Hydrothermal syntheses, crystal structure and luminescent properties of four zinc(II) coordination polymers based on tipodal imidazole

Article abstract of DOI:10.1016/j.ica.2013.01.003

Four new Zn(II) coordination polymers [Zn(tib)₂(H ₂O)₂(NO₃)₂]_n (1), [Zn(tib)₂Cl₂]_n (2), [Zn(tib)(L ₁)]_n (3) and [Zn(tib) (L₂) (H ₂O)]_n (4) [tib = 1,3,5,-tris(1-imidazolyl) benzene, H ₂L₁ = 5-hydroxyisophthalic acid and H₂L ₂ = 5-methylisophthalic acid] have been prepared and characterized by elemental, IR, XRPD and X-ray diffraction analyses. The structure determination reveals that complex 1 is a 2D layer network and exhibits a typical (4,4)-topological net, which further assembles into a 3D (3,6)-connected framework with (4⁴.6¹⁰.8) topological symbol via hydrogen bonding interactions. Complex 2 shows a 2D (3,6)-connected topological net the Schl?fli symbol of (4³)₂(4⁶.6 ⁶.8³). Complex 3 features a (4,4)-topological net and further assembles into a 3D pcu framework by hydrogen bonding interactions. Complex 4 is a 1D ladder-like chains structure. Furthermore, the photoluminescence properties are investigated.

Full text of DOI:10.1016/j.ica.2013.01.003

Inorganica Chimica Acta 399 (2013) 79–84
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Hydrothermal syntheses, crystal structure and luminescent properties of four
zinc(II) coordination polymers based on tipodal imidazole
⇑
Feng Guo
Key Laboratory of Coordination Chemistry and Functional Materials in Universities of Shandong, Dezhou University, Shandong 253023, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 July 2012
Received in revised form 8 December 2012
Accepted 4 January 2013
Available online 12 January 2013
Four new Zn(II) coordination polymers [Zn(tib)2(H2O)2(NO3)2]n (1), [Zn(tib)2Cl2]n (2), [Zn(tib)(L1)]n (3) and
[Zn(tib) (L2) (H2O)]n (4) [tib = 1,3,5,-tris(1-imidazolyl) benzene, H2L1 = 5-hydroxyisophthalic acid
and H2L2 = 5-methylisophthalic acid] have been prepared and characterized by elemental, IR, XRPD and
X-ray diffraction analyses. The structure determination reveals that complex 1 is a 2D layer network and
exhibits a typical (4,4)-topological net, which further assembles into a 3D (3,6)-connected framework
with (44.610.8) topological symbol via hydrogen bonding interactions. Complex 2 shows a 2D (3,6)-
connected topological net the Schläfli symbol of (43)2(46.66.83). Complex 3 features a (4,4)-topological
net and further assembles into a 3D pcu framework by hydrogen bonding interactions. Complex 4 is a
1D ladder-like chains structure. Furthermore, the photoluminescence properties are investigated.
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
Crystal structure
Luminescence
Coordination polymer
1. Introduction
synthesized under hydrothermal conditions. The luminescent
properties of the complexes were also investigated.
The construction of metal–organic coordination polymers have
been given considerable attention, not only for their promising
applications as functional material but also for their intriguing aes-
thetic structures and topological features [1–11]. On the basis of this
background, many metal–organic coordination polymers have been
constructed via the interaction of metal ions with well defined
bridging organic ligands. Although the rapid progress in metal–or-
ganic coordination polymers has been made, it is also a significant
challenge to rationally prepare and control the structures and com-
position of target products in crystal engineering since many factors
could affect on the construction, such as organic ligands, pH value,
solvent system, anion and so on [13–16]. Among these factors, the
most effective and facile method to construct new metal–organic
coordination polymers is the judicious selection of the appropriate
organic ligands. Imidazole-containing ligands have proven to be a
class of aromatic N-donor for the construction of the novel metal–
organic coordination polymers [16–23].
2. Experimental
2.1. Materials and physical measurements
All reagents and solvents employed were commercially available
and were used as received without further purification. Elemental
analysis was carried out on a Carlo Erba 1106 full-automatic trace
organic elemental analyzer. FT-IR spectra were recorded with a Bru-
ker Equinox 55 FT-IR spectrometer as a dry KBr pellet in the 400–
4000 cmÀ1 range. Solid-state fluorescence spectra were recorded
ona F-4600 equipped witha xenon lamp and a quartzcarrier at room
temperature(slit width = 5 nm and scan rate = 15 nm sÀ1). The pow-
der X-ray powder diffraction (XRPD) measurements were per-
formed on a Bruker D8 diffractometer operated at 40 kV and
40 mA using Cu Ka radiation (k = 0.15418 nm).
In this paper, we used the 1,3,5,-tris(1-imidazolyl) benzene and
dicarboxylate ligands to construct different dimensional networks
and topology. The tib ligand has been previously used in the con-
struction of MOFs (metal–organic frameworks) with specific struc-
tures and topologies, all of which demonstrating that tib is a useful
ligand in construction of MOCPs [24–26]. In this paper, four new
coordination polymers [Zn(tib)2(H2O)2(NO3)2]n (1), [Zn(tib)2Cl2]n
(2), [Zn(tib)(L1)]n (3) and [Zn(tib)(L2)(H2O)]n (4) were successfully
2.2. Syntheses
2.2.1. Preparation of [Zn(tib)2(H2O)2(NO3)2]n (1)
A mixture of Zn(NO3)2Á6H2O (0.149 g, 0.5 mmol), tib (0.138 g,
0.5 mmol) and deionized water (15 mL) was sealed in a 25 mL Tef-
lon-lined stainless steel vessel and heated at 160 °C for 96 h, and
cooled to room temperature. The colorless block crystals were ob-
tained and washed with alcohol for several times (Yield: 41% based
on Zn). Anal. Calc. for C30H28ZnN14O8: C, 46.31; H, 3.63; N, 25.20.
Found: C, 46.28; H, 3.65; N, 25.21%. IR: 3417 br, 1624 s, 1519 s,
1454 m, 1345 m, 1250 m, 1114 m, 1010 m, 940 m, 856 m, 728 m.
⇑
Tel.: +86 534 8989927; fax: +86 534 8985835.
E-mail address: guofeng1510@yeah.net
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.01.003

80
F. Guo / Inorganica Chimica Acta 399 (2013) 79–84
2.2.2. Preparation of [Zn(tib)2Cl2]n (2)
absorption correction was applied using the SADABS programs [27].
All the structures were solved by direct methods and refined by
full-matrix least-squares methods on F2 using the program SHEXL
97 [28]. All non-hydrogen atoms were refined anisotropically.
The hydrogen atoms were located by geometrically calculations,
and their positions and thermal parameters were fixed during
the structure refinement. The C atoms (C29A, C29B, C30A, C30B,
C35A, C35B, C36A and C36b) in complex 4 are disordered two posi-
tions. The crystallographic data are summarized in Table 1. The
date of relevant bond lengths and angles are listed in Table S1.
A mixture of ZnCl2 (0.068, 0.5 mmol), tib(0.138 g, 0.5 mmol)
and deionized water (15 mL) was sealed in a 25 mL Teflon-lined
stainless steel vessel and heated at 160 °C for 96 h, and cooled to
room temperature. The colorless block crystals were obtained
and washed with alcohol for several times (Yield: 46% based on
Zn). Anal. Calc. for C30H24ZnN12Cl2: C, 43.38; H, 2.91; N, 20.23%.
Found: C, 43.43; H, 2.89; N, 20.27. IR: 3445 br, 1611s, 1510 m,
1371 m, 1238 m, 1157 m, 1076 m, 9734 m, 849 m, 754 m.
2.2.3. Preparation of [Zn(tib)(L1)]n (3)
A mixture of Zn(NO3)2Á6H2O (0.149 g, 0.5 mmol),tib (0.138 g,
0.5 mmol), H2L1 (0.5 mmol, 0.091 g) and NaOH (0.04 g, 1 mmol)
and deionized water (18 mL) was sealed in a 25 mL Teflon-lined
stainless steel vessel and heated at 160 °C for 96 h, and cooled to
room temperature. The colorless block crystals were obtained
and washed with alcohol for several times (Yield: 45% based on
Zn). Anal. Calc. for C23H16ZnN6O5: C, 52.94; H, 3.09; N, 16.11.
Found: C, 53.01; H, 3.12; N, 16.06%. IR: 1625 s, 1567 s, 1401 m,
1353 m, 1242 m, 1111 m, 1069 m, 975 m, 853 m, 788 m.
3. Results and discussions
3.1. Description of crystal structures
3.1.1. [Zn(tib)2(H2O)2(NO3)2]n (1)
Single crystal X-ray diffraction analysis revealed that compound
1 crystallizes in the monoclinic space group P21/n, and each asym-
metric unit consists of Zn(II) ion, one tib ligands and one coordina-
tion water molecule. As illustrated in Fig. 1a, the Zn(II) ion is
located at an inversion center with an octahedral geometry sur-
rounded by four nitrogen atoms from four different tib ligands
occupying the basal positions [Zn(1)–N(1) = 2.153(2) Å and
Zn(1)–N(4) = 2.140(2) Å] and two water molecule forming the api-
cal positions [Zn(1)–O(1w) = 2.197(2) Å].
The tib ligands link Zn(II) ions to form a two-dimensional layer.
The nitrate ions distribute in the middle of layers. The nitrate ions
and coordinated water molecules interact by the intermolecular
hydrogen bonds which lead to form a three-dimensional frame-
work (Fig. 2b). The hydrogen-bonded right- and left-helical chains
are constructed by oxygen atoms of nitrate ions and oxygen atoms
of coordinated water molecules through the hydrogen bonds
[O1wÁ Á ÁO1 3.036(4) Å and O1wÁ Á ÁO3 2.818(3) Å]. The pitch of the
hydrogen-bonded helical chain is 11.513 Å. In the view of topology,
the 3D supramolecular framework can be simplified the 3,6-con-
nected net with (44.610.8) topological symbol. The tib ligands link
2.2.4. Preparation of [Zn(tib) (L2) (H2O)]n (4)
The compound 4 was obtained by the similar method as de-
scribed for 3 by using of H2L2 (0.5 mmol, 0.09 g) in place of H2L1.
The colorless crystals were obtained in pure phase, washed with
water and ethanol, and dried at room temperature (Yield: 55%
based on Zn). Anal. Calc. for C24H20ZnN6O5: C, 53.59; H, 3.75; N,
15.62. Found: C, 53.67; H, 3.72; N, 15.61%. IR: 3434 br, 1620 s,
1514 m, 1408 s, 1358 m, 1255 m, 1112 m, 1070 m, 941 m, 854
m, 763 m.
2.3. X-ray crstallography
Diffraction intensity data of the single crystals of four
compounds were collected on
a Bruker SMART APEXII CCD
diffractometer equipped with a graphite monochromated Mo K
a
radiation (k = 0.71073 Å) by using a
x-scan mode. Empirical
Table 1
Crystallographic data and structure refinement summary for complexes 1–4.
Complex
1
2
3
4
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
C
30H28ZnN14O8
C30H24Cl2N12Zn
688.88
C23H16ZnN6O5
521.79
monoclinic
P21/c
C24H20ZnN6O5
537.85
778.05
monoclinic
P21/n
trigonal
triclinic
ꢀ
ꢀ
P31c
P1
10.628(7)
11.513(7)
13.554(9)
90.000
109.744(8)
90.000
1561.0(12)
21.655
3039
11.472(3)
11.472(3)
15.217(4)
90.000
90.000
120.000
1734.4(12)
21.319
1057
9.699(5)
8.020(1)
b (Å)
c (Å)
13.677(5)
16.584(5)
90.000
93.644 (5)
90.000
2195.5(15)
41.579
5004
17.175(3)
17.577(3)
97.742(2)
96.306(2)
96.306(2)
2358.3(7)
21.515
a
(°)
b (°)
c
(°)
V (Å3)
ZDcalc (mg/m3)
Independent reflections (I > 2
F(000)
r
(I))
6309
1104
800
704
1064
h (°)
Limiting indices
2.38–27.52
À7 6 h 6 13
À14 6 k 6 14
À17 6 l 6 16
1.053
R1 = 0.0335
wR2 = 0.0851
R1 = 0.0406
wR2 = 0.0888
0.493 and À0.308
2.05–27.58
À14 6 h 6 14
À10 6 k 6 14
À19 6 l 6 19
1.016
R1 = 0.0581
wR2 = 0.0.1511
R1 = 0.0684
wR2 = 0.1552
0.464and À0.335
1.93–27.51
À12 6 h 6 12
À17 6 k 6 16
À21 6 l 6 20
1.040
R1 = 0.0381
wR2 = 0.0974
R1 = 0.0524
wR2 = 0.1041
0.633 and À0.301
2.27–22.32
À8 6 h 6 10
À22 6 k 6 21
À22 6 l 6 19
1.002
R1 = 0.0508
wR2 = 0.1074
R1 = 0.0988
wR2 = 0.1266
0.478 and À0.350
Goodness-of-fit (GOF) on F2
R1a,wR2 [I > 2
r(I)]
b
R1a,wR2 (all data)
b
Largest difference in peak and hole (e/Å3)
a
R =
wR = [
R
(||F0| À |FC||)/
R|F0|.
b
R
w(|F0|2 À |FC|2)2/
R .
w(F02)]1/2

F. Guo / Inorganica Chimica Acta 399 (2013) 79–84
81
Fig. 1. (a) Local coordination geometry of the central Zn(II) atom of compound (all hydrogen atoms are omitted for clarity; (b) Viewing of the left- and right helical chains. The
hydrogen bonds are indicated by dotted lines; (c) The 3,6-connected net formed via the interaction of sql and hcb layers interwove.
Fig. 2. (a) Local coordination geometry of the central Zn(II) atom of compound (all hydrogen atoms are omitted for clarity); (b) the (3,6)-connected framework with the
Schläfli symbol of (43)2(46.66.83).
the Zn(II) ions to form the (4,4)-connected sql layer, and the coor-
dinated water molecules and nitrate ions link Zn(II) ions to form
the 3-connected hcb topology (Figs. S1 and S2). The sql layer and
the hcb layer are interwove to form the (3,6)-connected net
(Fig. 2c).
The Zn(II) ion can be viewed as a node which is six-connector
since it is linked by six tib ligands and each tib ligand can be re-
garded as a three-connector. Such connectivity repeats to give
the 2D framework with the Schläfli symbol of (43)2(46.66.83)
(Fig. 2b).
3.1.3. [Zn(tib)(L1)]n (3)
3.1.2. [Zn(tib)2Cl2]n (2)
X-ray crystallography reveals that compound 3 crystallizes in
monoclinic space group P21/c. As shown in Fig. 3a, each Zn(II) ion
is surrounded by two oxygen atoms [Zn(1)–O(1) = 1.931(2) Å and
Zn(1)–O(3) = 1.946(2) Å] from two individual L1 ligands and two
nitrogen atoms [Zn(1)–N(1) = 2.025(2) Å and Zn(1)–N(6) =
2.027(2) Å] from tib ligands, showing a tetrahedral geometry. In
tib ligand, one of imidazole group does not participate in the
The single-crystal X-ray diffraction analysis revealed that there
is one crystallographically independent zinc(II) atom in compound
2. As illustrated in Fig. 2a, Zn(II) ion is coordinated by six nitrogen
atoms [Zn–N = 2.195(3) Å] from different tib ligands, forming an
octahedral geometry. The dihedral angle of phenyl ring and imid-
azole rings is 43.94° (Fig. S3).

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F. Guo / Inorganica Chimica Acta 399 (2013) 79–84
Fig. 3. (a) Local coordination geometry of the central Zn(II) atom of compound (all hydrogen atoms are omitted for clarity; (b) simplification of the structure to a (4,4)
network; (c) 3D supramolecular structure via hydrogen bonding interactions; (d) the pcu topology for the 3D supramolecular structure.
Fig. 4. (a) Local coordination geometry of the central Zn(II) atom of compound (all hydrogen atoms are omitted for clarity; (b) 32-membered tetrametal ring formed by L2
ligands; (c) the 1D chains formed by tib ligands; (d) the 1D ladder-like chain formed by L2 and tib ligands.
coordination, and thus each tib ligand connects two zinc(II) ions.
The Zn(II) ions are linked by carboxylate groups to form a chain
and further connected by tib ligands to form a two-dimensional
layer (Fig. 3b). The 2D layers are further assembled by the intermo-
lecular hydrogen bonding interaction with a H(5) Á Á ÁO(2) distance
of 1.95 Å and the angle of 168° [O(5)–H(5) Á Á ÁO(2)], which leading
to the formation of a 3D framework (Fig. 3c).
Considered the hydrogen bonding interaction, The Zn(II) can be
regarded as six-connected nodes and the 3D supramolecular struc-
ture can be rationalized as a 6-connected pcu net with a Schäfli
symbol of (412Á63) (Fig. 3d).
3.1.4. [Zn(tib)(L2)(H2O)]n (4)
The single crystal X-ray diffraction study reveals that compound
4 crystallizes in triclinic space group P1. As depicted in Fig. 4a, the
ꢀ
structure of the compound 4 contains two crystallographically un-
ique (but the coordination number and geometry identical) zinc
atoms. The Zn1 is coordinated by three oxygen atoms [Zn(1)–
O(1) = 1.967(2) Å, Zn(1)–O(5) = 2.410(3) Å and Zn(1)–O(7) = 2.068(3) Å]
and two nitrogen atoms [Zn(1)–N(1) = 2.043(3) Å and Zn(1)–
N(7) = 2.027(3) Å], exhibiting a square–pyramidal geometry. The
tib ligands link zinc(II) atoms to form a 1D zigzag chain along c-
axis. The L2 ligands connect zinc atoms to construct 32-membered

F. Guo / Inorganica Chimica Acta 399 (2013) 79–84
83
Fig. 5. Fluorescent emission spectra of compounds 1–4 in the solid state at room temperature.
tetrametal ring. The 32-membered tetrametal rings and 1D zigzags
are combined to form a 1D ladder-like chain.
complexes. Structural comparisons indicate that the coexistent
groups of organic ligands on the dicarboxylate ligand play an
important role in governing the structures of complexes 3 and 4.
Furthermore, the complexes 1–4 exhibit emission in the solid state
at room temperature.
3.2. Structure diversity of the complexes 1–4
When the metal salts are changed from Zn(NO3)2Á6H2O to ZnCl2,
the topological structures of the complexes 1 and 2 are changed
from the 3D supramocular structure to 2D layer structure. In 3
and 4, the 5-position substituted groups are changed which lead
to the structure from 3D supramolecular to 1D ladder-like chain.
Acknowledgment
We thank the support of this work by Natural Science Founda-
tion of Shandong Province (ZR2011BL024).
3.3. XRPD of the complexes
Appendix A. Supplementary material
In order to check the phase purity of compounds 1–4, the X-ray
powder diffraction (XRPD) patterns were measured at room tem-
perature. As shown in Fig. S4, the peak positions of the simulated
and experimental XRPD patterns are in agreement with each other,
demonstrating the good phase purity of the compounds.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2013.01.003.
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