Synthesis of near-infrared absorbing bisquarylium dyes bearing unsymmetrically extended π-conjugation structures

Article abstract of DOI:10.1055/s-2002-20034

Novel cationic bisquarylium dyes 3 and 4 were prepared by the reaction of benzothiazolinosquarylium dye 2 with a series of 4-substituted 3-hydroxy or 3-ethoxycyclobut-3-ene-1,2-diones. These dyes exhibit large and intense absorptions in the near-infrared region with varying absorption maxima in the range of 771 to 815 nm.

Full text of DOI:10.1055/s-2002-20034

PAPER
413
Synthesis of Near-Infrared Absorbing Bisquarylium Dyes Bearing
Unsymmetrically Extended -Conjugation Structures
Synthesis of
B
h
isquarylium
i
D
ye
s
geyuki Yagi,* Kazuhisa Nakai, Yutaka Hyodo, Hiroyuki Nakazumi*
Department of Applied Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka
599-8531, Japan
Fax +81(72)2549913; E-mail: yagi@ams.osakafu-u.ac.jp
Received 26 October 2001; revised 6 December 2001
dye 2, it is possible to obtain various cationic SQ deriva-
Abstract: Novel cationic bisquarylium dyes 3 and 4 were prepared
tives by employing a variety of aromatic/heterocyclic
components. In the present paper, we report stepwise syn-
thesis of novel cationic SQ homologues, namely,
by the reaction of benzothiazolinosquarylium dye 2 with a series of
4-substituted 3-hydroxy or 3-ethoxycyclobut-3-ene-1,2-diones.
These dyes exhibit large and intense absorptions in the near-infrared
region with varying absorption maxima in the range of 771 to 815 bisquarylium dyes bearing unsymmetrically extended -
nm.
conjugation structures, as shown in Figure 1.
Key words:: squarylium dyes, X-ray crystallographic analysis,
heterocycles -conjugation structures, chromophores
Bu
N
O
O
OH
OH
O
O
S
S
+
N
Squarylium (SQ) dyes are 1,3-disubstituted compounds
derived from squaric acid (3,4-dihydroxycyclobut-3-ene-
1,2-dione), bearing either aromatic or heterocyclic elec-
tron-donating components,1 and exhibit interesting photo-
chemical properties such as photoconductivity and large
and intense light absorption in the visible and/or near-in-
frared regions. Thus, SQ dyes are applicable to industrial
uses such as xerographic photoreceptors,2 media for opti-
cal recording using a diode laser,3 photoconductive layers
in organic solar cells,4 chemosensors,5 and so on. Howev-
er, the traditional synthetic method of SQ dyes can offer
only a symmetrical structure bearing the same electron-
donating components.6 From this point of view, the devel-
opment of synthetic methodology for novel SQ dyes and
their related compounds is of much importance for the ex-
tension of their utility. Recently, several unsymmetrical
SQ dyes have been reported independently,7–9 and thus,
variability of electronic structures of SQ dyes have been
widely extended. On the other hand, in the course of our
research on the preparation of SQ dyes, we found that a
novel cationic SQ homologue 1 is exclusively produced
by the reaction of 1-alkyl-2-methylbenzothiazolium and
squaric acid in the absence of quinoline which is usually
added to obtain a typical SQ dye in an efficient yield.10
The formation of the cationic dye 1 is achieved by an elec-
trophilic attack of the intermediate on the methine carbon
of the SQ dye 2 once formed, as shown in Scheme 1. In
contrast to the dye 2, the dye 1 exhibits a large and intense
OH
Bu
I
H+
S
Bu
+
N
N
O
O
S
O
Bu
I
Bu
S
N
+
N
+
Bu
HO
OH
S
2
- H2O
O
Bu
Bu
+
N
N
OH
S
S
O
O
+
N
Bu
S
I
1
Scheme 1
The mono-substituted squaric acids 5a and 5b
[Scheme 2(a)] were chosen as candidates for the electro-
philic intermediates to obtain the dyes 3a and 3b, respec-
tively. These were prepared according to an analogous
procedure to the one reported previously [Scheme 2(b)].9
Although the preparation of 6a–c was also examined ac-
cording to a similar method, isolation and purification by
normal procedures such as column chromatography and
recrystallization were not successful except for 6a: even
in the case of 6a, the optimized yield by using reverse-
phase column chromatography of an octadecylsilicate-en-
docapped stationary phase was only 37%.9 Instead, the
ethyl esters 7a–c were employed as equivalents for 6a–c,
each of which was synthesized in a satisfactory yield (50–
75%) from 8a–c and 3,4-diethoxy-1,2-dioxocyclobut-3-
absorption in the near-infrared region (
797 nm in
max
CHCl3), and the X-ray analysis indicated that this out-
standing spectral feature is due to the largely extended -
conjugation structure consisting of two squaryl subunits.
If the intermediate is isolated and allowed to attack the SQ
Synthesis 2002, No. 3, 18 02 2002. Article Identifier:
1437-210X,E;2002,0,03,0413,0417,ftx,en;F08201SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

414
S. Yagi et al.
PAPER
Bu
N
+
OH
N
O
R1
S
O
O
Bu
S
+
X
4a: R1
4b: R1
4c: R1
=
=
=
X = BPh4
X = BPh4
X = BPh4
N
Me
3a: R1
3b: R1
=
=
NEt2
X = I
S
N
Me
N
X = I
N
Figure 2 The molecular structure of 7a (ORTEP drawing). All hy-
Me
drogen atoms are omitted for clarity
Figure 1 The structures of the bisquarylium dyes 3 and 4
As shown in Scheme 3, the reactions of the SQ dye 2 with
the mono-substituted squaric acid derivatives 5 and 7
were examined in butan-1-ol/benzene containing HI
(Method A) and in butan-1-ol containing H2SO4 (Method
B) to obtain the dyes 3 and 4, respectively. For 5a and 5b,
the reactions with 2 proceeded in 3–4 hours to afford the
bisquarylium dyes 3a and 3b as iodides in 72 and 35%
yields, respectively. The Method A failed to obtain the
dyes corresponding to 4a–c from 2 and 7a–c. On the other
hand, by the Method B, 7a–c reacted with 2 to afford hy-
drogensulfates of 4a–c. For convenience of handling, 4a–
c were isolated as tetraphenylborates via anion exchange
using sodium tetraphenylborate. The total yields of 4a–c
from 2 and 7a–c were 12,10, and 17% yields, respective-
ly. Under the conditions of the Method B, the initial reac-
tant mixture of 1 equivalent of 7 and 2 equivalents of 2
with 4 equivalents of H2SO4 afforded an optimized yield.
One can see that the ethyl esters 7a–c were converted to
the intermediate 6a–c in situ by acid-promoted hydrolysis
to react with the dye 2. The cationic bisquarylium dyes 3
ene according to a similar procedure to Terpetschnig’s
method [Scheme 2(b)].8 The structures of these intermedi-
ates were confirmed by 1H NMR, IR, and EI or FAB MS
spectra as well as elemental analyses. In addition, the
structure of 7a was proved by X-ray crystallographic anal-
ysis. As shown in Figure 2, it was confirmed that the eth-
yloxy and indolinylidenemethyl groups have been
introduced at the 3- and 4-positions of the 1,2-dioxo-3-cy-
clobutene ring, respectively.
(a)
X
R2
O
R1
R1
O
O
N
N
O
Me
R2
OH
Y
6a: X = C(CH3)2, Y = OH
7a: X = C(CH3)2, Y = OEt
5a: R1 = R2 = Et
5b: R1, R2 = -(CH2)3-
6b: X = S, Y = OH
7b: X = S, Y = OEt
1
and 4 were characterized by H NMR, Vis-NIR absorp-
tion, IR, and FAB MS spectra as well as elemental analy-
ses.
6c: X = -CH=CH-, Y = OH
7c: X = -CH=CH-, Y = OEt
(b)
R2
H+
1) benzene, rt
Cl
O
O
R1
2
5 or 7
3 or 4
2) H2O/AcOH, reflux
method A or B
N
5a,b
R1
Cl
yield:
3a, 72% 4a, 12%
3b, 35% 4b, 10%
4c, 17%
R2
O
O
EtO
EtO
X
NEt3, EtOH
7a-c
Scheme 3
N
Me
A selected region of the 1H NMR spectrum of 4a in CDCl3
is shown in Figure 3(a). Several signals of the dye skele-
ton were split into two peaks, as seen for N-methyl pro-
tons in the indolin component (Ha) and two methine
protons (Hd, He), although no decoalescence was observed
for the signals of the tetraphenylborate anion (not shown).
8a-c
Scheme 2 The structures of the intermediates for the preparation of
the bisquarylium dyes (a), and the synthetic Schemes (b) of their pre-
paration
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PAPER
Synthesis of Bisquarylium Dyes
415
These split signals were coalesced in DMSO-d6 solution
by raising the temperature to 80 °C as shown in
Figure 3(b). Similar results were obtained for the other
bisquarylium dyes. Taking it into consideration that the
stoichiometry of the dye skeleton and the tetraphenylbo-
rate anion is 1:1, conformational isomerization based on
some bond rotations slower than the NMR time scale
would occur in CDCl3, although the detailed structures of
the conformers have not been revealed. Another notable
NMR profile is that the signal of the OH proton in the cy-
clobutene is observed in the quite lower magnetic field
(18.3–18.7 ppm) in each dye. This spectral peculiarity
originates from high acidity of the proton as well as the
magnetic deshielding effect from the negatively charged
oxygen in the other cyclobutene ring. In the X-ray struc-
ture of the dye 1,10 the OH group forms a hydrogen bond
with the neighboring oxygen to maintain the planarity of
the -conjugation structure, and in addition, the reported
value of pKa of 1 is 4.9.5a Therefore, judging from the 1H
NMR spectroscopy, the dyes 3 and 4 also form intramo-
lecular hydrogen bondings to afford similar -conjugation
structures to 1.
Table Absorption Spectral Dataa of the Bisquarylium Dyes 3 and 4
Compound
max (nm)
771
/mol–1 dm3 cm–1
1.04 105
3a
3b
815
792
797
812
1.34 105
4a
2.52 105
4b
3.05 105
4c
2.69 105
a In CHCl3 at 20 °C.
benzothiazolium component attached to the methine car-
bon between two cyclobutene moieties deviates from the
-conjugation plane of the bisquarylium skeleton, the
electronic properties of the cationic dyes 3 and 4 are main-
ly determined by the large -conjugation system consist-
ing of two unsymmetrically introduced electron-donating
components across two cyclobutenes.
Figure 4 Vis-NIR absorption spectra of 4c (solid line) and 1 (da-
shed line) in CHCl3: 4c = 2.82 10–6 M; 1 = 2.06 10–6
M
In summary, we have found that the benzothiazoli-
nosquarylium dye 2 reacts with 3-hydroxy and 3-ethoxy-
cyclobut-3-ene-1,2-diones
bearing
aromatic
and
heterocyclic substituents at the 4-positions, respectively,
to afford novel cationic SQ homologues, namely,
bisquarylium dyes. These dyes exhibit large light-absorp-
tions in the near-infrared region. The properties of the
dyes varied from the aromatic/heterocyclic components
introduced in the -conjugation systems. Although SQ
dyes and their related compounds possess complicated
electronic structures and it is not so easy to expect their re-
action with various reagents, the present study shows the
possibility of preparation of other novel SQ derivatives
and, furthermore, should contribute to more understand-
ing of their chemical properties.
Figure 3 1H NMR spectra of 4a (a) in CDCl3 at 23 °C and (b) in
DMSO-d6 at 80 °C
The dye 1 exhibits a large absorption in the near-infrared
region, and a similar light-absorbing property was ob-
served for the dyes 3 and 4, as summarized in the Table.
As a typical example, the Vis-NIR spectrum of 4c is
shown in Figure 4, with the reference spectrum of 1. The
values of max of the bisquarylium dyes vary from 771 to
815 nm, and the molar absorption coefficient for each dye
is >1 105 mol–1 dm3 cm–1. The max and are similar to
those of 1, indicating the formation of the cationic SQ ho-
mologues. Considering that in the X-ray structure of 1 the
1H NMR spectra were obtained on a JEOL JNM-GX 270 FT-NMR
(270 MHz) or a JEOL -500 FT-NMR (500 MHz) spectrometer,
and the chemical shifts are reported in ppm downfield from an in-
ternal TMS reference. Vis-NIR spectra were obtained on a Shimad-
zu UV-3100 spectrometer. IR spectra were recorded on a Horiba
Synthesis 2002, No. 3, 413–417 ISSN 0039-7881 © Thieme Stuttgart · New York

416
S. Yagi et al.
PAPER
FT-200 spectrometer using KBr pellets. EI mass spectra were ob-
tained on a Shimadzu QP-5000 mass spectrometer. FAB mass spec-
tra were obtained on a Finnigan MAT TSQ-70 mass spectrometer,
using 3-nitrobenzyl alcohol as a matrix. Elemental analyses were
recorded on a Yanaco CHN-CORDER MT3 recorder.
The preparation of 5b was reported previously,9 and 5a was also
prepared in a similar manner to 4-[4-(dibutylamino)phenyl]-3-hy-
droxy-1,2-dioxocyclobut-3-ene.9
3-Ethoxy-4-(2H-dihydoro-1-methyquinolin-2-ylidenemethyl)-
cyclobut-3-ene-1,2-dione (7c)
For the preparation of 7c, compound 8c (2.28 g, 8.10 mmol) and
3,4-diethoxycyclobut-3-ene-1,2-dione (1.36 g, 7.99 mmol) were
employed, and the reaction scale was adjusted to the molar amount
of 8c. The product obtained by silica gel chromatography (CH2Cl2
as eluent) was recrystallized from benzene to afford reddish orange
crystals of 7c (1.68 g, 75%); mp 216–218 °C.
IR (KBr): 1762, 1686 cm–1.
4-[4-(Diethylamino)phenyl]-3-hydroxy-1,2-dioxocyclobut-3-
ene (5a)
The compound 5a was obtained from of 4-[4-(diethylamino)phe-
nyl]-3-chlorocyclobut-3-ene-1,2-dione11 (1.87 g, 7.09 mmol) in
86% yield; mp 220–222 °C (dec.).
1H NMR (CDCl3): = 1.51 (t, J = 7.3 Hz, 3 H), 3.68 (s, 3 H), 4.86
(q, J = 7.3 Hz, 2 H), 5.27 (s, 1 H), 7.23 (d, J = 7.3 Hz, 1 H), 7.34–
7.37 (m, 2 H), 7.40–7.55 (m, 2 H), 8.54 (d, J = 9.8 Hz, 1 H).
EI MS: m/z (%) = 281 (M+, 51), 196 (M+ – 2CO – C2H5, 100).
IR (KBr): 1763, 1711, 1576 cm–1.
Anal. Calcd for C17H15NO3: C, 72.58; H, 5.37; N, 4.98. Found: C,
72.94; H, 5.26; N, 4.57.
1H NMR (270 MHz, DMSO-d6): = 1.13 (t, J = 7.0 Hz, 6 H,
NCH2CH3), 3.45 (br, 4 H, NCH2CH3), 6.92 (br, 2 H, ArH), 7.89 (d,
J = 7.3 Hz, 2 H, ArH) (1 H for the hydroxy group was not ob-
served).
Dye 3a; Typical Procedure
Method A: A stirred solution of 2 (508 mg, 1.04 mmol) and 5a (245
mg, 1.00 mmol) in a mixture of butan-1-ol–benzene (40 mL, 4:1, v/
v) was heated in an oil bath kept at 120 °C in the presence of HI (2
equiv, supplied as hydroiodic acid) for 3 h. After cooling, EtOH (50
mL) was added to the reaction mixture, and the solution was al-
lowed to stand for 24 h. The resulting solid was separated by filtra-
tion and purified by silica gel column chromatography (CH2Cl2 as
eluent) to afford solid 3a (610 mg, 72%). The dye 3b was similarly
prepared.
FAB MS: m/z: 246 ([M + H]+).
Anal. Calcd for C14H15NO3: C, 68.56; H, 6.16; N, 5.71. Found: C,
68.58; H, 6.22; N, 5.68.
3-Ethoxy-4-(1,3,3-trimethylindolin-2-ylidenemethyl)cyclobut-
3-ene-1,2-dione (7a); Typical Procedure
To a dispersed solution of 8a (3.02 g, 10.0 mmol) in EtOH (20 mL)
was added dropwise Et3N (1.03 g, 10.2 mmol) and an ethanolic so-
lution (20 mL) of 3,4-diethoxycyclobut-3-ene-1,2-dione (1.71 g,
10.1 mmol). The mixture was stirred at r.t. for 2 h under N2. The sol-
vent was removed on a rotary evaporator, and the residue was puri-
fied by silica gel column chromatography (CH2Cl2 as eluent)
followed by recrystallization from benzene–hexane to afford orange
crystals of 7a (2.13 g, 72%); mp 147–148 °C.
IR (KBr): 1747, 1602 cm–1.
1H NMR (500 MHz, DMSO-d6, 80 °C): = 0.79 (t, J = 7.3 Hz, 3 H),
0.94 (t, J = 7.3 Hz, 3 H), 1.14 (t, J = 6.9 Hz, 6 H), 1.26 (sext, J = 7.3
Hz, 2 H), 1.44 (sext, J = 7.3 Hz, 2 H), 1.78–1.84 (m, 4 H), 3.44 (q,
J = 6.9 Hz, 4 H), 4.74–4.69 (m, 4 H), 6.63 (s, 1 H), 6.77 (d, J = 8.2
Hz, 2 H), 7.60 (t, J = 7.8 Hz, 1 H), 7.73 (t, J = 7.8 Hz, 1 H), 7.81 (d,
J = 8.2 Hz, 2 H), 7.87 (t, J = 7.8 Hz, 1 H), 7.96 (t, J = 7.8 Hz, 1 H),
8.04 (d, J = 7.8 Hz, 1 H), 8.20 (d, J = 7.8 Hz, 1 H), 8.39 (d, J = 7.8
Hz, 1 H), 8.47 (d, J = 7.8 Hz, 1 H), 18.31 (br, 1 H).
IR (KBr): 1772, 1724 cm–1.
1H NMR (270 MHz, CDCl3): = 1.53 (t, J = 7.3 Hz, 3 H), 1.63 (s,
6 H), 3.37 (s, 3 H), 4.70 (q, J = 7.3 Hz, 2 H), 5.36 (s, 1 H), 6.89 (d,
J = 7.3 Hz, 1 H), 7.07 (t, J = 7.3 Hz, 1 H), 7.25–7.30 (m, 2 H).
FAB MS: m/z = 716 ([M – I]+).
Anal. Calcd for C42H42IN3O4S2 H2O: C, 58.53; H, 5.15; N, 4.88.
Found: C, 58.72; H, 5.10; N, 4.92.
EI MS: m/z (rel. int., %) = 297 (M+, 75), 212 (M+ – 2CO – C2H5,
100).
Dye 3b
Yield: 35%.
IR (KBr): 1747, 1610 cm–1.
Anal. Calcd for C18H19NO3: C, 72.71; H, 6.44; N, 4.71. Found: C,
72.84; H, 6.41; N, 4.50.
3-Ethoxy-4-(1-methylbenzothiazol-2-ylidenemethyl)cyclobut-
3-ene-1,2-dione (7b)
1H NMR (DMSO-d6, 23 °C): = 0.75 (t, J = 7.3 Hz, 3 H), 0.90 (t,
J = 7.3 Hz, 3 H), 1.22 (m, 2 H), 1.41 (m, 2 H), 1.75 (m, 4 H), 1.84
(m, 4 H), 2.65 (m, 4 H), 3.37 (m, 4 H), 4.70 (m, 2 H), 4.77 (m, 2 H),
6.68 (s, 1 H), 7.35–8.60 (m, 10 H) (the broad signal assigned to OH
is at ca. 18.5–19.0 ppm).
The preparation of 7b was carried out according to that of 7a using
8b (1.46 g, 5.07 mmol) and 3,4-diethoxycyclobut-3-ene-1,2-dione
(0.860 g, 5.05 mmol) as starting materials. The reaction scale was
adjusted to the molar amount of 8b. The product obtained by silica
gel chromatography (CH2Cl2 as eluent) was recrystallized from
benzene to afford orange crystals of 7b (1.01 g, 70%); mp 220–223
°C.
FAB MS: m/z = 740 ([M - I]+).
Anal. Calcd for C44H42IN3O4S2 H2O: C, 59.66; H, 5.01; N, 4.74.
Found: C, 59.73; H, 4.98; N, 4.78.
IR (KBr): 1765, 1693 cm–1.
Dye 4a; Typical Procedure
1H NMR (CDCl3): = 1.52 (t, J = 7.3 Hz, 3 H), 3.55 (s, 3 H), 4.84
(q, J = 7.3 Hz, 2 H), 5.46 (s, 1 H), 7.09 (d, J = 7.9 Hz, 1 H), 7.17 (t,
J = 7.9 Hz, 1 H), 7.35 (t, J = 7.9 Hz, 1 H), 7.30 (d, J = 7.9 Hz, 1 H).
Method B: A butan-1-ol solution (40 mL) of 7a (0.297 g, 1.00
mmol) containing H2SO4 (4 mmol) was heated at 120 °C for 2 h. To
the mixture was added 2 (977 mg, 2.00 mmol) in a single portion,
and the mixture was stirred at the same temperature for 6 h. After
cooling, the solvent was removed by distillation at reduced pres-
sure, and the residue was washed with a small amount of H2O. The
crude product was purified by silica gel column chromatography
(CH2Cl2–MeOH, 15:1, v/v, as eluent), and recrystallized from
EtOH–hexane. The crystals were dissolved in CH2Cl2 (10 mL), and
to the solution was added dropwise a MeOH solution (4 mL) of so-
dium tetraphenylborate (102 mg, 0.298 mmol). The mixture was
EI MS: m/z (%) = 287 (M+, 34), 202 (M+ – 2CO – C2H5, 100).
Anal. Calcd for C15H13NO3S 0.25H2O: C, 61.73; H, 4.66; N, 4.80.
Found: C, 61.52; H, 4.40; N, 4.52.
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Synthesis of Bisquarylium Dyes
417
stirred at 60 °C for 1 h. After cooling, the solvent was removed by
evaporation, and the residue was washed with a small amount of
H2O and recrystallized from CH2Cl2–hexane to afford crystals of 4a
(126 mg, 12%). The dyes 4b and 4c were similarly prepared.
= 82.01(1)°, volume: 788.7(2) Å3, Z = 2, dcalcd = 1.252 g cm–3,
unique reflections: 1694 (I > 5.00 (I)), final R = 0.048, RW = 0.083.
Selected bond lengths (Å): N1–C6, 1.362(7); N1–C13, 1.406(7);
O1–C1, 1.207(7); O2–C2, 1.211(7), O3–C3, 1.317(7); C1–C2,
1.529(9); C1–C4, 1.496(8); C2–C3, 1.461(8); C3–C4, 1.391(8);
C4–C5, 1.411(7); C5–C6, 1.369(8); C6–C7, 1.532(7); C7–C8,
1.513(8); C8–C9, 1.376(8); C8–C13, 1.385(8); C9–C10, 1.390(9);
C10–C11, 1.370(9); C11–C12, 1.385(8); C12–C13, 1.381(8).
IR (KBr): 1749, 1558 cm–1.
1H NMR (500 MHz, DMSO-d6, 80 °C): = 0.76 (t, J = 7.3 Hz, 3 H),
0.94 (t, J = 7.3 Hz, 3 H), 1.22 (sext, J = 7.3 Hz, 2 H), 1.44 (sext,
J = 7.3 Hz, 2 H), 1.60 (s, 6 H), 1.76–1.82 (m, 4 H), 3.57 (s, 3 H),
4.59 (br, 2 H), 4.73 (m, 2 H), 5.66 (s, 1 H), 6.43 (s, 1 H), 6.77 (t,
J = 7.3 Hz, 4 H), 6.91 (t, J = 7.3 Hz, 8 H), 7.16–7.21 (m, 9 H), 7.29
(br, 1 H), 7.35 (t, J = 7.8 Hz, 1 H), 7.45 (d, J = 7.8 Hz, 1 H), 7.53
(br, 1 H), 7.66 (t, J = 7.8 Hz, 1 H), 7.87 (t, J = 7.8 Hz, 1 H), 7.92 (d,
J = 7.8 Hz, 1 H), 7.96 (t, J = 7.8 Hz, 1 H), 8.11 (br, 1 H), 8.41 (d,
J = 7.8 Hz, 1 H), 8.48 (d, J = 7.8 Hz, 1 H), 18.67 (br, 1 H).
Selected bond angles (°): C6–N1–C13, 111.7(4); C6–N1–C16,
125.0(5); C13–N1–C16, 123.1(5); O1–C1–C2, 134.2(6); O1–C1–
C4, 137.0(6); C2–C1–C4, 88.8(5); O2–C2–C1, 136.3(6); O2–C2–
C3, 137.9(6); C1–C2–C3, 85.8(5); O3–C3–C2, 136.4(5); O3–C3–
C4, 127.8(5); C2–C3–C4, 95.8(5); C1–C4–C3, 89.6(5); C1–C4–
C5, 144.2(5); C3–C4–C5, 126.1(5); C4–C5–C6, 131.7 (5); N1–C6–
C5, 120.8(5); N1–C6–C7, 108.3(4); C5–C6–C7, 130.8(5).
FAB MS: m/z = 740 ([M – BPh4]+).
A single crystal of 7a suitable for X-ray crystallographic analysis
was obtained by slow evaporation of a saturated solution of 7a in
benzene. All reflection data were collected on a Rigaku AFC5-R
diffractometer using graphite monochromated Mo-K radiation. In-
tensity data were collected in the range of 3 < 2 < 55° by using the
-2 scan technique. The structure was solved by a direct method
and refined by a full-matrix least-squares procedure. All non-hydro-
gen atoms were refined with anisotropic thermal parameters. In all
calculations, the TEXSAN program was used.
Anal. Calcd for C68H62BN3O4S2: C, 77.04; H, 5.89; N, 3.96. Found:
C, 76.60; H, 5.76; N, 3.98.
Dye 4b
Yield: 10%.
IR (KBr): 1743, 1579 cm–1.
1H NMR (500 MHz, DMSO-d6, 80 °C): = 0.77 (t, J = 7.3 Hz, 3 H),
0.95 (t, J = 7.3 Hz, 3 H), 1.20 (sext, J = 7.3 Hz, 2 H), 1.44 (sext,
J = 7.3 Hz, 2 H), 1.73–1.79 (m, 4 H), 3.92 (s, 3 H), 4.44 (m, 2 H),
4.69 (m, 2 H), 6.15 (m, 2 H), 6.77 (t, J = 7.3 Hz, 4 H), 6.90 (t, J = 7.3
Hz, 8 H), 7.19 (m, 8 H), 7.38–7.47 (m, 2 H), 7.54–7.58 (m, 2 H),
7.74–7.82 (m, 3 H), 7.91 (br, 1 H), 7.96–98 (m, 2 H), 8.33 (br, 1 H),
8.42 (br, 1 H), 18.56 (br, 1 H).
References
(1) Sprenger, H.-E.; Ziegenbein, W. Angew. Chem., Int. Ed.
Engl. 1968, 7, 530.
FAB MS: m/z = 731 ([M + H – BPh4]+).
(2) (a) Tam, A. C. Appl. Phys. Lett. 1980, 37, 978. (b) Law, K.
Y.; Bailey, F. C. J. Imaging Sci. 1987, 31, 172.
(3) (a) Matsuoka, M. In Absorption Spectra of Dyes for Diode
Lasers; Bunshin: Tokyo, 1990, 51. (b) Fabian, J.;
Nakazumi, H.; Matsuoka, M. Chem. Rev. 1992, 92, 1197.
(4) (a) Merritt, V. Y.; Hovel, H. J. Appl. Phys. Lett. 1976, 29,
414. (b) Loutfy, R. O.; Hsiao, C. K.; Kazmaier, P. M.
Photogr. Sci. Eng. 1983, 27, 5.
Anal. Calcd for C65H56BN3O4S3 0.5H2O: C, 73.71; H, 5.42; N, 3.97.
Found: C, 73.46; H, 5.24; N, 4.00.
Dye 4c
Yield: 17%.
IR (KBr): 1749, 1633 cm–1.
1H NMR (500 MHz, DMSO-d6, 80 °C): = 0.77 (t, J = 7.3 Hz, 3 H),
0.93 (t, J = 7.3 Hz, 3 H), 1.22 (sext, J = 7.3 Hz, 2 H), 1.42 (sext,
J = 7.3 Hz, 2 H), 1.69–1.79 (m, 4 H), 3.32 (s, 3 H), 4.33 (br, 2 H),
4.71 (br, 2 H), 6.00 (s, 1 H), 6.08 (s, 1 H), 6.77 (t, J = 7.3 Hz, 4 H),
6.91 (t, J = 7.3 Hz, 8 H), 7.18–7.21 (m, 8 H), 7.33–7.62 (m, 4 H),
7.78–7.87 (m, 4 H), 7.94 (t, J = 7.8 Hz, 1 H), 8.00 (br, 1 H), 8.15
(br, 1 H), 8.35–8.37 (m, 1 H), 8.45 (d, J = 7.8 Hz, 1 H), 8.85 (br, 1
H), 18.67 (br, 1 H).
(5) (a) Thomas, K. G.; Thomas, K. J.; Das, S.; George, M. V.
Chem. Commun. 1997, 597. (b) Kukrer, B.; Akkaya, E. U.
Tetrahedron Lett. 1999, 40, 9125. (c) Dilek, G.; Akkaya, E.
U. Tetrahedron Lett. 2000, 41, 3721.
(6) (a) Trebs, A.; Jacob, K. Angew. Chem., Int. Ed. Engl. 1965,
4, 694. (b) Maahs, G.; Hegenberg, P. Angew. Chem., Int. Ed.
Engl. 1966, 5, 888.
(7) Law, K. Y.; Bailey, F. C. J. Org. Chem. 1992, 57, 3278.
(8) Terpetschnig, E.; Lakowicz, J. R. Dyes and Pigments 1993,
21, 227.
FAB MS: m/z = 724 ([M – BPh4]+).
(9) Yagi, S.; Hyodo, Y.; Matsumoto, S.; Takahashi, N.; Kono,
H.; Nakazumi, H. J. Chem. Soc., Perkin Trans. 1 2000, 599.
(10) Nakazumi, H.; Natsukawa, K.; Nakai, K.; Isagawa, K.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1001.
Anal. Calcd for C67H58BN3O4S2: C, 77.07; H, 5.60; N, 4.02. Found:
C, 76.71; H, 5.62; N, 3.88.
X-Ray Crystallographic Analysis of 7a
(11) Hyodo, Y.; Nakazumi, H.; Yagi, S.; Nakai, K. J. Chem. Soc.,
Perkin Trans. 1 2001, 2823.
Formula: C18H19NO3, molecular weight: 297.35, crystal system: tri-
clinic, space group: P1, cell constants: a = 9.508(2) Å,
b = 11.657(1) Å, c = 7.3640(6) Å, = 97.091(8)°, = 101.29(1)°,
Synthesis 2002, No. 3, 413–417 ISSN 0039-7881 © Thieme Stuttgart · New York