Organic carboxylate anions effect on the structures of a series of Mn(II) complexes based on 2-phenylimidazo[4,5-f]1,10-phenanthroline ligand

Article abstract of DOI:10.1016/j.jssc.2009.06.031

In our efforts to tune the structures of Mn(II) complexes by selection of organic carboxylic acid ligands, six new complexes [Mn(PIP)₂Cl₂] (1), [Mn(PIP)₂(4,4′-bpdc)(H₂O)]·2H₂O (2), [Mn(PIP)₂

Full text of DOI:10.1016/j.jssc.2009.06.031

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Journal of Solid State Chemistry 182 (2009) 2392–2401
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Organic carboxylate anions effect on the structures of a series of Mn(II)
complexes based on 2-phenylimidazo[4,5-f]1,10-phenanthroline ligand
Ã
Xiuli Wang , Yongqiang Chen, Guocheng Liu, Hongyan Lin, Jinxia Zhang
Faculty of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
In our efforts to tune the structures of Mn(II) complexes by selection of organic carboxylic acid ligands,
six new complexes [Mn(PIP)2Cl2] (1), [Mn(PIP)2(4,40-bpdc)(H2O)] ꢀ 2H2O (2), [Mn(PIP)2(1,4-bdc)] (3),
[Mn(PIP)(1,3-bdc)] (4), [Mn(PIP)2(2,6-napdc)] ꢀ H2O (5), and [Mn(PIP)(1,4-napdc)] ꢀ H2O (6) were
obtained, where PIP ¼ 2-phenylimidazo[4,5-f]1,10-phenanthroline, 4,40-H2bpdc ¼ biphenyl-4,40-dicar-
boxylic acid, 1,4-H2bdc ¼ benzene-1,4-dicarboxylic acid, 1,3-H2bdc ¼ benzene-1,3-dicarboxylic acid,
2,6-H2napdc ¼ 2,6-naphthalenedicarboxylic acid, 1,4-H2napdc ¼ 1,4-naphthalenedicarboxylic acid. All
complexes have been structurally characterized by IR, elemental analyses, and single crystal X-ray
Received 27 February 2009
Received in revised form
29 May 2009
Accepted 17 June 2009
Available online 24 June 2009
Keywords:
Hydrothermal synthesis
Crystal structure
Carboxylate anion
Manganese complexes
Properties
diffraction. Structural analyses show that complexes
1 and 2 possess mononuclear structures,
complexes 3, 4, and 5 feature chain structures, and complex 6 exhibits a 2D (4,4) network. The
structural difference of 1–6 indicates that organic carboxylate anions play important roles in the
formation of such coordination architectures. Furthermore, the thermal properties of complexes 1–6
and the magnetic property of 4 have been investigated.
& 2009 Elsevier Inc. All rights reserved.
1. Introduction
carboxylate as the anion ligands (Chart 1). In addition, 1,10-
phenanthroline (phen) has been widely used to build
The rational design and synthesis of new discrete or polymeric
transition metal-organic coordination architectures have received
intense interest due to their fascinating structural topologies and
potential applications as functional materials [1–7]. These
coordination polymers can be specially designed by the careful
selection of metal centers with preferred coordination geometries,
the nature of the anions, template, the structure of the connecting
ligands, and the reaction conditions [8–23]. In addition, H-
supramolecular architectures because of its excellent
coordinating ability and large conjugated system that can easily
form p–p interactions. However, far less attention has been given
to their derivatives [29,32]. We previously reported on the
synthesis and characterization of some complexes based on
phen derivative and carboxylate anions [33–36]. As an extension
of our previous work, another important phen derivative 2-
phenylimidazo[4,5-f]1,10-phenanthroline (PIP) was used as the
secondary ligand (Chart 1). Compared with 1,10-phenanthroline,
bonding,
p–p stacking, and host–guest interactions also affect
the results, and they may further link discrete subunits or low-
dimensional entities into high-dimensional supramolecular net-
works [24–28]. Among those mentioned above, the selection of
organic carboxylate anions are extremely important because
changing the structures of the anions can control and adjust the
structures of coordination polymers, even for complexes contain-
ing the same secondary organic ligand and metal cation. Up to
now, the effect of organic carboxylate anions on the structure
formation of coordination polymers has been investigated.
However, studies on Mn(II) complexes are limited in the presence
of 1,10-phenanthroline derivatives [29–31].
this ligand contains both an extended
ring, capable of acting as hydrogen bond acceptors/donors or of
forming coordination interactions to some metal ions, as well as
p-system and a imidazole
extending the
p-system themselves [37]. Hence, it is a good
candidate for the construction of complexes. In contrast to the
exo-bidentate dipyridyl ligands, selecting of multi-carboxylates
bridge ligands are important in the terminal ligands system. Since
carboxylates can connect metal ions or metal clusters into
coordination polymers exhibiting intriguing structural and
dimensional diversities. Thus, six organic carboxylic acid or
carboxylate anion: malonate, biphenyl-4,40-dicarboxylic acid
(4,40-H2bpdc), benzene-1,4-dicarboxylic acid (1,4-H2bdc), benzene-
1,3-dicarboxylic acid (1,3-H2bdc), 2,6-naphthalenedicarboxylic acid
(2,6-H2napdc) and 1,4-naphthalenedicarboxylic acid (1,4-H2napdc)
with different shape, size, and flexibility, have been used in this
work. In the presence of secondary N-donor chelating ligand PIP, a
series of Mn(II) complexes have been isolated: [Mn(PIP)2Cl2] (1),
In order to investigate the effect of the anions on the formation
of Mn(II) complexes, particularly the organic carboxylate anions,
we selected six structurally different organic carboxylic acids or
Ã
Corresponding author. Fax: +86 416 3400158.
E-mail address: wangxiuli@bhu.edu.cn (X. Wang).
0022-4596/$ - see front matter & 2009 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2009.06.031

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X. Wang et al. / Journal of Solid State Chemistry 182 (2009) 2392–2401
2393
1386s, 1338m, 1213s, 1128m, 1080s, 823m, 732m. Anal. Calcd. for
38H24Cl2MnN8: C 63.50; H 3.34; N 15.60%. Found: C 63.65; H
C
3.19; N 15.49%.
2.2.2. [Mn(PIP)2(4,40-bpdc)(H2O)] ꢀ 2H2O ð2Þ
A mixture of Mn(CH3COO)2 ꢀ 4H2O (0.1 mmol), PIP (0.05 mmol),
biphenyl-4,40-dicarboxylic acid (0.05 mmol), NaOH (0.12 mmol),
and H2O (8 ml), stirred for 20 min, was sealed to a Teflon-lined
stainless steel autoclave (25 ml) and kept at 160 1C for 5 days.
After the mixture was slowly cooled to room temperature, yellow
block crystals suitable for X-ray diffraction of complex 2 were
obtained in 30% yield (based on Mn). IR (KBr pellet, cmꢁ1): 3425w,
3062w, 2362m, 1570s, 1460m, 1386s, 1070m, 947m, 821w, 731m.
Anal. Calcd. for C52H30MnN8O7: C 65.88; H 2.22; N 12.00%. Found:
C 65.71; H 2.02; N 12.19%.
2.2.3. [Mn(PIP)2(1,4-bdc)] ð3Þ
3 was obtained by the similar method to that for 2, excepted
for using benzene-1,4-dicarboxylic acid (16.6 mg, 0.1 mmol)
instead of biphenyl-4,40-dicarboxylic acid and NaOH (0.12 mmol).
Yield: 25% (based on Mn). IR (KBr pellet, cmꢁ1): 3421w, 3062w,
2360m, 1568s, 1458s, 1386s, 1070m, 948m, 821m, 786m. Anal.
Calcd. for C46H26MnN8O4: C 68.23; H 3.21; N 13.24%. Found: C
68.39; H 3.11; N 13.10%.
Chart 1. Ligands used in the paper.
[Mn(PIP)2(4,40-bpdc)(H2O)] ꢀ 2H2O (2), [Mn(PIP)2(1,4-bdc)] (3),
[Mn(PIP)(1,3-bdc)] (4), [Mn(PIP)2(2,6-napdc)] ꢀ H2O (5), and
[Mn(PIP)(1,4-napdc)] ꢀ H2O (6). On the basis of synthesis and
structural characterization, the influence of organic carboxylate
linkers on the control of the final complex structures and the role of
weak intermolecular forces in the creation of molecular
architectures are discussed. Moreover, thermal properties of the
2.2.4. [Mn(PIP)(1,3-bdc)] ð4Þ
4 was obtained by the similar method to that for 3, excepted
for using benzene-1,3-dicarboxylic acid instead of benzene-1,4-
dicarboxylic acid. Yield: 30% (based on Mn). IR (KBr pellet, cmꢁ1):
342w, 3061w, 2360m, 1572s, 1460s, 1358s, 1072m, 831m, 732m.
Anal. Calcd. for C27H16MnN4O4: C 62.91; H 3.05; N 10.87%. Found:
C 62.74; H 2.82; N 11.01%.
complexes 1–6 and the magnetic property of
investigated in the solid state.
4 have been
2.2.5. [Mn(PIP)2(2,6-napdc)] ꢀ H2O ð5Þ
5 was obtained by the similar method to that for 1, excepted for
using 2,6-naphthalenedicarboxylic acid instead of CH2(COONa)2,
MnSO4 instead of MnCl2 and NaOH (0.32 mmol). Yield: 28% (based
on Mn). IR (KBr pellet, cmꢁ1): 3504m, 3066w, 2362m, 1772w,
1570s, 1400s, 1074m, 958w, 829w, 734m, 702m, 680w. Anal.
Calcd. for C50H30MnN8O5: C 68.42; H 3.42; N 12.77%. Found: C
68.23; H 3.56; N 12.59%.
2. Experimental section
2.1. Materials and instrumentation
All chemicals purchased were of reagent grade and used
without further purification. PIP was synthesized by the methods
of the literature [38] and characterized by FT-IR spectra and 1H
NMR. FT-IR spectra (KBr pellets) were taken on a Magna FT-IR 560
spectrometer. Elemental analyses (C, H, and N) were performed on
a Perkin-Elmer 240C analyzer. Thermogravimetric data for the
complexes 1–6 were collected on a Pyris Diamond thermal
analyzer. Fluorescence spectra were performed on a Hitachi F-
4500 fluorescence/phosphorescence spectrophotometer at room
temperature. Powder X-ray diffraction (PXRD) data were collected
2.2.6. [Mn(PIP)(1,4-napdc)] ꢀ H2O ð6Þ
A mixture of Mn(NO3)2 ꢀ 6H2O (0.2 mmol), PIP (0.05 mmol), 1,4-
naphthalenedicarboxylic acid (0.2 mmol), NaOH (0.41 mmol), and
H2O (8 ml), stirred for 20 min, was sealed to a Teflon-lined
stainless steel autoclave (25 ml) and kept at 160 1C for 5 days.
After the mixture was slowly cooled to room temperature, yellow
block crystals suitable for X-ray diffraction of complex 6 were
obtained in 20% yield (based on Mn). IR (KBr pellet, cmꢁ1): 3504w,
3215w, 2360m, 1571s, 1458s, 1357s, 1074m, 835m, 732m, 580w.
Anal. Calcd. for C31H18MnN4O5: C 64.03; H 3.10; N 13.77%. Found:
C 64.18; H 2.97; N 13.84%.
on a Bruker D8-ADVANCE diffractometer equipped with CuKa at a
scan speed of 11 minꢁ1. Magnetic susceptibility measurement for
4 was carried out using a Quantum Design MPMS XL-5 SQUID
magnetometer at field of 1000 Oe. Diamagnetic correction was
estimated from Pascal’s constants [39].
2.3. X-ray crystallographic measurements
2.2. Synthesis
All diffraction data were collected using a Bruker Apex CCD
2.2.1. [Mn(PIP)2Cl2] ð1Þ
diffractometer (MoK
a
radiation, graphite monochromator,
˚
A
mixture of MnCl2 ꢀ 4H2O (0.1 mmol), PIP (0.1 mmol),
l
¼ 0.71073 A). The structures were solved by direct methods
CH2(COONa)2 (0.1 mmol), and H2O (10 ml), stirred for 20 min,
was sealed to a Teflon-lined stainless steel autoclave (25 ml) and
kept at 180 1C for 3 days. After the mixture was slowly cooled to
room temperature, yellow block crystals suitable for X-ray
diffraction of complex 1 were obtained in 38% yield (based on
Mn). IR (KBr pellet, cmꢁ1): 3060w, 2360m, 1608w, 1581s, 1477m
with SHELXS-97 and Fourier techniques and refined by the full-
matrix least-squares method on F2 with SHELXL-97 [40,41]. All
non-hydrogen atoms were refined anisotropically, and hydrogen
atoms of the ligands were generated theoretically onto the specific
atoms and refined isotropically with fixed thermal factors, and the
H atoms of water molecules were located in different Fourier

ARTICLE IN PRESS
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X. Wang et al. / Journal of Solid State Chemistry 182 (2009) 2392–2401
˚
Table 1
anions with the Mn–Cl distance is 2.506(1) A. The adjacent
discrete mononuclears are arranged into a 3D supramolecular
Crystal data and structure refinement parameters for complexes 1–6.
architecture by inter-molecular
face-to-face distances between PIP ligands are from 3.551 to
p–p interactions (Fig. S1). The
Complex
1
2
3
˚
3.591 A (the dihedral angle is 1.021, 1.491, and 2.201, respectively).
Formula
C
38H24Cl2MnN8
C52H34MnN8O7
937.81
C46H28MnN8O4
811.70
Fw
718.49
Moreover, the open supramolecular framework has channels with
the estimated solvent-accessible void volume, which is 21.6% of
the total crystal volume, as shown in Fig. 1b. Interestingly,
CH2(COONa)2 plays a key role in the formation of 1. All our
attempts to separate complex 1 into good-quality for X-ray
analysis have been thus far unsuccessful without the presence
of CH2(COONa)2.
Crystal system
Space group
Orthorhombic
Pnna
Orthorhombic
Pna21
Triclinic
Pꢁ1
8.6553(5)
17.5733(17)
9.674(2)
˚
a (A)
28.2681(18)
15.2024(10)
15.7815(15)
16.4858(16)
10.464(2)
10.670(3)
˚
b (A)
˚
c (A)
a
b
g
(deg)
90
90
90.52(4)
115.38(3)
111.47(3)
890.3(4)
90
90
(deg)
(deg)
90
90
3
3719.6(4)
4572.1(8)
˚
V (A )
D (g cmꢁ3
Z
3.1.2. [Mn(PIP)2(4,40-bpdc)(H2O)] ꢀ 2H2O ð2Þ
)
1.283
1.362
1.514
Complex 2 has similar neutral coordination environment to
that of 1, also showing distorted octahedral geometry (see Fig. 2a).
Each Mn(II) ion was coordinated by four nitrogen atoms from
PIP ligands and two oxygen atoms from 4,40-bpdc and one
4
4
1
F(000)
1372
1932
417
m
(mmꢁ1
)
0.536
16 989
3170
0.352
22 565
8118
0.433
4527
Tot. data
Uniq. data
Rint
3078
˚
water molecule, respectively, [Mn(1)–N ¼ 2.272(6)–2.345(6) A,
0.0423
0.0652/0.1483
1.040
0.0838
0.0848/0.1878
0.976
0.0375
0.0597/0.1095
0.991
˚
Ra/wRb
Mn(1)–O ¼ 2.114(6)–2.187(6) A]. Moreover, there are two
GOF on F2
disordered uncoordinated water molecules in 2, which can link
hydrogen bond acceptor by weak interactions to stabilize the
structure of complex 2. In complex 2, the PIP ligand plays an
Complex
Formula
4
5
6
C
27H16MnN4O4
C50H30MnN8O5
877.76
C31H18MnN4O5
581.43
Fw
515.38
important role in the formation of
supramolecular chain by stacking interactions (see Fig. 2b).
The face-to-face distance between the paired PIP rings is about
a 1D infinite zigzag
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
P2/n
Monoclinic
P21/c
p–p
15.3556(9)
12.716(2)
12.2521(12)
˚
a (A)
˚
3.629(5) A.
15.9303(9)
11.6747(18)
14.079(2)
15.1778(15)
16.9597(12)
˚
b (A)
18.8663(14)
˚
c (A)
a
b
g
(deg)
90
90
90
3.1.3. [Mn(PIP)2(1,4-bdc)] ð3Þ
109.37(1)
90
90.754(3)
90
127.606(5)
90
(deg)
Complex 3 forms a 1D polymeric chain. As shown in Fig. 3a, the
Mn(II) ion features a distorted octahedral geometry, coordinated
by four nitrogen atoms from two PIP ligands with the Mn(1)–N
(deg)
3
4353.7(5)
2089.8(6)
2498.5(4)
˚
V (A )
D (g cmꢁ3
Z
)
1.573
1.395
1.546
4
˚
distances of 2.298(4)–2.319(4) A, and two oxygen atoms from two
8
2
˚
F(000)
2104
902
1188
different 1,4-bdc ligands [Mn(1)–O ¼ 2.114(3) A]. In 3, the 1,4-bdc
m
(mmꢁ1
)
0.652
13 393
5115
0.376
0.581
9499
ligands only assume a kind of coordination mode, namely,
bridging bis(monodentate). The adjacent Mn(II) ions are bridged
by 1,4-bdc ligands to form a 1D linear chain with the distance of
Mn–Mn is 11.357 A. Compared with those of 1 and 2, the arranged
fashion of the PIP ligands in 3 is different, leading to a structure
Tot. data
10 538
3699
Uniq. data
Rint
3034
0.0303
0.0375/0.0842
1.012
0.0671
0.0535/0.0913
1.058
0.0353
0.0341/0.0790
1.012
Ra/wRb
˚
GOF on F2
suitable to form
from adjacent 1D chains are paired to furnish
resulting in 2D supramolecular layer (Fig. 3b). The face-to-face
p
–
p
interactions. Thus, the lateral PIP ligands
a
R ¼
S(||F0|ꢁ|FC||)/S|F0|.
p–p
interactions
b
wR2 ¼ [
S
w(|F0|2ꢁ|FC|2)2/( w|F0|2)2]1/2
S .
˚
distance between the paired PIP rings is 3.744(4) A (the dihedral
angle is 14.271). In fact, stacking interactions play
p–p
an important role in the formation and stabilization of the
supramolecular structure [29]. In addition, the 2D supramolecular
layers are further extended into a 3D supramolecular framework
synthesis maps. All the crystal data and structure refinement
details for the six complexes are given in Table 1. The data of
relevant bond distances and angles are listed in Table S1, and
hydrogen-bonding geometries are summarized in Table S2.
Crystallographic data for the structures reported in this paper
have been deposited in the Cambridge Crystallographic Data
Center with CCDC reference numbers 715046–715051 for
compounds 1–6, respectively.
(Fig.
3c)
through
hydrogen
˚
bonds
[the
distance
N(4)–H(4B) ꢀ ꢀ ꢀ O(2) of 2.780(5) A]. Thus, the weak noncovalent
interactions are important in the formation of the final
supramolecular structure of 3. It is noteworthy that the
structure of 3 is entirely different from that of the related
complex [Mn(1,4-bdc)(phen)] [42], which possesses a dinuclear
[Mn2(phen)2(1,4-bdc)4] building block bridged by two
m-
carboxylate to form a 3D structure. The result is probably due to
the larger steric hindrance of PIP ligand.
3. Results and discussion
3.1. Structure descriptions of complexes 126
3.1.4. [Mn(PIP)(1,3-bdc)] ð4Þ
3.1.1. [Mn(PIP)2Cl2] ð1Þ
To investigate the influence of the spacer of ligand (the
position of carboxyl group) on the structure of complex, 1,3-
H2bdc ligand instead of 1,4-H2bdc ligand was used, and a new
The structure of 1 consists of two PIP ligands, two chlorine
anions and a Mn(II) cation. The perspective view of 1 is shown in
Fig. 1a, and the selected bond distances and angles are listed in
Table S1. The Mn(II) ion was coordinated in a distorted octahedral
geometry by four nitrogen atoms of two PIP ligands with normal
complex
4 was obtained and structurally determined. The
coordination environment of complex 4 consists of two Mn(II)
ions [Mn(1), Mn(1A)], four nitrogen atoms from two PIP ligands
and eight oxygen atoms from different 1,3-bdc ligands (Fig. 4a).
˚
Mn–N distances from 2.300(3) to 2.304(3) A, and two chlorine

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2395
geometry is best described as a distorted octahedral geometry
˚
with the distance of Mn–O 2.136(2) A, and Mn–N from 2.323(3) to
˚
2.377(3) A. Furthermore, there exists an uncoordinated guest
water molecule for 5. The adjacent Mn(II) ions are linked by 2,6-
napdc of which the two carboxyl groups all adopt bridging
bis(monodentate) coordination mode to form 1D zigzag chains
along the c-axis (Fig. S3). Moreover, the adjacent 1D zigzag chains
are further extended into a 3D supramolecular architecture by
inter-molecular hydrogen bond interactions [N(4)–H(4A) ꢀ ꢀ ꢀ
˚
O(1) ¼ 2.724(5) A] (Fig. 5b).
3.1.6. [Mn(PIP)(1,4-napdc)] ꢀ H2O ð6Þ
Complex 6, obtained by using 1,4-H2napdc, exhibits a 2D (4,4)
grid by dinuclear Mn2 units with the Mn(1) ꢀ ꢀ ꢀ Mn(1A) distance is
˚
4.970 A (see Fig. 6b). Fig. 6a illustrates the coordination
environments of the Mn(II) ions. Each Mn(II) ion was
coordinated by four carboxylic oxygen atoms of two different
˚
1,4-napdc ligands (Mn–O ¼ 2.124(2)–2.237(2) A, which are close
to those of [Mn(1,4-napdc)]n with the Mn–O distances are in the
˚
range of 2.110(2)–2.260(2) A [43]), and two nitrogen atoms from
PIP ligand with normal Mn–N distances [from 2.224(2) to
˚
2.295(3) A]. Moreover, there exists one lattice water molecule,
which itself acting as a hydrogen bond donor to oxygen atom of
carboxylic groups to form intra-molecular hydrogen bond
stabilized the structure of 6. The dinuclear Mn2 units are linked
by 1,4-napdc of which the two carboxyl groups adopt different
coordination models [bridging mono(bidentate) and chelating
mono(bidentate)] to form 2D network. The coordination model of
1,4-napdc is different from that of the related complex [Mn(1,4-
napdc)]n [43]. The difference is probably related to the extended
p
-system of PIP ligand. It is noteworthy that there are different
types of interactions compared with those of complexes 1–5.
The neighboring 2D layers interacted by stacking interactions
between the PIP and 1,4-napdc ligands [face-to-face distances ca.
p–p
p–p
˚
3.478(2) and 3.696(2) A], leading to a 3D supramolecular structure
(Fig. S4).
Fig. 1. View of (a) the coordination environment of Mn(II) in 1 (symmetry code: A:
x,ꢁyꢁ1/2,ꢁz+1/2); (b) space-filling diagram of the packing down the a–axis in 1,
showing the rectangular channels.
3.2. Effect of organic carboxylate anions and PIP ligand on the
structures of the complexes
By selecting the different organic carboxylate ligands under
hydrothermal condition, six new Mn(II) complexes have been
successfully obtained. Although both the phen and PIP molecules
are planar, there is an additional phenyl group present in the PIP
ligand. The bulky phenyl group in the backbone may significantly
increase the steric hindrance of the PIP ligand, leading to
structural differences in their complexes [44]. In complexes 1
Each Mn(II) ion is located in a distorted octahedral geometry, with
˚
Mn–N distances from 2.276(2) to 2.308(2) A, and Mn–O distances
˚
varying from 2.122(1) to 2.342(2) A, respectively. It was noted that
the coordination environment of the Mn(II) ion is clearly different
from complexes 1–3, probably as a result of steric arrangement
from the aromatic dicarboxylate groups. Two carboxylate groups
of 1,3-bdc ligands adopted bridging bidentate and chelating
bidentate coordination modes linking dinuclear Mn2 units
and 2, the
The discrete molecules interact through
p
–
p
interactions of the PIP ligands in them are similar.
interactions between
p–p
the PIP ligands to form 3D open supramolecular framework and
1D infinite zigzag supramolecular chains, respectively. Although
complexes 3–5 all show chain structures, the weak interactions of
the PIP ligands in them are slightly different. In 3, the linear chains
˚
[Mn(1) ꢀ ꢀ ꢀ Mn(1A) ¼ 4.081 A] to form a unique ribbon chain
structure along the c-axis (Fig. S2). Interestingly, the PIP ligands
are alternately attached to both sides of the ribbon chain
improving stabilization by
p
–
p
interactions of intra-molecule.
interact through p–p interactions between the PIP ligands to form
Furthermore, all the chains are extended by hydrogen-bonding
˚
a 3D supramolecular
2D supramolecular layer. Furthermore, H-bonding interaction
[N(4)–H(4A) ꢀ ꢀ ꢀ O(4), 2.855(2) A] into
extends the structure into 3D supramolecular structure. However,
network (Fig. 4b).
the
5, the supramolecular architectures assembled via H-bonding
interactions. For 6, there are two types of interactions (one
type of interaction between the PIP ligands, another type of
interaction between the PIP and 1,4-napdc ligands), the
adjacent 2D layers were arranged to 3D supramolecular structure
via interactions.
Generally, the role of organic carboxylate ligands can be
illustrated in terms of their differences in shape, size, and
p–p interactions do not play a critical role in complexes 4 and
p–p
3.1.5. [Mn(PIP)2(2,6-napdc)] ꢀ H2O ð5Þ
p–p
To evaluate the effect of two phenyl groups of the dicarbox-
ylate ligand on the framework formation of complex, we selected
2,6-H2napdc to react with manganese salt and obtained complex
5. In 5, each Mn(II) ion was linked by two oxygen atoms of
carboxylate and four nitrogen atoms of PIP (Fig. 5a). The overall
p–p
p–p

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Fig. 2. View of (a) the coordination environment of Mn(II) in 2; (b) the 1D chain formed through p–p weak interactions.
flexibility. To date, metal Pb(II) complexes based on organic acids
and PIP mixed ligands have been prepared and characterized by
Ma and co-workers, where illustrating that the organic acids and
neutral chelating ligands have important influences on the
structures of complexes [32,44]. In this work, to investigate the
influence of the flexibility of organic carboxylate on the structures
of metal Mn(II) complexes, we selected malonate anion as organic
carboxylate ligand. Unfortunately, malonate anion cannot coordi-
nate to Mn(II) ion in 1, as shown in Fig. 1a. However, all our
attempts to separate complex 1 into good-quality for X-ray
analysis have been thus far unsuccessful in the absence of
malonate anion. Because the hydrothermal reaction takes place
in a sealed vessel in certain conditions, it is very difficult to assess
the role of each of the reagents used. However, as is the case in the
results reported here, some reagents may control the formation of
the product in ways that are difficult to predict beforehand [45].
For 2, the rigid-rod tether 4,40-H2bpdc was employed, intending to
observe the effect of long rigid ligand on the assembly of
complexes. However, the expected dimension was not obtained
in 2. In addition, the effect of aromatic carboxylate ligands with
different shape and size on the structures of complexes is also
revealed by the structural differences of 3–6. In contrast with 1,4-
H2bdc, 1,3-H2bdc, 2,6-H2napdc, and 1,4-H2napdc, the common
feature of the four ligands is that each contains two carboxyl
groups. However, 2,6-H2napdc and 1,4-H2napdc have larger
conjugated
p-system from the additional benzene ring. In
contrast, the 1,4-bdc and 1,3-bdc ligands possess different steric
hindrance. The two carboxylate groups have 1801 and 1201 angles,
respectively. 1,4-bdc is very rigid and the two carboxyl groups
adopt bridging bis(monodentate) coordination mode, which
resulted a 1D linear chain in 3. Different from 1,4-bdc, the
carboxyl groups of 1,3-H2bdc are at 1,3-positions, which are
convenient bridging units for linking the adjacent metallic
clusters, and bridge two adjacent metal ions to form a 1D
ribbon chain in 4. It is noted that complex 4 has dinuclear Mn2
repeating units. Thus, it is clear that the shape of aromatic
dicarboxylate ligands (the position of carboxyl group) is an
important factor during the formation of complexes. We select
2,6-H2napdc and 1,4-H2napdc, intending to observe the size
effect on the assembly of the structures in 5 and 6. Furthermore,
the rodlike napdc possess interesting features that are conducive
to the formation of versatile coordination structures [46]. As can
be seen in complex 5, two carboxyl groups of the 2,6-napdc
ligand bridge Mn(II) ion, which is similar to that of complex 3,
whereas the different 1D chains structure was observed in 5.
Complexes 4 and 5 show different 1D chain structures, and

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Fig. 3. View of (a) the coordination environment of Mn(II) in 3 (symmetry code: A: ꢁx+2, ꢁy+2, ꢁz+1); (b) the 2D supramolecular structure formed between 1D chains by
weak interactions; (c) stacking of the 2D supramolecular network leading to the 3D structure by hydrogen-bonding interactions.
p–p
the chains recognize each other under the direction of hydrogen
bond interactions to give 3D supramolecular structures. It should
be noted that the 2D layer framework was obtained in complex 6.
Like that of complexes 3 and 4, the influence of carboxylate
positions on the complex structures is also demonstrated by
the structural differences of 5 and 6. Compared with 1,4-bdc,
the 1,4-napdc ligands possess an additional benzene ring. Mean-
while, the planar 1,4-napdc anion has a conjugated p-electron
system. These features allow the 1,4-napdc ligand have more
chance to assemble the higher dimensional complex in presence
of PIP ligand. Obviously, as far as complexes 1–6 are con-
cerned, the organic carboxylate ligands are the most critical
factors in determining the final structures of the coordination
complexes.

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. . .
Fig. 4. View of (a) the coordination environment of Mn(II) in 4 (symmetry code: A: ꢁx, y, ꢁz+1/2; B: x, ꢁy+1, zꢁ1/2); (b) the 3D network formed by N–H
interactions between 1D ribbon chains along the c-axis.
O weak
3.3. Powder X-ray diffractions and thermal properties of
burned, the weight loss of 88.31% (calcd. 88.53%), the remaining
weight corresponds to MnO. The TGA curve of 3 indicates that
only one weight loss stage exists in the region of 239–356 1C. The
weight loss at this stage is observed to be 91.03%, corresponding to
the decomposition of PIP ligand and 1,4-bdc (calcd. 91.22%), the
remaining weight corresponds to MnO. The decomposition of
complex 4 was similar to that of complex 3, but showed higher
thermal stability. Here a rapid mass loss began at 334 1C and
completed by 418 1C, which corresponds to the loss of 86.52%
(calcd. 86.21%). For 5, a slight decrease in mass about 2.17% at
87–110 1C marks the expulsion of water molecule of crystal-
lization. Elimination of the remaining components in 5 began at
230 1C corresponding to the decomposition of the organic ligands,
the weight loss of 89.48% (calcd. 89.73%). The TGA trace of
complex 6 exhibits two main steps of weight loss, too. The first
step started at 154 1C and completed at 177 1C, which corresponds
to the release of lattice water molecules. The second step covers
from 237 to 333 1C, during which the organic ligands are burned,
the weight loss of 87.33% (calcd. 87.47%), the remaining weight
corresponds to MnO.
complexes 126
Figs. S5–10 (supporting information) present the powder X-ray
diffraction patterns for complexes 1–6. The PXRD patterns of all
complexes are in good agreement with their corresponding
simulated patterns, indicating phase purities of these samples.
The difference in reflection intensities between the simulated and
the experimental patterns is due to the different orientation of the
crystals in the powder samples [47].
In order to investigate thermal stability of the bulk materials,
thermogravimetric analysis (TGA) was carried out for 1–6 (Fig.
S11). The TGA curve of 1 showed that it was stable up to 311 1C and
began to decompose upon heating up to about 510 1C, giving a
weight loss of about 17.68%, which is consistent with the removal
of organic ligands (calcd. 17.55%). The TGA curve for 2 shows two
weight-loss stages: the first starts at 40 1C up to 100 1C, giving a
weight loss of about 3.68%, corresponding to the loss of
uncoordinated water molecules (calcd. 3.86%); the second step
covers from 301 to 486 1C, during which the organic ligands are

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2399
. . .
Fig. 5. View of (a) the coordination environment of Mn(II) in 5 (symmetry code: A: ꢁxꢁ1/2, y,ꢁz+1/2); (b) the 3D supramolecular structure formed by N–H
interactions between 1D zigzag chains in 5, viewed along the c-axis.
O weak
3.4. Magnetic property of complex 4
and T ¼ ꢁ4.00 K. The negative constant indicates dominant
antiferromagnetic interactions between Mn(II)–Mn(II) through
the carboxylic bridge [51,52].
The magnetic behaviors of 4 in the temperature range 2–300 K
are shown as plots of the product
in Fig. 7. At 300 K, the value of magnetic moments (
determined from the equation meff ¼ 2.828(
MT)1/2, is 8.23
slightly smaller than that expected value 10.95 mB for the isolated
two Mn(II) ions (S ¼ 5; g ¼ 2.0) [48–50]. The MT value has little
changes before 50 K with the decreasing of temperature. With the
continuous decreasing of temperature, the MT value decreases
sharply and reach the minimum value of 1.20 emu K molꢁ1
w
MT versus T and 1/wM versus T
eff), which is
B, and
m
w
m
4. Conclusions
w
In summary, six new Mn(II) complexes were synthesized and
structurally characterized. Single crystal structure analysis shows
that 1 and 2 possess mononuclear structures, 3, 4, and 5 present
different 1D chains structures, while 6 is a 2D (4,4) network
complex. These results indicate that organic carboxylate anions
play an important role in the structure control of Mn(II)
w
(3.10 mB
) at 2 K. The 1/wM versus T plot in Fig. 7 displays
Curie–Weiss paramagnetic behavior from 30 to 300 K. The best
linear fit of wMꢁ1(T) data above 30 K yields C ¼ 8.62 emu K molꢁ1

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complexes, which is very significant in the design and syntheses
of Mn(II)-based inorganic–organic hybrid materials.
Supporting information available
X-ray crystallographic information files (CIF) for 1–6, selected
bond distances and angles, together with TGA spectra are
available free of charge via the Internet at http://pubs.acs.org.
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (no. 20871022) and Natural Science Founda-
tion of Liaoning Province (no. 20061073).
Appendix A. Supplementary material
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.jssc.2009.06.031.
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