Near-infrared absorbing compounds based on π-extended tetrathiafulvalene open-cage fullerenes

Article abstract of DOI:10.1021/jo5000048

Tetrathiafulvalene (TTF) is attached to open-cage fullerenes through a quinoxaline junction. The resulting linear π-conjugation system shows intense absorption in the near-infrared region. A unique o-diaminobenzene-induced furan ring formation process from a conjugated 1,4-dione moiety was observed on the rim of a 18-membered orifice.

Full text of DOI:10.1021/jo5000048

Article
pubs.acs.org/joc
Near-Infrared Absorbing Compounds Based on π‑Extended
Tetrathiafulvalene Open-Cage Fullerenes
Yuming Yu,†,‡ Liang Xu,†,‡ Xincheng Huang,†,‡ and Liangbing Gan*,†,‡,§
†Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory for Organic Solids, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100080, China
‡Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, China
§State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Shanghai 200032, China
S
* Supporting Information
ABSTRACT: Tetrathiafulvalene (TTF) is attached to open-cage fullerenes
through a quinoxaline junction. The resulting linear π-conjugation system
shows intense absorption in the near-infrared region. A unique o-
diaminobenzene-induced furan ring formation process from a conjugated
1,4-dione moiety was observed on the rim of a 18-membered orifice.
azafullerenes.8 The number of such fullerene-based NIR
materials is still quite limited because selective multifunction-
alization of fullerene is a challenging problem.
INTRODUCTION
■
Near-infrared (NIR) absorption materials have attracted much
attention because of their applications in various fields such as
Fullerene derivatives with a covalently linked chromophore
solar-cell, bioimaging, sensing, and nonlinear optics. Organic
can also show absorption in the NIR region.9 A variety of
compounds consist of most of the known NIR absorption
materials. Phthalocyanines and naphthalocyanines, metal
tetrathiafulvalene (TTF)−fullerene derivatives have been
prepared with various linkage strategies.9c,d Many of these
complex dyes, polyene, polymethine, squaraines, quinines,
and azo dyes are among the well-studied organic compounds.1
Chemical modifications of existing chromophores continue to
be a hot topic to optimize their properties for practical
applications. For example, (indigo-N,N′-diarylimine) boron
chelate complexes2 and indeno[2,1-b]fluorenes3 were recently
reported as NIR absorption materials. All these organic
compounds have a planar conjugated π-system.
TTF−fullerene dyads show excellent charge-transfer properties
and NIR absorption. The energy gap for a fluorinated fullerene
TTF dyad is as low as 0.5 eV.10 Several fullerene−heptamethine
dyads have been synthesized through the Prato reaction, which
shows intense absorption around 800 nm.11 Azulenocyanine
fullerene derivatives also show intense NIR absorption.12
Open-cage fullerene derivatives13 with electron-donating
group(s) is another type of fullerene-based NIR material.
Compound 1 shows intense near-IR absorption as a result of
the imino and enamine moieties acting as electron-donating
groups.14 Compound 2 has a linear π-conjugated connection
between the thiophene oligomer and the fullerene cage. Cross-
talking between the donor and acceptor in the conjugated
system leads to intramolecular charge-transfer absorbance in
the NIR region.15
Fullerenes have a spherical π-system and show intense
absorption in the UV region but have no absorption in the NIR
region. Reduction of fullerene results in fullerene radical anion
•−
radical C60 with absorptions at 1075, 1058, and 991 nm and
fullerene dianion C602− with absorptions at 1020−1030 and 933
nm.4 These anionic species are not stable in air. Dianionic
polymeric (C702−)n chains show absorptions in the NIR region
with three main bands at 890, 1200, and 1550 nm.5 Chemical
modification of the spherical π-system has been proven an
effective method to prepare fullerene-based NIR materials.
Compared to the classical planar π-systems, much remains to
be done to explore the full potential of fullerene-based NIR
materials. We have reported a number of open-cage fullerene
6
7
Fullerene multiadducts C60F15R3 and C60R6 show NIR
absorption as a result of the change of the spherical π-system.
Introduction of a heteroatom into the fullerene cage can also
shift the absorption into the NIR region as in the case of
Received: January 2, 2014
Published: February 11, 2014
© 2014 American Chemical Society
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Scheme 1. Preparation of Open-Cage Compounds with
Extended π-Systems
derivatives through a peroxide-mediated reaction pathway.16
Most of the open-cage fullerenes show orange-red color. Here,
we report the synthesis of π-extended open-cage fullerene
derivatives with donor chromophores such as TTF connected
through a quinoxaline junction.
RESULTS AND DISCUSSION
■
Compounds 3a and 3b were prepared as we have previously
reported.17 To remove the two tert-butyl peroxo groups in
compounds 3a and 3b, they were reduced with cuprous
bromide to form compounds 4a and 4b, respectively (Scheme
1). The regioselectivity is due to H-bonding between the
resulting hydroxyl group and the imino nitrogen. Coordination
of the imino nitrogen to copper in the transition state of the
reduction process probably also played a role in the observed
regioselective reduction of the tert-butyl peroxo groups.
Sequential treatment of compound 4 with PCl5 and SnCl2
resulted in formation of compound A through reductive
aromatization18 and opening of the iodo acetal moiety. It was
not possible to purify the intermediate product of the PCl5
reaction and compound A. Presumably, the hydroxyl group was
replaced by chlorine after treatment with PCl5, and aqueous
workup resulted in the opening of the iodo acetal moiety. The
same procedure was applied to a similar compound before to
remove the two tert-butyl peroxo groups.17a
The crude product A was used directly to react with the o-
diaminoaromatic compounds. Steric hindrance is an important
factor for this amination reaction. The bis-adducts 5a and 5b
were obtained for the less bulky 1,2-diaminobenzene.
Monoadducts 6a, 6b, and 6c were obtained for the bulky o-
diaminoaromatic compounds. Formation of compounds 6a−c
suggests that condensation between the vicinal dione and 1,2-
diaminobenzene took place before the addition on the rim of
the orifice in the formation of bisadducts 5a and 5b.
Regioisomer of compounds 5a and 5b with the diaminophenyl
group on the same side as the imino ArN group was detected
but could not be fully characterized. The cooperative action of
the o-diamino groups was necessary for selective formation of
isolable products. Treating compound A with aniline and
aniline derivatives gave complex mixtures.
To get more information about the structure of compound
A, we treated compound 4 with trifluoromethanesulfonic acid
and obtained a mixture of compounds 7 and 8 (Scheme 2). A
nonoxidizing silver salt such as AgSbF6 could also give a
mixture of 7 and 8, but AgClO4 resulted in oxidation of the
vicinal dione and decarboxylation which is analogous to the
decarboxylation of 3 by AgClO4.17a Separation of compounds 7
and 8 was difficult because of easy conversion between them on
the silica gel column. o-Diaminobenzene reacted with 7 and 8
to form compound 9 in the same way as the reaction with
compound A.
Single crystals of compounds 5b and 7a were obtained from
slow evaporation of their solution in CH2Cl2/hexane and
CDCl3, respectively. The structure of 5b showed that the
hydroxyl group forms intramolecular H-bonding with one of
the quinoxaline nitrogen atoms. The H-bond distance O−H···
N is 2.66 Å. The isopropylphenyl group points toward the
fullerene cage. The fullerene pentagon baring the quinoxaline is
planar with the quinoxaline ring. The phenyl group bound to
the furan ring is in a 45° orientation with respect to the
quinoxaline ring. Such an orientation explains the selective
formation of monoadduct with more bulky o-diaminoaromatic
compounds as in the case of compounds 6a−c. The space-
filling model of 5b shows close contact between the o-
diaminoaryl groups.
The X-ray structure of compound 7a showed clearly the
presence of the hydrate moiety (Figure 1). The space-filling
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in compound 7a (1.20 Å), indicating that the orifice is quite
rigid and not affected by the addition of different groups. In the
unit cell of both compounds 5b and 7a, there is a pair of
enantiomers.
Scheme 2. Addition of o-Diaminobenzene to Open-Cage
Fullerenes
The presence of a mixture of compounds 7 and 8 were
1
evident on their H NMR spectra. The ratio can be easily
determined from integration of the corresponding OH group
or phenyl protons. For the aniline derivatives the ratio is 40:60
for 7a and 8a (Figure 2); for the p-isopropylaniline derivatives
1
Figure 2. H NMR spectrum of compounds 7a and 8a in CDCl3.
the ratio is 13:87 for 7b and 8b. The two hydroxyl groups on
the hydrated carbon appear at 3.79 and 5.17 ppm for 7a and at
3.84 and 5.15 ppm for 7b. The difference of the two hydroxyl
groups probably results from the shielding effect of the cage;
thus, the chemical shift at 3.79 and 3.84 ppm should be
assigned to the hydroxyl group above the orifice for compounds
7a and 7b ,respectively. The other hydroxyl group on the
hexagon appears at 8.80 and 8.97 ppm, respectively, for 7a and
7b, which are comparable to that for compounds 8a (7.89
ppm) and 8b (8.08 ppm).
UV−vis−NIR spectra revealed clear conjugation effect
between the spherical π-system and the planar diaminoaromatic
ring in compounds 5 and 6 (Figure 3). Compound 9b with two
sp3 carbons separating the spherical π-system and the
quinoxaline π-system has an orange-red color and showed
Figure 1. X-ray structure of 5b (above) and 7a (below). For clarity,
hydrogen atoms on the alkyl and aryl groups for the ellipsoid models
were not drawn. Ellipsoids were at 50%. Color scheme: gray = C, blue
= N, red = O, white = H.
model indicates that the hydroxyl group above the orifice acts
like a stopper and blocks the orifice. There is no apparent H-
bond for the two hydroxyl groups in the hydrate moiety. The
other hydroxyl group at the para position to the tert-butyl
peroxo group forms intramolecular H-bond with the imino
hydrogen atom as mentioned above to explain the
regioselective reduction of compounds 3a and 3b. Unlike the
case in compound 5b, the phenyl group in 7a points away from
the fullerene cage. The carbonyl bond distance (1.21 Å) in 5b is
virtually the same as that of the corresponding carbonyl group
Figure 3. UV−vis−NIR spectra of compounds 5b, 6a, 6c, 9b, and 10
in CHCl3. Absorption coefficient for 6c at 790 nm in a 1.0 × 10−4 mol·
L−1 solution is 6.0 × 103 L·mol−1·cm−1.
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strong absorption in the UV region but has weak absorption
above 800 nm. In contrast, the analogous compound 5b
without the hydroxyl and tert-butylperoxo groups has a greenish
color and showed broad absorption peaks at 680 and 760 nm.
Compared to compound 5b, compound 6a has a similar
conjugation π-system but without the diaminobenzene on the
rim of the orifice. The UV−vis absorption spectrum of 6a is
very similar to that of 5b, indicating the diaminobenzene
addend on the rim of the orifice has little effect on the π-
system. The UV−vis absorption spectrum of the diaminonaph-
thalene derivative 6b is slightly red-shifted due to extended π-
conjugation compared to the 4,5-dimethyl-1,2-diamino deriv-
ative 6a (see the Supporting Information for the spectrum of
6b).
Compound 6c has an extended π-conjugation system from
the TTF moiety to the fullerene cage. It showed intense
absorption in the near-infrared region with absorption onset at
1352 nm in chloroform (Figure 3). Changing the solvent to
toluene and 1,4-dioxane resulted in a blue-shift of the
absorption centered at 797 nm by 45 and 60 nm, respectively.
Such a solvatochromism phenomenon indicates possible
intramolecular charge transfer. Addition of trifluoroacetic acid
to the solution of compound 6c resulted in gradual red-shift of
the absorption band at 797 to 1035 nm while other bands in
the UV region remained almost unaffected. The red-shift could
be reversed upon addition of pyridine. This halochromic
phenomenon further supports the charge transfer nature of the
band in the near-infrared region for the TTF derivative 6c.
Addition of trifluoroacetic acid to compounds 5a, 5b, 6a, and
6b did not show noticeable shift of absorption bands. For
comparison, the ninhydrin analogue 10 was synthesized by
treating ninhydrin with the diamino TTF derivative (Scheme
3). The absorption of compound 10 in chloroform starts at 710
nm with a broad band centered at 572 nm.
Figure 4. Cyclic voltammogram of 6c in 1,2-dichlorobenzene solution
containing tetrabutylammonium hexafluorophosphate (Bu4NPF6, 0.1
M) as a supporting electrolyte at 25 °C with a scan rate of 0.1 V/s.
attached compound 2, which has a band gap of 1.05 eV.
Hummelen et al. reported the first fullerene derivative with the
addend connected to the fullerene sphere via alternating
double-single bonds.19 But the overlap between the addend
orbitals and the cage orbitals is quite limited due to orbital
misalignment. A maximal red-shift of 11 nm was observed for a
benzylidene [5,6] fulleroid.
CONCLUSIONS
■
Scheme 3. Synthesis of Compound 10
In summary, o-diaminoaromatic compounds react readily with
carbonyl groups on the rim of open-cage fullerenes. The
conjugated 1,4-dione moiety forms a furan ring upon addition
of the o-diaminobenzene. The vicinal dione moiety forms
quinoxaline ring connecting planar chromophores with the
spherical π-system in a linear π-conjugation pattern. The redox
active fullerene-based NIR materials may have potential
applications in areas such as photodynamic therapy.
EXPERIMENTAL SECTION
■
All the reagents were used as received. Dichloromethane was distilled
over phosphorus pentaoxide. Compound 3 was prepared according to
the reported procedure.17a The reactions were carried out under
atmospheric conditions. NMR spectra were recorded at room
temperature (298 K). Chemical shifts are given in ppm relative to
TMS or CDCl3 (for 13C NMR). ESI-FT-ICR-HRMS spectra were
recorded with CHCl3/CH3OH or CDCl3/CH3OH as the solvent, and
positive-mode spectra were recorded. FTIR spectra were recorded in
the microscope mode. Chromatographic purifications were carried out
with silica gel of mesh 200−300.
Cyclic voltammetry measurements for compounds 6a, 6b,
and 6c showed three reduction peaks with reduction onset at
−0.67, −0.59, and −0.68 V (vs Fc/Fc+), respectively. A
reversible oxidation peak with onset at 0.16 V (vs Fc/Fc+) was
also observed for compound 6c corresponding to the oxidation
of the TTF moiety (Figure 4). The calculated HOMO−LUMO
gap for compound 6c is 0.84 eV.
Caution: A large amount of peroxide is involved in some of the
reactions. Care must be taken to avoid possible explosion.
The linear π-conjugated system in compounds 5 and 6 is
analogous to that in compound 215 reported by Xiao et al. in
that they have the same quinoxaline junction between the
addend chromophore and the open-cage fullerene. Comparison
of their UV−vis−NIR spectra and the HOMO−LUMO gap
indicate that the present TTF-open-cage fullerene derivative
shows stronger donor−acceptor interaction than the thiophene
Preparation of Compounds 4. CuBr (0.5 mmol) and H2O (0.3
mmol) were added to a solution of 3b (325 mg, 0.25 mmol) in
CH2Cl2 (20 mL) at room temperature. The mixture was stirred in the
dark, and progress of the reaction was monitored by TLC. When the
starting material 3b vanished and the desired product 4b reached its
maximum yield, the reaction mixture was directly chromatographed on
a silica gel column and eluted with toluene/ethyl acetate = 100:1. The
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orange band was collected and evaporated to give 4b. Compound 4a
was prepared using the same procedure (Table 1).
spectrum could not be obtained due to low solubility. ESI-FT-ICR-
HRMS: C78H18N5O3 (M + H+) calcd 1072.1404, found 1072.1414.
Characterization Data for 5b. H NMR (500 MHz, CDCl3) δ:
1
8.72 (d, J = 8.2 Hz, 1H), 8.59 (s, 1H), 8.18−8.01 (m, 2H), 7.95 (t, J =
7.4 Hz, 1H), 7.17 (d, J = 8.1 Hz, 2H), 6.97 (d, J = 8.1 Hz, 2H), 6.88
(d, J = 7.4 Hz, 1H), 6.73 (t, J = 7.5 Hz, 1H), 6.34 (t, J = 7.5 Hz, 1H),
5.32 (d, J = 7.7 Hz, 1H), 5.30 (s, 1H), 4.45 (s, 2H), 2.81−2.76 (m,
1H), 1.12−1.09 (m, 6H). 13C NMR (125 MHz, CDCl3) all signals
represent 1C except as noted, δ: 191.04, 161.27, 154.80, 152.18,
151.75, 151.01, 150.46, 150.44, 150.41, 150.38, 149.75, 149.73, 149.41,
149.15, 148.85, 148.71, 148.62, 147.97, 147.78, 147.75, 147.32, 147.11,
146.99, 146.32, 146.24, 146.11, 146.03, 145.34, 144.92, 144.90, 144.85,
144.70, 144.21, 144.04, 143.98, 143.96, 143.45, 143.36, 143.13, 142.98,
142.82, 142.61, 142.42, 141.26, 140.35, 140.24, 139.70, 139.04, 138.64,
138.16, 137.70, 136.24, 135.44, 135.12, 134.99, 134.97, 134.04, 131.84,
131.65, 131.12, 131.01, 130.78, 130.28, 129.41, 128.79(2C),
127.58(2C), 122.52, 119.99, 117.98(2C), 117.46, 115.58, 114.40,
108.63, 80.21, 65.04, 33.74, 24.04, 23.95. ESI-FT-ICR-HRMS:
C81H24N5O3 (M + H+) calcd 1114.1874, found 1114.1903.
Table 1. Preparation of Compounds 4a and 4b
entry
3 (mg)
product
Ar
mg (yield, %)
1
2
73
4a
4b
Ph
p-iPr-C6H4
56.8 (83)
266 (85)
325
1
Characterization Data for 4a. H NMR (400 MHz, CDCl3) δ:
7.75 (d, J = 7.5 Hz, 2H), 7.53 (t, J = 7.7 Hz, 2H), 7.39 (t, J = 7.4 Hz,
1H), 7.35 (s, 1H), 2.34 (s, 3H), 1.33 (s, 9H). 13C NMR spectrum
could not be obtained due to low solubility. ESI-FT-ICR-HRMS:
C72H19INO9 (M + H+) calcd 1168.0099, found 1168.0075.
1
Characterization Data for 4b. H NMR (400 MHz, CDCl3) δ:
7.78 (d, J = 7.5 Hz, 2H), 7.47 (s, 1H), 7.38 (d, J = 7.0 Hz, 2H), 2.93−
3.10 (m, 1H), 2.33 (s, 3H), 1.33 (d, J = 6.7 Hz, 6H), 1.31 (s, 9H). 13C
NMR (CDCl3, 100 MHz) all signals represent 1C except noted, δ:
187.55, 183.99, 179.90, 166.91, 154.24, 149.99, 149.81, 149.58, 149.55,
149.50, 149.44, 149.25, 149.15 (2C), 149.07, 149.01, 148.46, 148.31,
148.19, 148.13, 147.88, 147.83, 147.58 (2C), 147.30, 147.14, 146.59,
146.04, 145.79, 145.22, 145.14, 144.63 (2C), 143.58 (2C), 143.45,
143.35 (2C), 143.27 (2C), 143.20, 142.98, 142.56, 142.53, 142.39,
142.26, 141.98, 141.64, 141.21, 141.13, 140.64, 140.21 (2C), 138.07,
136.00, 133.17, 132.66, 129.50, 128.88, 126.86 (2C), 124.40 (2C),
108.56, 82.31, 82.24, 79.56, 58.40, 34.13, 26.92 (3C), 24.15 (2C),
22.12. ESI-FT-ICR-HRMS: C75H25INO9 (M + H+) calcd 1210.0569,
found 1210.0581.
A crystal of 5b suitable for X-ray diffraction was obtained from a
mixture of dichloromethane and hexane. Crystal data: triclinic, P-1.
Unit cell dimensions: a = 13.809(4) Å, α = 100.669(3)°, b =
14.082(4) Å, β = 106.061(2)°, c = 16.063(5) Å, γ = 107.353(3)°,
volume = 2740.2(13) Å3. Final R indices [I > 2σ(I)]: R1 = 0.0707 wR2
= 0.1793. Crystallographic data have been deposited in the Cambridge
Crystallographic Data Centre as deposition no. CCDC-967768.
Preparation of Compounds 6. PCl5 (1.2 equiv of 4a) was added
to a solution of 4a (32 mg, 0.0264 mmol) in CH2Cl2 (10 mL) at room
temperature. The mixture was stirred vigorously, and progress of the
reaction was monitored by TLC. When the starting material 4a
vanished and the desired product reached its maximum yield (about 10
min), 10 mL water was added to the reaction mixture and the reaction
was quenched. Then the water layer was extracted with dichloro-
methane three times, the extractions were combined and dried with
anhydrous sodium sulfate. Then the solution was concentrated to 10
mL. SnCl2 (1.5 equiv of 4a) was added to the concentrated solution
under vigorously stirring. When the starting material vanished and the
desired intermediate reached its maximum yield (about 10 min), 10
mL of 1 M HCl aqueous solution was added to the reaction mixture
and the reaction was quenched. Then aqueous layer was extracted with
dichloromethane three times. The dichloromethane extractions were
combined and dried with anhydrous sodium sulfate and evaporated to
give the crude intermediate A. Acetic acid (2 mL) and
diaminobenezene (2 equiv of 4a) were added to a solution of
intermediate A in CH2Cl2 (10 mL) at room temperature. The mixture
was stirred vigorously, and progress of the reaction was monitored by
TLC. When the desired product 6a reached its maximum yield (about
6 h), the reaction mixture was washed with water and extracted with
dichloromethane three times. The dichloromethane extractions were
combined and dried with anhydrous sodium sulfate, concentrated to
about 2 mL by rotary evaporator, and then chromatographed on a
silica gel column and eluted with toluene/ethyl acetate = 100:1. The
green band was collected and evaporated to give 6a. Compounds 6b
and 6c were prepared using the same procedure (Table 3).
Preparation of Compounds 5. PCl5 (1.2 equiv of 4b) was added
to a solution of 4b (120 mg, 0.099 mmol) in CH2Cl2 (20 mL) at room
temperature. The mixture was stirred vigorously, and progress of the
reaction was monitored by TLC. When the starting material 4b
vanished and the desired product reached its maximum yield (about 5
min), 10 mL of water was added to the reaction mixture, and the
reaction was quenched. Then the water layer was extracted with
dichloromethane three times. The dichloromethane extraction
solutions were combined and dried with anhydrous sodium sulfate.
Then the solution was concentrated to 20 mL. SnCl2 (1.5 equiv of 4b)
was added to the concentrated solution under vigorously stirring.
When the starting material vanished and the desired intermediate
reached its maximum yield (about 10 min), 10 mL of 1 M HCl
aqueous solution was added to the reaction mixture, and the reaction
was quenched. The aqueous layer was extracted with dichloromethane
three times. The dichloromethane extraction solutions were combined
and dried with anhydrous sodium sulfate and evaporated to give the
crude intermediate A. Acetic acid (2 mL) and diaminobenezene (10
equiv of 4b) was added to a solution of intermediate A in CH2Cl2 (20
mL) at room temperature. The mixture was stirred vigorously, and
progress of the reaction was monitored by TLC. When the desired
product 5b reached its maximum yield (about 6 h), the reaction
mixture was washed with water and extracted with dichloromethane
three times. The dichloromethane extraction solutions were combined
and dried with anhydrous sodium sulfate, concentrated to about 2 mL
by rotary evaporator. and chromatographed on a silica gel column and
eluted with toluene/ethyl acetate = 100:1 (volume ratio). The green
band was collected and evaporated to give 5b. Compound 5a was
prepared using the same procedure (Table 2).
1
Characterization Data for 6a. H NMR (400 MHz, CDCl3) δ:
8.32 (s, 1H), 8.04 (s, 1H), 7.10 (d, J = 8.3 Hz, 2H), 6.98 (d, J = 8.3
Hz, 2H), 2.73−2.66(m, 1H), 2.63 (s, 3H), 2.57 (s, 3H), 1.00 (d, J =
6.4 Hz, 3H), 0.98 (d, J = 6.4 Hz, 3H). 13C NMR (125 MHz, CDCl3)
1
Characterization Data for 5a. H NMR (400 MHz, CDCl3) δ:
8.74 (d, J = 8.5 Hz, 1H), 8.65 (s, 1H), 8.13−8.07 (m, 2H), 8.03−7.92
(m, 1H), 7.41−7.28 (m, 2H), 7.06−7.00 (m, 3H), 6.91 (d, J = 7.3 Hz,
1H), 6.75 (t, J = 7.5 Hz, 1H), 6.35 (t, J = 7.4 Hz, 1H), 5.32 (s, 1H),
5.30 (d, J = 8.2 Hz, 1H), 4.48 (s, 1H), 4.47 (s, 1H). 13C NMR
a
Table 3. Preparation of compounds 6a−6c
entry
4 (mg)
product
Ar
Ar′
mg (yield, %)
1
2
3
32
6a
6b
6c
p-iPr-C6H4
A
B
C
10.1 (37)
25.7 (46)
10.0 (23)
63.6
38.8
Table 2. Preparation of Compounds 5a and 5b
entry
4 (mg)
product
Ar
mg (yield, %)
a
A = 4,5-dimethyldiaminobenezene; B = 2,3-diaminonaphthalene; C =
1
2
94
5a
5b
Ph
p-iPr-C6H4
9.1 (10)
5,6-diamino-2-(4,5-bis(hexylthio)-1,3-dithio-2-ylidene)benzo[d]-1,3-
dithiole.
120
12.7 (11)
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all signals represent 1C except noted, δ: 185.56, 185.26, 183.96,
160.67, 155.14, 151.81, 150.38, 150.36, 149.71, 149.68, 149.57, 149.48,
149.23, 149.22, 149.19, 149.18, 148.65, 147.26, 146.97, 146.77, 146.67,
146.57, 146.51, 146.45, 146.09, 146.01, 145.97, 145.94, 145.92, 145.82,
145.78, 145.36, 145.20, 144.54, 143.94, 143.84, 143.55, 143.39, 143.24,
143.15, 143.11, 143.04(2C), 142.85(2C), 142.81, 142.47, 142.10,
141.85, 141.33, 141.15, 140.39, 140.12, 139.77, 137.41, 137.29, 137.14,
136.95, 136.45, 133.99, 133.03, 131.39, 131.24, 130.56(2C),
129.19(2C), 127.15(3C), 118.72(2C), 33.62, 23.91, 22.64, 20.54,
20.50. FT-IR (microscope): 3362, 2955, 2922, 2852, 1743, 1660, 1634,
1567, 1493, 1462, 1373, 1218, 1125, 1097, 1082, 1022, 870, 844, 741
cm−1. ESI-FT-ICR-HRMS: C77H20N3O3 (M + H+) calcd 1034.1499,
found 1034.1488.
J = 7.4 Hz, 1H), 5.17 (s, 1H), 3.79 (s, 1H), 1.23 (s, 9H). ESI-FT-ICR-
HRMS: C70H18NO9 (M + H+) calcd 1016.0982, found 1016.0969.
A crystal of 7a suitable for X-ray diffraction was obtained by slow
evaporation of chloroform-d. Crystal data: triclinic, P-1. Unit cell
dimensions: a = 13.942(3) Å, α = 68.08(3)°, b = 14.382(3) Å, β =
71.71(3)°, c = 15.520(3) Å, γ = 71.78(3)°, volume = 2672.8(9) Å3.
Final R indices [I > 2σ(I)]: R1 = 0.1397 wR2 = 0.3273.
Crystallographic data have been deposited in the Cambridge
Crystallographic Data Centre as deposition no. CCDC-967767.
1
Characterization Data for 7b. H NMR (500 MHz, CDCl3) δ:
8.97 (s, 1H), 7.91 (d, J = 7.9 Hz, 2H), 7.43 (d, J = 7.9 Hz, 2H), 5.15
(s, 1H), 3.84 (s, 1H), 3.02−3.07 (m, 1H), 1.35 (d, J = 6.6 Hz, 6H),
1.22 (s, 9H). ESI-FT-ICR-HRMS: C73H24NO9 (M + H+) calcd
1058.1446, found 1058.1423.
1
Characterization Data for 6b. H NMR (400 MHz, CDCl3) δ:
1
Characterization Data for 8a. H NMR (400 MHz, CDCl3) δ:
9.15 (s, 1H), 8.84 (s, 1H), 8.25 (d, J = 7.8 Hz, 1H), 8.13 (d, J = 7.8
Hz, 1H), 7.93−7.56 (m, 2H), 7.12 (d, J = 8.1 Hz, 2H), 7.00 (d, J = 8.1
Hz, 2H), 2.65−2.74 (m, 1H), 1.01 (d, J = 6.4 Hz, 3H), 0.99 (d, J = 6.4
Hz, 3H). 13C NMR (125 MHz, CDCl3) all signals represent 1C except
noted, δ: 185.56, 185.31, 183.90, 160.10, 155.40, 151.72, 151.26,
150.33(2C), 149.70, 149.59, 149.51, 149.26(2C), 149.22(2C), 148.68,
146.93, 146.85, 146.64, 146.60, 146.53, 146.49, 146.38, 146.05, 145.96,
145.92(2C), 145.91, 145.87, 145.81, 145.34, 145.13, 144.66, 143.83,
143.78, 143.51, 143.37, 143.12, 143.00(2C), 142.98(2C), 142.83(2C),
142.80, 142.40, 141.20, 140.49, 139.97, 139.82, 139.66, 139.47, 138.93,
137.33(2C), 137.13, 136.99, 136.25, 134.76, 134.35, 134.03, 133.01,
131.26, 131.12, 130.42, 129.03, 128.79, 128.59, 128.47, 127.41,
127.27(2C), 127.09, 126.17, 118.48, 33.62, 23.92(2C). FT-IR
(microscope): 2956, 2923, 2852, 1743, 1561, 1494, 1460, 1381,
1337, 1217, 1160, 1125, 1079, 1052, 882, 842, 750 cm−1. ESI-FT-ICR-
HRMS: C79H18N3O3 (M + H+) calcd 1056.1325, found 1056.1323.
7.89 (s, 1H), 7.76 (d, J = 7.5 Hz, 2H), 7.57 (t, J = 7.8 Hz, 2H), 7.43 (t,
J = 7.4 Hz, 1H), 1.24 (s, 9H). ESI-FT-ICR-HRMS: C71H20NO9 (M +
CH3OH + H+) calcd 1030.1109, found 1030.1114.
1
Characterization Data for 8b. H NMR (500 MHz, CDCl3) δ:
8.08 (s, 1H), 7.79 (d, J = 7.9 Hz, 2H), 7.43 (d, J = 7.9 Hz, 2H), 3.02−
3.07 (m, 1H), 1.35 (d, J = 6.6 Hz, 6H), 1.24 (s, 9H). C74H26NO9 (M +
CH3OH + H+) calcd 1072.1602, found 1072.1590.
Preparation of Compounds 9. Acetic acid (1 mL) and
diaminobenezene (5 mg, 0.046 mmol)) were added to a solution of
7b and 8b (15.0 mg) in CH2Cl2 (10 mL) at room temperature. The
mixture was stirred vigorously, and progress of the reaction was
monitored by TLC. When the desired product 9b reached its
maximum yield (about 4 h), the reaction mixture was washed with
water and extracted with dichloromethane three times. The dichloro-
methane extraction solutions were combined and dried with
anhydrous sodium sulfate, concentrated, and chromatographed on a
silica gel column eluting with dichloromethane/ethyl acetate = 100:1.
The first red-orange band was collected and evaporated to give 9b.
Compound 9a was prepared using the same procedure (Table 5).
1
Characterization Data for 6c. H NMR (500 MHz, CDCl3) δ:
8.28 (s, 1H), 8.00 (s, 1H), 7.09 (d, J = 7.9 Hz, 2H), 6.96 (d, J = 7.9
Hz, 2H), 2.93 (t, J = 7.1 Hz, 2H), 2.87 (t, J = 7.1 Hz, 2H), 2.72−2.66
(m, 1H), 1.82−1.63 (m, 4H), 1.53−1.40 (m, 4H), 1.42−1.25 (m, 8H),
1.00 (d, J = 6.4 Hz, 3H), 0.98 (d, J = 6.4 Hz, 3H), 0.96−0.87 (m, 6H).
13C NMR (125 MHz, CDCl3) all signals represent 1C except noted, δ:
185.68, 185.37, 183.98, 160.17, 155.75, 151.57, 150.35(2C), 150.05,
149.71, 149.63, 149.51, 149.20(4C), 148.63, 147.02, 146.91, 146.71,
146.65, 146.55, 146.47, 146.37, 146.14, 145.98(2C), 145.87(2C),
145.85, 145.32, 145.18, 144.79, 143.92, 143.81, 143.53, 143.38, 143.19,
143.07(2C), 143.06(2C) 143.00, 142.89(2C), 142.84(2C), 142.34,
142.01(2C), 141.22, 140.20, 139.51, 139.48, 138.80, 137.45, 137.27,
137.01(2C), 136.26, 133.88, 133.02, 131.31, 131.23, 128.16, 127.97,
127.43, 127.22(2C), 125.58, 121.91, 120.68, 118.69(2C), 115.08,
109.04, 36.49, 36.44, 33.64, 31.40, 31.36, 29.87, 29.79, 28.34, 28.29,
23.92(2C), 22.63, 22.58, 14.10, 14.06. FT-IR (microscope): 2954,
2924, 2853, 1743, 1560, 1493, 1456, 1342, 1157, 1125, 1098, 1052,
1019, 868, 840, 775, 755 cm−1. ESI-FT-ICR-HRMS: C91H40N3O3S6
(M + H+) calcd 1414.1388, found 1414.1360.
Table 5. Preparation of Compounds 9a and 9b
entry
7 and 8 (mg)
product
Ar
mg (yield, %)
1
2
52.2
15.0
9a
9b
Ph
p-iPr-C6H4
36.7 (61)
14.6 (82)
1
Characterization Data for 9a. H NMR (400 MHz, CDCl3) δ:
8.44 (s, 1H), 8.15 (d, J = 6.0 Hz, 1H), 8.14 (s, 1H), 7.95−7.82 (m,
3H), 7.76 (d, J = 7.6 Hz, 2H), 7.62 (t, J = 7.8 Hz, 2H), 7.45 (t, J = 7.4
Hz, 1H), 6.78 (d, J = 7.4 Hz, 1H), 6.67 (t, J = 7.4 Hz, 1H), 6.23 (t, J =
7.4 Hz, 1H), 4.89 (d, J = 7.5 Hz, 1H), 4.61 (s, 1H), 4.22 (s, 1H), 4.15
(s, 1H), 1.06 (s, 9H). 13C NMR (CDCl3, 125 MHz): all signals
represent 1C except noted, δ: 190.62, 162.41, 154.97, 151.25, 150.93,
150.86, 150.84, 150.41, 150.04, 149.61, 149.44, 149.18, 148.93(2C),
148.85, 148.80, 148.71, 148.41, 148.34, 148.27(2C), 148.23, 147.97,
147.88, 147.84, 147.71, 147.61, 147.53, 147.23, 147.13(2C), 146.23,
145.39, 145.34, 145.21, 144.41, 144.25, 143.94, 143.66, 143.27, 143.04,
142.51, 142.29, 141.38, 141.07, 141.03, 140.65, 139.42, 139.21, 139.06,
138.85, 137.88, 136.31, 135.98, 134.86, 134.27, 131.98, 131.17, 130.73,
130.31, 130.09, 129.01, 128.49, 128.44(2C), 126.94, 122.60(2C),
122.38, 120.08, 117.48, 114.50, 114.12, 108.10, 86.56, 81.32, 79.08,
76.52, 64.81, 26.60(3C). ESI-FT-ICR-HRMS: C82H28N5O6 (M + H+)
calcd 1178.2034, found 1178.2002.
Preparation of Compounds 7 and 8. CF3SO3H (1.5 equiv of
4b) in 2 mL of dichloromethane was added to a solution of 4b (34.7
mg, 0.0286 mmol) in CH2Cl2 (10 mL) at room temperature. The
mixture was stirred vigorously, and progress of the reaction was
monitored by TLC. When the starting material 4b vanished and the
desired product 7b and 8b reached its maximum yield (about 0.5 h),
the reaction mixture was directly chromatographed on a silica gel
column and eluted with dichloromethane/ethyl acetate = 20:1. The
orange band was collected and evaporated to give 7b and 8b.
Compounds 7a and 8a were prepared using the same procedure
(Table 4).
1
Characterization Data for 9b. H NMR (500 MHz, CDCl3) δ:
8.45 (s, 1H), 8.32 (s, 1H), 8.20 (d, J = 8.2 Hz, 1H), 7.99−7.88 (m,
2H), 7.86−7.83 (m, 3H), 7.49 (d, J = 8.0 Hz, 2H), 6.77 (d, J = 7.4 Hz,
1H), 6.66 (t, J = 7.4 Hz, 1H), 6.24 (d, J = 7.4 Hz, 1H), 4.91 (d, J = 7.6
Hz, 1H), 4.60 (s, 1H), 4.20 (s, 1H), 4.15 (s, 1H), 3.15−3.07 (m, 1H),
1.42 (d, J = 6.8 Hz, 6H), 1.04 (s, 9H). 13C NMR (125 MHz, CDCl3)
all signals represent 1C except noted, δ: 190.58, 161.60, 154.97,
151.28, 150.96, 150.88, 150.86, 150.44, 150.09, 149.64, 149.47, 149.20,
148.96(2C), 148.88, 148.83(2C), 148.75, 148.44, 148.36, 148.30(2C),
148.29, 148.11, 148.04(2C), 147.92, 147.63, 147.57, 147.30, 147.18,
146.31, 145.42, 145.36, 145.24, 144.55, 144.47, 144.40, 143.99, 143.73,
1
Characterization Data for 7a. H NMR (400 MHz, CDCl3) δ:
8.80 (s, 1H), 7.93 (d, J = 7.5 Hz, 2H), 7.57 (t, J = 7.8 Hz, 2H), 7.37 (t,
Table 4. Preparation of Compounds 7a+8a and 7b+8b
entry
4 (mg)
product
Ar
mg (yield, %)
1
2
46
7a+8a
7b+8b
Ph
p-iPr-C6H4
21.1 (52)
15.0 (50)
34.7
2161
dx.doi.org/10.1021/jo5000048 | J. Org. Chem. 2014, 79, 2156−2162

The Journal of Organic Chemistry
Article
143.34, 143.04, 142.92, 142.60, 142.34, 141.38, 141.11, 140.68, 140.34,
139.45, 139.23, 139.09, 138.87, 137.89, 136.41, 136.00, 134.93, 134.38,
131.88, 131.12, 130.72, 130.35, 130.01, 129.04, 126.47(2C),
123.86(2C), 122.39, 120.07, 117.50, 114.54, 114.16, 108.07, 86.59,
81.26, 79.09, 76.63, 64.89, 34.14, 26.61(3C), 24.17, 24.14. ESI-FT-
ICR-HRMS: C85H34N5O6 (M + H+) calcd 1220.2504, found
1220.2527.
Peregudov, A. S.; Soulimenkov, I. V.; Polyakova, N. V.; Troshin, P. A.
Chem.Eur. J. 2010, 16, 12947.
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2005, 127, 26.
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Wudl, F. Science 1995, 269, 1554. (b) Nuber, B.; Hirsch, A. Chem.
Commun. 1996, 1421. (c) Vostrowsky, O.; Hirsch, A. Chem. Rev. 2006,
106, 5191. (d) Zhang, G. H.; Huang, S. H.; Xiao, Z.; Chen, Q.; Gan, L.
B.; Wang, Z. M. J. Am. Chem. Soc. 2008, 130, 12614. (e) Huang, H.;
Zhang, G. H.; Wang, D.; Xin, N. N.; Liang, S. S.; Wang, N. D.; Gan, L.
B. Angew. Chem., Int. Ed. 2013, 52, 5037.
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Commun. 2003, 148.
(11) (a) Bouit, P.-A.; Spanig, F.; Kuzmanich, G.; Krokos, E.; Oelsner,
C.; Garcia-Garibay, M. A.; Delgado, J. L.; Martin, N.; Guldi, D. M.
Chem.Eur. J. 2010, 16, 9638. (b) Villegas, C.; Krokos, E.; Bouit, P.-
A.; Delgado, J. L.; Guldi, D. M.; Martin, N. Energy Environ. Sci. 2011, 4,
679.
Procedure for Preparation of Compounds 10. 5,6-Diamino-2-
(4,5-bis(hexylthio)- 1,3-dithio-2-ylidene)benzo[d]-1,3-dithiole (158
mg, 0.306 mmol) and ninhydrin (54.5 mg, 0.306 mmol) were
dispersed in EtOH (20 mL). The mixture was heated to reflux for 2 h.
A deep blue solid was observed in the solution. The reactants were
cooled to room temperature, and the resulting solid was obtained by
filtration. After the solid was washed with EtOH several times, pure
product 10 was obtained (155.6 mg, yield: 79%). Characterization data
for 10. 1H NMR (400 MHz, CDCl3) δ: 7.81 (d, J = 7.1 Hz, 1H), 7.70
(d, J = 7.1 Hz, 1H), 7.66−7.54 (m, 2H), 7.47−7.40 (2H), 2.80 (t, J =
7.2 Hz, 4H), 1.77−1.52 (m, 4H), 1.45−1.40 (4H), 1.31−1.29 (8H),
0.90 (t, J = 6.5 Hz, 6H). 13C NMR (100 MHz, CDCl3) all signals
represent 1C except noted, δ: 188.99, 156.28, 148.25, 144.43, 141.64,
141.57, 141.13, 140.77, 136.31, 136.25, 131.96, 127.45, 127.26, 124.26,
122.04, 121.37, 119.90, 114.10, 106.77, 36.16(2C), 31.24(2C), 29.65,
29.63, 28.16(2C), 22.46(2C), 13.95(2C). FT-IR (microscope): 2955,
2926, 2855, 1731, 1608, 1465, 1448, 1330, 1191, 1171, 1140, 1094,
1045, 914, 888, 866, 776, 731 cm−1. ESI-FT-ICR-HRMS:
C31H32N2OS6 (M+) calcd 640.0833, found 640.0841.
(12) Ince, M.; Hausmann, A.; Martinez-Diaz, M. V.; Guldi, D. M.;
Torres, T. Chem. Commun. 2012, 48, 4058.
ASSOCIATED CONTENT
* Supporting Information
Selected spectroscopic data for all new compounds and
crystallographic data for 5b and 7a (CIF). This material is
available free of charge via the Internet at http://pubs.acs.org.
(13) (a) Murata, M.; Murata, Y.; Komatsu, K. Chem. Commun. 2008,
6083. (b) Vougioukalakis, G. C.; Roubelakis, M. M.; Orfanopoulos, M.
Chem. Soc. Rev. 2010, 39, 817. (c) Gan, L. B.; Yang, D. Z.; Zhang, Q.
Y.; Huang, H. Adv. Mater. 2010, 22, 1498. (d) Shi, L. J.; Gan, L. B. J.
Phys. Org. Chem. 2013, 26, 766.
(14) Liu, S. M.; Zhang, C. Q.; Xie, X.; Yu, Y. Y.; Dai, Z. F.; Shao, Y.
H.; Gan, L. B.; Li, Y. L. Chem. Commun. 2012, 48, 2531.
(15) Xiao, Z.; Ye, G.; Liu, Y.; Chen, S.; Peng, Q.; Zuo, Q. Q.; Ding, L.
M. Angew.Chem. Int. Ed. 2012, 51, 9038.
(16) For recent examples, see: (a) Xu, L.; Zhang, Q. Y.; Zhang, G.;
Liang, S. S.; Yu, Y. M.; Gan, L. B. Eur. J. Org. Chem. 2013, 7272.
(b) Xin, N. N.; Yang, X. B.; Zhou, Z. S.; Zhang, J. X.; Zhang, S. X.;
Gan, L. B. J. Org. Chem. 2013, 78, 1157. (c) Shi, L. J.; Yang, D. Z.;
Colombo, F.; Yu, Y. M.; Zhang, W.-X.; Gan, L. B. Chem.Eur. J. 2013,
19, 16545.
(17) (a) Yu, Y. M.; Shi, L. J.; Yang, D. Z.; Gan, L. B. Chem. Sci. 2013,
4, 814. (b) Yu, Y. M.; Xie, X.; Zhang, T.; Liu, S. M.; Shao, Y. H.; Gan,
L. B.; Li, Y. L. J. Org. Chem. 2011, 76, 10148.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: gan@pku.edu.cn.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support was provided by NNSFC (Grant Nos.
21272013 and 21132007) and MOST (2011CB808401). We
thank Z. Xiao and L. M. Ding for CV measurements.
(18) (a) Xin, N. N.; Huang, H.; Zhang, J. X.; Dai, Z. F.; Gan, L. B.
Angew. Chem., Int. Ed. 2012, 51, 6163. (b) Zhang, J. X.; Xin, N. N.;
Gan, L. B. J. Org. Chem. 2011, 76, 1735.
(19) Kooistra, F. B.; Leuning, T. M.; Martinez, E. M.; Hummelen, J.
C. Chem. Commun. 2010, 46, 2097.
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