Synthesis of novel unsymmetrical squarylium dyes absorbing in the near-infrared region

Article abstract of DOI:10.1039/a907335c

Novel unsymmetrical squarylium dyes which absorb in the near-infrared region were synthesized by a stepwise procedure via intermediate 4-substituted 3-hydroxycyclobut-3-ene-1,2-diones. By introducing benz[c,d]indoline or benzo[b]pyran moieties at one end

Full text of DOI:10.1039/a907335c

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Synthesis of novel unsymmetrical squarylium dyes absorbing in the
near-infrared region†
Shigeyuki Yagi,* Yutaka Hyodo, Shinya Matsumoto, Naoki Takahashi, Hiroshi Kono and
Hiroyuki Nakazumi*
1
Department of Applied Materials Science, College of Engineering,
Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
Received (in Cambridge, UK) 10th September 1999, Accepted 1st December 1999
Novel unsymmetrical squarylium dyes which absorb in the near-infrared region were synthesized by a stepwise
procedure via intermediate 4-substituted 3-hydroxycyclobut-3-ene-1,2-diones. By introducing benz[c,d]indoline
or benzo[b]pyran moieties at one end as an electron-donating component, the SQ dyes exhibited their absorption
maxima at 739–821 nm with large molar absorption coefficients (log ε = 4.96–5.18) in CHCl3. The X-ray analysis
for one of these dyes was also examined to confirm the overall structure of the unsymmetrical SQ dye.
been reported: one is Law’s method, a [2 ϩ 2] cycloaddition
Introduction
reaction between arylketenes and tetraethoxyethylene followed
by treatment with basic alumina and subsequent acid hydrolysis
(Scheme 1, a),6 and the other is Terpetschnig’s method, the
Organic near-infrared absorbing dyes (NIR dyes) have been
widely investigated in terms of the requirement for optical
recording using a Ga–Al–As diode laser (oscillator wavelength;
780–830 nm).1 Cyanine dyes have attracted much attention
because of their advantage of large absorption of light, and a
synthetic procedure has been already established. However,
they also have disadvantages of formation of dye aggregates,
less stability upon exposure to the light, and so on. Thus, it is
necessary to develop new molecular skeletons of NIR dyes
which have the potential to overcome these problems.
Squarylium (SQ) dye is a 1,3-disubstituted product yielded
by condensation of squaric acid (3,4-dihydroxy-1,2-dioxocyclo-
but-3-ene) with two aromatic or heterocyclic compounds, and
belongs to a class of polymethyne dyes such as cyanine dyes.
It exhibits an effective light absorption (ε > 105 dm3 molϪ1 cmϪ1)
and is resistant to photodegradation. Thus, SQ dyes are
very attractive for photonics applications such as photo-
conductors in xerographic devices2 and organic solar cells3 as
well as optical recording media. The traditional synthesis of SQ
dyes, however, affords symmetrical products,4 and the variation
of types of π-conjugation systems is limited. There have been
reported only a few examples of NIR SQ dyes, which are
limited to symmetrical SQ dyes and their related compounds.5
Previously, Law and Bailey reported a stepwise synthesis of
unsymmetrical SQ dyes, where the intermediate, 4-aryl-3-
hydroxycyclobutene-1,2-dione, was synthesized followed by
condensation with another electron-donating aromatic unit.6
Terpetschnig and Lakowicz also synthesized unsymmetrical SQ
dyes by a different method from Law’s.7 To the best of our
knowledge, however, no unsymmetrical NIR SQ dyes have so
far been reported.
Here we report the stepwise synthesis of a series of novel
unsymmetrical SQ dyes absorbing in the NIR region, by using
strongly electron-donating heterocyclic components at one end.
The X-ray structure for one of these dyes is also reported.
Scheme 1 Two synthetic procedures so far reported for preparation
of precursors of unsymmetrical SQ dyes. (a) Law’s method, and
(b) Terpetschnig’s method.
reaction of aromatic or heterocyclic compounds with 3,4-
diethoxycyclobut-3-ene-1,2-dione followed by acid hydrolysis
(Scheme 1, b).7 We obtained dye precursors 6 and 7 by using
different starting materials. The preparation of compounds 6
and 7 is described in Scheme 2. 3,4-Dichlorocyclobut-3-ene-1,2-
dione 38 reacted with compounds 1 and 2 under mild conditions
(in CH2Cl2, rt) to afford intermediates 4 and 5, respectively. The
subsequent acid hydrolysis yielded dye precursors 6 and 7.
Compounds 6a and 6b were normally purified by silica gel
Results and discussion
Two independent methods for preparing 4-substituted 3-
hydroxycyclobut-3-ene-1,2-diones as dye precursors have so far
† 1H NMR data and elemental analyses for compounds 8a and 8b
are available as supplementary data. For direct electronic access see
http://www.rsc.org/suppdata/p1/a9/a907335c/
DOI: 10.1039/a907335c
J. Chem. Soc., Perkin Trans. 1, 2000, 599–603
This journal is © The Royal Society of Chemistry 2000
599

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Fig. 1 The PLUTO drawing of 12. All hydrogen atoms are neglected
for clarity.
Scheme 2
column chromatography, whereas compound 7 could not be
isolated by the same procedure. Purification by reversed-phase
column chromatography (octadecyl silicate) enabled com-
pound 7 to be isolated in a pure form. All these inter-
mediates showed two intense peaks of C᎐O stretchings in their
᎐
IR spectra at 1763–1774 cmϪ1 and 1675–1716 cmϪ1, which are
characteristic for 4-substituted 3-hydroxycyclobut-3-ene-1,2-
diones.6
The condensation of dye precursors 6 and 7 with various
heterocyclic compounds was carried out under azeotropic con-
ditions in a mixed solvent of butan-1-ol and benzene (4:1, v/v)
containing a small amount of quinoline. The reactions employ-
ing N-alkylbenz[c,d]indolium
8 and 4-methyl-2-phenyl-1-
benzopyrylium 9 were examined to afford unsymmetrical SQ
dyes 10–15 in 19–73% yields (Scheme 3). Isolation and purifi-
Fig. 2 The UV-vis absorption spectra of (a) 11 and (b) 12 in CHCl3 at
20 ЊC. The concentrations are 1.7 × 10Ϫ5 and 9.4 × 10Ϫ6 M, respectively.
cation could be achieved in the usual manner: silica gel column
chromatography followed by recrystallization. These dyes,
except dye 13, were characterized by 1H NMR, IR and UV–vis
spectra and elemental analyses. Dye 13 exhibited low solubility,
and so the structure was confirmed by IR and UV–vis spectra
and elemental analysis. The yield and UV–vis spectral data for
each dye are shown in Table 1. The X-ray crystallographic
analysis for dye 12 was also examined to confirm the structural
character of the unsymmetrical SQ dye. The PLUTO drawing
is shown in Fig. 1. Two molecules of 12 in the unit cell contain
one molecule of benzene and two molecules of water.
The unsymmetrical SQ dyes prepared here possess their
absorption maxima in the NIR region (739–821 nm), although
unsymmetrical SQ dyes so far reported have exhibited their
absorption in the visible region (λmax < 700 nm).6,7 Represen-
tative absorption spectra are shown for dyes 11 and 12 in Fig. 2.
Typical symmetrical SQ dyes have large molar absorption co-
Scheme 3
600
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Table 1 Structures, yields, and UV–vis spectral data for unsymmetrical SQ dyes 10–15
λmax/nm
a
Compd.
Reactants
Ar1
Ar2
Yield (%)
58
(log ε/dm3 molϪ1 cmϪ1
)
10
6a and 8a
729 (4.92)
794 (5.03)
11
6a and 9
20
712 (4.99)
782 (5.18)
12
13
6b and 8c
6b and 9
71
19
751 (4.92)
821 (4.96)
725 (5.01)
800 (5.10)
14
7 and 8b
7 and 9
55
73
720 (4.97)
774 (5.00)
15
682 (5.02)
739 (4.98)
a In CHCl3 at 293 K.
efficients (ε > 105 dm3 molϪ1 cmϪ1) with narrow half widths.9
On the other hand, in the spectra of dyes 11 and 12, two
absorption maxima were observed, and the shapes of the
spectra were broad compared to those of symmetrical SQ dyes.
A similar tendency was observed in the spectra of dyes 10 and
13–15. These spectral features seem to be characteristic for
unsymmetrical SQ dyes in which the electron-donating ability
of the one aromatic moiety is very different from that of the
other.
Although one might be afraid that the two absorption
maxima originate from a mixture of two symmetrical SQ dyes
derived from two couplers (in the case of dye 12, julolidine 1b
and benzindolium 8c), through coupler exchanges, this possibil-
ity can be excluded by the following experimental evidence: the
absorption maxima of dyes 16 and 17 in CHCl3 are at 660 nm
and 881 nm, respectively, both of which differ from any absorp-
tion peaks of 12 described in Table 1. Furthermore, dye 12
possesses a different Rf value on silica gel thin-layer chromato-
graphy (benzene–acetone, 5:1, v/v, as eluent) from those of
dyes 16 and 17 (0.48, 0.32 and 0.65 for 12, 16 and 17, respect-
ively), and only one spot on the TLC plate for dye 12 indicated
that the isolated dye 12 was a single product. For the other
unsymmetrical dyes, overlap of the original spectra and those
of coupler-derived SQ dyes was not found and similar results
were obtained in the TLC study. Thus, it was confirmed that the
two absorption maxima of unsymmetrical SQ dyes prepared
here were genuine.
Conclusion
In conclusion, we achieved the synthesis of novel NIR dyes
containing an unsymmetrical squarylium skeleton. The key
essence is to introduce heterocyclic components possessing
large π-conjugation systems and strong electron-donating
properties. The unsymmetrical structure was revealed by the
X-ray crystallographic analysis for dye 12, and this is the first
example of a crystal structure analysis of NIR SQ dyes. The
J. Chem. Soc., Perkin Trans. 1, 2000, 599–603
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results obtained here should stimulate development of synthesis
of SQ dyes, aiming at application to optics devices.
([M Ϫ 2CO Ϫ CH3]ϩ ϩ 2, 33%), 231 ([M Ϫ 2CO]ϩ, 70%), 233
([M Ϫ 2CO]ϩ ϩ 2, 24%), 287 (Mϩ, 28%), 289 (Mϩ ϩ 2, 11%);
Anal. Calcd for C16H14NO2Cl: C, 66.79; H, 4.90; N, 4.87.
Found: C, 66.98; H, 4.74; N, 4.96%.
Experimental
1H NMR spectra (270 MHz) were recorded on a JEOL JNM-
GX 270 spectrometer in CDCl3 and DMSO-d6 using TMS (0
ppm) and CHD2SOCD3 (2.49 ppm) as internal standards,
respectively. IR spectra were taken for KBr disks of samples
and recorded on a HORIBA FT-200 spectrometer. Mass
spectra were obtained by EI and FAB techniques on a
Finnigan MAT MS spectrometer. For the FAB-mass spec-
troscopic measurement, 3-nitrobenzyl alcohol was used as a
matrix. Melting points were determined by differential thermal
analyses with a RIGAKU TAS 100 analyzer under nitrogen
atmosphere (flow rate: 100 mL minϪ1) using Al2O3 as a refer-
ence. The temperature-raising rate programmed was 10 ЊC
minϪ1.
4-(N,N-Dibutylaminophenyl)-3-hydroxycyclobut-3-ene-1,2-dione
6a
A solution of 4a (704 mg, 2.2 mmol) in AcOH–water (4:1, v/v,
9 mL) was stirred at reflux for 4 h. After cooling, the precipitate
was separated by filtration, and stirred in ether–hexane (1:1,
v/v, 20 mL) for 30 min. Filtration afforded 6a as a yellow solid;
1
yield, 83%; mp 253 ЊC (decomp.); H NMR (DMSO-d6) δ 0.90
(t, J = 7.3 Hz, 6H), 1.31 (sextet, J = 7.3 Hz, 4H), 1.48 (m, 4H),
3.40 (m, 4H), 6.85 (d, J = 7.9 Hz, 2H), 7.32 (d, J = 7.9 Hz, 2H)
(the OH proton was not observed); IR (KBr) 1763, 1716 cmϪ1
(C᎐O); FAB-MS m/z 302 ([M ϩ H]ϩ); Anal. Calcd for C H -
᎐
18 23
NO3ؒ0.5H2O: C, 69.65; H, 7.79; N, 4.51. Found: C, 70.45; H,
7.73; N, 4.48%.
Benzindolium 8 was obtained by the reported procedure.10 1
H
NMR data and elemental analyses for 8a and 8b are available
as supplementary materials. Benzopyrylium 9 was prepared
according to the reported procedure.11 Dyes 1612 and 175d were
obtained by the usual procedure4 from julolidine (2,3,6,7-
tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline) and benzindolium
8c, respectively.
4-(2,3,6,7-Tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)-3-
hydroxycyclobut-3-ene-1,2-dione 6b
A solution of 4b (905 mg, 3.4 mmol) in AcOH–water (4:1, v/v,
30 mL) was stirred at reflux for 4 h. After cooling, the precipi-
tate was separated by filtration, and stirred in ether (100 mL)
for 30 min. Filtration afforded 6b as a yellow solid; yield, 81%;
1
mp 248 ЊC (decomp.); H NMR (DMSO-d6) δ 1.86 (quintet,
4-(N,N-Dibutylaminophenyl)-3-chlorocyclobut-3-ene-1,2-dione
4a
J = 6.1 Hz, 4H), 2.69 (t, J = 6.1 Hz, 4H), 3.26 (t, J = 6.1 Hz,
4H), 7.40 (s, 2H) (the OH proton was not observed); IR (KBr)
1763, 1716 cmϪ1 (C᎐O); EI-MS m/z 213 ([M Ϫ 2CO]ϩ, 100%),
A mixture of 1a (2.05 g, 9.98 mmol) and 3 (2.26 g, 15.0 mmol)
in CH2Cl2 (20 mL) was stirred for 24 h at ambient temperature.
The solvent was removed by a rotary evaporator, and the resi-
due was purified by silica gel column chromatography (benzene
as eluent) to afford 4a as a yellow solid; yield, 22%; mp 80 ЊC;
1H NMR (CDCl3) δ 0.98 (t, J = 7.3 Hz, 6H), 1.39 (sextet, J = 7.3
Hz, 4H), 1.63 (quintet, J = 7.3 Hz, 4H), 3.40 (t, J = 7.3 Hz, 4H),
6.76 (d, J = 9.2 Hz, 2H), 8.13 (d, J = 9.2 Hz, 2H); IR (KBr)
᎐
269 (Mϩ, 61%); Anal. Calcd for C16H15NO3: C, 71.36; H, 5.61;
N, 5.20. Found: C, 71.07; H, 5.43; N, 4.93%.
4-(1,3,3-Trimethylindolin-2-ylidenemethyl)-3-hydroxycyclobut-
3-ene-1,2-dione 7
A solution of 5 (2.23 g, 7.75 mmol) in AcOH–water (4:1, v/v,
22 mL) was stirred at reflux for 5 h. After cooling, the precipi-
tate was separated by filtration. Purification by ODS column
chromatography (Nakalai Tesque, inc., Cosmosil 75C18-OPN,
MeOH–water (2:1, v/v) as eluent) followed by recrystallization
from CH2Cl2 afforded 7 as a yellow solid; yield, 37%; mp 205 ЊC
1795, 1759 cmϪ1 (C᎐O); EI-MS m/z 319 (Mϩ, 100%), 321
᎐
(Mϩ ϩ 2, 26%); Anal. Calcd for C18H22NO2Cl: C, 67.60; H,
6.93; N, 4.38%. Found: C, 67.79; H, 7.00; N, 4.45%.
4-(2,3,6,7-Tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)-3-
chlorocyclobut-3-ene-1,2-dione 4b
1
(decomp.); H NMR (CDCl3) δ 1.55 (s, 6H), 3.34 (s, 3H), 5.45
(s, 1H), 7.01 (d, J = 7.3 Hz, 1H), 7.11 (t, J = 7.3 Hz, 1H), 7.25
A mixture of 1b (1.73 g, 9.98 mmol) and 3 (1.81 g, 12.0 mmol)
in CH2Cl2 (20 mL) was stirred for 24 h at ambient temperature.
The solvent was removed by a rotary evaporator, and the resi-
due was purified by silica gel column chromatography (CH2Cl2
as eluent) followed by recrystallization from CHCl3 to afford
4b as an orange solid; yield, 39%; mp 208 ЊC (decomp.); 1H NMR
(CDCl3) δ 1.98 (quintet, J = 6.1 Hz, 4H), 2.77 (t, J = 6.1 Hz,
4H), 3.37 (t, J = 6.1 Hz, 4H), 7.69 (s, 2H); IR (KBr) 1774, 1749
(t, J = 7.3 Hz, 1H), 7.38 (t, J = 7.3 Hz, 1H) (the OH proton was
not observed); IR (KBr) 1764, 1726 cmϪ1 (C᎐O); EI-MS m/z 198
᎐
([M Ϫ 2CO Ϫ CH3]ϩ, 100%), 269 (Mϩ, 28%); Anal. Calcd for
C16H15NO3: C, 71.36; H, 5.61; N, 5.20. Found: C, 71.43; H, 5.55;
N, 5.19%.
General procedure for unsymmetrical SQ dyes: preparation of 10
A mixture of 6a (151 mg, 0.501 mmol), 8a (141 mg, 0.501
mmol) and quinoline (84 mg, 0.65 mmol) in butan-1-ol–
benzene (4:1, v/v, 20 mL) was heated at reflux for 4 h with
removal of water by using a Dean–Stark distillation apparatus.
After cooling, the solvent was removed by a rotary evaporator,
and the residue was purified by silica gel column chromato-
graphy (CH2Cl2–methanol, 30:1, as eluent). Recrystallization
from benzene afforded a crystal of 10.
cmϪ1 (C᎐O); EI-MS m/z 231 ([M Ϫ 2CO]ϩ, 100%), 233
᎐
([M Ϫ 2CO]ϩ ϩ 2, 31%), 287 (Mϩ, 30%), 289 (Mϩ ϩ 2, 9.7%);
Anal. Calcd for C16H14NO2Cl: C, 66.79; H, 4.90; N, 4.87%.
Found: C, 66.30; H, 4.61; N, 5.22%.
4-(1,3,3-Trimethylindolin-2-ylidenemethyl)-3-chlorocyclobut-3-
ene-1,2-dione 5
To a stirred solution of 3 (3.04 g, 20.2 mmol) in benzene
was added dropwise a solution of 1,3,3-trimethyl-2-methylene-
indoline (3.46 g, 20.0 mmol). The reaction mixture was stirred
for 20 min at ambient temperature. An orange precipitate was
formed, which was separated by filtration. Purification by silica
gel column chromatography (dichloromethane as eluent) fol-
lowed by recrystallization from CHCl3 afforded 5 as an orange
1
Compound 10. Yield 58%; mp 199 ЊC (decomp.); H NMR
(CDCl3) δ 0.98 (t, J = 7.3 Hz, 6H), 1.39 (sextet, J = 7.3 Hz,
4H), 1.64 (quintet, J = 7.3 Hz, 4H), 3.41 (t, J = 7.3 Hz, 4H),
3.78 (s, 3H), 6.33 (s, 1H), 6.71 (d, J = 9.2 Hz, 2H), 7.14 (d,
J = 7.9 Hz, 1H), 7.50 (t, J = 7.9 Hz, 1H), 7.61 (d, J = 7.9 Hz,
1H), 7.85 (t, J = 7.9 Hz, 1H), 7.98 (d, J = 7.9 Hz, 1H), 8.29 (d,
J = 9.2 Hz, 2H), 9.36 (br s, 1H); IR (KBr) 1605, 1583 cmϪ1
(C᎐O); FAB-MS m/z 464 (Mϩ); Anal. Calcd for C H -
1
solid; yield, 47%; mp 239 ЊC (decomp.); H NMR (CDCl3)
δ 1.65 (s, 6H), 3.52 (s, 3H), 5.53 (s, 1H), 7.03 (d, J = 7.3 Hz, 1H),
7.18 (t, J = 7.3 Hz, 1H), 7.35 (m, 2H); IR (KBr) 1764, 1726 cmϪ1
(C᎐O); EI-MS m/z 231 ([M Ϫ 2CO Ϫ CH ]ϩ, 100%), 233
᎐
31 32
N2O2: C, 80.14; H, 6.94; N, 6.03%. Found: C, 80.16; H, 6.98;
N, 5.89%.
᎐
3
602
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Compound 11. Benzene–acetone (7:1, v/v) was used as eluent
for silica gel column chromatography. Further purification was
carried out by recrystallization from benzene–hexane; yield
20%; mp 197 ЊC (decomp.); 1H NMR (CDCl3) δ 0.99 (t, J = 7.3
Hz, 6H), 1.40 (sextet, J = 7.3 Hz, 4H), 1.60–1.71 (m, 4H), 3.44
(t, J = 7.3 Hz, 4H), 6.74 (d, J = 8.5 Hz, 2H), 6.92 (s, 1H), 7.40
(dt, J = 1.2 and 7.9 Hz, 1H), 7.48–7.65 (m, 5H), 8.12 (dd, J = 1.2
and 7.9 Hz, 1H), 8.21–8.24 (m, 2H), 8.36 (d, J = 8.5 Hz, 2H),
8.02 (d, J = 7.9 Hz, 1H), 8.11 (m, 2H), 9.02 (s, 1H); IR (KBr)
1598 cmϪ1; EI-MS m/z 471 (Mϩ); Anal. Calcd for C32H25NO3:
C, 81.51; H, 5.34; N, 2.97%. Found: C, 81.03; H, 5.26; N, 2.65%.
X-Ray structural analysis‡
A single crystal of 12 suitable for the X-ray crystallographic
analysis was obtained as a clathrate by recrystallization from a
benzene solution of 12 in hexane by slow solvent diffusion. All
data were collected on a Rigaku AFC-5R diffractometer. The
final refinement converged with the unweighted and weighted
agreement factor 0.123 and 0.091, respectively. The structure is
not of sufficient quality to allow discussion of bond lengths and
angles. There were so few reflections that it was not meaningful
to refine anisotropic thermal parameters, and the five carbon
atoms in the N-hexyl group of 12 were disordered in the crystal.
Crystal data: C34H34N2O2ؒH2Oؒ0.5(C6H6), molecular weight
9.58 (s, 1H); IR (KBr) 1622, 1595 cmϪ1 (C᎐O); FAB-MS m/z
᎐
503 (Mϩ); Anal. Calcd for C34H33NO3: C, 81.08; H, 6.60; N,
2.78%. Found: C, 81.36; H, 6.45; N, 2.87%.
Compound 12. Benzene–acetone (5:1, v/v) was used as eluent
for silica gel column chromatography. Further purification was
carried out by recrystallization from benzene; yield 71%; mp
181 ЊC (decomp.); 1H NMR (CDCl3) δ 0.88 (t, J = 7.3 Hz, 3H),
1.25–1.48 (m, 6H), 1.87 (quintet, J = 7.3 Hz, 2H), 1.98 (quintet,
J = 6.1 Hz, 4H), 2.80 (t, J = 6.1 Hz, 4H), 3.38 (t, J = 6.1 Hz,
4H), 4.20 (t, J = 7.3 Hz, 2H), 6.36 (s, 1H), 7.10 (d, J = 7.9 Hz,
1H), 7.50 (t, J = 7.9 Hz, 1H), 7.60 (d, J = 7.9 Hz, 1H), 7.86 (t,
J = 7.9 Hz, 1H), 7.94 (s, 2H), 7.97 (d, J = 7.9 Hz, 1H), 9.26 (br s,
¯
559.73, triclinic, space group: P1, cell parameters: a = 14.427(6)
Å, b = 15.199(6) Å, c = 7.498(3) Å, α = 98.72(3)Њ, β = 99.51(3)Њ,
γ = 106.61(3)Њ, V = 1519(2) Å3, Z = 2, Dcalc = 1.224 g cmϪ3,
unique reflections 3825, final R = 0.123, Rw = 0.091.
1H); IR (KBr) 1595, 1581 cmϪ1 (C᎐O); FAB-MS m/z 502 (Mϩ);
᎐
Anal. Calcd for C34H34N2O2: C, 81.24; H, 6.82; N, 5.57%.
Found: C, 81.62; H, 6.77; N, 5.24% (the elemental analysis
was carried out after the sample had been thoroughly dried in
vacuo).
‡ CCDC reference number 207/388. See http://www.rsc.org/suppdata/
p1/a9/a907335c/ for crystallographic files in .cif format.
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Compound 13. This compound was purified by washing with
DMF followed by ether, due to low solubility. The H NMR
1
spectrum could not be obtained; yield 19%; mp 246 ЊC
(decomp.); IR (KBr), 1614, 1597 cmϪ1 (C᎐O); FAB-MS m/z 471
᎐
(Mϩ); Anal. Calcd for C32H25NO3: C, 81.51; H, 5.34; N, 2.97%.
Found: C, 81.13; H, 5.16; N, 2.92%.
Compound 14. CH2Cl2–AcOEt (5:1, v/v) was used as eluent
for silica gel column chromatography. Further purification was
carried out by recrystallization from CH2Cl2–hexane; yield
55%; mp 196 ЊC (decomp.); 1H NMR (CDCl3) δ 0.99 (t, J = 7.3
Hz, 3H), 1.49 (sextet, J = 7.3 Hz, 2H), 1.97 (quintet, J = 7.3 Hz,
2H), 1.82 (s, 6H), 3.67 (s, 3H), 4.11 (t, J = 7.3 Hz, 3H), 6.04 (s,
1H), 6.25 (s, 1H), 6.95 (d, J = 7.9 Hz, 1H), 7.07 (d, J = 7.9 Hz,
1H), 7.21 (dt, J = 1.2 and 7.9 Hz, 1H), 7.32–7.42 (m, 2H), 7.45–
7.51 (m, 2H), 7.80 (t, J = 7.9 Hz, 1H), 7.89 (d, J = 7.9 Hz, 1H),
9.06 (d, J = 7.9 Hz, 1H); IR (KBr) 1600 cmϪ1; EI-MS m/z 474
(Mϩ); Anal. Calcd for C32H30N2O2: C, 80.98; H, 6.37; N, 5.90%.
Found: C, 81.32; H, 6.47; N, 6.00%.
9 M. Matsuoka, Absorption Spectra of Dyes for Diode Lasers,
Bunshin, Tokyo, 1990, pp. 51–59.
10 S. Yagi, K. Maeda and H. Nakazumi, J. Mater. Chem., 1999, 9,
2991.
Compound 15. CH2Cl2–MeOH (50:1, v/v) was used as eluent
for silica gel column chromatography. Further purification was
carried out by recrystallization from EtOH; yield 80%; mp
262 ЊC (decomp.); 1H NMR (CDCl3) δ 1.80 (s, 6H), 3.86 (s, 3H),
6.30 (s, 1H), 6.74 (s, 1H), 7.29–7.36 (m, 2H), 7.40–7.58 (m, 8H),
11 R. Witzinger and H. Tobel, Helv. Chim. Acta, 1957, 40, 1305.
12 K.-Y. Law, F. C. Bailey and L. J. Bluett, Can. J. Chem., 1986, 64,
1607.
Paper a907335c
J. Chem. Soc., Perkin Trans. 1, 2000, 599–603
603