Synthesis, crystal structure, and characterization of a novel coordinated polymer [Cu2I4(Nppch)2]

Article abstract of DOI:10.1080/15533174.2011.591350

Solution reaction of CuI and KI in DMF/H₂O with a solution of Nppch in CH₃OH/H₂O gave rise to a three-dimensional (3D) supramolecular compound based on a binuclear [Cu₂I ₄(Nppch)₂] unit (Nppch = N-(4-pyridyl) pyridinium chloride hydrochloride). The crystal structural analysis indicated that the complex crystallized in a monoclinic space group, P2(1)/n, a = 9.6821(19) A, b = 11.414(2) A, c = 12.096(2) A, β = 103.17(3)°, V = 1301.6(4) A³, Z = 2. The complex possessed a novel three-dimensional supramolecular framework formed by hydrogen bonds among repeating [Cu ₂I₄(Nppch)2] binuclear units. The compound was further characterized with infrared (IR) spectra, ultraviolet spectral properties, thermal analysis, and fluorescence properties. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2011.591350

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:1086–1090, 2011
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.591350
Synthesis, Crystal Structure, and Characterization of a
Novel Coordinated Polymer [Cu2I4(Nppch)2]
Hong-Mei Wang, Na Xu, and Yun-Yin Niu
Department of Chemistry, Zhengzhou University, Zhengzhou, P. R. China
In this article, we report the synthesis, crystal structure, ultra-
violet spectrum, and luminescent and thermogravimetric prop-
erties of a novel coordination polymer with the repeating unit
[Cu2I4(Nppch)2].
Solution reaction of CuI and KI in DMF/H2O with a solution
of Nppch in CH3OH/H2O gave rise to a three-dimensional (3D)
supramolecular compound based on a binuclear [Cu2I4(Nppch)2]
unit (Nppch = N-(4-pyridyl) pyridinium chloride hydrochloride).
The crystal structural analysis indicated that the complex crys-
tallized in a monoclinic space group, P2(1)/n, a = 9.6821(19) Å, b
= 11.414(2) Å, c = 12.096(2) Å, β = 103.17(3)◦, V = 1301.6(4)
Å3, Z = 2. The complex possessed a novel three-dimensional
supramolecular framework formed by hydrogen bonds among re-
peating [Cu2I4(Nppch)2] binuclear units. The compound was fur-
ther characterized with infrared (IR) spectra, ultraviolet spectral
properties, thermal analysis, and fluorescence properties.
EXPERIMENTAL
General Information and Materials
Pyridine, ethyl acetate, sulfoxide chloride, and absolute ethyl
alcohol were obtained from Aldrich Chemical Company. The
infrared (IR) spectrum was recorded on a Shimazu IR435
spectrometer as KBr disk (4000–400 cm−1). Thermal analy-
ses were performed on a Netzsch STA 449C thermal analyzer
from 30 to 600◦C at a heating rate of 10◦C min−1 in air. The
ultraviolet–visible (UV-vis) spectra were measured on a Lambda
35 UV–visible spectrophotometer. Photoluminescent measure-
ment of the compound [Cu2I4(Nppch)2] and the cation Nppch
in CH3OH solution was conducted on a Hitachi F-4500 spec-
trophotometer and the data were collected at room temperature.
Keywords copper(I) complex, crystal structure, luminescent proper-
ties, thermogravimetric properties
INTRODUCTION
Since its discovery, the coordinative bond approach has
attracted much attention[1] and has been widely used in the
construction of supramolecular coordination compounds by
self-assembly.[2] So far, a wide range of one-dimensional (1D),
two-dimensional (2D), and three-dimensional (3D) infinite
solid-state supramolecular coordination compounds have been
synthesized and structurally characterized.[3] In recent years,
the solid-metal supramolecular polymer has gradually become
one of the most active research areas of chemical engineering
and molecular sciences.[4–8] Furthermore, potential applications
of supramolecular coordination compounds have been found in
chemical sieving, sensing, and catalysis.[9] Recently, we selected
transition metal iodides as reactants because the transition-
metal-directed self-assembly is a highly synthesis method, and
polyiodides have the ability to form various extended networks.
Synthesis of the N-(4-Pyridyl) Pyridinium Chloride
Hydrochloride (Nppch)
Sulfoxide chloride (4.9 mL, 0.067 mol) was added to the
mixture of pyridine (8.2 mL, 0.1 mol) and ethyl acetate (4.9
mL) under stirring at 0◦C. The reaction was kept heating at
75–80◦C and refluxing for 6 h. After reaction, the temperature
was cooled to room temperature and supernatant was dumped.
At last, Nppch, a yellow powder, was obtained by washing with
absolute ethyl alcohol and drying. The reaction route is shown
in Scheme 1.[10]
SOCl2
N
H
N
CH3COOC2H5
N
Cl
Cl
Received 17 March 2011; accepted 29 March 2011.
The authors gratefully acknowledge the financial support of the
National Science Foundation of China (NSFC, numbers 20671083 and
21171148).
Address correspondence to Yun-Yin Niu, Department of Chem-
istry, Zhengzhou University, Zhengzhou 450001, P. R. China. E-mail:
niuyy@zzu.edu.cn
SCH. 1.
Synthesis of the Compound [Cu2I4(Nppch)2]
A solution of Nppch (0.1 mmol, 23.4 mg) in CH3OH/H2O
(3 mL) was added to a solution of CuI (0.1 mmol, 12.2
1086

A NOVEL COORDINATED COPPER POLYMER
1087
TABLE 1
Crystallographic data and structural refinement for compound
[Cu2I4(Nppch)2]
1939.16(w), 1642.64(w), 1622.34(s), 1585.09(s), 1495.70(s),
1466.97(s), 1407.48(s), 1263.40(m), 1223.02(m), 1147.75(m),
1099.58(w), 1070.08(w), 1049.23(m), 1019.82(m), 964.56(w),
936.42(w), 832.43(s), 768.50(s), 667.68(s), 617.54(s),
554.49(s), 486.21(w).
Empirical formula
Formula weight
Crystal system
Space group
Crystal size(mm)
a (Å)
C20H18Cu2I4N4
949.06
Monoclinic
P2(1)/n
0.16 × 0.12 × 0.11
9.6821 (19)
11.414 (2)
12.096 (2)
90
103.17 (3)
90
1301.6 (4)
2.422
X-Ray Structural Determination
Crystallographic data for [Cu2I4(Nppch)2] were collected at
293(2) K using Mo-Kα radiation (λ = 0.71073 Å) on a Rigaku
RAXIS-IV image plate area detector. The structures were solved
with the SHELX program by direct methods and expanded using
the Fourier technique. The hydrogen atoms were assigned with
common isotropic displacement factors and included in the final
refinement by using geometrical constraints, but all the non-
hydrogen atoms were treated anisotropically.
b (Å)
c (Å)
α (◦)
ß (◦)
γ (◦)
V (Å3)
Dc (mg m−3
Z
)
RESULTS AND DISCUSSION
2
µ (mm−1
)
6.392
Crystal Structure of the Compound [Cu2I4(Nppch)2]
Compound [Cu2I4(Nppch)2] crystallizes in the monoclinic
space group P2(1)/n, and crystal data and refinement details are
summarized in Table 1. Selected bond lengths and bond angles
were listed in Table 2.
Single-crystal x-ray diffraction analysis revealed that the
compound [Cu2I4(Nppch)2] was a dimeric compound. As is
shown in Figure 1, in this binuclear compound, the coordina-
tion circumstances of the two Cu atoms are the same and they are
tetrahedrally coordinated by µ2-I, terminal atom I(2), and N(1)
from cation [Nppch]+. The coordination number of atom Cu is
four if the Cu–Cu bond (2.84 Å) is not taken into consideration.
The asymmetric unit of the compound [Cu2I4(Nppch)2] con-
Reflections collected/unique 8304/3144
R(int)
0.0283
Final R indices
R indices (all data)
Goodness-of-fit on F∧2
Largest peak, hole (e Å−3
F(000)
R1 = 0.0305a, wR2 = 0.0594a,b
R1 = 0.0424, wR2 = 0.0642
1.031
)
1.527, –1.188
872
Temperature, K
293(2)
aR1 = ꢁFo| − |Fcꢁ/|Fo|.
bwR2 = [w(Fo2 – Fc2)2/w(Fo2)2]1/2
.
mg) and KI (0.5 mmol, 83.0 mg) in dimethylformamide sists of two parts: [Nppch]+ and [Cu2I4]2−. In the [Cu2I4]2- part,
DMF/H2O (3 mL). A little white precipitation appeared and Cu(1)–I(1)–Cu(1)#1–I(1)#1 can form a parallelogram, while
DMF was continually added until the precitation disappeared the bonds of Cu(1)–I(1) and Cu(1)#1–I(1)#1 are 2.647 Å and
completely. Then the mixed solution was placed in the 2.659 Å, respectively, and the angles of Cu(1)–I(1)–Cu(1)#1
dark. One week later, blue-green crystals were obtained and I(2)–Cu(1)–Cu(1)#1 are 68.68◦ and 136.96◦, respectively.
at ambient temperature. Yield: 62.3%. Anal.: Calcd. for In the [Nppch]+ part, two pyridine ring are linked by the bond
C20H18Cu2I4N4: C, 25.31; H, 1.91; N, 5.90%. Found: C, 25.32; N(2)–C(3), and the dihedral angle between the two pyridine
H, 1.96; N, 5.93%. IR (cm−1, KBr): 3068.52(w), 3039.22(m), rings is 38.96◦.
TABLE 2
Selected bond lengths (Å) and angles (◦) for compound [Cu2I4(Nppch)2]
I(1)–Cu(1)
2.6467(8)
2.6589(9)
2.6152(8)
64.68(2)
108.04(10)
103.99(10)
102.16(10)
115.32(2)
113.87(2)
112.16(3)
Cu(1)–N(1)
Cu(1)–I(1)#1
Cu(1)–Cu(1)#1
N(1)–Cu(1)–Cu(1)#1
I(1)#1–Cu(1)–Cu(1)#1
I(1)–Cu(1)–Cu(1)#1
I(2)–Cu(1)–Cu(1)#1
C(1)–N(1)–Cu(1)
C(5)–N(1)–Cu(1)
2.093(3)
2.6589(9)
2.8383(12)
115.00(10)
57.45(2)
57.87(3)
136.96(4)
121.5(3)
I(1)–Cu(1)#1a
I(2)–Cu(1)
Cu(1)–I(1)–Cu(1)#1
N(1)–Cu(1)–I(2)
N(1)–Cu(1)–I(1)
N(1)–Cu(1)–I(1)#1
I(1)–Cu(1)–I(1)#1
I(2)–Cu(1)–I(1)#1
I(2)–Cu(1)–I(1)
121.6(3)
aSymmetry transformations used to generate equivalent atoms: #1, –x, –y, –z + 2.

1088
H.-M. WANG ET AL.
FIG. 1. The binuclear compound [Cu2I4(Nppch)2]; the hydrogen atoms are not displayed, for clarity.
In the solid-state structure, there exists only one type of bonds (as shown in Table 3) are relatively weak, they play a very
intermolecular interactions From the packing diagram of the important role in holding the crystal framework. The structure
compound [Cu2I4(Nppch)2] (as shown in Figure 2), it is shown is formed by a layer accumulation with an arrangement in op-
that hydrogen bonds (C–H···I) exit between atom I of each posite directions. As a result of these C–H···I inducing contacts,
construction unit and the H atom from cation [Nppch]+ of the the repeating [Cu2I4(Nppch)2] construction unit grows infinitely
neighboring construction unit. Although the C–H···I hydrogen in the a, b, and c directions, and then a final supramolecular
FIG. 2. Three-dimensional supramolecular framework of compound [Cu2I4(Nppch)2] (along a axis) with C–H···I interaction shown by the dotted lines.

A NOVEL COORDINATED COPPER POLYMER
1089
TABLE 3
0.8
D–H···A interactions and their distances and angles
273nm
parameters for the compound
0.6
0.4
0.2
0.0
D–H···A interaction
D D···A (Å) D H···A (Å) ∠DHA (◦)
C(2)–H(2A)···I(2)
C(6)–H(6A)···I(2)
C(10)–H(10A)···I(2)
C(4)–H(4A)···I(1)
C(10)–H(10A)···I(1)
3.938
3.934
3.789
4.003
3.797
3.100
3.127
3.053
3.087
3.151
150.93
146.06
137.28
168.58
128.21
241nm
200 250 300 350 400 450 500 550 600
structure is built (Figure 2). Indeed, all these intermolecular
interactions are weak, undeniably, but that may make this binu-
clear complex increase its melting point and become stable.
Wavelength (nm)
FIG. 4. Ultraviolet and visible spectrogram of compound [Cu2I4(Nppch)2].
Ultraviolet Spectrum Properties
The UV-vis absorption of compound Nppch and
[Cu2I4(Nppch)2] in CH3OH solution is shown in Figure 3 and
Figure 4. The electronic spectra of cation Nppch and compound
[Cu2I4(Nppch)2] showed bands at 203 nm and 257 nm, and at
241 nm and 273 nm. By comparison, it is known that these
bands at 241 nm and 273 nm of compound [Cu2I4(Nppch)2],
are probably dominated by π···π transfer, while accompanied
by a red shift due to coordinating of the metal atoms and organic
ligands and the introduction of auxochrome I.
while the maximum emission wavelength of [Cu2I4(Nppch)2]
was 365 nm when the maximum excitation wavelength was set
at 330 nm. By comparison, we observe that the emission wave-
length of compound exhibited a blue shift, which is tentatively
assumed as the metal-to-ligand charge transfer transition.[12]
Thermogravimetric Properties
The thermal gravimetry–differential scanning calorimetry
(TG-DSC) curve for compound [Cu2I4(Nppch)2] is shown in
Figure 6. From TG, it is observed that the decomposition pro-
cess of the compound [Cu2I4(Nppch)2] contains two stages. The
first stage took place in the range of 227.0–567.4◦C and total
weight loss is 50.04% (theoretical weight loss 46.50%), which
probably corresponded to the elimination of organic cations and
some I atoms. The second stage mainly involved burning of the
inorganic framework, that is, odd I atoms, while total weight
loss is 17.20%. From the preceding data, we tentatively as-
sume that the last product is CuO. DSC analysis of compound
[Cu2I4(Nppch)2] showed a small and narrow endothermic peak
Luminescent Properties
The study of luminescent properties of metal–organic frame-
works (MOFs) is of great interest owing to their higher thermal
stability than the pure organic ligand and the ability to affect
the emission wavelength and intensity of the organic material
by metal coordination.[11] The fluorescence spectra of cation
Nppch and compound [Cu2I4(Nppch)2] are shown in Figure 5.
When the excitation wavelength was set at 325 nm, the emission
wavelength of organic cation Nppch were 380 nm and 500 nm,
3.0
2.5
2.0
1.5
1.0
0.5
0.0
203nm
257nm
200 250 300 350 400 450 500 550 600
Wavelength (nm)
FIG. 5. Solid-state fluorescence spectra of compound [Cu2I4(Nppch)2] and
Nppch at room temperature.
FIG. 3. Ultraviolet and visible spectra of Nppch.

1090
H.-M. WANG ET AL.
FIG. 6. TG-DSC curve of the compound [Cu2I4(Nppch)2].
around 238.1◦C and a large and broad exothermic peak around
653.3◦C.
5. Thanasekaran, P.; Liao, R.T.; Liu, Y.H.; Rajendran, T.; Rajagopal, S.; Lu,
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SUPPLEMENTARY MATERIAL
8. Steel, P.J. Acc. Chem. Res. 2005, 38, 243–250.
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Center,
CCDC number. 816382. Copies of this information may be ob-
tained free of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: 44-1223-336-033; e-mail: de-
posit@ccdc.cam.ac.uk; or www: http://www. ccdc. cam.ac.uk).
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