Preparation and characterization of regioisomerically pure 1,7-disubstituted perylene bisimide dyes

Article abstract of DOI:10.1021/jo048880d

A detailed study on bromination and subsequent imidization of perylene bisanhydride with cyclohexylamine is reported. The present results reveal that previously reported 1,7-difunctionalized perylene bisimides are presumably contaminated with the respecti

Full text of DOI:10.1021/jo048880d

Preparation and Characterization of Regioisomerically Pure
1,7-Disubstituted Perylene Bisimide Dyes
Frank Wu¨rthner,*,† Vladimir Stepanenko,† Zhijian Chen,† Chantu R. Saha-Mo¨ller,†
Nikolaus Kocher,‡ and Dietmar Stalke‡
Institutes of Organic Chemistry and Inorganic Chemistry, University of Wu¨rzburg,
Am Hubland, 97074 Wu¨rzburg, Germany
wuerthner@chemie.uni-wuerzburg.de
Received July 2, 2004
A detailed study on bromination and subsequent imidization of perylene bisanhydride with
cyclohexylamine is reported. The present results reveal that previously reported 1,7-difunctionalized
perylene bisimides are presumably contaminated with the respective 1,6 regioisomers. N,N′-
Dicyclohexyl-1,7-dibromoperylene bisimide 1,7-3 is obtained for the first time in isomerically pure
form, and its structure is unequivocally confirmed by X-ray analysis. By using regioisomerically
pure 1,7-dibromoperylene bisimide 1,7-3, 1,7-dipyrrolidinylperylene bisimides 4a-c and 1,7-
dipyrrolidinylperylene bisanhydride 5 as well as the unsymmetrically difunctionalized 1-bromo-
7-pyrrolidinyl- and 1-cyano-7-pyrrolidinylperylene bisimides 7 and 8 are synthesized in good yield.
Introduction
functionalization of perylene bisimide. The chemical
modification at imide groups does not significantly effect
the optical and electronic properties of this chromophore
because of nodes in the HOMO and LUMO orbitals at
the imide nitrogen atoms.9,10 However, these properties
are drastically changed on functionalization of the perylene
core with electron-donor or -acceptor groups. Such core-
functionalized perylene bisimides are usually synthesized
from the respective halogenated, in particular, bromi-
nated, derivatives in the case of difunctionalized perylene
bisimides. In a 1997 patent,11 BASF disclosed a procedure
for the bromination of perylene bisanhydride 1 and
subsequent imidization of brominated product as well as
exchange of bromine atoms in bisimides by phenoxy and
alkyne groups. This patent claimed that the bromination
of perylene bisanhydride 1 under the conditions applied
forms selectively 1,7-dibromoperylene bisanhydride 1,7-2
(Scheme 1), and consequently, the subsequent imidiza-
Derivatives of perylene-3,4:9,10-tetracarboxylic acid
bisimide are of increasing interest as functional dyes for
applications in molecular electronic devices such as
photovoltaic cells,1 organic field-effect transistors (OFETs),2
and light-emitting diodes (OLEDs).3 These dyes were also
used in electrophotography (xerographic photoreceptors),4
fluorescent light collectors,5 and lasers.6 Furthermore,
liquid crystallinity of perylene bisimides has been re-
cently demonstrated7 as well as nano- and mesoscopic
supramolecular architectures.8
Distinct optical and electronic properties are required
for the application of perylene bisimides in optoelectron-
ics. The desired properties may be achieved by proper
* To whom correspondence should be addressed. Tel: + 49 (0)931-
8885340. Fax: + 49-(0)931-8884756.
† Institute of Organic Chemistry.
‡ Institute of Inorganic Chemistry.
(1) Recent publications: (a) Breeze, A. J.; Salomon, A.; Ginley, D.
S.; Gregg, B. A.; Tillmann, H.; Ho¨rhold, H.-H. Appl. Phys. Lett. 2002,
81, 3085-3087. (b) Yakimov, A.; Forrest, S. R. Appl. Phys. Lett. 2002,
80, 1667-1669. (c) Schmidt-Mende, L.; Fechtenko¨tter, A.; Mu¨llen, K.;
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2003, 4, 983-985. (b) Struijk, C. W.; Sieval, A. B.; Dakhorst, J: E. J.;
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T. J.; Picken, S. J.; van de Craats, A. M.; Warman, J. M.; Zuilhof, H.;
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Cormier, R. A.; Gregg, B. A. Chem. Mater. 1998, 10, 1309-1319.
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11, 754-758. (b) Wu¨rthner, F.; Sautter, A. Chem. Commun. 2000, 445-
446. (c) Schenning, A. P. H. J.; van Herrikhuyzen, J.; Ionkheijm, P.;
Chen, Z.; Wu¨rthner, F.; Meijer, E. W. J. Am. Chem. Soc. 2002, 124,
10252-10253. (d) Dobrawa, R.; Wu¨rthner, F. Chem. Commun. 2002,
1878-1879. (e) van der Boom, T.; Hayes, R. T.; Zhao, Y.; Bushard, P.
J.; Weiss, E. A.; Wasielewski, M. R. J. Am. Chem. Soc. 2002, 124,
9582-9590. (f) Peeters, E.; van Hal, P. A.; Meskers, C. J.; Janssen, R.
A. J.; Meijer, E. W. Chem. Eur. J. 2002, 8, 4470-4474. (g) You, C.-C.;
Wu¨rthner, F. J. Am. Chem. Soc. 2003, 125, 9716-9725.
(3) (a) Angadi, M. A.; Gosztola, D.; Wasielewski, M. R. Mater. Sci.
Eng. B 1999, 63, 191-194. (b) Kraft, A.; Grimsdale, A. C.; Holmes, A.
B. Angew. Chem., Int. Ed. 1998, 37, 402-428. (c) Ranke, P.; Bleyl, I.;
Simmerer, J.; Haarer, D.; Bacher, A.; Schmidt, H. W. Appl. Phys. Lett.
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Seybold, G.; Stange, A. (BASF AG) German Pat. DE 3545004, 1987;
Chem. Abstr. 1988, 108, 77134c.
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10.1021/jo048880d CCC: $27.50 © 2004 American Chemical Society
Published on Web 10/19/2004
J. Org. Chem. 2004, 69, 7933-7939
7933

Wu¨rthner et al.
SCHEME 1. Bromination of Perylene
SCHEME 2. Isomeric Products Formed in the
Bisanhydride (1) According to the BASF Patent11
Bromination and Subsequent Imidization of
Perylene Bisanhydride 1a
tion leads to isomerically pure 1,7-dibrominated bisim-
ides. In the past years, numerous disubstituted perylene
bisimides (PBIs) with interesting functionalities,12 in-
cluding liquid crystalline13,14 PBIs, dendrimers,15 orga-
nogels,16 and polymers,17 were synthesized from 1,7-
dibrominated perylene bisimides prepared according to
the patent procedure11 and applied in light-harvesting
systems,16 LEDs,17 molecular switches,18 wires,19 and
logic gates.20
Our results presented here reveal that the previously
reported difunctionalized perylene bisimides are appar-
ently mixtures of 1,7 and 1,6 regioisomers rather than
isomerically pure compounds. Surprisingly, only one13b
of the above-cited publications has drawn attention to
this problem, while the other reports only mentioned 1,7-
disubstituted perylene bisimides. The reason for this may
be that, on one hand, the precursor of difunctionalized
perylene bisimides, i.e., 1,7-dibromoperylene bisanhy-
dride 1,7-2, is virtually insoluble in any organic solvent
and, thus, its characterization was made only by elemen-
tal analysis and mass spectrometry which do not dif-
ferentiate regioisomers, and on the other hand, isomeric
mixtures of the subsequently prepared perylene bisimides
can be observed only by high-field (> 400 MHz) 1H NMR.
Thus, in one of our earlier publications14 on liquid-
crystalline PBIs we did not recognize the presence of
a Reagents and conditions: (a)11 Br2, I2 (catalytic), 100% H2SO4,
85 °C, 11 h; (b)11 H11C6-NH2, N-methylpyrrolidinone, 85 °C, 6 h;
(c) H11C6-NH2, H2O/n-PrOH (2:1), Ar, 80 °C, 10 h.
problem and have reinvestigated in detail all the steps
in the synthesis of disubstituted perylene bisimides to
assign unequivocally the respective isomers and to
develop methods for their purification. Here, we report
that 1,7-dibromoperylene bisimide can be obtained in
isomerically pure form, and the nucleophilic replacement
of bromine atoms affords pure difunctionalized bisimide
derivatives.
Results and Discussion
1
isomeric impurities on the basis of 400 MHz H NMR.
In the course of our intensive research work on perylene
bisimide chemistry, we became meanwhile aware of this
The bromination of perylene bisanhydride 1 was
repeated according to the patent procedure11 [Scheme 2,
reaction conditions (a)], and the crude product, which is
insoluble in organic solvents, was investigated by 600
MHz 1H NMR spectroscopy in concentrated D2SO4 (96-
98% in D2O). Three sets of signals with different intensi-
(12) (a) Zhao, Y.; Wasielewski, M. R. Tetrahedron Lett. 1999, 40,
7047-7050. (b) Lukas, A. S.; Zhao, Y.; Miller, S. E.; Wasielewski, M.
R. J. Phys. Chem. B 2002, 106, 1299-1306. (c) van der Boom, T.; Hayes,
R. T.; Zhao, Y.; Bushard, P. J.; Weiss, E. A.; Wasielewski, M. R. J.
Am. Chem. Soc. 2002, 124, 9582-9590. (d) Fuller, M. J.; Walsh, C. J.;
Zhao, Y.; Wasielewski, M. R. Chem. Mater. 2002, 14, 952-953. (e)
Ahrens, M. J.; Fuller, M. J.; Wasielewski, M. R. Chem. Mater. 2003,
15, 2684-2686.
(13) (a) Rohr, U.; Schlichting, P.; Bo¨hm, A.; Gross, M.; Meerholz,
K.; Bra¨uchle, C.; Mu¨llen, K. Angew. Chem., Int. Ed. 1998, 37, 1434-
1437. (b) Rohr, U.; Christopher, K.; Mu¨llen, K.; van de Craats, A.;
Warman, J. J. Mater. Chem. 2001, 11, 1789-1799.
(14) Wu¨rthner, F.; Thalacker, C.; Diele, S.; Tschierske, C. Chem.
Eur. J. 2001, 7, 2247-2253.
(15) (a) Serin, J. M.; Brousmiche, D. W.; Fre´chet, J. M. J. Chem.
Commun. 2002, 2605-2607. (b) Serin, J. M.; Brousmiche, D. W.;
Fre´chet, J. M. J. J. Am. Chem. Soc. 2002, 124, 11848-11849.
(16) Sugiyasu, K.; Fujita, N.; Shinkai, S. Angew. Chem. Int. Ed.
2004, 43, 1229-1233.
(17) (a) Thelakkat, M.; Po¨sch, P.; Schmidt, H.-W. Macromolecules
2001, 34, 7441-7447. (b) Ego, C.; Marsitzky, D.; Becker, S.; Zhang,
J.; Grimsdale, A: C.; Mu¨llen, K.; MacKenzie, J. D.; Silva, C.; Friend,
R. H. J. Am. Chem. Soc. 2003, 125, 437-443.
1
ties were observed in the H NMR spectrum (Figure 1)
indicating that at least three different products are
formed in the bromination of bisanhydride 1. In the
region between 8.7 and 9.1 ppm three doublets and three
singlets appear, and further, three doublets are over-
lapped to a multiplet at 9.65-9.75 ppm. This signal
pattern implies that 1,7- and 1,6-dibromoperylene bisan-
hydrides (1,7-2 and 1,6-2) and tribrominated perylene
1,6,7-2′ (Scheme 2) are formed in the bromination of
perylene bisanhydride 1. (Further evidence for structural
assignment of these compounds is provided below.) The
integration areas of the doublets at 8.79, 8.82, and 8.89
ppm (Figure 1) reveal that 1,7-2, 1,6-2, and 1,6,7-2′ are
fomed in a ratio of ca. 76:20:4.
Since the brominated perylene bisanhydrides are
insoluble in organic solvents and, therefore, could not be
purified by any means, the crude product mixture was
used for the subsequent imidization with cyclohexy-
lamine under the reaction conditions reported in the
(18) Giaimo, J. M.; Gusev, A. V.; Wasielewski, M. R. J. Am. Chem.
Soc. 2002, 124, 8530-8531.
(19) Weiss, E. A.; Ahrens, M. J.; Sinks, L. E.; Gusev, A. V.; Ratner,
M. A.; Wasielewski, M. R. J. Am. Chem. Soc. 2004, 126, 5577-5584.
(20) Guo, X.; Zhang, D.; Zhu, D. Adv. Mater. 2004, 16, 125-130.
7934 J. Org. Chem., Vol. 69, No. 23, 2004

1,7-Disubstituted Perylene Bisimide Dyes
FIGURE 1. 1H NMR (600 MHz, D2SO4, calibrated for TMS)
spectrum of bromination products of perylene bisanhydride 1.
FIGURE 2. 1H NMR spectroscopic monitoring of recrystal-
lization; 600 MHz 1H NMR spectra: (a) regioisomeric mixture
of 1,7-3 and 1,6-3 before recrystallization, (b) after one and
(c) after three repetitive recrystallizations, (d) spectrum of
mother liquor of first recrystallization of the residue obtained
after condensation of the solution of first recrystallization.
BASF patent [Scheme 2, reaction conditions (b)].11 As
expected, the imidization afforded a mixture of 1,7- and
1,6-dibromoperylene bisimides (1,7-3 and 1,6-3) and
tribrominated bisimide 1,6,7-3′. For the imidization of
perylene bisanhydride derivatives reaction conditions
different from those used in the above-mentioned patent
were employed;15b therefore, we have also carried out the
imidization of brominated products of perylene bisanhy-
dride 1 in a 2:1 mixture of H2O/n-PrOH, instead of
N-methylpyrrolidinone, at 80 °C [Scheme 2, reaction
conditions (c)], and similar results were obtained as under
the reaction conditions (b). In contrast to brominated
perylene bisanhydrides 2, the respective perylene bisim-
ides 3 are soluble in organic solvents to facilitate their
further purification. The silica gel column chromatogra-
phy of the product mixture obtained after imidization of
2 with CH2Cl2 as eluent allowed the separation of the
minor component tribrominated bisimide 1,6,7-3′, which
was obtained in ca. 1% yield and characterized by 1H and
13C NMR and MS. However, the regioisomeric 1,7- and
1,6-dibromoperylene bisimides (1,7-3 and 1,6-3) could not
be separated by column chromatography, and a 80:20
mixture (determined by 600 MHz 1H NMR) of 1,7-3 and
1,6-3 was obtained in 61% yield. Fortunately, the major
regioisomer 1,7-3 could be separated by repetitive re-
crystallization of the 80:20 mixture of 1,7-3 and 1,6-3
from CH2Cl2/MeOH (1:1). The recrystallization process
was monitored by 600 MHz 1H NMR spectroscopy (Figure
2) to assess the number of recrystallization steps required
for complete purification. After three successive recrys-
tallizations, the regioisomer 1,7-3 could be obtained in
pure form as the 1H NMR spectrum (Figure 2c) reveals.
In mother liquor, the minor isomer 1,6-3 is enriched as
the NMR spectrum shows (Figure 2d); however, the latter
could not be obtained in pure form. It is noteworthy that
the characteristic signals, in particular the doublets, of
the regioisomers 1,7-3 and 1,6-3 are only separated in
high-field 1H NMR spectra since the chemical shifts differ
very little (0.006 ppm for the doublets at 9.42-9.46 ppm;
see Figure 2a), while at lower field these signals overlap.
This might be the reason why in former publications on
1,7-difunctionalized perylene bisimides the problem of
regioisomers was not recognized. Although our NMR data
are in agreement with those reported13b,15b for 1,7-
dibromoperylene bisimides, an unequivocal assignment
of the NMR signals to the individual regioisomers 1,7-3
and 1,6-3 is not possible due to the symmetry of both
isomers. Fortunately, single crystals of the major isomer,
obtained after repetitive recrystallization (Figure 2c),
were grown on covering its CH2Cl2 solution by MeOH
layer. The X-ray analysis confirmed unequivocally the
structure of the major isomer as 1,7-dibromoperylene
bisimide 1,7-3 (Figure 3; note that the numbering of the
carbon atoms in the anisotropic displacement parameter
plot is not in accordance with the nomenclature of the
compound). The fact that the imidization of the crude
bromination products of perylene bisanhydride 1 with
cyclohexylamine (Scheme 2) afforded N,N′-dicyclohexyl-
1,7-dibromoperylene bisimide 1,7-3 as the major product,
it can be concluded that the corresponding 1,7-dibromop-
erylene bisanhydride 1,7-2 is the major product in the
bromination of perylene bisanhydride 1. Thus, the struc-
tures of the major products of bromination of 1 and
subsequent imidization are now unequivocally assigned.
To our knowledge, this is the first crystal structure
reported for 1,7-disubstituted perylene bisimide dyes. The
selected crystallographic data of 1,7-3 are given in ref
21, and the characteristic features of the crystal are
described below.
Dibromoperylene bisimide 1,7-3 crystallizes in the
triclinic space group P-1. The central six-membered ring
of 1,7-3 is twisted (Figure 3, right part) with a dihedral
angle of 24° associated with bay area carbon atoms C8-
C9-C10-C11 and C18-C19-C20-C1, which is almost
identical with the dihedral angle of previously reported
tetraphenoxy-substituted diazadibenzoperylenes22 and
14° smaller than that observed for tetrachloro-substituted
perylene bisimides.23 This twist also induces axial chiral-
ity in this 1,7-disubstituted perylene bisimide dye. How-
ever, 1,7-3 crystallizes as a racemate in a centrosymmet-
(21) Selected crystallographic data for 1,7-dibromoperylene bisimide
1,7-3. Crystal system: triclinic, space group: P-1, unit cell dimen-
sions: a ) 10.9311(8) Å, b ) 14.0064(10) Å, c ) 21.9075(16) Å, R )
72.6050(10)°, â ) 81.3230(10)°, γ ) 70.8890(10)°, V 3019.1(4) Å3, Z )
2, density (calcd) 1.656 g/cm3, R indices [I > 2σ(I)]: R1 ) 0.0558, wR2
) 0.1515, R indices (all data): R1 ) 0.0775, wR2 ) 0.1665.
(22) Wu¨rthner, F.; Sautter, A.; Schilling, J. J. Org. Chem. 2002, 67,
3037-3044.
(23) Chen, Z.; Debije, M. G.; Debaerdemaeker, T.; Osswald, P.;
Wu¨rthner, F. ChemPhysChem 2004, 5, 137-140.
J. Org. Chem, Vol. 69, No. 23, 2004 7935

Wu¨rthner et al.
FIGURE 3. Molecular structure of 1,7-dibromoperylene bisimide 1,7-3 (left) and view along the N-N axis showing the twisted
perylene backbone (right). The anisotropic displacement parameters are depicted at the 50% probability level.
SCHEME 3. Chemical Transformations of
ric space group. All C-C bond lengths of the perylene
Isomerically Pure 1,7-Dibromoperylene Bisimide
backbone range between 1.35 and 1.46 Å, indicating the
1,7-3a
presence of π-conjugation for all C-C bonds. The longest
bonds in the perylene unit are the C9-C10 and C19-
C20 bonds, which connect the two naphthalene units at
a length of 1.46 Å. This bond length is identical with that
observed for the parent perylene bisimide (without sub-
stituents in the bay area),24 indicating that, although the
perylene unit in 1,7-3 is significantly twisted, the degree
of conjugation is similar in both disubstituted and
unsubstituted perylene bisimides.
Once we have obtained reasonable amounts of isomeri-
cally pure 1,7-dibromoperylene bisimide 1,7-3, this sub-
strate was used for the synthesis of 1,7-difunctionalized
perylene bisimides and bisanhydrides. The transforma-
tions are shown in Scheme 3.
The nucleophilic substitution of regioisomerically pure
1,7-dibromoperylene bisimide 1,7-3 with pyrrolidine at
55 °C according to Wasielewski’s method12a (Scheme 3
(a)) afforded the corresponding dipyrrolidinyl bisimide 4a
as a green solid in 67% yield after column chromatogra-
phy. Once the substitution reaction was carried out at
46 °C, the monopyrrolidinyl bisimide 7 was obtained in
28% yield after column chromatographic purification. The
latter substrate was converted to the hitherto unknown
unsymmetrically difunctionalized monocyano monopyr-
rolidinyl bisimide 8 by cyanation with Zn(CN)2 in the
presence of Pd(0) catalyst according to standard litera-
ture procedure (Scheme 3 (f)).12e
The saponification of 4a in 2-propanol with 100-fold
excess of KOH afforded the hitherto unknown 1,7-
dipyrrolidinylperylene bisanhydride 5 in 62% yield. This
novel building block was successfully applied for the
synthesis of regioisomerically pure 1,7-dipyrrolidinylp-
erylene bisimides. Thus, the condensation reaction of 5
with 3,4,5-tridodecyloxyaniline and 4-dodecylaniline ac-
cording to standard procedure25 gave the corresponding
difunctionalized symmetrical perylene bisimides 4b and
4c in 44% and 33% yield, respectively.
a Reagents and conditions: (a) pyrrolidine, 55 °C, Ar, 24 h, 67%
of 4a; (b) KOH (100 equiv), -iPrOH, reflux, 2 h, 62% of 5; (c) KOH
(50 equiv), i-PrOH/H2O (6:1), reflux, 2.75 h, 88% of 6; (d) 4-dode-
cylaniline or 3,4,5-tridodecyloxyaniline, Zn(OAc)2, quinoline, 180
°C, 18-24 h, 44% of 4b and 33% for 4c; (e) pyrrolidine, 46 °C, Ar,
24 h, 28% of 7; (f) Pd2(dba)3, 1,1-bis(diphenylphosphino)ferrocene,
Zn(CN)2, dioxane, 110 °C, Ar, 20 h, 84% of 8.
pure dipyrrolidinyl-functionalized perylene monoimide
monoanhydride 6 that may serve as a building block for
the synthesis of electron-donor functionalized unsym-
metrical perylene bisimides. After optimization of re-
ported reaction conditions,12b a partial saponification of
4a was achieved in a 6:1 mixture of 2-propanol-water
with 50-fold excess of KOH under reflux. Under these
reaction conditions, bisimide 4a was converted up to 45%
after ca. 2.75 h and only monoimide monoanhydride 6
was formed. The prolongation of reaction time leads to
the generation of bisanhydride 5. Therefore, the reaction
was terminated after this time, and column chromato-
graphic purification of the crude mixture afforded 6 in
Since perylene monoimide monoanhydrides are impor-
tant starting materials for the synthesis of unsym-
metrical perylene bisimide,26 we have searched for reac-
tion conditions for partial saponification of 4a to obtain
(24) Klebe, G.; Graser, F.; Ha¨dicke, E.; Berndt, J. Acta Crystallogr.,
Sect. B: Struct. Sci. 1989, B45, 69-77.
(25) Wu¨rthner, F.; Sautter, A.; Schmid, D.; Weber, P. J. A. Chem.
Eur. J. 2001, 7, 894-902.
(26) Nagao, Y.; Naito, T.; Abe, Y.; Misono, T. Dyes Pigm. 1996, 32,
71-83.
7936 J. Org. Chem., Vol. 69, No. 23, 2004

1,7-Disubstituted Perylene Bisimide Dyes
The resulting precipitate was separated by filtration through
a G4 funnel, washed with 300 g of 86% sulfuric acid and a
large amount of water, and dried in a vacuum to give 42.0 g
(95%) of a red powder. The crude product could not be purified
since it is insoluble in organic solvents. The analysis of this
crude product by 600 MHz 1H NMR in concentrated D2SO4
(96-98% in D2O) revealed that 1,7- and 1,6-dibromo- and 1,7,6-
tribromoperylene bisanhydrides were formed in a ratio of 76:
20:4 (Figure 1). MS (EI, 70 eV) m/z): 547.8 (45.9), 548.8 (16.0),
549.8 (92.0), 550.1 (24.2), 551.8 (45.9) [M+] (calcd 550.1).
HRMS (EI): calcd for C24H6Br2O6 547.8525, found 547.8523.
1,7-Dibromoperylene-3,4:9,10-tetracarboxylic Acid Bis-
anhydride (1,7-2). 1H NMR (600 MHz, D2SO4, calibrated for
TMS): δ ) 9.68 (d, 2H, J ) 8.2 Hz), 9.01 (s, 2H), 8.79 (d, 2H,
J ) 8.3 Hz).
1,6-Dibromoperylene-3,4:9,10-tetracarboxylic Acid Bis-
anhydride (1,6-2). 1H NMR (600 MHz, D2SO4, calibrated for
TMS): δ ) 9.70 (d, 2H, J ) 8.1 Hz), 8.98 (s, 2H), 8.82 (d, 2H,
J ) 8.1 Hz).
Imidization of Crude Bromination Product.11 A sus-
pension of brominated perylene bisanhydrides (0.95 g, 1.72
mmol) obtained in the above reaction, cyclohexylamine (0.502
g, 5.07 mmol), and acetic acid (0.50 g, 8.33 mmol) in 20 mL of
N-methyl-2-pyrrolidinone was stirred at 85 °C under Ar for 6
h. After the mixture was cooled to room temperature, the
precipitate was separated by filtration, washed with 100 mL
of MeOH, and dried in a vacuum. The crude product was
purified by silica gel column chromatography with CH2Cl2 as
eluent. The first band was collected and after evaporation of
solvent, and N,N′-dicyclohexyl-1,6,7-tribromoperylene bisimide
1,6,7-3′ was obtained as a red powder (13 mg, 1%). The second
band contained a mixture of N,N′-dicyclohexyl-1,7- and -1,6-
dibromoperylene bisimide (1,7-3 and 1,6-3) as a red powder
(755 mg, 61%), and 600 MHz 1H NMR analysis revealed a 80:
20 ratio. The regioisomeric dibromoperylene bisimides 1,7-3
and 1,6-3 could not be separated by column chromatography.
Regioisomerically pure 1,7-dibromoperylene bisimide was
obtained by repetitive crystallization. In a typical procedure,
450 mg of the 80:20 mixture of N,N′-dicyclohexyl-1,7- and 1,6-
dibromoperylene bisimide was dissolved in 100 mL of CH2-
Cl2. The solution was poured into a cylinder-shaped glass
container (diameter: 5 cm, height: 14 cm) through a glass
funnel with a filter paper, and 120 mL MeOH was very
carefully layered on the top of CH2Cl2 solution by a syringe.
The container was sealed and kept at room temperature for 2
weeks to grow red crystals (280 mg, 62%). The recrystallization
was repeated two more times to obtained pure 1,7-dibromo-
perylene bisimide 1,7-3 (100 mg, 22%).
analytically pure form in 88% yield (relative to the
converted amount of 4a), and the unreacted starting
material 4a was recovered.
Conclusions
Our detailed study has shown that the bromination
and subsequent imidization of perylene bisanhydride 1
with cyclohexylamine leads to a mixture of regioisomeric
1,7- and 1,6-dibromoperylene bisimides 1,7-3 and 1,6-3
and tribrominated bisimide 1,6,7-3′. Since the regioiso-
mers 1,7-3 and 1,6-3 are only detectable by high-field 1H
NMR spectroscopy and cannot be separated by conven-
tional silica gel column chromatography, we suspect that
the previously reported 1,7-difunctionalized perylene
bisimides, which were synthesized from 1,7-dibromop-
erylene bisimide obtained according to the BASF patent,11
are contaminated with the respective 1,6 isomers. Thus,
one of the objectives of this contribution is to draw
attention of chemists as well as material scientists to this
apparently less considered problem of regioisomeric
impurity in 1,7-difunctionalized perylene bisimide probes.
We have obtained isomerically pure 1,7-dibromop-
erylene bisimide 1,7-3 after column chromatographic
removal of tribrominated bisimide 1,6,7-3′ and three
successive recrystallization of a ca. 80:20 mixture of 1,7-3
and 1,6-3. The structure of 1,7-3 was confirmed by X-ray
analysis. Although the present purification method is
rather cumbersome, to date no attractive alternative is
available for the preparation of regioisomerically pure
1,7-dibromoperylene bisimides that are important pre-
cursors for the synthesis of 1,7-difunctionalized perylene
bisimides. Regioisomerically pure 1,7-dibromoperylene
bisimide 1,7-3 has shown to be a versatile building block
for the synthesis of pure 1,7-difunctionalized perylene
bisimide derivatives. In this work, we have shown that
the two bromine substituents can be exchanged even in
a sequential manner leading to donor-acceptor substi-
tuted PBIs. Partial saponification to imide anhydrides
is possible as well. Therefore, we anticipate that on the
basis of this study several pure PBI derivatives with
interesting properties will become available.
Experimental Section
N,N′-Dicyclohexyl-1,7-dibromoperylene-3,4:9,10-tetra-
1
carboxylic Acid Bisimide (1,7-3). Mp > 400 °C. H NMR
General Methods. Solvents and reagents were obtained
from commercial sources and used as received. NMR spectra
were recorded at room temperature on 600 MHz (1H) and 400
MHz spectrometers. The solvents for spectroscopic studies
were of spectroscopic grade and used as received. UV/vis
spectra were measured on a spectrophotometer equipped with
a temperature controller. The steady-state fluorescence spectra
were measured on a convertional spectrofluorometer and
fluorescence quantum yields were determined by the optically
dilute method with fluorescein (Φf ) 0.92 in 1 N NaOH
aqueous solution) and cresyl violet (Φf ) 0.54 in methanol) as
reference.
(600 MHz, CDCl3, TMS): δ 9.45 (d, 2H, J ) 8.2 Hz), 8.86 (s,
2H), 8.65 (d, 2H, J ) 8.0 Hz), 5.02 (m, 2H), 2.54 (m, 4H), 1.20-
2.00 (m, 16H). 13C NMR (100 MHz, CDCl3, TMS): δ 163.3,
162.7, 137.9, 132.7, 132.6, 129.9, 129.2, 128.4, 127.0, 123.7,
123.3, 120.7, 54.3, 29.1, 26.5, 25.4. MS (EI, 70 eV) m/z: 710.0
(20.6), 712.0 (44), 714.0 (22.9) [M+] (calcd 710.0). UV/vis (CH2-
Cl2): λmax/nm (ꢀ/L mol-1 cm-1) ) 527 (49 800), 492 (33 700),
466 (13 600), 390 (5300), 276 (26 400). Fluorescence (CH2Cl2):
λmax ) 543 nm, fluorescence quantum yield Φf ) 0.94. Anal.
Calcd for C36H28Br2N2O4: C, 60.69; H, 3.96; N, 3.93. Found:
C, 60.10; H, 4.00; N, 3.92.
Bromination of Perylene Bisanhydride 1.11 A mixture
of 31.3 g (80.0 mmol) of perylene-3,4:9,10-tetracarboxylic acid
bisanhydride (1) and 472 g of 100 wt % sulfuric acid was stirred
for 12 h at room temperature, and subsequently I2 (0.77 g, 3.0
mmol) was added. The reaction mixture was heated to 85 °C,
and 28.2 g (176 mmol) of bromine was added dropwise over a
time period of 8 h. After bromine addition, the reaction mixture
was heated for an additional 10 h at 85 °C and cooled to room
temperature. The excess bromine was removed by a gentle
stream of N2 gas, and 65 mL of water was added carefully.
N,N′-Dicyclohexyl-1,6,7-tribromoperylene-3,4:9,10-tet-
racarboxylic Acid Bisimide (1,6,7-3′). Mp > 400 °C. 1H
NMR (400 MHz, CDCl3, TMS): δ 9.41 (d, 1H, J ) 8.0 Hz),
8.87 (s, 1H), 8.78 (s, 2H), 8.67 (d, 1H, J ) 8.2 Hz), 5.02 (m,
2H), 2.52 (m, 4H), 1.9-1.2 (m, 16H). 13C NMR (150 MHz,
CDCl3, TMS): δ 163.0, 162.9, 162.6, 162.5, 137.4, 136.6, 136.4,
133.3, 133.1, 131.4, 131.2, 130.8, 130.7, 129.5, 127.9, 125.9,
125.2, 124.2, 123.8, 123.7, 123.4, 123.3, 122.9, 121.3, 54.4, 54.3,
29.2, 29.1, 29.1, 29.0, 26.5, 26.5, 25.4, 25.3. MS (EI, 70 eV)
m/z: 790.0 (30.5), 791.0 (12.9), 792.0 (30.6), 793.0 (13) [M+]
J. Org. Chem, Vol. 69, No. 23, 2004 7937

Wu¨rthner et al.
(calcd 791.3). UV/vis (CH2Cl2): λmax/nm (ꢀ/L mol-1 cm-1) ) 529
and 10 mL of quinoline was heated under stirring at 180 °C
for 24 h under Ar. A 45 mL portion of 15% HCl was poured
into the cooled mixture under stirring. The resulting precipi-
tate was separated by filtration, washed with 20 mL of water
and 10 mL of methanol, dried at 40 °C/10-1 mbar, and purified
by column chromatography (THF/hexane (1/2, v/v)) to yield 111
(36 900), 495 (26 000), 424 (8100), 271 (23 000).
N,N′-Dicyclohexyl-1,7-dipyrrolidinylperylene-3,4:9,10-
tetracarboxylic Acid Bisimide (4a). A mixture of 95.0 mg
(0.133 mmol) of 1,7-3 and 4.30 g (59.7 mmol) of pyrrolidine
was stirred under Ar for 24 h at 55 °C (external). Subsequently,
the reaction mixture was poured into 15 mL of 10% HCl under
stirring and extracted with methylene chloride (3 × 20 mL),
dried over MgSO4, and concentrated by rotary evaporation.
The resulting precipitate was purified by column chromatog-
raphy on silica gel (CH2Cl2/hexane (40/1, v/v)) to yield 62 mg
(67%) of a green solid. Mp > 400 °C. 1H NMR (400 MHz,
CDCl3, TMS): δ 8.41 (s, 2H), 8.31 (d, J ) 8.1 Hz, 2H), 7.56 (d,
J ) 8.1 Hz, 2H), 5.04-5.10 (m, 2H), 3.65-3.82 (m, 4H), 2.72-
2.89 (m, 4H), 2.56-2.66 (m, 4H), 1.80-2.10 (m, 12H), 1.76-
1.78 (m, 6H), 1.20-1.50 (m, 6H). 13C NMR (100 MHz, CDCl3):
δ 163.5, 163.4, 145.4, 132.8, 128.7, 125.5, 122.6, 121.1, 119.7,
118.4, 116.9, 52.7, 51.0, 28.1, 25.6, 24.7, 24.5. MS (EI, 70 eV)
m/z: 692.3 (100) [M+], 693.3 (48.8) [M+ + H] (calcd 692.3).
HRMS (EI): calcd for C44H44N4O4 692.3362, found 692.3370.
UV/vis (CH2Cl2): λmax/nm (ꢀ/L mol-1 cm-1) ) 700 (38 700), 436
(15 400), 346 (50 600), 314 (24 700), 275 (25 300). Fluorescence
(CH2Cl2): λmax ) 736 nm, fluorescence quantum yield Φf )
0.25.
1,7-Dipyrrolidinylperylene-3,4:9,10-tetracarboxylic Acid
Bisanhydride (5). A mixture of 100 mg (0.15 mmol) of 4a,
600 mg (15.0 mmol) of KOH, and 5 mL of i-PrOH was brought
to reflux. The mixture was stirred for 2 h and poured under
stirring into 17 mL of AcOH. The resulting green precipitate
was concentrated by centrifugation, washed with water and
methanol, and purified by recrystallization from tetrachloro-
ethane/ethyl acetate to give 47 mg (62%) of 5. Mp > 400 °C.
1H NMR (400 MHz, CDCl3, TMS): δ 8.47 (s, 2H), 8.42 (d, J )
8.1 Hz, 2H), 7.60 (d, J ) 8.1 Hz, 2H), 3.69-3.81 (m, 4H), 2.80-
2.92 (m, 4H), 2.03-2.17 (m, 8H). 13C NMR (100 MHz, tetra-
chlorethane-d2): δ 160.6, 146.6, 135.2, 130.3, 129.5, 128.4,
124.1, 122.4, 118.0, 117.6, 114.7, 52.6, 25.7. MS (EI, 70 eV)
m/z: 530.1 (100) [M+], 531.2 (35.9) [M+ + H] (calcd 530.14).
HRMS (EI): calcd for C32H22N2O6 530.1479, found 530.1480.
UV/vis (CH2Cl2): λmax/nm (ꢀ/L mol-1 cm-1) ) 709 (33 500), 435
(13 380), 318 (22 420), 276 (18 670), 252 (37 330). Fluorescence
(CH2Cl2): λmax ) 744 nm, fluorescence quantum yield Φf )
0.18.
N,N′-Di(4-dodecylphenyl)-1,7-dipyrrolidinylperylene-
3,4:9,10-tetracarboxylic Acid Bisimide (4b). A mixture of
33.0 mg (0.062 mmol) of 5, 78.0 mg (0.30 mmol) of 4-dodecy-
laniline, 20.0 mg (0.10 mmol) of Zn(OAc)2, and 5 mL of
quinoline was heated under stirring at 180 °C for 18 h under
Ar. A 7 mL portion of 15% HCl was poured into the cooled
mixture under stirring. The resulting precipitate was sepa-
rated by filtration, washed with 40 mL of water, dried at 40
°C/10-3 mbar, and purified by column chromatography (CH2-
Cl2/CH3OH (50/1, v/v)) to yield 28 mg (44%) of 4b. Mp: 116-
118 °C. 1H NMR (400 MHz, CDCl3, TMS): δ 8.48 (s, 2H), 8.39
(d, J ) 8.1 Hz, 2H), 7.61 (d, J ) 8.1 Hz, 2H), 7.37 (d, J ) 8.4
Hz, 4H), 7.25 (d, J ) 8.4 Hz, 4H), 3.65-3.80 (m, 4H), 2.75-
2.91 (m, 4H), 2.68-2.72 (m, 4H), 1.90-2.10 (m, 4H), 1.66-
1.73 (m, 4H), 1.20-1.45 (m, 40H), 0.80-0.95 (m, 6H). 13C NMR
(100 MHz, CDCl3): δ 164.4, 164.3, 146.6, 143.4, 134.6, 133.1,
130.2, 129.4, 128.3, 126.9, 123.9, 122.5, 121.9, 121.1, 119.3,
118.3, 52.2, 35.8, 31.9, 31.3, 29.7, 29.7, 29.6, 29.6, 29.6, 29.5,
29.4, 25.8, 22.7, 14.1. MS (EI, 70 eV) m/z: 1016.5 (100) [M+],
1017.4 (75.2) [M+ + H]. HRMS (EI): calcd for C68H80N4O4
1016.610, found 1016.604. UV/vis (CH2Cl2): λmax/nm (ꢀ/L mol-1
cm-1) ) 706 (45 760), 435 (17 950), 315 (28 400), 245 (63 570).
Fluorescence (CH2Cl2): λmax ) 745 nm, fluorescence quantum
yield Φf ) 0.20. Anal. Calcd for C68H80N4O4‚H2O (1035): C,
78.85; H, 7.77; N, 5.40. Found: C, 79.21; H, 8.06; N, 5.38.
1
mg (33%) of 4c. Mp: 93-95 °C. H NMR (400 MHz, CDCl3,
TMS): δ 8.45 (s, 2H), 8.40 (d, J ) 8.1 Hz, 2H), 7.65 (d, J ) 8.1
Hz, 2H), 6.59 (s, 4H), 4.03-4.06 (m, 4H), 3.94-3.97 (m, 8H),
3.65-3.75 (m, 4H), 2.73-2.81 (m, 4H), 1.95-2.04 (m, 8H),
1.75-2.04 (m, 12H), 1.20-1.52 (m, 108H), 0.84-0.90 (m, 18H).
13C NMR (100 MHz, CDCl3): δ 164.4, 164.3, 153.6, 146.7,
138.2, 130.6, 130.3, 124.2, 122.6, 121.2, 119.4, 118.4, 106.9,
73.5, 69.1, 52.3, 31.9, 30.4, 29.8, 29.7, 29.7, 29.4, 29.4, 26.2,
26.1, 25.8, 22.7, 14.1. MS (MALDI-TOF) m/z: 1787.5 [M+],
1788.5 [M+ + H] (calcd 1787.7). UV/vis (CH2Cl2): λmax/nm (ꢀ/L
mol-1 cm-1) ) 707 (44 800), 436 (18 300), 346 (28 600), 271
(38 600), 245 (73 700). Fluorescence (CH2Cl2): λmax ) 741 nm,
fluorescence quantum yield Φf ) 0.34.
N-Cyclohexyl-1,7-dipyrrolidinylperylene-3,4:9,10-tet-
racarboxylic acid-3,4-anhydride-9,10-imide (6). A mixture
of 50.0 mg (0.072 mmol) of 4a, 200 mg (3.60 mmol) of KOH,
0.5 mL of water, and 3 mL of i-PrOH was brought to reflux.
The mixture was stirred for 2.75 h and poured under stirring
into 10 mL of AcOH. The resulting green precipitate was
extracted with 40 mL of methylene chloride, washed with
water, dried over MgSO4, and concentrated by rotary evapora-
tion. Column chromatography on silica gel (chloroform/acetone/
hexane (10/1/9, v/v/v)) afforded 28 mg of the starting material
4a and 17 mg (88%) of 6. Mp: 300-302 °C. 1H NMR (400 MHz,
CDCl3, TMS): δ 8.44 (s, 1H), 8.36 (s, 1H) 8.34 (d, J ) 8.1 Hz,
1H), 8.30 (d, J ) 8.1 Hz, 1H) 7.61 (d, J ) 8.1 Hz, 1H), 7.43 (d,
J ) 8.1 Hz, 1H), 5.03-5.10 (m, 1H), 3.62-3.79 (m, 4H), 2.71-
2.90 (m, 4H), 2.55-2.64 (m, 2H), 1.90-2.10 (m, 10H), 1.70-
1.85 (m, 3H), 1.35-1.55 (m, 3H). 13C NMR (100 MHz, CDCl3,
TMS): δ 164.4, 161.3, 160.8, 147.1, 146.2, 135.8, 133.4, 130.2,
130.2, 128.7, 126.4, 124.7, 124.3, 123.5, 123.1, 122.3, 122.1,
120.9, 120.4, 119.6, 117.1, 116.8, 114.2, 53.9, 52.4, 52.3, 29.2,
26.6, 25.8, 25.8, 25.5. MS (EI, 70 eV) m/z: 611.2 (100) [M+],
612.2 (41.4) [M+ + H] (calcd 611.2). HRMS (EI): calcd for
C38H33N3O5 611.2420, found 611.2420. UV/vis (CH2Cl2): λmax
/
nm (ꢀ/L mol-1 cm-1) ) 708 (35 870), 436 (14 520), 317 (24 130),
275 (21 900), 250 (45 000). Fluorescence (CH2Cl2): λmax ) 746
nm, fluorescence quantum yield Φf ) 0.14. Anal. Calcd for
C38H33N3O5: C, 74.53; H, 5.39; N, 6.86. Found: C, 74.36; H,
5.54; N, 6.87.
N,N′-Dicyclohexyl-1-bromo-7-pyrrolidinylperylene-
3,4:9,10-tetracarboxylic Acid Bisimide (7). In a three-
necked round-bottom flask equipped with a magnetic stirrer,
reflux condenser, and thermometer was stirred a mixture of
95.0 mg (0.133 mmol) of 1,7-3 and 4.30 g (59.7 mol) of
pyrrolidine under Ar for 24 h at 46 °C (internal). The mixture
was poured under stirring into 10 mL of 10% HCl. The
resulting green precipitate was separated by filtration, washed
with water (2 × 10 mL) and 10 mL of methanol, dried at 60
°C/10-3 mbar, and purified by column chromatography (CH2-
Cl2) to yield 26.0 mg (28%) of 7 as a green powder. Mp > 350
1
°C. H NMR (400 MHz, CDCl3, TMS): δ 9.52 (d, J ) 8.3 Hz,
1H), 8.87 (s, 1H), 8.63 (d, J ) 8.3 Hz, 1H), 8.51 (s, 1H), 8.46
(d, J ) 8.3 Hz, 1H), 7.43 (d, J ) 8.3 Hz, 1H), 4.98-5.10 (m,
2H), 3.69-3.75 (m, 2H), 2.75-2.85 (m, 2H), 2.50-2.64 (m, 4H),
1.98-2.18 (m, 4H), 1.89-1.93 (m, 4H), 1.72-1.77 (m, 6H),
1.30-1.47 (m, 6H). 13C NMR (100 MHz, CDCl3): δ 164.3, 164.2,
163.9, 163.2, 148.4, 137.5, 134.6, 134.2, 131.5, 130.5, 129.7,
129.5, 128.0, 127.3, 125.5, 123.9, 123.4, 122.5, 121.8, 121.4,
118.9, 117.3, 114.9, 54.0, 53.9, 52.7, 29.2, 29.1, 26.6, 25.9, 25.5.
MS (MALDI-TOF) m/z: 701.2 [M+] (calcd 701.2). UV/vis (CH2-
Cl2): λmax/nm (ꢀ/L mol-1 cm-1) ) 656 (27 300), 437 (15 000),
296 (25 900). Fluorescence (CH2Cl2): λmax ) 734 nm, fluores-
cence quantum yield Φf ) 0.19. Anal. Calcd for C40H36-
BrN3O4: C, 68.38; H, 5.16; N, 5.98. Found: C, 68.15; H, 5.16;
N, 6.06.
N,N′-Di(3,4,5-tridodecyloxyphenyl)-1,7-dipyrrolidinylp-
erylene-3,4:9,10-tetracarboxylic Acid Bisimide (4c). A
mixture of 100 mg (0.188 mmol) of 5, 518 mg (0.80 mmol) of
3,4,5-tridodecyloxyaniline, 50.0 mg (0.25 mmol) of Zn(OAc)2,
7938 J. Org. Chem., Vol. 69, No. 23, 2004

1,7-Disubstituted Perylene Bisimide Dyes
N,N′-Dicyclohexyl-1-cyano-7-pyrrolidinylperylene-3,4:
9,10-tetracarboxylic Acid Bisimide (8). N,N′-Dicyclohexyl-
1-bromo-7-pyrrolidinylperylene bisimide 7 (100 mg, 0.142
mmol), zinc cyanide (67.0 mg, 0.568 mmol), 1,1′-bis(diphe-
nylphosphino)ferrocene (5.0 mg, 0.01 mmol), and tris(diben-
zylideneacetone)dipalladium(0) (10.0 mg, 0.010 mmol) were
refluxed in 6 mL of dioxane for 20 h under argon. The reaction
mixture was diluted with 20 mL of chloroform and filtered
through Celite, and the solvent was removed on a rotary
evaporator. The crude product was purified by silica gel column
chromatography (with CHCl3 as eluent) to yield 77 mg (84%)
of 8. Mp > 350 °C. Rf ) 0.19 (CHCl3). 1H NMR (400 MHz,
CDCl3, TMS): δ 9.50 (d, J ) 8.3 Hz, 1H), 8.85 (s, 1H), 8.74 (d,
J ) 8.1 Hz, 1H), 8.56 (s, 1H), 8.55 (d, J ) 7.7 Hz, 1H), 7.34 (d,
J ) 8.1 Hz, 1H), 5.01-5.07 (m, 2H), 3.70-3.90 (m, 2H), 2.62-
2.82 (m, 2H), 2.54-2.60 (m, 4H), 2.10-2.20 (m, 2H), 2.00-
2.10 (m, 2H), 1.90-1.93 (m, 4H), 1.73-1.76 (m, 6H), 1.32-
1.49 (m, 6H). 13C NMR (100 MHz, CDCl3): δ 164.3, 164.2,
164.0, 163.3, 149.8, 144.2, 138.5, 136.1, 135.8, 133.8, 132.9,
130.4, 129.9, 129.3, 128.5, 126.6, 125.1, 124.6, 122.9, 122.5,
122.0, 120.7, 118.9, 117.8, 103.9, 54.6, 54.4, 53.4, 29.6, 29.4,
26.9, 26.2, 25.8. MS (EI, 70 eV) m/z: 648.2 (32.4) [M+], 649.2
(16.5) [M+ + H] (calcd 648.3). HRMS (EI) calcd for C41H36N4O4
648.2739, found 648.2733. UV/vis (CH2Cl2): λmax/nm (ꢀ/L mol-1
cm-1) ) 684 (27 600), 476 (6600), 425 (15 800), 300 (23 100).
Fluorescence (CH2Cl2): λmax ) 754 nm, fluorescence quantum
yield Φf ) 0.10. Anal. Calcd for C41H36N4O4: C, 75.90; H, 5.59;
N, 8.64. Found: C, 75.27; H, 5.75; N, 8.54.
total of 32 463 reflections were collected, and 10 628 unique
reflections (|I| > 2σ |I|) were solved by direct methods and
refined on F2 using the full-matrix least-squares methods of
SHELXL 97.28 An empirical absorption correction was em-
ployed. Hydrogen atoms were calculated and included in the
refinement. Non-hydrogen atoms were assigned with aniso-
tropic displacement parameters, converging to a final R factor
2
of 0.0558 and a weighted R factor of 0.1515 (w ) 1/[σ2(Fo ) +
2
(0.0950P)2 + 5.1855P], where P ) (Fo + 2Fc2)/3).
Crystallographic data of 1,7-dibromoperylene bisimide 1,7-3
have been deposited with the Cambridge Crystallographic
Data Centre (CCDC Nr. 242920).
Acknowledgment. Financial support by the Deut-
sche Forschungsgemeinschaft (Grant No. WU 317/3-1)
and the Fonds der Chemischen Industrie is gratefully
acknowledged. This work is dedicated to Prof. Wolfdieter
A. Schenk on the occasion of his 60th birthday.
Supporting Information Available: X-ray crystallo-
graphic data of 1,7-dibromoperylene bisimide 1,7-3 (CIF). This
material is available free of charge via the Internet at
http://pubs.acs.org.
JO048880D
(27) (a) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615-
619. (b) Kottke, T.; Lagow, R. J.; Stalke, D. J. Appl. Crystallogr. 1996,
29, 465-468.
(28) Sheldrick, G. M. SHELXL-97 program for crystal structure
refinement, University of Go¨ttingen, 1996.
Crystal Structure Determination. All data were collected
from shock-cooled crystals on a Bruker Smart-Apex diffracto-
meter at 173 K27 (graphite-monochromated Mo KR radiation,
λ ) 71.073 pm) in the range θmin ) 2.50° to θmax ) 25.05°. A
J. Org. Chem, Vol. 69, No. 23, 2004 7939