Self-assembly of two 1D tube-like metal-organic networks based on flexible bis(benzimidazole) ligand and 5-nitroisophthalate

Article abstract of DOI:10.1134/S0036023612050269

Two new polymeric networks, [Co(pbbm)(nip)] · H₂O (1) and [Ni(pbbm)(nip) · (H₂O)] (2) (pbbm = 1,1-(1,3-propanediyl)bis- 1H-benzimidazole, H₂nip = 5-nitroisophthalic acid) have been hydro-thermally synthesized and structura

Full text of DOI:10.1134/S0036023612050269

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 5, pp. 700–706. © Pleiades Publishing, Ltd., 2012.
COORDINATION COMPOUNDS
SelfꢀAssembly of Two 1D TubeꢀLike MetalꢀOrganic Networks
Based on Flexible Bis(Benzimidazole) Ligand
and 5ꢀNitroisophthalate1
X. L. Wang, J. X. Zhang, L. L. Hou, G. C. Liu, H. Y. Lin, and J. W. Zhang
Department of Chemistry, Bohai University, Jinzhou 121000, P. R. China
eꢀmail: wangxiuli@bhu.edu.cn
Received December 28, 2010
Abstract—Two new polymeric networks, [Co(pbbm)(nip)]
(pbbm = 1,1ꢀ(1,3ꢀpropanediyl)bisꢀ1Hꢀbenzimidazole, H2nip = 5ꢀnitroisophthalic acid) have been hydroꢀ
thermally synthesized and structurally characterized by singleꢀcrystal Xꢀray diffraction. Complex is an
interesting oneꢀdimensional (1D) tubeꢀlike chain utilizing [Co2(pbbm)2] metallocycle as subunit. Complex
is also an interesting 1D tubeꢀlike chain based on [Ni2(pbbm)2] loop subunit. In the title complexes, the
stacking and Hꢀbonding interactions extend the 1D tube into 3D supramolecular framework, respectively.
The structural differences between the title complexes indicate the importance of metal ions for the creation
⋅
H2O (
1
)
and [Ni(pbbm)(nip)
⋅
(H2O)] (2)
1
2
π
π–
of molecular architectures. Furthermore, the luminescent properties of 1 and 2 were investigated.
DOI: 10.1134/S0036023612050269
1
Metalꢀorganic complexes have been experiencing which all utilized the small inorganic anions, such as,
SCN–,
− and 2− as the secondary ligands. To our
great growth in the field of crystal engineering and
inorganic chemistry due to their versatile structures
and numerous potential applications as new solid
materials [1–5]. Selfꢀassembly of metalꢀorganic netꢀ
works from organic ligands and metal ions is an imporꢀ
tant aspect in this field [6]. An effective strategy is that
the metal ions are linked by a kind of organic ligand to
generate discrete moieties (cluster or quadrate unit)
first as the subunits, then the subunits are connected
by the second organic ligand to form polymeric strucꢀ
tures [7–11]. As is known, the selfꢀassembly and
structures of metalꢀorganic complexes is highly deterꢀ
mined by the coordination geometry of the ligands and
metal ions [12, 13]. Thus, selection of a suitable
organic ligand with certain flexibility is crucial to the
construction of coordination polymers.
ClO4 SO4
knowledge, however, combination of the flexible
ligand pbbm (Scheme 1) with organic aromatic carꢀ
boxylate anions for construction of metalꢀorganic
complexes is less investigated.
COOH
N
N
N
N
HOOC
NO2
H2nip
Scheme 1
pbbm
. Structures of the H2nip
and pbbm ligands in this work.
Here, we select the flexible ligand pbbm as main
ligand and 5ꢀnitroisophthalic acid (H2nip) as the secondꢀ
ary organic ligand, and two new coordination polymers
As is known, the bis(benzimidazole)ꢀbased ligand
has been widely used to construct metalꢀorganic comꢀ
plexes [14–17]. However, the flexible bis(benzimidaꢀ
zole)ꢀbased ligands can bend or rotate to adopt the
appropriate conformations in the assembly process,
which have been less investigated [18, 19]. Recently,
Lang’s group has reported two 1D chain structures
[(Cu(SCN)2(prbbm)]n and [{(CuSCN)2(prbbm)2}
2MeCN]n [20], and Hou’s group has also reported two
1D chain structures [Cd(pbbm)2(ClO4)2]n and
[Co(pbbm)(nip)]
⋅
H2O (1)
and [Ni(pbbm)(nip)
⋅
(H2O)] ( have been successfully synthesized under
2)
hydrothermal conditions, which contain quadrate
metallocycle as the subunits and the subunits are ultiꢀ
mately extended into one dimensional (1D) tubeꢀlike
chains. In addition, the luminescent property of the
complexes have also been investigated in the solid
state.
⋅
{[Cd(pbbm)SO4(H2O)2] · CH3OH}n (prbbm = pbbm =
1,1ꢀ(1,3ꢀpropanediyl)bisꢀ1Hꢀbenzimidazole) [21],
EXPERIMENTAL
Solvents and starting materials for synthesis were
commercially available and used as received. Ligand
1
The article is published in the original.
700

SELFꢀASSEMBLY OF TWO 1D TUBEꢀLIKE METALꢀORGANIC NETWORKS
701
Table 1. Crystal data and structure refinements for comꢀ
pounds and
pbbm was prepared according to the literature [22] and
characterized by Fourier transform infrared (FTꢀIR)
spectra. FTꢀIR spectra (KBr pellets) were taken on a
Magna FTꢀIR 560 spectrometer. Elemental analyses
(C, H, and N) were performed on a PerkinꢀElmer
240°C analyzer. Fluorescence spectra were recorded
at room temperature on a Hitachi Fꢀ4500 fluoresꢀ
cence/phosphorescence spectrophotometer.
1
2
1
2
Formula
FW
C25H21CoN5O7 C25H21NiN5O7
562.40
562.18
Crystal system
Space group
Triclinic
Triclinic
P
ꢀ1
Pꢀ1
Synthesis of [Co(pbbm)(nip)]
⋅ H2O (1). The mixꢀ
ture of CoCl2 6H2O (0.024 g, 0.1 mmol), H2nip
⋅
a
b
(Å)
(Å)
(Å)
9.882(5)
11.505(5)
11.625(5)
64.261(5)
89.834(5)
77.205(5)
1154.4(9)
2
9.566(5)
10.073(5)
13.450(5)
72.470(5)
84.166(5)
74.869(5)
1192.6(10)
2
(0.021 g, 0.1 mmol) and pbbm (0.014 g, 0.05 mmol)
was dissolved in 8 mL of distilled water and stirred for
0.5 h. Then the pH was adjusted to 6.0 by 0.1 M NaOH
solution. Consequently, the resulting mixture was
transferred and sealed in a 25 mL Teflonꢀlined stainꢀ
c
α
β
γ
(
°)
(
°)
less steel vessel, which was heated at 150
and then, the reaction system was cooled to room temꢀ
perature at a rate of
C h–1. Purpleꢀred block crystals
of suitable for Xꢀray diffraction were isolated by
°
C for 50 h,
(°)
(Å3)
V
Z
D
μ
5
°
1
mechanical separation from amorphous solid in 37%
yield (based on Co(II) salt).
(g cm–3)
(mm–1)
1.618
1.566
0.803
0.871
For C25H21CoN5O7 anal. calcd. (%): C, 53.34; H,
3.73; N, 12.45.
F
(000)
578
580
θmax
(
°)
2.73–25.00
2.69–25.00
Found (%): C, 53.12; H, 3.78; N, 12.56.
Index ranges
–11
–13
–13
≤
≤
≤
h
k
l
≤
11
13
13
–11
–11
–14
≤
≤
≤
h
k
l
≤
9
IR (KBr)
( ,
cm–1): 3364 (m), 3109 (w), 3091 (w),
ν
2360 (s), 1629 (s), 1560 (m), 1515 (s), 1458 (s), 1398 (m),
1348 (s), 1240 (s), 1080 (s), 736 (s), 704 (s), 684 (w).
≤
≤
11
≤
≤
15
Synthesis of [Ni(pbbm)(nip)
thetic procedure for is the same as that for
that Ni(NO3)2 6H2O (0.029 g, 0.1 mmol) was used
instead of CoCl2 6H2O. Green crystals of suitable
for Xꢀray diffraction were isolated by mechanical sepꢀ
aration from amorphous solid in 43% yield (based on
Ni(II) salt).
⋅
(H2O)] (2)
.
The synꢀ
Reflections collected
Unique reflections
Rint
8240
4019
8478
4149
2
1
except
⋅
⋅
2
0.0166
0.0136
a
b
R1
,
wR2
0.0413
0.1134
0.0273
0.0701
[I
> 2σ(
I)]
a
b
R1
,
wR2
0.0467
0.1174
0.0286
0.0710
For C25H21NiN5O7 anal. calcd. (%): C, 53.56; H,
3.39; N, 12.50.
(all data)
GOF on F2
Δρmax (e Å–3)
Δρmin (e Å–3)
1.092
0.703
1.056
0.552
Found (%): C, 53.83; H, 3.41; N, 12.44.
IR (KBr)
( ,
cm–1): 3325 (m), 3107 (w), 3078 (w),
ν
2935 (w), 2360 (s), 1624 (s), 1556 (m), 1519 (s), 1461 (s),
1390 (m), 1344 (s), 1257 (m), 1072 (m), 738 (s), 725 (s),
669 (m).
–0.641
–0.461
aR
=
b wR
=
{
[w(F 2 −
о
F
− Fc
F .
о
∑
∑
∑
о
1 2
1
2
Fc2)2]
[w(F 2)2]}
.
о
Xꢀray crystallography. A Bruker Apex CCD difꢀ
∑
fractometer (Mo
K radiation, graphite monochromaꢀ
α
tor, = 0.71073 Å) was used to collect data. The strucꢀ
λ
tures were solved by direct methods with SHELXSꢀ97
and Fourier techniques and refined by the fullꢀmatrix
leastꢀsquares method on F2 with SHELXLꢀ97 [23,
24]. All nonꢀhydrogen atoms were refined anisotropiꢀ
cally, hydrogen atoms of the ligands were generated
theoretically onto the specific atoms and refined isoꢀ
tropically with fixed thermal factors. The Hꢀatoms of
water molecules have not been localized. All the crysꢀ
tal data and structure refinement details for the two
bond distances and angles are listed in Table 2. Crysꢀ
tallographic data for the structures reported in this
paper have been deposited in the Cambridge Crystalꢀ
lographic Data Center with CCDC reference numbers
798759–798760 for complexes 1 and 2, respectively.
RESULTS AND DISCUSSION
[Co(pbbm)(nip)] H2O ( : Compound
ꢀ1. The asymmetric unit conꢀ
⋅
1)
1 crystalꢀ
complexes are given in Table 1. The data of relevant lizes in the space group
P
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 5 2012

702
WANG et al.
Table 2. Selected bond lengths (
d
, Å) and angles (
ω
, deg) for
1 and 2
Compound
1
Co(1)–O(3A)
2.005(2)
2.081(3)
2.391(4)
Co(1)–N(1)
2.054(2)
2.146(2)
Co(1)–O(1)
Co(1)–N(3B)
Co(1)–O(2)
O(3A)Co(1)N(1)
N(1)Co(1)O(1)
N(1)Co(1)N(3B)
O(3A)Co(1)O(2)
O(1)Co(1)O(2)
113.48(10)
95.63(11)
94.96(10)
89.86(10)
57.86(11)
O(3A)Co(1)O(1)
O(3A)Co(1)N(3B)
O(1)Co(1)N(3B)
N(1)Co(1)O(2)
N(3B)Co(1)O(2)
144.62(12)
101.27(9)
95.48(10)
152.76(10)
93.90(10)
Symmetry code: A:
x – 1, y, z; B: –x, –y, –z.
Compound
2
Ni(1)–O(1)
2.0054(14)
2.0880(14)
2.1033(17)
Ni(1)–N(1)
2.0726(18)
2.0845(15)
2.2563(16)
94.48(6)
Ni(1)–O(7A)
Ni(1)–N(3)
Ni(1)–O(2)
Ni(1)–O(6A)
O(1)Ni(1)N(1)
91.70(6)
91.25(6)
83.00(6)
93.65(6)
96.30(6)
O(1)Ni(1)O(7A)
O(1)Ni(1)O(2)
O(7A)Ni(1)O(2)
N(1)Ni(1)N(3)
O(2)Ni(1)N(3)
N(1)Ni(1)O(6A)
O(2)Ni(1)O(6A)
N(1)Ni(1)O(7A)
N(1)Ni(1)O(2)
O(1)Ni(1)N(3)
O(7A)Ni(1)N(3)
O(1)Ni(1)O(6A)
O(7A)Ni(1)O(6A)
N(3)Ni(1)O(6A)
100.14(6)
164.42(5)
170.38(6)
88.19(7)
154.87(5)
60.55(5)
91.97(5)
86.53(5)
104.50(6)
Symmetry code: A: x, y – 1, z.
sists of one independent Co(II) atom, one pbbm from two different nip ligands, and two nitrogen atoms
from two pbbm ligands, showing a distorted square
pyramidal coordination geometry [CoN2O3]. The basal
plane of Co(II) atom is defined by N1, O1, O2, and
O3A atoms. The apical site is occupied by N3B atom.
The Co–N bond length is 2.054(2) and 2.146(2) Å, and
the Co–O bond lengths range from 2.005(2) to
2.391(4) Å. All the bond lengths are in agreement with
those reported in other Co(II) complexes of N,Oꢀ
mixed ligands [25].
ligand and one nip anion, as shown in Fig. 1. The
Co(II) atom is fiveꢀcoordinated by three oxygen atoms
a
b
c
In complex 1, two pbbm molecules act as bridging
linkers to connect with two cobalt ions, resulting in the
generation of a rectangular loop [Co2(pbbm)2] (Fig. 2a).
The completely deprotonated nip anions act as the
secondary bridging linkers to connect two cobalt ions
of the [Co2(pbbm)2] loops, giving rise to a 1D tubeꢀ
like chain (Figs. 2b and 2c).
Co
O
N
N1
C
O3A
Co1
O1
N3B
O2
There are evident faceꢀtoꢀface
π
– stacking interꢀ
π
actions between the interdigitated ligands, with the
overlapping mainly occurring between the benzimidaꢀ
zole rings moieties. The
adjacent 1D tubes to produce a 2D supramolecular
layers. The centerꢀtoꢀcenter distance for the
π
–
π
stacking interactions link
π π
–
stacking interactions is 3.978 Å. The adjacent 2D
supramolecular architectures are further connected by
Fig. 1. Coordination environment of the Co(II) atom in
(thermal ellipsoids are at the 30% probability level).
1
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 5 2012

SELFꢀASSEMBLY OF TWO 1D TUBEꢀLIKE METALꢀORGANIC NETWORKS
703
a
b
c
(a)
(b)
(c)
Fig. 2. (a) Rectangular metallocycle. (b and c) View of a 1D tube of 1.
b
c
a
Fig. 3. The 3D supramolecular structure of
1
formed through hydrogen bonding and
π
–
π
interactions between different 1D tubes.
a kind of hydrogen bonding interaction between the
carbon atom of benzimidazole group and the oxygen
atom from carboxylate [C(1)–H(1A)···O(2) 3.168
161°] to form a 3D supramolecular network (Fig. 3).
Å,
c
a
b
[Ni(pbbm)(nip) (H2O)] ( : When Ni(NO3)2
⋅
2
)
⋅
6H2O, instead of CoCl2
ble with the pbbm and nip under the same reaction
condition, a new coordination polymer , similar to
that of complex , was isolated. Singleꢀcrystal Xꢀray
diffraction reveals that complex is also a 1D tube
⋅
6H2O, was selected to assemꢀ
N1
O7A
O1
Ni1
2
O6A
O2
1
2
N3
based on the rectangular metallocycle [Ni2(pbbm)2],
which is composed of two pbbm ligands and two nickel
Ni
ions. As shown in Fig. 4, the asymmetric unit of 2 conꢀ
sists of one nickel ion, one nip ligand, one pbbm molꢀ
ecule, and one coordinated water molecule. The cenꢀ
tral nickel ion is sixꢀcoordinated by two nitrogen
atoms from two pbbm ligands, three oxygen atoms
from two nip ligands, and one oxygen atom from the
coordinated water molecule, which is different from
O
N
C
that of complex
range of 2.0054(14)–2.2563(16) Å, and the Ni–N
1. The Ni–O bond lengths are in the
Fig. 4. Coordination environment of the Ni(II) atom in
(thermal ellipsoids are at the 30% probability level).
2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 5 2012

704
WANG et al.
c
a
b
(а)
(b)
(c)
Fig. 5. (a) rectangular metallocycle. (b and c) View of a 1D tube of 2.
a
c
b
Fig. 6. The 3D supramolecular structure of
2
formed through hydrogen bonding and
π
– interactions between different 1D tubes.
π
bond lengths are 2.0726(18) and 2.1033(17) Å, respecꢀ plexes. Both compound
tively.
Similar to that of complex
connected by two pbbm ligands to generate a rectanꢀ
gular metallocycle in (Fig. 5a). The remaining coorꢀ
1
and
chain structure. Although the same ligands were used
under similar synthetic conditions, the compound
based on Co(II) center is slightly different from comꢀ
pound based on the Ni(II) center. The coordination
environments of the metal ions is different: complex
is fiveꢀcoordinated, while complex is sixꢀcoordiꢀ
2 showed 1D tubeꢀlike
1
1, two nickel ions are
2
2
1
dination sites of the nickel ion are occupied by the
oxygen atoms of nip ligands and coordinated water
2
molecule. Thus, the rectangular metallocycle are infiꢀ nated, which indicate that the metal centers play an
nitely connected by nip ligands to give rise to a 1D tube
(Figs. 5b and 5c).
important role in the assembly process. In addition, it
can be seen that the pbbm ligand can rotate and bend
around the –CH2 group freely when coordinating to
the central metals and the conformation of pbbm can
change correspondingly, leading to the subtle distincꢀ
tion of the metallocycle subunits and the resultant
structures. Several metal complexes based on pbbm
Indeed, there are multiple supramolecular interacꢀ
tions in complex 2. The intermolecular hydrogenꢀ
bonding interactions between the carbon atom of benꢀ
zimidazole group and the oxygen atom of carboxylate
[
C(4)–H(4A)···O(7) 3.476
Å
, 161 ] link the 1D tube
°
to generate 2D supramolecular layer. The
π
– stackꢀ ligand have been reported. However, Co(II) and
π
ing interactions (3.816 Å) between benzimidazole rings
further connect the 2D supramolecular architecture to
give rise to a 3D supramolecular network (Fig. 6).
Ni(II) complexes constructed from pbbm ligand are
limited. In the previously reported related complexes,
two new 1D chain structures [(Cu(SCN)2(prbbm)]n
with channel, and [{(CuSCN)2(prbbm)2}
with double chain have been reported by Lang et al. [20],
two new 1D chain structures [Cd(pbbm)2(ClO4)2]n
⋅
2MeCN]n
In this work, we selected the flexible bis(benzimiꢀ
dazole) pbbm as the main ligand and H2nip as the secꢀ
ondary ligand to assemble with different metal ions
Co(II) and Ni(II), and obtained two related comꢀ
(
1
)
with
doubleꢀstranded
ribbons
and
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 5 2012

SELFꢀASSEMBLY OF TWO 1D TUBEꢀLIKE METALꢀORGANIC NETWORKS
2500
705
2
pbbm
1
6000
4000
2000
0
2000
1500
1000
500
0
300
400
Wavelength (nm)
500
300 350
400
450
Wavelength (nm)
500
550
Fig. 7. The emission spectra of 1, 2 and pbbm ligand in the solid state at room temperature.
{[Cd(pbbm)SO4(H2O)2]
looped chains based on two kinds of rings have been lar metalꢀorganic frameworks.
reported by Hou et al. [21]. However, complexes and
are 1D tubeꢀlike chains constructed by metallocycle
⋅
CH3OH}n (2) with 1D impetus for further design and synthesis of nanotubuꢀ
1
2
ACKNOWLEDGMENTS
subunits and nip anions and ultimately extended to 3D
supramolecular networks by hydrogen bonding and
Financial supports of this research by the NCETꢀ
09ꢀ0853, No. 20871022 and Talentꢀsupporting Program
Foundation of Liaoning Province (No. 2009R03) are
greatly acknowledged.
π
– stacking interactions, which is different from the
π
above reported complexes.
The photoluminescent behaviors of polymers 1, 2
and free ligand pbbm were studied in the solid state at
room temperature (Fig. 7). The free ligand pbbm disꢀ
play luminescence with emission maxima at 445 nm
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