Synthesis, crystal structure and properties of cobalt(II) and nickel(II) coordination polymers supported by functionalized dicarboxylate ligands

Article abstract of DOI:10.1016/j.poly.2009.06.022

Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands, namely, [Co^IIL¹(2,2′-bpy)(H₂O)] (1), [Ni^IIL¹(2,2′-bpy)(H₂O)]·H₂O (2), [Co

Full text of DOI:10.1016/j.poly.2009.06.022

Polyhedron 28 (2009) 2667–2672
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, crystal structure and properties of cobalt(II) and nickel(II)
coordination polymers supported by functionalized dicarboxylate ligands
*
Yanhong Zhou, Li Guan, Hong Zhang
Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands,
namely, [CoIIL1(2,20-bpy)(H2O)] (1), [NiIIL1(2,20-bpy)(H2O)]ꢀH2O (2), [CoI2I(L2)2(2,20-bpy)2(H2O)] (3) and
[NiI2I(L2)2(2,20-bpy)2(H2O)] (4), where H2L1 = 2,5-dibenzoylterephthalic acid, H2L2 = 4,6-bis(4-methylbenzoyl)
isophthalic acid and 2,20-bpy = 2,20-bipyridine, were synthesized and characterized by elemental analysis, IR
Received 10 May 2009
Accepted 3 June 2009
Available online 16 June 2009
spectra and thermogravimetric analysis. Complex 1 exhibits a zigzag chain with a C–Hꢀ ꢀ ꢀ
between the phenyl ring proton and the phenyl ring of an adjacent chains to form a 2D supramolecular sheet.
interaction between the pyridine
ring proton and the pyridine ring. Complexes 3 and 4 are isomorphous with helical chains that extend in the
same direction and further link to one another by supramolecular forces into a 2D structure. Moreover, mag-
netic and luminescence properties have been investigated for 1 and 2, respectively.
Ó 2009 Elsevier Ltd. All rights reserved.
p interaction
Keywords:
Coordination polymers
Carboxylate ligands
Helical chain
Complex 2 contains two helical chains which extend into 2D via a C–Hꢀ ꢀ ꢀ
p
Cobalt(II) and nickel(II)
1. Introduction
isophthalic acid, may be useful for luminescent and/or magnetic
properties of coordination polymers. In addition, in this work we
The design and synthesis of metal–organic frameworks (MOFs)
are continuously attractive among coordination and material
chemistry, not only due to the frequently novel motifs of their
architectures but also their potential applications in gas storage,
chemical separations, ion exchange, non-linear optics, magnetism
and heterogeneous catalysis [1–17]. A great variety of interesting
architectures have been reported including helix, brick wall, hon-
eycomb, layer, ladder, grids, boxes and herringbone [18–26], of
which helical coordination polymers are particularly attractive
because of their fascinating structures and applications in many
fields [27–34]. Although discrete helices and low-dimensional heli-
cal coordination polymers are now abundant, the assembly of such
helical units into higher order networks is still a challenge.
also introduce 2,20-bipyridine as an auxiliary ligand to control
the structure and dimensionality of the resulting coordination
polymers [35–37]. The synthesis and structural characterization
of four new coordination polymers [CoIIL1(2,20-bpy)(H2O)] (1),
[NiIIL1(2,20-bpy)(H2O)]ꢀH2O (2), [Co2II(L2)2(2,20-bpy)2(H2O)] (3) and
[NiI2I(L2)2(2,20-bpy)2(H2O)] (4) are reported here. Furthermore, inter-
esting luminescence and magnetic properties have been studied for
complexes 1 and 2, respectively.
2. Experimental
2.1. Materials and physical measurements
In an attempt to construct helical frameworks, we choose func-
tionalized dicarboxylate ligands to give birth to new complexes. So
four new coordination polymers of Co(II) and Ni(II) were obtained
by using benzoyl-substituted terephthalic acid (H2L1) and meth-
ylbenzoyl-substituted isophthalic acid (H2L2) (Chart 1) as ligands.
The choice of these ligands was based on the following consider-
ations: (1) Each ligand has six oxygen atoms potentially available
for metal coordination; (2) the aromatic substituent may rotate
around the central phenyl ring. This flexibility may be significant
Reagents were purchased commercially and were used without
further purification. The ligands H2L1 and H2L2 were synthesized
according to the literature method [38]. The FI-IR spectra were re-
corded using KBr pellets in the range 4000–400 cmꢁ1 on a Mattson
Alpha-Centauri spectrometer. Elemental analyses for C, H and N
were performed on a Perkin–Elmer 2400 Elemental Analyzer. The
thermal behaviors were studied by TGA on a Perkin–Elmer Ther-
mal Analyzer under N2 with a heating rate of 5 °C/min. The fluores-
cence spectrum for
2 was obtained using a Cary Eclipse
in realizing interesting structures; (3) the extended
p-system of
luminescence spectrophotometer (VARIAN. USA). The tempera-
ture-dependent magnetic susceptibility of 1 was measured with
crystalline samples on a Quantum Design MPMS XL-5 Squid mag-
netometer in a magnetic field of 1000 Oe under the temperature
range 2–300 K.
the substituted ligands, which are derived from terephthalic and
* Corresponding author. Tel.: +86 431 85099372; fax: +86 431 85684009.
E-mail address: zhangh@nenu.edu.cn (H. Zhang).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.06.022

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Y. Zhou et al. / Polyhedron 28 (2009) 2667–2672
O
HOOC
COOH
COOH
CH3
H
3 C
HOOC
O
1
O
O
2
2 L
H
H2 L
Chart 1.
2.2. Synthesis
(Yield: 72% based on Ni(NO3)2ꢀ6H2O). Anal. Calc. for C32H23NiN2O8:
C, 61.71; H, 3.7; N, 4.5. Found: C, 61.62; H, 3.85; N, 4.42%. IR (KBr,
cmꢁ1): 1673s, 1660m, 1576m, 1552s, 1490w, 1353s, 1249s,
1026w, 772s, 634w, 521m.
2.2.1. Synthesis of [CoIIL1(2,20-bpy)(H2O)] (1)
To
mixture containing H2L1 (18.7 mg, 0.05 mmol),
a
Co(NO3)2ꢀ6H2O (0.73 mg, 0.025 mmol) and 20 mL H2O, was added
aqueous NaOH (0.05 M) to adjust the pH of the mixture to be
5.0, and then 2,20-bpy (0.40 mg, 0.025 mmol) was added. The
resulting mixture was stirred for 30 min and then filtered. Upon
standing the filtrate for about a month, the purple-colored cube-
shaped crystals were obtained, washed by H2O and air-dried
(yield: 54% based on Co(NO3)2ꢀ6H2O). Anal. Calc. for C32H21CoN2O7:
C, 63.53; H, 3.47; N, 4.63. Found: C, 63.43; H, 3.6; N, 4.42%. IR (KBr,
cmꢁ1): 1678s, 1594m, 1560m, 1395s, 1326m, 1246m, 1020w,
951w, 929w, 770s, 532s.
2.2.3. Synthesis of [CoI2I(L2)2(2,20-bpy)2(H2O)] (3)
The pH of an aqueous solution containing H2L2 (20.2 mg,
0.05 mmol), Co(NO3)2ꢀ6H2O (0.73 mg, 0.025 mmol) and 18 mL
H2O was adjusted with K2CO3 to 6.0, and then 2,20-bpy (0.40 mg,
0.025 mmol) was added. The resulting mixture was stirred for
30 min, filtered, and then transferred to a Teflon-lined stainless
steel vessel (25 mL), sealed, heated to 150 °C and maintained at
that temperature for 4 days, then finally cooled at a rate of 5 °C/h
to room temperature. This afforded purple-colored cube-shaped
crystals of 3, which were washed by H2O and air-dried (Yield:
66% based on Co(NO3)2ꢀ6H2O). Anal. Calc. for C68H49Co2N4O13: C,
65.39; H, 3.93; N, 4.49. Found: C, 65.28; H, 4.14; N, 4.30%. IR
(KBr, cmꢁ1): 1657s, 1603s, 1582m, 1384s, 1260m, 920w, 896m,
768s, 738m, 655w, 506w.
2.2.2. Synthesis of [NiIIL1(2,20-bpy)(H2O)]ꢀH2O (2)
To
a
mixture containing H2L1 (18.7 mg, 0.05 mmol),
Ni(NO3)2ꢀ6H2O (0.72 mg, 0.025 mmol) and 20 mL H2O, was added
aqueous NaOH (0.05 M) to adjust the pH of the mixture to be
8.0, and then 2,20-bpy (0.40 mg, 0.025 mmol) was added. The
resulting mixture was stirred for 30 min and then transferred to
a Teflon-lined stainless steel vessel (25 mL), sealed, heated to
160 °C and maintained at that temperature for 3 days, then finally
cooled at a rate of 5 °C/h to room temperature. Blue-colored cube-
shaped crystals were obtained, washed by H2O and air-dried
2.2.4. Synthesis of [NiI2I(L2)2(2,20-bpy)2(H2O)] (4)
Complex 4 was synthesized by starting with Ni(NO3)2ꢀ6H2O
(0.72 mg, 0.025 mmol) under similar conditions to 3, except that
the pH of the reaction mixture was 8.5. Blue-colored cube-shaped
crystals of 4 were obtained (Yield 58% based on Ni(NO3)2ꢀ6H2O).
Table 1
Crystal data and structure refinement for complexes 1ꢁ4.
Complex
1
2
3
4
Formula
fw
T (K)
C32H21N2O7Co
604.44
293(2)
C32H23N2O8Ni
622.22
296(2)
C68H49N4O13Co2
1247.97
296(2)
C68H49N4O13Ni2
1247.53
293(2)
k (Å)
0.71069
triclinic
P1
0.71073
monoclinic
P21/c
13.9956(8)
20.7637(12)
10.2864(6)
90.00
110.7600(10)
90.00
2795.2(3)
4
0.71073
monoclinic
P21/c
16.0141(9)
17.5279(10)
22.2579(13)
90.00
102.5850(10)
90.00
6097.5(6)
4
0.71069
monoclinic
P21/c
15.852(12)
17.539(13)
22.255(17)
90.00
102.687(10)
90.00
6036.4(8)
4
Crystal system
Space group
a (Å)
b (Å)
c (Å)
9.373(12)
11.673(15)
13.808(18)
75.243(2)
75.941(2)
71.844(2)
1366.1(3)
2
1.469
0.682
0.0356
0.0920
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dc (g/cm3)
1.474
0.751
0.0337
0.0941
1.359
0.612
0.0389
0.0839
1.373
0.693
0.0369
0.0831
l
(mmꢁ1
)
r
a
R1 [I > 2
(I)]
(I)]
R1 (all data)
b
wR2 [I > 2
r
0.0428
0.0379
0.0805
0.0652
wR2 (all data)
0.0953
0.0966
0.0965
0.0914
Goodness-of-fit
1.103
1.066
0.992
1.008
Transmission (max/min)
D/r (max/min)
F(0 0 0)
0.903/0.822
0.460/ꢁ0.269
620
0.874/0.835
0.746/ꢁ0.718
1276
0.907/0.863
0.248/ꢁ0.262
2572
0.901/0.861
0.331/ꢁ0.332
2580
P
P
a
R1
wR2
=
||F0|ꢁ|Fc||/ |F0|.
P
P
b
2
=
[w(F0 ꢁFc2)2]/ [w(F02)2]1/2
.

Y. Zhou et al. / Polyhedron 28 (2009) 2667–2672
2669
Fig. 1a. Coordination environment of Co atom in 1 with the ellipsoids draw at the
30% probability level, all hydrogen atoms are omitted for clarity.
Fig. 1b. A view of a 2D diagram in 1 via C–Hꢀ ꢀ ꢀp interactions.
Anal. Calc. for C68H49Ni2N4O13: C, 65.41; H, 3.93; N, 4.49. Found: C,
65.32; H, 4.14; N, 4.30%. IR (KBr, cmꢁ1): 1658s, 1604s, 1579s,
1552s, 1490m, 1388s, 1042w, 896m, 769s, 739m, 571w, 413w.
2.3. X-ray crystallography
Single crystals of 1–4 were glued to a fiberglass for data collec-
tion on a SMART (Bruker, 2002) diffractometer equipped with Mo K
a
radiation. Empirical absorption corrections were applied to the
data using ABSCOR [39]. The structure was solved by the direct meth-
od followed by the difference Fourier method and refined by full-
matrix least-squares on F2 using the SHELXTL-97 package [40]. All
non-hydrogen atoms were refined anisotropically, the hydrogen
atoms of organic ligands and coordinated water were located geo-
metrically. Due to the small crystallographic disorder for 2, hydro-
gen atoms of the lattice water molecule were not located. The
crystal data and structure refinements of 1ꢁ4 are summarized in
Table 1 and selected bond lengths and angles are listed in the sup-
plementaryinformation (S1 Table S1).
Fig. 2a. Coordination environment of the Ni atom in 2 with the ellipsoids draw at
the 30% probability level, all hydrogen atoms are omitted for clarity.
3. Results and discussion
bipyramidal with its equatorial plane defined by the O(1), N(2)
and O(1 W) atoms; the axial positions are occupied by O(3) and
N(1). The Co–O bond lengths, from 2.012(2) to 2.107(2) Å, and
the Co–N bond lengths, from 2.086(2) to 2.131(2) Å, are within
the normal range [41–43]. The two carboxylate groups show
monodentate coordination (Scheme 1a) and the dihedral angles
between the 1-, 4-carboxylate groups and their corresponding phe-
nyl rings are both 173.26°. In the overall structure of 1, units of
[Co(bpy)]2+ are connected by the bridging L1 ligands to generate
a zigzag chain with a pitch of 15.65 Å. Adjacent chains extend into
3.1. Structure description
3.1.1. Structure description of 1
Crystallographic analysis shows that complex 1 is an infinite
zigzag chain coordination polymer. As shown in Fig. 1a, the Co
atom is five-coordinate with two carboxylate O atoms (O1 and
O3) of two different L1 ligands, two N atoms (N1 and N2) of the
chelating 2,20-bpy and one O atom (O1 W) of the aqua ligand.
The coordination geometry can be described as distorted trigonal
O
O
O
O
M
O
M
O
O
O
M
O
M
O
O
O
Scheme 1. The L1 ligand adopts two distinct coordination modes, namely bridging bis(mono-dentate) and chelating bisdentate coordination modes.

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Y. Zhou et al. / Polyhedron 28 (2009) 2667–2672
Fig. 3a. Coordination environment of the Co(1) and Co(2) atoms in 3 with the
ellipsoids drawn at the 30% probability level, all hydrogen atoms are omitted for
clarity.
coordinate with a distorted octahedral geometry. The six-coordi-
nate atoms are two N atoms of the 2,20-bpy ligand (N1 and N2),
two O atoms (O1 and O2) of a chelating carboxylate group, an O
atom (O4) from the other monodentate carboxylate group of the
L1 ligand and an O atom (O1 W) of an aqua ligand (Fig. 2a). The
average Ni–O and Ni–N bond lengths are 2.093(2) and 2.043(2) Å,
respectively. The dihedral angles between the 1-, 4-carboxylate
groups and their corresponding phenyl rings are both 145.89 (or
148.1)°. Doubly chelate (both carboxylate groups chelating) and
doubly monodentate L1 ligands alternate with the Ni atoms in
complex 2 (Scheme 1a and b).
It is clear from the above description that subtle differences ex-
ist in the coordination of the same ligand with Ni and Co ions. The
combination of two twisted carboxylate groups and the rotated
phenyl ring result in two strand chains in 2, the two distinct chains
Fig. 2b. A perspective views of two infinite helical chains in 2.
a 2D supramolecular sheet via a C–Hꢀ ꢀ ꢀ
C–H moiety of the benzene rings in one chain and the benzene
rings of adjacent chains (Hꢀ ꢀ ꢀ 3.60 Å, C–Hꢀ ꢀ ꢀ 146°, Fig. 1b).
p interaction between the
coexist and are oppositely arranged via a C–Hꢀ ꢀ ꢀ
p interaction
(Fig. 2b). The [Ni(bpy)]2+ units are joined by independent L1 spac-
ers to generate an infinite helical chain with a period of 20.09 Å.
p
p
Those chains further extend into 2D via a C–Hꢀ ꢀ ꢀ
tween the pyridine ring proton and the pyridine ring of adjacent
chains (Hꢀ ꢀ ꢀ 3.18 Å, C–Hꢀ ꢀ ꢀ 96°, Fig. 2c).
p interaction be-
3.1.2. Structure description of 2
Crystallographic determination shows that there are two helical
chains with opposite directions. In complex 2 the Ni atom is six-
p
p
Fig. 2c. The perspective view of a 2D helical diagram in 2 via C–Hꢀ ꢀ ꢀ
p interactions.

Y. Zhou et al. / Polyhedron 28 (2009) 2667–2672
2671
Scheme 2. The coordination modes of the deprotonated H2L2 ligand.
Fig. 3b. The 2D diagram of helical chain via C–Hꢀ ꢀ ꢀ
p interactions in 3.
Fig. 4. Solid-state photoluminescent spectra of 2.
3.1.3. Structure description of 3 and 4
Complex 3 is also a helical chain. As shown in Fig. 3a, there are
two kinds of Co atoms (Co(1) and Co(2)) in 3. The Co(1) is six-coor-
dinate with a distorted octahedral geometry. The equatorial plane
is defined by N(1), N(2), O(2) and O(1 W) atoms; the axial positions
are occupied by O(3) and O(6) atoms (O(3)–Co(1)–O(6) 160.84(8)°).
The Co(1)–O and Co(1)–N bond lengths are 2.024(2)–2.246(2) Å
and 2.090(2)–2.100(2) Å, respectively. Co(2) is also six-coordinate,
but the coordination polyhedron is more like a trigonal antiprism.
In this complex Co(1) adopts the chelate-monodentate carboxylate
groups coordination and Co(2) employs chelate carboxylate groups
coordination (Scheme 2a and b) to afford an infinite helical chain
with a period of 25.60 Å. These chains progress in one direction
and further extend into a 2D supramolecular sheet via C–Hꢀ ꢀ ꢀ
interactions between the pyridine ring proton and a phenyl ring
(Hꢀ ꢀ ꢀ 3.50, 3.46 Å and C–Hꢀ ꢀ ꢀ 117, 101°, Fig. 3b).
Complex 4 is isostructural with 3 but Ni atoms instead of Co
atoms.
p
p
p
ꢁ1
Fig. 5. Plots of the temperature dependence of
v
MT and vM at 2–300 K.
The different coordination polymers formed under slightly dif-
ferent reaction conditions, such as the pH is lower for 1 and 3 than
for 2 and 4, otherwise we can only obtain a precipitate not a crys-
talline product, which suggests that the assembly is sensitive to
the synthetic conditions, including temperature (ambient or under
hydrothermal conditions), pH and the nature of ligand and metal
ion. At the same time, supramolecular forces also play an impor-
tant role in constructing the MOFs.
quent weight loss from 300 to 402 °C is probably due to organic li-
gand decomposition (Obsd. 64.7%, Calc. 63.5%). The residue is
Co2O3 (Obsd. 27.57%, Calc. 27.46%). For 2, the TG curve exhibits
three steps of weight loss. The first step is 2.84% from 100 to
140 °C and is possibly due to the loss of the water molecule of crys-
tallization (Calc. 2.89%). The second weight loss is 2.99% in the
temperature range 140–180 °C, ascribable to the loss of the aqua
ligand (Calc. 2.89%). The third step from 200 to 400 °C is due to
the decomposition of the organic ligand (Obsd. 65.71%, Calc.
61.71%). The remaining residue is probable NiO (Obsd. 13.62%,
Calc. 12.05%). Complexes 3 and 4 are isomorphic with three steps
of weight loss. For 3, the first step is 1.40% in the temperature
range 100–200 °C, corresponding to the loss of the coordinated
3.2. Thermal analysis
The thermal stability of 1ꢁ4 were studied by TGA and are re-
corded in Fig. S1a–d (in the Supplementary data). For 1, the weight
loss incurred between 118 and 256 °C corresponds to the loss of
the coordinated water molecule (Obsd. 3.01%, Calc. 2.98%). Subse-

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Y. Zhou et al. / Polyhedron 28 (2009) 2667–2672
water molecule (Calc. 1.44%). The second step is due to the release
of the organic ligand in the temperature range 200–550 °C (Obsd.
64.17%, Calc. 65.38%), and the remaining weight (Obsd. 12.46%,
Cacl. 13.30%) is assigned to Co2O3.
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H2L1 ligand, and this is assigned to an intraligand
p
?
p
transition
*
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3.4. Magnetic properties
The magnetic properties of 1 were studied in the temperature
range 2–300 K (Fig. 5). The
v
MT value at 300 K is 3.528 cm3 K
molꢁ1, larger than the value for a spin-only S = 3/2 system
(1.875 emu K molꢁ1). This is expected as there is a significant
first-order orbital contribution to the magnetic moment for a
five-coordinate high spin cobalt(II) ion [48]. Upon lowering the
temperature
v
MT decreases to 1.191 cm3 K molꢁ1 at 2 K. The fitting
of the curve for the vMꢁ1 versus T plot to the Curie–Weiss law gives
a
good result in the temperature range of 50–300 K with
C = 3.931 cm3 K molꢁ1 and h = ꢁ41.191 K, consistent with the pres-
ence of an antiferromagnetic interaction in 1.
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(4), four new coordination polymers, were synthesized and character-
ized. In addition, magnetic and luminescence properties have
been studied for 1 and 2, respectively. It is anticipated that more me-
tal–organic frameworks (MOFs) employing L1, L2 or other analogous
ligands will be produced and possibly realized in functioned
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Appendix A. Supplementary data
CCDC 691998, 703442, 701829 and 702993 contain the supple-
mentary crystallographic data for compounds 1, 2, 3 and 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, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.poly.2009.06.022.
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