Deeply colored anionic polymethine dyes derived from bis(2,2,3,3,4,4,5,5- octafluoropentyl) 9H7-fluorene-2,7-disulfonate

Article abstract of DOI:10.1007/s11172-009-0102-7

Anionic symmetric polymethine dyes have been synthesized based on bis(2,2,3,3,4,4,5,5-octafluoropentyl) 9i/-fluorene-2,7-disulfonate, which exhibit intensive absorption in the near IR region of the spectrum: pentamethine with an open polymethine chain (λ_max = 790 nm) and nonamethine with six- and five-membered saturated rings at δ,δ'- positions of the chain (λ_max = 1044 and 1086 nm, respectively). To make comparisons, anionic dyes with analogous structure of the polymethine chain, viz., 1,3-dimethylbarbituric and 1,3-diethylthiobarbituric acid derivatives, have been also synthesized. Quantum chemical analysis of the electron struc-ture of the dyes has been performed. Their solvatochromism in polar solvents depends weakly on electrophilicity and nucleophilicity of the medium and is primarily determined by universal interactions. This is the reason that they, in contrast to cationic dyes, retain a high selectivity of absorption (sharp absorption bands) and universal contour of electronic bands in strong polar solvents even with the long polymethine chain. Special solvatochromic effects of the anionic dyes in weakly polar media have been revealed and interpreted. The role of a counterion in these effects has been analyzed.

Full text of DOI:10.1007/s11172-009-0102-7

Russian Chemical Bulletin, International Edition, Vol. 58, No. 4, pp. 828—837, April, 2009
828
Deeply colored anionic polymethine dyes derived
from bis(2,2,3,3,4,4,5,5ꢀoctafluoropentyl) 9Hꢀfluoreneꢀ2,7ꢀdisulfonate
I. V. Kurdyukova,a N. A. Derevyanko,a A. A. Ishchenko,a and D. D. Mysykb
aInstitute of Organic Chemistry, National Academy of Sciences of Ukraine,
5 ul. Murmanskaya, 02094 Kiev, Ukraine.
Fax: 380 (44) 573 2643. Eꢀmail: alexish@i.com.ua
bDonetsk National Technical University,
58 ul. Artema, 83000 Donetsk, Ukraine.
Eꢀmail: mysyk@yandex.ru
Anionic symmetric polymethine dyes have been synthesized based on bis(2,2,3,3,4,4,5,5ꢀ
octafluoropentyl) 9Hꢀfluoreneꢀ2,7ꢀdisulfonate, which exhibit intensive absorption in the near
IR region of the spectrum: pentamethine with an open polymethine chain (λmax = 790 nm) and
nonamethine with sixꢀ and fiveꢀmembered saturated rings at δ,δ´ꢀpositions of the chain
(λ
= 1044 and 1086 nm, respectively). To make comparisons, anionic dyes with analogous
max
structure of the polymethine chain, viz., 1,3ꢀdimethylbarbituric and 1,3ꢀdiethylthiobarbituric
acid derivatives, have been also synthesized. Quantum chemical analysis of the electron strucꢀ
ture of the dyes has been performed. Their solvatochromism in polar solvents depends weakly
on electrophilicity and nucleophilicity of the medium and is primarily determined by universal
interactions. This is the reason that they, in contrast to cationic dyes, retain a high selectivity of
absorption (sharp absorption bands) and universal contour of electronic bands in strong polar
solvents even with the long polymethine chain. Special solvatochromic effects of the anionic
dyes in weakly polar media have been revealed and interpreted. The role of a counterion in
these effects has been analyzed.
Key words: fluorene, anionic dyes, intimate ion pairs, solvatochromism, absorption spectra,
organofluorine compounds.
Fragments of heterocyclic compounds are commonly
In the present work, a method for the synthesis of
fluorene derivative containing octafluoropentyloxysulfonyl
substituents at positions 2 and 7 has been developed
(Scheme 1).
used as terminal groups in polymethine (cyanine) dyes.1
Development of deeply colored dyes (i.e., absorbing light
in the longꢀwave region of the spectrum)2 usually is based
on the choice of suitable heterocycles. The aim of this
work consists in the study of possibility to synthesize polyꢀ
methine dyes, absorbing light in the practically important
near IR region of the spectrum, based on aromatic carꢀ
bocycles. A fluorene core was used as such a carbocycle.
This choice is due to the developed πꢀsystem, high elecꢀ
tronic symmetry, and the presence of methylene group,
which owing to the neighboring benzene rings can be poꢀ
tentially active in the reactions of cyanine condensation.
However, we failed to activate it in unsubstituted fluorene
in the reactions under consideration even in the presence
of very strong organic bases, such as sodium ethoxide,
potassium tertꢀbutoxide, 1,8ꢀdiazabicyclo[5.4.0]undecꢀ7ꢀ
ene (DBU), and N,N,N´,N´ꢀtetramethylnaphthaleneꢀ1,8ꢀ
diamine ("proton sponge").
Scheme 1
R = CH2(CF2)3CF2H
One of the methods to activate the methylene group
can be introduction of electronꢀwithdrawing substituents
into the fluorene core, thus raising CH acidity of this group.
Note that unsubstituted fluorene has рКa = 20.5.3
This substituent is an acceptor by both the inductive
(σI = 0.67) and mesomeric (σR = 0.21) effects.4 Its elecꢀ
tronꢀwithdrawing power is higher than that of a nitro group
(σI = 0.58 and σR = 0.20) and is inferior to only the
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 811—820, April, 2009.
1066ꢀ5285/09/5804ꢀ0828 © 2009 Springer Science+Business Media, Inc.

Deeply colored anionic polymethine dyes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
829
strongest out of known electron acceptors, i.e., polyfluoꢀ
roalkyl sulfones, for example, trifluoromethylsulfonyl
group (for CF3SO2 σI = 0.73 and σR = 0.31)4. Fluoroꢀ
alkoxysulfonyl substituents are easy to identify by NMR
spectroscopy and mass spectrometry, as well as they inꢀ
crease solubility of compounds obtained.
Electronꢀwithdrawing power of the octafluoropentylꢀ
oxysulfonyl group turned out to suffice activity of comꢀ
pound 3 in the reaction of cyanine condensation in the
presence of a strong base. Thus, its reaction with Nꢀ[5ꢀ
anilinopentaꢀ2,4ꢀdienylidene]anilinium chloride (4) in the
presence of DBU furnished pentamethine dye 5 with an
open polymethine chain (Scheme 2).
It is significant that with such a short chain, the abꢀ
sorption maximum of product 5 is in the near IR region
of the spectrum (λmax = 790 nm). For comparison,
it should be noted that anionic dyes with the same length
of the polymethine chain, based on the widely prolifeꢀ
rated withdrawing hetero fragment of diethylthiobarbiꢀ
turic acid (which considerably deepens the color),
absorb light in more shortꢀwave region (by 130 nm) than
dye 5.5 The bands of cationic pentamethine dyes, deriꢀ
vatives of classic heterocycles indolenine, benzothiꢀ
azole, and benzoxazole,6 are also hypsochromically shiftꢀ
ed with respect to the absorption band of compound 5 by
~120—150 nm.
As it follows from the results of quantum chemical
calculation, out of all possible positions of the fluorene
core capable of substitution, electron density increases on
excitation only in positions 2 and 7 of unsubstituted anaꢀ
log 5a (Fig. 1). According to the MO perturbation theory,
electronꢀwithdrawing substituents in such positions should
cause a longꢀwave shift of the absorption bands. In fact,
the absorption maximum for dye 5 (790 nm) is bathochroꢀ
Fig. 1. Electron charge distribution in the anion of dye 5a in the
ground and excited (in parentheses) states.
mically shifted relatively to the λmax of unsubstituted polyꢀ
methine 5a (740 nm)7 by 50 nm.
Note that the substituents at positions 2 and 7 of the
fluorene residue, being the metaꢀorienting with respect to
the polymethine chain, do not directly conjugate with the
main polymethine chromophore. However, due to the
presence of the fiveꢀmembered ring, they are capable of
conjugating with the named chromophore by more long
way involving all the bonds of the system. This is illustꢀ
rated by the second canonical structure of dye 5 with
the negative charge on one of the oxygen atoms. From
it, one can see that the largest length of the chromoꢀ
phore is reached upon substitution at positions 2 and 7 in
comparison with other possible positions. This process
makes additional contribution to the deepening of the
color of anionic polymethines based on 2,7ꢀdisubstituted
fluorene.
Scheme 2
R = CH2(CF2)3CF2H

830
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kurdyukova et al.
Scheme 3
R = CH2(CF2)3CF2H; 8, m = 2 (7, 9), 3 (6, 8); An = BF4 (6), ClO4 (7)
The condensation of compound 3 with NꢀmethylꢀNꢀ
[3ꢀ{3ꢀ[3ꢀ(NꢀmethylꢀNꢀphenylamino)propꢀ2ꢀenylidene]ꢀ
2ꢀphenylcyclohexꢀ1ꢀenꢀ1ꢀyl}propꢀ2ꢀenylidene]anilinium
tetrafluoroborate (6) and NꢀmethylꢀNꢀ[3ꢀ{3ꢀ[3ꢀ(Nꢀmeꢀ
thylꢀNꢀphenylamino)propꢀ2ꢀenylidene]ꢀ2ꢀphenylcycloꢀ
pentꢀ1ꢀenꢀ1ꢀyl}propꢀ2ꢀenylidene]anilinium perchlorate2
(7) gives rise to dyes 8 and 9, respectively (Scheme 3).
Note that for comparison, starting from 1,3ꢀdimethylꢀ
barbituric (10) and 1,3ꢀdiethylthiobarbituric (11) acids,
we also synthesized anionic dyes 12—15 (Scheme 4).
However, because of higher CH acidity of these hetꢀ
erocycles (рКa = 4.68 and 3.75, respectively8) as comꢀ
pared to compound 3, the reaction takes place in the presꢀ
ence of triethylamine a base weaker than DBU. The polyꢀ
methine chain of compounds 8, 12, and 14 contains a sixꢀ
membered ring. From the one hand, being a framework
group, it increases stability of the dyes. From the other
hand, the data of quantum chemical calculation show that
the negative charge in the ground state is concentrated in
δ,δ´ꢀpositions, as in all the odd positions of the polymeꢀ
thine chain (the carbon atom bonding the fluorene residue
and polymethine chain is considered as the first atom),
which considerably decreases in the excited state. Thereꢀ
fore, the saturated sixꢀmembered ring with electronꢀdoꢀ
Scheme 4
Compound
X
O
S
O
R
Me
Et
m
—
—
3
Compound
X
O
S
S
R
Me
Et
m
2
3
10
11
12
13
14
15
Me
Et
2

Deeply colored anionic polymethine dyes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
831
nating effect in these positions, according to the Ferstꢀ
er—Dewar—Nott rule, decreases the excitation energy of
the dye. A combination of three factors, viz., the develꢀ
oped πꢀsystem of fluorene due to the specificity of its subꢀ
stitution at positions 2 and 7 mentioned above, the long
polymethine chain, and the concerted effect of the withꢀ
drawing substituent in the core and the donating substituꢀ
ent in the chain, provides very deep color of dye 8. Its
absorption maximum reaches 1044 nm, which is 208 and
166 nm more bathochromic than λmax for dyes 12 and 14,
respectively (Figs 2 and 3).
However, it is far inferior to the latter in the intensity
of absorption. It is due to the fact that the auxochromic
effect of the ionized oxygen atom, which is conjugated
with the polymethine chromophore through the sulfur
atom bearing considerable partial positive charge, is much
weaker than when it is directly conjugated with the chroꢀ
mophore. Yet further deepening of the color should be
reached upon introduction of saturated fiveꢀmembered ring
in δ,δ´ꢀpositions of the polymethine chain of the dye 8
instead of sixꢀmembered ring. This can be rationalized in
view that compound 9, in contrast to compound 8, is
capable of hyperconjugation not only of αꢀmethylene
groups of the ring with the chromophore chain, but also
directly between themselves.2 The absorption maximum
for the dye 9 reached 1086 nm in DMSO, which is deeper
by 218 and 170 nm than for its anionic analogs 13 and 15,
respectively (Fig. 4). This value along with the value of λmax
for the dye 3 is a top for the known anionic polymethine
dyes. However, the dye 9 has proved extremely unstable in
both the solid state and solution. It decomposed even
during recording of the absorption spectrum, which was
indicated by the increase in intensity and broadening of
the shortꢀwave side of the absorption band (see Fig. 2). We
failed in isolation of compound 9 in the individual state.
Cationic dyes based on the classic heterocycles menꢀ
tioned above come nearer to this region of absorption when
polymethine chain is longer. For example, cationic cyaꢀ
nine 16 (see Ref. 2) with λmax = 1026 nm in dichloꢀ
romethane (Fig. 5) contains eleven methine group in the
chain, whereas compound 8, nine of such groups.
ε•10–5/L mol–1 cm–1
1
0.5
0.4
0.3
2
4
3
0.2
5
0.1
600
800
1000
λ/nm
Fig. 2. Electronic absorption spectra of dye 8 in DMSO (1),
DMF (2), acetone (3), dichloromethane (4), and dichloroꢀ
methane with preliminary added DBU (5).
A unique feature of anionic dyes 8 and 9 is their high
selectivity of absorption (sharpness of the absorption band)
ε•10–5/L mol–1 cm–1
ε•10–5/L mol–1 cm–1
1
6
2.0
5
2.0
2
4
3
1.5
1.0
1.5
7
1.0
0.5
2
1
0.5
5
4
3
400
600
800
λ/nm
600
800
1000
λ/nm
Fig. 3. Electronic absorption spectra of dyes 12 (1—5) and 14 (6, 7)
in DMSO (1, 6), DMF (2), acetone (3), ethanol (4), and dichloꢀ
romethane (5, 7).
Fig. 4. Electronic absorption spectra of dyes 9 (1), 13 (2, 3), and
15 (4, 5) in DMSO (1, 2, 4) and dichloromethane (3, 5).

832
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kurdyukova et al.
ε•10–5/L mol–1 cm–1
Such tendencies in absorption spectra in polar solvents
are characteristic of anionic dyes 12—15 with terminal
heterocyclic groups. However, the intensities and shapes
of the bands for them change more considerably than for
polymethine 8 (see Figs 2—4). Consequently, they are
stronger subjected to specific solvation than dye 8. Most
likely, this is due to the greater unevenness in the charge
distribution in the chromophores of dyes 12—15 in compaꢀ
rison with the chromophore of polymethine 8 because of
stronger electronꢀwithdrawing power of barbituric and thioꢀ
barbituric residues in comparison with the fluorene one.
Unexpectedly, it turned out that in very weak in nuꢀ
cleophilicity and electrophilicity dichloromethane, anionic
dyes 8, 9, and 12—15 exhibit abnormal absorption curve
(see Figs 2—5). For compound 8, a sharp decrease in
intensity of the main band is observed and a new band with
3
2.0
1.5
1.0
0.5
2
1
400
600
800
1000
λ/nm
Fig. 5. Electronic absorption spectra of dye 16 in DMSO (1),
acetone (2), and dichloromethane (3).
λmax = 574 nm arises in the shortꢀwave region. Analogous
tendencies, rather less pronounced, are also observed for
dyes 12—15. Their bands are characterized by smaller fall
in intensities of the main maxima and weaker exhibition
of the new bands on the shortꢀwave edge with its noticeꢀ
able broadening. Upon addition of strongly polar solvents
such as acetonitrile, DMF, or DMSO to a solution of dyes
8 and 12—15 in dichloromethane, their absorption specꢀ
tra change toward restoration of the contours observed in
the individual polar solvents. This process is much stronꢀ
ger pronounced for compounds 12—15 than for dye 8.
It was found that the shape of the band for dyes 8, 9,
and 12—15 in dichloromethane, in contrast to polar solꢀ
vents, strongly depends on the nature of a counterion.
This indicates that the dyes form intimate ion pairs in the
solvent mentioned.
It is known6 that in weakly polar media, such pairs can
easily aggregate due to the electrostatic attraction forces
between opposite charges of counterions according to the
scheme Ct+...An–. This leads to noticeable changes in
absorption spectra.6 The fact that solutions of dyes 8, 9,
and 12—15 in dichloromethane obey the Lambert—Beer
law in the range of concentrations from 10–6 to 5•10–5
mol L–1 testifies that the dyes under study in the working
concentration range exist as monomeric nonassociated
intimate ion pairs.
Such a high probability to form intimate ion pairs in
dichloromethane and such significant spectral effects due
to them are not characteristic of the classic polymethine
dyes. The point is that in dichloromethane, they usually
exist as solvent separated ion pairs or even solvated ions.6
Electronic absorption spectra for these forms do not virtuꢀ
ally differ.6 To form fairly intimate ion pairs, solvents much
less polar and less solvating than dichloromethane are usuꢀ
ally required, for example, aliphatic and aromatic hydroꢀ
carbons.6 These were the solvents, in which, using cationꢀ
ic polymethines as an example, it was for the first time
found that the color of dyes in weakly polar media is deterꢀ
mined not only by the structure of chromophore but also
in strong polar solvents (see Figs 2 and 4), since it is very
problematic to reach it for the heterocycleꢀbased polyꢀ
methines with the long polymethine chain.6 It is due to
the considerably uneven distribution of the charge in the
chromophore when the chain is elongated, which leads to
the increase of specific electrostatic interactions with
functional groups of the solvent (nucleophilic and electroꢀ
philic solvation).6 This fact is clearly illustrated using
cationic thiapentacarbocyanine 9 as an example, for which
a replacement of weakly nucleophilic dichloromethane
(nucleophilicity B = 23 cm–1) with strongly nucleoꢀ
philic DMSO (В = 362 cm–1) leads to a considerable
fall in intensity and broadening of the absorption band
(see Fig. 5). Conversely, anionic dyes 8 and 9 have high
selectivity of absorption in both strongly nucleophilic and
strongly electrophilic solvents (see Figs 2 and 4) including
protonꢀdonor solvents. In all these solvents, the shape
of their absorption band retains the universal cyanine
contour, the sharp asymmetric one with very proꢀ
nounced vibrational maximum on the shortꢀwave side
of the band (see Figs 2 and 4). The intensity and contour
of the band virtually do not change. Consequently,
the dyes mentioned are weakly subjected to specific solvaꢀ
tion. This is confirmed by the fact that in polar solvents,
solvatochromism of dye 8 is determined primarily by
the universal interactions depending on the refractive inꢀ
dex of the solvent nD. For instance, polymethine 8 is
colored deeper in DMSO (λmax = 1044 nm) than in aceꢀ
tone (λmax = 1029 nm). Such a solvatochromic shift, acꢀ
cording to the stated rule on the influence of solvents
on the coloration of dyes,6 can be only due to the higher
value of nD for the former (nD = 1.4770) as compared to
the latter (nD = 1.3588), since considerably higher nuꢀ
cleophilicity and electrophilicity (E) of DMSO (E = 3.2)
should cause opposite effects (for acetone, B = 224 cm–1
and E = 2.1).

Deeply colored anionic polymethine dyes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
833
by the nature of a counterion.6 Anionic dyes 8, 9, and 12—15,
as it was noted above, are considerably weaker subjected
to specific solvation than cationic polymethines. Thereꢀ
fore, the solvent interferes with the electrostatic attraction
of counterions during formation of the intimate ion pair
for the former less as compared to the latter. Such an
attraction in the anionic dyes under study is even stronger
because of the positive charge on their counter cations is
more localized than the negative charge on widely prolifꢀ
erated counter anions ClO4–, BF4–, I– of cationic dyes. In
addition, an enhancement of electrostatic interactions of
oppositely charged counterions is possible for dyes 8, 9,
and 12—15 due to the hydrogen bonds between the proton
of the cation and the oxygen atoms of the anionic chroꢀ
mophore. In this connection, anionic dyes can form intiꢀ
mate pairs in more polar and solvating solvents than catꢀ
ionic dyes.
A hypsochromic shift of the absorption band during
formation of intimate ion pairs indicates that the energy of
the excited state of the dye decreases weaker as compared
to the ground state and, consequently, electrostatic atꢀ
traction of opposite charges of counterions in the state S1
is less than in the state S0. Most likely, this is due to
the reduction of the negative charge upon excitation in
the region of the cation localization. According to the
Franck—Condon principle, during absorption of a quanꢀ
tum of light cation has no time to rearrange in response to
the new electronic distribution in the anion of the dye,
even if it is more favorable than in the ground state.
Cation, localizing in the region of negatively charged
atom of the chromophore and exhibiting electronꢀ
withdrawing properties, according to the Ferster—Deꢀ
war—Nott1 rule, should also cause additional shortꢀwave
shift of the absorption band in weakly polar solvents.
Localization of the cation in the ion pair of dyes 8, 9,
and 12—15 in the region of any negatively charged atom
of the chromophore leads to a disturbance of its electronic
symmetry. It could have been retained only in the case if
the counterion is positioned in the region of the central
atom (meso position) of the polymethine chain. However,
a positive charge is concentrated on it (see Fig. 1), that
virtually excludes placement of the cation in this region.
Disturbance of the symmetry in the charge distribution in
the chromophore of an intimate ion pair causes alternaꢀ
tion of single and double bonds in it. This results in the
hypsochromic shift of the band and enhancement of viꢀ
bronic interactions; the latter, similarly to unsymmetric
polymethines,9 cause the broadening and fall in intensity
of the band.
However, it is not enough to explain the spectral efꢀ
fects observed in weakly polar solvents only by electrostatꢀ
ic influence of counterion in the ion pair on the absorption
spectra of the dyes under study, since they lead not only to
a hypsochromic shifts and broadening absorption bands,
but also to the emergence of new shortꢀwave bands
(see Figs 2—4). The latter circumstance points that chemꢀ
ical interaction can occur between counterions in the intiꢀ
mate ion pairs of the anionic dyes. It is logically to supꢀ
pose that in the process of electrophilic attack of a cation
on an anionic chromophore, a transition of the proton
from the former to the latter will take place. This, in turn,
will lead to a disturbance of the chromophore system.
If such a suggestion is true, then the spectral effect of
a protonꢀdonating cation (in our case, triethylammonium
and octahydropyrimido[1,2ꢀa]azepinium) in weakly polar
solvents should be similar to the action of acid additives.
To check this suggestion, we synthesized an analog of dye
12, compound 12a, with aprotic tetrabutylammonium catꢀ
ion (Scheme 5).
In polar solvents, the absorption spectra of compounds
12 and 12a are identical. However, already in dichloꢀ
romethane they are sharply different (Fig. 6). Upon addiꢀ
tion of acetic acid to a solution of dye 12a in dichloꢀ
romethane, a gradual drop in intensity of the longꢀwave
maximum down to its extinction occurs (Fig. 7). At the
same time, a new band with the shape characteristic of
polymethine dyes appears on the shortꢀwave edge, intenꢀ
sity of which increases. Its maximum coincides with that
for the shortꢀwave extreme in the spectrum of dye 12 in
dichloromethane (see Fig. 6). In less polar than dichloꢀ
romethane toluene, in which yet more intimate ion pairs
are formed, the absorption spectrum of dye 12 completely
imitates that for compound 12a in a mixture of dichloꢀ
romethane with acetic acid (see Figs 6 and 7) not only in
position of the curve, but also in the shape. Conversely, in
the spectrum of dye 12a in toluene, there are no bands
characteristic of acidic solutions (see Fig. 6). Addition of
a polar solvent or a base to a solution of dye 12 in toluene
Scheme 5

834
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kurdyukova et al.
ε•10–5/L mol–1 cm–1
Similarities in the changes of absorption spectra of dye
12 in weakly polar solvents and its cationic analog 12a in
acetic acid suggest that the anionic chromophore is protoꢀ
nated with the cation in polymethines 8, 9, and 12—15 in
dichloromethane and toluene. Apparently, they are first
protonated at the ionized oxygen atom to form stable neuꢀ
tral merocyanine form. The band contour, typical of cyaꢀ
nines, agrees with its merocyanine character, whereas
virtual identity of the contours for dyes 8 and 12—15
(see Figs 2—4) indicates the similarity of their protonated
forms. The absorption band of the merocyanine form is
hypsochromically shifted with respect to the band of the
anionic form because there is no more freely moving negaꢀ
tive charge in the chromophore. In this steps of protonaꢀ
tion, a recovery of the anionic form is possible upon addiꢀ
tion of both a base and a polar ionizing solvent. Note that
when dye 8 is dissolved in dichloromethane with prelimiꢀ
nary added DBU, the absorption spectrum also adopts the
shape characteristic of that in polar solvents (see Fig. 2).
Since a considerable negative charge is concentrated on
a number of carbon atoms of the chromophore, the proton
of the hydroxy group of the merocyanine form can migrate
to one of them. Then, the conjugation will be disturbed in
the polyene form of the dye and, consequently, a hypsoꢀ
chromic shift and broadening of the absorption band will
take place. Exactly such a picture has been described above.
With time, the tautomeric equilibrium should shift from
the merocyanine form to polyene as less acidic. This agrees
with the emergence and grow in intensity of the shortꢀ
wave wide bellꢀlike band when solutions of dyes 8, 9, and
12—15 are kept in weakly polar solvents. For compound
8, this process is very pronounced already in dichloꢀ
romethane, whereas for 12—15, in less polar toluene. The
higher sensitivity and, consequently, lower stability of the
first, apparently, is due to the higher fraction of the
polyene form in the tautomeric equilibrium in compariꢀ
son with the latter. This can be explained by a consiꢀ
derable reduction of the negative charge on the auxoꢀ
chromic oxygen atom of dye 8 as compared to those for
compounds 12—15 because of neighboring electronꢀwithꢀ
drawing sulfur atom. The polyene form emerged can deꢀ
compose irreversibly, for example, under the action of
air oxygen.
2.0
1.5
1.0
0.5
4
6
5
1
2
3
400
600
800
λ/nm
Fig. 6. Electronic absorption spectra of dyes 12 (1—3) and 12a
(4—6) in dichloromethane (1, 4), toluene (2, 5), and water (3, 6).
or in a mixture of dichloromethane with acetic acid, reꢀ
spectively, restors the shape of the curve to the shape in
polar solvents. In 100% acetic acid, the shortꢀwave band
of compound 12a with λmax = 564 nm virtually disapꢀ
pears, rather a hypsochromically shifted by 135 nm bellꢀ
like band appears instead (see Fig. 7). In the spectrum of
dye 12 in toluene, analogous band appears in several hours
after dissolution, whereas intensity of the curve with
λmax = 562 nm noticeably decreases. It is indicative that
these changes, in contrast to the initial ones leading to
significant restoration of the curve shape, are irreversible
under the action of both a base in the first case and a polar
solvent in the latter. At the same time, the absorption
spectrum of polymethine 12a in toluene changes reversꢀ
ibly upon addition of a polar solvent.
ε•10–5/L mol–1 cm–1
1
2.0
2
1.5
1.0
0.5
5
Note that dyes 12—15 have abnormal absorption specꢀ
tra in water too, despite its high polarity and ionizing
power (see Fig. 6). The spectra of compounds 12 and 12a
in water are virtually the same and resemble the spectrum
of dye 12 in dichloromethane in the shape of the bands,
rather with different ratio of intensities of the shortꢀwave
and longꢀwave maxima. The specificity of the water effect
consists in the fact that it, from the one hand, is capable of
enhancement of the cation—anion interactions due to the
hydrophobic interactions, i.e. increases possibility for the
formation of the intimate ion pair,10 and, from the other
hand, is an efficient transportation channel for a proton.11
3
4
6
400
600
800
λ/nm
Fig. 7. Electronic absorption spectra of dye 12a in a mixture
of dichloromethane with acetic acid in the ratios 100 : 0 (1),
100 : 0.5 (2), 100 : 2.5 (3), 100 : 5 (4), 100 : 10 (5), and 0 : 100 (6).

Deeply colored anionic polymethine dyes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
835
fluorenꢀ9ꢀylidene]pentꢀ2ꢀenꢀ3ꢀide (5). A mixture of compound 3
(150 mg, 0.2 mmol) and Nꢀ(5ꢀanilinopentaꢀ2,4ꢀdienylidene)ꢀ
anilinium chloride (4) (30 mg, 0.105 mmol) in pyridine (3.5 mL)
was heated in a burner flame until complete dissolution, DBU
(3 drops) was added, and this was heated at 135 °C for 20 min in
an oil bath. The solvent was evaporated at reduced pressure.
A dry residue was dissolved in acetonitrile and chromatographed
on alumina with acetonitrile in the presence of DBU as the
eluent. Concentration of pure fraction gave an oily mass. The
yield was 60 mg (35%). Found (%): C, 42.07; H, 3.03; S, 7.21.
C60H46F32N2O12S4. Calculated (%): C, 41.82; H, 2.69; S, 7.44.
EAS (DMSO), λmax/nm (ε): 790 (122000). 1H NMR (CD3CN),
δ: 1.579—1.750 (m, 4 H, CH2 cation); 1.880—1.986, 2.495—2.574
(both m, 2 H each, CH2 cation); 3.229 (t, 2 H, CH2 cation,
J = 6.0 Hz); 3.412 (t, 2 H, CH2 cation, J = 5.7 Hz); 3.446—3.520
(m, 2 H, CH2 cation); 4.623 (t, 8 H, O—CH2, J = 13.8 Hz);
6.369 (tt, 4 H, CF2H, J1 = 51.6 Hz, J2 = 5.4 Hz); 7.254—8.668
(m, 17 H, Ar).
2,3,4,6,7,8,9,10ꢀOctahydropyrimido[1,2ꢀa]azepinꢀ1ꢀium
1,9ꢀbis[2,7ꢀbis(2,2,3,3,4,4,5,5ꢀoctafluoropentyloxysulfonyl)ꢀ
fluorenꢀ9ꢀylidene]ꢀ5ꢀphenylꢀ4,6ꢀtrimethylenenonaꢀ2,4,6ꢀtrienꢀ8ꢀ
ide (8). A mixture of compound 3 (76 mg, 0.1 mmol) and Nꢀmethꢀ
ylꢀNꢀ[3ꢀ{3ꢀ[3ꢀ[NꢀmethylꢀNꢀphenylamino)propꢀ2ꢀenylidene]ꢀ
2ꢀphenylcyclohexꢀ1ꢀenꢀ1ꢀyl}propꢀ2ꢀenylidene]anilinium tetꢀ
rafluoroborate (6) (27 mg, 0.055 mmol) in pyridine (1 mL)
was heated until complete dissolution, after addition of DBU
(2 drops), it was heated for another 3 min. The solvent was
entirely evaporated at reduced pressure. The residue was washed
2 times with dry diethyl ether and decanted, a residual diethyl
ether was evaporated. Chromatography on silica gel (eluent,
acetonitrile with DBU (3 drops per 50 mL of the solvent) gave
product 8 (36 mg, 38%). Found (%): C, 46.57; H, 3.26; S, 6.54.
C73H59F32N2O12S4. Calculated (%): C, 46.33; H, 3.14; S, 6.78.
EAS (DMSO), λmax/nm (ε): 1044 (55300). 1H NMR (DMSOꢀd6),
δ: 1.503—1.709 (m, 4 H, CH2 cation); 1.880—1.986, 2.453—2.494
(both m, 2 H each, CH2 cation); 3.193 (t, 2 H, CH2 cation,
J = 6.0 Hz); 3.402 (t, 2 H, CH2 cation, J = 5.7 Hz); 3.422—3.487
(m, 2 H, CH2 cation); 4.919 (t, 8 H, O—CH2, J = 13.8 Hz);
6.515 (d, 2 H, H(1), H(6), J = 12.0 Hz); 7.039 (tt, 4 H, CF2H,
J1 = 50.7 Hz, J2 = 5.4 Hz); 7.387—7.885 (m, 9 H, Ar, H(3),
H(4)); 7.990 (t, 2 H, H(2), H(5), J = 13.2 Hz); 8.194, 8.386
(both s, 1 H each, Ar).
In fact, in alcohols, in which these both factors are proꢀ
nounced much weaker than in water, the shape of the
curve for dyes 12—15 comes nearer to that in polar aprotic
solvents (see Fig. 3).
In conclusion, a new type of deeply colored polymeꢀ
thine dyes containing no heterocycles as terminal groups
has been synthesized, the fluorene with electronꢀwithdrawꢀ
ing substituents has been shown to be a promising such
group. However, it should be taken into account that staꢀ
bility of the dyes strongly depend on the choice of a counꢀ
terion: it should not contain a proton. This factor is necesꢀ
sary to consider when choosing condensing agent in the
synthesis of the dyes. The point is that the cyanine
condensation can be applied to fluorene even with the
strongly electronꢀwithdrawing octafluoropentyloxysulfoꢀ
nyl groups at positions 2 and 7 still only in the presence
of strong organonitrogen bases (which form a countercaꢀ
tion containing the proton abstracted by them from
the methylene group of the substituted fluorene) due to
the low CH acidity. Therefore, a search for new strong
organic bases not inclined to capture a proton in these
reactions is actual.
Experimental
Absorption spectra were recorded on a Shimadzu UVꢀ3100
spectrophotometer in 1ꢀcm cuvettes with the concentration of
a dissolved substance being 10–5 mol L–1. Solvents were purified
following known procedures.12 Silica gelꢀ60 (Fluka) and alumiꢀ
naꢀ90 (Merck) were used for chromatography. Purity of the dyes
was monitored by TLC (Silufol UVꢀ254, acetonitrile was the
1
eluent). H NMR spectra were recorded on a Varian VXRꢀ300
spectrometer (299.945 MHz) with Me4Si as the internal stanꢀ
dard. Melting points were determined in unsealed capillary tubes
and uncorrected.
Bis(2,2,3,3,4,4,5,5ꢀoctafluoropentyl) 9Hꢀfluoreneꢀ2,7ꢀdiꢀ
sulfonate (3). A suspension of 2,7ꢀdi(chlorosulfonyl)fluorene
(1)13 (3.63 g, 0.01 mol) in the solution of freshly distilled
2,2,3,3,4,4,5,5ꢀoctafluoropentanꢀ1ꢀol (2) (9.28 g, 0.02 mol),
freshly distilled pyridine (2.4 g, 0.03 mol), and anhydrous acetoꢀ
nitrile (5 mL) was heated for 40 min at 80—90 °C with stirring.
A precipitate was completely dissolved after ~15 min, the heatꢀ
ing was stopped followed by addition of propanꢀ2ꢀol (15 mL) to
the mixture. A precipitate was filtered off, washed with propanꢀ
2ꢀol (3×5 mL), and stirred in hot water (50 mL). The hot mixꢀ
ture was filtered and the precipitate was washed with water on
the filter. The yield was 8 g (90%). M.p. 167—167.5 °C. Diester 3
was dissolved in boiling dioxane (25 mL) and the solution was
diluted with hot water (10 mL). Compound 3 (5.56 g, 74%) with
m.p. 167—167.5 °C was crystallized from the solution. Found
(%): C, 36.67; H, 1.99; S, 8.48. C23H14F16O6S2. Calculated (%):
C, 36.62; H, 1.87; S, 8.50. EAS (EtOH), λmax/nm (ε): 283
2,3,4,6,7,8,9,10ꢀOctahydropyrimido[1,2ꢀa]azepinꢀ1ꢀium
1,9ꢀbis[2,7ꢀbis(2,2,3,3,4,4,5,5ꢀoctafluoropentyloxysulfonyl)ꢀ
fluorenꢀ9ꢀylidene]ꢀ5ꢀphenylꢀ4,6ꢀdimethylenenonaꢀ2,4,6ꢀtrienꢀ8ꢀ
ide (9). A mixture of compound 3 (76 mg, 0.1 mmol) and Nꢀmethꢀ
ylꢀNꢀ[3ꢀ{3ꢀ[3ꢀ[NꢀmethylꢀNꢀphenylamino)propꢀ2ꢀenylidene]ꢀ
2ꢀphenylcyclopentꢀ1ꢀenꢀ1ꢀyl}propꢀ2ꢀenylidene]anilinium perꢀ
chlorate (7) (27 mg, 0.055 mmol) in DMSO (1 mL) was heated
until complete dissolution followed by addition of DBU (2 drops)
and heating for another 3 min. The solvent was completely evapꢀ
orated at reduced pressure. The dry residue was washed with
anhydrous diethyl ether. We failed in isolation of the product
in pure form because of its decomposition. EAS (DMSO),
λ
max/nm: 1086.
1
(31800), 295 (26700), 306 (32000). H NMR (CDCl3), δ: 4.168
Triethylammonium 5ꢀ(3ꢀ{3ꢀ[3ꢀ(1,3ꢀdimethylꢀ2,4,6ꢀtrioxoꢀ
(s, 2 H, CH2); 4.556 (t, 4 H, O—CH2, J = 13.2 Hz); 6.003 (tt, 2 H,
CF2H, J1 = 51.9 Hz, J2 = 5.1 Hz); 8.031—8.101 (m, Ar); 8.197
(s, 2 H, Ar).
2,3,4,6,7,8,9,10ꢀOctahydropyrimido[1,2ꢀa]azepinꢀ1ꢀium
1,5ꢀbis[2,7ꢀbis(2,2,3,3,4,4,5,5ꢀoctafluoropentyloxysulfonyl)ꢀ
tetrahydropyrimidinꢀ5(2H)ꢀylidene)propꢀ1ꢀenyl]ꢀ2ꢀphenylcycloꢀ
hexꢀ2ꢀenꢀ1ꢀylidene}propꢀ1ꢀenyl)ꢀ1,3ꢀdimethylꢀ2,6ꢀdioxoꢀ1,2,3,6ꢀ
tetrahydropyrimidinꢀ4ꢀolate (12). A mixture of 1,3ꢀdimethylbarꢀ
bituric acid (10) (31 mg, 0.2 mmol) and compound 6 (54 mg,
0.1 mmol) in minimum pyridine with addition of triethylamine

836
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kurdyukova et al.
was heated in the burner flame for 3 min, that led to precipiꢀ
tation of the product. The mother liquor was purified by chroꢀ
matography on silica gel (eluent, acetonitrile with triethylꢀ
amine) and recrystallized from acetonitrile. The yield was
44 mg (68%). M.p. 196 °C. Found (%): C, 67.18; H, 7.06;
N, 10.89. C36H45N5O6. Calculated (%): C, 67.16; H, 7.05;
by chromatography on silica gel (eluent, acetonitrile with addiꢀ
tive of triethylamine), and recrystallized from acetonitrile. The
yield was 40 mg (55%). M.p. 212 °C. Found (%): C, 65.05;
H, 7.33; N, 9.51; S, 8.78. C40H53N5O4S2. Calculated (%):
C, 65.03; H, 7.30; N, 9.57; S, 8.76. EAS (DMSO), λmax/nm (ε):
878 (222800). 1H NMR (DMSOꢀd6), δ: 1.129 (t, 12 H, CH3CH2N,
J = 6.6 Hz); 1.163 (t, 9 H, CH3CH2N cation, J = 7.5 Hz);
1.820—1.949 (m, 2 H, CH2 ring); 2.582 (t, 4 H, CH2 ring,
J = 4.8 Hz); 3.081 (q, 6 H, CH3CH2N cation, J = 7.5 Hz); 4.376
(q, 8 H, CH3CH2N, J = 6.6 Hz); 6.498 (d, 2 H, H(1), H(6),
J = 13.2 Hz); 7.119—7.191 (m, 2 H, Ar); 7.184 (d, 2 H, H(3),
H(4), J = 13.8 Hz); 7.464—7.543 (m, 3 H, Ar); 7.765 (t, 2 H,
H(2), H(5), J = 13.5 Hz).
1
N, 10.88. EAS (DMSO), λmax/nm (ε): 836 (112900). H NMR
(DMSOꢀd6), δ: 1.162 (t, 9 H, CH3CH2N, J = 7.5 Hz);
1.811—1.940 (m, 2 H, CH2 ring); 2.488—2.593 (m, 4 H, CH2
ring); 3.081 (q, 6 H, CH3CH2N, J = 7.5 Hz); 6.400 (d, 2 H,
H(1), H(6), J = 13.5 Hz); 7.090—7.187 (m, 2 H, Ar); 7.137
(d, 2 H, H(3), H(4), J = 13.2 Hz); 7.430—7.541 (m, 3 H, Ar);
7.640 (t, 2 H, H(2), H(5), J = 13.2 Hz).
Tetrabutylammonium 5ꢀ(3ꢀ{3ꢀ[3ꢀ(1,3ꢀdimethylꢀ2,4,6ꢀtriꢀ
oxotetrahydropyrimidinꢀ5(2H)ꢀylidene)propꢀ1ꢀenyl]ꢀ2ꢀphenylꢀ
cyclohexꢀ2ꢀenꢀ1ꢀylidene}propꢀ1ꢀenyl)ꢀ1,3ꢀdimethylꢀ2,6ꢀdioxoꢀ
1,2,3,6ꢀtetrahydropyrimidinꢀ4ꢀolate (12a). A 2ꢀfold excess of tetꢀ
rabutylammonium iodide (74 mg, 0.2 mmol) was added to
a solution of dye 12 (63 mg, 0.1 mmol) in EtOH and this was
diluted with a large amount of water. A precipitate obtained was
washed clean with water. The yield was 56 mg (71%). M.p.
209—210 °C. Found (%): C, 70.39; H, 8.28; N, 8.96. C46H65N5O6.
Calculated (%): C, 70.47; H, 8.36; N, 8.93. EAS (CH2Cl2),
Triethylammonium 5ꢀ(3ꢀ{3ꢀ[3ꢀ(1,3ꢀdiethylꢀ4,6ꢀdioxoꢀ2ꢀ
thioxotetrahydropyrimidinꢀ5(2H)ꢀylidene)propꢀ1ꢀenyl]ꢀ2ꢀphenylꢀ
cyclopentꢀ2ꢀenꢀ1ꢀylidene}propꢀ1ꢀenyl)ꢀ1,3ꢀdiethylꢀ6ꢀoxoꢀ2ꢀthiꢀ
oxoꢀ1,2,3,6ꢀtetrahydropyrimidinꢀ4ꢀolate (15). A mixture of comꢀ
pound 7 (53 mg, 0.1 mmol) and acid 11 (40 mg, 0.2 mmol) was
dissolved in minimum pyridine, this was heated up followed by
addition of triethylamine (5 drops). The reaction course was
monitored spectrophotometrically on the maximum at 908 nm.
After the reaction was complete, the product was precipitated
with anhydrous diethyl ether and chromatographed on silica gel
(eluent, dichloromethane with additives of acetonitrile and triꢀ
ethylamine). The pure fraction was concentrated. The yield was
30 mg (41.8%). M.p. 188 °C. Found (%): C, 65.19; H, 7.10;
N, 9.71; S, 8.95. C39H51N5O4S2. Calculated (%): C, 65.24;
H, 7.16; N, 9.75; S, 8.93. EAS (CH2Cl2), λmax/nm (ε): 908
(183500). 1H NMR (DMSOꢀd6), δ: 1.148 (t, 12 H, CH3CH2N,
J = 6.9 Hz); 1.166 (t, 9 H, CH3CH2N cation, J = 7.2 Hz); 2.882
(s, 4 H, CH2 ring); 3.038—3.151 (m, 6 H, CH3CH2N cation);
4.400 (q, 8 H, CH3CH2N, J = 6.9 Hz); 6.847 (d, 2 H, H(1),
H(6), J = 13.2 Hz); 7.258—7.348 (m, 2 H, Ar); 7.408 (d, 2 H,
H(3), H(4), J = 13.8 Hz); 7.496—7.604 (m, 3 H, Ar); 7.680 (t, 2 H,
H(2), H(5), J = 13.2 Hz).
λ
max/nm (ε): 830 (210300). 1H NMR (DMSOꢀd6), δ: 0.890
(t, 12 H, CH3CH2CH2CH2N, J = 6.9 Hz); 1.265 (q, 8 H,
CH3CH2CH2CH2N, J = 6.9 Hz); 1.451—1.600 (m, 8 H,
CH3CH2CH2CH2N); 1.780—1.895 (m, 2 H, CH2 ring); 2.461
(s, 8 H, CH3CH2CH2CH2N); 3.056—3.181 (m, 4 H, CH2 ring);
3.074 (s, 12 H, CH3N); 6.366 (d, 2 H, H(1), H(6), J = 13.8 Hz);
7.050—7.172 (m, 2 H, Ar); 7.106 (d, 2 H, H(3), H(4), J =
= 13.5 Hz); 7.400—7.511 (m, 3 H, Ar); 7.605 (t, 2 H, H(2), H(5),
J = 14.1 Hz).
Triethylammonium 5ꢀ(3ꢀ{3ꢀ[3ꢀ(1,3ꢀdimethylꢀ2,4,6ꢀtriꢀ
oxotetrahydropyrimidinꢀ5(2H)ꢀylidene)propꢀ1ꢀenyl]ꢀ2ꢀphenylꢀ
cyclopentꢀ2ꢀenꢀ1ꢀylidene}propꢀ1ꢀenyl)ꢀ1,3ꢀdimethylꢀ2,6ꢀdioxoꢀ
1,2,3,6ꢀtetrahydropyrimidinꢀ4ꢀolate (13). A mixture of acid 10
(31 mg, 0.2 mmol) and compound 7 (53 mg, 0.1 mmol) in miniꢀ
mum pyridine with addition of triethylamine was heated in
a burner flame for 3 min, that led to precipitation of the product.
The mother liquor was concentrated and purified by chromatogꢀ
raphy on silica gel (eluent, acetonitrile with triethylamine). The
product was recrystallized from a large amount of acetonitrile to
obtain compound 13 (18 mg, 29%). M.p. 201 °C. Found (%):
C, 66.70; H, 6.82; N, 11.15; C35H43N5O6. Calculated (%):
C, 66.75; H, 6.88; N, 11.12. EAS (acetone), λmax/nm (ε): 854
Quantum chemical calculations were performed using the
AM1 ab initio method with a standard set of parameters.14 The
initial optimization of molecular geometries by the same method
was made using the limited Hartree—Fock method and the Polꢀ
lock—Rebiere algorithm with accuracy 0.001 kcal Å–1 mol–1
.
References
1. A. I. Kiprianov, Tsvet i stroenie tsianinovykh krasitelei [Color
and Structure of Cyanine Dyes], Naukova Dumka, Kiev, 1979,
666 pp. (in Russian).
1
(225000). H NMR (DMSOꢀd6), δ: 1.196 (t, 9 H, CH3CH2N,
J = 7.0 Hz); 2.458—2.512 (m, 2 H, CH2 ring); 3.041—3.110
(m, 6 H, CH3CH2N); 3.152 (s, 12 H, CH3N); 6.725 (d, 2 H,
H(1), H(6), J = 13.8 Hz); 7.228—7.278 (m, 2 H, Ar); 7.383 (d, 2 H,
H(3), H(4), J = 13.5 Hz); 7.501 (t, 2 H, H(2), H(5), J = 13.8 Hz);
7.434—7.557 (m, 3 H, Ar).
Triethylammonium 5ꢀ(3ꢀ{3ꢀ[3ꢀ(1,3ꢀdiethylꢀ4,6ꢀdioxoꢀ2ꢀ
thioxotetrahydropyrimidinꢀ5(2H)ꢀylidene)propꢀ1ꢀenyl]ꢀ2ꢀphenylꢀ
cyclohexꢀ2ꢀenꢀ1ꢀylidene}propꢀ1ꢀenyl)ꢀ1,3ꢀdiethylꢀ6ꢀoxoꢀ2ꢀthiꢀ
oxoꢀ1,2,3,6ꢀtetrahydropyrimidinꢀ4ꢀolate (14). A mixture of comꢀ
pound 6 (54 mg, 0.1 mmol) and 1,3ꢀdiethylthiobarbituric acid
(11) (40 mg, 0.2 mmol) was dissolved in minimum pyridine and
heated for 1 min followed by addition of triethylamine (5 drops).
The reaction course was monitored spectrophotometrically on
the maximum at 878 nm. After the reaction was complete, the
product was precipitated with anhydrous diethyl ether, purified
2. A. I. Tolmachev, Yu. L. Slominskii, A. A. Ishchenko, NATO
ASI Series. 3, Eds S. Daehne, U. ReschꢀGenger, O. S. Wolfbeis,
Kluwer Academic Publishers, Dordrecht—Boston—London,
1998, 52, p. 385.
3. W. S. Matthews, J. E. Bares, J. E. Bartmess, F. G. Bordwell,
F. J. Cornforth, G. E. Drucker, Z. Margolin, R. J. McCalꢀ
lum, G. J. McCollum, N. R. Vanier, J. Am. Chem. Soc.,
1975, 97, 7006.
4. V. I. Popov, V. T. Skripkina, S. P. Protsyk, A. A. Skrynnikoꢀ
va, B. M. Krasovitskii, L. M. Yagupol´skii, Ukr. Khim. Zh.,
1991, 57, 843 (in Russian).
5. A. V. Kulinich, N. A. Derevyanko, A. A. Ishchenko, J. Phoꢀ
tochem. Photobiol. A, 2007, 188, 207.
6. A. A. Ishchenko, Stroenie i spektral´noꢀlyuminestsentnye
svoistva polimetinovykh krasitelei [Structure and Spectroꢀlumiꢀ

Deeply colored anionic polymethine dyes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
837
nescent Properties of Polymethine Dyes], Naukova Dumka,
Kiev, 1994, 232 pp. (in Russian).
7. R. Kuhn, H. Fischer. F. A. Neugebauer, H. Fischer, Ann.,
1962, 654, 64.
8. H. G. Mantner, E. M. Clauton, J. Am. Chem. Soc., 1959, 81,
6270.
9. A. A. Ishchenko, N. A. Derevyanko, V. A. Svidro, Dyes and
Pigments, 1992, 19, 169.
12. A. J. Gordon, R. A. Ford, The Chemist’s Companion. A Handꢀ
book of Practical Data, Techniques and References, John Wiley
and Sons, New York, 1972, 541 pp.
13. P. C. Dutto, D. Mandal, J. Ind. Chem. Soc., 1956, 33, 721;
Abstr. Zh. Khim., 1958, 26136.
14. J. J. P. Stewart, J. Computer—Aided Molecular Design, 1990,
4, 1.
10. A. A. Ishchenko, N. A. Derevyanko, S. V. Popov, Yu. L.
Slominskii, V. A. Koval´, S. A. Shapovalov, N. O. Mchedꢀ
lovꢀPetrosyan, Izv. Akad. Nauk, Ser. Khim., 1997, 950 [Russ.
Chem. Bull. (Engl. Transl.), 1997, 46, 950].
11. T. Moriya, Bull. Chem. Soc. Jpn, 1983, 56, 6.
Received October 7, 2008;
in revised form December 24, 2008