The rational syntheses of manganese-chloranilate compounds: Crystal structures and magnetic properties

Article abstract of DOI:10.1016/S0277-5387(01)00628-3

[Mn(CA)(terpy)]_n (1) and {[Mn(CA)(bipym)_0.5(H₂O)](H₂O)(C₂ H₅OH)}_n (2) (H₂CA=chloranilic acid, terpy = 2,2′:6′,2″-terpyridine and bipym = 2,2′-bipyrimidine) have been synthesized and their crystal structures determined by a single-crystal X-ray diffraction. Compound 1 is made up of infinite chains of chloranilate-bridged manganese(II), affording a zig-zag pattern, with terpyridine ligands stacking between the chains. Compound 2 has a novel honeycomb layered structure, where each hexagon consists of six Mn(II) ions, four CA^2- and two bipym ligands. Mn(II) ions in both compounds are unusually hepta-coordinated. Magnetic susceptibility measurements of both compounds show weak antiferromagnetic coupling between the nearest Mn(II) ions.

Full text of DOI:10.1016/S0277-5387(01)00628-3

Polyhedron 20 (2001) 1417–1422
www.elsevier.nl/locate/poly
The rational syntheses of manganese–chloranilate compounds:
crystal structures and magnetic properties
M.K. Kabir a, M. Kawahara b, H. Kumagai c, K. Adachi a, S. Kawata a,*, T. Ishii b,
S. Kitagawa d
a Department of Chemistry, Faculty of Science, Shizuoka Uni6ersity, 836 Ohya, Shizuoka 422-8529, Japan
b Department of Chemistry, Tokyo Metropolitan Uni6ersity, Minami Ohsawa, Hachiouji, Tokyo 192-0397, Japan
c Institute for Molecular Science, Myoudaiji, Okazaki, Aichi 444-8585, Japan
d Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto Uni6ersity, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
Received 17 September 2000; accepted 9 November 2000
Abstract
[Mn(CA)(terpy)]n (1) and {[Mn(CA)(bipym)0.5(H2O)](H2O)(C2H5OH)}n (2) (H2CA=chloranilic acid, terpy=2,2%:6%,2¦-ter-
pyridine and bipym=2,2%-bipyrimidine) have been synthesized and their crystal structures determined by a single-crystal X-ray
diffraction. Compound 1 is made up of infinite chains of chloranilate-bridged manganese(II), affording a zig–zag pattern, with
terpyridine ligands stacking between the chains. Compound 2 has a novel honeycomb layered structure, where each hexagon
consists of six Mn(II) ions, four CA2− and two bipym ligands. Mn(II) ions in both compounds are unusually hepta-coordinated.
Magnetic susceptibility measurements of both compounds show weak antiferromagnetic coupling between the nearest Mn(II) ions.
© 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Manganese(II); Chloranilic acid; 2,2%:6%,2¦-Terpyridine; 2,2%-Bipyrimidine; Honeycomb layer; Magnetism
charged. This potentiality allows for the coordination
of transition-metal ions through CA2− bridges and
permits the probable propagation of magnetic super-ex-
change interactions between the paramagnetic centers
[4]. Moreover, CA2− is able to form a monomeric
building block, chain, and layer structures of various
metal ions [5–7]. Extensive magneto-structural work
has also been carried out with metal complexes contain-
ing bipym, which is known to transmit strong antiferro-
magnetic coupling when coordinating in the
bis-bidentate mode to the metal ions lying in the same
plane of nitrogen atoms [8–11]. On the other hand,
nitrogen atoms containing planar organic molecule
terpy can act as a non-bridging neutral ligand. How-
ever, terpy and bipym with the common ligand, H2CA,
control the dimensionality of the crystal structures
and help to design predictable molecular architectures.
In this regard, two compounds of manganese–
chloranilate system, [Mn(CA)(terpy)]n (1) and
{[Mn(CA)(bipym)0.5(H2O)](H2O)(C2H5OH)}n (2) have
1. Introduction
Metal–organic hybrid compounds with higher di-
mensional network structures are currently under in-
tense investigation in the field of molecule-based
magnets [1–3]. The proper choice of bridging ligands is
important since they affect the magnetic exchange path-
ways between paramagnetic metal centers and influence
the magnetic strength and behavior of the materials, as
well as the dimensionality of the assembled compounds.
Usage of mixed organic ligands with the suitable metal
ions helps to obtain predictable molecular architecture.
In this context manganese assembled structures of chlo-
ranilic acid (H2CA) are rationally designed by using
2,2%:6%,2¦-terpyridine (terpy) and 2,2%-bipyrimidine
(bipym). The dianion of chloranilic acid (CA2−) con-
sists of two allyl systems connected by CꢀC single
bonds, with four oxygen atoms partially negatively
* Corresponding author. Tel./fax: +81-5423-84757.
E-mail address: scskawa@ipc.shizuoka.ac.jp (S. Kawata).
been synthesized. Compound 1 consists of CA2−
-
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00628-3

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M.K. Kabir et al. / Polyhedron 20 (2001) 1417–1422
bridged chain of Mn(II) and compound 2 is made up of
honeycomb layer with [Mn(CA)(bipym)0.5(H2O)] units.
In this paper we present the crystal structures and the
magnetic properties of the two compounds.
2.2. Syntheses
2.2.1. [Mn(CA)(terpy)]n (1)
To the solution of terpyridine (0.116 g) in 1:1 (v/v)
EtOH/H2O (100 ml), manganese chloride hexahydrate
(0.063 g) was mixed. After stirring for a few minutes a
yellow powder of Mn(terpy)Cl2 was precipitated out
from the mixture (yield 85%). Then a solution of
sodium salt of chloranilic acid (0.1 mM) in 1:1 (v/v)
EtOH/H2O was added to an aqueous solution of [Mn-
(terpy)Cl2] (0.1 mM) in the tubes without mixing the
two solutions. Red plate-like crystals began to form in
a week. One of these crystals was used for X-ray
crystallography.
2. Experimental
2.1. Materials
2,2%-Bipyrimidine, 2,2%:6%,2¦-terpyridine, chloranilic
acid, manganese chloride and manganese perchlorate
were purchased from commercial sources and used as
received.
2.2.2. {[Mn(CA)(bipym)0.5(H2O)](H2O)(C2H5OH)}n (2)
An aqueous solution of manganese perchlorate hexa-
hydrate (0.26 g, 1 mmol) was transferred to a glass
tube. Then a mixture of 2,2%-bipyrimidine and chlo-
ranilic acid (0.20 g, 1 mmol) in 1:1 (v/v) EtOH/H2O
was poured into the tube without mixing the two
solutions. Red-purple plate crystals began to form at
ambient temperature in a week. One of these crystals
was used for X-ray crystallography.
Table 1
Crystallographic data for 1 and 2
1
2
Formula
MnO4Cl2N3C21H11
495.18
triclinic
MnO7Cl2N2C12H13
423.09
triclinic
Formula weight
Crystal system
Space group
Diffractometer
(
(
P1 (c2)
P1 (c2)
Rigaku AFC7R
10.259(2)
10.250(2)
9.997(2)
98.00(2)
113.76(1)
85.17(2)
952.2(3)
2
Rigaku AFC7R
9.903(3)
11.165(2)
8.778(2)
111.97(1)
97.77(2)
69.86(2)
845.1(4)
2
,
a (A)
2.3. Crystallographic data collection and refinement of
the structures
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
Crystallographic data for the complexes 1 and 2 were
collected on a Rigaku AFC7R diffractometer with Mo
Ka radiation at room temperature. Crystallographic
data for the complexes are given in Table 1. The
structures were solved by direct methods (Rigaku
texsan crystallographic software package of Molecular
Structure Corporation) and refined with full-matrix
least-squares technique (SHELXL-93) [12] to R=0.052,
wR2=0.158 (1); R=0.040, wR2=0.126 (2). All non-
hydrogen atoms were refined with anisotropic displace-
ment parameters. The hydrogen atoms were located in
the Fourier maps. However, they were not refined.
3
,
V (A )
Z
Dcalc (g cm−3
)
1.727
10.10
498.00
0.052; 0.158
55.0
1.663
11.33
428.00
0.040; 0.126
55.0
v (Mo Ka) (cm−1
F(000)
)
a
R, wR2
2qmax (°)
Goodness-of-fit
1.03
1.07
a R=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ; Rw=[ꢀw(F2o−Fc2)2/ꢀw(Fo2)2]1/2 where
w=[|2(F2o)+(0.0643P)2+0.0000P]−1 (1);
0.6178P]−1 (2) and P=(Fo2+2Fc2)/3.
[|2(F2o)+(0.0672P)2+
2.4. Physical measurements
Table 2
,
Selected bond distances (A) and angles (°) for 1
Temperature dependence of magnetic susceptibility
of the polycrystalline samples were measured from 2 to
300 K using a Quantum Design Model MPMS com-
puter-controlled SQUID magnetometer. Corrections
for the diamagnetism of the complex were estimated
from Pascal%s table.
Bond distances
MnꢀO(1)
MnꢀO(3)
MnꢀN(1)
MnꢀN(3)
2.188(3)
2.260(4)
2.361(3)
2.312(4)
MnꢀO(2)
MnꢀO(4)
MnꢀN(2)
2.293(4)
2.324(3)
2.256(3)
Bond angles
O(1)ꢀMnꢀO(2)
O(1)ꢀMnꢀO(3)
O(1)ꢀMnꢀO(4)
O(1)ꢀMnꢀN(1)
N(2)ꢀMnꢀN(3)
O(2)ꢀMnꢀN(1)
O(2)ꢀMnꢀN(3)
O(2)ꢀMnꢀN(2)
71.9(1)
106.4(1)
82.2(1)
87.3(1)
70.9(1)
84.4(1)
82.2(1)
86.8(1)
O(3)ꢀMnꢀO(4)
O(2)ꢀMnꢀO(3)
N(1)ꢀMnꢀN(2)
O(2)ꢀMnꢀO(4)
O(1)ꢀMnꢀN(3)
O(3)ꢀMnꢀN(3)
O(1)ꢀMnꢀN(2)
O(3)ꢀMnꢀN(2)
69.3(1)
158.5(1)
70.3(1)
130.1(1)
123.7(1)
114.3(1)
150.7(1)
86.0(1)
3. Results and discussion
3.1. Crystal structures
The structure of compound 1 is made up of neutral
[Mn(CA)(terpy)] units. Each Mn(II) ion in 1 is unusu-

M.K. Kabir et al. / Polyhedron 20 (2001) 1417–1422
1419
Fig. 1. (a) ORTEP drawing of 1 with the atom numbering scheme and thermal ellipsoids at the 50% probability level. Hydrogen atoms are omitted
for clarity. (b) View of a one-dimensional chain formed by 1.
ally hepta-coordinated [13,14]; four oxygen atoms from
the two CA2− and three nitrogen atoms from one
terpyridine. Selected bond distances and angles of the
compound are listed in Table 2 and an ORTEP [15]
drawing with the atom numbering scheme is shown in
Fig. 1(a). The geometry around the Mn(II) ion is not
ideal, pentagonal bipyramidal as found for the seven
coordinated Mn(II) ions [14], but rather distorted octa-
hedral. The CA2− bridges Mn(II) ions, which leads to
infinite chains exhibiting a zig–zag pattern along the
(0,1,−1) direction with terpyridine ligands stacking
between the chains (Fig. 1(b)). The nearest CꢀC dis-
stacking interaction makes three-dimensional packing
structure. The electroneutrality of the chain is sup-
ported by the three nitrogen atoms of the terminal
terpyridene. There are two types of CA2− in the chain,
but MnꢀMn distances through the CA2− are almost
,
the same; average distance is 8.39 A. However, this
MnꢀMn separation is a little larger than the MnꢀMn
,
(8.201 A) separation in the chain of {[Mn(CA)-
(H2O)2](H2O)}n [16]. Two CA2− rings around a man-
ganese ion in 1 are not parallel, dihedral angle being
78.53°. Thus, the chain becomes zig–zag.
Compound 2 is formally made up of neutral
[Mn(CA)(bipym)0.5(H2O)] units and interstitial water
,
tance of the stacked terpyridine ligands is 3.57 A. This

1420
M.K. Kabir et al. / Polyhedron 20 (2001) 1417–1422
and ethanol molecules. The Mn(II) ion in 2 is also
unusually hepta-coordinated; two nitrogen atoms of
bipym, four oxygen atoms of two CA2− anions and
one oxygen from a water molecule. An ORTEP drawing
of 2 with the atom numbering scheme is shown in Fig.
2(a) and the selected bond distances and angles are
listed in Table 3. Two coordinated CA2− are not in the
same plane of bipym. The dihedral angles between
bipym and CA2− planes are 0.00 and 88.15°. Two
CA2− rings make the zig–zag chain, which is very
similar to that of 1. The seven-coordinated manganese
atom adopts the distorted pentagonal bipyramidal ge-
ometry. Manganese atoms make parallel sheets linked
by two CA2− anions and one bipym ligand. Each sheet
is made up of CA2− bridged corrugated chains of
manganese ions that are connected by bipym ligands,
leading to the formation of a honeycomb network.
Thus the two-dimensional polymer, as shown in Fig.
Fig. 2. (a) ORTEP drawing of the 2 with the atom numbering scheme and thermal ellipsoids at the 50% probability level. Hydrogen atoms are
omitted for clarity. (b) View of a layer of 2 (hydrogen atoms and solvent molecules have been omitted for clarity).

M.K. Kabir et al. / Polyhedron 20 (2001) 1417–1422
1421
Table 3
3.2. Magnetic properties
,
Selected bond distances (A) and angles (°) for 2
The temperature dependence of the molar magnetic
Bond distances
susceptibility  for 1 and 2 are measured over the
M
MnꢀO(1)
MnꢀO(3)
MnꢀO(5)
MnꢀN(2)
2.222(2)
2.201(2)
2.175(3)
2.381(3)
MnO(2)
MnꢀO(4)
MnꢀN(1)
2.304(3)
2.282(2)
2.390(3)
temperature range 2–300 K in a field of 0.5 T. The 
M
vs. T and MT vs. T plots for 1 are shown in Fig. 3.
MT of 1 exhibits a continuous decrease upon cooling,
with MT=4.4 at the room temperature. This behavior
is the characteristic of antiferromagnetic interaction
Bond angles
O(1)ꢀMnꢀO(2)
O(1)ꢀMnꢀO(4)
O(1)ꢀMnꢀO(5)
O(2)ꢀMnꢀO(3)
O(3)ꢀMnꢀO(5)
N(1)ꢀMnꢀN(2)
O(3)ꢀMnꢀN(1)
O(4)ꢀMnꢀN(1)
O(5)ꢀMnꢀN(1)
70.69(8)
135.0(1)
87.11(9)
101.6(1)
168.48(9)
68.84(9)
99.44(9)
76.56(9)
82.00(10)
O(3)ꢀMnꢀO(4)
O(1)ꢀMnꢀO(3)
O(2)ꢀMnꢀO(4)
O(2)ꢀMnꢀO(5)
O(4)ꢀMnꢀO(5)
O(1)ꢀMnꢀN(2)
O(3)ꢀMnꢀN(2)
O(4)ꢀMnꢀN(2)
O(5)ꢀMnꢀN(2)
72.02(8)
85.59(8)
76.19(8)
84.4(1)
119.27(8)
79.54(9)
83.27(9)
133.10(8)
86.64(10)
between high-spin Mn(II) ions through CA2−. CA2−
-
mediated antiferromagnetic interaction is well sup-
ported by the calculation assuming Heisenberg-type
chain using Fisher’s formula, scaled to a spin value of
5/2 for Mn(II):
M=Ng2i2S(S+1)/3kT(1+u)/(1−u)
u=coth(2JS(S+1)/kT)−kT/2JS(S+1)
where the parameters have their usual meaning. The
best fit leads to the following parameters: g=2.022,
J= −0.50 cm−1. The J values of −0.74 and −0.65
cm−1 are reported for the similar CA2− bridged chain
of hexacoordinated Mn(II) ions [16]. The absolute
value of J in 1 is a little smaller than that reported for
these compounds, which maybe due to the larger
MnꢀMn separation in 1.
The  vs. T and MT vs. T plots for 2 are shown in
M
Fig. 4. The product of the molar susceptibility and
temperature, MT exhibits a continuous decrease upon
cooling, with MT=4.4 at the room temperature. 
M
per Mn(II) ion of the complex 2 shows the antiferro-
magnetic interaction similar to 1. The honeycomb layer
of 2 consists of CA2− bridged chain connected by
bipym, where antiferromagnetic exchange pathways
through bipym and CA2− are possible. Both the CA2−
and bipym are able to mediate exchange coupling be-
Fig. 3. Temperature dependence of  (ꢀ) and MT (ꢁ) of 1. Solid
M
line represents fit of 1 to Fisher one-dimensional chain model.
2(b), extending in the ab plane is formed by the repeti-
tion of CA2− and bipym-bridged hexagons. The aver-
age distance between the nearest Mn(II) ions in the
CA2−-bridged chain of 2 is 8.34 A, which is very
,
similar to that of 1. One ethanol and one water
molecule are located in the hole of each hexagon of the
sheets. However, the thermal parameters of the carbon
and oxygen atoms of ethanol molecules are too high,
which suggests the presence of disorder. The interstitial
water molecules are hydrogen-bonded with the coordi-
nated oxygen atoms of CA2−. From the structural view
of the two compounds it can be concluded that the
MnꢀCA2− chain is able to extend its dimensionality
with the bridging ligand bipym.
Fig. 4. Temperature dependence of  (ꢀ) and MT (ꢁ) of 2. Solid
line represents fit of 2 to Fisher one-dimensional chain model.
M

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M.K. Kabir et al. / Polyhedron 20 (2001) 1417–1422
tween the Mn(II) ions. In this regard, the J values of
−0.93 and −0.74 cm−1 have been reported for CA2−
and bipym bridged chain structures of Mn(II) ions in
{[Mn(CA)(H2O)2](H2O)}n and [Mn(bipym)(NO3)2], re-
spectively [16,17]. For compound 2, two simple models
can be considered to evaluate the magnitude of the
exchange coupling. The first model is based on a
Heisenberg-type chain of CA2−, in which interchain
interactions are treated with the molecular field approx-
imation [18]. The second model is a honeycomb Heisen-
berg two-dimensional lattice [19]. Attempts to fit the
magnetic data of 2 to the second model lead to a bad
fit. On the basis of the first model, magnetic data are
analyzed using Fischer’s formula scaled to a spin value
of 5/2 for Mn(II). The best fit for MT leads to the
parameters g=2.033, J= −0.49 cm−1, J= −0.06
Data Center, CCDC Nos. 149139 and 149140. Copies
of this information may be obtained free of charge
from The Director, CCDC, 12 Union Road, Cam-
bridge, CB2 1EZ, UK (fax: +44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www:http://www.ccdc.
ac.uk).
Acknowledgements
This research was supported by a Grant-in-Aid for
Scientific Research (No. 12640537) and by a Grant-in-
Aid for Scientific Research on Priority Areas (No.
12023216, Metal-assembled Complexes) from the Min-
istry of Education, Science, Sports and Culture, Japan.
cm−1 and z=2 (solid line in Fig. 4), where the inter-
.
chain coupling constant J% is associated with bipym.
The degree of interaction between the Mn(II) centers
through CA2− and bipym is different, which is at-
tributed from the large difference between J and J%
values. Moreover, the value of J is almost the same for
both compounds 1 and 2. Although the interaction is
possible through both CA2− and bipym, the lower
value of J% suggests that the effective pathway for the
magnetic interaction in 2 is CA2−, not bipym.
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ions making honeycomb layer structure, whereas the
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5. Supplementary material
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic