Syntheses, structures and characterization of two Ni(II) and Pb(II) coordination polymers constructed by 2-(4-Fluorophenyl)-1Himidazo[4,5-f][1,10] phenanthroline and Flexible 4,4'-Oxybis(benzoate) Ligands

Article abstract of DOI:10.5560/ZNB.2012-0104

Two coordination polymers, [Ni(H₂O)(L)(OBA)] (1) and [Pb(L) ₂(OBA)]·3H₂O (2) [L=2-(4-fluorophenyl)-1H- imidazo[4,5- f ][1,10]phenanthroline and OBA=4,4'-oxybis(benzoate)], have been synthesized under hydrothermal conditions, and characterized by elemental analysis, and IR and UV=Vis spectra. Crystal data for 1: C₃₃H ₂₁FN₄NiO₆, triclinic, space group PI, a=13.8490(10), b=14.932(2), c=14.993(3) A, a =107.534(4), b =94.670(4), g =103.836(5)°, V =2830.9(7) A3, Z =4. Crystal data for 2: C52H36F2N8O8Pb, orthorhombic, space group Pna21, a=16.256(4), b=16.085(5), c=17.810(3) A, V =4657 (2) A3, Z =4. In 1, OBA dianions bridge Ni(II) atoms to form two crystallographically distinct chains. These chains are further extended into a 2D supramolecular architecure through π-π interactions. In 2, each OBA dianion links neighboring Pb(II) atoms to yield a helical chain. Further, π-π interactions among adjacent chains give rise to a 3D supramolecular architecture.

Full text of DOI:10.5560/ZNB.2012-0104

Syntheses, Structures and Characterization of Two Ni(II) and Pb(II)
Coordination Polymers Constructed by 2-(4-Fluorophenyl)-1H-
imidazo[4,5-f][1,10]phenanthroline and Flexible 4,4’-Oxybis(benzoate)
Ligands
Dan Li, Shu-Jiang Wang, Yuan-Rui Wang, and Qian Qiao
College of Chemistry and Chemical Engineering, Changchun University of Technology,
Changchun 130012, People’s Republic of China
Reprint requests to Prof. Qian Qiao. E-mail: qiaoqianccut@yahoo.com.cn
Z. Naturforsch. 2012, 67b, 799 – 805 / DOI: 10.5560/ZNB.2012-0104
Received April 17, 2012
Two coordination polymers, [Ni(H2O)(L)(OBA)] (1) and [Pb(L)2(OBA)]·3H2O (2) [L = 2-
(4-fluorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline and OBA = 4,4’-oxybis(benzoate)], have
been synthesized under hydrothermal conditions, and characterized by elemental analysis, and IR
¯
and UV/Vis spectra. Crystal data for 1: C33H21FN4NiO6, triclinic, space group P1, a = 13.8490(10),
◦
3
˚
˚
b = 14.932(2), c = 14.993(3) A, α = 107.534(4), β = 94.670(4), γ = 103.836(5) , V = 2830.9(7) A ,
Z = 4. Crystal data for 2: C52H36F2N8O8Pb, orthorhombic, space group Pna21, a = 16.256(4),
b = 16.085(5), c = 17.810(3) A, V = 4657 (2) A , Z = 4. In 1, OBA dianions bridge Ni(II) atoms
to form two crystallographically distinct chains. These chains are further extended into a 2D
supramolecular architecure through π-π interactions. In 2, each OBA dianion links neighboring
Pb(II) atoms to yield a helical chain. Further, π-π interactions among adjacent chains give rise to
a 3D supramolecular architecture.
3
˚
˚
Key words: Crystal Structure, Coordination Polymer,
2-(4-Fluorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, 4,4’-Oxybis(benzoate)
Introduction
For example, 1,10-phenanthroline (phen) has been
widely used to construct supramolecular architectures
In recent years, the design and synthesis of coor- because of its excellent coordination ability and large
dination polymers has attracted much attention from conjugated system that can easily form π-π inter-
chemists, not only for their great potential for a wide actions [14]. However, less attention has been paid
range of applications, such as in catalysts and sensors, to its derivative 2-(4-fluorophenyl)-1H-imidazo[4,5-
and in gas storage and separation, but also owing to f]1,10phenanthroline (L) [13 – 15].
their intriguing framework architectures and topolo-
In this work, two coordination polymers,
gies [1 – 6]. Usually, the structure of a coordination [Ni(H2O)(L)(OBA)] (1) and [Pb(L)2(OBA)]·3H2O
polymer can be controlled and modified by selecting (2), have been synthesized under hydrothermal con-
the coordination geometry preferred by the metal ion ditions. Their structures have been determined by
and the chemical structure of the organic ligand [7 – 9]. single-crystal X-ray diffraction analyses, and the
In this regard, dicarboxylate and N-containing chelat- compounds characterized by IR and UV/Vis spectra,
ing ligands are excellent candidates for the construc- elemental analyses, and magnetic susceptibility data.
tion of coordination polymers [10 – 12]. The 4,4’-
oxybis(benzoate) dianion (L) is an example of a flex- Results and Discussion
ible dicarboxylate owing to the presence of an ether
linkage between the two rigid phenylene rings. On Structure description of 1
the other hand, N-containing chelating ligands have
been intensely investigated as auxiliary ligands for
Selected bond lengths and angles for
the construction of novel coordination polymers [13]. [Ni(H2O)(L)(OBA)] (1) and [Pb(L)2(OBA)]·3H2O (2)
c
ꢀ 2012 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
Fig. 1 (color online). OR-
TEP view of the two crys-
tallographically indepen-
dent molecular entities of
1 showing the local co-
ordination environment of
the Ni(II) centers (15%
probability displacement
ellipsoids).
are listed in Table 1. The asymmetric unit of 1 contains
two crystallographically independent Ni(II) atoms,
two unique OBA dianions, two unique L ligands,
and two unique coordinated water molecules (Fig. 1).
Each Ni(II) atom is six-coordinated by three oxygen
atoms from two different OBA anions and one water
molecule, and two nitrogen atoms from one L ligand
in a distorted octahedral environment. Two nitrogen
atoms (N5, N6 for Ni1 and N1, N2 for Ni2) and two
oxygen atoms (O10, O1W for Ni1 and O2, O2W for
Ni2) constitute the equational plane, while two oxygen
atoms (O9, O7i for Ni1 and O1, O5i for Ni2) occupy
the axial positions. The Ni–O bond lengths range
˚
from 2.015(3) to 2.145(3) A, and the Ni–N distances
˚
vary from 2.06(4) to 2.075(4) A. Each OBA anion
bridges two neighboring Ni(II) atoms to yield two
crystallographically independent chains (Fig. 2). It is
Fig. 2 (color online). View of the 2D supramolecular archi-
tecture of 1 formed by π-π interactions.
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D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
801
Table 1. Selected bond
lengths (A) and angles
(deg) for 1 and 2 with esti-
mated standard deviations
in parenthesesa.
Compound 1
Distances
Ni(1)–O(7)i
Ni(1)–O(10)
Ni(1)–O(9)
Ni(1)–O(1W)
Ni(1)–N(5)
˚
2.015(3)
2.105(3)
2.127(3)
2.064(3)
2.075(4)
2.062(3)
Ni(2)–O(5)i
Ni(2)–O(1)
Ni(2)–O(2)
Ni(2)–O(2W)
Ni(2)–N(1)
Ni(2)–N(2)
2.093(3)
2.111(3)
2.145(3)
2.081(3)
2.072(3)
2.060(4)
Ni(1)–N(6)
Angles
O(7)i–Ni(1)–N(6)
O(7)i–Ni(1)–O(1W)
O(7)i–Ni(1)–N(5)
O(1W)–Ni(1)–N(5)
N(6)–Ni(1)–O(10)
N(5)–Ni(1)–O(10)
N(6)–Ni(1)–O(9)
N(5)–Ni(1)–O(9)
O(10)–Ni(1)–O(9)
N(6)–Ni(1)–O(1W)
N(6)–Ni(1)–N(5)
O(7)i–Ni(1)–O(10)
O(1W)–Ni(1)–O(10)
O(7)i–Ni(1)–O(9)
O(1W)–Ni(1)–O(9)
Compound 2
95.91(12)
93.15(11)
88.53(12)
172.95(13)
163.59(11)
93.66(12)
102.58(11)
93.69(12)
62.42(10)
92.90(13)
80.12(13)
99.11(11)
92.83(12)
161.49(11)
86.88(11)
N(2)–Ni(2)–O(5)i
O(2W)–Ni(2)–O(5)i
N(1)–Ni(2)–O(5)i
N(2)–Ni(2)–O(2W)
N(1)–Ni(2)–O(2)
N(2)–Ni(2)–O(1)
N(1)–Ni(2)–O(1)
O(2)–Ni(2)–N(2)
O(1)–Ni(2)–O(2)
N(1)–Ni(2)–O(2W)
N(2)–Ni(2)–N(1)
O(5)i–Ni(2)–O(2)
O(2W)–Ni(2)–O(2)
O(5)i–Ni(2)–O(1)
O(2W)–Ni(2)–O(1)
93.65(12)
91.78(12)
98.58(12)
171.47(12)
159.52(12)
89.39(13)
98.53(12)
93.10(13)
61.89(10)
92.72(13)
79.97(14)
101.10(11)
92.31(12)
162.89(11)
87.35(12)
Distances
Pb(1)–O(4)i
2.458(4)
2.86(2)
2.509(5)
2.773(6)
Pb(1)–O(1)
Pb(1)–N(1)
Pb(1)–N(5)
2.770(4)
2.519(6)
2.778(5)
Pb(1)–O(5)i
Pb(1)–N(2)
Pb(1)–N(6)
Angles
O(4)i–Pb(1)–N(2)
O(4)i–Pb(1)–N(1)
O(4)i–Pb(1)–N(6)
N(1)–Pb(1)–N(6)
N(2)–Pb(1)–N(5)
O(4)i–Pb(1)–O(1)
N(1)–Pb(1)–O(1)
O(1)–Pb(1)–N(5)
79.53(15)
75.61(16)
157.16(17)
86.86(17)
129.13(14)
73.17(15)
134.12(17)
143.47(14)
N(6)–Pb(1)–N(5)
N(2)–Pb(1)–N(1)
N(2)–Pb(1)–N(6)
O(4)i–Pb(1)–N(5)
N(1)–Pb(1)–N(5)
N(2)–Pb(1)–O(1)
O(1)–Pb(1)–N(6)
59.81(17)
64.77(17)
79.79(17)
130.05(15)
82.31(16)
77.07(15)
111.27(17)
a Symmetry transformations used to generate equivalent atoms for 1: i x, y, z−1; for 2: i −x−2, −y, z−1/2.
Fig. 3 (color online). Schematic representation of the 2D
supramolecular architecture of 1 formed by π-π interactions.
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802
D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
noteworthy that the L ligands are only located on one
side of the chain, with π-π stacking interactions be-
tween neighboring chains (with a centroid-to-centroid
˚
distance of 3.710 A and a face-to-face distance of
˚
3.524 A). Through these π-π stacking interactions,
neighboring chains are interlinked to generate a 2D
supramolecular layer (Figs. 2 and 3). It is noted that
a large number of 1D coordination polymers have
been reported so far, however, examples with two
crystallographically independent chains are rarely
observed in this system [13 – 15].
Structure description of 2
As shown in Fig. 4, the asymmetric unit of 2 con-
tains one Pb(II) atom, one OBA dianion, two L lig-
ands, and three water molecules. Each Pb(II) atom is
seven-coordinated by three carboxylate oxygen atoms
from two different OBA dianions, and four nitrogen
atoms from two L ligands. The Pb–N distances range
Fig. 4 (color online). ORTEP view of 2 showing the local co-
ordination environment of the Pb(II) center with hydrogen
atoms and non-coordinated water molecules omitted for clar-
ity (15% probability displacement ellipsoids).
˚
from 2.458(4) to 2.778(5) A, and the Pb–O distances
˚
are 2.458(4) and 2.86(2) A. These distances are close
to those reported for [Pb(L)(1,3-bdc)]·2.5H2O (1,3-
bdc = 1,3-benzenedicarboxylate) [16]. The OBA an- an encompassing sphere, however, holodirected refers
ions are in a bidentate bridging mode and link two to those cases where the bonds to the ligand atoms
neighboring Pb(II) atoms to form a fascinating helical are located throughout the surface of an encompass-
˚
chain with a Pb···Pb distance of 15.632 A (Fig. 5). Dif- ing sphere. In compound 2, the arrangement of three
ferent from those of 1, in 2, the L ligands are attached O and four N atoms for the seven-coordinated Pb(II)
on both sides of the helical chains. π-π Stacking in- atom suggests a gap or hole in the coordination geom-
teractions among neighboring chains (with a centroid- etry around this atom. Thus, its coordination sphere is
˚
centroid distance of 3.459 A and a face-to-face dis- hemidirected [16].
˚
tance of 3.361 A) extend the adjacent helical chains
It is noteworthy that the structure of 2 is entirely
different from that of [Pb(L)(1,3-bdc)]·2.5H2O [16],
into a 3D supramolecular architecture (Fig. 6).
Generally, the geometries of Pb(II) complexes can where the Pb(II) atoms are bridged by the 1,3-bdc
be classified as holo- and hemidirected [15]. Hemidi- ligands to yield a linear chain structure. The lig-
rected refers to Pb(II) complexes where the bonds to ands L are only located on one side of the chain,
the ligand atoms are directed through only part of where π-π interactions among neighboring chains
Fig. 5 (color online). View
of the helical chain struc-
ture of 2.
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D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
803
Fig. 7. Plot of the temperature dependence of χm T (open
squares) and χm−1 (open triangles) for compound 1.
Fig. 6 (color online). View of the 3D supramolecular archi-
tecture of 2 formed by π-π interactions.
to 380 nm for 1 and from 200 to 400 nm for 2 prob-
ably originate from the π → π∗ transitions of the lig-
ands [18].
result in a supramolecular ladder. It should be
pointed out that compound 2 and the related com-
pound [Pb(OBA)(L’)2]·2H2O (L’ = 4-(1H-1,3,7,8-
tetraazacyclopenta[l]phenanthren-2-yl)phenol) have
similar N-donor ligands [17], but they show different
chain structures. Compound 2 displays a helical chain
structure with a Pb···Pb···Pb angle of 69.45◦, whereas
the other reported compound shows a more linear
chain structure with the Pb···Pb···Pb angle of 155.98◦.
Magnetic properties
The temperature-dependent magnetic susceptibil-
ity of compound 1 has been measured at an applied
magnetic field of 1 kOe (1 kOe = 7.96 × 104 A m−1
)
in the temperature range of 2 – 300 K (Fig. 7). For
1, the χmT value at 300 K is 1.046 cm3 mol−1 K,
which is corresponding to the expected value of non-
interacting Ni(II) ions [19]. Upon cooling, the val-
ues of χmT gradually increase, exhibit a maximum
value of 1.138 cm3 mol−1 K at 100 K, and then keep
almost constant from 100 to 26 K before going down
quickly to a minimum value of 0.622 cm3 mol−1 K at
2 K. This feature shows the occurrence of a weak fer-
romagnetic coupling between the Ni(II) ions [20]. The
magnetic susceptibility in the temperature range of
300 – 26 K obeys the Curie-Weiss law with the Curie
constant C = 1.067 cm3 mol−1 K, and the Weiss con-
stant Θ = 3.738 K.
IR spectra
The OH stretching vibrations of water molecules in
complexes 1 and 2 are observed at 3364–3437 and
3071 – 3454 cm−1, respectively. The strong peaks at
1684 and 1596 cm−1 for 1 and at 1691 and 1526 cm−1
for 2 are assigned to the asymmetric and symmetric
stretching vibrations of the OBA carboxylate groups.
The bands at 1160 and 1408 cm−1 can be attributed to
the C=N and C-N stretching vibrations of the L lig-
ands [18].
Experimental Section
UV/Vis absorption spectra
General
All materials were of analytical or reagent grade and used
as received without further purification. Elemental analysis
was carried out with a Perkin-Elmer 240C analyzer. The
FT-IR spectra were recorded from KBr pellets in the range
4000 – 400 cm−1 on a Mattson Alpha-Centauri spectrometer.
The UV/Vis absorption spectra of compounds 1 and
2 were measured in the crystalline state at room tem-
perature. The absorption bands of compound 1 from
550 to 700 nm may result from the d-d spin-allowed
transition of the d8 (Ni2+) ion. The bands from 200 Diffuse reflectance UV/Vis spectra were measured from 200
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D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
Table 2. Crystal structure
data for 1 and 2.
Compound
Formula
1
2
C33H21FN4NiO6
C52H36F2N8O8Pb
Mr
647.25
1146.08
Crystal size, mm3
Crystal system
Space group
0.27×0.22×0.17
triclinic
¯
P1
0.29×0.23×0.19
orthorhombic
Pna21
˚
a, A
13.8490(10)
14.932(2)
14.993(3)
107.534(4)
94.670(4)
103.836(5)
2830.9(7)
4
16.256(4)
16.085(5)
17.810(3)
90
90
90
4657(2)
4
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
3
˚
V, A
Z
Dcalcd, g cm−3
µ(MoKα ), mm−1
F(000), e
1.52
0.7
1328
1.64
3.7
2272
hkl range
θ range, deg
Refl. collect. / unique /Rint
Data / ref. parameters
R1 / wR2 [I >2 σ(I)]
R1 / wR2 (all data)
GoF (F2)
−16 → 12, −17 → 15, ±17
1.44 – 25.03
17788 / 9987 / 0.0383
9987 / 818
0.0406 / 0.0846
0.0832 / 0.0904
0.810
−15 → 19, −15 → 19, −21 → 17
1.71 – 25.03
18132 / 7623 / 0.0268
7623 / 589
0.0263 / 0.0619
0.0396 / 0.0633
0.923
x (Flack)
∆ρmax/min, e A
–
−0.003(5)
−3
˚
0.87 / −0.88
0.66 / −0.75
to 800 nm using barium sulfate as standard on a Varian Cary 9.78; found C 54.62, H 3.01, N 10.33. − IR (KBr, cm−1):
500 spectrometer. Temperature-dependent magnetic suscep- ν = 3454w, 3071w, 1684w, 1691s, 1608m, 1526s, 1484s,
tibility data for compound 1 were obtained on a Quantum 1390s, 1289s, 1243s, 1148s, 1072m, 1025w, 947w, 842s,
Design MPMSXL SQUID magnetometer under an applied 806m, 730m, 618m.
field of 1 kOe over the temperature range of 2 – 300 K.
X-Ray structure determinations
Syntheses of compounds 1 and 2
Single-crystal X-ray diffraction data for 1 and 2 (Table 2)
were recorded on an Oxford Diffraction Gemini R Ultra
NiCl2·6H2O (1 mmol), L (1 mmol) and H2OBA (1 mmol)
were dissolved in 10 mL distilled water, followed by addi-
tion of triethylamine until the pH value of the system was
adjusted to between 5 and 6. The resulting solution was
stirred for about 30 min at r. t., sealed in a 23 mL Teflon-
lined stainless-steel autoclave and heated at 421 K for 3 d
under autogeneous pressure. After the mixture had been
cooled to room temperature at a rate of 10 oC·h−1, blue
crystals of 1 were obtained. Yield: 19% based on Ni(II). −
Anal. for C33H21FN4NiO6 (%): calcd. C 61.24, H 3.27, N
8.66; found C 61.53, H 3.40, N 8.29. − IR (KBr, cm−1):
ν = 3437m, 3364w, 1773w, 1684m, 1596s, 1533s, 1496m,
1408s, 1243s, 1160s, 1065w, 1000w, 954w, 877w, 800w,
776w, 723w, 641w. The preparation of 2 was similar to that
of 1 except that Pb(NO3)2 (0.5 mmol) was used instead of
NiCl2·6H2O (0.1 mmol). Crystals of 2 suitable for single-
crystal X-ray diffraction analysis were collected by filtra-
tion, washed several times with distilled water and dried in
air at ambient temperature. Yield 39% based on Pb(II). −
diffractometer with graphite-monochromatized MoKα radi-
˚
ation (λ = 0.71073 A) at 293 K. The structures were solved
by Direct Methods with SHELXS-97 [21] and refined by full-
matrix least-squares techniques using the SHELXL-97 [22]
program. Non-hydrogen atoms were refined with anisotropic
displacement parameters. The hydrogen atoms attached to
the carbon atoms were generated geometrically. Some wa-
ter H atoms of 1 and 2 were not located in difference Fourier
maps.
CCDC 875856 (1) and 875857 (2) contain the supple-
mentary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data request/
cif.
Acknowledgement
This work was supported by the National Science Foun-
Anal. for C52H36F2N8O8Pb (%): calcd. C 54.49, H 3.17, N dation of China (no. 21171026).
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D. Li et al. · Ni(II) and Pb(II) Coordination Polymers
805
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