Synthesis, crystal structure, magnetic properties of a manganese(II) coordination polymer with double-helix chains

Article abstract of DOI:10.1007/s10870-011-0225-1

Abstract A new heterocyclic carboxylate ligand, 5-(40- pyridyl)-3-methyl- benzoic acid (Hpmba), was synthesized to construct a Mn(II) coordination polymer, namely [Mn(pmba)2]n (1). Complex 1 crystallizes in monoclinic space group C2/c, with a = 17.44(2), β = 17.040(12), c = 8.680(15) A , β = 111.258(13), V = 2404(5) A 3, and Z = 4. Single-crystal X-ray diffraction studies show that complex 1 has a 3D metal-organic supramolecular framework consisting of double helical chains. Magnetic studies for complex 1 show antiferromagnetic coupling between the nearest Mn(II) ions, with g = 2.11 and J = -10.1 cm_-1. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s10870-011-0225-1

J Chem Crystallogr (2012) 42:205–209
DOI 10.1007/s10870-011-0225-1
ORIGINAL PAPER
Synthesis, Crystal Structure, Magnetic Properties
of a Manganese(II) Coordination Polymer
with Double-Helix Chains
•
•
•
Jin-Zhong Gu Zhu-Qing Gao Dong-Yu Lv
Wei Dou
Received: 20 June 2011 / Accepted: 17 November 2011 / Published online: 30 November 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A new heterocyclic carboxylate ligand, 5-(40-
pyridyl)-3-methyl-benzoic acid (Hpmba), was synthesized
to construct a Mn(II) coordination polymer, namely
[Mn(pmba)2]n (1). Complex 1 crystallizes in monoclinic
enantiomorph separation [1–6]. The construction of helical
structures is the result of a combination of various forces,
including not only strong interactions (for example metal–
ligand coordination bonds) [7, 8] but also weaker interac-
tions such as hydrogen bonds [9, 10] and p–p stacking
interactions [11, 12]. We have made efforts for the design
and construction of helical structures by coordination
interactions between the ligand and the metal. Up to now, we
have synthesized a series of such complexes with single-,
double-, and multi-stranded helices [13–16]. Herein, we
report the synthesis, crystal structure, magnetic properties of
a Mn(II) compound with double helix chains.
space group C2/c, with a = 17.44(2), b = 17.040(12),
3
˚
˚
c = 8.680(15) A, b = 111.258(13), V = 2404(5) A , and
Z = 4. Single-crystal X-ray diffraction studies show that
complex 1 has a 3D metal-organic supramolecular frame-
work consisting of double helical chains. Magnetic studies
for complex 1 show antiferromagnetic coupling between the
nearest Mn(II) ions, with g = 2.11 and J = -10.1 cm-1
.
Keywords Manganese (III) coordination polymer ꢀ 5-(40-
Pyridyl)-3-methyl-benzoic acid ꢀ Double helical chains ꢀ
Magnetic property
Experimental
Materials and Physical Measurements
Introduction
All chemicals and solvents were of A.R. grade and used
without further purification. Carbon, hydrogen and nitrogen
were determined using an Elementar Vario EL elemental
analyzer. IR spectra were recorded using KBr pellets and a
Bruker EQUINOX 55 spectrometer. Thermogravimetric
analysis (TG) data were collected on a Netzsch TG-209
instrument with a heating rate of 10 °C/min. Magnetic
susceptibility data were collected in the 2–300 K temper-
ature range with a Quantum Design SQUID Magnetometer
MPMS XL-7 with a field of 0.1 T. A correction was made
for the diamagnetic contribution prior to data analysis.
Recently, the design and synthesis of transition metal
coordination polymers with helical structures have received
enormous attention not only for their intriguing structures
but also for their potential applications in molecular recog-
nition, nonlinear optical materials, asymmetric catalysis,
J.-Z. Gu (&) ꢀ D.-Y. Lv ꢀ W. Dou
Key Laboratory of Nonferrous Metal Chemistry and Resources
Utilization of Gansu Province, and College of Chemistry and
Chemical Engineering, Lanzhou University, Lanzhou 730000,
China
Synthesis of 5-(40-Pyridyl)-3-Methyl-Benzoic Acid
(Hpmba)
e-mail: gujzh@lzu.edu.cn
Z.-Q. Gao
School of Chemistry and Biology Engineering,
Taiyuan University of Science and Technology,
Taiyuan 030021, China
Following the protocol of Chia and Lautens [17],
a mixture of 4-pyridylboronic acid (0.068 g, 0.55 mmol),
123

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J Chem Crystallogr (2012) 42:205–209
5-Bromo-3-methylbenzoic acid (0.11 g, 0.5 mmol), K2CO3
(0.21 g, 1.5 mmol), Pd(OAc)2 (0.056 g, 0.025 mmol) and
50 mL C2H5OH was stirred and refluxed for 8 h. Then as
much alcohol as possible was distilled off. The residue was
partitioned between water and acetic ether (40 mL,
v:v = 1:1). Then the water layer was collected. Some of
white precipitate was obtained during 0.5 M hydrochloric
acid was added to the water layer until pH = 6.0, and
collected by filtration, washed with water, and dried in
oven at 105 °C for 6 h. Yield 0.075 g, 70%. Found for
C13H11NO2 (213.23 g mol-1): C, 72.86; H, 5.57; N, 6.28.
Anal. Calcd: C, 73.22; H, 5.20; N, 6.57. IR (KBr, cm-1): m
(CO2) 1697. 1H NMR (400 MHz, DMSO-d6): d 2.466
(s, 3H), d 7.743 (s, 1H), d 7.813 (d, J = 9.8 Hz, 2H),
d 7.872 (s, 1H), d 8.485 (s, 1H), d 8.700 (d, J = 11.6 Hz,
2H), d 13.415 (bs, 1H).
Table 1 Crystallographic data and refinement summary for
complex 1
Synthesis of [Mn(pmba)2]n (1)
Formula
C26H20N2MnO4
479.38
A mixture of MnSO4ꢀ2H2O (0.034 g, 0.2 mmol), Hpmba
(0.085 g, 0.4 mmol), NaOH (0.016 g, 0.4 mmol) and H2O
(10 mL) was stirred at room temperature for 15 min, and
then sealed in a 25 mL Teflon-lined stainless steel vessel,
and heated at 160 °C for 3 days, followed by cooling to
room temperature at a rate of 10 °C/h. Colourless block-
shaped crystals of 1 were isolated manually, and washed
with distilled water. Yield 0.039 g, 80% (based on Mn).
Found for C26H20N2MnO4 (479.38 g mol-1): C, 65.57; H,
3.98; N, 5.43. Anal. Calcd: C, 65.14; H, 4.20; N, 5.84. IR
(KBr, cm-1): mas(CO2) 1620 and 1561, ms(CO2) 1447 and
1387.
Mr
Crystal system
Space group
Monoclinic
C2/c
˚
a (A)
17.44(2)
17.040(12)
8.680(15)
111.258(13)
2404(5)
4
˚
b (A)
˚
c (A)
b (8)
3
V (A )
˚
Z
T (K)
Dcalc (g cm-3
293(2)
)
1.325
Crystal size (mm3)
0.28 9 0.26 9 0.24
988
F(000)
l (Mo-Ka)/mm-1
h (8)
X-ray Crystallography
0.582
2.39–25.20
8457
Single-crystal data for compound 1 were collected at
293(2) K on a Bruker Smart 1000 CCD diffractometer with
Reflections collected
Rint
0.0931
˚
Mo-Ka radiation (k = 0.71073 A). The structure was
Independent reflections(I C 2r(I)) 2174
solved using direct method, which yielded the positions of
all non-hydrogen atoms. These were refined first isotropi-
cally and then anisotropically. All the hydrogen atoms were
placed in calculated positions with fixed isotropic thermal
parameters and included in structure factor calculations
during the final state of full-matrix least-squares refine-
ment. All calculations were performed using the SHEL-
XTL-97 system [18]. The crystallographic data are
summarized in Table 1. The selected bond lengths and
angles are listed in Table 2.
Max. and min. transmission
Limiting indices
0.8728/0.8539
-19 B h B 20, -20 B k B 20,
-10 B l B 10
Parameters
-3
151
˚
D(q)(eꢀA
Goodness-of-fit
)
0.276, -0.304
1.025
Final R indices [I [ 2r(I)]
R indices (all data)
CCDC No.
R1 = 0.0573, wR2 = 0.1007
R1 = 0.0963, wR2 = 0.1149
824906
˚
Table 2 Selected bond lengths (A) and bond angles (°) for complex 1
Mn(1)–O(1)
2.112(3)
Mn(1)–O(1)#1
2.112(3)
Mn(1)–O(2)#2
2.124(3)
Mn(1)–O(2)#3
2.124(3)
Mn(1)–N(1)#4
2.314(3)
Mn(1)–N(1)#5
2.314(3)
O(1)#1–Mn(1)–O(1)
O(1)#1–Mn(1)–O(2)#3
O(1)#1–Mn(1)–N(1)#4
O(2)#3–Mn(1)–N(1)#4
O(2)#2–Mn(1)–N(1)#5
94.25(16)
102.21(13)
89.24(13)
83.88(13)
83.88(13)
O(1)#1–Mn(1)–O(2)#2
O(1)–Mn(1)–O(2)#3
O(1)–Mn(1)–N(1)#4
O(1)#1–Mn(1)–N(1)#5
O(2)#3–Mn(1)–N(1)#5
86.14(13)
86.14(13)
169.92(11)
169.92(11)
87.45(13)
O(1)–Mn(1)–O(2)#2
O(2)#2–Mn(1)–O(2)#3
O(2)#2–Mn(1)–N(1)#4
O(1)–Mn(1)–N(1)#5
N(1)#4–Mn(1)–N(1)#5
102.21(13)
167.84(15)
87.45(13)
89.24(13)
88.92(18)
Symmetry codes: #1: -x, y, -z ? 1/2; #2: -x, -y, -z ? 1; #3: x, -y, z - 1/2; #4: x - 1/2, y - 1/2, z - 1; #5: -x ? 1/2, y - 1/2, -z ? 3/2
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J Chem Crystallogr (2012) 42:205–209
Results and Discussion
Syntheses
207
carboxylate atoms and two N atoms from six different
pmba ligands, forming a distorted octahedral geometry
with three O atoms and one N atom from four individual
pmba ligands occupy the equatorial positions, one O atom
and one N atom from two different pmba ligand occupy the
axial positions. The Mn–O distances range from 2.112(3)
Hpmba was synthesized by the Suzuki reaction and
compound 1 was obtained by hydrothermal reaction
(Scheme 1). The reaction route is as follows:
˚
˚
to 2.124(4) A, the Mn–N distances are 2.314(4) A, which
are in good agreement with those observed in other Mn(II)
complexes [13, 19, 20]. The pmba ligand adopts the
coordination mode of l3-tridentate and its carboxylic group
adopts l2–g1–g1 bridging mode in syn–syn conformation,
as shown in Scheme 2. The phenyl and pyridyl rings are
not coplane with the dihedral angle of ca. 42.71°.
Description of Crystal Structure
Crystallographic analysis reveals that complex 1 crystal-
lizes in the monoclinic space group C2/c. As shown in
Fig. 1, the Mn(II) atom is six-coordinated by four
The carboxylate of the pmba ligand bridges alternately
two Mn(II) ions in syn–syn coordination mode to form
infinite right-handed or left-handed helical C–O–Mn chains
(Fig. 2). The MnꢀꢀꢀMn separation in the chain is
N
Br
Ν
Pd(OAc)2 K2CO3
+
O
˚
4.848(4) A. The two types of helical chains are intercon-
C2H5OH reflux 8 h
H3C
O
B(OH)2
N
OH
nected to each other through the Mn(II) centers to produce
double-helix chains. The chains are further extended into a
H3C
OH
Scheme 2 The coordination
mode of the pmba ligand in
complex 1
MnSO4 2H2O NaOH
160 oC 3 d
Mn
N
1
O
H3C
OH
Scheme 1 The synthetic routes for the ligand and compound 1
Μ
n
O
H3C
Mn
O
μ
3-tridentate
Fig. 1 The coordination environment of Mn2? in 1. (H atoms were
omitted for clarity). Symmetry code: i -x, y, -z ? 1/2; ii -x, -y,
-z ? 1; iii x, -y, z - 1/2; iv x - 1/2, y - 1/2, z - 1; v -x ? 1/2,
y - 1/2, -z ? 3/2
Fig. 2 View of double-helix chains of compound 1
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J Chem Crystallogr (2012) 42:205–209
Fig. 3 View of 2D sheet
of compound 1 through the
coordination interaction
of pmba ligands
Fig. 5 The TG curve for compound 1
Fig. 4 View of the 3D framework of compound 1 along c axis
(H atoms were omitted for clarity)
The temperature-dependent magnetic properties of 1 are
shown in Fig. 6 in the form of vMT versus T curve. The
vMT value of 4.58 cm3 mol-1 K (6.05 lB) at room tem-
perature is close to the value of 4.38 cm3 mol-1 K (5.92 lB)
expected for magnetically isolated high-spin Mn(II)
(SMn = 5/2, g = 2.0). The vMT values steadily decreases
with decreasing temperature to reach minimum values of
3.86 cm3 mol-1 K at 46.9 K. Between 46.9 and 300 K, the
magnetic susceptibilities can be fitted to the Curie–
3D metal-organic supramolecular framework by the coor-
dination interaction of the pmba ligands (Figs. 3, 4).
Thermal Analysis and Magnetic Properties
In order to examine the thermal stability of the network,
thermal gravimertric analysis (TG) was conducted on
crystalline samples of compound 1 between 20 and 800 °C.
As shown in Fig. 5, complex 1 is stable up to 425 °C, but
decomposes above 425 °C, which corresponds to decom-
position of the ligand.
Weiss law, vM = CM/(T - h), with CM = 4.77 cm3 mol-1
,
h = -14.6 K. These results indicate an antiferromagnetic
interactions between the nearest Mn(II). Upon further
cooling, the vMT values increase up to maximum of
4.56 cm3 mol-1 K at TN = 37.8 K, and then decrease with
123

J Chem Crystallogr (2012) 42:205–209
209
Supplementary Data
CCDC 824906 contains the supplementary crystallographic
data for this article. The data can be obtained free of charge
from The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (fax: ?44-1223-336-033; email: depos-
it@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgments This study was supported by the National
Natural Science Foundation of China (Project No. 21071068).
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A new Mn(II) coordination polymer [Mn(pmba)2]n (1)
based on Hpmba has been synthesized and structurally
characterized. It has a 3D metal-organic supramolecular
framework consisting of double-helix chains. Magnetic
analysis indicates weak antiferromagnetic coupling
between Mn(II) ions. This study shows that Hpmba is a
useful bridging ligand for the construction of coordination
polymers with helical structures.
¨
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¨
123