Hydrogen-bonding-induced chirality organization and stabilization of redox species of polyaniline-unit molecules by introduction of amino acid pendant groups

Article abstract of DOI:10.1002/asia.201100390

The chirality organization of polyaniline-unit molecules was achieved by the introduction of amino acid pendant groups through intramolecular hydrogen bonding, which plays an important role in the stabilization of the chirality-organized redox species. Another interesting feature of the synthesized polyaniline-unit molecules is the luminescent switching properties based on the redox states of the phenylenediamine moiety. Getting organized: The chirality organization of polyaniline-unit molecules was achieved by the introduction of pendant amino acid groups through intramolecular hydrogen bonding; these groups play an important role in the stabilization of the chirality-organized redox species.

Full text of DOI:10.1002/asia.201100390

FULL PAPERS
DOI: 10.1002/asia.201100390
Hydrogen-Bonding-Induced Chirality Organization and Stabilization of
Redox Species of Polyaniline-Unit Molecules by Introduction of Amino Acid
Pendant Groups
Toshiyuki Moriuchi,* Satoshi D. Ohmura, Kenji Morita, and Toshikazu Hirao*[a]
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Chem. Asian J. 2011, 6, 3206 – 3213

Abstract: The chirality organization of polyaniline-unit molecules was achieved by
the introduction of amino acid pendant groups through intramolecular hydrogen
bonding, which plays an important role in the stabilization of the chirality-organ-
ized redox species. Another interesting feature of the synthesized polyaniline-unit
molecules is the luminescent switching properties based on the redox states of the
phenylenediamine moiety.
Keywords: amino acids · chirality ·
hydrogen bond · polyaniline · redox
chemistry
Introduction
of self-assembling properties of amino acids, which contain
both chiral centers and hydrogen bonding sites, is consid-
ered to be a convenient approach to highly ordered systems.
We have already demonstrated that the introduction of
amino acids or dipeptide chains into the molecular scaffold,
such as ferrocene,[11c,12] pyridine,[13] or urea,[14] permits chiral-
ity organization through intramolecular and/or intermolecu-
lar hydrogen bonding interactions. The introduction of
amino acid pendant groups into phenylenediamines or qui-
nonediimines is considered to be a convenient strategy to
induce chirality into a p-conjugated backbone of polyani-
lines,[15] thus affording hydrogen-bonded chiral polymers
wherein redox species of polyanilines are expected to be sta-
bilized by hydrogen bonding. From these points of view,
herein, we report the introduction of amino acid pendant
groups into polyaniline-unit molecules to induce chirality-or-
ganized structures and stabilize redox species by intramolec-
ular hydrogen bonding interactions.
p-Conjugated polymers have attracted much attention for
their potential applications in various electrical materials de-
pending on their electronic properties.[1] Much progress has
been made in understanding the chemistry and physics of p-
conjugated polymers. Polyanilines are one of these promis-
ing electrically conducting p-conjugated polymers with
chemically stability. Polyanilines exist in three different dis-
crete redox forms: as the fully reduced leucoemeraldine
base, as semioxidized emeraldine base, and as the fully oxi-
dized pernigraniline base.[1b] Redox properties have been
controlled previously by the introduction of an acceptor
unit.[2] Attaining structural and chiral control through fur-
ther functionalization still needs further investigation. Re-
search has focused on chiral polyanilines owing to their po-
tential applications in molecular recognition and chiral sepa-
ration.[3] Several methods have been used for the synthesis
of chiral polyanilines, including by doping with a chiral
acid,[4] polymerization of aniline in the presence of a chiral
acid dopant,[5] and the template polymerization of aniline in
the presence of a chiral molecular template.[6] Another inter-
esting function of polyanilines is the coordination properties
of the two nitrogen atoms on the quinonediimine moiety.
The quinonediimine moiety of the emeraldine base form
have been found to be capable of complexation to afford
novel conjugated polymer complexes.[7] The polymer com-
plex can effectively serve as an oxidation catalyst.[8] Also,
controlled complexation with redox-active quinonediimine
derivatives has been used to create conjugated polymeric
complexes, conjugated trimetallic macrocycles, and conju-
gated bimetallic complexes, depending on the coordination
mode.[9] Furthermore, chirality induction of p-conjugated
polyanilines through chiral complexation with the chiral pal-
ladium(II) complexes has been achieved to afford the chiral
conjugated polymer complexes.[10] On the other hand, con-
trol of hydrogen bonding interactions has attracted much at-
tention in the design of various molecular assemblies by
virtue of their directionality and specificity.[11] The utilization
Results and Discussion
The phenylenediamine derivatives 1red-l and 1red-d, which
contain amino acid pendant groups l-Ala-OMe and d-Ala-
OMe, respectively, and derivative 2red-l, which contains
the pendant groups l-Pro-OMe, were synthesized from the
corresponding carboxylic acid form of the phenylenediamine
derivative and l/d-amino acid methyl ester hydrochloride
salt (Scheme 1). Phenylenediamine derivatives 1red-l and
2red-l were oxidized into quinonediimine derivatives 1ox-l
and 2ox-l, respectively, by treatment with iodosobenzene or
lead(IV) acetate as an oxidant (Scheme 1). The oxidized
forms, 1ox-l and 2ox-l, could be reduced again to 1red-l
and 2red-l with hydrazine monohydrate. The thus-obtained
phenylenediamine and quinonediimine derivatives were
fully characterized by spectroscopic and elemental analysis.
1
In the H NMR spectra of 1red-l in [D2]dichloromethane
(1.0ꢁ10À2 m), the NH signals for the phenylenediamine
moiety were hardly perturbed by the addition of an aliquot
of [D6]dimethylsulfoxide to [D2]dichloromethane (CD2Cl2:
8.05 ppm, CD2Cl2/[D6]DMSO (9:1): 8.01 ppm) although the
alanine amido NH signals showed a slight down-field shift
(CD2Cl2: 7.02 ppm, CD2Cl2/[D6]DMSO (9:1): 7.22 ppm).
The FT-IR spectrum of 1red-l in dichloromethane (1.0ꢁ
10À2 m) showed stretching bands for the hydrogen-bonded
and non-hydrogen-bonded NH protons in solution at 3343
and 3426 cmÀ1, respectively. The NH protons of the phenyl-
[a] Dr. T. Moriuchi, S. D. Ohmura, K. Morita, Prof. Dr. T. Hirao
Department of Applied Chemistry
Graduate School of Engineering
Osaka University
Yamada-oka, Suita, Osaka 565-0871 (Japan)
Fax : (+81)6-6879-7415
E-mail: moriuchi@chem.eng.osaka-u.ac.jp
hirao@chem.eng.osaka-u.ac.jp
AHCTUNGTRENNUNG
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201100390.
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in the CD spectrum of 1red-d (Figure 1c), thus indicating
that a chiral molecular arrangement based on the regulated
structures held together by intramolecular hydrogen bond-
ing is formed. ICD at the absorbance region of the p-conju-
gated moiety based on the chirality-organized structure
through the intramolecular hydrogen bonding was also ob-
served in the CD spectrum of the quinonediimine derivative
1ox-l (Figure 1e). The chirality organization of 2red-l
through intramolecular hydrogen bonding was supported by
the appearance of ICD in the absorbance region of the p-
conjugated moiety in the CD spectrum (Figure 1 f).
On the basis of these observations, the structural elucida-
tion of 1red-l was investigated by single-crystal X-ray spec-
troscopy.[16] The crystal structure of 1red-l revealed the for-
mation of intramolecular hydrogen bonds between the
amino NH proton of the phenylenediamine moiety and the
carbonyl oxygen atom, which resulted in an anti-conforma-
tion of the p-conjugated moiety (Figure 2a). Owing to p-
conjugation of 1red-l, the orientation of each terminal ben-
zene ring should be within a limited range of locations par-
allel to the central benzene ring. However, the steric inter-
action between the hydrogen atom at C(3) (C(23)) and the
hydrogen atom at C(25) (C(5)) causes the terminal benzene
ring of 1red-l to rotate away from this orientation, thereby
resulting in a conformation with a dihedral angle of 138.3(2)
and 138.1(2)8 between the terminal benzene and central
benzene rings; this rotation results in a propeller twist be-
tween the planes of the two terminal benzene rings (Fig-
ure 2a). The chirality of the alanine moieties is considered
to induce a propeller twist in the p-conjugated moiety. The
molecular structure of 1red-d composed of the correspond-
ing d-amino acid (-d-Ala-OMe) is a mirror image of 1red-l,
which indicates that it is a conformational isomer (Fig-
ure 2c).[16] As a result, the introduction of amino acid pend-
ant groups into the phenylenediamine moiety was found to
induce the chirality organization through the intramolecular
hydrogen bonds. The phenylenediamine derivative 1red-l
exhibited the sheet-like self-assembly through the intermo-
lecular hydrogen bonding networks, wherein each molecule
is bound to two neighboring molecules in an 18-membered
hydrogen-bonded ring (O(1)gN(3*), 2.832(5) ꢂ; O-
Scheme 1. The phenylenediamine and quinonediimine derivatives bearing
amino acid pendant groups.
alanine amido NH protons might participate in weak hydro-
gen bonds in solution. The alanine amido NH protons were
hardly perturbed by the addition of an aliquot of
[D6]dimethyl sulfoxide to [D2]dichloromethane (CD2Cl2:
10.35 ppm, CD2Cl2/[D6]DMSO (9:1): 10.34 ppm) in the
1H NMR spectra of 1ox-l in [D2]dichloromethane (1.0ꢁ
10À2 m). The quinonediimine moiety of 1ox-l was also indi-
cated to be regulated by intramolecular hydrogen bonds.
The FT-IR spectrum of 1ox-l in dichloromethane (1.0ꢁ
À1
10À2 m) showed a N H stretch at 3207 cm , which confirms
À
the hydrogen bonding in 1ox-l. The 1H NMR spectra of
2red-l in [D2]dichloromethane (1.0ꢁ10À2 m) shows that the
NH protons of the phenylenediamine moiety were hardly
perturbed by the addition of an aliquot of [D6]dimethyl sulf-
oxide to [D2]dichloromethane (CD2Cl2: 7.13 ppm, CD2Cl2/
[D6]DMSO (9:1): 7.13 ppm). The FT-IR spectrum of 2red-l
AHCTUNGTREG(NNUN 11*)gN(13), 2.842(5) ꢂ; Figure 2b). The mirror-image
sheet-like molecular arrangement was observed in the crys-
tal packing of 1red-d (Figure 2d).
in dichloromethane (1.0ꢁ10À2 m) showed hydrogen-bonded
N H stretching bands at 3360 cm in the solution state.
À1
À
These results indicate that the NH protons of the phenyle-
nediamine moiety form intramolecular hydrogen bonds.
The electronic spectrum of the phenylenediamine 1red-l
in dichloromethane exhibited a broad absorption at around
400 nm, which is probably due to a low-energy charge-trans-
fer transition of the p-conjugated moiety (Figure 1a). It
should be noted that 1red-l exhibited an induced circular
dichroism (ICD) at the absorbance region of the p-conjugat-
ed moiety in the CD spectrum (Figure 1c). This result indi-
cates that the chirality induction of the p-conjugated back-
bone aniline oligomer is achieved by chirality organization
through the intramolecular hydrogen bonding. The mirror
image of the CD signals observed with 1red-l was obtained
The redox processes of 1 and 2 were investigated by cyclic
voltammetry. The phenylenediamine derivative 1red-l in di-
chloromethane showed two one-electron redox waves (E1/
2 =0.19 and 0.55 V vs. Fc/Fc+), which can be assigned to suc-
cessive one-electron-oxidation processes of the phenylenedi-
amine moiety to give the corresponding oxidized species, as
shown in Figure 3a. The two one-electron redox waves
(E1/2=0.21 and 0.58 V vs. Fc/Fc+) based the successive one-
electron-oxidation processes of the phenylenediamine
moiety were also observed in the cyclic voltammogram of
the phenylenediamine derivative 2red-l (Figure 3c). Inter-
estingly, the quinonediimine derivative 1ox-l exhibited two
one-electron redox waves
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Chirality Organization and Stabilization of Redox Species of Polyaniline-Unit Molecules
Figure 1. The electronic spectra of a) 1red-l and 1red-l·+, b) 1ox-l and 1ox-l·À in acetonitrile (1.0ꢁ10À4 m). The CD spectra of c) 1red-l and 1red-d,
f) 2red-l in dichloromethane (1.0ꢁ10À4 m), and d) 1red-l and 1red-l·+, e) 1ox-l and 1ox-l·À in acetonitrile (2.5ꢁ10À4 m) at 298 K under a nitrogen atmos-
phere.
Figure 2. Molecular structures of a) 1red-l and c) 1red-l. A portion of a layer containing a sheet-like molecular arrangement through the intermolecular
hydrogen bonding networks in the crystal packing of b) 1red-l and d) 1red-d.
Chem. Asian J. 2011, 6, 3206 – 3213
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T. Moriuchi, T. Hirao et al.
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Figure 3. Cyclic voltammograms of a) 1red-l, b) 1ox-l, c) 2red-l, and
d) 2ox-l in dichloromethane (5.0ꢁ10À4 m) containing 0.1m Bu4NClO4 at a
platinum working electrode with scan rate 100 mVsÀ1 at 298 K under an
argon atmosphere.
(E1/2=À1.25 and À1.03 V vs. Fc/Fc+) can be assigned to the
successive one-electron-reduction processes of the quinone-
diimine moiety to give the corresponding reduced species
(Figure 3b). Generally, the generated radical anion appears
to be unstable, although this depends on the availability of a
proton source. In the case of 1ox-l, the formation of intra-
molecular hydrogen bonds is thought to stabilize the corre-
sponding reduced species. On the contrary, the reduction
waves (Epc =À1.80 and À1.34 V vs. Fc/Fc+) of the quinone-
diimine derivative 2ox-l shifted cathodically compared with
1ox-l (Figure 3d). Compared with the non-hydrogen-
bonded quinonediimine, the hydrogen-bonded analogue be-
comes stabilized as an electron sink. Accordingly, the redox
properties of the quinonediimine moiety are considered to
be modulated by the formation of hydrogen bonding.
To gain insight into the chirality-organized redox species
of 1red-l and 1ox-l, the redox behavior was investigated
spectroscopically. The chemical oxidation of 1red-l in aceto-
nitrile with an equimolar amount of NOBF4 resulted in the
formation of the phenylenediamine radical cation 1red-l·+,
which showed a broad absorption at around 750 nm in the
electronic spectrum (Figure 1a).
Figure 4. ESR spectra of a) 1red-l·+ in acetonitrile (1.0ꢁ10À3 m) and
b) 1ox-l·À in dichloromethane (1.0ꢁ10À3 m) at 298 K under a nitrogen at-
mosphere (black), and the simulated spectra (light gray).
anion 1ox-l·À could be obtained by the chemical reduction
of 1ox-l in dichloromethane with an equimolar amount of
CoCp2. The generated semiquinonediimine radical anion
1ox-l·À was characterized by broad bands at around 610 and
750 nm in its electronic spectrum (Figure 1b). An ICD at
around 550-800 nm based on the semiquinonediimine radical
anion in the CD spectrum (Figure 1e) suggests the forma-
tion of the chirality-organized structure through intramolec-
ular hydrogen bonding. The formation of intramolecular hy-
drogen bonds in the semiquinonediimine radical anion was
also confirmed by the observation of hyperfine coupling in
the ESR spectrum (AN =5.38 G; AH =2.63 G; AH =1.02 G;
AH =0.65 G; AH =0.57 G), and superhyperfine splitting
owing to two equivalent nitrogen and two equivalent proton
nuclei (AN =1.03 G; AH =0.72 G) (Figure 4b); this splitting
indicates a stabilization of the semiquinonediimine radical
anion by the formation of intramolecular hydrogen bonds.
The luminescent switching of the phenylenediamines
bearing ethoxycarbonyl groups has been already demon-
strated.[17] The reduced form 1red-l exhibited strong lumi-
nescence at 559 nm (Figure 5a). On the contrary, weak lumi-
nescence was observed with the oxidized form 1ox-l. These
findings indicate that redox switching of the luminescent
properties is achieved by changing the redox state of the p-
conjugated moiety. The redox switching of the luminescent
It is noteworthy that 1red-l·+ exhibited an ICD at around
750 nm, based on the phenylenediamine radical cation in
the CD spectrum (Figure 1d). This result indicates the pres-
ervation of the chirality-organized structure through intra-
molecular hydrogen bonding. The ESR spectrum of 1red-l·+
showed the signals centered around g=2.0036, with hyper-
fine coupling as shown in Figure 4a; this result indicates
that the unpaired electron is located mostly on the phenyl-
ACHTUNGTRENNUNGenediamine moiety. The ESR signal could be approximately
simulated by assuming the following parameters: AN =5.60
G; AH =6.18 G; AH =2.17 G; AH =1.12 G; AH =0.97 G;
AH =0.50 G (Figure 4a). The semiquinonediimine radical
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Chirality Organization and Stabilization of Redox Species of Polyaniline-Unit Molecules
atmosphere at 298 K. Fluorescence
emission spectra were recorded using
a
SHIMADZU RF-5300PC spectro-
fluorometer under an argon atmos-
phere at 298 K. ESR spectrum was
taken on a JEOL X-band spectrome-
ter (JES-RE1XE). CD spectra were
recorded using a JASCO J-720 spec-
tropolarimeter. UV/Vis. and CD meas-
urements were conducted using 1 cm
path length quartz cuvettes. Cyclic vol-
tammograms were recorded on a BAS
CV-50W voltammetry analyzer under
an argon atmosphere at 298 K.
General Procedure for Synthesis of
Phenylenediamine 1red
Figure 5. a) Emission spectra of 1red-l (lex =409 nm) and 1ox-l (lex =409 nm) and b) 2red-l (lex =375 nm)
and 2ox-l (lex =375 nm) in dichloromethane (1.0ꢁ10À4 m) at 298 K under a nitrogen atmosphere.
A mixture of diethyl 2,5-bis(phenyla-
mino)terephthalate
1.5 mmol) and sodium hydroxide
(ca. 132 mg) in tetrahydrofuran
(15 mL) was refluxed for 24 h. After
(607 mg,
properties was also observed between 2red-l and 2ox-l
the reaction was completed, the solvent was evaporated and the residue
was dried in vacuo. Water (15 mL) was added to the residue, and the so-
lution was acidified with a 1m HCl aqueous solution. The violet precipi-
tate was isolated by filtration, washed with water, and dried in vacuo.
Dry dichloromethane (50 mL) was added to a mixture of the thus-ob-
tained violet solid, 1-hydroxybenzotriazole (676 mg, 5.0 mmol), l- or d-
alanine methyl ester hydrochloride (698 mg, 5.0 mmol), and triethylamine
(4.4 mL). The mixture was stirred at 08C and a solution of 1-ethyl-3-(3-
dimethylaminopropyl)carbodiimide hydrochloride (959 mg, 5.0 mmol) in
dry dichloromethane (40 mL) was added dropwise to the mixture over
1 h. Then, the mixture was stirred at ambient temperature for 48 h. The
resulting mixture was diluted with dichloromethane (20 mL) and washed
with saturated NaHCO3 aqueous solution (2ꢁ30 mL), water (30 mL),
and saturated NaCl aqueous solution (30 mL). After separating and dis-
carding the water phase, the organic phase was dried on Na2SO4. After
evaporation of the solvent, a mixture was purified by column chromatog-
raphy on silica gel (from n-hexane to n-hexane/ethyl acetate=1:1) to
give 1red (1red-l: 620 mg; 1red-d: 607 mg) as an orange solid, Rf =0.28
(ethyl acetate). The obtained compound was recrystallized from ethyl
acetate/n-hexane.
(Figure 5b).
Conclusions
In conclusion, the chirality organization of polyaniline-unit
molecules was achieved by the introduction of amino acid
pendant groups through intramolecular hydrogen bonding.
Furthermore, the intramolecular hydrogen bonds were
shown to play an important role in the stabilization of the
redox species of polyaniline-unit molecules, wherein the
chirality-organized structures are preserved through intra-
molecular hydrogen bonding. Another interesting feature of
the designed polyaniline-unit molecules is the luminescent-
switching properties based on the redox states of the phenyl-
enediamine moiety. Our strategy for chirality organization
through intramolecular hydrogen bonding provides an effi-
cient and feasible route to chiral redox-active molecules, in
which hydrogen bonding is envisioned to play an important
role as a proton dopant and a binding unit for the controlled
assembly of p-conjugated moieties. These chirality-organ-
ized redox-active phenylenediamines or quinonediimines
are considered to have potential as promising functionalized
materials and asymmetric redox catalysts. Future work will
concentrate on the design of hydrogen-bonded chiral
1red-l: 95% yield of isolated product; m.p. 161–1638C (uncorrected);
1H NMR (400 MHz, CD2Cl2): d=8.04 (s, 2H), 7.58 (s, 2H), 7.27 (t, J=
7.5 Hz, 4H), 7.07 (d, J=7.5 Hz, 4H), 6.93~6.98 (m, 4H), 4.63 (quint, J=
7.2 Hz, 2H), 3.69 (s, 6H), 1.39 (d, J=7.2 Hz, 6H); 13C NMR (100 MHz,
CD2Cl2): 173.5, 167.5, 143.5, 136.8, 129.8, 125.8, 121.9, 119.2, 118.8, 52.8,
48.9, 18.2 ppm; IR (KBr): n˜ =3374, 3323, 2990, 2951, 1750, 1630, 1602,
1588, 1534, 1498, 1437, 1263 cmÀ1; IR (CH2Cl2, 1.0ꢁ10À2 m): n˜ =3426,
3343, 2986, 2955, 1741, 1649, 1600, 1587, 1530, 1496, 1437, 1262,
1212 cmÀ1
;
HRMS (FAB) m/z: [M]+ 518.2177, C28H30N4O6 (calc.
518.2165); Anal. Calcd. for C28H30N4O6: C, 64.85; H, 5.83; N, 10.80;
Found: C, 64.64; H, 5.67; N, 10.75.
polyaniACHTUNGTRENNUNGlines.
1red-d: 93% yield of isolated product; m.p. 161–1638C (uncorrected);
1H NMR (400 MHz, CD2Cl2): d=8.04 (s, 2H), 7.58 (s, 2H), 7.27 (t, J=
7.5 Hz, 4H), 7.07 (d, J=7.5 Hz, 4H), 6.93~6.98 (m, 4H), 4.63 (quint, J=
7.2 Hz, 2H), 3.69 (s, 6H), 1.39 (d, J=7.2 Hz, 6H); 13C NMR (100 MHz,
CD2Cl2)): 173.5, 167.5, 143.5, 136.8, 129.8, 125.8, 121.9, 119.2, 118.8, 52.8,
48.9, 18.2 ppm; IR (KBr): n˜ =3374, 3323, 2990, 2951, 1750, 1630, 1602,
1588, 1534, 1498, 1437, 1263 cmÀ1; IR (CH2Cl2, 1.0ꢁ10À2 m) 3426, 3343,
Experimental Section
General Methods
2986, 2955, 1741, 1649, 1600, 1587, 1530, 1496, 1437, 1262, 1212 cmÀ1
;
All reagents and solvents were purchased from commercial sources and
were further purified by standard methods if necessary. Solvents were
dried by refluxing in the presence of appropriate drying reagents, distilled
under an argon atmosphere, and stored in the dry box. 1H NMR spectra
were recorded on a JEOL JNM-ECP 400 or a JNM-ECS 400 (400 MHz)
spectrometer with tetramethylsilane as an internal standard. Mass spectra
were run on a JEOL JMS DX-303 spectrometer. UV/Vis. spectra were
recorded using a HITACHI U-3500 spectrophotometer under an argon
HRMS (FAB) m/z: [M]+ 518.2181, C28H30N4O6 (calc. 518.2165); Anal.
Calc. for C28H30N4O6: C, 64.85; H, 5.83; N, 10.80; Found: C, 64.77; H,
5.56; N, 10.74.
General Procedure for Synthesis of Quinonediimine 1ox
A mixture of phenylenediamine 1red (51.8 mg, 0.1 mmol) and iodosyl-
benzene (44.0 mg, 0.2 mmol) in dry dichloromethane (10 mL) was re-
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T. Moriuchi, T. Hirao et al.
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fluxed under argon atmosphere for 3 h. The resulting mixture was filtered
and the filtrate was evaporated in vacuo. After evaporation of the sol-
vent, a mixture was purified by column chromatography on silica gel
(from n-hexane to ethyl acetate) to give 1ox (1ox-l: 46.5 mg; 1ox-d:
46.4 mg) as a red-brown solid, Rf =0.65 (ethyl acetate).
(from n-hexane to ethyl acetate) to give 2ox-l (45.4 mg) as a red-brown
solid, Rf =0.38 (ethyl acetate/n-hexane=4:1).
2ox-l: 80% yield of isolated product; m.p. 94–958C (uncorrected);
1H NMR (400 MHz, CD2Cl2) as a mixture of two syn/anti isomers, d=
7.45–7.40 (m, 4H), 7.25–7.22 (m, 2H), 6.94–6.84 (m, 6H), 4.51–4.49 (m,
1.5H), 4.31 (d, J=8.2 Hz, 0.5H), 3.66–3.65 (m, 2H), 3.60–3.46 (m, 2H),
2.27–2.17 (m, 2H), 2.04–1.89 (m, 6H); 13C NMR (100 MHz, CD2Cl2) as a
mixture of two syn/anti isomers: 172.8, 172.6, 165.8, 165.8, 155.8, 155.5,
155.4, 149.9, 149.8, 149.7, 144.6, 144.1, 129.5, 126.3, 126.2, 122.6, 121.9,
121.0, 60.7, 58.9, 52.7, 52.5, 48.7, 46.4, 31.4, 29.8, 29.5, 25.1, 23.0 ppm; IR
1ox-l: 90% yield of isolated product; m.p. 193–1968C (uncorrected);
1H NMR (400 MHz, CD2Cl2): d=10.34 (d, J=7.2 Hz, 2H), 8.02 (s, 2H),
7.50 (t, J=7.3 Hz, 4H), 7.33 (t, J=7.3 Hz, 2H), 7.05 (d, J=8.4 Hz, 4H),
4.61 (quint., J=7.0 Hz, 2H), 3.71 (s, 6H), 1.45 (d, J=6.9 Hz, 6H);
13C NMR (100 MHz, CD2Cl2): 173.4, 162.6, 157.4, 148.2, 134.4, 130.3,
129.7, 127.3, 122.0, 52.7, 49.4, 18.4 ppm; IR (KBr): n˜ =3454, 3184, 1739,
1663, 1570, 1552, 1481, 1452, 1147, 693 cmÀ1; IR (CH2Cl2, 1.0ꢁ10À2 m)
(KBr): n˜ =2953, 1742, 1647, 1574, 1430, 1200, 1175, 699 cmÀ1
; IR
(CH2Cl2, 1.0ꢁ10À2 m): n˜ =2955, 1744, 1643, 1575, 1435, 1200, 1177,
703 cmÀ1; HRMS (EI) m/z: [M+Na]+ 591.2225, C32H32N4O6Na (calc.
591.2220); Anal. Calc. for C32H32N4O6·0.5 H2O: C, 65.55; H, 5.71; N, 9.70;
Found: C, 66.51; H, 5.66; N, 9.60.
3207, 2991, 2955, 1743, 1662, 1571, 1526, 1482, 1452, 1216, 1149, 696 cmÀ1
;
HRMS (FAB) m/z: [M]+ 516.2003, C28H28N4O6 (calc. 516.2009); Anal.
Calc. for C28H28N4O6: C, 65.12; H, 5.43; N, 10.85; Found: C, 64.83; H,
5.32; N, 10.87.
Generation of 1ox-l·À
1ox-d: 91% yield of isolated product; m.p. 193–1968C (uncorrected);
1H NMR (400 MHz, CD2Cl2): d=10.34 (d, J=7.2 Hz, 2H), 8.02 (s, 2H),
7.50 (t, J=7.3 Hz, 4H), 7.33 (t, J=7.3 Hz, 2H), 7.05 (d, J=8.4 Hz, 4H),
4.61 (quint., J=7.0 Hz, 2H), 3.71 (s, 6H), 1.45 (d, J=6.9 Hz, 6H);
13C NMR (100 MHz, CD2Cl2): 173.4, 162.6, 157.4, 148.2, 134.4, 130.3,
129.7, 127.3, 122.0, 52.7, 49.4, 18.4 ppm; IR (KBr): n˜ =3454, 3184, 1739,
1663, 1570, 1552, 1481, 1452, 1147, 693 cmÀ1; IR (CH2Cl2, 1.0ꢁ10À2 m):
n˜ =3207, 2991, 2955, 1743, 1662, 1571, 1526, 1482, 1452, 1216, 1149,
For spectroscopic purposes, 1ox-l·À was generated by treatment of 1ox-l
(1.0ꢁ10À3 m) with 1.0 equiv of cobaltocene in acetonitrile. The cobalto-
cene and cobaltocenium ion present in the reaction mixture did not sig-
nificantly interfere with the electronic spectrum because of their low ex-
tinction coefficients below 400 nm.
Generation of 1red-l·+
696 cmÀ1
;
HRMS (FAB) m/z: [M]+ 516.2010, C28H28N4O6 (calc.
For spectroscopic purposes, 1red-l·+ (1.0ꢁ10À3 m) was generated by treat-
ment of 1red-l with 1.0 equiv of nitrosonium tetrafluoroborate in aceto-
nitrile.
516.2009).
Synthesis of Phenylenediamine 2red-l
mixture of diethyl 2,5-bis(phenylamino)terephthalate (606 mg,
UV/Vis Measurements
A
UV/Vis spectra of 1l and 2l were measured using a Hitachi U-3500
spectrophotometer in deaerated acetonitrile or dichloromethane (1.0ꢁ
10À4 m) under a nitrogen atmosphere at 298 K.
1.5 mmol) and sodium hydroxide (ca. 132 mg) in tetrahydrofuran
(15 mL) was refluxed for 24 h. After the reaction was completed, the sol-
vent was evaporated and the residue was dried in vacuo. Water (15 mL)
was added to the residue, and the solution was acidified with a 1m HCl
aqueous solution. The violet precipitate was isolated by filtration, washed
with water, and dried in vacuo. Dry dichloromethane (40 mL) was added
to a mixture of the thus-obtained violet solid, 1-hydroxybenzotriazole
(676 mg, 5.0 mmol), l-proline methyl ester hydrochloride (828 mg,
5.0 mmol), and triethylamine (4.4 mL). The mixture was stirred at 08C,
and a solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydro-
chloride (959 mg, 5.0 mmol) in dry dichloromethane (40 mL) was drop-
wise added to the mixture over 1 h. Then, the mixture was stirred at am-
bient temperature for 60 h. The resulting mixture was diluted with di-
chloromethane (20 mL), washed with saturated NaHCO3 aqueous solu-
tion (2ꢁ30 mL), water (30 mL), and saturated NaCl aqueous solution
(30 mL). After separating and discarding the water phase, the organic
phase was dried on Na2SO4. After evaporation of the solvent, a mixture
was purified by column chromatography on silica gel (from n-hexane to
n-hexane/ethyl acetate=1:4) to give 2red-l (583 mg) as a yellow solid,
Rf =0.50 (ethyl acetate/n-hexane=4:1).
CD Measurements
CD spectra of 1 and 2red-l were measured using a JASCO J-720 spectro-
polarimeter under a nitrogen atmosphere at 298 K in deaerated acetoni-
trile or dichloromethane with the concentrations of 1.0ꢁ10À4 or 2.5ꢁ
10À4 m, respectively.
Emission Measurements
Emission spectra of 1l and 2l were measured using a SHIMADZU
RF5300-PC spectrofluorophotometer in a deaerated dichloromethane so-
lution (1.0ꢁ10À5 m) under a nitrogen atmosphere at 298 K.
ESR Measurements
ESR spectra of 1red-l·+ and 1ox-l·À were measured using a JEOL X-
band spectrometer (JES-RE1XE) under a nitrogen atmosphere at 298 K.
1red-l·+ was measured in deaerated acetonitrile with the concentration
of 1.0ꢁ10À4
m
under non-saturating microwave-power conditions
(1.0 mW) operating at 9.0610 GHz. 1ox-l·À was measured in deaerated
dichloromethane with the concentration 1.0ꢁ10À4 m under non-saturating
microwave-power conditions (1.5 mW) operating at 9.0546 GHz.
2red-l: 78% yield of isolated product; m.p. 154–1568C (uncorrected);
1H NMR (400 MHz, CD2Cl2): d=7.36 (s, 2H), 7.26 (t, J=7.8 Hz, 4H),
7.12 (s, 2H), 7.08 (d, J=7.8 Hz, 4H), 6.91 (t, J=7.3 Hz, 2H) 4.56–4.59
(m, 2H), 3.73 (s, 6H), 3.47–3.60 (m, 4H), 2.24–2.33 (m, 2H), 2.00–1.81
(m, 6H); 13C NMR (100 MHz, CD2Cl2): 173.2, 168.5, 143.5, 134.5, 129.8,
127.6, 121.2, 118.0, 117.3, 59.3, 52.8, 49.9, 29.8, 25.6 ppm; IR (KBr): n˜ =
X-ray Structure Analysis
Measurements for 1red-l were made on a Rigaku RAXIS-RAPID Imag-
ing Plate diffractometer with graphite-monochromated MoKa radiation
and measurements of 1red-d were made on a Rigaku RAXIS-RAPID
Imaging Plate diffractometer with graphite-monochromated CuKa radia-
tion. The structures of 1red-l and 1red-d were solved by direct methods
and expanded using Fourier techniques. The non-hydrogen atoms were
refined anisotropically. The H atoms involved in hydrogen bonding were
located in electron-density maps. The remainder of the H atoms were
placed in idealized positions and allowed to ride with the C atoms to
which each was bonded. Crystallographic details and hydrogen bonds are
given in the Supporting Information, Tables S1 and S2, respectively.[16]
3279, 3195, 2970, 2954, 1750, 1618, 1549, 1498, 1456, 1289, 1175, 750 cmÀ1
;
IR (CH2Cl2, 1.0ꢁ10À2 m): n˜ =3360, 2992, 2982, 1732, 1632, 1600, 1586,
1559, 1497, 1477, 1274, 1178, 754 cmÀ1; HRMS (EI) m/z: [M+Na]+
593.2384, C32H34N4O6Na (calc. 593.2376); Anal. Calc. for C32H34N4O6: C,
67.40; H, 6.00; N, 9.80; Found: C, 67.27; H, 5.90; N, 9.70.
Synthesis of Quinonediimine 2ox-l
A mixture of phenylenediamine 2red-l (54.2 mg, 0.1 mmol) and iodosyl-
benzene (26.4 mg, 0.1 mmol) in dry dichloromethane (5.0 mL) was re-
fluxed under argon atmosphere for 6 h. The resulting mixture was filtered
and the filtrate was evaporated in vacuo. After evaporation of the sol-
vent, a mixture was purified by column chromatography on silica gel
3212
www.chemasianj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2011, 6, 3206 – 3213

Chirality Organization and Stabilization of Redox Species of Polyaniline-Unit Molecules
1999, 40, 3009–3012; c) T. Hirao, S. Yamaguchi, S. Fukuhara, Synth.
Met. 1999, 106, 67–70.
Acknowledgements
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We thank Dr. T. Suenobu and Prof. S. Fukuzumi at Osaka University for
the ESR spectroscopic analysis. This work was supported by Grant-In-
Aids for Science Research on Innovative Areas (No. 22108516 and
23111711) from the Ministry of Education, Culture, Sports, Science and
Technology, Japan. Thanks are also due to the Analytical Center, Gradu-
ate School of Engineering, Osaka University, for the use of the NMR
spectrometers. S.D.O. expresses special thanks to the Osaka University
Global COE (center of excellence) Program “Global Education and Re-
search Center for Bio-Environmental Chemistry”.
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[16] Crystal data for 1red-l: C28H30N4O6, M=518.57, monoclinic, space
group P21 (No. 4), a=14.8203(6) ꢂ, b=5.0199(2) ꢂ, c=
17.7205(7) ꢂ, b=95.8060(17)8, V=1311.58(9) ꢂ3, Z=2, T=4.08C,
D
calc =1.313 gcmÀ3
,
(MoKa)=0.94 cmÀ1
mACHTUNGTERUNNNG , MoKa radiation (l=
0.71075 ꢂ), R1=0.0832, wR2=0.2456. Crystal data for 1red-d:
C28H30N4O6, M=518.57, monoclinic, space group P21 (No. 4), a=
14.8463(3) ꢂ, b=5.03545(9) ꢂ, c=17.7458(3) ꢂ, b=95.7702(10)8,
V=1319.91(9) ꢂ3, Z=2, T=4.08C, Dcalc =1.313 gcmÀ3, m
ACHTUNGTRENNUNG
7.672 cmÀ1
,
0.1182. CCDC 816048 (1red-l) and CCDC 816049 (1red-d) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallograph-
ic Data Center via www.ccdc.cam.ac.uk/data_request/cif.
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Received: April 18, 2011
Published online: September 26, 2011
Chem. Asian J. 2011, 6, 3206 – 3213
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
3213