Synthesis and electrophysical properties of the fullerene C60-1,3,5-trimethoxybenzene conjugate

Article abstract of DOI:10.1134/S1070428015070088

A conjugate of fullerene C₆₀ with methyl 3-oxo-3-(2,4,6-trimethoxyphenyl)propanoate (monoacylation product of 1,3,5-trimethoxybenzene with methyl 3-chloro-3-oxopropanoate) has been synthesized under the Bingel-Hirsch conditions. Redox propertie

Full text of DOI:10.1134/S1070428015070088

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 7, pp. 940–942. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © S.A. Torosyan, V.V. Mikheev, Yu.N. Biglova, M.S. Miftakhov, 2015, published in Zhurnal Organicheskoi Khimii, 2015, Vol. 51,
No. 7, pp. 960–962.
Synthesis and Electrophysical Properties
of the Fullerene C60–1,3,5-Trimethoxybenzene Conjugate
S. A. Torosyana, V. V. Mikheevb, Yu. N. Biglovab, and M. S. Miftakhova
a Ufa Institute of Chemistry, Russian Academy of Sciences, pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
e-mail: bioreg@anrb.ru
b Bashkir State University, ul. Zaki Validi 32, Ufa, 450076 Bashkortostan, Russia
Received May 15, 2015
Abstract—A conjugate of fullerene C60 with methyl 3-oxo-3-(2,4,6-trimethoxyphenyl)propanoate (monoacyla-
tion product of 1,3,5-trimethoxybenzene with methyl 3-chloro-3-oxopropanoate) has been synthesized under
the Bingel‒Hirsch conditions. Redox properties of the conjugate have been studied by cyclic voltammetry.
DOI: 10.1134/S1070428015070088
Nowadays, solar energy transduction into electrical
energy is a global problem [1–3]. Bulk heterojunction
solar cells utilize combinations of p-donor and
n-acceptor materials [4]. Small molecules in which
donor and acceptor fragments are covalently bonded to
each other may be used as micro models of bulk-
heterojunction photovoltaic devices [5, 6]. In this
article we describe one such compound obtained from
fullerene C60 and keto ester 1 which was prepared by
Friedel–Crafts acylation of 1,3,5-trimethoxybenzene
with methyl 3-chloro-3-oxopropanoate. The reaction of
1 with C60 under the Bingel‒Hirsch conditions [7]
afforded adduct 2 in more than 50% yield (Scheme 1).
Molecule 2 contains a donor trimethoxyphenyl
fragment and acceptor methyl 3-oxopropanoate residue
linked through C2 to methanofullerene. Therefore, it
can be regarded as a “push–pull” system where the
acceptor and donor fragments are cross-conjugated,
which should enable a fundamental photovoltaic
process, absorption of light, generation of excitons,
and charge separation within a single molecule.
The electrophysical characteristics of fullerene
derivative 2 were determined by studying redox prop-
erties in o-dichlorobenzene by cyclic voltammetry
(CV) in comparison with fullerene conjugate 3
([60]PCBM) which is widely used in organic solar
Scheme 1.
OMe
O
OMe
OMe
OMe
O
O
MeOC(O)CH2C(O)Cl
AlCl3
C60, CBr4
PhMe, DBU
OMe
O
MeO
MeO
OMe
MeO
OMe
OMe
2
1
O
OMe
3, [60]PCBM
940

SYNTHESIS AND ELECTROPHYSICAL PROPERTIES
Electrochemical properties of methanofullerenes 2 and 3a
941
Compound
no.
E
LUMO, eV
EHOMO, eV
on
,b V
r ed
E1red, V
E2red, V
E3red, V
E4red, V
E
Eg, eV (DFT)
(DFT)c
(DFT)d
2
3
‒0.86
‒0.88
–1.28
–1.35
–1.77
–1.94
‒2.07
‒
‒0.75
‒0.78
‒4.05 (‒3.75) ‒5.70 (‒5.52) 1.65 (1.77)
‒4.02 (‒3.68) ‒5.61 (‒5.48) 1.59 (1.80)
a
b
c
d
The reduction potentials Ered were determined against Fc/Fc+ redox couple (internal standard) using Ag/Ag+ electrode.
on
E
is the reduction wave onset potential relative to Fc/Fc+ according to the CV data.
red
on
ELUMO = −(E + 4.8) (eV) [9].
red
on
EHOMO = −(E + 4.8) (eV).
ox
cells [7, 8]. On the basis of the data of cyclic voltam- of the sorbent per gram of substrate; freshly distilled
metry we determined the electron affinities of 2 and 3 solvents were used as eluents. Cyclic voltammograms
(first reduction potential, E1red) which is related to the were recorded for 10–3 M solutions of 2 and 3 in o-di-
energy of the lowest unoccupied molecular orbital chlorobenzene in an inert atmosphere at room tempera-
(LUMO) and its ionization potential (first oxidation ture on a P-30JM Elins potentiostat‒galvanostat
potential) which is related to the energy of the highest equipped with a three-electrode cell (working vitreous
occupied molecular orbital. The difference in the glass electrode, d = 5 mm2, opposite platinum elec-
LUMO and HOMO energies is the width of the forbid- trode, and reference Ag/Ag+ electrode, 0.01 mol/L in
den band gap of the acceptor (Eg) (see table).
MeCN; scan rate 50 mV/s; supporting electrolyte
0.1 M Bu4NPF6 in acetonitrile); ferrocene (Fc) was
used as internal standard. The electronic structures of
2 and 3 were calculated at the DFT B3LYP/6-31G(d)
level of theory using Gaussian 09 software package.
The first reduction potentials of compounds 2 and 3
are close to each other. This means that fullerene deriv-
atives are characterized by similar LUMO levels. The
LUMO and HOMO energies of 2 and 3 determined by
cyclic voltammetry are consistent with those calculated
for the isolated molecules in terms of the density func-
tional theory (see table). The LUMO energy of 2 is
lower by 0.03 eV than that of 3. Presumably, the
powerful donor effect of the trimethoxyphenyl frag-
ment is compensated to a somewhat greater extent by
the electron-withdrawing effect of the carbonyl group,
which is responsible for the close LUMO energies of
compounds 2 and 3.
Friedel–Crafts acylation of 1,3,5-trimethoxyben-
zene with methyl 3-chloro-3-oxopropanoate. Methyl
3-chloro-3-oxopropanoate, 0.19 mL (1.78 mmol), was
added in one portion under stirring to a suspension of
0.23 g (1.78 mmol) of anhydrous aluminum chloride in
20 mL of anhydrous dichloroethane, cooled to 0°C,
and a solution of 0.3 g (1.78 mmol) of 1,3,5-tri-
I, μA
150
EXPERIMENTAL
The IR spectra were recorded on a Shimadzu IR
Prestige-21 spectrometer from samples prepared as
thin films. The UV spectra were measured on
a Shimadzu UV-1800 UV-Vis spectrophotometer. The
1H NMR spectra were obtained on a Bruker AM-300
spectrometer at 300.13 MHz from solutions in CDCl3
using tetramethylsilane as internal reference. The
13C NMR spectra were taken on a Bruker Avance-500
spectrometer at 125.77 MHz. The MALDI mass spec-
tra were obtained on a Voyager-D STR TOF instru-
ment. The progress of reactions was monitored by TLC
on Sorbfil plates (Russia); spots were detected by
calcination or treatment with an alkaline solution of
potassium permanganate. The products were isolated
by column chromatography on silica gel using 30‒60 g
0
2
3
–150
–300
–2500
–2000
–1500
E, mV (Fc/Fc+)
–1000
–500
0
Cyclic voltammograms of methanofullerenes 2 and 3.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

TOROSYAN et al.
942
1
methoxybenzene in 5 mL of dichloroethane was then
added dropwise. When the reaction was complete
(TLC), the mixture was treated with 20 mL of cold
water and stirred for 10 min, and 2 mL of concentrated
aqueous HCl was added. The organic phase was sepa-
rated, and the aqueous phase was extracted with several
portions of dichloroethane. The extracts were com-
bined with the organic phase, washed with water, dried
over MgSO4, and evaporated. The residue was sub-
jected to silica gel column chromatography (petroleum
ether‒ethyl acetate, 2:1) to isolate 0.39 g (82%) of
methyl 3-oxo-3-(2,4,6-trimethoxyphenyl)propanoate
(1) as pale rose crystals with mp 85.0°C. IR spectrum,
ν, cm–1: 3004, 2954, 2845, 1735, 1581, 1123, 1029,
1670, 1600, 1233, 1131, 731, 520. H NMR spectrum,
δ, ppm: 3.84 s (3H, OMe) 3.96 s (3H, OMe), 4.00 s
(6H, OMe), 6.20 s (2H, Harom). 13C NMR spectrum, δC,
ppm: 53.42 (OMe), 55.57 (OMe), 56.45 (2C, OMe),
60.94 (C3′), 73.97 (C1, C9), 90.86 (Cm), 109.87 (Ci);
137.60, 140.15, 140.72, 140.84, 141.65, 141.88,
142.11 (2C), 142.86 (4C), 143.79 (2C), 144, 31 (2C),
145.54 (2C), 144.65 (2C), 145.00 (4C), 145.46,
145.58, 147.08 (C60); 162.18 (Co), 165.19 (Cp), 165.30
(CO2), 185.45 (C=O). Mass spectrum: m/z 986.010
[M]+. C73H14O6. Calculated: M 986.079.
The spectra were recorded at the Khimiya Joint
Center, Ufa Institute of Chemistry, Russian Academy
of Sciences. This study was performed under financial
support by the Russian Foundation for Basic Research
(project nos. 14-02-97008, 14-03-31610 mol_a).
1
814. H NMR spectrum, δ, ppm: 3.85 s (3H, OMe),
3.95 (3H, OMe), 4.00 (6H, OMe), 6.15 (2H, CH2).
13C NMR spectrum, δC, ppm: 52.89 (CH2), 55.36
(OMe), 55.89 (OMe), 56.18 (2C, OMe), 90.69 (Ci),
91.05 (Cm), 162.29 (Co), 162.92 (Cp), 167.06 (C=O).
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015