Facile synthesis of a luminescent copper(I) coordination polymer containing a flexible benzotriazole-based ligand: An effective catalyst for three-component azide-alkyne cycloaddition

Article abstract of DOI:10.1016/j.ica.2019.119136

A straightforward method for the synthesis of a new luminescent copper(I) coordination polymer (CP) containing the ligand 1,3-bis(1H-benzotriazol-1-ylmethyl)benzene (L) through a self-assembly process with copper(I) iodide is reported. The CP was characte

Full text of DOI:10.1016/j.ica.2019.119136

InorganicaChimicaActa498(2019)119136
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Research paper
Facile synthesis of a luminescent copper(I) coordination polymer containing
a flexible benzotriazole-based ligand: An effective catalyst for three-
component azide-alkyne cycloaddition
⁎
Nelson Nuñez-Dallosa,b, Alvaro Muñoz-Castroc, Mauricio Fuentealbad, Edwin G. Péreze,
,
⁎
John J. Hurtadoa,
a Departamento de Química, Universidad de los Andes, Carrera 1 No. 18A-12, 111711 Bogotá, Colombia
b Departamento de Química y Bioquímica, Facultad de Ciencias e Ingeniería, Universidad de Boyacá, Carrera 2ª Este No. 64-169, 150003 Tunja, Colombia
c Laboratorio de Química Inorgánica y Materiales Moleculares, Universidad Autónoma de Chile, Llano Subercaceaux 2801, San Miguel, Santiago, Chile
d Instituto de Química, Pontificia Universidad Católica de Valparaíso, Casilla 4059 Valparaíso, Chile
e Departamento de Química Orgánica, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago 7820436, Chile
A R T I C L E I N F O
A B S T R A C T
Keywords:
A straightforward method for the synthesis of a new luminescent copper(I) coordination polymer (CP) con-
taining the ligand 1,3-bis(1H-benzotriazol-1-ylmethyl)benzene (L) through a self-assembly process with copper
(I) iodide is reported. The CP was characterized by infrared, NMR, UV–Vis and photoluminescence spectroscopy,
high resolution mass spectrometry (ESI), elemental and thermogravimetric analyses, single-crystal and powder
X-ray diffraction, and relativistic density functional theory calculations. Furthermore, this one-dimensional
copper(I) benzotriazole-based coordination polymer catalyzed the three-component azide-alkyne cycloaddition
reaction to obtain 1,4-disubstituted 1,2,3-triazoles in good to excellent yields (up to 95%) from organic halides,
sodium azide and terminal alkynes.
Copper(I) coordination polymer
Luminescence
Catalysis
Azide-alkyne cycloaddition
Click chemistry
1. Introduction
coordinates through the N3-nitrogen of the 1,2,3-triazole ring [1,2,13].
We have been interested in the synthesis and characterization of air-
Coordination polymers (CPs) based on d10 metal ions have been
investigated recently because of their potential applications in sensing
[1], luminescent materials [2,3] and catalysis [4–6]. Among CPs,
copper(I) CPs are attractive as catalysts for various organic transfor-
mations due to the abundance of starting materials, low cost, easy
preparation, high thermal stability, facile reactivity and broad tolerance
of functional groups on substrates [7,8]. Moreover, the use of cheaper
earth-abundant metals such as copper in organic synthesis is appealing
as a sustainable alternative [9–12].
stable 1-D CPs through the self-assembly of copper(I) halides with N-
donor bis(1H-benzotriazol-1-ylmethyl)arene ligands, as well as their
uses in modified screen-printed electrodes for the voltammetric de-
termination of dyes [1] and in transparent composite films for ultra-
violet (UV) shielding [2]. Nevertheless, these CPs have not been studied
in catalysis.
In this sense, the Cu(I)-catalyzed “click” azide-alkyne cycloaddition
reaction gives easy access to 1,4-disubstituted 1,2,3-triazoles, which
have applications in drug discovery and polymer synthesis [16,17]. In
addition, this reaction tolerates a variety of functional groups, is in-
sensitive to water and oxygen, and isolation of the products is simple
[18,19]. These features led us to think that Cu(I) CPs might be added
directly into the reaction mixture and be efficient catalysts for the
“click” cycloaddition reaction, thus avoiding the use of excess ligand or
additives. To the best of our knowledge, there are limited reports on the
use of Cu(I) CPs for the azide-alkyne cycloaddition reaction [8].
According to our interest in exploring the role of CPs as catalysts in
organic synthesis, we now report a new copper(I) benzotriazole-based
In contrast to porous metal organic frameworks (MOFs), one-di-
mensional (1-D) CPs have scarcely been studied in catalysis. Whereas
MOFs using rigid ligands retain their structural integrity during a cat-
alytic reaction, CPs with flexible ligands allow the framework to re-
spond reversibly to the presence of substrates [6,13,14]. This property
could be of great interest in the development of new catalytic systems.
Over the last decade, flexible benzotriazole-based ligands have been
used in the synthesis of CPs due to the coordinating ability of the
benzotriazole moiety [15]. In these complexes, the metal center
⁎ Corresponding authors.
E-mail addresses: eperezh@uc.cl (E.G. Pérez), jj.hurtado@uniandes.edu.co (J.J. Hurtado).
https://doi.org/10.1016/j.ica.2019.119136
Received 15 July 2019; Received in revised form 5 September 2019; Accepted 6 September 2019
Availableonline07September2019
0020-1693/©2019ElsevierB.V.Allrightsreserved.

N. Nuñez-Dallos, et al.
InorganicaChimicaActa498(2019)119136
coordination polymer in one dimension (1-D) as an efficient catalyst for
three-component azide-alkyne cycloadditions to obtain 1,4-dis-
ubstituted 1,2,3-triazoles from organic halides, sodium azide and
terminal alkynes under mild reaction conditions (T < 50 °C, 5% mol
catalyst, in air) and short reaction time (t < 3 h).
Table 1
Crystal data and structure refinement for Cu(I) CP.
Empirical formula
C20H16CuIN6
Formula weight
530.83
Temperature/K
293(2)
Crystal system
Monoclinic
Space group
P21/n (no. 14)
2. Experimental section
a/Å
11.2216(11)
b/Å
11.4710(11)
2.1. General
c/Å
15.0558(16)
α/°
90
β/°
92.770(6)
All reagents and solvents were purchased from commercial sources
and used as received. All solvents used in this work were of analytical
grade. The reactions were monitored by thin layer chromatography
(TLC) on silica gel plates and observed under UV lamps (254 nm or
365 nm). The ligand 1,3-bis(1H-benzotriazol-1-ylmethyl)benzene (L)
was prepared by a modified literature procedure [20–22], in one-step
process at reflux, using commercially available reagents (m-xylylene
dibromide and 1H-benzotriazole), and without using an organic base.
Detailed synthesis and characterization are shown in the
Supplementary Information.
γ/°
90
Volume/Å3
1935.8(3)
Z
4
ρcalc g/cm3
1.821
μ/mm−1
14.261
F(0 0 0)
1040.0
Crystal size/mm3
Radiation
0.36 × 0.152 × 0.102
Cu Kα (λ = 1.54178)
2Θ range for data collection/°
Index ranges
9.61 to 131.3
−13 ≤ h ≤ 13, −13 ≤ k ≤ 13, −17 ≤ l ≤ 17
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indexes [I > = 2σ (I)]
Final R indexes [all data]
Largest diff. peak/hole/e Å−3
42,946
3322 [Rint = 0.1041, Rsigma = 0.0511]
NMR data were recorded on a Bruker Avance 400 spectrometer
(400.13 MHz for 1H; 100.61 MHz for 13C). 1H and 13C NMR chemical
shifts are reported in parts per million (ppm) relative to TMS, with the
residual solvent peak used as an internal reference. High resolution
mass spectra (HRMS) were obtained on an Agilent Technologies Q-TOF
6520 spectrometer via electrospray ionization (ESI) in the positive ion
mode. Infrared spectra (FT-IR) were recorded on a Thermo Nicolet
Nexus 470 ESP FT-IR spectrometer using KBr discs. Elemental analysis
(C, H and N) was performed with a Thermo Scientific™ FLASH 2000
CHNS/O Analyzer. Thermogravimetric analysis (TGA) was performed
on a NETZSCH STA 409 PC/PG instrument in a nitrogen atmosphere
with a continuous flow of 100 mL min−1 and a heating rate of
10 °C min−1, from 30 to 700 °C. Melting points were determined in
open capillary tubes on a Mel-Temp® Electrothermal melting point
apparatus and are uncorrected.
3322/0/254
1.062
R
1 = 0.0591, wR2 = 0.1155
R1 = 0.0984, wR2 = 0.1347
0.65/−1.43
2.3. X-ray crystallography
Single crystals of the Cu(I) CP for X-ray structural analysis were
obtained after a few days by slow evaporation in acetonitrile solution. A
suitable crystal was selected and mounted using
a MiTeGen
MicroMount. Intensity data were collected at room temperature on a
Bruker D8 VENTURE diffractometer equipped with a bidimensional
CMOS Photon100 detector, using graphite monochromated Cu-Kα ra-
diation. The structure solution and refinement were carried out with
OLEX2 [23]. The structure was solved by direct methods using the
SHELXS software [24]. The complete structure was refined by the full
matrix least-squares procedures on the reflection intensities (F2) with
the SHELXL software [25]. All non-hydrogens were refined with ani-
sotropic displacement coefficients, and all hydrogen atoms were placed
in idealized locations. Molecular graphics were generated using Mer-
cury 3.3 [26]. Color codes for molecular graphics were orange (Cu),
blue (N), grey I, white (H) and purple (I). Crystal data and details of
data collection for the Cu(I) CP are reported in Table 1.
The electronic absorption spectra were measured in DMSO solution
with a Varian Cary 100 Conc (Agilent Technologies) spectrophotometer
from 200 to 800 nm, and in a quartz cuvette having a path length of
1 cm. Solid state emission and excitation spectra of the Cu(I) CP (at
λ
ex = 342 nm; λem = 538 nm) were recorded by using a CARY Eclipse
(Agilent Technologies) fluorescence spectrophotometer with the solid
sample holder accessory at room temperature (20 °C). Both the excita-
tion and emission slit widths were 5 nm. During the luminescence
measurements, a low voltage detector was used for the complex due to
its strong solid-state emission.
Powder X-ray diffraction data were collected at room temperature
on a Rigaku Ultima III X-ray diffractometer with Cu-Kα radiation
(λ = 1.54056 Å). The samples were scanned using a step size of 0.02°
2.2. Synthesis of the 1-D Cu(I) coordination polymer catena-poly[bis-μ-
[1,3-bis(1H-benzotriazol-κN3-1-ylmethyl)benzene]dicopper(I)-di-μ-iodo]
and
a scan speed of 2 s per step (Fig. S8, see Supplementary
Information).
CuI (241 mg, 1.24 mmol) was added to a solution of 1,3-bis(1H-
benzotriazol-1-ylmethyl)benzene (400 mg, 1.16 mmol) in acetonitrile
(24 mL). The resulting solution was stirred for 1 h at room temperature,
giving a yellow solid. The precipitate was isolated by vacuum filtration,
washed with acetonitrile, and dried under vacuum. Yield: 510 mg
(82%). mp 236–238 °C. IR (KBr, cm−1): ν 3059 (w), 3029 (w), 2969
(w), 2932 (w), 1611 (w), 1591 (w), 1497 (w), 1454 (m), 1313 (m),
1270 (w), 1224 (s), 1162 (m), 1135 (w), 1114 (m), 1002 (w), 971 (w),
901 (w), 779 (s), 757 (s), 741 (s). 1H NMR (400 MHz, DMSO‑d6): δ
(ppm) 8.05 (d, J = 7.6 Hz, 2H), 7.73 (d, J = 8.1 Hz, 2H), 7.46 (t,
J = 7.4 Hz, 2H), 7.41 – 7.34 (m, 3H), 7.31 (d, J = 7.1 Hz, 1H), 7.25 (d,
J = 7.1 Hz, 2H), 5.94 (s, 4H). Anal. Calcd. for C20H16N6CuI: C, 45.25;
H, 3.04; N, 15.83. Found: C, 44.20; H, 3.27; N, 15.10. HRMS (ESI+) m/
2.4. Computational details
Relativistic density functional theory calculations [27] were carried
out using the ADF code [28], incorporating scalar (SR) corrections via
the one-component ZORA Hamiltonian [29]. We employed the triple-ξ
Slater basis set, plus two polarization functions (STO-TZ2P) for valence
electrons, within the generalized gradient approximation (GGA) ac-
cording to the Perdew-Burke-Ernzerhof (PBE) exchange-correlation
functional [30,31] because of its improved performance on long-range
interactions and relatively low computational cost [32–36]. The frozen
core approximation was applied to the [1s2-3p6] shells for Cu, [1s2-4p6]
for I, and [1s2] for C and N, leaving the remaining electrons to be
treated variationally. Geometry optimizations were performed without
any symmetry restraint, via the analytical energy gradient method
z 341.1524 [L + H]+, 592.9076 [Cu2I(L)]+, 743.2182 [Cu(L)2]+
,
933.0518 [Cu2I(L)2]+, 1124.8863 [Cu3I2(L)2]+. UV–vis (DMSO) [λmax
(log ε), nm (M−1 cm−1)]: 263 (4.29), 283 (4.12).
2

N. Nuñez-Dallos, et al.
InorganicaChimicaActa498(2019)119136
implemented by Versluis and Ziegler [37]. An energy convergence
criterion of 10−4 Hartree, gradient convergence criteria of 10−3 Har-
tree/Å and radial convergence criteria of 10−2 Å were employed for the
evaluation of the relaxed structures. The PBE functional at the scalar
relativistic level and the Davidson method were employed in the TD-
DFT calculations [38–41] to calculate the optical properties.
100
80
60
40
20
0
-2.0
-6.0
2.5. Catalytic activity for three-component azide-alkyne cycloadditions
Catalyst Cu(I) CP (5% mol), organic bromide (1.0 mmol), NaN3
(1.2 mmol), alkyne (1.2 mmol) and CH3CN (2 mL) were placed in a
screw cap vial. Then, the reaction mixture was stirred at 50 °C and was
monitored by TLC on silica gel plates using petroleum ether – ethyl
acetate (2:1). The yields were determined in situ by 1H NMR using a
known quantity of 1,3,5-trimethoxybenzene as internal standard. After
completion of the reaction, the solvent was evaporated under reduced
pressure and the 1,2,3-triazole products were purified using silica gel
column chromatography. All the products were characterized by 1H and
13C NMR, and ESI-HRMS spectra (Figs. S18–S32, see Supplementary
Information).
-10.0
-14.0
TG
DTG
50 150 250 350 450 550 650 750
Temperature (°C)
Fig. 2. Thermogravimetric analysis (TGA) and derivative thermogravimetry
(DTG) of the Cu(I) CP in a nitrogen atmosphere.
The infrared (IR) spectrum of the Cu(I) CP showed the characteristic
bands of the ligand (Figs. S5–S7). However, the band at 1313 cm−1
,
3. Results and discussion
assigned to the combination of the N]N stretching and ring breathing
vibrations of benzotriazole, appears at a lower wavenumber compared
to the free ligand (1342 cm−1). The band at 1114 cm−1, due to the
NeN stretching vibration of the benzotriazole group, shifts towards
3.1. Synthesis and characterization of 1-D Cu(I) coordination polymer
The Cu(I) CP was synthesized efficiently by the self-assembly reac-
tion of stoichiometric amounts of Cu(I) iodide and 1,3-bis(1H-benzo-
triazol-1-ylmethyl)benzene (L). The synthesis was performed at room
temperature in acetonitrile, in the presence of air, with a short reaction
time (1 h) and using a simple combination of reagents (Fig. 1). The
product was obtained as a yellow solid in good yield (82%) with a
melting point of 236–238 °C; moreover, it was air and moisture stable
and insoluble in water and common organic solvents (e.g. chloroform,
dichloromethane, ethyl acetate, acetone and ethanol). Neither the li-
gand nor the Cu(I) CP syntheses require the use of a glove box or
Schlenk techniques. Besides, the purification is straightforward and
does not involve the use of chromatography. The CP was structurally
characterized as a 1-D coordination polymer with formula [Cu2(μ-I)2(μ-
L)2]n, by means of infrared and photoluminescence spectroscopy, ele-
mental and thermogravimetric analyses, single-crystal and powder X-
ray diffraction. Elemental and thermogravimetric analyses of the Cu(I)
CP are consistent with a 1:1 (metal:ligand) stoichiometry.
higher wavenumbers when compared to the free ligand (1080 cm−1
)
[43]. These results indicate that the benzotriazole moieties of the ligand
are coordinated to the metal atom.
3.2. X-ray diffraction analysis
Suitable single crystals of the Cu(I) CP for X-ray diffraction (XRD)
analysis were obtained after a few days by slow evaporation in acet-
onitrile solution. Single-crystal XRD analysis revealed that the complex
consists of a 1-D coordination polymer with formula [Cu2(μ-I)2(μ-L)2]n
(Table 1, Figs. 1 and 3). The Cu(I) CP crystallizes in the monoclinic
crystal system with space group P21/n (14). The asymmetric unit
contains one Cu(I) center, one iodine atom and one ligand L (Fig. 3a). In
the molecular structure, the coordination geometry around the Cu
atoms is distorted tetrahedral Cu(N3bt)2I2, considering coordination by
two ligands through the N atoms in the 3-position of the benzotriazole
rings and two iodine atoms. On the basis of the geometric parameters
for coordination number CN = 4, τ4 (0.92) and τ4′ (0.91) values, Cu
atom adopts almost ideal tetrahedral geometry [44–46].The inorganic
subunit in the compound is a {Cu2(μ-I)2} binuclear core with a planar
rhomboid structure. The flexible organic ligand 1,3-bis(1H-benzo-
triazol-1-ylmethyl)benzene adopts a bidentate-bridging coordination
mode, forming infinite linear chains and bridging the dimeric {Cu2(μ-
The thermogravimetric analysis (TGA) curve of the Cu(I) CP under
nitrogen from 30 to 700 °C showed high thermal stability. The com-
pound was found to be stable up to 314 °C (Fig. 2). This decomposition
temperature (Tdec) is defined as the temperature of 5% weight loss [42].
During the heating process, the TGA curve showed two stages of weight
loss at 344 and 614 °C. Finally, the remaining weight at 700 °C (34.6%,
Calcd. 35.8%) is consistent with residual Cu(I) iodide.
Fig. 1. Synthesis and molecular structure of the 1-D
Cu(I) CP with displacement ellipsoids drawn at the
50% probability level. Copper, iodine, nitrogen and
carbon atoms are shown in orange, purple, blue and
grey, respectively. Hydrogen atoms are shown as
spheres of arbitrary radius. (For interpretation of the
references to color in this figure legend, the reader is
referred to the web version of this article.)
CuI
N
N
N
N
N
N
CH3CN
rt, 1h
self-assembly
3

N. Nuñez-Dallos, et al.
InorganicaChimicaActa498(2019)119136
(a)
(b)
Fig. 3. (a) Asymmetric unit of the Cu(I) CP with displacement ellipsoids drawn at the 50% probability level. (b) Crystal packing of the 1-D Cu(I) CP. Hydrogen atoms
are omitted for clarity.
I)2} units as shown in Figs. 1 and 3b. This type of structure is similar to
what we found in catena-poly[bis-μ-[2,6-bis(1H-benzotriazol-κN3-1-yl-
methyl)pyridine]dicopper(I)-di-μ-iodo], obtained from Cu(I) iodide and
2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine [2]. The Cu···Cu distance
in the {Cu2(μ-I)2} units is 2.829 Å, which is close to the sum of the van
der Waals radii of copper(I) (2.8 Å), implying metal–metal bonding
interactions. Literature data support Cu(I)···Cu(I) interactions with
metal-to-metal distances in the range of 2.6 to 3.0 Å [47–51]. The
multidentate and flexible ligand exhibits a bidentate-bridging co-
ordination rather than a bidentate chelate coordination. Based on the
crystal structure, the coordination polymer is formed under mild re-
action conditions through a self-assembly process driven by metal-li-
gand coordination and is stabilized by metal-metal bonding interac-
tions.
(L = 1,3-bis(1H-benzotriazol-1-ylmethyl)benzene) was employed (Fig.
S11) to evaluate the experimental excitation maximum and the corre-
sponding emission by using time-dependent DFT calculations. The ob-
tained optimized ground state structure agrees well with the char-
acterization from X-ray diffraction, with Cu···Cu distances of 2.793 Å
(Exp. 2.829 Å). The CueI distance is 2.673 Å (Exp. 2.606 Å), with a
CueN length of 2.099 Å (Exp. 2.126 Å). Thus, the model is able to re-
produce geometrical parameters of the extended CP structure.
For the Cu(I) CP, the calculated excitation maximum is located at
331 nm (Exp. 342 nm) involving a metal-to-ligand charge transfer
(MLCT), from an orbital centered at {Cu2(μ-I)2} centered section to a
ligand-localized orbital involving 1,3-bis(1H-benzotriazol-1-ylmethyl)
benzene (Fig. 5). This spin-allowed transition leads to an excited singlet
state (Sn*) with a ligand-based character, originated from the singlet
ground state (S0) as summarized in the given Jablonski diagram
(Fig. 5). Interestingly, the S0 → Sn* transition involves a charge transfer
from the {Cu2(μ-I)2} core towards the benzotriazole moiety, in a metal-
to-ligand charge transfer (MLCT) process. Next, a non-radiative inter-
system crossing (ISC) gives the respective triplet excited state (Tn*),
followed by a non-radiative decay towards the lowest energy triplet
excited state (T1*), which in turn leads to the phosphorescence calcu-
lated at 543 nm (Exp. 538 nm), in agreement to the Kasha’s rule [52].
The lowest triplet excited state (T1*) is centered in the benzyl group
attached to the benzotriazole derivative. Overall, the computational
results show that the entire excitation-emission process can be de-
scribed as a {Cu2(μ-I)2} core → ligand centered transition, and a ra-
diative decay from a benzotriazole-functional group localized orbital to
recover the ground-state (S0). Moreover, the experimental excitation
and emission maxima wavelengths of the Cu(I) CP are slightly different
from those that we observed in catena-poly[bis-μ-[2,6-bis(1H-benzo-
triazol-κN3-1-ylmethyl) pyridine]dicopper(I)-di-μ-iodo] (λex = 323 nm;
In order to confirm the identity and phase purity of the powder
sample, a powder XRD pattern was analyzed using the Rietveld method
based on the single crystal results (Figs. S8 and S9). The experimental
powder XRD pattern for the Cu(I) CP matches its simulated pattern
determined from the single-crystal XRD experiment, indicating the
presence of mainly one crystalline phase in the bulk solid and showing
that the single crystal structure is representative of the powder.
3.3. Photoluminescence studies
The solid-state excitation and emission spectra of the Cu(I) CP at
room temperature showed a λex = 342 nm and a strong green emission
between 500 and 630 nm with a maximum at λem = 538 nm as shown
in Fig. 4. In order to provide insights about the origin of the emission
process, the optical properties of the Cu(I) CP have been studied the-
oretically. A molecular model involving three [Cu2(μ-I)2(μ-L)2]n units
150
100
50
Excitation
Emission
0
300 350 400 450 500 550 600 650
Wavelength (nm)
Fig. 5. Jablonski diagram showing the proposed radiative pathways for the 1-D
Cu(I) CP. The CP exhibited strong green photoluminescence at room tempera-
ture in the solid state (λem = 538 nm). Fluorescence response in the picture was
excited at 365 nm using a UV lamp. (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. Solid state excitation and emission spectra of the Cu(I) CP
(λex = 342 nm; λem = 538 nm) at room temperature.
4

N. Nuñez-Dallos, et al.
InorganicaChimicaActa498(2019)119136
λem = 532 nm) [2]. Nevertheless, these types of coordination polymers
could be considered as useful structural templates to tailor the emissive
wavelength according to the selected benzotriazole functionalization.
The behavior of the Cu(I) CP was investigated in solution by 1H
NMR, UV–vis spectroscopy and high-resolution mass spectrometry
(HRMS) using electrospray ionization (ESI). The compound was in-
soluble in common organic solvents and water, but a small amount
could be dissolved using strongly coordinating solvents such as DMSO
and acetonitrile. In solution, the complex loses its luminescence. The 1H
NMR spectrum of the Cu(I) CP in DMSO‑d6 showed no changes in the
chemical shifts (δ) of the ligand (Figs. S1, S3 and S4). The UV–visible
absorption spectrum of the free ligand in DMSO showed the absorption
bands of π-π* transitions at 264 and 284 nm (Fig. S12). The UV–vis
spectrum of the Cu(I) CP in DMSO showed that the absorption bands of
the ligand were not significantly affected by the metal atom (Fig. S13).
The HRMS (ESI+) spectrum of the Cu(I) CP in acetonitrile exhibited the
ion peaks (m/z) of [Cu3I2(L)2]+, [Cu2I(L)2]+, [Cu(L)2]+, [Cu2I(L)]+
and [L + H]+ (Figs. S14–S17). The isotopic peak patterns support the
presence of copper (Fig. S16). These results suggested the loss of lu-
minescence as a result of the decomplexation of the coordination
polymer in polar aprotic solvents with high dielectric constant.
Table 3
Cu(I) CP-catalyzed synthesis of 1,4-disubstituted 1,2,3-triazoles.a
N
N
Br
N
R1
NaN3
R2
R1
R2
Cl
N
N
N
N
N
N
N
N
N
Cl
95 %
76 %
62 %
Cl
Cl
N
N
N
N
N
N
OH
80 %
88 %
a
Optimal conditions found in Table 2 (entry 12).
agreement with those described in the literature [18,53,54]. The
compound 3-(1-(3-chlorobenzyl)-1H-1,2,3-triazol-4-yl)propan-1-ol is
new (Figs. S18–S32). This Cu(I) CP-catalyzed synthesis was effective for
alkynes with various functional groups (arene, alcohol and alkane)
(Table 3).
We hypothesize that the 1-D Cu(I) CP can act as a reservoir of active
Cu(I) catalyst species in solution as is shown in Fig. S17 [16]. The Cu(I)
CP catalyst showed higher catalytic activity than the salt copper(I) io-
dide under the same reaction conditions (Table 2, entry 14), which
suggests that the coordination with the N-donor ligand decreases the
Lewis acidity of the metal center, facilitating the reaction. According
with Zhu and co-workers, the triple bond of a terminal alkyne could be
a π acceptor from an electron-rich metal center (π-backbonding with
copper(I)) and assist the formation of the copper/alkyne/azide ternary
complex predisposed for cycloaddition [55]. Furthermore, the higher
catalytic activity might be attributed to the synergistic effect between
the two metal centers in the binuclear {Cu2(μ-I)2} core (Fig. 1), as
proposed recently by Guo, Ye and co-workers for binuclear complexes
[8,56]. Future work within our group will focus on the mechanism of
this 1-D Cu(I) CP-catalyzed click reaction.
3.4. Catalytic activity for three-component azide-alkyne cycloadditions
It was found that the Cu(I) CP serves as an efficient supramolecular
catalyst for three-component azide-alkyne cycloadditions to obtain 1,4-
disubstituted 1,2,3-triazoles from organic halides, sodium azide and
terminal alkynes under mild reaction conditions (T < 50 °C, 5% mol
catalyst, in air) and short reaction time (t < 3 h). Moreover, no addi-
tional base or reducing agent is required, and the isolation and pur-
ification of organic azides are avoided in this one-pot synthesis.
Screening of reaction conditions revealed that CH3CN was the most
suitable solvent (Table 2, entry 12), and the reaction did not take place
in the absence of Cu(I) species (Table 2, entry 8). Furthermore, the
isolated Cu(I) CP catalyst (Table 2, entry 12) showed higher catalytic
activity than the Cu(I) CP formed in situ during the catalysis under the
same reaction conditions (Table 2, entry 13). Results are summarized in
Tables 2 and 3. The 1,4-disubstituted 1,2,3-triazoles were obtained in
good to excellent yields (62–95%) and the spectral data were in
4. Conclusions
Table 2
In conclusion, we have reported the synthesis and structural char-
acterization of a new one-dimensional (1-D) coordination polymer with
the formula [Cu2(μ-I)2(μ-L)2]n. This compound was easily obtained
through a self-assembly process of copper(I) iodide with the ligand 1,3-
bis(1H-benzotriazol-1-ylmethyl)benzene (L) and was isolated in good
yield (82%) as an air- and moisture-stable solid. The flexible organic
ligand adopted a bidentate-bridging coordination mode, forming in-
finite linear chains and bridging the binuclear {Cu2(μ-I)2} core. The CP
exhibited high thermal stability and strong green photoluminescence at
room temperature. The catalytic activity of the CP was studied in click
chemistry, which revealed good performance in three-component
azide-alkyne cycloadditions to obtain 1,4-disubstituted 1,2,3-triazoles
in good to excellent yields from organic halides, sodium azide and
terminal alkynes. Finally, the facile synthesis of these types of 1-D co-
ordination polymers and the possibility of chemical modification of the
organic ligand for tuning make Cu(I) CPs promising candidates for
catalysis.
Optimization of the reaction conditions.a
Cl
Cl
N
N
Br
N
NaN3
Entry
Catalyst
% mol
T (°C)
Time (h)
Solvent
Yield (%)
1
Cu(I) CP
CuI
2
2
2
5
10
5
5
–
r.t.
r.t.
80
80
80
80
80
80
80
80
80
50
50
50
2
2
2
2
2
3
3
3
3
3
3
3
3
3
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
EtOH
trace
trace
29
2
3
Cu(I) CP
Cu(I) CP
Cu(I) CP
Cu(I) CP
CuI
4
55
5
83
6
94b
84b
n.r.
37
7
8
–
9
Cu(I) CP
Cu(I) CP
Cu(I) CP
Cu(I) CP
Cu(I) CPc
CuI
5
5
5
5
5
5
10
11
12
13
14
DCE
n.r.
81
CH3CN-H2O (1:1)
CH3CN
CH3CN
CH3CN
95b
85
Declaration of Competing Interest
74b
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
a
b
c
1H NMR yields using 1,3,5-trimethoxybenzene as internal standard.
Isolated by column chromatography.
Cu(I) CP formed in situ.
5

N. Nuñez-Dallos, et al.
InorganicaChimicaActa498(2019)119136
Acknowledgements
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The authors thank the School of Science of the Universidad de los
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Appendix A. Supplementary data
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Supplementary information available: experimental details and
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