Reliable and reproducible separation of 3,9-and 3,10-dibromoperylenes and the photophysical properties of their alkynyl derivatives

Article abstract of DOI:10.1002/ejoc.201700807

We developed a reliable and reproducible method for the separation of 3,9-dibromoperylene and 3,10-dibromoperylene resulting from bromination of perylene by using sequential and repeated recrystallization. Because of the unprecedented purities of the dibromoperylenes, they exhibit the high-est melting temperatures so far reported. In addition, various alkynylperylenes were prepared from the dibromoperylenes, and we investigated the photophysical characteristics of these alkynyl derivatives in detail.

Full text of DOI:10.1002/ejoc.201700807

A Journal of
Accepted Article
Title: Reliable and Reproducible Separation of 3,9- and 3,10-
Dibromoperylenes and the Photophysical Properties of their
Alkynyl Derivatives
Authors: Koichiro Hayashi and Masahiko Inouye
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700807
Link to VoR: http://dx.doi.org/10.1002/ejoc.201700807
Supported by

10.1002/ejoc.201700807
European Journal of Organic Chemistry
FULL PAPER
Reliable and Reproducible Separation of 3,9- and 3,10-
Dibromoperylenes and the Photophysical Properties of their
Alkynyl Derivatives
Koichiro Hayashi, and Masahiko Inouye*
Abstract: We developed a reliable and reproducible separation
method of 3,9-dibromoperylene and 3,10-dibromoperylene resulted
from bromination of perylene by using sequential and repeated
recrystallization. Because of the unprecedented purities of the
dibromoperylenes, they exhibited the highest melting temperatures
so far reported. In addition, various alkynylperylenes were prepared
from the dibromoperylenes, and we investigated the photophysical
characteristics of these alkynyl derivatives in detail.
regioisomerically pure derivatives.[9c] Very recently, Yamada et
al. synthesized 3,9- and 3,10-bis(4-methoxyphenyl)perylenes
and investigated the physical properties of their oxidized
products. In this study, moderately purified 3,9- and 3,10-
dibromoperylenes were used, and further purification was
carried out in the next derivatization stage to obtain analytically
pure samples.
Our group has reported about the substitution effect of
alkynyl-groups on pyrene. As the number of alkynyl-substituents
increased in pyrenes, the fluorescence quantum yields
increased accompanied by red-shifts of the absorption and
emission maxima.[10] Furthermore, the alkynyl-group could be a
good scaffold for fabricating the fluorophores to appropriate
Introduction
Since its high fluorescence quantum yield, perylene has long
been attractive in a variety of research fields. Indeed, perylene
and the derivatives proved to be possible candidates such as in
structures convenient for their applications.
Recently, we
reported dialkynylpyrene-based [3] and [4]rotaxanes that emit
only blue light from the monomeric pyrene[11] and that exhibit
circularly polarized luminescence from the excimer,[12]
respectively. When extending the system to other fluorophores,
we came up against difficulties for obtaining regioisomerically
pure dibromoperylene. Herein, we wish to report a reliable and
reproducible separation method of 3,9-dibromoperylene and
3,10-dibromoperylene and the photophysical characteristics of
their alkynyl derivatives in detail.
organic
semiconductors,[1]
organic
electroluminescence
materials,[2] and biological probes.[3] To utilize them for materials
of optical interest, halogenation, especially bromination of the
perylene nucleus is most preferred, bearing in mind the following
substitution by organometallic strategies.
In this context,
preparation of 3-bromoperylene (1) was well established, and
the many different kinds of mono-substituted perylenes were
synthesized starting from 1.[4,5] On the other hand, a limited
number of preparative methods are available for pure
dibromoperylenes owing to the difficulty for separating the
arising two regio-isomers of 3,9-dibromoperylene (2) and 3,10-
dibromoperylene (3). In 1925, Zinke et al. reported the first
synthesis and separation of the dibromoperylenes.[6] After that,
Uchida et al. published a different synthetic method for them and
determined the isomer possessing a higher melting temperature
being 2 by the X-ray structure analysis in 1979.[7] For both the
reports, the separation was performed by repeated
recrystallization, while we hardly reproduced the result because
the details are unclear. There are a few other reports for
separating the isomers, however, their NMR data showed
contaminants of another isomer.[8] This situation causes their
melting temperatures to be incompatible among the published
papers. Possibly from these reasons, dibromoperylene was
usually used as a regio-mixture for the applications,[2c,9] so that
there are few reports about the photophysical properties of the
Results and Discussion
Dibromoperylenes were synthesized by a similar method to that
reported by Uchida et al., as follows.[7] Perylene was suspended
in benzene, and bromine was slowly added to the suspension at
40 °C. The reaction mixture was stirred for 3 h at the same
temperature and filtered after cooling to room temperature. The
precipitate was found to be an approximately 1:1 mixture of 3,9-
dibromoperylene (2) and 3,10-dibromoperylene (3) with some
1
minor products by H NMR measurement. We tried to separate
the regioisomers obeying the reported procedures, but all in vain
because of lack of details in experimental procedure.[6−8] After
much trial and error, we finally established a reproducible
separation method by sequential and repeated recrystallization.
1
Figure 1 shows H NMR spectral changes of dibromoperylenes
during the course of the recrystallization process. First, the 1:1
mixture was allowed to recrystallization from aniline-
nitrobenzene (1:1), and the recrystallization from the same
solvent system was repeated until the amount of 2 came to be
slightly predominant to that of 3 in the precipitate (Figure 1a).
Using only the precipitate and discarding all the mother liquors
proved to be crucial for succeeding the final separation. The 2-
predominated precipitate was further purified by recrystallization
from toluene-hexane (3:1). Repeated recrystallization with the
Koichiro Hayashi, Prof. Dr. Masahiko Inouye
Graduate School of Pharmaceutical Sciences, University of Toyama
Toyama 930-0194 (Japan)
E-mail: inouye@pha.u-toyama.ac.jp
http://www.pha.u-toyama.ac.jp/yakka/index.html
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejoc.201700807
European Journal of Organic Chemistry
FULL PAPER
1
1
1
1
1
1
1
1
1
2
2
2
1
R
R
R
R
R
R
R2
R2
R3
=
H
R3
R1
,
,
:
:
:
:
:
:
:
:
:
=
=
=
=
=
=
=
=
=
=
=
=
=
=
:
10
:
11
:
12
:
13
:
14
:
15
=
=
=
=
=
=
=
=
=
1
2
3
4
5
6
7
8
9
R
R
R
R
R
R
R
R
R
Br, R
Br, R
Br, R
R3
3
H
H
tBuPh
tBuPh
tBuPh R2
H,
Br, R
H,
tBuPh
same solvent system (10 times on average) gave pure 2 as
micro pale orange needles (29% yields; m.p. 304−306 °C)
(Figure 1d). The mother liquors arisen from the recrystallization
by using this solvent system were found to contain 3 a little more
than 2 (Figure 1e) and now used for isolating 3. Pure 3 was
obtained as filamentous yellow crystals (23% yields; m.p.
267−268 °C) by repeated recrystallization from toluene-hexane
(4:1~5:1) (Figure 1h). Because of the unprecedented purities of
the dibromoperylenes, they exhibited the highest melting
1
1
1
1
1
=
H
,
R3 Br
R3 tBuPh
=
=
,
H,
=
H,
TMS R2
R3
R3
H
TEGPh R2
=
H
=
=
,
,
H,
H,
TMS R2 TMS R3
H
H
TEGPh R2 TEGPh R3
=
=
=
=
,
,
,
,
TMS R2
R3 TMS
R3 TEGPh
=
TEGPh R2
=
=
=
=
,
,
H,
H,
H,
=
TEG
R2
R3
H
=
H
,
TEG R2 TEG R3
R3 R2
,
,
=
TEG R2
R3 TEG
=
=
,
H,
:
:
TMS
tBuPh
tBu
TMS
temperatures, compared to those so far reported.
Each
O
1
dibromoperylene was identified by comparing the H NMR data
to the published ones.[8c] More detailed information for the
separation is provided in Figure S1 in the Supporting Information.
For reference, 3-bromoperylene (1) was also synthesized[4c] and
derivatized to mono-substituted perylenes.
NH2
O
O
N
H
NH2
4
:
:
TEG
TEGPh
4
R1
NBS/DMF
1
1
1
2
R
R
R
Br, R
Br, R
Br, R
R3
H
1
:
1
:
2
:
3
=
=
=
=
=
=
=
=
for
H,
2
2
3
Br, R
H
R3 Br
=
H,
Br2/benzene
and
2
3
for
R3 R2
Perylene
(R1
2
3
=
=
=
R
R
H)
TMS
1
1
1
R2
R3
H
=
CuI
:
4
:
5
:
6
=
=
=
=
=
,
R
R
R
TMS
,
Pd(PPh3)4
H,
TMS R2 TMS R3
TMS R2
H
–
=
1
3
,
,
R3 TMS
=
=
,
Figure 1. 1H NMR spectra of dibromoperylenes during the course of
recrystallization process a−d) for 3,9-dibromoperylene and e−h) for 3,10-
dibromoperylene.
=
H,
2:1
THF/piperidine
NH2
CuI
O
4
,
A series of alkynylperylenes 4−15 were prepared through
Sonogashira coupling reaction[13] between 1−3 and various
1
1
1
:
7
:
8
:
9
=
=
=
=
=
=
R
R
R
TEG
R2
,
R3
H
=
Pd(PPh3)4
H,
TEG R2 TEG R3
H
–
1
3
,
,
TEG R2
R3 TEG
=
=
,
=
H,
2:1
THF/piperidine
acetylene derivatives (Scheme 1).
Reacting 1−3 with
trimethylsilylacetylene afforded 3-(trimethylsilylethynyl)perylene
(4), 3,9-bis(trimethylsilylethynyl)perylene (5), and 3,10-
bis(trimethylsilylethynyl)perylenes (6), respectively (TMS series).
Other alkynylperylenes were similarly prepared from 1−3 with a
tetraethylene glycol-substituted acetylene (7−9: TEG series), 4-
tBu
CuI
=
1
,
:
10
:
11
:
12
=
=
=
R
R
R
tBuPh R2
R3
H
=
Pd(PPh3)4
,
H,
1
1
tBuPh R2 tBuPh R3
H
–
1
3
=
=
=
R3 tBuPh
,
,
(tert-butylphenyl)acetylene (10−13: tBuPh series), and
a
tBuPh R2
=
=
,
H,
2:1
THF/piperidine
tetraethylene glycol-substituted phenylacetylene (13−15: TEGPh
series). The teraethylene glycol-substituted 7−9 and 13−15
were designed in order to disclose their photophysical properties
in H2O.
1
1
1
K2CO3
:
16
:
17
:
18
=
=
=
=
R
R
R
C
C
C
CH,
CH,
CH,
R2
R2
R2
R3
H
=
H,
C
R3
H
–
4
6
=
=
=
CH,
R3
=
C
CH
=
THF/MeOH 5:1
H,
O
O
N
H
NH2
4
19
Br
1
1
1
:
:
:
=
=
=
=
Pd(PPh3)4
13
14
15
R
R
R
TEGPh R2
R3
H
=
,
H,
R2
R2
TEGPh
R3
R3
–
=
=
=
H
16 18
TEGPh
TEGPh
,
,
,
=
TEGPh
=
H,
2:1
THF/piperidine
Scheme 1. Preparation of alkynylperylenes 4−15.
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10.1002/ejoc.201700807
European Journal of Organic Chemistry
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Figure 2 revealed UV-vis spectra of the alkynylperylenes
4−15 (1.0 × 10-5 M) in CHCl3, and Table 1 lists their absorption
maxima (λabs) along with the absorption coefficients (ε). The
spectra were also measured in cyclohexane, ethanol, and H2O,
and these data are summarized in Figure S2, S3, and Table S1
in the Supporting Information. All the spectra in CHCl3 showed
well-resolved vibrational structures similar to those of parent
fluorescence maxima appearing at the shortest wavelengths
(λem) and fluorescence quantum yields (Φf) in CHCl3. The
quantum yields were determined by a relative method using 3-
(trimethylsilylethynyl)perylene (4) as a reference (Φf = 0.88 in
cyclohexane[5]).
As well as the absorption spectra, the
fluorescence spectra displayed well-resolved vibrational
structures. Although the fluorescence quantum yields were
found to increase with increasing the number of
trimethylsilylethynyl groups in the series of alkynylpyrenes,[10]
bis(trimethylsilylethynyl)-substituted perylenes 5 and 6 showed
lower quantum yields (Φf = 0.65 and 0.79, respectively) than
mono-substituted 4 (Φf = 0.95). Yamaji et al. discussed that the
intersystem crossing process could be enhanced by interactions
such as a vibronic coupling of triple bonds to the perylene
nucleus.[5] The same mechanism might work in this case,
causing the lower quantum yields. The emission maxima and
quantum yields of the TMS series 4−6 were larger than those of
the TEG series 7−9, probably due to the effect of the σ-π
interaction above mentioned. In H2O, the TEGPh series 13−15
strongly aggregated on the basis of the UV-vis spectra, so that
no accurate quantum yields were determined even at 1.0 × 10-6
M (Figure S5b and Table S1 in the Supporting Information). At a
higher concentration (1.0 × 10-5 M), 13−15 exhibited new broad
and structure-less emission bands probably because of the
corresponding emissions from their excimers. The emission
maxima appeared around 650 nm, and the emission bands
approached near-infrared region (Figure S5d in Supporting
Information).
perylene.
The
absorption
maximum
of
3,9-
bis(trimethylsilylethynyl)perylene (5) appeared at 483 nm, which
is bathochromically shifted 21 nanometers than that of mono-
alkynyl derivative 4, accompanied by the increased absorption
coefficient. The 3,10-counterpart 6 displayed the absorption
maximum in a little longer wavelength than 5. This tendency
was seen not only in this TMS series but also in all the series
(TEG, tBuPh, and TEGPh) studied here. The absorption
coefficients of the TMS series 4−6 were significantly large,
comparing with those of the TEG series 7−9. This is probably
because of the π-elongation originated from σ-π interaction
between the acetylenic π and the neighboring C-Si σ bonds on
4−6 in the same manner as mono-alkynylperylenes[5] and
alkynylpyrenes.[10] Absorption maxima of the π-extended tBuPh
and TEGPh series 10−15 further shifted to longer wavelengths.
In addition, the bandwidths of the spectra were rather broadened
due to increments in their vibrational states caused by an
attachment of the π-extended units. In H2O, the TEG series 7−9
and especially TEGPh series 13−15 exhibited structure-less,
broad absorption spectra, owing to the self-aggregations through
stacking of their large π-planes (Figure S3a and S3b in the
Supporting Information).
Figure 2. UV-vis spectra of alkynylperylenes 4−15 (1.0 × 10-5 M) in CHCl3.
Conditions: 25 °C, path length = 10 mm.
Figure 3. Fluorescence spectra of alkynylperylenes 4−15 (1.0 × 10-6 M) in
CHCl3. Conditions: 25 °C, λex = 450 nm, path length = 10 mm.
Fluorescence spectra of the alkynylperylenes 4−15 (1.0 ×
10-6 M) were measured under aerobic conditions in CHCl3
(Figure 3), cyclohexane, ethanol, and H2O (Figure S4, S5, and
Table S1 in the Supporting Information). Table 2 lists their
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Table 1. Summary of photophysical properties of alkynylperylenes 4−15 in
CHCl3.
450 nm was determined by using 3-(trimethylsilylethynyl)perylene (4) (λex
= 450 nm, Φf = 0.88[5] in cyclohexane) as a reference compound and
calculated according to the following equation (Φsample
= Φstandard ×
2
[Astandard / Asample] × [Isample / Istandard] × [nsample / nstandard2]). In this equation,
Φsample and Φstandard are the quantum yields of a sample and standard,
respectively. Asample, Isample and nsample are the optical density, the
integrated emission intensity at the excitation wavelength, and the
refractive index for the sample, respectively. Astandard, Istandard and nstandard
are those for the standard.
Acknowledgements
We thank Ms. Yoshiko Kaneda (University of Toyama Central
Library) for helpful literature research. This work was supported
by a Grant-in-Aid for Scientific Research on Innovative Areas
“Stimuli-responsive Chemical Species for the Creation of
Functional Molecules (No.2408)” (JSPS KAKENHI Grant
Number JP15H00932)
Keywords: Hydrocarbons • Alkynes • Fluorescence • UV/Vis
spectroscopy • Photophysics
a
-5
[Alkynylperylene] = 1.0 × 10 M, each λabs is an absorption band appearing
b
-6
[1]
[2]
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3615–3645. b) V. Settels, A. Schubert, M. Tafipolski, W. Liu, W. Stehr,
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Am. Chem. Soc. 2014, 136, 9327−9337.
at the longest wavelength. [Alkynylperylene] = 1.0 × 10 M, λex = 450 nm,
each λem is an emission band appearing at the shortest wavelength. c Each Φf
was determined by using 3-(trimethylsilylethynyl)perylene (Φf
=
0.88[5] in
cyclohexane) as a reference compound.
a) D. Di, L. Yang, J. M. Richter, L. Meraldi, R. M. Altamimi, A. Y.
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Conclusions
In summary, we developed a reliable and reproducible method
to separate the two regioisomers, 3,9-dibromoperylene and
3,10-dibromoperylene
by
sequential
and
repeated
[3]
[4]
a) P. Singh, L. S. Mittal, G. Bhargava, S. Kumar, Chem. Asian J. 2017,
12, 890−899. b) O. S. Kwon, H. S. Song, H. Kim, N. Artzi, J.-H. Kim,
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B. Gao, Y. Wu, Tetrahedron Lett. 2015, 56, 2749–2753.
recrystallization. Their purities were guaranteed on the basis of
the 1H NMR spectra and of the highest melting temperatures. In
addition, various alkynylperylenes were prepared from the
dibromoperylenes, and their photophysical properties were
investigated in detail. We would feel amply rewarded if the
present study proved helpful to whom it may concern. Of course,
the rotaxane formation using regioisomerically pure
dialkynylperylenes is now underway in our laboratory.
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Garakyaraghi, F. N. Castellano, G. D. Scholes, J. Am. Chem. Soc.
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Experimental Section
General Methods
[8]
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Kang, D.-H. Hwang, Macromolecules 2012, 45, 2367−2376. b) J.-H.
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reference on a JEOL ECA 500 II at 500 MHz (1H) and a JEOL ECA 500 II
at 125 MHz (13C) spectrometers at 25 °C or 40 °C. IR spectra were
measured on a JASCO FT/IR-460 plus spectrometer. Mass spectra were
obtained by the ESI method on a JEOL JMS-T100LC mass spectrometer.
Absorption and fluorescence spectra were recorded using a JASCO V-
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Spectroscopic Measurements
Steady state absorption and fluorescence were recorded at 25 °C using a
10 mm path length cell. The fluorescence quantum yields (Φf) of 4-15 at
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4467–4470.
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Entry for the Table of Contents
FULL PAPER
Reliable and reproducible separation
method of 3,9-dibromoperylene and
3,10-dibromoperylene: Pure 3,9- and
3,10-dibromoperylene were obtained
Separation method
K. Hayashi, M. Inouye*
Page No. – Page No.
by
sequential
and
repeated
Br2
Reliable and Reproducible Separation
of 3,9- and 3,10-Dibromoperylenes
and the Photophysical Properties of
their Alkynyl Derivatives
recrystallization.
properties of their alkynyl derivatives
were investigated in various solvents.
Photophysical
Pure
Br
Pure
Br
3,10-
3,9-
Sequential
and
Repeated
Recrystallization
Br
Br
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