[60]Fullerene cycloaddition across hindered acenes

Article abstract of DOI:10.1039/b710300j

The Diels-Alder cycloadditions of [60]fullerene across sterically hindered 6,13-bis(2′,6′-dialkylphenyl)pentacenes, 1 and 2, produce fullerene-acene monoadducts 3 and 4. In both cases, further [60]fullerene cycloaddition to form cis-bis[60]fullerene adducts is retarded by steric resistance between the [60]fullerene moieties and the o-dialkyl substituents. Instead, the fullerene moieties of monoadducts 3 and 4 sensitize the formation of ¹O₂ which subsequently cycloadds across the acene backbone to produce novel syn and anti [60]fullerene-dioxo bisadducts, 8-11. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b710300j

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
[60]Fullerene cycloaddition across hindered acenesw
Irvinder Kaur and Glen P. Miller*
Received (in Montpellier, France) 9th July 2007, Accepted 25th October 2007
First published as an Advance Article on the web 6th November 2007
DOI: 10.1039/b710300j
The Diels–Alder cycloadditions of [60]fullerene across sterically hindered 6,13-bis(20,60-
dialkylphenyl)pentacenes, 1 and 2, produce fullerene–acene monoadducts 3 and 4. In both cases,
further [60]fullerene cycloaddition to form cis-bis[60]fullerene adducts is retarded by steric
resistance between the [60]fullerene moieties and the o-dialkyl substituents. Instead, the fullerene
1
moieties of monoadducts 3 and 4 sensitize the formation of O2 which subsequently cycloadds
across the acene backbone to produce novel syn and anti [60]fullerene–dioxo bisadducts, 8–11.
bis(20,60-diethylphenyl)pentacene, 2, using modified Kafafi4
Introduction
procedures (Scheme 1). Thus, readily available pentacene-
6,13-dione is treated with an appropriate phenyllithium to
produce an aromatic diol in 77–78% yield. The diols are
reductively aromatized in 88–93% yield using sodium iodide,
sodium hypophosphite5 and acetic acid to produce the corre-
sponding 6,13-disubstituted pentacenes in a relatively clean
state. Once prepared, 1 and 2 can be stored for months in the
solid state (dark) without significant decomposition. In solu-
tion phase, however, they degrade unless protected from light
and oxygen. There was no attempt to purify 1 and 2 using
chromatographic methods since all such operations would
require dissolving and maintaining these compounds in solu-
tion phase for unacceptably long durations.
The chemistry between fullerenes and acenes is of interest
because the corresponding fullerene–acene adducts represent
new molecular architectures that are considered precursors to
cyclacenes and single-walled nanotubular compounds
(SWNCs).1 To date, [60]fullerene has been successfully
cycloadded across several phenyl substituted acenes.2 The
phenyl substituents direct the regiochemistries of these addi-
tions and provide for enhanced solubilities of the acenes and
the corresponding fullerene–acene adducts. An interesting
feature of this chemistry is that [60]fullerenes add in a diaster-
eoselective syn fashion across the acenes due to favorable
[60]fullerene–[60]fullerene p–p stacking interactions in both
the ground states and the transition states that precede them.
To date, there are no reported cases of [60]fullerene cycloaddi-
tion across a phenyl substituted acene in which the reaction
stops at the monoadduct stage. In all known examples, the
addition of the first [60]fullerene addend is followed by a
second, more facile syn addition. In one case, a third syn
addition was also reported.3
Fullerene–acene chemistries
Compounds 1 and 2 were separately reacted with 5 equivalents
of [60]fullerene in boiling carbon disulfide solvent (46 1C) in
the dark under nitrogen for 8–16 h. The only observed
[60]fullerene–acene products were the corresponding mono-
adducts, 3 and 4 (Fig. 2) formed in 86 and 84% yield,
respectively. Reactions were also successfully performed in
boiling toluene (111 1C) giving 3 and 4 in 83 and 81% yield,
respectively. No traces of unreacted acene were observed in
any of the reactions. Washing the crude product mixtures with
chloroform effectively removes the chloroform soluble [60]full-
erene–acene monoadducts from unreacted [60]fullerene.
Attempts to remove trace impurities via chromatographic
methods were complicated by the photo-oxidative instabilities
of 3 and 4 (vide infra). They were nonetheless characterized by
Here, we report two unusual [60]fullerene cycloadditions
across sterically hindered 6,13-disubstituted pentacenes. We
have prepared and studied pentacenes with both 6,13-bis(20,60-
dimethylphenyl) and 6,13-bis(20,60-diethylphenyl) substituents
(Fig. 1). For both pentacenes, [60]fullerene cycloaddition stops
at the monoadduct stage due to steric resistance associated
with the second addition. Upon standing in solution under
ambient conditions, the [60]fullerene monoadducts add singlet
1
oxygen in facile fashion. Both syn and anti O2 adducts form.
Results and discussion
Acene syntheses
For this study, we synthesized two sterically hindered 6,13-
disubstituted pentacenes—the known 6,13-bis(20,60-dimethyl-
phenyl)pentacene, 1, and the previously unknown 6,13-
Department of Chemistry and Materials Science Program, University
of New Hampshire, Durham, NH, USA. E-mail: glen.miller@unh.edu;
Fax: +1 603 862 4278; Tel: +1 603 862 2456
Fig. 1 Structural drawings of 6,13-bis(20,60-dimethylphenyl)penta-
cene, 1, and 6,13-bis(20,60-diethylphenyl)pentacene, 2.
w Electronic supplementary information (ESI) available: 1H and 13C
NMR spectra, LDI mass spectra. See DOI: 10.1039/b710300j
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 459–463 | 459

View Article Online
Scheme 1 Synthesis of hindered acenes 1 and 2.
1
a combination of H NMR spectroscopy, 13C NMR spectro-
scopy and MALDI mass spectrometry. Both 3 and 4 exhibit
two sets of alkyl signals in their 1H and 13C NMR spectra due
to slow rotation of the hindered phenyl substituents. In each
case, one o-alkyl substituent is syn with respect to the fullerene
addend while the other is anti. Two additional aliphatic 13C
NMR signals are observed for both 3 and 4 at approximately
56 and 72 ppm6 corresponding to the sp3 carbons on the
Fig. 3 MM2 minimized structures for the hypothetical bis[60]fuller-
ene adduct of 6,13-bis(20,60-diethylphenyl)pentacene, 6, and the
known bis[60]fullerene adduct of 6,13-diphenylpentacene, 7. The
carbons of closest contact on adjacent [60]fullerene moieties are 3.6
and 3.1 A apart on 6 and 7, respectively.
Subsequent reactions of 3 and 4 with excess [60]fullerene also
failed to produce 5 and 6. Clearly, the o-alkyl groups on 3 and
4 retard the approach of a second [60]fullerene to either face of
the acene. But while the kinetics of a second [60]fullerene
cycloaddition are not ideal, an examination of MM2 calcu-
lated structures for hypothetical 5 and 6 (Fig. 3) also indicates
a thermodynamic problem. For comparison, 7 is a known,
thermally stable cis-bis[60]fullerene adduct of 6,13-diphenyl-
pentacene7 in which the carbons of closest contact on adjacent
[60]fullerene moieties are 3.07 A apart as determined by X-ray
crystal structure analysis.8 MM2 calculations nearly reproduce
the X-ray crystal structure for 7 by placing nearest neighbor
[60]fullerene carbon atoms 3.08 A apart. The same method
indicates that steric interactions between [60]fullerene moieties
and o-alkyl groups prevent an optimal separation between
[60]fullerenes on hypothetical 5 and 6. For 5 and 6, the
carbons of closest contact on adjacent [60]fullerene moieties
are calculated to be 3.6 A apart. Space filling models for 6 and
7 reveal that this extra 0.5 A of separation significantly reduces
[60]fullerene–[60]fullerene p–p stacking interactions (Fig. 3).
The p–p stacking interactions are key to bis[60]fullerene
adduct stability. In this regard, we note the absence of forma-
tion of all C2h trans-bis[60]fullerene adducts originating from
6,13-disubstituted pentacenes.2 The trans-bis[60]fullerene ad-
ducts are devoid of [60]fullerene–[60]fullerene p–p stacking
interactions.
pentacene backbone and the [60]fullerene moiety, respectively.
13
A total of 47 and 44
C
signals is observed for 3 and 4,
sp2
respectively, in the congested Csp2 region where 47 signals are
expected in each case. The 3 missing signals for 4 are attributed
to coincidental overlap. MALDI mass spectra of 3 and 4
reveal base peaks corresponding to the parent acenes (M+
C60) as well as signals corresponding to [60]fullerene (M+
acene) and in the case of 3, a molecular ion at m/z 1206.
ꢁ
ꢁ
Although the reactions producing 3 and 4 utilized 5-fold
excesses of [60]fullerene, they did not produce the correspond-
ing cis-bis[60]fullerene adducts, 5 and 6, as has been observed
in other [60]fullerene–6,13-disubstituted pentacene examples.2
Singlet oxygen addition
Compounds 3 and 4 are stable when stored in the solid state.
However, upon standing in solution under ambient condi-
tions, both 3 and 4 readily add singlet oxygen. In this way,
[60]fullerene–dioxo adducts of the corresponding 6,13-disub-
stituted pentacenes are formed in quantitative yield. Thus,
compound 3 forms a 4 : 1 mixture of syn-8 to anti-9 [60]full-
erene–dioxo adducts while compound 4 forms a 4 : 1 mixture
of syn-10 to anti-11 [60]fullerene–dioxo adducts.
Fig.
(bottom) [60]fullerene–6,13-bis(20,60-dimethylphenyl)pentacene mono-
adduct
and [60]fullerene–6,13-bis(20,60-diethylphenyl)pentacene
2
ChemDraw representation (top) and MM2 minimized
3
monoadduct 4.
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2007
460 | New J. Chem., 2008, 32, 459–463

View Article Online
Scheme 2 Proposed mechanism for the facile oxidations of 3 and 4
with 1O2. The oxidation of 3 to produce [60]fullerene–dioxo bisadducts
8 and 9 is illustrated.
1
Fig. 4 MM2 structures for the O2 adducts of 3 and 4: syn-8, anti-9,
syn-10 and anti-11. Oxygen atoms are shown in red.
then immediately trapped in an intramolecular reaction. This
behavior suggests that functionalized fullerenes bearing oxida-
tively sensitive addends may possess limited lifetimes, espe-
cially in solution. On the other hand, the facile formation of
1O2 suggests potential applications for functionalized fuller-
enes in photodynamic therapies.13
Compounds 8–11 (Fig. 4) have been isolated via flash silica
column chromatography and characterized by a combination
1
of H NMR spectroscopy, 13C NMR spectroscopy, MALDI
mass spectrometry and UV–Vis spectrophotometry. The
MALDI mass spectra of 8 and 9 are especially revealing. Each
shows a molecular ion at m/z 1238 as well as fragment ions at
m/z 1222 (M+ ꢁ O), 1206 (M+ ꢁ O2), 518 (M+ ꢁ C60), 502
Conclusion
(M+ ꢁ C60 ꢁ O), 486 (M+ ꢁ C60 ꢁ O2) and 720 (C60+). H
1
In conclusion, [60]fullerene cycloadds across sterically hin-
dered 6,13-bis(20,60-dialkylphenyl)pentacenes to produce full-
erene–acene monoadducts, 3 and 4. Further [60]fullerene
cycloadditions to form cis-bis[60]fullerene adducts are not
and 13C NMR spectra for compounds 8–11 include signals due
to new methine protons (B5.5–5.7 ppm) and carbons (B77
ppm) on the acene backbone confirming that each possesses a
bridged dioxo rather than a quinone structure. Each 1H NMR
spectrum contains two sets of AA0XX0 multiplets indicating
that the dioxygen bridge is connected at C7 and C12 of the
acene backbone (a penultimate ring). The 13C NMR spectra
for 8 and 9 both contain a total of 46 Csp2 signals, as expected.
Those for compounds 10 and 11 contain 42 and 43 Csp2
signals, respectively. The 4 missing signals for 10 and the 3
missing signals for 11 are attributed to coincidental overlap in
the highly congested Csp2 region of the 13C NMR spectra.
Compounds 8 and 10 are assigned syn structures whereas 9
and 11 are assigned anti structures based upon their respective
orders of elution on polar silica columns with CH2Cl2 as
eluant. Thus, the less polar 9 elutes faster than 8 and the less
polar 11 elutes faster than 10.
1
observed. Instead, O2 cycloadds across the acene backbone
to produce novel [60]fullerene–dioxo bisadducts 8–11. The
addition of highly reactive 1O2 occurs preferentially (4 : 1)
across the syn face of the acene, strongly suggesting that the
fullerene moieties on 3 and 4 sensitize its formation.
Experimental
General procedures
Compounds 1-bromo-2,6-dimethylbenzene and 1-bromo-2,6-
diethylbenzene and reagent n-butyllithium (1.6 M solution in
hexanes) were purchased from Aldrich Chemical Co. and used
without further purification. All reactions, unless otherwise
noted, were carried out under a slow stream of N2. All reaction
containers were flame dried under vacuum before use. Solvents
were purified by standard methods and dried as required.
NMR spectra were recorded on a Varian AC 500 spectro-
meter. 1H and 13C NMR samples were internally referenced to
TMS (0.00 ppm). MALDI-TOF mass spectra were acquired
on a Shimadzu-Biotech mass spectrometer. Fast atom bom-
bardment high resolution mass spectra were obtained at the
Notre Dame University mass spectrometry facility.
Singlet oxygen addition to 3 and 4 occurs across the center
rings of the anthracene moieties that remain after [60]fullerene
addition. Compared to larger acenes, anthracene is relatively
stable to air oxidation, even though it is known to sensitize 1O2
formation.9 Typically, when 1O2 adducts of anthracenes are
sought, a separate dye-sensitizer is added.10 The facile oxida-
tion of 3 and 4 suggests the mechanism illustrated in Scheme 2
in which the photoexcited [60]fullerene moiety sensitizes for-
mation of highly reactive 1O2 which predominantly adds to the
proximate syn face of the acene backbone. [60]Fullerene is
Syntheses
1
known to sensitize O2 formation11 as are numerous functio-
nalized fullerenes.12 The reactions reported here are interesting
6,13-Bis(20,60-dimethylphenyl)-6,13-dihydropentacene-6,13-
1
in that the O2 is formed in the presence of [60]fullerene and
diol. A solution of 1-bromo-2,6-dimethylbenzene (2.17 g,
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 459–463 | 461

View Article Online
11.8 mmol) was stirred in dry THF (75 mL) and cooled to ꢁ78
1C in a dry ice–acetone bath. Upon cooling, n-butyllithium
(3.35 mL, 9.8 mmol) was added and the solution was stirred
for 5 h at ꢁ78 1C. Pentacene-6,13-dione (0.5 g, 2 mmol) was
then added to the pale yellow solution and the mixture was
allowed to gradually warm to RT with stirring overnight. To
the reaction mixture was added 1 M HCl (50 mL). Following
extraction with CH2Cl2 (100 mL), the organic layer was
washed with water and dried over CaCl2. The solvent was
removed under vacuum until only B10 mL remained, at which
point hexanes (100 mL) were added, resulting in the formation
of a white precipitate. The desired diol was isolated by vacuum
126.0, 125.4, 125.2, 26.7, 14.9. LDI-MS m/z: 542 [M+]. HRMS
(FAB+) m/z = 542.2971 (M+), calcd m/z 542.2974. UV–Vis
lmax(nm): 605, 558, 520.
[60]Fullerene–6,13-bis(20,60-dimethylphenyl)pentacene mono-
adduct (3). To a flame dried, N2-charged round-bottomed flask
fitted with a reflux condenser was added [60]fullerene (0.19 g,
0.26 mmol) dissolved in carbon disulfide (25 mL). Pentacene 1
(0.025 g, 0.052 mmol) was then added and the resulting purple
solution was allowed to boil for a period of 8 h. The resulting
brown solution was concentrated under vacuum, extracted
with CHCl3, and the solvent evaporated to yield the crude
1
1
monoadduct 3 in 86% yield (53.5 mg). H NMR (500 MHz,
filtration (0.66 g, 78%). H NMR (500 MHz, CDCl3): d 7.73
CD2Cl2): d 8.02 (s, 2H), 7.83 (m, 2H), 7.64 (m, 2H), 7.48 (m,
2H), 7.39 (m, 6H), 7.26 (d, 2H, J = 6.58 Hz), 5.6 (s, 2H), 2.05
(s, 6H), 1.81 (s, 6H). 13C NMR (125.68 MHz, CD2Cl2): d
156.5, 156.1, 148.1, 147.0, 146.9, 146.74, 146.69, 146.11 (2),
146.09, 146.06 (2), 146.00, 145.95, 145.92, 145.8, 145.2, 145.1,
143.63, 143.5, 143.1, 142.62, 142.57, 142.52, 142.49, 142.36,
142.18, 142.16, 140.6, 140.3, 138.6, 138.3, 137.9, 137.25,
137.21, 137.1, 134.9, 132.5, 130.7, 128.72, 128.66, 128.42,
128.37, 128.0, 127.1, 126.2, 125.9, 72.3, 56.5, 21.0, 20.6.
MALDI-MS m/z: 1206 [M+], 720 [C60], 486 [M+ ꢁ C60].
UV–Vis lmax(nm): 435.
(s, 4H), 7.7 (m, 4H), 7.4 (m, 4H), 7.22 (t, 2H, J = 7.56 Hz),
7.12 (m, 4H), 2.4 (bs, 12H), 2.20 (s, 2H). 13C NMR (125.68
MHz, CDCl3): d 143.5, 139.1, 137.7, 133.4, 131.1, 127.9,
127.2, 126.9, 126.3, 79.8, 25.3. LDI-MS m/z: 520 [M+], 503
[M+ ꢁ OH], 486 [M+ ꢁ 2(OH)].
6,13-Bis(20,60-diethylphenyl)-6,13-dihydropentacene-6,13-diol.
A procedure similar to that utilized for the synthesis of 6,13-
bis(20,60-dimethylphenyl)-6,13-dihydropentacene-6,13-diol
was followed using 1-bromo-2,6-diethylbenzene (2.0 g, 9.4
mmol), n-BuLi (2.66 mL, 7.8 mmol) and pentacene-6,13-dione
(0.4 g, 1 mmol). In this way, the desired diol was produced in
[60]Fullerene–6,13-bis(20,60-diethylphenyl)pentacene monoad-
duct (4). A procedure similar to that utilized for the synthesis
of crude monoadduct 3 was utilized to produce crude mono-
adduct 4 in 84% yield (48.9 mg). For this reaction, [60]full-
erene (0.17 g, 0.24 mmol) and pentacene 2 (0.025 g, 0.046
mmol) were dissolved in carbon disulfide (25 mL) and heated
to boiling for 8 h. 1H NMR (500 MHz, CDCl3): d 8.10 (s, 2H),
7.86 (m, 2H), 7.56 (m, 4H), 7.45 (m, 4H), 7.40 (m, 4H), 5.51 (s,
2H), 2.59 (m, 2H), 2.33 (m, 4H), 1.91 (m, 2H), 1.08 (t, 6H, J =
7.56 Hz), 0.69 (t, 6H, J = 7.56 Hz). 13C NMR (125.68 MHz,
CDCl3): d 156.3, 155.8, 147.9, 146.78, 146.71, 146.52, 146.50,
146.01, 145.95, 145.80 (2), 145.75, 145.71, 145.5, 145.0, 144.9,
144.1, 143.52, 143.45, 143.42, 143.3, 142.9 (2), 142.5, 142.2,
142.03, 141.95, 141.90, 140.4, 140.1, 137.6, 136.9, 136.1, 134.4,
131.9, 131.1, 128.9, 128.6, 127.6, 126.7, 126.29, 126.26, 125.9,
125.5, 72.0, 56.2, 27.4, 26.7, 15.2, 15.0. MALDI-MS m/z: 720
[C60], 542 [M+ ꢁ C60]. UV–Vis lmax(nm): 434.
1
77% yield (0.57 g). H NMR (500 MHz, CDCl3): d 7.73 (s,
4H), 7.7 (m, 4H), 7.38 (m, 4H), 7.35 (t, 2H, J = 7.57 Hz), 7.2
(m, 4H), 3.4 (bm, 8H), 2.4 (bm, 12H), 2.2 (s, 2H). 13C NMR
(125.68 MHz, CDCl3): d 142.4, 139.5, 133.2, 129.8, 128.8,
127.9, 127.6, 127.5, 126.2, 79.9, 31.6, 14.1. LDI-MS m/z: 576
[M+], 559 [M+ ꢁ OH], 542 [M+ ꢁ 2(OH)].
6,13-Bis(20,60-dimethylphenyl)pentacene (1). A suspension
of 6,13-bis(20,60-dimethylphenyl)-6,13-dihydropentacene-6,13-
diol (0.5 g, 1 mmol), sodium iodide (0.99 g, 6.7 mmol) and
sodium hypophosphite (1.09 g, 9.08 mmol) was prepared in
glacial acetic acid (25 mL) and heated at reflux for 1.5 h in a
round-bottomed flask that was equipped with a reflux con-
denser. The flask was wrapped in foil to block ambient light
throughout the reaction. After cooling, the reaction mixture
was filtered and washed with water (50 mL) and methanol (25
mL). After drying at reduced pressure, 6,13-bis(20,60-dimethyl-
1
phenyl)pentacene (1) was obtained in 88% yield (0.41 g). H
[60]Fullerene–6,13-bis(20,60-dimethylphenyl)pentacene–dioxo
adducts (8 and 9). Upon standing in chloroform solution
exposed to air in ambient light, monoadduct 3 is oxidized to
a 4 : 1 mixture of syn-8 : anti-9. The [60]fullerene–dioxo
adducts were isolated using flash column chromatography
(silica gel) with CH2Cl2 as eluent. syn [60]fullerene–dioxo
adduct (8): 1H NMR (500 MHz, CD2Cl2): d 7.63 (m, 2H),
7.47 (m, 2H), 7.34 (d, 4H, J = 4.42 Hz), 7.32 (s, 4H), 7.2 (t,
2H, J = 4.40 Hz), 5.63 (s, 2H), 5.52 (s, 2H), 2.00 (s, 6H), 1.86
(s, 6H). 13C NMR (125.68 MHz, CD2Cl2): d 156.2 (2), 148.1,
146.98, 146.95, 146.8, 146.7, 145.98, 145.94, 145.90, 145.88,
145.86, 145.84, 145.81, 145.1, 143.5, 143.4, 143.1, 143.0,
142.61, 142.57, 142.55, 142.51 (2), 142.15, 142.10, 141.1,
140.5, 140.1, 138.7, 138.6, 137.7, 137.6, 137.2, 135.9, 135.3,
133.5, 129.3, 129.1, 128.6, 128.4, 128.3, 127.8, 127.6, 126.8,
124.3, 77.8 (Csp3–O), 72.7, 56.3, 21.4, 20.6. MALDI-MS m/z:
1238 [M+], 1222 [M+ ꢁ 16], 1206 [M+ ꢁ 32], 720 [C60], 518
NMR (500 MHz, CDCl3): d 8.14 (s, 4H), 7.74 (m, 4H), 7.5 (t,
2H, J = 7.56 Hz), 7.4 (d, 4H, J = 7.56 Hz), 7.22 (m, 4H), 1.8
(s, 12H). 13C NMR (125.68 MHz, CDCl3): d 138.4, 138.2,
135.5, 131.5, 128.6, 128.0, 127.9, 127.7, 125.0, 124.7, 20.1.
LDI-MS m/z: 486 [M+]. HRMS (FAB+) m/z = 486.2341
(M+), calcd m/z 486.2348. UV–Vis lmax(nm): 604, 557, 518.
6,13-Bis(20,60-diethylphenyl)pentacene (2). A procedure simi-
lar to that utilized for the synthesis of pentacene 1 was utilized
to produce pentacene 2 in 93% yield (0.35 g). The procedure
utilized 6,13-bis(20,60-diethylphenyl)-6,13-dihydropentacene-
6,13-diol (0.4 g, 0.7 mmol), sodium iodide (0.71 g, 4.8 mmol)
and sodium hypophosphite (0.8 g, 7 mmol). 1H NMR (500
MHz, CDCl3): d 8.15 (s, 4H), 7.72 (m, 4H), 7.65 (t, 2H, J =
7.57 Hz), 7.48 (d, 4H, J = 7.57 Hz), 7.21 (m, 4H), 2.11 (q, 8H,
J = 7.56 Hz), 0.81 (t, 12H, J = 7.56 Hz). 13C NMR (125.68
MHz, CDCl3): d 144.1, 137.5, 135.3, 131.4, 128.9, 128.8, 128.4,
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2007
462 | New J. Chem., 2008, 32, 459–463

View Article Online
[M+ ꢁ C60], 502 [M+ ꢁ C60 ꢁ 16], 486 [M+ ꢁ C60 ꢁ 32].
UV–Vis lmax(nm): 436. anti [60]fullerene–dioxo adduct (9): 1H
NMR (500 MHz, CD2Cl2): d 7.54 (m, 2H), 7.37 (m, 2H), 7.35
(d, 2H, J = 7.56 Hz), 7.31 (m, 2H), 7.22 (d, 2H, J = 7.54 Hz),
7.16 (m, 2H), 7.07 (m, 2H), 5.63 (s, 2H), 5.49 (s, 2H), 2.20 (s,
6H), 1.65 (s, 6H). 13C NMR (125.68 MHz, CD2Cl2): d 155.74,
155.66, 147.6, 146.6, 146.5, 146.3, 146.2, 145.68, 145.66,
145.51, 145.49, 145.43, 145.39, 145.37, 145.34, 144.8, 144.7,
143.2, 143.0, 142.62, 142.57, 142.24, 142.17, 142.10 (2), 142.0,
141.70, 141.65, 140.12, 140.10, 139.7, 138.8, 137.8, 137.5,
137.2, 136.7, 136.4, 134.5, 132.8, 128.6, 128.0, 127.8, 127.7,
127.2, 126.2, 123.1, 77.2 (Csp3–O), 72.2, 55.7, 20.7,
20.4. MALDI-MS m/z: 1238 [M+], 1222 [M+ ꢁ 16], 1206
[M+ ꢁ 32], 720 [C60], 518 [M+ ꢁ C60], 502 [M+ ꢁ C60 ꢁ 16],
486 [M+ ꢁ C60 ꢁ 32]. UV-Vis lmax(nm): 435.
Acknowledgements
This work was supported by the Center for High-rate Nano-
manufacturing (National Science Foundation, Nanoscale
Science and Engineering Centers Program, Award # NSF-
0425826).
References
1 G. P. Miller, S. Okana and D. Toma
124, 121102-1–121102-5.
2 For a review, see: J. Briggs and G. P. Miller, C. R. Chim., 2006, 9,
916–927.
3 G. P. Miller and J. Briggs, Org. Lett., 2003, 5, 4203–4206.
4 M. A. Wolak, B.-B. Jang, L. C. Palilis and Z. H. Kafafi, J. Phys.
Chem. B, 2004, 108, 5492–5499.
5 N. Vets, M. Smet and W. Dehaen, Synlett, 2005, 217–222.
6 See Experimental for precise chemical shift values.
´
nek, J. Chem. Phys., 2006,
7 G. P. Miller and J. Mack, Org. Lett., 2000, 2, 3979–3982.
8 G. P. Miller, J. Briggs, J. Mack, P. A. Lord, M. M. Olmstead and
A. L. Balch, Org. Lett., 2003, 5, 4199–4202.
[60]Fullerene–6,13-bis(20,60-diethylphenyl)pentacene–dioxo
adducts (10 and 11). Upon standing in chloroform solution
exposed to air in ambient light, monoadduct 4 is oxidized to a
4 : 1 mixture of syn-10 : anti-11. The dioxo bisadducts were
isolated using flash column chromatography (silica gel) with
CH2Cl2 as eluent. syn [60]fullerene–dioxo adduct (10): 1H
NMR (500 MHz, CD2Cl2): d 7.53 (m, 2H), 7.49 (t, 2H, J =
7.56 Hz), 7.45 (m, 2H), 7.39 (d, 2H, J = 7.56 Hz), 7.33 (m,
6H), 5.60 (s, 2H), 5.48 (s, 2H), 2.34 (m, 4H), 2.19 (m, 2H), 2.08
(m, 2H), 1.02 (t, 12H, J = 7.56 Hz). 13C NMR (125.68 MHz,
CD2Cl2): d 156.22, 156.18, 148.1, 147.0, 146.79, 146.73, 146.2,
146.06, 146.03, 145.94, 145.93, 145.8, 145.2, 144.3, 143.7,
143.55, 143.51, 143.2, 143.1, 142.7, 142.58, 142.55, 142.48,
142.2, 142.1, 141.1, 140.6, 140.3, 138.7, 137.8, 137.2, 136.5,
134.2, 133.1, 129.8, 128.7, 128.4, 127.8, 126.9, 126.8, 125.2,
124.5, 77.7 (Csp3–O), 72.7, 56.3, 27.9, 27.3, 15.0, 14.3. MALDI-
MS m/z: 720 [C60], 574 [M+ ꢁ C60], 558 [M+ ꢁ C60 ꢁ 16], 542
[M+ ꢁ C60 ꢁ 32]. UV-Vis lmax(nm): 436. anti [60]fullere-
9 See for example: M. Nowakowska, Makromol. Chem., 1978, 179,
2953–2958.
10 See for example: (a) W. Fudickar and T. Linker, Chem.–Eur. J.,
2006, 12, 9276–9283; (b) E. P. Niu, A. W. H. Mau and K. P.
Ghiggino, Aust. J. Chem., 1991, 44, 695–704; (c) A. Guarini and P.
Tundo, J. Org. Chem., 1987, 52, 3501–3508.
11 J. W. Arbogast, A. P. Darmanyan, C. S. Foote, F. N. Diederich, R.
L. Whetten, Y. Rubin, M. M. Alvarez and S. J. Anz, J. Phys.
Chem., 1991, 95, 11–12.
12 (a) K. K. Chin, S.-C. Chuang, B. Hernandez, M. Selke, C. S. Foote
and M. A. Garcia-Garibay, J. Phys. Chem. A, 2006, 110,
13662–13666; (b) M. E. Milanesio, M. G. Alvarez, V. Rivarola,
J. J. Silber and E. N. Durantini, Photochem. Photobiol., 2005, 81,
891–897; (c) C. Yu, T. Canteenwala, M. E. El-Khouly, Y. Araki,
K. Pritzker, O. Ito, B. C. Wilson and L. Y. Chiang, J. Mater.
Chem., 2005, 15, 1857–1864; (d) B. Vileno, A. Sienkiewicz, M.
Lekka, A. J. Kulik and L. Forro, Carbon, 2004, 42, 1195–1198; (e)
S. R. Wilson, M. E. Yurchenko, D. I. Schuster, E. N. Yurchenko,
O. Sokolova, S. E. Braslavsky and G. Klihm, J. Am. Chem. Soc.,
2002, 124, 1977–1981; (f) D. Latassa, O. Enger, C. Thilgen, T.
Habicher, H. Offermanns and F. Diederich, J. Mater. Chem., 2002,
12, 1993–1995; (g) J. L. Bourdelande, J. Font and R. Gonzalez-
Moreno, Helv. Chim. Acta, 2001, 84, 3488–3494; (h) F. Prat, C.
Marti, S. Nonell, X. Zhang, C. S. Foote, M. R. Gonzalez, J. L.
Bourdelande and J. Font, Phys. Chem. Chem. Phys., 2001, 3,
1638–1643; (i) R. Stackow, G. Schick, T. Jarrosson, Y. Rubin
and C. S. Foote, J. Phys. Chem. B, 2000, 104, 7914–7918; (j) F.
Prat, R. Stackow, R. Bernstein, W. Qian, Y. Rubin and C. S.
Foote, J. Phys. Chem. A, 1999, 103, 7230–7235; (k) J. L. Bourde-
lande, J. Font, R. Gonzalez-Moreno and S. Nonell, J. Photochem.
Photobiol., A, 1998, 115, 69–71; (l) C. S. Foote, ACS Symp. Ser.,
1995, 616, 17–23; (m) J. L. Anderson, Y.-Z. An, Y. Rubin and C. S.
Foote, J. Am. Chem. Soc., 1994, 116, 9763–9764.
1
ne–dioxo adduct (11): H NMR (500 MHz, CD2Cl2): d 7.50
(m, 4H), 7.36 (m, 6H), 7.15 (m, 2H), 7.09 (m, 2H), 5.70 (s, 2H),
5.46 (s, 2H), 2.76 (m, 2H), 2.44 (m, 2H), 2.21 (m, 2H), 1.79 (m,
2H), 1.15 (t, 6H, J = 7.56 Hz), 0.64 (t, 6H, J = 7.56 Hz). 13
C
NMR (125.68 MHz, CDCl3): d 156.3, 156.1, 148.1, 147.1,
146.9, 146.73, 146.69, 146.18, 146.14, 146.00, 145.97, 145.94,
145.82, 145.78, 145.2, 145.1, 144.1, 143.7, 143.4, 143.1, 143.03,
143.00, 142.8, 142.56, 142.51, 142.14, 142.07, 140.64, 140.56,
140.1, 138.6, 138.1, 137.0, 136.7, 133.8, 132.8, 129.5, 128.2,
127.5, 126.8, 126.5, 125.6, 124.1, 77.6 (Csp3–O), 72.8, 56.3,
13 See for example: (a) O. Stoilova, C. Jerome, C. Detrembleur, A.
Mouithys-Mickalad, N. Manolova, I. Rashkov and R. Jerome,
Polymer, 2007, 48, 1835–1843; (b) C. Detrembleur, O. Stoilova, R.
Bryaskova, A. Debuigne, A. Mouithys-Mickalad and R. Jerome,
Macromol. Rapid Commun., 2006, 27, 498–504; (c) S. Wang, R.
Gao, F. Zhou and M. Selke, J. Mater. Chem., 2004, 14, 487–493.
27.2, 27.0, 15.0, 14.5. MALDI-MS m/z: 720 [C60], 574 [M+
ꢁ
C60], 558 [M+ ꢁ C60 ꢁ 16], 542 [M+ ꢁ C60 ꢁ 32]. UV–Vis
lmax(nm): 436.
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 459–463 | 463