Pentarylene- and hexarylenebis(dicarboximide)s: Near-infrared-absorbing polyaromatic dyes

Article abstract of DOI:10.1002/anie.200502998

(Figure Presented) In the red: The synthesis and optical properties of homologous ladder-type near-infrared-absorbing chromophores, namely, two pentarylenebis(dicarboximide)s (green traces; see picture) as well as a hexarylenebis(dicarboximide) (yellow trace) have been studied. A strong bathochromic shift of the absorption maximum is noted with an increasing degree of annulation as is evident from the other traces.

Full text of DOI:10.1002/anie.200502998

Angewandte
Chemie
along the molecular long axis, we have obtained the higher
homologues terrylenebis(dicarboximide) (2) and quaterryl-
enebis(dicarboximide) (3; Figure 1). In comparison to the
absorption maximum of perylenebis(dicarboximide) (1),
NIR Dyes
Figure 1. Chemical structures of rylenebis(dicarboximide)s and
bis(rylenedicarboximide)-a,d-1,5-diaminoanthraquinone.
DOI: 10.1002/anie.200502998
Pentarylene- and Hexarylenebis(dicarboximide)s:
Near-Infrared-Absorbing Polyaromatic Dyes**
those of 2 and 3 are shifted bathochromically. Quaterrylene-
bis(dicarboximide) (3) is a deeply colored dye with a strong
absorption in the NIR region.[9] Both chromophores exhibit
high thermal, chemical, and photochemical stabilities
together with high extinction coefficients.[8–11] Recently we
introduced an alternative and surprisingly facile approach
toward NIR absorbers by the coupling and fusion of a
perylenedicarboximide with a 1,5-diaminoanthraquinone to
Neil G. Pschirer, Christopher Kohl, Fabian Nolde,
Jianqiang Qu, and Klaus Müllen*
Although a large variety of dyes are commercially available
today, there is an ongoing need for new chromophoric
systems[1–3] and low-band-gap materials.[4] For example,
near-infrared (NIR) emission has received increased atten-
tion for applications in bioassays and medicine[5] while NIR
absorption is demanded for laser-welding of plastics or
efficient blocking of heat rays. Most of the commercially
available NIR materials are not suitable for such purposes
owing to their insufficient stability.[6] Over the last decade we
have developed several NIR-absorbing polyaromatic dyes.[7–9]
By extending the p system of perylenebis(dicarboximide)s
afford
bis(perylenedicarboximide)-a,d-1,5-diaminoanthra-
quinone (4), a NIR absorber with a remarkably strong
absorption around 1100 nm and extraordinary thermal and
photochemical inertness.[7]
If we take into consideration the outstanding role of
quaterrylenebis(dicarboximide) (3), then the extension of the
framework of rylenebis(dicarboximide)s appears a logical
next step to induce a narrowing of the HOMO–LUMO gap,
thereby causing a further bathochromic shift in the absorption
spectrum.[12] Herein, we describe the synthesis and attractive
optical properties of homologous ladder-type chromophores,
namely the pentarylenebis(dicarboximide)s 6 and 7 as well as
the hexarylenebis(dicarboximide) 8.
We selected two different construction concepts for the
penta- and hexarylenebis(dicarboximide)s 6, 7, and 8: 1) The
“nitronaphthalene method” in which one nitronaphthalene
unit is attached to a perylenedicarboximide, the bisaryl
product is fused, and the nitro group is replaced by a halide
to provide a halogen-substituted terrylenedicarboximide as a
precursor for the penta- or hexarylenebis(dicarboximide)s 7
and 8 (Scheme 1); or 2) the “bisbromorylene method” in
[*] Dr. N. G. Pschirer, Dr. C. Kohl, F. Nolde, Dr. J. Qu, Prof. Dr. K. Müllen
MaxPlanck Institute for Polymer Research
Ackermannweg 10, 55128 Mainz (Germany)
Fax: ( +49)6131-379-350
E-mail: muellen@mpip-mainz.mpg.de
[**] We gratefully acknowledge BASF AG and the Deutsche For-
schungsgemeinschaft (Sonderforschungsbereich 625) for financial
support, as well as Dr. R. Sens and Dr. C. Lennartz (BASF AG) for
their calculations.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2006, 45, 1401 –1404
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1401

Communications
nitroterrylenedicarboximide (12) in 35%
yield, after isolation and purification by
column chromatography.
11-Nitroterrylenedicarboximide (12) is
readily soluble in all common organic
solvents (120 mgmLÀ1 CH2Cl2) at room
temperature and serves as a starting mate-
rial for the preparation of 7 and 8. Reduc-
tion of 12 with Pd/C and hydrogen gave 11-
aminoterrylene (5) in 78% yield. Attempts
to produce a halogenated terrylene by the
Sandmeyer reaction delivered the non-
halogenated terrylene as the major prod-
uct and only small quantities of the desired
compound. The amount obtained, how-
ever, was sufficient for the homocoupling
of the iodinated terrylenemonoimide or
the Suzuki coupling of the monoimide with
perylenemono-
Scheme 1. Reagents and conditions: a) [Pd(PPh3)4], K2CO3 (aq), ethanol/toluene, 808C, 16 h, 100%;
b) DBN, NaOtBu, diglyme, 708C, 2 h 35%; c) Pd/C, H2, ethanol/CHCl3, room temperature, 15 h, 78%;
d) NaNO2, HCl, THF, Et2O, MeCN, À108C, NaI; e) for 8: B(OR)2, [Pd(PPh3)4], KOAc, toluene; for 7: 9,
K2CO3 (aq), [Pd(PPh3)4], ethanol/toluene; f) K2CO3, ethanolamine, 1358C. DBN=1,5-diazabicyclo-
[4.3.0]non-5-ene.
imide 9 to form the bis(terrylenemonoi-
mide) or perylenemonoimide-terrylene-
monoimide bichromophores, respectively,
which were then directly cyclized (without
which two perylenedicarboximides are coupled to a bisbro-
monaphthalene or -perylene and fused in a one-step (6) or
two-step (7 and 8) sequence to form the corresponding penta-
or hexarylenediimide (Schemes 2 and 3).
isolation) through an oxidative cyclodehydrogenation to yield
8 or 7 in high purity and yield (last step) after purification.
To obtain these higher rylenediimides in an improved
overall yield, a second approach was investigated. Extension
of the framework by introducing a naphthalene or perylene
unit between two perylenemonoimides (the bisbromorylene
method) involves the palladium-catalyzed coupling reaction
of perylenemonoimides with a bisbromo-functionalized naph-
thalene or perylene followed by a final bond closure to a
double-stranded rylene structure. To avoid the use of toxic
stannyl compounds as intermediates in the Stille coupling
reaction, the boronic esters of 9-bromoperylenedicarboxi-
mide (13) and 9 were subjected to Suzuki coupling with 1,4-
bisbromonaphthalene (14) to give the bisperylenylnapthalene
derivatives 15 and 17 in good yields (15 72%, 17 75%). The
boronic ester of 9 was coupled with 1,9(10)-bisbromoperylene
(16) to provide 18 in 79% yield (Scheme 3).
The final cyclization steps were carried out through an
oxidative cyclodehydrogenation. Several dehydrogenation
methods to form rylene structures from polynaphthalene
and/or polyperylene units are described in the literature. Clar
et al. applied successfully an aluminum chloride/sodium
chloride melt to “cake” polynaphthalene derivatives
together.[14,15] We developed milder conditions for the cycli-
zation to oligorylenes under the influence of AlCl3/CuCl2 and
FeCl3.[16]
Scheme 2. Reagents and conditions: a) [Pd(PPh3)4], K2CO3 (aq), etha-
nol/toluene, 808C, 72%; b) AlCl3, chlorobenzene, 758C, 20 min, 24%.
The nitronaphthalene method requires the boronic ester
of 1-bromo-5-nitronaphthalene (10) which was prepared
according to the procedure of Miyaura et al.[13] with bis(pi-
nacolato)diboron and [PdCl2(dppf)] (dppf = 1,1’-bis(diphe-
nylphosphino)ferrocene). The boronic ester was coupled to
the diphenoxy-substituted 9-bromoperylenedicarboximide
(9) under standard Suzuki conditions to form the terrylene
precursor 11 in quantitative yield (Scheme 1). In the subse-
quent step, 11 was cyclized with sodium tert-butoxide/1,5-
diazabicyclo[4.3.0]non-5-ene as base in diglyme to give 11-
While both 2,6-diisopropylphenyl and 1-heptyloctyl sub-
stituents at the imide structure improve the synthesis of
pentarylenediimide by enhancing the solubility, the alkyl
substitution has the advantage that no dealkylation has to be
feared during the Lewis acid assisted cyclization step. To
obtain the fully annulated ladder-type structure 6, the
bisperylenyl(naphthalene) derivative 15 was allowed to
react with aluminum chloride in chlorobenzene to afford 6,
which was obtained as a black–green precipitate in 24% yield.
The pentarylenediimide 6 is only slightly soluble in organic
1402
www.angewandte.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 1401 –1404

Angewandte
Chemie
against the inverse squared length of the
p system, where the length L is taken as
the N–N distance of the force-field
geometries of rylenes 1, 2, 3, 7, and 8,
an ideal particle-in-the-box behavior (E
ꢀ 1/L2) was indeed observed (see
Figure 3).
In the case of the pentarylene deriv-
atives 6 and 7, the absorption maximum
is additionally influenced by the number
of phenoxy substituents in the bay
region of the chromophore. The max-
imum absorption of the unsubstituted
pentarylene 6 lies at 831 nm, whereas
that for the tetrasubstituted pentarylene
7 lies at 877 nm. This is a consequence of
the destabilization of the HOMO by
antibonding contributions of the phen-
oxy groups. The bathochromic shift of
the first electronic transition upon phen-
oxy substitution in the bay position of 6
is best reproduced by ZINDO/s calcu-
lations, which give values of 745 nm for 6
and 777 nm for 7. These calculations
show a bathochromic shift of approxi-
Scheme 3. Reagents and conditions: a) [Pd(PPh3)4], K2CO3 (aq), ethanol/toluene, 808C;
b) FeCl3/nitromethane, CH2Cl2, room temperature, 24 h; c) K2CO3, ethanolamine, 1358C, 4 h.
solvents (< 0.5 mgmLÀ1 CH2Cl2) at room temperature and is
better regarded as a pigment than a dye.
It was then of particular interest to see if we could
synthesize , through the bisbromorylene method the more-
soluble tetraphenoxy-substituted derivatives 7 and 8, which
were already obtained by the nitronapthalene method. The
cyclization of 17 and 18 to the tetraphenoxy-pentarylene 7
and -hexarylene 8 was achieved under milder conditions in a
two-step process to avoid the undesirable dealkylation of
phenoxy and imide substituents by strong Lewis acids. The
first cyclization of 17 and 18 was obtained with FeCl3/
nitromethane in CH2Cl2 at room temperature. After hydrol-
ysis and washing, the target compounds were formed by a
mild base-promoted cyclization with K2CO3/ethanolamine.
Figure 2. Absorption spectra of the entire tetraphenoxy-substituted
rylenediimide series in CHCl3: perylenebis(dicarboximide) (red), ter-
rylenebis(dicarboximide) (blue), quaterrylenebis(dicarboximide) (tur-
quoise), pentarylenebis(dicarboximide) 7 (green), and hexarylenebis(di-
carboximide) 8 (yellow).
This method provides the NIR absorbers 7 and 8 in an overall
yield of over 25%.
As a result of the substitution with four tert-octylphenoxy
groups in the bay positions, penta- and hexarylene derivative
7 and 8 are soluble in all common organic solvents
(> 1 mgmLÀ1 CH2Cl2). The synthesized penta- and hexaryl-
enediimides were characterized by mass spectrometry and IR
and UV/Vis/NIR spectroscopy, while the measurement of
1H NMR spectra was only successful in the case of 7. The
absorption spectra of penta- and hexarylene derivatives 7 and
8 demonstrate a strong bathochromic shift of the absorption
maximum with an increasing degree of annulation (Figure 2).
The absorption maximum of 7 is found at 877 nm whereas
that for 8 lies at 953 nm. By examining the entire rylenedi-
imide series (perylenediimide 1 to hexarylenediimide 8), it is
apparent that the energy of the absorption maximum is
shifted to lower energies upon increasing the length of the
p system, as is to be expected from a simple particle-in-a-box
picture. When the maximum absorption energy was plotted
mately 100 nm compared to the observed values, a typical
effect of gas-phase calculations. In each case, the absorption
bands exhibit a similar vibrational structure, which is typical
for rylenediimides.
As a result of the extension of the aromatic p system along
the molecular long axis, not only does a bathochromic shift
become apparent but the absorption coefficients increase
also: e = 235mÀ1 cmÀ1 for the pentarylenediimide 7, e =
293mÀ1 cmÀ1 for the hexarylenediimide 8. Such absorption
coefficients are phenomenal and, to our knowledge, are the
highest reported among all the known organic dyes in this
region of the NIR spectrum. Theoretic elucidation of the
electronic transition properties of penta- and hexarylene as
Angew. Chem. Int. Ed. 2006, 45, 1401 –1404
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
1403

Communications
[4] L. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik, J. R.
Reynolds, Adv. Mater. 2000, 12, 481 – 494.
[5] V. Mantareva, D. Petrova, L. Avramov, I. Angelov, E. Borisova,
M. Peeva, D. Wöhrle, J. Porphyrins Phthalocyanines 2005, 9, 47 –
53.
[6] P. Gregory, High-Technology Applications of Organic Colorants,
Plenum, New York, 1991.
[7] C. Kohl, S. Becker, K. Müllen, Chem. Commun. 2002, 23, 2778 –
2779.
[8] F. Holtrup, G. Müller, H. Quante, S. de Feyter, F. C.
De Schryver, K. Müllen, Chem. Eur. J. 1997, 3, 219 – 225.
[9] H. Quante, K. Müllen, Angew. Chem. 1995, 107, 1487 – 1489;
Angew. Chem. Int. Ed. Engl. 1995, 34, 1323 – 1325.
[10] Y. Nagao, H. Iwawaki, K. Kozawa, Heterocycles 2002, 56, 331 –
340.
[11] Y. Geerts, H. Quante, H. Platz, R. Mahrt, M. Hopmeier, A.
Böhm, K. Müllen, J. Mater. Chem. 1998, 8, 2357 – 2369.
[12] M. Adachi, Y. Nagao, Chem. Mater. 1999, 11, 2107 – 2114.
[13] T. Ishiyama, M. Murata, N. Miyaura, J. Org. Chem. 1995, 60,
7508 – 7510.
Figure 3. Correlation between the maximum absorption energy and the
inverse squared length of the p system (see text). A particle-in-the-box
behavior is observed (Eꢀ1/L2). Plotted points represent the tetraphe-
noxy-substituted rylene dyes (left to right) 8, 7, 3, 2, and 1.
[14] E. Clar, Chem. Ber. 1948, 81, 52 – 63.
[15] E. Clar, W. Kelly, R. M. Laird, Monatsh. Chem. 1956, 87, 391.
[16] K.-H. Koch, K. Müllen, Chem. Ber. 1991, 124, 2091 – 2100.
[17] J. Fabian, R. Zahradnik, Angew. Chem. 1989, 101, 693 – 710;
Angew. Chem. Int. Ed. Engl. 1989, 28, 677 – 694; J. Fabian, M.
Nakazumi, T. J. Matsuoka, Chem. Rev. 1992, 92, 1197 – 1226.
extended p-conjugated derivatives of perylenediimide sub-
stantiate these excellent spectral properties. Compounds 6, 7,
and 8 display an impressive stability and their solutions
remained unchanged over weeks in sunlight. The photo-
stability of 8 was compared with its lower homologue, the
quaterrylenediimide 2, whose excellent photochemical stabil-
ity was reported previously.[10] Exposure of solutions of 8 and
2 in THF(10 À6 mÀ1) in quartz cuvettes to UV light (l =
365 nm) for 9 h led to no significant changes in their
absorption intensities. From a practical point of view, it is
important to mention the almost colorless solutions of the
penta- and hexarylenediimide derivatives 6, 7, and 8. A
negligible absorption in the visible region together with their
extraordinary high extinction coefficients in the NIR, which is
only comparable to a few squarylium dyes,[17] predestine them
for many technological applications, such as security printing.
In conclusion, two synthetic approaches give access to an
extended homologous series of NIR-absorbing rylenebis(di-
carboximide)s. The absorption spectra of pentarylenediimide
6 and 7 as well as hexarylenediimide 8 are characterized by an
extremely intense absorption between 830 and 960 nm. In
addition to these remarkable photophysical properties, the
penta- and hexarylene derivatives still display good chemical
and thermal stability, as already observed for their smaller
homologues, the perylene-, terrylene-, and quaterrylenedi-
imides.
Received: August 23, 2005
Published online: January 20, 2006
Keywords: aromaticity · dyes/pigments · fused-ring systems ·
.
perylenes · UV/Vis spectroscopy
[1] M. Linke-Schätzel, A. D. Bhise, H. Gliemann, T. Koch, T.
Schimmel, T. S. Balaban, Thin Solid Films 2004, 451, 16 – 21.
[2] F. Würthner, S. Ahmed, C. Thalacker, T. Debaerdemaeker,
Chem. Eur. J. 2002, 8, 4742 – 4750.
[3] P. Coppo, M. Duati, V. N. Kozhevnikov, J. W. Hofstraat, L.
De Cola, Angew. Chem. 2005, 117, 1840 – 1844; Angew. Chem.
Int. Ed. 2005, 44, 1806 – 1810.
1404 www.angewandte.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 1401 –1404