Synthesis and UV/Vis spectra of J-aggregating 5,5′,6,6′-tetrachlorobenzimidacarbocyanine dyes for artificial light-harvesting systems and for asymmetrical generation of supramolecular helices

Article abstract of DOI:10.1002/ejoc.200300095

A new class of dyes, in which the self-assembling property of surfactants is combined with the capability for light energy propagation over long distances in dye J-aggregates, is described. This has been achieved by the syntheses of achiral 5,5′,6,6′-tetrachlorobenzimidacarbocyanine dyes 1, possessing systematically varied hydrophobic and hydrophilic substituents at their nitrogen atoms. These substituents are introduced into the 5,6-dichlorobenzimidazole precursor 3 by substitution, either firstly by nucleophilic reaction with ω-bromoalkylnitriles and secondly by quaternization with alkyl bromides (route II) or firstly by nucleophilic reaction with alkyl bromides and secondly by quaternization with ω-bromoalkylnitriles or ω-bromoalkyl esters (route III) and subsequent saponification. The UV/Vis spectra of 20 differently substituted dyes containing the same chromophore 1 have been investigated. The spectra of the dye monomers in dimethyl sulfoxide are nearly identical, with no signs of optically activity, whereas in aqueous alkaline solutions quite different spectra are obtained for the dyes, indicating the formation of different aggregates depending on the nitrogen substituents. One of these types of J-aggregate is optically inactive and displays a single red-shifted (with respect to the dye monomers) absorption band, resembling the behaviour of J-aggregates of common cyanine dyes. In the cases of strongly amphiphilic 5,5′,6,6′-benzimidacarbocyanines 1 with 1,1′-dialkyl substituents longer than hexyl and 3,3′-bis(2-carboxyethyl), 3,3′-bis(3-carboxypropyl) or 3,3′-bis(3-sulfopropyl) substituents, a new type of J-aggregate is formed, and is distinguished by a doubly or even triply split J-absorption band that displays optical activity. A third type of aggregate showing different spectral behaviour occurs when the dyes contain very short 3,3′-bis(carboxymethyl) substituents or strongly hydrophobic fluorinated octyl groups, or when all four nitrogen atoms are identically substituted by hydrophilic 3-carboxypropyl groups. The various types of dye aggregates have been characterized through UV/Vis spectroscopic parameters such as the positions and widths of the absorption and fluorescence bands, the Stokes' shifts, the coupling constants, and the strength of the J-band splitting. The results provide new prospects for the development of new artificial light-harvesting systems as well as for the understanding of the evolution of asymmetry in the biosphere. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejoc.200300095

FULL PAPER
Synthesis and UV/Vis Spectra of J-Aggregating 5,5Ј,6,6Ј-
Tetrachlorobenzimidacarbocyanine Dyes for Artificial Light-Harvesting
Systems and for Asymmetrical Generation of Supramolecular Helices
[b][‡‡]
Andreas Pawlik,[a][‡] Andre Ouart,
Stefan Kirstein,[a][‡‡‡] Hans-Werner Abraham,[b] and
´
Siegfried Daehne*[c][‡‡‡‡]
In commemoration of Walter König and of Günter Scheibe[†]
Keywords: Aggregation / Amphiphiles / Chirality / Cyanine dyes / UV/Vis spectroscopy
A new class of dyes, in which the self-assembling property of
behaviour of J-aggregates of common cyanine dyes. In the
surfactants is combined with the capability for light energy cases of strongly amphiphilic 5,5Ј,6,6Ј-benzimidacarbocyan-
propagation over long distances in dye J-aggregates, is de- ines 1 with 1,1Ј-dialkyl substituents longer than hexyl and 3,3Ј-
scribed. This has been achieved by the syntheses of achiral bis(2-carboxyethyl), 3,3Ј-bis(3-carboxypropyl) or 3,3Ј-bis(3-sul-
5,5Ј,6,6Ј-tetrachlorobenzimidacarbocyanine dyes 1, possessing fopropyl) substituents, a new type of J-aggregate is formed,
systematically varied hydrophobic and hydrophilic substitu-
and is distinguished by a doubly or even triply split J-absorp-
ents at their nitrogen atoms. These substituents are introduced tion band that displays optical activity. A third type of aggreg-
into the 5,6-dichlorobenzimidazole precursor 3 by substitution, ate showing different spectral behaviour occurs when the dyes
either firstly by nucleophilic reaction with ω-bromoalkylnitriles
contain very short 3,3Ј-bis(carboxymethyl) substituents or
and secondly by quaternization with alkyl bromides (route II)
strongly hydrophobic fluorinated octyl groups, or when all four
or firstly by nucleophilic reaction with alkyl bromides and sec- nitrogen atoms are identically substituted by hydrophilic 3-car-
ondly by quaternization with ω-bromoalkylnitriles or ω-bro- boxypropyl groups. The various types of dye aggregates have
moalkyl esters (route III) and subsequent saponification. The been characterized through UV/Vis spectroscopic parameters
UV/Vis spectra of 20 differently substituted dyes containing such as the positions and widths of the absorption and fluores-
the same chromophore 1 have been investigated. The spectra
cence bands, the StokesЈ shifts, the coupling constants, and
of the dye monomers in dimethyl sulfoxide are nearly identical, the strength of the J-band splitting. The results provide new
with no signs of optically activity, whereas in aqueous alkaline prospects for the development of new artificial light-harvesting
solutions quite different spectra are obtained for the dyes, in- systems as well as for the understanding of the evolution of
dicating the formation of different aggregates depending on asymmetry in the biosphere.
the nitrogen substituents. One of these types of J-aggregate is
optically inactive and displays a single red-shifted (with re-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
spect to the dye monomers) absorption band, resembling the Germany, 2003)
Introduction
ver halide photography since 1873.[1] In the last three dec-
ades they have been widely applied in laser physics as active
laser media and passive Q-switches,[2] as well as in nonlinear
optics.[3] In a polar environment such as water, many cyan-
ine dyes form so-called J-aggregates, which possess red-
shifted and remarkably narrow J-bands of very high ab-
sorbance and fluorescence intensity relative to the absorp-
tion spectra of the corresponding monomeric molecules.[4]
Such aggregates are increasingly becoming important in
high technology fields such as imaging sciences, photonics,
optoelectronics and nonlinear optics, because they are cap-
able of very fast electron transfer and excitonic energy
propagation processes across long distances. In this way
they are able to store light energy and to release it at any
time and at any spot where it is needed.[5,6] Furthermore,
these properties also make them candidates for artificial
light-harvesting systems in PET reactions.[7]
Cyanines are common dyes in spectral sensitization of
photoinduced electron transfer (PET) reactions, used in sil-
[a]
Max-Planck-Institute of Colloids and Interfaces,
Am Mühlenberg 2, 14476 Golm/Potsdam, Germany
[b]
Institute of Chemistry, Humboldt University,
Brook-Taylor-Straße 2, 12489 Berlin, Germany
[c]
Federal Institute for Materials Research and Testing,
Richard-Willstaetter-Straße 11, 12489 Berlin, Germany
[‡]
New adress: Degussa AG, Paul-Baumann-Straße 1, 45764
Marl, Germany
[‡‡]
New adress: Pfizer GmbH. 76139 Karlsruhe, Pfizerstraße 1,
Germany
[‡‡‡]
New adress: Institute of Physics, Humboldt University of
Berlin, Newtonstrasse 15, 12489 Berlin, Germany
[‡‡‡‡] New private adress: Kastanienallee 6, 12587 Berlin, Germany
[†]
Walter König originated the polymethine concept in 1926,[45]
Günther Scheibe discovered light energy migration in
aggregated polymethines in 1937.[46]
Eur. J. Org. Chem. 2003, 3065Ϫ3080
DOI: 10.1002/ejoc.200300095
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3065

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
Hitherto, the main obstacle for broader applications of ments.[13,14] Their exciton delocalization length spans over
J-aggregates in the fields described above had been that the about 40 molecules at 1.5 K.[13] Even at room temperature
morphologies of the J-aggregates could not be controlled. it amounts to about 15 molecules.[14]
It was only by chance that one-dimensional threads or two-
Self-organization of dye 1 derivatives in aqueous alkaline
dimensional layers were formed when cyanine dyes were solution yields supramolecular entities with distinct spectral
dissolved in aqueous solutions,[4] adsorbed on silver hal- behaviour[11,15] and different morphologies[16] depending on
ides,[8] or embedded in LangmuirϪBlodgett layers.[7] In or- the various substituents on the 1,1Ј,3,3Ј-nitrogen atoms.
der to overcome this problem, the J-aggregation capability Even minor structural variations in the substituents may
of cyanine dyes was combined by one of us[6,9] with the well effect drastic changes in the supramolecules’ architectures,
explored self-organization property of amphiphilic mol- apart from certain spectral modifications. For instance, dye
ecules in supramolecular chemistry,[10] by making the cyan- 1C, m ϭ 2, n ϭ 4, forms achiral monomolecular layers in a
ine molecules themselves strongly amphiphilic through the ’’brickwork’’ arrangement,[4,16] dye 1C, m ϭ 8, n ϭ 3, gener-
introduction on one hand of hydrophobic substituents such ates optically active nanotubes,[17] dye 1B, n ϭ 3, with 3,3Ј-
as long alkyl groups and, on the other hand, of polar, bis(3-carboxypropyl) substituents instead of 3,3Ј-bis(3-sul-
hydrophilic substituents such as acidoalkyl groups.[9,11]
fopropyl) moieties, is likewise optically active[18] and gives
The 5,5Ј,6,6Ј-tetrachloro-1,1Ј-dialkyl-3,3Ј-bis(ω-acidoal- chiral superhelices of unequal parity,[16,19] while dye 1B, n ϭ
kyl)benzimidacarbocyanine chromophore 1 (c.f. Scheme 1) 4, with 3-carboxypropyl groups each prolonged only by one
was used first, as a model compound. The J-aggregates of methylene group, yields stacks of achiral bilayer ribbons.[16]
the 1,1Ј-diethyl-3,3Ј-bis(4-sulfobutyl)-substituted chromo- The spectral behaviour and morphologies of such nanopar-
phore (dye, 1C, m ϭ 2, n ϭ 4) are applied technically in ticles are further strongly modified in the presence of sur-
spectral sensitization of photographic silver halide emul- factants[15,20,21] and of alcohols.[15,22,23] For instance, the
sions.[4] The free energy for aggregate formation of these superhelices of dye 1B, n ϭ 3, can be uncoiled to form sin-
compounds is much higher than any other intermolecular gle helices,[23] converted into nanotubes of varying diam-
interaction energy in organic chemistry, amounting to eters,[20,21] or even transformed into single- and double-
96 kJ·molϪ1 per dye dimer.[12] The exciton propagation walled vesicles.[20]
ability of these J-aggregates has been intensely investigated
The excitonic energy propagation abilities indicated by the
by time-resolved laser spectroscopic techniques such as spectral behaviour in the visible region are maintained in
time-resolved fluorescence spectroscopy, ultrafast pump- most of the self-organized supramolecular particles of dyes
probe spectroscopy and accumulated photon echo experi- 1. Owing to the spectral behaviour in the visible region, the
Scheme 1. Investigated 5,5Ј6,6Ј-tetrachlorobenzimidacarbocyanine dyes 1
3066
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
excitonic energy propagation ability is maintained in most designated amphipipes.[22] The new linear and nonlinear
of the self-organized supramolecular particles of dyes 1. spectral features of cylindrically shaped amphipipes
This has been definitely verified in the case of the cylindri- prompted Knoester et al. to extend the molecular exciton
cal helices of dye 1A, m ϭ 8, by use of time-resolved fluor- model developed by McRae and Kasha for one- and two-
escence spectroscopy, ultrafast pump-probe spectroscopy dimensional J-aggregates[28] to three-dimensional molecu-
and accumulated photon echo experiments.[24,25] It turned lar cylinders.[22,29,30]
out[25] that the excitons are not only cyclically delocalized
An especially interesting topic in this new field of re-
through the ring planes of the cylinders but also along cer- search is the spontaneous generation of optically active J-
tain segments of them. The delocalization lengths of the aggregates from the achiral dye monomers, first discovered
excitons in cylindrical helices amount to about 95 molecules by De Rossi et al.,[18] using dye 1A, m ϭ 8, with 1,1Ј-dioctyl
at 1.5 K and are reduced to about 70 molecules at 80 K.
and 3,3Ј-carboxypropyl substituents. The J-absorption
Previously in supramolecular chemistry it has been as- band is split into two or even three peaks, depending on
sumed that the driving forces of self-organization are usu- the preparation conditions.[15,22] These peaks exhibit strong
ally hydrogen bonding, hydrophobicity, van der Waals, circular dichroism in the form of couplets, which had first
Coulomb and charge transfer interactions and, occasion- been interpreted in terms of Davydov splitting caused by
ally, weak π-π interactions of aromatic building units.[10,26] the presence of translationally nonequivalent molecules in
Such forces have free energies of association approaching the unit cell.[18] Later, H. Kuhn et al.[31] and Kirstein et
60 kJ·molϪ1 at maximum.[10,15] By way of contrast, the pre- al.[11] suggested helical models to explain the J-aggregates’
vailing driving force of self-organization of J-aggregates is optical activity. This was indeed confirmed by von
the already mentioned, much stronger π-π coupling be- Berlepsch et al.,[16] by cryotransmission electron microscopy
tween the chromophores, reaching values of 100 kJ·molϪ1 (cryo-TEM). The J-aggregates of dye 1A, m ϭ 8 (identical
and more.[12,15] The strong coupling is obviously caused by with 1B, n ϭ 3, cf. Table 1) spontaneously and enantioselec-
the extremely high π-electronic polarizabilities of polyme- tively generate the previously mentioned superhelices con-
thine dyes,[27] which closely approach the ideal polyme- sisting of three to ten rope-like twisted single strands, the
thine state.[5]
spectral behaviour of which correlates well with Knoester’s
This new class of supramolecular amphiphiles with pig- new exciton model for three-dimensional molecular cylin-
ment interaction performing exciton migration has been ders, as described above.
Table 1. UV/Vis absorption and fluorescence data of monomeric dyes 1 in dimethyl sulfoxide solution: Maximum molar extinction
coefficient: εmax; wavelength of the absorption (abs) and fluorescence (em) maximum: λmax; halfwidth (FWHM) of the absorption (abs)
and fluorescence (em) band: ∆ν˜1/2; StokesЈ shift: ∆Stokes
[a]
abs
abs
em
em
Dye
εmax
λ
∆ν˜
λ
∆ν˜
∆
Stokes
Aggregate
Type
max
1/2
max
1/2
[103 cm2 mmolϪ1
]
[nm]
[cmϪ1
]
[nm]
[cmϪ1
]
[cmϪ1
]
Series A
1A, m ϭ 2
1A, m ϭ 4
1A, m ϭ 6
1A, m ϭ 7
1A, m ϭ 8
1A, m ϭ 10
1A, m ϭ 11
1A, m ϭ 12
71%
51%
184.0
89%
185.5 Ϯ2.4
56%
524.5
528.5
528
1142
1215
1114
1357
1436
1421
1395
1249
540
547
545
546
547
546
546
546
1052
1072
1051
1044
1038
1045
1050
1099
547
640
591
624
693
660
660
589
I
I
I
528
528
527
527
II
II
II
II, I
II
51%
22%
529
Series B
1B, n ϭ 1
1B, n ϭ 2
1B, n ϭ 3[b]
1B, n ϭ 4
1B, n ϭ 5
85%
65%
185.5 Ϯ2.4
183.1 Ϯ2.7
81%
526
527
528
529
528
1068
1208
1436
1262
1345
540
545
547
544
546
912
980
1038
1052
1037
493
627
693
521
624
III
III
II
I
I
Series C
1C, (BIC) m ϭ 2, n ϭ 3
1C, (TDBC) m ϭ 2, n ϭ 4
1C, m ϭ 4, n ϭ 4
77%
185.6 Ϯ1.1
21%
182.1 Ϯ2.2
183.3 Ϯ3.1
27%
525.7
525
1195
1157
1297
1922
1373
1326
542
543
546
549
547
546
1004
1024
1036
1058
1015
983
572
631
624
689
658
624
I
I
I
III
I ϩ II
I
528
529
1C, m ϭ 8, n ϭ 2[c]
1C, m ϭ 8, n ϭ 3
528.5
528
1C, m ϭ 8, n ϭ 4
Series D/E
1D
1E
83%
56%
527
1357
1755
545.5
548
1091
1074
644
796
III
III
525.1
[a]
Percentage of εmax calculated on the assumption that the average molar extinction coefficient εmax of dyes 1 amounts to 185.0 [103
cm2 mmolϪ1]. Identical with 1A, m ϭ 8. In methanol.
[b]
[c]
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3067

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
In order to obtain deeper insight into the relationships sulfoalkyl) substituted dyes, or with ω-bromoalkylnitriles or
between the structures of the dye monomers and the mor- alkanoic acid ethyl esters in the case of the 3,3Ј-bis(ω-car-
phologies of their supramolecular aggregates, the substitu- boxyalkyl) substituted dyes, and subsequently saponified.
ents on the 1,1Ј- and 3,3Ј-nitrogen atoms of the 5,5Ј,6,6Ј- Two equivalents of the 1-alkyl-3-(ω-carboxyalkyl)-5,6-di-
tetrachlorobenzimidacarbocyanine chromophore 1 were chloro-2-methylbenzimidazolium bromides 6 thus obtained
systematically varied, and the spectral behaviour in the vis- are transformed into the respective benzimidacarbocyanine
ible region both of the monomers and of the aggregates of dyes 1 by treatment with iodoform in the presence of so-
these new dyes in solution is described.
dium methoxide.[9]
For economic reasons we developed new synthetic routes,
also shown in Scheme 2. 4,5-Dichloro-ortho-phenylenedi-
amine (2) was condensed with acetic acid according to Dan-
degaonker and Kanabur,[32] yielding the 5,6-dichlorobenzi-
midazole 3, which serves as the starting compound for
variation both of the substituents on the 1,1Ј- and the 3,3Ј-
nitrogen atoms.
Results and Discussion
Synthetic Routes
According to the literature, 5,5Ј,6,6Ј-tetrachloro-1,1Ј-di-
n-alkyl-3,3Ј-bis(ω-carboxyalkyl)benzimidacarbocyanine
dyes 1 are synthesized in a four-step procedure (c.f.
In reaction route II, the 3-(3-cyanopropyl) group is first
Scheme 2, route I) starting from 2,4,5-trichloronitrobenzene introduced through nucleophilic reaction between 3 and ω-
7, which is converted by treatment with n-alkylamines into bromoalkylnitriles to give compounds 4, which are con-
4,5-dichloro-ortho-nitroanilines 8. Reduction and simul- comitantly quaternized with n-alkyl bromides and hydro-
taneous cyclization with acetic acid then gives 4,5-dichloro- lysed to give 1-alkyl-3-(3-carboxypropyl)-5,6-dichlorobenzi-
2-methylbenzimidazoles 5. These are quaternized, either midazoles 6. Finally, as in ref.[9] condensation of two equiv-
with the respective sultones in the case of the 3,3Ј-di-(ω- alents of 6 with iodoform in alkaline medium gives dyes 1.
Scheme 2. Synthetic routes to the 5,5Ј6,6Ј-tetrachlorobenzimidacarbocyanines 1
3068
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
If 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is used instead n ϭ 2; and 1C, m ϭ 8, n ϭ 3, because of the very poor
of the common sodium methoxide, the reaction can be per- yields of this procedure. This limitation was considered jus-
formed at room temperature.
tifiable since the main objective of the syntheses was to in-
In reaction route III, the 1-alkyl substituents are first in- vestigate relationships between the structures of monomeric
troduced in 3 by nucleophilic reaction with the correspond- chromophores and their ability to generate supramolecular
ing alkyl bromides, giving compounds 5. These are trans- aggregates in solution. Since the precursors 6 do not absorb
formed into precursors 6 through quaternization either with in the visible region and as all dyes give the same anion of
ω-bromoalkanoic acid ethyl esters or with ω-bromoalkylni- the ’’betaine salt’’ in aqueous sodium hydroxide solution
triles, with subsequent hydrolysis. In the case of the independently of the composition of the solid dye samples,
3,3Ј-bis(ω-sulfoalkyl)-substituted dyes, quaternization is it is assumed that the molar extinction coefficients of all
achieved through the usual reaction with the corresponding dyes 1 should be about 185.0·103 cm2/mmol.
sultones.[33] Dyes 1 were purified in the usual way[9] by pre-
cipitation from methanol or dimethyl sulfoxide solutions by
addition of small amounts of water.
UV/Vis-Spectra
Monomeric Dyes
The positions and widths (FWHM) of the visible region
absorption and fluorescence bands of the monomeric dyes
1 in dimethyl sulfoxide solution at room temperature are
independent of concentration and are nearly identical, as
shown in Table 1. As mentioned above, their maximum mo-
lar extinction coefficient (εmax) was assumed to be 185.0·103
cm2/mmol. The purities of the dyes indicated in Table 1
were calculated from this value, and the measured εmax val-
ues of the dyes’ aggregates used in Figure 1Ϫ5 were cor-
rected accordingly.
The dyes 1 thus synthesized are compiled in Scheme 1
and are classified into Series 1A, which possess constant
3,3Ј-bis(3-carboxypropyl) groups and varied 1,1Ј-dialkyl
groups of different chain length, Series 1B, with constant
1,1Ј-dioctyl substituents and varied 3,3Ј-bis(ω-carboxyal-
kyl) groups of different lengths, and Series 1C, containing
1,1Ј-dialkyl and 3,3Ј-bis(ω-sulfoalkyl) substituents with di-
verse variation in their lengths. Finally, dyes 1D and 1E
possess 1,1Ј- and 3,3Ј-substituents of different kinds.
Dyes 1 exist as three differently ionized species (c.f.
Schemes 1 and 2). When two protonated carboxylic groups
are present the positive charge of the chromophore is com-
pensated by a bromide counter-ion, as in 1A, m ϭ 8 [species
a) in Scheme 1]. Such species are designated ’’bromides’’. In
the case of the ’’betaines’’, one carboxylate anion compen-
sates for the positively charged chromophore [species b) in
Scheme 1]. Some dyes, such as 1B, n ϭ 1 and 1B, n ϭ 5,
were obtained as mixtures of the bromide and betaine moi-
eties. Exchange of the remaining carboxylic proton for a
metal ion yields ’’betaine salts’’ such as 1A, m ϭ 11, and
the dyes of Series 1C, which usually form hydrates [species
c) in Scheme 1].
In Series A, with constant 3,3Ј-bis(3-carboxypropyl) sub-
stituents and 1,1Ј-dialkyl groups of varied lengths, the posi-
tions of the absorption wavelengths are slightly red-shifted
from 524.5 nm to 529.0 nm with lengthening of the alkyl
chains. Broadening of the bandwidth from about 1140 cmϪ1
to 1400 cmϪ1 takes place concomitantly. The same effect
happens with the fluorescence maxima, which are shifted
from about 540 nm to 547 nm, causing increase in the Sto-
kes’ shifts from about 550 cmϪ1 to 650 cmϪ1. Unlike those
of the absorption bands, the widths of the fluorescence
bands remain nearly constant, being narrower than the ab-
sorption bands at about (900 Ϯ 150) cmϪ1
.
Similar behaviour can be observed in Series B, with con-
stant 1,1Ј-dioctyl groups and varying 3,3Ј-bis(ω-carboxyal-
kyl) substituents. The positions of the absorption and fluor-
escence maxima are the more red-shifted the greater the ω-
carboxyalkyl chain length, again causing increases in the
Stokes’ shifts. In this case the widths of the absorption and
fluorescence bands increase with growing chain length in
the 3,3Ј- substituents. This may presumably indicate
stronger steric impact.
The spectroscopic data for dye D, with four equal N-car-
boxypropyl substituents, are similar to those of dyes 1A
with alkyl groups of medium length, such as 1A, m ϭ 7.
The same is true for the absorption maximum of dye E, the
structure of which is nearly identical to that of dye 1A, m ϭ
8, except for the substitution of the 1,1Ј-dioctyl groups by
fluorinated ones, possessing much higher hydrophobicity.
The half-width of this dye, at 1755 cmϪ1, is the broadest of
all the dyes investigated.
The varying compositions of some dyes, containing dif-
ferent portions of bromide, betaine, betaine salt, and crystal
water or other solvent molecules, which may even change
from sample to sample, hampers the definite analytical
characterization of the synthesized dyes. Furthermore, el-
emental analysis is highly inaccurate because the molecular
formulas, and thus the elemental compositions, of the dye
betaines 1 are very similar to those of two betainic precur-
sor molecules 6 [e.g. 1A, m ϭ 8: C41H54Cl4N4O4, 808.70; 2
ϫ (6, m ϭ 8): C40H56Cl4N4O4, 798.71]. Only combined
HPLC and MS measurements were able to show that dyes
1 would often contain some greater or lesser portion of the
corresponding precursor 6, indicating an incomplete reac-
tion between 6 and iodoform to give dyes 1. This is the
reason why we had originally reported about variable molar
extinction coefficients (εmax) of dyes 1 between 20.0 and
180.0 103 cm2/mmol.[9] Although quantitative separation of
the amphiphilic dyes 1 from their amphiphilic precursors 6
can be achieved by recrystallization from dimethyl sulfoxide
with a temperature gradient between 5 and 100 °C,[15] this
was carried out only with dyes 1A, m ϭ 6; 1A, m ϭ 8 (equal
Aggregated Dyes
Much more interesting is the spectral behaviour of dyes
to 1B, n ϭ 3); 1B, n ϭ 4; 1C, m ϭ 2, n ϭ 4; 1C, m ϭ 8, 1 in 10Ϫ2  aqueous sodium hydroxide solution. Alkaline
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3069

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
conditions are necessary in order to ensure that the second to produce methanol contents of less than 10% (v/v) in the
carboxy groups of the dyes’ bromide and betaine species final samples. The absorption bands of the aggregated dyes
are ionized to form the betaine salt anions (Schemes 1Ϫ2). are usually strongly red-shifted with respect to their mono-
Furthermore, because of the poor solubilities of most of mers, indicating the existence of J-aggregates. Their spectro-
the dyes in sodium hydroxide solution, methanolic stock scopic data in the visible region are listed in Table 2. Only a
solutions were prepared in some instances and diluted with few examples also show hypsochromically shifted H-bands.
10Ϫ2  sodium hydroxide solution by at least 1:10 or more, Because of the typical exchange-narrowing of the J-absorp-
Table 2. UV/Vis absorption and fluorescence data of J-aggregates in aqueous solution: wavelength of the absorption (abs) and fluorescence
(em) maximum: λmax; halfwidth (FWHM) of the long-wave absorption (abs) and fluorescence (em) band: ∆ν˜1/2; coupling strength: ∆ν˜;
exciton splitting: ∆. (* : Using the long wavelength absorption band)
abs
abs
abs
em
Dye
Aggregate
Type
λ
∆ν˜
∆ν˜
∆ν˜
1/2
∆ν˜
∆
Remarks
Circular
Dichroism
max
1/2
1/2
[nm]
[cmϪ1
]
[nm]
[cmϪ1
]
[cmϪ1
]
Series A
1A, m ϭ 2[a]
1A, m ϭ 4[a]
1A, m ϭ 6[b]
1A, m ϭ 7[b]
I
595
340
350
291
312*
595
588
580
601
304
280
339
199
2259
1886
1638
Ϫ
Ϫ
Ϫ
monomer-aggregate
equilibrium
monomer-aggregate
equilibrium
monomer-aggregate
equilibrium
none
none
none
yes
I
587
I
578
II
578/602
2314* 691 no monomer
detectable
2273* 486
2460* 876 no monomer
detectable
2446* 772 no monomer
detectable
1A, m ϭ 8[a]
1A, m ϭ 10[a]
II
II
562/583, 600 120*
602
606
216
210
yes
yes
575/606
578/605
573/604
153*
219*
130*
1A, m ϭ 11[a]
1A, m ϭ 12[a]
II
II
605
175
232
yes
604.5
2347* 896 temperature-dependent yes
changes of the
spectrum
Series B
1B, n ϭ 1[b]
1B, n ϭ 2[a]
1B, n ϭ 2[a]
III
III
I
483/574
590/601
593
405*
244*
633
fluorescence
not detectable
fluorescence
not detectable
fluorescence
not detectable
1589*
Ϫ
H-aggregates
none
yes
2336* 813 time dependent
equilibrium
2112
Ϫ
time dependent
equilibrium after
6 days
none
1B, n ϭ 3[a]
1B, n ϭ 4[c]
II
I
562/583, 600 120*
602
585
216
333
2273* 486
yes
none
586
307
1875
Ϫ
no monomer
detectable
monomer aggregate
equilibrium
1B, n ϭ 5[a]
I
582
365
582
315
1757
Ϫ
none
Series C
1C, (BIC), m ϭ 2,
n ϭ 3[a]
I
I
I
588.5
587
331
212
237
588.5
588
292
260
282
2030
2011
1860
Ϫ
Ϫ
Ϫ
Ϫ
monomer detectable
monomer detectable
none
none
none
1C, (TDBC), m ؍ 2,
n ؍ 4[c]
1C, m ϭ 4, n ϭ 4[a]
585.5
585.5
monomer aggregate
equilibrium
H-aggregates
1C, m ϭ 8, n ϭ 2[b] III
1C, m ϭ 8, n ϭ 3[a] II
502/585
584/601
184*
234*
586
601
358
397
1809*
2283
[d]
484 time dependent
equilibrium
Ϫ
yes
1C, m ϭ 8, n ϭ 3[a]
1C, m ϭ 8, n ϭ 4[b]
I
I
591.5
595
410
322
fluorescence
not detectable
2015
2132
time dependent
equilibrium
no monomer
detectable
none
none
599
538
296
Ϫ
Series D/E
1D[b]
1E[b]
III
III
519
546
1134
1298
1428
Ϫ
Ϫ
only monomer
detectable
J-aggregates
none
none
fluorescence
not detectable
829
[a]
[b]
[c]
10Ϫ2  aqueous sodium hydroxide solution.
10Ϫ2  aqueous sodium hydroxide solution containing up to 10% (v/v) methanol.
10Ϫ3  aqueous sodium hydroxide solution.
3070
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
tion bands,[30,34] their half-widths (FWHM) are smaller
than those of the longest-wavelength absorption bands of
their monomers by factors of 2 to 9 (Table 1).
Type I J-Aggregates
The observed spectra in the visible region can be grouped
into three characteristic types (Table 2). In principle, J-ag-
gregates of type I show the same behaviour as the well-
known TDBC (1C, m ϭ 2, n ϭ 4) J-aggregates. Only one
J-absorption band is formed, displaying strong resonance
fluorescence in the immediate neighbourhood of the ab-
sorption band. All J-aggregates are optically inactive, and
the maximum molar extinction coefficient (ε) strongly in-
creases with increasing concentration. The aggregates exist
in equilibria with monomer molecules, as shown by the
existence of isosbestic points. Figure 1 shows the absorption
spectrum of dye 1A, m ϭ 6 at different concentrations as an
example, while two further examples of the ε concentration
dependence of type I J-aggregates are shown in Figure 2.
No monomer absorption could be detected with dyes 1B,
n ϭ 4 and 1C, m ϭ 8, n ϭ 4, due to their very strong
aggregation tendency.
Figure 2. Maximum molar extinction coefficients (ε) of type I J-
aggregates in 10Ϫ2  aqueous sodium hydroxide solution contain-
ing up to 10% (v/v) methanol at room temperature and dependence
on concentration c (r ϭ correlation coefficient); a: 1C, m ϭ 8, n ϭ
2; r ϭ 0.96 b: 1A, m ϭ 6; r ϭ 0.99
dye series 1C, m ϭ 2, n ϭ 4; 1C, m ϭ 4, n ϭ 4; and 1C,
m ϭ 8, n ϭ 4, with elongated 1,1Ј-alkyl substituents, the J-
aggregates of the 1,1Ј-dibutyl derivative 1C, m ϭ 4, n ϭ 4,
have the shortest absorption and fluorescence band wave-
lengths, whereas the widths of both bands increase continu-
ously with elongation of the alkyl groups. On the other
hand, the widths of both bands are less in the J-aggregates
of dye 1C, m ϭ 2, n ϭ 4, containing longer 3,3Ј-sulfoalkyl
chains than the related dye 1C, m ϭ 2, n ϭ 3.
The coupling strength ∆ν˜ between the molecules within
the J-aggregates can be estimated from the red shifts be-
tween the positions of the absorption maxima of the mono-
mers and those of the J-aggregates.[35] In series A these de-
crease with increasing 1,1Ј-alkyl chain length, probably due
to enhanced steric hindrance. The same is true with series
B when the 3,3Ј-bis(ω-carboxyalkyl) chains are lengthened.
In series C, the J-aggregates of the two dyes with the 3,3Ј-
bis(3-sulfopropyl) substituents Ϫ 1C, m ϭ 2, n ϭ 3 and 1C,
m ϭ 8, n ϭ 3 Ϫ have nearly the same coupling strength. In
J-aggregates of dyes with 3,3Ј-bis(4-sulfobutyl) substituents
the coupling strength of the 1,1Ј-dibutyl-substituted J-ag-
gregates 1C, m ϭ 4, n ϭ 4 is the smallest, in relation to
those of the related dyes 1C, m ϭ 2, n ϭ 4 (TDBC) and
1C, m ϭ 8, n ϭ 4, having shorter or longer 1,1Ј-dialkyl
substituents, respectively, the same as with series A.
Figure 1. Absorption spectra of dye 1A, m ϭ 6 in 10Ϫ2  aqueous
sodium hydroxide solution at different concentrations and room
temperature, representing type I J-aggregates a: 6.7 ϫ 10Ϫ7 ; b:
2.0 ϫ 10Ϫ6 ; c: 1.9 ϫ 10Ϫ5 ; d: 4.0 ϫ 10Ϫ4

Unlike those in the spectra of the monomer dyes, the po-
sitions, and halfwidths, of the type I J-aggregate bands vary
with the length of the 1,1Ј-alkyl substituents. In series A,
dyes 1A, m ϭ 2; 1A, m ϭ 4 and 1A, m ϭ 6, the absorption
maxima are the more blue-shifted the longer the chain
lengths of the 1,1Ј-dialkyl groups. On the other hand,
FWHM of the absorption and fluorescence band vary arbi-
trarily. The half-width of the absorption band of the dye J-
aggregate 1A, m ϭ 6, at 291 cmϪ1, is clearly smaller than
Type II J-Aggregates
Type II J-aggregates are characterized by an exciton-split
those of others, whereas it is dye 1A, m ϭ 4, that has the J-band, the components of which display optical ac-
smallest fluorescence band, with FWHM equal to 280 tivity.[11,18] It turns out that the basic precondition for the
cmϪ1
.
formation of this type is the amphiphilic nature of the dye
In series B, only the J-aggregates of dyes 1B, n ϭ 4, and monomers, with 1,1Ј-dialkyl substituents longer than hexyl
1B, n ϭ 5, belong to type I, showing features nearly the and 3,3Ј-bis(ω-carboxyalkyl) substituents with ethyl or pro-
same as in dye 1A, m ϭ 6.
pyl chains. As can be seen in Table 2, the dyes 1A, m ϭ 7;
In series C, all dye J-aggregates belong to type I, with the 1A, m ϭ 8; 1A, m ϭ 10; 1A, m ϭ 11; 1A, m ϭ 12; 1B, n ϭ
exception of dye 1C, m ϭ 8, n ϭ 3. Astonishingly, in the 2; 1B, n ϭ 3; and 1C, m ϭ 8, n ϭ 3 belong to this type. As
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3071

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
the preparation conditions of the J-aggregates and on the
alcohol content of the alkaline aqueous solution.[15,22,23]
As with type I J-aggregates, the positions and the half-
widths of the components of the exciton-split J-bands vary
with the nitrogen substituents. The most impressive results
are the very small bandwidths of the longest-wavelength
components of dyes 1A, m ϭ 8, and 1A, m ϭ 12, which
amount to 120 to 130 cmϪ1, respectively. These are the
smallest values ever observed in conjugated organic com-
pounds at room temperature. Furthermore, the degree of
exciton splitting (∆) varies from dye to dye. As it depends
on the intermolecular arrangement of the molecules in the
crystal lattice it is understandable that it may depend on
the substitution pattern of dyes 1.
Figure 3. Absorption spectra of dye 1A, m ϭ 10 in 10Ϫ2  aqueous
sodium hydroxide solution at different concentrations and room
temperature, representing type II J-aggregates; a: 1.7 ϫ 10Ϫ5 ; b:
It must be emphasized that no exciton splitting takes
place in the fluorescence spectra. The emission is nearly in
resonance with the longest-wavelength component of the J-
absorption band, the same as with the J-aggregates of type
I. However, as discussed elsewhere,[24] the fluorescence kine-
tics of type I and type II J-aggregates are quite different.
Type I J-aggregates exhibit single-exponential fluorescence
decay at low temperature,[13] whereas the fluorescence decay
of type II J-aggregates is multi-exponential.[36] The pressure
dependence of the absorption and fluorescence spectra,
measured up to 50 kbar, is also completely different in the
two aggregate types, intimating for the first time that type
II J-aggregates might be hollow cylinders.[37]
2.2 ϫ 10Ϫ5 ; c: 4.4 ϫ 10Ϫ4

an example, Figure 3 shows the concentration-dependent
spectra of the J-aggregates of dye 1A, m ϭ 10. Unlike the
case of type I J-aggregates, there is no equilibrium between
dye monomers and J-aggregates, although the shoulder
near to 510 nm seems to indicate the presence of a certain
amount of monomers absorbing at 527 nm. Figure 4 gives
the concentration dependence of the molar extinction coef-
ficients (ε) of the J-aggregates of dyes 1A, m ϭ 7 and 1A,
m ϭ 8. The slope of this dependence is evidently lower than
that of type I J-aggregates. Depending on concentration,
temperature and alcohol content, the J-aggregates of dyes
1A, m ϭ 11; 1B, n ϭ 2; and 1C, m ϭ 8, n ϭ 3, are in
equilibrium with type I J-aggregates.
Usually, the ratio between the maximum intensities of the
two exciton split components of the J-absorption band indi-
cated in Table 2 remains constant at different concen-
trations. It may change in some instances, however, due to
overlap with a third absorption band at higher energies,
which appears in Figure 3 at around 540 nm. The origin of
this band is disputed. Its appearance strongly depends on
˜
For estimation of the coupling strengths ∆ν between the
dye molecules in type II J-aggregates, the differences be-
tween the maximum absorption wavelengths of the dye
monomers and the positions of the longest-wavelength
components of the exciton-split J-bands are given in
Table 2. As with type I J-aggregates, the coupling strongly
depends on the nitrogen substituents. In all instances it is
greater than 2000 cmϪ1 meaning that on average the coup-
ling is stronger than in type I J-aggregates.
Type III Dye Aggregates
The type III aggregates in Table 2 include some excep-
tional cases. Aqueous sodium hydroxide solutions of dye
1D, with four 1,1Ј,3,3Ј-(3-carboxypropyl) substituents,
consist only of monomers, with an absorption maximum
at 519 nm and a fluorescence maximum at 538 nm. Its
absorption spectrum in 10Ϫ2  aqueous sodium hydroxide
solution is concentration-independent between 10Ϫ6 and
10Ϫ3 mol/L.
The absorption spectrum of dye 1E, which contains two
fluorinated 1,1Ј-dioctyl groups of very high hydrophobicity,
in aqueous sodium hydroxide solution is shown in the upper
part of Figure 5. The compound has a very broad spectrum
that, apart from the monomer absorption at 528 nm, seems
to consist of a blue-shifted H-band indicated as a shoulder
at 480 nm and a red-shifted broad J-band close to 560 nm,
which does not fluoresce. Its absorption spectrum is like-
Figure 4. Maximum molar extinction coefficients (ε) of the long-
wave exciton split J-absorption band of type II J-aggregates in 10Ϫ2
 aqueous sodium hydroxide solution containing up to 10% (v/v)
methanol at room temperature and dependence on concentration c
(r ϭ correlation coefficient); a: 1A, m ϭ 7; r ϭ 0.97 b: 1A, m ϭ 8;
r ϭ 0.98
3072
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
spectrum of dye 1B, n ϭ 1, is shown in the middle part
of Figure 5. Besides the J-band at 574 nm, it also shows a
pronounced H-band at 483 nm. The absorption spectrum
of dye 1B, n ϭ 2, shown in the lower part of Figure 5, dis-
plays several absorption bands at longer and shorter wave-
lengths than the monomers, varying strongly with concen-
tration and preparation conditions. The absorption spec-
trum of dye 1C, m ϭ 8, n ϭ 2, with a J-band at 585 nm, a
shoulder at 541 nm and an H-band at 502 nm, is similar to
that of dye 1B, n ϭ 1.
Conclusions
The synthesis of 5,5Ј,6,6Ј-tetrachlorobenzimidacarbocy-
anine dyes 1 via the benzimidazoles 3 opens alternative
routes for the introduction of different substituents at the
1,1Ј- or 3,3Ј-positions of the dyes through the use of the
common precursor 3. This offers new potential for wide
variation of the substitution patterns of dyes 1 at their ni-
trogen atoms.
Whereas the UV/Vis spectra of the monomeric dyes 1
with their different substituents at the nitrogen atoms are
nearly identical, the spectra of their aggregates in alkaline
aqueous solution can be controlled by the nature of their
1,1Ј- and 3,3Ј-substituents. Three different types of aggre-
gates can be distinguished. The first type are dyes with n-
alkyl substituents shorter than heptyl, which usually exhibit
only one red-shifted J-aggregate absorption band, as is also
well-known with many other cyanine dyes. Such dyes either
form monomolecular layers or bilayer ribbons, as has been
demonstrated by cryo-TEM investigations.[16] The second
type are dyes containing 1,1Ј-diheptyl and longer alkyl
groups in combination with 3,3Ј-bis(2-acidoethyl) or 3,3Ј-
bis(3-acidopropyl) substituents. These dyes possess exciton
split J-bands, which exhibit circular dichroism in the form
of couplets. It is feasible to assume that the common cause
of this behaviour is spontaneous and asymmetrical genera-
tion of supramolecular helices, as had been shown by cryo-
TEM in the case of dye 1A, m ϭ 8.[16,19] The third type are
exceptional dyes of very high hydrophilicity or hydro-
phobicity, such as 1D, 1E, and 1B, n ϭ 1. Such dyes give
H-aggregates that also display blue-shifted absorption
bands. The self-organization of dyes 1 is therefore obviously
governed by their molecular configurations and confor-
mations, which have their origins in rather sensitive equilib-
ria between the dyes’ coupling strengths, steric factors, as
well as in the hydrophobic and hydrogen-bridging forces of
their substituents.[38]
Figure 5. Absorption spectra of dyes belonging to the type III J-
aggregates in 10Ϫ2  aqueous sodium hydroxide solution (1 B, n ϭ
2) or in aqueous sodium hydroxide solution containing up to 10%
(v/v) methanol (1E, 1 B, n ϭ 1) at room temperature above: dye
1E; middle: dye 1B, n ϭ 1; a: 1.0 ϫ 10Ϫ5  ;b: 2.8 ϫ 10Ϫ5 , c: 4.5
ϫ 10Ϫ5  below: dye 1B, n ϭ 2; a: 2.3 ϫ 10Ϫ7  ; b: 9.5 ϫ 10Ϫ7
; c: 2.8 ϫ 10Ϫ6

wise concentration-independent between 10Ϫ6 and 10Ϫ3
mol/L.
Outlook
The J-aggregates of dyes 1B, n ϭ 1; 1B, n ϭ 2 and 1C,
As the research team for amphipipes no longer exists,
m ϭ 8, n ϭ 2, may be added to type III because their con- owing to the retirement of its team leader (S.D.), it is hoped
centration- and time-dependent spectra in aqueous sodium that the following outlook will stimulate further research in
hydroxide solution are rather complicated. The absorption this challenging new field. It will be easy to start with work
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3073

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
as some of the dyes described have recently become com- first experiments.[18] However, this could be not confirmed
mercially available.[39]
when the purified dye 1A, m ϭ 8, described in this paper
(i) Apart from dyes 1 investigated in this paper, nothing was used. In this case, helices with a positive CD couplet
is known about the influence of further structural alter- were preferentially generated.[15,43] These contradictory re-
ations on the amphipipe features, such as lengthening and/ sults urgently need further investigation.
or substitutions of the polymethine chain, symmetrical and
Furthermore, dye 1A, m ϭ 8 also seems to be a promising
asymmetrical variation of the heterocyclic residues, or model compound with which to test results of vortex-in-
modifications of the substituents’ acidic/basic natures. The duced chirality recently published by Ribo et al.[44] The au-
search for other chromophores that form J-aggregates thors claim that the handedness of helical aggregates
would also be important. For instance, the strange physico- formed by self-organization of mutually shifted disk-like
chemical properties of the J-aggregates of amphiphilic porphyrin molecules is governed by the direction of the vor-
merocyanine dyes synthesized by Balli et al.[40] already tex flow. In the case of dye 1A, m ϭ 8, it would be not the
point to the existence of amphipipes with entirely different mutual shift of aggregated molecules but the twist direction
molecular structures.
of the molecules that would determine the handedness of
(ii) As the spectral behaviour and the morphology of the first formed helical dye dimer. If the twist of the mol-
each amphipipe usually depends strongly on its micro- ecules can be controlled by the direction of a vortex flow,
environment (e.g., on the presence of hydroxylic com- this could offer the potential to induce chirality by macro-
pounds, surfactants, and presumably of proteins), the num- scopic mechanical forces.
ber of possible amphipipe architectures still to be brought
to light will be raised exponentially when such compounds
are intercalated in amphipipes.
(iii) As exciton delocalization is the most important fea-
Experimental Section
ture of the new self-organized nanoscopic particles, the dy-
namics of this process need to be investigated in detail in
terms of their dependence on the amphipipes’ morphologies
and on their molecular structures.
General: As the IUPAC nomenclature of polymethine dyes is rather
complicated we applied the designations used in scientific pho-
tography, which emphasizes the true symmetrical C2v structure of
the dyes with equivalent terminal heterocycles. Examples of the
correct IUPAC designation of some configurations of dye 1A, m ϭ
8 that have been determined by X-ray structure analyses in the
crystalline state and by NMR COSY and NOESY experiments in
the liquid state[38] are given in Scheme 3. The all-trans configura-
tion a is the prevailing one.
Measurements in solutions were performed under argon. For prep-
aration of monomeric dye solutions the samples were dissolved in
dimethyl sulfoxide by sonication for two minutes. In order to pre-
pare J-aggregate solutions the samples were either directly dis-
solved in 10Ϫ2  aqueous sodium hydroxide solution by stirring
under argon for 2 d, or else a methanolic stock solution was pre-
pared and then diluted with 10Ϫ2  aqueous sodium hydroxide
solution, it being ensured that the final methanol content did not
exceed 10% (v/v).
(iv) Almost nothing is known about the ability of amphi-
pipes to spectrally sensitize photoinduced electron transfer
(PET) reactions. However, there is little doubt that they will
do so, because J-aggregates act as spectral sensitizers in
photographic processes and it has recently been shown that
the supramolecular J-aggregates of pseudoisocyanine (PIC)
spectrally sensitize hydrogen production in the presence of
electron acceptors and donors.[41] Thus the development of
artificial light-harvesting systems seems possible. It might
be even conceivable to mimic natural photosynthetic reac-
tion centres through intercalation of amphiphilic molecules
with strong electron acceptor and/or electron donor func-
tions into amphipipes.
(v) Finally, the spontaneous and asymmetrical generation
UV/Vis spectra were run at room temperature either with a Zeiss
of helical amphipipes in alkaline aqueous solution provides Specord M 400 spectrometer or with a Bruins Omega 10 spec-
trometer. The maximum molar extinction coefficients (εmax) [103
new model systems with which to acquire deeper insight in
cm2·mmolϪ1] of dye 1 monomers given in Table 1 are mean values,
each of three independent determinations. In instances of contami-
nated dye samples the purity of the dye is given as a percentage
determined on the assumption that the εmax values of all dyes in
dimethyl sulfoxide solution are equal and amount to 185.0 103
cm2·mmolϪ1. The J-aggregates’ maximum extinction coefficients
(ε) used in the Figures have been corrected for the varying purities
of the different dyes indicated in Table 1. The values apply to the
weight of monomeric molecules, which means that, in principle,
the evolution of the asymmetry of life.[42] In the case of dye
1A, m ϭ 8, the asymmetrical generation of superhelices
seems to be promoted by intramolecular interaction be-
tween the two hydrophobic octyl groups, as well as by the
formation of an intramolecular hydrogen bond, both of
which are able to induce an intramolecular twist of a single
molecule.[19,38] As a twisted molecule can only dimerize
with another one with the same twist sign, the handedness
will be preserved. Such a dimer then acts as a template for they should be multiplied by the (unknown) number of coupled
molecules. For solutions at concentrations higher than 10Ϫ4 mol/
L, microcuvettes (20Ϫ500 µm) were used. The data measured at
those concentrations therefore have an error of Ϯ 15%.
the generation of a helix, which transfers its chirality to
most of the subsequently formed helices. Since there is
equal probability that the first formed dimer will have either
left-handed or right-handed twist, one has to expect that
on repetition of the experiment, samples with preferred left-
handed and with preferred right-handed helices should be
Fluorescence spectra were recorded with a 8100 spectrofluorimeter
from Spectronics Instruments. The fluorescence spectra of mono-
meric molecules were excited at 475 nm. Fluorescence spectra of J-
obtained with equal parity. This, indeed, happened in our aggregates were excited at 500 nm and a front face equipment was
3074  2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
thermobalance. Samples (1Ϫ5 mg) were heated at 5 K/min to 200
°C in loosely covered ceramic crucibles under an argon flow. A
Finnigan MAT 95 high-resolution mass spectrometer was addition-
ally applied for the purified dye 1A, m ϭ 8.
Sources of Compounds: 1-Aminohexane (99%), 1-bromoheptane
(99%), 1-bromooctane (99%), 1-bromodecane (98%), 1-bromo-
undecane (98%), 4-bromobutyronitrile (97%), Ethyl bromoacetate
(98%), ethyl 3-bromopropionate (99%), ethyl 5-bromopentanoate
(98%), ethyl 6-bromohexanoate (99%), 1,8-diazabicyclo[5.4.0]-
undec-7-ene (98%), 1,3-propanesultone (99%), sodium bromide
(99%), hydrobromic acid (48% w/w aq. soln.), absolute N,N-di-
methylformamide (99.8%, water Ͻ 0.005%), and absolute methanol
(99.8%, water Ͻ 0.005%) were purchased from Aldrich. Other sol-
vents used were of HPLC grade. The water used was deionized.
(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl) iodide (97%) was ob-
tained from ABCR GmbH (Gelest, Inc, USA). Iodoform (99%),
sodium hydroxide (99%), and acetic acid (96%) were purchased
from Merck. 4,5-Dichloro-1,2-phenylenediamine (2) (97%), lithium
hydroxide monohydrate (99%) and 1,2,4-trichloro-5-nitrobenzene
(7) (97%) were obtained from Fluka.
The dyes 5,5Ј,6,6Ј-tetrachloro-1,1Ј-diethyl-3,3Ј-bis(3-sulfopropyl)-
benzimidacarbocyanine (BIC) 1C, m ϭ 2, n ϭ 3; 5,5Ј,6,6Ј-tetra-
chloro-1,1Ј-diethyl-3,3Ј-bis(4-sulfobutyl)benzimidacarbocyanine
(TDBC) 1C, m ϭ 2, n ϭ 4; 5,5Ј,6,6Ј-tetrachloro-1,1Ј-dioctyl-3,3Ј-
Scheme 3. cis-trans Configurations of 5,5Ј,6,6Ј-tetrachloro-1,1Ј-di-
octyl-3,3Ј-bis(3-carboxypropyl)benzimidacarbocyanine dye 1A,
m ϭ 8. The IUPAC designations are (letter s means formal single
bond): a: 4-{2(E)-[2(E),3(sE)-(3-carboxypropyl-5,6-dichloro-1-
octyl-3H-benzimidazol-1-ium-2-yl)prop-2-en-1-ylidene]-5,6-
dichloro-3-octyl-2,3-dihydro-1H-benzimidazol-1-yl}butanoate; b:
4-{2(Z)-[2(E),3(sZ)-(3-carboxypropyl-5,6-dichloro-1-octyl-3H-
benzimidazol-1-ium-2-yl)prop-2-en-1-ylidene]-5,6-dichloro-3-
octyl-2,3-dihydro-1H-benzimidazol-1-yl}butanoate; c. 4-{2(Z)-
[2(E),3(sE)-(3-carboxypropyl-5,6-dichloro-1-octyl-3H-benzimid-
azol-1-ium-2-yl)prop-2-en-1-ylidene]-5,6-dichloro-3-octyl-2,3-
dihydro-1H-benzimidazol-1-yl}butanoate
bis(3-sulfoethyl)benzimidacarbocyanine 1C,
m ϭ 8, n ϭ 2;
5,5Ј,6,6Ј-tetrachloro-1,1Ј-dioctyl-3,3Ј-bis(3-sulfopropyl)benzimida-
carbocyanine 1C, m ϭ 8, n ϭ 3; and 3,3Ј-bis(3-carboxypropyl)-
5,5Ј,6,6Ј-tetrachloro-1,1Ј-dioctylbenzimidacarbocyanine 1A, m ϭ 8
were purchased from FEW Chemicals GmbH.[39] Dye 1C, m ϭ 2,
n ϭ 4 (TDBC) contained 6 mol crystal water. Dye 1A, m ϭ 8, was a
1:1 mixture of the bromide and the betaine. Recrystallization from
dimethyl sulfoxide (DMSO) yielded the pure betaine, containing
0.5 mol DMSO. The dyes 1A, m ϭ 2; 1A, m ϭ 4; 1A, m ϭ 6; 1A,
m ϭ 12; 1C, m ϭ 4, n ϭ 4; and 1C m ϭ 8, n ϭ 4, were provided
by the authors of ref.[9] Recrystallization of 1A, m ϭ 6, from
DMSO gave the pure betaine, containing 1 mol crystal water and
2 mol DMSO. If the synthesis of the dyes was repeated, the analyti-
cal data and those of their precursors are indicated in the follow-
ing descriptions.
used to prevent reabsorption. All fluorescence spectra were cor-
rected for the wavelength sensitivity of the spectrometer and the
intensity fluctuations of the excitation lamp.
1H NMR spectra were recorded either with a Varian Unityplus 500
(500 MHz) or with a Varian Unityplus 300 (300 MHz) spectrometer.
Tetramethylsilane (TMS) was used as reference compound.
Preparation of the Intermediate Compounds
4,5-Dichloro-N-hexyl-2-nitroaniline (8, m ؍ 6): This compound was
prepared according to ref.[9] by treatment of 2,4,5-trichloronitrob-
enzene (7) with 1-aminohexane. Melting point, yield, and CHN
analysis are compiled in Table 3.
LSIMS mass spectra were determined with an Autospec spec-
trometer (Micromass) with Magic Bullet as matrix. HPLC/MS was
used to test purification procedures of dyes 1A, m ϭ 8, and 1B, 5,6,-Dichloro-1-hexyl-2-methylbenzimidazole 5, m ؍ 6: This com-
n ϭ 4. For the same purpose, thermoanalytical investigations DTA/
pound was prepared according to ref.[9] by reduction of 8, m ϭ 6,
MS (ESI positive) were performed in a SETARAM TAG 24/16 and cyclization with acetic acid.
Table 3. Melting points, yields, empirical formulae, molecular mass and CHN elemental analysis for compounds 4, 5 and 8
Compound M.p. (°C) Yield (%) Empirical formula Mol. mass (g/mol) C content
H content
N content
calcd. found calcd. found calcd. Found
4, n ϭ 3
150Ϫ152
111Ϫ113
89Ϫ90
107Ϫ109
89Ϫ90
43
47
44
69
51
25
C12H11Cl2N3
C14H18Cl2N2
C15H20Cl2N2
C16H22Cl2N2
C19H28Cl2N2
C12H16Cl2N2O2
268.15
285.22
299.24
313.29
355.35
291.19
53.75
58.95
60.21
61.34
64.22
49.50
53.50
58.27
60.35
60.14
64.25
49.40
4.14
6.36
6.74
7.08
7.94
5.54
4.07
6.41
6.94
6.85
8.20
5.64
15.67
9.82
9.36
8.94
7.88
9.62
15.56
9.49
9.24
8.70
7.65
9.52
5, m ϭ 6
5, m ϭ 7
5, m ϭ 8[a]
5, m ϭ 11
8, m ϭ 6
34Ϫ35
[a]
Synthesized as in ref.[9]
.
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3075

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
was necessary to add water (100 mL). After filtration, the residue
was washed with water (300 mL), dried, extracted hot with toluene
and recrystallized from ethanol. Melting points, yields, and CHN
analyses of the compounds are also listed in Table 3.
3-(3-Carboxypropyl)-5,6-dichloro-1-hexyl-2-methylbenzimidazolium
Bromide 6A, m ؍ 6 and 3-(3-Carboxypropyl)-5,6-dichloro-1-heptyl-
2-methylbenzimidazolium Bromide 6A, m ؍ 7: These compounds
were prepared according to ref.[9] from 5, m ϭ 6, and 5, m ϭ 7,
respectively, by treatment with 4-bromobutyronitrile and sub-
sequent hydrolysis. Melting points, yields and CHN analyses of the
compounds are compiled in Table 3.
General Procedures for the Preparation of 3-(3-Carboxypropyl)-5,6-
dichloro-2-methyl-1-octylbenzimidazolium Bromide 6A, m ؍ 8; 3-(3-
Carboxypropyl)-5,6-dichloro-1-decyl-2-methylbenzimidazolium Bro-
mide 6A, m ؍ 10; 3-(3-Carboxypropyl)-5,6-dichloro-2-methyl-1-un-
decylbenzimidazolium Bromide 6A, m ؍ 11; 3-(Carboxymethyl)-5,6-
dichloro-2-methyl-1-octylbenzimidazolium Bromide 6B, n ؍ 1; 3-(2-
Carboxyethyl)-5,6-dichloro-2-methyl-1-octylbenzimidazolium Bro-
mide 6B, n ؍ 2; 3-(4-Carboxybutyl)-5,6-dichloro-2-methyl-1-octyl-
benzimidazolium Bromide 6B, n ؍ 4); 3-(5-Carboxypentyl)-5,6-di-
chloro-2-methyl-1-octylbenzimidazolium Bromide 6B, n ؍ 5; 5,6-Di-
chloro-2-methyl-1-octyl-3-(3-sulfopropyl)benzimidazolium Bromide
6C, m ؍ 8, n ؍ 3; and 3-(3-Carboxypropyl)-5,6-dichloro-1-(1-H,1-
H,2-H,2-H-perfluorooctyl)-2-methylbenzimidazolium Bromide 6E:
1H NMR: 4, n ؍ 3 (CDCl3): δ ϭ 2.13Ϫ2.22 (m, 2 H, NCH2CH2),
2.40 (t, NCCH2, J ϭ 6.6 Hz, 2 H), 2.64 (s, 3 H, 2-CH3), 4.25 (t,
J ϭ 7.1 Hz, 2 H, NCH2), 7.41 (s, 1 H, 7-H), 7.76 (s, 1 H, 4-H)
ppm; 5, m ؍ 6 (CDCl3): δ ϭ 0.89 (t, J ϭ 7.0 Hz, 3 H, CH2CH3),
1.27Ϫ1.36 (m, 6 H, 3 ϫ CH2), 1.75Ϫ1.78 (m, 2 H, NCH2CH2),
2.58 (s, 3 H, 2-CH3), 4.03 (t, J ϭ 7.5 Hz, 2 H, NCH2), 7.37 (s, 1
H, 7-H), 7.74 (s, 1 H, 4-H) ppm; 5, m ؍ 7 (CDCl3): δ ϭ 0.88 (t,
J ϭ 6.8 Hz, 3 H, CH2CH3), 1.28Ϫ1.35 (m, 8 H, 4 ϫ CH2),
1.75Ϫ1.81 (m, 2 H, NCH2CH2), 2.58 (s, 3 H, 2-CH3), 4.03 (t, J ϭ
7.5 Hz, 2 H, NCH2), 7.37 (s, 1 H, 7-H), 7.74 (s, 1 H, 4-H) ppm; 5,
m ؍ 8 (CDCl3): δ ϭ 0.88 (t, J ϭ 6.8 Hz, 3 H, CH2CH3), 1.26Ϫ1.33
(m, 10 H, 5 ϫ CH2), 1.74Ϫ1.79 (m, 2 H, NCH2CH2), 2.58 (s, 3 H,
2-CH3), 4.03 (t, J ϭ 7.4 Hz, 2 H, NCH2), 7.36 (s, 1 H, 7-H), 7.74
(s, 1 H, 4-H) ppm; 5, m ؍ 11 ([D6]DMSO): δ ϭ 0.85 (t, J ϭ 6.7 Hz,
3 H, CH2CH3), 1.22Ϫ1.27 (m, 16 H, 8 ϫ CH2), 1.65Ϫ1.70 (m, 2
H, NCH2CH2), 2.53 (s, 3 H, 2-CH3), 4.17 (t, J ϭ 7.3 Hz, 2 H,
NCH2), 7.74 (s, 1 H, 7-H), 7.87 (s, 1 H, 4-H) ppm; 8, m ؍ 6
(CDCl3): δ ϭ 0.91 (t, J ϭ 7.0 Hz, 3 H, CH2CH3), 1.31Ϫ1.47 (m, 6
H, 3 ϫ CH2), 1.68Ϫ1.77 (m, 2 H, NCH2CH2), 3.22Ϫ3.28 (m, 2 H,
NCH2), 6.95 (s, 1 H, 3-H), 7.95 (br. s, 1 H, NH), 8.26 (s, 1 H, 6-
H) ppm.
The reaction conditions are listed in Table 5. As with dyes 1, 6A in
all formulas is (n ϭ 3) and 6B in all formulas is (m ϭ 8). The
formula of 6E given in Scheme 2 means (n
Ϫ(CH2)2Ϫ(CF2)6ϪF instead of Ϫ(CH2)8H.
ϭ 3) and
The appropriate 3-alkyl-5,6-dichlorobenzimidazoles 4 or 5 were
heated with an excess of the corresponding reactant with the reac-
tion times t1 and temperatures T1 given in Table 5. Each reaction
product was suspended in acetone (20Ϫ30 mL) and heated for 30
minutes. After cooling to room temperature, the residue was filtered
off and washed with acetone (20Ϫ30 mL). The sulfobetaine 6C,
m ϭ 8, n ϭ 3, was purified by heating in acetone (70 mL), filtration
after cooling to room temperature, and washing of the residue with
acetone (50 mL). This procedure was repeated twice. The ester or
nitrile groups of the intermediate products were subsequently hy-
drolysed by heating at reflux in half-diluted hydrobromic acid (48%
in weight, aq. soln, 40Ϫ60 mL) for the time t2 indicated in Table 5.
After the mixture had cooled to room temperature, the precipitate
was filtered off and washed with aqueous hydrobromic acid (5% w/
w, 10 mL). The obtained salt was dissolved in boiling water
(50Ϫ100 mL) and filtered hot. In order to avoid the formation of
betaine salts, the hot filtrate was mixed with aqueous hydrobromic
acid (48% in weight, 2Ϫ5 mL). The crystallized benzimidazoles 6
were isolated by removal of the mother liquor by suction, washed
with aqueous hydrobromic acid (5% in weight, 10 mL) and dried
in air. Melting points, yields and CHN analyses are compiled in
Table 6.
General Procedure for the Preparation of 5,6-Dichloro-1-(3-cyano-
propyl)-2-methylbenzimidazole 4, n ؍ 3; 5,6-Dichloro-1-heptyl-2-
methylbenzimidazole 5, m ؍ 7; 5,6-Dichloro-2-methyl-1-octylbenzi-
midazole 5, m ؍ 8; and 5,6-Dichloro-2-methyl-1-undecylbenzimida-
zole 5, m ؍ 11: 5,6-Dichloro-2-methylbenzimidazole (3) was dis-
solved in dimethyl sulfoxide under the reaction conditions given in
Table 4. After addition of the appropriate amount of pulverized
sodium hydroxide, the solution was stirred at room temperature for
4 h. The reactant was then added. Further stirring at room tem-
perature for the time given, subsequent filtration, and washing of
the residue with water and n-hexane yielded 5, m ϭ 7; 5, m ϭ 8;
and 5, m ϭ 11, respectively. Purification by hot extraction with
hexane likewise gave the products listed in Table 3. Product 5, m ϭ
11, was additionally recrystallized from toluene/cyclohexane, 1:4
(v/v). In order to precipitate 4, n ϭ 3, from the stirred solution it
1H NMR: 6A, m ؍ 6, (CD3OD): δ ϭ 0.92 (t, J ϭ 7.1 Hz, 3 H,
CH2CH3), 1.35Ϫ1.47 (m, 6 H, 3 ϫ CH2), 1.86Ϫ1.91 (m, 2 H,
NCH2CH2CH2CH2), 2.12Ϫ2.17 (m, 2 H, CH2CH2COOH), 2.54 (t,
J ϭ 6.6 Hz, 2 H, CH2COOH), 2.97 (s, 3 H, 2-CH3), 4.44Ϫ4.55 (m,
4 H, NCH2), 8.28 (s, 1 H, 4/7-H), 8.34 (s, 1 H, 4/7-H) ppm; 6A,
m ؍ 7, ([D6]DMSO): δ ϭ 0.86 (t, J ϭ 6.8 Hz, 3 H, CH2CH3),
Table 4. Reaction conditions for synthesis of the benzimidazoles 4
and 5
4, n ϭ 3 5, m ϭ 7 5, m ϭ 8 5, m ϭ 11
Starting
material 3 (mmol) 124.0
DMSO
NaOH
(g)
25.0
7.0
34.8
75
1.68
42
15.0
74.6
150
4.00
100
3
12.0
59.7
100
2.64
65.9
4
1.27Ϫ1.34 (m,
8 H, 4 ϫ CH2), 1.73Ϫ1.76 (m, 2 H,
NCH2CH2CH2CH2), 1.97Ϫ2.02 (m, 2 H, CH2CH2COOH), 2.43 (t,
J ϭ 7.3 Hz, 2 H, CH2COOH), 2.92 (s, 3 H, 2-CH3), 4.42Ϫ4.49 (m,
4 H, NCH2), 8.55 (s, 1 H, 4/7-H), 8.56 (s, 1 H, 4/7-H), 12.27 (br. s,
1 H, COOH) ppm; 6A, m ؍ 8, ([D6]DMSO): δ ϭ 0.84 (t, J ϭ
6.5 Hz, 3 H, CH2CH3), 1.24Ϫ1.31 (m, 10 H, 5 ϫ CH2), 1.72Ϫ1.74
(ml)
(g)
(mmol) 140
1
50
5.60
Reactant[a]
2
(g)
20.7
7.52
42.0
1
29.0
150
3
15.5
66
3
(mmol) 140
(m,
2
H, NCH2CH2CH2CH2), 1.95Ϫ2.00 (m,
2
H,
Reaction
time
Product
(days)
(g)
4
CH2CH2COOH), 2.42 (t, J ϭ 7.2 Hz, 2 H, CH2COOH), 2.92 (s, 3
H, 2-CH3), 4.41Ϫ4.49 (m, 4 H, NCH2), 8.56 (s, 2 H, 4-H and 7-
H) ppm; 6A, m ؍ 10, ([D6]DMSO): δ ϭ 0.85 (t, J ϭ 6.7 Hz, 3 H,
CH2CH3), 1.24Ϫ1.33 (m, 14 H, 7 ϫ CH2), 1.71Ϫ1.76 (m, 2 H,
NCH2CH2CH2CH2), 1.95Ϫ2.05 (m, 2 H, CH2CH2COOH), 2.43 (t,
J ϭ 7.2 Hz, 2 H, CH2COOH), 2.93 (s, 3 H, 2-CH3), 4.43Ϫ4.51 (m,
14.3[b]
4.62
15.4
16.1
51.4
10.7[b]
30.1
(mmol) 53.3.
[a]
1: 4-bromobutyronitrile; 2: 1-bromoheptane; 3: 1-bromooctane;
[b]
4: 1-bromoundecane. after additional purification, see text.
3076
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
Table 5. Reaction conditions for synthesis of the benzimidazole bromides 6
6A,
6A,
6A,
6A,
6A,
6B,
n ϭ 1
6B,
n ϭ 2
6B,
n ϭ 4
6B,
n ϭ 5
6C,
n ϭ 3,
m ϭ 8
6E
see text
m ϭ 6[a] m ϭ 7[a] m ϭ 8
m ϭ 10 m ϭ 11
Starting
material
(mmol)
(g)
5, m ϭ 6 5, m ϭ 7 5, m ϭ 8 4, n ϭ 3 5, m ϭ 11 5, m ϭ 8 5, m ϭ 8 5, m ϭ 8 5, m ϭ 8 5, m ϭ 8 4, n ϭ 3
9.58
3.00
1
18.6
5.00
2
20.0
4.42
180
2
11.3
4.00
1
13.0
1.92
150
3
19.2
6.00
3
30.1
5.02
150
2
16.0
5.00
4
24.0
4.34
150
2
16.0
5.00
5
24.0
5.02
150
2
9.99
3.13
6
20.0
4.46
150
2
24.9
7.80
7
28.7
3.50
150
3
14.9
4.00
8
16.5
7.80
180
2
Reactant[b]
(mmol)
(g)
1
1
15.0
2.22
150
2
T1 (°C)
t1 (h)
100
5
100
5
t2 (h)
12
12
4
3.60
7.50
6
5.81
11.4
6
3.80
7.27
4
6.21
13.7
4
1.95
4.18
4
5.42
11.0
4
3.18
6.26
Ϫ
5.73
13.2
7
3.47
4.66
Product (g)
Product
(mmol)
[a]
Kindly provided by the authors of ref.[9] [b] 1: 4-Bromobutyronitrile; 2: 1-decyl bromide; 3: ethyl bromoacetate; 4: ethyl 3-bromopropi-
onate; 5: ethyl 5-bromopentanoate; 6: ethyl 6-bromohexanoate; 7: 1,3-propanesultone; 8: 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl iodide.
Table 6. Melting points, yields, empirical formulas, molecular weights and CHN elemental analyses for compounds 6
Compound
M.p.
(°C)
Yield Empirical formula
(%)
Mol. mass C content
H content
N content
(g/mol)
calcd. found calcd. found calcd. found
6A, m ϭ 6
6A, m ϭ 7
6A, m ϭ 8[a]
6A, m ϭ 10
6A, m ϭ 11
6B, n ϭ 1
6B, n ϭ 2
6B, n ϭ 4
6B, n ϭ 5
252Ϫ253 29
246Ϫ247 54
206Ϫ207 78
156Ϫ157 61
156Ϫ157 64
214Ϫ216 71
200Ϫ201 26
214Ϫ215 69
254Ϫ255 63
C18H25BrCl2N2O2
C19H27BrCl2N2O2
C20H29BrCl2N2O2
C22H33BrCl2N2O2
C23H35BrCl2N2O2
C18H25BrCl2N2O2
C19H27BrCl2N2O2
C21H31BrCl2N2O2
C22H33BrCl2N2O2
C19H28Cl2N2O3S
C16H19BrCl2N2O4·H2O
452.25
466.27
480.23
508.32
522.35
452.22
466.24
494.30
508.32
435.41
472.16
47.81
48.94
50.01
51.98
52.89
47.81
48.95
51.03
51.98
52.41
40.70
47.82
48.94
48.07
51.77
52.89
47.44
48.69
51.01
52.08
51.91
40.76
5.57
5.84
6.09
6.54
6.75
5.57
5.84
6.32
6.54
6.48
4.48
5.59
5.86
5.85
6.56
6.70
5.67
5.85
6.44
6.68
6.44
4.50
6.19
6.01
5.83
5.51
5.36
6.20
6.01
5.67
5.51
6.43
5.93
6.32
6.05
5.82
5.51
5.44
6.03
5.95
5.45
5.41
6.26
6.03
6C, m ϭ 8, n ϭ 3 281Ϫ282 53
6D, see text
6E, see text
236Ϫ238 29
197Ϫ200 31
C20H16Br0.35Cl2F13I0.65N2O2 744.69
F-content: calcd.: 33.17 found: 33.19
[a]
Ref.[9]: 207Ϫ209 °C.
4 H, NCH2), 8.56 (s, 2 H, 4-H and 7-H), 12.23 (br. s, 1 H, COOH)
1.72Ϫ1.82 (m, 4 H, NCH2CH2), 2.29 (t, J ϭ 7.4 Hz, 2 H,
ppm; 6A, m ؍ 11, ([D6]DMSO): δ ϭ 0.85 (t, J ϭ 6.7 Hz, 3 H, CH2COOH), 2.93 (s, 3 H, 2-CH3), 4.44Ϫ4.50 (m, 4 H, NCH2),
CH2CH3), 1.24Ϫ1.32 (m, 16 H, 8 ϫ CH2), 1.73Ϫ1.75 (m, 2 H, 8.565 (s, 1 H, 4/7-H), 8.569 (s, 1 H, 4/7-H), 12.08 (br. s, 1 H,
NCH2CH2CH2CH2), 1.97Ϫ2.02 (m, 2 H, CH2CH2COOH), 2.43 (t, COOH) ppm; 6B, n ؍ 5, (CD3OD): δ ϭ 0.89 (t, J ϭ 7.0 Hz, 3 H,
J ϭ 7.3 Hz, 2 H, CH2COOH), 2.92 (s, 3 H, 2-CH3), 4.42Ϫ4.49 (m, CH2CH3), 1.30Ϫ1.52 (m, 12 H, 6 ϫ CH2), 1.64Ϫ1.70 (m, 2 H,
4 H, NCH2), 8.555 (s, 1 H, 4/7-H), 8.560 (s, 1 H, 4/7-H), 12.26 (s, CH2CH2CO2H), 1.86Ϫ1.94 (m, 4 H, NCH2CH2), 2.32 (t, J ϭ
1 H, COOH) ppm; 6B, n ؍ 1, ([D6]DMSO): δ ϭ 0.85 (t, J ϭ 7.3 Hz, 2 H, CH2COOH), 2.95 (s, 3 H, 2-CH3), 4.46Ϫ4.50 (m, 4
6.9 Hz, 3 H, CH2CH3), 1.23Ϫ1.33 (m, 10 H, 5 ϫ CH2), 1.74Ϫ1.77 H, NCH2), 8.28 (s, 1 H, 4/7-H), 8.30 (s, 1 H, 4/7-H) ppm; 6C, m ؍
(m, 2 H, NCH2CH2), 2.89 (s, 3 H, 2-CH3), 4.54 (t, J ϭ 7.5 Hz, 2 8, n ؍ 3 ([D6]DMSO): δ ϭ 0.86 (t, J ϭ 6.6 Hz, 3 H, CH2CH3),
H, NCH2), 5.36 (s, 2 H, NCH2CO2H), 8.54 (s, 1 H, 4/7-H), 8.60 1.25Ϫ1.32 (m, 10 H,
(s, 1 H, 4/7-H) ppm; 6B, n ؍ 2, ([D6]DMSO): δ ϭ 0.86 (t, J ϭ NCH2CH2CH2CH2), 2.07Ϫ2.14 (m, 2 H, CH2CH2S), 2.55 (t, J ϭ
7.0 Hz, 3 H, CH2CH3), 1.25Ϫ1.37 (m, 10 H, 5 ϫ CH2), 1.71Ϫ1.77 6.9 Hz, 2 H, CH2S), 2.91 (s, 3 H, 2-CH3), 4.41 (t, J ϭ 7.4 Hz, 2 H,
(m, H, NCH2CH2CH2), 2.90 (t, 6.8 Hz, H, NCH2CH2CH2CH2), 4.61 (t, J ϭ 7.4 Hz, 2 H, SCH2CH2CH2),
5 ϫ CH2), 1.73Ϫ1.75 (m, 2 H,
2
J
ϭ
2
NCH2CH2COOH), 2.96 (s, 3 H, 2-CH3), 4.47 (t, J ϭ 7.5 Hz, 2 H, 8.52 (s, 1 H, 4/7-H), 8.58 (s, 1 H, 4/7-H) ppm; 6D (CD3OD): δ ϭ
NCH2CH2CH2), 4.65 (t, 2 H, NCH2CH2CO2H), 8.55 (s, 1 H, 4/7- 2.13Ϫ2.18 (m, 4 H, NCH2CH2), 2.55 (t, J ϭ 6.5 Hz, 4 H,
H), 8.56 (s, 1 H, 4/7-H), 12.59 (br. s, 1 H, COOH) ppm; 6B, n ؍ CH2COOH), 3.00 (s, 3 H, 2-CH3), 4.53 (t, J ϭ 7.7 Hz, 4 H, NCH2),
4, ([D6]DMSO): δ ϭ 0.86 (t, J ϭ 6.9 Hz, 3 H, CH2CH3), 1.24Ϫ1.39 8.34 (s, 2 H, 4-H and 7-H) ppm; 6E ([D6]DMSO): δ ϭ 1.96Ϫ2.01
(m, 10 H, 5 ϫ CH2), 1.57Ϫ1.63 (m, 2 H, CH2CH2CO2H), (m, 2 H, CH2CH2COOH), 2.43 (t, J ϭ 7.4 Hz, 2 H, CH2COOH),
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3077

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
2.97 (s, 3 H, 2-CH3), 2.94Ϫ3.08 (m, 2 H, CH2CF2), 4.51 (t, J ϭ the mother liquor by suction, washed with water (100 mL) and
FULL PAPER
7.5 Hz,
2
H, NCH2CH2CH2), 4.86 (t,
J
ϭ
7.1 Hz,
2
H, dried to yield dyes 1A, m ϭ 10 and 1B, n ϭ 1 as green powders
and 1E (1.01 g) as a red powder.
NCH2CH2CF2),), 8.56 (s, 1 H, 4/7-H), 8.59 (s, 1 H, 4/7-H) ppm.
1,3-Bis(3-carboxypropyl)-5,6-dichloro-2-methylbenzimidazolium
Bromide 6D: Compound 6D [the formula given in Scheme 2 means
(n ϭ 3) and Ϫ(CH2)3ϪCOOH instead of Ϫ(CH2)mH] was prepared
from 3 by addition of sodium hydroxide (0.80 g, 20.0 mmol) to a
solution of 3 (4.02 g, 20.0 mmol) in dimethyl sulfoxide (30 mL).
This solution was stirred at room temperature for 3 h. 4-Bromobu-
tyronitrile (3.70 g, 25.0 mmol) was then added and stirring was
continued for 1 d. Water (20 mL) was then added, and the precipi-
tate was filtered off, washed with water (100 mL) and dried. The
product was again heated at 150 °C with 4-bromobutyronitrile
(7.40 g, 50.0 mmol) for 4 h. After cooling to room temperature, the
mixture was suspended in acetone (20 mL), stirred for 1 h and fil-
tered. The residue was washed with acetone (30 mL), dried, mixed
with water (20 mL) and hydrobromic acid (48% in weight, aq. soln.,
20 mL) and heated under reflux for 4 h. After filtration the product
was washed with water (100 mL) and recrystallized from hydro-
bromic acid (5% w/w). The yield of 6D·H2O was 2.70 g
(5.72 mmol). Melting points, yields, and CHN analyses are also
given in Table 6.
In order to workup 1A, m ϭ 7, the reaction mixture was dropped
into water (200 mL) containing acetic acid (4 mL) and sodium bro-
mide (12 g, 117 mmol). The dye was isolated by removal of the
mother liquor by suction and dissolved in 200 mL methanol. Pre-
cipitation by addition of water (50 mL), storing for 24 h at 6 °C,
filtration and washing with water (100 mL) yielded 1A, m ϭ 7.
For workup of 1A, m ϭ 11 the reaction mixture was dropped into
water (50 mL) containing acetic acid (1 mL) and sodium bromide
(4 g, 38.9 mmol). The precipitate was isolated by removal of the
mother liquor by suction and washed with water (50 mL). The dye
was the tetrahydrate of the betaine lithium salt.
3,3Ј-Bis(2-carboxyethyl)-5,5Ј,6,6Ј-tetrachloro-1,1Ј-dioctylbenz-
imidacarbocyanine 1B, n ؍ 2, 3,3Ј-Bis(4-carboxybutyl)-5,5Ј,6,6Ј-
tetrachloro-1,1Ј-dioctylbenzimidacarbocyanine 1B, n ؍ 4, 3,3Ј-Bis(5-
carboxypentyl)-5,5Ј,6,6Ј-tetrachloro-1,1Ј-dioctylbenzimida-
carbocyanine 1B,
n ؍ 5; 1,1Ј3,3Ј-Tetrakis(3-carboxypropyl)-
5,5Ј,6,6Ј-tetrachlorobenzimidacarbocyanine 1D:
The appropriate benzimidazolium bromide 6 and iodoform were
similarly mixed with half the total amount of methanol according
to the reaction conditions given in Table 7. The second half of the
General Procedure for the Preparation of 3,3Ј-Bis(3-carboxypropyl)-
5,5Ј,6,6Ј-tetrachloro-1,1Ј-diheptylbenzimidacarbocyanine 1A, m ؍ 7;
3,3Ј-Bis(3-carboxypropyl)-5,5Ј,6,6Ј-tetrachloro-1,1Ј-didecylbenz-
imidacarbocyanine 1A, m ؍ 10; 3,3Ј-Bis(3-carboxypropyl)-5,5Ј,6,6Ј-
tetrachloro-1,1Ј-diundecylbenzimidacarbocyanine Lithium Salt Beta-
ine 1A, m ؍ 11; 3,3Ј-Bis(carboxymethyl)-5,5Ј,6,6Ј-tetrachloro-1,1Ј-
dioctylbenzimidacarbocyanine 1B, n ؍ 1; and 3,3Ј-Bis(3-carboxy-
propyl)-5,5Ј,6,6Ј-tetrachloro-1,1Ј-bis(3,3,4,4,5,5,6,6,7,7,8,8,8-tri-
decafluorooctyl)benzimidacarbocyanine 1E: A 1.5-fold molar excess
of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was added dropwise
with stirring at room temperature to the appropriate benzimidazol-
ium bromide 6 and iodoform in dimethylformamide according to
the reaction conditions given in Table 7. The solution warmed up
slightly. After 3 h, a further 1.5-fold molar excess of DBU was ad-
ded and stirring was continued for 12 h.
methanol, containing metallic sodium [1B,
n ϭ 2: (0.40 g,
17.4 mmol); 1B, n ϭ 4: (0.38 g, 16.5 mmol); 1B, n ϭ 5: 19 g
(8.26 mmol); 1D: (0.37 g, 16.1 mmol)] was then added dropwise
and the mixture were heated at reflux for 30 minutes (1D: 5 mi-
nutes). The reddish-violet reaction mixture was poured into a solu-
tion consisting of aqueous sodium hydroxide (1 , 200 mL), meth-
anol (200 mL) and sodium bromide (8.0 g, 77.7 mmol). After acidi-
fication with glacial acetic acid the precipitates of 1B, n ϭ 2; 1B,
n ϭ 4 and 1B, n ϭ 5 were isolated by removal of the mother liquor
by suction and washed with water.
In order to purify 1B, n ϭ 2 and 1B, n ϭ 5, the residue was ex-
tracted hot with methanol, the extraction volume was concentrated
to 150 mL under reduced pressure, and the solution was added
dropwise to a solution of sodium bromide (5.0 g, 48.6 mmol) in
water (150 mL). The precipitated dye was isolated by removal of
the mother liquor by suction, washed with water and dried, yielding
1B, n ϭ 2 and 1B, n ϭ 5.
For workup of 1A, m ϭ 10; 1B, n ϭ 1; and 1E the reaction mixture
was dropped into water (50 mL) containing acetic acid (1 mL) and
an excess of sodium bromide (4.0 g, 38.9 mmol), and the residue
was isolated by removal of the mother liquor by suction and
washed with water. The residue was then dissolved in dimethyl sul-
foxide (100 mL), filtered and again dropped into a solution of
acetic acid (1 mL) and sodium bromide (4.0 g, 38.9 mmol) in water
(200 mL). The obtained dye was isolated by removal of the mother
liquor by suction, washed with water (50 mL), once more dissolved
in dimethyl sulfoxide (100 mL; 200 mL for 1E) and filtered. A solu-
tion of acetic acid (1 mL) and sodium bromide (2.0 g, 19.4 mmol)
in water (50 mL; for 1E: 100 mL water, 2 mL acetic acid, 4.0 g
(38.9 mmol) sodium bromide) was gently dropped into the dye
solution, which was stored at 6 °C for 12 h, isolated by removal of
In order to isolate 1B, n ϭ 4, the residue was dissolved in dimethyl
sulfoxide (200 mL) and filtered. The filtrate was added dropwise to
a solution of acetic acid (2 mL) and sodium bromide (5.0 g) in
water (100 mL). After the mixture had been kept at 6 °C for 24 h,
water (100 mL) was added and the precipitate was filtered off,
washed with water and dried, yielding the bromide of 1B, n ϭ 4,
m.p. 98Ϫ104 °C. Recrystallization from DMSO gave the pure beta-
ine, m.p. 203Ϫ206 °C.
Table 7. Reaction conditions for synthesis of the 5,5Ј,6,6Ј-tetrachlorobenzimidacarbocyanines
Product
1A, m ϭ 7 1A, m ϭ 10 1A, m ϭ 11 1B, n ϭ 1 1B, n ϭ 2
1B, n ϭ 4
6B, n ϭ 4
3.00 6.07
1.22 3.10
1B, n ϭ 5 1D, see text 1E, see text
6B, n ϭ 5 6D, see text 6E, see text
Starting material 6A, m ϭ 7 6A, m ϭ 10 6A, m ϭ 11 6B, n ϭ 1 6B, n ϭ 2
(g) (mmol)
CHI3 (g) (mmol) 2.83 7.19
6.60 14.2
2.00 3.93
0.79 2.01
3.50 6.70
1.34 3.40
2.49 5.51 1.94 4.16
1.10 2.79 1.29 3.28
1.53 3.01 2.00 4.24
0.69 1.75 0.98 2.49
3.00 4.03
0.85 2.16
Solvent (ml)
Product (g)
(mmol)
DMF (30) DMF (8)
DMF (14) DMF (10) MeOH (16) MeOH (16) MeOH (8) MeOH (8) DMF (10)
2.24
2.60
red
0.18
0.20
green
0.29
0.30
green
0.54
0.70
green
0.27
0.32
red
0.78
0.85
green
0.41,
0.45
green
0.35,
0.46
red
0.56,
0.44
red
Colour
3078
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080

J-Aggregating 5,5Ј,6,6Ј-Tetrachlorobenzimidacarbocyanine Dyes
FULL PAPER
1
Table 8. Melting points, yields, empirical formulas, molecular weights, mass spectra and H NMR chemical shifts of the polymethinic
8,8Ј,9-H and aromatic 4,4Ј,7,7Ј protons of the 5,5Ј,6,6Ј-tetrachlorobenzimidacarbocyanine dyes 1
Dye
M.p.
(°C)
Yield Empirical formula
(%)
Mol. mass MS[a]
1H NMR[b]
8,8Ј-H 9-H 4,7-H 4Ј,7Ј-H
(g/mol)
(m/z)
1A, m ϭ 6
1A, m ϭ 7
1A, m ϭ 8
1A, m ϭ 10 105Ϫ109 10
1A, m ϭ 11 128Ϫ134
1B[h], n ϭ 1 220Ϫ224 26
145Ϫ146
9
C37H47BrCl4N4O4
C39H51BrCl4N4O4
C41H54Cl4N4O4 * 0.5DMSO 847.78
833.56
861.62
754[c]
782[c]
[M ϩ H]ϩ 5.97
7.86 8.00
7.87 7.99
7.86 7.99
7.83 7.27
7.87 8.01
7.80 7.93
7.86 8.00
7.85 8.02
7.84 7.99
7.88 8.00
8.01
8.01
8.01
7.51
8.02
7.96
8.02
8.03
ϩ
126Ϫ129 37
[M ϩ H]
5.91
5.95
5.93
5.97
5.76
5.84
5.86
5.80
5.91
Ͼ 150[d] 14
809.2961[e][f] [M ϩ H]
ϩ
ϩ
C45H63BrCl4N4O4
945.73
970.87
779.63
861.57
836.77
900.85
866[c]
905[e][g]
754[e]
782[c]
838
[M ϩ H]
[Li2M]ϩ
[M ϩ H]
[M ϩ H]
[M ϩ H]
[M ϩ H]
9
C47H65Cl4LiN4O4 * 4H2O
C37H46Cl4N4O4 * 1.5H2O
C39H51BrCl4N4O4
C43H58Cl4N4O4
C45H62Cl4N4O4 * 2H2O
C39H53Cl4N4NaO6S2 * 4H2O 974.85
765.47
C33H34Cl4N4O8 * 0.5H2O
C41H28Cl4F26N4O4
ϩ
ϩ
ϩ
ϩ
1B, n ϭ 2
1B, n ϭ 4
111Ϫ117 17
Ͼ 188[d] 28
1B[h], n ϭ 5 105Ϫ111 30
1C, m ϭ 8, 251Ϫ255 25
n ϭ 3
866[e]
925[e,g]
ϩ
[Na2M]
8.08
ϩ
1D
1E
262Ϫ264 22
138Ϫ145 22
758[e]
1276
[M ϩ H]
[betaine]
5.85
5.83
7.83 7.90
8.04 7.34
ϩ
1276.47
7.44
[a] According to Cl/Br elemental analyses, dye 1B, n ϭ 1 contained 5% dye bromide and 1B, n ϭ 5 10% bromide. [b] Beginning of thermal
decomposition according to DTA. [c] Usually the basis peak is given. With dyes 1B, n ϭ 1 and 1D only, the masses of the molecular ions
possessed relative intensities of 14% and 34%, respectively, indicating partial decomposition of the dyes during the ionization procedure.
The given mass numbers of the molecular ions corresponded to the natural composition of the chlorine isotopes 35Cl337Cl.
Split off
[d]
HBr. Split off solvent molecules. High resolution MS, 35Cl ϭ 34.968853; 37Cl ϭ 36.965903. Substitution of Hϩ by Liϩ or Naϩ,
respectively. Solvent: [D6]dimethyl sulfoxide, with the exception of 1A, m ϭ 10; 1A, m ϭ 11 and 1E, the NMR spectra of which were
measured in chloroform-D1. The protons in the 8,8Ј-position give a doublet, that in 9-position a triplet with coupling constants J8/9
[e]
[f]
[g]
[h]
3
ϭ
13Ϫ14 Hz. Whereas the chemical shifts of the 8-H and 9-H protons were nearly independent of the nitrogen substituents in the 1- and
the 3-positions, as well as of the solvent used, the singlets of the aromatic protons in the 4- and the 7-positions were significantly shifted
to higher fields in chloroform than in DMSO.
For workup of 1D, the reddish-violet reaction mixture was poured
into an aqueous solution (400 mL) of sodium hydroxide (8.0 g,
4.12Ϫ4.20 (m, 4 H, NCH2CH2), 5.03 (s, 4 H, CH2CO2H) ppm; 1B,
n ؍ 2, ([D6]DMSO): δ ϭ 0.79Ϫ0.83 (m, 6 H, CH2CH3), 1.15Ϫ1.28
200 mmol) and sodium bromide (8.0 g, 77.7 mmol) and stirred for (m, 20 H, 10CH2), 1.65Ϫ1.75 (m, 4 H, NCH2CH2CH2), 2.73Ϫ2.78
1 h. After filtration, acetic acid (20 mL) was added and the solution
was stored for 2 d. The precipitate was isolated by removal of the
mother liquor by suction, washed three times with cold ethanol
(m, 4 H, NCH2CH2COOH), 4.24Ϫ4.30 (m, 4 H, NCH2CH2CH2),
4.45Ϫ4.48 (m, H, NCH2CH2COOH) ppm; 1B,
([D6]DMSO): δ ϭ 0.78Ϫ0.83 (m, 6 H, CH2CH3), 1.19Ϫ1.27 (m, 20
4
n ؍ 4
(40 mL each), and heated in ethanol (80 mL) for 10 minutes. After H, 10 ϫ CH2), 1.54Ϫ1.60 (m, 4 H, CH2CH2COOH), 1.70Ϫ1.75
cooling to room temperature, dye 1D was isolated by removal of
the mother liquor by suction and dried in vacuo over P4O10.
(m, 8 H, NCH2CH2), 2.22Ϫ2.27 (m, 4 H, CH2COOH), 4.29Ϫ4.47
(m, 8 H, NCH2) ppm; 1B, n ؍ 5 ([D6]DMSO): δ ϭ 0.78 (t, J ϭ
6.8 Hz, 6 H, CH2CH3), 1.13Ϫ1.30 (m, 24 H, 12 ϫ CH2), 1.47Ϫ1.50
(m, 4 H, CH2CH2COOH), 1.68Ϫ1.72 (m, 8 H, NCH2CH2), 2.02
(t, J ϭ 7.1 Hz, 4 H, CH2COOH), 4.24Ϫ4.29 (m, 8 H, NCH2) ppm;
1C, m ؍ 8, n ؍ 3 ([D6]DMSO): δ ϭ 0.78Ϫ0.83 (m, 6 H, CH2CH3),
Melting points, yields, mass spectra and the 1H NMR chemical
shifts of the aromatic and polymethinic protons of the dyes are
compiled in Table 8.
1H NMR: 1A, m ؍ 6, ([D6]DMSO): δ ϭ 0.79Ϫ0.85 (m, 6 H,
CH2CH3), 1.20Ϫ1.35 (m, 12 H, 6 ϫ CH2), 1.72Ϫ1.82 (m, 4 H,
1.19Ϫ1.28 (m, 20 H, 10
ϫ CH2), 1.72Ϫ1.78 (m, 4 H,
NCH2CH2CH2CH2), 2.04Ϫ2.08 (m, 4 H, CH2CH2S), 2.50Ϫ2.55
(m, 4 H, CH2S), 4.29Ϫ4.34 (m, 4 H, NCH2CH2CH2CH2),
4.40Ϫ4.44 (m, 4 H, NCH2CH2CH2S) ppm; 1D ([D6]DMSO): δ ϭ
1.87Ϫ1.93 (m, 8 H, NCH2CH2), 2.21Ϫ2.25 (m, 8 H, CH2COOH),
4.21Ϫ4.26 (m, 8 H, NCH2) ppm; 1E (CDCl3): δ ϭ 2.00Ϫ2.04 (m,
4 H, NCH2CH2CH2), 2.39Ϫ2.42 (m, 4 H, NCH2CH2CH2),
NCH2CH2CH2CH2), 1.82Ϫ1.95 (m,
4 H, CH2CH2COOH),
2.12Ϫ2.19 (m, 4 H, CH2COOH), 4.11Ϫ4.41 (m, 8 H, NCH2) ppm;
1A, m ؍ 7, ([D6]DMSO): δ ϭ 0.79Ϫ0.83 (m, 6 H, CH2CH3),
1.18Ϫ1.35 (m, 16 H,
8
ϫ
CH2), 1.71Ϫ1.80 (m,
4 H,
NCH2CH2CH2CH2), 1.85Ϫ1.97 (m,
4
H, CH2CH2COOH),
2.26Ϫ2.30 (m, 4 H, CH2COOH), 4.23Ϫ4.33 (m, 8 H, NCH2) ppm;
1A, m ؍ 8, ([D6]DMSO): δ ϭ 0.78Ϫ0.82 (m, 6 H, CH2CH3),
2.62Ϫ2.71 (m,
4 H, NCH2CH2CF2), 4.18Ϫ4.22 (m, 4 H,
NCH2CH2CH2), 4.60Ϫ4.65 (m, 4 H, CH2CH2CF2) ppm.
1.16Ϫ1.35 (m, 20 H, 10
ϫ
CH2), 1.72Ϫ1.80 (m,
4 H,
NCH2CH2CH2CH2), 1.86Ϫ1.95 (m,
2.20Ϫ2.28 (m, 4 H, CH2COOH), 4.20Ϫ4.35 (m, 8 H, NCH2) ppm;
1A, m ؍ 10, (CDCl3): δ ϭ 0.85 (t, J ϭ 6.9 Hz, 6 H, CH2CH3),
4
H, CH2CH2COOH),
Acknowledgments
The correspondence author (S. D.) is greatly indebted to the Au-
4 H, thorities of the Federal Institute for Materials Research and Testing
H, CH2CH2COOH),
1.23Ϫ1.35 (m, 28 H, 14
NCH2CH2CH2CH2), 2.02Ϫ2.09 (m,
2.48Ϫ2.52 (m, 4 H, CH2COOH), 4.20Ϫ4.25 (m, 8 H, NCH2) ppm; who gave him the opportunity to continue his research work after
ϫ
CH2), 1.82Ϫ1.87 (m,
4
(BAM), especially to its President, Prof. Dr. Manfred Hennecke,
1A, m ؍ 11, ([D6]DMSO): δ ϭ 0.79Ϫ0.84 (m, 6 H, CH2CH3),
1.17Ϫ1.27 (m, 32 H, 16 CH2), 1.72Ϫ1.80 (m, H,
NCH2CH2CH2CH2), 1.85Ϫ1.92 (m,
his retirement in 1994. The authors thank Prof. Dr. Helmuth
Möhwald, Max-Planck-Institut für Kolloid- und Grenzflächenfor-
H, CH2CH2COOH), schung, Potsdam, for his generous support of this work and Prof.
ϫ
4
4
2.12Ϫ2.15 (m, 4 H, CH2COOH), 4.20Ϫ4.36 (m, 8 H, NCH2) ppm; Dr. Martin Demuth, Max-Planck-Institut für Strahlenchemie,
1B, n ؍ 1, ([D6]DMSO): δ ϭ 0.80Ϫ0.83 (m, 6 H, CH2CH3), Mülheim/Ruhr, for placing his laboratory at their disposal in order
1.20Ϫ1.35 (m, 20 H, 10 ϫ CH2), 1.61Ϫ1.72 (m, 4 H, NCH2CH2),
to repeat the experiments on chiral parity violation. The authors
Eur. J. Org. Chem. 2003, 3065Ϫ3080
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3079

A. Pawlik, A. Ouart, S. Kirstein, H.-W. Abraham, S. Daehne
FULL PAPER
[25]
[26]
[27]
S. S. Lampoura, C. Spitz, S. Daehne, J. Knoester, K. Duppen,
J. Phys. Chem. B 2002, 106, 3103Ϫ3111.
H. Engelkamp, S. Middelbeek, R. J. M. Nolte, Science 1999,
284, 785Ϫ788.
S. Daehne, K.-D. Nolte, Chem. Commun. (London) 1972,
1056Ϫ1057.
are also obliged to Dr. Wolfgang Liebscher, Berlin, for suggesting
the correct IUPAC nomenclature of dye 1A, m ϭ 8. Skilled analyti-
cal aid from the Department of Analytical Chemistry and Refer-
ence Materials, (BAM), Berlin, and from the Institute of Applied
Chemistry at Adlershof (ACA), Berlin, is gratefully acknowledged.
The work has been supported by the Deutsche Forschungsgemein-
schaft DFG (Sonderforschungsbereich 337, and Projects DA 268/
6Ϫ1, Ϫ2; AB 74/5Ϫ1, Ϫ2, Ϫ3; KI 544/1Ϫ1, 3Ϫ1) and INTAS
(Project 97Ϫ10434).
[28] [28a]
E. G. Mc Rae, M. Kasha, in Physical Processes in Radi-
ation Biology (Eds.: L. Augenstein, R. Mason, B. Rosenberg)
Academic Press, New York, 1964, 23Ϫ42. [28b]M. Kasha, H. R.
Rawls, M. A. El-Bayoumi, Pure Appl. Chem. 1965, 11,
371Ϫ392.
M. Bednarz, J. Knoester, J. Phys. Chem. B 2001, 105,
12913Ϫ12923.
C. Didraga, J. A. Klugkist, J. Knoester, J. Phys. Chem. B
2002, 11474Ϫ11486.
H. Kuhn, C. Kuhn, in J-Aggregates, (Ed.: C. Kobayashi),
World Scientific, Singapore, 1996, 1Ϫ40.
S. H. Dandegaonker, V. V. Kanabur, Monatsh. Chem. 1968,
99, 1467Ϫ1472.
E.-J. Poppe, Z. wiss. Photogr., Photophys. Photochem. 1969,
63, 149Ϫ158.
E. W. Knapp, Chem. Phys. 1984, 85, 73Ϫ82.
M. Lindrum, S. Daehne, phys. stat. solid. 1995, (b) 189, 51Ϫ57.
U. De Rossi, S. Daehne, U. Gomez, H. Port, Chem. Phys. Let-
ters 1998, 287, 395Ϫ402.
C. Spitz, S. Daehne, Ber. Bunsenges. Phys. Chem. 1998, 102,
738Ϫ744.
[29]
[30]
[31]
[32]
[33]
[1]
N. Tyutyulkov, J. Fabian, A. Mehlhorn, F. Dietz, A. Tadger,
Polymethine Dyes, Structure and Properties, St. Kliment Ohrid-
ski University Press, Sofia, 1991.
[2]
K. H. Drexhage, Top. Appl. Phys. 2nd Ed., 1990, 1 (Dye La-
sers), 144Ϫ274.
[3]
F. Würthner, R. Wortmann, K. Meerholz, ChemPhysChem
2002, 3, 17Ϫ31.
[4]
A. H. Herz, Adv. Colloid Interface Sci. 1977, 8, 237Ϫ298.
[5]
G. Bach, S. Daehne, Cyanine Dyes and Related Compounds, in
Rodd’s Chemistry of Carbon Compounds, 2nd. Suppl. to 2nd.
Ed. (Ed.: M. Sainsbury), Elsevier Science, Amsterdam, Laus-
anne, New York, Oxford, Shannon, Tokyo, 1997, Vol. IVB,
Chapter 15; pp. 383Ϫ481.
[34]
[35]
[36]
[6]
S. Daehne, Bunsenmagazin 2002, 4, 81Ϫ92.
[37]
[38]
[39]
[7]
D. Möbius, Adv. Mater. 1995, 7, 437Ϫ444.
[8]
J. E. Maskasky, LANGMUIR 1991, 7, 407Ϫ421.
[9]
S. Daehne, R. Radeglia, G. Reck, A. Ouart, R. Peichert, H.-
W. Abraham, S. Kirstein, to be published.
FEW Chemicals GmbH., Industriepark Wolfen-Thalheim, P.
O. B. 1340, D-06756 Wolfen, Germany.
U. De Rossi, J. Moll, M. Spieles, G. Bach, S. Daehne, J. Kri-
wanek, M. Lisk, J. prakt. Chem. Chem.-Ztg. 1995, 337,
203Ϫ208.
[10]
J.-M. Lehn, Supramolecular Chemistry, VCH-Verlagsgesell-
[40] [40a]
E. Langhals, H. Balli, Helv. Chim. Acta 1985, 68,
schaft, Weinheim,1995.
A. Pawlik, S. Kirstein, U. De Rossi, S. Daehne, J. Phys. Chem.
[40b]
[11]
1782Ϫ1797.
M. Kussler, H. Balli, Helv. Chim. 1989, 72,
17Ϫ28; 295Ϫ306.
B 1997, 101, 5646Ϫ5651.
S. Makio, N. Kanamura, J. Tanaka, Bull. Chem. Soc., Jpn.
[41] [41a] C. Königstein, R. Bauer, Int. J. Hydrogen Energy 1993, 18,
735Ϫ741. [41b] C. Königstein, M. Neumann-Spallart, R. Bauer,
Electrochim. Acta 1998, 43, 2435Ϫ2445.
[12]
1980, 53, 3120Ϫ3124.
J. Moll, S. Daehne, J. R. Durrant, D. A. Wiersma, J. Phys.
[13]
[42] [42a] B. L. Feringa, R. A. van Delden, Angew. Chem. 1999, 111,
Chem. 1995, 102, 6362Ϫ6370.
M. Van Burgel, D. A. Wiersma, K. Duppen, J. Chem. Phys.
[42b]
[14]
3624Ϫ3645; Angew. Chem. Int. Ed. 1999, 38, 3418Ϫ3438.
´
M. Avalos, R. Babiano, P. Cintas, J. L. Jimenez, J. C. Palacios,
1995, 202, 20Ϫ33.
A. Ouart, Von chiralen Superhelices zu achiralen Nano-
[15]
Chem. Commun. 2000, 887Ϫ892.
[43]
In order to rule out either slight differences in the experimental
operation of different examiners or chiral contamination of our
laboratory as causes of the contradictory results, the experi-
ment was repeated in the lab of Prof. Dr. Martin Demuth, Max
Planck Institute of Radiation Chemistry, Muelheim at the
Ruhr, on August 3, 2001. The experimentalists S. Daehne, U.
De Rossi and A. Ouart each time applied a stock solution of
dye 1A, m ϭ 8 in ethanol (10Ϫ2 , 1.0 mL), which was added
dropwise with stirring to aqueous sodium hydroxide solution
(10Ϫ2 , 9.0 mL) yielding the optically active J-aggregate solu-
tion. Sixteen tests gave 15 positive CD couplets and only one
negative CD couplet.
strukturen: Spektroskopische und strukturelle Untersuchungen
von J-Aggregaten achiraler Cyaninfarbstoffe, Thesis, Humboldt
University, Berlin, 2000. http://dochost. rz. hu-berlin. de/dis-
sertationen/ouart-andre-2000Ϫ09Ϫ28.
[16]
H. von Berlepsch, C. Böttcher, A. Ouart, C. Burger, S. Daehne,
S. Kirstein, J. Phys. Chem. B 2000, 104, 5255Ϫ5262.
[17]
H. von Berlepsch, to be published, private communication.
[18]
U. De Rossi, S. Daehne, S. C. J. Meskers, H. P. J. M. Dekkers,
Angew. Chem. 1996, 108, 827Ϫ830; Angew. Chem. Int. Ed.
Engl. 1996, 35, 760Ϫ763.
S. Kirstein, H. von Berlepsch, C. Böttcher, C. Burger, A. Ouart,
[19]
G. Reck, S. Daehne, ChemPhysChem 2000, 146Ϫ150.
H. von Berlepsch, C. Böttcher, A. Ouart, M. Regenbrecht, S.
[44] [44a]
[20]
´
J. M. Ribo, J. Crusats, F. Sagues, J. Claret, R. Rubires,
Science 2001, 292, 2063Ϫ2066.
[44b]
R. Rubires, J.-A. Farrera,
J. M. Ribo, Chem. Eur. J. 2001, 7, 436Ϫ446.
Akari, U. Keiderling, H. Schnablegger, S. Daehne, S. Kirstein,
LANGMUIR 2000, 16, 5908Ϫ5916.
H. von Berlepsch, M. Regenbrecht, S. Daehne, S. Kirstein, C.
[45]
[21]
W. König: Über den Begriff der Polymethinfarbstoffe und eine
davon ableitbare allgemeine Farbstoff-Formel als Grundlage
einer neuen Systematik der Farbenchemie, J. Prakt. Chem. [2]
1926, 112, 1Ϫ36.
Böttcher, LANGMUIR 2002, 18, 2901Ϫ2907.
[22]
C. Spitz, J. Knoester, A. Ouart, S. Daehne, Chem. Phys. 2002,
275, 271Ϫ284.
[46] [46a]
[46b]
[23]
G. Scheibe, Angew. Chem. 1937, 50, 212Ϫ219.
G.
H. von Berlepsch, S. Kirstein, C. Böttcher, LANGMUIR 2002,
18, 7699Ϫ7705.
C. Spitz, Exzitonische Anregungen in zylindrischen J-Aggre-
Scheibe, A. Schöntag, F. Katheder, Fluoreszenz und Energiefort-
leitung in reversibel polymerisierten Farbstoffen, Naturwissen-
schaften 1939, 27, 499Ϫ501.
[24]
gaten, Thesis, Free University, Berlin, 1999. http://www. diss.
fu-berlin/ 1999/15.
Received February 13, 2003
3080
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3065Ϫ3080