Hydrothermal synthesis, crystal structure and photoluminescence of two 1D Zn(II) coordination polymers

Article abstract of DOI:10.1016/j.molstruc.2008.09.009

Two new 1D Zn(II) coordination polymers, [Zn(Bript)(phen)]_n (1) and [Zn(cca)(bimb)] (2) (H₂Bript = 4-bromineisophthalic acid; phen = 1,10-phenanthroline; H₂cca = 2-carboxycinnamic acid; bimb = 1,2-bis(imidazol-1′-yl)butane

Full text of DOI:10.1016/j.molstruc.2008.09.009

Journal of Molecular Structure 919 (2009) 185–188
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Hydrothermal synthesis, crystal structure and photoluminescence of two 1D
Zn(II) coordination polymers
b
Yan Huang a, Bing Yan a,c, , Min Shao
*
a Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China
b Department of Chemistry, College of Science, Shanghai University, Shanghai 200444, China
c State Key Lab of Coordination Chemistry, Nanjing University, Nanjing 210093, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 July 2008
Received in revised form 28 August 2008
Accepted 8 September 2008
Available online 21 September 2008
Two new 1D Zn(II) coordination polymers, [Zn(Bript)(phen)]n (1) and [Zn(cca)(bimb)] (2) (H2Bript =
4-bromineisophthalic acid; phen = 1,10-phenanthroline; H2cca = 2-carboxycinnamic acid; bimb =
1,2-bis(imidazol-10-yl)butane) have been synthesized by hydrothermal reactions and characterized by
IR, elemental analysis and X-ray single-crystal analyses. In complex 1, Bript ligands adopt chelate-bridg-
ing coordination mode to link Zn(II) ions into a 1D helical ribbon. In complex 2, cca ligands and bimb
ligands link Zn(II) ions into two kinds of macro-rings and the two kinds of macro-rings are arrayed alter-
nately into the final 1D double-strand chain. Furtherly, the one-dimensional chains are assembled into
Keywords:
Zn(II) coordination polymer
Hydrothermal synthesis
4-Bromineisophthalic acid
2-Carboxycinnamic acid
Photoluminescent property
three-dimensional networks by
of complexes 1 and 2 have also been investigated.
p
ꢀ
p stacking interactions. In addition, the photoluminescent properties
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
conformational freedom from
a
(ꢀ(CH2)4ꢀ) spacer [10–14].
4-bromineisophthalic acid (H2Bript) is the derivator of iso-
phthalic acid and its metal complexes have rarely been reported.
2-Carboxycinnamic acid (H2cca) is an unsymmetrical dicarbox-
ylic acid and its metal complexes have been rarely reported
[15–18]. Taking account of the above, we selected 4-brominei-
sophthalic acid or 2-carboxycinnamic acid as bridging ligands
and introduced phen or bimb as auxiliary ligands to react with
Zn(II) ions. Two new 1D complexes, [Zn(Bript)(phen)]n (1) and
[Zn(cca)(bimb)] (2) were obtained. The details of their synthesis,
structure and photoluminescent properties are reported.
The self-assembly of Zn(II) coordination polymers has
received considerable interest, not only because of their intrigu-
ing variety of architectures and topologies, but also because of
their potential applications on the materials with photolumines-
cent and nonlinear optical (NLO) properties, or permanent poros-
ities [1–7]. In general, polyfunctional ligands containing oxygen
and/or nitrogen atoms, such as polyacids with suitable spacers
have been extensively used in the construction of Zn(II) coordi-
nation polymers. They are not only versatile ligands for coordi-
nation bonding, but also can provide hydrogen bond donors
and acceptors.
2. Experimental
In addition, auxiliary ligands with aromatic rings such as
1,10-phenanthroline (phen) may be used to assembly supramo-
2.1. Materials and methods
lecular architecture via C–HꢁꢁꢁO hydrogen bonds and
p–p aro-
matic interactions [8], and helpful to increase the thermal
stability of MOFs [9]. By comparison with pyridine-containing li-
gands, imidazole-containing 1,2-bis(imidazol-10-yl)butane (bimb)
is less used, even though it exhibits the special ability to formu-
1,2-Bis(imidazol-10-yl)butane (bimb) was synthesized by the
literature method [19]. Other reagents were purchased commer-
cially and used without further purification. Elemental analyses
(C, H, N) were determined with an Elementar Cario EL elemental
analyzer. IR spectra were recorded with a Nicolet Nexus 912
AO446 spectrophotometer (KBr pellet), 4000–400 cmꢀ1 region.
The luminescence (excitation and emission) spectra for the solid
complex sample were determined with a Perkin-Elmer LS-55
spectrophotometer, whose excitation and emission slit width
were 10 and 5 nm, respectively.
late
a large membered ring because of its flexibility and
* Corresponding author. Address: Department of Chemistry, Tongji University,
Siping Road 1239, Shanghai 200092, China. Tel.: +86 21 65984663; fax: +86 21
65982287.
E-mail address: byan@tongji.edu.cn (B. Yan).
0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2008.09.009

186
Y. Huang et al. / Journal of Molecular Structure 919 (2009) 185–188
Table 2
2.2. Preparation of the complexes
Selected bond distances (Å) and bond angles (°) for complexes 1, 2
2.2.1. [Zn(Bript)(phen)]n (1)
Complex 1
Zn(1)–O(1)
Zn(1)–O(2)#1
Zn(1)–O(4)
O(2)#1–Zn(1)–O(1)
O(4)–Zn(1)–O(1)
2.084(2)
1.967(2)
1.929(2)
97.12(10)
90.71(10)
Zn(1)–N(1)
Zn(1)–N(2)
2.124(2)
2.202(3)
Complex 1 was synthesized from the reaction mixture of
Zn(CH3COO)2ꢁ2H2O (66 mg, 0.3 mmol), 4-bromineisophthalic acid
(72.87 mg, 0.3 mmol), 1,10-phen (59.5 mg, 0.3 mmol), NaOH
(12 mg, 0.3 mmol) and water (5 ml) in a 15 ml Teflon reactor,
under autogenous pressure at 120 °C for 3 days and then cooled
to room temperature at a rate of 10 °C/h. Colorless crystals of com-
plex 1 suitable for X-rays four-circle diffraction analysis were
obtained (yield: 60% based on Zn). Elemental analysis: Calc. for
1: C, 49.08; H, 2.30; N, 5.71. Found: C, 49.12; H, 2.25; N, 5.73%.
IR spectra exhibits patterns of bands in the range of 4000–400
cmꢀ1: 1411 cmꢀ1 (vsCOOꢀ), 1546 cmꢀ1 (vasCOOꢀ).
O(4)–Zn(1)–O(2)#1
N(1)–Zn(1)–N(2)
110.15(11)
76.40(10)
Complex 2
Zn(1)–O(1)
Zn(1)–O(3)#1
O(1)–Zn(1)–O(3)#1
O(1)–Zn(1)–N(4)#2
1.9502(19)
1.9632(18)
97.55(8)
Zn(1)–N(1)
Zn(1)–N(4)#2
O(1)–Zn(1)–N(1)
N(4)#2–Zn(1)–N(1)
2.020(2)
2.017(2)
119.84(9)
110.25(8)
104.31(9)
methods on F2 using the program SHELXL-97 [20]. All non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were
placed in geometrically calculated positions. The crystallographic
data and experimental details for structural analyses are summa-
rized in Table 1. Selected bond lengths for compounds 1 and 2
are listed in Table 2.
2.2.2. [Zn(cca)(bimb)] (2)
Complex 2 was synthesized from the reaction mixture of
Zn(CH3COO)2ꢁ2H2O (66 mg, 0.3 mmol), 2-carboxycinnamic acid
(57.6 mg, 0.3 mmol), bimb (57 mg, 0.3 mmol) and water (5 ml) in
a 15 ml Teflon reactor, under autogenous pressure at 140 °C for 3
days and then cooled to room temperature at a rate of 10 °C/h. Col-
orless crystals of complex 2 suitable for X-rays four-circle diffrac-
tion analysis were obtained (yield: 55% based on Zn). Elemental
analysis: Calc. for 2: C, 53.96; H, 4.27; N, 12.59. Found: C, 53.92;
H, 4.30; N, 12.62%. IR spectra exhibit patterns of bands in the range
of 4000–400 cmꢀ1: 1419 cmꢀ1 (vsCOOꢀ), 1642 cmꢀ1 (vasCOOꢀ).
3. Results and discussion
3.1. Description of crystal structures
Complex 1 crystallizes in the monoclinic system, with space
group C2/c. X-ray crystallographic analysis shows that it exhibit
1D zigzag chain (Fig. 1). In the crystal structure of complex 1
(Fig. 2), each Zn(II) atom is primarily coordinated by two nitrogen
atoms from a chelating phen ligand and three oxygen atoms from
three carboxylate ends of three Bript ligands in a distorted trigonal
dipyramidic geometry, in which the O1 and N2 occupy the axial
2.3. X-ray crystallography
Diffraction data of the title complexes were collected on a Bru-
ker SMART 1000 CCD area detector diffractometer with graphite-
monochromatized Mo-Ka radiation (k = 0.71073 Å) in u and x
scan modes. All the structures were solved by direct methods using
the program SHELXS-97 and refined by full-matrix least-squares
Table 1
Crystallographic data for complexes 1 and 2
Compound
1
2
Formula
Mn
C20H11BrN2O4Zn
488.59
C20H19N4O4Zn
444.76
Temperature (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
273(2)
Monoclinic
C2/c
26.483(3)
9.8657(12)
16.786(2)
90
126.1150(10)
90
296(2)
Triclinic
ꢀ
P1
Fig. 1. The 1D zigzag chain of complex 1.
8.5198(12)
11.1221(15)
11.2395(15)
77.195(2)
79.9290(10)
74.721(2)
994.1(2)
2
a
(°)
b (°)
c
(°)
V (Å3)
3542.9(7)
8
1.832
Z
Dcalcd (mg/m3)
Absorption
coefficient
1.486
1.270
3.673
(mmꢀ1
)
F(000)
1936
458
Crystal size (mm)
h Range for data
collection (°)
0.30 ꢂ 0.20 ꢂ 0.20
0.20 ꢂ 0.20 ꢂ 0.15
2.27–25.04
2.43–25.05
Index ranges
ꢀ29 6 h 6 31, ꢀ9 6 k 6 11,
ꢀ19 6 l 6 17
8961
ꢀ10 6 h 6 0, ꢀ13 6 k 6 8,
ꢀ12 6 l 6 13
5209
Reflections collected
Data [I > 2
parameters
Goodness-of-fit on F2 1.047
R1 indices [I > 2 (I)] 0.0313
wR2 indices (all data) 0.0765
r
(I)]/
3135/257
3462/263
1.066
0.0335
0.0851
r
Largest diff. peak/
0.759/ꢀ0.868
0.490 /ꢀ0.306
hole (e/Å3)
Fig. 2. Diagram showing the coordination environment of the Zn(II) in complex 1.

Y. Huang et al. / Journal of Molecular Structure 919 (2009) 185–188
Fig. 3. The 1D zigzag chain formed by Bript ligands linking dinuclear units for complex 1, phen ligands have been omitted for clarity.
Fig. 4. The 1D double-strand chain of complex 2.
187
positions. The bond distances of Zn–N1, Zn–N2 and Zn–O are
2.124(2), 2.202(3) and 1.929(4)–2.084(2) Å, respectively. The pen-
dant carboxy O3 atom has no significant interaction with Zn(II), be-
cause the distance of ZnꢁꢁꢁO3 is 3.173(4) Å. Selected bond distances
and bond angles for complex 1 are listed in Table 2.
Each cca ligand is completely deprotonated and adopts biden-
tate coordination mode to link two Zn(II) ions (Fig. 4). It’s worthy
noting that the two Zn(II) ions with the separation of 6.9938(8) Å
are bridged by two cca ligands into an eighteen-membered ring.
Each Bript ligand is completely deprotonated and adopts che-
late-bridging coordination mode to link three Zn(II) ions (Fig. 3).
Two Zn(II) ions related by a twofold axis are bridged by a pair of
l
-carboxylate ends into a dinuclear unit (ZnꢁꢁꢁZn 3.697(2) Å) and
each two of such dinuclear units are connected together by shar-
ing the Bript ligands to form a 1D zigzag chain (Fig. 3). In addi-
tion, adjacent chains are packed through the
p–p stacking
interactions between the lateral phen ligands with face-to-face
distance of 3.553(4) Å into a three-dimensional network in the
solid.
Complex 2 crystallizes in the triclinic system, with space group
P1. X-ray crystallographic analysis shows that it presents 1D dou-
ꢀ
ble-strand chain (Fig. 4). As shown in Fig. 5, each Zn(II) atom is
four-coordinated by two oxygen atoms from two cca ligands and
two nitrogen atoms from two bimb ligands to form a tetrahedron
geometry. The bond distances of Zn–O1 and Zn–O3 are 1.950(2)
and 1.963(2) Å, respectively, and those of Zn–N1 and Zn–N4 are
2.020(2) and 2.017(2) Å, respectively. Selected bond distances
and bond angles for complex 2 are listed in Table 2.
Fig. 5. Diagram showing the coordination environment of the Zn(II) in complex 2.
Fig. 6. The emission spectra of complex 1 (a) and complex 2 (b).

188
Y. Huang et al. / Journal of Molecular Structure 919 (2009) 185–188
Bimb ligands also adopt bidentate coordination mode to link two
Zn(II) ions, and the two Zn(II) ions with the separation of
10.2975(11) Å are bridged by two bimb ligands into an twenty-
two-membered ring, which is twisted with respect to the eigh-
teen-membered ring with the dihedral angel of 63.843(11)°. The
two kinds of macro-rings are arrayed alternately into the final 1D
double-strand chain, and adjacent chains are packed through the
Acknowledgement
The authors gratefully acknowledged the financial support from
the National Natural Science Foundation of China (20671072).
Appendix A. Supplementary data
p–p stacking interactions between the bimb heterocyclic rings
with face-to-face distance of 3.440(9) Å into a three-dimensional
network in the solid (Fig. S1).
Crystallographic data (excluding structure factor) for the struc-
ture reported in this paper have been deposited with the Cam-
bridge Crystallographic Data Center as supplementary
publication (No: CCDC-651943 for complex 1 and CCDC-684848
for complex 2). Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK
(fax: (+44) 1223-336-033; e-mail: deposit@ccdc.cam.ac.uk). Sup-
plementary data associated with this article can be found, in the
online version, at doi:10.1016/j.molstruc.2008.09.009.
3.2. Photoluminescent properties
Complexes 1 and 2 exhibit intense blue photoluminescence
upon the radiation of UV light in the solid state at the room tem-
perature (Fig. 6). Complex 1 displays luminescence with an emis-
sion maximum at 413 nm when excited at 339 nm (Fig. 6a).
While the emission spectra of free H2Bript ligand shows one emis-
sion at 362 nm, indicating that H2Bript ligand has no emission in
the visible region, when bound to a zinc center blue luminescence
is observed. The lower energy band is assigned to ligand-to-metal
charge transfer (LMCT), and the observed luminescence of complex
1 is attributed to the coordinated H2Bript ligand. As shown in
Fig. 6b, the free H2cca ligand displays luminescence with an emis-
sion maximum at 427 nm when excited at 372 nm, which is attrib-
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p ?
p* transition. In Comparison with that of the free
H2cca ligand, complex 2 shows similar luminescence. However,
there is a red-shift between the emission spectra of complex 2
and free H2cca ligand. The emission peak position is at 440 nm
when excited at 385 nm (Fig. 6b). The red-shift may be attributed
to the enlargement of conjugation after coordination and thus the
lowering of emission state level of the ligand [16].
4. Conclusions
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In summary, we have successfully synthesized two 1D Zn(II)
coordination polymers. For complex 1, Bript ligands link Zn(II) ions
into a 1D zigzag chain. For complex 2, cca lignds and bimb ligands
link Zn(II) ions into two kinds of macro-rings and the two kinds of
macro-rings are arrayed alternately into the final 1D double-strand
chain. Furtherly, the one-dimensional chains are assembled into
three-dimensional networks by
pꢀp stacking interactions.