Synthesis, crystal structure, and luminescent property of one 2-D zinc(II) coordination polymer with 5-methoxyisophthalate and 1,4-bis(imidazol-1-yl)- butane ligands

Article abstract of DOI:10.1080/15533174.2012.684266

A two-dimensional (2-D) coordination polymer, {[Zn(L) (bimb)] ·(H₂O)}n (1) (H2L=5-methoxyisophthalate, bimb=1,4- bis(imidazol-1-yl)-butane), was synthesized and structurally characterized by single-crystal X-ray diffraction analysis. This complex belongs to monoclinic system with space group P21/n, and exhibits a 2-D corrugated (4,4) net containing alternately arranged leftand right-handed helical chains. In addition, such 2-D layers are further interlinked by the interlayer supramolecular interactions, generating an overall 3-D porous framework. Studies on luminescent property of 1 show the solid-state emission originating from an intraligand π → π* transition of L ligand. Copyright Taylor & Francis Group, LLC 2013.

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Synthesis, Crystal Structure, and Luminescent Property
of One 2-D Zinc(II) Coordination Polymer With 5-
methoxyisophthalate and 1,4-bis(imidazol-1-yl)-butane
Ligands
Xiao-Gang Yang a & Shao-Ming Fang a
a Zhengzhou University of Light Industry, Henan Provincial Key Laboratory of Surface &
Interface Science , Zhengzhou , Henan , P. R. China
Accepted author version posted online: 12 Sep 2012.Published online: 03 Dec 2012.
To cite this article: Xiao-Gang Yang & Shao-Ming Fang (2013) Synthesis, Crystal Structure, and Luminescent Property of
One 2-D Zinc(II) Coordination Polymer With 5-methoxyisophthalate and 1,4-bis(imidazol-1-yl)-butane Ligands, Synthesis and
Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1, 76-79, DOI: 10.1080/15533174.2012.684266
To link to this article: http://dx.doi.org/10.1080/15533174.2012.684266
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:76–79, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.684266
Synthesis, Crystal Structure, and Luminescent Property
of One 2-D Zinc(II) Coordination Polymer With
5-methoxyisophthalate and 1,4-bis(imidazol-1-yl)-butane
Ligands
Xiao-Gang Yang and Shao-Ming Fang
Zhengzhou University of Light Industry, Henan Provincial Key Laboratory of Surface & Interface
Science, Zhengzhou, Henan, P. R. China
boxylic acids, have been extensively used in the preparation of a
variety of metal-carboxylate complexes owing to their rich coor-
dination modes.[5,6] In contrast, coordination polymers with the
5-methoxyisophthalate ligand have rarely been reported.[7,8] On
the other hand, the introduction of additional N-donor ligands to
such synthetic systems can modify the structures and properties
of the resulting materials. Bis(imidazole) ligands with –CH2–
spacers are good candidate for N-donor bridging ligands. The
two imidazole rings can freely twist around the –CH2– group to
meet the requirements of the coordination geometries of metal
atoms in the assembly process.[9] In this context, we report
the synthesis, crystal structure, and luminescent property of one
new 2-D zinc(II) complex, {[Zn(L)(bimb)]·(H2O)}n (1) (H2L =
5-methoxyisophthalate, bimb=1,4-bis(imidazol-1-yl)-butane).
A
two-dimensional (2-D) coordination polymer, {[Zn(L)
(bimb)]·(H2O)}n (1) (H2L=5-methoxyisophthalate, bimb=1,4-
bis(imidazol-1-yl)-butane), was synthesized and structurally char-
acterized by single-crystal X-ray diffraction analysis. This complex
belongs to monoclinic system with space group P21/n, and exhibits
a 2-D corrugated (4,4) net containing alternately arranged left-
and right-handed helical chains. In addition, such 2-D layers are
further interlinked by the interlayer supramolecular interactions,
generating an overall 3-D porous framework. Studies on lumines-
cent property of 1 show the solid-state emission originating from
an intraligand π→π∗ transition of L ligand.
Keywords 5-methoxyisophthalate, crystal structure, luminescent
property, zinc(II) complex
INTRODUCTION
EXPERIMENTAL
The rational design and controlled synthesis of metal–organic
frameworks (MOFs), also known as coordination polymers,
has attracted considerable attention not only on their intriguing
structural diversity but also on their potential applications.[1–3]
In this field, mixed-ligand MOFs, most of which contain N-
containing ligands introduced into metal-polycarboxylate sys-
tems, have proven to be a good choice for the construction of
such networks. The combination of different ligands may re-
sult in greater tunability of structural frameworks than that with
single ligands.[4]
Materials and General Methods
All the starting reagents and solvents were commercially
available and used as received without further purification. IR
spectra were measured on a TENSOR 27 (Bruker, Germany) FT-
IRspectrometerwithKBrpellets intherangeof4000–400cm−1
.
Elemental analyses of C and H were performed on a Vario EL III
elemental analyzer (Germany). The emission/excitation spectra
were recorded on an F-7000 (HITACHI, Japan) spectropho-
tometer at room temperature.
Among the organic ligands, the versatile carboxyl com-
pounds, especially aromatic benzene–based di- or multicar-
Synthesis of the Complex 1
A mixture of H2L (0.10 mmol), bimb (0.10 mmol),
Zn(OAc)2·2H2O (0.10 mmol), NaOH (0.10 mmol), and H2O
(16 mL) was placed in a Teflon-lined stainless steel vessel,
heated to 140◦C for three days, and then cooled to room tem-
perature over 24 h. Colorless block crystals of 1 were obtained.
Yield: 45% (based on Zn). Anal. Calcd. (%) for C19H22N4O6Zn:
C 48.78, H 4.74, N 11.98. Found (%): C 48.70, H 4.65, N 11.89.
IR (KBr pellet, cm−1): 3412 (s), 2909 (m), 2051 (m), 1628 (s),
1573 (s), 1360 (s), 1112 (s), 1039 (m), 860 (m), 773 (m), 724
(m), 650 (m).
Received 29 February 2012; accepted 1 April 2012.
This work was supported by the National Natural Science Fund
of China (21171151), Henan Outstanding Youth Science Fund
(114100510017), and Program for New Century Excellent Talents in
University (NCET-10-0143).
Address correspondence to Xiao-Gang Yang, Zhengzhou Univer-
sity of Light Industry, Henan Provincial Key Laboratory of Surface
& Interface Science, Zhengzhou, Henan 450002, P. R. China. E-mail:
yxg2233@126.com
76

2-D ZINC(II) COORDINATION POLYMER
77
TABLE 1
Crystallographic data for 1
TABLE 3
Selected H-bonding geometries (Å, ◦) for 1
Empirical formula
Formula weight
Crystal system
Space group
a/Å
C19H22N4O6Zn D−H···A
d(D−H) d(H···A) d(D···A) D−H···A
467.78
Monoclinic
P21/n
C15–H15A···O2a
0.97
0.96
0.83
0.96
0.93
2.54
2.57
2.16
3.02
3.16
3.451(6)
3.465(8)
2.761(6)
3.777(7)
3.667(6)
156
155
129
136
116
C9–H9A···N4b
O6–H2W···O2
C9–H9B···Cg1c
C19–H6A···Cg2d
Symmetry codes for 1: a = –x + 3/2, y + 1/2, –z + 1/2; b = –x
+ 3/2, y – 1/2, –z + 1/2; c = –x, –y, –z; d = x + 1, y, z. Cg1 is the
centroid of the C1–C2–C3–C4–C5–C6 phenyl ring of L ligand. Cg2
is the centroid of the N1–C10–C11–N2–C12 imidazole ring of bimb
ligand.
8.303(3)
17.057(5)
17.057(5)
90
96.465(4)
90
b/Å
c/Å
α/◦
β/◦
γ /◦
V/Å3
2400.4(12)
4
Z
D/g cm−3
μ/mm−1
Rint
1.294
1.061
0.0567
1.086
experimental details for structural analyses are summarized in
Table 1. Selected bond lengths and angles as well as hydrogen-
bonding geometries are listed in Tables 2 and 3.
GOF
T /K
296(2)
0.0610/0.1755
0.0870/0.1900
RESULTS AND DISCUSSION
a
R1 /wR2b [I >2σ(I)]
a
R1 /wR2b (All data)
Synthesis and General Characterization
A direct mixing of the solutions of metal salt and organic
ligand usually results in white precipitations that are difficult to
be structurally characterized, and thus a hydrothermal method
was applied in this study, which has been proven to be a power-
ful approach for the preparation of various crystalline materials.
The compositions of 1 were confirmed by microanalytical and
IR techniques. The absence of characteristic absorption peaks of
carboxyl in the IR spectra of 1 indicates the complete deproto-
nation of H2L, and as a result, the antisymmetric and symmetric
stretching vibrations of carboxylate are found at 1573 cm−1 and
1360 cm−1, respectively.
aR1 = ꢀ(||Fo| − |Fc||)/ꢀ|Fo|. bwR2 = [ꢀw(|Fo|2 − |Fc|2)2/
2 2 1/2
ꢀw(Fo ) ]
.
Crystal Structure Determination
X-ray single-crystal diffraction data for 1 were collected on
a Bruker Smart 1000 CCD diffractometer (Germany) at 293(2)
K with Mo-Kα radiation (λ = 0.71073Å) by ω scan mode. The
program SAINT[10] was used for integration of the diffraction
profiles. Semiempirical absorption corrections were applied us-
ing SADABS program.[11] All the structures were solved by
direct methods using the SHELXS program of the SHELXTL
package and refined by full-matrix least-squares methods with
SHELXL.[12] Metal atoms in complex 1 were located from the
E-maps and other non-hydrogen atoms were located in succes-
sive difference Fourier syntheses and refined with anisotropic
thermal parameters on F2. Hydrogen atoms of carbon were in-
cluded in calculated positions and refined with fixed thermal
parameters riding on their parent atoms. The hydrogen atoms of
water molecules were located from Fourier difference maps with
suitable restraint. CCDC number 866638 contains the supple-
mentary crystallographic data for 1. Crystallographic data and
Crystal Structure Description
For {[Zn(L)(bimb)]·(H2O)}n (1), single-crystal X-ray
diffraction analysis reveals that complex 1 features a 3-D porous
framework arising from 2-D coordination sheets interlinked
through interlayer supramolecular interactions. Each asymmet-
ric unit contains one Zn(II) atom, one L ligand, one bimb ligand,
and one lattice water molecule. The central Zn(II) atom is coor-
dinated by two oxygen atoms (Zn1−O: 1.941(2) and 1.961(2)
Å) from two L, and two nitrogen atoms (Zn1−N: 1.986(3) and
2.004(3) Å) from two bimb ligands, displaying a distorted tetra-
hedral geometry (see Figure 1). All the Zn−O/N bond distances
and the bond angles around each Zn(II) center are in the normal
range.
TABLE 2
Selected bond lengths (Å) and angles (◦) for 1
The L dianions act as bidentate bridging ligands, joining the
Zn(II) centers together to result in a 1-D polymeric [Zn(L)]n
chain along the crystallographic [100] direction. These poly-
meric chains are extended by bimb spacers to form a 2-D cor-
rugated [Zn(L)(bimb)]n coordination polymer layer containing
alternately arranged left- and right-handed helical chains (see
Figure 1). Each helical chain is formed by bimb ligands bridging
Zn(II) atoms, which are generated around the crystallographic
Zn(1)–O1
1.941(2)
1.986(3)
Zn1–O4#1
Zn1–N1
1.961(2)
2.004(3)
Zn1–N4#2
O1–Zn1–O4#1
108.64(10) O1–Zn1–N4#2 109.52(11)
O4#1–Zn1–N4#2 118.31(12)
O1–Zn1–N1
99.42(11)
O4#1—Zn1–N1
109.72(11) N4#2–Zn1–N1 109.57(12)
Symmetry transformations used to generate equivalent atoms: #1
= x + 1/2, –y +1/2, z + 1/2, #2 = –x + 5/2, y – 1/2, –z +1/2.

78
X.-G. YANG AND S.-M. FANG
FIG. 1. View of (a) local coordination environment of Zn(II) atom in 1, (b) the 2-D layer running parallel to the ac plane, (c) the left- and right-handed helixes
constructed by Zn(II) atoms and bimb ligands, and (d) the 3-D supramolecular framework viewed along the a-axis. The symmetry-related atoms labeled with the
suffixes A and B are generated by the symmetry operations (x + 1/2, –y + 1/2, z + 1/2) and (–x + 5/2, y – 1/2, –z +1/2). All hydrogen atoms are omitted for clarity
(color figure available online).
maximum at 440 nm. In order to understand the nature of such
emission bands, the luminescent property of the free H2L lig-
and has also been measured (λex = 295 nm and λem = 416 nm).
We can presume that these emissions are neither metal-to-ligand
21 axis with a pitch of 17.507 Å (see Figure 1). The perimeters of
the grid spaces in 1 are defined by the Zn···Zn distances across
the L ligands (9.355 Å) and the bimb ligands (13.406 Å). The
adjacent [Zn(L)(bimb)]n layers stack in a simple AAA pattern
along the a crystal direction giving rise to a 3-D supramolecular
framework, which are fixed via interlayer C–H···O, C–H···N,
and C–H···π interactions between L and bimb ligands (see Fig-
ure 1 and Table 3). Notably, two types of channels are observed
in the framework, the L moieties protrude inside the voids of
one type and the lattice water molecules reside in the other type
via O–H···O hydrogen-bonds (see Table 3). The effective free
volume of 1 was calculated by PLATON[13] analysis as 24.1% of
the crystal volume (578.5 out of the 2400.3 Å3 unit cell volume).
Luminescent Property
Metal–organic coordination polymers constructed from d10
metal centers and relevant organic linkers are promising
candidates for their various potential applications in chemical
sensors and electroluminescent displays.[14] Thus, solid-state
emission spectra of 1 have been investigated at room temper-
ature (see Figure 2). Excitation of the microcrystalline sample
of 1 at 342 nm produces intense luminescence with the peak
FIG. 2. Solid-state emission spectra of 1 at room temperature (color figure
available online).

2-D ZINC(II) COORDINATION POLYMER
79
charge transfer nor ligand-to-metal charge transfer in nature, be-
cause Zn(II) ion with d10 configuration is difficult to oxidize or to
reduce, and should mainly be ascribed to the intraligand π→π∗
transitions, namely ligand-to-ligand charge transfer.[15] The red
shift of the band in comparison to those of the free ligands
should be ascribed to the deprotonated effect of the dicarboxyl
compounds and the metal–ligand coordinative interactions.[16]
5. Yaghi, O. M.; O’Keeffe, M. N.; Ockwig, W.; Chae, H. K.; Eddaoudi, M.;
Kim, J. Reticular synthesis and the design of new materials. Nature 2003,
423, 705–714.
6. Li, C.-P.; Du, M. Role of solvents in coordination supramolecular systems.
Chem. Commun. 2011, 47, 5958–5972.
7. Ma, L.-F.; Wang, Y. Y.; Liu, J. Q.; Yang, G. P.; Du, M.; Wang, L. Y. Deli-
cate substituent effect of isophthalate tectons on the structural assembly of
diverse 4-connected metal–organic frameworks (MOFs). CrystEngComm
2009, 11, 1800–1802.
8. Ma, L.-F.; Liu, B.; Wang, L.-Y.; Li, C.-P.; Du, M. Copper(II) 5-
methoxyisophthalate coordination polymers incorporating dipyridyl co-
ligands: syntheses, crystal structures, and magnetic properties. Dalton
Trans. 2010, 39, 2301–2308.
9. Qin, J.-S.; Du, D.-Y.; Li, S.-L.; Lan, Y.-Q.; Shao, K.-Z.; Su, Z.-M. pH-
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date chains, Zn(II) ions and flexible ligands: crystallizing in polar and
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SUPPLEMENTARY MATERIALS
Crystallographic data for the structural analyses have been
deposited to the Cambridge Crystallographic Data Center,
CCDC No. 866638. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union Road, 265
Cambridge, CB2 1EZ, UK (Fax: +44-1223-336033; E-mail:
deposit@ccdc.cam.ac.uk, or http://www.ccdc.cam. ac.uk).
10. Bruker. SAINT Software Reference Manual; Madison, WI: Bruker AXS,
1998.
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Software; Go¨ttingen, Germany: University of Go¨ttingen, 1996.
12. Sheldrick, G. M. SHELXTL NT, Version 5.1; Program for Solution and Re-
finement of Crystal Structures; Go¨ttingen, Germany: University of Go¨ttin-
gen, 1997.
13. Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht, the
Netherlands: Utrecht University, 2002.
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syntheses, crystal structures, and properties. Cryst. Growth Des. 2010, 10,
3699–3709.
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