Synthesis and crystal structures of coordination complexes containing Cu2I2 units and their application in luminescence and catalysis

Article abstract of DOI:10.1002/cplu.201300249

The reaction of bis- or tris-chelating nitrogen-containing ligands (L1-L5) with CuI gave rise to five coordination complexes consisting of Cu ₂I₂ dimeric units. L1 in complex 1 adopts a cis conformation and links Cu₂I₂ into a dinuclear structure. L2 and L3 in complexes 2 and 3 exhibit a trans conformation, and the alternative linkage of L2 or L3 and Cu₂I₂ results in the formation of a 1D chain. In complex 4, two pyrazolyl-pyridine units of L4 at the same side of the central phenyl ring are connected to Cu₂I₂ forming a tetranuclear macrocycle, and the third pyrazolyl-pyridine unit at the other side of the central phenyl ring further links the macrocycle into a 1D chain. L5 bridges Cu₂I₂ in a cis conformation forming a tetranuclear complex, which is very different from 1 owing to the difference of the electronic property between pyrazolyl and triazolyl rings. The coordination nitrogen atoms in two pairs of ortho-positioned nitrogen-containing chelating rings in L1 and L5 are directed toward opposite and the same directions, respectively. Complexes 1-4 containing pyrazolyl-pyridine units showed luminescence whereas no clear emission was observed in complex 5 containing triazolyl-pyridine units, despite the fact that they were investigated under the same conditions. The application of complexes 1-5 in the copper(I)-catalyzed Ullmann cross-coupling reaction and azide-alkyne cycloaddition reaction was preliminarily evaluated. Making a difference: Five copper(I) complexes consisting of Cu₂I₂ units (see figure for example) have been prepared by using readily available bis- or tris-chelating nitrogen-containing ligands. These complexes possess different crystal structures, luminescence properties, and catalytic performances owing to the difference in steric and electronic properties of the organic ligands. Copyright

Full text of DOI:10.1002/cplu.201300249

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DOI: 10.1002/cplu.201300249
Synthesis and Crystal Structures of Coordination
Complexes Containing Cu2I2 Units and Their Application in
Luminescence and Catalysis
Huaixia Zhao,[a, b] Xinxiong Li,[a] Jinyun Wang,[a] Liuyi Li,[a] and Ruihu Wang*[a]
The reaction of bis- or tris-chelating nitrogen-containing li-
gands (L1–L5) with CuI gave rise to five coordination com-
plexes consisting of Cu2I2 dimeric units. L1 in complex 1
adopts a cis conformation and links Cu2I2 into a dinuclear struc-
ture. L2 and L3 in complexes 2 and 3 exhibit a trans conforma-
tion, and the alternative linkage of L2 or L3 and Cu2I2 results in
the formation of a 1D chain. In complex 4, two pyrazolyl-pyri-
dine units of L4 at the same side of the central phenyl ring are
connected to Cu2I2 forming a tetranuclear macrocycle, and the
third pyrazolyl-pyridine unit at the other side of the central
phenyl ring further links the macrocycle into a 1D chain. L5
bridges Cu2I2 in a cis conformation forming a tetranuclear com-
plex, which is very different from 1 owing to the difference of
the electronic property between pyrazolyl and triazolyl rings.
The coordination nitrogen atoms in two pairs of ortho-posi-
tioned nitrogen-containing chelating rings in L1 and L5 are di-
rected toward opposite and the same directions, respectively.
Complexes 1–4 containing pyrazolyl-pyridine units showed lu-
minescence whereas no clear emission was observed in com-
plex 5 containing triazolyl-pyridine units, despite the fact that
they were investigated under the same conditions. The appli-
cation of complexes 1–5 in the copper(I)-catalyzed Ullmann
cross-coupling reaction and azide–alkyne cycloaddition reac-
tion was preliminarily evaluated.
Introduction
The rational design and synthesis of metal–organic coordina-
tion complexes have attracted considerable attention owing to
their intriguing structures and potential applications in lumi-
nescence, catalysis, magnetism, gas storage, and separation.[1–3]
With the development of supramolecular chemistry and crystal
engineering, specific structural architectures may be predicted
and modulated to a certain degree through the judicial selec-
tion of organic ligands and metal ions. The focus of current re-
search has shifted away from simply constructing new archi-
tectures to generating new functional complexes and exploit-
ing their applications.[4] In this context, the well-characterized
di- or polynuclear metal clusters were used extensively as sec-
ondary building units (SBUs), which were held together by
bridging multidentate ligands to produce extended frame-
works with specific functions.[4d,5–7] For example, the deliberate
combination of rigid di- or polycarboxylate ligands and carbox-
ylate-bridged SBUs gave rise to porous coordination com-
plexes, which possessed promising applications in gas storage
and separation.[6,7] However, the versatile coordination modes
of the carboxylate group usually complicate the control and
modification of the target products. On the other hand, nitro-
gen-containing heterocyclic ligands were well known for their
simple coordination mode and strong coordination ability to
transition-metal ions.[8] The charge-neutral SBUs may be con-
nected by them into extended structures with predictable
structures and properties, but the research in this field is
seldom explored in comparison with the carboxylate ligands.[9]
The coordination complexes of copper(I) halides or pseudo-
halides are of great interest in coordination chemistry owing
to their attractive luminescence and catalytic properties.[10–14]
The copper ion possesses labile coordination modes with coor-
dination numbers from 2 to 5, which may form several fasci-
nating charge-neutral SBUs with halides or pseudohalides (X),
such as rhomboid Cu2X2 dimers,[12] cubane-like or step-cubane
Cu4X4 tetramers,[13] and even high nuclear CunXn clusters or
chains.[14] The interlinkage of the CuX SBUs with rigid or flexi-
ble bi- or multidentate nitrogen-containing ligands leads to
the formation of various coordination complexes with intrigu-
ing structures and properties, in which the coordination envi-
ronments of CuX aggregates are highly influenced by the
steric and electronic characters of the nitrogen-containing li-
gands. It was well known that N,N-chelating ligands may form
stable copper(I) complexes;[15] a range of N,N-chelating ligands
have recently been found to serve as the efficient supports of
copper(I) species in copper(I)-catalyzed organic reactions,[15,16]
and to a certain degree the presence of these ligands deter-
mines reaction rate and selectivity by varying the electronic
density and steric hindrance of the catalytically active species.
Mechanistic investigations of the catalytic reactions have also
[a] H. Zhao, Dr. X. Li, Dr. J. Wang, Dr. L. Li, Prof. R. Wang
State Key Laboratory of Structural Chemistry
Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences, Fuzhou, Fujian 350002 (P. R. China)
Fax: (+86)591-83714946
E-mail: ruihu@fjirsm.ac.cn
[b] H. Zhao
University of Chinese Academy of Sciences
Beijing 100049 (P. R. China)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cplu.201300249.
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Results and Discussion
shown that formation of the specific copper(I) complexes has
substantial effects on the catalytic systems.[17] Although contri-
butions of multidentate N,N-chelating ligands have been realiz-
ed in copper(I)-catalyzed organic reactions, the structures of
copper(I) precatalysts have rarely been investigated.[18]
Syntheses
Ligands L1–L4 were readily synthesized through a nucleophilic
substitution reaction of the corresponding bromomethyl com-
pounds, 3-(2-pyridyl)pyrazole, and NaOH in H2O/toluene/
NBu4OH,[20c,23,24] whereas synthesis of L5 was achieved by
simply mixing 2-ethynylpyridine, 1,2-di(bromomethyl)benzene,
NaN3, ascorbic acid, CuSO4·5H2O, and Na2CO3 in DMF/H2O
under the standard click conditions.[25] Direct treatment of L1–
L5 with CuI in DMF/MeCN immediately gave rise to a great
deal of pale yellow powder, which was insoluble in water and
common organic solvents, such as THF, ethanol, acetone, and
ethyl acetate. Single crystals suitable for X-ray diffraction were
obtained through carefully layering a MeCN solution of CuI on
the top of DMF/CH2Cl2 solutions of L1–L5.
As an extension of our effort to search for non-phosphine
catalytic systems based on nitrogen-containing chelating li-
gands,[19] we became interested in 3-(2-pyridyl)pyrazolyl deriva-
tives with a methylene unit, in which two or three chelating
pyrazolyl-pyridine units are connected to a central aromatic
core through a flexible methylene linker. The assembly of
these ligands with transition-metal ions or rare-earth ions pro-
duced many interesting polyhedral cages, molecular cubes,
and helical chains,[20,21] but the coordination polymers based
on these ligands and di- or multinuclear metal SBUs are still
unexplored. Inspired by the interesting luminescence and cata-
lytic properties of copper complexes from CunXn aggregates
and nitrogen-containing chelating ligands,[15–18,22] herein we
report the syntheses and crystal structures of five copper(I) co-
ordination complexes from bis- or tris-chelating pyrazolyl-pyri-
dine or triazolyl-pyridine ligands (Scheme 1). They consist of
Structural description
Crystal structure of complex 1
Single-crystal X-ray diffraction analysis indicated that com-
plex 1 crystallizes in the monoclinic space group P2(1) and is
a dinuclear complex (see Table 1). As shown in Figure 1a, the
asymmetric unit consists of one L1 ligand, two copper(I) ions,
and two m2-I counterions. Each copper(I) ion is coordinated by
two m2-I anions and two nitrogen atoms from the pyrazolyl-
pyridine chelating ring in a distorted tetrahedral geometry. The
coordination angles range from 78.012(4) to 117.073(2)8 (see
Table 2). Two m2-I anions bridge two independent copper(I)
ions forming a Cu2I2 dimer, in which the Cu···Cu separation of
2.589(4) ꢁ is much shorter than the sum of van der Waals radii
(2.80 ꢁ),[26] thus implying the presence of Cu···Cu interactions.
The bond angles I(1)ꢀCu(1)ꢀI(2) and I(1)ꢀCu(2)ꢀI(2) in the Cu2I2
dimer are 115.83(8) and 116.89(8)8, respectively, whereas the
bond angles of Cu(1)ꢀI(2)ꢀCu(2) and Cu(1)ꢀI(1)ꢀCu(2) are
59.81(6) and 59.82(8)8, respectively. L1 adopts a cis configura-
tion, in which two pyrazolyl-pyridine chelating units locate the
same side of the central phenyl ring, and are almost perpen-
dicular to the central phenyl ring. The twisting angles among
two pyrazolyl-pyridine units and the central phenyl ring are
82.8 and 87.28, respectively, whereas the dihedral angle be-
tween two pairs of pyrazolyl-pyridine rings is 16.38. The coordi-
nation nitrogen atoms in two pairs of pyrazolyl-pyridine rings
are directed toward each other, and the interlinkage of bis-che-
lating L1 and Cu2I2 results in the formation of a dinuclear com-
plex, which is very different from a double helicate complex
from L1 and [Cu(MeCN)4][PF6], thus suggesting counter anions
have an important effect on structures.[20e] It should be men-
tioned that the phenyl ring in complex 1 is almost parallel to
the adjacent pyridyl ring of the other dinuclear unit with a tilt
angle of 4.808 and a centroid-to-centroid distance of 4.14 ꢁ,
whereas the centroid-to-centroid distance and the tilt angle in
two parallel pyridyl rings between the adjacent dinuclear units
are 3.87 ꢁ and 16.868, respectively, which suggests the pres-
ence of weak p–p stacking interactions (Figure 1b).
Scheme 1. Bis- or tris-chelating pyrazolyl-pyridine or triazolyl-pyridine li-
gands L1–L5.
well-separated Cu2I2 units and are held at specific distances
from each other. Their luminescence properties and application
in the copper(I)-catalyzed Ullmann cross-coupling reaction and
azide–alkyne cycloaddition reaction were initially investigated.
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Table 1. Crystal data and structure refinement results for complexes 1–5.
Complexes
1
2
3
4
5
empirical formula
formula weight
crystal system
space group
a [ꢁ]
C24H20Cu2I2N6
773.34
monoclinic
P2(1)
9.108(2)
14.33(2)
9.859(2)
103.83(2)
1249(3)
2
C27H27Cu2I2N7O
846.44
monoclinic
P21/c
17.166(7)
9.863(3)
19.772(8)
114.440(5)
3048(2)
4
C12H10CuIN3
386.67
monoclinic
P21/c
7.160(4)
16.703(10)
11.543(5)
114.50(3)
1256.2(1)
4
C38.5H37ClCu3I3N10
C24H21Cu2I2N9
816.38
monoclinic
P21/c
10.864(2)
16.963(2)
16.793(2)
92.279(9)
3092.2(6)
4
1246.55
monoclinic
C2/c
29.785(1)
17.473(7)
17.374(7)
90.756(8)
9042(6)
8
b [ꢁ]
c [ꢁ]
b [8]
volume [ꢁ3]
Z
1calcd [mgmꢀ3
]
2.056
4.199
740
1.845
3.454
1640
2.045
4.176
740
1.831
3.545
4808
1.754
3.400
1568
m [mmꢀ1
F(000)
]
reflections collected
unique reflections
parameters
11745
5294
307
23061
6920
354
9430
2822
154
34367
10060
518
23673
6993
335
Rint
S on F2
0.1022
0.965
0.0528
1.063
0.0736
0.889
0.0407
1.097
0.0424
1.093
R1 [I>2s(I)][a]
wR2 (all data)[b]
D1max and D1min [eꢁꢀ3
0.0615
0.1459
1.407 and ꢀ2.097
0.0478
0.1048
0.953 and ꢀ1.364
0.0431
0.1125
1.248 and ꢀ1.137
0.0759
0.2232
1.509 and ꢀ1.276
0.0532
0.1442
0.967 and ꢀ0.555
]
[a] R=ꢀj jF0 jꢀjFc j j)/ꢀjF0 j. [b] wR=[ꢀw(F0 ꢀFc2)2/ꢀw(F0 )2]1/2
.
2
2
Crystal structure of complex 2
Complex 2 crystallizes in the monoclinic space group P21/c and
is a 1D chain. As shown in Figure 2a, the asymmetric unit con-
tains one L2 ligand, two crystallographically independent cop-
per(I) ions, two m2-I counterions, and one DMF lattice molecule.
Both copper(I) ions display a distorted tetrahedral geometry
comprising two m2-I ions and two nitrogen atoms from the pyr-
azolyl-pyridine chelating ring. The bond angles around cop-
per(I) are in the range from 78.351(2) to 123.202(2)8, which are
comparable with those in complex 1. Two m2-I ions are bound
to two symmetry-related copper(I) ions forming a Cu2I2 rhom-
boid dimer, in which copper(I) ions are separated by distances
of 2.558(7) and 2.659(3) ꢁ, respectively. The bond angles of
I(1)ꢀCu(1)ꢀI(1A) and I(2)ꢀCu(2)ꢀI(2B) in the dimer are 121.01(3)
and 118.72(3)8, respectively, which are slightly larger than their
analogues in complex 1, whereas the bond angles of Cu(1)ꢀ
I(1)ꢀCu(1 A) and Cu(2)ꢀI(2)ꢀCu(2B) are comparable with those
in complex 1. L2 adopts a trans conformation, in which two
chelating pyrazolyl-pyridine units locate at the opposite faces
of the central phenyl ring. The twisting angles between the
chelating pyrazolyl-pyridine units and phenyl ring are 74.836(6)
and 82.992(9)8, respectively, whereas the dihedral angle be-
tween two pairs of pyrazolyl-pyridine units is 63.88, which is
different from those in complex 1. The bis-chelating L2 ligand
joins two independent Cu2I2 units together giving rise to a 1D
chain. As shown in Figure 2b, the 1D chain is further organ-
ized into a 2D architecture by p–p stacking interactions
among the pyrazolyl-pyridine units of L2.
Figure 1. a) Molecular structure of complex 1 with thermal ellipsoids at the
50% level. b) Packing diagram along the c axis in complex 1.
Crystal structure of complex 3
Complex 3 also crystallizes in the monoclinic space group
P21/c and is a 1D chain consisting of Cu2I2 dimers but, different
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Table 2. Selected bond lengths [ꢁ] and angles [o] for complexes 1–5.[a]
Complex 1
Table 2. (Continued)
Complex 1
N(7A)ꢀCu(2)ꢀN(8A)
N(1)ꢀCu(1)ꢀI(1)
N(1)ꢀCu(1)ꢀI(2)
N(7A)ꢀCu(2)ꢀI(2)
N(7A)ꢀCu(2)ꢀI(1)
Cu(1)ꢀI(1)ꢀCu(2)
79.80(17)
114.39(15)
109.84(13)
115.57(14)
121.19(14)
59.41(3)
N(1)ꢀCu(1)ꢀN(2)
N(2)ꢀCu(1)ꢀI(1)
N(2)ꢀCu(1)ꢀI(2)
N(8A)ꢀCu(2)ꢀI(2)
N(8A)ꢀCu(2)ꢀI(1)
Cu(2)ꢀI(2)ꢀCu(1)
79.49(18)
127.95(14)
112.20(14)
129.37(14)
100.07(13)
59.60(3)
I(1)ꢀCu(1)
2.624(3)
2.584(3)
2.097(10)
2.111(9)
2.589(4)
115.83(8)
79.60(40)
107.0(3)
106.0(2)
126.6(3)
112.6(3)
59.82(8)
I(1)ꢀCu(2)
2.569(3)
2.609(4)
2.089(9)
2.069(9)
–
I(2)ꢀCu(1)
I(2)ꢀCu(2)
Cu(1)ꢀN(1)
Cu(1)ꢀN(2)
Cu(2)ꢀN(6)
Cu(2)ꢀN(5)
Cu(1)ꢀCu(2)
–
I(2)-Cu(1)-I(1)
N(2)ꢀCu(1)ꢀN(1)
N(1)ꢀCu(1)ꢀI(2)
N(1)ꢀCu(1)ꢀI(1)
N(2)ꢀCu(1)ꢀI(2)
N(6)ꢀCu(2)ꢀI(1)
Cu(1)ꢀI(2)ꢀCu(2)
I(1)ꢀCu(2)ꢀI(2)
N(5)ꢀCu(2)ꢀN(6)
N(2)ꢀCu(1)ꢀI(1)
N(6)ꢀCu(2)ꢀI(2)
N(5)ꢀCu(2)ꢀI(1)
N(5)ꢀCu(2)ꢀI(2)
Cu(2)ꢀI(1)ꢀCu(1)
116.89(8)
78.00(40)
112.4(3)
114.0(3)
117.1(3)
112.3(3)
59.81(6)
[a] Symmetry transformations used to generate equivalent atoms for 2:
(A) ꢀx+1, ꢀy, ꢀz; (B) ꢀx, ꢀy+1, ꢀz; for 3: (A) ꢀx+1, ꢀy, ꢀz; for 4:
(A) ꢀx, y, ꢀz+5/2; (B) ꢀx+1/2, ꢀy+1/2, ꢀz+2; for 5: (A) ꢀx, ꢀy, ꢀz+1.
Complex 2
I(1)ꢀCu(1)
2.572(1)
2.617(1)
2.103(4)
2.624(1)
2.119(4)
2.559(2)
121.01(3)
79.53(16)
113.11(11)
114.79(11)
110.58(12)
107.89(11)
58.99(3)
I(1)ꢀCu(1A)
2.624(1)
2.601(1)
2.090(4)
2.601(1)
2.102(5)
2.659(2)
118.72(3)
78.35(16)
116.83(12)
103.96(11)
123.20(11)
110.81(12)
61.28(3)
I(2)ꢀCu(2)
I(2)ꢀCu(2B)
Cu(1)ꢀN(1)
Cu(1)ꢀN(2)
Cu(1)ꢀI(1A)
Cu(2)ꢀI(2B)
Cu(2)ꢀN(5)
Cu(2)ꢀN(6)
Cu(1)ꢀCu(1A)
I(1)ꢀCu(1)ꢀI(1A)
N(2)ꢀCu(1)ꢀN(1)
N(2)ꢀCu(1)ꢀI(1)
N(2)ꢀCu(1)ꢀI(1A)
N(6)ꢀCu(2)ꢀI(2B)
N(5)ꢀCu(2)ꢀI(2)
Cu(1)ꢀI(1)ꢀCu(1A)
Cu(2)ꢀCu(2B)
I(2B)ꢀCu(2)ꢀI(2)
N(6)ꢀCu(2)ꢀN(5)
N(1)ꢀCu(1)ꢀI(1)
N(1)ꢀCu(1)ꢀI(1A)
N(5)ꢀCu(2)ꢀI(2B)
N(6)ꢀCu(2)ꢀI(2)
Cu(2B)ꢀI(2)ꢀCu(2)
Complex 3
I(1)ꢀCu(1)
2.654(2)
2.101(5)
2.547(2)
121.44(4)
122.83(14)
102.30(15)
58.56(4)
Cu(1)ꢀI(1A)
Cu(1)ꢀN(2)
–
N(2)ꢀCu(1)ꢀN(1)
N(1)ꢀCu(1)ꢀI(1A)
N(1)ꢀCu(1)ꢀI(1)
–
2.550(2)
2.079(5)
–
78.60(20)
112.82(14)
110.91(15)
–
Cu(1)ꢀN(1)
Cu(1)ꢀCu(1A)
I(1A)ꢀCu(1)ꢀI(1)
N(2)ꢀCu(1)ꢀI(1A)
N(2)ꢀCu(1)ꢀI(1)
Cu(1A)ꢀI(1)ꢀCu(1)
Figure 2. a) View of the 1D chain in complex 2. b) View of the 2D layer
formed by p–p stacking interactions among the neighboring chains in com-
plex 2.
Complex 4
I(1)ꢀCu(1)
2.631(2)
2.574(4)
2.602(2)
2.122(7)
2.060(6)
2.093(7)
2.622(2)
2.080(6)
2.671(2)
78.80(30)
103.52(19)
130.8(2)
77.30(30)
114.0(2)
110.4(2)
78.0(3)
I(1)ꢀCu(1A)
2.596(2)
2.569(2)
2.622(2)
2.569(2)
2.126(8)
2.569(2)
2.110(7)
2.606(2)
2.671(2)
127.7(2)
108.94(18)
107.53(5)
117.11(19)
112.69(19)
118.24(5)
107.4(2)
109.25(18)
115.35(5)
61.87(4)
–
I(2)ꢀCu(2)
I(3)ꢀCu(2B)
from that in complex 2, its asymmetric unit consists of one
copper(I) ion, one Iꢀ, and one half of the L3 ligand (Figure 3a).
L3 exhibits a trans configuration, and two pairs of pyrazolyl-
pyridine units are parallel to each other owing to central sym-
metry. The twisting angle between the pyrazolyl-pyridine unit
and the central phenyl ring is 70.98. Two m2-I ions are bound to
two symmetry-related copper(I) ions forming a Cu2I2 dimer, in
which the bond angles of I(1)ꢀCu(1)ꢀI(1A) and Cu(1)ꢀI(1)ꢀ
Cu(1A) are 121.44(4) and 58.56(4)8, respectively. The neighbor-
ing Cu2I2 units are linked by bis-chelating L3 forming a 1D
chain. The centroid-to-centroid distance and tilt angle between
pyrazolyl and pyridine rings from different chains are 3.758 ꢁ
and 19.0328, respectively, which suggests the presence of
a weak p–p stacking interaction. Thus, the 1D chain is further
organized into a 2D layer by p–p stacking interaction (Fig-
ure 3b).
I(3)ꢀCu(3)
I(2)ꢀCu(3B)
Cu(1)ꢀN(1)
I(3)ꢀCu(2B)
Cu(1)ꢀN(2)
Cu(2)ꢀN(4)
Cu(2)ꢀN(5)
Cu(2)ꢀI(3B)
Cu(3)ꢀI(2B)
Cu(3)ꢀN(7)
Cu(3)ꢀN(9)
Cu(1)ꢀCu(1A)
Cu(3)ꢀCu(2B)
N(2)ꢀCu(1)ꢀI(1A)
N(2)ꢀCu(1)ꢀI(1)
I(1A)ꢀCu(1)ꢀI(1)
N(5)ꢀCu(2)ꢀI(3B)
N(5)ꢀCu(2)ꢀI(2)
I(3B)ꢀCu(2)ꢀI(2)
N(7)ꢀCu(3)ꢀI(3)
N(9)ꢀCu(3)ꢀI(2B)
I(3)ꢀCu(3)ꢀI(2B)
Cu(2)ꢀI(2)ꢀCu(3B)
–
Cu(2)ꢀCu(3B)
N(2)ꢀCu(1)ꢀN(1)
N(1)ꢀCu(1)ꢀI(1A)
N(1)ꢀCu(1)ꢀI(1)
N(5)ꢀCu(2)ꢀN(4)
N(4)ꢀCu(2)ꢀI(3B)
N(4)ꢀCu(2)ꢀI(2)
N(9)ꢀCu(3)ꢀN(7)
N(9)ꢀCu(3)ꢀI(3)
N(7)ꢀCu(3)ꢀI(2B)
Cu(1A)ꢀI(1)ꢀCu(1)
Cu(2B)ꢀI(3)ꢀCu(3)
124.63(19)
117.0(2)
59.81(5)
62.20(4)
Complex 5
I(1)ꢀCu(1)
2.592(1)
2.636(1)
2.084(4)
2.100(4)
2.595(1)
109.02(3)
I(1)ꢀCu(2)
I(2)ꢀCu(2)
Cu(1)ꢀN(2)
Cu(2)ꢀN(8A)
–
2.644(1)
2.584(1)
2.123(5)
2.105(5)
–
I(2)ꢀCu(1)
Crystal structure of complex 4
Cu(1)ꢀN(1)
Cu(2)ꢀN(7A)
Cu(1)ꢀCu(2)
I(1)ꢀCu(1)ꢀI(2)
Complex 4 crystallizes in the monoclinic space group C2/c and
is a 1D chain. As shown in Figure 4a, three crystallographically
independent copper(I) ions adopt a distorted tetrahedral ar-
I(2)ꢀCu(2)ꢀI(1)
109.03(3)
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rangement provided by two m2-I
anions and two nitrogen atoms
from L4. The m2-I anions are
bound to symmetry-related cop-
per(I) ions forming Cu2I2 dimers,
in which the Cu···Cu distances
are in the range from 2.606(3) to
2.670(8) ꢁ, and the bond angles
of IꢀCuꢀI and CuꢀIꢀCu are
107.53(5)–118.24(5)
and
59.81(5)–62.20(4)8, respectively.
L4 exhibits a tris-chelating bridg-
ing mode. Two pyrazolyl-pyri-
dine units in L4 are on the same
side of the central phenyl ring,
and the twisting angles between
two pyrazolyl-pyridine units and
the central phenyl ring are 89.7
and 83.78, respectively, whereas
the dihedral angle between two
pairs of pyrazolyl-pyridine rings
is 15.38. Two pairs of pyrazolyl-
pyridine units from different L4
ligands bridge Cu2I2 forming
a tetranuclear macrocycle. The
other pyrazolyl-pyridine unit at
the other side of the central
phenyl ring in L4 further links
the macrocycles into a 1D chain
Figure 4. a) The coordination environment of copper(I) in complex 4 with thermal ellipsoids at the 50% level.
b) View of the 1D chain in complex 4.
(Figure 4b). There are no short contacts or noteworthy weak
interactions between the adjacent chains.
Crystal structure of complex 5
Complex 5 crystallizes in the monoclinic space group P21/c and
is a discrete tetranuclear structure. As shown in Figure 5, cop-
per(I) ions display a distorted tetrahedral geometry and are co-
ordinated by two m2-I anions and two nitrogen atoms from the
triazolyl-pyridine chelating unit. Two m2-I anions bridge two
Figure 3. a) View of the 1D chain in complex 3. b) View of the 2D layer
formed by p–p stacking interactions among the neighboring chains in com-
plex 3.
Figure 5. Molecular structure of complex 5 with thermal ellipsoids at the
50% level.
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crystallographically independent copper(I) ions forming a Cu2I2
dimeric unit with Cu···Cu distance of 2.595(1) ꢁ. L5 adopts a cis
conformation, and the twisting angles between chelating tria-
zolyl-pyridine units and the phenyl ring are 106.8 and 74.88, re-
spectively, whereas the dihedral angle between two pairs of
triazolyl-pyridine units is 32.98. Different from those in com-
plex 1, the coordination nitrogen atoms in two pairs of triazol-
yl-pyridine chelating rings in L5 point toward the same direc-
tion, thus resulting in bis-chelating L5 linking two Cu2I2 units
into a tetranuclear macrocycle. The closest Cu···Cu separation
in the macrocycle is 6.703 ꢁ. There are no short contacts or
noteworthy weak interactions between the adjacent macrocy-
cles.
Thermogravimetric analysis
The thermal stabilities of complexes 1–5 were investigated on
pale yellow powders under a nitrogen atmosphere. As shown
in Figure 6, thermogravimetric analysis (TGA) curves of com-
Figure 6. TGA curves of complexes 1–5.
plexes 1–3 showed that their thermal stabilities are similar to
each other and stable up to 3358C. However, 4.8 and 4.6%
weight loss before 1408C was observed in complexes 4 and 5,
respectively, corresponding to removal of three and two water
molecules (calcd: 4.4%), respectively, and subsequent decom-
position was observed after 320 and 2988C in 4 and 5, respec-
tively.
Luminescence properties
The copper(I) complexes consisting of Cu2I2 units were well
known to show promising luminescence properties,[26] which
prompted us to explore their luminescence behaviors. Com-
plexes 1–5 are pale yellow powders under ambient light. Com-
plexes 1–4 emitted intense green, orange, yellow, and orange-
red light under UV irradiation, respectively, whereas no emis-
sion was observed for complex 5. The solid-state luminescence
spectra of complexes 1–4 at room temperature were further
studied. As shown in Figure 7, they displayed emission maxima
at 566, 604, 575, and 625 nm, respectively, upon excitation
around 370 nm, which is in good agreement with the light ob-
Figure 7. Emission spectra of ligands (blue dashed lines) and complexes
(solid black lines) for (a) L1 and complex 1, (b) L2 and complex 2, (c) L3 and
complex 3, (d) L4 and complex 4.
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served under UV irradiation. The free ligands L1–L4 showed
a maximum emission band at 440, 402, 508, and 440 nm, re-
spectively, if L2 was excited at 340 nm and L1, L3, and L4 were
excited at 370 nm. Shoulder peaks at 418, 441, and 417 nm
were also observed in L1, L3, and L4, respectively. In compari-
son with the respective free ligands, a clear redshift was ob-
served in complexes 1–4, which suggested that the lumines-
cence property of L1–L4 is affected remarkably by the chela-
tion of copper(I) ions, thereby resulting in the delocalization of
the p-electron system. The closest distances of Cu···Cu in 1–4
are in the range of 2.547(2)–2.671(2) ꢁ, which are lower than
the sum of the van der Waals radii of copper(I) (2.80 ꢁ). There-
fore, their emission is attributed primarily to a combination of
iodide-to-copper charge transfer and copper-centered transi-
tion from 3d10 to 3d94s and from 3d10 to 3d94p in copper(I)
centers.[13b,26,27] Notably, no clear emission was observed in L5
and complex 5 if they were investigated under the same con-
ditions, thus suggesting that the type of coordination group in
the organic ligands has an important effect on luminescence
properties.
by using complex 4 as a copper source. Among the organic
and inorganic bases examined, it was found that KOH was the
most efficient and gave rise to N-(4-phenyl)imidazole in a quan-
titative yield (Table 3, entry 9). Other bases, such as K2CO3 and
K3PO4, were slightly less efficient and provided the target prod-
uct in 76 and 91% GC yields, respectively (Table 3, entries 6
and 7). However, Et3N was ineffective for the cross-coupling re-
action under the same conditions (Table 3, entry 8). Investiga-
tion of a variety of solvents revealed that the use of DMSO
was superior to DMF, EtOH, and THF (Table 3, entries 9–12). No
desirable product was observed if neat water was used as a re-
action medium (Table 3, entry 13), but a trace amount of water
has no detectable effect on the reaction.
Under the above-mentioned optimized conditions, the gen-
erality of the Ullmann cross-coupling reaction between aryl
halides and azoles was explored. The effect of varying aryl io-
dides was examined by using imidazole as a substrate (Table 4,
entries 1–7). Aryl iodides bearing electron-withdrawing groups,
such as ꢀF, ꢀCF3, and ꢀNO2, afforded the corresponding prod-
ucts in almost quantitative yields (Table 4, entries 2–4); their
turnover number (TON) was 10. The reaction of electron-rich
iodotoluene with imidazole also gave rise to the desired prod-
uct in excellent GC yield (Table 4, entry 5). Interestingly, the
steric effect of a methyl group at the ortho, meta, and para po-
sition had no significant effect on the cross-coupling reaction
(Table 4, entries 5–7). In addition to imidazole, other azoles,
such as pyrrole, pyrazole, and triazole, also coupled efficiently
with 4-iodotoluene, and the corresponding products were ob-
tained in quantitative yields (Table 4, entries 8–10). Notably, the
N-arylation reaction of imidazole with aryl bromides, such as 4-
bromoacetophenone and 4-bromonitrobenzene, gave the re-
sulting products in 75 and 100% GC yields, respectively
(Table 4, entries 11 and 12). The heteroaromatic 2-bromopyri-
dine also reacted completely with imidazole under the opti-
mized conditions (Table 4, entry 13). However, the catalytic
system is inefficient for aryl bromides bearing electron-donat-
ing groups and aryl chlorides. Although the catalytic activity in
the five complexes is comparable with those reported from
copper(I) coordination polymers,[18a,b] it is much lower than
those from CuI supported by bidentate nitrogen-containing
chelating ligands, such as phenanthroline and their derivative-
s.[15a,b] It was reported that the use of the organic ligands may
enhance the catalytic activity in the Ullmann cross-coupling re-
action through increasing the solubility of copper salts in reac-
tion media and the electronic density on the catalytically
active species.[19d] As a result, low catalytic performances in
complexes 1–5 probably resulted from their insolubility in the
reaction media, which inhibited the effective contact between
substrates and catalytically active sites.
Catalytic performances in N-arylation and azide–alkyne
cycloaddition reactions
The copper(I) complexes consisting of Cu2I2 units have been re-
ported to serve as catalyst precursors in the Ullmann cross-
coupling reaction and azide–alkyne cycloaddition reaction.[18a]
Ullmann cross-coupling reaction of iodobenzene and imidazole
was initially tested using complexes 1–5 as precatalysts and
Cs2CO3 as a base at 1108C in DMSO. Product N-(4-phenyl)imi-
dazole was obtained in a good gas chromatographic (GC) yield
(Table 3, entries 1–5). Complex 4 displayed the best catalytic
activity among the five complexes and gave the target product
in 93% GC yield (Table 3, entry 4). The effect of bases and sol-
vents on the cross-coupling reaction was further investigated
Table 3. Ullmann cross-coupling reaction of imidazole and iodobenzene
under different conditions.[a]
Entry
Cu complex
Base
Solvent
Yield [%][b]
1
2
3
4
5
6
7
8
1
2
3
4
5
4
4
4
4
4
4
4
4
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
K3PO4
Et3N
KOH
KOH
KOH
KOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
85
82
80
93
85
76
91
<1
100
58
To extend the scope of organic reactions catalyzed by the
five complexes consisting of Cu2I2 dimers, the copper(I)-cata-
lyzed azide–alkyne cycloaddition reaction was also investigat-
ed. To avoid the potential hazards of organic azides in the
course of isolation and purification, a three-component one-
pot reaction of alkyl halides, sodium azide, and alkynes was
performed. As shown in Table 5, the catalytic activity of com-
plexes 1–5 was originally examined in the reaction of benzyl
9
10
11
12
13
EtOH
THF
H2O
35
40
<1
KOH
[a] Reaction conditions: aryl halide (0.5 mmol), imidazole (0.75 mmol),
base (1.0 mmol), copper(I) amount in complex (0.050 mmol), solvent
(2.0 mL), 1108C, 24 h, under N2. [b] Yield based on GC analysis.
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different alkyne substrates. Reac-
tion of phenylacetylene bearing
electron-donating groups with
benzyl bromide and NaN3 pro-
ceeded readily to give the target
isolated products in high yields
(Table 5, entries 11 and 12). Nota-
bly, the use of 2-pyridylacetylene
and oct-1-yne also gave rise to
the desired products in quantita-
tive yields under the same con-
ditions (Table 5, entries 13 and
14).
Table 4. Ullmann cross-coupling reaction of aryl halides and azoles catalyzed by complex 4.[a]
Entry
ArꢀX
Azole
Product
Yield [%][b]
TON
1
2
3
4
5
quant. (92)
97 (94)
10
10
10
10
9
96 (92)
quant.
94 (90)
6
7
93
90
9
9
8
quant. (91)
quant.
10
10
10
8
Discussion of structure of the
complexes
9
It was well known that organic
ligands play a crucial role in the
synthesis of coordination com-
plexes, in which the symmetry,
configuration, length, steric, and
electronic characters of the
spacers between coordination
sites of the organic ligands have
important effects on the struc-
tures and properties of the final
products.[2,6] The strong chelat-
10
11
12
13
quant. (90)
75
quant.
10
10
quant.
[a] Reaction conditions: aryl halide (0.5 mmol), imidazole (0.75 mmol), KOH (1.0 mmol), Cu amount in com-
plex 4 (0.05 mmol), DMSO (2.0 mL), 1108C, 24 h, under N2. [b] Yield based on GC analysis; the yield of isolated
product is given in parentheses.
bromides, NaN3, and phenylacetylene at 258C in neat water
under ambient atmosphere. Complex 2 showed the highest
catalytic activity and gave the desired product in a quantitative
GC yield with TON of 50, whereas complex 3 provided the de-
sired product in the lowest yield, despite its structure being
similar to that of complex 2. The use of 1 and 5 gave the
target product in 88 and 58% GC yields, respectively. The
slightly lower catalytic activity of 5 can probably be ascribed
to the poor electron-donor ability of the triazolyl group in L5
in comparison with the pyrazolyl group in L1, as well as the
difference between their crystal structures. However, a 77% GC
yield was obtained on using complex 4 as a precatalyst, al-
though it is highly efficient for the copper-catalyzed Ullmann
cross-coupling reaction. These results further suggested that
the steric and electronic characters of bis- or tris-chelating ni-
trogen-containing ligands have an important effect on crystal
structures and catalytic performances, although all five com-
plexes consist of Cu2I2 dimeric units.
ing ability of pyrazolyl/triazolyl-pyridine units in L1–L5 may
exert structural constraint and induce specific geometric pref-
erence of copper(I). As a result, it is not surprising that com-
plexes 1–5 consist of Cu2I2 dimeric units. At the same time, the
flexible methylene linker between the chelating units and the
central aromatic core may allow L1–L5 to rotate freely in the
assembly processes to satisfy the coordination geometry of
copper(I), thereby resulting in the preferable conformation of
L1–L5. As shown in Scheme 1, L1 adopts a cis conformation
and coordinates to Cu2I2 to form a dinuclear structure in which
the coordination nitrogen atoms of two ortho-positioned pyra-
zolyl-pyridine units are directed toward opposite positions.
However, the distances of meta- and para-positioned pyrazolyl-
pyridine units in L2 and L3 are larger than that in L1, so it is
difficult to obtain the same dinuclear structure as complex 1
even in a cis conformation. Alternatively, L2 and L3 in a trans
conformation link Cu2I2 into a 1D chain. If the bulkier tris-che-
lating L4 is used, the two pyrazolyl-pyridine units at the same
side of the central phenyl ring connect Cu2I2 to form a tetranu-
clear macrocycle, and the third pyrazolyl-pyridine unit from the
other side further links the macrocycle into a 1D chain. In com-
parison with the pyrazole group, the triazole group is known
to be more electron-deficient, and interesting results between
the reaction of L1–L4 and CuI prompted us to investigate the
coordination behavior of triazolyl-pyridine. Similar to L1, L5
also adopts a cis conformation, but the coordination nitrogen
atoms in two ortho-positioned triazolyl-pyridine units point
toward the same direction; thus, the interlinkage of L5 and
Cu2I2 results in the formation of a tetranuclear complex. The
Complex 2 was further applied to azide–alkyne cycloaddition
of electron-rich and electron-poor benzyl bromides at 258C in
neat water. The corresponding isolated triazolyl products were
obtained in moderate to good yields (Table 5, entries 6–8). In-
terestingly, the electron-poor and hindered benzyl bromide, 1-
(bromomethyl)-2,3,4,5,6-pentafluorobenzene, also reacted with
phenylacetylene and sodium azide, affording the target prod-
uct in 33% GC yield (Table 5, entry 9). The use of 1,3-bis(bro-
momethyl)benzene resulted in the formation of a disubstituted
triazolyl product in 90% isolated yield (Table 5, entry 10). The
three-component cycloaddition reaction was also extended to
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Tables S1–S5 in the Supporting
Information, iodide and copper(I)
carry the most negative and pos-
itive charge, respectively. The
natural charges of copper(I) in
Table 5. Three-component azide–alkyne cycloaddition of aryl halides, alkynes, and NaN3 promoted by com-
plexes 1–5.[a]
complex 5
(0.70653
and
Entry Complex Aryl halide
Alkyne
Product
Yield [%][b]
88
TON
44
0.71039e) are more positive
than those from 0.67817 to
0.69868e in complexes 1–4,
which is probably ascribable to
the difference of electronic char-
acters between pyrazolyl and tri-
azolyl groups. The charge of
iodide ions in the five complexes
is in the range from ꢀ0.69291 to
ꢀ0.67916e. Clearly, iodide ions
in 4 and 5 are slightly more neg-
ative than in 1–3. All of the ni-
trogen atoms in 1–5 possess
a negative charge; the natural
charge of the pyridyl nitrogen
atom is in the range from
ꢀ0.54797 to ꢀ0.53004e, which
is much more negative than
other nitrogen atoms ranging
from ꢀ0.05781 to ꢀ0.36946e.
The uncoordinated nitrogen
atoms are less negative and the
charge is in the range from
ꢀ0.05781 to ꢀ0.19188e. Nota-
bly, 2-positioned nitrogen atoms
of triazolyl groups in complex 5
are the least negative and their
charge ranges from ꢀ0.08997 to
ꢀ0.05781e. Studies of the high-
est occupied molecular orbital
(HOMO) and lowest unoccupied
molecular orbital (LUMO) have
revealed that the HOMO in com-
1
2
3
4
5
1
2
3
4
5
quant. (95) 50
25
77
58
13
39
29
6
7
8
2
2
2
82 (70) 41
– (60) 30
– (80) 40
9
2
33
17
10
11
2
2
– (90) 45
– (90) 45
12
13
14
2
2
2
92 (91) 46
99 (90) 50
quant.
50
[a] Reaction conditions: alkyl halide (0.5 mmol), alkyne (0.6 mmol), NaN3 (0.6 mmol), Cu amount in com-
plexes 1–5 (0.01 mmol), H2O (1.5 mL), 258C, 12 h. [b] Yield based on GC analysis; the yield of isolated product
is given in parentheses.
structural difference in complexes 1 and 5 is probably ascriba-
ble to the difference of electronic characters between pyrazolyl
and triazolyl groups, which further results in different lumines-
cence and catalytic performances. In complexes 1–5, L1–L5 co-
ordinate to copper(I) in a stable chelating mode, and the Nꢀ
CuꢀN bond angles in the five-membered chelating rings are in
the range from 77.30(30) to 79.80(17)8, whereas the CuꢀIꢀCu
and IꢀCuꢀI bond angles in the Cu2I2 dimeric unit are 58.56(4)–
62.20(4) and 107.53(5)–121.44(4)8, respectively, which are com-
parable with those from copper(I) complexes consisting of
Cu2I2 units.[12]
Theoretical study
To obtain a better understanding of the electronic characters
in complexes 1–5, their charge distributions and molecular or-
bital analyses based on X-ray crystal structures were imple-
mented by using Gaussian 03.[28–33] As shown in Figure 8 and
Figure 8. Electrostatic potential mapped onto the electron density surface in
complexes 1–5.
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assigned to isotropic thermal parameters, and allowed to ride on
their parent carbon atoms before the final cycle of refinement.
Crystal data as well as details of data collection and refinement for
complexes 1–5 are summarized in Table 1. Selected bond lengths
and bond angles are given in Table 2.
plexes 1–5 consists primarily of the contribution from Cu2I2 di-
meric units, whereas the LUMO is mainly occupied by pyrazol-
yl-pyridine or triazolyl-pyridine chelating units (Figure S1).
Conclusion
CCDC 930571 (1), 930572 (2), 930573 (3), 930574 (4), and 930575
(5) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
Five copper(I) complexes have been prepared by using readily
available bis- or tris-chelating nitrogen-containing ligands, and
their luminescence properties as well as application in the Ull-
mann cross-coupling reaction and azide–alkyne cycloaddition
reaction were investigated. Although the five complexes con-
sist of Cu2I2 units, they showed different luminescence proper-
ties and catalytic performances. In comparison with organic li-
gands containing pyrazolyl-pyridine units, no luminescence
emission was observed in the ligand containing triazolyl-pyri-
dine units and its coordination polymers. Low catalytic per-
formances of complexes 1–5 in the Ullmann cross-coupling re-
action probably resulted from their poor solubility in reaction
media. This study has demonstrated that the combination of
CuI aggregates and chelating nitrogen-containing ligands is an
efficient route for the design and synthesis of coordination
polymers with luminescence and catalytic properties, which is
helpful to understand the structures of precatalysts in copper-
catalyzed organic reactions. Further study will focus on widen-
ing the scope of nitrogen-containing ligands and catalytic reac-
tions to seek a green and cheap catalytic system.
Theoretical study
The calculations of electronic structures were performed by using
density functional theory with the hybrid Becke three-parameter
Lee–Yang–Parr (B3LYP) functional.[29] The input structures were ex-
tracted as model complexes derived from experimentally deter-
mined geometries obtained from the X-ray crystallographic data.
Then, natural bond orbital analysis was implemented.[30] In these
calculations, the Lanl2dz effective core potential was used to de-
scribe the inner electrons of iodine and copper atoms, whereas its
associated double basis set of Hay and Wadt was employed for the
remaining outer electrons.[31] An all-electron basis set 6-31+G**
was used for nonmetal N, C, and H atoms. To describe precisely
the electronic properties, one additional d-type and f-type polariza-
tion functions were employed for the iodine [I(ad =0.266)] and
copper [Cu(af =0.240)] atoms.[32] All calculations were implement-
ed in the Gaussian 03 program.[33] Visualization of the frontier mo-
lecular orbital and electrostatic potential mapped onto the elec-
tron density surface were performed by GaussView.
Experimental Section
Syntheses
General methods
The ligands L1,[23] L2,[20c] L3,[24] L4,[24] and L5[25] were synthesized ac-
cording to literature methods. Other chemicals and solvents were
Complex 1: A solution of CuI (0.760 g, 0.4 mmol) in MeCN (10 mL)
was added slowly to a stirred solution of L1 (0.117 g, 0.2 mmol) in
CH2Cl2 (2 mL), to afford an immediate pale yellow precipitate. After
the mixture was stirred at 608C for 14 h, the crude product was
isolated by filtration, washed with MeCN and CH2Cl2, and dried
under vacuum to give a pale yellow powder. Yield: 80% (0.70 g). IR
(KBr): n˜ =3431 (w), 3121 (w), 1603 (s), 1503 (m), 1436 (vs), 1330 (m),
1231 (s), 1063 (m), 764 (vs), 713 (m), 621 cmꢀ1 (w); elemental analy-
sis calcd (%) for C24H20Cu2I2N6: C 37.27, H 2.61, N 10.87; found:
C 37.33, H 2.79, N 10.87. Single crystals suitable for X-ray diffraction
were obtained through careful layering of a MeCN solution of CuI
on top of a DMF/CH2Cl2 solution of L1.
1
commercially available and used as received. H and 13C NMR spec-
tra were recorded on a Bruker Avance III NMR spectrometer at 400
and 100 MHz, respectively, with CDCl3 as a locking solvent unless
otherwise indicated. The chemical shifts are reported relative to
1
TMS for H and 13C NMR spectra. IR spectra were recorded with KBr
pellets by using a PerkinElmer instrument. Fluorescence spectra
were measured on an FLS920 Edinburgh Analytical instrument.
TGA was performed on a Mettler TGA/SDTA 851e analyzer with
a heating rate of 108Cminꢀ1 under a nitrogen atmosphere. Gas
chromatography (GC) analyses were performed on a Shimadzu GC-
2014 instrument equipped with a capillary column (RTX-5, 30 mꢂ
0.25 mm) and a flame ionization detector. Elemental analyses were
performed on an Elementar Vario MICRO elemental analyzer.
Complex 2: The complex was synthesized by the same procedure
as that for complex 1 except that L1 was replaced by L2. Yield
86%. IR (KBr): n˜ =3849 (w), 3747 (m), 3659 (w), 3444 (w), 3103 (w),
2365 (m), 1606 (vs), 1492 (m), 1436 (vs), 1365 (m), 1233 (s), 1159
(w), 1094 (w), 1044 (w), 766 (vs), 738 (s), 624 cmꢀ1 (w); elemental
analysis calcd (%) for C24H20Cu2I2N6: C 37.27, H 2.61, N 10.87; found:
C 36.93, H 2.72, N 10.59.
X-ray crystallography
Single crystals of complexes 1–5 were mounted on a glass fiber for
X-ray diffraction analysis. Data sets were collected on a Rigaku
AFC7R apparatus equipped with graphite-monochromated MoKa
radiation (l=0.71073 ꢁ) from a rotating-anode generator at 293 K.
Intensities were corrected for Lorentz polarization factors and em-
pirical absorption by using the y scan technique. The structures
were solved by direct methods and refined on F2 with full-matrix
least-squares techniques by means of the Siemens SHELXTL ver-
sion 5 package of crystallographic software.[28] All of the non-hy-
drogen atoms were refined anistropically. Positions of hydrogen
atoms were generated geometrically (CꢀH bond fixed at 0.96 ꢁ),
Complex 3: The complex was synthesized by the same procedure
as that for complex 1 except that L1 was replaced by L3. Yield
75%. IR (KBr): n˜ =3427 (w), 2932 (w), 1602 (s), 1491 (w), 1432 (vs),
1385 (m), 1229 (s), 1159 (w), 1056 (m), 762 (vs), 737 (s), 605 cmꢀ1
(w); elemental analysis calcd (%) for C24H20Cu2 I2N6: C 37.27, H 2.61,
N 10.87; found: C 37.15, H 2.70, N 10.98.
Complex 4: The complex was synthesized by the same procedure
as that for complex 1 except that L1 was replaced by L4 with
metal-to-ligand molar ratio of 3:1. Yield 89%. IR (KBr): n˜ =3446 (w),
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2013, 78, 1491 – 1502 1500

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3106 (w), 2921 (m), 2359 (w), 1603 (s), 1436 (vs), 1376 (w), 1341
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calcd (%) for C36H39Cu3I3N9O3: C 35.53, H 3.23, N 10.36; found:
C 35.56, H 3.15, N 10.20.
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Complex 5: The complex was synthesized by the same procedure
as that for complex 1 except that L1 was replaced by L5. Yield
84%. IR (KBr): n˜ =3434 (w), 3102 (w), 2926 (w), 2332 (w), 1604 (s),
1487 (m), 1436 (vs), 1384 (m), 1233 (s), 1094 (m), 959 (w), 766 (vs),
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N 13.73.
General procedures for the Ullmann cross-coupling reaction
A 25 mL Schlenk tube equipped with a magnetic stirring bar was
charged with Cu complex (0.05 mmol Cu), aryl halide (0.5 mmol),
azole (0.75 mmol), base (1.0 mmol), and dry solvent (2 mL) under
a nitrogen atmosphere. The tube was sealed and the mixture was
stirred at 1108C for 24 h. After the resulting mixture was cooled to
room temperature, water (5 mL) was added and the product was
extracted with ethyl acetate (3ꢂ5 mL). The combined organic layer
was dried over anhydrous Na2SO4 and the solvent was removed
under reduced pressure. The crude products were purified by flash
column chromatography on silica gel to afford the desired prod-
ucts. The identity of the products was confirmed by comparison
with spectroscopic data in the literature.
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General procedures for three-component azide–alkyne cy-
cloaddition
A mixture of alkyl halide (0.5 mmol), alkyne (0.6 mmol), NaN3
(39 mg, 0.6 mmol), Cu complex (0.01 mmol Cu), and water (1.5 mL)
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This study was financially supported by the 973 Program
(2010CB933501, 2011CBA00502), Natural Science Foundation of
China (21273239), Natural Science Foundation of Fujian Province
(2011J01064), and “One Hundred Talent Project” from the Chinese
Academy of Sciences.
Keywords: click chemistry
N ligands · Ullmann reaction
·
copper
·
luminescence
·
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Received: July 5, 2013
Published online on September 4, 2013
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