Synthesis, reaction, and optical properties of cyclic oligomers bearing 9,10-diphenylanthracene based on an aromatic tertiary amide unit

Article abstract of DOI:10.1039/c3ra46652c

Novel cyclic aromatic amide oligomers containing highly fluorescent 9,10-diphenylanthracene units were prepared by condensation of a monomer with amino and ester functional groups using lithium bis(trimethylsilyl)amide. The cyclic trimer (C3A, 40%) and tetramer (C4A, 8%) were isolated using preparative gel permeation chromatography. Some of the aromatic proton signals derived from anthracene were observed in the upfield region (6.96-6.87 ppm) in the ¹H nuclear magnetic resonance spectrum of C3A. X-ray crystallographic analysis indicated that three anthracene moieties are inclined with respect to the cyclic skeleton and partly overlap each other. The fluorescence peak maximum of C3A (438 nm) showed a small red-shift compared with that of an acyclic model compound (425 nm). Reduction of the amide carbonyl group in C3A gave the cyclic trimer HC3A, which has a tertiary amine unit. The fluorescence peak maximum of HC3A (489 nm) was largely red-shifted from that of C3A and exhibited strong solvent dependence. A linear correlation was observed between the Stokes shift (Δν), ranging from 2981 to 6646 cm^-1, and the Reichardt's solvent polarity parameter [E_T(30)].

Full text of DOI:10.1039/c3ra46652c

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PAPER
Synthesis, reaction, and optical properties of cyclic
oligomers bearing 9,10-diphenylanthracene based
on an aromatic tertiary amide unit†
Cite this: RSC Adv., 2014, 4, 6752
Ryohei Yamakado,a Shin-ichi Matsuoka,a Masato Suzuki,a Daisuke Takeuchi,b
c
d
a
*
Hyuma Masu, Isao Azumaya and Koji Takagi
Novel cyclic aromatic amide oligomers containing highly fluorescent 9,10-diphenylanthracene units were
prepared by condensation of a monomer with amino and ester functional groups using lithium
bis(trimethylsilyl)amide. The cyclic trimer (C3A, 40%) and tetramer (C4A, 8%) were isolated using
preparative gel permeation chromatography. Some of the aromatic proton signals derived from
1
anthracene were observed in the upfield region (6.96–6.87 ppm) in the H nuclear magnetic resonance
spectrum of C3A. X-ray crystallographic analysis indicated that three anthracene moieties are inclined
with respect to the cyclic skeleton and partly overlap each other. The fluorescence peak maximum of
C3A (438 nm) showed a small red-shift compared with that of an acyclic model compound (425 nm).
Reduction of the amide carbonyl group in C3A gave the cyclic trimer HC3A, which has a tertiary amine
unit. The fluorescence peak maximum of HC3A (489 nm) was largely red-shifted from that of C3A and
exhibited strong solvent dependence. A linear correlation was observed between the Stokes shift (Dn),
ranging from 2981 to 6646 cmꢀ1, and the Reichardt's solvent polarity parameter [ET(30)].
Received 13th November 2013
Accepted 23rd December 2013
DOI: 10.1039/c3ra46652c
www.rsc.org/advances
chromophores and the relative orientation of their dipole
moments. Accordingly, both the chemical structure and the
Introduction
three-dimensional arrangement have to be taken into account
when developing new materials with optimal properties for
optoelectronic applications. A number of cyclic oligomers,
including [2,2]paracyclophane,7–12 calix[4]arene,13–15 bicyclo
[4.4.1]undecane,16–18 and pillar[5]arene,19,20 have been used as
scaffolds for the three-dimensional arrangement of p-conju-
gated systems. For example, Bazan et al.7–9 and Morisaki
et al.10–12 independently reported that the [2,2]paracyclophane
unit shows transannular through-space p–p interactions and is
an excellent building block for the elongation of p-conjugated
systems. It has also been demonstrated that an enantiopure
ortho-difunctionalized [2,2]paracyclophane chiral skeleton can
align p-conjugated oligomers to give optically active proper-
ties.21 We previously investigated the alignment of pyrene using
cyclic aromatic amide trimer, meta-calix[3]amide, as the scaf-
fold.22 As a result of steric effects, the pyrenyl groups attached to
the benzene ring were aligned in a screw-like fashion; this was
conrmed by X-ray crystallographic analysis. However, the
distance and orientation of p-conjugated chromophores on the
benzene ring are difficult to control, especially in the solution
state, because meta-calix[3]amide has a conformational exi-
bility derived from syn and anti isomers.23 Recently, we achieved
three-dimensional arrangement of bithiophenes with dynamic
triple-stranded helicity using the planar chirality of meta-calix[3]
amide.24 Although the interconversion between syn and anti
isomers was nicely suppressed, the synthetic procedure
The well-dened three-dimensional spatial arrangement of
p-conjugated chromophores has been attracting much atten-
tion with regard to the fundamental understanding of the
relationship between this spatial arrangement and the opto-
electronic properties of a compound.1,2 This is because such
organic molecules are mostly used not in an isolated state but in
a condensed state (lm or crystal) in optoelectronic devices
such as light-emitting diodes,3 eld-effect transistors,4 and
photovoltaic cells.5 In uorescence resonance energy transfer
(FRET) between energy-donor and energy-acceptor chromo-
¨
phores, the FRET efficiency can be described by the Forster
equation.6 The efficiency of this energy transfer is inversely
proportional to the sixth power of the distance between the two
aDepartment of Materials Science and Engineering, Nagoya Institute of Technology,
Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan
bChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho,
Midori-ku, Yokohama, 226-8503, Japan
cCenter for Analytical Instrumentation, Chiba University, 1-33 Yayoi-cho, Inage-ku,
Chiba, Chiba, 263-8522, Japan
dFaculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi,
Chiba, 274-8510, Japan
† Electronic supplementary information (ESI) available: Experimental details and
characterization data, GPC proles, MALDI-TOF mass spectra, UV/uorescence
spectra, and X-ray crystal structures of materials. CCDC 961419 and 961420. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c3ra46652c
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consisted of multi-step reactions to be concerned with the low coupling reaction with 4-methoxycarbonylphenylboronic acid
efficiency. We then envisaged that the install of p-conjugated pinacol ester, giving 1 as a yellow powder in 82% yield. The cyclic
chromophores directly in the cyclic structure would be better oligomerization of 1 was performed using a 1 M tetrahydrofuran
strategy to furnish the precision arrangement of p-conjugated (THF) solution of lithium bis(trimethylsilyl)amide (LiHMDS)
chromophores and the aromatic tertiary amide unit must be an (Scheme 2). According to the method previously reported by
excellent linker to construct the molecule.
Yokozawa et al.,34 a THF solution of 1 was slowly added to
ꢁ
9,10-Diphenylanthracene (DPA) and its derivatives are highly LiHMDS (5 equiv. relative to 1) at room temperature and 0 C
uorescent, and they are useful so materials for the light-emit- (Method A). Although 1 was almost completely consumed irre-
ting application.25,26 Accordingly, it is important to investigate the spective of the reaction temperature (Fig. S20,† broken line), a
relationship between the three-dimensional arrangement and the proton signal assignable to the methyl ester was clearly detected
optical properties. Yoshizawa et al. reported a tubular macrocycle in the 1H NMR spectrum, implying the production of linear
containing four anthracene units connected by meta-phenylene oligomers instead of cyclic oligomers. Higher-molecular-weight
linkers.27 Despite the close arrangement of the chromophores, the oligomers were obtained by carrying out the reaction at room
compound showed neither excimer emission nor uorescence temperature. In contrast, when the cyclic oligomerization was
quenching, as a result of the enforced orthogonal conformation. performed by dropwise addition of LiHMDS to a THF solution of
Toyota et al.28 and Zhao et al.29 synthesized aryleneethynylene 1 (Method B), no proton signal derived from the methyl ester was
1
macrocycles containing the 9,10-anthrylene unit, and demon- observed in the H NMR spectrum. In the matrix-assisted laser
strated self-assembly behavior in the solution and liquid-crystal- desorption/ionization-time of ight (MALDI-TOF) mass spectrum
line phases. However, currently known macrocycles mostly of the crude products, cyclic oligomers (3-mer–6-mer) were
have hydrocarbon frameworks.30–32 The introduction of hetero- specically detected. No signicant temperature dependence was
atoms and push–pull interactions is expected to impart charge- observed in the gel permeation chromatography (GPC) proles
transfer properties to cyclic oligomers bearing p-conjugated between room temperature and 0 ꢁC (Fig. S20,† solid line). Cyclic
chromophores.33
trimer (C3A) and tetramer (C4A) were isolated, using preparative
In this paper, we will describe the synthesis of new cyclic GPC, in 40% and 8% yields, respectively. Cyclic trimer C3A was
aromatic amide trimer (C3A) and tetramer (C4A) containing the preferentially obtained, as in the cyclic oligomerization of other
DPA unit. The conformations in the solution and solid states aminobenzoic acid derivatives.35–37 The carbonyl stretching
were studied using nuclear magnetic resonance (NMR) spec- vibrations of the amide bond were conrmed by infrared (IR)
troscopy and X-ray crystallography, and ultraviolet (UV) absorp- spectroscopy (C3A: 1649 cmꢀ1, C4A: 1645 cmꢀ1), and the cyclic
tion/uorescence spectroscopy were measured to discuss their architectures were veried by the MALDI-TOF mass spectra
optical properties. Reduction of the amide carbonyl group was (Fig. S21 and S22†). Subsequently, reduction of the amide
also performed to investigate the inuence of the linker on the carbonyl group in C3A was carried out using LiAlH4 and AlCl3 in
optical properties.
THF–Et2O, giving the cyclic trimer HC3A, which has a methylene
group between the benzene ring and the nitrogen atom, in 71%
yield (Scheme 2). The peak derived from the amide carbonyl
group completely disappeared in the IR spectrum, and the
structure of HC3A was identied from the 1H NMR spectrum
(Fig. S15†) and MALDI-TOF mass spectrum (Fig. S23†). Acyclic
model compound 2 was also synthesized as shown in ESI.†
Results and discussion
Synthesis
Monomer 1, containing amino and ester functional groups, was
synthesized as shown in Scheme 1. 4-Iodoacetanilide was alky-
lated with NaH and 1-bromooctane to obtain 3 in 85% yield. The
Suzuki coupling reaction of 3 with 10-bromoanthracene-9-
boronic acid was performed using Pd(PPh3)4, giving 4 in 68%
Characterization
1
yield. The acetyl group in 4 was removed using concentrated HCl, The H NMR spectrum of C3A showed seven proton signals in
and the obtained product 5 was subjected to a second Suzuki the aromatic region, which were fully assigned using H–H
Scheme 1 Synthetic route to monomer 1. Condition and reagents: (i) NaH (55% oil suspension), 1-bromooctane, DMF, 100 ꢁC; (ii) K2CO3,
Pd(PPh3)4, THF, H2O, reflux; (iii) conc. HCl, ethylene glycol, dioxane, reflux; (iv) 4-methoxycarbonylphenyl boronic acid pinacol ester, K2CO3,
Pd(PPh3)4, THF, H2O, reflux.
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Scheme 2 Synthetic route to cyclic aromatic oligomers C3A, C4A, and HC3A. The chemical structure of acyclic model compounds 2 and DPAA.
correlation spectroscopy (COSY) (Fig. S11†) and rotating Over- the rotational energy barrier was difficult because the paired
hauser enhancement and exchange spectroscopy (ROESY) proton signal at the down eld region was overlapped with
1
(Fig. S12†). It should be noted that two broad multiplet signals other proton signals. In contrast, in the H NMR spectrum of
with a combined integral ratio of 12 appeared at 6.96–6.87 ppm C4A, the corresponding proton signals of the anthracene ring
at room temperature; these were assigned to the f and g protons were observed in the normal region (7.27–7.09 ppm) (Fig. S13†).
of the anthracene ring (Fig. 1). Since this upeld shi is not The difference between the chemical shis in the spectra of C3A
observed in acyclic model compound 2, the shielding effect by and C4A is probably originated from the conformations and
the other anthracene rings located in close proximity is the ring sizes of the cyclic oligomers; this was further investigated
most probable cause. Variable-temperature NMR studies using X-ray crystallography.
showed that the corresponding proton signals broadened with
The relative positions of the three DPA groups were deter-
decreasing temperature, and a signal with an integral ratio of 6 mined by X-ray crystallography, using cyclic aromatic amide
was observed at 6.4 ppm at 223 K (Fig. S17†). It can be deduced oligomers with n-propyl substituents on the amide nitrogen
that the rotational motion of anthracene rings is suppressed at (C3A0 and C4A0) instead of C3A and C4A. Single crystals of C3A0
low temperatures, resulting in separate detection of intra- and C4A0 were obtained by recrystallization from CHCl3 and
annular (f and g) and extra-annular (f0 and g0) protons. The hexane. Fig. 2 shows the crystal structure of C3A0; three
signals from the b and c protons also broadened with anthracene moieties are inclined with respect to the cyclic
decreasing temperature, but the proton signals derived from skeleton and partly overlap each other (Fig. 2b). The phenyl and
the benzene ring did not show obvious changes within the anthracene planes have a twisted conformation, with (N)Ph–
examined temperature range. Unfortunately, the calculation of Anth(Ph) and (Ph)Anth–Ph(CO) torsion angles of 78.2ꢁ and
Fig. 1 Expanded 1H NMR spectrum of C3A in CDCl3.
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and some of the neighboring column molecules lled the space
between the molecules (Fig. 3c).
The UV and uorescence spectra of C3A, C4A and 2 in
dichloromethane (DCM) were recorded (Fig. 4). The UV spec-
trum of C3A and C4A are similar to that of 2. In contrast, the
uorescence peak maximum of C3A (lmax ¼ 438 nm) and C4A
(lmax ¼ 439 nm) were slightly red-shied compared with that of
2 (lmax ¼ 425 nm). The relative uorescence quantum yields of
C3A (15%) and C4A (6%) were lower than that of DPA (87%). The
uorescence spectra were independent of the solution concen-
tration between 10ꢀ4 and 10ꢀ6 M. Consequently, the red-shied
uorescence emission of C3A and C4A can be explained by
intramolecular non-bonding interactions among three anthra-
cene units (vide supra). The difference of the uorescence
spectra between C3A and C4A was not detected because the
overlap of the p-cloud is not signicant in C3A. We also inves-
tigated the photophysical experiments in the solid state
(Fig. S25†). The emission maximum of C3A in solid state is
red-shied as compared to that in solution due to the inter-
molecular p–p interaction. Furthermore C4A showed a larger
red-shi than that of C3A. As shown in Fig. 2 and 3, C4A has a
higher planarity than C3A, therefore C4A make the intermo-
lecular p–p interaction efficiently in the solid state.
Fig. 2 Crystal structure of C3A0. (a) Thermal ellipsoidal model. The
ellipsoids are drawn at 50% probability level while isotropic hydrogen
atoms are represented by spheres of arbitrary size. (b) Space-filling
model. (c) Packing structure indicated by stick model along c axis.
Labels, disordered atoms, and solvent molecules are omitted for clarity.
The absorption and emission spectra of C3A and HC3A were
then investigated to clarify the inuence of linker on the optical
properties of the molecules. In DCM, the UV spectrum of HC3A
became broader and the uorescence band (lmax ¼ 489 nm) was
shied to longer wavelength by 50 nm compared with that of
C3A (438 nm) (Fig. 5a). This red-shi could be related to twisted
intramolecular charge transfer (TICT) from the electron-
donating aniline moiety to the electron-accepting anthracene
unit. To further support this suggestion, the UV and uores-
cence spectra were measured in various solvents. Both the UV
and uorescence spectra demonstrated a small solvent depen-
dence in the case of C3A (Fig. S24†), indicating that the ground-
state and excited-state structures of C3A were not affected by the
solvent character. In sharp contrast, the uorescence spectrum
of HC3A became broader and gradually red-shied with
increasing solvent polarity (Fig. 5b). As indicated in Fig. 5c, the
87.2ꢁ, respectively, on average. It is of particular interest that
C3A0 forms a chiral crystal (space group: P21) as a result of xing
of the axis chirality, although C3A0 is achiral in the solution
state. In contrast, four anthracene moieties lie horizontally and
a plane of mirror symmetry is observed in the case of C4A0
ꢀ
(space group: P1) (Fig. 3). The crystals stacked along the a-axis
Fig. 3 Crystal structure of C4A0. (a) Thermal ellipsoidal model. The
ellipsoids are drawn at 50% probability level while isotropic hydrogen
atoms are represented by spheres of arbitrary size. (b) Space-filling
model. Packing structure indicated by stick model along c axis (c) and a Fig. 4 UV and fluorescence spectra of C3A (solid line), C4A (broken
axis (d). Labels, disordered atoms and solvent molecules are omitted line), and 2 (dotted line) in DCM (r.t., 10ꢀ5 M). See Table S1† for
for clarity.
maximum wavelengths.
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Fig. 5 (a) UV and fluorescence spectra of C3A (solid line) and HC3A (broken line) in DCM (r.t., 10ꢀ5 M). (b) Solvent-dependent fluorescence
spectra of HC3A (r.t., 10ꢀ5 M). (c) Plot between the Stokes shift of HC3A and ET(30) value. Abbreviation: CH; cyclohexane, DOX; 1,4-dioxane,
EtOAc; ethyl acetate, DCM; dichloromethane, DMAc; N,N-dimethylacetamide, DMF; N,N-dimethylformamide, DMSO; dimethyl sulfoxide.
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Fig. 6 UV and fluorescence spectra of HC3A (solid line) and DPAA (broken line) (r.t., 10ꢀ5 M) in (a) CH and (b) DMSO.
Stokes shi (Dn) showed a linear correlation with the Reich- three anthracene moieties are arranged in a triangular manner
ardt's solvent polarity parameter [ET(30)].38 According to the and partly stacked intramolecularly, in both the solution and
previous reports,39–42 these phenomena are consistent with TICT solid states. Reduction of the carbonyl group in C3A gave the
from the aniline moiety to the anthracene unit in HC3A.
cyclic trimer HC3A, constructed from electron-donating aniline
Fig. 6 shows the UV and uorescence spectra of HC3A and a and electron-accepting anthracene units. The uorescence
reference compound, N,N-dipropyl-4-(10-phenyl-9-anthracenyl) spectrum of C3A showed a small red-shi from that of acyclic
aniline (DPAA). The absorption peak maxima of HC3A and model compound 2. The uorescence spectrum of HC3A was
DPAA were similar in both cyclohexane and dimethyl sulfoxide largely red-shied from that of C3A and the collection of spectra
(DMSO), but the tailings to the longer wavelength were detected in various solvents suggested the occurrence of TICT from the
in HC3A. In cyclohexane, which is less polar than DMSO, the aniline moiety to the anthracene unit.
uorescence band of HC3A (lmax ¼ 449 nm) was shied by 5 nm
to a longer wavelength than that of DPAA (lmax ¼ 444 nm), as a
Experimental section
result of intramolecular interactions among three anthracene
moieties similarly to C3A. In contrast, in more polar DMSO, the
uorescence maximum of HC3A (lmax ¼ 543 nm) was blue-
shied by 16 nm compared with that of DPAA (lmax ¼ 559 nm).
Accordingly, HC3A was less sensitive to solvent polarity than
DPAA was. We suggest that TICT in the excited state of HC3A is
relatively blocked compared with DPAA as a result of restricted
bond rotation because of the cyclic architecture. On protonation
of the aniline moiety in HC3A with triuoroacetic acid, a
signicant blue-shi of the uorescence spectrum and an
increase in the emission intensity were observed (Fig. S27†). It
can be deduced that the electron density of the aniline moiety is
decreased by protonation and, as a result, TICT from the aniline
moiety to the anthracene unit is inhibited. Moreover, the orig-
inal UV and uorescence spectra were recovered by addition of
excess triethylamine to the proton adduct of HC3A. The
complete recovery of spectra indicates that the deprotonation
was selectively occurred and no electronic interaction between
triethylamine and anthracene43 can be ignored.
Materials and instruments
All materials were obtained from commercial suppliers and used
without purication. 4-Iodoacetanilide44 and N,N-dipropyl-4-(10-
phenyl-9-anthracenyl)aniline
(DPAA)45
were
synthesized
following to the previous reports. 1H and 13C NMR spectra were
investigated on Bruker (Billerica, MA, USA) Avance 200, 400, 500,
and 600 FT-NMR spectrometers using tetramethylsilane
(1H NMR, d 0.00) and solvent residual peaks as the internal
standards (1H NMR and 13C NMR). IR spectra were recorded on a
JASCO (Tokyo, Japan) FT-IR 460Plus spectrophotometer in the
attenuated total reectance (ATR) method. Melting points (M.p.)
were determined on a Yanaco (Kyoto, Japan) micro melting point
apparatus MP-500D. MALDI-TOF MS analyses were performed on
a JEOL (Tokyo, Japan) JMS-S3000 in the spiral mode using
dithranol as a matrix. Purications with preparative GPC were
carried out on a Japan analytical industry (Tokyo, Japan) LC-9210
system using tandem JAIGEL 1H, 2H, and 2.5H columns (CHCl3
as an eluent, ow rate ¼ 3.5 mL minꢀ1) equipped with an
ultraviolet (UV) detector monitored at 254 nm. UV and uores-
cence spectra were recorded on a Shimadzu (Kyoto, Japan)
UV-1650PC spectrophotometer and a Shimadzu RF-5300PC
Conclusion
In conclusion, we prepared a novel cyclic aromatic amide trimer spectrouorometer, respectively, using a 10 mm quartz cell.
(C3A) and tetramer (C4A) containing the DPA unit. The spec- Fluorescence quantum yields (QY) in solution were determined
troscopic and X-ray crystallographic data for C3A show that relative to quinine sulfate in 0.05 M H2SO4 having a QY of 0.55.
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4-methoxycarbonylphenylboronic acid pinacol ester (0.71 g,
2.7 mmol) in THF (17 mL), and the system was heated to reux
overnight. Aer an aqueous phase was extracted with ethyl
acetate, the combined organic phase was washed with brine.
Aer drying over MgSO4, solvents were removed by the
rotary evaporator. The resulting solid residue was puried by
recrystallization from DCM and hexane to yield yellow powder
(0.82 g, 82%).
Monomer synthesis
N-Octyl-4-iodoacetanilide (3). NaH (55% oil suspension)
(0.58 g, 14 mmol) was added to a solution of 4-iodoacetanilide
(3.2 g, 12 mmol) in DMF (60 mL) at 0 C, and stirred at room
ꢁ
temperature for 30 min. 1-Bromooctane (3.1 mL, 18 mmol) was
added to the solution and the system was heated to 100 ꢁC for 24
h. The reaction mixture was poured into water and an aqueous
phase was extracted with ethyl acetate. The combined extracts
were dried over MgSO4 and solvents were removed by the rotary
evaporator. The crude product was puried by SiO2 chroma-
tography (DCM then DCM–ethyl acetate ¼ 1/1) to obtain yellow
liquid (3.8 g, 85%). 1H NMR (d, 200 MHz, ppm, CDCl3) 7.75 (d,
J ¼ 7.9 Hz, 2H), 6.93 (d, J ¼ 7.9 Hz, 2H), 3.65 (t, J ¼ 7.4 Hz, 2H),
1.46 (m, 2H), 1.36–1.17 (10H), 0.87 (t, J ¼ 5.2 Hz, 3H). 13C NMR
(d, 50 MHz, ppm, CDCl3) 170.0, 142.9, 140.2, 137.5, 131.5, 129.0,
93.3, 49.0, 32.0, 29.3, 27.8, 22.8, 13.5. IR (cmꢀ1) 2923, 2854,
1658, 1581, 1484, 1400, 1288, 1058, 1008, 831, 717.
N-Octyl-4-(10-bromo-9-anthracenyl)acetanilide (4). 2 M aq.
K2CO3 (5.0 mL) and Pd(PPh3)4 (65 mg, 50 mmol) were added to a
mixture of 3 (0.65 g, 2.2 mmol) and 10-bromoanthracene-9-
boronic acid (1.0 g, 2.7 mmol) in THF (20 mL), and the system
was heated to reux overnight. Aer an aqueous phase was
extracted with ethyl acetate, the combined organic phase was
washed with brine. Aer drying over MgSO4, solvents were
removed by the rotary evaporator. The crude product was
puried by ash chromatography (acetone–hexane ¼ 3/5) to
obtain yellow powder (1.0 g, 92%).
M.p. 192–193 ꢁC. 1H NMR (d, 600 MHz, ppm, CDCl3) 8.28 (d,
J ¼ 8.4 Hz, 2H), 7.86 (m, 2H), 7.61–7.55 (4H), 7.32, (m, 4H), 7.26
(d, J ¼ 8.7 Hz, 2H), 6.82 (d, J ¼ 8.7 Hz, 2H), 3.82 (bs, 1H), 3.24 (t,
J ¼ 6.9 Hz, 2H), 1.72 (m, J ¼ 6.9 Hz, 2H) 1.48 (m, J ¼ 6.9 Hz, 2H),
1.42–1.27 (8H), 0.90 (t, J ¼ 6.8 Hz, 3H). 13C NMR (d, 150 MHz,
ppm, CDCl3) 167.1, 147.9, 144.6, 138.5, 135.1, 132.1, 131.6, 130.3,
129.7, 129.6, 129.3, 127.5, 126.9, 126.3, 125.3, 124.8, 112.4, 52.2,
44.2, 31.9, 29.7, 29.5, 29.2, 27.2, 22.7, 14.2. IR (cmꢀ1) 3400, 2923,
2853, 1707, 1606, 1521, 1478, 1433, 1391, 1319, 1271, 1176, 1111,
1020, 942, 818, 765, 709, 670, 609. Anal. calcd for C36H37NO2: C,
83.85; H, 7.23; N, 2.72. Found: C, 83.65; H, 7.30; N, 2.65%.
General procedure of cyclic oligomerization
Method A. A THF solution of 1 (0.2 M, 0.5 mL) was added
dropwise to a THF solution of LiHMDS (1.0 M in THF, 0.5 mL),
and the system was stirred for 6 h. Aer saturated NH4Cl was
added, an aqueous phase was extracted with DCM. A combined
organic phase was dried over MgSO4 and solvents were removed
by the rotary evaporator.
M.p. 135–136 ꢁC. 1H NMR (d, 200 MHz, ppm, CDCl3) 8.64 (d,
J ¼ 9.7 Hz, 2H), 7.68–7.55 (4H), 7.51–7.34 (6H), 3.83 (t, J ¼ 8.0
Hz, 2H), 2.03 (s, 3H), 1.73–1.60 (2H), 1.36–1.17 (10H), 0.88 (t, J ¼
6.6 Hz, 3H). 13C NMR (d, 50 MHz, ppm, CDCl3) 170.2, 142.8,
138.0, 136.3, 133.9, 131.0, 130.2, 129.4, 128.2, 127.2, 126.7,
Method B. A THF solution of LiHMDS (1.0 M in THF, 0.5 mL)
was added dropwise to a THF solution of 1 (0.1 M, 1.0 mL), and
the system was stirred for 6 h. Aer saturated aq. NH4Cl was
added, an aqueous phase was extracted with DCM. A combined
organic phase was dried over MgSO4 and solvents were removed
by the rotary evaporator. The crude product was puried by
preparative GPC (CHCl3 as an eluent) to obtain cyclic oligomers.
C3A. Yield, 40%. M.p. > 300 ꢁC. 1H NMR (d, 600 MHz, ppm,
CDCl3) 7.64 (d, J ¼ 8.0 Hz, 6H), 7.54 (d, J ¼ 8.9 Hz, 6H), 7.47
(d, J ¼ 8.9 Hz, 6H), 7.41 (d, J ¼ 8.2 Hz, 6H), 7.39–7.36 (12H), 6.94
(m, 6H), 6.89 (m, 6H), 4.21 (t, J ¼ 7.8 Hz, 6H), 1.91 (m, 6H), 1.54
(m, 6H), 1.38 (m, 6H), 1.36–1.30 (18H), 0.91 (t, J ¼ 6.8 Hz, 9H).
13C NMR (d, 150 MHz, ppm, CDCl3) 170.9, 143.5, 140.7, 137.9,
136.8, 136.6, 136.3, 132.4, 131.0, 130.0, 129.9, 129.4, 128.5,
126.9, 126.6, 126.0, 125.9, 50.5, 32.3, 29.9, 29.7, 28.5, 27.5, 23.1,
14.6. IR (cmꢀ1) 3904, 3059, 2925, 2852, 1648, 1603, 1511, 1438,
1377, 1293, 1177, 1020, 943, 828, 766, 670, 611. MALDI-TOF MS
calcd for C105H100N3O3 (M + H+): 1451.78. Found: 1451.73. Anal.
calcd for C105H99N3O3: C, 86.92; H, 6.88; N, 2.90. Found: C,
86.33; H, 6.93; N, 2.77%.
124.3, 123.3, 93.3, 49.0, 32.0, 29.3, 27.8, 22.8, 13.5. IR (cmꢀ1
2958, 2920, 2853, 1638, 1592, 1511, 1402, 1296, 1026, 936, 879,
765, 751, 620.
N-Octyl-4-(10-bromo-9-anthracenyl)aniline
eneglycol (2 mL) and conc. HCl (8 mL) were added to a solution
)
(5).
Ethyl-
of 4 (1.3 g/2.6 mmol) in DOX (6 mL), and the system was stirred
ꢁ
for 48 h at 100 C. The reaction mixture was neutralized using
saturated aq. Na2CO3, and an aqueous phase was extracted with
DCM. The combined organic phase was washed with brine.
Aer drying over MgSO4, solvents were removed by the rotary
evaporator. The crude product was puried by column chro-
matography (ethyl acetate–hexane ¼ 1/1) to obtain yellow
powder (0.85 g, 71%).
M.p. 85–86 ꢁC. 1H NMR (d, 200 MHz, ppm, CDCl3) 8.57 (d, J ¼
8.8 Hz, 2H), 7.80 (d, J ¼ 8.8 Hz, 2H), 7.55 (t, J ¼ 7.9 Hz, 2H), 7.34
(d, J ¼ 7.9 Hz, 2H), 7.12 (d, J ¼ 8.3 Hz, 2H), 6.77 (d, J ¼ 8.8 Hz,
2H), 3.79 (bs, 1H), 3.19 (t, J ¼ 6.7 Hz, 2H), 1.69 (m, 2H), 1.36–1.17
(10H), 0.90 (t, J ¼ 6.3 Hz, 3H). 13C NMR (d, 50 MHz, ppm, CDCl3)
147.9, 138.5, 133.1, 131.5, 130.2, 129.0, 128.2, 126.4, 125.4, 123.7,
122.0, 113.4, 44.1, 31.9, 29.6, 29.5, 29.4, 27.8, 22.8, 13.5. IR
(cmꢀ1) 3943, 3443, 2946, 2916, 2847, 1604, 1518, 1464, 1437,
1341, 1289, 1258, 1179, 1029, 933, 874, 813, 756, 722, 654, 611.
Monomer (1). 2 M aq. K2CO3 (6.8 mL) and Pd(PPh3)4 (52 mg,
40 mmol) were added to a mixture of 5 (0.78 g, 1.7 mmol) and
1
ꢁ
C4A. Yield 8%. M.p. > 300 C. H NMR (d, 600 MHz, ppm,
CDCl3) 7.67 (d, J ¼ 7.9 Hz, 6H), 7.60 (d, J ¼ 8.3 Hz, 6H), 7.57 (d,
J ¼ 8.3 Hz, 6H), 7.43 (d, J ¼ 8.3 Hz, 6H), 7.41 (d, J ¼ 8.3 Hz, 6H),
7.35 (d, J ¼ 8.3 Hz, 6H), 7.15 (t, J ¼ 7.0 Hz, 6H), 7.11 (t, J ¼ 7.0 Hz,
6H), 4.18 (t, J ¼ 7.4 Hz, 6H), 1.90 (m, 6H), 1.52 (m, 6H), 1.43 (m,
6H), 1.37 (m, 6H), 1.36–1.17 (18H), 0.90 (t, J ¼ 7.0 Hz, 9H). IR
(cmꢀ1) 3820, 3020, 2955, 2923, 2851, 1723, 1645, 1511, 1378,
1290, 1121, 1020, 764, 670, 612. MALDI-TOF MS calcd for
C
140H133N4O4 (M + H+): 1935.03. Found: 1934.50.
6758 | RSC Adv., 2014, 4, 6752–6760
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Reduction of amide carbonyl group
Notes and references
C3A (29 mg/0.02 mmol) in THF (0.24 mL) was added dropwise to
ether (0.48 mL) solution of LiAlH4 (9.0 mg/0.24 mmol) and AlCl3
(32 mg/0.24 mmol) at 0 ꢁC, and the system was stirred for 2 h at
room temperature. The reaction mixture was quenched with
cold H2O (2 mL), cold 2 M aq. NaOH (2 mL), and H2O (6 mL).
Aer an aqueous phase was extracted with DCM, the combined
organic phase was washed with brine. Aer drying over MgSO4,
solvents were removed by the rotary evaporator. The crude
product was puried by preparative GPC (CHCl3 as an eluent) to
obtain HC3A (26 mg, 93%). M.p. 127–128 C. H NMR (d, 600
MHz, ppm, CDCl3) 7.69 (m, 6H), 7.54 (m, 6H), 7.50 (d, J ¼ 7.5
Hz, 6H), 7.41 (d, J ¼ 7.5 Hz, 6H), 7.25 (d, J ¼ 7.9 Hz, 6H), 7.97
(12H), 6.90, (d, J ¼ 7.43 Hz, 6H), 4.90 (s, 6H), 3.78 (t, J ¼ 7.4 Hz,
6H), 1.97 (m, 6H), 1.50 (m, 6H), 1.46–1.31 (24H), 0.95 (t, J ¼ 6.1
Hz, 9H). 13C NMR (d, 150 MHz, ppm, CDCl3) Not available due
to low solubility. IR (cmꢀ1) 3063, 2928, 2853, 1606, 1518, 1395,
1183, 1027, 767, 672. MALDI-TOF MS Calcd for C105H105N3c+
(Mc+): 1407.83. Found: 1407.83.
´
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X-ray crystallographic analysis
Crystallographic data were collected on a CCD diffractometer
˚
with Cu Ka (l ¼ 1.54178 A) radiation. Data collections were
carried out at low temperature using liquid nitrogen. All of
the crystal structures were solved by direct methods with
SHELXS-97 and rened with full-matrix least-squares
SHELXL-97.46 All non-hydrogen atoms were rened aniso-
tropically and hydrogen atoms were included at their calcu-
lated positions.
Crystal data for C3A0. C90H69N3O3$5CHCl3, Mr ¼ 1837.32,
˚
ꢀ3
monoclinic, P21, a ¼ 22.2423(5), b ¼ 9.3087(2), c ¼ 22.5200(6) A,
3
ꢁ
˚
b ¼ 103.449(2) , V ¼ 4534.83(19) A , Z ¼ 2, Dc ¼ 1.346 Mg m
,
2qmax ¼ 135.74ꢁ, T ¼ 173 K, 30 648 reections measured, 12 985
unique (Rint ¼ 0.0334), m ¼ 4.570 mmꢀ1. The nal R1 and wR2
were 0.0856 and 0.2403 (I > 2s(I)), 0.1008 and 0.2640 (all data).†
Some atoms of propyl groups and chloroform molecules are
disordered to two positions respectively. The occupancies of the
disordered atoms were rened.
Crystal data for C4A0. C120H92N4O4$6CHCl3, Mr ¼ 2370.18,
˚
ꢀ
triclinic, P1, a ¼ 10.5211(2), b ¼ 13.4415(3), c ¼ 21.8375(4) A,
a ¼ 92.4470(10), b ¼ 96.5220(10), g ¼ 111.4330(10)ꢁ,
3
˚
V
¼
2844.21(10) A ,
Z
¼
1, Dc
¼
1.384 Mg mꢀ3
,
2qmax ¼ 136.06ꢁ, T ¼ 120 K, 35 078 reections measured, 9867
unique (Rint ¼ 0.0300), m ¼ 4.417 mmꢀ1. The nal R1 and wR2
were 0.0905 and 0.2627 (I > 2s(I)), 0.1174 and 0.2948 (all
data).† Some atoms of propyl groups and chloroform mole-
cules are disordered to two positions respectively. The
occupancies of the disordered atoms were rened.
¨
H. Mohwald and T. Nakanishi, Nat. Commun., 2013, 4, 1969.
Acknowledgements
26 Y. Fujiwara, R. Ozawa, D. Onuma, K. Suzuki, K. Yoza and
K. Kobayashi, J. Org. Chem., 2013, 78, 2206.
27 K. Hagiwara, Y. Sei, M. Akita and M. Yoshizawa, Chem.
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This work was performed under the Cooperative Research
Program of the “Network Joint Research Center for Materials
and Devices”. We thank Prof. S. Higashibayashi and Prof. A.
Nagai (IMS) for kindly donating the instruments.
This journal is © The Royal Society of Chemistry 2014
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Paper
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6760 | RSC Adv., 2014, 4, 6752–6760
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