Organosulfur-based fullerene materials

Article abstract of DOI:10.1080/10426507.2010.523033

Chemical functionalizations of an endohedral metallofullerene, La ₂@I_h-C₈₀, and an empty fullerene, C ₆₀, are demonstrated using organosulfur compounds. A novel donor-acceptor system of La₂@I_h

Full text of DOI:10.1080/10426507.2010.523033

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Organosulfur-Based Fullerene Materials
Professor Tsukasa Nakahodo a , Professor Midori O. Ishitsuka a , Dr
Yuta Takano a , Professor Takahiro Tsuchiya a , Professor Dr. Takeshi
Akasaka a , Professor M. Angeles Herranz b , Nazario Martin b , Dirk
M. Guldi c & Shigeru Nagase d
a Life Science Center of Tsukuba Advanced Research Alliance,
University of Tsukuba, Tsukuba, Japan
b Department of Organic Chemistry, University Complutense of
Madrid, Madrid, Spain
c Department of Chemistry and Pharmacy Interdisciplinary Center
for Molecular Materials, University of Erlangen, Erlangen, Germany
d Department of Theoretical and Computational Molecular Science,
Institute for Molecular Science, Okazaki, Japan
Version of record first published: 12 Jul 2011
To cite this article: Professor Tsukasa Nakahodo, Professor Midori O. Ishitsuka, Dr Yuta Takano,
Professor Takahiro Tsuchiya, Professor Dr. Takeshi Akasaka, Professor M. Angeles Herranz, Nazario
Martin, Dirk M. Guldi & Shigeru Nagase (2011): Organosulfur-Based Fullerene Materials, Phosphorus,
Sulfur, and Silicon and the Related Elements, 186:5, 1308-1311
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Phosphorus, Sulfur, and Silicon, 186:1308–1311, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.523033
ORGANOSULFUR-BASED FULLERENE MATERIALS
Tsukasa Nakahodo,1 Midori O. Ishitsuka,1 Yuta Takano,1
Takahiro Tsuchiya,1 Takeshi Akasaka,1 M. Angeles Herranz,2
Nazario Martin,2 Dirk M. Guldi,3 and Shigeru Nagase4
1Life Science Center of Tsukuba Advanced Research Alliance, University
of Tsukuba, Tsukuba, Japan
2Department of Organic Chemistry, University Complutense of Madrid,
Madrid, Spain
3Department of Chemistry and Pharmacy Interdisciplinary Center for Molecular
Materials, University of Erlangen, Erlangen, Germany
4Department of Theoretical and Computational Molecular Science,
Institute for Molecular Science, Okazaki, Japan
Abstract Chemical functionalizations of an endohedral metallofullerene, La2@Ih-C80, and an
empty fullerene, C60, are demonstrated using organosulfur compounds. A novel donor–acceptor
system of La2@Ih–C80-exTTF (3) synthesized using the Prato reaction shows photo-induced
intramolecular charge separation. On the other hand, the photoreaction of C60 with N-p-
toluenesulfonyl sulfilimine affords N-tosyl-1,2-aziridinofullerene (5). The first reversible in-
terconversion of 1,2-aziridinofullerene and 1,6-azafulleroid was found for mono-substituted
fullerenes by thermal rearrangement of 5 to 6. S,S-Diphenylsulfilimines (7) with an electron-
donating group on the N atom reacts with C60 to afford corresponding aziridinofullerenes
(8–10) regioselectively.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords Aziridinofullerenes; donor–acceptor systems; endohedral metallofullerenes; π-
extended tetrathiafulvalene; sulfilimine
INTRODUCTION
Exohedral chemical derivatizations of fullerenes have been developed extensively for
examination of their potential usefulness as fullerene-based organic materials.1 Organosul-
fur compounds represent a unique feature of materials. We believe that a combination of
Received 2 July 2010; accepted 6 September 2010.
Financial support from a Grant-in-Aid for Scientific Research on Innovation Areas (No. 20108001, “pi-
Space”); a Grant-in-Aid for Scientific Research (A) (No. 20245006), The Next Generation Super Computing
Project (Nanoscience Project); Nanotechnology Support Project; and Grant-in-Aid for Scientific Research on
Priority Area (Nos. 20036008, 20038007, 20045002) from the Ministry of Education, Culture, Sports, Science,
and Technology of Japan is acknowledged.
Address correspondence to Takeshi Akasaka, Life Science Center of Tsukuba Advanced Research Alliance,
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan. E-mail: akasaka@tara.tsukuba.ac.jp
1308

ORGANOSULFUR-BASED FULLERENE MATERIALS
1309
fullerene and organosulfur compounds forms a new class of organic compounds and thereby
opens a new field in material science. In this context, here we present novel functional-
ized fullerenes with organosulfur compounds to afford the corresponding fullerene-based
materials, which have important chemical and physical properties.
RESULTS AND DISCUSSION
Novel donor–acceptor dyads based on an endohedral metallofullerene, La2@Ih–C80,
were synthesized regioselectively using 1,3-dipolar cycloaddition (Prato reaction) of π-
extended tetrathiafulvalene (exTTF) containing azomethine ylides regioselectively (Scheme
1).2 The cyclic voltammetry (CV) of dyad 3 reveals the redox active character of the system
attributable to the presence of both donor and acceptor groups (exTTF and La2@Ih–C80,
respectively). Despite the proximity between the exTTF and La2@Ih–C80, only a weak elec-
tronic interaction was observed in the ground state, as evidenced by absorption spectroscopy
and CV measurements of 2 and 3. On the other hand, transient absorption spectroscopy
experiments confirmed the intramolecular interaction of 3 in the excited state. The fast
formation of a radical ion pair state (6.0 × 1010 s−1), that is, the reduction of the electron
accepting La2@C80 and the oxidation of exTTF, evolves with lifetimes as long as several
nanoseconds (3.0 × 108 s−1) in toluene. These rate constants are one tenth of those of
a similar system based on C60 (exTTF-C60),3 implying high efficiency of intramolecular
electron transfer in exTTF-La2@C80 per unit of time.
Scheme 1 (Color figure is available online.)
Sulfilimine has been known to generate an N-substituted nitrene in thermal or photo-
chemical reactions. It has been reported that N-sulfenyl sulfilimine generates a sulfenylni-
trene under mild conditions. Nitrenes react easily with alkenes to afford the corresponding
three-membered aziridines. In this context, a nitrene is expected to be a key intermediate for
aziridination of fullerene instead of azide, which presents crucial difficulties related to toxi-
city and explosivity. We conducted photoreaction of C60 with N-p-toluenesulfonyl (N-tosyl)
sulfilimine (4) having a dibenzothiophene (DBT) structure to accomplish the regioselective
synthesis of N-tosyl 1,2-aziridinofullerene ([6,6]-closed C60NTs, 5) (Scheme 2). Results
Scheme 2

1310
T. NAKAHODO ET AL.
show that 5 thermally rearranges to the 1,6-azafulleroid (6) and that the photochemical ring-
closure of 6 takes place to afford 5. This is the first reported reversible interconversion of
1,2-aziridinofullerene and 1,6-azafulleroid for mono-substituted fullerenes. The structures
of 5 and 6 were characterized using NMR spectra and X-ray crystallographic analyses.4
Scheme 3
Sulfilimines with an electron-donating group on the N atom are well known to undergo
Michael-type reactions, followed by concomitant elimination of sulfide to afford the corre-
sponding aziridines. In these reactions, sulfilimines act as a nucleophile to the electrophilic
olefins. Furthermore, C60 has a characteristic feature—its low LUMO level and electron-
accepting property—acting as an electrophilic olefin. In this context, sulfilimines might
react with C60 to afford corresponding aziridinofullerenes. We have studied the thermal
reaction of S,S-diphenylsulfilimines (7) with C60 and regioselectively synthesized a bis-
aziridinated fullerene and a tris-aziridinated fullerene (Scheme 3). These structures (8a, 8b,
8c, 9a, 9b, 10b) were determined through spectroscopic analyses. Among these, the struc-
ture of bis-aziridinated[60]fullerene, C60(NCH3)2 (9a), was determined using single-crystal
X-ray analysis (Figure 1). Results show that the multi-aziridination occurs exclusively at
the same six-membered ring of C60 to afford one isomer of the bis-adduct and tris-adduct.5
Figure 1 ORTEP drawing of 9a showing thermal ellipsoids at a 50% probability level. (Color figure is available
online.)

ORGANOSULFUR-BASED FULLERENE MATERIALS
1311
EXPERIMENTAL
See Supplemental Materials (available online).
CONCLUSION
Several novel derivatives based on fullerenes and organosulfur compounds were
synthesized and then characterized using spectroscopic measurements. The combination
of organosulfur and fullerenes is expected to enhance electronic and physical properties of
carbon allotropes.
REFERENCES
1. For reviews, see: (a) Hirsch, A. The Chemistry of Fullerenes; Wiley-VCH: Weinheim, Germany,
2005; (b) Guldi, D. M.; Mart´ın, N. Fullerenes: From Synthesis to Optoelectronic Properties;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 2002.
2. Takano, Y.; Herranz, M. A.; Martin, N.; Radhakrishnan, S. G.; Guldi, D. M.; Tsuchiya, T.; Nagase,
S.; Akasaka, T. J. Am. Chem. Soc. 2010, 132, 8048–8055.
3. D´ıaz, M. C.; Herranz, M. A.; Illescas, B. M.; Martin, N. J. Org. Chem. 2003, 68, 7711–7721.
4. Nakahodo, T.; Okada, M.; Morita, H.; Yoshimura, T.; Ishitsuka, M. O.; Tsuchiya, T.; Maeda, Y.;
Fujihara, H.; Akasaka, T.; Gao X.; Nagase, S. Angew. Chem. Int. Ed. 2008, 47, 1298–1300.
5. Okada, M.; Nakahodo, T.; Ishitsuka, M. O.; Nikawa, H.; Tsuchiya, T.; Akasaka, T.; Fujie, T.;
Yoshimura, T.; Slanina, Z.; Nagase, S. Chem. Asian J. 2011, 6, 416–423.