Highly regiospecific synthetic approach to monobay-functionalized perylene bisimide and Di(perylene bisimide)

Article abstract of DOI:10.1021/ol901168k

Monobay-dichlorinated perylene bisimide and di pery lene bisimide have been regiospecifically synthesized from tetrachlorinated perylene bisimide in different copper-mediated reaction conditions, thus opening a new avenue to their monobay-functionalizatio

Full text of DOI:10.1021/ol901168k

ORGANIC
LETTERS
2009
Vol. 11, No. 14
3084-3087
Highly Regiospecific Synthetic Approach
to Monobay-Functionalized Perylene
Bisimide and Di(perylene bisimide)
Yonggang Zhen,†,‡ Hualei Qian,†,‡ Junfeng Xiang,† Jianqiang Qu,§ and
Zhaohui Wang*,†
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China, Graduate School of the Chinese
Academy of Sciences, Beijing 100190, China, and BASF Aktiengesellschaft, GVP/
C-A030 67056 Ludwigshafen, Germany
wangzhaohui@iccas.ac.cn
Received May 26, 2009
ABSTRACT
Monobay-dichlorinated perylene bisimide and diperylene bisimide have been regiospecifically synthesized from tetrachlorinated perylene bisimide
in different copper-mediated reaction conditions, thus opening a new avenue to their monobay-functionalization.
Due to good chemical and physical stabilities, intense
photoluminescence, high electron affinity, and carrier mobil-
ity,1 perylene-3,4,9,10-tetracarboxylic acid bisimides (PBIs)
have received a great deal of attention as promising organic
n-type semiconducting materials which have found wide-
spread applications as light-harvesting arrays,2 field effect
transistors,3 light-emitting diodes,4 and photovoltaics5 in the
past decades. Chemical modifications both at the imide
groups and in the bay regions are two different successful
synthetic strategies for perylene bisimide derivatives. How-
ever, the dramatic change of optical and electronic properties
can only be achieved by the bay-functionalization because
of nodes in the HOMO and LUMO orbitals at the imide
nitrogen atoms.1b Therefore, the functionalization of a
perylene aromatic core is a current research topic to develop
the applications of these chromophores in electronic devices.
Tetrachloro- and dibromo-substituted PBIs have taken im-
portant parts in the synthesis of functional perylene dyes such
as phenoxy,6 aryl,7 cyano,3a pyrrolidino,8 sulfur,9 fluorine,10
† Institute of Chemistry, Chinese Academy of Sciences.
‡ Graduate School, Chinese Academy of Sciences.
§ BASF Aktiengesellschaft, GVP/C-A030.
(1) (a) Zollinger, H. Color Chemistry, 3rd ed.; VCH: Weinheim, 2003.
(b) Wu¨rthner, F. Chem. Commun. 2004, 14, 1564.
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M. R. J. Am. Chem. Soc. 2007, 129, 3173.
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10.1021/ol901168k CCC: $40.75
Published on Web 06/24/2009
 2009 American Chemical Society

and perfluoroalkyl11 substitution in bay regions by nucleo-
philic halogen-exchange reactions.
without K2CO3, while 2Cl-diPBI (4) as well as 4Cl-diPBI
(2b) was obtained in 15% yield using amounts of CuI,
L-proline, and K2CO3 (Scheme 1). Compounds 3 and 4 show
To the best of our knowledge, functionaliztion in the
monobay region of PBI is mostly originated from unselective
and irreproducible monobay-nitration and monobay-bromi-
nation. Until now, there has been no precedent on the
synthesis of monobay-dichlorinated PBIs, which are key
intermediates for monobay-functionalized PBIs. (Figure 1).
Scheme 1
good solubility in common organic solvents such as dichlo-
romethane, chloroform, toluene, and tetrahydrofuran. Their
structures are unambiguously identified by 1H NMR and 13
NMR spectroscopy and MALDI-TOF.
C
Figure 1. PBI (1a), 4Cl-PBI (1b), diPBI (2a), and 4Cl-diPBI (2b).
Surprisingly, there were no other isomers of 2Cl-PBI (3)
obtained in the above reaction as evidenced by HMBC
experiments. The JCH correlations between protons Hb (δ
3
Utilization of soluble copper complexes or salts with
mono- or bidentate chelating ligands such as amino acids,
diamines, and phosphines has made a great contribution to
the development of Ullmann-like coupling reactions in the
formation of C-N, C-O, C-S, and C-C bonds in recent
years.12 Recently, we reported the facile synthesis of triply
linked di(perylene bisimides) (diPBIs) and tri(perylene
bisimides) (triPBIs) using the system of CuI, L-proline, and
K2CO3.13
Herein, we present the copper-mediated synthesis for
monobay-dichlorinated perylene bisimide (2Cl-PBI) and
di(perylene bisimides) (2Cl-diPBI), providing a new efficient
avenue to construct monobay-functionalized PBIs and diPBIs
which are expected to possess extraordinary optoelectronic
features.
8.83) and Hd (δ 8.80) and carbonyl carbons (δ 162, δ 163)
determined the assignments of Ha (δ 8.67), Hb, and Hd. The
3
presence of JCH coupling from protons both Hb and Hd to
Cc (δ 127.3) and the absence of 3JCH coupling from protons
Ha and Hd to the same carbon was consistent with the
structure of 2Cl-PBI 3 rather than other isomers (see the
Supporting Information).
Furthermore, to determine the molecular structure of 2Cl-
PBI (3), crystals suitable for single-crystal X-ray structure
analysis were obtained by slow evaporation of a solution of
3 in methol at room temperature. Owing to the big difference
of electrostatic repulsion and steric encumbrance in chlorine
and hydrogen substituents, the twisting of central six-
membered ring is unsymmetrical with dihedral angle of 34.6°
and 9.9°, respectively, while the tetrachloroperylene bisimide
has a torsional angle of 36.7°14 (Figure 2).
Starting from tetrachloro-PBI (1b) (4Cl-PBI), 2Cl-PBI (3)
was prepared at 75 °C in 48% yield (98% based on the
recovered 4Cl-PBI) under the system of CuI and L-proline
Notably, we also found that only monobay-dichlorinated
diPBI (2Cl-diPBI, 4) was produced in the reaction, although
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Figure 2. ORTEP drawing of the molecular structure of 2Cl-PBI
(3): (a) top view; (b) side view. The solvent molecules are omitted
for clarity.
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Org. Lett., Vol. 11, No. 14, 2009
3085

diPBI complex 6 and then changed to 2Cl-diPBI (4) when the
reaction was quenched with aqueous acid, whereas without
K2CO3 the five-membered organocopper ring 5 decomposed
to 2Cl-PBI after treatment with aqueous acid (Scheme 2).
Due to broad and red-shifted absorption spectra and
extremely strong eletron-accepting ability in contrast with
PBIs,13a we are particularly interested in chemical modi-
cation of diPBI to develop novel electronic materials.
Therefore, we decided to introduce functional units such
as a nitrogen group into the monobay region of diPBI
selectively to explore the subtle changes of optical and
electronic properties. Buchwald-Hartwig couping reaction
between aryl halides and amines is a successful synthetic
strategy for C-N formation;15 accordingly, we present
the synthesis of monobay-functionalized diPBI derivative
7 in 92% yields by cross-coupling of 2Cl-diPBI with ethyl
4-aminobenzoate (Scheme 3).
Scheme 2
Scheme 3
The absorption spectra of 2Cl-PBI (3), 2Cl-diPBI (4), and
its derivative 7 in CHCl3 show a well-defined vibronic fine
structure of the S0-S1 transition (Figure 3). The orange
there are three isomers according to the different sites of
two chlorine atoms in the bay regions. From the ROESY
spetrum, an obvious cross-peak was observed between two
protons Ha and Hb (δ 9.45, δ 9.35) of bay regions which
1
have been assigned on the basis of H-1H COSY and
HMBC, suggesting that the two protons are in the same bay
region. The result was definitely in accord with the structure
of 2Cl-diPBI (4) providing reliable evidence to exclusion of
other isomers (see the Supporting Information).
The regiospecific synthesis of monobay-chlorinated PBI and
diPBI provided important clues to comprehension of this
copper-mediated reaction mechanism. Thus, we proposed the
monobay copper(III)-substituted PBI complex 5 as a key
intermediate in the reaction pathway. First, CuI and L-proline
formed copper chelate, which is more reactive toward the
oxidation addition at one bay position, and then an intramo-
lecular substitution involving the adjacent carbon atom at bay
positon affords the intermediate 5. Under basic conditions, it
reacted with 4Cl-PBI to afford 4Cl-diPBI (2b) or self-coupled
to give another intermediate monobay copper(III)-substituted
Figure 3. UV-vis absorption spectra of PBI (1a) (black dash line),
4Cl-PBI (1b) (orange dash line), 2Cl-PBI (3) (blue dash line), diPBI
(2a) (purple solid line), 4Cl-diPBI (2b) (red solid line), 2Cl-diPBI
(4) (yellow solid line), and 7 (green solid line) in CHCl3 at room
temperature.
3086
Org. Lett., Vol. 11, No. 14, 2009

solution of 2Cl-PBI (3) shows two major bands at 486 and
521 nm (εmax ) 54600 M-1 cm-1) with a slight hypsochromic
shift relative to PBI (1a), probably due to the electron-
withdrawing effect of chlorine substituents. The blue solution
of 2Cl-diPBI (4) exhibits five major bands at 410, 506, 542,
614, and 670 nm (εmax ) 84050 M-1 cm-1). Similarly, the
maximum absorption of 2Cl-diPBI (4) is blue-shifted by 14
nm in comparison with diPBI 2a.
The absorption spectrum of 7 shows major bands at 671,
615, 578, and 414 nm (εmax) 76980 M-1 cm-1). Given that
there is relatively weak absorption in region of 500-550
nm for 7, its solution is green rather than violet relative to
2Cl-diPBI (4).
reduction potentials vs Fc/Fc+ are -0.45, -0.75, -1.47, and
-1.64 V for 4. Similar to 2Cl-PBI (3), the first reduction
potential of 4 is between that of diPBI (2a) and 4Cl-diPBI
(2b).
Cyclic voltammogram of 7 exhibits two reversible reduc-
tion waves and two quasireversible reduction waves. Its half-
wave potentials vs Fc/Fc+ are -0.57, -0.85, -1.60, and
-1.77 V, more negative in comparison with 2CldiPBI (4)
probably due to the incorporation of the electron-donating
nitrogen group.
In summary, we report a highly regiospecific synthesis of
monobay-dichloronated PBI and diPBI from tetrachloro-PBI
by an amino acid promoted CuI-mediated reaction, establish-
ing a new synthetic protocol to monobay-functionalized PBIs
and diPBIs. A monobay copper-substituted PBI complex was
also proposed as an important intermediate. The introduction
of a nitrogen group directly on the core has a drastic influence
on the optical and electronic properties of diPBIs, as
expected. Further studies on monobay-functionalization of
PBIs and diPBIs and their applications in electronic devices
such as photovoltaic cells are currently underway.
Cyclic voltammetry of 2Cl-PBI (3) in CH2Cl2 shows one
reversible reduction wave and one quasireversible reduction
wave. The half-wave reduction potentials vs Fc/Fc+ are
-0.85 and -1.10 V for 3 (table 1). Obviously, the first
Table 1. Half-Wave Redox Potential (in V vs Fc/Fc+)a
E1r
E2r
E3r
E4r
Acknowledgment. For financial support of this research,
we thank the National Natural Science Foundation of China
(Grant Nos. 50873106, 20721061), 973 Program (Grant No.
2006CB932101), the Chinese Academy of Sciences, and
BASF SE.
4Cl-PBI (1b)
2Cl-PBI (3)
PBI (1a)
4Cl-diPBI (2b)
2Cl-diPBI (4)
diPBI (2a)
7
-0.74
-0.85
-0.96
-0.41
-0.45
-0.46
-0.57
-1.06
-1.10
-1.22
-0.69
-0.75
-0.73
-0.85
-1.39
-1.47
-1.49
-1.60
-1.52
-1.64
-1.66
-1.77
Supporting Information Available: Experimental pro-
cedure and characterization of new compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
a Measured in 0.1 M solution of Bu4NPF6 in dichloromethane with a
scan rate of 100 mV/s.
OL901168K
reduction potentials of PBI (1a), 2Cl-PBI (3), and 4Cl-PBI
(1b) is proportional to the number of electron-withdrawing
chlorine atoms in bay regions. Cyclic voltammetry of 2Cl-
diPBI (4) in CH2Cl2 exhibits two reversible reduction waves
and two quasireversible reduction waves. The half-wave
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Wu¨rthner, F. ChemPhysChem 2004, 5, 137.
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Org. Lett., Vol. 11, No. 14, 2009
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