 6; it has the Lonsdaleite
(hexagonal diamond) topology. This is very unusual; there
are only a few reports of coordination polymers with this
topology,29 despite its simplicity;tetrahedral nodes more
usually form networks with the cubic diamond topology.30
Magnetic Properties of 1, 3, and 4. The magnetic proper-
ties of 1 and 3 were investigated by solid-state magnetic
susceptibility (χm) measurements in the 2.0-300 K range in
a DC field of 10 000 Oe. The magnetic properties of
complexes 1 and 3 in the form of both χMT and χM versus
T plots are shown in Figures 7 and 8, respectively. The
values of χMT at 300 K are 4.0049 and 3.6176 cm3 K mol-1
for 1 and 3, respectively, both of which are lower than that
expected (4.38 cm3 K mol-1) for one magnetically isolated
high-spin Mn(II) ion. Decreasing the temperature leads to
the χmT values of 1 and 3 gradually decreasing, reaching
0.1647 and 0.05562 cm3 K mol-1 at 2.0 K for 1 and 3,
respectively. These features are typical of a significant
antiferromagnetic coupling in 1 and 3. The χm values of 1
and 3 rise sharply to reach a maximum of 0.08037 cm3
mol-1 at 14 K for 1 and 0.03014 cm3 mol-1 at 50.4 K for 3,
then decrease rapidly to 0.07853 cm3 mol-1 at 8.1 K for 1
and 0.02685 cm3 mol-1 at 11.1 K for 3, and finally rise
sharply again to 0.08236 and 0.02774 cm3 mol-1 for 1 and 3
at 2 K, respectively. The characteristics of χm in the
low-temperature range for both 1 and 3 might be attrib-
uted to the presence of trace of paramagnetic impurities.31
Figure 3. (a) A view of the coordination environment of the Mn(II) ion
and the binding fashions of the 4-aba and N3 ligands in 3 with
-
displacement ellipsoids drawn at the 30% probability level. Symmetry
codes: (A) x, -y + 1.5, z + 0.5; (B) -x + 1, -y + 2, -z + 1; (C) -x + 1,
y - 0.5, -z + 0.5; (D) x - 1, y, z; (E) x + 1, y, z; (F) -x + 1, y + 0.5, -z
+ 0.5; (G) x, -y + 1.5, z - 0.5; (H) x + 1, -y + 1.5, z + 0.5; (I) x - 1, -y
-
+ 1.5, z - 0.5. (b) The 2D sheet in 3 constructed by Mn(II) ions, N3
anions, and the carboxlato groups of 4-aba ligands with 4-aminophenyl
groups omitted for clarity.
˚
with a Cu
Cu distance of 3.4145(6) A and a Cu-
3 3 3
N-Cu angle of 116.851(8)°. Each 1D chain is then
linked to four other 1D chains by the μ2,η3-bridging
gly ligands via the coordination of the amino group and
one carboxylato oxygen atom to one Cu(II) ion from one
1D chain and the other oxygen atom to another Cu(II)
ion in an adjacent chain. This means the carboxylato
group of the gly ligand acts as an anti-anti bridge
connecting Cu(II) ions from adjacent 1D chains with a
˚
Cu
Cu distance of 6.0532(12) A. Thus, a 3D frame-
3 3 3
(29) (a) Sreenivasulu, B.; Vittal, J. J. Cryst. Growth Des. 2003, 3, 635–637.
(b) Kitazawa, T.; Kikuyama, T.; Takeda, M.; Iwamoto, T. J. Chem. Soc.,
Dalton Trans. 1995, 3715–3720.
(30) Batten, S. R. J. Solid State Chem. 2005, 178, 2475–2479.
(31) (a) Gao, E. Q.; Cheng, A. L.; Xu, Y. X.; He, M. Y.; Yan, C. H. Inorg.
work is constructed as shown in Figure 5d. Alterna-
tively, one can say that the neighboring Cu(II) ions
are connected by μ2,η3-bridging gly ligands to form
one-dimensional chains (Figure 5c) running along the c
axis, which are further bridged by the μ-1,1-bridging
N3 ions into the three-dimensional framework.
Therefore, there exist two kinds of chains in 4: -Cu-
ꢁ
ꢁ
Chem. 2005, 44, 8822–8835. (b) Thetiot, F.; Triki, S.; Pala, J. S.; Galan-
ꢁ
ꢁ
Mascaros, J. R.; Martinez-Agudo, J. M.; Dunbar, K. R. Eur. J. Inorg. Chem.
2004, 3783–3791. (c) Zhao, W.; Song, Y.; Okamura, T. A.; Fan, J.; Sun, W.
Y.; Ueyama, N. Inorg. Chem. 2005, 44, 3330–3336.
-

Article
Inorg. Chem., Vol. 48, No. 11, 2009
4681
Figure 5. (a) A viewof the coordinationenvironment of the Cu(II) ion and the bindingfashions of the gly and N3- ligands in 4 with displacement ellipsoids
drawn at the 30% probability level. Symmetry codes: (A) x-1/2, -y + 2, z; (B) x, y - 1, z; (C) -x + 1, -y + 2, z - 1/2; (D) x, y + 1, z; (E) -x + 1, -y + 2,
z + 1/2; (F) x + 1/2, -y + 2, z. (b) The 1D chain in 4 constructed by Cu(II) ions and N3- anions. (c) The 1D chain in 4 constructed by Cu(II) ions and gly
anions. (d) A view of the 3D metal-organic framework of 4. Hydrogen atoms are omitted for clarity.
Figure 7. Plots of χm and χmT vs T for 1. Solid lines show the best fit of
the data according to the proposed model.
Figure 6. The unusual Lonsdaleite topology of 4. Spheres represent the
two different Cu nodes, although topologically both nodes are equivalent.
The two types of cavities in the Lonsdaleite net are highlighted. Green
bonds represent the gly bridges, while blue bonds represent the azide
bridges.
1 is through a bridging end-to-end N3- ion between the
manganese(II) centers, which creates an infinite -Mn-
N3-Mn- chain, and is treated as the intrachain interac-
tion. Type 2 is through a double carboxylato bridge of
-1
Fitting of the χm
- T above 100 K using the
two 3,5-daba ligands between the Mn(II) ions from
adjacent chains, which is taken as the interchain interac-
tion. Similar to the case of 1, 3 also exhibits a 2D sheet
from the point of view of magnetic exchange as the bridge
of 4-aba between the adjacent 2D sheets cannot effec-
tively transmit magnetic exchange. Every two adjacent
Mn(II) ions in the chain along the c axis transmit the
magnetic exchange through the bridges of one syn-anti
carboxylato group and one end-to-end N3- ion simulta-
neously. The interchain magnetic exchange is performed
Curie-Weiss law χm = C/(T - θ) gives the Curie cons-
tants C = 4.35 and 4.65 cm3 K mol-1 and the Weiss
constants θ = -24.59 and -84.07 K for 1 and 3, respec-
tively. The negative θ values also support the presence
of overall antiferromagnetic interactions in the two
complexes.
Magnetically, 1 presents a 2D network because the
Mn(II) ions from neighboring 2D sheets are bridged
by 3,5-daba via the coordination of its two amino
groups, which do not transmit magnetic exchange effec-
tively. There are two types of Mn(II)-Mn(II) mag-
netic exchange interactions in the 2D network of 1. Type
-
by double end-on N3 ions. Thus, the experimental
magnetic behavior of 1 and 3 can be simulated using
the analytical expression derived by Fisher for a 1D

4682 Inorg. Chem., Vol. 48, No. 11, 2009
Chen et al.
a ferromagnetic interaction between the neighboring
Mn(II) ions. It might be caused by the small Mn-
NEO-azido-Mn angle (99.97(8)°), which is consistent with
the related cases reported33,34 and confirms again the
conclusion that one of the driving effects for magnetic
interactions through the EO-azido bridge in Mn(II)
compounds seems to be the value of the bridging angle
of Mn-NEO-azido-Mn.4,34
The magnetic properties of 4 were investigated by solid-
state magnetic susceptibility (χm) measurements in the
1.8-300 K range in a DC field of 2000 Oe. The magnetic
properties of complex 4 in the form of both χMT and
χ
M versus T plots are shown in Figure 9. The χmT value of
4 at 300 K is 1.1290 cm3 K mol-1, which is higher than
that (0.75 cm3 K mol-1) expected for two magnetically
isolated high-spin CuII ions. With the decrease of tem-
perature, the χmT values increase slowly, and below 50 K,
they rise up more quickly to reach a maximum of 5.65 cm3
K mol-1 at 7.0 K. This behavior indicates the occurrence
of a relative strong ferromagnetic coupling in 4. On
Figure 8. Plots of χm and χmT vs T for 3. Solid lines show the best fit of
the data according to the proposed model.
Heisenberg chain of classical spins (S
H = -JΣiΣi+1)
magnetic exchange estimated by the mean field model:
=
with a consideration of interchain
5/2,
32
further cooling, they decrease sharply to 1.10 cm3
K
Ng2β2SðS þ 1Þð1 þ uÞ
mol-1 at 1.8 K (Figure 9). Fitting the data to the
Curie-Weiss law χm = C/(T - θ) above 100 K, as show
in Figure S7 (Supporting Information), gives a Curie
constant of 1.01 cm3 K mol-1 and a positive Weiss
constant of 31.34 K, which suggest the presence of
dominant ferromagnetic coupling in 4. Considering its
structure, there are two sets of magnetic exchange path-
ways. One consists of one EO azido bridge, and the other
consists of one anti-anti carboxylato bridge. It has been
shown previously that the EO azido bridge in basal-
basal dispositions favors an antiferromagnetic interac-
tion when the Cu-N-Cu angle is larger than 104° from
density functional calculations4 or 108.5° from an experi-
mental study.5 The Cu-N-Cu angles in our case of 4 are
116.85(11) and 117.29(1)°, which indicates an occurrence
of antiferromagnetic coupling through the EO azido
bridge in 4. The anti-anti carboxylato group in the case
of 4 connects two Cu(II) ions through the axial-equator-
ial pathway with a dihedral angle of 70.194° between
the mean equatorial planes of adjacent copper atoms.
According to the reported cases, this kind of anti-
anti-carboxylato bridge in Cu(II) complexes usually
mediates a ferromagnetic interaction between CuII ions.35
χchain
¼
3kTð1 -uÞ
χchain
χ2D
¼
1 -ð2zJ0=Ng2β2Þχchain
where N is Avogadro’s number, β is Bohr’s magneton, k is
Boltzmann’s constant, and u is the Langevin function:
u = coth[JS(S + 1)/kT] - kT/[JS(S + 1)].
The low-temperature increase of χm in antiferromag-
netic systems is usually attributed to the presence of a
certain amount of paramagnetic impurities.31 Following
this line, we simulated the experimental data of 1 and 3
to the following equation over the whole 2-300 K
temperature range:
χm ¼ χ2Dð1 -FÞ þ ½Ng2β2SðS þ 1Þ=3kTꢀF
where F is the amount of the paramagnetic impurities
[presumably a mononuclear Mn(II) complex]. The best
least-squares fit of the theoretical equation to experimen-
tal data leads to g = 2, J = -2.50(1) cm-1, zJ0 = -0.42
(4) cm-1, and F = 0.76% with an agreement factor of R =
8.06 ꢁ 10-5 for 1 and g = 2, J = -7.14(1) cm-1, zJ0 =
0.22(3) cm-1, and F = 0.15% with an agreement factor of
R = 3.51 ꢁ 10-4 for 3. These values again indicate the
presence of dominant weak antiferromagnetic interaction
between the neighboring Mn(II) ions in both 1 and 3. The
intrachain J (J = -2.50(1) cm-1) and interchain J (zJ0 =
-0.42(4) cm-1) of 1 are ascribed to the EE-azido and
double syn-anti-carboxylato bridges, respectively, which
usually lead to antiferromagnetic interactions. With the
fitting model in mind, the J value of -7.14(1) cm-1 for 3 is
attributed to the bridges of one syn-anti carboxyla
(33) (a) Zhang, H. Y.; Liu, C. M.; Zhang, D. Q.; Gao, S.; Zhu, D. B. Inorg.
Chem. Commun. 2007, 10, 897–901. (b) Gao, E. Q.; Bai, S. Q.; Yue, Y. F.;
Wang, Z. M.; Yan, C. H. Inorg. Chem. 2003, 42, 3642–3649. (d) Abu-
Youssef, M. A. M.; Escuer, A.; Gatteschi, D.; Goher, M. A. S.; Mautner, F.
A.; Vicente, R. Inorg. Chem. 1999, 38, 5716–5723. (e) Villanueva, M.; Mesa,
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J. L.; Urtiaga, M. K.; Cortes, R.; Lezama, L.; Arriortua, M. I.; Rojo, T. Eur.
J. Inorg. Chem. 2001, 1581–1586. (f) Abu-Youssef, M. A. M.; Escuer, A.;
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(34) (a) Tang, L. F.; Zhang, L.; Li, L. C.; Cheng, P.; Wang, Z. H.; Wang, J.
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(35) (a) Colacio, E.; Dominguez-Vera, J. M.; Ghazi, M.; Kivekas, R.;
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Klinga, M.; Moreno, J. M. Eur. J. Inorg. Chem. 1999, 441–445. (b) Delgado,
to group and one end-to-end N3 ion. The interchain
ꢁ
F. S.; Ruiz-Perez, C.; Sanchiz, J.; Lloret, F.; Julve, M. CrystEngComm 2006,
J (zJ0 = 0.22(3) cm-1) of 3 corresponds to the magnetic
coupling mediated by the double EO-azido bridges,
which confirms that the EO-azido bridge in 3 mediates
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Article
Inorg. Chem., Vol. 48, No. 11, 2009
4683
Figure 9. Plots of χm and χmT vs T for 4 measured in an applied field of 2
kOe. The solid lines represent the theoretical fits in the high-temperature
region (see text). Inset: Plots of χm vs T measured between 2.00 and 8.5 K
at the indicated applied fields (solid lines are a guide for the eye).
Figure 10. Temperature-dependent ac magnetic susceptibilities of 4
under different frequencies (10, 100, 499, and 997 Hz) with a zero DC
field and an oscillating field of 2.5 Oe. Solid lines are guides for the eye.
The magnetic susceptibility data revealed that the ferro-
magnetic coupling is relatively strong and the antiferro-
magnetic coupling is relatively weak. According to the
structural analysis, compound 4 would be three-dimen-
sional, with a large ferromagnetic coupling (J) mediated
by the anti-anti-carboxylato bridge within the -Cu-
anti-anti-COO--Cu- chain and a weak antiferromag-
netic coupling mediated by the EO azido bridge within the
-Cu-EO-N3--Cu- chain. The weak antiferromag-
netic coupling mediated by the EO azido bridge can also
be understood as an interchain coupling (zJ0) between the
neighboring -Cu-anti-anti-COO--Cu- chains. Con-
sequently, the experimental magnetic behavior of 4 can be
simulated using the expression proposed by Baker et al.
for a Heisenberg ferromagnetic S = 1/2 chain based on
the Hamiltonian H = -JΣSiSi+136 with a consideration
of interchain magnetic exchange estimated by mean field
model:
Figure 11. Field dependence of the magnetization at different tempera-
tures and below 50 kOe for 4. Inset: The whole field dependence of the
magnetization between -50 and +50 kOe, emphasizing the absence of a
hysteresis effect.
ꢀ ꢁ
2=3
Ng2β2
4kT
A
B
lower temperatures and became less prominent and
finally disappeared at an applied field of 8 and
10 kOe, indicating that the interchain antiferromagnetic
interactions are overcome by the external field. These
features are characteristic of metamagnetic behaviors. To
confirm the appearance of magnetic transition and to
determine the critical temperature, the ac susceptibilities
(in phase χ0 and out-of-phase χ00) measured as a function
of temperature in the low-temperature range were
obtained by a 2.5 Oe ac field oscillating at 10, 100,
499, and 997 Hz under a zero DC field as shown in
Figure 10. The in-phase part, χ0, of all of the frequencies
exhibits a frequency-independent maximum value at 6 K (TN).
The ZFCMs and FCMs at 100 Oe reveal no divergence, as
shown in Figure S8 (Supporting Information).
χchain
¼
where A = 1.0 + 5.7979916x + 16.902653x2
+
29.376885x3 + 29.832959x4 + 14.036918x5, B = 1.0 +
2.7979916x + 7.0086780x2 + 8.6538644x3 + 4.5743114x4,
and x = J/2kT.
χchain
χ3D
¼
1 -ð2zJ0=Ng2β2Þχchain
The best fit for 4 in the temperature range of 18-300 K as
shown in Figure 9 gives J = 149(1) cm-1, g = 2.29(1),
and zJ0 = -0.23(2) cm-1 with an agreement factor
of R = 1.91 ꢁ 10-4. These coupling constants clearly
confirm that the anti-anti-carboxylato bridge mediates a
strong ferromagnetic interaction and the EO azido bridge
favors a weak antiferromagnetic interaction in 4.
Further magnetic investigation reveals that 4 is a meta-
magnet. The field-cooled magnetizations under different
fields are shown in the inset of Figure 9. At a low field,
the χm versus T curves all display a maximum, suggesting
the occurrence of 3D antiferromagnetic ordering in 4.
Upon increasing the field, the maximum moved to
The metamagnetic behavior of 4 is also confirmed by
the field-dependent magnetization measured at different
temperatures, as depicted in Figure 11. The curves mea-
sured at 2, 3, and 4 K, which are below critical tempera-
ture, present
a pronounced sigmoid shape. The
magnetization measured at 4 K increases linearly below
4 kOe, then more quickly below 10 kOe. At last, it rises
very slowly, reaching a saturation value of ca. 2.10 NμB at
50 kOe, which is close to the saturation value of 2.0 NμB
anticipated for a pair of S = 1/2 spins with g = 2.12,14 The
critical field is ca. 6030 Oe, determined by the
peak position of the dM/dH derivative curve at 4 K.
(36) Baker, G. A.; Rushbrooke, G. S.; Gilbert, H. E. Phys. Rev. 1964, 135,
A1272.

4684 Inorg. Chem., Vol. 48, No. 11, 2009
Chen et al.
The sigmoidal feature of the field-dependent magnetiza-
tion diminishes when the temperature is at or above 6 K,
consistent with the TN value. No detectable magnetic
hysteresis was observed at 2 K as shown in the inset of
Figure 11. All of these measurements mentioned above
clearly indicate the metamagnetic behavior in 4 with
a critical temperature of 6 K and a critical field of
ca. 6030 Oe.12,37
with a flexible amino acid as the secondary bridging ligand in
metal-azido complexes. Magnetic susceptibility measure-
ments reveal dominant antiferromagnetic couplings for 1
and 3 but a dominant ferromagnetic coupling for 4, which
displays metamagnetic behavior with a magnetic phase
transition at a critical temperature of 6 K and transition
field of ca. 6030 Oe. The results further confirm the conclu-
sion that the EE azido and syn-anti carboxylato bridges
easily induce an antiferomagnetic interaction, and the mag-
netic interaction through the EO azido bridge has a depen-
dence on the value of the M-N-M bond angle. Moreover,
the anti-anti carboxylato bridge in 4 mediates a ferromag-
netic interaction.
Conclusions
Four three-dimensional metal-azido coordination poly-
mers were obtained with different amino carboxylic acids as
secondary bridging ligands. The results revealed that the
addition of different amino carboxylates as coligands leads to
a variation of the coordination modes of the azido bridge and
different resulting structural topologies of the metal-azido
compounds formed. Complex 3 displays an interesting 3,6-
connected topological structure that has never been reported
previously, and 4 is the first example of coordination polymer
Acknowledgment. We gratefully thank Prof. Dr. You
Song for the discussion of magnetic properties, and we
also acknowledge the financial support from the National
Natural Science Foundation of China (No. 20461001),
Guangxi Natural Science Foundation (No. 0639031), and
Ten-hundred-thousand Talents Program in New Century
of Guangxi Province, China.
(37) (a) Monfort, M.; Resino, I.; Ribas, J.; Stoeckli-Evans, H. Angew.
Chem., Int. Ed. 2000, 39, 191–193. (b) Mukherjee, P. S.; Dalai, S.; Chaudhuri,
N. R.; Zangrando, E.; Lloret, F. Chem. Commun. 2001, 1444–1445. (c) Gao,
E.-Q.; Wang, Z.-M.; Yan, C.-H. Chem. Commun. 2003, 1748–1749. (d) Liu,
T.; Zhang, Y.; Wang, Z.; Gao, S. Inorg. Chem. 2006, 45, 2782–2784. (e) Das,
A.; Rosair, G. M.; ElFallah, M. S.; Ribas, J.; Mitra, S. Inorg. Chem. 2006, 45,
3301–3306.
Supporting Information Available: X-ray crystallographic
files in CIF format for complexes 1-4, a PDF file containing
Figures S1–S8. These materials are available free of charge via
the Internet at http://pubs.acs.org.