Synthesis and characterization of dioxopyrrolopyrrole derivatives having electron-withdrawing groups

Article abstract of DOI:10.1002/ejoc.201200761

New dioxopyrrolopyrrole (DPP) derivatives bearing electron-withdrawing groups have been synthesized, and their photophysical properties and redox behaviors have been examined. The electron-accepting abilities of the derivatives were elucidated by cyclic voltammetry (CV) and redox titration analysis. The introduction of the electron-withdrawing groups modulated the redox properties of the DPP core, and the addition of the 1,1,4,4- tetracyanobutadiene (TCBD) moieties created a multi-redox system. The application of TD-DFT (time-dependent density functional theory) revealed the HOMO and LUMO of the compounds, and the calculation results were consistent with the photophysical and electrochemical properties of the compounds. The TCBD moieties provided the dye molecule with unique physical properties such as broad charge-transfer absorption bands and reversible multi-redox behavior. Copyright

Full text of DOI:10.1002/ejoc.201200761

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DOI: 10.1002/ejoc.201200761
Synthesis and Characterization of Dioxopyrrolopyrrole Derivatives Having
Electron-Withdrawing Groups
Takuya Yamagata,[a] Junpei Kuwabara,[a] and Takaki Kanbara*[a]
Keywords: Nitrogen heterocycles / Substituent effects / Cycloaddition / Density functional calculations / Charge transfer /
Electrochemistry
New dioxopyrrolopyrrole (DPP) derivatives bearing electron-
withdrawing groups have been synthesized, and their photo-
physical properties and redox behaviors have been exam-
ined. The electron-accepting abilities of the derivatives were
elucidated by cyclic voltammetry (CV) and redox titration
analysis. The introduction of the electron-withdrawing
groups modulated the redox properties of the DPP core, and
the addition of the 1,1,4,4-tetracyanobutadiene (TCBD)
moieties created a multi-redox system. The application of
TD-DFT (time-dependent density functional theory) revealed
the HOMO and LUMO of the compounds, and the calcula-
tion results were consistent with the photophysical and
electrochemical properties of the compounds. The TCBD
moieties provided the dye molecule with unique physical
properties such as broad charge-transfer absorption bands
and reversible multi-redox behavior.
conjugation, its introduction onto a DPP derivative is ex-
pected to provide a molecule with a high electron affinity
and result in a well-ordered stacking structure in the solid
state. 1,1,4,4-Tetracyanobutadiene (TCBD) is another inter-
esting electron-withdrawing group that can add properties
to a molecule, such as a tunable CT (charge-transfer) ab-
sorption character and high electron-accepting poten-
tial.[10–12] The TCBD group can easily be introduced by a
[2+2] cycloaddition reaction between tetracyanoethylene
(TCNE) and electron-rich alkynes.[10] This is generally a
fast, atom-economic, catalyst-free, and high-yielding reac-
tion. Recently, Shoji et al. reported that an electrochemical
reduction resulted in significant color changes to TCBD de-
rivatives.[11] Therefore, the introduction of TCBD into dye
molecules such as DPP derivatives should result in a dra-
matic color change when reduced.
Herein, we report the syntheses of DPP derivatives
bearing electron-withdrawing components such as penta-
fluorophenyl and TCBD groups, and we describe the inves-
tigation of the effects of the substituents on the properties
of the DPP molecules. These derivatives have been charac-
terized by X-ray crystallography, absorption spectroscopy,
emission spectroscopy, electrochemistry, and theoretical cal-
culations.
Introduction
Dioxopyrrolopyrrole (DPP) and its derivatives were orig-
inally used as imaging colorants, surface coatings, and color
filters because of their brilliant colors and high stabilities.[1]
The efficient emissions of DPP derivatives are now utilized
in a variety of new fields such as fluorescent molecular
probes,[2] bioimaging,[3] and dye lasers.[4] As DPP deriva-
tives have high extinction coefficients and carrier mobilities,
they have also been used in the applications of organic solar
cells and organic thin-film transistors (OTFTs).[5] Because
the properties of DPP derivatives strongly depend on the
substituents of the aromatic groups attached to the central
DPP core,[1a,6] understanding the substituent effects is im-
portant for applications in optoelectronic materials.
In our previous studies, we reported the use organome-
tallic cross-coupling reactions for the syntheses of DPP de-
rivatives bearing electron-donating groups.[2a,6] Alterna-
tively, the introduction of electron-withdrawing substitu-
ents, such as cyano and fluoro groups, onto the DPP struc-
ture should provide the molecule with a high electron affin-
ity.[7–9] Indeed, it has been reported that (trifluoromethyl)-
phenyl-substituted DPP derivatives can serve as n-type or-
ganic semiconductors.[5i,5j] Because a pentafluorophenyl
group has electron-withdrawing ability and extends the π
[a] Tsukuba Research Center for Interdisciplinary Materials
Science (TIMS), Graduate School of Pure and Applied
Sciences, University of Tsukuba,
Results and Discussion
Synthesis
1-1-1 Tennodai, Tsukuba 305-8573, Japan
Fax: +81-29-853-4490
Methylated DPP 1 was synthesized in 62% yield by a
reaction between pigment red 254 and iodomethane in the
presence of K2CO3 in DMF (N,N-dimethylformamide).[13]
The introduction of the methyl groups to pigment red 254
E-mail: kanbara@ims.tsukuba.ac.jp
Homepage: http://www.ims.tsukuba.ac.jp/~kanbara_lab/
index.htm
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200761.
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resulted in a molecule with good solubility in organic sol- pling reaction, catalyzed by Pd(OAc)2 with dicyclo-
vents and allowed for the product to be further function- hexyl(2Ј,6Ј-dimethoxybiphenyl-2-yl)phosphane (SPhos)[15]
alized by organometallic cross-coupling reactions. A palla- as the ligand, introduced the pentafluorophenyl groups to
dium-catalyzed borylation of aryl chloride 1 led to aryl give compound 3 in 24% yield (see Scheme 1).
boronate ester 2.[14] The reaction of compound 1 with bis-
It has been reported that copper-free Sonogashira cou-
(pinacolato)diboron in the presence of Pd(OAc)2 with 2-(di- pling reactions enable the use of aryl chlorides as coupling
cyclohexylphosphanyl)-2Ј,4Ј,6Ј-triisopropylbiphenyl (XPhos) partners.[16] In accordance with this report, the reaction of
gave compound 2 in 63% yield. A Suzuki–Miyaura cou- compound 1 with 4-ethynyl-N,N-dimethylaniline was con-
ducted to synthesize compound 4 (see Scheme 2). For the
synthesis of a new TCBD derivative, a [2+2] cycloaddition/
cycloreversion sequence of 4 with TCNE was investigated,
according to the procedures described in the literature.[10b]
The reaction of 4 with TCNE proceeded smoothly in
CH2Cl2 at room temp. to give 5 in 67% yield.
Solid-State Structures
The solid-state molecular structures of 1–5 were exam-
ined by X-ray diffraction. The crystal structures of 1–5 are
shown in Figure 1 and the Supporting Information. Single
crystals of 3 suitable for X-ray diffraction studies were ob-
tained by slow diffusion of hexane into a solution of the
compound in CHCl3. Compound 3 crystallized to form tri-
¯
clinic crystals with the space group P1, containing two mo-
lecules with slightly different configurations in the unit cell.
The structure had an inversion center at the midpoint of C-
2 and C-2*. Single crystals of 5 were obtained by slowly
concentrating a solution in CHCl3. Compound 5 crys-
tallized to form orthorhombic crystals with the space group
Pbca and had an inversion center at the midpoint of C-2
and C-2*. The TCBD moieties of compound 5 were highly
distorted. The torsion angle between the two dicyanovinyl
planes was 66.9° in 5. As the absolute value of this torsion
angle was below 90°, the TCBD moiety adopted an s-cis
conformation. Michinobu et al. also reported that TCBD
derivatives substituted with aryl groups at both the 2- and
3-positions preferred the s-cis conformation.[10b]
Scheme 1. Synthesis of 3.
Scheme 2. Synthesis of 5.
2
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Synthesis and Characterization of Dioxopyrrolopyrrole Derivatives
Figure 1. ORTEP drawing with thermal ellipsoids shown at the 30% probability level. (a) 1, (b) 3, and (c) 5. Atoms with asterisks are
crystallographically equivalent to those with the same number without an asterisk. Hydrogen atoms are omitted for clarity.
The substituents on the phenyl group affected the dihe- tuted compound 5 showed two broad bands with maxima
dral angle between the DPP core and the adjacent phenyl at 461 and 535 nm. To understand the nature of the elec-
groups. Compound 4 exhibited a smaller dihedral angle tronic transitions of compound 5, a series of TD-DFT
(32°) than 1 (42°), 3 (40°), and 5 (42°). These results pointed (time-dependent density functional theory) calculations
to the extended conjugation of the DPP core and phenyl were conducted on the optimized geometry of the com-
ring π orbitals in 4. The electron-donating substituents in- pounds.
creased the electron density of the phenyl rings, resulting in
efficient conjugation between the DPP core and the phenyl
rings.[2a]
UV/Vis Absorption Spectroscopy
The photophysical properties of compounds 1–5 are
summarized in Table 1. The UV/Vis absorption spectra
were measured in CHCl3 (see Figure 2). The molar ab-
sorbance coefficient (ε) of 4 (4.32ϫ104 Lmol–1 cm–1) was
about double that of 1 (1.94ϫ104 Lmol–1 cm–1). In ad-
dition, the absorbance maximum (λmax) of 4 was at a longer
wavelength than that of 1. As the electron-donating ability
of the substituents caused a redshift in the λmax value,[6]
Figure 2. UV/Vis absorption spectra of 1–5 in CHCl3.
the difference between the λmax values was attributed to the
effects of the electron-donating substituent. In spite of the
electron-withdrawing ability of the pentafluorophenyl
groups, the λmax value of 3 was larger than that of chlo-
TD-DFT Calculations
rophenyl-substituted compound 1. The results signified that
To elucidate the relationship between the substituents
the introduction of pentafluorophenyl groups extended the and the absorption spectra, compounds 1, 3, and 5 were
π conjugation. The absorption spectra of the TCBD-substi- examined by performing theoretical calculations.[17] After
Table 1. Photophysical properties of 1–5.
Compound
UV[a]
ε [Lmol–1 cm–1]
PL in solution[a]
Excitation
spectra [nm]
Stokes shift in
solution [cm–1]
Φf[c]
λmax [nm]
(λem [nm])[b]
in solution[a]
1
2
3
4
5
485
485
490
522
461, 535
19400
19000
21900
533
543
551
619
541
472
483
493
538
526
1857
2074
2259
3002
207.2
0.87
0.87
0.86
0.72
Ͻ0.01
43200
54500, 23900
[a] Absolute fluorescence quantum yields in chloroform. [b] Emission spectra were measured with excitation spectra (PL = photolumines-
cence). [c] Fluorescence quantum yields were measured with excitation at λmax in UV/Vis absorption.
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the optimization of the geometric structures, time-depend- Table 2. List of calculated electronic transitions of 5 in the gas
phase.
ent density functional theory calculations were performed
at the B3LYP level with the 6-31G basis set implemented in
the Gaussian 03 program suite.[18,19] As shown in Figure 3,
the HOMO of 5 was localized at the DPP core, whereas the
LUMO of 5 covered the DPP core and one of the di-
cyanovinyl moieties. Table 2 summarizes the main electronic
excitations with the composition, oscillator strengths, and
assignments for 5. The results of the TD-DFT calculations
indicated that compound 5 had two main transitions in the
long wavelength region. One of the two transitions was
from the HOMO to the LUMO (ƒ = 0.318), which was
assigned to the π-π* transition of the DPP core. The other
was the transition from the HOMO-2 to the LUMO (ƒ =
0.371), which was assigned to the intramolecular charge-
Calcd. for 5 [nm]
Composition
ƒ[a]
HOMO Ǟ LUMO
HOMO–1 Ǟ LUMO+1
HOMO–2 Ǟ LUMO
(0.47)
(–0.13)
(–0.46)
626
0.318
HOMO–2 Ǟ LUMO
HOMO–1 Ǟ LUMO+1
HOMO Ǟ LUMO
(0.49)
(–0.11)
(0.42)
604
0.371
0.691
387
HOMO–1 Ǟ LUMO+3
(0.64)
[a] Oscillator strengths.
The HOMO and LUMO energy levels of 1, 3, and 5 are
transfer (ICT) absorption from the N,N-dimethylanilino summarized in Table 3. Although both the HOMO and
groups to the TCBD moieties and the DPP core. On the LUMO of 5 were at lower energy levels than those of 1,
basis of the energy band gap, these transitions corre- the difference in the LUMOs between 1 and 5 was more
sponded to the absorptions at 626 and 604 nm in the theo- significant (0.79 eV) than that between their HOMOs
retical calculations. From the results, the broad, experimen- (0.34 eV). Therefore, the TCBD moieties strongly affected
tally observed absorption around 535 nm was considered to the LUMO, resulting in the narrow energy band gap. The
include the two aforementioned transitions. The theoretic- LUMO of 3 was also lower than that of 1. This result indi-
ally predicted absorption wavelength of compound 5 corre- cated that the fluoro group on the phenyl ring provided
sponded to a wavelength longer than the one corresponding DPP with a low-lying LUMO. The optical band gaps of 1,
to experimental values. This was due to various factors 3, and 5 from the absorption edges are 2.32, 2.09, and
(such as solvent effects) that were not taken into account in 1.88 eV, respectively. The trend of band gaps (1 Ͼ 3 Ͼ 5)
the theoretical calculations.
was consistent with the results from the DFT calculations
Figure 3. Molecular orbitals of compound 5.
4
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Synthesis and Characterization of Dioxopyrrolopyrrole Derivatives
(see Table 3). However, the values of optical band gap are spectrum partly overlapped with the absorption spectrum.
somewhat smaller than the calculated values, presumably An overlap between the absorption spectrum and the emis-
because of the effects of solvent.
sion spectrum generally indicates self-absorption, and this
is one of the reasons for the negligible emission. A photoin-
duced electron transfer from the TCBD moieties to the
DPP core could also have quenched the emission.[20]
Table 3. HOMO–LUMO energies and energy band gap of 1, 3, and
5 on the basis of the TD-DFT calculations.
Compound
HOMO [eV]
LUMO [eV]
Band gap [eV]
1
3
5
–5.58
–5.63
–5.92
–2.91
–3.10
–3.70
2.67
2.53
2.22
Electrochemistry
The introduction of electron-withdrawing substituents
should enhance the electron-accepting ability of the DPP
core. To elucidate the electrochemical redox behaviors, com-
pounds 1–5 were evaluated by cyclic voltammetry (CV)
measurements. The redox potentials of 1–5 are summarized
in Table 4. Compounds 1–5 exhibited irreversible oxidation
waves in the oxidation region. In contrast, compounds 1, 3,
and 5 exhibited reversible reduction waves (see Figure 5).
Compounds 2 and 4 showed a quasi-reversible reduction
wave. These waves corresponded to reductions of the DPP
core.[21] The reduction potential of 3 [–1.578 V vs Fc+/Fc
(ferrocenium/ferrocene)] was less negative than that of 1
(–1.638 V). This result signified that the pentafluorophenyl
substituent enhanced the electron-accepting ability of the
DPP core. As compound 4 with the electron-donating N,N-
dimethylanilino substituent had a more negative reduction
potential than those of 1–3, it was clear that the substituent
affected the electronic state of the DPP core through the
adjacent aromatic ring.[6] Interestingly, the voltammogram
of compound 5 exhibited three reversible steps at –0.88 V,
Emission Spectra
The emission spectra of compounds 1–5 are shown in
Figure 4. The photophysical data are also included in
Table 1. The dependence of the maximum emission wave-
length (λem) on the substituents was similar to that of the
maximum absorption wavelength (1 Ͻ 3 Ͻ 4). The maxi-
mum emission wavelength of 3 exhibited a small redshift
(18 nm) when compared to the λem value of 1. The results
also supported the theory that the pentafluorophenyl
groups extended the π conjugation. Among the DPP deriva-
tives, 4 exhibited the largest redshift (86 nm). The extended
π conjugation and the electron-donating ability of the N,N-
dimethylanilino groups resulted in a redshift in its emission
maximum.[2a,6] Compounds 1–4 had high fluorescence
quantum yields (0.72–0.87) in solution at room temp. (see
Table 1). In contrast, the TCBD-substituted compound 5
exhibited a negligible emission in solution (Φf Ͻ 0.01). As
compound 5 exhibited a small Stokes shift, the emission
Figure 5. Cyclic voltammograms of compounds 1, 3, and 5 in
CH2Cl2 (1ϫ10–3 m) containing Bu4NPF6 (0.1 m). Sweep rate =
100 mVs–1.
Figure 4. Normalized emission spectra of 1–5 in CHCl3.
Table 4. Summary of electrochemical data[a] for compounds 1–5.
1red
2red
3red
1ox
1red
E1/2
[V][b]
E1/2
[V][b]
E1/2
[V][b]
Eonset [V][c]
Eonset
[V][d]
HOMO[e] [eV]
LUMO[f] [eV]
1
2
3
4
5
–1.638
–1.625[g]
–1.578
0.632
0.612
0.666
0.044
0.802
–1.561
–1.554
–1.503
–1.581
–0.759
–5.43
–5.41
–5.47
–4.84
–5.60
–3.24
–3.25
–3.30
–3.22
–4.04
–1.779[g]
–0.878
–1.204
–1.979
[a] Redox potentials were measured in CH2Cl2 (1ϫ10–3 m) containing Bu4NPF6 (0.1 m). Sweep rate 100 mVs–1. Potential in V vs Fc+/Fc.
[b] Half-wave potential. [c] Determined from the onset potentials of the oxidation wave. [d] Determined from the onset potentials of the
reduction wave. [e] Determined from the onset potentials of the oxidation wave (vs Fc+/Fc) using the equation (HOMO = –4.8 – Eonset1ox).
[f] Determined from the onset potentials of the reduction wave (vs Fc+/Fc) using the equation LUMO = –4.8 – Eonset1red. [g] Quasi-
reversible redox process.
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Figure 6. Redox process of compound 5.
–1.20 V, and –1.98 V. The reduction waves at –0.88 V and duction of the TCBD moieties. The formation of a tetraan-
–1.20 V corresponded to two-electron reductions, and the ionic species could account for the color change and the
reduction wave at –1.98 V corresponded to a one-electron absorption in the near-infrared region (see Figure 6).
reduction. On the basis of the literature, the first two re-
duction waves were assigned to the successive reductions of
the TCBD moiety.[10a] The two two-electron reductions
were evidence that the two TCBD moieties in compound 5
were reduced independently (see Figure 6). The indepen-
dent reduction of the TCBD moieties indicated a negligible
electrochemical interaction between the TCBD moieties
through the DPP core. The reduction wave at –1.98 V was
assigned to the reduction of the DPP core.[12] The relatively
negative reduction potential was probably due to the elec-
tron-donating effects of the dianionic TCBD moieties.
The HOMO and LUMO levels of 1–3 could be deter-
mined by their oxidation and reduction onset potentials,
under the premise that the energy level of the ferrocene/
ferrocenium couple is 4.8 eV below the vacuum level.[22]
The LUMO value deduced from the electrochemistry of 3
Figure 7. Changes in UV/Vis absorption spectrum of 5 in CH2Cl2
(2ϫ10–5 m) upon addition of Cp2Co.
was lower than that of 1. This result was consistent with
the results calculated by TD-DFT (see Table 3).
Conclusions
The introduction of electron-withdrawing groups low-
Redox Titration Analysis
ered the LUMO levels of the DPP derivatives and enhanced
The redox changes of 5 were accompanied by color the electron-accepting abilities of the DPP core. In particu-
changes. Thus, to elucidate the redox behaviors of the lar, compound 5, bearing TCBD moieties, showed unique
TCBD moieties, titrations were performed by UV/Vis spec- electrochemical responses such as a reversible five-electron
troscopy. In the UV/Vis spectrum of 5, the absorption reduction. Compound 5 also possessed a characteristic
bands at 461 and 535 nm decreased upon the addition of broad absorption band consisting of a DPP core π–π* tran-
cobaltocene (Cp2Co, E1/2 = –1.33 V vs Fc+/Fc, in CH2Cl2) sition and charge transfer from the TCBD moieties to the
with isosbestic points at 406 and 623 nm (see Figure 7). The DPP core. The absorption bands could be changed by
color of the solution gradually changed from brown to red, chemically reducing the TCBD moieties. As the combina-
which was accompanied by a new absorption peak at tion of TCBD moieties on a DPP core gave rise to interest-
771 nm. As compound 5 exhibited no response to ferrocene, ing physical properties, in the future, compound 5 could
the color change of the solution was caused by the re- have applications in new optoelectronic materials.
6
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Synthesis and Characterization of Dioxopyrrolopyrrole Derivatives
cooling to room temp., the mixture was diluted with CHCl3 and
water. The organic layer was separated and then washed with water
and brine. The product was isolated by column chromatography on
Experimental Section
General Methods: NMR spectroscopic data were recorded with
Bruker Avance-400, -500, and -600, JEOL EX-270, and ECS-400
NMR spectrometers. Hexafluorobenzene (δ = –164.9 ppm) was em-
ployed as an external standard in the 19F NMR spectra. Elemental
analyses were carried out with a Perkin–Elmer 2400 CHN Elemen-
tal Analyzer. UV/Vis spectra were recorded with a JASCO V-
630iRM spectrophotometer. PL spectra were recorded with an FP-
6200 spectrophotometer. Fluorescence quantum yields were ob-
tained by a Hamamatsu Photonics absolute PL quantum yield
measurement system C9920-02. MALDI mass spectra were re-
corded with a Kratos-Shimadzu AXIMA-CFR plus MALDI-TOF
MS and Applied Biosystems SCIEX TOF/TOFTM 5800. ESI-HR
mass spectra were recorded with a Waters Synapt G2.
1
silica gel (CHCl3) to give compound 3 (30.6 mg, 24%). H NMR
(600 MHz, CDCl3): δ = 3.41 (s, 6 H), 7.63 (AAЈBBЈ, 4 H), 8.06
(AAЈBBЈ, 4 H) ppm. 13C{1H} NMR (150 MHz, CDCl3): δ = 29.6,
110.1, 114.8–115.0 (m), 128.7, 129.4, 129.4, 130.7, 138.0 (dm, JF
=
253.1 Hz), 139.5 (dm, JF = 182.6 Hz), 144.2 (dm, JF = 248.7 Hz),
147.8, 162.5 ppm. 19F NMR (376 MHz, CDCl3): δ = –145.8 (dd,
JF = 19.2, 8.1 Hz, 4 F), –157.1 (t, JF = 20.3 Hz, 2 F), –164.5 (m, 4
F) ppm. MALDI-MS: calcd. for C32H15F10N2O2 [M + H]+ 649.1;
found 649.1. C32H14F10N2O2 (648.45): calcd. C 59.27, H 2.18, N
4.32; found C 58.96, H 2.64, N 4.25.
Compound 4: A mixture of 1 (116 mg, 0.3 mmol), 4-ethynyl-N,N-
dimethylaniline (218 mg, 1.5 mmol), Cs2CO3 (255 mg, 1.3 mmol),
[23]
Electrochemical Measurements: The electrochemical measurements
were carried out with a standard three-electrode configuration.
Bu4NPF6 (0.1 m solution) in dichloromethane was used as a sup-
porting electrolyte with platinum wire auxiliary electrodes and car-
bon working electrodes. All of the measurements were carried out
under nitrogen, and potentials were related to an Ag/Ag+ reference
electrode. The potentials were calibrated with a ferrocene/ferrocen-
ium redox couple (Fc/Fc+).
PdCl2(CH3CN)2
(3.1 mg, 0.012 mmol), and XPhos (17.2 mg,
0.036 mmol) in acetonitrile (6.0 mL) was stirred under nitrogen at
room temp. for 30 min. The mixture was then stirred at 80 °C for
12 h. After cooling to room temp., the mixture was diluted with
CHCl3 and water. The organic layer was separated and then
washed with water and brine. The product was isolated by column
chromatography on silica gel (CHCl3/ethyl acetate, 20:1) to give
compound 4 (82.9 mg, 46%). An analytically pure sample was ob-
tained by recrystallization from a concentrated solution in CHCl3.
1H NMR (270 MHz, CDCl3): δ = 3.02 (s, 12 H), 3.38 (s, 6 H), 6.68
(d, J = 8.9 Hz, 4 H), 7.44 (d, J = 8.9 Hz, 4 H), 7.63 (d, J = 8.6 Hz,
4 H), 7.91 (d, J = 8.6 Hz, 4 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 29.8, 40.2, 87.5, 109.3, 109.6, 111.8, 126.5, 129.0,
129.3, 130.4, 131.4, 133.0, 147.8, 150.4, 162.6 ppm. MALDI-MS:
calcd. for C40H34N4O2 [M]+ 602.3; found 602.3. C40H34N4O2
(602.72): calcd. C 79.71, H 5.69, N 9.30; found C 79.63, H 6.01, N
8.87.
Computational Details: The geometrical structures were optimized
at the B3LYP level for 1, 3, and 5 with a 6-31G basis set im-
plemented in the Gaussian 03 program suites.[18a] Using the opti-
mized geometries of 1, 3, and 5, TD-DFT calculations were per-
formed at the B3LYP level to predict their absorptions.
Compound 1: A suspension of pigment red 254 (1.07 mg, 3.0 mmol)
and K2CO3 (4.56 g, 33 mmol) in DMF (50 mL) was heated at
120 °C under nitrogen. At this temperature and with vigorous stir-
ring, a solution of methyl iodide (1.87 mL, 30 mmol) in DMF
(24 mL) was added dropwise. The mixture was stirred at 120 °C for
3 h. After cooling to room temp., the mixture was diluted with
CHCl3 and water. The organic layer was separated and then
washed with water and brine. The product was isolated by column
chromatography on silica gel (CHCl3) to give compound 1 (721 mg,
62%). 1H NMR (270 MHz, CDCl3): δ = 3.32 (s, 6 H), 7.49 (d, J =
8.9 Hz, 4 H), 7.83 (d, J = 8.9 Hz, 4 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 29.4, 109.4, 126.2, 129.2, 130.4, 137.6,
147.4, 162.4 ppm. MALDI-MS: calcd. for C20H15Cl2N2O2 [M +
H]+ 385.1; found 385.0. C20H14Cl2N2O2 (385.24): calcd. C 62.35,
H 3.66, N 7.27; found C 62.00, H 3.87, N 7.26.
Compound 5: TCNE (9.6 mg, 0.075 mmol) was added to a solution
of 4 (15.1 mg, 0.025 mmol) in CH2Cl2 (1.3 mL) under nitrogen. The
mixture was stirred at room temp. for 5.5 h. The solvent was re-
moved under reduced pressure at room temp. The product was iso-
lated by column chromatography on silica gel (CHCl3/ethyl acetate,
5:1) to give compound 5 (14.3 mg, 67%). An analytically pure sam-
ple was obtained by recrystallization from a concentrated solution
1
in CHCl3. H NMR (270 MHz, CDCl3): δ = 3.20 (s, 12 H), 3.39
(s, 6 H), 6.76 (AAЈBBЈ, 4 H), 7.82 (AAЈBBЈ, 4 H), 7.88 (d, J =
8.6 Hz, 4 H), 8.09 (d, J = 8.6 Hz, 4 H) ppm. 13C{1H} NMR
(150 MHz, CDCl3): δ = 29.9, 40.2, 74.3, 88.5, 111.0, 111.4, 111.7,
112.5, 113.4, 114.1, 117.6, 129.9, 129.9, 130.0, 132.5, 134.0, 147.1,
154.6, 162.0, 162.3, 167.6 ppm. MALDI-MS: calcd. for
C52H35N12O2 [M + H]+ 859.3; found 859.3. HRMS (ESI): calcd.
for C52H34N12O2Na [M + Na]+ 881.2825; found 881.2841.
Compound 2: A mixture of 1 (385 mg, 1.0 mmol), bis(pinacolato)-
diboron (1.78 g, 7.0 mmol), KOAc (687 mg, 7.0 mmol), Pd2(dba)3
(45.8 mg, 0.050 mmol), and XPhos (11.9 mg, 0.025 mmol) in diox-
ane (2.0 mL) was stirred under nitrogen at 110 °C for 4 h. After
cooling to room temp., the mixture was diluted with CHCl3 and
water. The organic layer was separated and then washed with water
and brine. The product was isolated by column chromatography on
silica gel (CHCl3/ethyl acetate, 10:1 Ǟ 8:1) to give compound 2
Crystal Structure Analysis: Intensity data were collected with Ri-
gaku R-AXIS Rapid and Bruker APEXII diffractometers with
Mo-Kα radiation (see Table 5). The crystals were mounted on glass
capillary tubes. A full-matrix least-squares refinement with aniso-
tropic thermal parameters method by the SHELXL-97 program
was used for non-hydrogen atoms. Hydrogen atoms were placed at
calculated positions and were included in the structure calculations
without further refinement of the parameters. CCDC-870567 (for
1), -870568 (for 2), -870569 (for 3), -870570 (for 4), and -870571
(for 5) contain the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
1
(360 mg, 63%). H NMR (400 MHz, CDCl3): δ = 1.37 (s, 24 H),
3.32 (s, 6 H), 7.85 (d, J = 8.4 Hz, 4 H), 7.96 (d, J = 8.4 Hz, 4 H)
ppm. 13C{1H} NMR (150 MHz, CDCl3): δ = 24.6, 29.4, 84.2,
109.8, 128.1, 130.3, 135.1, 148.5, 162.5 ppm. MALDI-MS: calcd.
for C32H38B2N2O6 [M + H]+ 569.3; found 569.3. C32H38B2N2O6 +
H2O (586.30): calcd. C 65.55, H 6.88, N 4.78; found C 65.82, H
6.52, N 4.77.
Compound 3: A mixture of 2 (114 mg, 0.2 mmol), pentafluoroiodo-
benzene (235 mg, 0.8 mmol), K3PO4 (170 mg, 0.8 mmol), Pd-
(OAc)2 (2.2 mg, 0.010 mmol), and SPhos (8.2 mg, 0.020 mmol) in
THF (4.0 mL) was stirred under nitrogen at 60 °C for 22 h. After
Supporting Information (see footnote on the first page of this arti-
cle): Experimental details and characterization data of reported
compounds.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7

Job/Unit: O20761
/KAP1
Date: 13-08-12 11:57:51
Pages: 10
T. Yamagata, J. Kuwabara, T. Kanbara
FULL PAPER
Table 5. Summarized crystallographic data for compound 1–5.
1
2
3·CHCl3, C3H7
4·2CHCl3
5·4CHCl3
Empirical formula
Formula mass
Crystal color
Crystal system
Lattice type
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C20H14Cl2N2O2 C32H38B2N2O6 C32H14F10N2O2·CHCl3·C3H7 C40H34N4O2·2CHCl3 C52H34N12O2·4CHCl3
385.25
568.28
810.92
841.49
1336.43
yellow
orange
orange
red
black
monoclinic
primitive
9.687(2)
13.872(3)
12.729(3)
monoclinic
primitive
10.5488(19)
11.991(2)
12.115(2)
triclinic
triclinic
orthorhombic
primitive
11.1785(5)
22.7758(10)
23.2958(12)
primitive
9.777(6)
11.856(7)
14.401(8)
80.053(7)
89.410(7)
85.507(7)
1639.1(17)
primitive
9.4194(13)
10.9720(17)
20.385(3)
77.849(4)
83.644(3)
71.787(4)
1954.1(5)
107.339(5)
108.602(4)
γ [°]
V [Å3]
1632.8(6)
P21/n (#14)
4
1452.4(5)
P21/c (#14)
2
5931.1(5)
Pbca (#61)
4
¯
¯
Space group
Z value
P1 (#2)
P1 (#2)
2
2
Dcalcd. [g/cm3]
F(000)
1.567
1.299
1.643
1.430
1.497
792
604
818
868
2712
μ (Mo-Ka) [cm–1]
No. of reflections measured
4.156
0.879
34.058
4.821
6.131
total: 14717
unique: 3540
(Rint = 0.164)
direct methods
(SIR92)
3540
total: 13595
unique: 3297
(Rint = 0.142)
direct methods
(SIR92)
191
total: 17938
unique: 7137
(Rint = 0.098)
direct methods
(SIR97)
460
total: 19349
unique: 8826
(Rint = 0.211)
direct methods
(SHELX97)
442
total: 53663
unique: 6752
(Rint = 0.159)
direct methods
(SIR92)
371
Structure solution
No. of variables
Reflection/parameter ratio
R1 [I Ͼ 2.00σ(I)]
15
0.1571
17.26
0.1139
15.52
0.1605
19.97
0.1766
18.2
0.0825
R (all reflections)
0.2104
0.1914
0.251
0.3606
0.1459
wR2 (all reflections)
Goodness-of-fit indicator
0.4188
1.273
0.2739
1.041
0.456
1.49
0.5244
1.171
0.2573
1.084
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Acknowledgment
The authors thank the Chemical Analysis Center of the University
of Tsukuba for the measurement of NMR, ESI-MS, MALDI-
TOF-MS, X-ray, and elemental data. T. Y. acknowledges the Uni-
versity of Tsukuba Research Infrastructure Support Program for
financial support. J. K. acknowledges the Foundation for Interac-
tion in Science and Technology and the Iketani Science and Tech-
nology Foundation for financial support.
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Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20761
/KAP1
Date: 13-08-12 11:57:51
Pages: 10
Synthesis and Characterization of Dioxopyrrolopyrrole Derivatives
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Received: June 7, 2012
Published Online: ᭿
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
9

Job/Unit: O20761
/KAP1
Date: 13-08-12 11:57:51
Pages: 10
T. Yamagata, J. Kuwabara, T. Kanbara
FULL PAPER
Dioxopyrrolopyrrole Derivatives
The redox properties of the DPP (dioxo-
pyrrolopyrrole) core were modulated by the
T. Yamagata, J. Kuwabara,
T. Kanbara* .................................... 1–10
introduction
of
electron-withdrawing
groups, which resulted in the enhancement
of the electron-accepting ability of the DPP
core. In particular, DPP derivatives with
1,1,4,4-tetracyanobutadiene (TCBD) moi-
eties exhibited a unique electrochemical re-
sponse such as undergoing a reversible five-
electron reduction.
Synthesis and Characterization of Dioxo-
pyrrolopyrrole Derivatives Having Elec-
tron-Withdrawing Groups
Keywords: Nitrogen heterocycles / Substitu-
ent effects / Cycloaddition / Density func-
tional calculations / Charge transfer / Elec-
trochemistry
10
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