Syntheses, structures, and magnetic properties of five coordination polymers constructed from biphenyl-3,4′,5-tricarboxylic acid and (bis)imidazole linkers

Article abstract of DOI:10.1039/c3ce42565g

Five coordination polymers (CPs), namely {[Ni_1.5(BPT)(1,4-bib) ₂(H₂O)]·(1,4-bib)_0.5·2H ₂O}_n (1), {[Co₂(BPT)(1,3-bimb) (μ₃-OH)]·H₂O}_n (2), {[Zn(HBPT)(1,3-bimb)]·H₂O}_n (3), {[Co ₂(BPT)(H₂BPT)(4,4′-bibp)₂]·2H ₂O}_n (4), and [Mn_2.5(BPT)(4,4′-bibp) _2.5(SO₄)(H₂O)]_n (5) (H ₃BPT = biphenyl-3,4′,5-tricarboxylic acid, 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene, 1,3-bimb = 1,3-bis(imidazol-1-ylmethyl) benzene, and 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl), were synthesized under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complex 1 exhibits unprecedented 2D + 2D → 3D parallel entangled networks consisting of trilayer (3,4,6)-connected (4 ⁴·5⁴·6⁶·8)(5·6 ⁴·8)₂(5²·6²) sheets. Complex 2 displays a 3D (3,10)-connected 3,10T9 net based on tetranuclear {Co₄(μ₃-OH)₂} clusters with the Schlaefli symbol (4¹⁸·6²⁴·8 ³)(4³)₂. Complex 3 shows an interesting 1D tube-like chain consisting of Zn₂(1,3-bimb)₂ loops. Complex 4 affords a 2D (4⁴·6²)-sql net constructed from {Co₂} dinuclear units. Complex 5 displays a 3D 6-connected (4¹²·6³)-pcu net consisting of α-Po primitive cubic nets based on {Mn₅(SO₄)₂} clusters. Moreover, magnetic studies indicate that complexes 2, 4 and 5 show antiferromagnetic properties. the Partner Organisations 2014.

Full text of DOI:10.1039/c3ce42565g

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PAPER
Syntheses, structures, and magnetic properties
of five coordination polymers constructed
from biphenyl-3,4′,5-tricarboxylic acid
and (bis)imidazole linkers†
Cite this: CrystEngComm, 2014, 16,
3203
ab
Liming Fan,ab Wei Zhang,a Weiliu Fan,b Liming Sunb
*
*
Xiutang Zhang,
and Xian Zhao
b
Five coordination polymers (CPs), namely {[Ni1.5(BPT)(1,4-bib)2(H2O)]·(1,4-bib)0.5·2H2O}n (1),
{[Co2(BPT)(1,3-bimb)(μ3-OH)]·H2O}n (2), {[Zn(HBPT)(1,3-bimb)]·H2O}n (3), {[Co2(BPT)(H2BPT)(4,4′-
bibp)2]·2H2O}n (4), and [Mn2.5(BPT)(4,4′-bibp)2.5(SO4)(H2O)]n (5) (H3BPT = biphenyl-3,4′,5-tricarboxylic
acid, 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene, 1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, and
4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl), were synthesized under hydrothermal conditions. Their
structures were determined by single-crystal X-ray diffraction analyses and further characterized by
elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG)
analyses. Complex 1 exhibits unprecedented 2D + 2D → 3D parallel entangled networks consisting of
trilayer (3,4,6)-connected (44·54·66·8)(5·64·8)2(52·62) sheets. Complex 2 displays a 3D (3,10)-connected
3,10T9 net based on tetranuclear {Co4(μ3-OH)2} clusters with the Schläfli symbol (418·624·83)(43)2. Com-
plex 3 shows an interesting 1D tube-like chain consisting of Zn2(1,3-bimb)2 loops. Complex 4 affords a
2D (44·62)-sql net constructed from {Co2} dinuclear units. Complex 5 displays a 3D 6-connected
(412·63)-pcu net consisting of α-Po primitive cubic nets based on {Mn5(SO4)2} clusters. Moreover, mag-
netic studies indicate that complexes 2, 4 and 5 show antiferromagnetic properties.
Received 17th December 2013,
Accepted 29th January 2014
DOI: 10.1039/c3ce42565g
www.rsc.org/crystengcomm
However, the controllable synthesis of prospective net-
works is still a far-reaching challenge since such materials
Introduction
Recent research into coordination polymers (CPs) has been
attractive in the field of materials science due to their fasci-
nating structures and new topological prototypes, as well as
their tremendous potential applications as functional mate-
rials in gas storage and separation,1 ion exchange,2 lumines-
cence,3 magnetism,4 photocatalysis,5 and heterogeneous
catalysis.6 Up to now, much effort has been devoted and a
large number of CPs with various architectures and excellent
properties have been obtained through the self-assembly of
selected or various designed organic ligands and metal ions
or metal–oxide building units.
are always dependent on many uncertain factors, such as
the coordination geometry preferred by the metal,7 solvent
systems,8 templates,9 pH values,10 counteranions,11 and the
chemical structures of the selected ligands.12 Among these
factors, the rational selection of the characteristic ligand
proved to be one efficient route for the construction of versa-
tile CPs. Generally, the length, rigidity, coordination modes,
and functional groups or substituents of polycarboxylate
ligands have consequential effects on the final structures of
CPs.13 Moreover, a recent study on coordination assemblies
using (bis)imidazole linkers as ancillary ligands provided a
reliable strategy for obtaining new topological prototypes
of coordination nets.14 The ancillary ligands have a great
effect on the coordination modes of the host polycarboxylate
aromatic acid and the final packing structures. With the
length of the ancillary ligands increasing, the longer separa-
tion of neighboring central ions makes the host aromatic poly-
carboxylate ligand adopt more “open” coordination modes
and the overall structure a higher degree of interpenetration.
The greater flexibility of ancillary ligands could make the
final structure more twisted and complicated.15 Thus, CPs
a Advanced Material Institute of Research, College of Chemistry and Chemical
Engineering, Qilu Normal University, Jinan, 250013, China.
E-mail: xiutangzhang@163.com
b State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100,
China. E-mail: zhaoxian@icm.sdu.edu.cn
† Electronic supplementary information (ESI) available: Additional figures, IR spectra,
powder XRD patterns and X-ray crystallographic data. CCDC 977304–977308 for
1–5. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c3ce42565g
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range of 400–4000 cm−1. Elemental analyses were carried out
using a CE instruments EA 1110 elemental analyzer. X-ray pow-
der diffraction peaks were measured using a PANalytical X-Pert
pro diffractometer with Cu-Kα radiation. Thermogravimetric
analyses (TGA) were performed under air conditions from
room temperature to 800 °C with a heating rate of 10 °C min−1
using a Perkin-Elmer TGA-7 thermogravimetric analyzer. The
magnetic measurements were made using Quantum Design
SQUID MPMS XL-7 instruments.
Scheme 1 Structures of H3BPT and three bis(imidazole) bridging ligands.
Synthesis of {[Ni1.5(BPT)(1,4-bib)2(H2O)]·(1,4-bib)0.5·2H2O}n (1)
A mixture of H3BPT (0.15 mmol, 0.043 g), 1,4-bib (0.20 mmol,
0.042 g), NiSO4·6H2O (0.20 mmol, 0.053 g), NaOH (0.30 mmol,
0.012 g), and 12 mL H2O was placed in a 25 mL Teflon-lined
stainless steel vessel and heated to 170 °C for 3 days,
followed by slow cooling (a descent rate of 10 °C h−1) to room
temperature. The green block crystals of 1 were obtained.
Yield: 53% (based on Ni). Anal. (%) calcd. for C90H76N20Ni3O18
(1901.84): C, 56.84; H, 4.03; N, 14.73. Found: C, 56.93; H, 3.76;
N, 14.15. IR (KBr pellet, cm−1): 3405 (m), 1603 (m), 1517 (s),
1387 (s), 1319 (m), 1074 (m), 831 (m), 713 (w).
Synthesis of {[Co2(BPT)(1,3-bimb)(μ3-OH)]·H2O}n (2)
A mixture of H3BPT (0.15 mmol, 0.043 g), 1,3-bimb (0.20 mmol,
0.048 g), Co(NO3)·6H2O (0.20 mmol, 0.058 g), NaOH (0.30 mmol,
0.012 g), and 12 mL H2O was placed in a 25 mL Teflon-lined
stainless steel vessel and heated to 170 °C for 3 days, followed
by slow cooling (a descent rate of 10 °C h−1) to room tempera-
ture. The red block crystals of 2 were obtained. Yield: 47%
(based on Co). Anal. (%) calcd. for C29H24Co2N4O8 (674.38): C,
51.65; H, 3.59; N, 8.31. Found: C, 51.43; H, 3.43; N, 8.77. IR
(KBr pellet, cm−1): 3467 (m), 1619 (s), 1596 (s), 1567 (s), 1398 (s),
1274 (w), 1087 (w), 978 (w), 836 (w), 722 (m).
Scheme 2 Various structures of complexes 1–5.
can be assembled from predetermined organic building blocks
through judicious selection of ligands and careful control of
reaction conditions. To the best of our knowledge, CPs based
on biphenyl-3,4′,5-tricarboxylic acid (H3BPT) in the presence of
(bis)imidazole linkers have never been documented to date.
Thus, these considerations inspired us to explore new
coordination frameworks with biphenyl-3,4′,5-tricarboxylic
acid (H3BPT) and bis(imidazole) bridging linkers (1,4-bib,
1,3-bimb, and 4,4′-bibp, Scheme 1). Herein, we reported the
syntheses and structural characterization of five new coordi-
nation polymers, {[Ni1.5(BPT)(1,4-bib)2(H2O)]·(1,4-bib)0.5·2H2O}n
(1), {[Co2(BPT)(1,3-bimb)(μ3-OH)]·H2O}n (2), {[Zn(HBPT)(1,3-
bimb)]·H2O}n (3), {[Co2(BPT)(H2BPT)(4,4′-bibp)2]·2H2O}n (4), and
[Mn2.5(BPT)(4,4′-bibp)2.5(SO4)(H2O)]n (5), which exhibit a sys-
tematic variation of architectures from a 1D ladder chain to
a 3D framework (Scheme 2) constructed from H3BPT and
three bis(imidazole) bridging linkers (1,4-bib, 1,3-bimb, and
4,4′-bibp). Magnetic studies indicate that complexes of 2, 4,
and 5 show antiferromagnetic behavior.
Synthesis of {[Zn(HBPT)(1,3-bimb)]·H2O}n (3)
A mixture of H3BPT (0.20 mmol, 0.057 g), 1,3-bimb (0.20 mmol,
0.048 g), ZnSO4·7H2O (0.30 mmol, 0.086 g), (NH4)6Mo7O24·4H2O
(0.81 mmol, 0.100 g), NaOH (0.20 mmol, 0.008 g), and 15 mL
H2O was placed in a 25 mL Teflon-lined stainless steel vessel
and heated to 170 °C for 3 days, followed by slow cooling
(a descent rate of 10 °C h−1) to room temperature. The color-
less block crystals of 3 were obtained. Yield: 42% (based on
Zn). Anal. (%) calcd. for C29H24N4O7Zn (605.89): C, 57.48; H,
3.99; N, 9.25. Found: C, 57.89; H, 4.03; N, 9.38. IR (KBr pellet,
cm−1): 3469 (m), 1621 (s), 1536 (s), 1394 (s), 1284 (w), 1109 (m),
944 (w), 778 (w), 730 (m).
Synthesis of {[Co2(BPT)(H2BPT)(4,4′-bibp)2]·2H2O}n (4)
A mixture of H3BPT (0.15 mmol, 0.043 g), 4,4′-bibp (0.40 mmol,
0.114 g), Co(NO3)·6H2O (0.40 mmol, 0.116 g), NaOH (0.30 mmol,
0.012 g), and 12 mL H2O was placed in a 25 mL Teflon-lined
stainless steel vessel and heated to 170 °C for 3 days, followed
by slow cooling (a descent rate of 10 °C h−1) to room tempera-
ture. The red block crystals of 4 were obtained. Yield: 47%
Experimental section
Materials and physical measurements
All chemicals were purchased from Jinan Henghua Sci. & Tec.
Co. Ltd. and used without further purification. IR spectra
were measured using a Nicolet 740 FTIR spectrometer at the
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Table 1 Crystal data for 1–5a
Compound
1
2
3
4
5
Empirical formula
Formula weight
C90H76N20Ni3O18
1901.84
C29H24Co2N4O8
674.38
C29H24N4O7Zn
605.89
C67H49Co2N8O14
1308.00
C120H88Mn5N20O22S2
2500.92
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Triclinic
P1
Monoclinic
P2(1)/n
12.337(2)
11.051(2)
21.819(4)
90
100.761(4)
90
2922.3(9)
4
Triclinic
P1
Monoclinic
P2(1)
11.7332(4)
15.2259(6)
16.1433(6)
90
102.4970(10)
90
2815.65(18)
2
Triclinic
P1
¯
¯
¯
13.4907(14)
13.5050(14)
13.7924(14)
102.084(2)
97.561(2)
116.001(2)
2136.0(4)
1
8.9151(10)
12.3303(13)
13.3052(14)
108.564(2)
107.760(2)
99.002(2)
1267.3(2)
2
12.150(3)
13.422(3)
17.825(4)
77.205(4)
70.985(4)
83.344(4)
2676.8(10)
1
α (°)
β (°)
γ (°)
V (Å3)
Z
Dcalcd (g cm−3
)
1.479
0.738
1.533
1.192
1.588
1.028
1.543
0.670
1.551
0.699
μ (mm−1
)
Rint
0.0168
0.0673
0.0420
0.0250
0.0342
Final R indices [I > 2σ(I)]
R indices (all data)
Gof
R1 = 0.0464
wR2 = 0.1283
R1 = 0.0582
wR2 = 0.1381
1.003
R1 = 0.0470
wR2 = 0.0971
R1 = 0.0811
wR2 = 0.1138
1.001
R1 = 0.0450
wR2 = 0.1228
R1 = 0.0574
wR2 = 0.1378
0.997
R1 = 0.0452
wR2 = 0.1183
R1 = 0.0519
wR2 = 0.1237
1.002
R1 = 0.0690
wR2 = 0.1102
R1 = 0.1185
wR2 = 0.1581
1.000
P
P
P
P
a
2
R1 = ||Fo| − |Fc||/ |Fo|, wR2 = [ w(Fo − Fc2)2]/ w(Fo2)2]1/2
.
(based on Co). Anal. (%) calcd. for C67H49Co2N8O14 (1308.00): C,
61.52; H, 3.78; N, 8.57. Found: C, 61.21; H, 3.71; N, 8.69. IR
(KBr pellet, cm−1): 3431 (m), 3128 (m), 1605 (m), 1509 (s),
1382 (s), 1301 (s), 1060 (m), 814 (m), 658 (w).
linkers. Crystallographic data for compounds 1–5 are given
in Table 1. Selected bond lengths and angles are listed in
Table S1.† Topological analysis of the coordination networks
of all of the compounds was performed using the program
package TOPOS.17
Synthesis of [Mn2.5(BPT)(4,4′-bibp)2.5(SO4)(H2O)]n (5)
Results and discussion
Synthesis and general characterization
The same synthesis procedure as for 4 was used except that
Co(NO3)·6H2O was replaced by MnSO4·H2O, giving yellow
block crystals. Yield: 43% (based on Mn). Anal. (%) calcd. for
In the present study, complexes 1–5 were prepared from the
solvothermal reaction of the related first transition metal salts
and H3BPT in the presence of rigid or flexible (bis)imidazole
bridging linkers (1,4-bib, 1,3-bimb, and 4,4′-bibp). All of the
complexes 1–5 are stable in the solid state upon extended
exposure to air. They have poor solubility in water and com-
mon organic solvents but can be slightly soluble in very high
polarity solvents.
Powder X-ray diffraction (PXRD) has been employed to
check the phase purity of the bulk samples in the solid state.
For complexes 1–5, the measured PXRD patterns closely match
the simulated patterns generated from the results of single
crystal diffraction, indicative of pure products (Fig. S1, ESI†).
The absorption bands in the range of 3400–3500 cm−1 for 1–5
can be attributed to the characteristic peaks of water O–H
vibrations. The vibrations at ca. 1520 and 1610 cm−1 corre-
spond to the asymmetric and symmetric stretching vibrations
of the carboxylate groups, respectively (Fig. S2†).
C
120H88Mn5N20O22S2 (2500.92): C, 57.63; H, 3.55; N, 11.20.
Found: C, 57.89; H, 3.72; N, 10.93. IR (KBr pellet, cm−1): 3445 (m),
3123 (m), 1604 (s), 1509 (vs), 1291 (s), 1051 (s), 819 (s), 724 (w).
X-ray crystallography
Intensity data collection was carried out using a Siemens
SMART diffractometer equipped with a CCD detector using
Mo-Kα monochromatized radiation (λ = 0.71073 Å) at 293(2)
or 296(2) K. The absorption correction was based on multiple
and symmetry-equivalent reflections in the data set using the
SADABS program based on the method of Blessing. The
structures were solved by direct methods and refined by full-
matrix least-squares using the SHELXTL package.16 All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
except those of water molecules were generated geometrically
with fixed isotropic thermal parameters and included in the
structure factor calculations. The approximate positions of
the water H atoms, obtained from a difference Fourier map,
were restrained to the ideal configuration of the water mole-
cules and fixed in the final stages of refinement. Four carbon
atoms from one phenyl ring of BPT3− in compound 1 are dis-
ordered and refined with an occupancy ratio of 40 : 60. For 1
and 4, there are some very large ADPs in the (bis)imidazole
Structure descriptions of
{[Ni1.5(BPT)(1,4-bib)2(H2O)]·(1,4-bib)0.5·2H2O}n (1)
The single-crystal X-ray diffraction analysis reveals that com-
¯
plex 1 crystallizes in the triclinic system, P1 space group. As
shown in Fig. 1a, there are one and a half of NiII ions, one
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completely deprotonated BPT3− ligand, two 1,4-bib ligands, one
coordinated water molecule, and guest molecules including
a half of 1,4-bib and two water molecules in the asymmetric
unit. The Ni(1) cation is coordinated by four oxygen atoms
from two BPT3− ligands and one water molecule and two nitro-
gen atoms from two individual 1,4-bib ligands, resulting
in a distorted octahedral geometry. Ni(2) is coordinated by
two oxygen atoms from two BPT3− ligands and two nitrogen
atoms from two 1,4-bib ligands. The bond lengths of Ni–O
and Ni–N are in the range of 1.9968(18)–2.1957(17) Å and
2.053(2)–2.121(2) Å, respectively. The ligand of BPT3− exhibits
a (κ0-κ1)-(κ0-κ1)-(κ1-κ1)-μ3 coordination mode (Mode I, Scheme 3)
and connects three NiII ions to form a 1D [Ni3(BPT)2]n ladder
chain (Fig. S3†).
Ni(1) ions are linked by 1,4-bib ligands to form a 2D
[Ni(1,4-bib)2]n net along the bc plane (Fig. S4†). Above and
below the [Ni(1,4-bib)2]n layer, two other layers are constructed
from the mixed ligands of 1,4-bib and BPT3−. These three
coordination planes are further linked through the (κ1-κ0)-μ1
carboxyl groups, generating a 2D network containing a cavity
with dimensions of 13.505(0) × 13.792(4) × 18.380(9) Å3
(Fig. 1b). The 2D networks are further connected with each
other, finally resulting in a 2D + 2D → 3D parallel framework
(Fig. 1c). It is noteworthy that the guest molecules (1,4-bib
and H2O) occupied the channels via hydrogen bonds, which
may be one important factor to stabilize the whole framework.
Further, PLATON18 calculated the void volume of 1 to be 1.8%
(38.2 out of the 2136.0 Å3 unit cell volume).
The topology analysis shows that the overall framework of
complex 1 can be described as a trinodal (3,4,6)-connected
net with the point symbol (44·54·66·8)(5·64·8)2(52·62) by
denoting BPT3−, Ni(1), and Ni(2) as 3-connected, 6-connected,
and 4-connected nodes, respectively (Fig. 1d).
Structure descriptions of {[Co2(BPT)(1,3-bimb)(μ3-OH)]·H2O}n (2)
The application of 1,3-bimb during the synthesis of 2, which
is more flexible and longer than 1,4-bib applied in complex 1,
resulted in a 3D high connected framework consisting of the
[Co4(μ3-OH)2]6+ tetrameric SBUs in 2. This proves that, with
the length and flexibility of the ancillary ligands increasing,
the longer separation of neighboring central ions makes the
host aromatic polycarboxylate ligand adopt more “open” coor-
dination modes and the overall structure exhibits a higher
degree of interpenetration.15c
Complex 2 crystallizes in the monoclinic system, P21/n
space group. The asymmetric unit of complex 2 consists of
two CoII ions, one BPT3− ligand, one 1,3-bimb ligand, one
μ3-OH− anion, and one lattice water molecule (Fig. 2a).
Four CoII ions are connected through μ3-OH, giving a
Fig. 1 (a) ORTEP representation of 1 with 50% thermal ellipsoid probability. Guest molecules and hydrogen atoms are omitted for clarity.
Symmetry codes: A: x, y, −1 + z; B: 2 − x, 1 − y, 1 − z; C: 2 − x, 1 − y, −z; D: x, 1 + y, z. (b) The unprecedented Ni2(BPT)(1,4-bib)2 trilayer. (c) The
2D + 2D → 3D parallel entangled networks viewed along the c axis. (d) The 2D + 2D → 3D interpenetrated (3,4,6)-connected topology
(44·54·66·8)(5·64·8)2(52·62) sheets in 1.
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Scheme 3 The coordination modes of H3BPT in complexes 1–5.
Fig. 2 (a) ORTEP representation of 2 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Symmetry codes: A: x, 1 + y, z;
B: 1.5 − x, 0.5 + y, 0.5 − z; C: 2 − x, 2 − y, 1 − z; D: 2.5 − x, 0.5 + y, 0.5 − z; E: −0.5 + x, 1.5 − y, 0.5 + z; F: 2 − x, 1 − y, 1 − z. (b) The Co4(COO)6(μ3-OH)2
SBUs in 2. (c) A perspective view of the 3D frameworks viewed along the b axis. (d) The 3D (3,10)-connected 3,10T9 topology with the Schläfli
symbol (418·624·83)2 in 2.
parallelogram [Co4(μ3-OH)2]6+ tetrameric SBU with Co⋯Co
distances of 3.403 Å and 3.094 Å (Fig. 2b). Co(1) is located
in a distorted octahedral {CoO5N} geometry, coordinated by
three carboxylate oxygen atoms from three BPT3− ligands,
two μ3-OH oxygen atoms, and one nitrogen atom from
a 1,4-bib ligand, whereas Co(2) is located in a distorted
trigonal bipyramidal CoO4N geometry, coordinated by four
carboxylate oxygen atoms from three different BPT3− ligands
and one μ3-OH, and one nitrogen atom from one 1,3-bimb
ligand. The Co–O bond lengths are in the range of
1.968(3)–2.253(3) Å, and the Co–N bond distances are
2.057(4) and 2.114(3) Å, respectively.
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The BPT3− ligand exhibits an unreported (κ1-κ1)-(κ1-κ1)-
geometry. The bond angles around the ZnII cation range from
94.28(12) to 123.15(12)°.
(κ0-κ2)-μ6 coordination mode (Mode II) linking the [Co4(μ3-OH)2]6+
tetrameric SBUs, finally resulting in a 2D [Co2(μ3-OH)(BPT)3]n
bilayer (Fig. S5†). The bilayers are further expanded by the
1,3-bimb ligands to form a 3D framework (Fig. 2c). The
Co⋯Co distances separated by μ6-BPT3− are 14.632, 14.540
and 14.051 Å.
The H3BPT ligands in complex 3 are partly deprotonated
and exhibit a (κ1-κ0)-(κ1-κ0)-μ2 coordination mode (Mode III).
Each HBPT2− ligand is connected to two ZnII ions to form a
1D straight [Zn(HBPT)]n chain. Two neighbouring chains
are linked via two bent 1,3-bimb ligands to form a 1D tube-
like chain consisting of rhombus [Zn2(1,3-bimb)2] meta-
llamacrocycles (Fig. 3b). The adjacent tube-like chains interacted
with each other through O–H⋯π [O4–H4w⋯π = 3.794(0) Å],
resulting in a supramolecular architecture (Fig. 3c).
From the viewpoint of structural topology, the whole
structure of complex 2 can be defined as a binodal (3,10)-
connected 3,10T9 topology with the short Schläfli symbol
(418·624·83)2 by denoting the [Co4(μ3-OH)2]6+ tetrameric SBUs
as ten-connected nodes and BPT3− ligands as three-connected
nodes (Fig. 2d).
Structure descriptions of {[Co2(BPT)(H2BPT)(4,4′-
bibp)2]·2H2O}n (4)
Structure descriptions of {[Zn(HBPT)(1,3-bimb)]·H2O}n (3)
The single-crystal X-ray diffraction analysis reveals that
Structure analysis reveals that complex 4 crystallizes in the
monoclinic system, P21 space group. As shown in Fig. 4a, the
asymmetric unit consists of two CoII ions, one BPT3− ligand,
one partly deprotonated H2BPT− ligand, two 4,4′-bibp ligands,
and two lattice water molecules. Both Co(1) and Co(2) are
penta-coordinated by three oxygen atoms from one BPT3−
ligand and one H2BPT− ligand and two nitrogen atoms from
two 4,4′-bibp ligands. The bond lengths of Co–O and Co–N
are in the range of 1.990(2)–2.104(2) and 2.072(3)–2.123(3) Å,
respectively.
¯
complex 3 crystallizes in the triclinic system, P1 space group.
As shown in Fig. 3a, there is one ZnII ion, one partly
deprotonated HBPT2− ligand, one 1,3-bimb ligand, and one
lattice water molecule in the asymmetric unit. Zn(1) is tetra-
coordinated, completed by two oxygen atoms from two differ-
ent HBPT2− ligands [Zn(1)–O(1) = 1.963(3) and Zn(1)–O(5B) =
1.964(2) Å] and two nitrogen atoms from two individual
1,3-bimb ligands [Zn(1)–N(1) = 2.046(3) and Zn(1)–N(4A) =
2.048(3) Å], resulting in a distorted tetrahedral coordination
Fig. 3 (a) ORTEP representation of 3 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Symmetry codes: A: −x, 2 − y,
2 − z; B: 1 + x, 1 + y, z. (b) Schematic view of the 1D tube-like chain and topology. (c) The 3D supramolecule connected through O–H⋯π
interactions.
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Fig. 4 (a) ORTEP representation of 4 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Symmetry codes: A: 2 − x,
−0.5 + y, 2 − z; B: 1 + x, y, 1 + z; C: −1 + x, y, −1 + z. (b) The 1D [Co2(BPT)(H2BPT)]n ladder chain. (c) The 2D networks constructed by the 1D chains
sharing the [Co2(COO)2] SBUs. (d) The (44·62)-sql topology of the 2D nets in 4.
2−
The BPT3− ligand exhibits two kinds of novel coordination
modes in the assembly of complex 4: the partly deprotonated
one exhibits a (κ1-κ1)-μ2 coordination mode (Mode IV), and
the completely deprotonated one displays a (κ0-κ0)-(κ1-κ1)-
(κ1-κ1)-μ4 coordination mode (Mode V). CoII ions are coordinated
by BPT3− and HBPT2− in staggered form, forming a [Co2(COO)2]
SBU based 1D ladder chain with the Co⋯Co distances being
3.965, and 4.682 Å, respectively (Fig. 4b). Along the c axis,
the 1D chains are linked by 4,4′-bibp ligands, resulting in a 2D
network (Fig. 4c). Topology analysis reveals that the whole
structure can be viewed as a (44·62)-sql net by denoting the
[Co2(COO)2] SBUs as 4-connected nodes (Fig. 4d).
ligands, one oxygen atom from a SO4 anion, one associated
water molecule, and two nitrogen atoms from two 4,4′-bibp
ligands. Mn(3) is coordinated by two oxygen atoms from two
2−
BPT3− ligands, another two oxygen atoms from one SO4
anion, and two nitrogen atoms from two 4,4′-bibp ligands.
The bond lengths of Mn–O and Mn–N are in the range of
2.120(2)–2.3326(19) and 2.220(3)–2.304(2) Å, respectively.
The BPT3− ligand in complex 5 is completely deprotonated
and exhibits a (κ1-κ0)-(κ1-κ1)-(κ1-κ1)-μ5 coordination mode
(Mode VI). MnII cations are bridged by (κ1-κ1)-μ2 carboxylate
2−
groups and μ3- SO4 anions to generate a 2D network
consisting of unprecedented pentanuclear [Mn5(COO)6(SO4)2]
SBUs with Mn⋯Mn distances being 4.053 Å (for Mn1–Mn3),
3.902 Å (for Mn2–Mn3), and 6.774 Å (for Mn1–Mn2) (Fig. 5b,
S6†). The networks are further linked by two 4,4′-bibp ligands
to result in a 3D framework (Fig. 5c).
From the viewpoint of structural topology, the whole 3D
structure exhibits a 6-connected pcu net with α-Po primitive
cubic nets with the short point symbol (412·63) by denoting
[Mn5(COO)6(SO4)2] SBUs as 6-connected nodes (Fig. 5d).
Structure descriptions of [Mn2.5(BPT)(4,4′-bibp)2.5(SO4)(H2O)]n (5)
A similar reaction environment to 4, except for MnSO4·H2O
replacing Co(NO3)·6H2O, results in one 3D 6-connected pcu
framework. Structure analysis reveals that complex 5 crystal-
¯
lizes in the triclinic system, space group P1. The asymmetric
unit of 5 contains two and a half of MnII ions, one BPT3−
2−
ligand, two and a half of 4,4′-bibp ligands, one SO4 anion,
and one coordinated water molecule as shown in Fig. 5a.
Mn(1) is hexa-coordinated, completed by four oxygen atoms
The diverse coordination modes of H3BPT and the
structural comparison
2−
from two different BPT3− ligands and two SO4 anions and
two nitrogen atoms from two individual 4,4′-bibp ligands,
resulting in a distorted octahedral coordination geometry.
Mn(2) is coordinated by two oxygen atoms from two BPT3−
As shown in Scheme 3 and Table 2, H3BPT exhibits versatile
coordination modes, resulting in different new topologies.
In complex 1, H3BPT is completely deprotonated and
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Fig. 5 (a) ORTEP representation of 5 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Symmetry codes: A: 1 − x, 2 − y,
1 − z; B: x, −1 + y, z; C: 1 − x, 1 − y, 1 − z; D: −x, 2 − y, 2 − z; E: x, y, 1 − z. (b) The [Mn5(COO)6(SO4)2] SBUs in compound 5. (c) A perspective view of
3D frameworks viewed along the b axis. (d) The 3D 6-connected pcu-α-Po topology with the Schläfli symbol (412·63) in 5.
Table 2 The coordination types of the H3BPT ligand and the roles of ancillary ligands in complexes 1–5 and other ancillary ligand modified CPsa
Compound
Coord. modes
Ancillary ligands/role
Dihedral angles (°)
Structure and topology
1
2
3
4
Mode I
Mode II
1,4-Bib/bridging + guest
1,3-Bimb/bridging
1,3-Bimb/bridging
4,4′-Bibp/bridging
4,4′-Bibp/bridging
Phen/cheating
Phen/cheating
Phen/cheating
Phen/cheating
20.27(1)
38.22(4)
37.99(3)
33.09(2)/16.20(8)
8.06(7)
23.86(8)
28.69(1)/30.12(8)
37.06(3)
8.61(1)
34.05(0)
2D → 3D (44·54·66·8)(5·64·8)2(52·62) net
3D (3,10)-connected (418·624·83)(43)2 net
1D tube-like chain
Mode III
Mode IV/V
Mode VI
Mode VII
Mode VIII/IX
Mode X
Mode XI
Mode XI
Mode XI
Mode XII
2D 4-connected (44·62) net
3D 6-connected (412·63) net
1D → 2D interdigitated structure
2D 4-connected (44·62) net
1D wave ladder chain
5
[Cd3(BPT)2(phen)3]19a
[Mn5(HBPT)4(phen)4]19b
[Cd2(BPT)(phen)2]19b
[Cu2(BPT)(phen)]19b
[Mn(HBPT)4(4,4′-bipy)0.5
2D 3-connected (4·82) net
2D 4-connected (44·62) net
2D 4-connected (44·62) net
2D 4-connected (44·62) net
19c
]
4,4′-Bipy/bridging
4,4′-Bipy/bridging
4,4′-Bipy/bridging
19b
[Cd(HBPT)(4,4′-bipy)0.5
[Co(HBPT)4(4,4′-bipy)0.5
]
34.95(1)
34.84(9)
19c
]
a
Note: all of the solvent molecules were omitted from the formulas. Abbreviation: phen = phenanthroline and 4,4′-bipy = 4,4′-bipyridine.
connects nickel ions via a (κ1-κ1)-(κ1-κ0)-(κ1-κ0)-μ3 coordina-
tion mode (Mode I), resulting in a ladder chain. The BPT3−
ligand in complex 2 exhibits a (κ1-κ1)-(κ1-κ1)-(κ0-κ2)-μ6 coordi-
nation mode (Mode II) and links CoII into a 3D framework in
the presence of 1,3-bimb ligands consisting of unreported
[Co4(μ3-OH)2]6+ tetrameric SBUs. With the help of 1,3-bimb
ligands, ZnII ions are coordinated by partly deprotonated
H2BPT− ligands ((κ1-κ0)-(κ1-κ0)-μ2, Mode III), resulting in a
supramolecular architecture. H3BPT exhibits two kinds of
new coordination modes in 4: a (κ1-κ1)-μ2 coordination mode
(Mode IV) for the partly deprotonated one and (κ0-κ0)-(κ1-κ1)-
(κ1-κ1)-μ4 for the completely deprotonated one (Mode V). CoII
ions are linked together to form one 2D structure. In 5, BPT3−
exhibits a (κ1-κ0)-(κ1-κ1)-(κ1-κ1)-μ5 coordination mode to link
MnII cations into a 3D framework containing 1D double helix
chains. To the best of our knowledge, Modes II, IV, and V
have never been documented up to now. As shown in the
Scheme 3 and Table 2, six other kinds of coordination modes
of H3BPT (Modes VII–XII) in the presence of phenanthroline
(phen) and 4,4′-bipyridine (4,4′-bipy) were reported.19 The
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results proved that the ancillary ligands have a great effect on
the coordination modes of the host polycarboxylate aromatic
acid and the final packing structures. The bis(imidazole)
bridging linkers have an advantage over other N-donors since
they can modulate their conformations and coordination
modes to satisfy the coordination geometry of metal centers
or metal clusters, resulting in an interpenetrated and high-
dimensional architecture.
Thermal analyses
The experiments of thermogravimetric analysis (TGA) were
performed on samples of 1–5 under a N2 atmosphere with a
heating rate of 10 °C min−1 as shown in Fig. S7.† For 1, the
first weight loss in the temperature range of 80–120 °C is
consistent with the removal of the coordinated and lattice
water molecules (obsd 5.4%, calcd 5.7%). The second weight
loss of 16.8% (calcd: 17.2%) at ca. 150 °C corresponds to the
loss of the guest molecule, 1,4-bib. Then the anhydrous net-
work starts to collapse above 275 °C. For 2, an initial weight
loss of 2.4% corresponds to the loss of solvent water mole-
cules (calcd: 2.6%). The second weight loss corresponds to
the loss of the organic ligands. For 3, the first weight loss
from 80 to 110 °C is attributed to the loss of lattice water
molecules (obsd 2.9%, calcd 3.0%). Above 290 °C, it starts to
lose its ligands as a result of thermal decomposition. For 4,
the loss of lattice water molecules (obsd 3.1%, calcd 2.8%) is
observed below 150 °C. The weight loss corresponding to the
release of organic ligands is observed above 310 °C. For 5,
the weight loss of water molecules is observed in the range of
95–125 °C (obsd: 1.9% and calcd: 1.4%). The decomposition
of organic ligands began at 295 °C.
Fig. 6 The temperature dependence of magnetic susceptibilities of 2
(a) and 4 (b) under a static field of 1000 Oe.
Magnetic properties
The variable-temperature magnetic susceptibility measure-
ments of 2, 4, and 5 were performed in the temperature
range of 2–300 K under a field of 1000 Oe. The temperature
−1
dependence of χMT and χM are displayed in Fig. 6 and 7.
The χMT value for 2 at room temperature is 5.75 cm3 K mol−1,
lower than the theoretical one (7.48 cm3 K mol−1) for four
high-spin Co(II) ions (S = 3/2) which can be attributed to the
susceptible contribution from the orbital angular momentum
at higher temperatures, indicating the overall antiferromag-
netic coupling.20 The χMT value for 4 at room temperature is
3.74 cm3 K mol−1, slightly lower than the value expected for
two isolated high-spin Co(II) ions (3.75 cm3 K mol−1). With the
temperature decreasing, the χMT value decreases evenly and
the value of χM increases continuously. The above features all
indicate overall antiferromagnetic coupling between Co(II)
centers.21 For 5, the value for χMT at room temperature is
11.56 cm3 K mol−1, lower than the value for five isolated high-
spin Mn(II) ions (21.87 cm3 K mol−1) which can be attributed
to the susceptible contribution from the orbital angular
momentum at higher temperatures, indicating the overall
antiferromagnetic coupling.22
Fig. 7 The temperature dependence of magnetic susceptibilities of
5 under a static field of 1000 Oe.
Conclusions
In summary, five coordination polymers were synthesized
based on biphenyl-3,4′,5-tricarboxylic acid (H3BPT) and three
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bis(imidazole) bridging linkers (1,4-bib, 1,3-bimb, and 4,4′-bibp)
under hydrothermal conditions. Structural comparison of
these networks reveals that the (bis)imidazole bridging
ligands have a great effect on the coordination modes of
H3BPT, such as Modes II, IV, and V, which have never been
documented to date. With the length of the (bis)imidazole
ligands increasing, the longer separation of neighboring cen-
tral ions makes the host aromatic polycarboxylate ligand
adopt more “open” coordination modes and the overall struc-
ture a higher degree of interpenetration. The greater flexibility
of ancillary ligands could make the final structure more
twisted and complicated. Moreover, magnetic studies indicate
that complexes 2, 4, and 5 have antiferromagnetic properties.
X. D. Chen and J. C. Zhao, Chem. Soc. Rev., 2014, 43, 473; (c)
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Notes
The authors declare no competing financial interest.
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S. Chen and H. Deng, CrystEngComm, 2013, 15, 1352; (c)
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Acknowledgements
Financial support from the Natural Science Foundation of
China (grant no. 21101097, 91022034 and 51172127), the
Excellent Youth Foundation of Shandong Scientific Commit-
tee (Grant JQ201015), and the Qilu Normal University is
acknowledged.
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