Photoinduced Dithiolation of Fullerene[60] with Dendrimer Disulfide

Article abstract of DOI:10.1246/cl.2003.1124

A new fullerodendrimer having fullerene-sulfur bonds as a linkage was prepared by the use of a binary system of organic dichalcogenide. Aggregation of the fullerodendrimer on mica surface was observed by atomic force microscopy (AFM) experiment.

Full text of DOI:10.1246/cl.2003.1124

1124
Chemistry Letters Vol.32, No.12 (2003)
Photoinduced Dithiolation of Fullerene[60] with Dendrimer Disulfide
Yutaka Takaguchi,ꢀ Yoshiaki Katayose,y Yasushi Yanagimoto, Jiro Motoyoshiya,y Hiromu Aoyama,y
Takatsugu Wakahara,yy Yutaka Maeda,yy and Takeshi Akasakaꢀyy
Faculty of Environmental Science and Technology, Okayama University, Okayama 700-8530
yFaculty of Textile Science and Technology, Shinshu University, Ueda 386-8567
yyCenter for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba 305-8577
(Received August 13, 2003; CL-030754)
A new fullerodendrimer having fullerene–sulfur bonds as a
linkage was prepared by the use of a binary system of organic
dichalcogenide. Aggregation of the fullerodendrimer on mica
surface was observed by atomic force microscopy (AFM) ex-
periment.
Fullerene-based derivatives have been attracting a great in-
terest in the field of structural and synthetic organic chemistry.1
In particular, there is an increasing focus on developing applica-
tions for fullerene-functionalized dendrimers, fullerodendrim-
ers, because of a variety of interesting features in supramolecular
chemistry and materials.2 Fullerodendrimers having fullerene–
carbon bonds as a linkage between C60 and dendritic wedge have
been extensively reported.2 Recently, we have described the re-
versible formation of fullerodendrimers by the use of a Diels–
Alder reaction of C60 with anthryl dendron.3 However, much less
is known about the fullerene–heteroatom bond within the ful-
lerodendrimer.4 In particular, fullerodendrimer containing a ful-
lerene–sulfur bond has never been reported. In the view point of
tunability of the property of C60,5–7 fullerodendrimer having a
fullerene–sulfur bond, might be quite useful. In this context,
we have found that the dendrimer disulfide underwent
addition reaction with C60 upon photoirradiation. This paper de-
scribes the first preparation and characterization of a fulleroden-
drimer (1) having fullerene–sulfur bonds as a linkage. Further-
more, aggregates of 1 on mica surface are also discussed.
Poly(amidoamine) dendrimer disulfide, (2a) and (2b), were
prepared by using a method as previously reported (Scheme 1).8
The treatment of bis(4-carbomethoxyphenyl)disulfide (3)
with ethylenediamine produced a core of dendrimer (4), quanti-
tatively. Subsequently, 4 was allowed to react with methyl acryl-
Scheme 2. Preparation of fullerodendrimer 1.
ate to give a dendrimer disulfide 2a in 70% yield. This two-step
process could be repeated to prepare dendrimer 2b in 92% yield.
1
The structures of 2a and 2b were confirmed by H, 13C NMR
spectroscopies, and MALDI-TOF MS.9
Ogawa and Sonoda reported that a binary system of organic
dichalcogenides, i.e., a (PhS)2–(PhSe)2 system, successfully ef-
fects the desired vicinal dichalcogenation of carbon–carbon un-
saturated compounds under radical conditions.10 In order to clar-
ify the utility of their system, we examined photoinduced
addition reaction of dendrimer disulfide with fullerene in the
presence of diphenyl diselenide as shown in Scheme 2.
In a typical run, a mixture of C60 (24 mg, 0.033 mM), dendri-
mer disulfide 2b (250 mg, 0.027 mM), and diphenyl diselenide
(51 mg, 163 mM) in o-dichlorobenzene (5 mL) was irradiated
with a high-pressure mercury lamp (ꢀ > 300 nm) at room tem-
perature under a nitrogen atmosphere for 20h to give dithiola-
tion product, fullerodendrimer 1b (12 mg, 0.005 mM), as brown
oil in 16% yield. In contrast, fullerodendrimer 1 was not ob-
tained in the absence of diphenyl diselenide at all. The fullero-
dendrimer 1 remained quite stable for several months when stor-
ed in a dark at room temperature.
The structures of fullerodendrimers 1a and 1b were con-
1
firmed by means of H and 13C NMR, UV–vis, and LD-TOF
mass spectroscopic analyses.11 The 13C NMR spectrum of ful-
lerodendrimer 1b shows 19 resonances in the aromatic region
(120–140 ppm), of which 15 signals correspond to the sp2 car-
bons for the C60 skeleton. These results clearly indicate that
the product has a C2v symmetry. The chemical shift of 1b at ꢁ ¼
58:4 is reasonably assigned to the connecting sp3 carbon of C60
framework. The UV–vis spectrum of 1b in toluene exhibited ab-
sorptions at 433 nm, which is known to be a typical absorption in
Scheme 1. Syntheses of PAMAM dendrimer disulfides 2a and 2b.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.12 (2003)
1125
a sulfur–carbon bond. This system is quite useful and versatile
for the synthesis of fullerodendrimer, although formation of ful-
lerodendrimer via photoreaction is quite rare. Aggregation of
fullerodendrimer 1b on mica surface might be important for
nano-science. Further work is in progress to explore the applica-
tions and advantages of fullerodendrimer formed by the photoin-
duced dithiolation reaction.
This work was partly supported by Research Foundation for
Materials Science, Saneyoshi Scholarship Foundation, and the
Ministry of Education, Culture, Sports, Science and Technology,
Japan (15750036).
Figure 1. Negative-ion LD-TOF mass spectrum of fullerodendrimer
1b.
References and Notes
the 1:1 adduct on the 6,6-ring junction.12 The LD-TOF mass
spectrum of 1b by the use of negative-ion mode showed a molec-
ular ion peak at m=z: 2256.62 (1b, C130H110N12O22S2 requires
m=z: 2256.47), together with peaks at m=z: 1536.41 ([M À
C60]À) and 1488.77 ([M À 2b/2]À) (Figure 1). The fulleroden-
drimer 1b has a more negative oxidation potential (Eo1x ¼ 0:77 V
vs SCE) than C60 (Eo1x ¼ 1:12 V vs SCE) by 0.35 V, although its
1
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2
3
A. Hirsch and O. Vostrowsky, Top. Curr. Chem., 217, 51 (2001) and
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Wakahara, T. Akasaka, M. Fujitsuka, and O. Ito, Angew. Chem., Int. Ed.,
41, 817 (2002). b) Y. Takaguchi, Y. Sako, Y. Yanagimoto, S. Tsuboi, J.
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44, 5777 (2003).
1
reduction potential (Ered ¼ À1:10 V vs SCE) was similar to that
of pristine C60.13
It is notable that the fullerodendrimer 1b is readily soluble in
acidic water (more than 30mg/mL at pH 1.50).
4
5
6
C. J. Hawker, K. L. Wooley, and J. M. J. Frechet, J. Chem. Soc., Chem.
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To obtain information on the state of aggregation of the den-
drimer, we examined the chloroform solution of 1b on mica sur-
face by atomic force microscopy (AFM) (Nanoscope III, Digital
Instruments, Santa Barbara. CA). A chloroform solution of 1b
(1.5 mM) was deposited on freshly cleaved mica under air, and
dried with nitrogen stream. The sample was then observed by
AFM in the tapping mode of operation with single crystal con-
ventional Si tip. The AFM image showed flat round-shaped ob-
jects corresponding to the aggregated 1b. The size of the aggre-
gates ranges from 100 to 220 nm in diameter and from 3 to 5 nm
in height. A typical object in Figure 2 measures 200 nm in diam-
eter and 3.7 nm in height. The aggregation of fullerodendrimer
1b in chloroform was also observed by dynamic light scattering
(DLS; 25 ꢁC, He–Ne laser). The particle size of the aggregate
was 45:9 Æ 0:2 nm in chloroform solution (1.5 mM). An analo-
gous result has been observed by Nakamura et al.14
7
8
a) M. Ohno, S. Kojima, Y. Shirakawa, and S. Eguchi, Tetrahedron Lett., 36,
6899 (1995). b) M. M. Alam, M. Sato, A. Watanabe, T. Akasaka, and O.
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Huang, D. R. Swanson, H. M. Brothers, II, and J. W. Klimash, Tetrahedron
Lett., 59, 3799 (2003).
9
Selected data for 2a: 1H NMR (CDCl3) ꢁ 2.43 (t, J ¼ 6:4 Hz, 8H), 2.62 (t,
J ¼ 5:6 Hz, 4H), 2.75 (t, J ¼ 6:4 Hz, 8H), 3.53 (s, 12H), 3.55 (q, J ¼
5:6 Hz, 4H), 7.20(t, J ¼ 5:6 Hz, 2H), 7.51 (d, J ¼ 8:8 Hz, 4H), 7.84 (d,
J ¼ 8:8 Hz, 4H); 13C NMR (CDCl3) ꢁ 32.5, 37.2, 48.7, 51.4, 52.7, 126.4,
128.0, 133.5, 139.9, 166.2, 173.0. For 2b: 1H NMR (CDCl3) ꢁ 2.33–2.42
(m, 32H), 2.63–2.68 (m, 20H), 2.79 (t, J ¼ 6:4 Hz, 8H), 3.18 (q, J ¼ 5:5 Hz,
8H), 3.55 (q, J ¼ 5:3 Hz, 4H), 3.63 (s, 24H), 6.83 (t, J ¼ 5:5 Hz, 4H), 7.49
(d, J ¼ 8:8 Hz, 4H), 7.83 (t, J ¼ 5:3 Hz, 2H), 7.91 (d, J ¼ 8:8 Hz, 4H); 13C
NMR (CDCl3) ꢁ 32.6, 33.7, 37.0, 37.6, 49.1, 49.2, 51.5, 52.5, 52.8, 126.1,
128.2, 133.6, 139.8, 166.1, 172.2, 172.9; MALDI-TOFMS for
C
70H110N12O22S2: m=z Calcd. 1536.83 [MHþ]; Found, 1536.07.
The results described herein show a new class of dendrimer
of C60, which attached to poly(amidoamine) dendron wedge via
10a) A. Ogawa and N. Sonoda, J. Synth. Org. Chem., Jpn., 54, 894 (1996). b) A.
Ogawa, H. Tanaka, H. Yokoyama, R. Obayashi, K. Yokoyama, and N.
Sonoda, J. Org. Chem., 57, 111 (1992). c) A. Ogawa and N. Sonoda,
Phosphorus, Sulfur Silicon Relat. Elem., 95, 331 (1994).
11 Selected data for 1a: 1H NMR (CDCl3) ꢁ 2.42–2.46 (m, 8H), 2.62–2.65 (m,
4H), 2.71–2.78 (m, 8H), 3.53 (s, 12H), 3.55 (q, J ¼ 5:6 Hz, 4H), 7.12–7.14
(m, 2H), 7.30(d, J ¼ 8:8 Hz, 4H), 7.49 (d, J ¼ 8:8 Hz, 4H); 13C NMR
(CDCl3) ꢁ 32.5, 37.2, 48.7, 51.4, 52.7, 61.7, 125.9, 126.5, 127.2, 127.5,
128.0, 128.7, 129.5, 129.7, 130.0, 131.5, 132.3, 132.6, 133.5, 133.9, 134.4,
135.6, 139.2, 139.8, 140.0, 166.2, 173.0; LD-TOFMS for C94H46N4O10S2:
m=z Calcd. 1455.49 [MÀ]; Found, 1455.94. For 1b: 1H NMR (CDCl3) ꢁ
2.38–2.44 (m, 32H), 2.66–2.69 (m, 20H), 2.80–2.82 (m, 8H), 3.19–3.20 (m,
8H), 3.49–3.52 (m, 4H), 3.64 (s, 24H), 6.77–6.83 (m, 4H), 7.43 (d,
J ¼ 7:2 Hz, 4H), 7.75–7.77 (m, 2H), 7.85 (d, J ¼ 7:2 Hz, 4H); 13C NMR
(CDCl3) ꢁ 32.6, 33.7, 37.0, 37.6, 49.1, 49.2, 51.5, 52.5, 52.8, 58.4, 126.1,
126.2, 127.2, 127.7, 128.0, 128.3, 129.1, 129.5, 129.9, 130.5, 131.5, 132.3,
132.6, 133.7, 133.9, 134.4, 135.6, 139.2, 139.9, 166.2, 172.3, 173.0; LD-
TOFMS for C130H110N12O22S2: m=z Calcd. 2256.47 [MÀ]; Found, 2256.62.
12 J. A. Schlueter, J. M. Seaman, S. Taha, H. Cohen, K. R. Lykke, H. H. Wang,
and J. M. Williams, Chem. Commun., 1993, 972.
13 Cyclic voltammogram of fullerodendrimer 1b shows irreversible redox
behavior. Then, 1b is not electrochemically stable.
0
2 µm
14 a) M. Sawamura, N. Nagahama, M. Toganoh, U. E. Hackler, H. Isobe, E.
Nakamura, S.-Q. Zhou, and B. Chu, Chem. Lett., 2000, 1098. b) S. Zhou, C.
Burger, B. Chu, M. Sawamura, N. Nagahama, M. Toganoh, U. E. Hackler,
H. Isobe, and E. Nakamura, Science, 291, 1944 (2001).
Figure 2. Atomic force microscope image of 1b on mica and height
profile corresponding to the line in the image.
Published on the web (Advance View) November 10, 2003; DOI 10.1246/cl.2003.1124