Silver nanoparticles embedded in modified polyallylamine resin as efficient catalysts for alkyne-azide 1,3-dipolar cycloaddition in water

Article abstract of DOI:10.1016/j.catcom.2015.11.005

A silver nanoparticle composite based on modified polyallylamine has been synthesized by a simple chemical route and its catalytic activity has been tested for alkyne-azide cycloaddition reaction. This silver nanocomposite shows an excellent catalytic activity at 80 °C for the synthesis of 1,4-disubstituted 1,2,3-triazole by alkyne-azide cycloaddition. The solid silver nanocomposite catalyst was characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry and thermogravimetric analysis. The developed catalyst is stable in air, easy to prepare and can be recovered easily and reused ten times without a significant decrease in activity.

Full text of DOI:10.1016/j.catcom.2015.11.005

Catalysis Communications 74 (2016) 110–114
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
Silver nanoparticles embedded in modified polyallylamine resin as
efficient catalysts for alkyne–azide 1,3-dipolar cycloaddition in water
a
b
a
Xian-Liang Zhao a, , Ke-Fang Yang
, Yan Zhang , Li-Wen Xu , Xiao-Qing Guo
⁎
b,⁎⁎
a
School of Biological and Chemical Engineering/School of Light Industry, Zhejiang University of Science and Technology, Hangzhou 310023, China
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Hangzhou 310012, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 July 2015
Received in revised form 16 September 2015
Accepted 10 November 2015
Available online 11 November 2015
A silver nanoparticle composite based on modified polyallylamine has been synthesized by a simple chemical
route and its catalytic activity has been tested for alkyne–azide cycloaddition reaction. This silver nanocomposite
shows an excellent catalytic activity at 80 °C for the synthesis of 1,4-disubstituted 1,2,3-triazole by alkyne–azide
cycloaddition. The solid silver nanocomposite catalyst was characterized by transmission electron microscopy,
Fourier-transform infrared spectroscopy, X-ray diffractometry and thermogravimetric analysis. The developed
catalyst is stable in air, easy to prepare and can be recovered easily and reused ten times without a significant de-
crease in activity.
Keywords:
Silver nanocomposite
Polyallylamine
Modified
© 2015 Published by Elsevier B.V.
Alkyne–azide cycloaddition
Recycle
Water
1. Introduction
have been used in the synthesis of metal nanoparticles [24–28]. Howev-
er, minimal work has been carried out where polyallylamine has been
The Huisgen 1,3-dipolar cycloaddition reaction between azides and
terminal alkynes is a widely studied “click” reaction to synthesize
1,2,3-triazoles [1]. This reaction has been applied extensively in phar-
maceuticals, drug discovery, agrochemicals, dyes, corrosion inhibitors,
photostabilizers, photographic materials and biochemistry [2–7]. The
copper-catalyzed alkyne–azide cycloaddition is regarded as the most
efficient click chemistry [8–10]. The heterogeneous nature of catalysts
offers advantages of thermal stability and reusability [11–14]. The cata-
lytic activity of copper nanoparticles (Cu NPs) in the azide–alkyne click
reaction has received much interest [15–21]. Silver nanoparticles
(Ag NPs) have been employed catalysts in organic synthesis, However,
Ag NPs have received less attention in terms of their application in the
azide–alkyne click reaction [22]. Although Jana et al. reported on a
silver–graphene nanocomposite for a “one-pot” azide–alkyne click reac-
tion, the application of other Ag NPs immobilized on polymers still
needs to be explored [23].
used as a capping agent to stabilize metal nanoparticles [29–31].
Among them, Kuo just reported the syntheses and characterization of
silver nanoparticles stabilized by poly(allylamine) (PAA) and by poly-
ethyleneiminated poly-(allylamine). The application of Ag NPs still
needs to be explored.
Herein, we describe the advantages of Ag NPs in modified poly-
allylamine as a simple, inexpensive and general and efficient heteroge-
neous catalyst for use in the Huisgen 1,3-dipolar reaction of alkyne–
azide cycloaddition in water.
2. Experimental
2.1. Instruments
Infrared spectra were recorded on a Perkin Elmer Fourier-transform
infrared (FTIR) spectrometer using KBr. FEI Technai G2 transmission
electron microscope was used for transmission electron microscopic
(TEM) image of sample. Thermogravimetric analysis (TGA) was carried
out on a Mettler-Toledo 851E instrument. X-ray diffraction patterns
were recorded on a Rigaku, D-5000 diffractometer, using Ni-filtered
Cu-K radiation (λ = 1.5405 Å). 1H NMR spectra were recorded on a
400 (Varian, Palo Alto, USA) spectrometer in CDCl3 solution with tetra-
methylsilane as an internal standard. Chemical shift values are given in
parts per million.
Polymers are excellent host materials for the preparation of metal
nanoparticles. Various synthetic polymers, such as poly(methyl meth-
acrylate), polystyrene, poly(vinyl alcohol) and poly(vinyl pyrrolidone),
⁎
Correspondence to: X.-L. Zhao, School of Biological and Chemical Engineering,
Zhejiang University of Science and Technology, Hangzhou 310023, China.
⁎⁎ Corresponding author.
E-mail addresses: xlzhao@iccas.ac.cn (X.-L. Zhao), kfyang@hznu.edu.cn (K.-F. Yang).
http://dx.doi.org/10.1016/j.catcom.2015.11.005
1566-7367/© 2015 Published by Elsevier B.V.

X.-L. Zhao et al. / Catalysis Communications 74 (2016) 110–114
111
Scheme 1. Synthesis for silver nanocomposite.
2.2. Preparation of silver nanocomposite
3. Results and discussion
The modified polyallylamine (10.0 g) was dissolved in water
(30.0 mL) to obtain a clear solution at room temperature. Silver ni-
trate (3.26 g) was dissolved in water (10.0 mL) and added into the
solution at room temperature. Ammonia water was added into the
solution to obtain a clear solution at room temperature. (3-
Glycidoxypropyl)methyldiethoxysilane (4.0 g) was added into the
mixture at room temperature. The mixture was heated to a viscous
solid at 120 °C, then cooled to room temperature. Hydrazine hydrate
(80 wt.%) (20 mL) was added and stirred at room temperature for
24 h. The resultant brown solid was washed with water and dried
at 60 °C for 12 h under vacuum to afford Ag NPs (16.2 g).
3.1. Preparation of Ag NPs
The synthesis strategy for the silver–polyamine nanocomposite is
shown in the Scheme 1. Polyallylamine was synthesized according our
previous work [32]. The modified polyallylamine has a strong tendency
to form gel in aqueous solution. This gel that contains hydroxy and
amino groups protects and stabilizes the Ag NPs in its strong gel mesh
and acts as an excellent surface capping agent in the process.
3.2. Catalyst characterization
3.2.1. FTIR spectra of Ag NPs and blank resin
The FTIR spectra of the blank and silver resin are shown in Fig. 1.
The O–H absorption band shifted slightly compared with that of blank
polymer composite in the FTIR analysis. This indicates that an interac-
tion occurs between these groups and nanosilver.
2.3. Application of silver nanocomposite as an efficient catalyst in organic
reactions
A mixture of benzylazide (133.0 mg, 1.0 mmol), phenylacetylene
(102.0 mg, 1.0 mmol), silver nanocomposite (10.0 mg) and water
(1.0 mL) was stirred at 80 °C in a test tube. The reaction was extracted
using dichloromethane (10.0 mL). The combined organic extract was
washed with water (5.0 mL) and dried using anhydrous magnesium
sulfate. The solvent was removed in vacuum and the crude product
was purified by flash chromatography on silica gel (eluent: ethyl
acetate/petroleum ether, 1:10) to afford a colorless solid 3a (0.223 g,
95%).
3.2.2. X-ray diffractometry of Ag NPs and blank resin
Fig. 2a shows the X-ray diffraction pattern of the blank resin. The
resin reflection at 2θ of 18.82° corresponds to the amorphous part of
the resin. The resin reflection at 2θ of 28.42°, 40.53°, 50.3°, 66.42° and
73.84° corresponds to the crystalline part of the resin [33–34].
Fig. 2b shows the X-ray diffraction pattern of the silver resin. The re-
flections at 2θ of 38.3°, 43.6°, 64.6° and 77.80° correspond to (111),
(200), (220) and (311) planes of silver, respectively [24–28]. The reflec-
tion of resin at 2θ of 19.22° corresponds to the amorphous part of the
Fig. 1. FTIR spectra of Ag NPs and blank resin.
Fig. 2. X-ray diffraction pattern of Ag NPs and blank resin.

112
X.-L. Zhao et al. / Catalysis Communications 74 (2016) 110–114
Fig. 3. TEM image of Ag NPs.
resin. The reflective crystalline part of the resin at 2θ disappeared com-
pared with the reflection of the blank resin. Nanosilver was stabilized by
amine and hydroxyl groups on the resin that destroy the crystalline part
of the resin.
between 370 and 450 °C and this is related to the sudden resin mass
loss. This result shows that the blank resin and Ag NPs have a greater
thermal stability.
3.2.3. TEM of Ag NPs and blank resin
3.3. Catalytic studies
Fig. 3a shows an image of the Ag NPs before using the reaction. The
TEM image indicates that the Ag NPs are dispersed uniformly in the
resin. Fig. 3b shows an image of the Ag NPs after they had been used
in the reaction. The TEM image (Fig. 3b) indicates that the Ag NPs
were stabilized by the resin. The Ag NPs are still dispersed uniformly
in the resin even in hot water. The results also proved that the activity
of Ag NPs can be used for reuse.
We investigated the catalytic activity of Ag NPs in the alkyne–azide
cycloaddition in water. To develop an optimal catalytic system, benzyl
azide and phenylacetylene were used as model reactants to test the cat-
alytic activities of Ag NPs. The results are summarized in Table 1. Water
is considered to be a benign environmental solvent, and was therefore
used as solvent to test the effect of temperature. As the temperature
rose from 50–80 °C, the triazole yield increased from 24% to 92% in
3.2.4. TGA of Ag NPs and blank resin
TGA of Ag NPs is compared with a blank resin in Fig. 4. The TGA curve
of the blank resin and the Ag NPs shows a mass loss (2 wt.%) below 100
°C that corresponds to the loss in physically adsorbed water. In the TGA
curve for the blank resin and Ag NPs, two regions exist that correspond
to different mass loss ranges. The first region is approximately 250 °C
and displays a mass loss that is attributable to the loss of trapped
water from the resin. A mass loss of approximately 50 wt.% occurred
Table 1
Temperature effects on the reaction of benzylazide with phenylacetylenea,b
.
T (°C)
Yield (%)
50
24
60
31
70
52
80
92
90
93
a
Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), Ag NPs (10.0 mg), water (1.0 mL),
8 h.
b
Isolated yield.
Table 2
Optimization of catalyst amount for reaction of benzylazide with phenylacetylenea,b
.
Entry
Amount of catalyst/g
Time/h
Yield/%
1
2
3
4
5
–
12
12
12
8
0
26
68
92
93
0.0010
0.0050
0.0100
0.0150
8
a
Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), water (1.0 mL), 80 °C.
Isolated yield.
b
Fig. 4. TGA of blank resin and Ag NPs.

X.-L. Zhao et al. / Catalysis Communications 74 (2016) 110–114
113
Table 3
Substrate scope of reaction between various azides and alkynes.a
Entry
1
R–N3
Alkyne
Time/h
8
Product
Yield/%b
95
2
3
4
1a
1a
1a
7
8
95
96
93
15
5
6
1a
1a
9
8
94
94
7
8
8
8
95
96
9
8
8
92
93
10
1e
a
Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), Ag NPs (10 mg), water (1.0 mL), 80 °C.
Isolated yield.
b
Fig. 5. Recycling of catalyst Ag NPs in aqueous reaction of benzylazide with phenylacetylene.

114
X.-L. Zhao et al. / Catalysis Communications 74 (2016) 110–114
8 h. The higher temperature did not accelerate the reaction time or pro-
mote the reaction yield (Table 1).
Appendix A. Supplementary data
The amount of catalyst was investigated. The results are summarized
in Table 2. Product 3a was formed in high yields with catalyst loadings
of 0.010 g (the catalyst includes of resin and Ag NPs). The reaction
was not carried out without catalyst. A higher amount of catalyst did
not accelerate the reaction time or promote the reaction yield much
more than catalyst loadings of 0.010 g. A lower yield of product 3a
was obtained with a lower amount of catalyst and in a reaction time
of 12 h.
Using optimal reaction conditions, various alkynes were reacted
with azides in the presence of Ag NPS in water (Table 3). Phenyl-
acetylene and electron-rich aromatic alkynes gave excellent results
with benzyl azide. However, an electron-deficient aromatic alkyne
needs a longer time to form the 1,2,3-triazole product under the same
reaction conditions. The reaction also gave an excellent yield when the
reaction time was extended to 15 h. Aliphatic alkynes required longer
reaction times to give high yields compared with electron-rich aromatic
alkynes, but the reactions were completed within 10 h.
We examined the recyclability of the nanosilver catalyst (Fig. 5).
Product 3a was dissolved in dichloromethane and the catalyst nano-
silver was filtered from the reaction mixture and used directly for an-
other cycle. As shown in Fig. 5, the catalyst showed no substantial
reduction in activity even after the tenth run. All reactions were com-
pleted in 8 h and afforded 3a in yields of 90–95%.
In conclusion, Ag NPs embedded in polyallylamine resin were used
as a novel and efficient catalyst for the azide–alkyne click reaction in
water. Attractive features of this procedure include its green reaction
conditions, medium reaction times, excellent yields and operational
simplicity. The catalysts can be recycled more than ten times without
an obvious loss in catalytic activity. We believe that this simple and
green procedure is a practical method for use in academia and chemical
industries. The scope and synthetic application of the nanosilver are
under investigation.
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2015.11.005.
References
[1] R. Huisgen, Angew. Chem. 75 (1963) 604–637.
[2] R.K. Iha, K.L. Wooley, A.M. Nystrom, D.J. Burke, M.J. Kade, C.J. Hawker, Chem. Rev.
109 (2009) 5620–5686.
[3] K. Kempe, A. Krieg, C.R. Becer, U.S. Schubert, Chem. Soc. Rev. 41 (2012) 176–191.
[4] A.H. El-Sagheer, T. Brown, Chem. Soc. Rev. 39 (2010) 1388–1405.
[5] J. Qin, J.W.Y. Lam, B.Z. Tang, Chem. Soc. Rev. 39 (2010) 2522–2544.
[6] Y. Hua, A.H. Flood, Chem. Soc. Rev. 39 (2010) 1262–1271.
[7] H.C. Kolb, M.G. Finn, K.B. Sharpless, Angew. Chem. Int. Ed. 40 (2010) 2004–2021.
[8] M. Meldal, C.W. Tornoe, C. Christensen, J. Org. Chem. 67 (2002) 3057–3064.
[9] V.V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem. Int. Ed. 41
(2002) 2596–2599.
[10] L.D. Pachón, J.H. van Maarseveen, G. Rothenberg, Adv. Synth. Catal. 347 (2005)
811–815.
[11] E. Girard, M. Onen, S. Aufort, E. Beauviere, J. Samson, Herscovici, Org. Lett. 8 (2006)
1689–1692.
[12] R.B.N.S. Baig, R.S. Varma, Green Chem. 14 (2013) 625–628.
[13] N. Mukherjee, S. Ahammed, S. Bhadra, B.C. Ranu, Green Chem. 15 (2013) 389–397.
[14] H. Lee, C.C. Wu, X. Fang, C.W. Liu, J.L. Zhu, Catal. Lett. 143 (2013) 572–577.
[15] R.P. Jumde, C. Evangelisti, A. Mandoli, N. Scotti, R. Psaro, J. Catal. 324 (2015) 25–31.
[16] T. Jin, M. Yan, Y. Yamamoto, ChemCatChem 4 (2012) 1217–1229.
[17] R.B.N. Baig, R.S. Varma, Green Chem. 14 (2012) 625–632.
[18] S. Park, M.S. Kwon, Y.K. Kim, J.S. Lee, J. Park, Org. Lett. 10 (2008) 497–500.
[19] F. Alonso, Y. Moglie, G. Radivoy, M. Yus, J. Org. Chem. 76 (2011) 8394–8405.
[20] F. Alonso, Y. Moglie, G. Radivoy, M. Yus, Adv. Synth. Catal. 352 (2010) 3208–3214.
[21] A. Pathigoolla, R.P. Pola, K.M. Sureshan, Appl. Catal. A Gen. 453 (2013) 151–158.
[22] M. Harmata, Silver in Organic Chemistry, John Wiley & Sons, Hoboken, 2010.
[23] N. Salam, A. Sinha, A.S. Roy, P. Mondal, N.R. Jana, S.M. Islam, RSC Adv. 4 (2014)
10001–10012.
[24] P.K. Khanna, N. Singh, S. Charan, V.V.V. Subbarao, R. Gokhale, U.P. Mulik, Mater.
Chem. Phys. 93 (2005) 117–121.
[25] S. Chou, C.Y. Ren, Mater. Chem. Phys. 64 (2000) 241–246.
[26] P.K. Khanna, R. Gokhale, V.V.V. Subbarao, J. Mater. Sci. 39 (2004) 3773–3776.
[27] Wu, X. Ge, Y. Huang, Z. Zhang, Q. Ye, Mater. Lett. 57 (2003) 3549–3553.
[28] L.A. Monti, J.T. Fourkas, D.J. Nesbitt, J. Phys. Chem. B 108 (2004) 1604–1612.
[29] P.L. Kuo, W.F. Chen, J. Phys. Chem. B 107 (2003) 11267–11272.
[30] L. Zhang, C. Wang, L.N. Zhu, Acta Chim. Sin. 67 (2009) 2095–2101.
[31] L. P, L.G. Min, R. Yuan, Y.Q. Chai, S.H. Chen, Microchim. Acta 171 (2010) 297–304.
[32] X.L. Zhao, K.F. Yang, Y.P. Zhang, J. Z., L.W. Xu, Chin. Chem. Lett. 25 (2014)
1141–1144.
Acknowledgments
[33] H.P. Klug, L.R. Alexander, X-ray Diffraction Procedures for Polycrystalline and
Amorphous Materials, Wiley-Interscience, 1974.
[34] R. Alexander, X-ray Diffraction Methods in Polymer Science, Kreiger Publishing,
1979.
We gratefully acknowledge financial support by the National
Natural Science Foundation of China (No. 21242004, No. 21302168,
No. 51203037).