Mechanistic Investigation on Copper–Arylacetylide Polymerization and Sensing Applications

Article abstract of DOI:10.1002/anie.202100953

Exploration of new polymerization reactions is very intriguing in fundamental and practical research, which will advance reaction theories and produce various functional materials. Herein, we report a new polymerization method based on the reaction of Cu^I and arylacetylide, which generates linear polymers with high molecular weight and low polydispersity index of molecular weight. The Cu–arylacetylide polymerization exhibits different characteristics with traditional polymerizations such as mild reaction temperature, air atmosphere reaction, high molecular weight, fast polymerization rate, and imprecise molar ratio between monomers. The bond formation path and activation energy of each step was investigated by density functional theory calculations to understand the reaction mechanism. The poly(Cu-arylacetylide)s exhibit strong fluorescence emission and inherent semiconductive properties, which have been used to fabricate an electronic device for streptavidin sensing.

Full text of DOI:10.1002/anie.202100953

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How to cite:
International Edition: doi.org/10.1002/anie.202100953
German Edition: doi.org/10.1002/ange.202100953
Supramolecular Polymers
Mechanistic Investigation on Copper–Arylacetylide Polymerization
and Sensing Applications
Quanduo Liang, Xiaoyong Chang, Ya-qiong Su, Samuel M. Mugo, and Qiang Zhang*
Abstract: Exploration of new polymerization reactions is very
intriguing in fundamental and practical research, which will
advance reaction theories and produce various functional
materials. Herein, we report a new polymerization method
tional polymers, organometallic polymers containing transi-
tion metals in either polymer backbones or side chains,
differentiate themselves from pure organic polymers with
their inherent thermal, magnetic, optical, and electrochemical
I
[2]
based on the reaction of Cu and arylacetylide, which generates
characteristics. For example, polymetallocenes containing
linear polymers with high molecular weight and low polydis-
persity index of molecular weight. The Cu–arylacetylide
polymerization exhibits different characteristics with tradi-
tional polymerizations such as mild reaction temperature, air
atmosphere reaction, high molecular weight, fast polymeri-
zation rate, and imprecise molar ratio between monomers. The
bond formation path and activation energy of each step was
investigated by density functional theory calculations to under-
stand the reaction mechanism. The poly(Cu-arylacetylide)s
exhibit strong fluorescence emission and inherent semicon-
ductive properties, which have been used to fabricate an
electronic device for streptavidin sensing.
metallocenes like nickelocene, cobaltocene, and ferrocene in
polymer backbones or side chains have been well investigated
[
3–5]
by Manners, Astruc, and Tang.
The cobaltocene and
ferrocene allow the polymers electrochemical responses as
the transition metals undergo a reversible redox reaction
[4]
under an electrical field. Multi-color changes also occur
along with the redox reaction, which has potential applica-
tions in film manufacture. The electrochemical redox behav-
ior of cobaltocene endowed polycobaltocene good perfor-
[5]
mance as anion-exchange membranes in alkaline fuel cells.
In another case, ruthenium-containing polymers were pre-
pared by Wu and Butt through the coordination reaction of
bis(terpyridyl)benzene groups in polymer side chains and
ruthenium, which leads to a fast photo-responsive and self-
healing properties due to the reversible photocleavage of the
Introduction
[
6]
In the last decade, non-covalent bonds, such as hydrogen
bonds, metal coordination, and host-guest interaction, have
been used as connecting nodes to synthesize supramolecular
polymers, which generate various special properties like self-
Ru-N coordination bonds. Organometallic polymers are
attracting more and more attention as a category of highly-
valued materials thanks to their unprecedented qualities with
their variety of newfound applications in the field of catalysis,
[
1]
[7]
healing and optoelectronic properties. As one of the func-
energy, sensing, electronic devices, drug delivery, etc.
I
Cu and acetylide can form m,h-coordination bonds
leading to charge transfer between them. Much effort has
been conducted to prepare Cu -alkynyl nanoclusters with
photoluminescent properties that have found various appli-
[
*] Q. Liang, Prof. Q. Zhang
I
State Key Laboratory of Electroanalytical Chemistry, Changchun
Institute of Applied Chemistry, Chinese Academy of Sciences
Changchun, 130022 (P. R. China)
[
8]
[9]
cations in organic optoelectronics, bioimaging, and catal-
[10]
I
and
ysis. The Cu -alkynyl nanoclusters were prepared by the
reaction of alkyl acetylide or aromatic acetylide with large
substituent groups. It has been reported that when the alkyl
School of Applied Chemistry and Engineering, University of Science
and Technology of China
Hefei, 230026 (P. R. China)
I
acetylide was changed to phenyl acetylide, the Cu -alkynyl
E-mail: qiang.zhang@ciac.ac.cn
coordination bonds grow in an infinite manner confirmed by
X. Chang
[11,12]
I
X-ray diffraction (XRD).
Since the Cu -alkynyl com-
Department of Chemistry, Southern University of Science and
Technology
Shenzhen, 518055 (P. R. China)
plexes are insoluble powder, their structure characterization
is limited to XRD. It is impossible to obtain the molecular
weight, polydispersity index of molecular weight (PDI), and
Prof. Y. Su
I
School of Chemistry, Xi’an Key Laboratory of Sustainable Energy
Materials Chemistry, MOE Key Laboratory for Nonequilibrium
Synthesis and Modulation of Condensed Matter, State Key Labo-
ratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong
University
investigate the dynamics and mechanism of Cu -alkynyl
polymerization reaction. In addition, owing to the insolubility
I
characteristic of Cu -alkynyl complexes, their practical uti-
lization in the development of luminescent coating and
electronic devices is still a challenge. It is very intriguing to
Xi’an, 710049 (P. R. China)
I
investigate the Cu -alkynyl reaction as a new polymerization
Prof. S. M. Mugo
Department of Physical Sciences, MacEwan University
Edmonton, ABT5J4S2 (Canada)
method that should be different from traditional polymeri-
zation methods like free radical polymerization, anionic
polymerization, cationic polymerization, etc. Desirably, the
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202100953.
I
unique fluorescence and conductivity properties of Cu -
alkynyl polymers are expected due to massive m,h-coordina-
&
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I
tion bonds. As such, Cu -alkynyl polymers are highly ame-
nable for use in applications such as sensing, luminescent
coating, electronic devices, etc.
In this submission, we focus on investigating the new
I
polymerization reaction, characterizing the new linear Cu -
alkynyl polymers, and exploring its applications in electronic
I
devices. Soluble Cu -alkynyl polymers were synthesized using
long alkyl chains p-substituted phenylacetylide. The long
I
alkyl chains overcome the crystallization driving force of Cu -
alkynyl backbones, which leads to good solubility in organic
I
solvents. Herein, we named the Cu -alkynyl compounds as
I
poly(Cu-arylacetylide)s rather than Cu -alkynyl complexes
due to their linear polymeric characteristics. The molecular
weight, PDI, polymerization rate, and the conformation of
polymer chains are investigated using various tools and the
I
growth manner of Cu -alkynyl backbones was proposed. The
experimental results combined with theory simulation pro-
vide an insightful understanding of the polymerization
reaction mechanism and the ensuing bond formation path-
ways. We further reveal that this reaction can be used to
synthesize a broad library of poly(Cu-arylacetylide)s via
homopolymerization or copolymerization using different
functional monomers. The poly(Cu-arylacetylide)s distin-
guish from other traditional organometallic polymers, as its
backbone is comprised of m,h-coordination and CuꢀCu bonds.
Scheme 1. Synthesis of poly(Cu-arylacetylide)s.
beyond test limitation of gel permeation chromatography
(GPC) after 1 min (Figure 1c and S3). When the polymeri-
The special structure allows poly(Cu-arylacetylide)s many
unique properties like degradability, fluorescence, and con-
ductivity. Finally, a biosensor was fabricated using biotin
containing poly(Cu-arylacetylide) to show the capability of
the poly(Cu-arylacetylide)s in electronic devices.
zation reaction was conducted at ꢀ208C, the M of
n
ꢀ1
400000 gmol was obtained after 1 min reaction (Figure 1d).
ꢀ
1
Then, the M slowly increases plateaus at 800000 gmol at
n
the terminal stage. Interestingly, the PDI of poly(Cu-arylace-
tylide) is 1.02 after 60 min, which is even lower than that of
some living free-radical polymerizations like atom transfer
radical polymerization (ATRP) and reversible addition-
Results and Discussion
[
13]
fragmentation chain transfer polymerization (RAFT).
Cu–Arylacetylide Polymerization Reaction
The dynamics of the polymerization reaction were measured
by monitoring the concentration changes of M1 with time
using a high-performance liquid chromatography-evaporative
light scattering detector (HPLC-ELSD) (Figure 1e). The
concentration of M1 dramatically dropped at the beginning of
the reaction, and the conversion rate of M1 slowed down with
time. The valence state of Cu in poly(Cu-arylacetylide) has
also been investigated using X-ray photoelectron spectrosco-
py (XPS), as shown in Figure 1 f. The peaks at 933.4 eV and
953.2 eV in the spectrum of P1 were associated with the 2p3/2
The polymerization of M1 and [Cu(MeCN) ]BF4 was
4
carried out with the catalyst of triethylamine (TEA) at room
temperature (Scheme 1). The polymerization reaction pro-
ceeds to propagate molecular chains via the coordination
1
+
reaction between alkynyl and Cu , which has been verified
by infrared spectroscopy (IR, Figure 1a and S1) and ultra-
ꢀ
1
violet spectroscopy (UV, Figure 1b). The peak at 2106 cm in
the IR spectrum of M1 was attributed to the stretching
vibration of alkynyl groups, while it shifted to 1927 cm after
the polymerization reaction (in the IR spectra of poly(Cu-
arylacetylide)s). The UV absorption peak of the benzene
group of M1 was found at 258 nm. When [Cu(MeCN) ]BF4
was added to the solution, the intensity of the peak
dramatically decreased and a new UV adsorption peak at
ꢀ1
1+
and 2p1/2 of Cu respectively, which slightly shift toward
higher binding energy in comparison with [Cu(MeCN) ]BF
(Figure S4). No satellite peaks of Cu were observed in the
Cu 2p binding energy region indicating Cu covalence state
4
4
2
+
4
[
14]
was + 1.
No fluorine was found in the XPS spectrum
ꢀ
(Figure 1g), which demonstrates the absence of BF4 in the
poly(Cu-arylacetylide)s. The atomic contents ratio of Cu and
C is 1:21.2 measured by XPS, respectively, which corresponds
to the Cu-arylacetylide molar ratio of 1:1 in P1.
4
84 nm appeared that is attributed to the d-p* charge transfer
1
+
(
between Cu and alkynyl group), which indicated that
coordination bonds formed between the alkynyl group and
1
+
Cu . The chemical structure of the poly(Cu-arylacetylide)
The crystal structure of poly(Cu-arylacetylide) was inves-
tigated by powder XRD (Figure 1h). The long alkyl chain of
M1 hindered the crystalline behavior of Cu-arylacetylide
backbones, which leads to the impossibility of obtaining
a high-quality XRD spectrum to reveal the chemical bond
parameters of the Cu-arylacetylide backbones. The M1 was
1
has also been characterized using H NMR (Figure S2). To
further understand the polymerization reaction, the reaction
kinetics was investigated as follows. We found the number-
average molecular weight (M ) of poly(Cu-arylacetylide)
n
ꢀ
1
reached 1000000 gmol for 1 min reaction at 208C and was
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Figure 1. The structure characterization of the poly(Cu-arylacetylide)s and kinetics of polymerization reaction. a) IR spectra of the poly(Cu-
arylacetylide)s. b) UV spectra of P1 and the monomers involved in the reaction. c) GPC spectra of P1 for different reaction times. d) M and PDI
n
of P1 as a function of reaction time measured by GPC. e) Concentration of the monomer (M1) as a function of reaction time measured by HPLC-
UV. f) XPS analysis of copper in [Cu(MeCN) ]BF and P1. g) XPS full spectra of [Cu(MeCN) ]BF and the poly(cu-arylacetylide)s. h) XRD patterns
4
4
4
4
of P1, P2, and Rietveld profile refinement plot of P2. i) Crystal structure of P2.
replaced by phenylacetylene (M2) to synthesize crystal
poly(Cu-phenylacetylide) (P2) for structure investigation.
The XRD spectrum of P2 was subjected to the Rietveld
profile refinement by using the General Structure Analysis
System (GSAS) program according to the structure of
(Table 1). Density functional theory (DFT) calculations were
conducted to optimize the crystal structures of P1 and P2 and
the corresponding CIF files have been provided in Supporting
Information (SI, Data S1 and S2) and The Cambridge
Crystallographic Data Centre (CCDC, 2061812 and
2061813). The optimized lattice parameters of P1 and P2
are listed in Table 1. The calculation result of P2 is in good
agreement with the result of XRD refinement, while a devia-
tion between the diffraction result and the calculation result
of P1 was found due to the presence of amorphous structures
in P1. Nevertheless, in the simulated P1 structure, the
arrangement of Cu and C atoms is consistent with that in P2
(Figure S5). The information on bond lengths and angles are
beneficial to understand the stereochemical structure of
poly(Cu-phenylacetylide)s.
[12,15]
CCDC-242490.
The crystal structure and crystallographic
data of P2 have been shown in Figure 1i and Table 1,
respectively. P2 belongs to the monoclinic system and the
space group is P2 . Viewed along the b axis, every four Cu
1
atoms form a period of the spiral ascending structure, and
phenylacetylenes are distributed around the Cu-Cu long
chain. Refined Cu-Cu distances are 2.45–2.65 ꢀ (Table S1),
while the Cu-C distances are 1.64–2.60 ꢀ. The distance
between Cu atoms is smaller than the van der Waals radius
of copper, which indicates the existence of weak interaction
between joint Cu atoms and the formation of coordination
[16]
bonds between Cu and phenylacetylene. It can be observed
that the XRD pattern of P1 bulges in the 2q range of 15–308,
which indicates the existence of amorphous components in
P1. Indexing the XRD peak positions of P1 gave triclinic cell
parameters, and P1 exhibited a larger unit cell volume than P2
Polymerization Mechanism
To further explore the polymerization mechanism, DFT
calculation was applied to investigate the bond formation
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Table 1: Cell parameters for powder structure P1 and P2.
As the monomer continued to approach the oligomer chain,
the s bond was replaced by a new coordination bond between
[
a]
[b]
[c]
[d]
P1
P2
P1
P2
Cu and alkynyl group due to the steric effect of the benzene
ring hindering the rotation of the molecular chain. When the
distance between Cu atoms is shorter than 2.7 ꢀ, it leads to
the formation of Cu-Cu interaction. When the monomer is
completely inserted into the oligomer, the molecular chain
continued to twist, arrange, and form a stable configuration
Crystal system
Space group
a [ꢀ]
Triclinic
P1
Monoclinic
P21
15.4(2)
5.174(7)
10.366(9)
90(0)
108.5(1)
90(0)
783.3(103)
1.59
Triclinic
P1
Monoclinic
P21
15.2659
3.78946
9.7428
90
111.561
90
524.18
–
24.406
23.674
11.733
84.5
140.8
83.3
4105.0
–
44.441
4.97866
9.5497
89.3079
125.708
92.0842
1714.463
–
b [ꢀ]
c [ꢀ]
a [8]
b [8]
(SI, Movie S1). The polymerization reaction is a thermody-
g [8]
namically favorable process with an energy downhill of
3.68 eV. The required largest activation energy is only 0.17 eV.
The polymerization reaction can also take place in the
manner of interfacial polymerization. As shown in Figure 3a,
two immiscible solvents (hexane and acetonitrile) were used
3
V [ꢀ ]
2
[d]
c
[
e]
Rwp [%]
Rp [%]
–
–
14.62
9.832
–
–
–
–
[
f]
[a] Unit cell parameters obtained by indexing peak positions of
to dissolve M1/TEA (in hexane) and [Cu(MeCN) ]BF (in
diffraction patterns using Jade 6 program. [b] Crystallographic parame-
ters obtained from Retvield refined results. [c] Crystallographic param-
4
4
acetonitrile). When the two solutions came into contact at
room temperature, a film formed on the interface within
2
eters obtained from DFT calculation results. [d] c =S w (y ꢀy )2/
i
i
i,0
i,c
2
(
N
ꢀN ). [e] R =S jy ꢀy j/S jy j. [f] R = jS w (y ꢀy ) /
obs
var
1/2
p
i
i,0
i,c
i
i,0
wp
i
i
i,0
i,c
2
S w (y ) j in which y and y are the observed and calculated
i
i
i,0
i,0
i,c
intensities at point i of the profile, respectively. Nobs is the number of
theoretical Bragg peaks in the 2q range considered. Nvar is number of the
[
12]
refined parameters. Statistical weights w are normally taken as 1/y .
i
i,0
path and its corresponding potential barrier (SI, Data S3). P2
was selected for the mechanism investigation due to its simple
chemical structure that can reduce computation load. To this
end, a theoretical model was constructed containing a short
1
+
Cu-phenylacetylene oligomer, a Cu ion, and a free phenyl-
1
+
acetylene monomer (Figure 2). The Cu ion and phenyl-
acetylene spontaneously reacted to form a Cu-phenylacety-
lene complex. The Cu-phenylacetylene complex got close to
the Cu-phenylacetylene oligomer from a far distance and
finally inserted into the Cu-phenylacetylene oligomer. The
bond formation process and activation energy of each step
have been shown in Figure 2. As the distance between the
monomer and the oligomer became shorter, the benzene rings
on the oligomer chain rotate to minimize system energy.
When the Cu···C distance is 2.1 ꢀ, a Cu-C coordination bond
Figure 3. a) Schematic diagram of P1 synthesized by interfacial poly-
merization. b) SEM image of P1 film prepared by interfacial polymer-
ization. c) SEM image of P1 film prepared by solution-casting. d) TEM
images of P1.
1
+
formed between the Cu and the phenyl unit of the oligomer.
Figure 2. DFT simulation of the Cu–arylacetylide polymerization reaction.
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4
ꢀ1
2
min. The Mn and PDI were 2.61 ꢁ 10 gmol and 1.35
rate, (vi) imprecise molar ratio between monomers, (vi)
tolerance of various polar and functional groups.
measured by GPC, respectively. This result demonstrates that
the Cu-arylacetylide polymerization reaction does not require
a precise molar ratio of reactants. Interfacial polymerization
is a powerful tool to prepare ultra-thin membranes on
substrate surfaces. For example, interfacial polymerization
has been demonstrated in preparing polyamide reverse
osmotic membranes using trimesoyl chloride and 1,2-phenyl-
Investigation on Morphology, Mechanical Properties, Water
Contact Angles, and Stability of Poly(Cu-arylacetylide)s
The morphologies of the poly(Cu-arylacetylide)s have
been investigated using SEM and TEM (Figure 3b–d and
Figure S, 6, 7). When the reaction was conducted in strong
polar solvents or the poly(Cu-arylacetylide)s were treated
using strong polar solvents like methanol, ethanol, acetone,
the poly(Cu-arylacetylide)s self-assembled into fibers with
a length of tens mm. When the Cu-arylacetylide polymeri-
zation reaction occurred in medium polar solvents or the
poly(Cu-arylacetylide)s were dissolved in medium polar
solvents like chloroform or hexafluoroisopropanol, smooth
and dense films were obtained by the methods of spin-coating
or solution-casting (Figure S8). The contact angle test of the
film shows that the water contact angle of P1 is 108.28
(Figure S9). P3-P5 exhibit lower water contact angles (95.98
for P3, 102.38 for P4, and 98.58 for P5) in comparison to P1 as
a result of introducing the hydrophilic substituent groups.
Nanoindentation tests were employed to investigate the
mechanical properties of the poly(Cu-arylacetylide) films
(Figure 4a). The hardness and elastic modulus of the poly(-
Cu-arylacetylide)s were in the range of 92.36–197.76 MPa and
3.30–8.42 GPa, respectively (Table S2), which are associated
[
17]
enediamine.
Thus the Cu-arylacetylide polymerization
reaction offers potentials for the preparation of ultra-thin
membranes and functionalization of substrate surfaces. To
explore the tolerance of the reaction, arylacetylide with biotin
groups (M2), PEO (M3), and -COOH were synthesized and
used to copolymerize with M1. A series of poly(Cu-arylace-
tylide)s with biotin groups (P3), PEO (P4), and -COOH (P5)
have been successfully synthesized with M of 5.96 ꢁ
n
4
ꢀ1
ꢀ1
4
ꢀ1
1
1
0 gmol
for P3, 6.87 ꢁ 10 gmol
for P4, and 4.97 ꢁ
4
0 gmol for P5 at ꢀ208C, which indicates that the Cu-
arylacetylide polymerization reaction can tolerate various
polar groups. Therefore, the Cu-arylacetylide polymerization
reaction can be used to prepare various materials with
desirable properties. For example, the biotin can form strong
non-covalent interactions with streptavidin with a dissociation
ꢀ
15
ꢀ1
constant of 10 molL . Streptavidin has been widely used
to tag proteins for signal amplification in immunoassay.
[18]
Therefore, the P3 can be used to recognize streptavidin-
conjugated biomolecules through the streptavidin-biotin
binding. It can be concluded that the Cu-arylacetylide
polymerization distinguishes other polymerization methods
with the following distinctive characteristics: (i) mild reaction
temperature (ꢀ208C to 308C), (ii) air atmosphere reaction
with M and intermolecular interaction. The P3 exhibited the
n
highest hardness and modulus due to the hydrogen bonds
between biotin groups. The thermal stability of poly(Cu-
arylacetylide)s has been studied by thermogravimetric anal-
ysis (TGA), which exhibited a two steps degradation process
without protecting gas, (iii) high molecular weight (M >
n
1
000000), (iv) low PDI (PDI < 1.1), (v) fast polymerization
Figure 4. Characterization of mechanical, thermal, and fluorescent properties of the poly(Cu-arylacetylide)s. a) Indentation load-depth responses
of the poly(Cu-arylacetylide)s. b) TGA thermograph of the poly(Cu-arylacetylide)s. c) DSC curves of the poly(Cu-arylacetylide)s. d) GPC curves of
the poly(Cu-arylacetylide)s after being treated by solution with different pH. e) Fluorescence emission spectra of the poly(Cu-arylacetylide)s.
f) Confocal micrographs of P1.
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at 2508C and 4008C, respectively (Figure 4b). The first weight
loss of around 2508C resulted from the degradation of ester
fluorescence intensity of the poly(Cu-arylacetylide)s. In
addition, when P1 is dispersed in a polar solvent (Figure S14),
the emission peaks exhibit a blue shift (Figure S15). The
strong fluorescence of P1 was also observed by a fluorescent
confocal microscope, as shown in Figure 4 f. To better under-
stand the fluorescent performance of poly(Cu-arylacetylide)s,
the decay behavior of P1 photoexcited carriers was inves-
tigated. The decay lifetime of carriers in P1 is approximately
64.78 ns (Figure S16), which indicates good separation effi-
ciency of photoexcited charges and allows poly(Cu-arylace-
tylide)s to find potential applications as photocatalysts. After
storage in the air atmosphere for 2 months, no distinct loss in
fluorescence intensity and UV absorption was observed,
which demonstrates that the fluorescence performance sta-
[19]
groups.
The second weight loss of around 4008C was
associated with the degradation of polymer backbones. In the
comparison of M1, the thermal stability of poly(Cu-arylace-
tylide)s was greatly enhanced, and higher residual masses
(
40–60%) were observed due to the presence of Cu in these
polymers. Differential scanning calorimetry (DSC) has been
utilized to characterize the thermal behavior of the poly(Cu-
arylacetylide)s (Figure 4c). A melting peak in the range of
1
1
40–1528C was observed, and the melting enthalpy of
6.64 Jg for P1 was obtained which was calculated from
ꢀ1
the DSC result. In addition, crystallization peaks near 1608C
were also observed, which corresponded to the crystallization
of copper-alkyne backbones, and corresponding crystalliza-
tion enthalpies for P1, P3, P4, and P5 were 260.6, 169.0, 136.3,
I
bility of Cu was greatly enhanced in the linear polymer
(Figure S17 and S18). The high stability was attributed to the
ꢀ
1
I
and 208.5 Jg , respectively. The stability of P1 in acidic and
basic environments was also tested by monitoring the changes
in molecular weight via GPC. The P1 was treated by aqueous
solutions of pH 1–12 for 1 h and the corresponding GPC
curves were shown in Figure 4d. The P1 is stable in the weak
acidic, neutral, and basic environment (pH > 4). It starts to
degrade into M1 and a small number of other products at the
solutions of pH < 4, which has been verified by gas chroma-
tography-mass spectrometry (GC-MS, Figure S10) and
electron transfer from arylacetylide to Cu in the poly(Cu-
arylacetylide)s.
Conductive Property and Application of Biotin Containing
Poly(Cu-arylacetylide)
The conductive performance of poly(Cu-arylacetylide)s is
expected, as they are comprised of Cu-Cu bonds and Cu-
acetylide coordination bonds. Figure S19 shows the current–
voltage (I–V) curves of P3 in the voltage range of ꢀ30 V to
1
H NMR (Figure S11). When the P1 was treated by a solution
of pH 1 for 1 h, it completely degraded into small molecules
and no high molecular weight polymer was detected by GPC.
The acid-degradable property for poly(Cu-arylacetylide)s
lend it to applications as a controlled drug delivery carrier.
For example, cancer progression, inflammation, and immune
dysfunctions generate acidic microenvironments that may
ꢀ5
30 V. A conductivity of 1.96 ꢁ 10 Scm was observed indicat-
ing that P3 is a kind of typical semiconductors. The I–V curves
exhibited excellent linear characteristics, which demonstrate
the typical Ohmic behavior and constant conductivity. The
semi-conductive performance allows the poly(Cu-arylacety-
lide)s to find applications in electronic sensors. Herein,
a streptavidin sensor was prepared using a silver interdigital
electrode coated by P3 to demonstrate biosensing applica-
tions (Figure 5a). The interaction between streptavidin and
biotin has been reported as one of the strongest non-covalent
interactions in nature with a dissociation constant on the
[20]
trigger the degradation of poly(Cu-arylacetylide)s. After
months of storage in the air and room temperature
2
environment, no changes in chemical structures and Mn
indicating the good stability of poly(Cu-arylacetylide)s (Fig-
ure S12).
ꢀ
15
ꢀ1 [24]
order of ꢁ 10 molL . The streptavidin is broadly used to
conjugate with biomolecules for immunoassay and biomolec-
ular recognition. The response of the sensor to streptavidin in
artificial urine and real urine samples was investigated. The
current of the sensor decreased rapidly and finally stabilized
with increasing the streptavidin amount (Figure 5b). The
current of the sensor did not change significantly when the
artificial urine or real urine was free of streptavidin, while it
shows a 90% decrease when the streptavidin concentration
increases from 0 to 3 mM (Figure 5c). The changes in current
are attributed to the variation of molecular chain conforma-
tion caused by streptavidin, which distorts the electron
transfer channels and leads to a resistance increase of P3
(Figure 5d). The limit of detection of the sensor was obtained
Fluorescent Property of Poly(Cu-arylacetylide)s
I
It has been reported that some Cu clusters exhibit strong
III
[21]
fluorescence emission, comparable to Ir complexes.
However, stability is a great challenge due to the d10 closed
I [22]
electronic configuration of Cu . In this study, the fluores-
cence of poly(Cu-arylacetylide)s has been investigated and
the results have been shown in Figure 4e. Poly(Cu-arylace-
tylide)s exhibits fluorescence properties in a wide range of
excitation light wavelengths (300–560 nm, 650–800 nm) (Fig-
ure S13). When the P1 was irradiated by 460 nm wavelength
light in chloroform, it exhibited two emission peaks at 515 nm
and 535 nm, respectively. The emission peaks at 490–550 nm
are attributed to a metal-perturbed ligand-centered p-p*
ꢀ1
as 35.0 nM, which is much higher than that (2.5 mgmL ) of
[25]
(
acetylide) emission, from metal-to-ligand or ligand-to-metal
Au nanoparticles/hydrogel composites reported by others.
[
12]
charge transfer transitions. It has been observed that the
biotin and carboxyl groups in the poly(Cu-arylacetylide)s led
to decreases in the fluorescence intensity, which is also found
Therefore, the sensor has the potential for biosensing
applications in a urine environment.
[23]
in other electron deficient acetylide complexes.
The
introduction of polar groups will cause a decrease in the
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Figure 5. Poly(Cu-arylacetylide)-based sensor for streptavidin detection. a) Schematic diagram and an optical picture of the poly(Cu-arylacetylide)-
based streptavidin sensor. b) Current response with time upon exposure to streptavidin. c) The current response of the device to streptavidin
concentration in artificial urine and real urine. d) The strategy of the poly(Cu-arylacetylide)-based sensor to detect streptavidin.
Conflict of interest
Conclusion
The authors declare no conflict of interest.
In summary, the poly(Cu-arylacetylide)s were synthesized
upon the polymerization reaction of Cu complex and
I
acetylide. The copper-arylacetylide polymerization reaction
is different from the traditional polymerization methods. It
has the characteristics of mild reaction conditions, a fast
reaction rate, and no need for protective gas. In addition, the
produced poly(Cu-arylacetylide)s have a high molecular
weight and a narrow molecular weight distribution without
precise control of the feed ratio. It has characteristics similar
to living polymerization but has easier reaction conditions in
comparison. The tolerance of the poly(Cu-arylacetylide)
makes it possible to introduce functional monomers into the
main chain and achieve specific sensing functions. The
poly(Cu-arylacetylide) exhibit strong fluorescence emission,
good fluorescence stability, and a long decay lifetime. The
conductive performance was observed, which allow the
poly(Cu-arylacetylide) to fabricate biosensors. The sensors
show the ability to sense streptavidin in the urine. This novel
polymerization method and the unique properties of poly(Cu-
arylacetylide)s exhibit profound research significance and
broad future application prospects.
Keywords: copper–arylacetylide polymerization ·
DFT calculations · poly(Cu-arylacetylide) ·
stimuli-responsive polymers · supramolecular polymers
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Manuscript received: January 20, 2021
Accepted manuscript online: February 8, 2021
Version of record online: && &&
,
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ꢀ 2021 Wiley-VCH GmbH
www.angewandte.org
&&&&
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Angewandte
Research Articles
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Research Articles
Supramolecular Polymers
For the first time, a copper–arylacetylide
polymerization exhibiting the character-
istics of mild reaction temperature, air
atmosphere reaction, high molecular
weight, and fast polymerization rate is
presented. DFT calculations show that
the polymerization is a thermodynami-
cally favorable process. The resulting
polymers exhibit strong fluorescence
emission and inherent semiconductive
properties.
Q. Liang, X. Chang, Y. Su, S. M. Mugo,
Q. Zhang*
&&&& — &&&&
Mechanistic Investigation on Copper–
Arylacetylide Polymerization and Sensing
Applications
&
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These are not the final page numbers!