Mixed-bridging manganese(II) and copper(II) complexes with azide and pyridylbenzoate N-oxide: Structures and magnetic properties

Article abstract of DOI:10.1016/j.ica.2012.03.050

Two Mn(II) and Cu(II) coordination polymers with azide and 4-(3-pyridyl)benzoic acid N-oxide (4,3-Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as [M(4,3-opybz)(μ- N₃)]_n (M = Mn, 1 and Cu, 2). Compound 1 consists of 2D coordination layers in which 1D coordination chains with uniform [(μ-EO-N₃)(μ-COO)(μ-O)] (EO = end-on, μ-O from N-oxide group) triple bridges are interlinked by the 4,3-opybz spacers. Compound 2 also presents a 2D coordination layers in which the Cu(II) ions are triply bridged in a fashion similar to 1, while the azide ions reside at different positions around the metal ions. Magnetic studies demonstrated that the magnetic coupling through the mixed triple bridge is antiferromagnetic in the Mn(II) compound (1) but ferromagnetic in the Cu(II) species (2).

Full text of DOI:10.1016/j.ica.2012.03.050

Inorganica Chimica Acta 392 (2012) 311–316
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Mixed-bridging manganese(II) and copper(II) complexes with azide and
pyridylbenzoate N-oxide: Structures and magnetic properties
a
a,
b
Xiu-Mei Zhang a, , Wei Gao , Jie-Ping Liu , En-Qing Gao
⇑
⇑
a College of Chemistry and Materials Science, Huaibei Normal University, 100 Dongshan Road, Huaibei, Anhui 235000, China
b Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two Mn(II) and Cu(II) coordination polymers with azide and 4-(3-pyridyl)benzoic acid N-oxide (4,3-
Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as
Received 17 November 2011
Received in revised form 21 March 2012
Accepted 24 March 2012
[M(4,3-opybz)(
l-N3)]n (M = Mn, 1 and Cu, 2). Compound 1 consists of 2D coordination layers in which
1D coordination chains with uniform [(
l
-EO-N3)( -COO)( -O)] (EO = end-on, -O from N-oxide group)
l
l
l
Available online 3 April 2012
triple bridges are interlinked by the 4,3-opybz spacers. Compound 2 also presents a 2D coordination
layers in which the Cu(II) ions are triply bridged in a fashion similar to 1, while the azide ions reside
at different positions around the metal ions. Magnetic studies demonstrated that the magnetic coupling
through the mixed triple bridge is antiferromagnetic in the Mn(II) compound (1) but ferromagnetic in the
Cu(II) species (2).
Keywords:
4-(3-Pyridyl)benzoate N-oxide
Mixed-bridging
Magnetic properties
Coordination polymers
Ó 2012 Published by Elsevier B.V.
1. Introduction
bridging ligands. The bifunctional ligands bearing carboxylate and
pyridyl-N oxide groups, such as 3-(or 4-) pyridylcarboxylates
The field of molecular magnetism has been of considerable
interest for decades, which aims at understanding the underlying
physics in molecular systems and constructing new magnetic
materials with potential applications [1–9]. The most important
strategy to access molecular magnetic materials is to connect para-
magnetic metal centers into polynuclear aggregates or polymeric
networks with short bridging groups that can induce efficient mag-
netic exchange. Among the most frequently used short bridges are
carboxylate and azide groups, which display exceptionally rich
coordination chemistry and magnetochemistry. Combining azide
and carboxylate into one system is an interesting approach to mag-
netic systems, but the known examples are still limited, mostly de-
rived from simple mono- (RCOOꢀ) or dicarboxylate [R(COOꢀ)2]
ligands (R = H, methyl, ethyl, phenylene) [10–22]. Recently, we
demonstrated that the use of zwitterionic dicarboxylate ligands
as carboxylate sources is an easy and efficient approach to 2D or
3D networks containing 1D chains with azide and carboxylate
bridges. Mixed azide and carboxylate bridges transmit antiferro-
magnetic (AFM) coupling in Mn(II) species but ferromagnetic
(FM) coupling in Cu(II) species [23–26]. The introduction of two
bridges in one complex enriches the diversity both in structure
and magnetism. Magnetic materials with specific magnetic behav-
iors could be designed and constructed by combining two or more
N-oxides [27–29] have also led to some co-bridging systems, with
various structures and magnetic properties. Such ligands in coordi-
nation behaviors make it possible to construct mixed bridged
complexes with azide/carboxylate, azide/oxide, or azide/carboxylate/
oxide as bridges. Generally speaking, the l2-oxygen and carboxyl-
ate mixed bridges mediate antiferromagnetic coupling between
Mn(II) ions [30–34]. However, only a very few structures of Cu(II)
complexes containing mixed azide and carboxylate bridges have
been reported and some of these compounds have a third bridge
(l-O) at axial positions around Cu(II) ions, which has little contri-
bution to magnetic exchange [26–29,35]. Recently a few co-bridging
complexes have been obtained from pyridylbenzoic acids N-oxides
by us, which exhibit different magnetic properties, such as FM
interactions in Co(II) and Ni(II) systems [36] but AFM interactions
in Mn(II) complexes [37]. In continuation of our work with 4-
(3-pyridyl)benzoic acid, to systematically investigate the construc-
tion and magnetism of the systems with simultaneous azide and
carboxylate bridges, here we present the structural and magnetic
study on two compounds with simultaneous azide and carboxylate
bridges, [M(4,3-opybz)(l-N3)]n (4,3-opybz = 4-(3-pyridyl)benzoate
N-oxide, Scheme 1, M = Mn, 1 and Cu, 2). They both consist of 2D
coordination layers in which 1D coordination chains with uniform
[(l-EO-N3)(l-COO)(l-O)] triple (EO = end-on, l-O from N-oxide
group) bridges are interlinked by the 4,3-opybz spacers. The struc-
tural difference mainly lie in the cis (1) or trans (2) coordination
geometry of azide around metal ions. Magnetic studies showed
that the magnetic coupling through the mixed triple bridge is
⇑
Corresponding authors. Fax: +86 561 3803233 (X.-M. Zhang).
E-mail addresses: zhangxiumeilb@126.com (X.-M. Zhang), jpliu@hbcnc.edu.cn
(J.-P. Liu), eqgao@chem.ecnu.edu.cn (E.-Q. Gao).
0020-1693/$ - see front matter Ó 2012 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.ica.2012.03.050

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X.-M. Zhang et al. / Inorganica Chimica Acta 392 (2012) 311–316
Table 1
Crystal data and structure refinements for compound 1 and 2.
Compound
1
2
Formula
Mr
Temperature (K)
Crystal system
Space group
a (Å)
C
12H8MnN4O3
C12H8CuN4O3
319.76.
296
monoclinic
P21/c
7.9405(3)
6.3841(2)
23.4650(7)
90
311.16
296
monoclinic
P21/c
8.1675(2)
23.4539(6)
6.5517(2)
90
Scheme 1. Chemical structure of 4,3-opybz.
b (Å)
c (Å)
antiferromagnetic in the Mn(II) compound (1) but ferromagnetic in
the Cu(II) species (2).
a
(°)
b (°)
100.8140(10)
90
1232.75(6)
4
1.677
1.083
94.6930(10)
90
1185.52(7)
4
1.792
1.855
c
(°)
2. Experimental
V (Å3)
Z
Dcalc (g cmꢀ3
)
2.1. Physical measurements
l
(mmꢀ1
)
Reflections collected
Unique reflections/Rint
R1 [I > 2r(I)]
wR2 (all data)
16575
15500
2844/0.0260
0.0259
0.0734
1.077
Elemental analyses were determined on an Elementar Vario
ELIII analyzer. The FT-IR spectra were recorded in the range 500–
4000 cmꢀ1 using KBr pellets on a Nicolet NEXUS 670 spectropho-
tometer. Temperature-dependent magnetic measurements were
carried out on a Quantum Design SQUID MPMS-5 magnetometer,
and diamagnetic corrections were made with Pascal’s constants.
2984/0.0193
0.0290
0.0767
1.093
Goodness-of-fit (GOF)
3. Results and discussion
2.2. Materials and synthesis
3.1. Description of the structures
All the solvents and reagents for synthesis were commercially
available and used as received. The ligand 4-(3-pyridyl)benzoic
acid N-oxide (4,3-Hopybz) was synthesized according to the liter-
ature methods for similar compounds [38].
Compounds 1 and 2 crystallize in the same space group (P21/c)
and contain 2D coordination layers in which 1D M(II) (M = Mn, 1;
Cu, 2) chains with uniform triple (l-EO-N3)(l-COO)(l-O) bridges
are connected by 4,3-opybz spacers. The two structures are de-
scribed together for the convenience of comparisons.
2.2.1. [Mn(4,3-opybz)(N3)]n (1)
The coordination environment of the metal ions and ligands are
shown in Fig. 1. The selected bond lengths and angles of 1 and 2
are listed in Table 2. In both compounds, the crystallographically
independent metal ions assume the distorted pseudo-octahedral
geometry. The metal atoms are in a cis-[N2O4] surrounding for 1
and a trans-[N2O4] surrounding for 2. The coordination sphere is
completed by two carboxylate oxygen atoms (O1, O2A at trans
positions in both compounds), two N-oxide oxygen atoms (O3B,
O3C at cis positions for 1 or at trans positions for 2) and two azide
nitrogen atoms (N2, N2A at cis positions for 1 or at trans positions
for 2). The M–O/N distances in each compound vary in the order
M–Ocarbxylate < M–Nazide < M–ON-oxide (see Table 2). The N-oxide
group oxygen atoms in 2 are at 2.475(1) and 2.669(2) Å from Cu,
defining the elongated axis of the Jahn–Teller distortion. Except
for the Cu–ON-oxide distances, the Cu–N/O distances in 2 are shorter
than Mn–N/O. The adjacent metal ions are triply bridged by a
carboxylate group in the syn–syn mode, an azide ligand in the
A mixture of MnCl2ꢁ4H2O (0.1 mmol, 0.020 g), NaN3(0.8 mmol,
0.052 g), and 4,3-Hopybz (0.025 mmol, 0.0062 g) was dissolved in
H2O (0.5 mL), CH3OH (0.5 mL) and DMSO (1.0 mL) in a Teflon-lined
stainless steel vessel (25 ml), heated at 70 °C for 4 days, and then
cooled to room temperature. Yellow plate crystals of 1 were
obtained. Yield: 75% based on 4,3-opybz. Anal. Calc. for
C
12H8MnN4O3: C, 46.32; H, 2.59; N, 18.01. Found: C, 46.53; H,
3.06; N, 17.53%. IR (KBr, cmꢀ1): 2096s, 1592m, 1545m, 1474w,
1397s, 1325w, 1177w, 887w, 786w.
2.2.2. [Cu(4,3-opybz)(N3)]n (2)
In a test tube, a mixture solution of 4,3-Hopybz (0.025 mmol,
0.0062 g) and NaN3 (0.2 mmol, 0.013 g) in water (3 mL) was lay-
ered carefully with 3 mL of methanol–water (1:1) and then a meth-
anol solution (3 mL) of Cu(ClO4)2ꢁ6H2O (0.10 mmol, 0.037 g). The
tube was sealed and left undisturbed at room temperature. X-
ray-quality green block crystals appeared 4 days later. Yield: 60%
based on 4,3-opybz. Anal. Calc. for C12H8CuN4O3: C, 45.07; H,
2.52; N, 17.52. Found: C, 45.33; H, 2.94; N, 17.32%. IR (KBr,
cmꢀ1): 2086s, 1585m, 1539m, 1466w, 1404s, 1297s, 1190m,
892m, 779w.
end-on (EO) and a N-oxide
l
-O group, with Mnꢁ ꢁ ꢁMn = 3.286(1) Å,
Mn–N–Mn = 96.07(6)° and Mn–O–Mn = 92.28(4)° for 1, CuꢁꢁꢁCu =
3.223(1) Å, Cu–N–Cu = 108.06(7)° and Cu–O–Cu = 77.47(4)° for 2.
The repetition of the triple bridges generates a 1D chain along
the c (for 1) or b (for 2) direction (Fig. 1). In 2, the azide and car-
boxylate bridges are in the equatorial–equatorial fashion, while
the N-oxide bridge adopts the axial–axial disposition (i.e., the
N-oxide oxygen atoms reside at the elongated axes of the two
Cu(II) ions it links). These features are of particular relevance to
the magnetic properties.
2.3. Crystallographic analysis
Diffraction data for 1 and 2 were collected at 293 K on a Bruker
Apex II CCD area detector equipped with graphite-monochromated
Mo Ka radiation (k = 0.71073 Å). Empirical absorption corrections
were applied using the SADABS program [39]. The structures were
solved by the direct method and refined by the full-matrix least-
squares method on F2, with all non-hydrogen atoms refined with
anisotropic thermal parameters [40]. All the hydrogen atoms at-
tached to carbon atoms were placed in calculated positions and re-
fined using the riding model. Selected crystal data are listed in
Table 1.
The 4,3-opybz ligand serves as interchain l4 bridge in both
compounds, with the syn–syn carboxylate group binding two metal
ions from one chain and the N-oxide group binding two metal ions
from another chain, Thus the chains are interlinked into a 2D layer
along the bc plane (Fig. 2a for 1 and Fig. 3a for 2). The change of the
metal coordination configuration from cis to trans make the layer
shape change from butterfly-like (in 1) to stair-like (in 2), as is
revealed by the side views shown in Fig. 2b (1) and Fig. 3b (2). In

X.-M. Zhang et al. / Inorganica Chimica Acta 392 (2012) 311–316
313
Fig. 1. Coordination structure in 1 (a) and 2 (b). Hydrogen atoms are not shown for clarity.
Table 2
vs. T plots in Fig. 4. The
3.94 emu K molꢀ1, lower than the spin-only value (4.375 emu K molꢀ1
expected for an isolated high-spin Mn(II) ion with g = 2.00. As the
temperature is lowered, the T value decreases monotonically,
while the value first increases to a broad maximum at 19 K, then
drops rapidly until 5 K, and finally increases rapidly again upon
further cooling to 2 K. The data above 100 K follow the Curie–
Weiss law with C = 4.36 cm3 K molꢀ1 and h = ꢀ31.5 K. The above
features indicate an antiferromagnetic coupling between neighbor-
vT value per Mn(II) at 300 K is about
Selected bond lengths (Å) and angles (°) for compounds 1 and 2.
)
1
2
v
Mn1–O1
Mn1–O2A
Mn1–N2
Mn1–N2A
Mn1–O3B
Mn1–O3C
2.114(1)
2.118(1)
2.199(1)
2.220(1)
2.255(1)
2.302(1)
178.43(5)
88.15(5)
91.36(5)
88.28(5)
93.27(5)
100.41(6)
86.96(4)
93.46(5)
174.32(5)
82.33(5)
82.73(5)
95.72(4)
81.73(5)
170.71(5)
94.78(5)
96.07(6)
92.28(4)
Cu1–O1
Cu1–O2A
Cu1–N2
Cu1–N2A
Cu1–O3B
Cu1–O3C
1.967(1)
1.941(1)
1.985(1)
1.997(1)
2.475(1)
2.669(2)
176.27(6)
92.65(6)
87.01(6)
90.39(6)
90.83(6)
165.77(4)
94.74(5)
81.84(5)
107.82(5)
85.75(5)
90.27(5)
93.34(5)
80.86(5)
85.24(5)
169.71(5)
108.06(7)
77.47(4)
v
O1–Mn1–O2A
O1–Mn1–N2
O2A–Mn1–N2
O1–Mn1–N2A
O2A–Mn1–N2A
N2–Mn1–N2A
O1–Mn1–O3B
O2A–Mn1–O3B
N2–Mn1–O3B
N2A–Mn1–O3B
O1–Mn1–O3C
O2A–Mn1–O3C
N2–Mn1–O3C
N2A–Mn1–O3C
O3B–Mn1–O3C
Mn1–N2–Mn1D
Mn1–O3C–Mn1D
O1–Cu1–O2A
O1–Cu1–N2
O2A–Cu1–N2
O1–Cu1–N2A
O2A–Cu1–N2A
N2–Cu1–N2A
O1–Cu1–O3B
O2A–Cu1–O3B
N2–Cu1–O3B
N2A–Cu1–O3B
O1–Cu1–O3C
O2A–Cu1–O3C
N2–Cu1–O3C
N2A–Cu1–O3C
O3B–Cu1–O3C
Cu1–N2–Cu1D
Cu1–O3C–Cu1D
ing Mn(II) ions. The rise in
v below 5 K may due to the presence of
any paramagnetic impurity.
According to the structural data, the system could be treated as
1D uniform chains in which magnetic exchange is mediated
through the [(l-EO-N3)(l-COO)(l-O)] triple bridge. The molar sus-
ceptibility of the chain is described by the well-known classical-
spin equation derived by Fisher [39].
Ng2b2SðS þ 1Þ 1 þ u
vchain
¼
ð1Þ
3kT
1 ꢀ u
where
u
is the Langevin function u = coth[JS(S + 1)/kT] ꢀ kT/
[JS(S + 1)], and J is the intrachain exchange parameter based on
P
the Hamiltonian H = ꢀJ SiSi+1. A
q parameter representing the mo-
For compound 1, A: x, ꢀy + 1/2, z ꢀ 1/2; B: ꢀx + 1, ꢀy + 1, ꢀz + 1; C: ꢀx + 1, y ꢀ 1/2,
ꢀz + 3/2; D: x, ꢀy + 1/2, z + 1/2; E: ꢀx + 1, y + 1/2, ꢀz + 3/2; for compound 2, A: ꢀx,
y ꢀ 1/2, ꢀz + 1/2; B: ꢀx, ꢀy, ꢀz + 1; C: x, ꢀy + 1/2, z ꢀ 1/2; D: ꢀx, y + 1/2, ꢀz + 1/2.
lar fraction of the paramagnetic impurity (assumed to be mononu-
clear Mn(II) species,
v
impurity = 4.375/T) has also been included to
account for the observed rise in
v below 5 K. With S = 5/2 and g
fixed at 2.00, the best fit in the whole temperature range by this
expression led to J = ꢀ3.44 cmꢀ1 and
q = 0.0048. This negative value
of J confirms the antiferromagnetic nature of the coupling of the
1, the metal ions in each layer are on two separate planes, while in
2, all the metal ions in a layer are coplanar. The nearest interchain
MꢁꢁꢁM distance spanned by the 4,3-opybz ligand is 11.547(1) Å for
1 and 11.535(1) Å for 2.
The layers are packed with weak interlayer hydrogen bonds,
which involve C–H groups from one layer and azide N atoms and
N-oxide O atoms from another layer (Fig. S1 for 1, Fig. S2 for 2
see the Supporting information). The shortest interlayer Mꢁ ꢁ ꢁM dis-
tances are 9.463(6) Å for 1 and 8.522(1) Å for 2.
Mn(II) spins through the mixed triple bridge.
The magnetic interaction through mixed bridges should be the
cooperative or competitive effect of the different exchange path-
ways. Generally speaking, the syn–syn carboxylate and l2-oxygen
mixed bridge always mediates antiferromagnetic coupling be-
tween Mn(II) ions, are confirmed by previous compounds with
the mixed
l2-oxygen and carboxylate bridges [30–34]. For the
EO azide bridges, Density function theory calculations [41] on
dinuclear model Mn(II) systems indicates that the bridge induces
ferromagnetic coupling for Mn–N–Mn angles >98°. In the case of
1, the Mn–N–Mn angles being 96.07°, lower than 98°, can give rise
to antiferromagnetic coupling. Magnetic analyses on 1 suggest that
all pathways collaborate to give the observed antiferromagnetic
3.2. Magnetic properties
The magnetic susceptibility (
v) of compound 1 was measured
under 1 kOe in the range of 2–300 K and is shown as
vT and
v

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X.-M. Zhang et al. / Inorganica Chimica Acta 392 (2012) 311–316
Fig. 2. Top (a) and side (b) views of the 2D layers in 1 formed by 4,3-opybz interlinking the chains.
ꢀ ꢁ
2=3
Ng2b2
4kT
A
B
coupling, and the magnitude of the J value is consistent with that
observed recently for an alternating chain, which is the only
vchain
¼
ð2Þ
known Mn(II) species with the (N3)(COO)(
l-O)] triple bridge[37].
with
Magnetic measurements were carried out on a polycrystalline
sample of 2 at an applied field of 1 kOe (Fig. 5). The
vT value per
A ¼ 1 þ 5:7979916x þ 16:902653x2 þ 29:376885x3 þ 29:832959x4 þ 14:036918x5
B ¼ 1 þ 2:7979916x þ 7:008678x2 þ 8:6538644x3 þ 4:5743114x4
Cu(II) at 300 K is about 0.66 emu K molꢀ1, higher than the spin-
only value (0.375 emu K molꢀ1) expected for a uncoupled S = 1/2
spins. As the temperature is lowered, the
v
value increase mono-
xchain
tonically, while the
v
T value first increases to a maximum at 3 K
h
i
v
¼
ð3Þ
of 7.21 emu K molꢀ1 and then decreases slightly upon further
cooling to 2 K. The data above 150 K follow the Curie–Weiss law
with C = 0.52 cm3 K molꢀ1 and h = 52.11 K. The high-temperature
behavior suggests dominant ferromagnetic coupling between
1 ꢀ zJ0xchain=ðNg2b2Þ
where x = J/2kT. The experimental susceptibility data has been fitted
by the above expressions with best-fit parameters J = 99.4 cmꢀ1
,
Cu(II) ions, while the low-temperature decrease of
vT may be
g = 2.13 and zJ0 = ꢀ0.013 cmꢀ1 (zJ0 describes the interchain antifer-
romagnetic interaction). The positive J value confirms the ferromag-
netic coupling through the mixed triple bridge.
attributed to the saturation effect and/or the presence of interchain
antiferromagnetic interactions. The isothermal magnetization
curve measured at 2 K (Fig. 6) also supports the ferromagnetic cou-
pling. The magnetization rises rapidly with the field and almost
saturates at 50 kOe, the saturation value of 1.07 Nb corresponding
to g = 2.14.
In compound 2, the Cu(II) ions are bridged by one N-oxide
group, one EO azide, and one syn–syn carboxylate group. As has
been noted, the N-oxide bridge adopts the axial–axial disposition
between Cu(II) ions. Because a Cu(II) ion in the axially elongated
To evaluate the interactions, the system can be treated as an infi-
nite uniform chain in which magnetic coupling is mediated through
the [(l-EO-N3)(l-COO)(l-O)] triple bridge. The susceptibility
octahedral environment features a dx2 -type magnetic orbital
ꢀy2
delocalized toward equatorial ligands with poor delocalization to-
ward axial ligands, the axial–axial N-oxide bridge in 2 is less
important pathway for magnetic exchange and may be neglected.
Thus, the effective exchange pathways in 2 include two dissimilar
equatorial–equatorial bridges: a syn–syn carboxylate and an EO
expression proposed by Baker et al. for Heisenberg ferromagnetic
S = 1/2 chains (Eq. (2) [42] based on the spin Hamiltonian
P
H = ꢀJ SiSi+1 and the mean field model accounting for interchain
interactions (Eq. (3)) [43] were used for magnetic analysis.
azide. Such mixed equatorial–equatorial
(l-EO-N3)(l-COO)

X.-M. Zhang et al. / Inorganica Chimica Acta 392 (2012) 311–316
315
Fig. 3. Top (a) and side (b) views of the 2D layers in 2 formed by 4,3-opybz interlinking the chains.
Fig. 5. Temperature dependence of
represent the best fit using Eqs. (2) and (3) (see text).
v
and
v
T for 2 under 1 kOe. The solid lines
Fig. 4. Temperature dependence of
represent the best fit to the conversional equation derived by Fisher for a uniform
chain (see text).
v and vT for 1 under 1 kOe. The solid lines
ferromagnetic interactions, with the J parameters in the range from
26 to 126 cmꢀ1, and there is a rough trend that the magnitude of
the interaction decreases with the Cu–N–Cu angle, which varies
in the wide range from 101° to 127°. The data for 2, J = 99.4 cmꢀ1
with Cu–N–Cu = 108.06(7)°, are consistent with the general trend.
bridges, with or without axial–axial bridges, have been found in a
number of Cu(II) species [26–29,35]. The magnetostructural data
for these compounds have been collected and analyzed elsewhere
by us [44]. The mixed bridges in all of these compounds induce

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X.-M. Zhang et al. / Inorganica Chimica Acta 392 (2012) 311–316
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We have described the syntheses, structures, and magnetic
properties of two Cu(II) and Mn(II) coordination polymers with
azide and 4,3-Hopybz. They both consist of 2D coordination layers
in which 1D coordination chains with uniform [(
l-EO-N3)(l-
COO)( -O)] triple bridges are interlinked by the 4,3-opybz spacers.
l
The structural difference is mainly due to the cis (1) or trans (2)
coordination geometry around metal ions. Magnetic studies
showed that the magnetic coupling through the mixed triple
bridge is antiferromagnetic in the Mn(II) compound (1) but ferro-
magnetic in the Cu(II) species (2).
Acknowledgment
We are thankful for the financial support from NSFC (51073064
and 91022017).
Appendix A. Supplementary material
CCDC 847143 and 847144 contain the supplementary crystallo-
graphic data for compounds 1 and 2, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplemen-
tary data associated with this article can be found, in the online
version, at http://dx.doi.org/10.1016/j.ica.2012.03.050.
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