Zn(II) porous material assembled from v-shaped dicarboxylate ligand and n-donor ancillary ligand

Article abstract of DOI:10.1080/15533170903433170

A new porous metal-organic framework, [Zn(fipbb)(bpp)]_n (1) (H₂fipbb = (4,4′-(hexafluoroisopropylidene)bis(benzoic acid) and bpp = 1,3-bis(4-pyridyl)propane), constructed from mixed flexible co-liagnds, has been synthesized under mil

Full text of DOI:10.1080/15533170903433170

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:658–661, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170903433170
Zn(II) Porous Material Assembled from V-Shaped
Dicarboxylate Ligand and N-Donor Ancillary Ligand
Yaru Liu1 and Yutian Pan2
1School of Science, North University of China, Taiyuan, Shanxi, P. R. China
2School of Mechatronic Engineering, North University of China, Taiyuan, Shanxi, P. R. China
On the other hand, supramolecuar networks with helicity are
highly fascinating. The chiral nature in helical arrangement may
also be associated with enantioselectivity, models of biological
systems and optoelectronic materials. Therefore, the exploit of
new systems possessing specific helicity has been an intensive
research field just now. It has been proved that by the appropriate
assembly of metal ions and longer and flexible organic ligand,
multifarious discrete helicates and coordination polymers con-
sisting of infinite helices can be rationally achieved.[12−15] In
recent years, the employment of mixed flexible ligands during
the self-assembly process has gradually become an effective
approach, which is expected to obtain networks with more di-
verse structural motifs compared to using only one type of lig-
ands. Thus, the auxiliary ligands containing an N-donor, such
as biprydidyl-like ligand, are introduced into the reactions sys-
tems so as to tune up metal coordinated sites.[16] Taking all
the above discussion into account, we focus our attention on
a V-shaped flexible 4,4ꢀ-(hexafluoroisopropylidene)bis(benzoic
acid)(H2fipbb) dicarboxylate ligand, whose has been employed
to build novel coordination polymer considering the following
viewpoints; (i) the rotate randomly backbones gives the poten-
tial ability to construct helical assembly; and ( ii) the potential
longer molecular backbones of such building blocks may lead
to the formation of porous MOFs with channels. Fortunately,
we have successfully synthesized a new coordination polymer,
[Zn(fipbb)(bpp)]n (1) (bpp = 1,3-bis(4-pyridyl)propane), which
is 2D open grid structure containing three types of helical chains.
A new porous metal-organic framework, [Zn(fipbb)(bpp)]n (1)
(H2fipbb = (4,4ꢀ-(hexafluoroisopropylidene)bis(benzoic acid) and
bpp = 1,3-bis(4-pyridyl)propane), constructed from mixed flex-
ible co-liagnds, has been synthesized under mild condition and
characterized by elemental analysis, IR and single-crystal X-ray
diffraction analysis. Compound 1 exhibits (4,4) grid network con-
taining multi-helical chains. Furthermore, two adjacent layers are
displaced by about one half of the polymer period along the di-
rection of extension and stacked with iterative sequence of ABAB.
This result revealed that the coordination mode of fipbb and metal
ion play important roles in controlling the resulting coordination
framework.
Keywords crystal structure, helical chain, porous network, Zn com-
plex
1. INTRODUCTION
Presently, the design and synthesis of new materials “on de-
mand” is becoming increasingly significant. Keeping this in
mind, new outstanding possibilities are presented in the area of
the synthesis of organo-inorganic polymeric materials, where a
particularly promising method to attaching to the predesign of
a material is a building-block approach.[1−5] Thus far, porous
coordination polymers have centered on the assembly of linear
rigid polycarboxylates, especially dicarboxylates and d-block
metal ions, as these metal ions have low coordination num-
ber and are easily connected to form kinds of frameworks.[6−8]
Yaghi et al. have successfully constructed plenty of metal-
organic frameworks (MOFs) using the self-assembly of d-block
metal ions and rigid dicarboxylates.[9−11] In contrast to the rigid
ligands, the conformation of flexible ones is variable; thus, they
can meet the coordination geometrical requirement of metal ions
through changing their conformation, which may provide more
possibility for the construction of novel architectures.
2. EXPERIMENTAL
Materials and Physical Measurements
All the reagents and solvents for synthesis and analysis were
commercially available and used directly. Elemental analyses
for carbon, hydrogen and nitrogen were performed on a Vario
EL III elemental analyzer. The infrared spectra (4000 ∼ 600
cm−1) were recorded by using KBr pellet on an AVATAR-370
(Nicolet) IR spectrometer (Japan). The crystal determination
was performed on a Bruker SMART APEX II CCD diffrac-
tometer (Germany) equipped with graphite-monochromatized
Received 1 July 2009; accepted 20 August 2009.
Address correspondence to Yaru Liu, School of Science, North Uni-
versity of China, Taiyuan 030051, Shanxi, China. E-mail: liuyaruzb@
126.com
˚
MoKα radiation (λ = 0.71073 A) (Germany).
658

ZN(II) POROUS MATERIAL
659
TABLE 1
Crystallographic data for 1
TABLE 2
◦
˚
Selected bond lengths (A) and angles ( ) for 1
Zn(1)-O(1)
Zn(1)-N(1)
1.9447(17) O(1)-Zn(1)-N(1) 114.61(8)
2.0677(19) N(1)-Zn(1)-N(1) 101.75(10)
Empirical formula
C30H22F6N2O4Zn
653.87
298(2)
Formula weight
Temperature (K)
O(1)-Zn(1)-O(1) 133.11(12) C(8)-O(1)Zn(1) 110.69(16)
˚
Wavelength (A)
0.71073
monoclinic
C2/c
Crystal system
Space group
Unit cell dimensions
monochromated Mo Kα radiation. The structure was solved
using direct methods and successive Fourier difference synthe-
sis (SHELXS-97),[17] and refined using the full-matrix least-
squares method on F2 with anisotropic thermal parameters for
all non-hydrogen atoms (SHELXL-97).[18] Metal atoms in all
the complexes were located from the E-maps and other non-
hydrogen atoms were located in successive difference Fourier
syntheses. All other hydrogen atoms were included in calculated
positions and refined with isotropic thermal parameters riding
on those of the parent atoms. The final agreement factor val-
ues are R1= 0.032, wR2= 0.1082, w= 1/[σ2(F0)2+ (0.08P)2]
whereP= (F02+ 2Fc2)/3. A summary of the crystallographic
data is given in Table 1. Selected bond distances and angles and
hydrogen-bonding geometric data are given in Table 2 and Table
3, respectively.
˚
a= 12.4777(19) A
˚
˚
b= 17.797(3) A
c= 13.250(2) A
β = 105.063(2)◦
3
˚
Volume, Z
2841.3(8)A , 4
Calculated density (Kg/m3)
Crystal size (mm3)
1.529
0.25×0.21×0.15
θ Range for data collection (◦) 2.04–25.20
Reflections collected
Independent reflection
Final R indices [I> 2σ (I)]
R indices (all data)
7021
2545
R1= 0.0320, wR2= 0.1082
R1= 0.0379, wR2= 0.1143
Synthesis of the Complex
To an methane aqueous solution (10 mL) containing H2fipbb
(0.2 mmol) was added Zn(NO3)2·4H2O (0.12 mmol) in water
at 30◦C. The pH of the resulting solution was adjusted to 6
using dilute NaOH (0.1 mol/L) and kept at 105◦C for two hours
to prepare compound 1. From that solution, colourless crystals
suitable for X-ray measurements were obtained. Yield: 58%.
Anal. calc. (%) for C30H22F6N2O4Zn: C, 55.10; N, 4.28; H, 3.39;
Found: C, 55.15; N, 4.26; H, 3.37. IR (KBr cm−1): 3118 (m),
2903 (w), 1615 (s), 1539 (s), 1398 (s), 1371 (s), 1248 (m), 1220
(w), 1182 (w), 1032 (m), 1021 (w), 982 (w), 832 (s).527(m).
3. RESULTS AND DISCUSSION
In compound 1, X-ray single-crystal structure determination
reveals that the asymmetric unit consists of one crystallograph-
ically Zn(II) ion, one Hfipbb dianion and one bpp ligand, as
illustrated in Figure 1. All carboxylic groups of H2fipbb are
deprotonated, in agreement with the IR data in which no char-
acteristic absorption bands of the -COOH group at 1700–1750
cm−1 are observed. For complex 1, the difference between the
asymmetric and symmetric stretches, ꢀνas(COO−)–νas(COO−),
are on the order of 200 cm−1 indicating that carboxyl groups
are either free or coordinated to the metal in a mono-dentate
fashion, consistent with the observed X-ray crystal structures of
1. The Zn has a tetrahedron coordination environment to con-
Crystallographic Data Collection and Structure
Determination
Single-crystal data were collected at 298(2) K on a struct from two O atoms (O1 and O1A) from two separated
Bruker Smart Apex II diffractometer equipped with graphite- fipbb ligands, and two N atoms (N1 and N2) from two different
FIG. 1. Coordination environment of Zn(II) in 1.

660
Y. LIU AND Y. PAN
TABLE 3
Selected H-bonding geometric data (A, ) for 1
◦
˚
D–H· · ·A
D· · ·A
D–H· · ·A symmetry codes
C1–H1· · ·O1
C6–H6B· · ·O2
3.0773(3) 113(6)
3.4840(2) 155(4)
1/2 + x,1/2 + y,z
C118–H11· · ·F1 2.9413(7) 107(8)
bpp ligands. The Zn-O and Zn-N distances are good agreed with
related Zn-carboxylate polymers.[15] The Zn unit show in Figure
2a is further extended through the connection of bpp ligands,
and results in the formation of a helical chain along the a axis
˚
and the pitch of the screw is 9.3 A. The bpp molecule exhibits a
TG conformation in the compound. As exhibited in Figure 2b,
the flexible V-shaped fipbb dianion ligand joins adjacent Zn1
atoms and leads to another helical chain along the b direction
FIG. 3. Corrugated 2D grid network in 1.
˚
and the pitch of the screw is 13.5 A, the torsion dihedral angle
the {[Co4(OH)(fipbb)(Hfipbb)(bpp)2].H2O}n and compound 1
in the prescience of same linkages indicate that the metal ions
can modulate the resulting structure, this result may be ascribed
to the radium difference of metal ions. The dimensions of the
of phenyl rings of fipbb is 69.5(3)◦. As shown in Figure 2c, the
adjacent bpp and fipbb connect Zn1 center atoms into a new
˚
helical chain the pitch of the screw is 22.8 A. The entire 2D net-
2
work of compound 1 is archiral due o the phenomenon that the
left-handed screws (L-heix) and the right-handed ones (R-helix)
arrange alternatively in the bc plane.
˚
net are 14.13 × 15.71 A , corresponding to the distance between
neighboring centers of Zn subunits at their corner. The covalent
skeleton of this 2D sheet can be also described as a unique heli-
cal tubular double layer in which the left and right helical chains
appear alternatively by sharing Zn subunits. By reducing multi-
dimensional structures to simple node-and-connection reference
nets, it plays an essential role in structural simplification. The
di-connector bpp ligands and fipbb occupy the opposite sides
and connect the center metal ions, extending the structural motif
into grid 2D framework (Figure 3). Thus, Zn atoms are depicted
as four–connected node, the framework can be represented sim-
ply by connecting the Zn nodes according to the connectiv-
ity defined by the bpp and fipbb ligands with (4,4) topology.
Furthermore, two adjacent layers are displaced by about one
half of the polymer period along the direction of extension and
stacked with iterative sequence of ABAB, as shown in Figure
4. The 2D sheets are further extended comparable C...H O and
C...H F interactions (see Table 3) to shape a 3D supramolecular
Significantly the bent fipbb and bpp moieties link Zn atoms
alternatively, which results into an undulating sheet net wth
a rhombic window, as shown in Figure 3. A relative coor-
dination polymer {[Co4(OH)(fipbb)(Hfipbb)(bpp)2].H2O}n ex-
hibits a three-dimensional pillared helical layer open net-
works with six-connected self-interpenetrating topology based
on a mixed binuclear paddle-wheel cluster and tetranuclear
cobalt(II) steplike cluster.[13] The structural difference between
FIG. 2. A viewing illustration of the three types of single-stranded helical
chains in 1.
FIG. 4. Schematic illustration of stacked with iterative sequence of ABAB
fashion.

ZN(II) POROUS MATERIAL
661
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Assembly of Zn(II) salt with V-shaped dicarboxylate in the
presence of flexible N-donor ligand leads to a new porous
coordination polymer containing muti-helical chains. This re-
sult revealed that the coordination mode of fipbb and metal
ion play important roles in controlling the resulting coordina-
tion framework. It is believed that the preliminary result pre-
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sign and synthesis of MOF material with specific structure and
properties.
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