Synthesis of arylated perylene bisimides through C - H bond cleavage under ruthenium catalysis

Article abstract of DOI:10.1021/ol902271b

"Chemical Equation Presented" Treatment of perylene bisimide (PBI) with various arylboronates in the presence of a ruthenium catalyst provides tetraarylated PBIs at 2,5,8,11-positions In good yields with perfect regioselectlvity. The electronic nature of

Full text of DOI:10.1021/ol902271b

ORGANIC
LETTERS
2009
Vol. 11, No. 23
5426-5429
Synthesis of Arylated Perylene
Bisimides through C-H Bond Cleavage
under Ruthenium Catalysis
Satomi Nakazono,‡ Shanmugam Easwaramoorthi,§ Dongho Kim,*,§
Hiroshi Shinokubo,*,† and Atsuhiro Osuka*,‡
Department of Applied Chemistry, Graduate School of Engineering, Nagoya
UniVersity, Nagoya 464-8603, Japan, Department of Chemistry, Graduate School of
Science, Kyoto UniVersity, Kyoto 606-8502, Japan, and Department of Chemistry,
Yonsei UniVersity, Seoul 120-749, Korea
hshino@apchem.nagoya-u.ac.jp; osuka@kuchem.kyoto-u.ac.jp; dongho@yonsei.ac.kr
Received October 1, 2009
ABSTRACT
Treatment of perylene bisimide (PBI) with various arylboronates in the presence of a ruthenium catalyst provides tetraarylated PBIs at 2,5,8,11-
positions in good yields with perfect regioselectivity. The electronic nature of the introduced aryl substituents has a significant impact on
their optical and electronic properties. This protocol has been applied to the synthesis of a water-soluble emissive PBI derivative.
Perylene tetracarboxylic acid bisimide (PBI) has received
much attention for wide areas of applications toward organic
material devices such as organic solar cells, organic light-
emitting diodes, field effect transistors, and biomedical
sensors.1
To gain desirable photophysical and electronic properties,
effective chemical syntheses of functional dyes are crucial.
However, chemical modification of the perylene moiety of
PBIs only relies on halogenation at bay positions, namely,
1,6,7,12-positions and the subsequent transformations, despite
their rich material chemistry. This is due to the higher
reactivity of the bay positions toward electrophilic substitu-
tions. In addition, substituent effects at the bay positions are
substantial due to the large contribution to the HOMO by
these positions. On the other hand, substitution at the
2,5,8,11-positions has been believed to be less effective to
modify the electronic nature of PBIs, but there has been no
experimental proof. Actually, the synthetic procedure of
2,5,8,11-substituted PBIs has been unavailable until our
recent report. We have reported that Ru-catalyzed C-H bond
activation is effective for alkylation of PBIs at 2,5,8,11-
positions.2 Introduction of alkyl groups at these positions
significantly enhances their solid state emission as well as
† Nagoya University.
‡ Kyoto University.
§ Yonsei University.
(1) (a) Herrmann, A.; Mu¨llen, K. Chem. Lett. 2006, 35, 978. (b)
Wu¨rthner, F. Chem. Commun. 2004, 1564. (c) Wasielewski, M. R. J. Org.
Chem. 2006, 71, 5051. (d) Langhals, H. HelV. Chim. Acta 2005, 88, 1309.
(e) Langhals, H. Heterocycles 1995, 40, 477. (f) Langhals, H. Molecular
DeVices. Chiral, Bichromophoric Silicones: Ordering Principles in Complex
Molecules in Silicon Based Polymers; Ganachaud, F.,; Boileau, S.,; Boury,
B., Eds.; Springer, 2008; p 51.
(2) Nakazono, S.; Imazaki, Y.; Yoo, H.; Yang, J.; Sasamori, T.; Tokitoh,
N.; Cedric, T.; Kageyama, H.; Kim, D.; Shinokubo, H.; Osuka, A.
Chem.sEur. J. 2009, 15, 7530.
10.1021/ol902271b CCC: $40.75
Published on Web 11/02/2009
 2009 American Chemical Society

their solubility in organic solvents without causing any
serious distortion of the PBI core. To examine the electronic
effect of other substituents at 2,5,8,11-positions, we under-
took introduction of a variety of aryl groups to PBI.3
Introduction of aryl groups is quite attractive to modulate
the electronic property and aggregation behavior of functional
π-systems.4
Scheme 1. Ru-Catalyzed Four-Fold Arylation of PBI 1
Direct C-H bond functionalization has proven to be a
powerful tool in organic synthesis.5,6 In particular, Kakiuchi
and Chatani have established an efficient protocol for direct
arylation of aromatic ketones with aryl boronates.7 Eventually
we found that this method is suitable for arylation of PBI at
2,5,8,11-positions.
Scheme 1 illustrates Ru-catalyzed 4-fold arylation of PBI.
In the presence of 20 mol % of RuH2(CO)(PPh3)3, a mixture
of bis(N-ethylpropyl)PBI 1 and phenyl boronic acid neo-
pentyl glycol ester was heated in refluxing pinacolone.
Despite the insolubility of 1 in pinacolone, the reaction
proceeded moderately. After silica gel separation, desirable
tetraphenyl PBI 2 was obtained in 57% yield, but triarylated
PBI was also detected in the reaction mixture (entry 1). The
reaction conditions were slightly modified by the addition
of mesitylene as a cosolvent to enable higher reaction
temperatures. Then the product was obtained in 83% yield
in shorter reaction time (entry 2). A variety of aryl boronates
participate in this reaction, and both electron-rich and
electron-deficient aryl groups can be introduced. Unfortu-
nately, the reaction with p-bromophenyl boronate proceeded
sluggishly to provide product 4 in 12% yield along with
recovery of 50% of 1 (entry 4). Strongly electron-deficient
substrate, p-nitrophenyl boronate, could not be used for
arylation of 1.8
a Reaction conditions: Bis(N-ethylpropyl)PBI 1 (0.10 mmol), arylboronic
acid neopentyl glycol ester, (0.7 mmol), RuH2(CO)(PPh3)3 (0.020 mmol),
pinacolone (0.5 mL), mesitylene (0.5 mL), 140 °C, 21 h. b The reaction
was carried out at 110 °C with 11 equiv of arylboronic ester without
mesitylene. c 50% of 1 was recovered.
All tetraaryl PBIs 2-7 were fully characterized by 1H and
13C NMR analysis as well as high-resolution ESI TOF mass
spectroscopy (Supporting Information, SI). Furthermore, the
solid-state structures of 4, 5, and 7 (Figure 1 and SI) were
determined by the X-ray diffraction analysis, elucidating the
highly planar structure of the perylene core. This character-
istic is in sharp contrast to the modified PBIs at bay areas,
of which perylene backbones are considerably twisted.9,10
The aryl groups are tilted to the perylene core by 50-60°,
and the C-C bond lengths between the perylene core and
the aryl groups range from 1.480 to 1.499 Å. These structural
features imply weak electronic communication between the
aryl substituents and the perylene moiety. In crystals, each
individual molecule is enough separated because of steric
hindrance of aryl groups, indicating the absence of π-π
stacking interaction.
Figure 2 shows UV/vis absorption and fluorescence spectra
of 1, 2, and 7. The absorption spectra of arylated PBIs except
7 are well matched with the sum spectra of 1 and aryl
substituents, suggesting weak interaction between the perylene
core and the substituents in the ground state. In contrast,
arylated PBIs at bay positions exhibit substantial bathochro-
mic shifts due to twisting of the perylene core.4a,b Introduc-
tion of p-(N,N-dimethylamino)phenyl groups, however,
(3) We have presented these results at the 55th Symposium on
Organometallic Chemistry, Japan 2008. Nakazono, S.; Shinokubo, H.;
Osuka, A. Abstracts of the 55th Symposium on Organometallic Chemistry,
Japan 2008; p 199.
(4) For selected examples on arylated PBI derivatives at bay areas, see:
(a) Qiu, W.; Chen, S.; Sun, X.; Liu, Y.; Zhu, D. Org. Lett. 2006, 8, 867.
(b) Chao, C.-C.; Leung, M.-K.; Su, Y. O.; Chiu, K.-Y.; Lin, T.-H.; Shieh,
S.-J.; Lin, S.-C. J. Org. Chem. 2005, 70, 4323. (c) Sugiyasu, K.; Fujita, N.;
Sinkai, S. Angew. Chem., Int. Ed. 2004, 43, 1229. (d) Ahrens, M. J.; Sinks,
L. E.; Rybtchinski, B.; Liu, W.; Jones, B. A.; Giaimo, J. M.; Gusev, A. V.;
Goshe, A. J.; Tiede, D. M.; Wasielewski, M. R. J. Am. Chem. Soc. 2004,
126, 8284. (e) Avlasevich, Y.; Mu¨ller, S.; Erk, P.; Mu¨llen, K. Chem.sEur.
J. 2007, 13, 6555. (f) Kelley, R. F.; Shin, W. S.; Rybtchinski, B.; Sinks,
L. E.; Wasielewski, M. R. J. Am. Chem. Soc. 2007, 129, 3173. (g)
Vajiravelu, S.; Ramunas, L.; Juozas Vidas, G.; Valentas, G.; Vygintas, J.;
Valiyaveettil, S. J. Mater. Chem. 2009, 19, 4268. (h) Li, Y.; Zheng, H.; Li,
Y.; Wang, S.; Wu, Z.; Liu, P.; Gao, Z.; Liu, H.; Zhu, D. J. Org. Chem.
2007, 72, 2878.
(5) (a) Handbook of C-H Transformations; Dyker, G., Ed.; Wiley-VCH:
Weinheim, 2005. (b) Kakiuchi, F.; Chatani, N. AdV. Synth. Catal. 2003,
345, 1077. (c) Godula, K.; Sames, D. Science 2006, 312, 67. (d) ActiVation
of UnreactiVe Bonds and Organic Synthesis; Murai, S., Ed.; Springer: Berlin,
1999. (e) Alberico, D.; Scott, M. E.; Lautens, M. Chem. ReV. 2007, 107,
174
.
(6) (a) Murai, S.; Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Kamatani, A.;
Sonoda, M.; Chatani, N. Nature 1993, 366, 529. (b) Kakiuchi, F.; Sekine,
S.; Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani, N.; Murai, S. Bull.
Chem. Soc. Jpn. 1995, 68, 62. (c) Kakiuchi, F.; Murai, S. Acc. Chem. Res.
(9) Crystal data for 4: C60H44Br4Cl6N2O4, Mw ) 1389.31, crystal size
0.40 × 0.20 × 0.10 mm, orange prism, monoclinic, space group P21/a (No.
14), a ) 18.099(4), b ) 8.285(3), c ) 19.042(5) Å, b ) 105.218(9)°, V )
2755.2(13) Å3, Z ) 2, Dcalc ) 1.675 g/cm3, T ) 123(2) K, R ) 0.0727 (I
> 2.0s(I)), Rw ) 0.2335 (all data), GOF ) 1.044 (I > 2.0s(I)).
(10) Crystal data for 7: C34H34.36Cl2.64N3O2, Mw ) 610.58, crystal size
0.40 × 0.20 × 0.05 mm, orange prism, triclinic, space group P-1 (No. 2),
a ) 9.294(4), b ) 10.196(4), c ) 18.474(8) Å, a ) 85.694(12), b )
83.861(14), g ) 66.290(13)°, V ) 1592.6(11) Å3, Z ) 2, Dcalc ) 1.273
g/cm3, T ) 123(2) K, R ) 0.0880 (I > 2.0s(I)), Rw ) 0.2814 (all data),
GOF ) 1.049 (I > 2.0s(I)).
2002, 35, 826
.
(7) (a) Kakiuchi, F.; Kan, S.; Igi, K.; Chatani, N.; Murai, S. J. Am. Chem.
Soc. 2003, 125, 1698. (b) Kakiuchi, F.; Matsuura, Y.; Kan, S.; Chatani, N.
J. Am. Chem. Soc. 2005, 127, 5936. (c) Kitazawa, K.; Kochi, T.; Sato, M.;
Kakiuchi, F. Org. Lett. 2009, 11, 1951.
(8) No reaction proceeded with pentafluorophenyl and 2-thienyl bor-
onates. The use of 1-naphthyl boronate resulted in formation of an
inseparable mixture of several atropisomers in 50% yield.
Org. Lett., Vol. 11, No. 23, 2009
5427

Introduction of aryl groups also affects their fluorescence
properties. In comparison to parent PBI 1 (Φf ) 0.98),
tetraphenyl PBI 2 exhibits much weaker emission (Φf )
0.16). Furthermore, fluorescence is perfectly quenched in 3
and 7, which have strongly donating substituents. On the
other hand, the quantum yield of 5 with an electron-
withdrawing p-(trifluorometyl)phenyl group is higher (Φf )
0.75) in solution.
Water-soluble fluorescent labels have been extensively
employed for single-molecule tracking in living cells.11
However, water-soluble PBIs with high fluorescence ef-
ficiency are still limited.12 This is mostly due to fluorescence
quenching because of aggregation in aqueous media and
interaction with substituents. To gain solubility in water, N,N-
dimethylamino groups of 7 were quaternarized. This conver-
sion would also block off the electron-donating character of
the amino group to attain a high fluorescence quantum yield
Figure 1. X-ray crystal structures. (a) Top view of 4, (b) top view
of 7, (c) side view of 4, and (d) side view of 7. The thermal
ellipsoids were scaled to the 50% probability level. Hydrogen atoms,
solvents, and aryl substituents in side views were omitted for clarity.
Scheme 2. Methylation of 7 and X-ray Structure of 8
Figure 2. (a) UV/vis absorption spectra of 1, 2, and 7 and (b)
fluorescence spectra of 1 and 2 measured in CH2Cl2.
resulted in dramatic color change to deep violet in CH2Cl2.
The absorption spectrum of 7 exhibits a broadened band
around 600-700 nm, covering the visible light region.
Theoretical calculations at the B3LYP/6-31G(d) level indi-
cate that degenerated HOMO and HOMO-1 of 7 are localized
on the aryl substituents not on the perylene core (Figure 3c).
On the basis of TD-DFT calculations, the absorption of 7 in
the low-energy region can be assigned as transitions from
HOMO or HOMO-1 to LUMO, which have large charge
transfer character.
by preventing intramolecular charge transfer interaction. Full
methylation was accomplished upon treatment with io-
domethane in the presence of AgOTf13 to cleanly furnish
(11) (a) Seisenberger, G.; Ried, M. U.; Endre, T.; Buning, H.; Hallek,
M.; Brauchle, C. Science 2001, 294, 1929. (b) Cotlet, M.; Hofkens, J.; Maus,
M.; Gensch, T.; Van der Auweraer, M.; Michiels, J.; Dirix, G.; Van Guyse,
M.; Vanderleyden, J.; Visser, A. J. W. G.; De Schryver, F. C. J. Phys.
Chem. B 2001, 105, 4999. (c) Margineanu, A.; Hofkens, J.; Cotlet, M.;
Habuchi, S.; Stefan, A.; Qu, J.; Kohl, C.; Mu¨llen, K.; Vercammen, J.;
Engelborghs, Y.; Gensch, T.; De Schryver, F. C. J. Phys. Chem. B 2004,
108, 12242.
(12) (a) Qu, J.; Kohl, C.; Pottek, M.; Mu¨llen, K. Angew. Chem., Int.
Ed. 2004, 43, 1528. (b) Kohl, C.; Weil, T.; Qu, J.; Mu¨llen, K. Chem.sEur.
J. 2004, 10, 5297. (c) Peneva, K.; Mihov, G.; Nolde, F.; Rocha, S.; Hotta,
J.; Braechmans, K.; Hofkens, J.; Uji-i, H; Herromann, A.; Mu¨llen, K. Angew.
Chem., Int. Ed. 2008, 47, 3372.
Figure 3. Calculated molecular orbitals at the B3LYP/6-31G(d)
level. (a) HOMO and (b) LUMO of 7.
(13) Ohara, Y.; Akiba, K.; Inamoto, N. Bull. Chem. Soc. Jpn. 1983, 56,
1508.
5428
Org. Lett., Vol. 11, No. 23, 2009

tetraanilinium salt 8 (Scheme 2). Because of high polarity
of 8, silica gel column chromatography was not suitable for
purification. After repeated recrystallization, the desired
compound was obtained in 49% yield.14 Ammonium salt 8
is soluble in polar solvents, such as MeOH, CH3CN, and
water, and achieves high fluorescence quantum yield (Φf )
0.83) in water as well as in CH3CN (Φf ) 0.75) (Table 1).
Table 2. Electrochemical Properties of Tetraaryl PBIsa
PBI
Ar
E2 (V)
E1 (V)
E1 (V)
red
red
ox
5
4
1
2
6
3
7
8b
p-CF3(C6H4)
p-Br(C6H4)
-
-1.244
-1.281
-1.309
-1.332
-1.338
-1.352
-1.414
-1.190
-0.988
-1.044
-1.107
-1.124
-1.156
-1.154
-1.314
-0.989
1.300
1.289
1.191
1.140
1.196
-
Ph
p-Me(C6H4)
p-MeO(C6H4)
p-Me2N(C6H4)
p-Me3N(C6H4)
Table 1. Optical Properties of Tetraaryl PBIs
-
-
PBI
ε (M-1cm-1
)
λmax (nm)a
λem (nm)b
Φf (solution)c
a Conditions: Potentials versus ferrocene/ferrocenium ion couple.
Working electrode: Pt. Counter electrode: Pt. Reference electrode: Ag/
AgClO4. Scan rate: 100 mV/s. Electrolyte: Bu4NPF6. Solvent: CH2Cl2.
b Solvent: CH3CN.
1
84000
64000
49000
80000
74000
67000
59000
58000
80000
524
527
532
528
525
529
528
537
525
531
541
-
539
536
543
-
0.98
0.16
-
0.15
0.75
0.02
-
2d
3
4
5
6
core via Ru-catalyzed C-H bond functionalization. Both
electron-rich and electron-deficient aryl groups can be
installed to PBI. The electronic nature of aryl substituents
has a significant impact on their optical and electrochemical
properties. In addition, we have applied the present protocol
to the synthesis of highly emissive water-soluble PBI 8.
Further direct functionalization of PBIs including introduction
of heteroatoms is currently underway in our group.
7
8e
8f
555
538
0.83
0.75
a The longest absorption maxima. b Excited at the longest absorption
maxima. c Absolute quantum yield determined by a calibrated integrating
sphere system within ( 3% errors. d Measured in toluene. e Measured in
water. f Masured in CH3CN.
The electrochemical properties of arylated PBIs have been
measured in CH2Cl2 by cyclic voltammetry (Table 2). For
5, one oxidation at 1.300 V and two reduction potentials at
-0.988 and -1.244 were observed as reversible waves
versus ferrocene/ferrocenium. No reversible oxidation waves
could be observed for 3 and 7. In comparison to the parent
PBI 1, positive shifts of oxidation and reduction potentials
were detected for 4 and 5, whereas electron-donating aryl
groups lead to negative shifts for 3 and 6. These results
clarify that HOMO and LUMO levels are substantially
influenced by the aryl substituents at 2,5,8,11-positions.
In summary, we have accomplished regioselective 4-fold
direct arylation of PBI at 2,5,8,11-positions of the perylene
Acknowledgment. This work was partly supported by a
Grant-in-Aid for Scientific Research (No. 21685011) from
MEXT, Japan. H.S. gratefully acknowledges financial sup-
port from the Iketani Science and Technology Foundation.
Helpful discussions with Prof. Fumitoshi Kakiuchi (Keio
University) are also acknowledged. The work at Yonsei
University was supported by Star Faculty, and World Class
University (no.2008-8-1955), of the Ministry of Education,
Science, and Technology of Korea and the AFSOR/AOARD
grant.
Supporting Information Available: General procedures,
spectral data for compounds, absorption and fluorescence
spectra. CIF file for the X-ray analysis of 4, 5, 7, and 8.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(14) Crystal data for 8: C76H86F12N6O18S4, Mw ) 1727.75, crystal size
0.20 × 0.10 × 0.05 mm, red prism, triclinic, space group P-1 (No. 2), a )
6.815(4), b ) 14.674(10), c ) 20.572(10) Å, a ) 70.543(19), b )
80.424(18), g ) 84.60(2)°, V ) 1910.9(19) Å3, Z ) 1, Dcalc ) 1.501 g/cm3,
T ) 123(2) K, R ) 0.0956 (I > 2.0s(I)), Rw ) 0.2600 (all data), GOF )
1.174 (I > 2.0s(I)).
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5429