Synthesis and properties of pyrazolino[60]fullerene-donor systems

Article abstract of DOI:10.1016/S0040-4020(02)00552-5

A series of pyrazolino[60]fullerenes has been prepared in one pot by 1,3-dipolar cycloaddition to C₆₀ of the corresponding nitrile imine, which was generated in situ from the corresponding hydrazone. A range of donors and acceptors were introdu

Full text of DOI:10.1016/S0040-4020(02)00552-5

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 5821±5826
Synthesis and properties of pyrazolino[60]fullerene-donor systems
a
b
b
c
Eva Espõldora, Juan Luis Delgado, Pilar de la Cruz, Antonio de la Hoz, Vicente Lopez-Arza
a
Â
Â
and Fernando Langab,p
a
Â
Escuela de Ingenieros Tecnicos Industriales, Universidad de Castilla-La Mancha, 45071 Toledo, Spain
bFacultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, 45071 Toledo, Spain
c
Â
Facultad de Ciencias Quõmicas, Universidad de Castilla-La Mancha, 45071 Toledo, Spain
Received 15 March 2002; revised 13 May 2002; accepted 30 May 2002
AbstractÐA series of pyrazolino[60]fullerenes has been prepared in one pot by 1,3-dipolar cycloaddition to C60 of the corresponding nitrile
imine, which was generated in situ from the corresponding hydrazone. A range of donors and acceptors were introduced as substituents.
Electrochemical and photophysical studies have revealed weak ground-state interactions between the organic addends and the fullerene
sphere. Steady-state ¯uorescence has shown that, in both toluene and benzonitrile solutions, an ef®cient electron transfer process takes place
when a strong donor is attached to the pyrazolino[60]fullerene system. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
electrochemistry and photophysical properties of a series
of pyrazolino[60]fullerene derivatives 2a±f bearing differ-
ent functional groups as substituents. Other pyrazolino[60]-
fullerene derivatives have shown similar electrochemical
behaviour.10
The photophysical properties of [60]fullerene derivatives1
and the inter- and intramolecular electron transfer reactions2
of these interesting molecules have been the focus of several
research groups in recent years. The reason for this interest
is the combination of the strong electron-accepting proper-
ties of fullerenes3 and the incorporation of donor moieties
onto the C60 core through a bridge.4 Therefore, a variety of
C60-bridge-donor dyads have been synthesized in the search
for systems with improved charge separation properties.5
2. Results and discussion
Synthesis. Compounds 2a±f were synthesized in two steps
from the corresponding aldehydes as shown in Scheme 1.
Hydrazones 1a±f were prepared in good yields by reaction
of the corresponding aldehyde with 4-nitrophenylhydrazine
in the presence of acetic acid using ethanol as the solvent.
Cycloadducts 2a±f were prepared by a modi®cation of our
previously described procedure.7 This modi®cation avoids
the use of microwave irradiation and the reaction can now
be carried out at room temperature. The corresponding
hydrazone was treated with N-chlorosuccinimide (NCS) in
the presence of pyridine using chloroform as the solvent; the
resulting chloro-derivative was reacted with Et3N and C60
Although 1,3-dipolar cycloaddition reactions have been
widely used to prepare fullerene derivatives, the func-
tionalization of C60 with 1,3-nitrile imines to give pyrazo-
lino[60]fullerenes has scarcely been exploited.6 In this
respect, we recently described the facile synthesis of several
pyrazolylpyrazolino[60]fullerenes by 1,3-dipolar cyclo-
addition between nitrile imines and C60.7 The nitrile imine
was generated in situ from the corresponding hydrazone and
NBS under microwave irradiation, a source of energy that
has proven useful when applied in fullerene chemistry.8
Interestingly, the pyrazolylpyrazolino[60]fullerenes pre-
pared in this way show ®rst and second reduction potentials
that are anodically shifted (,150 mV) relative to other
1,2-dihydrofullerenes (such as pyrrolidino[60]fullerenes)
and are better than the C60 itself.9 We attributed this shift
to the electronegative character of the nitrogen atom linked
to the C60 core. In this paper we report the synthesis,
Keywords: fullerene; electron transfer; electrochemistry.
Corresponding author. Address: Departamento de Quõmica Organica,
p
Â
Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La
Mancha, 45071 Toledo, Spain; Fax: 134-925-268840;
e-mail: fernando.lpuente@uclm.es
Scheme 1.
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00552-5

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E. Espõldora et al. / Tetrahedron 58 (2002) 5821±5826
5822
Table 1. Fluorescence data of compounds 2a±f
Compound
lmax (nm)/intensity (a.u.)
Toluene
Benzonitrile
2a
2b
705/0.249
772/0.138
631/0.068
716/0.085
719/0.108
705/0.081
725/0.083
±
704/0.128
766/0.073
620/0.090
717/0.070
725/0.075
728/0.016
2c
2d
2e
2f
±
±
±
Figure 1. UV±Vis spectra of 2a (´ ´ ´), 2e (- - -) and 2f (Ð) in carbon
disul®de.
moieties in the ground state and a broad band is observed in
the region 450±550 nm when CS2 is used as the solvent
(Fig. 1). This band is stronger and red-shifted with respect
to those seen in CH2Cl2 and is consistent with the electro-
chemical studies detailed below. Comparable effects have
been found in other donor-C60 systems.11
for 45 min. Under these conditions adducts 2a±f were
obtained in 24±43% yield (49±82% based on reacted
C60). The adducts were puri®ed by column chromatography
(silica gel, toluene) followed by centrifugation in hexane,
methanol and diethyl ether.
Fluorescence spectra. The ¯uorescence spectra of 2a±f
were measured in both toluene and benzonitrile upon
excitation at 430 nm at room temperature. Solutions with
the same absorbance were employed so that the ¯uorescence
intensity and the quantum yields could be correlated.
The new cycloadducts 2a±f were characterized by MALDI
or FAB-MS as well as by 1H, 13C NMR, FT-IR and UV±Vis
spectroscopy. In all cases the molecular ions were observed
in the mass spectra, using MALDI or FAB techniques in
positive ion mode, at m/z values corresponding to the MH1
On using toluene as the solvent (see Fig. 2 and Table 1),
the ¯uorescence spectrum of pyrazolino[60]fullerene 2a
(RˆPh) is similar to those of other fullerene derivatives,
showing an emission maximum at 705 nm with a shoulder
at 772 nm as a consequence of the inter-system crossing into
the triplet excited state.
1
fragment (see Section 4). The H NMRof 2a±f show all
the expected signals and the p-substituted phenyl groups
appeared as AA0XX0 systems with JAXˆJA X ˆ9-10 Hz
0
0
0
0
0
0
and JAX ˆ JA XˆJAA ˆJXX ˆ0 as described in Section 4.
Absorption spectra. The UV±Vis spectra of this family of
cycloadducts are similar to those described for other
pyrazolino[60]fullerenes;8 the absorption peak at 430 nm,
typical of [6,6] adducts, appears as a shoulder, shaded by
the p-nitrophenyl group. Nevertheless, some differences
between the UV±Vis spectra of some adducts (2e and 2f)
and the superposition of the isolated components is
observed. These discrepancies are indicative of weak
electronic interactions between the substituent and the C60
The intensities of the emission maxima in 2b±d are lower
(see Table 1) and the maxima are red shifted (716, 719 and
725 nm, respectively) with respect to those of 2a. This trend
indicates that the excited state is partially quenched.
Emission was not observed (Fig. 2) when a strong donor
such as N,N-dimethylaniline (2e) was linked to the pyrazo-
lino[60]fullerene system.
This quenching can be explained in terms of a photoinduced
electron transfer process (PET), which is not common in
non-polar solvents like toluene.
Related fulleropyrrolidines incorporating N,N-dimethyl-
aniline and ferrocene moieties, e.g. fulleropyrrolidines 312
and 411b (Chart 1), show ¯uorescence in non-polar solvents.
On the other hand, as shown in Table 1, the ¯uorescence
intensity in benzonitrile was reduced (to about 1/2 that in
Figure 2. Fluorescence spectra of compounds 2a (Ð), 2e (- - -) and 2f (´ ´ ´)
in toluene.
Chart 1.

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E. Espõldora et al. / Tetrahedron 58 (2002) 5821±5826
5823
compounds was examined using cyclic voltammetry (CV)
and Osteryoung square-wave voltammetry (OSWV). These
studies were carried out at room temperature in o-dichloro-
benzene/acetonitrile (4:1) as solvent and using tetrabutyl-
ammonium perchlorate (TBAP) as the supporting
electrolyte (see Section 4). In order to investigate the
in¯uence of the substituent R1 on the pyrazolino system
we considered the ®rst reversible reduction potential. The
OSWV data of the prepared fullerene derivatives are
presented in Table 2 along with those of C60 for comparison
purposes.
The cyclic voltammogram (CV) of all the pyrazolino[60]-
fullerenes (2a±f) show four quasi-reversible reduction
waves for the fullerene moiety, which is similar to the situa-
tion found for the parent C60. In addition, another non-rever-
sible reduction wave (between the second and the third
fullerene reduction waves) is observed and this can be
reasonably assigned to the p-nitrophenyl moiety, as
suggested by comparison with the reduction potential of
nitrobenzene. The in¯uence of strong electron donors,
such as ferrocene or N,N-dimethylaniline, and electron
acceptors, such as pyridine, was studied. Clearly, the intro-
duction of an electron acceptor like pyridine (2b) results in
the most positive ®rst reduction potential in this series
(20.91 V) and the molecule has a better electron af®nity
than the parent C60 (20.95 V). On the other hand, electron
donors like furan (1c) or N,N-dimethylaniline (1e) afford the
most negative value (20.95 V) in this series and the ®rst
reduction potential is similar to that of C60 (20.95 V). It is
not clear whether this in¯uence of the nature of the sub-
stituent on the electron af®nity of the fullerene derivative
can be explained in terms of through-bond or through-space
interactions between the substituent and the fullerene
surface.
Figure 3. Fluorescence spectra of compound 2e upon addition of increasing
amounts of tri¯uoroacetic acid.
toluene for 2a, to 1/1.2 for 2b, to 1/1.5 for 2c and to 1/20 for
2d) with solvatochromic red-shifts of the maxima in all
cases. This solvatochromic effect in benzonitrile in com-
parison to toluene has been assigned to a weak CT
character.13 This quenching of the ¯uorescence is ascribed
to a weak PET interaction when the polarity of the solvent is
increased and, consequently, the charge separated state
should be more stable.
Addition of TFA to a benzonitrile solution of 2e (RˆN,N-
dimethylaniline) causes an enhancement in the ¯uorescence
(Fig. 3), suggesting a quenching of the PET process as the
lone electron pairs of both nitrogen atoms (N,N-dimethyl-
aniline group and pyrazoline ring) become unavailable. One
of the electron pairs (or both) should be responsible for the
PET process;14 the addition of base (pyridine) again causes a
quenching of the ¯uorescence, indicating the reversibility of
the process.
Comparison of the reduction potentials of the p-nitrophenyl
moiety in this series shows a shift to more negative values as
the electron±donor ability of the substituent on the other
side of the molecule (see Scheme 1 and Table 2) is
increased. This reduction potential is shifted by 60 mV
when a strong electron-donor, such as N,N-dimethylaniline
(2e) or ferrocene (2f), is linked to the pyrazoline ring, thus
demonstrating the electronic communication between the
C-substituent and the sp3 nitrogen atom of the pyrazoline
ring; consequently, the electron transfer process from this
nitrogen atom should be favoured when an electron donor is
incorporated within the molecule as a C-substituent.
Electrochemical studies. Most C60 monoadducts show small
negative shifts (ca. 100 mV) in the reduction potential when
compared with those of the parent C60 as a result of the
partial loss of conjugation upon derivatisation.3,15 Neverthe-
less, we have recently shown that several pyrazolylpyrazo-
lino[60]fullerenes show an anodic shift (up to 80 mV
for Ered1) compared to C60
9,10
itself, and this is due to the
inductive effect of the nitrogen atom close to the C60 cage.
Similar behaviour has also been found in isoxazolino[60]-
fullerenes.16 The redox behaviour of the newly synthesized
3. Summary
Table 2. Redox potentials (OSWV) of organofullerenes 2a±f, and C60
Pyrazolino[60]fullerene derivatives functionalized with
different substituents have been synthesized in one pot by
1,3-dipolar cycloaddition between C60 and the correspond-
ing nitrile imine generated in situ from the appropriate
hydrazone. In contrast with other families of fullerene
derivatives, systems based on pyrazolino[60]fullerene
present a similar electron af®nity to pristine C60 as a conse-
quence of the inductive effect of the nitrogen atom close to
the fullerene cage. Both electrochemical and photophysical
studies revealed that there are small ground-state inter-
actions between the organic addend and the fullerene
1
2
3
4
5
Compound
Ered
Ered
Ered
Ered
Ered
C60
2a
2b
2c
2d
2e
2f
20.95
20.93
20.91
20.95
20.92
20.95
20.94
21.36
21.33
21.32
21.36
21.32
21.35
21.35
±
21.83
21.87
21.82
21.84
21.85
21.91
21.92
22.29
22.24
22.22
22.33
22.22
22.28
22.30
21.70
21.66
21.70
21.70
21.72
21.72
V vs. Ag/AgNO3; GCE as working electrode; 0.1 M TBAP; ODCB/MeCN
(4:1); scan rate: 100 mV s21
.

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E. Espõldora et al. / Tetrahedron 58 (2002) 5821±5826
5824
sphere. Steady-state ¯uorescence indicates that an ef®cient
photoinduced electron transfer process occurs in these
systems in benzonitrile solutions. When a strong donor,
such as ferrocene or N,N-dimethylaniline, is linked to the
pyrazoline ring, ¯uorescence is not observed in toluene
solutions, indicating the ef®ciency of the photoinduced
electron transfer process for this kind of system even in
non-polar solvents.
(cm21) 3199.4, 1600.0, 1540.3, 1493.9, 1341.4, 1215.5,
1129.3, 990.1, 917.1, 835.6, 744.8, 691.8, 552.5, 489.9;
1H NMR(CDCl ) d 7.19 (d, 2H, Jˆ9 Hz), 7.55 (d, 2H,
3
Jˆ6 Hz), 8.23 (d, 2H, Jˆ9 Hz), 8.66 (d, 2H, Jˆ6 Hz); 13C
NMR(CDCl ) d 150.7, 139.1, 138.1, 126.4, 126.2, 120.8,
3
112.8, 112.5; Anal. calcd for C12H10N4O2: C, 59.50; H, 4.16;
N, 23.13. Found: C, 59.23; H, 3.89; N, 22.86.
4.2.3. 2-Furaldehyde 4-nitrophenylhydrazone (1c).
)
Yield: 66%; mp: 152±1538C; FT-IR(KBr) n (cm21
3254.9, 1585.2, 1496.5, 1489.0, 1297.2, 1272.9, 1172.1,
1169.1, 1172.1, 1070.2, 1015.8, 939.2, 883.5, 842.1,
823.2, 748.3, 694.0, 593.3, 493.3, 416.6; 1H NMR
(CDCl3) d 6.47 (dd, 1H, Jˆ2, 4 Hz), 6.66 (d, 1H, Jˆ
4 Hz), 7.08 (d, 2H, Jˆ9 Hz), 7.55 (d, 1H, Jˆ2 Hz), 7.67
(s, 1H), 7.96 (s, 1H), 8.16 (d, 2H, Jˆ9 Hz); 13C NMR
(CDCl3) d 149.7, 149.5, 144.4, 140.6, 131.5, 126.4, 112.2,
112.0, 111.9; Anal. calcd for C11H9N3O3: C, 57.14; H, 3.92;
N, 18.17. Found: C, 56.94; H, 3.87; N, 17.85.
4. Experimental
4.1. General remarks
All cycloaddition reactions were performed under Argon.
C60 was purchased from MERCorporation (Tucson, AZ);
the corresponding starting materials were purchased from
ACROS. TLC using Merck silica gel 60-F254 was used to
1
monitor cycloaddition reactions. H and 13C NMRspectra
were recorded on a Varian Mercury 200 apparatus. UV±Vis
absorption spectra were obtained on a Shimatzu spectro-
photometer. FT-IRspectra were recorded on a Nicolet
Impact 410 spectrophotometer using KBr disks. Fluores-
cence spectra were obtained on a JASCO FP-750 spectro-
photometer.
4.2.4. 2-Thiophenecarboxaldehyde 4-nitrophenylhydra-
zone (1d). Yield: 60%; mp: 196±1978C; FT-IR(KBr)
n
(cm21) 2406.6, 1605.8, 1591.0, 1549.7, 1493.9, 1478.8,
1462.2, 1325.8, 1295.7, 1274.8, 1233.0, 1169.5, 1105.7,
1042.2, 998.7, 929.1, 838.4, 748.7, 696.1, 657.02, 553.7,
1
489.6; H NMR(CDCl ) d 7.05 (d, 1H, Jˆ4 Hz), 7.09 (d,
3
2H, Jˆ9 Hz), 7.20 (dd, 1H, Jˆ4, 5 Hz), 7.36 (d, 1H, Jˆ
5 Hz), 8.01 (s, 1H), 8.18 (d, 2H, Jˆ9 Hz); 13C NMR
(CDCl3) d 149.3, 140.5, 139.2, 136.1, 128.7, 127.8, 127.7,
126.3, 111.9; Anal. calcd for C11H9N3O2S: C, 53.43; H,
3.67; N, 16.99. Found: C, 53.18; H, 3.42; N, 16.74.
FAB mass spectra were obtained on a VG AutoSpec spec-
trometer, using m-nitrobenzyl alcohol as a matrix, and
MALDI-TOF mass spectra were obtained on a Bruker
Re¯exIII spectrometer. Cyclic voltammetry measurements
were carried out on an Autolab PGSTAT 30 potentiostat
using a BAS MF-2062 Ag/0.01 M AgNO3, 0.1 M TBAP
in ACN reference electrode, an auxiliary electrode consist-
ing of a Pt wire, and a Metrohm 6.1247.000 conventional
glassy carbon electrode (3 mm o.d.) as a working electrode,
directly immersed in the solution. A 10 mL electrochemical
cell from BAS, Model VC-2, was also used. The reference
potential was shifted by 290 mV towards a more negative
potential compared with the Ag/AgCl scale. E1/2 values
were taken as the average of the anodic and cathodic peak
4.2.5. 4-(N,N-dimethylamino)benzaldehyde 4-nitro-
phenyl hydrazone (1e). Yield: 64%; mp: 177±1788C;
FT-IR(KBr) n (cm21) 3290.6, 2899.5, 2813.3, 1593.4,
1527.1, 1494.0, 1321.5, 1361.3, 1182.3, 1162.4, 1116.1,
990.1, 950.3, 811.1, 751.4, 685.1, 638.7, 592.3, 519.3,
479.6; 1H NMR(CDCl 3) d 3.02 (s, 6H), 6.71 (d, 2H,
Jˆ9 Hz), 7.06 (d, 2H, Jˆ10 Hz), 7.56 (d, 2H, Jˆ9 Hz),
8.16 (d, 2H, Jˆ10 Hz); 13C NMR(CDCl ) d 151.6, 150.1,
3
potentials. Scan rate: 100 mV s21
.
142.8, 139.8, 128.4, 126.5, 122.1, 112.2, 111.5, 40.5; Anal.
calcd for C15H16N4O2: C, 63.37; H, 5.67; N, 19.71. Found:
C, 62.92; H, 5.50; N, 19.42.
4.2. Preparation of hydrazones. General procedure
4.2.6. Ferrocenecarboxaldehyde 4-nitrophenylhydra-
zone (1f). Yield: 70%; mp: 183±1858C; FT-IR(KBr)
A solution of the corresponding aldehyde (3.3 mmol),
4-nitrophenylhydrazine (3.3 mmol) and two drops of acetic
acid in 15 mL of ethanol was heated under re¯ux for 10 min.
The mixture was cooled to room temperature, ®ltered and
the solid was recrystallized from ethanol.
n
(cm21) 3292.8, 1598.1, 1534.0, 1479.2, 1459.4, 1323.9,
1307.7, 1271.0, 1208.9, 1168.8, 1109.3, 1061.5, 1042.9,
1023.7, 999.8, 946. 8, 928.3, 836.1, 813.8, 750.4, 693.7,
1
544.1, 531.6, 495.5; H NMR(CDCl ) d 4.20 (s, 5H),
3
4.40 (s, 2H), 4.62 (s, 2H), 7.03 (d, 2H, Jˆ9 Hz), 8.17 (d,
4.2.1. Benzaldehyde 4-nitrophenylhydrazone (1a). Yield:
85%; mp: 189±1908C; FT-IR(KBr) n (cm21) 3257.5,
1593.4, 1547.0, 1295.2, 1155.8, 1096.1, 990.1, 930.4,
2H, Jˆ9 Hz); 13C NMR(CDCl ) d 142.2, 126.5, 125.6,
3
113.0, 111.5, 73.5, 71.0, 70.4, 69.9, 69.3, 69.5, 69.1, 67.6;
Anal. calcd for C17H15FeN3O2: C, 58.48; H, 4.30; N, 12.04.
Found: C, 57.78; H, 4.16; N, 11.70.
1
837.6, 744.7, 671.8, 526.4, 479.6; H NMR(CDCl 3) d
7.14 (d, 2H, Jˆ9 Hz), 7.38 (dd, 1H, Jˆ3, 4 Hz), 7.41 (dd,
2H, Jˆ4, 6 Hz), 7.70 (dd, 2H, Jˆ3, 6 Hz), 7.81 (s, 1H), 8.04
(s, 1H), 8.20 (d, 2H, Jˆ9 Hz); 13C NMR(CDCl ) d 112.0,
4.3. Synthesis of cycloadducts. General procedure
3
126.5, 127.0, 129.1, 130.0, 134.3, 141.5, 144.1, 152.6; Anal.
calcd for C13H11N3O2: C, 64.72; H, 4.60; N, 17.42. Found:
C, 64.75; H, 4.72; N, 17.44.
To a solution under argon of the appropriate hydrazone
(0.07 mmol) in 10 mL of dry chloroform was added pyri-
dine (10 mL). The mixture was cooled to 08C, 18 mg
(0.014 mmol) of NCS was added and the mixture was stirred
for 15 min; [60]fullerene (50 mg, 0.07 mmol) and Et3N
4.2.2. 4-Pyridinecarboxaldehyde 4-nitrophenylhydra-
zone (1b). Yield: 64%; mp: 263±2658C; FT-IR(KBr)
n

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E. Espõldora et al. / Tetrahedron 58 (2002) 5821±5826
5825
(7 mg, 0.07 mmol) were then added. The solution was
allowed to reach room temperature and stirred for 45 min.
The solvent was removed under reduced pressure and the
resulting solid was puri®ed by silica gel ¯ash chroma-
tography, using toluene as eluent. Centrifugation with
methanol and diethyl ether achieved further puri®cation of
the solid.
65% based on reacted C60). FT-IR(KBr) n (cm21) 3339.2,
1584.2, 1509.2, 1324.5, 1261.1, 1192.8, 1109.9, 1045.7,
1
842.2, 812.8, 746.3, 524.9, 476.2; H NMR(CDCl 3) d
3.06 (s, 6H), 6.82 (d, 2H, Jˆ9 Hz), 8.16 (d, 2H, Jˆ9 Hz),
8.26 (d, 2H, Jˆ10 Hz), 8.33 (d, 2H, Jˆ10 Hz); 13C NMR
(CDCl3/CS2 1:1) d 151.5, 150.3, 147.1, 146.7, 146.4, 146.2,
145.5, 144.9, 144.4, 144.1, 143.4, 143.2, 142.7, 142.4,
140.6, 139.6, 137.3, 136.3, 130.6, 125.7, 119.2, 112.2,
40.4; UV±Vis (CH2Cl2) lmax (nm) (log 1) 657.5 (2.53),
486.0 (3.35), 390.5 (3.92), 319.5 (4.29); MALDI-TOF
m/z: 1002 (M11), 852 (M2150), 720 (C60).
4.3.1. 10-(4-Nitrophenyl)-30-phenylpyrazolino[40,50:1,2]-
[60]fullerene (2a). Yield: 34 mg (43, 82% based on reacted
C60). FT-IR(KBr) n (cm21) 3443.1, 2926.0, 1580.1, 1500.5,
1321.5, 1255.2, 1102.8, 837.6, 744.7, 671.8, 526.0; 1H
4.3.6.
10-(4-Nitrophenyl)-30-(ferrocenyl)pyrazolino-
NMR(CDCl ) d 7.55 (dd, 1H, Jˆ2, 6 Hz), 8.21 (dd, 2H,
3
[40,50:1,2][60]fullerene (2f). Yield: 18 mg (24, 49% based
Jˆ2, 6 Hz), 8.22 (dd, 2H, Jˆ6, 6 Hz), 8.27 (d, 2H, Jˆ
on reacted C60). FT-IR(KBr) n (cm21) 2899.4, 1585.1,
1491.6, 1460.5, 1318.5, 1273.2, 1105.4, 842.6, 745.9,
10 Hz), 8.35 (d, 2H Jˆ10 Hz); 13C NMR(CDCl /CS2 1:1)
3
d 146.8, 146.4, 146.0, 145.7, 144.9, 143.3, 142.8, 142.5,
142.3, 137.3, 130.5, 129.5, 129.3, 128.6, 127.7, 127.2,
125.6, 119.5, 97.2; UV±Vis (CH2Cl2) lmax (nm) (log 1)
617.0 (2.68), 491.0 (3.25), 375.0 (4.45), 318.5 (4.68);
FAB-MS m/z: 960 (M11), 720 (C60).
1
525.6, 477.7; H NMR(CDCl ) d 4.23 (s, 5H), 5.49 (t,
3
Jˆ2 Hz), 5.28 (t, Jˆ2 Hz), 8.21 (d, 2H, Jˆ10 Hz), 8.33
(d, 2H, Jˆ10 Hz); 13C NMR(CDCl /CS2 1:1) d 150.5,
3
150.0, 147.4, 146.6, 146.4, 146.0, 145.9, 145.0, 144.7,
143.3, 142.7, 142.4, 142.2, 140.4, 139.7, 137.2, 135.6,
127.8, 125.6, 119.4, 69.5; UV±Vis (CH2Cl2) lmax (nm)
(log 1) 672.0 (2.72), 609.5 (2.91), 405.9 (4.15), 319.5
(4.29); MALDI-TOF m/z: 1067 (M11), 917 (M2150),
720 (C60).
4.3.2.
10-(4-Nitrophenyl)-30-(4-pyrimidyl)pyrazolino-
[40,50:1,2][60]fullerene (2b). Yield: 23 mg (34, 69%
based on reacted C60). FT-IR(KBr) n (cm21) 3409.8,
1730.6, 1154.8, 1508.2, 1489.4, 1328.2, 1263.8, 1244.1,
1107.4, 1040.3, 878.2, 844.9, 817.6, 746.3, 676.2, 562.8,
1
544.4, 526.0; H NMR(CDCl ) d 8.21 (d, 2H, Jˆ6 Hz),
3
8.26 (d, 2H, Jˆ9 Hz), 8.37 (d, 2H, Jˆ9 Hz), 8.81 (d, 2H,
Jˆ6 Hz); 13C NMR(CDCl 3/CS2 1:1) d 150.8, 149.3, 146.8,
146.4, 146.3, 145.8, 145.6, 144.7, 143.5, 143.3, 142.7,
142.4, 142.2, 140.8, 139.8, 139.4, 137.3, 136.7, 125.7,
122.9, 120.3; UV±Vis (CH2Cl2) lmax (nm) (log 1) 606.0
(2.96), 488.5 (3.56), 388.0 (4.64), 318 (4.9); MALDI-TOF
m/z: 961 (M11), 720 (C60).
Acknowledgements
This work was ®nancially supported by a grant from
Â
Ministerio de Ciencia y Tecnologõa of Spain (Projects
BQU2001-1512 and BQU2001-1095). One of us (E. E.) is
indebted to the Junta de Comunidades de Castilla-La
Mancha for a fellowship.
4.3.3.
10-(4-Nitrophenyl)-30-(2-furanoyl)pyrazolino-
[40,50:1,2][60]fullerene (2c). Yield: 31 mg (43, 76% based
on reacted C60). FT-IR(KBr) n (cm21) 3456.3, 2922.6,
2852.2, 1618.0, 1459.8, 1323.2, 1270.8, 1209.6, 1110.2,
References
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825.9, 745.4, 529.5, 470.3; H NMR(CDCl ) d 6.66 (dd,
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1H, Jˆ3, 2 Hz), 7.39 (d, 1H, Jˆ3 Hz), 7.68 (d, 1H, Jˆ
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