Four new compounds based on terephthalate and 2-(4-Pyridyl)benzimidazole ligands

Article abstract of DOI:10.1002/zaac.201000279

Four new compounds based on H₂BDC and PyBIm [H₂BDC = 1,4-benzenedicarboxylatic acid, PyBIm = 2-(4-pyridyl)benzimidazole], (PyBIm)(H₂BDC)_0.5 (1), Co(PyBIm)₂(HBDC)(BDC) _0.5 (2), Ni(PyBIm)

Full text of DOI:10.1002/zaac.201000279

ARTICLE
DOI: 10.1002/zaac.201000279
Four New Compounds Based on Terephthalate and 2-(4-
Pyridyl)benzimidazole Ligands
Chang-Kun Xia,[a,b] Yun-Long Wu,[a] and Ji-Min Xie*[a]
Keywords: Benzimidazoles; Terephthalates; Cobalt; Nickel; Zinc; Magnetic properties
Abstract. Four new compounds based on H2BDC and PyBIm layer. Complex 2 crystallizes isostructural to 3 in triclinic space group
¯
[H2BDC = 1,4-benzenedicarboxylatic acid, PyBIm = 2-(4-pyridyl)benz- P1, in 1D chains. The hydrogen-bonding interactions between uncoor-
imidazole], (PyBIm)(H2BDC)0.5 (1), Co(PyBIm)2(HBDC)(BDC)0.5 (2), dinated N, N–H and COOH groups in 2 connect the 1D chains into a
Ni(PyBIm)2(HBDC)(BDC)0.5 (3), and Zn(BDC)(PyBIm)·H2O (4), were 2D layer. Complex 4 displays a 1D structure, which is finally extended
synthesized by hydrothermal methods and characterized by X-ray dif- to a 3D supramolecular framework by hydrogen bonding and π–π pack-
fraction. Compound 1 contains two types of hydrogen bonding N–H···N ing interactions. The magnetic properties of compounds 2 and 3 were
and O–H···N, which connect the molecules into a two-dimensional (2D) studied as well.
blies. When PyBIm is deprotonated the ligand displays a triden-
Introduction
tate coordination mode[5] (Scheme 1).
The unique strength, direction, and complementarity of non-
Recently, we synthesized a series of metal-organic complexes
covalent interactions such as hydrogen bonding and π···π inter-
with the PyBIm ligand, such as [Ag2(PyBIm)2(H2O)2]SO4·H2O,
actions play a central role in the creation of molecular architec-
tures for molecular self-assembly and molecular recognition in
[Ag3(PyBIm)3(μ2-SO4)(HSO4)]·3H2O, and [Ag2(PyBIm)2(μ2-
SO4)]·4H2O [4d], [Ag(PyBIm)(H2O)]NO3.[4a] In these com-
chemical, physical, and biological science.[1] The benzimida-
plexes, the PyBIm ligand adopts bidentate coordination modes,
zole and its ramification with abundant non-coordinating N–H
and the N–H group of BIm does not coordinate to the metal
groups provide a good choice for studying hydrogen-bonding
ions, however, its hydrogen bonding interactions have impor-
interactions.[2] Among the benzimidazole deviates, the 2-(4-
tant influence on the packing of the complexes. As part of our
pyridyl)benzimidazole (PyBIm) with three N donors can act as
continuing investigation on this type of PyBIm complexes, we
a good candidate to construct metal-organic frameworks, more-
herein report four new compounds based on H2BDC (1,4-ben-
over, the N–H group plays an important role in formation of
zenedicarboxylatic acid) and PyBIm ligands, namely,
the metal-organic complexes. When PyBIm is in neutral form,
(PyBIm)(H2BDC)0.5 (1), Co(PyBIm)2(HBDC)(BDC)0.5 (2),
the ligand displays monodentate[3] or bidentate[4] coordination
Ni(PyBIm)2(HBDC)(BDC)0.5 (3), and Zn(BDC)(PyBIm)·H2O
modes (Scheme 1). In the case of the monodentate mode, the
(4).
imino nitrogen atom (Npy) from pyridyl ring directly coordi-
nates with the metal ions, whereas the N–H group and the im-
Experimental Section
Materials and General Methods
ino nitrogen atom (NBIm) from the BIm ring behave as hydro-
gen bonding donor (H–D) and acceptor (H–A), respectively. In
the case of the bidentate mode, the ligand acts as bridge to join
two metal ions with two imino nitrogen atoms from BIm and
pyridyl rings, whereas the N–H group acts as H–D. Therefore,
the PyBIm ligand provides in both coordination modes weak
interaction sites for the construction of supramolecular assem-
The ligand 2-(4-pyridyl)benzimidazole (ByBIm) was synthesized ac-
cording to the procedure reported by Alcade et al..[6] Other reagents
and solvents employed were commercially available and used without
further purification. Elemental analyses were carried out with an
EA1110 CHNS-0 CE element analyzer and the IR spectra (KBr pellets)
were recorded with a Nicolet Magna 750 FT-IR spectrometer in the
range 400–4000 cm–1. Thermogravimetric analyses (TGA) were per-
formed with a Netzsch STA-499C thermoanalyzer under nitrogen (30–
800 °C) at a heating rate of 10 °C·min–1. Variable temperature mag-
netic susceptibilities were measured with a model CF-1 superconduc-
ting extracting sample magnetometer; the powdered samples were kept
in the capsule for weighing.
* Prof. Dr. J.-M. Xie
Fax: +86-511-88791800
E-Mail: jsuxie@163.com
[a] School of Chemistry and Chemical Engineering
Jiangsu University
Zhenjiang, 212013, P. R. China
[b] State Key Laboratory of Coordination Chemistry
Nanjing University
Nanjing, 210093, P. R. China
Syntheses of the Compounds
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201000279 or from the
author.
[(PyBIm)(H2BDC)0.5
] (1): A solution of Mn(CH3COO)2·4H2O
(0.16 g, 0.64 mmol), PyBIm (0.24 g, 1.22 mmol), 1,4-H2BDC acid
282
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 637, 282–288

Compounds with Terephthalate and 2-(4-Pyridyl)benzimidazole Ligands
Scheme 1. Three types of coordination modes for the PyBim ligands.
(0.102 g, 0.61 mmol), and H2O (15 mL) was stirred under ambient package.[8] The hydrogen atoms were generated geometrically except
conditions. Afterwards, the mixture was sealed in a Teflon-lined steel for water molecules. Crystallographic data are summarized in Table 1.
vessel and heated at 160 °C for 5 days. After slow cooling to room Selected bond lengths and angles are listed in Table 2.
temperature, the resulting product was recovered by filtration, washed
Crystallographic data for the structural analysis have been deposited
with the Cambridge Crystallographic Data Centre, reference numbers
CCDC-773909, -773910, -773911, and -773912 for compounds 1–4.
Copies of this data may be obtained from The Director, CCDC, 12
Union Road, CB2 1EZ, UK (Fax: +44-1233-336033; E-Mail: de-
posit@ccdc.cam.ac.uk or www: http:// www.ccdc.cam.ac.uk.)
with distilled water and dried in air (Yield 80 % ). C16H12N3O2: calcd.
C 69.06; N 15.10; H 4.35 %; found: C 69.13; N 14.87; H 4.74 %. IR
(KBr): ν = 3455 s, 1854 m, 1695 s, 1613 s, 1534 m, 1505 m, 1447 w,
˜
1433 s, 1372 m, 1314 s, 1277 s, 1210 m, 1131 m, 1060 s, 1014 s, 970
s, 879 m, 842 s, 772 s, 750 s, 723 s, 696 m, 616 w, 563 m, 481 s cm–1.
Co(PyBIm)2(HBDC)(BDC)0.5 (2):
A solution of CoCl2·4H2O
(0.152 g, 0.64 mmol), PyBIm (0.24 g, 1.22 mmol), 1,4-H2BDC acid
(0.160 g, 0.96 mmol), NaOH (0.022 g, 0.55 mmol) and H2O (15 mL)
was stirred under ambient conditions. Afterwards, the mixture was
sealed in a Teflon-lined steel vessel and heated at 130 °C for 5 days.
After slow cooling to room temperature, the resulting product was
recovered by filtration, washed with distilled water and dried in air
Supporting Information (see footnote on the first page of this article):
TGA and DSC traces of compounds 1–4. Inverse susceptibility with
linear regression based upon Curie–Weiss law for complexes 2 and 3.
(Yield 85 %). C36H25CoN6O6: calcd. C, 62.08; N, 12.06; H, 3.62 %; Results and Discussion
found: C, 61.79; N, 12.32; H, 3.91 %. IR (KBr): ν = 3422 s, 3196 s,
˜
Syntheses
1932 m, 1674 s, 1613 s, 1563 s, 1550 m, 1507 s, 1430 s, 1408 s, 1316
m, 1273 m, 1234 m, 1214 m, 1014 s, 958 m, 884 m, 842 s, 814 m,
789 s, 739 s, 698 s, 682 s, 532 m cm–1.
Complexes 2–4 were synthesized with transition metal chlo-
rides in hydrothermal reaction condition, respectively. How-
ever, a series of parallel experiments show that when the metal
chlorides were replaced with the corresponding metal acetates,
the complexes could not be obtained, which may be due to the
influence of CH3COO–. It is worthwhile to note that, more
interestingly, the organic compound 1 was isolated from the
similar reaction condition with Mn(CH3COO)2·4H2O as initial
reagent. However, if the synthesis was carried out under the
same reaction conditions but in absence of Mn2+ or Co2+ ions,
no compound 1 could be obtained, which suggests that the
presence of metal ions is important to obtain the structure al-
though the role of the metal ions in the system remains unclear.
Ni(PyBIm)2(HBDC)(BDC)0.5 (3): Complex 3 was synthesized in an
analogous procedure to 2, except NiCl2·4H2O (0.144 g, 0.64 mmol)
was used instead of CoCl2·4H2O (Yield 80 %). C36H25NiN6O6: calcd.
C, 62.10; N, 12.07; H, 3.62 %; found: C, 61.79; N, 12.09; H, 4.04 %.
IR (KBr): ν = 3424 s, 3195 s, 1932 m, 1672 s, 1614 s, 1567 s, 1542
˜
m, 1508 s, 1430 s, 1406 s, 1315 m, 1258 m, 1258 m, 1214 m, 1017
s, 957 m, 884 m, 845 s, 814 m, 788 s, 740 s, 701 m, 682 s, 532 m
cm–1.
Zn(PyBIm)(BDC)·H2O (4): A solution of ZnCl2·4H2O (0.137 g,
1.00 mmol), PyBIm (0.195 g, 1.00 mmol), 1,4-H2BDC acid (0.166 g,
1.00 mmol), NaOH (0.034 g, 0.85 mmol) and H2O (15 mL) was
stirred under ambient condition. Afterwards, the mixture was sealed in
a Teflon-lined steel vessel and heated at 130 °C for 5 days. After slow
cooling to room temperature, the resulting product was recovered by
filtration and washed with distilled water and dried in air (Yield 90 %).
C20H15N3O5Zn: calcd. C, 54.26; N, 9.49; H, 3.41 %; found: C, 54.62;
Thermal Properties
Compound 1 does not show apparent weight losses up to
250 °C. A sharp weight loss occurs between 250–360 °C,
which displays the decomposing of the overall molecule. Be-
cause no coordination or crystal water molecules are present
in the complexes 2 and 3, the two complexes are rather stable
and have no weight losses up to 370 °C. Complex 4 loses its
coordination water in the range of 45–150 °C, the observed
weight loss is 3.98 %, which is in accordance with the calcu-
lated weight loss (4.07 %).
N, 9.55; H, 3.88 %. IR (KBr): ν = 3451 s, 3052 s, 1869 m, 1614 s,
˜
1563 w, 1536 m, 1500 m, 1478 m, 1448 w, 1371 m, 1277 s, 1143 m,
1130 m, 1060 s, 1015 s, 970 s, 879 m, 842 s, 771 m, 745 s, 705 m,
695 m, 593 m, 563 m cm–1.
X-ray Crystallography
Suitable single crystals of 1–4 were carefully selected under an optical
microscope and glued to thin glass fibers. The diffraction data were
collected with a Siemens Smart CCD diffractometer with graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å) at 293 K. An empir-
ical absorption correction was applied using the SADABS program.[7]
The structures were solved by direct methods and refined by full-ma-
Crystal Structures
Compound 1 crystallizes in orthorhombic space group Pbca.
trix least-squares methods on F2 by using the SHELXTL-97 program As shown in Figure 1, in the molecule structure the PyBIm co-
Z. Anorg. Allg. Chem. 2011, 282–288
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283

C.-K. Xia, Y.-L. Wu, J.-M. Xie
ARTICLE
Table 1. Crystal data and structure refinement parameters for compounds 1–4.
1
2
3
4
Formula
C16H12N3O2
278.29
C36H25CoN6O6
696.55
C36H25NiN6O6
696.33
C20H15ZnN3O5
442.72
Molecular mass
Crystal system
Orthorhombic
Pbca
Triclinic
Triclinic
Triclinic
¯
¯
¯
Space group
P1
P1
P1
a /Å
7.4475(3)
10.2079(5)
35.2470(18)
90
9.6096(13)
10.4902(11)
15.864(2)
95.121(3)
107.158(7)
94.574(4)
1512.4(3)
2
9.651(5)
10.462(5)
15.876(9)
95.288(17)
107.099(9)
94.983(11)
1514.7(14)
2
8.7966(10)
9.0647(10)
12.7578(18)
102.534(5)
106.203(3)
90.450(5)
951.1(2)
2
b /Å
c /Å
α /°
β /°
90
90
γ /°
V /Å3
2679.6(2)
8
Z
T /K
293(2)
293(2)
293(2)
293(2)
Dcalc /g·cm–3
F(000)
1.380
1.530
1.527
1.546
1160
716
718
452
Reflections collected
Independent reflections
Data/restrain/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
Electron density
15788
11852
11827
7425
3063
6862
6850
4311
3063 / 0 / 194
1.148
6862 / 0 / 446
1.115
6850 / 0 / 446
1.106
4311 / 0 / 270
1.064
0.0502, 0.1194
0.0527, 0.1211
0.222, –0.219
0.0641, 0.1181
0.0940, 0.1360
0.478, –0.436
0.0702, 0.1227
0.1106, 0.1442
0.335, –0.494
0.0452, 0.1138
0.0550, 0.1210
1.188, –0.521
Table 2. Selected bond lengths /Å and angles /° for compounds 1–4.
1
C(13)–O(1)
C(1)–N(1)
C(6)–N(2)
1.309(2)
1.337(2)
1.323(2)
C(13)–O(2)
C(5)–N(1)
C(6)–N(3)
1.208(2)
1.333(2)
1.364(2)
2
Co(1)–O(1)
1.995(2)
2.167(2)
2.172(3)
89.57(9)
90.05(1)
94.66(1)
93.27(1)
176.96(1)
Co(1)–O(2)
2.035(2)
2.154(2)
2.171(3)
150.24(9)
60.86(8)
87.84(1)
88.26(1)
88.89(1)
Co(1)–O(5)
Co(1)–O(6)
Co(1)–N(1)
Co(1)–N(4)
O(2)–Co(1)–O(6)
O(2)–Co(1)–N(1)
O(5)–Co(1)–N(1)
O(6)–Co(1)–N(1)
N(4)–Co(1)–N(1)
O(2)–Co(1)–O(5)
O(6)–Co(1)–O(5)
O(2)–Co(1)–N(4)
O(5)–Co(1)–N(4)
O(6)–Co(1)–N(4)
3
Ni(1)–O(1)
2.021(3)
2.141(3)
2.114(3)
154.74(1)
92.83(1)
94.29(1)
93.05(1)
177.19(1)
Ni(1)–O(2)
2.015(3)
2.107(3)
2.111(3)
92.72(1)
62.35(1)
85.83(1)
88.25(1)
89.20(1)
Ni(1)–O(5)
Ni(1)–O(6)
Ni(1)–N(1)
Ni(1)–N(4)
O(1)–Ni(1)–O(6)
O(1)–Ni(1)–N(1)
O(5)–Ni(1)–N(1)
N(1)–Ni(1)–O(6)
N(1)–Ni(1)–N(4)
O(1)–Ni(1)–O(5)
O(5)–Ni(1)–O(6)
O(1)–Ni(1)–N(4)
O(5)–Ni(1)–N(4)
N(4)–Ni(1)–O(6)
4
Zn(1)–O(1)
1.932(2)
1.943(3)
107.87(9)
106.33(1)
106.18(1)
Zn(1)–O(3)
Zn(1)–N(1)
O(1)–Zn(1)–O(1 W)
O(3)–Zn(1)–O(1 W)
O(3)–Zn(1)–N(1)
1.930(2)
2.049(3)
100.96(1)
125.14(1)
108.86(1)
Zn(1)–O(1W)
O(3)–Zn(1)–O(1)
O(1)–Zn(1)–N(1)
O(1W)–Zn(1)–N(1)
crystallizes with H2BDC in 2:1 ratio. The dihedral angle be- H···N and O–H···N. The neutral PyBIm molecules are linked
tween the pyridyl and H2BDC rings amounts 9.2°, whereas by N3–H3A···N2i (symmetry code i: –x+1/2, y–1/2, z) interac-
the angle between benzimidazoyl and pyridyl rings is 26.2°, tions to a 1D chain with a N–H···N distance of 2.944(2) Å
respectively. There are two types of hydrogen bonding N– and a N–H···N bond angle of 155.2° (Figure 2). Complex 4
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Compounds with Terephthalate and 2-(4-Pyridyl)benzimidazole Ligands
¯
crystallizes in triclinic space group P1. As sTo the best of our
knowledge, this type of self-complementary N–H···N hydrogen
bonds is quite rare.[9] The chains are further linked by O1–
H1B···N1ii interactions (symmetry code ii: x–1, y, z) to a 2D
“zigzag” sheet with an O–H···N distance of 2.654(2) Å and an
O–H···N bond angle of 174(2)° (Figure 3). It is more interest-
ing that the “zigzag” sheets are interpenetrating to form a 2D
layer-like structure with ca. 16 Å thickness (Figure 4).
Figure 3. 2D “zigzag” sheet formed by N–H···N and O–H···N interac-
tions.
Figure 1. Molecular structure of compound 1.
It is noteworthy that weak interactions exist among the mole-
cules of 2. The hydrogen bonding interactions are formed be-
¯
Complex 2 crystallizes in triclinic space group P1, contain- tween the non-coordinated carboxyl groups (COOH) of tereph-
ing
a
crystallographically independent cobalt(II) atom thalate ligands and the nitrogen heterocyclic rings of 2-(4-
[CoN2O4] as coordination center. As shown in Figure 5, in the pyridyl)benzimidazole) ligands. The O4–H4B···N5iii (symme-
cobalt atom is coordinated by four oxygen and two nitrogen try code iii: –x+1, –y+2, –z+1) distance is 2.669(4) Å with a
donors in a distorted octahedral arrangement, with two oxygen corresponding bond angle of 173°, whereas the N3–H3A···O3iv
atoms from chelating bis-bidentate carboxyl groups (Co1–O5 (symmetry code iv: x–1, y–1, z) distance amounts to
2.167(2) Å; Co1–O6 2.154(2) Å) and two oxygen atoms from 2.801(4) Å with a bond angle of 169.8° (Figure 7). The overall
two bridging bidentate carboxyl groups (Co1–O1A structure displays a two-dimensional sheet formed by hydro-
1.995(2) Å; Co1–O2 2.035(2) Å). The O1A, O2, O5, and O6 gen bonding with windows of 11.66 Å × 12.94 Å (Figure 8).
atoms are almost coplanar with a mean deviation of 0.001 Å. On the other hand, π–π stacking interactions of the aromatic
The axial positions of the octahedral arrangement are com- rings of PyBIm ligands exist in the one-dimensional chain with
pleted by two nitrogen atoms from the terminal PyBIm ligands face-to-face distances of 3.888–4.006 Å and dihedral angles of
(Co1–N1 2.172(3) Å; Co1–N4 2.171(3) Å). In the structure of 6.1–18.3° for pair of rings.
2, two cobalt(II) coordination units ([CoN2O4]) are linked to-
Complex 3 crystallizes isostructural to complex 2. We know
gether by two carboxyl groups of two terminal HBDC– ligands, that the ionic radius of NiII is 0.83 Å, which is slight shorter
forming an eight-membered ring (–Co1–O1A–C1A–O2A– than that of CoII (0.89 Å). So the distances of Ni–O and Ni–
Co1A–O1–C1–O2–) with a mean deviation of 0.1162 Å. The N are somewhat shorter than the corresponding bond lengths
Co···Co separation amounts to 4.106 Å, which is obviously of 2 [Ni1–O1 2.021(3), Ni1–O2 2.015(3), Ni1–O5 2.141(3),
larger than that in the similar eight-membered ring in the dinu- Ni1–O6 2.107(3), Ni1–N1 2.114(3), and Ni1–N4 2.111(3) Å].
clear cobalt complex Co2(1,4-H2BDC2(dabco)]·4DMF·H2O The Ni···Ni separation is 4.255 Å in the two nickel(II) coordi-
(Co···Co = 2.684 Å).[10]
nation units ([NiN2O4]2), and the hydrogen bonding interac-
In complex 2, the terephthalate anions exist in two different tions as well as π–π stacking interactions are similar to those
coordination modes (HBCD– and BCD2–). The HBCD– anion, of the complex 2.
¯
Complex 4 crystallizes in triclinic space group P1. As shown
as terminal ligand, coordinates to two cobalt atoms (Co1 and
Co1A) and employs its two carboxyl oxygen atoms (O1 and in Figure 9, the zinc atom is tetracoordinated by two oxygen
O1A) in a syn-syn mode. In contrast to the HBCD– anion, the atoms (O1 and O3) from two monodentate carboxyl groups
BCD2– anion acts as bridging ligand with bis-chelating mode, and one nitrogen atom (N1) from the terminal PyBIm ligand
it connects the metal coordination units [CoN2O4]2 into a one- and one water molecule (O1W), forming a slightly distorted
dimensional chain (Figure 6).
tetrahedral coordination unit [ZnNO3]. The Zn1–O distances
Figure 2. 1D PyBIm chain formed by N–H···N hydrogen bonding (dashed line).
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285

C.-K. Xia, Y.-L. Wu, J.-M. Xie
ARTICLE
Figure 4. (a) Interpenetration of “zigzag” sheets. (b) 2D layer-like structure formed by the interpenetration of “zigzag” sheets.
Figure 5. Locally expanded unit in complex 2. Hydrogen atoms were
omitted for clarity.
Figure 8. 2D sheet formed by the hydrogen bonding with windows of
11.66 Å × 12.94 Å.
amount to 1.932(2), 1.930(2), and 1.943(3) Å, and the Zn1–
N1 distance is 2.049(3) Å. The O–Zn–O bond angles are
100.96(10), 107.87(9) and 125.1(1)°, and the N–Zn–O angles
Figure 6. 1D polymeric chain formed by dimetal units in complex 2.
are 106.2(1), 106.33(10), and 108.86(10)°, respectively.
Figure 9. Locally expanded unit of complex 4.
Figure 7. Hydrogen bonding interactions formed between the non-co-
ordinated carboxyl groups (COOH) and the nitrogen heterocyclic
rings.
Like in complex 2, the PyBIm molecule in 4 acts as a termi-
nal ligand, which coordinates to the metal atom through a ni-
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Compounds with Terephthalate and 2-(4-Pyridyl)benzimidazole Ligands
Figure 10. View of the 1D “zigzag” chain in complex 4.
trogen atom, whereas the BDC2– anion in 4 adopts a monoden-
tate μ2-bridging coordination mode, which is different to that
in 2. The coordination units [ZnNO3] are connected by BDC2–
anions into a one-dimensional “zigzag” chain with a Zn···Zn
separation of 11.09 Å (Figure 10). Hydrogen bonding interac-
tions exist in the zigzag chains, and connect the chains into a
2D sheet (Figure 11) with a O1W–H1C···N2v (symmetry code
v: –x+1, –y+2, –z+2) distance of 2.668(3) Å and a bond angle
of 170(5)°. Moreover, the sheets are further joined by π–π
packing interactions (Figure 12) to form a three-dimensional
framework (Figure 13), in which the interpenetrating aromatic
rings are parallel to each other with face-to-face distances of
3.858(9) Å.
Figure 12. π–π Packing interactions in complex 4.
Figure 11. 2D sheet formed by hydrogen bonding interactions in com-
plex 4.
In the structures of complexes 2–4, the PyBIm molecule only
acts as the monodentate terminal ligand, different to other re-
ported structures where it shows bi- or tridentate coordination
[4, 5]. This may be ascribed to the employment of the tereph-
thalate ligand, which has a strong bridging function and shows
preferential coordination. Compared to the oxygen atoms of
the terephthalate ligand, the NBIm atoms have stronger steric
hindrance. So, PyBIm preferentially adopts a terminal coordi-
nation mode using the Npy atom with weaker steric hindrance.
On the other hand, the different hydrothermal reaction condi-
tions may also be important to the difference of the coordina-
tion modes for PyBIm. Therefore, studying how to control the
reaction conditions to carry out target-directed synthesis re-
mains an important and active subject.
Figure 13. 3D framework formed by hydrogen bonding and π–π pack-
ing interactions.
Z. Anorg. Allg. Chem. 2011, 282–288
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
287

C.-K. Xia, Y.-L. Wu, J.-M. Xie
ARTICLE
Magnetic Properties
Conclusions
The temperature-dependent magnetic susceptibilities of com-
plexes 2 and 3 were measured from 2 to 300 K. For complex
2, the μeff value (per CoII ions) at 300 K amounts to 4.37 μB
(Figure 14), which is larger than the one expected for the spin-
only[11, 12] case (μeff = 3.87 μB, S = 3/2, g = 2.0). The μeff value
of compound 2 decreases gradually to 4.04 μB at about 46 K
and then decreases sharply to 1.13 μB at 2 K with cooling. The
Curie–Weiss law is obeyed for 2 with a Curie constant of C =
1.24 cm3·K·mol–1, θ = –9.79 K. These results indicate a possi-
ble weak antiferromagnetic interaction in 2.
Four new compounds based on PyBIm and terephthalate li-
gands, in which the weak interactions are important for con-
struction of the compounds, were prepared and characterized.
The successful preparation of the compounds further demon-
strates that the PyBIm ligand is a good candidate for construc-
tion of new metal-organic complexes.
Acknowledgement
The μeff value of complex 3 amounts to 2.27 μB at 300 K,
and decreases smoothly to 2.05 μB at 41 K (Figure 15), which
is much lower than the spin-only value for an uncoupled NiII
ion (μeff = 2.83 μB, S = 1, g = 2.0). The μeff value decreases
rapidly from 41 K with cooling, reaches its minimum value of
0.55 μB at 2 K. The Curie–Weiss law is obeyed for compound
3 in the range of 14 to 300 K with a Curie constant of C =
0.68 cm3·K·mol–1, θ = –16.83 K. These results also indicate a
possible weak antiferromagnetic interaction in 3.
This work was financially supported by Start-up Fund for Advanced
Professional of Jiangsu University (No. 08JDG031), and partly sup-
ported by Industry High Technology Foundation of Jiangsu
(BG2007025).
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Received: July 14, 2010
Published Online: November 11, 2010
Figure 15. Plot of μeff andχM versus T for complex 3.
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Z. Anorg. Allg. Chem. 2011, 282–288