DOI: 10.1002/chem.200901318

Regioselective Ru-Catalyzed Direct 2,5,8,11-Alkylationof Perylene Bisimides
Satomi Nakazono,[b] Yusuke Imazaki,[b] Hyejin Yoo,[c] Jaesung Yang,[c]Takahiro Sasamori,[d] Norihiro Tokitoh,[d] Tassel C dric,[e] Hiroshi Kageyama,*[e]Dongho Kim,*[c] Hiroshi Shinokubo,*[a] and Atsuhiro Osuka*[b]Perylene tetracarboxylic acid bisimides (PBIs) are an important class of dyes and pigments for widespread practicaluse, which have been extensively investigated for a longtime both in academia and industry.[1] Recently, they havealso received much attention as n-type semiconducting materials.[2] Furthermore, owing to high fluorescence quantum
efficiency and photostability, they have been a popularmotif for single-molecule spectroscopy.[3] Chemical modifications of PBIs are quite important to gain desirable photophysical and electronic properties as well as solubility. In
spite of their rich material chemistry, functionalization of
the perylene core of PBIs relies on halogenation of the bay
area (1,6,7,12-positions) and subsequent transformations(Scheme 1).[4] Selective functionalization at 2,5,8,11-positions remains unavailable to date.[5]Here we wish to disclose the first selective synthesis of
2,5,8,11-substituted PBIs. We have envisioned the potential[a] Prof. Dr. H. Shinokubo
Department of Applied Chemistry
Graduate School of Engineering, Nagoya University
Chikusa-ku, Nagoya 464-8603 (Japan)
E-mail: hshino@apchem.nagoya-u.ac.jp[b] S. Nakazono, Y. Imazaki, Prof. Dr. A. Osuka
Department of Chemistry, Graduate School of Science
Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
E-mail: osuka@kuchem.kyoto-u.ac.jpScheme 1. Functionalization of perylene bisimides.

of direct functionalization of PBIs by organometallic andcatalytic means: ruthenium-catalyzed C H bond activation
and addition strategy, namely, the Murai–Chatani–Kakiuchi
protocol (Scheme 2).[6] This reaction can introduce alkyl
substituents to the proximal position of the directing groups.
Successful installation of alkyl chains at the 2,5,8,11-positions of PBIs would allow greater modification of properties
in the solid state or condensed phase.
The reaction procedure is quite simple. A mixture ofbis(N-ethylpropyl)PBI 1 a and trimethylvinylsilane washeated in mesitylene at 165 8C for 60 h in the presence of[c] H. Yoo, J. Yang, Prof. Dr. D. Kim
Department of Chemistry, Yonsei University
Seoul 120-749 (Korea)
E-mail: dongho@yonsei.ac.kr[d] Dr. T. Sasamori, Prof. Dr. N. Tokitoh
Institute for Chemical Research
Kyoto University, Kyoto 611-0011 (Japan)[e] T. C dric, Prof. Dr. H. Kageyama
Department of Chemistry, Graduate School of Science
Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
E-mail: kage@kuchem.kyoto-u.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200901318.

7530

Scheme 2. Ru-catalyzed selective alkylation of perylene bisimides.

2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

C hem. E ur. J. 2009, 15, 7530 – 7533

C O M M U NIC ATIO N
6 mol % of [RuH2(CO)ACHTUNGRE(PPh3)3]. After silica-gel separation,
tetraalkylated PBI 2 a was obtained in 94 % yield(Scheme 2). The alkylation of N-(2,6-diisopropyl)phenylPBI
1 b needed longer reaction times due to its lower solubility,
but afforded the desired product 2 b in almost quantitative
yield. After tetraalkylation, solubility in organic solvents issignificantly enhanced: 2 a is soluble in ethyl acetate and 3 a
is soluble in warm hexane. A particularly attractive feature
is facile introduction of the alkoxylsilyl side chain (6 a) thatserves as a docking group for inorganic substrates (seebelow).
UV/Vis absorption and fluorescence spectra are shown in
Figure 1. As expected, the alkylation does not significantly
change the absorption and emission properties in the solution state, but somewhat lowers molar extinction coefficientsof the lowest energy absorption band. Fluorescence quantum yields in toluene are almost the same as the parent
PBIs 1 a and 1 b. Importantly, alkylated PBIs fluoresce evenin the solid state with intense red emission.[7] For example, apowder sample of 3 a emits at 635 nm with a much enhanced
quantum yield of 0.59 (Table 1). The fluorescence spectra in
the solid state are broad and substantially red-shifted, suggesting emission from aggregates of PBI. In sharp contrast
to the solution state, quantum yields in the solid state heavily depend on the introduced alkyl groups, implying the importance of alkyl substituents that influence the crystal
packing. Absorption spectra in the solid state were measured for microdispersion of PBIs (Figure 1c).[8] PBI 1 a exhibits a broad and blue-shifted spectrum, which is typical for
H-type aggregates. For 3 a and 4 a, the absorption features insolution including the vibronic bands were preserved in thesolid sate, but 3 a showed 12 nm of red-shift. These results
Figure 1. a) UV/vis absorption spectra in toluene. b) Emission spectra intoluene and solid state emission spectra. c) Solid-state absorption spectra
indicate smaller intermolecular electronic interaction inof dispersion of PBIs in water.
crystal than parent PBI 1 a by the introduced alkyl substituents.
The structure of PBI 4 a has been clearly elucidated by
the X-ray analysis (Figure 2 and Figure S31).[9] Introduction
Using trimethoxysilyl groups, 6 a can be chemisorbed on aglass surface via the following process: 1) recovery of theof four alkyl groups does not result in any distortion of theOH groups on the glass surface, 2) dropping a toluene soluflat perylene core. This is in sharp contrast to bay-area subtion of 6 a on the surface; 3) removal of the physisorbed
stitution, which often induces severe twist in perylene. EachPBI. We were able to obtain a fluorescence image of single
molecule of 4 a aligns in a parallel manner without stacking.
molecules of 6 a adsorbed on glass surface. The fluorescence
Obviously, the interaction between alkyl groups is essential
is still observable, even though the molecule is exposed toto form this type of aggregation. In contrast, PBI 2 a exhibits
the herringbone arrangementwith distinct p-stacking of aninterplanar distance of about Table 1. Photophysical properties of alkylated PBIs.
3.6 .[10] Two molecules are PBI e [m 1 cm 1] l [nm][a] l [nm][b] Stokes shift [cm 1] F (solution) l [nm] (solid) F (solid)[c]
maxem
fem
f
crossed with each other by 668,
1a8.43 104
526
533
250
1.06760.07
resulting from steric hindrance 2 a 5.97 104
522
533
414
0.91
640
0.41
of bulky silylethyl substituents. 3 a 6.42 104
521
533
380
0.94
635
0.59
521
533
451
0.95
644
0.24
Although it was difficult to 4 a 5.30 104
4525
534
339
0.92
634
0.08
obtain a nice single crystal of 5 a 5.19 104
527
534
249
0.97
–0.01
1b8.50 10
3 a, the synchrotron powder X524
534
357
0.94
584
0.02
2b
6.29 104
ray diffraction (SXRD) re- 3 b 6.80 104
523
533
358
0.94
591
0.09
vealed a high crystallinity of 3 a [a] The longest absorption maxima. [b] Excited at the longest absorption maxima. [c] Excited at 470 nm. Absowith the triclinic symmetry.
lute quantum yields were determined by a calibrated integrating sphere system within 3 % errors. Powder
samples were prepared by recrystallization of alkylated PBIs from CHCl3/CH3CN.

C hem. E ur. J. 2009, 15, 7530 – 7533

2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

7531

H. Shinokubo, H. Kageyama, D. Kim, A. Osuka et al.

of a few seconds that is probably induced by interaction between PBI and covalent-bonded glass substrate, such as
electron transfer to the impurity sites in the glass (Figure 3and Figure S34).[11]In conclusion, we have developed a direct introduction ofalkyl groups to 2,5,8,11-positions of perylene bisimides on
the basis of ruthenium-catalyzed C H bond activation. Suchalkylations have a significant influence on the solid-state
properties as exemplified by the intense red emission. The
usefulness of this protocol has been demonstrated by preliminary single-molecule spectroscopy of 6 a on glass surface,which was facilitated through facile introduction of alkoxylsilyl groups to PBI. Thus, we can study the inherent opticalproperties of single molecules without any hindrance fromthe surrounding polymer matrix. This direct protocol represents a promising perspective for a chelation-assisted strategy for the selective functionalization of PBIs at 2,5,8,11-positions.

Acknowledgements
Figure 2. X-ray structure of 4 a. a) Top view and b) side view. The thermal ellipsoids are at the 50 % probability level. Crystal packing of c) 4 aand d) 2 a.

air and not in the polymer (PMMA) matrix where the singlemolecules can be dispersed, immobilized, and fluoresce. We
measured the fluorescence intensity trajectories (FITs) ofsingle molecules both on glass surface and in the polymermatrix. While one-step and stable FITs are observed in thepolymer matrix, the representative FIT of 6 a on glass surface shows fluorescence intensity fluctuation with off-states

The work at Kyoto and Nagoya Universities was supported by a Grantin-Aid for Scientific Research (No. 21685011) from MEXT, Japan. Helpful discussion with Prof. Fumitoshi Kakiuchi (Keio University) is acknowledged. We also thank Mr. Yoshihiro Tsujimoto (Kyoto University)and Dr. Jungeun Kim (SPring-8) for the SXRD measurement at
BLO2B2 in SPring-8 and its analysis and Prof. Ryo Sasai and Mr. Hiroki
Kusumoto (Nagoya University) to obtain diffuse reflectance spectra. H.S.
gratefully acknowledges financial support from the Asahi Glass Foundation. The work at Yonsei University was supported by the Star Faculty
and World Class University Programs (No. 2008-8-1955) from MEST ofKorea and the AFSOR/AOARD grant (No. FA4869-08-1-4097). H.Y.
and J.Y. acknowledge the fellowship of the BK21 program from theMEST.

Keywords: alkylation · fluorescenceruthenium · single-molecule studies

Figure 3. a) Fluorescence image and b) fluorescence intensity trajectoryof 6 a on glass surface.

7532

www.chemeurj.org·perylenes·[1] a) A. Herrmann, K. M llen, C hem. L ett. 2006, 35, 978; b) F. W rthner, C hem. C ommun. 2004, 1564; c) M. R. Wasielewski, J. O rg.
C hem. 2006, 71, 5051; d) H. Langhals, H elv. C him. A cta 2005, 88,1309; e) H. Langhals, H eterocycles 1995, 40, 477; f) H. Langhals, M olecular D evices. C hiral, B ichromophoric Silicones : O rdering Principles in C omplex M olecules in Silicon B ased Polymers (Eds.: F. Ganachaud , S. Boileau , B. Boury), Springer, Heidelberg, 2008, pp. 51 –63.
[2] B. A. Jones, A. Facchetti, M. R. Wasielewski, T. J. Marks, J. A m.
C hem. Soc. 2007, 129, 15259, and references therein.
[3] F. C. De Schryver, T. Vosch, M. Cotlet, M. van der Auweraer, K.
M llen, J. Hofkens, A cc. C hem. Res. 2005, 38, 514.
[4] a) Y. Zhao, M. R. Wasielewski, Tetrahedron L ett. 1999, 40, 7047;b) M. J. Ahrens, M. J. Fuller, M. R. Wasielewski, C hem. M ater. 2003,15, 2684; c) F. W rthner, V. Stepanenko, Z. Chen, C. R. SahaMoller, N. Kocher, D. Stalke, J. O rg. C hem. 2004, 69, 7933; d) U.
Rohr, P. Schlichting, A. Bçhm, M. Gross, K. Meerholz, C. Br uchle,K. M llen, A ngew. C hem. 1998, 110, 1463; A ngew. C hem. Int. E d.
1998, 37, 1434; e) H. Qian, Z. Wang, W. Yue, D. Zhu, J. A m. C hem.
Soc. 2007, 129, 10664; f) H. Qian, C. Liu, Z. Wang, D. Zhu, C hem.
C ommun. 2006, 4587; g) W. Qiu, S. Chen, X. Sun, Y. Liu, D. Zhu,O rg. L ett. 2006, 8, 867; h) Y. Avlasevich, S. Muller, P. Erk, K.
M llen, C hem. E ur. J. 2007, 13, 6555.

2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

C hem. E ur. J. 2009, 15, 7530 – 7533

Alkylation of Perylene Bisimides

C O M M U NIC ATIO N[5] 2,11-Functionalized PBIs were reported in patent without synthetic
procedures. T. Asami, K. Tsubushi, A. Goto, A. Ishikawa, Jpn.
Kokai Tokkyo Koho, JP 10306216, 1998 [C hem. A bstr. 1998, 130,59 042].
[6] a) S. Murai, F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani, M.
Sonoda, N. Chatani, N ature 1993, 366, 529; b) F. Kakiuchi, S. Sekine,Y. Tanaka, A. Kamatani, M. Sonoda, N. Chatani, S. Murai, B ull.
C hem. Soc. Jpn. 1995, 68, 62; c) F. Kakiuchi, S. Murai, A cc. C hem.
Res. 2002, 35, 826.
[7] For solid-state fluorescence of N,N’-bis(2,4-dimethylpent-3-yl)PBI,
see: H. Langhals, O. Krotz, K. Polborn, P. Mayer, A ngew. C hem.
2005, 117, 2479; A ngew. C hem. Int. E d. 2005, 44, 2427. The absolute
quantum yield was not reported.
[8] Dispersion was prepared by adding a THF solution of PBIs into vigorously stirred water.
[9] Crystal data for 4 a: C66H86N2O4, M w = 971.37, triclinic, space groupP1̄ (No. 2), a = 6.299(3), b = 10.967(6), c = 19.506(9) , a =78.896(19), b = 85.019(19), g = 84.60(2)8, V = 1313.2(11) 3, Z = 1,C hem. E ur. J. 2009, 15, 7530 – 7533

1calcd = 1.228 g cm 3, T = 123(2) K, 12 876 measured reflections, 5966
unique reflections, R = 0.0587 (I > 2.0s(I)), R w = 0.1800 (all data),
GOF = 1.086 (I > 2.0s(I)).
[10] Preliminary crystal data for 2 a: C54H77N2O4Si4, M w = 930.54, orthorhombic, space group Pcan (No. 60), a = 9.905(4), b = 30.784(12), c =35.381(14) , V = 10 789(7) 3, Z = 8, 1calcd = 1.146 g cm 3, T =90(2) K, 46 252 measured reflections, 8468 unique reflections, R =0.1803 (I > 2.0s(I)), R w = 0.4670 (all data), GOF = 1.187 (I > 2.0s(I)).
2 a also afforded single crystals form dioxane with different packing(SI). CCDC 726128 (4 a), 726126 (2 a), and 726127 (2 a from dioxane) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif[11] L. Zang, R. Liu, M. W. Holman, K. T. Nguyen, D. M. Adams, J. A m.
C hem. Soc. 2002, 124, 10640.
Received: May 18, 2009
Published online: July 2, 20092009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org7533