One-Pot Multicomponent Tandem Reactions and Polymerizations for Step-Economic Synthesis of Structure-Controlled Pyrimidine Derivatives and Poly(pyrimidine)s

Article abstract of DOI:10.1021/acs.macromol.8b02335

The development of new polymerization methodologies for the construction of π-conjugated polymers with unique electronic and photophysical properties is of great importance. Multicomponent tandem polymerizations (MCTPs), featured with high synthetic efficiency and convenience, have proved their potential in the synthesis of polymers with π-conjugated structures. Herein, a new multicomponent tandem reaction of alkyne, guanidine hydrochloride, DMSO, and O₂ was reported through the combination of four sequential Glaser coupling-nucleophilic addition-heterocyclization-oxidation reactions in a one-pot procedure. The corresponding MCTP of diyne, guanidine hydrochloride, DMSO, and O₂ was also developed in the presence of CuCl, N,N,N′,N′-tetramethylethylenediamine, and Cs₂CO₃ to afford conjugated poly(pyrimidine) with well-defined structure, high yield of 87%, and high molecular weight of 25300 g/mol. A mechanistic study of the reaction and a kinetic study of the polymerization were conducted, enabling facile modulation of polymer mainchain structure from rigid conjugated backbone to flexible nonconjugated backbone by simply tuning the atmosphere of the MCTP from air to nitrogen. The poly(pyrimidine)s enjoy outstanding thermal stability and good solubility, whose hydrophobicity and photophysical property are influenced by their subtle structural difference. This MCTP directly converts monomers with simple structure to complex heterocycle-containing products in a step-economic manner and constructs new functional substituted pyrimidine rings embedded in the polymer main chain, providing a compact approach for the efficient and convenient synthesis of structurally controllable poly(heterocycle)s and the construction of polymer materials with potential high-tech applications.

Full text of DOI:10.1021/acs.macromol.8b02335

Article
pubs.acs.org/Macromolecules
Cite This: Macromolecules XXXX, XXX, XXX−XXX
One-Pot Multicomponent Tandem Reactions and Polymerizations
for Step-Economic Synthesis of Structure-Controlled Pyrimidine
Derivatives and Poly(pyrimidine)s
Wen Tian,† Rongrong Hu,*,† and Ben Zhong Tang*,†,‡
†State Key Laboratory of Luminescent Materials and Devices, Center for Aggregation-Induced Emission, South China University of
Technology, Guangzhou 510640, China
‡Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and
Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
S
* Supporting Information
ABSTRACT: The development of new polymerization methodologies for the construction of π-conjugated polymers with
unique electronic and photophysical properties is of great importance. Multicomponent tandem polymerizations (MCTPs),
featured with high synthetic efficiency and convenience, have proved their potential in the synthesis of polymers with π-
conjugated structures. Herein, a new multicomponent tandem reaction of alkyne, guanidine hydrochloride, DMSO, and O2 was
reported through the combination of four sequential Glaser coupling−nucleophilic addition−heterocyclization−oxidation
reactions in a one-pot procedure. The corresponding MCTP of diyne, guanidine hydrochloride, DMSO, and O2 was also
developed in the presence of CuCl, N,N,N′,N′-tetramethylethylenediamine, and Cs2CO3 to afford conjugated poly(pyrimidine)
with well-defined structure, high yield of 87%, and high molecular weight of 25300 g/mol. A mechanistic study of the reaction
and a kinetic study of the polymerization were conducted, enabling facile modulation of polymer mainchain structure from rigid
conjugated backbone to flexible nonconjugated backbone by simply tuning the atmosphere of the MCTP from air to nitrogen.
The poly(pyrimidine)s enjoy outstanding thermal stability and good solubility, whose hydrophobicity and photophysical
property are influenced by their subtle structural difference. This MCTP directly converts monomers with simple structure to
complex heterocycle-containing products in a step-economic manner and constructs new functional substituted pyrimidine
rings embedded in the polymer main chain, providing a compact approach for the efficient and convenient synthesis of
structurally controllable poly(heterocycle)s and the construction of polymer materials with potential high-tech applications.
complex structures such as heterocycle-containing conjugated
polymers generally suffer from tedious procedures, time-
consuming monomer preparation, and painful isolation/
purification, which remain a great challenge. New synthetic
methodologies with high efficiency and convenience are hence
urgently needed for the construction of advanced functional
polymers with unique structures.
Of all the recently developed polymerization methodologies
for the synthesis of conjugated polymers,24−28 multicompo-
nent tandem polymerization (MCTP) is a powerful strategy
because of its high synthetic efficiency, simple procedure,
INTRODUCTION
■
The development of modern polymer materials is highly
dependent on the exploration of new polymerization method-
ologies.1,2 π-Conjugated polymers, including linear conjugated
and cross-conjugated structures such as benzophenone and
divinyl ketones with unique electronic and photophysical
properties,3,4 have attracted much attention and are in great
demand in the applications such as fluorescence chemo-
sensors,5,6 organic light-emitting diodes,7,8 polymer solar
cells,9−11 thermoelectric materials,12−14 and organic field-effect
transistors.15−18 Today, the widely used synthetic methods for
π-conjugated polymers are mainly transition-metal-catalyzed
coupling reactions such as Suzuki−Miyaura, Heck, Sonoga-
shira, and Stille reactions.19−23 The syntheses of polymers with
Received: November 1, 2018
© XXXX American Chemical Society
A
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diverse product structure, and high atom economy. Most
importantly, the in-situ construction of new functional groups
such as heterocycles in MCTPs is difficult to achieve by other
synthetic approaches.29−31 Multiple steps are combined in a
specific order in a one-pot MCTP with simple monomers and
procedures. The intermediate formed from the first step
directly undergoes the following reactions upon addition of
new reagents without any isolation and purification, producing
desired product with high efficiency and specificity. For
example, conjugated polythiophenes and polypyrazoles with
well-defined structures, high molecular weights (Mws), and
high yields can be facilely obtained through the MCTPs
consisted of the modified Sonogashira coupling reaction of
alkyne/carbonyl chloride and the sequential addition−
cyclization reactions.32,33 Moreover, MCTP is also efficient
in controlling the sequence of functional moieties on polymer
main chains. For example, structural-regulated and sequence-
controlled poly(tetrahydropyrimidine)s can be accessed via a
metal-free MCTP of activated alkynes, aromatic diamines, and
formaldehyde. The polymer backbone structure can be further
modulated from poly(tetrahydropyrimidine)s to poly(dihydro-
pyrrolone)s by simply changing the temperature and monomer
loading ratio.34
Scheme 1. Proposed Multicomponent Tandem Reaction
and Its Mechanism
Glaser coupling is a well-known reaction to produce 1,3-
diyne under the catalysis of CuCl and N,N,N′,N′-tetramethyl-
ethylenediamine (TMEDA) (reaction A), which is extensively
used in polymer synthesis.35−37 Recently, a heterocyclization
between 1,4-diphenyl-1,3-diyne (2) and guanidine hydro-
chloride (3) (reaction B) was reported in the presence of
Cs2CO3 in DMSO to produce carbonyl-2-aminopyrimidine
(4) in excellent yield.38 In this work, taking advantage of the
common high efficiency, simple operation, and mild conditions
of both reactions A and B, a multicomponent tandem reaction
(MCTR) (reaction C) was designed by combining these two
reactions in a one-pot procedure to afford the pyrimidine
product concisely from simple reactants. In the proposed
MCTR, the intermediate 1,3-diyne 2 is produced in situ from
Glaser coupling reaction of phenylacetylene (1), which then
undergoes further reaction with the freshly added 3 directly in
the reaction solution. Through a nucleophilic addition, an
anion of buta-1,2,3-triene intermediate A might be formed,
followed by heterocyclization and aromatization to afford
compound 5, which then undergoes oxidation to furnish
product 4 (Scheme 1).38−40 Through similar one-pot
coupling−addition−cyclization−oxidation multiple steps, the
corresponding MCTP is also developed for the compact
synthesis of poly(pyrimidine) with high yield and large Mw
from simple monomers. The tetraphenylethene-containing
diyne monomer is designed because its twisted bulky structure
can prevent intermolecular interactions and hence benefit the
solubility of product, which also endows the poly(pyrimidine)
with aggregation-induced emission characteristics. Further-
more, the chemical structure and properties of the poly-
(pyrimidine) can be tuned by simply modulating the reaction
atmosphere, demonstrating the controllability of this MCTP.
THF, DMF, o-DCB, and DMSO at room temperature for 4 h
in the presence of CuCl and TMEDA (Table S1). Guanidine
hydrochloride (3), Cs2CO3, and DMSO were then added into
the reaction solution without any pretreatment to conduct the
following reactions in situ at 120 °C for 12 h. As expected, the
desired carbonyl-2-aminopyrimidine (4) was directly produced
in all the tested solvents with good to excellent yields,
suggesting good compatibility of these two reactions. Among
all the tested solvents, o-DCB or DMSO provided the best
results. The amount of CuCl was then optimized in DMSO to
achieve 94% yield of 4, demonstrating the successful
combination of the coupling−addition−cyclization−oxidation
reaction pathways in this one-pot MCTR.
Multicomponent Tandem Polymerization. To utilize
this MCTR in the synthesis of aromatic heterocyclic-
containing conjugated polymers and develop the correspond-
ing polymerization, diyne monomer 6 was synthesized, and its
polymerization was conducted under the aforementioned
optimal conditions of the MCTR. As the first step, 6 was
reacted in DMSO in air at 50 °C in the presence of CuCl and
TMEDA. However, insoluble precipitates were formed in 15
min in DMSO due to the poor solubility of the polymer
intermediate P1′ generated from the self-coupling of 6, which
inhibited further tandem reactions of P1′ with the newly added
monomer 3, Cs2CO3, and DMSO at 120 °C (Scheme 2A). To
balance the reactivity of all the reactions and solubility of the
polymer intermediate or product, various solvent systems were
tested for the first step of the MCTP. o-DCB was found to
possess both good solubility of P1′ and good compatibility
with the following reactions. The o-DCB/DMSO mixed
solvents with varied ratios were hence investigated for the
MCTP, and o-DCB/DMSO (v/v, 1:1) was the optimal
solvent, delivering soluble polymer with high yield of 87%
and a large Mw of 25300 g/mol (Table S2).
RESULTS AND DISCUSSION
■
Multicomponent Tandem Reaction. To combine Glaser
coupling reaction of alkyne and the reaction of 1,3-diyne and
guanidine hydrochloride into a one-pot MCTR, it is crucial
that the solvents and conditions of each reaction are
compatible. The Glaser coupling reaction of phenylacetylene
(1) was hence performed in different solvents such as CH2Cl2,
The monomer concentration of 6, temperature, and reaction
time of the second step were then optimized in o-DCB/DMSO
(v/v, 1:1) (Tables S3−S5). Increasing the concentration of 6
B
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Scheme 2. Multicomponent Tandem Polymerizations for the Synthesis of (A) P1 in Air or (B) P2 under Nitrogen
Figure 1. 1H NMR spectra of (A) 6, (B) 8, (C) P1, (D) 9, and (E) P2 and 13C NMR spectra of (F) 6, (G) 8, (H) P1, (I) 9, and (J) P2 in DMSO-
d6.
C
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Figure 2. (A) Stacked in-situ IR profiles collected at different instants of the polymerization solution of 3 and 6 in DMSO in air after the addition
of 3. (B) In-situ IR spectra of DMSO and DMSO solutions of 3, 6, 8, and P1, and the polymerization solution of 3 and 6 after reaction in air for 12
h. (C) Time-dependent peak intensity at 1662, 1557, 1360, and 1186 cm−1. (D) 3D-FTIR profile of the polymerization solution of 3 and 6 in air.
from 0.05 to 0.1 M or elongating the first step-reaction time at
low monomer concentration could both improve the polymer-
ization result. Further increasing the concentration to 0.2 M
led to insoluble gel. Raising the temperature of the second step
above 120 °C benefits neither yield nor Mw. The time course
of the MCTP suggested that satisfactory results could be
obtain in 8 h after the addition of 3.
To elucidate which oxidant, DMSO or O2 in air, provides
the oxygen atom in the carbonyl group of the product, the
second steps of the MCTR and MCTP were performed under
nitrogen, affording compound 5 in 88% yield and polymer P2
with a Mw of 19300 g/mol in 83% yield, respectively (Scheme
2B). This evidence proved that O2 in air contributed the
oxygen atoms to the newly formed carbonyl groups.
S2). The NMR spectra of 6, 8, 9, P1, and P2 were then
compared to confirm the polymer structures. In the H NMR
1
spectra, the resonance of terminal alkyne protons Ha of
monomer 6 at δ 4.16 and 4.18 from trans-/cis-isomers,
respectively, disappeared in all the spectra of 8, 9, P1, and P2,
suggesting the total consumption of alkyne functional groups.
Meanwhile, in the spectra of 8 and P1, new peaks emerged at δ
∼ 7.28, representing the characteristic aromatic protons Hb on
the newly formed pyrimidine rings. The strong electron-
withdrawing pyrimidine rings and carbonyl groups had
influenced their neighboring aromatic protons and resulted
in two new peaks at δ ∼ 7.88 (Hc) and 7.75 (Hd) downfield.
On the other hand, in the spectra of 9 and P2, a new CH2 peak
at δ ∼ 3.76 (He) and a new NH2 peak at δ ∼ 6.57 (Hf) both
emerged, and only a single peak appeared at δ ∼ 7.70
downfield, representing the neighboring aromatic protons Hd
of the pyrimidine rings and proving the absence of carbonyl
group in 9 and P2 (Figure 1A−E). Similarly, in the 13C NMR
spectra of 8, 9, P1, and P2, the resonances of the acetylene
Structural Characterization. Model compounds 8 and 9
were then synthesized to assist the structural characterization
(Scheme S1). The HR-MS analyses of the compounds were
783.3282 (8, calcd 783.3250) and 769.3426 (9, calcd
769.3457), proving their expected structures (Figures S1 and
D
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carbons of 6 at δ 83.28 and 81.14 disappeared, and the
characteristic pyrimidine carbon resonance at δ 103.97−104.77
appeared. Most importantly, the carbonyl peaks at δ ∼ 193.02
emerged only in the spectra of 8 and P1, and the methylene
peaks at δ ∼ 43.01 emerged only in the spectra of 9 and P2
(Figure 1F−J). It should be noticed that in both the structures
of P1 and P2, there are three possible moieties randomly
distributed on the polymer backbone which do not show
difference in their NMR spectra (Scheme 2). The NMR
analysis confirmed the expected product structures, suggesting
that by simply tuning the reaction atmosphere from air to
nitrogen, the carbonyl groups could be completely replaced
with the methylene groups in the products, which proves the
crucial role of O2 in the oxidation.
The polymerization was also monitored under nitrogen by
the in-situ IR spectrum for comparison (Figure S4). Different
than the polymerization in air, the peak intensity at 1662 cm−1
shows continuous decrease because no carbonyl group is
formed in such conditions, which only represents the CN
stretching vibration from monomer 3. Similarly, the peak
intensities at 1560, 1361, and 1186 cm−1 also increased upon
polymerization because of the formation of pyrimidine rings in
P2.
Under the guidance of the in-situ IR analysis, the
polymerization times of the MCTP of 3 and 6 were further
optimized in air with less time (Table S6). A high yield of 87%
and Mw of 16800 g/mol can be obtained in 3 h, demonstrating
high efficiency of this polymerization.
Solubility, Hydrophobicity, and Thermal Stability.
The subtle structural difference between P1 and P2 has a large
influence on their physical properties such as solubility and
hydrophobicity. Although they both share a large number of
rigid aromatic components, P1 with carbonyl bridges possesses
a more rigid polymer backbone than P2 with flexible
methylene bridges. While they both can be well dissolved in
polar solvents such as DMSO and DMF, P2 possess better
solubility than P1 in other organic solvents such as THF.
Moreover, both P1 and P2 enjoy good film-forming ability
which can be spin-coated on glass slides to form tough thin
films. The static water contact angles of the polymer films were
then measured to be 118° (P1) and 76° (P2) by the sessile
drop method, suggesting a more hydrophobic surface of P1
than that of P2 (Figure 3A,B).
To investigate the role of DMSO in this reaction besides
solvent, DMSO-d6 was used as the solvent for the MCTR of 1
and 3 under nitrogen while the other reaction conditions
maintain the same to afford product 5′. From the comparison
1
of the H NMR spectra of 5 and 5′, it is obvious that the
characteristic methylene peak located at δ ∼ 3.89 and the
aromatic pyrimidine peak located at δ ∼ 7.07 have both
dramatically decreased from the spectra of 5 to that of 5′, while
the other peaks remain unchanged, indicating that the
methylene group and pyrimidine proton in 5′ are deuterated
(Figure S3). In other words, these protons are partially
originated from DMSO-d6.
Moreover, in the IR spectra of 8, 9, P1, and P2, the
absorption peak of 6 associated with the stretching vibration of
CC at 2104 cm−1 and the absorption peaks of P1′ associated
with the stretching vibration of CC−CC at 2202−2140
cm−1 were absent, demonstrating the total conversion of CC
or CC−CC bonds (Figure S4). Meanwhile, new
absorption bands emerged at 3400 and 3481 cm−1 in all the
spectra of 8, 9, P1, and P2, proving the formation of NH2
groups. The new absorption peak of the stretching vibration of
CO at ∼1666 cm−1 emerged only in the spectra of 8 and P1,
which was not observed in the spectra of 9 and P2, in
accordance with their expected structures.
Kinetic Study of the MCTP. In-situ IR spectrometry was
then used to monitor the MCTP after the addition of 3,
Cs2CO3, and DMSO under the optimized conditions in air.
The stacked 2D-FTIR profile suggested that three new peaks
emerged in the spectra of the polymerization system at ∼1557,
1360, and 1186 cm−1, corresponding to the stretching
vibrations from the CN of the pyrimidine rings, C−NH2,
and C−C near the carbonyl group (Figure 2A).41,42 The in-situ
IR spectra of 3, 6, 8, P1, and DMSO were compared with the
polymerization mixture to confirm each peak (Figure 2B),
indicating that the carbonyl peak from the product at ∼1674
cm−1 is overlapped with the peak from 3 at 1662 cm−1. The
time-dependent peak intensity and the kinetic variation of the
3D-FTIR profiles at 1186, 1360, 1557, and 1662 cm−1 were
recorded to follow the track of the consumption of the
reactants and the generation of the pyrimidine rings (Figure
2C,D). The intensity of the newly formed pyrimidine peaks
increased rapidly in 3 h, which were then gradually saturated,
suggesting rapid completion of the reaction. Meanwhile, the
peak intensity at 1662 cm−1 dropped promptly in the first 9
min due to the fast consumption of guanidine hydrochloride,
which was then rapidly increased and became saturated in
about 3 h because of the newly formed carbonyl group in P1
located in the same area.
Figure 3. Water contact angle of (A) P1 and (B) P2. (C) TGA
thermograms under N2 with a heating rate of 10 °C min−1.
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Figure 4. (A) Absorption spectra of 8, 9, P1, and P2 in DMF solutions. Concentration: 10 μM. (B) Emission spectra of 8, 9, P1, and P2 in solid
states. (C) Emission spectra of P1 in DMF/H2O mixtures (10 μM) with different fw. λem = 361 nm. (D) Plots of the relative peak emission
intensity (I/I0) of 8, 9, P1, and P2 versus the water fractions.
The large number of aromatic components and the
conjugated structures endow these poly(pyrimidine)s excellent
thermal stability, although significant difference is observed for
P1 and P2. Thermogravimetric analysis of the polymers under
nitrogen suggested that the degradation temperatures with 5
wt % weight loss for P1 and P2 are 428 and 529 °C,
respectively, and a high yield of carbonized residue of 72 wt %
was achieved for both polymers even when they were heated to
850 °C, proving their high thermal resistance (Figure 3C).
Compared with the carbonyl bridges in P1 that may break to
form radical species under pyrolysis, the CH2 bridges in P2 are
more stable, which leads to a higher decomposition temper-
ature of P2.
Photophysical Properties. With their large conjugated
structure, the photophysical properties of 8, 9, P1, and P2 are
systematically investigated to reveal their structure−property
relationship. The absorbance of these compounds was
measured in DMF solutions, and the absorption maxima of 8
and P1 are 356 and 361 nm, respectively, which were red-
shifted compared with that of 9 (323 nm) and P2 (339 nm),
suggesting the extended cross-conjugation from the electron-
withdrawing carbonyl bridge (Figure 4A). The photo-
luminescence behaviors of them were then investigated. The
DMF solutions of 8 and P1 are faintly emissive, while those of
9 and P2 are totally nonemissive. However, in their solid
states, their emission was greatly enhanced with fluorescence
quantum efficiencies up to 56%, demonstrating typical
aggregation-induced emission characteristics which benefited
from their tetraphenylethene moieties. The emission maxima
of 8 (512 nm) and P1 (549 nm) are red-shifted compared with
that of 9 (450 nm) and P2 (537 nm), respectively (Figure 4B).
For 8 and P1, the emission maxima of their solid powders also
red-shifted compared with those of their DMF solutions,
indicating the existence of intermolecular interactions and
more planar configuration in the solid states than in solutions
(Table S7).
Moreover, the photoluminescence properties of these
compounds were then studied in DMF/water mixtures with
different water contents (Figure 4C,D and Figures S6−S8).
Compound 8 was nonemissive in DMF solution or DMF/
F
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solvent was removed under reduced pressure, the crude product was
obtained and purified by silica gel chromatography (petroleum ether/
ethyl acetate = 6/1, v/v) to obtain compound 8 as a yellow powder in
water mixtures with low water content (<60 vol %), which
showed rapidly enhanced emission when a large amount of
poor solvent, water, was added. Polymer P1, on the other
hand, is faintly emissive in DMF solution at 527 nm because of
the restriction of intermolecular motions by the polymer
backbone. The emission intensity of P1 is gradually increased
upon addition of water and reaches maximum in 40 vol %
aqueous media. Compounds 9 and P2 showed a similar trend,
but their fluorescence enhancements in aqueous media are
generally higher compared with that of 8 and P1, possibly
because of their relatively flexible molecular structures. Unlike
the small molecules, in the presence of a large amount of water,
the polymer emission became saturated or even slightly
dropped, probably due to the poor solubility of the polymers
in such aqueous media.
In this work, a one-pot multicomponent tandem reaction
combining Glaser coupling reaction of alkyne and following
addition−heterocyclization−oxidation reactions of cumulative
diyne, guanidine, DMSO, and oxygen in a sequential manner
was reported. The corresponding multicomponent tandem
polymerization was developed for the efficient and convenient
synthesis of conjugated poly(pyrimidine)s with well-defined
structure, high molecular weight, and high yield. The MCTP
directly converts monomers with simple structure to complex
heterocycle-containing products in a step-economic manner
and also constructs new functional units in situ, which features
high synthetic efficiency that is difficult to realize by other
synthetic methods. A mechanistic study of the reaction
suggests that the solvent molecule DMSO and oxygen in air
also participated in the reaction, and a kinetic study of the
MCTP by in-situ IR spectra proves the fast speed of the
polymerization. Furthermore, the polymer main-chain struc-
ture can be switched from rigid conjugated backbone to
flexible nonconjugated backbone by simply tuning the reaction
atmosphere from air to nitrogen, demonstrating high
convenience of structural control. The poly(pyrimidine)
products enjoy outstanding thermal resistance with high
decomposition temperature and high char yield. The subtle
structural difference in the poly(pyrimidine)s endows them
different hydrophobicity and photophysical properties. With
the unique functional groups of these poly(pyrimidines) such
as amino groups, pyrimidine groups, and potential multiple
hydrogen bonds, it is anticipated that these polymer materials
can find various applications in self-assembly, metal chelation,
and fluorescence sensors. The multicomponent tandem
polymerization may provide a fascinating synthetic platform
for the efficient and convenient construction of heterocycle-
containing conjugated polymer materials with diverse
structures and multifunctionalities.
1
93% yield. H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 7.89−
7.87 (d, 2H), 7.76−7.74 (d, 2H), 7.28 (s, 1H), 7.17−7.12 (m, 20H),
7.13−7.08 (d, 2H), 7.01−6.98 (m, 14H). 13C NMR (125 MHz,
DMSO-d6) δ (ppm): 193.02, 165.37, 164.74, 163.50, 149.51, 146.46,
143.38, 143.23, 143.16, 143.08, 143.01, 142.71, 141.96, 140.39,
140.09, 140.01, 134.93, 133.21, 131.56, 131.34, 131.11, 131.04,
130.52, 128.05, 128.42, 128.35, 127.53, 127.30, 127.23, 126.85,
130.97. FT-IR (KBr disk), v (cm−1): 3490, 3408, 3050, 3019, 1666,
1596, 1569, 1535, 1441, 1359, 1257, 1217, 747, 698, 623. HRMS:
calcd for C57H41N3O: 783.3250; found: 783.3282.
Synthetic Procedure of the MCTR under Nitrogen. Into a 50
mL Schlenk tube equipped with a magnetic stirrer were placed CuCl
(2 mg, 0.02 mmol) and TMEDA (7 mg, 0.06 mmol) in 2 mL of o-
DCB. The mixture was bubbled with a slow stream of oxygen and
stirred at 50 °C for 15 min. Monoyne 7 (356 mg, 1.0 mmol) was
dissolved in 3 mL of o-DCB, which was then added into the catalyst.
The resulting solution was stirred for 4 h at room temperature.
Afterward, guanidine hydrochloride (3) (115 mg, 1.2 mmol), Cs2CO3
(652 mg, 2.0 mmol), and 5 mL of DMSO were added. The reaction
mixture was stirred at 120 °C under nitrogen for 12 h. After the
reaction mixture was cooled to room temperature, 150 mL of NaCl
solution (5 M) was added, and ethyl acetate (3 × 50 mL) was used to
extract the product for three times. The organic phases were
combined and dried with MgSO4. After the solvent was removed
under reduced pressure, the crude product was obtained and purified
by silica gel chromatography (petroleum ether/ethyl acetate = 6/1, v/
1
v) to obtain compound 9 as a white powder in 89% yield. H NMR
(500 MHz, DMSO-d6) δ (TMS, ppm): 7.73−7.72 (d, 2H), 7.15−
6.94 (m, 34H), 6.90−6.88 (d, 2H), 6.88 (s, 1H), 6.57 (s, 2H), 3.76 (s,
2H). 13C NMR (125 MHz, DMSO-d6) δ (ppm): 170.83, 164.17,
163.87, 145.85, 143.68, 143.60, 143.46, 143.31, 141.81, 141.73,
140.84, 140.46, 137.25, 135.60, 131.41, 131.19, 131.04, 128.95,
128.27, 127.23, 127.00, 126.49, 126.00, 104.71, 43.01. FT-IR (KBr
disk), v (cm−1): 3490, 3408, 3292, 3180, 3059, 3028, 1620, 1575,
1535, 1496, 1441, 1353, 1075, 1026, 756, 698, 626. HRMS: calcd for
C57H43N3: 769.3457; found: 769.3426.
Synthetic Procedure of the MCTP in Air. Into a 50 mL Schlenk
tube equipped with a magnetic stirrer were placed CuCl (0.8 mg,
0.008 mmol) and TMEDA (2.8 mg, 0.024 mmol) in 2 mL of o-DCB.
The mixture was bubbled with a slow stream of oxygen and stirred at
50 °C for 15 min. Diyne 6 (152 mg, 0.40 mmol) was dissolved in 2
mL of o-DCB, which was then added into the catalyst. The resulting
solution was stirred for 2 h at room temperature. Afterward, guanidine
hydrochloride (3) (46 mg, 0.48 mmol), Cs2CO3 (261 mg, 0.80
mmol), and 4 mL of DMSO were added. The reaction mixture was
stirred at 120 °C in air for 12 h. The polymerization mixture was
diluted with 5 mL of DMSO, which was then added dropwise into
200 mL of methanol through a cotton filter to form precipitates. The
precipitates were allowed to stand for 4 h, which were then filtered,
washed with methanol (3 × 20 mL), and dried under vacuum at 45
°C to a constant weight to afford P1 as a yellow powder in 87% yield.
Mw = 25300 g/mol and Mw/Mn = 1.90. 1H NMR (500 MHz, DMSO-
d6) δ (TMS, ppm): 7.88, 7.75, 7.27, 7.12, 6.98. 13C NMR (125 MHz,
DMSO-d6) δ (ppm): 192.96, 165.37, 164.62, 163.50, 149.29, 146.22,
142.78, 142.03, 141.21, 140.84, 135.15, 133.28, 131.11, 128.50,
127.38, 126.85, 103.97. FT-IR (KBr disk), v (cm−1): 3490, 3408,
3194, 3059, 3019, 1669, 1599, 1565, 1535, 1441, 1402, 1356, 1250,
1220, 1181, 1014, 975, 754, 698.
EXPERIMENTAL SECTION
■
Synthetic Procedure of the MCTR in Air. Into a 50 mL Schlenk
tube equipped with a magnetic stirrer were placed CuCl (2 mg, 0.02
mmol) and TMEDA (7 mg, 0.06 mmol) in 2 mL of o-DCB. The
mixture was bubbled with a slow stream of oxygen and stirred at 50
°C for 15 min. Monoyne 7 (356 mg, 1.0 mmol) was dissolved in 3 mL
of o-DCB, which was then added into the catalyst. The resulting
solution was stirred for 4 h at room temperature. Afterward, guanidine
hydrochloride (3) (115 mg, 1.2 mmol), Cs2CO3 (652 mg, 2.0 mmol),
and 5 mL of DMSO were added. The reaction mixture was stirred at
120 °C in air for 12 h. After the reaction mixture was cooled to room
temperature, 150 mL of NaCl solution (5 M) was added, and ethyl
acetate (3 × 50 mL) was used to extract the product for three times.
The organic phases were combined and dried with MgSO4. After the
Synthetic Procedure of the MCTP under Nitrogen. Into a 50
mL Schlenk tube equipped with a magnetic stirrer were placed CuCl
(0.8 mg, 0.008 mmol) and TMEDA (2.8 mg, 0.024 mmol) in 2 mL of
o-DCB. The mixture was bubbled with a slow stream of oxygen and
stirred at 50 °C for 15 min. Diyne 6 (152 mg, 0.40 mmol) was
dissolved in 2 mL of o-DCB, which was then added into the catalyst.
The resulting solution was stirred for 2 h at room temperature.
Afterward, guanidine hydrochloride (3) (46 mg, 0.48 mmol), Cs2CO3
(261 mg, 0.80 mmol), and 4 mL of DMSO were added. The reaction
G
DOI: 10.1021/acs.macromol.8b02335
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mixture was stirred at 120 °C under nitrogen for 12 h. The
polymerization mixture was diluted with 5 mL of DMSO, which was
then added dropwise into 200 mL of methanol through a cotton filter
to form precipitates. The precipitates were allowed to stand for 4 h,
which were then filtered, washed with methanol (3 × 20 mL), and
dried under vacuum at 45 °C to a constant weight to afford P2 as a
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1
yellow powder in 83% yield. Mw = 19300 g/mol, Mw/Mn = 1.81. H
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NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 7.70, 7.03, 6.93, 6.57,
3.72. 13C NMR (125 MHz, DMSO-d6) δ (ppm): 170.75, 164.17,
163.95, 145.92, 143.75, 143.23, 141.73, 141.59, 140.61, 140.24,
137.25, 135.90, 131.19, 129.32, 128.95, 128.35, 127.08, 126.63,
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.macro-
mol.8b02335.
■
S
Materials and instruments; synthetic procedures and
characterizations of 4 and 5; experimental procedures
for in-situ IR measurements; solvent study of the small
molecular reaction and polymerization; optimization on
the concentration, temperature, and time; HR-MS
spectra of 8 and 9; regular IR spectra, 13C NMR spectra,
1
and the original H and 13C NMR spectra of 4, 5, 5′, 8,
9, P1, and P2; in-situ IR profiles for the polymerization
under nitrogen; PL spectra of 8, 9, and P2 in DMF/
water mixtures; photophysical properties of model
compounds and polymers (PDF)
AUTHOR INFORMATION
Corresponding Authors
*(R.H.) E-mail msrrhu@scut.edu.cn.
*(B.Z.T.) E-mail tangbenz@ust.hk.
ORCID
■
Rongrong Hu: 0000-0002-7939-6962
Ben Zhong Tang: 0000-0002-0293-964X
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T.; Wang, J. Y.; Pei, J. Embedding Electron-Deficient Nitrogen Atoms
in Polymer Backbone Towards High Performance n-Type Polymer
Field-Effect Transistors. Chem. Sci. 2016, 7, 5753−5757.
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IR Conjugated Polymers/Molecules for Organic Electronics. Chem.
Rev. 2015, 115, 12633−12665.
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was partially supported by the National Science
Foundation of China (21774034, 21822102, 21490573,
21490574, and 21788102), the Natural Science Foundation
of Guangdong Province (2016A030306045 and
2016A030312002), and the Innovation and Technology
Commission of Hong Kong (ITC-CNERC14SC01).
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