Synthesis of bis-aminosubstituted indocyanine dyes for their use in polymeric compositions

Article abstract of DOI:10.1016/j.dyepig.2014.05.002

The synthesis of a set of open-chain bis-aminosubstituted cyanine dyes as well as others with cyclic fragments in the polymethine chain is presented. These dyes are suitable for the development of polymeric compositions with variable optical characteristics as they can be covalently incorporated into the polymer.

Full text of DOI:10.1016/j.dyepig.2014.05.002

Accepted Manuscript
Synthesis of bis-aminosubstituted indocyanine dyes for their use in polymeric
compositions
Sergey Miltsov , Vladimir Karavan , Mikhail Goikhman , Irina Podeshvo , Sara
Gómez-de Pedro , Mar Puyol , Julian Alonso-Chamarro
PII:
S0143-7208(14)00180-6
10.1016/j.dyepig.2014.05.002
DYPI 4372
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 18 December 2013
Accepted Date: 1 May 2014
Please cite this article as: Miltsov S, Karavan V, Goikhman M, Podeshvo I, Gómez-de Pedro S, Puyol
M, Alonso-Chamarro J, Synthesis of bis-aminosubstituted indocyanine dyes for their use in polymeric
compositions, Dyes and Pigments (2014), doi: 10.1016/j.dyepig.2014.05.002.
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ACCEPTED MANUSCRIPT
Synthesis of bis-aminosubstituted indocyanine dyes for their use in
polymeric compositions
Sergey Miltsova,*, Vladimir Karavana, Mikhail Goikhmana, b, Irina Podeshvob, Sara Gómez-de
Pedroc, Mar Puyolc and Julian Alonso-Chamarroc
a St. Petersburg State University, Universitetskii pr. 26, Petrodvorets, St. Petersburg, 198504 Russia
b Institute of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi pr. 31, St. Petersburg, 199004 Russia
c Sensors & Biosensors Group, Analytical Chemistry, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
*
Corresponding author. Tel.: +7(911)757-35-52; E-mail address: smiltsov2004@mail.ru
Abstract
The synthesis of a set of open-chain bis-aminosubstituted cyanine dyes as well as others with cyclic
fragments in the polymethine chain is presented. These dyes are suitable for the development of
polymeric compositions with variable optical characteristics as they can be covalently incorporated
into the polymer.
Keywords: Cyanine dyes; Diamine dyes; Chromophores; Amino substitution; bis-amino dyes;
Chromophore-containing polymeric systems.
1. Introduction
The development of chromophore-containing polymeric systems is an area of growing interest due
to their wide applications in optoelectronics [1-3]. Two types of polymeric systems exist depending
on the method of incorporating the chromophore into the polymeric matrix; the “guest”-“host”
systems, in which chromophore molecules (“guest”) are dispersed in the polymeric matrix (the
“host”) [4], and systems, where chromophore or luminophore groups are covalently incorporated into
the main [5] or side chains of the polymer [6]. The latter are of special interest because they do not
present some drawbacks [7], which are typical for “guest”-“host” systems, such as (i) limited
solubility of the chromophore into the polymeric matrix, (ii) an heterogeneous distribution of the
chromophore within the matrix, (iii) poor temperature-time stability of the photophysical properties,
and (iv) low optical quality of samples and high level of optical loss due to light scattering from
structural heterogeneities.
Cyanine dyes are an important type of chromophores, which have been widely used to modify
polymers in order to confer them of valuable photophysical properties. For instance, cyanine dyes
have been employed in the design of electroluminescent polymer materials that are based on
composites with antracene containing polyimides [8], polyaniline [9] and photorefractive polyimide
composites [10]. However, all these approaches are based on the “guest”-“host” systems, the
drawbacks of which are intended to be solved.
Recently, we reported the first example of a polymeric system with the cyanine chromophore 1 in the
main chain (Fig. 1) and demonstrated its excellent electro-optical and optical properties [11].
H2N
NH2
Cl
N
N
Et
Et
I
1
Fig. 1. Structure of cyanine dye 1 and scheme of the previous published polymeric system with a
cyanine chromophore in the main chain
In the present study, we have performed the synthesis of a set of structural analogues of diamine 1
and related dyes, which could be therefore used as components of polymeric compositions with
variable optical characteristics.

ACCEPTED MANUSCRIPT
2. Experimental
2.1. General (apparatus and procedures)
All starting materials for the dyes syntheses have been purchased form Aldrich Chemical Co. MS-ES
measurements have been made in a Bruker micrOTOF. 1H NMR spectra have been measured in a
Bruker DPX-300 at 300 MHz. Reproducibility problems have been found in the elemental analysis
due to the hard combustion of this kind of compounds. Spectrophotometric studies have been
performed in a UV-VIS-NIR Scanning Spectrophotometer Shimadzu UV-3101PC. The absorption
spectra have been recorded between 1000 and 400 nm. The concentration of dye solutions used
was of 1×10-5 mol L-1 (unless otherwise indicated) in ethanol 99.8 %.
2.2. Preparation of intermediate compounds
5-Acetylamino-2,3,3-trimethylindoleninium iodide 2 was obtained by reduction of 5-nitro-2,3,3-
trimethylindolenine [12] followed by acetylation of the resulted amine by acetic anhydride and
quaternization of the latter acetamide with ethyl iodide [11]. The penthamethinecyanine salt 3 was
obtained by formylation of cyclohexanone [13]. The synthesis of dye 4 and hemicyanine dye 11 were
described in recent articles of our research group [11, 14, 15]. The synthesis of trimethine salts
17a,b was described elsewhere [16,17]. Sodium nitromalonaldehyde monohydrate 20 was obtained
according to [18]. Pentamethine salt 24 was prepared as described in [19].
2.3. Synthesis of meso-substituted bis-acetylamino dyes (5a-e, 8, 9, 12, 13, 15, 18a-b, 21, 24)
2.3.1. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-methoxy-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (5a)
Dye 4 (753 mg, 1mmol) was dissolved in 10 mL of dry DMF, where a 30 % solution of sodium
methylate in methanol (2.3 mL, 10 mmol) was added. The mixture was kept at room temperature
overnight. The mixture was neutralized with 2 N HCl in methanol (5 mL) and the volatiles were
0
evaporated in vacuo (t < 40 C). The residue was recrystallized from methanol, containing sodium
iodide (500 mg in 10 mL of methanol). The resulted crystals were washed with ether, water and
ether again, and dried on air. Yield 389 mg (52 %). 1H NMR (DMSO-d6) δ (ppm) 1.28 (br. t, J = 7.2
Hz, 6H), 1.62 (s, 12H), 1.79 (br. s, 2H), 2.06 (s, 6H), 2.58 (br. s, 4H), 3.92 (s, 3H), 4.16 (q, J = 7.2
Hz, 4H), 6.11 (d, J = 14 Hz, 2H), 7.32 (d, J = 8.7 Hz, 2H), 7.56 (d, J = 8.7 Hz, 2H), 7.86 (s, 2H), 8.45
(d, J =14 Hz, 2H), 10.38 (s, 2H). λmax (EtOH) = 748 nm (ε = 2.70x105 L mol-1 cm-1). ES-MS+
621.3696 (cal. 621.3788 for C39H49N4O3).
2.3.2. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-(1-piperidinyl )-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide
(5b)
Dye 4 (753 mg, 1mmol) was dissolved in 10 mL of methanol and after addition of piperidine (850 mg,
10 mmol) the mixture was kept at room temperature overnight. The volatiles were evaporated in
vacuo and resulted crystals were washed with ether, water and ether again. Yield 690 mg (86 %). 1H
NMR (DMSO-d6) δ (ppm) 1.23 (br. t, J = 7 Hz, 6H), 1.60 (s, 12H), 1.74 (br. s, 2H), 1.82 (br. s, 6H),
2.06 (s, 6H), 2.48 (br. s, 4H), 3.66 (br. s, 4H), 4.03 (br. q, J = 7.2 Hz, 4H), 5.87 (d, J = 14 Hz, 2H),
7.16 (d, J = 8 Hz, 2H), 7.46 (d, J = 8 Hz, 2H), 7.57 (d, J =14 Hz, 2H), 7.71 (s, 2H), 10.02 (s, 2H). λmax
(EtOH) = 708 nm (ε = 6.34 x 104 L mol-1 cm-1). ES-MS+ 674.4174 (cal. 674.4334 for C43H56N5O2).
2.3.3. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-(4-methylphenoxy)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-,
iodide (5c)
Dye 4 (753 mg, 1mmol) was dissolved in 10 mL of dry DMF, where a solution of sodium 4-
methylphenolate (10 mmol) in 10 mL of dry DMF (freshly prepared from 1.240 g (10 mmol) of 4-
methylphenol and 400 mg (10 mmol) of 60 % NaH in mineral oil) was added. The mixture was stirred
0
at 60 C for 6 hours. After acidification and evaporation of solvents, the residue was triturated with
water. The solids were filtered out and purified on silica (1-5 % MeOH in CH2Cl2). Yield 479 mg (58

ACCEPTED MANUSCRIPT
1
%). H NMR (DMSO-d6) δ (ppm) 1.24 (t, J = 7 Hz, 6H), 1.26 (s, 12H), 1.91 (br.s, 2H), 2.05 (s, 6H),
2.23 (s, 3H), 2.69 (br. s, 4H), 4.13 (q, J = 7 Hz, 4H), 6.12 (d, J = 14 Hz, 2H), 7.03 (d, J = 8.0 Hz, 2H),
7.20 (d, J = 8.0 Hz, 2H), 7.30 (d, J = 8.7 Hz, 2H), 7.52 (d, J = 8.7 Hz), 7.71 (s, 2H), 7.77 (d, J = 14
Hz, 2H), 10.20 (s, 2H). λmax (EtOH) = 797 nm (ε = 3.76 x 105 L mol-1 cm-1). ES-MS+ 697.4150 (cal.
697.4117 for C45H53N4O3).
2.3.4. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-(4-methylphenylmercapto)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-
dimethyl-, iodide (5d)
From dye 4 and sodium 4-methylthiophenolate.The followed procedure was the same as for 5c.
Yield 379 mg (45 %). 1H NMR (DMSO-d6) δ (ppm) 1.28 (t, J = 7 Hz, 6H), 1.42 (s, 12H), 1.92 (br.s,
2H), 2.05 (s, 6H), 2.20 (s, 3H), 2.73 (br. s, 4H), 4.17 (br.q, J = 7 Hz, 4H), 6.26 (d, J = 14 Hz, 2H),
7.15 (m, 4H), 7.33 (d, J = 8.5 Hz, 2H), 7.52(d, J = 8.5 Hz), 7.74 (s, 2H), 8.57 (d, J =14 Hz, 2H),
10.06 (s, 2H). λmax (EtOH) = 825 nm (ε = 3.75 x 105 L mol-1 cm-1). ES-MS+ 713.3864 (cal. 713.3889
for C45H53N4O2S).
2.3.5. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-(4-chlorophenyl)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-,
iodide (5e)
Dye 4 (722 mg, 1 mmol), 4-chlorophenylboronic acid (189 mg, 1.2 mmol) and anhydrous potassium
carbonate (207 mg, 1.5 mmol) were mixed with 10 mL of 85% aqueous i-propanol. 0.5 mL of stock
solution of Pd[C(NHNHC6H4NO2)-NCyclohexyl](CNCyclohexyl)[Cl2 in CHCl3 (10-6 mol mL-1) were
added, and the mixture was kept at reflux for one hour. After cooling, the mixture was neutralized
0
with 2 N HCl in methanol and kept at -15 C overnight. The solid was filtered out and recrystallized
from methanol. The resulted crystals were washed with ether, water and ether again, and dried on
air. Yield 654 mg (79%). 1H NMR (DMSO-d6) δ (ppm) 1.13 (s, 12H), 1.22 (br. t, J = 7,2 Hz, 6H), 1.93
(br. s, 2H), 2.04 (s, 6H), 2.67 (br. s, 4H), 4.12 (q, J = 7.2 Hz, 4H), 6.16 (d, J = 14 Hz, 2H), 7.00 (d, J
= 14 Hz, 2H), 7.27 (d, J = 8.0 Hz, 2H), 7.29 (d, J = 8.7 Hz, 2H), 7.49 (d, J = 8.7 Hz, 2H), 7.67-7.75
(m, 4H), 8.43 (d, J =13.0 Hz, 2H), 10.14 (s, 2H). λmax (EtOH) = 793 nm (ε = 3.16 x 105 L mol-1 cm-1).
ES-MS+ 701.3578 (cal. 701.3622 for C44H50N4ClO2)
2.3.6. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-chloro-1-cyclopenten-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (8)
A solution of pentamethine salt 7 (482.5 mg, 1 mmol), 5-acetylamino-2,3,3-trimethyliondoleninium
iodide 2 (744 mg, 2 mmol) and anhydrous sodium acetate (200 mg, 2.5 mmol) in absolute EtOH was
refluxed for 30 min. After cooling the precipitated solid was recrystallized from methanol. The
resulted crystals were washed with ether, water and ether again and dried on air. Yield 620 mg
(84%). 1H NMR (DMSO-d6) δ (ppm) 1.29 (m, 6H), 1.62 (s, 12H), 2.06 (s, 6H), 2.92 (s, 4H), 4.18 (m,
4H), 6.09 (d, J = 14.5 Hz, 2H), 7.36 (d, J = 8.0 Hz, 2H), 7.52 (d, J = 8.0 Hz, 2H), 7.70 (d, J = 14.5
Hz, 2H), 7.82 (br.s, 2H), 10.13(s, 2H). λmax (EtOH) 837 nm (ε =7.70x104 l/mol cm). ES-MS+
611,3163 (cal. 611,3153 for C37H44ClN4O2).
2.3.7. 3H-Indolium, 5-acetylamino-2-[2-[3-[2-(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-
indol-2-ylidene)ethylidene]-2-(3-trifluoromethylphenylamino)-1-cyclopenten-1-yl]ethenyl]-1-ethyl-3,3-
dimethyl-, iodide (9)
A solution of dye 8 (369 mg, 0.5 mmol) and 3-trifluoromethylaniline (805 mg, 5 mmol) in absolute
EtOH was refluxed for 6 h. After evaporation of methanol in vacuo the residue was washed with
ether and recrystallized from methanol. The resulted crystals were washed with ether and dried on
air. Yield 328 mg (76%). 1H NMR (DMSO-d6) δ (ppm) 1.30 (s, 12H), 2.03 (s, 6H), 2.80 (s, 4H), 4.01
(m, 4H), 5.72 (br.s, 2H), 7.18 (br.s, 2H), 7.41 (d, J = 8 Hz, 2H), 7.53 - 7.78 (m, 8H), 9.90 (br.s, 1H),
9.98 (s, 2H). λmax (EtOH) 757 nm (ε =1.57ꢀ105 l/mol cm). ES-MS+ 736,3861 (cal. 736,3838 for
C44H49F3N5O2).
2.3.8.
3H-Indolium,
5-acetylamino-2-[2-[3-[2-(1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-chloro-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (12)
A mixture of 392 mg (0.76 mmol) of dye 11, 282 mg (0.76 mmol) of quaternary salt 2 and 60 mg of
sodium acetate were refluxed in 15 mL of methanol for 10 min. The crude product remained after
evaporation of all volatiles, which was purified on silica (0-5% MeOH in CH2Cl2) resulting in 347 mg

ACCEPTED MANUSCRIPT
of dye 12 (yield 68 %). (DMSO-d6) δ (ppm) 1.22 - 1.37 (m, 6H), 1.66 (s, 12H), 1.85 (br. s, 2H), 2.07
(s, 3H), 2.71 (br. s, 4H), 4.19 (m, 2H), 4.29 (m, 2H), 6.21 (d, J = 13.5 Hz, 1H), 6.41 (d, J = 14.0 Hz,
1H), 7.23 (m, 1H), 7.32 -7.45 (m, 7.56, 1H), 7.48 (d, J = 9.0 Hz, 1H), 7.53 - 7.67 (m, 2H), 7.90 (s,
2H), 8.18 (d, J =13.5 Hz, 1H), 8.28 (d, J =14.0 Hz, 1H), 10.20 (s, 1H). λmax (EtOH) = 797 nm (ε =
2.53 x 105 L mol-1 cm-1).ES-MS+ 568.3094 (cal. 568.3094 for C36H43ClN3O). ES-MS- 98.9440 (cal.
-
98.9485 for ClO4 ).
2.3.9.
3H-Indolium,
5-acetylamino-2-[2-[3-[2-(1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(4-acetylaminophenoxy)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-,
iodide (13)
Yield 503 mg (62 %) from dye 12 and sodium 4-acetylaminophenolate, using the procedure for 5c.
(DMSO-d6) δ (ppm) 1.24(m, 3H), 1.27(m, 3H), 1.29 (s, 6H), 1.30 (s, 6H), 1.94 (m, 2H), 1.98 (s,
3H), 2.00 (s, 3H), 2.71 (m, 4H), 4.11 (m, 2H), 4.19 (m, 2H), 6.09 (d, J = 14 Hz, 1H), 6.23 (d, J =
14.5 Hz, 1H), 7.09 (d, J = 9.0 Hz, 2H), 7.15 (t, J = 7.5 Hz, 1H), 7.27- 7.36 (m, 2H), 7.38(d, J = 8.5
Hz, 2H), 7.47 (d, J = 7.5 Hz, 1H), 7.53 (d, J = 9.0 Hz, 1H), 7.60 (d, J = 9.0 Hz, 2H), 7.73 (br.s, 1H),
7.77 (d, J = 14 Hz, 1H), 7.85 (d, J = 14.5 Hz, 1H), 9.86 (s, 1H), 10.10 (s, 1H). λmax (EtOH) = 782 nm
(ε = 2.65 x 105 L mol-1 cm-1). ES-MS+ 683.3948 (cal. 683.3961 for C44H51N4O3).
2.3.10. 3H-Indolium, 5-acetylamino-2-[[3-[(5-acetylamino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-
2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-1-ethyl-3,3-dimethyl-, inner salt
(15)
A mixture of squaric acid (114 mg, 1 mmol), 5-acetylamino-2,3,3-trimethyliondoleninium iodide 2
(744 mg, 2 mmol) and quinoline (516 mg, 8 mmol) were refluxed in 30 mL of a 1:1 mixture of n-
butanol and benzene with Dean-Stark trap for 6 hours. After cooling the volatiles in vacuo the
1
residue was recrystallized from methanol, yielding 475 mg (84 %) of 16. H NMR (DMSO-d6) δ
(ppm) 1.23 (br. t, 6H), 1.66 (s, 12H), 2.05 (s, 6H), 4.09 (br.s, 4H), 5.73 (s, 2H), 7.25 (d, J = 8.7 Hz,
2H), 7.52 (d, J = 8 Hz, 2H), 7.69 (s, 2H), 10.0 (s, 2H). λmax (EtOH) = 655 nm (ε = 3.72 x 105 L mol-1
cm-1). ES-MS+ 566.2930 (cal. 566.2893 for C34H38N4O4).
2.3.11. 3H-Indolium, 2-[5-(1-ethyl-1,3-dihydro-5-acetylamino-3,3-dimethyl-2H-indol-2-ylidene)-1,3-
pentadien-1-yl]-1-ethyl-5-acetylamino-3,3-dimethyl-, iodide (18a)
Acetic anhydride (200 mg, 2 mmol) was added dropwise to a solution of N-(3-anilino-3-
propenylidene)aniline perchlorate 17a (323 mg, 1 mmol) and diisopropylethylamine (DIEA, 0.38 mL,
2 mmol) in 7 mL of CH2Cl2. The mixture was kept at room temperature for 3 hours and added to the
solution of salt 2 (746 mg, 2 mmol) and anhydrous sodium acetate (430 mg, 5.2 mmol) in 25 mL of
methanol. Methylene chloride was distilled off and the remaining methanol solution was heated at
0
reflux for 8 hours. After reducing to 10 mL the solution was kept at -15 C overnight. The resulted
1
crystals were washed with ether, water and ether again, and dried on air. Yield 469 mg (72 %). H
NMR (DMSO-d6) δ (ppm) 1.26 (m, 6H), 1.65 (s, 12H), 2.06 (s, 6H), 4.10 (m, 4H), 6.25 (d, J = 13 Hz,
2H), 6.52 (t, J = 13 Hz, 1H), 7.32 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 9.0 Hz, 2H), 7.70 (d, J = 9.0 Hz,
2H), 7.88 (br.s, 2H), 8.26 (t, J = 13 Hz, 1H), 10.08 (s, 2H). λmax (EtOH) = 674 nm (ε = 2.26 x 105 L
mol-1 cm-1). ES-MS+ 525.3229 (cal. 525.3229 for C33H41N4O2).
2.3.12.
3H-Indolium,
2-[3-chloro-5-(1-ethyl-1,3-dihydro-5-acetylamino-3,3-dimethyl-2H-indol-2-
ylidene)-1,3-pentadien-1-yl]-1-ethyl-5-acetylamino-3,3-dimethyl-, iodide (18b)
A solution of N-(3-anilino-2-chloro-2-propenylidene)aniline hydrochloride 17b (293 mg, 1 mmol), 5-
acetylamino-2,3,3-trimethyliondoleninium iodide 2 (746 mg, 2 mmol) and anhydrous sodium acetate
(200 mg, 2.5 mmol) in absolute EtOH was refluxed for 2 hours. After cooling, the precipitated solid
was recrystallized from methanol. The resulted crystals were washed with ether, water and ether
again, and dried on air. Yield 370 mg (62 %). 1H NMR (DMSO-d6) δ (ppm) 1.31 (t, J = 7 Hz, 6H),
1.68 (s, 12H), 2.06 (s, 6H), 4.18 (br.t, 4H), 6.24 (d, J = 13.5 Hz, 2H), 7.34 - 7.54 (m, 4H), 7.94 (br.s,
2H), 8.39 (d, J = 13.5 Hz, 2H), 10.14 (s, 2H). λmax (EtOH) = 676 nm (ε = 2.30 x 105 L mol-1 cm-1). ES-
MS+ 559.2729 (cal. 559.2840 for C33H40ClN4O2).
2.3.13.
3H-Indolium,
2-[3-nitro-5-(1-ethyl-1,3-dihydro-5-acetylamino-3,3-dimethyl-2H-indol-2-
ylidene)-1,3-pentadien-1-yl]-1-ethyl-5-acetylamino-3,3-dimethyl-, iodide (21)
A solution of 2-nitromalonic dialdehyde sodium salt monohydrate 20 (139 mg, 1 mmol), 5-
acetylamino-2,3,3-trimethyliondoleninium iodide 2 (746 mg, 2 mmol) and anhydrous sodium acetate
(200 mg, 2.5 mmol) in absolute EtOH was refluxed for 1 hour. After cooling, the precipitated solid

ACCEPTED MANUSCRIPT
was recrystallized from methanol. The resulted crystals were washed with ether, water and ether
1
again, and dried on air. Yield 432 mg (62 %). H NMR (DMSO-d6) δ (ppm) 1.40 (m, 6H), 1.74 (s,
12H), 2.09 (s, 6H), 4.37(m, 4H), 6.96 (d, J = 15 Hz, 2H), 7.50 - 7.69(m, 4H), 8.00 (s, 2H), 8.37 (d, J =
15 Hz, 2H), 10.27(s, 2H). λmax (EtOH) = 610 nm (ε = 7.10 x 104 L mol-1 cm-1). ES-MS+ 570.3058 (cal.
570.3080 for C33H40N5O4).
2.3.14.
3H-Indolium, 2-[5-(1-ethyl-1,3-dihydro-5-acetylamino-3,3-dimethyl-2H-indol-2-ylidene)-
1,3,5-heptatrien-1-yl]-1-ethyl-5-acetylamino-3,3-dimethyl-, Iodide (24)
From 2 mmol of salt 2 and 1 mmol of N-(5-anilino-2,4-pentadienylidene)aniline hydrochloride 23. The
1
followed procedure was the same as for 18a. Yield 515 mg (76 %). H NMR (DMSO-d6) δ (ppm)
1.27 (m, 6H), 1.61 (s, 12H), 2.06 (s, 6H), 4.09 (m, 4H), 6.32 (d, J = 13 Hz, 2H), 6.51 (t, J = 13 Hz,
2H), 7.29 (d, J = 8.0 Hz, 2H), 7.49 (d, J = 8.0 Hz, 2H), 7.61 -7.92 (m, 3H), 7.81 (br.s, 2H), 10.05 (s,
2H). λmax (EtOH) = 776 nm (ε = 2.30 x 105 L mol-1 cm-1). ES-MS+ 551.3377 (cal. 551.3386 for
C35H43N4O2).
2.4. Syntheses of bis-amino dyes (6a-e, 14, 16, 19a-b, 22, 25).
2.4.1. General procedure for deprotection of bis-acetylamino dyes.
1 eq of bis-acetylamino dye and 12 eq (1.05 mL / 1 mmol of dye) of boron trifluoride - methanol
complex 50 % in methanol (20 mL / 1 mmol of dye) were heated under reflux for 4-6 hours (VIS
control). After cooling, 15 eq (2.2 mL / 1mmol of dye) of triethylamine were added, and all volatiles
were evaporated in vacuo. The residue was stirred with 50 mL of water for an hour. The filtered solid
was washed with ether and dried on air.
2.4.1.1.
3H-Indolium,
5-amino-2-[2-[3-[2-(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-methoxy-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (6a)
1
Yield 85%. H NMR (DMSO-d6) δ (ppm) 1.25 (br.t, 6H), 1.51 (s,12H), 1.77 (br.s, 2H), 2.54 (br.s,
4H), 3.88 (s, 3H), 4.08 (br.s, 4H), 5.98 (d, J = 13.5 Hz, 2H), 6.58 (d, J = 7 Hz, 2H), 6.72 (s, 2H), 7.06
(d, J = 7 Hz, 2H), 7.84 (d, J = 13.5 Hz, 2H). 1H NMR (DMSO-d6 + CF3COOH) δ (ppm) 1.28 (m, 6H),
1.63 (s, 12H), 1.79 (br.s, 2H), 2.57 (br.s, 4H), 3.89 (s, 3H), 4.15 (br.s, 4H), 6.15 (d, J = 14Hz, 2H),
7.06 (d, J = 8 Hz, 2H), 7.19 (s, 2H), 7.31 (d, J = 8 Hz, 2H), 7.87 (d, J = 14 Hz, 2H). λmax (EtOH) =
806 nm (ε = 1.63 x 105 L mol-1 cm-1). ES-MS+ 537.3499 (cal. 537.3576 for C35H45N4O).
2.4.1.2.
3H-Indolium,
5-amino-2-[2-[3-[2-(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(1-piperidinyl )-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (6b)
Yield 78 %. 1H NMR (DMSO-d6) δ (ppm) 1.22 (m, 6H), 1.59 (s, 12H), 1.74 (br.s, 8H), 2.48 (br.s, 4H),
3.30 (br.s, 4H), 4.01 (br.s, 4H), 5.20 (br.s, 4H), 5.73 (d, J = 12.5 Hz, 2H), 6.56 (m, 2H), 6.70 (s, 2H),
6.99 (d, J = 8 Hz, 2H), 7.74 (d, J = 12.5 Hz, 2H). 1H NMR (DMSO-d6 + CF3COOH) δ (ppm) 1.22 (m,
6H), 1.60 (s, 12H), 1.80 (br.s, 8H), 2.48 (br.s, 4H), 3.63 (br.s, 4H), 4.03 (br.s, 4H), 5.86 (d, J = 13 Hz,
2H), 7.00 - 7.30 (m, 6H), 7.52 (d, J = 13 Hz, 2H). λmax (EtOH) = 760 nm (ε = 3.25 x 104 L mol-1 cm-1).
ES-MS+ 590.4123 (cal. 590.4210 for C39H52N5).
2.4.1.3.
3H-Indolium,
5-amino-2-[2-[3-[2-(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(4-methylphenoxy)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (6c)
Yield 73 %. 1H NMR (DMSO-d6 + CF3COOH) δ (ppm) 1.23 (br.t, 6H), 1.27 (s,12H), 1.92 (br.s, 2H),
2.22 (s, 3H), 2.69 (br.s, 4H), 4.12 (br.q, 4H), 6.18 (d, J = 14 Hz, 2H), 7.01 (d, J = 8 Hz, 2H), 7.09 (d,
J =8 Hz, 2H), 7.13 - 7.24 (m, 4H), 7.31 (d, J = 8 Hz, 2H), 7.70 (d, J = 14 Hz, 2H). λmax (EtOH) = 825
nm (ε = 1.56 x 105 L mol-1 cm-1). ES-MS+ 613.3930 (cal. 613.3906 for C41H49N4O).
2.4.1.4.
3H-Indolium,
5-amino-2-[2-[3-[2-(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(4-methylphenylmercapto)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-,
iodide (6d)
Yield 67 %. 1H NMR (DMSO-d6 + CF3COOH) δ (ppm) 1.25 (br.t, 6H), 1.42 (s,12H), 1.88 (br.s, 2H),
2.20 (s, 3H), 2.73 (br.s, 4H), 4.15 (br.q, 4H), 6.28 (d, J = 14 Hz, 2H), 6.98 (d, J = 8 Hz, 2H), 7.14 (br.
s, 6H), 7.31 (d, J = 8 Hz, 2H), 8.47 (d, J = 14 Hz, 2H). λmax (EtOH) = 850 nm (ε = 1.19 x 105 L mol-1
cm-1). ES-MS+ 629.3700 (cal. 629.3678 for C41H49N4S).
2.4.1.5.
3H-Indolium,
5-amino-2-[2-[3-[2-(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(4-chlorophenyl)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (6e)

1H NMR (DMSAO-Cd6C)EδP(TppEmD) 1M.0A9 N(sU,12SHC),R1I.P19T(br.t, 6H), 1.91 (br.s, 2H), 2.61 (br.s,
Yield 82 %.
4H), 4.03 (br.q, 4H), 5.28 (br.s, 4H), 6.00 (br.s, 2H), 6.54 (br. s, 2H), 6.61 ( s, 2H). 6.88 (br.s, 2H).
7.01 (br.s, 2H), 7.23 (d, J = 8 Hz, 2H), 7.67 (d, J = 8 Hz, 2H). λmax (EtOH) = 822 nm (ε = 1.63 x 105
L mol-1 cm-1). ES-MS+ 617.3400 (cal. 617.3400 for C40H46N4Cl).
2.4.1.6.
3H-Indolium,
5-amino-2-[2-[3-[2-(1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)ethylidene]-2-(4-aminophenoxy)-1-cyclohexen-1-yl]ethenyl]-1-ethyl-3,3-dimethyl-, iodide (14)
1
Yield 76 %. H NMR (DMSO-d6) δ (ppm) 1.17 (br.t, 6H), 1.27 (s,8H), 1.30 (s,6H),1.88(m, 2H),
2.65(br.s, 4H), 3.92 (m, 2H), 4.25 (m, 2H), 5.17 - 6.17(br.s, 4H), 5.78(d, J = 13 Hz, 1H), 6.35 (d, J =
15 Hz, 1H), 6.56 - 6.77 (m, 4H), 6.80 - 6.93(m, 2H), 6.93 - 7.15(m, 2H), 7.15 - 7.45 (m, 3H), 7.52 (d,
J = 13 Hz, 1H), 7.89 (d, J = 15 Hz, 1H) λmax (EtOH) = 788 nm (ε = 7.91 x 104 L mol-1 cm-1). ES-MS+
599.3731 (cal. 599.3750 for C40H47N4O).
2.4.1.7.
3H-Indolium,
5-amino-2-[[3-[(5-amino-1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-
ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-1-ethyl-3,3-dimethyl-, inner salt
(16).
Yield 79 %. 1H NMR (DMSO-d6 + CF3COOH) δ (ppm) 1.28 (br.t, 6H), 1.70 (s,12H), 4.13 (br.q, 4H),
5.85 (s, 2H), 7.34 (br,d, J = 8.7 Hz, 2H), 7.43 (d, J = 8 Hz, 2H), 7.49 (br.s, 2H). λmax (EtOH) = 669
nm (ε = 1.42 x 105 L mol-1 cm-1). ES-MS+ 482.2662 (cal. 482.2682).
2.4.1.8. 3H-Indolium, 2-[5-(1-ethyl-1,3-dihydro-5-amino-3,3-dimethyl-2H-indol-2-ylidene)- 1,3-
pentadien -1-yl]-1-ethyl-5-amino-3,3-dimethyl-, iodide (19a)
1
Yield 72 %. H NMR (DMSO-d6) δ (ppm) 1.23 (m, 6H), 1.60 (s, 12H), 4.02(m, 4H), 5.57(br. s, 4H),
6.09 (d, J = 13 Hz, 2H), 6,38 (br.t, 1H), 6.60 (d, J = 7.5 Hz, 2H), 6.76 (s, 2H), 7.08 (d, J = 7.5 Hz,
2H), 8.07 (br.t, 2H). λmax (EtOH) = 700 nm (ε = 9.64 x 104 L mol-1 cm-1). ES-MS+ 441.2977 (cal.
441.3018 for C29H36ClN4).
2.4.1.9. 3H-Indolium, 2-[3-chloro-5-(1-ethyl-1,3-dihydro-5-amino-3,3-dimethyl-2H-indol-2-ylidene)-
1,3-pentadien-1-yl]-1-ethyl-5-amino-3,3-dimethyl-, iodide (19b)
Yield 94 %. 1H NMR δ (ppm) 1.29 (m, 6H), 1.64 (s, 12H), 4.09(m, 4H), 5.40 (br.s, 4H), 6.13 (d, J =
13 Hz, 2H), 6.61 (m, 2H), 6.79 (s, 2H), 7.16 (d, J = 8.5 Hz, 2H) 8.38 (d, J = 13 Hz, 2H). λmax (EtOH)
= 688 nm (ε = 1.10 x 105 L mol-1 cm-1). ES-MS+ 475.2640 (cal. 475.2628 for C29H36ClN4).
2.4.1.10. 3H-Indolium, 2-[3-nitro-5-(1-ethyl-1,3-dihydro-5-amino-3,3-dimethyl-2H-indol-2-ylidene)-
1,3-pentadien-1-yl]-1-ethyl-5-amino-3,3-dimethyl-, iodide(22)
Yield (92 %). 1H NMR (DMSO-d6 +CF3COOH) δ (ppm) 1.38 (m, 6H), 1.70 (s, 12H), 4.31(overlapped
with water), 6.77-6.97 (m, 4H), 7.05 (s, 2H), 7.46 (d, J = 9 Hz, 2H), 8.31 (d, J = 15 Hz, 2H). λmax
(EtOH) = 638 nm (ε = 4.70 x 104 L mol-1 cm-1). ES-MS+ 428.2846 (cal. 486.2868 for C29H36N5O2).
2.4.1.11. 3H-Indolium, 2-[5-(1-ethyl-1,3-dihydro-5-amino-3,3-dimethyl-2H-indol-2-ylidene)- 1,3,5-
heptatrien-1-yl]-1-ethyl-5-amino-3,3-dimethyl-, iodide (25)
1
Yield (74 %). H NMR (DMSO-d6) δ (ppm) 1.24 (m, 6H), 1.56 (s, 12H), 4.11(m, 4H), 5.30(br.s, 4H),
6.16 (d, J = 14 Hz, 2H), 6.37 (t, J = 12.5 Hz, 2H), 6.58 (d, J = 8.5 Hz, 2H), 6.71 (s, 2H), 7.05 (d, J
= 8.5 Hz, 2H), 7.51 (t, J = 12.5 Hz, 1H), 7.66 (t, J = 12 Hz, 2H). λmax (EtOH) = 804 nm (ε = 1.45 x 105
L mol-1 cm-1). ES-MS+ 467.3155 (cal. 467.3175 for C31H39N4).
3. Results and discussion
Cyanine dyes are usually prepared via condensation of quaternized nitrogen heterocycles containing
activated methyl groups with unsaturated dialdehydes or their derivatives (anils, acetals, etc). In
order to prepare the starting heterocyclic salts as well as to perform condensation to obtain the
aminosubstituted cyanines, amino-groups should be protected. Thus, deprotection only can be
undertaken on very last step, being the key step for the whole synthetic route. Since cyanine dyes
are rather labile compounds, this deprotection step is likely to proceed in very mild conditions.
Recently, we have developed an effective procedure that allows accomplishing the cleavage of
acetylated amino dyes in high yields by simple refluxing their methanolic solutions in the presence of

ACCEPTED MANUSCRIPT
boron trifluoride [20]. In the present work, we have successfully used this method for the liberation of
target diamines from their acetylated derivatives.
Dye 1, used previously in polymer compositions by our research group (Fig. 1), has a vinylic chlorine
atom, which exhibits considerable reactivity towards various nucleophiles [14, 21] and can be
involved in side reactions in course of polymerization. In order to overcome this drawback, we
prepared from dye 4 (protected dye 1) various meso-substituted derivatives 5a-d, which were further
converted into free diaminodyes 6a-d by the above procedure [20] (Scheme 1):
Scheme 1. Preparation of meso-substituted derivatives from dye 1 and their deprotection. Nu = a)
CH3O-, b) c-C5H10N-, c) 4-CH3C6H4O-, d) 4-CH3C6H4S-
It is known that meso-chlorosubstituted analogues of 4 can be arylated by means of Suzuki reaction
[22]. Thus, we performed this reaction with dye 4 and 4-chlorophenylboronic acid, using the
palladium-based catalyst, which was also developed by our research group [23] (Scheme 2):
Scheme 2. Arylation of dye 4 by a palladium-based catalyst and its deprotection.
As it has been stated in other works, preparation attempts of dye 4 analogues with five-membered
ring in the polimethine chain, according to the Scheme 1, leads to meso-anilinoderivatives. This
happens because of the increased reactivity of the corresponding meso-chlorinated dyes towards
nucleophilic substitution by aniline, which is released in the course of the process [24]. In this sense,
we tried to use the 5-membered bis-anil 7, containing weakly-basic 3-trifluromethylaniline to obtain
dye 8 in high yield. Corresponding meso-anilinosubstituted dye 9 was prepared only by 6-hour
heating in ethanol with 10-fold excess of 3-trifluromethylaniline (Scheme 3). Unfortunate attempts of
deacetylation of dye 8 lead to a complex mixture, probably rising from the substitution of highly
reactive meso-chlorine by liberated amino groups.

ACCEPTED MANUSCRIPT
Scheme 3. Scheme of the synthesis of dye 4 analogues with five-membered ring in the polimethine
chain (dyes 8 and 9).
All the above dyes are suitable for their incorporation into the main chain of polyamide polymers.
However, it is also of special interest to obtain polymeric compositions with cyanine chromophores in
the side chain, which is attached by two points to the polymeric chain. For this reason we have
synthesized diaminodye 15 following the route depicted on Scheme 5. From hemicyanine 12 [15]
and salt, 2 we prepared unsymmetrical dye 13 containing one acetylamino group. The second one
was introduced in the meso-position of 13 in the same manner as in the case of dye 5c, resulting on
the diacetylamino dye 13, which was successfully deprotected in the usual way giving diaminodye
14 in good yield (Scheme 5):
Cl
Cl
Et3N
NHPh
+
N
Et
NHPh
PhHN
Cl
N
CH3
CH3COOH
ClO4
Et
I
11
3
10
NHCOCH3
NHCOCH3
2
NaOAc
H
N
CH3
NHCOCH3
Cl
OH
O
O
N
Et
N
Et
N
Et
N
Et
CH3OH
ClO4
I
12
NH2
13
BF3
CH3OH
NH2
O
N
N
Et
Et
I
14
Scheme 4. Syntheses of dyes 12, 13 and 14.
Up to now, all synthesized dyes were containing iodide-anion salts. The presence of these highly
oxidizable species in polymer films could decrease its stability as well as change its properties. In
order to avoid this problem, we also prepared zwitterionic diaminosquarine 15. The synthesis of bis-
acetylaminosquarine dye 16 was carried out according to reported procedure [25] and its
subsequent deprotection was performed in the usual manner (Scheme 5):

ACCEPTED MANUSCRIPT
Scheme 5. Synthesis of zwitterionic diaminosquarine 16.
In order to modify the flexibility of future developed polymers, we have also synthesized three open-
chain pentamethine and one heptamethine dyes (Schemes 6-8). Thereby, we have used the
conventional procedures for the synthesis of dyes 18b and 22. However, we have observed that the
absence of substituent in the meso-position of trimethine salts 17a and 23 generated very low
reactivity, resulting in a low yield of 24 (<15%) and only traces of 18a after 10-hour reflux. For the
synthesis of these dyes, we have successfully applied the recently disclosed protocol [26], which
required preliminary acetylation of salts 17a and 23. In the case of 18a-b, 21 and 24, the further
deacetylation resulted on the target diaminodyes 19a-b, 22 and 25 in good yields.
Scheme 6. Syntheses of open-chain pentamethine dyes 18a,b and 19a,b. X = a) ClO4, b) Cl.
Y = a) H-, b) Cl-.
Scheme 7. Syntheses of open-chain pentamethine dyes 21 and 22.

ACCEPTED MANUSCRIPT
Scheme 8. Syntheses of open-chain heptamethine dyes 24 and 25.
4. Conclusions
To sum up, we have synthesized bis-aminosubstituted cyanine dyes with cyclic fragments in the
polymethine chain as well as open-chained. All them are potential chromophores to be employed in
the development of chromophore-containing polymeric systems by their covalently incorporation into
the main or the side chains of the polymer. In this way, problems related to solubility, heterogeneous
distribution, stability or low optical quality present in typical “guest”-“host” systems could be avoided.
Acknowledgements
We acknowledge the Center for Magnetic Resonance and the Center for Chemical Analysis and
Materials Research of Saint Petersburg State University for performing the NMR and ES-MS
studies. The group of sensors and biosensors want to thank the financial support by the Spanish
Ministry of Science and Innovation (MICINN) through projects CTQ2009-12128 and CTQ2012-
36165, co-funded by FEDER, and Catalonia Government through SGR 2009 -0323.
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- Synthesis of bis-aminosubstituted cyanine dyes with variable optical characteristics.
- Chromophores for the development of polymeric systems with optical properties.
- Chromophore-containing polymeric systems development by covalent incorporation.