Syntheses, structural diversities and magnetic properties of four new Co(II) coordination polymers with phthalic acid derivatives

Article abstract of DOI:10.1016/j.poly.2012.12.032

Four new 3D Co(II) coordination polymers, [Co(4apa)(H₂O)] (1), [Co(bpy)(3npa)] (2), [Co(bpy)_1.5(3adpa)] (3) and [Co(btx) _0.5(4npa)(H₂O)₂] (4) (H₂4apa = 4-aminophthalic acid, bpy = 4,4′-bipy

Full text of DOI:10.1016/j.poly.2012.12.032

Polyhedron 51 (2013) 283–291
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses, structural diversities and magnetic properties of four new Co(II)
coordination polymers with phthalic acid derivatives
⇑
Shi-Yuan Zhang, Na Xu , Wei Shi, Peng Cheng, Dai-Zheng Liao
Department of Chemistry, Key Laboratory of Advanced Energy Material Chemistry, MOE, and TKL of Metal and Molecule Based Material Chemistry, Nankai University,
Tianjin 300071, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new 3D Co(II) coordination polymers, [Co(4apa)(H2O)] (1), [Co(bpy)(3npa)] (2), [Co(bpy)1.5(3adpa)]
(3) and [Co(btx)0.5(4npa)(H2O)2] (4) (H24apa = 4-aminophthalic acid, bpy = 4,40-bipyridine, H23npa = 3-
nitrophthalic acid, H23adpa = 3-(4-amino-1,3-dioxoisoindolin-2-yl)phthalic acid, btx = 1,4-bis(1,2,4-tria-
zole-1-ylmethyl)benzene, H24npa = 4-nitrophthalic acid), have been synthesized and characterized by
single crystal X-ray diffraction, PXRD and magnetic susceptibility measurements. An interesting in situ
acylation reaction of 3-aminophthalic acid (H23apa) has been found in the formation of coordination
polymer 3. The Co(II) ions of each polymer lie in distorted octahedral environments and are bridged
Received 1 August 2012
Accepted 21 December 2012
Available online 11 January 2013
Keywords:
Co(II) coordination polymer
Phthalic acid
Crystal structure
Magnetic property
by l1,3 carboxylate groups to form 2D (1), 1D (2 and 3) and dimer (4) structures, which are further assem-
bled through ligands into different 3D structures due to the influence of the substituent groups. Studies of
the temperature dependence of the magnetic susceptibilities in the range 2–300 K reveal antiferromag-
netic interactions in 1–4 between the Co(II) ions transmitted by l1,3 carboxylate groups.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
quenched by the ligand field. On the other hand, carboxylato li-
gands exhibit an extensively documented ability to bridge metal
Functional coordination polymers have attracted considerable
attention in the past decades due to their valuable properties, such
as magnetism [1], luminescence [2], catalysis [3], and adsorption
[4]. In this context, magnetic coordination polymers are of special
interest. The magnetic properties of coordination polymers are
attributed to (i) spin carriers such as metal ions providing the
source of magnetic moments, and (ii) different bridging ligands
providing superexchange pathways between the spin carriers. To
better understand the magnetic properties of coordination poly-
mers there have been many efforts in the strategy of synthesis
and analysis of magneto-structural correlations [1,5], but it is still
a great challenge to assemble spin carriers to the skeleton of coor-
dination polymers with predetermined structures and targetted
magnetic properties. The way to solve of this problem lies in the
understanding of magneto-structural correlations more thor-
oughly through both experimental and theoretical investigations.
Co(II) ion is one of the interesting candidates of spin carriers
and usually leads to fascinating magnetic properties. In an octahe-
dral coordination geometry, its magnetic moment includes contri-
butions from not only the spin angular momentum but also the
orbital angular momentum, different from other first-row transi-
tion metal ions whose orbital angular momentums are always
ions, forming 1D, 2D and 3D coordination networks [1a,f,6]. Car-
boxylate groups can adopt many types of bridging conformations,
such as triatomic syn-syn, anti-syn, and anti–anti. Ferro- or antifer-
ro-magnetic interactions can be effectively transmitted through
such three atom bridges [7]. However, due to the structural diver-
sities of Co(II) coordination polymers, a detailed understanding of
magneto-structural correlations in such systems is still unclear
[1c]. Our previous studies show that phthalic acid is a good bridg-
ing ligand to build molecular magnetic materials due to its flexibil-
ity of coordination modes [8]. As a continuation of this work, four
phthalic acid derivatives (H24apa = 4-aminophthalic acid,
H23npa = 3-nitrophthalic acid, H23apa = 3-aminophthalic acid,
H24npa = 4-nitrophthalic acid) were selected because of their abil-
ities to adopt various coordination modes like phthalic acid but
with different substituent groups. It is noted that H23adpa (H2-
3adpa = 3-(4-amino-1,3-dioxoisoindolin-2-yl)phthalic acid) was
formed by the in situ acylation reaction of 3-aminophthalic acid
(H23apa) in the formation of coordination polymer 3. Furthermore,
net neutral linear linkers 4,40-bipyridine (bpy) and 1,4-bis(1,2,4-
triazole-1-ylmethyl)benzene (btx) were employed as co-ligands.
Four new 3D coordination polymers, [Co(4apa)(H2O)] (1), [Co(b-
py)(3npa)] (2), [Co(bpy)1.5(3adpa)] (3) and [Co(btx)0.5(4npa)(H2-
O)2] (4), were successfully synthesized and characterized. Studies
of the temperature dependence of the magnetic susceptibilities
in the range 2–300 K reveal antiferromagnetic interactions in 1–4
⇑
Corresponding author.
E-mail address: naxu@nankai.edu.cn (N. Xu).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.032

284
S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
between the Co(II) ions transmitted by the anti–syn carboxylate
groups.
dried in air. Yield: 76% based on bpy. Anal. Calc. for C18H11CoN3O6
(424.23): C, 50.96; H, 2.61; N, 9.91. Found: C, 50.96; H, 2.62; N,
9.79%.
2. Experimental
2.2.3. [Co(bpy)1.5(3adpa)] (3)
A mixture of Co(NO3)2ꢀ6H2O (0.116 g, 0.40 mmol), 4,40-bipyri-
dine (0.048 g, 0.30 mmol), 3-aminophthalic acid (0.054 g,
0.30 mmol), NaOH (0.016 g, 0.40 mmol) and H2O (10 mL) was
sealed in a 25 mL Teflon-lined stainless steel vessel and heated at
150 °C for 2 days, and then cooled to room temperature. Red
block-shaped crystals were filtered off, washed with water and
dried in air. Yield: 64% based on bpy. Anal. Calc. for C31H20CoN5O6
(617.45): C, 60.30; H, 3.26; N, 11.34. Found: C, 60.04; H, 3.74; N,
11.56%.
2.1. General considerations
All reagents and solvents employed were commercially avail-
able and used as received without further purification. Elemental
analyses for C, H and N were performed on a Perkin-Elmer 240
CHN elemental analyzer. Powder X-ray diffraction measurements
were measured on a D/Max-2500 X-ray diffractometer using Cu
Ka radiation. Variable-temperature magnetic susceptibilities were
measured on a SQUID MPMS XL-7 magnetometer. Diamagnetic cor-
rections were made with Pascal’s constants for all the constituent
atoms and sample holders.
2.2.4. [Co(btx)0.5(4npa)(H2O)2] (4)
A mixture of Co(NO3)2ꢀ6H2O (0.116 g, 0.40 mmol), 1,4-bis(1,2,4-
triazol-1-ylmethyl) benzene (0.024 g, 0.10 mmol), 4-nitrophthalic
acid (0.042 g, 0.20 mmol), NaOH (0.008 g, 0.20 mmol) and H2O
(10 mL) was sealed in a 25 mL Teflon-lined stainless steel vessel
and heated at 150 °C for 2 days, and then cooled to room temper-
ature. Red block-shaped crystals were filtered off, washed
with water and dried in air. Yield: 73% based on btx. Anal. Calc.
for C14H13CoN4O8 (424.21): C, 39.64; H, 3.09; N, 13.21. Found:
C, 39.78; H, 3.00; N, 12.98%.
2.2. Syntheses
2.2.1. [Co(4apa)(H2O)] (1)
A mixture of Co(NO3)2ꢀ6H2O (0.116 g, 0.40 mmol), 4-aminoph-
thalic acid (0.054 g, 0.30 mmol), NaOH (0.016 g, 0.40 mmol) and
H2O (10 mL) was sealed in a 25 mL Teflon-lined stainless steel
vessel and heated at 150 °C for 2 days, and then cooled to room
temperature. Red block-shaped crystals were filtered off, washed
with water and dried in air. Yield: 67% based on 4apa. Anal.
Calc. for C8H9CoNO5 (258.08): C, 37.23; H, 3.51; N, 5.43. Found:
C, 37.45; H, 3.80; N, 5.59%.
2.3. Crystal structure determination
Diffraction data of the four compounds were collected at 150 or
293 K on an Oxford Supernova diffractometer equipped with
2.2.2. [Co(bpy)(3npa)] (2)
graphite-monochromated Mo K
a radiation (k = 0.71073 Å) using
A mixture of Co(NO3)2ꢀ6H2O (0.116 g, 0.40 mmol), 4,40-bipyri-
dine (0.016 g, 0.10 mmol), 3-nitrophthalic acid (0.042 g,
0.20 mmol), NaOH (0.008 g, 0.20 mmol) and H2O (10 mL) was
sealed in a 25 mL Teflon-lined stainless steel vessel and heated at
150 °C for 2 days, and then cooled to room temperature. Red
block-shaped crystals were filtered off, washed with water and
the -scan technique. Lorentz polarization and absorption correc-
x
tions were applied. The structures were solved by the direct meth-
od and refined with the full-matrix least-squares technique using
the SHELXTL program package [9]. Anisotropic thermal parameters
were assigned to all non-hydrogen atoms. The hydrogen atoms
were set in calculated positions and refined as riding atoms with
Table 1
Data collection and processing parameters for 1–4.
1
2
3
4
Formula
Formula weight
T (K)
C8H7CoNO5
256.08
150(2)
C18H11CoN3O6
424.23
150(2)
C31H20CoN5O6
617.45
293(2)
C14H13CoN4O8
424.21
150(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P2(1)/c
10.3115(4)
7.3868(3)
14.2596(7)
90
monoclinic
P2(1)/n
7.1044(8)
23.403(2)
10.8747(15)
90
monoclinic
P21/c
11.5656(5)
21.4632(6)
11.8959(5)
90
monoclinic
C2/c
37.186(3)
5.9373(4)
14.9209(9)
90
a
(°)
b (°)
126.966(3)
90
867.82(6)
4
1.960
1.977
113.173(10)
90
1662.2(3)
4
1.695
1.078
108.644(4)
90
2798.01(19)
1
1.466
0.668
112.981(8)
90
3032.8(4)
8
1.858
1.192
c
(°)
V (Å3)
Z
q
l
(g/cm3)
(mmꢁ1
)
h (°)
Index ranges
2.88–25.99
ꢁ12 6 h 6 12, ꢁ9 6 k 6 8,
ꢁ17 6 l 6 17
3334
2.68–26.00
ꢁ8 6 h 6 4, ꢁ28 6 k 6 21,
ꢁ12 6 l 6 13
6888
2.62–25.01
ꢁ13 6 h 6 13, ꢁ25 6 k 6 24,
ꢁ9 6 l 6 14
10418
2.38–25.50
ꢁ44 6 h 6 44, ꢁ7 6 k 6 5,
ꢁ17 6 l 6 18
5769
Reflections collected
Independent reflections
1707 (0.0282)
3269 (0.0282)
4930 (0.0282)
2810 (0.0282)
(Rint
)
Data/restraints/
parameters
1707/0/140
3269/24/253
0.949
4930/15/389
1.062
2810/0/256
1.016
Goodness-of-fit (GOF) on 1.044
F2
R1,
R1,
x
x
R2 [I > 2
R2 (all data)
r
(I)]
0.0356, 0.0846
0.0425, 0.0872
0.0560, 0.1432
0.0987, 0.1832
0.0801, 0.2429
0.1263, 0.2643
0.0316, 0.0741
0.0410, 0.0770

S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
285
Table 2
Selected bond lengths (Å) for 1–4.
1a
2b
Co(1)–O(4)#1
Co(1)–O(1)
Co(1)–O(2)#2
2.035(2)
2.073(2)
2.091(2)
Co(1)–O(3)#2
Co(1)–O(5)
Co(1)–N(1)#3
2.093(2)
2.136(2)
2.210(3)
Co(1)–O(2)#1
Co(1)–O(3)
Co(1)–O(1)
2.051(4)
2.074(4)
2.086(3)
Co(1)–O(4)#2
Co(1)–N(2)#3
Co(1)–N(1)
2.098(4)
2.142(4)
2.187(4)
3c
4d
Co(1)–O(3)
Co(1)–O(2)#1
Co(1)–N(2)
2.104(4)
2.106(4)
2.123(6)
Co(1)–N(1)#2
Co(1)–O(1)
Co(1)–N(3)
2.129(6)
2.149(4)
2.190(5)
Co(1)–O(1)#1
Co(1)–O(4)#2
Co(1)–O(3)
2.0740(15)
2.0777(15)
2.1042(14)
Co(1)–N(1)
Co(1)–O(8)
Co(1)–O(7)
2.1268(19)
2.1287(18)
2.1352(18)
a
b
c
Symmetry transformations used to generate equivalent atoms: #1 x, ꢁy + 1/2, zꢁ1/2; #2 ꢁx + 2, yꢁ1/2, ꢁz + 1/2; #3 ꢁx + 1, ꢁy, ꢁz.
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + 1, ꢁy, ꢁz + 1; #2 ꢁx + 2, ꢁy, ꢁz + 1; #3 x + 1, ꢁy + 1/2, z + 1/2.
Symmetry transformations used to generate equivalent atoms: #1 x, ꢁy + 1/2, zꢁ1/2; #2 x ꢁ 1, ꢁy + 1/2, z ꢁ 1/2.
Symmetry transformations used to generate equivalent atoms: #1 x, ꢁy + 1, zꢁ1/2; #2 ꢁx + 1/2, ꢁy + 3/2, ꢁz + 1.
d
Fig. 1. (a) ORTEP plot of [Co(4apa)(H2O)] (1). Thermal ellipsoids are shown at 30% probability. (b) The 1D structure in 1. (c) The 2D structure formed by
bridges. (d) The 3D network of 1. All H atoms are omitted for clarity.
l1,3-carboxylate
a common fixed isotropic thermal parameter. The crystallographic
data, bond lengths and selected angles of 1–4 are listed in Tables 1
and 2 and S1, respectively.
2.210 Å. The
the anti–syn mode. The neighboring Co(II) ions are linked by dou-
ble and single 1,3-bridging carboxylate groups in an alternating
l1,3-carboxylate group links adjacent Co(II) ion in
l
way, forming a 1D structure with Coꢀ ꢀ ꢀCo distances of 4.3804
and 4.8425 Å, respectively (Fig. 1b). A 2D structure is formed in
the bc plane via the connection of
l1,3-carboxylate bridges
3. Results and discussion
(Fig. 1c). The layers are further linked by the amino and carboxyl-
ate groups of 4apa2ꢁ, forming a 3D framework (Fig. 1d).
3.1. Structural description
3.1.1. [Co(4apa)(H2O)] (1)
3.1.2. [Co(bpy)(3npa)] (2)
As shown in Fig. 1a, the Co(II) ion is six-coordinated and located
in a slightly distorted octahedral environment surrounded by five
O atoms (O1, O2A, O3A and O4A from the carboxylate groups of
4apa2ꢁ anions; O5 from the H2O molecule) and one N atom (N1A
from the amino group of the 4apa2ꢁ anion). The Co–O bond lengths
are in the range 2.035–2.136 Å and the Co–N bond length is
The central Co(II) ion is surrounded by four oxygen atoms (O1,
O2A, O3 and O4A) from the carboxylate groups of 3npa2ꢁ and two
nitrogen atoms (N1 and N2A) from bpy in a slightly distorted octa-
hedral geometry (Fig. 2a). The nitro group of 3npa2ꢁ does not coor-
dinate to the Co(II) ions. The Co–O and Co–N bond lengths are in
the ranges 2.051–2.098 Å and 2.142–2.187 Å, respectively. Each

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S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
Fig. 2. (a) ORTEP plot of [Co(bpy)(3npa)] (2). Thermal ellipsoids are shown at 30% probability. (b) The 1D structure in 2. All bpy ligands are omitted for clarity. (c) The 3D
structure of 2. All H atoms are omitted for clarity.
Scheme 1. In situ acylation reaction of 3-aminophthalic acid to give 3-(4-amino-1,3-dioxoisoindolin-2-yl) phthalic acid.
l
1,3-carboxylate group links adjacent Co(II) ions in anti–syn mode.
(Scheme 1) occurred during the formation of 3. The Co(II) ion lies
in a slightly distorted octahedral coordination geometry, sur-
rounded by three O atoms (O1, O2A and O3) from the carboxylate
groups of 3adpa2ꢁ and three N atoms (N1A, N2 and N3) from bpy
(Fig. 3a). The Co–O and Co–N bond lengths are in the ranges
2.104–2.149 Å and 2.129–2.190 Å, respectively. Adjacent Co(II)
Two adjacent Co(II) ions are connected by double 1,3-carboxylate
l
bridges to form a 1D structure along the a axis with Coꢀ ꢀ ꢀCo dis-
tances of 4.4996(3) and 4.8375(4) Å (Fig. 2b). The chains are fur-
ther connected via bpy in the bc plane, resulting in
coordination network (Fig. 2c).
a 3D
ions are bridged by a l1,3-carboxylate group in the anti–syn mode
to form a 1D structure along the c axis (Fig. 3b) with adjacent
Coꢀ ꢀ ꢀCo distances of 5.9587(2) and 5.9628(2) Å. The chains are
further linked by bpy ligands, forming a 3D coordination network
(Fig. 3c).
3.1.3. [Co(bpy)1.5(3adpa)] (3)
Single crystal X-ray diffraction reveals that a hydrothermal
in situ acylation reaction of 3-aminophthalic acid (H23apa) to give
3-(4-amino-1,3-dioxoisoindolin-2-yl)phthalic
acid
(H23adpa)

S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
287
Fig. 3. (a) ORTEP plot of [Co(bpy)1.5(3adpa)] (3). Thermal ellipsoids are shown at 30% probability. (b) The 1D Co–COO–Co structure in 3. (c) The 3D structure of 3. All H atoms
are omitted for clarity.
3.1.4. [Co(btx)0.5(4npa)(H2O)2] (4)
phthalate in 3 serve as a bridge between two Co(II) ions in
g1 and l1 g0 fashions. The large steric hindrance of the
3-position substituent group prevents the double bridged mode
The Co(II) ion is coordinated by five O atoms (O1A, O3 and O4A
from the carboxylate groups of 4npa2ꢁ anions; O7 and O8 from
H2O molecules) and one N atom (N1) from btx (Fig. 4a) to form a
slightly distorted octahedral environment. Similar to 2, the nitro
group of 4npa2ꢁ does not coordinate to the Co(II) ions. The Co–O
bond lengths are in the range 2.0740–2.1352 Å and Co–N bond
length is 2.1268 Å. Two neighboring Co(II) ions are bridged by
l2–
g1
:
– :
g1
(Scheme 2C). For 4, the nitro group does not coordinate to any Co(II)
ion, and the ligand adopts l2– : – :
g1 g1 and l1 g1 g0 fashions to link
three Co(II) ions into the final framework (Scheme 2D).
3.2. Magnetic studies
two l1,3-carboxylate groups in the anti–syn mode to form a dimer
structure with a Coꢀ ꢀ ꢀCo distance of 4.7592(5) Å. The dimers are
connected by the carboxylate groups from two 4npa2ꢁ anions,
forming a chain along the c axis with a nearest Coꢀ ꢀ ꢀCo distance
(between dimers) of 5.6817(3) Å (Fig. 4b). In the bc plane, the di-
The magnetic susceptibilities of 1–4 were measured in the tem-
perature range 2–300 K, as shown in Fig. S2. At room temperature,
the
v
MT values of 3.22 (1), 3.24 (2), 2.56 (3) and 3.26 (4) cm3
K molꢁ1 are much higher than the expected 1.88 cm3 K molꢁ1 for
mers (polyhedrons in Fig. 4c) are linked via l1,3-carboxylate groups
the spin-only value of one free Co(II) ion (S = 3/2), but the
of 4npa2ꢁ to form 2D structures, which are further linked by btx,
forming a 3D framework (Fig. 4d).
values are close to 3.38 cm3 K molꢁ1 MT = Nb2/(3k) [L(L + 1) +
(v
4S(S + 1))], L = 3, S = 3/2) where the contribution of the orbital angu-
The substituent group of phthalic acid plays an important role in
the final structure. As shown in Scheme 2A and B, the two carbox-
ylate groups of 4-aminophthalic acid or 3-nitrophthalic acid bridge
lar momentum of the octahedral Co(II) ion is taken into account.
3.2.1. [Co(4apa)(H2O)] (1)
three Co(II) ions in a l2– :g
g1 1 fashion. The difference in the coordi-
Upon cooling, vMT decreases gradually until ca. 50 K and then it
decreases rapidly to 0.16 cm3 K molꢁ1 at 2 K. A maximum value of
0.18 cm3 molꢁ1 at 5 K is observed for the magnetic susceptibility,
suggesting possible antiferromagnetic interactions between the
Co(II) ions. The data in the range 10–300 K obey the Curie–Weiss
nation mode of the two ligands is the additional coordination bond
between the amino group and the Co(II) ions in 1. Due to the posi-
tion of the amino group, neighboring Co(II) ions are linked by dou-
ble and single
way in 1, whilst neighboring Co(II) ions are linked only by double
1,3-bridging carboxylate groups in 2. The carboxylate groups of
l1,3-bridging carboxylate groups in an alternating
law
[v
M = C/(T – h)] with C = 3.5 cm3 K molꢁ1 and h = ꢁ23 K.
l
Though the orbital angular momentum of the hexacoordinated

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S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
Fig. 4. (a) ORTEP plot of [Co(btx)0.5(4npa)(H2O)2] (4). Thermal ellipsoids are shown at 30% probability. (b) The 1D structure in 4. (c) The 2D structure linked by carboxylate
groups. (d) The 3D structure of 4. All H atoms are omitted for clarity.
ble. As shown in the crystallographic part (Fig. 1), 1 is comprised of
Co
Co
a 2D structure in which each Co(II) ion is linked to the neighboring
Co(II) ion by single or double anti–syn carboxylate bridges, with
very small geometrical differences. The layers are further linked
into a 3D framework by the 4apa2ꢁ ligands, which transmit much
NO2
O
O
O
Co
NH
O
O
O
O
Co
weaker magnetic coupling due to the long distance and
r-type C–
Co
N bond. Thus, from the magnetic point of view, the 3D structure
can be reduced to a 2D magnetic structure. We analyzed the mag-
netic data with two methods. Firstly, if we assume that only one
magnetic exchange parameter is necessary to study the coupling
between the Co(II) ions, an approximate expression Eq. (1) [10]
suitable for 1D/2D Co(II) complexes can be applied to estimate
the magnetic interactions.
O
Co
Co
A
B
ꢀ
ꢁ
ꢀ
ꢁ
NH2
ꢁE1
ꢁE2
v
MT ¼ A exp
þ B exp
ð1Þ
kT
kT
Co
In this expression, A + B equals the Curie constant, and E1, E2
O
O
O
O
represent ‘‘activation energies’’ corresponding to the spin–orbit
coupling and the magnetic interaction, respectively. The best
N
O2N
O
O
O
Co
fit
gave
A + B = 3.5 cm3 K molꢁ1
,
E1/k = 63 K,
E2/k = 4.3 K,
R[(vM)obs
O
(J = ꢁ3.0 cmꢁ1
,
v
MT / exp(J/kT)), R = 5.8 ꢂ 10ꢁ5 (R =
v ) R[(v )
M calc]2/ M obs]2). Secondly, taking into account that double
Co
ꢁ (
O
anti–syn carboxylate bridges may transmit stronger magnetic cou-
pling than the single bridges, the magnetic structure can be consid-
ered as double-bridged dimers linked by single-bridged
carboxylates. For this case, the Magsaki program [11] through a
numerical matrix diagonalization based on the following Hamilto-
nian Eq. (2) suitable for a dimeric Co(II) system can be applied to fit
the magnetic data (red dash line in Fig. S2(a)).
Co
O
Co
C
D
Scheme 2. Coordination modes of phthalic acid derivatives in 1 (A), 2 (B), 3 (C) and
4 (D).
2
^
^
^ ^
^
^
H ¼ ꢁð3=2Þ
j
^
kL ꢀ S þ
D
ðLz ꢁ LðL þ 1Þ=3Þ þ b½ꢁð3=2Þ
j
L þ geSꢃ
high-spin Co(II) ions prevents quantitative analysis of the magnetic
behavior by the spin Hamiltonian, an approximation is still possi-
^
ꢀ H ꢁ JS1 ꢀ S2
ð2Þ

Table 3
Selected magneto-structural data for
l1,3-carboxylate bridged Co(II) complexes.
Compounda
Bridging mode
syn–syn
Nuclearityb
dimer
Fitting methods
C (cm3 K molꢁ1
3.30
)
H
(K)
J (cmꢁ1
ꢁ0.12
ꢁ0.03
)
Ref.
Ng2b2
14þ5X6 þX10
[Co(btx)(IPA)]
ꢁ3.7
ꢁ8.4
[10a]
[10a]
vCo
vCo
x
3
¼
¼
þ TIP X ¼ expðꢁJ=kBTÞ
7þ5X6 þ3X10 þX12
kB
Nb2
3kT
T
n
h
i
h
i
o
2
2
2
2
ꢂ
ꢃ
2
7ð3ꢁAÞ
12ðAþ2Þ
2ð11ꢁ2AÞ
176ðAþ2Þ
675A
ðAþ5Þ2 x
20ðAþ2Þ
27A
[Co3(btx)3(BTA)2(H2O)2]
syn–syn
trimer
3.37
5Ax
2
þ
þ
þ
exp
þ
ꢁ
ꢂ expðꢁ4AxÞ
=
5
25A
45
9
ꢆ
ꢄ
ꢂ
ꢃ
ꢅꢇ
3 þ 2 exp
ꢁ
þ expðꢁ4AxÞ vM
¼
v
Co=½1 ꢁ vCoð2zJ0=Ng2b2Þꢃ
5Ax
2
P
P
i
i
i
^
^
^
^
[Co(ppdc)(H2O)2]n
[Co2(4,40-bpy)(Memal)2(H2O)2]n
anti–anti
anti–syn
2D
2D
3.11
–
ꢁ13.3
–
ꢁ0.23
ꢁ0.05
[13]
[14]
H ¼ ꢁð25=9ÞJ i;jSeff ꢀ Seff ꢁ GðT; JÞbH iSeff
h
iꢁ1
P
9Nb2
6
Cn
vM
¼
¼
25jJj g20
3
H
þ
H
¼ 12kT=25jJj
nꢁ1
n¼1
H
[Co(L1OO)(H2O)][ClO4]ꢀ2H2O
[Co(bpe)(bba)]n
[Co(4apa)(H2O)]
anti–syn
1D
0:25þ0:074975xþ0:075235x2
–
–
ꢁ2.65
Ferro
ꢁ3.0
[15]
Nb2 g2
vM
–
x ¼ ð25=9ÞjJjkT; G(T,J) function instead of the g factor
1:0þ0:9931xþ0:172135x2 þ0:757825x3
kT
anti–syn
anti–syn
dimer
2D
3.34
3.5
1.20
ꢁ23
[16]
this work
ꢈ
ꢈ
ꢈ
ꢉ
ꢉ
ꢉ
ꢈ
ꢈ
ꢈ
ꢉ
ꢉ
ꢉ
ꢁE1
ꢁE2
v
v
MT ¼ A exp
MT ¼ A exp
MT ¼ A exp
þ B exp
þ B exp
kT
kT
ꢁE1
ꢁE2
[Co(bpy)(3npa)]
anti–syn
anti–syn
anti–syn
1D
1D
3.5
2.7
ꢁ19
ꢁ17
ꢁ5.8
this work
this work
kT
kT
ꢁE1
ꢁE2
[Co(bpy)1.5(3adpa)]
ꢁ0.16
v
þ B exp
kT
kT
^
^
^
^
^
^
^
^
[Co(btx)0.5(4npa)(H2O)2]
[Co3(ac)4(bpe)3(dca)2]n
[Co3(pybz)2(pico)2]n
dimer
trimer
2D
3.5
–
ꢁ19
–
ꢁ0.12
ꢁ1.6
ꢁ1.4
this work
[17]
H ¼ ꢁð3=2ÞkkL ꢀ S þ
D
ðLz2 ꢁ LðL þ 1Þ=3Þ þ b½ꢁð3=2Þ
j
S þ geSꢃ ꢀ H ꢁ JS1 ꢀ S2
P
syn–syn &
syn–syn &
l
l
-oxo
-oxo
H ¼ ꢁ2 i¼x;y;zJ1iðS1iS2i þ S2iS3i
Þ
Seff ¼ 1=2
ꢈ
ꢉ
ꢈ
ꢉ
ꢁE1
ꢁE2
2.96
ꢁ2.51
[18]
v
MT ¼ A exp
þ B exp
kT
kT
P
P
P
2
2
2
2
^
^
^ ^
^ ^
^
^
[Co2(bta)(H2O)6]nꢀ2nH2O
[Co(H2O)(phda)]nꢀ3nH2O
syn–syn &
syn–syn &
l
-oxo
-oxo
dimer
dimer
–
–
–
–
+5.4
[7]
[7]
H ¼ ꢁJS1S2
ꢁ
i¼1aikiLiSi þ i¼1Di½Lzi ꢁ 2=3ꢃ þ bH i¼1ðꢁ
a
iLi þ geSiÞ
P
P
P
P
2
2
^
^
^ ^
^ ^
^
^
l
+2.11
H ¼ nn ꢁ JSiSj ꢁ nnaikiLiSi þ nnDi½Lzi ꢁ 2=3ꢃ þ bH nnðꢁ
a
iLi þ geSiÞ
H2IPA = isophthalic acid, H3BTA = benzene-1,3,5-tricarboxylic acid, H2ppdc = p-phenylenediacrylic acid, Memal = methylmalonate dianion, L1OO = 3-[(2-(pyridin-2-yl)ethyl){2-(pyridin-2-yl)methyl}amino]propionate],
bpe = 1,2-bis(4-pyridyl)ethane, H2bba = isophthalic acid, dca = dicyanamide, ac = acetate, bpe = 1,2-bis-(4-pyridyl)ethane, pybz = 4-(pyridin-4-yl)benzoate, pico = 3-hydroxypicolinate, H4bta = 1,2,4,5-benzenetetracarboxylic acid,
H2phda = 1,4-phenylenediacetic acid.
a
b
The nuclearity of the compounds is based on the magnetic point of view.

290
S.-Y. Zhang et al. / Polyhedron 51 (2013) 283–291
In Eq. (2),
parameter,
j
is orbital reduction factor, k is spin–orbit coupling
groups assume a triatomic anti–syn bridging conformation in 1–4.
Based on the magnetic data, the large and negative Weiss con-
stants indicate not only spin–orbit coupling of the Co(II) ions, but
also significant antiferromagnetic interactions between the Co(II)
ions bridged by double l1,3-carboxylate groups in 1 and 2, which
is further confirmed by quantitative analysis of the data. Analysis
of the magnetic data for 3 and 4 suggests weak antiferromagnetic
interactions between the Co(II) ions bridged by single l1,3-carbox-
ylate groups. The relevant magneto-structural data, including the
bridging mode together with the exchange parameters, for selected
D
is the axial splitting parameter, J is isotropic ex-
change interaction. The best fit gave J = ꢁ3.0 cmꢁ1
, j = 0.93,
k = ꢁ130 cmꢁ1
,
D
= ꢁ351 cmꢁ1
,
gz = 6.1, gx = 3.2, h = ꢁ0.12 K,
P
R(
v
) = 3.4 ꢂ 10ꢁ3
,
R(
l
) = 1.0 ꢂ 10ꢁ4 [R(
v) =
(vobsd
–
v0cacld)2/
P
P
P
(v
obsd)2, R(
l
) =
(lobsd
–
l0cacld)2/
(l
obsd)2]. The negative J and
h values suggest intradimer antiferromagnetic and interdimer anti-
ferromagnetic interactions in 1. Actually, the more the parameters,
the more difficult it is to obtain both the reasonable parameters
and the best fitting curve. The current fitting curve resembled to
the experimental one as closely as possible, with all the parameters
in a physically reasonable range.
l1,3-carboxylate bridged Co(II) complexes are listed in Table 3. A
few examples show weak antiferromagnetic interactions across
the syn–syn conformation, and most of the examples possess anti-
ferromagnetic interactions through the anti–anti and anti–syn con-
formations. Our work also shows that the double-bridging mode
always leads to larger magnetic interactions compared to the sin-
gle-bridging mode, which is similar to the case of Cu(II) species.
3.2.2. [Co(bpy)(3npa)] (2)
Both the shapes of the vM versus T curve and the
curve are similar to those of 1. Upon cooling, MT decreases grad-
vMT versus T
v
ually until ca. 75 K and then drops to 0.13 cm3 K molꢁ1 at 2 K. A
maximum is observed of 0.11 cm3 molꢁ1 at 10 K for the magnetic
susceptibility. All these features suggest the possibility of an anti-
ferromagnetic interaction between the Co(II) ions. Fitting the data
(12–300 K) with Curie–Weiss law gave C = 3.5 cm3 K molꢁ1 and
h = ꢁ19 K. Taking into account that the magnetic interaction be-
tween the Co(II) ions transmitted by l1,3 carboxylate groups in a
1D system should be larger than that of bpy in 2, Eq. (1) was ap-
plied to fit the magnetic susceptibility data, and the fitting results
4. Conclusions
In summary, by using phthalic acid derivatives as ligands, four
Co(II) coordination polymers have been synthesized and structur-
ally characterized. In the four coordination polymers, the adjacent
Co(II) ions are bridged by l1,3 carboxylate groups in the anti–syn
mode to form 2D (1), 1D (2 and 3) and dimer (4) magnetic struc-
tures, which are linked into 3D crystal structures. The different
3D structures, as well as the magnetic structures, come from the
different substituent group and/or the co-ligands. It is noted that
an interesting in situ acylation reaction was observed in the forma-
tion of coordination polymer 3. Magnetic studies reveal antiferro-
magnetic interactions between the Co(II) ions in 1–4. This work
shows a strategy to tune the subtle bridging mode to influence
the magnetic configuration, which will lead to the development
of new molecular magnetic materials.
are
A + B = 3.5 cm3 K molꢁ1
,
E1/k = 51 K,
E2/k = 8.4 K,
(J = ꢁ5.8 cmꢁ1), R = 1.7 ꢂ 10ꢁ3. The results indicate the existence
of antiferromagnetic interactions between adjacent Co(II) ions
transmitted by the double l1,3 carboxylate groups.
3.2.3. [Co(bpy)1.5(3adpa)] (3)
The
v
MT value decreases gradually to 1.73 cm3 K molꢁ1 at 12 K
as the temperature decreases, and then increases to 1.90 cm3
K molꢁ1 at 2 K. The data (35–300 K) obey the Curie–Weiss law with
C = 2.7 cm3 K molꢁ1 and h = ꢁ17 K. From a magnetic point of view,
3 could be considered as a 1D magnetic structure, though the crys-
tal structure is 3D. The magnetic susceptibility data were fitted
Acknowledgments
using Eq. (1). The best fit parameters were A + B = 2.8 cm3 K molꢁ1
,
This work was supported by the National Natural Science Foun-
dation of China (21151001, 21171100 and 90922032) and the Fun-
damental Research Funds for the Central Universities.
E1/k = 59 K, E2/k = 0.23 K, (J = ꢁ0.16 cmꢁ1), R = 2.8 ꢂ 10ꢁ4. The neg-
ative and small J value suggests a weak antiferromagnetic interac-
tion between adjacent Co(II) ions, transmitted by the l1,3
carboxylate groups.
Appendix A. Supplementary material
3.2.4. [Co(btx)0.5(4npa)(H2O)2] (4)
CCDC 884148–884151 contain the supplementary crystallo-
graphic data for 1–4. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2012.12.032.
The
the temperature to 7 K. Below this temperature,
value of 2.22 cm3 K molꢁ1 at 2 K. The shape of the
v
MT value decreases slightly to 2.15 cm3 K molꢁ1 on lowing
vMT increases to a
vMT versus T
curve is similar to that of 3. Fitting the data (35–300 K) to the Cur-
ie–Weiss law gave C = 3.5 cm3 K molꢁ1 and h = ꢁ19 K. Taking into
account the dimeric structure in 4, the Magsaki program was ap-
plied to fit the magnetic data for a quantitative estimation of the
magnetic interaction. The best fit gives J = ꢁ0.12 cmꢁ1
, j = 0.93,
k = ꢁ136 cmꢁ1
,
D
= ꢁ632 cmꢁ1
,
gz = 7.0, gx = 2.5, h = 0.18 K,
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