Photochromic properties of cationic merocyanine dyes. Thermal stability of the spiropyran form produced by irradiation with visible light

Article abstract of DOI:10.1039/a905098a

A series of novel cationic merocyanine dyes were prepared by condensation of 1,2,3,3-tetramethylindolium derivatives and 3-formyl-4H-1- benzothiopyran or -benzopyran derivatives, and their photochromic properties were investigated, especially focusing on the substituent effect in the indolium moiety. These dyes were converted into the spiropyran (SP) form so as to be colorless by irradiation with visible light, although, left under darkness, the colored merocyanine (MC) form was reproduced. The thermal coloration was affected by two factors: the substituent in the indolium moiety and the counter anion. An electron-donating substituent such as a methoxy group at the 5 position effectively retarded the thermal coloration, whereas an electron-withdrawing group such as a nitro group accelerated it. These substituent effects afforded good linearity for the Hammett rule with para σ parameters, indicating that decrease of the electron density in the indoline moiety of the SP form facilitated heterolytic cleavage of the bond between the spiro carbon and the oxygen of the pyran ring.

Full text of DOI:10.1039/a905098a

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J O U R N A L O F
Photochromic properties of cationic merocyanine dyes.
Thermal stability of the spiropyran form produced by
irradiation with visible light{
Shigeyuki Yagi, Katsumi Maeda and Hiroyuki Nakazumi*
C H E M I S T R Y
Department of Applied Materials Science, College of Engineering,
Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, 599-8531, Japan
Received 25th June 1999, Accepted 30th September 1999
A series of novel cationic merocyanine dyes were prepared by condensation of 1,2,3,3-tetramethylindolium
derivatives and 3-formyl-4H-1-benzothiopyran or -benzopyran derivatives, and their photochromic properties
were investigated, especially focusing on the substituent effect in the indolium moiety. These dyes were
converted into the spiropyran (SP) form so as to be colorless by irradiation with visible light, although, left
under darkness, the colored merocyanine (MC) form was reproduced. The thermal coloration was affected by
two factors: the substituent in the indolium moiety and the counter anion. An electron-donating substituent
such as a methoxy group at the 5 position effectively retarded the thermal coloration, whereas an electron-
withdrawing group such as a nitro group accelerated it. These substituent effects afforded good linearity for the
Hammett rule with para s parameters, indicating that decrease of the electron density in the indoline moiety
of the SP form facilitated heterolytic cleavage of the bond between the spiro carbon and the oxygen
of the pyran ring.
Introduction
Photochromic compounds have attracted much attention in
terms of potential applications in erasable optical recording
1
2
media, materials for transmittance control, photo-switching
3
devices, and so on. Among them, indolinospiropyrans as well
as fulgides and diarylethenes are the most popular photo-
chromic organic dyes, and their photochromic properties such
as kinetic and thermodynamic pro®les for interconversion
between the merocyanine (MC) and spiropyran (SP) forms
4
triggered by photoirradiation have been investigated in detail.
Scheme 1
Unfortunately, spiropyrans possess a few points to be over-
come: the MC form is less stable than the SP form, and thus,
from the viewpoint of applications, i.e. achievement of
interconversion in the photon±photon mode, the thermal
stability of the MC form is essential. Attempts to stabilize the
MC form have been demonstrated by formation of the J-
structural assignment and thermal stability, especially focusing
on substituent effects on the indolium moiety.
Results and discussion
5
6
aggregate, chelation of a metal ion, and copolymerization to
7
polymer backbones. As another defect, the limitation of
Preparation of merocyanine dye
Merocyanine dyes were typically prepared in a similar manner
9
to that reported previously. As shown in Scheme 2, condensa-
synthetic methods to prepare
a variety of spiropyran
derivatives has afforded little chance for wider utilization.
Thus, synthetic approaches to novel spiropyran derivatives and
analogues and assessment of their photochromic properties are
urgently required.
In the course of our researches to develop novel photo-
8
chromic compounds, we previously reported merocyanine
2
tion of 5-substituted indolium salt 1?X (X~ClO
4
, I or BPh
4
)
with 3-formyl-4H-1-benzothiopyran-4-one 2, 3-formyl-4H-1-
benzopyran-4-one 3, or 3-formyl-2-phenyl-4H-1-benzothio-
pyran-4-one 4 afforded 5±10 and 13 in 23±81% yields. The
dyes bearing more extended p conjugation, 11 and 12, were
prepared by condensation of benz[c,d]indolium perchlorate 16
with 2 and 3 in 17 and 46% yields, respectively. The
merocyanine dyes discussed here and their absorption
maxima are summarized in Table 1. For 5±8, the substituent
dyes which are converted into the SP form by irradiation with
visible light, changing from yellow-orange to colorless
9
Scheme 1). The dyes can be regarded as analogues of the
(
MC form of indolinospiropyran and afforded the possibility to
design novel photochromic spiropyran derivatives. They are
essentially stable in the MC form. In this paper, we report
preparation of a series of cationic merocyanine dyes, their
2
at the 5 position is varied from Hto MeO, Me, Br, and NO .
Benzothiopyrano-merocyanine dyes exhibited absorption
maxima at longer wavelengths than those of the benzopyr-
ano-merocyanines: the bathochromic shifts in the benzothio-
pyrano series ranged from 38 to 64 nm among the dyes with the
same substituent at the 5 position. The dyes 11 and 12 showed
their absorption maxima at 522 and 488 nm, respectively,
owing to the strong electron-donating property of the
benzindolium moiety and the extension of the p-conjugation
{Elemental analyses for compounds 6±10 and 13 are available as
supplementary data. For direct electronic access see http://
www.rsc.org/suppdata/jm/1999/2991/, otherwise available from
BLDSC (SUPPL. NO. 57663, pp. 3) or the RSC Library.
J. Mater. Chem., 1999, 9, 2991±2997
This Journal is # The Royal Society of Chemistry 1999
2991

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Scheme 2 Reagents and conditions: i, EtOH, re¯ux; ii, 1-iodohexane, K
2
CO
3
4
, DMF, 80 ³C; iii, 70% HClO , AcOH, re¯ux.
system. Substitution at the 5 position of 5a±8a leads to
bathochromic shifts of the absorption maxima, ranging from 2
to 31 nm. The effect of the introduction of a phenyl group to
the benzothiopyran ring on the absorption maximum was
small: the bathochromic shift was 7 nm, in comparison to that
between 5a (or 7a) and 9 (or 10). Each merocyanine dye was
1
identi®ed by H NMR, UV-vis and IR spectra and elemental
analysis.
Molecular structure of merocyanine dyes
In the MC form of indolinospiropyrans, several stereoisomers
are possible in terms of the photoisomerization of the central
ethenyl double bond as shown in Fig. 1; (s-trans, s-trans),
Table 1 UV-vis absorption spectral features of compounds 5±11 in
at 20 ³C
CHCl CHCl
2
2
(s-trans, s-cis), (s-cis, s-trans) and (s-cis, s-cis) isomers. The
molecular structure of the cationic merocyanine dye was
con®rmed by the X-ray structural analysis of 13. The ORTEP
1
2
3
21
21
Compound X Y R
R
l
max/nm log (e/dm mol cm
)
5
5
5
5
5
6
6
6
6
6
7
7
7
7
7
8
8
8
8
8
9
1
1
1
1
a
b
c
d
e
a
b
c
d
e
a
b
c
d
e
a
b
c
d
e
ClO
ClO
ClO
ClO
ClO
ClO
ClO
ClO
ClO
ClO
I
I
I
I
I
I
I
I
I
4
4
4
4
4
4
4
4
4
4
S
S
S
S
S
H
H
MeO H
456
467
458
468
481
403
429
409
413
427
456
470
459
468
487
403
430
409
414
423
460
463
522
488
456
4.54
4.48
4.49
4.59
4.60
4.48
4.41
4.44
4.54
4.48
4.58
4.53
4.57
4.60
4.57
4.51
4.45
4.50
4.54
4.59
4.33
4.56
4.49
4.39
4.49
Me
Br
NO
H
H
H
H
2
O H
O MeO H
O Me
O Br
O NO
H
H
H
H
2
S
S
S
S
S
H
MeO H
Me
Br
H
H
H
H
NO
2
O H
O MeO H
O Me
O Br
O NO
2
H
H
H
I
ClO
I
4
S
S
S
H
H
Ð
C
C
6
H
H
5
0
1
2
3
6
5
ClO
ClO
4
H
H
H
4
O Ð
4
S H
Fig. 1 Isomers of an indolinospiropyran: (a) (s-trans, s-trans), (b)
(
BPh
s-trans, s-cis), (c) (s-cis, s-trans) and (d) (s-cis, s-cis) isomers.
2992
J. Mater. Chem., 1999, 9, 2991±2997

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Table 2 Ef®ciency of the conversion of the merocyanine dyes 5±12 into
the SP form upon photoirradiation and kinetic data for the thermal
coloration
a
b
23 21 b,c
s
Compound
Ef®ciency (%)
k/10
5
5
5
5
6
6
6
6
7a
7b
7
7
8
8
a
b
c
d
a
b
c
88
82
88
77
93
81
90
71
76
81
85
65
84
76
85
67
61
65
56
53
81
b
0.449
0.0120
0.0247
14.9
0.170
0.0151
0.0471
d
15.1
Fig. 2 The ORTEP drawing of compound 13. All hydrogen atoms and
the tetraphenylborate anion are neglected for clarity.
3.89
0.425
0.995
c
d
a
b
14.9
drawing of 13 is shown in Fig. 2. From the structural analysis,
it was con®rmed that the merocyanine dyes adopted the
geometry resembling the (s-trans, s-cis) of the MC form of
2.44
0.624
0.801
8c
8d
9
1
indolinospiropyrans. In the H NMR spectra of 5±13, coupling
37.9
0.000458
0.0190
4.05
17.3
0.586
of the methyne protons of the central double bond was
observed (J~16 Hz), indicating the trans con®guration of the
bond. Thus, the structure obtained by the X-ray analysis is
likely to be adopted in solution.
1
1
1
1
a
0
1
2
3
In CHCl
2
CHCl
2
at 20 ³C. Determined by UV-vis spectroscopy.
c
Substituent effects on isomerization to the spiropyran form by
photoirradiation
Standard deviations are v3%.
As reported previously, merocyanine dyes 5a and 6a isomerized
to the SP form on irradiation by visible light (w390 nm),
con®rmed by H NMR spectra of the dyes just after
1
photoirradiation. In the spectra the two methyne protons
were magnetically coupled with each other (J~12 Hz) and the
peak of the N-methyl protons appeared at 3.0 ppm, which are
9
characteristic of the SP form. In the UV-vis spectrum,
remarkable bleaching of the absorbance at lmax was observed
for each dye, and the original spectrum was recovered when left
under darkness. Typical UV-vis absorption spectra of the
merocyanine and the spiropyran forms are shown for 7c in
Fig. 3. The ef®ciency of decoloration was w65% for 5±8 and
1
3. The other dyes also exhibited similar decoloration upon
photoirradiation and thermal coloration, although conversion
into the SP form was less effective for 9±12. The thermal
coloration obeyed ®rst order kinetics, and the ef®ciency of
decoloration upon irradiation and the rate constant k of the
thermal coloration for each dye are summarized in Table 2. For
nitro-substituted dyes 5e±8e the rate constants could not be
determined because the thermal isomerization was too fast. The
rate of the thermal coloration was affected mainly by two
factors: electron-donating or -withdrawing properties of the
substituent at the 5 position and the character of the counter
anion. The larger the electron-donating property of the
substituent was, the more the rate of the thermal coloration
Fig. 4 Correlation between Hammett's substituent constant s
p
and log
(k
X
/k
H
) (X~H, MeO, Me or Br) for compounds 5 ($) and 7 (#).
was decreased: the rate constants of bromo-substituted dyes
d±8d were larger than those of the methoxy-substituted dyes
by factors of 35±1240. As shown in Fig. 4, dealing with the
Hammett para substituent constant s afforded good linear-
5
p
10
ity. These results indicate that decrease of the elctron density
in the indoline moiety accelerates heterolytic cleavage of the
bond between the spiro carbon and the oxygen atom of the
pyran ring.
Effect of counter anions on thermal coloration
As mentioned above, the thermal coloration was also affected
by the counter anion. Comparison between compounds 5 (or 6)
and 7 (or 8) showed that exchange of the counter anion from
perchlorate to iodide led to acceleration of the thermal
coloration. The tetraphenylborate dye 13 exhibited a similar
kinetic pro®le to the corresponding perchlorate dye 5a,
indicating that the iodide anion plays an important role in
Table 3 r Values for dyes 5±8 obtained by Hammett's plots
Dye
Counter anion
r
2
5
6
7
8
ClO
ClO
4
6.39 (¡0.43)
5.88 (¡0.86)
3.08 (¡0.20)
3.63 (¡0.58)
2
4
Fig. 3 UV-vis spectra of (a) the merocyanine and (b) the spiropyran
2
I
2
5
23
forms of compound 7c (1.9610 mol dm ). Spectrum (b) was
obtained upon irradiation by visible light (lw390 nm).
2
I
J. Mater. Chem., 1999, 9, 2991±2997
2993

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promoting the thermal coloration. The anion effect on the
thermal coloration was clearly shown in the slopes of the
Hammett plots for dyes 5±8 given in Table 3. The r values are
similar for 5 and 6 and for 7 and 8, respectively, where the
perchlorate dyes yielded larger slopes than the iodides by a
factor of ca. 2. Thus, the substituent effect at the 5 position of
the indolium was more marked in the perchlorates than in the
iodides. Although we can not offer a de®nitive answer for the
effect of counter anions at this point, this might be due to the
softer character of iodide anion than that of perchlorate.
251 ³C (decomp.); dH (DMSO-d ) 1.78 (s, 6H), 3.90 (s, 3H),
6
4.08 (s, 3H), 7.18 (dd, J~2.4 and 8.9, 1H), 7.54 (d, J~2.4, 1H),
7.77 (dt, J~1.2 and 8.0, 1H), 7.84±7.90 (m, 2H), 8.05±8.11 (m,
2H), 8.38 (d, J~16.3, 1H), 8.52 (dd, J~1.2 and 8.0, 1H), 9.54
2
1
(s, 1H); IR (KBr) 1623 cm
SCl: C, 58.04; H, 4.66; N, 2.94. Found: C, 58.14;
H, 4.39; N, 2.81.
(CLO). Calc. (%) for
23 6
C H22NO
1
,3,3,5-Tetramethyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethe-
nyl)indolium perchlorate 5c. This compound was prepared by
2
condensation of 1c?ClO
decomp.); d (DMSO-d
H), 7.46 (dd, J~0.6 and 8.0, 1H), 7.71 (s, 1H), 7.74±7.84 (m,
4
and 2; yield 69%; mp 261 ³C
(
3
H
6
) 1.77 (s, 6H), 2.47 (s, 3H), 4.08 (s,
Conclusion
The novel merocyanine dyes, 5±13, were prepared as analogues
of the indolinospiropyrans. The molecular structure was
con®rmed by X-ray crystallography showing that the geometry
around the central ole®n was (s-trans, s-cis). These dyes
exhibited negative photochromic properties, and substitution
at the 5 position of the indolium ring with an electron-donating
group or introduction of a phenyl group at the 2 position of the
benzothiopyran ring brought about retardation of the thermal
coloration. The rate for thermal conversion from the SP form
to the MC form was affected by the counter anion: the SP form
of the perchlorate dye was converted more slowly than that of
the iodide. Results obtained here should contribute to
investigation of novel photochromic spiropyrans and their
analogues.
2H), 7.87 (dt, J~1.4 and 8.0, 1H), 8.05±8.14 (m, 2H), 8.32 (d,
J~16.3, 1H), 8.52 (dd, J~1.4 and 8.0, 1H), 9.62 (s, 1H); IR
2
1
(KBr) 1624 cm
60.06; H, 4.82; N, 3.05. Found: C, 59.78; H, 4.80; N, 3.25.
(CLO). Calc. (%) for C23
5
H22NO SCl: C,
5-Bromo-1,3,3-trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium perchlorate 5d. This compound was pre-
2
pared by condensation of 1d?ClO4 and 2; yield 63%; mp
284 ³C (decomp.); dH (DMSO-d ) 1.80 (s, 6H), 4.08 (s, 3H),
6
7.78 (dt, J~1.2 and 8.0, 1H), 7.84±7.92 (m, 3H), 8.07 (dd,
J~0.8 and 8.0, 1H), 8.15 (d, J~16.3, 1H), 8.23 (d, J~1.4, 1H),
8.37 (d, J~16.3, 1H), 8.52 (dd, J~1.2 and 8.0, 1H), 9.66 (s,
2
1
1H); IR (KBr) 1626 cm
C H NO SBrCl?H O: C, 48.68; H, 3.90; N, 2.58. Found:
(CLO). Calc. (%) for
2
2
19
5
2
C, 48.52; H, 3.52; N, 2.94.
Experimental
1
1
,3,3-Trimethyl-5-nitro-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium perchlorate 5e. This compound was pre-
H NMR spectra (270 MHz) were recorded on a JEOL JNM-
GX 270 spectrometer in CDCl , DMSO-d , CD CN and
2
pared by condensation of 1e?ClO4 and 2; yield 71%; mp
3
6
3
CD
3
COCD
3
using TMS (0 ppm), CHD
2
SOCD
3
(2.49 ppm),
CHD CN (1.93 ppm) and CD HCOCD (2.04 ppm) as inter-
272 ³C (decomp.); dH (DMSO-d ) 1.88 (s, 6H), 4.12 (s, 3H),
6
2
2
3
7.79 (dt, J~1.0 and 7.7, 1H), 7.89 (dt, J~1.4 and 7.7, 1H), 8.08
(dd, J~1.0 and 7.7, 1H), 8.17 (d, J~8.9, 1H), 8.24 (d, J~16.3,
1H), 8.46±8.57 (m, 3H), 8.88 (d, J~2.0, 1H), 9.73 (s, 1H); IR
nal standards, respectively, IR spectra were recorded on a
Horiba FT-200 spectrometer for KBr disks of samples. Melting
points were determined by differential thermal analyses with a
Rigaku TAS 100 analyzer under nitrogen atmosphere (¯ow
rate: 100 mL min ) by the use of Al
temperature rate programmed was 10 ³C min
2
1
(KBr) 1632 cm (CLO). Calc. (%) for C H N O SCl: C,
2
2
19
2
7
53.83; H, 3.90; N, 5.71. Found: C, 53.55; H, 3.51; N, 5.85.
2
1
2 3
O as a reference. The
2
1
.
1,3,3-Trimethyl-2-(4-oxo-4H-1-benzopyran-3-ylethenyl)indo-
lium perchlorate 6a. This compound was prepared by con-
2
4 4
Indolium salts 1?X (X~ClO , I or BPh ) were prepared by
the conventional reaction of the corresponding 2,3,3-trimethyl-
indolinine derivatives with methyl iodide followed by anion
exchange in the cases of perchlorates and tetraphenylborate,
2
densation of 1a?ClO
4
and 3; yield 33%; mp 259 ³C (decomp.);
dH (DMSO-d ) 1.80 (s, 6H), 4.06 (s, 3H), 7.62±7.68 (m, 3H),
6
7
J~16.4, 1H), 8.22 (dd, J~1.2 and 7.9, 1H), 8.49 (d, J~16.4,
.83 (1H, dd, J~1.2 and 8.3, 1H), 7.87±7.97 (m, 3H), 8.19 (d,
1
each of which was con®rmed by H NMR spectra and
1
1
12
13
elemental analyses. Compounds 2, and 3 and 14 were
prepared by the reported procedures. The solvent used in UV-
vis studies, CHCl CHCl , was of spectroscopic grade.
21
1
H), 9.33 (s, 1H); IR (KBr) 1657 cm (CLO).
2
2
5
-Methoxy-1,3,3-trimethyl-2-(4-oxo-4H-1-benzopyran-3-yl-
ethenyl)indolium perchlorate 6b. This compound was prepared
General procedure for the preparation of compounds 5±10 and 13
2
by condensation of 1b?ClO
(
4
and 3; yield 55%; mp 249 ³C
decomp.); dH (DMSO-d ) 1.78 (s, 6H), 3.90 (s, 3H), 4.04 (s,
2
A mixture of indolium salt 1?X (0.3 mmol) and the aldehyde
6
3
H), 7.18 (dd, J~2.4 and 8.8, 1H), 7.54 (m, 1H), 7.64 (dt,
2, 3 or 4 (0.33 mmol) in ethanol (5 mL) was heated at re¯ux for
J~0.8 and 8.0, 1H), 7.82 (dd, J~0.8 and 8.0, 1H), 7.87 (d,
J~8.8, 1H), 7.93 (dt, J~1.6 and 8.0, 1H), 8.10 (d, J~16.3,
7
±42 h. After cooling, the solid was separated by ®ltration and
washed with diethyl ether (50 mL63) to afford the merocya-
nine dye.
1
H), 8.21 (dd, J~1.6 and 8.0, 1H), 8.42 (d, J~16.3, 1H), 9.28
2
1
(
s, 1H); IR (KBr) 1647 cm (CLO).
1,3,3-Trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethenyl)-
indolium perchlorate 5a. This compound was prepared by
1,3,3,5-Tetramethyl-2-(4-oxo-4H-1-benzopyran-3-ylethenyl)-
indolium perchlorate 6c. This compound was prepared by
2
condensation of 1a?ClO
decomp.); d (DMSO-d
.67 (m, 2H), 7.78 (dt, J~1.2 and 7.6, 1H), 7.85±7.96 (m, 3H),
.07 (dd, J~1.2 and 8.2, 1H), 8.15 (d, J~16.3, 1H), 8.36 (d,
4
and 2; yield 35%; mp 264 ³C
) 1.79 (s, 6H), 4.10 (s, 3H), 7.63±
2
(
H
6
condensation of 1c?ClO and 3; yield 77%; mp 259 ³C
6
(decomp.); d (DMSO-d ) 1.78 (s, 6H), 2.47 (s, 3H), 4.04 (s,
4
7
8
H
3H), 7.45 (dd, J~0.8 and 8.3, 1H), 7.64 (dt, J~1.0 and 7.8,
1H), 7.71 (s, 1H), 7.81±7.85 (m, 2H), 7.93 (dt, J~1.6 and 7.8,
1H), 8.14 (d, J~16.3, 1H), 8.21 (dd, J~1.6 and 7.8, 1H), 8.45
J~16.3, 1H), 8.53 (dd, J~1.2 and 8.2, 1H), 9.63 (s, 1H); IR
2
1
(
5
KBr) 1623 cm
(CLO). Calc. (%) for C H NO SCl: C,
2
2
20
5
2
1
9.26; H, 4.52; N, 3.14. Found: C, 58.82; H, 4.43; N, 3.06.
(d, J~16.3, 1H), 9.30 (s, 1H); IR (KBr) 1657 cm (CLO).
5-Methoxy-1,3,3-trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium perchlorate 5b. This compound was pre-
5-Bromo-1,3,3-trimethyl-2-(4-oxo-4H-1-benzopyran-3-ylethe-
nyl)indolium perchrorate 6d. This compound was prepared by
2
2
pared by condensation of 1b?ClO
4
and 2; yield 51%; mp
condensation of 1d?ClO
4
and 3; yield 71%; mp 277 ³C
2
994 J. Mater. Chem., 1999, 9, 2991±2997

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(
decomp.); dH (DMSO-d ) 1.81 (s, 6H), 4.04 (s, 3H), 7.64 (dt,
6
dH (DMSO-d ) 1.79 (s, 6H), 3.90 (s, 3H), 4.04 (s, 3H), 7.17 (dd,
6
J~1.0 and 7.7, 1H), 7.83 (dd, J~1.0 and 8.0, 1H), 7.84±7.97
m, 3H), 8.18±8.24 (m, 3H), 8.46 (d, J~16.3, 1H), 9.34 (s, 1H);
IR (KBr) 1655 cm (CLO).
J~2.4 and 8.8, 1H), 7.56 (d, J~2.4, 1H), 7.63 (dt, J~0.8 and
8.0, 1H), 7.82 (dd, J~0.8 and 8.0, 1H), 7.88 (d, J~8.8, 1H),
7.94 (dt, J~1.6 and 8.0, 1H), 8.11 (d, J~16.3, 1H), 8.21 (dd,
J~1.6 and 8.0, 1H), 8.42 (d, J~16.3, 1H), 9.33 (s, 1H); IR
(
2
1
2
1
1,3,3-Trimethyl-5-nitro-2-(4-oxo-4H-1-benzopyran-3-ylethe-
nyl)indolium perchlorate 6e. This compound was prepared by
(KBr) 1659 cm (CLO).
2
condensation of 1e?ClO4 and 3; yield 61%; mp 268 ³C
1,3,3,5-Tetramethyl-2-(4-oxo-4H-1-benzopyran-3-ylethenyl)-
indolium iodide 8c. This compound was prepared by con-
(
H 6
decomp.); d (DMSO-d ) 1.89 (s, 6H), 4.09 (s, 3H), 7.66 (dt,
2
J~1.0 and 7.8, 1H), 7.84 (dd, J~1.0 and 8.5, 1H), 7.95 (dt,
J~1.6 and 7.8, 1H), 8.18±8.24 (m, 2H), 8.36 (d, J~16.1, 1H),
densation of 1c?I and 3; yield 61%; mp 254 ³C (decomp.); dH
6
(DMSO-d ) 1.78 (s, 6H), 2.47 (s, 3H), 4.04 (s, 3H), 7.46 (dd,
8
.52 (dd, J~2.2 and 8.9, 1H), 8.54 (d, J~16.1, 1H), 8.89 (d,
2
J~0.6 and 8.5, 1H), 7.64 (dt, J~0.8 and 7.8, 1H), 7.72 (d,
J~0.6, 1H), 7.82 (dd, J~0.8 and 8.0, 1H), 7.83 (d, J~8.5, 1H),
1
J~2.2, 1H), 9.39 (s, 1H); IR (KBr) 1659 cm (CLO).
7
J~1.6 and 7.8, 1H), 8.45 (d, J~16.3, 1H), 9.33 (s, 1H); IR
.94 (dt, J~1.6 and 8.0, 1H), 8.15 (d, J~16.3, 1H), 8.22 (dd,
1
,3,3-Trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethenyl)-
indolium iodide 7a. This compound was prepared by con-
densation of 1a?I and 2; yield 75%; mp 256 ³C (decomp.); d
2
1
(KBr) 1651 cm (CLO).
2
H
(
DMSO-d
6
) 1.79 (s, 6H), 4.10 (s, 3H), 7.63±7.67 (m, 2H), 7.79
dt, J~1.2 and 7.6, 1H), 7.85±7.96 (m, 3H), 8.07 (dd, J~0.9
5-Bromo-1,3,3-trimethyl-2-(4-oxo-4H-1-benzopyran-3-ylethe-
nyl)indolium iodide 8d. This compound was prepared by the
condensation of 1d?I and 3; yield 78%; mp 248 ³C (decomp.);
(
and 8.2, 1H), 8.16 (d, J~16.5, 1H), 8.37 (d, J~16.5 , 1H), 8.53
(
2
2
1
dd, J~1.2 and 8.2, 1H), 9.64 (s, 1H); IR (KBr) 1624 cm
CLO).
dH (DMSO-d ) 1.81 (s, 6H), 4.04 (s, 3H), 7.65 (dt, J~1.0 and
7.7, 1H), 7.83 (dd, J~1.0 and 8.0, 1H), 7.84±7.97 (m, 3H),
6
(
8
.18±8.24 (m, 3H), 8.46 (d, J~16.3, 1H), 9.34 (s, 1H); IR (KBr)
2
1
5-Methoxy-1,3,3-trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium iodide 7b. This compound was prepared by
condensation of 1b?I and 2; yield 23%; mp 256 ³C (decomp.);
dH (DMSO-d ) 1.78 (s, 6H), 3.90 (s, 3H), 4.08 (s, 3H), 7.18 (dd,
J~2.4 and 8.9, 1H), 7.55 (d, J~2.4, 1H), 7.77 (dt, J~1.0 and
1655 cm (CLO).
2
1,3,3-Trimethyl-5-nitro-2-(4-oxo-4H-1-benzopyran-3-ylethe-
nyl)indolium iodide 8e. This compound was prepared by the
6
2
condensation of 1e?I and 3; yield 51%; mp 248 ³C (decomp.);
8
8
8
.0, 1H), 7.86 (d, J~8.9, 1H), 7.88 (dt, J~1.4 and 8.0, 1H),
.05±8.11 (m, 2H), 8.28 (d, J~16.3, 1H), 8.52 (dd, J~1.4 and
.0, 1H), 9.61 (s, 1H); IR (KBr) 1628 cm (CLO).
dH (DMSO-d ) 1.89 (s, 6H), 4.09 (s, 3H), 7.66 (dt, J~0.8 and
7.8, 1H), 7.84 (dd, J~0.8 and 7.8, 1H), 7.95 (dt, J~1.6 and 7.8,
6
2
1
1H), 8.18±8.24 (m, 2H), 8.36 (d, J~16.1, 1H), 8.52 (dd, J~2.2
and 8.8, 1H), 8.54 (d, J~16.1, 1H), 8.89 (d, J~2.2, 1H), 9.41 (s,
2
1
1,3,3,5-Tetramethyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethe-
nyl)indolium iodide 7c. This compound was prepared by
1H); IR (KBr) 1659 cm (CLO).
2
condensation of 1c?I
(
and 2; yield 44%; mp 264 ³C
decomp.); dH (DMSO-d ) 1.77 (s, 6H), 2.47 (s, 3H), 4.08 (s,
1,3,3-Trimethyl-2-(4-oxo-2-phenyl-4H-1-benzothiopyran-3-
ylethenyl)indolium perchlorate 9. This compound was prepared
6
2
3
2
H), 7.46 (dd, J~0.6 and 8.0, 1H), 7.71 (s, 1H), 7.74±7.84 (m,
H), 7.87 (dt, J~1.4 and 8.0, 1H), 8.05±8.14 (m, 2H), 8.32 (d,
by condensation of 1a?ClO
4
and 4; yield 70%; mp 243 ³C
(decomp.); dH (DMSO-d ) 1.29 (s, 6H), 4.00 (s, 3H), 7.52±7.61
6
J~16.3, 1H), 8.52 (dd, J~1.4 and 8.0, 1H), 9.60 (s, 1H); IR
2
(m, 2H), 7.66 (d, J~15.9, 1H), 7.70±7.78 (m, 6H), 7.81 (dt,
J~1.2 and 8.0, 1H), 7.88±7.95 (m, 2H), 8.07 (dd, J~1.0 and
1
(
KBr) 1624 cm (CLO).
8
.0, 1H), 8.42 (d, J~15.9, 1H), 8.55 (dd, J~1.2 and 8.0, 1H);
2
1
5-Bromo-1,3,3-trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium iodide 7d. This compound was prepared by
IR (KBr) 1632 cm (CLO).
2
condensation of 1d?I and 2; yield 35%; mp 281 ³C (decomp.);
1,3,3,-Trimethyl-2-(4-oxo-2-phenyl-4H-1-benzothiopyran-3-
ylethenyl)indolium iodide 10. This compound was prepared by
dH (DMSO-d ) 1.80 (s, 6H), 4.07 (s, 3H), 7.78 (dt, J~1.2 and
8
6
2
.0, 1H), 7.84±7.92 (m, 3H), 8.07 (dd, J~0.8 and 8.0, 1H), 8.15
d, J~16.3, 1H), 8.23 (d, J~1.4, 1H), 8.37 (d, J~16.3, 1H),
condensation of 1a?I and 4; yield 63%; mp 233 ³C (decomp.);
(
dH (DMSO-d ) 1.30 (s, 6H), 4.00 (s, 3H), 7.57±7.61 (m, 2H),
7.66 (d, J~15.9, 1H), 7.70±7.78 (m, 6H), 7.81 (dt, J~1.2 and
8.0, 1H), 7.89±7.95 (m, 2H), 8.06 (dd, J~1.0 and 8.0, 1H), 8.41
6
2
1
8
.53 (dd, J~1.2 and 8.0, 1H), 9.65 (s, 1H); IR (KBr) 1624 cm
(
CLO).
(
d, J~15.9, 1H), 8.55 (dd, J~1.2 and 8.0, 1H); IR (KBr)
2
1
1,3,3-Trimethyl-5-nitro-2-(4-oxo-4H-1-benzothiopyran-3-
ylethenyl)indolium iodide 7e. This compound was prepared by
1626 cm (CLO).
2
condensation of 1e?I and 2; yield 70%; mp 260 ³C (decomp.);
1,3,3-Trimethyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethenyl)-
indolium tetraphenylborate 13. This compound was prepared
d
7
1
3
H
(DMSO-d ) 1.88 (s, 6H), 4.12 (s, 3H), 7.79 (dt, J~1.0 and
6
2
.7, 1H), 7.89 (dt, J~1.4 and 7.7, 1H), 8.09 (dd, J~1.0 and 7.7,
H), 8.18 (d, J~8.9, 1H), 8.24 (d, J~16.3, 1H), 8.46±8.57 (m,
by condensation of 1a?BPh
4
and 2; yield 81%; mp 191 ³C
(decomp.); dH (DMSO-d ) 1.79 (s, 6H), 4.09 (s, 3H), 6.78 (t,
6
2
1
H), 8.88 (d, J~2.0, 1H), 9.77 (s, 1H); IR (KBr) 1630 cm
J~7.3, 4H), 6.92 (t, J~7.3, 8H), 7.15±7.21 (m, 8H), 7.63±7.66
(m, 2H), 7.78 (dt, J~1.2 and 7.9, 1H), 7.84±7.95 (m, 3H), 8.07
(
CLO).
(
J~16.5 Hz, 1H), 8.53 (dd, J~1.2 and 7.9, 1H), 9.62 (s, 1H); IR
dd, J~1.2 and 7.9, 1H), 8.15 (d, J~16.5, 1H), 8.36 (d,
1,3,3-Trimethyl-2-(4-oxo-4H-1-benzopyran-3-ylethenyl)indo-
lium iodide 8a. This compound was prepared by condensation
2
1
(KBr) 1633 cm (CLO).
2
of 1a?I and 3; yield 69%; mp 254 ³C (decomp.); d (DMSO-d )
H
6
1
.80 (s, 6H), 4.06 (s, 3H), 7.62±7.68 (m, 3H), 7.83 (dd, J~1.2
1-Hexyl-2-(4-oxo-4H-1-benzothiopyran-3-ylethenyl)[c,d]indo-
lium perchlorate 11. A mixture of compounds 16 (0.25 mmol)
and 6 (0.38 mmol) in ethanol (10 mL) was heated at re¯ux for
10 h. The hot reaction mixture was ®ltered to separate the
resultant solid, which was dispersed in ether (30 mL) and
stirred for 30 min. Filtration afforded 11 as a solid; yield 17%;
and 8.3, 1H), 7.87±7.97 (m, 3H), 8.19 (d, J~16.4, 1H), 8.22 (dd,
J~1.2 and 7.9, 1H), 8.49 (d, J~16.4, 1H), 9.33 (s, 1H); IR
2
1
(
KBr) 1651 cm (CLO).
5-Methoxy-1,3,3-trimethyl-2-(4-oxo-4H-1-benzopyran-3-
ylethenyl)indolium iodide 8b. This compound was prepared by
condensation of 1b?I and 3; yield 80%; mp 260 ³C (decomp.);
mp 230 ³C (decomp.); dH (CD CN) 0.87 (t, J~7.3, 3H), 1.26±
3
2
1.49 (m, 4H), 1.63 (quint, J~7.3, 2H), 2.18 (quint, J~7.3, 2H),
J. Mater. Chem., 1999, 9, 2991±2997
2995

View Article Online
4
.91 (t, J~7.3, 2H), 7.71 (dt, J~1.2 and 7.9, 1H), 7.80 (dt,
into ice±water to yield a precipitate. Recrystallization of the
precipitate from ethanol afforded 16 as crystals; yield 50%
J~1.2 and 7.9, 1H), 7.89 (dd, J~1.2 and 7.9, 1H), 7.99 (t,
J~7.9, 1H), 8.20 (t, J~7.9, 1H), 8.36 (d, J~7.9, 1H), 8.44 (d,
J~7.9, 1H), 8.55 (dd, J~1.2 and 7.9, 1H), 8.70 (d, J~15.9,
(0.97 g); mp 200 ³C (decomp.); dH (CDCl ) 0.87 (t, J~7.3, 3H),
3
1.25±1.38 (m, 4H), 1.43±1.51 (m, 2H), 2.01 (quint, J~7.3, 2H),
3.27 (s, 3H), 4.70 (t, J~7.3, 2H), 7.88 (t, J~7.9, 1H), 8.04 (t,
J~7.9, 1H), 8.15 (d, J~7.9, 1H), 8.23 (d, J~7.9, 1H), 8.55 (d,
J~7.9, 1H), 8.72 (d, J~7.9, 1H). Calc. (%) for C H NO Cl:
1
1
H), 8.71 (d, J~7.9, 1H), 8.79 (d, J~15.9, 1H), 9.21 (d, J~7.9,
2
1
H), 9.42 (s, 1H); IR (KBr) 1622 cm (CLO). Calc. (%) for
C H NO SCl: C, 64.18; H, 5.00; N, 2.67. Found: C, 64.26; H,
4
2
8
26
5
18 22
4
.84; N, 2.58.
C, 61.45; H, 6.30; N, 3.98. Found: C, 61.17; H, 6.35; N, 3.60.
X-ray structural analysis{
1-Hexyl-2-(4-oxo-4H-1-benzopyran-3-ylethenyl)benz[c,d]in-
dolium perchlorate 12. This compound was prepared by the
similar method to 11 using 3; yield 46%; mp 239 ³C (decomp.);
A single crystal of compound 13 suitable for X-ray crystal-
lographic analysis was obtained by recrystallization from
ethanol±acetonitrile. All data were collected on a Rigaku AFC-
d
(
2
(
H
(CD
quint, J~7.3, 2H), 2.21 (quint, J~7.3, 2H), 4.93 (t, J~7.3,
H), 7.65 (dt, J~1.8 and 7.9, 1H), 7.85 (d, J~7.9, 1H), 7.94
dt, J~1.8 and 7.9, 1H), 8.06 (t, J~7.9, 1H), 8.24 (t, J~7.9,
H), 8.32 (dd, J~1.8 and 7.9, 1H), 8.45 (d, J~7.9, 1H), 8.52 (d,
3 3
COCD ) 0.88 (t, J~7.3, 3H), 1.28±1.50 (m, 4H), 1.64
5
R diffractometer with graphite-monochromated Mo-Ka
radiation in the range 3v2hv55³ using v±2h scan mode.
The structure was solved by direct methods and re®ned by full
matrix least squares, using the TEXSAN crystallographic
software.
The 26 non-hydrogen atoms were assigned anisotropic
thermal parameters, and others isotropic thermal parameters.
There were so few re¯ections that it was not meaningful to
re®ne more than a limiting number of anisotropic thermal
parameters.
1
J~7.9, 1H), 8.72 (d, J~15.9, 1H), 8.79 (d, J~7.9, 1H), 9.06 (d,
J~15.9, 1H), 9.18 (s, 1H), 9.32 (d, J~7.9, 1H); IR (KBr)
2
1
1
5
655 cm (CLO). Calc. (%) for C28
6
H26NO Cl: C, 66.21; H,
.16; N, 2.76. Found: C, 66.25; H, 5.13; N, 2.80.
3
-Formyl-2-phenyl-4H-1-benzothiopyran-4-one 4. A mixture
1
4
of 3-hydroxy-2-phenyl-4H-1-benzothiopyran-4-one (1.81 g,
.75 mmol) and pyridinium dichromate (5.08 g, 13.5 mmol) in
dry dichloromethane was stirred for 25 h at ambient tempera-
ture. Ether (50 mL) and anhydrous MgSO were added and the
mixture was stirred for 15 min, followed by ®ltration. The
ltrate was washed with 5 M HCl, water and saturated brine,
6
Crystal data. C46
H40BNOS, M~665.70, monoclinic, space
(no. 14), a~9.648(5), b~20.874(5),
group
P2 /c
1
3
Ê
Ê
4
c~17.800(3) A, b~94.32(3)³, V~575(2) A , T~296 K,
2
1
Z~4, m(Mo-Ka)~1.21 cm
8
The ®nal wR(F ) was 0.075, R1~0.078.
, 8750 re¯ections measured,
259 unique (Rint~0.096) which were used in all calculations.
®
2
and dried over anhydrous MgSO . The solvent was removed by
4
an evaporater, and the residue puri®ed by silica gel column
chromatography (dichloromethane±ethyl acetate, 20 : 1, v/v, as
eluent). Further puri®cation by recrystallization from benzene
afforded compound 4 as ivory crystals; yield 39% (698 mg); mp
Photoirradiation studies
The molar absorption coef®cient of each dye was measured
with a solution which was left under darkness for more than
3 h. Irradiation by visible light was carried out with a solution
1
1
H 3
66 ³C; d (CDCl ) 7.42 (m, 8H), 8.58 (dd, J~1.8 and 7.3, 1H),
2
1
21
0.2 (s, 1H); IR (KBr) 1701 cm (HCLO), 1614 cm (CLO);
2
5
23
z
z
of 2610 mol dm , using a Xe lamp (Ushio, 400 W) as a
light source through a Toshiba L-39 glass ®lter. The cell holder
of the spectrometer was kept at 20 ³C during the measurement.
Upon irradiation, a sample solution was kept at a distance of
EI-MS (m/z) 266 (84, M ), 237 (100%, [M2CHO] ). Calc. (%)
for C H O S: C, 72.16; H, 3.78. Found: C, 72.11; H, 3.55.
1
6
10
2
2
-(2,2-Dimethyl-4,6-dioxo-1,3-dioxacyclohex-5-cylidene)-1-
4
5 cm from a light source. The rate constant k of the thermal
coloration for each dye was con®rmed by plotting
log{(A 2A )/(A 2A )} against the time to afford good
linearity, where A` is the absorbance at lmax at the time
when no more spectral change occurs under darkness, A that
hexyl-1,2-dihydrobenz[c,d]indoline 15. A stirred mixture of
compound 14 (2.22 g, 7.5 mmol), 1-iodohexane (3.18 g,
`
0
`
t
1
2 3
5 mmol) and K CO (2.07 g, 15 mmol) in DMF (30 mL)
was heated at 80 ³C for 8 h. After cooling, the solvent was
removed by an evaporator and water added to the residue,
followed by extraction with dichloromethane (62). The
extracts were combined, washed with water (62) and saturated
0
just after photoirradiation, and A that at time t (s) under
t
darkness after photoirradiation is stopped.
15
4
brine, and dried over anhydrous MgSO . The solvent was
removed by an evaporator, and the residue puri®ed by silica gel
column chromatography (hexane±ethyl acetate, 2 : 1, v/v, as
eluent). Recrystallization from benzene±hexane afforded 15 as
References
1
M. Irie, Mol. Cryst. Liq. Cryst., 1993, 227, 263; Denshi Shashin
Gakkaishi, 1996, 35, 344.
H 3
orange crystals; yield 80% (2.28 g); mp 165 ³C; d (CDCl ) 1.34
2
T. Sakagami, in Chemistry of Organic Photochromism, Kagaku
Sosetsu, No. 28, Chem. Soc. Jpn., Gakkai Shuppan Center,
Tokyo, 1996, p. 149 and references therein.
(
t, J~7.3, 3H), 1.25±1.36 (m, 6H), 1.83 (s, 6H), 1.89 (quint,
J~7.3, 2H), 4.37 (t, J~7.3, 2H), 7.52 (d, J~7.9, 1H), 7.61 (t,
J~7.9, 1H), 7.81 (t, J~7.9, 1H), 7.84 (d, J~7.9, 1H), 8.17 (d,
3
(a) R. Blonder, I. Willner and A. F. B uÈ ckmann, J. Am. Chem. Soc.,
1998, 120, 9335; (b) I. Willner, Acc. Chem. Res., 1997, 30, 347;
(c) K. Kimura, T. Yamashita and M. Yokoyama, J. Phys. Chem.,
2
1
J~7.9, 1H), 9.01 (d, J~7.9, 1H); IR (KBr) 1664 cm (CLO);
z z
EI-MS (m/z) 379 (8.6, M ), 236 (100%, [M2C H O ] ). Calc.
6
7
4
1992, 96, 5614; (d) S. L. Gilat, S. H. Kawai and J.-M. Lehn,
J. Chem. Soc., Chem. Commun., 1993, 1439.
(
%) for C23
4
H25NO : C, 72.80; H, 6.64; N, 3.69. Found: C,
7
2.85; H, 6.61; N, 3.22.
4
5
For a review R. Guglielmetti, in Photochromism. Molecules
and Systems, Studies in Organic Chemistry, eds. H. Durr and
H. Bouas-Laurent, Elsevier, Amsterdam, 1990, p. 314 and
references therein.
E. Ando, M. Miyazaki, K. Morimoto, H. Nakahara and
K. Fukuda, Thin Solid Films, 1985, 133, 21; H. Tomioka and
T. Itoh, J. Chem. Soc., Chem. Commun., 1991, 532; A. Miyata,
Y. Unuma and Y. Higashigaki, Bull. Chem. Soc. Jpn., 1991, 64,
1-Hexyl-2-methylbenz[c,d]indolium perchlorate 16. To a
re¯uxed solution of compound 15 (2.09 g, 5.5 mmol) in
acetic acid (15 mL) was added dropwise perchloric acid
(
70%, 900 mg, 6.1 mmol). The reaction mixture soon changed
to dark green, and carbon dioxide evolved. After the gas
evolution ceased, the reaction mixture was cooled and poured
1719; J. Hibino, M. Suziki and Y. Kishimoto, Nihon Kagaku
Kaishi, 1992, 1125.
6
7
T. Tamaki and K. Ichimura, J. Chem. Soc., Chem. Commun., 1989,
1477.
A. Miyashita, M. Hirano, S. Nakano and H. Nohira, J. Mater.
{
1
CCDC reference number 1145/187. See http://rsc.org/suppdata/jm/
999/2991/ for crystallographic ®les in .cif format.
2996
J. Mater. Chem., 1999, 9, 2991±2997

View Article Online
Chem., 1993, 3, 221; A. Miyashita, S. Nakano, M. Hirano and
H. Nohira, Chem. Lett., 1993, 501.
in Photochromism, ed. G. H. Brown, Wiley-Interscience, New
York, 1971, p. 49.
8
S. Watanabe, H. Nakazumi, S. Kado, K. Maeda and T. Kitao,
J. Chem. Res., 1990, (S)50; (M)546; S. Watanabe, H. Nakazumi,
K. Maeda and T. Kitao, J. Chem. Soc., Chem. Commun., 1990,
11 C. H. Chen and G. A. Reynolds, J. Org. Chem., 1979, 44, 3144.
12 A. Nohara, T. Umetani and Y. Sanno, Tetrahedron, 1974, 30,
3553.
4
21.
13 N. P. Vasilenko, F. A. Mikhalenko and J. I. Rozhinsky, Dyes
Pigments, 1981, 2, 231.
14 H. Nakazumi, T. Endo, H. Sonoda and T. Kitao, J. Heterocycl.
Chem., 1985, 22, 821.
9
0
H. Nakazumi, K. Maeda, S. Yagi and T. Kitao, J. Chem. Soc.,
Chem. Commun., 1992, 1188.
Plotting the s constant afforded large deviation from linearity.
z
1
15
For practical purposes, the decreasing rate of the SP form was
monitored.
This may be because the positive charge is located not on the
nitrogen atom in the indoline ring but on the benzothiopyran or
benzopyran moiety. For Hammett-type analyses of the thermal
decoloration for typical indolinospiropyrans, see R. C. Bertelson,
Paper 9/05098A
J. Mater. Chem., 1999, 9, 2991±2997
2997