Novel MnII coordination compounds constructed from benzoate and various bipyridyl ligands: Magnetic property and catalytic activity

Article abstract of DOI:10.1016/j.poly.2012.05.040

Three new Mn^II-benzoates coordination polymers containing various bipyridyl ligands (3,3′-dipicoylamine (3), 3-methylisoquinoline (4), and 4,4′-dithiopyridine (5)) and a [Mn₆(O ₂CPh)₁₀(μ₄-OH)₂(CH ₃OH)₃(H₂O)]·1.5(C₄H ₄N₂) cluster (1) have prepared and their structures were determined. The bipyridyl ligands can act as bridging ligands to produce 1-D or 2-D polymeric compounds. The pyrazine produced a Mn₆ cluster molecule, and 3-methylisoquinoline did a benzoate-bridged 1-D Mn^II compound. The Mn₆ cluster (1) and 1-D Mn^II compounds (3) and (4) show antiferromagnetic property. The compounds 1, 3, and 4 have catalyzed efficiently the transesterification of a variety of esters, while 5 has displayed a very slow conversion. The thermal stabilities of these complexes were also examined.

Full text of DOI:10.1016/j.poly.2012.05.040

Polyhedron 42 (2012) 282–290
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Novel MnII coordination compounds constructed from benzoate and various
bipyridyl ligands: Magnetic property and catalytic activity
In Hong Hwang a, Young Dan Jo a, Ha-Yeong Kim b, Juhye Kang a, Jin Young Noh a, Min Young Hyun a,
Cheal Kim a, , Youngmee Kim b, , Sung-Jin Kim b
⇑
⇑
a Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea
b Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Three new MnII-benzoates coordination polymers containing various bipyridyl ligands (3,30-dipicoyl-
Article history:
amine (3), 3-methylisoquinoline (4), and 4,40-dithiopyridine (5)) and
a
[Mn6(O2CPh)10(l4-
Received 16 February 2012
Accepted 30 May 2012
Available online 9 June 2012
OH)2(CH3OH)3(H2O)]ꢀ1.5(C4H4N2) cluster (1) have prepared and their structures were determined. The
bipyridyl ligands can act as bridging ligands to produce 1-D or 2-D polymeric compounds. The pyrazine
produced a Mn6 cluster molecule, and 3-methylisoquinoline did a benzoate-bridged 1-D MnII compound.
The Mn6 cluster (1) and 1-D MnII compounds (3) and (4) show antiferromagnetic property. The com-
pounds 1, 3, and 4 have catalyzed efficiently the transesterification of a variety of esters, while 5 has dis-
played a very slow conversion. The thermal stabilities of these complexes were also examined.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
MnII complexes
Bipyridyl ligands
Magnetic property
Catalytic activities
Transesterification
1. Introduction
manganese complexes containing various carboxylate ligands
[40–42] as well as their metal–organic frameworks with 4,40-
Coordination polymers are currently of great interest and repre-
sent an active area of coordination chemistry due to their potential
applications as functional materials ranging from gas storage [1–6]
to ion-exchange [7,8], magnetism [9], catalysis [10–19], and
molecular sensing [20,21]. Since the control of structure and topol-
ogy of assemblies is one of the major goals in coordination polymer
chemistry, many efforts have been devoted to rational design of
specific coordination polymers including one-, two-, and three-
dimensional structures. As a part of our work towards rational de-
sign and preparation of functional coordination polymers with
intriguing structures and potential applications in catalysis, we
have recently carried out a systematic study of zinc metal–organic
complexes from the mixed-ligand systems of multifunctional or-
ganic ligand benzoate and bridging ligands such as pyrazine, its
derivatives [22], 1,2-bis(4-pyridyl)ethane [23], and 1,2-bis(4-pyri-
dyl)ethene [24]. Importantly, the assembly process of the zinc ben-
zoates has been highly influenced by solvent system, metal to
ligand ratio, and types of bipyridyl ligands.
bipyridine (4,40-bpy) have been reported [43,44]. Nevertheless,
there needs still more understanding concerning the factors that
determine their syntheses and the resulting structures, and the
attainment of rational control to give rise to desired topologies
and specific properties still remains a great challenge.
As an extension of our previous work, in this study, we have fur-
ther investigated the complex formation of manganese–benzoates
with various bipyridyl ligands such as pyrazine (pyz), 4,40-bipyri-
dine (4,40-bpy), 3,30-dipicoylamine (3,30-dpicam), 3-methylisoquin-
oline, 4,40-dithiopyridine (4,40-dtp), since the use of the various
bipyridyl ligands as spacers may lead to new polymeric networks
with intriguing structures and potential applications especially in
catalysis. Herein, we report the synthesis, single crystal X-ray
structures, magnetic behaviors, thermal properties, and catalytic
reactivity of five MnII polymers [Mn6(O2CPh)10
(l4-OH)2(CH3OH)3
(H2O)]ꢀ1.5(C4H4N2) (1), previously reported [Mn(O2CPh)2(4,40-bpy)]n
(2) [45–47], [{Mn2(O2CPh)4(H2O)2(3,30-dpicam)2}ꢀ2(H2O)]n (3), [{Mn2
(O2CPh)5}ꢀ(CH3OH)(C10H9N)]n (4), and [{Mn(O2CPh)2(4,40-dtp)2}ꢀ
(H2O)ꢀ0.5(HO2CPh)]n (5).
The MnII coordination compounds have been considered in the
fields of supramolecular chemistry and crystal engineering for
their remarkable magnetic properties [25–30], rich biochemistry
[31–35], and catalytic activities [36–39]. Previously, several
2. Experimental
2.1. Materials
⇑
Corresponding authors. Tel.: +82 2 970 6693; fax: +82 2 973 9149 (C. Kim),
tel.: +82 2 3277 3589; fax: +82 2 3277 3419 (Y. Kim).
Mn(NO3)2ꢀH2O, C6H5COONH4, 4,40-dithiopyridine, 3,30-dipicoyl-
E-mail addresses: chealkim@snut.ac.kr (C. Kim), ymeekim@ewha.ac.kr (Y. Kim).
amine, pyrazine, 3-methylisoquinoline, 4-nitrophenyl acetate,
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.05.040

I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
283
phenyl acetate, 4-methylphenyl acetate, 4-nitrophenyl benzoate,
2.4. [Mn(O2CPh)2(4,40-bpy)]n (2)
phenyl benzoate, 4-chlorophenyl benzoate, 4-methylphenyl benzo-
ate, vinyl acetate, methylacetate, methylbenzoate, ethanol, metha-
nol, and benzene were purchased from Aldrich and were used as
received. 4-Fluorophenyl acetate and 4-nitrophenyl benzoate were
obtained from Lancaster.
Compound 2 has been prepared by the literature procedure
[45–47].
2.5. [{Mn2(O2CPh)4(H2O)2(3,30-dpicam)2}ꢀ2(H2O)]n (3)
A mixture of Mn(NO3)2 (22.8 mg, 0.125 mmol), C6H5COONH4
(35.5 mg, 0.25 mmol) and H2O (4 mL) was placed in a screw vial
and 4 mL methanol solution of 3,30-dipicoylamine (3,30-dpicam)
2.2. Instrumentation
Elemental analysis for carbon, nitrogen, and hydrogen was car-
ried out by using a vario MACRO (Elemental Analysensysteme, Ger-
many) in the Laboratory Center of Seoul National University of
Science and Technology, Korea. IR spectra were measured on a
BIO RAD FTS 135 spectrometer as KBr pellets. Thermogravimertic
analyses (TGA) were carried out on a Shimadzu TA50 integration
thermal analyzer. Product analysis for the transesterification reac-
tion was performed on either a Hewlett-Packard 5890 II Plus gas
chromatograph interfaced with Hewlett-Packard Model 5989B
mass spectrometer or a Donam Systems 6200 gas chromatograph
equipped with a FID detector using 30-m capillary column (Hew-
lett-Packard, HP-1, HP-5, and Ultra 2). Magnetic susceptibility
measurements on powder samples were carried out in the temper-
ature range from 5 to 300 K in an applied magnetic field of 5000 G
using a Quantum Design MPMS-5 SQUID magnetometer.
(45.9 lL, 0.25 mmol) was added. Yellowish crystals of compound
3 suitable for X-ray analysis were obtained by slow evaporation
in two weeks. Purity of bulk sample of 3 was checked by powder
XRD (see Fig. S1 in Supporting Information). The yield was
32.7 mg (49.1%) for compound 3. IR (KBr):
m
(cmꢁ1) = 3358(brs),
3051(w), 1623(m), 1599(m), 1541(s), 1400(s), 1195(w), 800(m),
723(m). Anal. Calc. for C52H54Mn2N6O12 (1064.89) 3: C, 58.65; H,
5.12; N, 7.89. Found: C, 58.81; H, 5.11; N, 8.13%.
2.6. [{Mn2(O2CPh)5}ꢀ(CH3OH)(C10H9N)]n (4)
A mixture of Mn(NO3)2 (91.3 mg, 0.5 mmol), C6H5COONH4
(142 mg, 1 mmol), 3-methylisoqunoline (146 mg, 1 mmol) and
methanol (3 mL) was added to a screw vial. Colorless crystals of
compound 4 suitable for X-ray analysis were obtained in a week.
Purity of bulk sample of 4 was checked by powder XRD (see
Fig. S2 in Supporting Information). The yield was 63.4 mg (28.5%)
2.3. [Mn6(O2CPh)10
(l
4-OH)2(CH3OH)3(H2O)]ꢀ1.5(C4H4N2) (1)
for compound 4. IR (KBr):
1523(w), 1395(s), 1150(w), 970(w), 716(s), 672(m). Anal. Calc. for
46H38Mn2NO11 (890.65) 4: C, 62.03; H, 4.31; N, 1.57. Found: C,
m
(cmꢁ1) = 3059(m), 1601(m), 1560(m),
A
mixture of Mn(NO3)2 (183 mg, 1 mmol), C6H5COONH4
C
(284 mg, 2 mmol), pyrazine (pyz) (161.8 mg, 2 mmol) and metha-
nol (6 mL) was added to a screw vial. Dark-brownish crystals of
compound 1 suitable for X-ray analysis were obtained by slow
evaporation in two weeks. The yield was 80.0 mg (26.6%) for com-
62.41; H, 4.57; N, 1.84%.
2.7. [{Mn(O2CPh)2(4,40-dtp)2}ꢀ(H2O)ꢀ0.5(HO2CPh)]n (5)
pound 1. IR (KBr):
1175(w), 1070(w), 1026(w), 840(w), 712(s). Anal. Calc. for
79H70Mn6N3O26 (1807.03) 1: C, 52.51; H, 3.90; N, 2.33. Found: C,
m
(cmꢁ1) = 3063(m), 1598(m), 1557(m), 1390(s),
A mixture of Mn(NO3)2 (22.8 mg, 0.125 mmol), C6H5COONH4
(35.5 mg, 0.25 mmol) and H2O (4 mL) was placed in a screw vial
and 4 mL ethanol solution of 4,40-dithiopyridine (4,40-dtp)
C
52.43; H, 4.07; N, 2.41%.
Table 1
Crystallographic data for compounds 1–5.
Complex
1
2a
3
4
5
Formula
Formula weight
T (K)
C
79H70Mn6N3O26
C38H40MnN6O6
731.70
293(2)
C52H54Mn2N6O12
1064.89
293(2)
C46H38Mn2NO11
890.65
170(2)
C41H36MnN4O8S4
895.92
173(2)
1807.02
170(2)
k (Å)
Space group
0.71073
0.71073
0.71073
P21/c
0.71073
0.71073
P2/n
ꢀ
ꢀ
ꢀ
P1
P1
I4
a (Å)
b (Å)
c (Å)
15.4195(15)
15.9942(16)
18.4670(19)
77.186(2)
9.1370(18)
10.267(2)
11.688(2)
64.49(3)
11.6568(12)
19.834(2)
11.6165(12)
90.00
25.3340(8)
25.3340(8)
12.8789(8)
90.00
13.013(2)
10.9422(18)
14.304(2)
90.00
a
(°)
b (°)
89.508(2)
62.990(2)
3934.3(7)
2
87.52(3)
71.77(3)
934.5(3)
1
108.671(2)
90.00
2544.4(5)
2
90.00
90.00
8265.8(6)
8
1.431
94.946(3)
90.00
2029.1(6)
2
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
1.525
1.300
1.390
1.466
Absorption coefficient (mmꢁ1
Crystal size (mm)
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
)
1.015
0.406
0.564
0.675
0.589
0.50 ꢂ 0.20 ꢂ 0.05
0.15 ꢂ 0.10 ꢂ 0.10
0.15 ꢂ 0.10 ꢂ 0.10
0.35 ꢂ 0.35 ꢂ 0.30
0.15 ꢂ 0.10 ꢂ 0.10
22035
4635
13958
23275
11072
15035 [Rint = 0.0235]
15035/5/1033
1.087
3127 [Rint = 0.0260]
3127/1/220
1.130
4972 [Rint = 0.0504]
4972/4/343
0.902
8113 [Rint = 0.0211]
8113/0/544
1.011
3993 [Rint = 0.0805]
3993/0/274
0.956
Final R indices [I > 2
r
(I)]
R1 = 0.0442,
wR2 = 0.1275
R1 = 0.0527,
wR2 = 0.1329
1.019 and ꢁ0.979
R1 = 0.0698,
wR2 = 0.2048
R1 = 0.0844,
wR2 = 0.2315
0.547 and ꢁ0.947
R1 = 0.0425,
wR2 = 0.0844
R1 = 0.0844,
wR2 = 0.0935
0.218 and ꢁ0.283
R1 = 0.0226,
wR2 = 0.0564
R1 = 0.0242,
wR2 = 0.0570
0.323 and ꢁ0.268
R1 = 0.0432,
wR2 = 0.1023
R1 = 0.0545,
wR2 = 0.1049
0.624 and ꢁ0.451
R indices (all data)
Largest difference in peak and hole
(e Åꢁ3
)
a
See Ref. [30].

284
I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
(56.2 mg, 0.25 mmol) was added. Yellowish crystals of compound
5 suitable for X-ray analysis were obtained by slow evaporation
in two weeks. Purity of bulk sample of 5 was checked by powder
XRD (see Fig. S3 in Supporting Information). The yield was
3. Results and discussion
3.1. Syntheses and general characterization
34.2 mg (30.5%) for compound 5. IR (KBr):
m
(cmꢁ1) = 3296(brs),
The structures of manganese(II)–benzoate complexes contain-
ing various bipyridyls have been investigated. All five compounds
are shown in Scheme 1. The MnII-benzoate complex with
4,40-bpy was reported previously [45–47]. The infrared spectra of
1–5 were fully consistent with their formulations. Very strong,
slightly broadened bands at ꢃ1600 and ꢃ1400 cmꢁ1 indicated
asymmetric and symmetric C@O stretching modes of the ligated
benzoate moieties [49–51]. The separation (d) between the
3059(m), 1603(m), 1566(s), 1480(w), 1414(m), 1388(s),
1282(w), 1220(w), 813(m), 720(s). Anal. Calc. for C41H36MnN4O8S4
(895.92) 5: C, 54.96; H, 4.06; N, 6.26. Found: C, 55.15; H, 4.39; N,
6.29%.
2.8. Catalytic activity of compounds 1, 3, 4, and 5
m
(CO2) frequencies (d =
m
asym(CO2) ꢁ
msym(CO2)) suggests that the
Catalytic reaction conditions: Ester (0.05 mmol) was dissolved
in methanol (1 mL), and the compounds 1, 3, 4, and 5 (2.0 mg,
1.10 ꢂ 10ꢁ3 mmol for 1, 1.0 mg, 0.93 ꢂ 10ꢁ3 mmol for 3, 1.0 mg,
1.12 ꢂ 10ꢁ3 mmol for 4, and 1.0 mg, 1.11 ꢂ 10ꢁ3 mmol for 5) were
added and shaken at 50 °C (450 rpm). Reaction conversion was
compounds 1 and 3–5 may have an unidentate or chelating or
bridging coordination [52]. The absence of any bands in the area
of ꢃ1710 cmꢁ1 indicates full deprotonation of all carboxylate
groups in 1–5 [49–51], which is consistent with the results of the
X-ray analysis.
monitored by GC/Mass analysis of 20 lL aliquots withdrawn peri-
odically from the reaction mixture. All reactions were run at least
three times and the average conversion yields are presented. Yields
were based on the formation of the products, methylacetate or
methylbenzoate.
3.1.1. [Mn6(O2CPh)10
(
l
4-OH)2(CH3OH)3(H2O)]ꢀ1.5(C4H4N2) (1)
Asymmetric unit contains six MnII ions, 10 benzoates, two l4
-
hydroxyl ligands, three methanol ligands, a water ligand, and one
and half pyz solvent molecules. Ten benzoate ligands bridge six
MnII ions to produce a Mn6 cluster as shown in Fig. 1. The coordi-
2.9. X-ray crystallography
nation mode for six benzoates is the simple bridging (g1
:
g1
:l
2),
and that of remaining four benzoates is the chelating/bridging
2). Two hydroxyl groups bridge four MnII ions, and four
The X-ray diffraction data for all four compounds were collected
on a Bruker SMART APX diffractometer equipped with a monochro-
(
g2 g1
: :l
mator in the Mo K
a
(k = 0.71073 Å) incident beam. Each crystal
outside MnII ions are coordinated by three methanol ligands and
a water ligand, respectively. The coordination geometry of all six
MnII ions is distorted octahedral. The Mn–Obenzoate bond distances
range from 1.9390(19) to 2.3356(19) Å, the Mn–Omethanol distances
range from 2.171(2) to 2.2121(19) Å, and the Mn–Owater distance is
2.1991(9) Å (Table 2). The Mn–Mn distances range from 2.8006(6)
to 3.1740(6) Å.
was mounted on a glass fiber. The CCD data were integrated and
scaled using the Bruker-SAINT software package, and the structure
was solved and refined using SHEXTL V6.12 [48]. All hydrogen atoms
were placed in the calculated positions. The crystallographic data
for compounds 1–5 are listed in Table 1. Structural information
was deposited at the Cambridge Crystallographic Data Center.
Scheme 1. Structures from MnII-(O2CPh) with various bipyridyl ligands.

I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
285
are simple bridging (g1 g1 2) and chelating/bridging (g2 g2
: :l : :l3)
modes. The coordination geometry of a MnII ion is distorted octa-
hedral. The Mn–Obenzoate bond distances range from 2.1300(11)
to 2.2936(11) Å (Table 2).
3.1.4. [{Mn(O2CPh)2(4,40-dtp)2}ꢀ(H2O)ꢀ0.5(HO2CPh)]n (5)
Asymmetric unit contains half of a MnII ion, a benzoate, a 4,40-
dtp, a water solvent molecule, and a benzoic acid molecule, and
symmetry operations (ꢁx + 3/2, y, ꢁz + 3/2), (x, y + 1, z), (x, y – 1,
z), and (ꢁx + 1/2, y, ꢁz + 3/2) produce a one-dimensional compound
5 (Fig. 4). The 4,40-dtp ligands bridge MnII ions to produce a one-
dimensional double chain. The coordination geometry of a MnII
0
ion is distorted octahedral constructed from four N4,4 -dtp atoms
and two Obenzoate atoms. The Mn–Obenzoate bond distance is
2.156(16) Å, and the Mn–N distances range from 2.3074(18) to
2.3172(19) Å (Table 2).
Three new MnII-benzoates coordination polymers containing
various bipyridyl ligands (3,30-dpicam, 3-methylisoquinoline, 4,40-
dtp) and
a
[Mn6(O2CPh)10
(l4-OH)2(CH3OH)3(H2O)]ꢀ1.5(C4H4N2)
cluster have prepared and their structures were determined
(Scheme 1). The MnII-benzoate complex with 4,40-bpy was reported
previously [45–47]. The bipyridyl ligands (4,40-bpy, 3,30dpica, and
4,40-dtp) can act as bridging ligands and produced 1-D (3 and
5) or 2-D (2 [45–47]) polymeric compounds containing MnII-
benzoates bridged by bipyridyls. The pyz ligand acts as a solvent
molecule since its size and bridging ability are smaller than other
bridging ligands, and then produced Mn6 cluster compound 1.
3-Methylisoquinoline ligand did not coordinate to a MnII ion,
and produced 1-D {Mn2(O2CPh)5} (4) containing methanol and
3-methylisoquinoline molecules. Several coordination modes of
benzoates were observed (Scheme 2). For 1, 10 benzoates coordi-
nate six MnII ions to produce a Mn6 cluster, and benzoates are in
the bridging (c) mode or the chelating/bridging (d) mode. For 2, ben-
zoates coordinate MnII ions, and they are in the bridging (c) mode.
For 3, benzoates act as bridging ligands (the (c) mode) as well as
monodentate terminal ligands (the (a) mode). New type of coordi-
nation mode (e) as well as bridging mode (c) was observed in 4.
For 5, only terminal monodentate benzoates were observed. These
results indicate that assistant bipyridyl ligands can influence both
coordination modes of carboxylates and structures of MnII-
(O2CPh) coordination polymers.
Fig. 1. Structure of [Mn6(O2CPh)10(l4-OH)2(CH3OH)3(H2O)] 1. All hydrogen atoms
and pyrazine molecules were omitted for clarity.
3.1.2. [{Mn2(O2CPh)4(H2O)2(3,30-dpicam)2}ꢀ2(H2O)]n (3)
Asymmetric unit contains a MnII ion, two benzoates, a 3,30-dpi-
cam ligand, a water, and a water solvent molecule, and symmetry
operations (ꢁx + 1, ꢁy + 2, ꢁz), (x, y, z + 1), and (x, y, z ꢁ 1) produce
a ladder type compound 3 (Fig. 2). Two benzoates bridge two
[Mn(O2CPh)(H2O)]+ units with the bridging mode (g1 g1
: :l2), and
these dinuclear units are connected by 3,30-dpicam ligands to pro-
duce a ladder type compound. The coordination geometry of a MnII
ion is distorted octahedral constructed from three Obenzoate, one
Owater and two Ndpicam atoms. The Mn–Obenzoate bond distances
range from 2.1044(19) to 2.1987(18) Å and the Mn–Owater distance
is 2.272(19) Å. The Mn–N distances are 2.262(2) and 2.266(2) Å
(Table 2). The Mnꢀ ꢀ ꢀMn distance in a dinuclear unit is 4.763(6) Å,
and that in a ladder is 11.617(1) Å.
3.2. Magnetic property
Variable-temperature magnetic susceptibility data of 1 and 3
3.1.3. [{Mn2(O2CPh)5}ꢀ(CH3OH)(C10H9N)]n (4)
were collected in the temperature range 2–300 K under a field of
Asymmetric unit contains two MnII ions, five benzoates, a meth-
anol solvent molecule and a 3-methylisoquinoline (C10H9N) mole-
cule, and symmetry operations (ꢁx + 1/2, ꢁy + 1/2, z ꢁ 1/2) and
(ꢁx + 1/2, ꢁy + 1/2, z + 1/2) produce a one-dimensional compound
4 (Fig. 3). The benzoate ligands bridge MnII ions to produce a one-
dimensional compound, and the coordination modes of benzoates
0.5 T. The resulting plots of
(Fig. 5). The effective magnetic moment at room temperature, leff
of 1, was 12.46 B which is much smaller than the spin-only effec-
tive moment of 14.49
vM and leff versus T for 1 are depicted
l
l
B for six MnII ions. In the region from 30 to
300 K, The vMꢁ1 values obey the Curie–Weiss law well with a Curie
constant of 21.45 emuT/mol and the h value of ꢁ34.00 K for 1, and
Table 2
Selected bond distances for compounds 1–5.
1
2a
3
4
5
Mn–O
Mn–Obenzoate
1.9390(19)–2.3356(19) Å
Mn–Omethanol
Mn–Onitrate
2.203(3) Å
Mn–Obenzoate
2.1044(19)–2.1987(18) Å
Mn–Owater
Mn–Obenzoate
2.1300(11)– 2.2936(11) Å
Mn–Obenzoate
2.1561(16) Å
2.171(2)–2.2121(19) Å
Mn–Owater
2.272(19) Å
2.1991(9) Å
Mn–N
Mn–Mn
–
2.263(3)–2.300(3) Å
–
2.262(2), 2.266(2) Å
–
–
–
2.3074(18)–2.3172(19) Å
–
2.8006(6)–3.1740(6) Å
a
See Ref. [30].

286
I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
Fig. 2. Structure of [{Mn2(O2CPh)4(H2O)2(3,30-dpicam)2}ꢀ2(H2O)]n 3. All hydrogen atoms were omitted for clarity.
Fig. 3. Structure of [{Mn2(O2CPh)5}ꢀ(CH3OH)(C10H9N)]n 4. All hydrogen atoms and 3-methylisoquinoline molecules were omitted for clarity.
Fig. 4. Structure of [{Mn(O2CPh)2(4,40-dtp)2}ꢀ(H2O)ꢀ0.5(HO2CPh)]n 5. All hydrogen atoms were omitted for clarity.
then we can say that there exist strong antiferromagnetic interac-
tions in a Mn6 cluster. The resulting plots of
M and vMꢁ1 versus T
say that there are antiferromagnetic interactions between Mn2+
ions. The resulting plots of
M and vMꢁ1 versus T for 5 are depicted
v
v
for 3 are depicted (Fig. 6). The effective magnetic moment at room
temperature, leff of 3, was 5.51 lB which is smaller than the spin-
only effective moment of 5.92 lB for a Mn2+ ion. The maximum
turning point of the vM value indicates that there are antiferro-
magnetic interactions between Mn2+ ions within a Mn2 unit. In
the region from 10 to 300 K, the vMꢁ1 values obey the Curie–Weiss
law well with a Curie constant of 3.87 emuT/mol and a h value of
ꢁ5.35 K for 3, and then we can say that there are antiferromagnetic
interactions between Mn2+ ions within a Mn2 unit. The significant
magnetic interaction between Mn2 units may not be observed
since the distance of 11.62 Å between Mn2 units is too long to
(Fig. 8). The effective magnetic moment at room temperature, leff
of 5, was 5.27 lB which is similar to the spin-only effective mo-
ment of 5.92 lB for a Mn2+ ion. The vM values obey the Curie–
ꢁ1
Weiss law well with a Curie constant of 3.49 emuT/mol and a h va-
lue of 1.95 K for 5, and then we can say that there is no significant
interaction between Mn2+ ions. This agrees with the long Mnꢀ ꢀ ꢀMn
distance of 10.942(2) Å.
3.3. Thermogravimetric analysis
To study the thermal stabilities of these complexes, thermal
gravimetric analysis (TGA) of compounds 1 and 3–5 was per-
formed (see the Supporting Information: Fig. S4–S7). The TGA
curve of compound 1 showed that the observed weight loss within
the temperature range 25–233 °C was 12.88% that corresponds to
the removal of three coordinated methanol molecules, a water
molecule and 1.5 pyrazine molecules (Calc. 12.97%). The second
ꢁ1
interact magnetically. The resulting plots of vM and vM versus
T for 4 are depicted (Fig. 7). The effective magnetic moment at
room temperature, leff of 4, was 5.98 lB which is similar to the
spin-only effective moment of 5.92 l
B for a Mn2+ ion. The vMꢁ1 val-
ues obey the Curie–Weiss law down to 20 K with a Curie constant
of 4.86 emuT/mol and a h value of ꢁ25.69 K for 4, and then we can

I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
287
Scheme 2. The observed coordination modes of benzoates.
The third gradual weight loss of 47.29% in the temperature range
of 246–800 °C corresponds to the loss of four coordinated benzo-
ates (Calc. 47.21%). The residue is consistent with two MnO2
(Obs. 21.90%, Calc. 19.52%). For compound 5, the first weight loss
in the range of 30–131 °C corresponded to the removal of two
water molecules (Obs. 3.51%, Calc. 4.02%). The second gradual
weight loss of 69.93% in the temperature range of 131–428 °C
might be attributed to the loss of the coordinated benzoic acid,
benzoate and two 4,40-dithiopyridines (Calc. 74.54%). The third
gradual weight loss of 13.52% in the temperature range of 428–
495 °C is exactly consistent with the loss of a coordinated benzoate
(Calc. 13.52%). The residue is consistent with one MnO2 (Obs
10.34%, Calc. 9.70%).
3.4. Catalytic transesterification reactions by the compounds 1–5
Since manganese has continuously gained prominence as a cat-
alyst for numerous transformations [53–55], the reactivity of the
complexes 1–5 was examined for the olefin epoxidation reaction
of cyclohexene as a substrate with various oxidants such as H2O2,
tert-butyl hydroperoxide (t-BuOOH), and m-chloroperbenzoic acid
(MCPBA) [56–58]. Unfortunately, all five complexes did not catalyze
olefin epoxidation reaction. Instead, we turned our interest to
transesterification reaction, because we have previously reported
that the redox-active Mn-containing polymers have shown moder-
ate catalytic reactivities for the transesterification reactions of a
range of esters with methanol under the mild conditions [45–47].
Treatment of phenyl acetate and methanol in the presence of 1, 3,
4, and 5 at 50 °C produced methyl acetate quantitatively within 3,
6, and 6 days for 1, 3, and 4, respectively, under the neutral condi-
tions (Eq. (1)), while the complex 5 showed very slow conversions
(24 days). Little transesterification occurred without the catalysts
in the same time period.
Fig. 5. Plots of temperature dependent susceptibilities (closed circles) and effective
magnetic moments (open circles) for 1.
gradual weight loss of 57.88% in the temperature range of 233–
800 °C is consistent with the loss of 10 coordinated benzoates
(Calc. 58.17%). The residue is consistent with six MnO2 (Obs.
29.25%, Calc. 28.87%). The TGA curve of compound 3 showed that
the observed weight loss within the temperature range 32–
137 °C was 2.60% that corresponds to the removal of solvent mol-
ecules (two water molecules, 3.38%). The second gradual weight
loss of 45.15% in the temperature range of 137–362 °C is consistent
with the loss of the coordinated two water molecules and a benzo-
ate (Calc. 45.87%). The third gradual weight loss of 35.21% in the
temperature range of 362–600 °C corresponds to the loss of two
coordinated 3,30-dipicoylamines (Calc. 37.42%). The residue is con-
sistent with two MnO (Obs. 14.50%, Calc. 13.32%). The TGA curve
for 4 displayed a weight loss of 17.47% from 32 to 191 °C, which
may be attributed to the loss of a methanol molecule and a 3-
methylisoquinoline per formula (Calc. 19.68%). The second gradual
weight loss of 13.35% in the temperature range of 191–246 °C is
consistent with the loss of a coordinated benzoate (Calc. 13.60%).
O
O
catalysts 1,3,4
HOCH3
..
OCCH3
+
CH3COCH3
ð1Þ
OH
+

288
I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
Fig. 6. Plots of temperature dependent susceptibilities (closed circles) and reciprocal susceptibilities (open circles) for 3. The fitted data are shown in the red line. (Color
online.)
Fig. 7. Plots of temperature dependent susceptibilities (closed circles) and effective magnetic moments (open circles) for 4. The fitted data are shown in the red line. (Color
online.)
Fig. 8. Plots of temperature dependent susceptibilities (closed circles) and reciprocal susceptibilities (open circles) for 5. The fitted data are shown in the red line. (Color
online.)
known as very efficient catalysts for transesterification reaction,
Compound 1 was most efficient, and the catalytic reactivity of 1
is comparable to some of the catalytic systems reported previously
in Zn-containing coordination and polymeric compounds that are
to our best knowledge [59,60].
Next, we have examined further the transesterification of other
esters with 1, 3, and 4. The results are shown in Table 3. The

I.H. Hwang et al. / Polyhedron 42 (2012) 282–290
289
Table 3
Transesterification of esters by methanol in the presence of compounds 1, 3, and 4 at 50 °C.a
Entry
Substrate
1 (time/days)b
3 (time/days)b
4 (time/days)b
1
2
3
4
5
6
7
8
9
4-Nitrophenyl acetate
4-Fluorophenyl acetate
Phenyl acetate
4-Methylphenyl acetate
4-Nitrophenyl benzoatec
4-Chlorophenyl benzoate
Phenyl benzoate
0.25
1.5
3
3
1.5
4
6
6
0.16
0.5
5
6
7
5
0.38
5
6
7
5
13
15
17
0.29
7
15
17
0.38
4-Methylphenyl benzoate
Vinyl acetate
a
All esters were completely converted to the corresponding products, methyl acetate and methyl benzoate. Reaction conditions: esters; 0.05 mmol, catalyst;
1.10 ꢂ 10ꢁ3 mmol for 1, 0.93 ꢂ 10ꢁ3 mmol for 3, and 1.12 ꢂ 10ꢁ3 mmol for 4, solvent; methanol (1 mL). See Section 2 for the detailed reaction conditions.
b
Time necessary for the complete conversion of substrate to product.
The solvent was a mixture of CH3OH/CH2Cl2 (1/1) because of low solubility of substrate in CH3OH.
c
substrates p-nitrophenyl acetate and benzoate with the electron-
withdrawing substituent have undergone faster transesterification
(entries 1 2, 5 and 6). Moreover, para-substituted phenyl acetate
groups (entries 1–4) have displayed better reactivity than para-
substituted phenyl benzoate groups (entries 5–8). Furthermore, vi-
nyl acetate was converted effectively to the product methyl acetate
within 0.29–0.38 days by 1, 3, and 4. It is worthwhile to note that
this catalytic system can be useful for preparing various esters by
transesterification. Detailed mechanistic studies are currently un-
der investigation.
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Cen-
tre, 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
http://dx.doi.org/10.1016/j.poly.2012.05.040.
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Three new MnII-benzoates coordination polymers containing
various bipyridyl ligands (3,30-dpicam, 3-methylisoquinoline, and
4,40-dtp) and a [Mn6] cluster have been prepared, and their struc-
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