Six heterometallic coordination polymers containing cobalt(II): Syntheses, crystal structures and magnetic properties

Article abstract of DOI:10.1016/j.poly.2014.02.035

Six new coordination polymers, [Co(NiL)(aipt)] (1), [Co₂(ML) (hipt)₂(CH₃OH)(H₂O)]·CH₃OH (M = Cu (2), Ni (3)), [Co₂(C₂O₄) ₂(CuL)₂] (4), [Co₄(NiL)₄(ipt) ₄(H₂O)₂] (5) and [Co(CuL)(tpt)] (6) (H ₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7, 13-dien; H₂aipt = 5-aminoisophthalic acid; H₂hipt = 5-hydroxyisophthalic acid; H₂ipt = isophthalic acid; H₂tpt = terephthalic acid), have been synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction. Complexes 1, 4 and 5 exhibit different infinite chain structures formed by CoNi (1), Co₂Cu ₂ (4), Co₄Ni₄ (5) units, respectively, via oxamide and diverse carboxylate bridges, while complexes 2, 3 and 6 exhibit different two-dimensional network structures formed by Co₂M or Co₂M₂ units via oxamide and 5-hydroxyisophthalate or terephthalate bridges. The results of magnetic determination show weak antiferromagnetic interactions in 1-3 and 5-6, and the spin-orbit coupling interaction of Co(II) is a primary factor in the magnetic behaviors.

Full text of DOI:10.1016/j.poly.2014.02.035

Polyhedron 74 (2014) 39–48
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Polyhedron
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Six heterometallic coordination polymers containing cobalt(II):
Syntheses, crystal structures and magnetic properties
a
a
a
a
a
Ya-Qiu Sun a, , Shang-Yuan Liu , Yan-Yan Xu , Lin Wu , Dong-Zhao Gao , Guo-Ying Zhang ,
⇑
Dai-Zheng Liao b
a Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic–Organic Hybrid Functional Material Chemistry,
Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, PR China
b Department of 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:
Six new coordination polymers, [Co(NiL)(aipt)] (1), [Co2(ML)(hipt)2(CH3OH)(H2O)]ꢀCH3OH (M = Cu (2), Ni
(3)), [Co2(C2O4)2(CuL)2] (4), [Co4(NiL)4(ipt)4(H2O)2] (5) and [Co(CuL)(tpt)] (6) (H2L = 2,3-dioxo-5,6,14,15-
dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien; H2aipt = 5-aminoisophthalic acid; H2hipt = 5-
hydroxyisophthalic acid; H2ipt = isophthalic acid; H2tpt = terephthalic acid), have been synthesized by
a solvothermal method and characterized by single-crystal X-ray diffraction. Complexes 1, 4 and 5 exhibit
different infinite chain structures formed by CoNi (1), Co2Cu2 (4), Co4Ni4 (5) units, respectively, via oxam-
ide and diverse carboxylate bridges, while complexes 2, 3 and 6 exhibit different two-dimensional net-
work structures formed by Co2M or Co2M2 units via oxamide and 5-hydroxyisophthalate or
terephthalate bridges. The results of magnetic determination show weak antiferromagnetic interactions
in 1–3 and 5–6, and the spin–orbit coupling interaction of Co(II) is a primary factor in the magnetic
behaviors.
Received 2 December 2013
Accepted 13 February 2014
Available online 5 March 2014
Keywords:
Coordination polymers
Heterometallic complex
Magnetism
Macrocylic oxamide complex
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
synthesized. The results reported here and previously reported
clearly show that solvothermal synthesis is a powerful and versa-
Coordination polymers have recently attracted much attention
because of their fascinating structures and their potential applica-
tion in magnetism, luminescence, adsorption, catalysis, etc. [1–6].
However, heterometallic coordination polymers, which often exhi-
bit novel electromagnetic properties, remain relatively scarce be-
cause of the coordinative complexity of the heterometallic ions
involved in the self-assembly process [7,8]. Recently, in order to
design and construct diverse oxamido-bridged heteropolynuclear
networks, we have chosen aromatic multicarboxylate ligands as
co-ligands. The results show that the marrying of the ML macrocy-
clic units with aromatic multicarboxylate ligands have indeed led
to novel and interesting one-dimensional, two-dimensional and
three-dimensional extended networks [9–12]. In the majority of
the coordination polymers, macrocylic oxamide complexes, ML,
were used as terminal ligands, which allowed us to synthesize
one and two-dimensional heterobimetallic systems in a more con-
trolled fashion [9–12]. Up to date, only the [Cd(HBTC)(CuL)]ꢀH2O
three-dimensional network with the sra topology has been
tile tool for preparing macrocyclic oxamide and organic acid
bridged coordination polymers [9–12].
On the other hand, the field of metal complex-based magnetic
materials has made great achievements in the last two decades
[13,14]. Especially, those containing cobalt(II) ions have received
particular attention because of the special magnetic properties of
4
Co(II) [15,16]. In an octahedral field, a single Co(II) ion has a T1g
ground state and magnetic behavior with a strong orbital contribu-
tion at high temperature (especially above 77 K). However, the
Co(II) center in real chemical systems do not display a strict octa-
hedral environment. In distorted octahedral systems, the degener-
4
acy of the T1g state is lifted. If the distortion is tetragonal, the
4
ground state becomes A2g and the excited level is 4Eg. Spin–orbit
coupling in these levels results in six Kramer’s doublets, with an
M = 1/2 ground state and an M = 3/2 first excited state. The orbi-
tal moment has then been incorporated, in part, into the ZFS.
Hence, the ZFS is much larger than for a metal ion with a quartet
ground state and no first order orbital moment, such as Cr(III).
Therefore, the advantage of using Co(II) to generate a large mag-
netic anisotropy is obvious. The large magnetic anisotropy would
favor the production of slow magnetic relaxation effects, which
are so-called single-molecule magnets (SMMs) and single chain
⇑
Corresponding author. Tel.: +86 022 23503778.
E-mail addresses: hxxysyq@mail.tjnu.edu.cn (Y.-Q. Sun), liaodz@nankai.edu.cn
(D.-Z. Liao).
http://dx.doi.org/10.1016/j.poly.2014.02.035
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

40
Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
magnets (SCMs). To date, many complexes containing the high-
spin Co(II) ion are SMMs and SCMs [17–21]. Moreover, from a
theoretical point of view, the magnetic exchange in polynuclear
complexes containing six-coordinated Co(II) ions is a challenging
subject because of the orbital angular momentum cause in the the-
oretical analysis of the magnetic data.
In this paper, in order to study the magnetic properties of het-
erometallic coordination polymers with larger magnetic anisotro-
pies, we chose 5-aminoisophthalate, 5-hydroxyisophthalate,
isophthalate, terephthalate and ML macrocyclic units as potential
bridging ligands to react with Co2+ metal ions. Three different types
of one-dimensional and three two-dimensional coordination poly-
mers were firstly obtained and used an approximate model to esti-
mate the magnetic exchange and spin–orbital interactions for
these complexes.
mixture was transferred to an 18 mL Teflon-lined reactor, heated
to 150 °C over 24 h and then kept at 150 °C for 72 h. Finally, the
reaction system was cooled to room temperature over 36 h, and
deep brown crystals of compound 2 and red crystals of compound
3 were isolated by filtering and washing with water. Anal. Calc. for
C
37H34Co2CuN4O15 2: C, 46.44; H, 3.56; N, 5.86. Found: C, 46.47; H,
3.58; N, 5.89%. Main IR bands, cmꢁ1: 3429 (m(br), O–H), 1642 (m,
C@O, COOꢁ), 1613 (m, C@O, oxamide), 1554 (s, C@N). Anal. Calc. for
C
37H34Co2N4NiO15 3: C, 46.68; H, 3.57; N, 5.89. Found: C, 46.66; H,
3.55; N, 5.85%. Main IR bands, cmꢁ1: 3423 (m(br), O–H), 1642 (m,
C@O, COOꢁ), 1610 (m, C@O, oxamide), 1551 (s, C@N).
2.3.3. Synthesis of [Co2(C2O4)2(CuL)2] (4)
A mixture of Co(Ac)2ꢀ6H2O (0.1 mmol), 2-aminoterephthalic
acid (0.05 mmol), CuL (0.05 mmol), H2O (10 mL) and CH3OH
(4 mL) was stirred for 40 min at room temperature, and the pH va-
lue of the solution was adjusted to about 8–9 with triethylamine
(0.01 mmol). The mixture was transferred to an 18 mL Teflon-lined
reactor, heated to 150 °C over 24 h and then kept at 150 °C for 72 h.
Finally, the reaction system was cooled to room temperature over
36 h, and deep brown–green crystals of compound 4 were isolated
(yield 38.5% based on Co) by filtering and washing with water.
Anal. Calc. for C84H64Co4Cu4N16O24 4: C, 46.42; H, 2.95; N, 10.32.
Found: C, 46.44; H, 2.93; N, 10.35%. Main IR bands: 1647 (s,
C@O, COOꢁ), 1611 (s, C@O, oxamide), 1563 (s, C@N).
2. Experimental
2.1. Materials and physical measurements
All the starting reagents were of A. R. grade and were used as
purchased. The complex ligand ML (M = Cu, Ni) was prepared as
described elsewhere [22]. Analyses of C, H and N were determined
on a Perkin-Elmer 240 Elemental analyzer. The IR spectra were re-
corded using the KBr disc technique on a Shimadzu IR-408 infrared
spectrophotometer in the 4000–600 cmꢁ1 range. X-ray powder dif-
fraction (XRPD) spectra for the powders were recorded on a Model
D/MAX-2550 V diffractometer (Rigaku, Japan). Variable-tempera-
ture magnetic susceptibilities were measured on an MPMS-7
SQUID magnetometer. Diamagnetic corrections were made with
Pascal’s constants for all the constituent atoms [23].
2.3.4. Synthesis of [Co4(NiL)4(ipt)4(H2O)2] (5)
A mixture of Co(Ac)2ꢀ6H2O (0.05 mmol), H2ipt (0.05 mmol), NiL
(0.025 mmol), H2O (10 mL) and CH3OH (4 mL) was stirred for
30 min at room temperature, and the pH value of the solution
was adjusted to about 7–8 with triethylamine (0.01 mmol). The
mixture was transferred to an 18 mL Teflon-lined reactor, heated
to 150 °C over 24 h and then kept at 150 °C for 72 h. Finally, the
reaction system was cooled to room temperature over 36 h, and
deep brown–red crystals of compound 5 were isolated (yield
45.3% based on Co). Anal. Calc. for C108H84Co4N16Ni4O26 5: C,
52.00; H, 3.37; N, 8.99. Found: C, 52.00; H, 3.39; N, 9.01%. Main
IR bands, cmꢁ1: 3416 (s(br), O–H), 1630 (s, C@O, COOꢁ), 1604 (s,
C@O, oxamide), 1564 (s, C@N).
2.2. X-ray crystallography
Single crystal X-ray diffraction analyses of 1–6 were carried out
on a Bruker Smart Apex II CCD diffractometer equipped with
graphite monochromated Mo K
a radiation (k = 0.71073 Å) using
the // scan technique at room temperature. Semi-empirical
x
absorption corrections were applied using SADABS. All structures
were solved by direct methods using the SHELXS program of the
SHELXTL package and refined with SHELXL. The crystallographic data
and selected bond lengths for 1–6 are listed in Tables 1 and 2.
2.3.5. Synthesis of [Co(CuL)(tpt)] (6)
A mixture of Co(Ac)2ꢀ6H2O (0.05 mmol), H2tpt (0.05 mmol),
CuL(0.025 mmol), H2O (10 mL) and CH3OH (4 mL) was stirred for
30 min at room temperature, and the pH value of the solution
was adjusted to about 7–8 with triethylamine (0.01 mmol). The
mixture was transferred to an 18 mL Teflon-lined reactor, heated
to 150 °C over 24 h and then kept at 150 °C for 72 h. Finally, the
reaction system was cooled to room temperature over 36 h, and
deep brown–green crystals of compound 6 were isolated (yield
65.4% based on Co). Anal. Calc. for C27H20CoCuN4O6 6: C, 52.35;
H, 3.23; N, 9.05. Found: C, 52.38; H, 3.27; N, 9.03%. Main IR bands,
cmꢁ1: 1637 (s, C@O, COOꢁ), 1603 (s, C@O, oxamide), 1584 (s, C@N).
2.3. Preparation of complexes of 1–6
2.3.1. Synthesis of [Co(NiL)(aipt)] (1)
A mixture of Co(Ac)2ꢀ6H2O (0.10 mmol), H2aipt (0.05 mmol),
NiL (0.05 mmol), H2O (10 mL) and CH3OH (4 mL) was stirred for
30 min at room temperature and the pH value of the solution
was adjusted to about 7–8 with triethylamine (0.01 mmol). The
mixture was transferred to an 18 mL Teflon-lined reactor, heated
to 150 °C over 24 h and then kept at 150 °C for 72 h. Finally, the
reaction system was cooled to room temperature over 36 h, and
deep brown–red crystals of 1 were obtained (yield 37.5% based
on Co). Anal. Calc. for C27H21CoN5NiO6 1: C, 51.50; H, 3.34; N,
11.13. Found: C, 51.46; H, 3.33; N, 11.08%. Main IR bands (KBr,
cmꢁ1): 3417 (w, N–H), 1627 (s, C@O, COOꢁ), 1605 (s, C@O,
oxamide), 1563 (s, C@N).
3. Results and discussion
3.1. Synthetic and spectral aspects
By using 5-aminoisophthalate, 5-hydroxyisophthalate, iso-
phthalate or terephthalate and macrocylic oxamide mixed ligands
as the metal linker, the coordination polymers 1–6 were obtained
in the same mixed-solvent systems, with the same times and tem-
perature under solvothermal conditions. Complexes 1, 2, 3, 5 and 6
were obtained at pH 7–8, while compound 4 was obtained at a rel-
atively higher pH 8–9, and the oxalate group in the product arises
from the hydrolysis of the oxamide ligand. Complexes 1–6 are
2.3.2. Synthesis of [Co2(ML)(hipt)2(CH3OH)(H2O)]ꢀCH3OH (M = Cu (2),
Ni (3))
A mixture of Co(Ac)2ꢀ6H2O (0.1 mmol), H2hipt (0.05 mmol), ML
(0.05 mmol), H2O (10 mL) and CH3OH (4 mL) was stirred for
30 min at room temperature and the pH value of the solution
was adjusted to about 7–8 with triethylamine (0.01 mmol). The

Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
41
Table 1
Crystal data and structure refinement for complexes 1–6.
Complexes
1
2
3
4
5
6
Formula
C
27H21CoN5 NiO6
C148H136Co8Cu4N16O60 C37H34Co2N4NiO15 C84H64Co4Cu4N16 O24 C108H84Co4N16Ni4O26 C27H20CoCuN4O6
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
629.13
3824.33
monoclinic
P21/c
11.794(5)
16.703(7)
18.492(7)
90
94.184(7)
90
3633(3)
1
951.25
monoclinic
P21/c
12.039(5)
16.306(6)
18.520(7)
90
94.551(6)
90
3624(2)
4
2171.39
monoclinic
P2(1)/n
9.7954(10)
24.686(3)
15.9523(16)
90
92.175(2)
90
3854.6(7)
2
2492.47
triclinic
P1
618.94
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
10.0384(8)
10.8925(8)
11.9122(9)
104.240(1)
97.433(1)
101.425(1)
1215.5(2)
2
13.9971(6)
17.0166(8)
22.1463(10)
82.0440(10)
73.2060(10)
86.3070(10)
4999.6(4)
2
9.9613(8)
12.0095(10)
12.2172(11)
68.5910(10)
85.854(2)
67.7730(10)
1255.91(18)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
rcalc, (g cmꢁ3
)
1.719
0.71073
1.748
0.71073
1.743
0.71073
1.871
0.71073
1.656
0.71073
1.637
0.71073
v
(Mo K
a
) (mmꢁ1
)
Crystal size (mm)
0.20 ꢂ 0.19 ꢂ 0.18 0.18 ꢂ 0.16 ꢂ 0.15
0.18 ꢂ 0.16 ꢂ 0.14 0.15 ꢂ 0.14 ꢂ 0.12
0.17 ꢂ 0.16 ꢂ 0.12
0.18 ꢂ 0.17 ꢂ 0.16
T (K)
296(2)
1.034
296(2)
1.048
173(2)
173(2)
1.023
296(2)
296(2)
Goodness-of-fit F2
1.018
1.005
1.051
Reflections collected/unique 25039/4835
18042/6392
0.0423
0.0378
0.0898
0.0628
0.1027
17815/6383
0.1180
0.0617
0.1293
0.1215
0.1562
19550/6787
0.0572
0.0418
0.0914
0.0715
0.1053
25917/17536
0.0293
0.0433
0.0757
0.0837
6523/4403
0.0170
0.0322
0.0778
0.0402
Rint
0.0096
0.0234
0.0639
0.0256
0.0655
a
R1 [I > 2
r
(I)]
b
wR2 [I > 2
r(I)]
a
R1 [all data]
b
wR2 [all data]
0.0892
0.0820
P
P
a
R1
=
||Fo| ꢁ |Fc||/ |Fo|.
P
P
b
wR2 = { [w(F2o ꢁ F2c)2]/ [w(Fo)2]}1/2
.
m
(C@O) and m(C@N) vibrations, respectively [24,25]. The IR spectra
Table 2
of 1–6 show no bands in the region 1680–1720 cmꢁ1, indicating
complete deprotonation of the carboxyl groups. For complex 1,
the band around 3417 cmꢁ1 is characteristic of the NH2 group
Selected bond distances (Å) for 1–6.
Compound 1
Ni(1)–N(1)
Co(1)–O(4)#1
Co(1)–O(5)#2
1.879(2)
2.007(1)
2.136(1)
Ni(1)–N(4)
Co(1)–O(3)
Co(1)–O(1)
1.894(1)
2.079(9)
2.216(1)
[25]. For complexes 2, 3 and 5, the bands around 3416–
3429 cmꢁ1 are characteristic of the hydroxyl group from H2O
and/or CH3OH.
Compound 2
Cu(1)–N(3)
Co(1)–O(4)
1.871(3)
2.008(3)
2.051(3)
Cu(1)–N(4)
Co(1)–O(8)
Co(2)–O(8)
1.897(3)
2.239(3)
2.182(3)
3.2. Structural description
Co(2)–O(11)#2
The ligands involved in this research and the coordination
modes of the aromatic multicarboxylates are listed in Scheme 1.
Single-crystal X-ray analysis revealed that complex 1 is an infinite
chain coordination polymer composed of tetranuclear Co2Ni2
building units. As shown in Fig. 1a, in the tetranuclear structure
of 1, the nickel ion is coordinated by four nitrogen atoms from
the macrocyclic organic ligand, with the [NiN4] geometry exhibit-
ing distorted square planarity. The Co1 center is six-coordinated
by two oxygen atoms from one oxamido ligand (Co1–
O1 = 2.215(1) and Co1–O2 = 2.075(1) Å) and four oxygen atoms
belonging to three different carboxylate groups from three sepa-
rated aipt2ꢁ ligands (the Co–O bond lengths range from 2.007(1)
to 2.208(1) Å). The adjacent Co1 and Co1A centers are connected
by two carboxylate groups from two aipt2ꢁ ligands, adopting a
bridging mode to construct a binuclear [Co2(CO2)2] unit, in which
the non-bonding Coꢀ ꢀ ꢀCo distance is 4.133(2) Å. Nickel ions and
[Co2(CO2)2] units are interlinked through the macrocyclic oxamide
ligand to form a heterotetranuclear Co2Ni2 unit. The structural
Co2Ni2 building units are further linked with each other through
the aipt2ꢁ ligand to create an infinite double chain. In the infinite
chain structure, each aipt2ꢁ ligand connects three cobalt ions with
carboxylate groups, adopting chelating and bridging coordination
modes, as shown in Scheme 1b and Fig. 1b. Furthermore, the 1D
infinite chains are linked together by N–Hꢀ ꢀ ꢀO hydrogen bonding
to form a 2D framework. The d (Hꢀ ꢀ ꢀO) and d (Nꢀ ꢀ ꢀO) distances
between the chains are 2.13 and 3.0153 Å, respectively.
Compound 3
Ni(1)–N(4)
Co(1)–O(3)
Co(2)–O(4)
1.926(5)
2.012(5)
2.079(5)
Ni(1)–N(1)
Co(1)–O(9)
Co(2)–O(9)
1.948(5)
2.297(5)
2.220(5)
Compound 4
Cu(1)–N(4)
Cu(2)–N(5)
Co(1)–O(11)
Co(2)–O(6)
1.972(4)
1.988(4)
2.058(3)
2.052(3)
Cu(1)–N(3)
Cu(2)–N(7)
Co(1)–O(3)
Co(2)–O(1)
2.004(4)
2.012(4)
2.161(3)
2.164(3)
Compound 5
Ni(1)–N(3)
Ni(2)–N(7)
Ni(3)–N(11)
Ni(4)–N(15)
Co(1)–O(13)
Co(2)–O(12)#1
Co(3)–O(5)
1.864(3)
1.867(3)
1.868(3)
1.872(3)
2.037(2)
1.978(3)
2.122(2)
2.030(2)
Ni(1)–N(4)
Ni(2)–N(5)
Ni(3)–N(12)
Ni(4)–N(13)
Co(1)–O(10)
Co(2)–O(17)
Co(3)–O(16)
Co(4)–O(23)
1.904(3)
1.897(3)
1.890(3)
1.903(3)
2.247(3)
2.295(3)
2.392(3)
2.335(3)
Co(4)–O(19)#2
Compound 6
Co(1)–O(5)
Cu(1)–N(1)
2.025(18)
1.930(2)
Co(1)–O(3)
Cu(1)–N(2)
2.176(2)
1.952(2)
Symmetry transformations: 1: #1 ꢁx + 2, ꢁy + 1, ꢁz + 2; #2 ꢁx + 1, ꢁy + 1, ꢁz + 2. 2:
#2 ꢁx, ꢁy + 1, ꢁz + 1. 5: #1 x + 1, y, z; #2 x ꢁ 1, y, z.
stable under ambient conditions and insoluble in common solvents
such as water, alcohol and acetonitrile. The crystalline phase purity
of 1, 5 and 6 was confirmed by their experimental XRPD patterns,
which match well with the corresponding simulated ones obtained
from the single-crystal data (Fig. S1).
Compounds 2 and 3 are isostructural, hence only the structure
of 2 will be discussed in detail as a representative example. The
asymmetric unit of 2 consists of two cobalt(II) ions, one copper(II)
ion, one macrocyclic oxamide group, two hipt2ꢁ ligands, two
For complexes 1–6, the IR spectra exhibit strong absorption
bands in the regions 1647–1603 and 1584–1541 cmꢁ1 due to

42
Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
Scheme 1. (a) The macrocyclic oxamide complex ligands (ML). (b) The coordination
modes of 5-aminoisophthalate (aipt2ꢁ). (c and d) The coordinated modes of 5-
hydroxyisophthalate (hipt2ꢁ). (e–h) The coordinated modes of isophthalate (ipt2ꢁ).
Fig. 1. (a) Perspective view of the Co2Ni2 unit (symmetry transformations used to
generate equivalent atoms: A, 2 ꢁ x, 1 ꢁ y, 2 ꢁ z; B, 1 ꢁ x, 1 ꢁ y, 2 ꢁ z). (b) The
polyhedral view of the self-assembled 1D double chain structure constructed by
[Co2(NiL)2(aipt)2].
CH3OH and one water molecule. As shown in Fig. 2a, the Co1 center
is linked to the Cu1 center via exo-cis oxygen donors of the macro-
cyclic oxamide ligand, in which the non-bonding Co1ꢀ ꢀ ꢀCu1 dis-
tance is 5.293(2) Å. The Cu1 center is coordinated by four
nitrogen atoms from the macrocyclic organic ligand, with the
[CuN4] geometry exhibiting distorted square planarity. The Co1
center is six-coordinated by two oxygen atoms from one oxamide
ligand and four carboxylate oxygen atoms from three different
hipt2ꢁ ligands. The coordination sphere of the Co1 center is a
distorted octahedron, which can be seen from the O–Co–O bond
angles, varying from 60.2(2)° to 173.1(2)°. The Co2 center coordi-
nates with four carboxylate oxygen atoms from four different
hipt2ꢁ ligands, one oxygen atom from H2O and one oxygen atom
from CH3OH, with a distorted octahedral [CoO6] geometry (the
Co–O bond lengths range from 2.073(5) to 2.220(5) Å). Adjacent
Co1 and Co2 centers are connected by three carboxylate groups
from three hipt2ꢁ ligands to construct a binuclear [Co2O2] cluster,
in which the non-bonding Co1ꢀ ꢀ ꢀCo2 distance is 3.106(1) Å. Two
asymmetric [Co2Cu] units are connected by two hipt2ꢁ ligands to
construct a hexanuclear [Co4Cu2] unit (Fig. 2b). The hexanuclear
[Co4Cu2] units are interlinked through bridging hipt2ꢁ ligands to
form a two-dimensional framework with nanometer pores, as
shown in Fig. 2c. Each nanometer pore is composed of six
[Co2O2] clusters, with a maximum Coꢀ ꢀ ꢀCo distance of 22.64 Å. In
the two-dimensional framework, one kind of hipt2ꢁ ligand
connects four Co(II) ions using carboxylate groups, adopting
two different bridging coordination modes (Scheme 1c), while an-
other kind of hipt2ꢁ ligand connects three Co(II) ions, with the
carboxylate groups adopting monodentate and bridging coordina-
tion modes (see Scheme 1d).
Single-crystal X-ray analysis revealed that 4 is an infinite chain
consisting of two crystallographic independent cobalt(II) ions and
two crystallographic independent copper(II) ions. As shown in
Fig. 3a, the Cu(II) ion is four-coordinated by four nitrogen atoms
from the macrocyclic organic ligand, with Cu1–N distances in the
range 1.972(4)–2.004(4) Å, to complete the distorted square planar
coordination geometry. The Co(II) ion is six-coordinated by two
oxygen atoms from one oxamido ligand, and four carboxylate oxy-
gen atoms from two different C2O24ꢁ ligands, with a distorted
octahedral [CoO6] geometry. The Co1–O bond lengths range from
2.058(3) to 2.161(3) Å. Two adjacent cobalt(II) ions are connected
by C2O24ꢁ ligands to construct a binuclear [Co2] unit, in which the
non-bonding Coꢀ ꢀ ꢀCo distance is 5.409(9) Å. Two Cu(II) ions and
the [Co2] unit are interlinked through the macrocyclic oxamide li-
gand to form a tetranuclear Cu2Co2 unit. Adjacent tetranuclear
Cu2Co2 units are connected by bridging C2O24ꢁ ligands to form a
one-dimensional zigzag framework (Fig. 3b). Furthermore, the 1D
infinite chains are linked together by C–Hꢀ ꢀ ꢀO hydrogen bonding
to form a 2D framework. The d (Hꢀ ꢀ ꢀO) and d (Cꢀ ꢀ ꢀO) distances
between the chains are 2.44 and 3.167 Å, respectively.
Single-crystal X-ray analysis revealed that 5 is a complicated
one-dimensional ladder-like polymer consisting of four crystallo-
graphically independent cobalt(II) ions and four crystallographi-
cally independent nickel(II) ions. As shown in Fig. 4a, in the
octanuclear structure of 5, each Co(II) ion is linked to a Ni(II) ion
via the exo-cis oxygen donors of the macrocyclic oxamide ligand

Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
43
Fig. 3. (a) Portion of the crystal structure of 4 showing the coordination environ-
ments of the Co(II) and Cu(II) ions. (b) View of the self-assembled 1D chain
structure constructed by [Co2(C2O4)2(CuL)2]; hydrogen atoms are removed for
clarity.
three different ipt2ꢁ igands, while the Co3 ion is seven-coordinated
by two oxygen atoms from one oxamido ligand and five carboxyl-
ate oxygen atoms from three different ipt2ꢁ ligands, with the
[CoO7] geometry exhibiting a distorted capped-octahedron. Two
adjacent Ni2Co2 and Ni3Co3 units are connected by two carboxyl-
ate groups from two different ipt2ꢁ ligands to construct a tetranu-
clear cluster, [Ni2Co2O2], in which the non-bonding Co2ꢀ ꢀ ꢀCo3
distance is 3.416(9) Å. Two [CoNi] units and one [Ni2Co2O2] cluster
are interlinked through an ipt2ꢁ ligand to form an octanuclear Co4-
Ni4 unit. Adjacent octanuclear Co4Ni4 units are connected by two
bridging ipt2ꢁ ligands to form a one-dimensional ladder-like chain
(Fig. 4b). In the one-dimensional framework, the ipt2ꢁ ligands have
four coordination modes. The first kind of ipt2ꢁ ligand connects
three Co(II) ions with the carboxylate groups adopting monoden-
tate and bridging coordination modes (Scheme 1e); the second
kind of ipt2ꢁ ligand connects two Co(II) ions with the carboxylate
groups adopting tridentate bridging coordination modes
(Scheme 1f); the third kind of ipt2ꢁ ligand connects two Co(II) ions
with the carboxylate groups adopting monodentate and bidentate-
chelating coordination modes (Scheme 1g); and the last kind of
ipt2ꢁ ligand connects two Co(II) ions with the carboxylate groups
adopting chelating coordination modes (Scheme 1h). Furthermore,
the 1D infinite chains are linked together with O–Hꢀ ꢀ ꢀO hydrogen
bonding to form a 2D framework. The d (Hꢀ ꢀ ꢀO) and d (Oꢀ ꢀ ꢀO) dis-
tances between the chains are 1.78–1.96 and 2.59–2.81 Å,
respectively.
Fig. 2. (a) Perspective view of the Co2Cu unit in 2. (b) Perspective view of the
Co4Cu2 unit in 2. (c) View of the self-assembled 2D sheet structure constructed by
[Co2(CuL)(hipt)2(CH3OH)(H2O)]2; hydrogen atoms and CuL ligands are removed for
clarity.
to form a [CoNi] unit. The Ni(II) ion is coordinated by four nitrogen
atoms from the macrocyclic organic ligand, with the [NiN4] geom-
etry exhibiting distorted square planarity. The Co1 center has a dis-
torted octahedral geometry with two oxygen atoms from one
oxamido ligand, three carboxylate oxygen atoms from two differ-
ent ipt2ꢁ ligands and one oxygen atom from a water molecule.
The Co1–O distances vary from 2.037(2) to 2.247(3) Å. The coordi-
nation environment of Co4 is the same as that of Co1. The Co2 ion
also has a distorted octahedral geometry with two oxygen atoms
from one oxamido ligand and four carboxylate oxygen atoms from
Single-crystal X-ray analysis revealed that complex 6 is a two-
dimensional network coordination polymer constructed from a
binuclear [Co2(CO2)2] unit, the macrocyclic oxamide CuL and tpt2ꢁ
linkers. As shown in Fig. 5a, the fundamental building unit for the
crystal structure of 6 is composed of [Co2(CuL)2(tpt)2]. The coordi-
nation geometry of the Cu(II) ion is slightly distorted square planar.
The Co1 center is six-coordinated by two oxygen atoms from an
oxamido ligand and four oxygen atoms belonging to three different

44
Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
Fig. 4. (a) Perspective view of THE Co4Ni4 unit in 5. (b) View of the self-assembled 1D ladder-like structure constructed by [Co4(NiL)4(ipt)4(H2O)2]; hydrogen atoms are
removed for clarity.
carboxylate groups from three separate tpt2ꢁ ligands. The Co1–O
distances vary from 2.024(2) to 2.176(2) Å. Two adjacent metal
measured vMT values are all higher than the spin-only values at
room temperature. This indicates an important contribution from
ions (Co1 and Co1A) are connected by two bridging l2-COO groups
the orbital momentum, typical for high-spin octahedral Co(II) with
the T1g ground state. So the contribution of the spin–orbit
4
to construct a binuclear [Co2(CO2)2] unit, in which the non-bonding
Coꢀ ꢀ ꢀCo distance is 4.381(5) Å. The copper ions and [Co2(CO2)2]
units are interlinked through the macrocyclic oxamide ligand to
form heterotetranuclear Cu2Co2 units. The Cu2Co2 units are further
linked with each other through tpt2ꢁ ligands to create a two-
dimensional network (Fig. 5b). In the two-dimensional framework,
one kind of tpt2ꢁ ligand connects four Co(II) ions with the carbox-
ylate groups adopting bridging coordination modes, and another
kind of tpt2ꢁ ligand connects two Co(II) ions with the carboxylate
groups adopting chelating coordination modes. From a topological
view of complex 6, the two-dimensional network consists of
Cu2Co2 SBUs, and each Cu2Co2 unit is connected through four
carboxylate groups. Consequently, the Cu2Co2 unit can be viewed
as a regular four-connected node. The tpt2ꢁ ligand is a linear linker.
Thus, polymer 6 has a uninodal 4-connected (4, 4) grid topology.
coupling of the Co(II) ion was considered according to van
Vleck’s equation [26]. The value
v
MT = 6.58 cm3 molꢁ1 K at 300 K
for a powder sample of 1 is larger than the spin-only value of
3.76 cm3 molꢁ1 K expected for the uncoupled CoI2I binuclear system
(Fig. S2). On lowering the temperature,
vMT decreases continuously
and reaches 2.31 cm3 molꢁ1 K at 2 K. On the basis of the crystal
structure of 1 and the fact that the NiII ion is diamagnetic in the
NiL subunit, the coupling topology deduced from the crystal
structure has to be considered as the Co2 binuclear unit. The
magnetic analysis was carried out using the spin Hamiltonian:
ˆ
ˆ
ˆ
ˆ
H = ꢁ2JSCo1SCo2 + gCobHZSZ where
J characterized the exchange
interaction for Co–Co. The susceptibility of the binuclear unit
CoCo,
vCoCo, is calculated from Eq. (1):
2Nb2g2Co
A
B
vCoCo
¼
ꢀ
ð1Þ
3.3. Magnetic properties
kT
A ¼ 14 þ 5 exp ðꢁ6J=kTÞ þ exp ðꢁ10J=kTÞ
B ¼ 7 þ 5 exp ðꢁ6J=kTÞ þ 3 exp ðꢁ10J=kTÞ þ exp ðꢁ12J=kTÞ
The magnetization measurements for complexes 1–3, 5 and 6
have been carried out under 1 kOe. For these complexes, the

Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
45
crystal structure of 2, the magnetic interactions for Coꢀ ꢀ ꢀCo through
the hipt2ꢁ bridges between adjacent tetranuclear [Co2(CuL)(hipt)2
(CH3OH)(H2O)] units can be neglected, because of the larger Coꢀ ꢀ ꢀCo
separation (about 9.75 Å). Thus, the coupling topology deduced from
the crystal structure has to be considered as the CuCo2 trinuclear
unit (shown in Scheme 2). The magnetic analysis was carried out
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ ˆ
using the spin Hamiltonian: H = ꢁ2J1SCo1SCo2 ꢁ 2J2SCu1SCo1 + gbHZSZ,
where J1 and J2 characterize the exchange interactions for Co–Co
and Cu–Co, respectively.
To the best of our knowledge, no formula to reproduce the mag-
netic susceptibility of such a complex system is available in the lit-
erature, so we used an approximate way to interpret the magnetic
behavior [28,29]. In this model, first we considered Co2 as a frag-
ment having coupling states of S = 3, 2, 1, 0. The populations of
each state at various temperatures can be derived as follows:
7
ꢄ
ꢄ
ꢄ
ꢄ
ꢅ
ꢅ
ꢅ
ꢅ
ꢄ
ꢅ
ꢅ
ꢅ
ꢅ
ꢄ
ꢄ
ꢄ
ꢄ
ꢅ
ꢅ
ꢅ
ꢅ
P3
P2
P1
P0
¼
¼
¼
¼
ð3Þ
ð4Þ
ð5Þ
ð6Þ
ꢁ6J1
ꢁ10J1
kT
ꢁ12J1
7 þ 5 exp
7 þ 5 exp
7 þ 5 exp
7 þ 5 exp
þ 3 exp
þ exp
þ exp
þ exp
þ exp
kT
kT
ꢄ
ꢅ
ꢁ6J1
5 exp
kT
ꢄ
ꢁ6J1
ꢁ10J1
kT
ꢁ12J1
þ 3 exp
kT
kT
ꢄ
ꢅ
ꢁ10J1
3 exp
kT
ꢄ
ꢁ6J1
ꢁ10J1
kT
ꢁ12J1
þ 3 exp
kT
kT
ꢄ
ꢅ
ꢁ12J1
exp
kT
ꢄ
ꢁ6J1
ꢁ10J1
ꢁ12J1
þ 3 exp
kT
kT
kT
Second, we evaluated the interactions of the fragment with one
Cu(II) ion. The magnetic susceptibilities of systems containing one
Cu(II) spin and each spin state derived from the central Co2 cluster
can be calculated as follows:
For the 1/2–3 system
ꢄ
ꢅ
2
3
ꢁ7J2
Fig. 5. (a) Perspective view of the Co2Cu2 unit in 6. (b) The view of the self-
assembled 2D sheet constructed by [Co(CuL)(tpt)]; hydrogen atoms and CuL ligands
are removed for clarity.
84g27=2 þ 35g52=2 exp
Nb2
4kT
kT
4
5
ꢄ
ꢅ
v3
¼
ð7Þ
ð8Þ
ꢁ7J2
4 þ 3 exp
kT
1
6
7
1
7
8
7
g7=2
¼
gCu
þ
gCo
g5=2 ¼ ꢁ gCu
þ
gCo
7
where a part of the orbital angular momentum of the Co(II) ion is
reflected in the temperature dependence of the gCo factor (Eq. (2))
[27].
For the 1/2–2 system
ꢄ
ꢅ
2
3
ꢁ5J2
10g23=2 þ 35g52=2 exp
Nb2
4kT
kT
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Nb2 F1
4
5
ꢄ
ꢅ
v2
¼
3kTvCo
ꢁ5J2
gCo
¼
¼
ð2Þ
2 þ 3 exp
Nb2SðSþ1Þ
kT
1
4
5
1
5
6
5
g5=2
¼
gCu
þ
gCo
g3=2 ¼ ꢁ gCu
þ
gCo
vCo
5
3kT F2
"
#
ꢀ
ꢁ
2
2
2
2 þ
þ
exp
7kð3ꢁAÞ 12ð2þAÞ
2kð11ꢁ2AÞ 176ðAþ2Þ
ꢁ5Ak
F1 ¼
þ
0
50
100
150
200
250
300
5kT
25A
45kT
675A
2kT
0.12
0.10
0.08
0.06
0.04
0.02
"
#
ꢀ
ꢁ
2
2
kðAþ5Þ 20ðAþ2Þ
ꢁ4Ak
6
4
2
0
þ
ꢁ
exp
9kT
27A
kT
ꢂ
ꢀ
ꢁ
ꢀ
ꢁꢃ
k
ꢁ5Ak
2kT
ꢁ4Ak
F2 ¼
3þ2exp
þexp
3kT
kT
A is the ligand field parameter and k is the spin–orbit coupling
parameter. The least-squares fit to the experimental data was
found with J = ꢁ6.80 ꢂ 10ꢁ3 cmꢁ1, A = 1.49 and k = ꢁ120. R, the
P
2
Cal
obsd
agreement
factor
defined
as
R ¼ ½ðvM
Þ
ꢁ ðvM
Þ
ꢃ =
P
2
obsd
½ðvM
Þ
ꢃ , is 2.15 ꢂ 10ꢁ5. The point below 14 K cannot be
reproduced with this model.
For complex 2, the
v
MT value is equal to 6.45 cm3 molꢁ1 K at
300 K, which is larger than the spin-only value (4.12 cm3 molꢁ1 K)
0
50
100
150
200
250
300
expected for the uncoupled CuIICo2II trinuclear system (SCu = 1/2 and
T/K
SCo = 3/2). On lowering the temperature,
vMT decreases continuously
and reaches 0.2 cm3 molꢁ1 K at 2 K (Fig. 6). On the basis of the
Fig. 6.
vM(O) vs. T and vMT (D) vs. T plots for complex 2.

46
Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
0
50
100
150
200
250
300
14
12
10
8
2.0
Scheme 2. The coupling topology deduced from the complex 2.
1.5
1.0
0.5
0.0
For the 1/2–1 system
ꢄ
ꢅ
ꢅ
2
3
ꢁ3J2
10g23=2 þ g21=2 exp
Nb2
4kT
kT
6
4
5
ꢄ
v1
¼
ð9Þ
ꢁ3J2
2 þ exp
kT
4
1
2
1
3
4
3
2
g3=2
¼
gCu
þ
gCo
g1=2 ¼ ꢁ gCu
þ
gCo
3
3
0
For the 1/2–0
ꢀ
ꢁ
Ng2Cub2
kT
1
2
1
2
0
50
100
150
200
250
300
v0
¼
þ 1
ð10Þ
T/K
Fig. 7.
v
M(O) vs. T and
v
MT ( ) vs. T plots for complex 5.
D
Last, the total magnetic susceptibility can be calculated by the
following equation:
vM ¼ P3v3 þ P2v2 þ P1v1 þ P0v0
where part of the orbital angular momentum of the Co(II) ion is re-
flected in the temperature dependence of the gCo factor (Eq. (2))
[27].
ð11Þ
0
50
100
150
200
250
300
0.12
0.10
0.08
0.06
0.04
0.02
6
4
2
0
The least-squares fit to the experimental data was found with
J1 = ꢁ7.72 cmꢁ1, J2 = ꢁ7.86 cmꢁ1, gCu = 2.00 (fixed), A = 1.20 and
k = ꢁ170 cmꢁ1 (fixed). The agreement factor, defined as
P
2
P
2
Cal
obsd
obsd
R ¼ ½ðvM
Þ
ꢁ ðvM
Þ
ꢃ = ½ðvM
Þ
ꢃ , is 1.59 ꢂ 10ꢁ4. The point
below 16 K cannot be reproduced with this model.
For complex 3, the
v
MT value is equal to 6.10 cm3 molꢁ1 K at
300 K, which is larger than the spin-only value (3.76 cm3 molꢁ1 K)
expected for the uncoupled Co2II binuclear system. On lowering the
temperature, v K
MT decreases continuously and reaches 3.02 cm3 molꢁ1
at 2 K (Fig. S3). Compounds 2 and 3 are isostructural, and the NiII ion
is diamagnetic in the NiL subunit. Thus, the coupling topology
deduced from the crystal structure has to be considered as the Co2
binuclear unit, and the fitting model is the same as for 1. The
least-squares fit to the experimental data was found with
J = ꢁ1.78 ꢂ 10ꢁ2 cmꢁ1, A = 1.25 and k = ꢁ140 cmꢁ1. The agreement
0
50
100
150
200
250
300
T/K
Fig. 8.
vM(O) vs. T and vMT (D) vs. T plots for complex 6.
P
2
P
2
obsd
Cal
obsd
factor, defined as R ¼ ½ðvMÞ ꢁ ðvMÞ ꢃ = ½ðvMÞ ꢃ , is
1.57 ꢂ 10ꢁ5. The point below 16 K cannot be reproduced with this
model.
The least-squares fit to the experimental data was found with
J = ꢁ1.10 ꢂ 10ꢁ2 cmꢁ1, A = 1.49 and k = ꢁ120 cmꢁ1. The agreement
P
2
P
2
Cal
obsd
obsd
factor, defined as R ¼ ½ðvM
Þ
ꢁ ðvM
Þ
ꢃ = ½ðvM
Þ
ꢃ , is
For complex 5, the
v
MT value is equal to 13.55 cm3 molꢁ1 K at
1.20 ꢂ 10ꢁ5. The point below 16 K cannot be reproduced with this
300 K, which is larger than the spin-only value (7.50 cm3 molꢁ1 K)
model.
expected for the uncoupled Co4II tetranuclear system. On lowering
The value v
MT = 6.39 cm3 molꢁ1 K at 300 K for a powder sample
the temperature,
vMT decreases continuously and reaches
of 6 is larger than the spin-only value of 6.00 cm3 molꢁ1 K expected
4.16 cm3 molꢁ1 K at 2 K (Fig.7). Complex 5 is a one-dimensional lad-
der-like chain formed by octanuclear [Co4(NiL)4(ipt)4(H2O)2] units
linked by ipt2ꢁ ligands. The magnetic interactions for Coꢀ ꢀ ꢀCo
through the ipt2ꢁ bridges between adjacent [Co4(NiL)4(ipt)4(H2O)2]
units can be neglected, because of the larger Coꢀ ꢀ ꢀCo separation
(about 9.40 Å). In the [Co4(NiL)4(ipt)4(H2O)2] unit, the NiII ion is dia-
magnetic in the NiL subunit, and the distances between the Co1 or
Co4 ion and the center Co2O2 cluster are 9.62 or 10.23 Å, respec-
tively. Thus, for the Co4Ni4 unit, the magnetic susceptibility of two
cobalt ions is added to that of the Co2O2 cluster. For the Co2O2 clus-
ter, the magnetic analysis was carried out using the theoretical
expression of the magnetic susceptibility deduced from the spin
for the uncoupled CuI2ICo2II tetranuclear system (Fig. 8). On lowering
the temperature, v
MT decreases continuously and reaches 0.25 cm3 -
molꢁ1 K at 2 K. On the basis of the crystal structure of 6, the mag-
netic interactions for Coꢀ ꢀ ꢀCo through the tpt2ꢁ bridges between
adjacent tetranuclear [Co2(tpt)4(CuL)2] units can also be neglected,
because of the larger Coꢀ ꢀ ꢀCo separation (about 9.96 Å). Thus, the
coupling topology deduced from the crystal structure has to be con-
sidered as the Cu2Co2 tetranuclear unit (shown in Scheme 3). The
magnetic analysis was carried out using the spin Hamiltonian:
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ ˆ
H = ꢁ2J1SCo1SCo1A ꢁ 2J2(SCu1SCo1 + SCu1ASCo1A) + gbHZSZ, where J1 and
J2 characterized the exchange interactions for Co–Co and Cu–Co,
respectively.
To date, no approximate model for such a system could be used.
To estimate a rough exchange constant, we tried to use an
ˆ
ˆ
ˆ
ˆ ˆ
Hamiltonian H = ꢁ2JSCo2SCo3 + gbHZSZ, and the magnetic susceptibil-
ity can be calculated from Eq. (1), while the expression of the total
magnetic susceptibility was obtained as follows:
vM
¼ vCoCo þ 2vCo
J1
J2
J2
Cu
where a part of the orbital angular momentum of the Co(II) ion is
reflected in the temperature dependence of the gCo factor (Eq. (2))
[27].
Co
Cu
Co
Scheme 3. The coupling topology deduced from the complex 6.

Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
47
Table 3
Distances and magnetic information for some coordination polymers containing cobalt(II) with macrocyclic oxamide and aromatic multicarboxylate bridge.
Compound
dCoꢀ ꢀ ꢀCo (Å)
dCoꢀ ꢀ ꢀCu (Å)
J1 (cmꢁ1
)
J2 (cmꢁ1
)
A
k (cmꢁ1
ꢁ120
)
1
2
3
5
6
7
4.1326
3.1055
3.1499
3.4158
4.3806
3.3467
ꢁ6.8 ꢂ 10ꢁ3
ꢁ7.72
1.49
1.20
1.25
1.49
1.21
1.23
This work
This work
This work
This work
This work
Ref. [16]
5.2930
ꢁ7.86
ꢁ170 (fixed)
ꢁ140
ꢁ1.8 ꢂ 10ꢁ2
ꢁ1.1 ꢂ 10ꢁ2
ꢁ2.68
ꢁ120
5.3870
5.2721
ꢁ4.18
ꢁ170 (fixed)
ꢁ170 (fixed)
ꢁ1.98
ꢁ11.88
J1 and J2 characterize the exchange interactions for Co–Co (carboxylate bridge) and Cu–Co (oxamide bridge), respectively; and compound 7 is [Co(nip)(CuL)(H2O)]n.
approximate model [28,29,12]. The least-squares fit to the experi-
for 6, Cuꢀ ꢀ ꢀCo distance (5.39 Å),
c(13.7)), and results in a relatively
greater antiferromagnetic coupling constant.
mental data was found with J1 = ꢁ2.68 cmꢁ1, J2 = ꢁ4.18 cmꢁ1
,
g
Cu = 2.00 (fixed), A = 1.21 and k = ꢁ170 cmꢁ1 (fixed). The agree-
P
2
P
2
Cal
obsd
obsd
ment factor, defined as R ¼ ½ðvM
Þ
ꢁ ðvM
Þ
ꢃ = ½ðvM
Þ
ꢃ , is
4. Conclusions
2.10 ꢂ 10ꢁ6. The point below 14 K cannot be reproduced with this
model.
Six heterometallic coordination polymers containing cobalt(II)
were synthesized with macrocyclic oxamide and aromatic multi-
carboxylate (including aipt2ꢁ, hipt2ꢁ, ipt2ꢁ and tpt2ꢁ) co-ligands
under the same solvothermal reaction conditions. This research re-
veals that the electronic effects and coordinated modes of different
aromatic multicarboxylate ligands play an important role in the
structure construction. In one compound, the greater number of
different coordinated modes of the multicarboxylate ligands leads
to the more complicated and diverse structure. Polymers 2 and 3
hold an unusual two-dimensional framework with nanometric
pores, and there are two coordinated modes for the hipt2ꢁ ligand.
Complex 5 is very novel one-dimensional ladder-like polymer con-
sisting of a Co4Ni4 unit, and there are four coordinated modes for
the ipt2ꢁ ligand in 5. In complexes 1–6, although the macrocyclic
oxamide complex ML was used as a terminal ligand, the coexis-
tence of macrocyclic oxamide and polycarboxylate bridged-ligands
have profound effects on the construction of coordination poly-
mers with different structures and magnetic properties. Complexes
1, 2, 3, 5 and 6 show weak antiferromagnetic exchange interactions
between the adjacent metal ions centers, and spin–orbit coupling
of Co(II) ion plays an important role in the magnetic behaviors.
The magnitude and nature of coupling interactions can be influ-
enced by a series of factors, so investigating the magnetic proper-
ties of oxamide and multicarboxylate bridging cores systems is
important for further enlightenment of the intimate relationship
of spin coupling.
For complexes 1, 2, 3, 5 and 6, we used approximate models to
estimate the magnetic exchange and spin–orbital interactions for
these complexes. The results show that spin–orbit coupling of
the Co(II) ion plays an important role in the magnetic behaviors,
and the point below 16 K cannot be reproduced with these mod-
els, which may be attributed to the zero-field splitting of the Co(II)
ion in the S = 1/2 state and/or intermolecular interactions. The
magnetic information for some coordination polymers containing
cobalt(II) ions with macrocyclic oxamide and aromatic multicarb-
oxylate bridges are listed in Table 3. In these complexes the para-
magnetic CoII ions bridged by OCO and/or O from carboxylate
groups show a weak antiferromagnetic coupling; the J1 values
are ꢁ6.80 ꢂ 10ꢁ3, ꢁ7.72, ꢁ1.78 ꢂ 10ꢁ2, ꢁ1.10 ꢂ 10ꢁ2, ꢁ2.68 and
ꢁ1.98 cmꢁ1. The absolute values can vary depending on ML, the
modes of connection, the angles and also on the distance. Of these
factors, the electronic effects of ML play an important role in
affecting the magnetic exchange between the Co(II) center;, it is
obvious that CuL > NiL (2, 6, 7 ꢄ 1, 3, 5). For complexes 1, 3 and
5, the antiferromagnetic exchange interactions exhibit 3 > 5 > 1,
which can be explained on the basis of the distance and modes
of connection. The larger distance and pairwise syn–anti OCO
bridging mode in 1 led to a reduction of the overlap integral be-
tween the magnetic orbital of Co(II), and resulted in a very small
antiferromagnetic coupling constant. For complexes 2, 6 and 7,
the antiferromagnetic exchange interactions exhibit 2 > 6 > 7; this
can also be rationalized by the distance and modes of connection.
In complex 2, the shorter distance (3.11 Å), syn–syn OCO and O
connections between nearest neighbor cobalt(II) ions and the
Co–O–Co angle of 89° will mediate relatively stronger antiferro-
magnetic exchange interactions than those of 6 and 7 (for 6,
Coꢀ ꢀ ꢀCo distance (4.38 Å), pairwise syn-anti OCO bridging mode;
for 7, Coꢀ ꢀ ꢀCo distance (3.35 Å), pairwise O bridging mode and
Co–O–Co angle of 97°). Moreover, the electronic effects due to
the different aromatic multicarboxylate bridges and molecular
topology might affect the magnetic properties.
Acknowledgments
This work was supported by the National Natural Science Foun-
dation of China (Nos. 20771083, 20901059, 21001081, 21043004
and 90922032) and the National Basic Research Program of China,
978 Program, 2007CB815305. The Education Commission of Tian-
jin (No. 20110510) and Tianjin Normal University (No.
52XC1102). Supported by the Program for Innovative Research
Team in University of Tianjin.
For complexes 2, 6 and 7, the antiferromagnetic interactions
through the oxamido group arise from the non-zero overlap be-
tween the magnetic orbitals around Cu(II) and Co(II), and the anti-
ferromagnetic exchange interactions exhibit 7 > 2 > 6. The
difference between the magnetic exchanges may be explained on
the basis of structural distortions and distances. In this regard,
Appendix A. Supplementary data
CCDC 952581–952586 contains the supplementary crystallo-
graphic data for complexes 1–6. 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,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
posit@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.2014.02.035.
one of the relevant factors is the value of the dihedral angle (
tween the mean equatorial plane of the metal ion and the oxamido
plane [30,31]; the smaller the value of , the greater the antiferro-
magnetic coupling. Complex 7 has a smaller value of (13.0) and a
shorter Cuꢀ ꢀ ꢀCo distance (5.27 Å), which leads to a greater overlap
integral than for 2 and 6 (for 2, Cuꢀ ꢀ ꢀCo distance (5.29 Å), (15.9);
c) be-
c
c
c

48
Y.-Q. Sun et al. / Polyhedron 74 (2014) 39–48
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