Synthesis and characterisation of long wavelength-absorbing donor/acceptor-substituted methine dyes

Article abstract of DOI:10.1515/znb-2016-0009

By the reaction of aromatic or heteroaromatic formyl compounds or their corresponding iminium salts with active methylene compounds a series of new methine dyes with long-wavelength absorption in the near-infrared spectral range were prepared.

Full text of DOI:10.1515/znb-2016-0009

Z. Naturforsch. 2016; 71(6)b: 651–658
Christoph Heichert and Horst Hartmann*
Synthesis and characterisation of long wavelength-
absorbing donor/acceptor-substituted methine dyes
DOI 10.1515/znb-2016-0009
an active methylene compound of the general structure 2,
in which one of the acceptor substituents in many cases is
a cyano moiety [8].
Received January 10, 2016; accepted January 22, 2016
Abstract: By the reaction of aromatic or heteroaromatic
formyl compounds or their corresponding iminium salts
with active methylene compounds a series of new methine
dyes with long-wavelength absorption in the near-infrared
spectral range were prepared.
Acc
Acc
O
+
Me
Acc'
Me
N
−
H O
2
N
Acc'
D
A
Me
Me
1
2
3
Keywords: active methylene compounds; (hetero)aro-
matic aldehydes; Knoevenagel condensation; methine
dyes; NIR absorption.
2
Results and discussion
The simple route to the dyes 3 stimulated us to synthesise
certain new D-A compounds by starting, instead of 1, with
a variety of aromatic and heteroaromatic aldehydes, such
1
Introduction
In recent years, a large variety of dyes of the general struc- as julolidine-carbaldehyde (4a), 3-guaiazulenecarbalde-
ture D-A, in which D represents a strong electron donor and hyde (5a), or their corresponding dimethyliminium salts
A a strong electron acceptor moiety, have been prepared 4b and 5b as well as few N,N-disubstituted 2-aminothio-
and used for different kinds of applications. For instance, phene-5-carbaldehydes 7. Whereas the aromatic alde-
such dyes have been used for determination of the solvent hydes and their iminium salts 4–5 are easily available by
polarity [1–3], as light absorbers in organic solar cells [4, 5] the Vilsmeier formylation of their formyl-free precursors,
or as molecular nanoprobes for biomedical imaging [6, 7]. the thiophenecarbaldehydes 7 are available by Vilsmeier
The last application field could be opened due to the ability formylation of N,N-disubstituted 2-aminothiophene-
of the appropriate dyes to form highly fluorescent nanodots 5-carboxylic acids 6b which decarboxylate in the course
which are able to bind strongly at several biomaterials.
of the formylation reaction yielding intermediate N,N-
The synthetic methods for preparing the mentioned disubstituted 2-aminothiophenes 6a. The 2-aminothio-
dyes are rather simple, using for example the Knoeve- phene-5-carboxylic acids 6b have been simply prepared
nagel condensation of a donor-substituted aromatic alde- by saponification of the corresponding N,N-disubstituted
hyde, such as 4-(dimethylamino)benzaldehyde (1), with methyl 2-aminothiophene-5-carboxylates 6c [9].
R3
R3
Me
X
POCl3/DMF
R2
Pri
R2
O
X
N
R (R = COOH)
N
N
S
S
R1
R1
4
5
6
7
Me
a: R = H
b: R = COOH
c: R = COOR
a: X = O
b: X = N Me BF
+
−
4
−
H O/OH
2
2
*
Corresponding author: Horst Hartmann, Fachrichtung Chemie und
Lebensmittelchemie, Technische Universität Dresden, D-01062
Dresden, Germany, Fax: +49-351-463-3494,
Active methylene compounds 2a–h and as N,N-
disubstituted 2-aminothiophene-5-carbaldehydes the
compounds 7a–c have been used as coupling partners
for the Knoevenagel condensation. Most of the active
E-mail: hartmann@iapp.de
Christoph Heichert: Fachrichtung Chemie und Lebensmittelchemie,
Technische Universität Dresden, D-01062 Dresden, Germany
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52ꢀꢀꢀꢀꢁꢀC. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptor
methylene compounds 2a–h are well known and could from 2-(diphenylamino)thiophene as donor part and
be ordered from suited suppliers or prepared by reported 2-(5-methylene-4-phenylthiazol-2(5H)-ylidene)malon-
methods.
onitrile as acceptor part, a positive solvatochromism
CN
CN
CN
H
3
C
Ph
NC
NC
NC
NC
O
O
O
CN
CN
N
N
CN
CN
S
S
S
S
O
2
O
2
CN
CN
O
CN
2g
2h
2a
2b
2c
2d
2e
2f
3
H C
N
S
N
S
N
S
O
O
O
7
a
7b
7c
CH
3
By heating equimolar amounts of a compound 2
with an appropriate aldehyde 4a, 5a or 7a in acetic
anhydride, under consumption of the starting material,
deeply coloured solutions were observed and by the
time crystalline precipitates of the corresponding Kno-
evenagel condensation products were formed. All the
products so obtained could be isolated by suction and
were generally obtained subsequently in good to excel-
lent yields.
The structures of the prepared compounds are given
in the Experimental section and follow unambiguously
from their analytical data. Thus, all compounds exhibit
distinct mass spectra and, except for the compound 8h
Fig. 1:ꢀAbsorption spectra of a donor/acceptor dye composed of
2
-diphenylaminothiophene as donor part and 2-(5-methylene-
4-phenylthiazol-2(5H)-ylidene)malonitrile as acceptor part in differ-
build up from 2-diphenylaminothiophene-carbaldehyde ent solvents.
(
7a) and benzo[b]thiophen-3[2H]-one 1,1-dioxide (2g),
1
characteristic H NMR signals between δ ≈ 7 and 8 ppm
as well as at about 9 ppm which are typical for their which ranges from 629 nm in toluene up to 675 nm in
carbocyclic or heterocyclic moieties as well as for the dichloromethane.
1
methine-bonded H atoms, respectively. In the H NMR
spectrum of the compound 8h, two sets of signals are
recorded. They indicate the existence of two isomers A 3 Experimental section
and B in the ratio 2:1.
1
In the visible spectral range, the methine dyes The H NMR spectra were recorded with a Bruker DRX 500
exhibit intense absorption bands in the red and near- P instrument at 500.13 MHz and the signals are recorded
infrared (NIR) spectral ranges. These absorptions in Hz. The UV/Vis spectra were measured with a Perkin
are responsible for the deep blue or green colour of Elmer Lambda 900 UV/VIS/NIR spectrometer and the
these compounds. Owing to their D-A character, the high-resolution mass spectra (HRMS) with a MAT 8200
absorption maxima of these compounds exhibit, as Finnigan spectrometer. The melting points were estimated
demonstrated in Fig. 1 for the compound prepared with a Boetius heating-table microscope.
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C. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptorꢂꢁꢀꢀꢀꢂ653
3
.78 (s, 3 H), 7.72 (d, J ꢀ=ꢀ 11.0 Hz, 1 H), 7.81 (dd, J ꢀ=ꢀ 11.0 Hz,
3
.1 Preparation of carbocyclic or heterocyclic
iminium tetrafluoroborates (general
procedure)
3
.0, 1 H), 8.83 (d, J ꢀ=ꢀ 3.0 Hz, 1 H), 9.15 (s, 1 H) ppm. – HRMS
+
(
(+)-ESI): m/z ꢀ=ꢀ 254.19033 (calcd. 254.19030 for [C H N] ).
1
8
24
Phosphoryl chloride (8.43 g, 55.0 mmol) was added drop-
wise at 0°C under stirring within 30 min to dimethylfor- 3.2 Preparation of carbocyclic or heterocyclic
mamide (25 mL). Stirring was continued for additional
carbaldehydes from the corresponding
1
5 min at 0°C, an aromatic or heteroaromatic compound
Vilsmeier salts (general procedure)
(50.00 mmol) was added and then the reaction was allowed
to defrost to ambient temperature and stirred for addi- A slurry of the desired N-methyl-methanaminium tetra-
tional 24 h at 40°C. The resulting deep yellow solution was fluoroborate, the Vilsmeier salt (50.00 mol), in methanol
cooled to 0°C and then poured into ice cold water (100 mL). (100 mL) was hydrolysed by the dropwise addition of a 5%
To isolate the desired product a 50% aqueous solution of aqueous solution of sodium hydroxide until a pH of approx-
tetrafluoroboric acid (30 mL) was added slowly under vig- imately 8.0–9.0 was observed. Thereby the hue of the ini-
orous stirring. Thereby the hue of the initially deep yellow tially deep yellow slurry changed to nearly colourless and
solution changed to nearly colourless and a crystalline a crystalline precipitate was formed. The reaction solution
precipitate was formed. The precipitate was filtered of by was diluted with water (200 mL), the precipitate filtered off
suction, washed with 0.5% aqueous tetrafluoroboric acid by suction, washed thoroughly with water until the filtrate
(
10 mL) followed by water (5 mL) and dried in air.
became neutral and dried in air at room temperature.
The following compounds were prepared in this way:
The following compounds were prepared in this way.
3
.1.1 N-[(1,2,3,5,6,7-Hexahydropyrido[3,2,1-ij]quinolin-
3.2.1 1,2,3,5,6,7-Hexahydropyrido[3,2,1-ij]quinoline-9-
9
-yl)methylene]-N-methylmethanaminium
carbaldehyde (4a)
tetrafluoroborate (4b)
Me
N
N
Me
O
N
BF4
Prepared from N-((1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]qui-
Prepared from 1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quino- nolin-9-yl)methylene)-N-methyl-methanaminium tetra-
line hydrobromide in a yield of 97%. Yellow crystalline fluoroborate in a yield of 98%. Beige crystalline powder
1
1
powder with an m.p. of 169–171°C. – H NMR (CDCl ): δ ꢀ=ꢀ with an m.p. of 84°C (Lit. m.p. 83–84°C [10]. – H NMR
3
1
.95 (quin, J ꢀ=ꢀ 6.0 Hz, 4 H), 2.74 (t, J ꢀ=ꢀ 6.0 Hz, 4 H), 3.39 (t, (CDCl ): δ ꢀ=ꢀ 2.11 (quin, J ꢀ=ꢀ 6.0 Hz, 4 H), 2.84 (t, J ꢀ=ꢀ 6.0 Hz,
3
J ꢀ=ꢀ 6.0 Hz, 4 H), 3.61 (s, 3 H) 3.65 (s, 3 H), 7.31 (s, 2 H), 8.07 4 H), 3.33 (t, J ꢀ=ꢀ 6.0 Hz, 4 H), 7.37 (s, 1 H), 9.65 (s, 1 H) ppm.
(
2
s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 229.16992 (calcd.
+
29.16990 for [C H N ] ).
15
21
2
3
.2.2 5-Isopropyl-3,8-dimethylazulene-1-carbaldehyde
(
5a)
3
.1.2 N-[(5-Isopropyl-3,8-dimethylazulen-1-yl)
methylene]-N-methylmethanaminium
tetrafluoroborate (5b)
O
Me
N
Prepared from N-[(5-isopropyl-3,8-dimethyazulen-1-yl)
methylene]-N-methylmethanaminium tetrafluoroborate
Me
BF4-
(
6b) in a yield of 98%. Black crystalline powder with an
1
Prepared from 5-isopropyl-3,8-dimethylazulene in a yield m.p. of 86–87°C (Lit. m.p. 85°C [11]. – H NMR (CDCl ): δ ꢀ=ꢀ
3
of 98%. Brown crystalline powder with an m.p. of 155– 1.38 (d, J ꢀ=ꢀ 7.0 Hz, 6 H), 2.57 (s, 3 H), 3.13 (s, 3 H), 3.16 (sep,
1
1
(
56°C. – H NMR (CDCl ): δ ꢀ=ꢀ 1.39 (d, J ꢀ=ꢀ 7.0 Hz, 6 H), 2.56 J ꢀ=ꢀ 7.0 Hz, 1 H), 7.41 (d, J ꢀ=ꢀ 2.0 Hz, 1 H), 7.57 (d, J ꢀ=ꢀ 2.0 Hz, 1
3
s, 3 H), 3.18 (s, 3 H), 3.19 (sep, J ꢀ=ꢀ 7.0 Hz, 1 H), 3.73 (s, 3 H), H), 8.22 (s, 1 H), 8.28 (s, 1 H), 10.62 (s, 1 H) ppm.
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54ꢀꢀꢀꢀꢁꢀC. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptor
2
-(4-phenylthiazol-2(5H)-ylidene)malononitrile (2c) [12]
3
.3 Preparation of the methine dyes D-A
in a yield of 97%. Dark green crystalline powder with an
(
general procedure)
m.p. of 217–218°C (dec.). – UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ
2
2
max
1
A mixture of an aromatic or heteroaromatic aldehyde 664 nm (5.05). – H NMR (CDCl ): δ ꢀ=ꢀ 2.00 (t, J ꢀ=ꢀ 6.0, 4 H),
3
(
10.00 mmol) and an active methylene compound (10.0 2.72 (t, J ꢀ=ꢀ 6.0 Hz, 4 H), 3.43 (t, J ꢀ=ꢀ 6.0 Hz, 4 H), 7.07 (s, 2
mmol) in acetic anhydride (15 mL) was stirred under H), 7.49 (s, 1 H), 7.53 (t, J ꢀ=ꢀ 7.5 Hz, 2 H), 7.57 (t, J ꢀ=ꢀ 7.5 Hz,
exclusion of moisture in a water bath at 90°C for 8 h. 1 H), 8.50 (d, J ꢀ=ꢀ 7.5 Hz, 2 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ
+
Under consumption of the starting material a deeply col- 408.13622 (calcd. 408.14088 for [C H N S] ).
2
5
20
4
oured solution was observed and by the time a crystalline
precipitate was formed. After cooling to 0°C the precipi-
tate was filtered off by suction, washed exhaustively with 3.3.3 2-{4-Methyl-5-[(2,3,6,7-tetrahydro-1H,5H-
methanol (100–200 mL) until the filtrate showed the
colour of the desired product in solution and then dried in
air at room temperature.
pyrido[3,2,1.ij]quinolin-9-yl)methylene]thiazol-
2(5H)-ylidene}malononitrile (8c)
The following compounds were so prepared.
Me
N
S
3
.3.1 (Z)-2-{5-(4-Dimethylamino)benzylidene]-4-
phenylthiazol-2(5H)-ylidene}malononitrile (8a)
N
CN
NC
Prepared from 1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quin-
oline-9-carbaldehyde (4a) and 2-(4-methylthiazol-2(5H)-
ylidene)malononitrile (2b) [12] in a yield of 97%. Green
crystalline powder with golden lustre and an m.p. of
209–211°C (dec.). – UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 659 nm
N
Me
S
N
2
2
max
CN
1
Me
(5.04). – H NMR (CDCl ): δ ꢀ=ꢀ 1.90 (t, J ꢀ=ꢀ 6.0 Hz, 4 H), 2.75
NC
3
(
t, J ꢀ=ꢀ 6.0 Hz, 4 H), 3.17 (s, 3 H), 3.46 (t, J ꢀ=ꢀ 6.0 Hz, 4 H),
Prepared from 4-(dimethylamino)benzaldehyde (1) and 7.32 (s, 2 H), 8.00 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ
+
2
-(4-phenylthiazol-2(5H)-ylidene)malononitrile (2c) [12] 346.12697 (calcd. 346.12527 for [C H N S] ).
2
0
18
4
in a yield of 91%. Green crystalline powder with golden
lustre and an m.p. of 295–296°C (dec.). – UV/Vis (CH Cl ):
2
2
1
λmax (lg εmax) ꢀ=ꢀ 630 nm (4.85). − H NMR (CDCl ): δ ꢀ=ꢀ 3.18 (s, 3.3.4 2-{5-[(5-Isopropyl-3,8-dimethylazulen-
3
6
H), 6.76 (d, J ꢀ=ꢀ 9.0 Hz, 2 H), 7.55 (t, J ꢀ=ꢀ 7.5 Hz, 2 H), 7.56
1-yl)methylene]-4-methylthiazol-2(5H)-
ylidene}malononitrile (8d)
(
(
(
d, J ꢀ=ꢀ 9.0 Hz, 2 H), 7.59 (s, 1 H), 7.61 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.77
d, J ꢀ=ꢀ 7.5 Hz, 2 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 356.10939
Me
Me
+
calcd. 356.10952 for [C H N S] ).
2
1
16
4
Me
Me
N
S
3
.3.2 (Z)-2-{5-[(1,2,3,5,6,7-Hexahydropyrido[3,2,1-ij]
quinolin-9-yl)methylene]-4-phenylthiazol-2(5H)-
ylidene}malononitrile (8b)
CN
Me
NC
Prepared from 5-isopropyl-3,6-dimethylazulene-1-car-
baldehyde (5a) and 2-(4-methylthiazol-2(5H)-ylidene)
malononitrile (2b) [12] in a yield of 98%. Dark green crys-
talline powder with an m.p. of 273–274°C (dec.). – UV/Vis
N
1
(
CH Cl ): λ (lg εmax) ꢀ=ꢀ 675 (4.83), 633 nm (4.75). – H NMR
S
2
2
max
N
(
CDCl ): δ ꢀ=ꢀ 1.40 (d, J ꢀ=ꢀ 7.0 Hz, 6 H), 2.63 (s, 3 H), 2.68 (s,
3
CN
NC
3
H), 3.18 (sep, J ꢀ=ꢀ 7.0 Hz, 1 H), 3.20 (s, 3 H), 7.49 (d, J ꢀ=ꢀ 11.0
Hz, 1 H), 7.67 (dd, J ꢀ=ꢀ 11.0 Hz, 2.0, 1 H), 8.04 (s, 1 H), 8.25 (d,
Prepared
from
1,2,3,5,6,7-hexahydropyrido[3,2,1- J ꢀ=ꢀ 2.0 Hz, 1 H), 8.61 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ
+
ij]quinoline-9-carbaldehyde
(4a)
and 371.14617 (calcd. 371.14562 for [C H N S] ).
2
3
21
3
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C. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptorꢂꢁꢀꢀꢀꢂ655
3
.3.5 2-{5-[(5-Isopropyl-3,8-dimethylazulen-
Prepared from 5-(diphenylamino)thiophene-2-carbalde-
1
-yl)methylene]-4-phenylthiazol-2(5H)-
hyde (7a) [9] and 1H-indene-1,3(2H)-dione (2d) in a yield
ylidene}malononitrile (8e)
of 86%. Brownish-red crystals with an m.p. of 298–299°C.
1
–
UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 519 nm (4.88). – H NMR
2
2
max
(
CDCl ): δ ꢀ=ꢀ 6.44 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.29 (t, J ꢀ=ꢀ 7.5 Hz, 2 H),
3
Me
7
4
.34 (d, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.41 (t, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.64 (d, J ꢀ=ꢀ
Me
Me
.5 Hz, 1 H), 7.65 (m, 2 H), 7.77 (m, 1 H), 7.78 (s, 1 H), 7.83
N
(
4
m, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 407.09803 (calcd.
S
+
07.09803 for [C H NO S] ).
2
6
17
2
CN
Me
NC
3
.3.8 (E,Z)-2-{[5-(Diphenylamino)thiophen-2-yl]
methylene}-benzo[b]thiophen-3[2H]-one 1,1-
dioxide (8h)
Prepared from 5-isopropyl-3,6-dimethylazulene-1-car-
baldehyde (5a) and 2-(4-phenylthiazol-2(5H)-ylidene)
malononitrile (2c) [12] in a yield of 98%. Green crystalline
powder with golden lustre and an m.p. of 271°C (dec.).
1
–
UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 696 (4.86), 652 (4.75). – H
2
2
max
O
N
S
NMR (CDCl ): δ ꢀ=ꢀ 1.39 (d, J ꢀ=ꢀ 7.0 Hz, 6 H), 2.62 (s, 3 H), 2.87
3
S
O
(
7
s, 3 H), 3.18 (sep, J ꢀ=ꢀ 7.0 Hz, 1 H), 7.44 (d, J ꢀ=ꢀ 11.0 Hz, 1 H),
O
.54 (t, J ꢀ=ꢀ 7.0 Hz, 2 H), 7.59 (t, J ꢀ=ꢀ 7.0 Hz, 1 H), 7.66 (d, J ꢀ=ꢀ
1
1
1.0 HZ, 1 H), 7.77 (d, J ꢀ=ꢀ 7.0 Hz, 2 H), 8.09 (s, 1 H), 8.25 (s,
H), 8.65 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 433.16172
Prepared from 5-(diphenylamino)thiophene-2-carbalde-
hyde 7a [9] and benzo[b]thiophen-3[2H]-one 1,1-dioxide
+
(
calcd. 433.16130 for [C H N S] ).
2
8
23
3
(
2g) [13] in a yield of 92% as a mixture of two isomers.
Pinkish red crystalline powder with an m.p. of 283°C. –
3
.3.6 2-{[5-(Diphenylamino)thiophen-2-yl]
methylene}malononitrile (8f)
1
UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 521 nm (4.83). – H NMR
2
2
max
(
CDCl ): δ ꢀ=ꢀ 6.44 (d, J ꢀ=ꢀ 4.5 Hz, 1 H, isomer A), 6.47 (d, J ꢀ=ꢀ
3
4
.5 Hz, 1 H, isomer B), 7.29 (dt, J ꢀ=ꢀ 7.5 Hz, 1.5 Hz, 2 H, isomer
A), 7.31 (dt, J ꢀ=ꢀ 7.5 Hz, 1.5 Hz, 2 H, isomer B), 7.33 (dd, J ꢀ=ꢀ
7.5 Hz, 1.0 Hz, 4 H, isomer A), 7.35 (dd, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 4
H, isomer B), 7.41 (dt, J ꢀ=ꢀ 7.5 Hz, 2.0 Hz, 4 H, isomer A), 7.43
N
S
CN
NC
(
dt, J ꢀ=ꢀ 7.5 Hz, 2.0 Hz, 4 H, isomer B), 7.62 (s, broad, 1 H,
isomer B), 7.64 (s, broad, 1H, isomer A), 7.68 (td, J ꢀ=ꢀ 7.5 Hz,
Prepared from 5-(diphenylamino)thiophene-2-carbalde- 1.0 Hz, 1 H, isomer B), 7.73 (td, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 1 H, isomer
hyde (7a) [9] and malononitrile (2a) in a yield of 69%. A), 7.74 (td, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 1 H, isomer B), 7.78 (td, J ꢀ=ꢀ 7.5
Orange crystals with an m.p. of 190–191°C. – UV/Vis Hz, 1.0 Hz, 1 H, isomer A), 7.83 (s, broad, 1 H, isomer B),
1
(
CH Cl ): λ (lg εmax) ꢀ=ꢀ 472 nm (4.73). H NMR ([D ]DMSO): 7.85 (s, broad, 1 H, isomer A), 7.89 (dt, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 1 H,
2
2
max
6
δ ꢀ=ꢀ 6.34 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.38 (t, J ꢀ=ꢀ 7.5 Hz, 2 H), 7.45 (d, isomer B), 7.91 (dt, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 1 H, isomer B), 7.92 (dt,
J ꢀ=ꢀ 7.5 Hz, 4 H), 7.51 (t, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.70 (d, J ꢀ=ꢀ 4.5 Hz, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz, 1 H, isomer A), 8.00 (dt, J ꢀ=ꢀ 7.5 Hz, 1.0 Hz,
1
H), 8.22 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 327.08347 1 H, isomer A) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 443.06442
+
+
(
calcd. 327.08308 for [C H N S] ).
(calcd. 443.06492 for [C H NO S] ).
2
0
13
3
25 17
3
3
.3.9 2-{2-[(5-Diphenylaminothiophen-2-yl)
methylene]-3-oxo-2,3-dihydro-1H-indene-1-
ylidene}malononitrile (8i)
3
.3.7 2-{[5-(Diphenylamino)thiophen-2-yl]methylen})-
H-indene-1,3(2H)-dione (8g)
1
NC
O
S
N
N
S
CN
O
O
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56ꢀꢀꢀꢀꢁꢀC. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptor
Prepared from 5-(diphenylamino)thiophene-2-carbalde- crystals with golden lustre and an m.p. of 258–260°C. –
1
hyde (7a) [9] and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene) UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 624 nm (4.93). – H NMR
2
2
max
malononitrile (2e) [14] in a yield of 84%. Brownish-green ([D ]DMSO): δ ꢀ=ꢀ 6.54 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.48 (t, J ꢀ=ꢀ 7.5 Hz, 2
6
crystals with golden lustre and an m.p. of 265–266°C. – H), 7.58 (t, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.63 (d, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.90 (t, J ꢀ=ꢀ
1
UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 591 nm (4.85). – H NMR 7.5 Hz, 1 H), 7.94 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.96 (d, J ꢀ=ꢀ 4.5 Hz, 1 H),
2
2
max
(
CDCl ): δ ꢀ=ꢀ 6.46 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.30 (t, J ꢀ=ꢀ 7.5 Hz, 2 H), 8.05 (d, J ꢀ=ꢀ 7.5 Hz, 1 H), 8.49 (s, 1 H), 8.60 (d, J ꢀ=ꢀ 7.5 Hz, 1 H)
3
7
.37 (d, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.46 (t, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.57 (t, J ꢀ=ꢀ ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 91.07655 (calcd. 419.07616
+
7
.5 Hz, 1 H), 7.61 (m, 2 H), 7.70 (d, J ꢀ=ꢀ 7.5 Hz, 1 H), 8.56 (d, for [C H N O S ] ).
2
6
17
3
2 2
J ꢀ=ꢀ 7.5 Hz, 1 H), 8.66 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ
+
4
55.11009 (calcd. 455.10931 for [C H N OS] ).
29
17
3
3
.3.12 2-{2-[(5-Diphenylaminothiophen-2-yl)
methylene]-4-methylylthiazol-2(5H)-ylidene}-
malononitrile (8l)
3
.3.10 2,2′-{2-[(5-(Diphenylamino)thiophen-
-yl)methylene]-1H-indene-1,3(2H)-
diylidene}dimalononitrile (8j)
2
Me
N
S
NC
S
N
N
S
NC
CN
NC
CN
NC
Prepared from 5-(diphenylamino)thiophene-2-carbalde-
hyde (7a) [9] and 2-(4-methylthiazol-2(5H)-ylidene)malo-
nonitrile (2b) [12] in a yield of 94%. Green crystals with
golden lustre and an m.p. of 225°C. – UV/Vis (CH Cl ): λ
Prepared from 5-(diphenylamino)thiophene-2-carbalde-
hyde (7a) [9] and 2,2′-(1H-indene-1,3(2H)-diylidene)
dimalononitrile (2f) [15] in a yield of 94%. Deep blue
2
2
max
1
(
lg εmax) ꢀ=ꢀ 655 nm (4.90). – H NMR (CD Cl ): δ ꢀ=ꢀ 2.59 (s, 3
2 2
crystalline powder with an m.p. of 229–230°C. – UV/Vis
H), 6.50 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.35–7.38 (m, 6 H), 7.46–7.49 (m,
1
(
CH Cl ): λ (lg εmax) ꢀ=ꢀ 666 nm (4.59). – H NMR (CDCl ):
2
2
max
3
5
H), 7.71 (s, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 424.08255
δ ꢀ=ꢀ 6.44 (s, broad), 7.38 (d, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.42 (t, J ꢀ=ꢀ 7. 5
Hz, 2 H), 7.50 (t, J ꢀ=ꢀ 7.5 Hz, 4 H), 7.56 (t, J ꢀ=ꢀ 5.5 Hz, 1 H),
+
(
calcd. 424.08167 for [C H N S ] ).
24
16
4 2
7
.58 (t, J ꢀ=ꢀ 5.5 Hz, 1 H), 7.65 (d, J ꢀ=ꢀ 5.0 Hz, 1 H), 8.42 (d,
J ꢀ=ꢀ 5.5 Hz, 1 H), 8.43 (d, J ꢀ=ꢀ 5.5 Hz, 1 H), 8.65 (s, broad,
1
5
H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 503.12051 (calcd. 3.3.13 2-{2-[(5-Diphenylaminothiophen-2-yl)
+
03.12019 for [C H N S] ).
methylene]-4-phenylthiazol-2(5H)-
ylidene}malononitrile (8m)
3
2
17
5
3
.3.11 2-{2-[(5-Diphenylaminothiophen-2-yl)
methylene]-1,1-dioxidobenzo[b]thiophen-3(2H)-
ylidene}malononitrile (8k)
N
S
S
N
NC
CN
NC
CN
S
N
O
Prepared from 5-(diphenylamino)thiophene-2-carbalde-
hyde (7a) [9] and 2-(4-phenylthiazol-2(5H)-ylidene)malo-
nonitrile (2c) [12] in a yield of 91%. Green crystals with
golden lustre and an m.p. of 308°C. – UV/Vis (CH Cl ): λ
S
O
2
2
max
1
Prepared from 5-(diphenylamino)thiophene-2-carbalde- (lg εmax) ꢀ=ꢀ 675 nm (4.94). – H NMR (CDCl ): δ ꢀ=ꢀ 6.47 (d,
3
hyde (7a) [9] and 2-(1,1-dioxobenzo[b]thiophen-3(2H) J ꢀ=ꢀ 4.5 Hz, 1 H), 7.31 (t, J ꢀ=ꢀ 7.0 Hz, 2 H), 7.34 (d, J ꢀ=ꢀ 7.0 Hz,
ylidene)malononitrile (2h) [16] in a yield of 92%. Green 4 H), 7.38 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.40 (t, J ꢀ=ꢀ 8.5 Hz, 4 H), 7.51 (t,
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C. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptorꢂꢁꢀꢀꢀꢂ657
J ꢀ=ꢀ 7.5 Hz, 2 H), 7.57 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.69 (s, 1 H), 7.70 (d, – HRMS ((+)-ESI): m/z ꢀ=ꢀ 419.10997 (calcd. 419.10915 for
+
J ꢀ=ꢀ 7.5 Hz, 2 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 486.09700 [C H N SO] ).
2
6
17
3
+
(
calcd. 486.09734 for [C H N S ] ).
29
18
4 2
3
.3.16 2,2′-{2-[5-(3,4-Dihydroquinolin-1(2H)
thiophen-2-yl)methylene]-1H-inden-1,3(2H)-
diylidene}dimalononitrile (8p)
3
.3.14 2-{5-[(5,5-(Di-p-tolylamino)thiophen-
2
-yl)methylene]-4-phenylthiazol-2(5H)-
ylidene}malononitrile (8n)
NC
N
S
NC
CN
Me
NC
N
S
S
N
Prepared from 5-(3,4-dihydroquinolin-1(2H)-yl)thiophene-
2-carbaldehyde (7c) [9] and 2,2′-(1H-indene-1,3(2H)-
diylidene)dimalononitrile (2f) [15] in a yield of 83%. Deep
blue crystalline powder with an m.p. of 246°C (dec.). – UV/
NC
CN
Me
Prepared from 5-(di-p-tolylamino)thiophene-2-carbalde-
hyde (7b) [9] and 2-(4-phenylthiazol-2(5H)-ylidene)malo-
nonitrile (2c) [12] in a yield of 93%. Green crystals with
golden lustre and an m.p. of 306°C. – UV/Vis (CH Cl ): λ
1
Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 672 nm (4.60). – H NMR (CDCl ):
2
2
max
3
δ ꢀ=ꢀ 2.18 (quin, J ꢀ=ꢀ 6.5 Hz, 2 H), 2.84 (t, J ꢀ=ꢀ 6.5 Hz, 2 H), 3.93
(t, J ꢀ=ꢀ 6.5 Hz, 2 H), 6.83 (s, broad, 1 H), 7.26 (d, J ꢀ=ꢀ 7.5 Hz,
1 H), 7.28 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.33 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.56 (d,
2
2
max
1
(
lg εmax) ꢀ=ꢀ 680 nm (4.96). – H NMR (CDCl ): δ ꢀ=ꢀ 2.35 (s, 6
3
J ꢀ=ꢀ 7.5 Hz, 1 H), 7.57 (t, J ꢀ=ꢀ 6.5 Hz, 1 H), 7.60 (t, J ꢀ=ꢀ 6.5 Hz, 1
H), 7.73 (d, J ꢀ=ꢀ 5.0 Hz, 1 H), 8.47 (d, J ꢀ=ꢀ 6.5 Hz, 1 H), 8.57 (d,
J ꢀ=ꢀ 6.5 Hz, 1 H), 8.69 (s, broad, 1 H) ppm. – HRMS ((+)-ESI):
H), 6.42 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.13 (d, J ꢀ=ꢀ 8.5 Hz, 4 H), 7.21 (d,
J ꢀ=ꢀ 8.5 Hz, 4 H), 7.38 (d, J ꢀ=ꢀ 4.5 Hz, 1 H), 7.51 (t, J ꢀ=ꢀ 7.5 Hz, 2
H), 7.56 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.70 (s, 1 H), 7.71 (d, J ꢀ=ꢀ 7.5 Hz, 2 H)
ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 514.12785 (calcd. 514.12868
+
m/z ꢀ=ꢀ 467.12087 (calcd. 467.12050 for [C H N S] ).
2
9
17
5
+
for [C H N S ] ).
31
22
4 2
3
.3.17 2-{5-[5-(3,4-Dihydroquinolin-1(2H)-yl)thiophen-
-yl)methylene]-4-phenylthiazol-2(5H)-
ylidene}malononitrile (8q)
2
3
.3.15 (Z)-2-{2-[(5-(3,4-Dihydroquinolin-1(2H)thiophen-
-yl)methylene]3-oxo-2,3-dihydro-1H-inden-1-
ylidene}malononitrile (8o)
2
N
S
S
NC
N
N
S
CN
NC
CN
O
Prepared from 5-(3,4-dihydroquinolin-1(2H)-yl)thiophene-
2
-carbaldehyde (7c) [9] and 2-(4-phenylthiazol-2(5H)-
Prepared from 5-(3,4-dihydroquinolin-1(2H)-yl)thio- ylidene)malononitrile 2c [12] in a yield of 83%. Green
phene-2-carbaldehyde (7c) [9] and 2-(3-oxo-2,3-dihydro- crystals with golden lustre and an m.p. of 254°C. – UV/Vis
1
1
H-inden-1-ylidene)malononitrile (2e) [14] in a yield (CH Cl ): λ (lg εmax) ꢀ=ꢀ 682 nm (5.00). – H NMR (CDCl ,
2
2
max
3
of 88%. Dark green spicular crystals with an m.p. of CF COOH): δ ꢀ=ꢀ 2.30 (quin, J ꢀ=ꢀ 6.5 Hz, 2 H), 2.94 (t, J ꢀ=ꢀ 6.5
3
2
15°C. – UV/Vis (CH Cl ): λ (lg εmax) ꢀ=ꢀ 596 nm (4.98). Hz, 2 H), 4.28 (t, J ꢀ=ꢀ 6.5 Hz, 2 H), 7.36 (d, J ꢀ=ꢀ 5.5 Hz, 1 H),
2 2 max
1
–
H NMR (CD Cl ): δ ꢀ=ꢀ 2.12 (quin, J ꢀ=ꢀ 6.5 Hz, 2 H), 2.79 7.40–7.49 (m, 4 H), 7.52 (d, J ꢀ=ꢀ 7.5 Hz, 2 H), 7.58 (t, J ꢀ=ꢀ 7.5 Hz,
2 2
(
5
t, J ꢀ=ꢀ 6.5 Hz, 2 H), 3.94 (t, J ꢀ=ꢀ 6.5 Hz, 2 H), 6.86 (d, J ꢀ=ꢀ 2 H), 7.68 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.76 (s, 1 H), 7.86 (d, J ꢀ=ꢀ 5.5,
.0 Hz, 1 H), 7.19 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.26 (d, J ꢀ=ꢀ 7.5 Hz, 1 1 H) ppm. J ꢀ=ꢀ 6.5 Hz, 1 H), 8.57 (d, J ꢀ=ꢀ 6.5 Hz, 1 H), 8.69
H), 7.31 (t, J ꢀ=ꢀ 7.5 Hz, 1 H), 7.75–7.65 (m, 4 H), 7.71 (d, J ꢀ=ꢀ (s, broad, 1 H) ppm. – HRMS ((+)-ESI): m/z ꢀ=ꢀ 455.09750
+
7
.5 Hz, 1 H), 8.52 (d, J ꢀ=ꢀ 7.5 Hz, 1 H), 8.61 (s, 1 H) ppm. (calcd. 455.09736 for [C H N S ] ).
2
6
16
4 2
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58ꢀꢀꢀꢀꢁꢀC. Heichert and H. Hartmann: Synthesis of long wavelength-absorbing donor/acceptor
Acknowledgments: The authors are grateful to Prof.
Dr. K. Leo, IAPP, TU Dresden, for the opportunity to per-
form this work in his laboratory and to Kao Germany
GmbH, Darmstadt, for financial support.
[5] S. Nauangruk, R. Fukuda, M. Ehara, J. Meeprasert, T. Khanasa,
S. Morada, T. Kaewin, S. Jungsuttiwong, T. Sudyoadsuk,
V. Promarak, J. Phys. Chem. C 2012, 116, 25652.
[
6] A. Singh, C.-K. Lim, Y.-D. Lee, J.-H. Maeng, S. Lee, J. Koh,
S. Kim, ACS Appl. Mater. Interfaces 2013, 5, 8881.
7] D. Belfield, Bioconjug. Chem. 2011, 22, 1438.
8] T. Deligeorgiev, A. Vasilev, S. Kaloyanova, J. J. Vaquero, Color
Technol. 2010, 126, 55.
[
[
References
[
9] H. Hartmann, ARKIVOC 2012, 3, 356.
[
10] P. A. S. Snith, T.-Y. Yu, J. Org. Chem. 1952, 17, 1286.
[11] W. Treibs, Tetrahedron Lett. 1967, 8, 4707.
[12] G. Seybold, DE 2801794, 1979.
[
1] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry,
Wiley-VCH, Weinheim, 2010.
[
[
2] C. Reichardt, Chem. Rev. 1994, 94, 2319.
[13] W. Ried, G. Oremek, Chem.-Ztg. 1980, 104, 12.
[14] H. Junek, Monatsh. Chem. 1964, 95, 1201.
[15] E. Gudriniece, P. Pastors, A. Ievins, Dokl. Akad. Nauk SSSR
1972, 204, 874.
3] J.-Y. Jayng, M. Matsuoka, K. Fukunishi, Dyes Pigm. 1996,
3
1, 141.
[
4] P. Qin, J. Wiberg, E. A. Gibson, M. Linder, L. Li, T. Brinck,
A. Hagfeldt, B. Albinsson, L. Sun, J. Phys. Chem. C 2010, 114, 4738.
[16] W. Baumann, FR 2438045, 1980.
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