Synthesis and properties of bismerocyanines linked by a 1,8-naphthylene skeleton. Novel solvatochromism based on change of intramolecular excitonic coupling mode

Article abstract of DOI:10.1021/ja973608p

A newly prepared bismerocyanine linked by a 1,8-naphthylene skeleton has two rotational isomers, syn and anti conformers, with respect to orientation of the two merocyanine chromophores. The NMR studies revealed that a polar solvent such as acetonitrile e

Full text of DOI:10.1021/ja973608p

J. Am. Chem. Soc. 1998, 120, 3623-3628
3623
Synthesis and Properties of Bismerocyanines Linked by a
1,8-Naphthylene Skeleton. Novel Solvatochromism Based on Change
of Intramolecular Excitonic Coupling Mode
Takashi Katoh,† Yoshio Inagaki,† and Renji Okazaki*,‡
Contribution from the Ashigara Research Laboratories, Fuji Photo Film Co. Ltd., 210 Nakanuma,
Minami-ashigara, Kanagawa 250-01, Japan, and Department of Chemistry, Graduate School of Science,
The UniVersity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan
ReceiVed October 16, 1997
Abstract: A newly prepared bismerocyanine linked by a 1,8-naphthylene skeleton has two rotational isomers,
syn and anti conformers, with respect to orientation of the two merocyanine chromophores. The NMR studies
revealed that a polar solvent such as acetonitrile enhanced a preference for the syn conformer to bring about
much larger bathochromic shift of the UV/vis absorption band than that of a 1-naphthyl-substituted merocyanine.
The INDO/S-CI calculation indicated that the UV/vis absorption bands of the syn and anti conformers are
hypsochromically and bathochromically shifted, respectively, compared to that of the 1-naphthylmerocyanine.
In accordance with the prediction based on an exciton coupling theory, the anti conformer fluoresces while
the syn conformer does not. A polarographic analysis indicated a positive shift of reduction potential and a
negative shift of oxidation potential compared to the corresponding value of the 1-naphthylmerocyanine. The
shift in the reduction potential of the bismerocyanine relative to the 1-naphthylmerocyanine in acetonitrile
was larger than those in chloroform. This was attributed to the difference in the syn/anti ratio.
Introduction
devices using reversible changes between different states has
been shown.9-13
It has been known for a long time that merocyanines, which
consist of a formally uncharged conjugate system with a
vinylogous amide structure,1,2 show solvatochromism.3,4 Sol-
vatochromism of merocyanines is ascribed to the drastic change
of a dipole moment on excitation and is related to relative
contributions of two canonical forms, nonpolar quinoid and
dipolar zwitterionic ones.5 Merocyanines are important as
spectral sensitizers in photographic materials6 and have attracted
much attention also in the field of nonlinear optics7 and solar
energy conversion.8 Recently, much concern about molecular
Some dyes form aggregates in an aqueous solution and show
spectral shifts.14 J-aggregates, which were discovered by Jelly15
and Scheibe16 in 1930s, have been characterized by their narrow
absorption peak and bathochromic shifts compared to the
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† Fuji Photo Film Co. Ltd.
‡ The University of Tokyo.
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Published on Web 04/04/1998

3624 J. Am. Chem. Soc., Vol. 120, No. 15, 1998
Katoh et al.
Figure 2. Schematic diagram of two rotational isomers of a biscyanine
Figure 1. Schematic diagram of the relationship between relative
orientation of chromophores and spectral shifts based upon molecular
exciton theory.
linked by a 1,8-naphthylene skeleton.
merocyanines having long alkyl chains aggregate in monomo-
lecular layers and show aggregate bands.21 Recently, Nu¨esch
et al. observed H- and J-aggregates of merocyanines in metal
oxide films made of TiO2, Al2O3, or ZrO2.22 Upon the basis of
X-ray crystallographic analysis of single crystals and scanning
force microscopy (SFM) analysis of monolayers, a brickstone-
work model was proposed as a structure of merocyanine
J-aggregates.23 Absorption bands of hypothetical merocyanine
aggregates were calculated with the exciton coupling theory to
suggest that H- and J-aggregates have large (ca. 90°) and small
slip angles (ca. 30°), respectively.24
There is much concern about orbital energy levels of a dye
aggregate, since today it is widely accepted that in spectral
sensitization of photographic emulsions an electron of the
excited state of a sensitizing dye transfers to a conduction band
of a silver halide crystal.9,25 However, little is known about
orbital energy levels of a dye aggregate. This is probably due
to the experimental difficulty in isolating a dye aggregate in
which the mode of a chromophore arrangement and the number
of constituent molecules are well defined. Many examples of
biscyanines26-28 and a few bismerocyanines29 in which more
than two chromophores were covalently linked have been
reported. Although some of these bismerocyanines with two
chromophores linked by a polymethylene chain to each other
showed aggregate absorption bands, the chromophore arrange-
ments remained ambiguous. Recently, biscyanines linked by a
1,8-naphthylene skeleton were prepared by our group and the
effects of the relative orientation of two chromophores on the
spectral shifts and the redox potentials were investigated.28 The
two rotational isomers, the syn and anti conformers, of (1,8-
naphthylene)biscyanines showed such spectral shifts as to be
expected for H- and J-aggregate models, respectively (Figure
corresponding monomeric dye. On the contrary, a hypsochro-
mically shifted aggregate is called an H-aggregate. Aggregates
of polymethine dyes have been of much interest because of their
unique photophysical and optical properties.17 The relationship
between relative orientation of chromophores and spectral shifts
of a dye aggregate has been explained in terms of molecular
exciton theory,18,19 in which an excited state of a dye aggregate
splits into two levels through the coupling of transition dipoles
(Figure 1). In a parallel dimer with a large slip angle (R), a
transition to the upper state of the two excited states is allowed
and hence the absorption of a dimer is hypsochromically shifted
compared to that of a monomeric dye. On the other hand, in a
head-to-tail dimer with a small slip angle (R), a transition to
the lower state is allowed and the absorption undergoes a
bathochromic shift.
Although many kinds of cyanines form J-aggregates in
aqueous solutions or in silver halide emulsions, few examples
of merocyanine J-aggregates have been reported.20-22 Making
use of Langmuir-Blodgett techniques, Kuhn et al. revealed that
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Bismerocyanines Linked by a 1,8-Naphthylene Skeleton
J. Am. Chem. Soc., Vol. 120, No. 15, 1998 3625
Scheme 1
2). Accordingly, the 1,8-naphthylene linkage is expected to be
suitable also for making model compounds of merocyanine
aggregates. In this paper, we describe the synthesis of (1,8-
naphthylene)bismerocyanine 1 and its novel solvatochromism
and pronounced shifts in redox potentials. We account for these
properties of the bismerocyanine in terms of a change in the
chromophore arrangement by rotational isomerization.
Figure 3. 1H NMR spectrum of (1,8-naphthylene)bismerocyanine 1
in CD2Cl2 at 298 K. O and 2 stand for the syn and anti conformers,
respectively. The arrows indicate the cross peaks of ROESY.
Table 1. Solvent Effect on the Syn/Anti Ratio of
(1,8-Naphthylene)bismerocyanine 1
a
solvents
ET(30) (kcal mol-1
)
syn:antib
CDCl3
CD2Cl2
DMSO-d6
CD3CN + 2% CD3OD
39
41
45
46
<5:95
24:76
52:48
90:10
a Values for CHCl3, CH2Cl2, DMSO, CH3CN, and CH3OH in ref 3.
1
1
b Determined by H NMR at 298 K.
Results and Discussion
chain protons were 13 Hz, indicating all-trans conformations
of the methine chains. The variable-temperature 1H NMR
spectra of 1 in DMSO-d6 revealed the coalescence temperature
to be 338 K and the free energy of the rotational isomerization
Synthesis. The bismerocyanine linked by a 1,8-naphthylene
skeleton 1 having rhodanine nuclei was prepared from 4,4′-
(1,8-naphthylene)bispyridinium 2 and enamine 3 in the presence
of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and acetic anhy-
dride (Scheme 1). Similarly, 1-naphthyl-substituted monomero-
cyanine 4 and prototypical monomerocyanine 6 were prepared
from 4-(1-naphthyl)pyridinium and pyridinium salts, 5 and 7,
respectively.
was calculated to be 75 kJ mol-1 32
.
UV/Vis Absorption Spectra. The absorption band of the
bismerocyanine 1 in CHCl3 (568 nm) was bathochromically
shifted compared to that of the corresponding monomerocyanine
4 (551 nm), while the absorption band of 1 in acetonitrile (516
nm) underwent a hypsochromic shift compared to 4 (550 nm)
(Figure 4). The absorption spectra of 1 in CH2Cl2-methanol
showed both the hypsochromic and bathochromic bands and
that the hypsochromic band becomes intense with increasing
the methanol fraction (Figure 5). The pronounced solvato-
chromism makes a striking contrast with very slight solvato-
chromic shifts of the corresponding monomerocyanines 4 and
6. The shape of the absorption band of 1 was independent of
the concentration, indicating that the spectral shifts were not
caused by intermolecular aggregation. The solvatochromism
of 1 was interpreted by the change of the syn/anti ratio, which
was supported by the INDO/S-CI calculation33 and the NMR
study described above. The calculation using the MM2-
1
Structures. The H NMR spectrum of the bismerocyanine
1 in CD2Cl2 at 298 K showed two sets of sharp signals (Figure
3). Warming of the sample solution caused a broadening of
signals, indicating that 1 exists as a mixture of two isomers in
CD2Cl2. The assignment of the anti conformers was confirmed
on the basis of the appearance of the cross peaks between the
3- and 5-positions of the pyridine rings and between the
5-position of the pyridine rings and the â-position of the methine
chain protons in the ROESY spectrum. The isomer ratio of
syn:anti in various solvents indicated that a polar solvent such
as acetonitrile enhanced a preference for the syn conformer
(Table 1). This solvent effect on the syn/anti ratio of 1 is in
accordance with a difference of the dipole moments between
the syn and anti conformers. The dipole moments of 1 (syn)
and 1 (anti) calculated with the AM1 method30 using the
MM231-optimized structures were 17.0 and 8.0 D, respectively.
The syn isomer must be more stabilized than the anti isomer in
a relatively polar solvent. The coupling constants of the methine
(32) The rotational barrier was estimated based on eq 1, where ∆ν is
the chemical shift difference between the individual rotameric signals of
methyl groups and Tc is the coalescence temperature: Gunther, F. NMR
Spectroscopy: An Introduction; John Wiley and Sons: New York, 1980;
p 180.
∆Gq (J mol-1) ) 19.14Tc(9.97 + log(Tc /∆ν))
(33) Ridley, J.; Zerner, M. Theor. Chim. Acta (Berlin) 1973, 32, 111.
(1)
(30) Dewer, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P. J.
Am. Chem. Soc. 1985, 106, 3902.
(31) Allinger, N. L. J. Am. Chem. Soc. 1977, 99, 8127.

3626 J. Am. Chem. Soc., Vol. 120, No. 15, 1998
Katoh et al.
Table 3. UV/Vis Absorption Maxima, Half-Widths, Fluorescence
Maxima, Relative Intensities, and Stokes Shifts of
(1,8-Naphthylene)bismerocyanine 1 and Monomerocyanine 4
fluorescencea
absorption
Stokes
λmax half-width λmax
relative
shift
compds solvents (nm)
(cm-1
2950
)
(nm) intensity (cm-1
)
1
CHCl3
CH3CN
CHCl3
566
516
551
646 1.34
638 1.0
2130
2480
1010
4
2740
2230
(standard)
CH3CN
550
582
a Excitation at absorption maxima at 298 K.
molecular exciton theory. The calculated orientation of the
transition dipole moments of 1 was along the long axis of the
merocyanine moieties. This suggests that the spectral shifts of
1 are based on an excitonic coupling between the two mero-
cyanine moieties.
Figure 4. UV/vis absorption spectra of (1,8-naphthylene)bismerocya-
nine 1 in chloroform (s) and acetonitrile (‚‚‚) at 298 K (3.0 × 10-6
mol dm-3).
The calculated absorption bands of 1 (syn) consist of an
intense transition at 397 nm (f ) 2.06, f is an oscillator strength)
and a weak one at 460 nm (f ) 0.06). The weak band of 1
(syn) corresponds to the theoretically forbidden transition to a
lower excited state of an H-aggregate, and the splitting of the
excited state was calculated to be 0.43 V. The calculated
absorption bands of 1 (anti) consist of an intense transition at
456 nm (f ) 1.15) and a weak one at 450 nm (f ) 0.39),
indicating that the excitonic coupling of 1 (anti) is only 0.036
V. The difference in the exciton coupling between 1 (syn) and
1 (anti) is explained by the orientation of dipole moments of
the merocyanine moieties. In 1 (syn) the two merocyanine
moieties point in the same direction, which strengthens the
transition dipole moment. On the other hand, in 1 (anti), the
two merocyanine moieties point in the reverse direction to
minimize the transition dipole moment. This explains why the
exciton coupling of 1 (anti) is smaller than that of 1 (syn).
Fluorescence Spectra. The relative intensity of the fluo-
rescence of 1 in CHCl3, in which only the anti isomer exists,
was larger than that of 4, and the Stokes shift of 1 in CHCl3
(2130 cm-1) was smaller than that of 4 (2480 cm-1). On the
other hand, 1 in CH3CN, in which the syn/anti ratio was 90:10,
did not fluoresce (Table 3). These observations agree with those
expected from molecular exciton theory:18,35 An H-aggregate
is expected to show weaker fluorescence than a monomer
because an internal conversion from an upper excited state to a
lower one occurs immediately and fluorescence from a lower
excited state is theoretically forbidden (Figure 1). The anti
isomer of 1 shows such spectral features of a J-aggregate as a
bathochromic shift and a smaller Stokes shift compared with
the corresponding monomerocyanine. On the other hand, the
syn isomer of 1 indicates such features of an H-aggregate as a
hypsochromic shift and a decrease of fluorescence. Therefore,
the anti and syn isomers of 1 correspond to model compounds
for minimum units of the J- and H-aggregates of merocyanine
dyes. The anti isomer of 1 shows broader absorption band than
that of 4 (Table 3). Usually, a J-aggregate is known to exhibit
a sharper absorption band compared to that of a monomer.36
This narrowing was attributed to the delocalization of excitons
over the aggregate, and the width of a J-band was theoretically
shown to decrease as the number of molecules constituting the
J-aggregate increases.37 It is considered that the narrowing of
the absorption band is not necessarily obvious for the bismero-
Figure 5. UV/vis spectral changes of 1 in various ratios of dichlo-
romethane and methanol at 298 K (1.0 × 10-5 mol dm-3).
Table 2. UV/Vis Absorption Spectra of
(1,8-Naphthylene)bismerocyanines 1 (syn) and 1 (anti) and
1-Naphthylmerocyanine 4 Calculated with the INDO/S-CI Method
λmax
compda (nm) f b
transition characterc
1 (syn)
460 0.06 -0.45(HfL) + 0.33(HfL+1) - 0.36(HfL+2)
397 2.06 -0.58(HfL+1)+0.60(H-1fL)
1 (anti) 456 1.15 -0.87(HfL)+0.36(H-1fL+1)
450 0.39 +0.80(HfL+1)-0.46(H-1fL)
4
422 1.16 0.94(HfL)
a The MM2-optimized structures were used. b Oscillator strength. c H
and L stand for HOMO and LUMO, respectively.
optimized structure of 1 indicated that the syn and anti
conformers showed hypsochromically and bathochromically
shifted absorption bands compared to that of 4, respectively
(Table 2).34 Accordingly, the hypsochromic shift of 1 observed
on increasing the polarity of the solvent is attributed to the
increase of the syn conformer population. The relationship
between the relative orientation of chromophores and the
calculated spectral shifts of 1 agreed with that expected by
(34) Usually the INDO/S-CI calculation underestimates the absorption
wavelength for organic dyes. Adachi, M.; Nakamura, S. Dyes Pigm. 1991,
17, 287. It was reported that the INDO/S-CI method is useful to predict
the spectral shifts of organic dye aggregates. Thompson, M. A.; Zerner,
M. C. J. Am. Chem. Soc. 1988, 110, 606. Adachi, M.; Yoneyama, M.;
Nakamura, S. Langmuir 1992, 8, 2240. Adachi, M.; Nakamura, S. J. Phys.
Chem. 1994, 98, 1796. Mizuguchi, J.; Rihs, G.; Karfunkel, H. R. J. Phys.
Chem. 1995, 99, 16217.
(35) Cooper, W.; Liebert, N. B. J. Photogr. Sci. Eng. 1972, 16, 25.
(36) Similar broadening was observed for biscyanines linked by a 1,8-
naphthylene skeleton. See ref 28.

Bismerocyanines Linked by a 1,8-Naphthylene Skeleton
J. Am. Chem. Soc., Vol. 120, No. 15, 1998 3627
result indicates that the reduction potentials of 1 are affected
by the syn/anti ratio.
Conclusion
A newly prepared bismerocyanine linked by a 1,8-naphth-
ylene skeleton has two rotational isomers, syn and anti conform-
ers, with respect to orientation of two merocyanine chro-
mophores. The syn and the anti conformers were found to have
a hypsochromic and a bathochromic absorption, respectively,
compared to a 1-naphthyl monomerocyanine. A polar solvent
such as acetonitirile enhanced a preference for the syn con-
former, causing a hypsochromic shift. The pronounced solva-
tochromism based on the change in an excitonic coupling mode
makes a striking contrast with very slight solvatochromic shift
of the corresponding monomerocyanine. The changes of
chromophore arrangements of the two merocyanine moieties
also induced the positive shift of reduction potential of the
bismerocyanine.
Figure 6. Redox potentials of (1,8-naphthylene)bismerocyanine 1 and
monomerocyanines 4 and 6 measured with polarography.
Experimental Section
General Method. The following spectroscopic and analytical
instruments were used: UV, Shimadzu UV-3100PC; 1H NMR, Bruker
ARX-300 or ARX-600 (reference to TMS); IR, JASCO IR-810; MS,
JEOL DX-303; redox potential, Yanaco P-1100 (reference to a saturated
calomel electrode (SCE)). A dropping mercury working and a rotating
Pt working electrode were used for a reduction and an oxidation
potential measurement, respectively, and 0.1 mol dm-3 Pr4NClO4 was
used as a supporting salt.
3-(2-Methoxyethyl)-2-thioxothiazolidin-4-one,38 4,4′-(1,8-naphthyl-
ene)bis(1,2-dimethylpyridinium) diiodide (2),39 1,2-dimethyl-4-(1-naph-
thyl)pyridinium iodide (5),39 and 1,2-dimethylpyridinium p-toluene-
sulfonate (7)40 were prepared by the reported method.
5-(Anilinomethylene)-3-(2-methoxyethyl)-2-thioxothiazolidin-4-
one (3). A solution of 3-(2-methoxyethyl)-2-thioxothiazolidin-4-one
(1.0 g, 5.2 mmol) and N,N′-diphenylformamidine (1.0 g, 5.1 mmol) in
ligroin (5 mL) was stirred at 110 °C for 1 h. After cooling, the
precipitates were filtered off and washed with ligroin to afford 3 (1.2
Figure 7. Schematic diagram of the orbital relationships of the HOMOs
and LUMOs of (1,8-naphthylene)bismerocyanines, 1 (syn) and 1 (anti).
cyanine 1, in which only two merocyanine moieties are placed
close together. The fluctuation of the relative orientation of
the merocyanine moieties in 1, which is not so rigidly restricted
as in a large aggregate or in a single crystal, is possibly an
additional factor for the broadening.
1
g, 81%) as orange crystals: mp 158 °C; H NMR (CDCl3, 298 K) δ
3.07 (s, 3H), 3.72 (t, 2H, J ) 6 Hz), 4.25 (t, 2H, J ) 6 Hz), 6.72 (d,
1H, J ) 14 Hz), 7.08 (d, 2H, J ) 8 Hz), 7.15 (t, 1H, J ) 8 Hz), 7.38
(t, 2H, J ) 8 Hz), 8.00 (d, 1H, J ) 14 Hz); IR (KBr) 1690, 1630,
1580, 1500, 1380, 1300, 1275, 1182, 1100, 975 cm-1
. Calcd for
Redox Potentials. To examine the effect of the chromophore
arrangement on the redox potentials of a merocyanine aggregate,
the redox potentials of 1, 4, and 6 in CH3CN or CH2Cl2 were
measured. The reduction potentials of 1 in both CH3CN and
CH2Cl2 were positively shifted compared to those of 4, while
the oxidation potentials of 1 shifted negatively (Figure 6). These
potential shifts are in accordance with expectations based on
orbital interaction between the two merocyanine moieties. The
HOMO of 1 is derived from the antibonding combinations of
the merocyanine moieties and the LUMO of 1 from the bonding
combination of the LUMOs of the merocyanine moieties (Figure
7). Accordingly, the HOMO level is destabilized and the
LUMO level is stabilized by orbital interaction.
C13H14N2O2S2: C, 53.04; H, 4.79; N, 9.52. Found: C, 52.85; H, 4.97;
N, 9.34.
4,4′-(1,8-Naphthylene)bis[1-methyl-2-[2-[3-(2-methoxyethyl)-4-
oxo-2-thioxothiazolidin-5-ylidene]ethylidene]pyridine] (1). To a
solution of 2 (0.1 g, 0.17 mmol) and 3 (0.16 g, 0.54 mmol) in CH3CN
(10 mL) was added DBU (0.1 g, 0.86 mmol) and acetic anhydride (0.1
g, 0.98 mmol), and the mixture was stirred at room temperature for 2
h. After addition of methanol (10 mL), about a half-volume of the
solvent was removed under reduced pressure. The precipitates were
filtered off and dissolved into methanol and dichloromethane. The
solvent was removed under reduced pressure until crystals appeared.
The precipitates were filtered off and washed with methanol to afford
1 (50 mg, 40%) as purple crystals: mp 295-297 °C (dec); λmax (CH2-
1
Cl2) 566 nm (ꢀ ) 79 000); H NMR (CD2Cl2, 300 K) syn conformer
The difference between the oxidation potentials of 4 in CH3-
CN and that in CH2Cl2 was 0.12 V, which was comparable to
the difference observed for 1 (0.16 V). While the difference
between the reduction potential of 4 in CH3CN and that in CH2-
Cl2 was small enough to ignore the solvent effect. The
difference of the reduction potentials between 1 and 4 in CH3-
CN (0.14 V) was larger than that in CH2Cl2 (0.07 V). This
δ 3.30 (s, 6H), 3.38 (s, 6H), 3.65 (t, 4H, J ) 8 Hz), 4.23 (t, 4H, J )
7 Hz), 4.70 (d, 2H, J ) 13 Hz), 6.08 (d, 2H, J ) 7 Hz), 6.93 (d, 2H,
J ) 7 Hz), 7.11 (s, 2H), 7.50 (d, 2H, J ) 13 Hz), 7.55 (d, 2H, J ) 7
Hz), 7.66 (t, 2H, J ) 7 Hz), 8.07 (d, 2H, J ) 7 Hz); anti conformer δ
3.32 (s, 6H), 3.38 (s, 6H), 3.65 (t, 4H, J ) 8 Hz), 4.23 (t, 4H, J ) 7
Hz), 4.83 (d, 2H, J ) 13 Hz), 6.37 (d, 2H, J ) 7 Hz), 6.98 (d, 2H, J
) 1 Hz), 7.11 (d, 2H, J ) 7 Hz), 7.43 (d, 2H, J ) 7 Hz), 7.58 (d, 2H,
(38) Carroll, B. H. (Eastman Kodak Co.) U.S. Patent 2,635,961, April
21, 1953.
(39) Katoh, T.; Inagaki, Y.; Ogawa, K.; Okazaki, R. Tetrahedron 1997,
22, 3557.
(40) Kosower, E. M.; Skorcz, J. A. J. Am. Chem. Soc. 1960, 82, 2195.
(37) Knapp, E. W.; Scherer, P. O. J.; Fischer, S. F. Chem. Phys. Lett.
1984, 111, 481. Knapp, E. W.; Fischer, S. F. Chem. Phys. Lett. 1984, 103,
479. Fidder, H.; Terpstra, J.; Wiersma, D. A. J. Chem. Phys. 1991, 94,
6895.

3628 J. Am. Chem. Soc., Vol. 120, No. 15, 1998
Katoh et al.
J ) 13 Hz), 7.63 (t, 2H, J ) 7 Hz), 8.07 (d, 2H, J ) 7 Hz); IR (KBr)
1-Methyl-2-[2-[3-(2-methoxyethyl)-4-oxo-2-thioxothiazolidin-5-
ylidene]ethylidene]pyridine (6). To a solution of 7 (0.56 g, 2.0 mmol)
and 3 (0.60 g, 2.0 mmol) in CH3CN (10 mL) was added DBU (0.36 g,
3.1 mmol) and acetic anhydride (0.40 g, 3.9 mmol), and the mixture
was stirred at room temperature for 12 h. After addition of methanol
(10 mL), the solvent was removed under reduced pressure until crystals
appeared. The precipitates were filtered off and dissolved into methanol
and dichloromethane. The solvent was removed under reduced pressure
until crystals appeared. The precipitates were filtered off and washed
with methanol to afford 6 (0.26 g, 46%) as purple crystals: mp 205
°C; λmax (DMSO) 548 nm (ꢀ ) 87 200); 1H NMR (DMSO-d6, 298 K)
δ 3.30 (s, 3H), 3.60 (t, 2H, J ) 7 Hz), 3.75 (s, 3H), 4.20 (t, 2H, J )
7 Hz), 5.22 (d, 1H, J ) 13 Hz), 6.75 (t, 1H, J ) 5 Hz), 7.52 (t, 1H, J
) 5 Hz), 7.80-90 (m, 2H), 7.95 (d, 1H, J ) 5 Hz); IR (KBr) 1650,
1570, 1500, 1420, 1260, 1240, 1150, 1120, 1060, 830 cm-1; MS m/z
308 (M+ ). Calcd for C14H16N2O2S2: C, 54.52; H, 5.23; N, 9.09.
Found: C, 54.67; H, 5.29; N, 9.26.
3420, 1640, 1520, 1418, 1296, 1258, 1210, 1180, 1118, 1058, 780 cm-1
;
MS m/z 741 (M+ ). Calcd for C38H36N4O4S4‚H2O: C, 60.08; H, 5.01;
N, 7.38. Found: C, 59.81; H, 4.85; N, 7.33.
1-Methyl-4-(1-naphthyl)-2-[2-[3-(2-methoxyethyl)-4-oxo-2-thioxothi-
azolidin-5-ylidene]ethylidene]pyridine (4). To a solution of 5 (0.12
g, 0.33 mmol) and 3 (0.15 g, 0.51 mmol) in CH3CN (10 mL) were
added DBU (0.1 g, 0.86 mmol) and acetic anhydride (0.1 g, 0.98 mmol),
and the mixture was stirred at room temperature for 2 h. After addition
of methanol (10 mL), the solvent was removed under reduced pressure
until crystals appeared. The precipitates were filtered off and dissolved
into methanol and dichloromethane. The solvent was removed under
reduced pressure until crystals appeared. The precipitates were filtered
off and washed with methanol to afford 4 (61 mg, 43%) as purple
crystals: mp 197-200 °C (dec); λmax (CH2Cl2) 551 nm (ꢀ ) 57 700);
1H NMR (DMF-d7, 298 K) δ 3.30 (s, 3H), 3.60 (t, 2H, J ) 7 Hz), 3.94
(s, 3H), 4.24 (t, 2H, J ) 7 Hz), 5.34 (d, 1H, J ) 13 Hz), 6.88 (d, 1H,
J ) 7 Hz), 7.6-7.8 (m, 4H), 7.90 (s, 1H), 8.0-8.3 (m, 5H); IR (KBr)
1640, 1560, 1520, 1418, 1260, 1218, 1180, 1120, 1060, 780 cm-1
;
MS m/z 434 (M+). Calcd for C24H22N2O2S2‚H2O: C, 63.77; H, 5.31;
N, 6.19. Found: C, 64.04; H, 5.49; N, 6.05.
JA973608P