Design and synthesis of dumbbell-shaped POSS-C 60 dyads with flexible spacer

Article abstract of DOI:10.1080/00397911.2011.589562

Using polyhedral oligomeric silsesquioxane (POSS) as starting material, novel dumbbell-shaped POSS-C₆₀ dyads with flexible spacers were designed and synthesized in good yields by esterification, subsequent etherification, and further 1,3-dipola

Full text of DOI:10.1080/00397911.2011.589562

This article was downloaded by: [University of Hong Kong Libraries]
On: 27 June 2013, At: 00:33
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/lsyc20
Design and Synthesis of Dumbbell-
Shaped POSS-C60 Dyads with Flexible
Spacer
Fafu Yang a b , Congcong Li a , Hongyu Guo a , Jinqi Ye a & Ziyu Jiao a
a College of Chemistry and Materials Science, Fujian Normal
University, Fuzhou, China
b Fujian Key Laboratory of Polymer Materials, Fuzhou, China
Accepted author version posted online: 20 Jan 2012.Published
online: 20 Aug 2012.
To cite this article: Fafu Yang , Congcong Li , Hongyu Guo , Jinqi Ye & Ziyu Jiao (2012): Design and
Synthesis of Dumbbell-Shaped POSS-C60 Dyads with Flexible Spacer, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 42:24, 3664-3669
To link to this article: http://dx.doi.org/10.1080/00397911.2011.589562
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation
that the contents will be complete or accurate or up to date. The accuracy of any
instructions, formulae, and drug doses should be independently verified with primary
sources. The publisher shall not be liable for any loss, actions, claims, proceedings,
demand, or costs or damages whatsoever or howsoever caused arising directly or
indirectly in connection with or arising out of the use of this material.

Synthetic Communications1, 42: 3664–3669, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.589562
DESIGN AND SYNTHESIS OF DUMBBELL-SHAPED
POSS-C60 DYADS WITH FLEXIBLE SPACER
Fafu Yang,1,2 Congcong Li,1 Hongyu Guo,1 Jinqi Ye,1
and Ziyu Jiao1
1College of Chemistry and Materials Science, Fujian Normal University,
Fuzhou, China
2Fujian Key Laboratory of Polymer Materials, Fuzhou, China
GRAPHICAL ABSTRACT
Abstract Using polyhedral oligomeric silsesquioxane (POSS) as starting material, novel
dumbbell-shaped POSS-C60 dyads with flexible spacers were designed and synthesized in
good yields by esterification, subsequent etherification, and further 1,3-dipolar cycloaddi-
tion of azomethine ylide generated in situ from aldehyde and sarcosine to C60
.
Keywords 1,3-Dipolar cycloaddition; fullerene; POSS; synthesis
INTRODUCTION
Fullerene has received much research interest because of its unique structure,
interesting properties, and promising applications in a variety of fields, such as
macromolecular materials, fuel cells, solar energy conversion and storage, and bio-
medical and life sciences.[1,2] However, their poor solubility and processability pose
difficulties in utilizing fullerene for practical applications. To overcome these disad-
vantages, one method was to synthesize the fullerene-grafted polymers, some of
which exhibited attractive properties,[3,4] for instance, fullerene-containing polyester
Received March 27, 2011.
Address correspondence to Fafu Yang, College of Chemistry and Materials Science, Fujian
Normal University, Fuzhou 350007, China. E-mail: yangfafu@fjnu.edu.cn
3664

POSS-C60 DYADS
3665
and p-conjugated polymers,[5] fullerene-containing poly(propylene oxide) mem-
brane.[6] However, the syntheses of these kinds of polymers were often complicated
and the contents of fullerene in them were difficult to adjust for different applications.
Another method was to prepare fullerene-doped polymers, such as sol-gel glasses,[7]
polymethyl methacrylate (PMMA),[8] and glass-polymer composites.[9] However,
the heterogeneous dispersion of fullerene in a polymetric matix often resulted in
aggregation, which was the obstacle to obtaining stable and homogeneous materials.
The polyhedral oligomeric silsequioxane (POSS) macromer, consisting of a
spherical inorganic silica core (Si8O12) surrounded by seven inert alkyl groups for
solubility and one reactive group, is a well-defined cluster whose diameter is approxi-
[10]
˚
mately 15 A.
POSS can be regarded as the smallest possible silica particle sur-
rounded by an organic surface.[11] Because of the special structure of POSS, the
POSS-fullerene dyad, in theory, should not only exhibit the interesting properties
based on fullerene units but also possess excellent homogenous dispersion in poly-
meric matries based on POSS units, preventing aggregation of fullerene and improv-
ing physical and mechanical properties.[12] Lately, Clarke et al. reported the first
examples of POSS-fullerene derivative with short and rigid phenyl groups.[13,14]
However, the short and rigid phenyl groups were not favorable for homogenous dis-
persion in polymers. The long and flexible aliphatic spacer would be an excellent can-
didate for preparing fullerene-POSS dyads possessing outstanding flexibility and
compatibility with polymers. In this article, we designed and synthesized novel
dumbbell-shaped polyhedral oligomeric silsesquioxane (POSS)-C60 dyads, in which
POSS and C60 were linked with long and flexible aliphatic spacers for the first time.
The synthetic route is shown in Scheme 1. The esterification of mono-hydroxy
POSS 1 was carried out by reacting mono-hydroxy POSS 1 with corresponding
x-bromo-substituted carboxylic acid, using N,N0-dicyclohexylcarbodiimide as
condensating agent and 4-dimethylaminopyridine as catalyst. Mono-x-bromo-
substituted POSS 2a and 2b were obtained in yields of 85% and 78%, respectively.
Subsequently, nucleophilic substitution of compound 2 with 4-hydroxybenzaldehyde
Scheme 1.

3666
F. YANG ET AL.
gave the desired mono-aldehyde-substituted POSS 3a or 3b in refluxing K2CO3=
MeCN system in 88% or 86% after column chromatography. After further treating
compound 3 with C60 and sarcosine, the novel dumbbell-shaped POSS-C60 dyad 4a
and 4b were prepared by 1,3-dipolar cycloaddition of azomethine ylide generated in
situ from aldehyde and sarcosine in yields of 55% and 61%, respectively. Although
novel dumbbell-shaped POSS-C60 dyads 4a and 4b were prepared in multiple steps,
the total yields of them were as high as 41% and 40%, respectively.
The structures of intermediate compounds 2 and 3 were characterized by
1
elemental analyses, electrospray ionization–mass spectrometry (ESI-MS), and H
NMR spectra. All these data were in accordance with the structures of compounds
2 and 3. The structures of target compounds of novel dumbbell-shaped POSS-C60
dyads 4a and 4b were confirmed by elemental analyses, ultraviolet (UV), infrared
(IR), ESI-MS, 1H NMR, and 13C NMR spectra. The UV spectra showed the typical
absorption features of mono-fulleropyrrolidine at 256, 308, and 430 nm. The ESI-MS
spectra exhibited corresponding molecular ion peaks at 1840.34 and 1910.22, respect-
1
ively. In the H NMR spectra, all the protons were well assigned. Especially, the
typical split of NCH2 (a and a0) on a pyrrole ring and ArH (c and d) were observed
clearly. All these spectral data were in accordance with the structures of fullero-
pyrrolidine derivatives in literatures.[1,2,13,14] Our further work will focus on prepar-
ing various polymers with compounds 4a and 4b to form stable and homogeneous
hybrid materials containing C60 units and nanometer silica particles.
EXPERIMENTAL
C60, POSS, 6-bromocaproic acid, 11-bromoundecanoic acid, 4-hydroxybenzal-
dehyde, sarcosine, N,N0-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and
KI were obtained from commercial suppliers and used without further purification.
The other organic and inorganic reagents were purified according to standard meth-
ods before use. The analysis of thin-layer chromatography (TLC) was performed
using precoated glass plates. Column chromatography was performed using silica
gel (200–300 mesh). IR spectra were recorded on a Perkin-Elmer PE-983 IR spec-
1
trometer as KBr pellets with absorption in cmꢀ1. H NMR and 13C NMR spectra
were recorded in CDCl3 on a Bruker-ARX 600 instrument at 30 ꢁC, using, tetra-
methylsilane (TMS) as internal standard. The UV–vis absorption spectra were mea-
sured on a computer-controlled Shimadzu UV2501-PC spectrophotometer. ESI-MS
spectra were obtained from DECAX-30000 LCQ Deca XP mass spectrometer.
Elemental analyses were performed on a Vario EL III Elemental Analyzer.
Syntheses of Compounds 2a and 2b
Compound 1 (0.5 g, 0.57 mmol), corresponding x-bromo-substituted car-
boxylic acid (0.60 mmol), N,N0-dicyclohexylcarbodiimide (0.13 g, 0.63 mmol), and
4-dimethylaminopyridine (0.02 g, 0.16 mmol) were dissolved in 10 mL CH2Cl2. The
mixture was stirred for 4 h under room temperature. Then the solvent was evapo-
rated under reduced pressure. The residue was precipitated in a 1:1 vol=vol mixture
of methanol and water, separated by centrifugation, and dried under vacuum.
The crude product was further purified by flash column chromatography on silica

POSS-C60 DYADS
3667
gel using a mixture of hexane–acetone (7:1) as eluant. Compounds 2a and 2b were
obtained as white powder in yields of 85% and 78%, respectively.
Compound 2a. 1H NMR (600 MHz, CDCl3) d ppm: 0.61 (m, 16H, SiCH2),
0.97 (d, 42H, J ¼ 6.6 Hz, CH3), 1.43–1.74 [m, 8H, (CH2)3CH2COO and
COOCH2CH2], 1.85 (m, 7H, SiCH2CH), 2.32 (t, 2H, J ¼ 7.2 Hz, CH2COO), 3.41
(t, 2H, J ¼ 6.6 Hz, CH2Br), 4.03 (t, 2H, J ¼ 6.6 Hz, COOCH2); MS m=z (%):
1051.71 (Mþ, 100). Anal. calcd. for C37H79BrO14Si8: C, 42.25; H, 7.57. Found C,
42.20; H, 7.64.
Compound 2b. 1H NMR (600 MHz, CDCl3) d ppm: 0.61 (m, 16H, SiCH2),
0.97 (d, 42H, J ¼ 6.6 Hz, CH3), 1.30 [m, 12H, (CH2)6CH2CH2Br], 1.43 (m, 2H,
CH2CH2COO), 1.56–1.72 (m, 4H, COOCH2CH2 and CH2CH2Br), 1.87 (m, 7H,
SiCH2CH), 2.30 (t, 2H, J ¼ 7.2 Hz, CH2COO), 3.42 (t, 2H, J ¼ 6.6 Hz, CH2Br),
4.04 (t, 2H, J ¼ 6.6 Hz, COOCH2); MS m=z (%): 1122.23 (Mþ, 100). Anal. calcd.
for C42H89BrO14Si8: C, 44.99; H, 7.99. Found: C, 44.93; H, 7.91.
Syntheses of Compounds 3a and 3b
Compounds 2a or 2b (0.35 mmol), and 4-hydroxybenzaldehyde (0.25 g,
2.0 mmol), and K2CO3 (0.27 g, 2.0 mmol) were refluxed in 50 mL MeCN overnight
and purged with N2. After cooling, the mixture was filtered and evaporated to dry-
ness on a rotavapor. Then the mixture was further purified by column chromato-
graphy on silica gel using a mixture of petroleum ether–CH2Cl2(5:1, v=v) as
eluant. The compounds 3a and 3b were obtained as grayish solids in yields of 88%
and 86%, respectively.
Compound 3a. 1H NMR (600 MHz, CDCl3) d ppm: 0.60 (m, 16H, SiCH2),
0.95 (d, 42H, J ¼ 6.6 Hz, CH3), 1.51–1.87 [m, 15H, (CH2)3CH2COO, COOCH2CH2
and SiCH2CH], 2.34 (t, 2H, J ¼ 7.2 Hz, CH2COO), 4.04 (m, 4H, ArOCH2 and
COOCH2), 6.98 (d, 2H, J ¼ 8.4 Hz, ArH), 7.83 (d, 2H, J ¼ 8.4 Hz, ArH), 9.88 (s,
1H, ArCHO); MS m=z (%): 1092.82 (Mþ, 100). Anal. calcd. for C44H84O16Si8: C,
48.34; H, 7.75. Found C, 48.43; H, 7.68.
Compound 3b. 1H NMR (600 MHz, CDCl3) d ppm: 0.59 (m, 16H, SiCH2),
0.94 (d, 42H, J ¼ 6.6 Hz, CH3), 1.21–1.88 [m, 25H, (CH2)8CH2OAr, COOCH2CH2
and SiCH2CH], 2.28 (t, 2H, J ¼ 7.2 Hz, CH2COO), 4.01–4.11 (m, 4H, CH2OAr
and COOCH2), 6.98 (d, 2H, J ¼ 8.4 Hz, ArH), 7.81 (d, 2H, J ¼ 8.4 Hz, ArH), 9.87
(s, 1H, ArCHO); MS m=z (%): 1162.84 (Mþ, 100). Anal. calcd. for C49H94O16Si8:
C, 50.59; H, 8.15. Found: C, 50.68; H, 8.06.
Syntheses of Compounds 4a and 4b
A mixture of compounds 3a or 3b (0.23 mmol), C60 (0.18 g, 0.25 mol), and sarco-
sine (0.26 g, 3.0 mmol) in dry toluene (200 mL) was refluxed for 48 h. After the reac-
tion mixture was cooled to room temperature, the solvent was removed under reduce
pressure and the residue was further purified by column chromatography [SiO2
200–300 mesh, petroleum ether=CH2Cl2(1:1, v=v) as eluant]. The compounds 4a
and 4b were obtained as brown solids in yields of 55% and 61%, respectively.

3668
F. YANG ET AL.
Compound 4a. 1H NMR (600 MHz, CDCl3) d ppm: 0.60 (m, 16H, SiCH2),
0.95 (d, 42H, J ¼ 6.6 Hz, CH3), 1.23–1.88 [m, 15H, (CH2)3CH2OAr, COOCH2CH2
and SiCH2CH], 2.27 (t, 2H, J ¼ 7.2 Hz, CH2COO), 2.77 (s, 3H, NCH3), 3.94 (t,
2H, J ¼ 6.6 Hz, OCH2), 4.02 (t, 2H, J ¼ 6.6 Hz, CH2OAr), 4.22 (d, 1H, J ¼ 9.6 Hz,
NCH2), 4.87 (s, 1H, ArCH), 4.95 (d, 1H, J ¼ 9.6 Hz, NCH2), 6.92 (d, 2H, J ¼ 8.4
ArH), 7.68 (bs, 2H, ArH); 13C NMR (150 MHz, CDCl3) d ppm: 8.56, 22.43,
22.65, 22.72, 24.07, 24.10, 24.98, 25.90, 25.93, 25.96, 29.27, 34.41, 40.22, 66.47,
67.80, 69.20, 70.21, 77.60, 83.40, 129.01, 136.01, 136.02, 136.80, 137.0, 139.80,
140.13, 140.34, 140.37, 141.76, 141.90, 142.05, 142.19, 142.23, 142.25, 142.30,
142.33, 142.35, 142.38, 142.48, 142.51, 142.76, 142.80, 142.89, 143.20, 143.36,
144.62, 144.84, 144.93, 145.36, 145.45, 145.49, 145.52, 145.55, 145.68, 145.71,
145.76, 146.0, 146.14, 146.16, 146.31, 146.35, 146.37, 146.43, 146.49, 146.52,
146.61, 146.75, 147.03, 147.51, 147.52, 153.90, 154.34, 156.60, 159.30, 173. FT-IR
(KBr) v=cmꢀ1: 3437, 2952, 1737, 1464, 1109, 836, 560, 481. UV-vis: 256, 308, and
429 nm. MS m=z (%): 1840.34 (Mþ, 100). Anal. calcd. for C106H89O15Si8N: C,
69.16; H 4.87; N, 0.76. Found: C, 69.24; H, 5.73; N, 0.67.
Compound 4b. 1H NMR (600 MHz, CDCl3) d ppm: 0.60 (m, 16H, SiCH2),
0.95 (d, 42H, J ¼ 6.6 Hz, CH3), 1.24–1.86 [m, 25H, (CH2)8CH2OAr, COOCH2CH2
and SiCH2CH], 2.28 (t, 2H, J ¼ 7.2 Hz, CH2COO), 2.77 (s, 3H, NCH3), 3.93 (t,
2H, J ¼ 6.6 Hz, OCH2), 4.01 (t, 2H, J ¼ 6.6 Hz, CH2OAr), 4.22 (d, 1H, J ¼ 9.6 Hz,
NCH2), 4.87 (s, 1H, ArCH), 4.95 (d, 1H, J ¼ 9.6 Hz, NCH2), 6.92 (d, 2H, J ¼ 8.4
ArH), 7.69 (bs, 2H, ArH); 13C NMR (150 MHz, CDCl3) d ppm: 8.57, 22.43, 22.65,
22.72, 24.07, 24.10, 25.22, 25.89, 25.93, 26.32, 29.41, 29.51, 29.56, 29.63, 29.64,
29.75, 34.57, 40.22, 66.38, 68.19, 69.20, 70.22, 77.61, 83.42, 128.90, 136.01, 136.80,
136.99, 139.79, 140.11, 140.33, 140.37, 141.75, 141.89, 142.05, 142.19, 142.22,
142.25, 142.30, 142.33, 142.35, 142.38, 142.48, 142.51, 142.77, 142.80, 142.88,
143.20, 143.36, 144.61, 144.84, 144.92, 145.36, 145.45, 145.49, 145.52, 145.55,
145.68, 145.71, 145.76, 146.0, 146.13, 146.16, 146.31, 146.34, 146.37, 146.42,
146.48, 146.52, 146.62, 146.75, 147.04, 147.50, 147.52, 153.92, 154.35, 156.62,
159.41, 174.01. FT-IR (KBr) v=cmꢀ1: 3440, 2952, 1737, 1464, 1108, 836, 572, 483.
UV-vis: 256, 307, and 430 nm. MS m=z (%): 1910.22 (Mþ, 100). Anal. calcd. for
C
111H99O15Si8N: C, 69.76; H, 5.22; N, 0.73. Found: C, 69.86; H, 5.17; N, 0.64.
ACKNOWLEDGMENTS
Financial support from the National Natural Science Foundation of China
(No. 20402002), Fujian Natural Science Foundation of China (No. 2009J01019),
and Program for Excellent Young Researchers in University of Fujian Province
(JA10056) were greatly acknowledged. Thanks go to Prof. Lei Zhu at Case Western
Reserve University for supplying the materials.
REFERENCES
1. Sawamura, M.; Kawai, K.; Matsuo, Y.; Kanie, K.; Kato, T.; Nakamura, E. Stacking of
conical molecules with a fullerene apex into polar columns in crystals and liquid crystals.
Nature 2002, 419, 702–705.

POSS-C60 DYADS
3669
2. Michinobu, T.; Nakanishi, T.; Hill, J.; Funahashi, M.; Ariga, K. Room-temperature
liquid fullerenes: An uncommon morphology of C60 derivatives. J. Am. Chem. Soc.
2006, 128, 10384–10387.
´
3. Segura, J. L.; Martın, N.; Guldi, D. M. Materials for organic solar cells: The C60=
p-conjugated oligomer approach. Chem. Soc. Rev. 2005, 34, 31–47.
4. Kuang, L.; Chen, Q.; Sargent, E. H.; Wang, Z. Y. Fullerene-containing polyurethane
films with large ultrafast nonresonant third-order nonlinearity at telecommunication
wavelengths. J. Am. Chem. Soc. 2003, 125, 13648–13649.
5. Yu, H.; Gan, L. H.; Hu, X.; Venkatraman, S. S.; Tam, K. C.; Gan, Y. Y. A novel
amphiphilic double-[60] fullerene-capped triblock copolymer. Macromolecules 2005, 38,
9889–9893
6. Sterescu, D. M.; Bolhuis-Versteeg, L.; Vegt, N. F. A.; Stamatialis, D. F.; Wessling, M.
Novel gas separation membranes containing covalently bonded fullerenes. Macromol.
Rapid Commun. 2004, 25, 1674–1681.
7. Maggini, M.; De Faveri, C.; Scorrano, G.; Prato, M.; Brusatin, G.; Guglielmi, M.;
Meneghetti, M.; Signorini, R.; Bozio, R. Synthesis and optical-limiting behavior of hybrid
inorganic–organic materials from the Sol–Gel processing of organofullerenes. Chem. Eur.
J. 1999, 5, 2501–2510.
8. Kost, A.; Tutt, L.; Klein, M. B.; Dougherty, T. K.; Elias, W. Optical limiting with C60 in
polymethyl methacrylate. Opt. Lett. 1993, 18, 334–336.
9. Gvishi, R.; Bhawalker, J. D.; Kumar, N. D.; Ruland, G.; Narang, U.; Prasad, P. N.;
Reinhardt, B. A. Multiphasic nanostructured composites for photonics: Fullerene-doped
monolith glass. Chem. Mater. 1995, 7, 2199–2202.
10. Hao, N.; Bo¨hning, M.; Goering, H.; Scho¨nhals, A. Nanocomposites of polyhedral oligo-
meric phenethylsilsesquioxanes and poly(bisphenol a carbonate) as investigated by dielec-
tric spectroscopy. Macromolecules 2007, 40, 2955–2964.
11. Tamaki, R.; Tanaka, Y.; Asuncion, M. Z.; Choi, J.; Laine, R. M. Octa(aminophenyl)
silsesquioxane as a nanoconstruction site. J. Am. Chem. Soc. 2001, 123, 12416–12417.
12. Costa, R. O. R.; Vasconcelos, W. L.; Tamaki, R.; Laine, R. M. Organic=inorganic nano-
composite star polymers via atom transfer radical polymerization of methyl methacrylate
using octafunctional silsesquioxane cores. Macromolecules 2001, 34, 5398–5407.
13. Clarke, D. J.; Matisons, J. G.; Simon, G. R.; Samoc, M.; Samoc, A. Polyhedral oligomeric
silsesquioxane bound fulleropyrrolidines. Appl. Organometal. Chem. 2008, 22, 460–465.
14. Clarke, D. J.; Matisons, J. G.; Simon, G. R.; Samoc, M.; Samoc, A. Polyhedral oligomeric
silsesquioxane-bound iminofullerene. Appl. Organometal. Chem. 2010, 24, 184–188.