Core expansion of perylenetetracarboxdiimide dyes with anthraquinone units for electron-accepting materials

Article abstract of DOI:10.1002/ejoc.201200980

A perylenetetracarboxdiimide derivative containing an anthraquinone unit has been synthesized by the phototriggered intramolecular cyclization of 2-anthraquinone-substituted perylenetetracarboxdiimide. The anthraquinone- substituted perylenetetracarboxdii

Full text of DOI:10.1002/ejoc.201200980

FULL PAPER
DOI: 10.1002/ejoc.201200980
Core Expansion of Perylenetetracarboxdiimide Dyes with Anthraquinone Units
for Electron-Accepting Materials
Liang Xu,[a,b] Chao Liu,[a,b] Zhihong Qin,[a,b] Runsheng Jiang,[a,b] and Yongjun Li*[a]
Keywords: Dyes/pigments / Chromophores / Photovoltaic device / Electron transfer / Fused-ring systems / Cyclization /
Electrochemistry / Density functional calculations
A
perylenetetracarboxdiimide derivative containing an
electron-accepting abilities with four reversible reduction
potentials. Photovoltaic devices of ITO/PEDOT:PSS/
P3HT:PDIs/Ca/Al were fabricated and power conversion effi-
ciencies of 0.16 and 0.39 were obtained for 1 and 2, respec-
tively.
anthraquinone unit has been synthesized by the phototrig-
gered intramolecular cyclization of 2-anthraquinone-substi-
tuted perylenetetracarboxdiimide. The anthraquinone-sub-
stituted perylenetetracarboxdiimide dyes showed excellent
zuki,[10] Stille,[11] and Sonogashira reactions,[12] or by tradi-
tional nucleophilic substitutions[13] and Diels–Alder reac-
tions.[14] For bay-substituted PDIs, photocyclization is an
efficient way to obtain ring-expanded molecules. We have
previously prepared core-extended perylene chromophores
by phototriggered intramolecular cyclization of perylenete-
tracarboxdiimides functionalized with a phenyl group, ni-
trogen-containing five-membered heteroaromatic rings
(imidazole, 1,2,4-triazole, and pyrazole), and an anthracene
group.[15]
Introduction
Perylenetetracarboxdiimide derivatives (PDIs) as organic
chromophores have been widely used in sensors,[1] logic
gates,[2] molecular machines,[3] organic electronic devices,[4]
organic photovoltaic devices,[5] organic field-effect transis-
tors,[6] and NIR absorbing dyes[7] owing to their thermal
and photochemical stabilities, high molar extinction coeffi-
cients, high fluorescence quantum yields, and exceptional
electron-accepting abilities. To further improve their physi-
cal and chemical properties, considerable attention has been
directed towards the modification of PDIs through high-
yielding synthetic routes. Two approaches are usually
adopted. One is to introduce substituents at the imide nitro-
gen atoms,[8] the other is to introduce substituents with elec-
tron-donor or -acceptor groups at the aromatic core in the
bay region, which could dramatically change the properties
of the PDIs. Not only the perylene core, but also the linkage
between the substituents and the PDI can be twisted by
direct C–C coupling of substituents in the bay positions. On
the one hand, this twisting could help to improve the solu-
bility of the PDIs by reducing π–π interactions between the
PDIs,[4b] but on the other hand, the twisting might weaken
the π-conjugative interactions due to the loss of planarity
of the molecules. Usually, bay-functionalized perylenetetra-
carboxdiimides are obtained from the corresponding
brominated derivatives.[9] Replacement of the bromo group
is achieved by metal-catalyzed C–C coupling, such as Su-
In most cases, perylenetetracarboxdiimides are employed
as electron-accepting units,[16] although on some occasions
they can also be used as electron-donating units.[17]
Whether a PDI acts as a donor or an acceptor clearly de-
pends on the nature of the substituent.[17c] When good elec-
tron acceptors such as fullerenes are attached to PDIs, elec-
tron transfer from the PDI to the fullerene can be ob-
served.[17a,18] As a traditional colorant, quinones are widely
used in the dyestuff industry.[19] In addition, they are also
involved in electron transport in biological systems and in
the photosynthesis of bacteria and plants.[20] Recently,
quinones have found applications in sensors,[19] optical re-
cording media,[21] and solar energy conversion.[22] Among
the derivatives of quinones, 9,10-anthraquinone (AQ) is
widely known as an electron-accepting group with low re-
duction potentials.[20a] In addition, the preparation of AQ
is relatively simple and it can be easily incorporated into π-
conjugated systems.[23] In light of this, we designed two new
PDI derivatives 1 and 2 with the 2-anthraquinone moiety
attached to the bay region. The solubility of 2 was ef-
ficiently improved because of the reduced π–π interactions
and the increased polarity of the molecule. Through the
phototriggered intramolecular cyclization of 2-anthra-
quinone-substituted perylenetetracarboxdiimide 2, we ob-
tained zigzag constitutional compound 1 in which the aro-
matic π system of the perylenetetracarboxdiimide is length-
[a] Beijing National Laboratory for Molecular Sciences (BNLMS),
CAS Key Laboratory of Organic Solids, Institute of Chemistry,
Chinese Academy of Sciences,
Beijing 100190, P. R. China
E-mail: liyj@iccas.ac.cn
Homepage: http://english.ic.cas.cn/
[b] Graduate University of Chinese Academy of Sciences,
Beijing 100049, P. R. China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200980.
300
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Dyes for Electron-Accepting Materials
ened along the equatorial axis. The photo- and electro- spectrum recorded for 2 shows a combination of an anthra-
chemical properties of these perylenetetracarboxdiimide quinone unit (200–300 nm) and a perylenetetracarboxdi-
dyes were also investigated, as were their applications in imide unit (450–550 nm). Because of steric constraints, the
photovoltaic devices.
anthraquinone moiety is rotated out of the perylene plane
with a dihedral angle of 56.1° (see Figure S4 in the Support-
ing Information) and so the π-conjugative interactions are
weakened; as a consequence, in comparison to the λmax
value of unsubstituted PDI (527 nm), the λmax for 2 is only
slightly redshifted by 3 nm to 530 nm. After cyclization, the
λmax value of 1 is blueshifted by 21 nm to 506 nm, partly
due to the electron affinity of the anthraquinone moiety.
The blueshifted absorption of 1 suggests that more energy
is needed for the optical transition.[29] Meanwhile, a new
absorption band peak at 346 nm can be seen. Compared
with unsubstituted PDI and 2, the absorption bands of 1
span a wider range in the UV/Vis spectrum. The maximum
extinction coefficient for 2 is 41139 m–1 cm–1, whereas that
of 1 is 55816 m–1 cm–1; the difference between these two val-
ues can be attributed to the large twist in compound 2.
Results and Discussion
Synthesis
The synthesis of compounds 2 and 1 is outlined in
Scheme 1. One of the starting materials, 2-(9,10-dioxo-9,10-
dihydroxy-2-anthryl)-4,4,5,5-tetramethyl-1,3,2-dioxaborol-
ane (4) was synthesized in two steps according to a litera-
ture report.[24] First, 2-aminoanthraquinone was converted
into 2-bromoanthraquinone by the Sandmeyer reaction.
Secondly, 2-bromoanthraquinone was treated with bis-
(pinacolato)diboron to give AQ-boronic ester 4. Another
starting material, 1-bromoperylenetetracarboxdiimide 3,
was again obtained according to the literature.[25] Suzuki
coupling of compounds 4 and 3 gave compound 2 in 81%
yield. Subsequent exposure to sunlight produced compound
1 in 90% yield within 5 min.
The colors and fluorescence emissions of unsubstituted
PDI, 2, and 1 are shown in Figure S2 in the Supporting
Information. The unsubstituted PDI is an orange color and
displays a light-yellow fluorescent emission. Introduction of
the anthraquinone substituent in the bay position caused a
redshift in the color, with 2 being a red color and exhibiting
a light-red emission. Cyclization of 2 in sunlight led to a
blueshift, with 1 a green-yellow color and displaying weak
green-yellow fluorescence emission.
The UV/Vis absorption and fluorescent spectra of 2 and
1 are presented in Figure 1 and the data are summarized in
Table 1. According to the literature,[11,26] unsubstituted PDI
Figure 1. UV/Vis absorption and fluorescence emission spectra of
shows an absorption band (450–550 nm) peak at 527 nm 2 and 1 in CH2Cl2.
with characteristic vibronic fine structure, which has been
attributed to perylene core πǞπ* transitions.[27] The ab-
In comparison with unsubstituted PDI (534 nm), the
sorption band at the longer wavelength can be assigned to maximum emission of 2 is redshifted by 45 nm to 579 nm,
the electronic S0 ǞS1 transition with the dipole moment with a Stokes shift of 49 nm, and the fluorescent quantum
along the long molecular axis, whereas the absorption band yield is about 0.78, measured relative to unsubstituted PDI
at the lower wavelength can be assigned to the electronic in CH2Cl2 solution as reference.[26a] Unsubstituted 9,10-
S0 ǞS2 transition with the dipole moment perpendicular to anthraquinone itself shows no photoluminescence. The de-
the long molecular axis.[13,28] The AQ group exhibits an ab- crease in the fluorescence intensity of the perylene core in
sorption band in the region 200–300 nm.[20b] The UV/Vis 2 is due to steric twisting of the perylene ring and the elec-
Scheme 1. Synthetic route to compounds 2 and 1. Reagents and conditions: a) KCO3, [Pd(Ph3P)4], toluene/ethanol (3:1); b) hν (sunlight
or sun lamp), CH2Cl2.
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301

L. Xu, C. Liu, Z. Qin, R. Jiang, Y. Li
FULL PAPER
Table 1. Photophysical and electrochemical data for 2 and 1.
and dipole moment are the major factors that affect the
optical properties. Increasing the polarity of the solvent
could lead to redshifts of the optical spectra and quenching
of the fluorescence emission. Protonic solvents may facili-
tate the formation of hydrogen bonds between the anthra-
quinone unit and hydrogen proton, which might also cause
weak redshifts.
The redox potentials of these compounds were deter-
mined by cyclic voltammetry in dichloromethane (Fig-
ure 2). The data are summarized in Table 1. According to
the literature,[33] one reversible oxidation potential at 1.65 V
(vs. SCE) and two reversible reduction potentials at –0.53
and –0.75 V (vs. SCE) were observed for unsubstituted
PDI. For anthraquinone-substituted PDI 2, one reversible
oxidation potential and four reversible reduction potentials
appeared, whereas for cyclized product 1, only four revers-
ible reduction potentials emerged. The oxidation potential
versus SCE is 1.71 V for 2. The reduction potentials versus
SCE are –0.55, –0.76, –1.04, and –1.38 V for 2, and –0.60,
–0.83, –1.16, and –1.45 V for 1. Compared with unsubsti-
tuted PDI, the oxidation potential of 2 is positively shifted
by 0.06 V, which indicates that the electron-deficient anthra-
Compound
2
1
Absorption[a] λmax [nm]
530
41139
579
0.78
506
55816
581
0.050
75
ε[a] [m–1 cm–1]
Fluorescence[b] λmax [nm]
[c]
Φfl
Stokes shift
49
Eox [V vs. SCE][d]
Ered [V vs. SCE][d,e]
1.71[e]
–0.55, –0.76,
–1.04, –1.38
–6.11/–3.85
2.26
–0.60, –0.83,
–1.16, –1.45
–/–3.80
HOMO/LUMO [eV][f]
Eg [eV][f]
[a] Measured in CH2Cl2 solution (1.0ϫ10–5 m). [b] Measured in
CH2Cl2 solution (1.0ϫ10–6 m) upon excitation at 500 nm. [c] In
CH2Cl2, N,NЈ-bis(2,6-diisopropylphenyl)perylene-3,4:9,10-tetracar-
boxylic acid diimide (unsubstituted PDI, Φfl = 1 in CHCl3)[26a] was
used as standard. [d] Performed in CH2Cl2 under N2 by using
nBu4NPF6 (0.05 m) as the supporting electrolyte, platinum as the
counter electrode, glassy carbon as the work electrode, and the sat-
urated calomel electrode (SCE) as the reference electrode. [e] Half-
wave potentials are given. [f] The HOMO and LUMO levels were
obtained directly from CV according to the method reported in the
literature.[36]
tron-accepting character of anthraquinone.[30] The cyclized quinone moiety renders oxidation more difficult. Further-
product 1 shows a maximum emission at 581 nm, which is more, after cyclization, the oxidation peak of 1 disappears,
redshifted by 47 and 2 nm compared with unsubstituted which may be due to intramolecular charge transfer from
PDI and 2, respectively. Meanwhile, the fluorescent quan- the perylenetetracarboxdiimide group to the anthraquinone
tum yield of 1 is only 0.050. The significant quenching of group.[34] The electronic communication between the PDI
the fluorescent intensity of 1 is possibly a result of efficient and AQ units might be reduced significantly as a result of
intramolecular electron transfer between the perylenetetra- the large twisting of the conjugated core, as verified by
carboxdiimide donor and the anthraquinone acceptor in- theoretical calculations (see Figure S4 in the Supporting In-
duced by excitation of the electron-donating perylenetetra- formation), and thus the two units are relatively indepen-
carboxdiimide chromophore.[31] The Stokes shift for 1 is dent such that the first two reduction potentials for 2 are
75 nm. The relatively large variation of the Stokes shift almost the same as those of unsubstituted PDI.[5b] How-
upon cyclization might be attributed to the stabilization of ever, after cyclization, the first two reduction potentials of
the HOMO by the anthraquinone acceptor and the destabi- 1 are negatively shifted by 0.05 and 0.07 V compared with
lization of the LUMO by the perylenetetracarboxdiimide those of 2, respectively. These shifts are probably due to the
donor.[32]
planar core of 1, which facilitates electronic communication
The photophysical properties of 2 and 1 in different sol- between the perylenetetracarboxdiimide and anthraquinone
vents were also investigated (see Figure S3 and Table S3 in units and renders intramolecular charge transfer between
the Supporting Information). Compared with the absorp- the two units more efficient.[35] The extended π-conjugated
tion spectra recorded in dichloromethane, blueshifts were system would increase the resonance energy and delocalize
only observed in cyclohexane and dibutyl ether. In cyclo- the negative charge more effectively, which could explain
hexane, the absorption λmax values of 2 and 1 are blue- why the fourth reduction potential is closer to the third re-
shifted by 12 and 10 nm, respectively, whereas in dibutyl duction potential in the case of 1.
ether blueshifts of 10 and 8 nm were observed. The absorp-
tion spectra show small changes in other solvents. The fluo-
rescence spectra are also influenced by solvent polarity.
Clear blueshifts were observed in the spectra recorded in
cyclohexane and dibutyl ether, whereas redshifts were de-
tected in methanol and DMF. In cyclohexane, the fluores-
cence emission λmax values of 2 and 1 are blueshifted by 8
and 13 nm, whereas in dibutyl ether blueshifts of 5 and
10 nm occur. In contrast, the fluorescence emission λmax
values of 2 and 1 are redshifted by 6 and 3 nm in methanol,
and by 4 and 4 nm in DMF. Meanwhile, significant fluores-
cence quenching was observed in strongly polar protonic
solvents. For example, the fluorescent quantum yields of 2
and 1 are only 0.24 and 0.038 in methanol. The polarity Figure 2. Cyclic voltammograms of 2 and 1 vs. SCE in CH2Cl2.
302
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Dyes for Electron-Accepting Materials
The HOMO and LUMO energy levels and the energy
gap of 2 and the LUMO energy level of 1 were evaluated
from the cyclic voltammograms. For unsubstituted PDI, the
HOMO and LUMO levels are –6.05 and –3.87 eV, respec-
tively, and the energy gap is 2.18 eV. The corresponding val-
ues for 2 are –6.11, –3.85, and 2.26 eV, whereas the LUMO
level for 1 is –3.80 eV. Thus, the anthraquinone substituent
in 2 lowers the HOMO level and moves the charge density
from the HOMO of the perylenetetracarboxdiimide core to
the LUMO of the anthraquinone substituent such that the
positive charge density resides on the perylenetetracarb-
oxdiimide core.[37] In this circumstance, better planarity of
the molecules would result in greater charge transfer and
delocalization leading to a LUMO with a higher energy.[38]
For the perylenetetracarboxdiimide core, the changes in
optical and redox properties are primarily due to the induc-
tive effect of the groups on the frontier orbitals. To investi-
gate the spectroscopic properties of these compounds from
a theoretical point of view, the molecular frontier orbitals
of 2 and 1 were studied by DFT at the B3LYP/6-31tG*
level of theory by using the Gaussian 03 program.[39] The
molecular orbital (MO) map of 2 (Figure 3) shows that
both the HOMO and LUMO are localized over the per-
ylenetetracarboxdiimide moiety, which indicates that no
charge transfer occurs in 2 in the ground state. As a result,
Figure 3. Calculated frontier orbitals for (a) the HOMO of 2,
(b) the LUMO of 2, (c) the HOMO of 1, and (d) the LUMO of 1.
in 2, the PDI and AQ units maintain their individual op- date the performances of solution-processed devices based
tical characteristics. For 1, the charge density in the HOMO on P3HT and PDIs have been rather poor (normally below
and LUMO is not simply concentrated on the perylenete- 0.05%).[4b] BHJ solar cell devices based on P3HT and com-
tracarboxdiimide ring, it is also located over the fused link- mercially available unsubstituted PDI only exhibit efficienc-
age between the perylenetetracarboxdiimide and the ies of 0.18%.[5b] Recently, BHJ solar cell devices composed
anthraquinone moiety. The calculated HOMO and LUMO of blends of P3HT and an asymmetric PDI derivative ex-
energies and the energy gap of 2 are –5.99, –3.54, and hibited efficiencies of 0.37%.[4b]
2.45 eV, which are in good agreement with the electrochemi-
As we discussed earlier, the absorption ranges of 2 and 1
cal experimental data, and the values calculated for 1 rela- are located in the middle of the visible region with suitable
tive to 2 are the same. The anthraquinone moiety plays an extinction coefficients. The LUMO energies of 2 (–3.85 eV)
important role in the LUMO+1 and LUMO+2 as a result and 1 (–3.80 eV) are close to that of PCBM ([6,6]-phenyl-
of its electron-withdrawing nature (see Figure S4 in the C61-butyric acid methyl ester) (–3.71 eV). The LUMO gap
Supporting Information). The quantum chemical calcula- (1.17 or 1.22 eV) and HOMO gap (1.40 eV) between P3HT
tions are in good agreement with the UV/Vis spectra and and 2 or 1 are large enough to guarantee efficient exciton
electrochemical data. The optimized configurations of 2 dissociation.[46] The difference between the LUMO of 2 and
and 1 show that the mean plane of the anthraquinone ring the HOMO of P3HT is as large as 1.40 eV, which could
is not parallel to the mean plane of the perylene ring, hav- lead to a high open circuit voltage (VOC) for solar cells.[47]
ing dihedral angles of 56.1 and 5.5°. Thus, upon cyclization, Thermogravimetric analysis (TGA) of 2 and 1 revealed that
the anthraquinone moiety and perylenetetracarboxdiimide they are both thermally stable over 350 °C. Given the
ring in 1 lie approximately in one plane, which leads to bet- features of 2 and 1, we investigated the performances of
ter conjugation and electron delocalization.
devices based on P3HT and 2 or 1. The indium/tin oxide
We also investigated the photovoltaic properties of 2 and (ITO) (150 nm)/poly(ethylenedioxythiophene):poly(styrene-
1. As we know, perylene diimide derivatives with large and sulfonic acid) (PEDOT:PSS, CLEVIOS A1 4083) (50 nm)/
tunable molar absorption coefficients have potential as P3HT:PDIs (100 nm)/Ca/Al devices were fabricated by
light-absorbing materials rather than purely as transport spin-coating a thin-layer of PEDOT:PSS onto the ITO glass
materials,[40] exhibit good electron-accepting properties,[41] substrate. Figure 4 shows the J–V curves for the devices
and may be highly conducting along the π–π stacking based on 2 and 1.
axis.[42] In addition, they are more easily functionalized
The photovoltaic properties including open circuit volt-
than fullerenes.[43] Thus, PDIs provide a much larger choice ages (VOC), short circuit current densities (JSC), fill factors
of acceptor materials for use in bulk heterojunction (BHJ) (FF), and power conversion efficiencies (PCEs) of the de-
solar cell devices.[5b,44] The electron-donating conjugated vices with 1:1 donor/acceptor weight ratios are summarized
polymers used in BHJ solar cell devices at present are in Table 2. Because VOC is related to the gap between the
mainly poly(3-hexylthiophene)s (P3HT).[45] However, to LUMO of the acceptor and the HOMO of the donor,[48] an
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303

L. Xu, C. Liu, Z. Qin, R. Jiang, Y. Li
FULL PAPER
Conclusions
Zigzag constitutional perylenetetracarboxdiimide deriva-
tive 1 containing an anthraquinone unit has been synthe-
sized by phototriggered intramolecular cyclization of 2-
anthraquinone-substituted perylenetetracarboxdiimide 2.
Significant visible color and fluorescence changes were ob-
served after cyclization. The two materials exhibit strong
electron-accepting abilities. Their application in organic so-
lar cells was also investigated with power conversion effi-
ciencies of 0.39 and 0.16 obtained for 2 and 1, respectively.
Although PDIs seem less suitable than fullerenes as compo-
nents of photovoltaic cells, we still believe that the role of
PDI dyes in organic solar cell devices remains bright.
Figure 4. J–V curves for the P3HT/PDIs devices with SA and PTA
treatment under AM 1.5 G illumination at 100 mWcm–2 (SA =
solvent annealing; PTA = pre-thermal annealing).
Experimental Section
acceptor with a lower LUMO causes a device to have a
lower VOC. This is borne out by the lower VOC level of the
device based on 2. In general, large π systems such as PDIs
are inclined to close molecular π–π packing, which has two
effects on efficiency. On one hand, it may be beneficial to
electron charge carriers and, on the other, it may aggravate
the intermolecular charge recombination.[49] Therefore find-
ing a balance between favorable molecular packing and a
suitable distorted molecular geometry is a key goal to real-
izing a high efficiency. Thus, in our view, it seems that with
the help of large substituents such as the anthraquinone
group in the bay positions, the molecular packing of PDI
could be largely suppressed and consequently the intermo-
lecular charge recombination minimized. At the same time,
this torsion of molecules does not lower the rate of charge
carriers significantly. Perhaps this is the reason why the
value of JSC for 2 is higher than that for 1. Finally, solar
cells with 2 exhibited a power conversion efficiency of
0.39%, which is more than two-fold that of the efficiency
(0.16%) achieved with 1.
Materials and Characterization: All reagents were obtained from
commercial suppliers and used as received unless otherwise noted.
Column chromatography was performed on silica gel (160–
200 mesh) and TLC was performed on precoated silica gel plates
and observed under UV light. NMR spectra were recorded with
Bruker Avance DPS-400 and DPS-600 spectrometers at room tem-
perature (298 K). Chemical shifts are referenced to residual solvent
peaks. MALDI-TOF MS was performed with a Bruker Biflex III
mass spectrometer. Electronic absorption spectra were recorded
with a JASCO V-579 spectrophotometer. Fluorescence excitation
and emission spectra were recorded with a Hitachi F-4500 fluorim-
eter.
Synthesis of 2: 1-Bromo-N,NЈ-bis(2,6-diisopropylphenyl)perylene-
3,4:9,10-tetracarboxdiimide (3; 158 mg, 0.2 mmol) and 2-(9,10-di-
oxo-9,10-dihydro-2-anthryl)-4,4,5,5-tetramethyl-1,3,2-dioxaborol-
ane (4; 99 mg, 0.3 mmol) were dissolved in toluene/ethanol (30 mL/
10 mL) and K2CO3 (42 mg) was added. [Pd(PPh3)4] (ca. 5 mg) was
added after bubbling N2 through the solution for 30 min. After
stirring at 80 °C for 3 h, the reaction mixture was concentrated in
vacuo. The resulting solid was dissolved in CH2Cl2 (50 mL),
washed with H2O (20 mL), and dried with anhydrous Na2SO4.
Concentrated in vacuo and purified by column chromatography
(CH2Cl2/hexane as eluent), yield 148 mg, 81%, m.p. Ͼ400 °C (de-
comp.). 1H NMR (400 MHz, CDCl3): δ = 8.87–8.82 (m, 2 H), 8.79–
8.76 (m, 2 H), 8.69 (s, 1 H), 8.54 (d, J = 8 Hz, 1 H), 8.49 (s, 1 H),
8.40 (d, J = 8 Hz, 1 H), 8.33 (d, J = 8 Hz, 1 H), 8.19 (d, J = 8 Hz,
1 H), 8.07 (d, J = 8 Hz, 1 H), 7.90–7.85 (m, 3 H), 7.53–7.45 (m, 2
H), 7.38–7.31 (m, 4 H), 2.80–2.71 (m, 4 H), 1.21–1.12 (m, 24
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 182.79, 182.56, 163.59,
163.56, 163.35, 163.29, 148.73, 145.77, 145.65, 139.73, 135.83,
135.54, 135.33, 134.82, 134.73, 134.59, 133.68, 133.58, 133.55,
133.30, 132.20, 132.10, 130.76, 130.66, 130.48, 129.90, 129.84,
129.69, 129.53, 128.56, 127.95, 127.70, 127.64, 124.24, 123.64,
123.50, 123.31, 123.02, 122.85, 32.05, 29.41, 29.29, 24.14, 22.82,
14.24 ppm. MS (MALDI-TOF): m/z = 916.3 [M]+. C62H50N2O4
(887.09): calcd. C 81.20, H 5.28, N 3.05; found C 81.16, H 5.30, N
3.04.
Table 2. Performance of ITO/PEDOT:PSS/P3HT:PDIs/Al bulk
heterojunction photovoltaic devices[a] under a simulated photovol-
taic light with 100 mWcm–2 illumination (AM 1.5 G).
Sample PCE [%] VOC [V]
JSC [mAcm–2]
FF [%]
Area [cm2]
2
1
0.39
0.16
0.52
0.58
1.50
0.65
47.36
40.36
0.044
0.168
[a] The fabrication of photovoltaic devices of ITO/PEDOT:PSS/
P3HT:PDIs/Ca/Al is described in the in the Supporting Infor-
mation.
With respect to the light absorption range, charge carrier
rate, and electron affinities, PDI dyes should outperform
fullerenes in solar cells. However, the results show other-
wise. The causes of the poor power conversion efficiencies
achieved with our systems are not well understood. One
explanation for this is that the close molecular packing may
lead to the self-trapping of excitons.[5b] Another explanation
is that the dissociation of the charge-transfer (CT) state into
mobile charge carriers could be severely delayed by the ef-
ficient charge-recombination (CR) process.
Synthesis of 1: Compound 2 (92 mg, 0.1 mmol) was dissolved in
CH2Cl2 (100 mL) in a quartz vessel and irradiated in direct sun-
light. The progress was monitored by TLC. About 5 min the photo-
cyclization was finished and the reaction mixture was concentrated
in vacuo. The crude product was purified by column chromatog-
raphy (CH2Cl2 as eluent), yield 82 mg, 90%, m.p. Ͼ350 °C (de-
1
comp.). H NMR (400 MHz, CDCl3): δ = 10.27 (s, 1 H), 9.85 (s, 1
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Dyes for Electron-Accepting Materials
81, 3085–3087; j) H. Langhals, S. Saulich, Chem. Eur. J. 2002,
8, 5630–5643.
H), 9.60 (d, J = 8.0 Hz, 1 H), 9.42–9.37 (m, 2 H), 9.22–9.17 (m, 2
H), 8.92 (d, J = 8.0 Hz, 1 H), 8.38 (t, J = 4.0 Hz, 1 H), 8.27 (t, J
= 4.0 Hz, 1 H), 7.88 (t, J = 4.0 Hz, 2 H), 7.59–7.54 (m, 2 H), 7.43
(t, J = 4.0 Hz, 4 H), 2.96–2.87 (m, 4 H), 1.27–1.23 (m, 24 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 186.71, 181.79, 163.18, 163.02,
162.94, 162.87, 161.62, 144.88, 135.02, 134.69, 134.59, 134.24,
134.00, 133.78, 133.48, 133.38, 132.72, 131.39, 130.18, 129.76,
129.66, 128.99, 128.23, 127.91, 127.82, 127.56, 127.48, 127.08,
126.76, 126.50, 125.99, 125.89, 124.79, 124.00, 123.74, 123.37,
122.96, 122.81, 122.57, 122.01, 121.73, 119.86, 35.57, 30.53, 28.44,
23.16, 23.09 ppm. MS (MALDI-TOF): m/z = 937.5 [M + Na]+.
C62H48N2O4 (885.07): calcd. C 81.38, H 5.07, N 3.06; found C
81.33, H 5.09, N 3.04.
[6] a) B. A. Jones, M. J. Ahrens, M.-H. Yoon, A. Facchetti, T. J.
Marks, M. R. Wasielewski, Angew. Chem. 2004, 116, 6523; An-
gew. Chem. Int. Ed. 2004, 43, 6363–6366; b) R. T. Weitz, K.
Amsharov, U. Zschieschang, E. B. Villas, D. K. Goswami, M.
Burghard, H. Dosch, M. Jansen, K. Kern, H. Klauk, J. Am.
Chem. Soc. 2008, 130, 4637–4645; c) H. Z. Chen, M. M. Ling,
X. Mo, M. M. Shi, M. Wang, Z. Bao, Chem. Mater. 2007, 19,
816–824; d) R. J. Chesterfield, J. C. McKeen, C. R. Newman,
P. C. Ewbank, D. A. da Silva Filho, J.-L. Brédas, L. L. Miller,
K. R. Mann, C. D. Frisbie, J. Phys. Chem. B 2004, 108, 19281–
19292; e) P. R. L. Malenfant, C. D. Dimitrakopoulos, J. D. Ge-
lorme, L. L. Kosbar, T. O. Graham, A. Curioni, W. Andreoni,
Appl. Phys. Lett. 2002, 80, 2517–2519.
[7] a) N. G. Pschirer, C. Kohl, F. Nolde, J. Qu, K. Müllen, Angew.
Chem. 2006, 118, 1429; Angew. Chem. Int. Ed. 2006, 45, 1401–
1404; b) L. Fan, Y. Xu, H. Tian, Tetrahedron Lett. 2005, 46,
4443–4447; c) Y. Li, Z. Qing, Y. Yu, T. Liu, R. Jiang, Y. Li,
Chem. Asian J. 2012, DOI: 10.1002/asia.201200243; d) M. J.
Lin, B. Fimmel, K. Radacki, F. Würthner, Angew. Chem. 2011,
123, 11039; Angew. Chem. Int. Ed. 2011, 50, 10847–10850.
[8] a) H. Quante, Y. Geerts, K. Müllen, Chem. Mater. 1997, 9,
495–500; b) F. Würthner, C. Thalacker, A. Sautter, Adv. Mater.
1999, 11, 754–758.
Supporting Information (see footnote on the first page of this arti-
cle): 1H and 13C NMR spectra for 1 and 2, photos of the visible
colors and visual fluorescence colors of 1 and 2, computational
investigations on 1 and 2, TGA profiles of 1 and 2, and process for
the fabrication of the solar cell devices, details of CV experiments.
Acknowledgments
[9] P. Rajasingh, R. Cohen, E. Shirman, L. J. W. Shimon, B. Rybt-
chinski, J. Org. Chem. 2007, 72, 5973–5979.
This work was supported by the National Nature Science Founda-
tion of China (NSFC) (grant number 21031006), the Chinese–Ger-
man NSFC–DFG joint fund (TRR 61), and the National Basic
Research 973 Program of China (grant numbers 2011CB932302
and 2012CD932900).
[10]
a) W. Qiu, S. Chen, X. Sun, Y. Liu, D. Zhu, Org. Lett. 2006,
8, 867–870; b) S. Muller, K. Müllen, Chem. Commun. 2005, 32,
4045–4046.
[11]
[12]
Y. Geerts, H. Quante, H. Platz, R. Mahrt, M. Hopmeier, A.
Bohm, K. Müllen, J. Mater. Chem. 1998, 8, 2357–2369.
Y. Avlasevich, C. Li, K. Müllen, J. Mater. Chem. 2010, 20,
3814–3826.
[1] a) W. Wang, W. Wan, H.-H. Zhou, S. Niu, A. D. Q. Li, J. Am.
Chem. Soc. 2003, 125, 5248–5249; b) L. Zang, R. Liu, M. W.
Holman, K. T. Nguyen, D. M. Adams, J. Am. Chem. Soc. 2002,
124, 10640–10641; c) N. I. Georgiev, A. R. Sakr, V. B. Bojinov,
Dyes Pigm. 2011, 91, 332–339; d) T. Heek, C. Fasting, C. Rest,
X. Zhang, F. Würthner, R. Haag, Chem. Commun. 2010, 46,
1884–1886.
[2] a) X. Guo, D. Zhang, D. Zhu, Adv. Mater. 2004, 16, 125–130;
b) Y. Li, H. Zheng, Y. Li, S. Wang, Z. Wu, P. Liu, Z. Gao, H.
Liu, D. Zhu, J. Org. Chem. 2007, 72, 2878–2885.
[3] a) J. Baggerman, D. C. Jagesar, R. A. L. Vallée, J. Hofkens,
F. C. De Schryver, F. Schelhase, F. Vögtle, A. M. Brouwer,
Chem. Eur. J. 2007, 13, 1291–1299; b) B. J. Slater, E. S. Davies,
S. P. Argent, H. Nowell, W. Lewis, A. J. Blake, N. R. Champ-
ness, Chem. Eur. J. 2011, 17, 14746–14751; c) Y. Li, H. Li, Y.
Li, H. Liu, S. Wang, X. He, N. Wang, D. Zhu, Org. Lett. 2005,
7, 4835–4838.
[4] a) X. Zhan, A. Facchetti, S. Barlow, T. J. Marks, M. A. Ratner,
M. R. Wasielewski, S. R. Marder, Adv. Mater. 2011, 23, 268–
284; b) C. Huang, S. Barlow, S. R. Marder, J. Org. Chem. 2011,
76, 2386–2407; c) W. Lu, J. P. Gao, Z. Y. Wang, Y. Qi, G. G.
Sacripante, J. D. Duff, P. R. Sundararajan, Macromolecules
1999, 32, 8880–8885.
[5] a) L. Schmidt-Mende, A. Fechtenkötter, K. Müllen, E. Moons,
R. H. Friend, J. D. MacKenzie, Science 2001, 293, 1119–1122;
b) C. Li, H. Wonneberger, Adv. Mater. 2012, 24, 613–636; c)
C. Ego, D. Marsitzky, S. Becker, J. Zhang, A. C. Grimsdale, K.
Müllen, J. D. MacKenzie, C. Silva, R. H. Friend, J. Am. Chem.
Soc. 2003, 125, 437–443; d) J. J. Dittmer, E. A. Marseglia,
R. H. Friend, Adv. Mater. 2000, 12, 1270–1274; e) Z. Liang,
R. A. Cormier, A. M. Nardes, B. A. Gregg, Synth. Met. 2011,
161, 1014–1021; f) B. A. Gregg, R. A. Cormier, J. Am. Chem.
Soc. 2001, 123, 7959–7960; g) Y. Liu, N. Wang, Y. Li, H. Liu,
Y. Li, J. Xiao, X. Xu, C. Huang, S. Cui, D. Zhu, Macromole-
cules 2005, 38, 4880–4887; h) Y. Liu, Y. Li, L. Jiang, H. Gan,
H. Liu, Y. Li, J. Zhuang, F. Lu, D. Zhu, J. Org. Chem. 2004,
69, 9049–9054; i) A. J. Breeze, A. Salomon, D. S. Ginley, B. A.
Gregg, H. Tillmann, H.-H. Horhold, Appl. Phys. Lett. 2002,
[13]
[14]
[15]
F. Würthner, Chem. Commun. 2004, 14, 1564–1579.
H. Langhals, S. Kirner, Eur. J. Org. Chem. 2000, 365–380.
a) Y. Li, Y. Li, J. Li, C. Li, X. Liu, M. Yuan, H. Liu, S. Wang,
Chem. Eur. J. 2006, 12, 8378–8385; b) Y. Li, L. Xu, T. Liu, Y.
Yu, H. Liu, Y. Li, D. Zhu, Org. Lett. 2011, 13, 5692–5695.
G. Horowitz, F. Kouki, P. Spearman, D. Fichou, C. Nogues,
X. Pan, F. Garnier, Adv. Mater. 1996, 8, 242–245.
a) Y. Liu, S. Xiao, H. Li, Y. Li, H. Liu, F. Lu, J. Zhuang, D.
Zhu, J. Phys. Chem. B 2004, 108, 6256–6260; b) S. Suzuki, M.
Kozaki, K. Nozaki, K. Okada, J. Photochem. Photobiol. C:
Photochem. Rev. 2011, 12, 269–292; c) Y. Zhao, M. R. Wasie-
lewski, Tetrahedron Lett. 1999, 40, 7047–7050.
[16]
[17]
[18]
[19]
[20]
R. K. Dubey, A. Efimov, H. Lemmetyinen, Chem. Mater. 2011,
23, 778–788.
R. M. F. Batista, E. Oliveira, S. P. G. Costa, C. Lodeiro,
M. M. M. Raposo, Org. Lett. 2007, 9, 3201–3204.
a) H. Görner, Photochem. Photobiol. 2003, 77, 171–179; b) J.
Yang, A. Dass, A.-M. M. Rawashdeh, C. Sotiriou-Leventis,
M. J. Panzner, D. S. Tyson, J. D. Kinder, N. Leventis, Chem.
Mater. 2004, 16, 3457–3468.
[21]
[22]
a) J. Fabian, H. Nakazumi, M. Matsuoka, Chem. Rev. 1992,
92, 1197–1226; b) C. Kohl, S. Becker, K. Müllen, Chem. Com-
mun. 2002, 23, 2778–2779.
C. A. Wijesinghe, M. Niemi, N. V. Tkachenko, N. K. Subbai-
yan, M. E. Zandler, H. Lemmetyinen, F. D’Souza, J. Por-
phyrins Phthalocyanines 2011, 15, 391–400.
[23]
[24]
M. Mamada, J.-i. Nishida, S. Tokito, Y. Yamashita, Chem.
Commun. 2009, 16, 2177–2179.
J. Hankache, O. S. Wenger, Chem. Commun. 2011, 47, 10145–
10147.
[25]
[26]
M. Thelakkat, H.-W. Schmidt, Adv. Mater. 1998, 10, 219–223.
a) C.-C. Chao, M.-k. Leung, Y. O. Su, K.-Y. Chiu, T.-H. Lin,
S.-J. Shieh, S.-C. Lin, J. Org. Chem. 2005, 70, 4323–4331; b)
F. O. Holtrup, G. R. J. Müller, H. Quante, S. De Feyter, F. C.
De Schryver, K. Müllen, Chem. Eur. J. 1997, 3, 219–225.
G. Seybold, G. Wagenblast, Dyes Pigm. 1989, 11, 303–317.
[27]
Eur. J. Org. Chem. 2013, 300–306
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
305

L. Xu, C. Liu, Z. Qin, R. Jiang, Y. Li
FULL PAPER
[28] R. Gvishi, R. Reisfeld, Z. Burshtein, Chem. Phys. Lett. 1993,
213, 338–344.
[29] a) J. Feng, D. Wang, H. Wang, D. Zhang, L. Zhang, X. Li, J.
Phys. Org. Chem. 2011, 24, 621–629; b) S. Chai, S.-H. Wen,
K.-L. Han, Org. Electron. 2011, 12, 1806–814.
[30] H. Langhals, T. Pust, Eur. J. Org. Chem. 2010, 3140–3145.
[31] S. Chen, Y. Liu, W. Qiu, X. Sun, Y. Ma, D. Zhu, Chem. Mater.
2005, 17, 2208–2215.
Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Re-
vision C.02, Gaussian, Inc., Wallingford, CT, 2004.
[40] Y. Nagao, Prog. Org. Coat. 1997, 31, 43–49.
[32] Y. Avlasevich, S. Müller, P. Erk, K. Müllen, Chem. Eur. J. 2007,
13, 6555–6561.
[41] E. E. Neuteboom, S. C. J. Meskers, P. A. van Hal, J. K. J.
van Duren, E. W. Meijer, R. A. J. Janssen, H. Dupin, G. Pour-
tois, J. Cornil, R. Lazzaroni, J.-L. Brédas, D. Beljonne, J. Am.
Chem. Soc. 2003, 125, 8625–8638.
[42] a) T. van der Boom, R. T. Hayes, Y. Zhao, P. J. Bushard, E. A.
Weiss, M. R. Wasielewski, J. Am. Chem. Soc. 2002, 124, 9582–
9590; b) S.-G. Liu, G. Sui, R. A. Cormier, R. M. Leblanc, B. A.
Gregg, J. Phys. Chem. B 2002, 106, 1307–1315.
[33] S. K. Lee, Y. Zu, A. Herrmann, Y. Geerts, K. Müllen, A. J.
Bard, J. Am. Chem. Soc. 1999, 121, 3513–3520.
[34] S. Leroy-Lhez, J. Baffreau, L. Perrin, E. Levillain, M. Allain,
M.-J. Blesa, P. Hudhomme, J. Org. Chem. 2005, 70, 6313–6320.
[35] Z. Yuan, Y. Xiao, X. Qian, Chem. Commun. 2010, 46, 2772–
2774.
[36] a) D. M. de Leeuw, M. M. J. Simenon, A. R. Brown, R. E. F.
Einerhand, Synth. Met. 1997, 87, 53–59; b) Y. Li, Y. Cao, J.
[43] C. Liu, Y. Li, C. Li, W. Li, C. Zhou, H. Liu, Z. Bo, Y. Li, J.
Phys. Chem. C 2009, 113, 21970–21975.
Gao, D. Wang, G. Yu, A. J. Heeger, Synth. Met. 1999, 99, 243– [44] G. D. Sharma, P. Suresh, J. A. Mikroyannidis, M. M. Sty-
248.
lianakis, J. Mater. Chem. 2010, 20, 561–567.
[45] a) W. Ma, C. Yang, X. Gong, K. Lee, A. J. Heeger, Adv. Funct.
Mater. 2005, 15, 1617–1622; b) G. Li, V. Shrotriya, J. Huang,
Y. Yao, T. Moriarty, K. Emery, Y. Yang, Nat. Mater. 2005, 4,
864–868.
[37] S. M. Bonesi, M. Fagnoni, A. Albini, J. Org. Chem. 2004, 69,
928–935.
[38] H. Graaf, W. Michaelis, G. Schnurpfeil, N. Jaeger, D. Schlett-
wein, Org. Electron. 2004, 5, 237–249.
[39] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
[46] a) J. Hou, Z. a. Tan, Y. Yan, Y. He, C. Yang, Y. Li, J. Am.
Chem. Soc. 2006, 128, 4911–4916; b) C. J. Brabec, C. Winder,
N. S. Sariciftci, J. C. Hummelen, A. Dhanabalan, P. A.
van Hal, R. A. J. Janssen, Adv. Funct. Mater. 2002, 12, 709–
712.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. [47] V. Dyakonov, Appl. Phys. A 2004, 79, 21–25.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R.
Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morok-
uma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzew-
ski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K.
[48] C. Liu, S. Xiao, X. Shu, Y. Li, L. Xu, T. Liu, Y. Yu, L. Zhang,
H. Liu, Y. Li, ACS Appl. Mater. Interfaces 2012, 4, 1065–1071.
[49] Y. Yi, V. Coropceanu, J.-L. Bredas, J. Mater. Chem. 2011, 21,
1479–1486.
Received: July 24, 2012
Published Online: November 26, 2012
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