Polycouplings of Alkynyl Bromides and Sulfonamides toward Poly

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Polycouplings of Alkynyl Bromides and Sulfonamides toward Poly(ynesulfonamide)s with Stable Csp−N Bonds Xiuying Wu,† Bo Wei,† Rongrong Hu,*,† and Ben Zhong Tang*,†,‡ †

State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Centre for Tissue Restoration and Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong

‡

S Supporting Information *

ABSTRACT: The development of new polymerization methodology is crucial for polymer materials. Alkyne polymerization based on versatile reactions of CC bonds have attracted much attention recently because they can produce a great diversity of polymer materials with unsaturated structures and potential semiconducting properties. Among that, the polymerizations between alkyne and amine/amide which afford nitrogen-substituted alkynes with the triple bonds strongly polarized by the nitrogen atoms are quite attractive but challenging. In this work, the polycoupling of alkynyl bromides and sulfonamides is reported as the first example to generate polymers with stable N−CC bonds in the polymer main chain. The polycoupling of various aromatic/aliphatic alkynyl bromides and sulfonamides can be carried out at mild condition in the presence of CuSO4· 5H2O, 1,10-phenanthroline, and K2CO3 at 65 °C under nitrogen, affording poly(ynesulfonamide)s with high molecular weights (up to 22 000 g/mol) in high yields (up to 95%). Incorporation of luminescent tetraphenylethene structure into the alkynyl bromide monomer can produce polymer with aggregation-induced emission property and aggregated state fluorescence quantum efficiency of 24.7%. The plentiful CC bonds of the polymers can serve as efficient ligands for organometallization with Co2(CO)8 to generate organometallics, which can be further pyrolyzed to afford magnetic ceramics with high magnetic susceptibility (Ms up to 80.9 emu/g) and low coercivity (Hc down to 0.008 kOe). This new polycoupling reaction provides an efficient tool for the construction of polymer materials with unique N−CC structures, which paves the way to advanced functionalities of polymers derived from ynesulfonamide structures.

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INTRODUCTION The development of new polymerization methodology is an essential goal in polymer chemistry, which can bring great opportunity to access novel polymer materials with unique structures and advanced functionalities. Traditional polymerizations, such as free radical polymerizations of alkenes, polycondensations of acids and alcohols/amines, and ringopening polymerizations of caprolactones, generally produce polymer products with saturated structures which are used as commodity polymers.1 The polymerization of alkynes, on the other hand, can generate polymers with electronically active unsaturated structure such as CC, CC, or aromatic rings and potential semiconducting properties.2 When such polymerizations are coupled with functional monomers, the resulting acetylenic polymers are demonstrated to be promising candidates for materials with luminescence,3 liquid crystallinity,4 chiroptical activity,5 magnetic susceptibility,6 biological compatibility,7 and so on. Among the alkyne polymerizations, the polymerizations between alkyne and amine/amide have attracted much attention because they generally enjoy inexpensive monomers, © XXXX American Chemical Society

high monomer conversion, atom economy, environmental benefit, and most importantly, they can afford C−N bondcontaining polymers with unique reactivity and functionalities.8 Multicomponent polymerizations (MCPs) of alkyne, amine, and a third monomer have been reported for the synthesis of C−N bond-containing polymers, such as In(III)- or Cu(I)catalyzed MCPs of alkyne, amine, and aldehyde,6,9 Cu(I)catalyzed MCPs of alkyne, amine, and sulfonyl azide,10 and metal-free MCP of activated alkyne, amine, and formaldehyde.11 However, the direct polymerization between alkyne and amine/amide is rarely reported due to the synthetic difficulty and the stability problem of the products. Most recently, polyhydroamination of alkyne is reported to produce regiospecific and stereoselective polyenamines with amine added on the triple bond to afford N−CHCH2 moieties.12,13 The development of polycouplings of alkynes and amines/ amides which generate poly(ynamine)s/poly(ynamide)s with Received: June 2, 2017 Revised: July 19, 2017

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DOI: 10.1021/acs.macromol.7b01155 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules Scheme 1. Synthetic Route of Model Compound 4

Scheme 2. Synthetic Routes of Polymers P1a−d/2a−c

alkyne.27 However, this reaction only applies to limited amides such as oxazolidinones. Danheiser et al. then reported a more generally applicable synthesis of ynamides: in the presence of CuI and potassium bis(trimethylsilyl)amide, a similar Nalkynylation reaction between alkynyl bromide and carbamates, ureas, or sulfonamides can proceed at room temperature to afford ynamides.28 Recently, Hsung et al. utilized a mild condition with inexpensive CuSO4·5H2O and 1,10-phenanthroline as catalyst and ligand, respectively, to directly realize efficient synthesis of ynamides from a large variety of substrates such as sulfonyl amide.29 Encouraged by this recent progress in the synthesis of ynamides, in this work, we developed a polycoupling between alkynyl bromides and sulfonyl amides to directly produce unique poly(ynesulfonamide)s under the catalysis of CuSO4· 5H2O and 1,10-phenanthroline. This polycoupling can be applied to a series of different alkynyl bromides and sulfonyl amides, producing poly(ynesulfonamide)s with large molecular weights and high yields. The poly(ynesulfonamide)s enjoy good chemical stability during synthesis and storage, high thermal resistance, and good solubility in common organic solvents. The remaining CC bonds in the poly(ynesulfonamide)s can be further reacted with metallic species to afford organometallics, which may undergo pyrolysis to furnish magnetic ceramics. In addition, functional units such as luminescent tetraphenylethene moiety can be incorporated in the monomer structure to produce functional poly(ynesulfonamide)s with aggregation-induced emission property. This polycoupling demonstrates the first example for the synthesis of poly(ynesulfonamide)s with unique N−Csp bonds and remaining CC bonds, indicating a new type of polymer

CC bonds retained in the polymer structure and newly formed unique N−Csp bonds involving sp-hybridized carbons are attractive because ynamines/ynamides are considered to possess an exceptionally fine balance of stability and reactivity and have found extensive application in organic synthesis.14 However, the synthesis of ynamine/ynamide is quite challenging with limited types of examples been reported so far. Ynamines are predominantly prepared through isomerization from propargyl amines.15−18 The electronic bias imposed by the nitrogen atom controls the stability and reactivity of the alkynes, and the ynamines with unsubstituted nitrogen atoms generally possess high reactivity. To increase the stability of ynamines, one efficient method is to introduce electron-withdrawing groups on the nitrogen atom.19 Special attention has hence been focused on ynamides for balancing reactivity and stability.14,20 In the ynamide structure, an electron-withdrawing group such as carbonyl or sulfonyl group is generally connected to the nitrogen atom which diminishes the electron density and the reactivity of the neighboring CC bond.21 Poly(ynamide)s with N−Csp bonds containing electronically active unsaturated structure may display great prospects in conductive materials, magnetic materials, bioactive pharmaceuticals, etc.2,22,23 Great effort has been devoted to develop efficient synthetic routes for ynamides. The ynamides are generally prepared through elimination reaction of the halo-enamides, and strong bases such as n-BuLi are commonly involved in the synthesis.24−26 Later, transition-metal-catalyzed coupling reaction is proved to be an efficient approach for the synthesis of ynamides. For example, Hsung et al. first reported a CuCNcatalyzed N−Csp bond formation, which directly generates chiral ynamides via N-alkynylation of amides from halogenated B

DOI: 10.1021/acs.macromol.7b01155 Macromolecules XXXX, XXX, XXX−XXX

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shortened compared with the small molecular reaction. After 24 h reaction, both yields and Mws of the product remain almost constant (Table S1). In this reaction, Cu(II) catalyst plays a crucial role for the C−N bond formation, and 1,10phenanthroline ligand exists significant rate acceleration effect.31,32 Raise of their concentration generally increases the polymerization yield and Mw of the product as shown in Table 3. The best polymerization result was achieved with [CuSO4· 5H2O] = 0.015 M, [1,10-phenanthroline] = 0.03 M, and [K2CO3] = 0.3 M, and polymer P1a/2a with a Mw of 18 000 g/ mol was obtained in 86% yield. Moreover, polymerization temperature was studied at 50−100 °C, which generally deliver satisfactory results with 65 °C as the optimized reaction temperature (Table S2). Furthermore, the general applicability of this polycoupling was investigated for a series of aromatic and aliphatic alkyne halides 1a−d and sulfonamides 2a−c (Table 4). The structures of polymer products are shown in Scheme S1. Under the above-mentioned optimized polymerization condition, the polycoupling between sulfonamide 2a and aromatic alkyne halides 1a−c generally produce polymers with high Mw in great yield. In comparison, the polycoupling between 2a and aliphatic alkyne halide 1d has a relatively low yield because the electron density on the alkyne bromide moiety of aliphatic alkyne bromide is higher compared with that of its aromatic analogues, which makes the bromine atom more difficult to leave, resulting in low reactivity. On the other hand, the polycoupling between alkyne halide 1c and aliphatic sulfonamides 2a,b generally possess better polymerization results with yield of up to 78% and high Mws of up to 22 000 g/mol compared with the polycoupling of 1c and the aromatic sulfonamide 2c because in 2c, the neighboring benzene ring can decrease the electron density of the nitrogen atom, which then decreases its basicity and nucleophilicity. Structural Characterization. The polymer structures were fully characterized by the standard spectroscopic techniques (Experimental Section), and the structures were confirmed through the comparison of the IR, 1H, and 13C NMR spectra of monomers, model compound, and polymers. In the IR spectra, the CC stretching vibration of monomer 1a at 2186 cm−1 and the N−H stretching vibration of monomer 2a at 3301 cm−1 are disappeared in the spectra of 4 and P1a/2a, suggesting the total consumption of the monomers (Figure 1). Meanwhile, the CC stretching vibrations of 4 and P1a/2a emerged at 2234 and 2229 cm−1, respectively. Similarly, in the IR spectra of P1b−d/2a and P1c/2b,c, the characteristic CC stretching vibration peaks appear at 2228−2239 cm−1, proving the formation of the ynamide structure (Figure S1). In the 1H NMR spectra, the triplet peak of 2a at δ 8.20 associated with the N−H resonance has disappeared in the spectra of 4 and P1a/2a. The double peak of 2a at δ 4.03 associated with the CH2 proton resonance has changed to a single peak and shifted to δ 4.62 and 4.65 in the spectra of 4 and P1a/2a, respectively, indicating the total conversion from the N−H group to N−CC group after the reaction (Figure 2). The aromatic C−H resonance of 2a at δ 7.82 has shifted to δ 7.85 and 8.00 in the spectra of 4 and P1a/2a, respectively. Other polymers also possess the CH2 proton resonance at δ 4.62−5.05 and the aromatic C−H resonance at δ 7.78−8.00, proving the expected structures (Figure S2). Similarly, in the 13 C NMR, the resonances of the two alkynyl carbons of 1a at δ 79.16/55.53 have shifted to δ 84.58/70.58 and δ 84.51/70.66 in the spectra of 4 and P1a/2a, respectively, proving the reaction

material with both academic value and potential advanced functionalities.

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RESULTS AND DISCUSSION Model Reaction. A model reaction was first carried out between 1,4-bis(bromoethynyl)benzene (1a) and N-benzyl-ptoluenesulfonamide (3) (Scheme 1). The coupling reaction was proceeded smoothly under nitrogen in DMSO at 65 °C with CuSO4·5H2O as catalyst, 1,10-phenanthroline as ligand, and K2CO3 as base. After 36 h reaction, ynesulfonamide product 4 with two CC bonds retained in the structure was obtained in 90% yield. Polymerization. The polymerization was then investigated under nitrogen in the presence of CuSO4·5H2O, 1,10phenanthroline, and K2CO3, using facilely available 1,4bis(bromoethynyl)benzene (1a) and 4,4′-oxybis(Nbenzylbenzenesulfonamide) (2a) as the monomers (Scheme 2). Solvents with different polarity such as toluene, THF, DMF, and DMSO were examined for the polymerization, suggesting that polar solvent is favored by this polycoupling reaction (Table 1).30 The best polymerization result was achieved in DMSO with the product’s Mw of 14 000 g/mol. Table 1. Effect of Solvent on the Polymerization of 1a and 2aa entry

solvent

yield (%)

Mwb

Mw/Mnb

1 2 3 4

toluene THF DMF DMSO

5 53 71 72

4000 4300 7500 14000

1.15 1.19 1.39 1.94

Carried out under nitrogen in the presence of CuSO4·5H2O, K2CO3, and 1,10-phenanthroline at 65 °C for 32 h. [1a] = [2a] = 0.1 M, [CuSO4·5H2O] = 0.01 M, [1,10-phenanthroline] = 0.02 M, and [K2CO3] = 0.2 M. bDetermined by GPC in THF on the basis of a linear polystyrene calibration. a

Monomer concentrations between 0.05 and 0.5 M were then tested for the polycoupling of 1a and 2a (Table 2). The Table 2. Effect of Monomer Concentration on the Polymerization of 1a and 2aa entry

[1a] (M)

yield (%)

Mwb

Mw/Mnb

1 2c 3 4 5

0.05 0.1 0.2 0.3 0.5

26 72 95 48 29

5600 14000 10000 4000 4800

1.26 1.94 1.39 1.09 1.10

Carried out in DMSO under nitrogen in the presence of CuSO4· 5H2O, K2CO3, and 1,10-phenanthroline at 65 °C for 32 h. [1a] = [2a], [CuSO4·5H2O] = 0.1[1a], [1,10-phenanthroline] = 0.2[1a], and [K2CO3] = 2[1a]. bDetermined by GPC in THF on the basis of a linear polystyrene calibration. cData was taken from Table 1, entry 4.

a

polymerization yield was gradually increased along with the monomer concentration until 0.2 M, which then decreased when the concentration exceeds 0.2 M. High monomer concentration might cause high solution viscosity which generally decreases the polymerization efficiency. The highest Mw value was obtained with the monomer concentration of 0.1 M. The polymerization time was then optimized, proving that the polycoupling can proceed well when the reaction time is C

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Macromolecules Table 3. Effect of Catalyst Concentration on the Polymerization of 1a and 2aa entry

[CuSO4·5H2O] (M)

[1,10-phenanthroline] (M)

[K2CO3] (M)

yield (%)

Mwb

Mw/Mnb

1 2c 3 4

0.005 0.010 0.015 0.020

0.01 0.02 0.03 0.04

0.1 0.2 0.3 0.4

74 73 86 81

5700 13100 18000 18000

1.29 1.84 1.68 1.67

Carried out in DMSO under nitrogen at 65 °C for 24 h. [1a] = [2a] = 0.1 M. bDetermined by GPC in THF on the basis of a linear polystyrene calibration. cData were taken from Table S1, entry 2. a

Table 4. Effect of Different Monomers on the Polymerizationa entry

polymer

yield (%)

Mwb

Mw/Mnb

1c 2 3 4 5 6

P1a/2a P1b/2a P1c/2a P1d/2a P1c/2b P1c/2c

86 86 86 70 78 31

18000 11000 19000 11000 22000 11000

1.68 1.30 1.28 1.21 1.11 1.10

Carried out in DMSO under nitrogen in the presence of CuSO4· 5H2O, K2CO3, and 1,10-phenanthroline at 65 °C for 24 h. [1a−d] = [2a−c] = 0.1 M, [CuSO4·5H2O] = 0.015 M, [1,10-phenanthroline] = 0.03 M, and [K2CO3] = 0.3 M. bDetermined by GPC in THF on the basis of a linear polystyrene calibration. cData were taken from Table 3, entry 3. a

Figure 1. FT-IR spectra of (A) 1a, (B) 2a, (C) 4, and (D) P1a/2a.

Figure 2. 1H NMR spectra of (A) 1a, (B) 2a, (C) 4, and (D) P1a/2a. The solvent peaks are marked with asterisks.

of alkynyl bromide (Figure 3). Meanwhile, the peak representing CH2 carbon of 2a at δ 46.12 has shifted to δ 55.00 and 55.08 in the spectra of 4 and P1a/2a, respectively. Other peaks such as aromatic carbon resonances of 1a at δ 122.36 and that of 2a at δ 158.56 both retained in the spectra of P1a/2a with slight shift. Solubility and Thermal Stability. Both compound 4 and the polymers can be easily dissolved in common organic solvents such as THF, DMSO, toluene, 1,4-dioxane, dichloromethane, and so on. Although ynesulfonamides are reported to possess rich chemical property and high reactivity,33−35 the poly(ynesulfonamide)s show good chemical stability during synthesis, isolation, purification, and storage. Upon addition of acid such as acetic acid, HCl, or trifluoroacetic acid, no significant decrease in the molecular weight can be observed, indicating good chemical stability toward acid. The poly(ynesulfonamide)s generally possess good thermal stability (Figure 4). All the six polymers exhibit high thermal resistance,

with their decomposition temperature at 5 wt % weight loss under nitrogen atomosphere ranging at 254−335 °C. Moreover, the residue weight at 800 °C can reach 66 wt %, probably due to the thermal cross-linking reaction of the CC bonds. Photophysical Properties. The photophysical properties of model compound 4 and P1a,b/2a prepared from conjugated alkynyl bromides were investigated. The absorption spectra of them in THF solution were first studied (Figure 5A). The absorption maxima of THF solutions of 4 and P1a/2a are located at 311 and 309 nm, respectively, and that of P1b/2a possesses a red-shifted absorption maximum at 340 nm, owing to the large conjugated tetraphenylethene structure. The solid powders of 4 and P1a/2a show faint emission at 402 nm, while the solid powder of P1b/2a emits brightly with its emission maximum located at 514 nm (Figure 5B). The luminescence behavior of P1b/2a was studied in THF/ water mixtures with different water volume fractions ( f w) D

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THF/water mixtures are also recorded in Figure 6B, which shows a gradual increase along with the water fraction with the highest ΦF value of 24.7% obtained in 95 vol % aqueous mixture. Ceramization and Magnetism. The remaining CC bonds of the poly(ynesulfonamide)s from the polycoupling can endow the materials unique functionalities. For example, these alkynyl bonds can serve as a versatile ligand in organometallic chemistry.37,38 In particular, they can react with Co2(CO)8 through complexation to afford organometallic polymers (Scheme 3). P1c/2a, P1c/2b, and P1d/2a were selected for the organometallization. After THF solution of Co2(CO)8 was added into the polymer solutions, the solution color became dark and carbon monoxide gas escaped from the solutions, generating organometallic polymers P1c/2a-{[Co(CO)3]2}x, P1c/2b-{[Co(CO)3]2}x, and P1d/2a-{[Co(CO)3]2}x in high yields within 1 h reaction. Despite that the organometallic polymers did not precipitate out from the reaction solution, they became insoluble after purification, probably because of the formation of supramolecular aggregates during the precipitation and drying processes. The IR spectra of these polymers before and after organometallization are compared in Figure S3. After complexation, the absorption bands of CC stretching vibration at 2234 cm−1 (P1c/2a), 2234 cm−1 (P1c/ 2b), and 2239 cm−1 (P1d/2a) disappeared, and three new strong peaks associated with cobalt carbonyl absorptions emerged at 2028−2096 cm−1 in each spectrum, proving that the carbonyl coordinated cobalt species has successfully integrated into the polymer at the molecular level. The organometallic polymers were then pyrolyzed at 800 °C under an argon atomosphere to afford magnetic ceramics MC1−MC3. The magnetization curves of MC1−MC3 suggest that with an increase in the strength of external magnetic field (H), the magnetizations of MC1−MC3 are swiftly increased and eventually saturated at high field (Figure 7). MC1−MC3 possess high saturation values in the range of 48.9−80.9 emu/g, and the coercivities (Hc) of them are found to be 0.008−0.02 kOe, suggesting that they are soft magnetic materials.

Figure 3. 13C NMR spectra of (A) 1a, (B) 2a, (C) 4, and (D) P1a/2a. The solvent peaks are marked with asterisks.

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CONCLUSIONS In this work, a facile CuSO4·5H2O-catalyzed polycoupling of alkynyl bromides and sulfonamides was reported for the synthesis of novel poly(ynesulfonamide)s with high molecular weight and high yield. The polymerization can be applied to various monomers including aromatic alkynyl bromides, aliphatic alkynyl bromides, and sulfonamides prepared from aromatic amines and aliphatic amines, which generally deliver satisfied polymerization results. The poly(ynesulfonamide)s possess good chemical stability toward acid and high thermal stability as well as good solubility in common organic solvents. The applications of these polymers with unique structure feature have been explored. Besides the functionalities directly incorporated in the monomer structures such as aggregationinduced emission, the in situ generated N−CC moiety can also lead to a series of functionalities. For example, the existence of the large number of triple bonds can bring the opportunity for organometallization with metallic species, which can be then fabricated to magnetic ceramics with high magnetization and low coercivity. Most importantly, the N− CC groups of the polymer products possess an exceptionally fine balance between stability and reactivity, which could offer unique and multiple opportunities for structure transformation

Figure 4. TGA thermograms with a heating rate of 20 °C/min under a nitrogen atmosphere.

(Figure 6A). In pure THF solution, a small emission peak is observed at 430 nm. When more than 40 vol % water exists in the mixed solution, the emission profile is changed to a broad peak at 495 nm. Further increase of the water fraction can gradually raise the emission intensity while keeping the emission maxima unchanged, demonstrating typical aggregation-induced emission phenomenon.36 The fluorescence quantum efficiencies (ΦFs) of the polymer nanoaggregates in E

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Figure 5. (A) Absorption spectra of 4, P1a/2a, and P1b/2a in THF solutions. (B) Normalized emission spectra of 4, P1a/2a, and P1b/2a in solid powder. Excitation wavelength: λex = 310 nm (4 and P1a/2a), λex= 340 nm (P1b/2a). Concentration: 10−5 M.

Figure 6. (A) Emission spectra of P1b/2a in THF/water mixtures with different water fractions ( f w). (B) Quantum yield of P1b/2a in THF/water mixtures with different water fractions (f w). Inset: photos of P1b/2a in THF/water mixtures ( f w = 95% and 0%) taken under the illumination of a UV lamp (365 nm). Excitation wavelength: 340 nm. Concentration: 10−5 M.

Scheme 3. Complexation with Cobalt Carbonyls and Ceramization to Magnetic Ceramics

further purification. Tetrahydrofuran and toluene were distilled from sodium benzophenone ketyl under dry nitrogen before use. Instruments. 1H and 13C NMR spectra were measured on a Bruker Avance 500 MHz spectrometer using deuterated dimethyl sulfoxide as solvent. FT-IR spectra were recorded on a Bruker Tensor II FT-IR spectrometer. High-resolution mass spectrometry measurements were performed on a Bruker maxis impact mass spectrometer. The number-average (Mn) and weight-average (Mw) molecular weights and polydispersity indices (PDI = Mw/Mn) of the polymers were estimated by a Waters Advanced Polymer Chromatography system equipped with photodiode array detector. Polystyrene was

to serve as a useful and versatile building blocks to access new functional polymer materials.

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EXPERIMENTAL SECTION

Materials. CuSO4·5H2O and 1,10-phenanthroline were purchased from Energy Chemical. K2CO3 was purchased from Richjoint Chemical. Co2(CO)8, DMF, and DMSO were purchased from Sigma-Aldrich. Alkynyl bromides 1a−d and sulfonamide 3, 2a−c were prepared according to the literature.39−42 The commercially available reactants and reagents were all used as received without F

DOI: 10.1021/acs.macromol.7b01155 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules

with methanol (3 × 30 mL) and dried in vacuum at 35 °C to a constant weight to afford the polymer. P1a/2a. A white solid was obtained in 86% yield (Table 4, entry 1). Mw = 18 000 g/mol, Mw/Mn = 1.68. IR (KBr thin film), v (cm−1): 3065, 3039, 2935, 2229, 1580, 1487, 1363, 1306, 1246, 1166, 1098, 1012, 931, 835, 736, 699, 595, 557. 1H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 8.00, 7.31, 7.16, 4.65 (CH2). 13C NMR (125 MHz, DMSO-d6) δ (TMS, ppm): 159.76, 134.40, 132.30, 130.71, 130.26, 128.76, 128.53, 128.31, 121.31, 119.80, 84.51, 70.66, 55.08. P1b/2a. A yellow solid was obtained in 86% yield (Table 4, entry 2). Mw = 11 000 g/mol, Mw/Mn = 1.30. IR (KBr thin film), v (cm−1): 3062, 3031, 2930, 2228, 1581, 1488, 1448, 1365, 1303, 1246, 1166, 1099, 1016, 932, 830, 770, 700, 598, 560. 1H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 7.97, 7.29, 7.05, 6.87, 4.62 (CH2). 13C NMR (125 MHz, DMSO-d6) δ (TMS, ppm): 159.72, 142.71, 142.57, 140.34, 134.47, 132.31, 130.95, 130.63, 130.23, 128.63, 128.25, 127.99, 127.85, 126.78, 120.09, 119.79, 83.23, 70.72, 55.10, 39.52. P1c/2a. A white solid was obtained in 86% yield (Table 4, entry 3). Mw = 19 000 g/mol, Mw/Mn = 1.28. IR (KBr thin film), v (cm−1): 3039, 2966, 2870, 2234, 1582, 1499, 1365, 1302, 1242, 1168, 1101, 1016, 935, 867, 826, 743, 698, 598, 559. 1H NMR (500 MHz, DMSOd6) δ (TMS, ppm): 8.00, 7.34, 7.25, 7.05, 6.83, 5.00 (CH2), 4.66 (CH2), 1.52 (CH3). P1d/2a. A brown solid was obtained in 70% yield (Table 4, entry 4). Mw = 11 000 g/mol, Mw/Mn = 1.21. IR (KBr thin film), v (cm−1): 3039, 2963, 2870, 2239, 1580, 1497, 1364, 1300, 1241, 1166, 1009, 827, 759, 702, 596, 556. 1H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 7.85, 7.25, 7.16, 7.03, 6.73, 4.78 (CH2), 4.51 (CH2), 1.49 (CH3). P1c/2b. A white solid was obtained in 78% yield (Table 4, entry 5). Mw = 22 000 g/mol, Mw/Mn = 1.11. IR (KBr thin film), v (cm−1): 3062, 2966, 2927, 2870, 2234, 1583, 1504, 1491, 1412, 1374, 1299, 1244, 1173, 1123, 1089, 1018, 873, 829, 766, 696, 621, 573. 1H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 8.00, 7.39, 7.07, 6.86, 5.03 (CH2), 3.48 (CH2), 1.53 (CH3), 1.18 (CH3). P1c/2c. A brown solid was obtained in 31% yield (Table 4, entry 6). Mw = 11 000 g/mol, Mw/Mn = 1.10. IR (KBr thin film), v (cm−1): 3045, 2969, 2873, 2237, 1582, 1500, 1366, 1303, 1243, 1169, 1105, 1004, 934, 865, 826, 739, 699, 632, 568. 1H NMR (500 MHz, DMSOd6) δ (TMS, ppm): 7.78, 7.42, 7.29, 7.07, 6.86, 5.05 (CH2), 1.55 (CH3). Preparation of Nanoaggregates. The stock THF solution of P1b/2a with a concentration of 1.0 × 10−3 M was prepared. 40 μL of the stock solution was added into a volumetric flask with proper amount of THF. Water was then added into the THF solution dropwise under vigorous stirring to afford 4 mL THF/water mixtures with a fixed concentration of 1.0 × 10−5 M and different water contents. PL measurements were conducted immediately after the transparent nanoaggregates were obtained. Metal Complexation. A typical procedure for metal complexation is given below with the preparation of P1c/2a-{[Co(CO)3]2}x as an example. 80 mg of P1c/2a was dissolved in 5 mL of distilled THF in a 25 mL Schlenk tube under nitrogen at room temperature. 5 mL of THF solution of Co2(CO)8 (103 mg, 0.30 mmol) was added dropwise into the solution. After reacting for 1 h, the reaction solution was added dropwise into 200 mL of n-hexane through a cotton filter. The precipitate was allowed to stand overnight and filter. The crude product was washed with n-hexane (3 × 30 mL) and dried under vacuum at 35 °C to a constant weight. P1c/2a-{[Co(CO)3]2}x was obtained as a black brown solid in 89% yield. P1c/2b-{[Co(CO)3]2}x was prepared from P1c/2b (69 mg) and Co2(CO)8 (89 mg, 0.26 mmol), and a black-brown solid was obtained in 84% yield. P1d/2a{[Co(CO)3]2}x was prepared from P1d/2a (103 mg) and Co2(CO)8 (109 mg, 0.32 mmol), and a black-brown solid was obtained in 86% yield. Pyrolytic Ceramization. A typical procedure for the pyrolysis is given below with the preparation of MC1 as an example. 113 mg of P1c/2a-{[Co(CO)3]2}x was pyrolyzed for 1 h under argon at 800 °C with the heating rate of 20 °C/min. After cooling, MC1 was obtained in 37% yield. Similarly, MC2 was obtained from 97 mg of P1c/2b-

Figure 7. Plots of magnetization (M) versus applied magnetic field (H) at 298 K for magnetoceramics MC1−MC3. Ms = saturation magnetization in an external field of ∼8 kOe, Mr = magnetic remanence at zero external field, and Hc = coercivity at zero magnetization.

utilized as standard and THF was used as the eluent in a flow rate of 0.5 mL/min. A set of monodispersed linear polystyrenes, covering the Mw range of 103−107 g/mol, were utilized as standards for molecular weight calibration. Thermogravimetric analysis was carried out on a Netzsch TG 209 F3 at a heating rate of 20 °C/min in a nitrogen flow. UV−vis absorption spectra were recorded on a Shimadzu UV-2600 spectrophotometer. Fluorescence spectra were recorded on a Horiba Fluoromax-4 spectrofluorometer. Absolute fluorescence quantum yields were recorded on a Hamamatsu C11347-11 Quantaurus-QY. A tube furnace of GSL-1600X was used for the pyrolysis of polymers. Magnetization curves were recorded on a Lake Shore 7037/9509-P vibrating sample magnetometer at room temperature. Model Reaction. N,N′-(1,4-Phenylenebis(ethyne-1,2-diyl))bis(Nbenzyl-4-methylbenzenesulfonamide) 4: Into a 50 mL two-neck round-bottom equipped with a magnetic stir bar were added 1,4bis(bromoethynyl)benzene 1a (0.56 g, 2.0 mmol), N-benzyl-ptoluenesulfonamide 3 (1.10 g, 4.2 mmol), CuSO4·5H2O (0.10 g, 0.4 mmol), 1,10-phenanthroline (0.14 g, 0.8 mmol), and K2CO3 (1.10 g, 8.0 mmol) under nitrogen. 10 mL of DMSO was then injected to dissolve the compounds by a syringe. After reacting at 65 °C for 36 h, the reaction mixture was cooled to room temperature and extracted with dichloromethane (3 × 50 mL) and water (100 mL). The crude product obtained after solvent evaporation was purified by column chromatography on silica gel using a hexane/ethyl acetate mixture (v/v 3:1) as eluent. A yellow solid was obtained in 90% yield. IR (KBr thin film), v (cm−1): 3037, 2929, 2234, 1594, 1498, 1450, 1354, 1164, 1098, 1016, 919, 814, 728, 658, 596, 551. 1H NMR (500 MHz, DMSO-d6) δ (TMS, ppm): 7.85 (d, 4H), 7.51 (d, 4H), 7.38−7.31 (m, 10H), 7.14 (s, 4H), 4.62 (s, 4H, CH2), 2.43 (s, 6H, CH3). 13C NMR (125 MHz, DMSO-d6) δ (TMS, ppm): 145.24, 134.55, 133.73, 130.64, 130.19, 128.76, 128.53, 128.31, 127.48, 121.31, 84.58, 70.58, 55.00, 21.14. HRMS: m/z 644.1829 (calcd 644.1803). Polymerizations. A typical procedure of the polymerization is given below with the polymerization of 1a and 2a as an example. Into a 10 mL Schlenk tube equipped with a magnetic stir bar were added 1,4bis(bromoethynyl)benzene 1a (56 mg, 0.2 mmol), 4,4′-oxybis[N(phenylmethyl)benzenesulfonamide] 2a (102 mg, 0.2 mmol), CuSO4· 5H2O (7 mg, 0.03 mmol), 1,10-phenanthroline (11 mg, 0.06 mmol), and K2CO3 (83 mg, 0.6 mmol) under nitrogen. 2 mL of DMSO was then injected to dissolve the compounds through a syringe. After reacting at 65 °C for 24 h, the reaction mixture was cooled to room temperature and added dropwise into 200 mL of methanol through a cotton filter to precipitate the polymer. The precipitate was allowed to stand overnight before filtration. The crude product was then washed G

DOI: 10.1021/acs.macromol.7b01155 Macromolecules XXXX, XXX, XXX−XXX

Article

Macromolecules {[Co(CO)3]2}x in 34% yield, and MC3 was prepared from 150 mg of P1d/2a-{[Co(CO)3]2}x in 33% yield.

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Theato, P., Ed.; Springer International Publishing: Cham, 2015; pp 17−42. (9) Liu, Y.; Gao, M.; Lam, J. W. Y.; Hu, R.; Tang, B. Z. CopperCatalyzed Polycoupling of Diynes, Primary Amines, and Aldehydes: A New One-Pot Multicomponent Polymerization Tool to Functional Polymers. Macromolecules 2014, 47, 4908−4919. (10) Lee, I.-H.; Kim, H.; Choi, T.-L. Cu-Catalyzed Multicomponent Polymerization To Synthesize a Library of Poly(N-sulfonylamidines). J. Am. Chem. Soc. 2013, 135, 3760−3763. (11) Wei, B.; Li, W.; Zhao, Z.; Qin, A.; Hu, R.; Tang, B. Z. MetalFree Multicomponent Tandem Polymerizations of Alkynes, Amines, and Formaldehyde toward Structure- and Sequence-Controlled Luminescent Polyheterocycles. J. Am. Chem. Soc. 2017, 139, 5075− 5084. (12) He, B.; Zhen, S.; Wu, Y.; Hu, R.; Zhao, Z.; Qin, A.; Tang, B. Z. Cu(I)-Catalyzed Amino-Yne Click Polymerization. Polym. Chem. 2016, 7, 7375−7382. (13) He, B.; Su, H.; Bai, T.; Wu, Y.; Li, S.; Gao, M.; Hu, R.; Zhao, Z.; Qin, A.; Ling, J.; Tang, B. Z. Spontaneous Amino-yne Click Polymerization: A Powerful Tool toward Regio- and Stereospecific Poly(β-aminoacrylate)s. J. Am. Chem. Soc. 2017, 139, 5437−5443. (14) DeKorver, K. A.; Li, H.; Lohse, A. G.; Hayashi, R.; Lu, Z.; Zhang, Y.; Hsung, R. P. Ynamides: A Modern Functional Group for the New Millennium. Chem. Rev. 2010, 110, 5064−5106. (15) Zaugg, H.; Swett, L.; Stone, G. Notes: An Unusual Reaction of Propargyl Bromide. J. Org. Chem. 1958, 23, 1389−1390. (16) Mahamoud, A.; Galy, J. P.; Vincent, E. J.; Barbe, J. Synthesis of (Allenic) N-Propadienyl- and (Acetylenic) N-(1-Propynyl)-acridanones using Phase-Transfer Catalysis. Synthesis 1981, 1981, 917−918. (17) Katritzky, A. R.; Ramer, W. H. Heterocyclic Ynammonium Salts. J. Org. Chem. 1985, 50, 852−856. (18) Majumdar, K. C.; Ghosh, S. K. Phase-Transfer-Catalysed Alkylative Elimination: Synthesis of 10-Enynyl Acridones from Acridones and 1-Aryloxy-4-chlorobut-2-ynes. Synth. Commun. 1994, 24, 217−231. (19) Hsung, R. P.; Zificsak, C. A.; Wei, L.-L.; Douglas, C. J.; Xiong, H.; Mulder, J. A. Lewis Acid Promoted Hetero [2 + 2] Cycloaddition Reactions of Aldehydes with 10-Propynyl-9(10H)-acridone. A Highly Stereoselective Synthesis of Acrylic Acid Derivatives and 1,3-Dienes Using an Electron Deficient Variant of Ynamine. Org. Lett. 1999, 1, 1237−1240. (20) Evano, G.; et al. A Journey in the Chemistry of Ynamides: From Synthesis to Applications. Chem. Lett. 2016, 45, 574−585. (21) Dunetz, J. R.; Danheiser, R. L. Copper-Mediated N-Alkynylation of Carbamates, Ureas, and Sulfonamides. A General Method for the Synthesis of Ynamides. Org. Lett. 2003, 5, 4011−4014. (22) Liaw, D.-J.; Wang, K.-L.; Huang, Y.-C.; Lee, K.-R.; Lai, J.-Y.; Ha, C.-S. Advanced Polyimide Materials: Syntheses, Physical Properties and Applications. Prog. Polym. Sci. 2012, 37, 907−974. (23) Evano, G.; Coste, A.; Jouvin, K. Ynamides: Versatile Tools in Organic Synthesis. Angew. Chem., Int. Ed. 2010, 49, 2840−2859. (24) Janousek, Z.; Collard, J.; Viehe, H. G. Reaction of Secondary Acetamides with N-Dichloromethylene-N,N-dimethylammonium Chloride. Angew. Chem., Int. Ed. Engl. 1972, 11, 917−918. (25) Joshi, R. V.; Xu, Z.-Q.; Ksebati, M. B.; Kessel, D.; Corbett, T. H.; Drach, J. C.; Zemlicka, J. Synthesis, Transformations and Biological Activity of Chloro Enamines and Ynamines Derived from Chloroalkenyl- and Alkynyl-N-substituted Purine and Pyrimidine Bases of Nucleic Acids. J. Chem. Soc., Perkin Trans. 1 1994, 1089− 1098. (26) Brückner, D. Synthesis of Ynamides and Ynol Ethers via Formamides and Formates. Synlett 2000, 1402−1404. (27) Frederick, M. O.; Mulder, J. A.; Tracey, M. R.; Hsung, R. P.; Huang, J.; Kurtz, K. C. M.; Shen, L.; Douglas, C. J. A CopperCatalyzed C−N Bond Formation Involving sp-Hybridized Carbons. A Direct Entry to Chiral Ynamides via N-Alkynylation of Amides. J. Am. Chem. Soc. 2003, 125, 2368−2369.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.7b01155. Reaction time course of polymerization of 1a and 2a; temperature course of polymerization of 1a and 2a; chemical structures of P1a−d/2a and P1c/2b,c; IR spectra of P1b−d/2a and P1c/2b,c; IR spectra of P1c/ 2a,b, P1c/2a,b-{[Co(CO)3]2}x, P1d/2a, and P1d/2a{[Co(CO)3]2}x (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*(R.H.) E-mail [email protected]; Tel +86-2223-7066. *(B.Z.T.) E-mail [email protected]; Tel +852-2358-7375. ORCID

Rongrong Hu: 0000-0002-7939-6962 Ben Zhong Tang: 0000-0002-0293-964X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was partially supported by the National Science Foundation of China (21404041, 21490573, and 21490574), the Young Elite Scientist Sponsorship Program of the China Association of Science and Technology (2015QNRC001), the Guangdong Natural Science Funds for Distinguished Young Scholar (2016A030306045), the Natural Science Foundation of Guangdong Province (2016A030312002), the National Basic Research Program of China (973 Program; 2013CB834701), and the Innovation and Technology Commission of Hong Kong (ITC-CNERC14SC01).

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DOI: 10.1021/acs.macromol.7b01155 Macromolecules XXXX, XXX, XXX−XXX