Synthesis and solvatochromic behavior of pyrene derivatives with 4-hydroxyphenyl and 4-hydroxyphenylethynyl groups

Article abstract of DOI:10.1246/bcsj.20130144

1-(4-Methoxyphenyl)pyrene (PyrPhOMe(1)), 1,3,6,8-tetrakis(4-methoxyphenyl) pyrene (PyrPhOMe(4)), 1-(4-methoxyphenylethynyl) pyrene (PyrC≡CPhOMe(1)), 1,3,6,8-tetrakis(4-methoxyphenylethynyl)pyrene (PyrC≡CPhOMe(4)), 1-(4-hydroxyphenylethynyl)pyrene (PyrC≡CPhOH(1)), and 1,3,6,8-tetrakis(4- hydroxyphenylethynyl)pyrene (PyrC≡CPhOH(4)) were synthesized via organometallic complex catalysis. Deprotection of the methoxy groups of PyrPhOMe(1) and PyrPhOMe(4) was conducted by treatment with BBr₃. Deprotonation of the OH groups of PyrPhOH(1), PyrPhOH(4), PyrC≡CPhOH(1), and PyrC≡CPhOH(4) through treatment with NaH caused a bathochromic shift in the absorption and photoluminescence (PL) peaks. The bathochromic shift of the deprotonated species increased with the donor number (DN) of the solvents. These observations can be explained as the consequence of intramolecular charge transfer (ICT) from the ONa groups to the pyrene core.

Full text of DOI:10.1246/bcsj.20130144

1174 Bull. Chem. Soc. Jpn. Vol. 86, No. 10, 1174-1182 (2013)
© 2013 The Chemical Society of Japan
Synthesis and Solvatochromic Behavior of Pyrene Derivatives
with 4-Hydroxyphenyl and 4-Hydroxyphenylethynyl Groups
Isao Yamaguchi* and Katsuhiko Sato
Department of Chemistry, Interdisciplinary Graduate School of Science and Engineering,
Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504
Received May 25, 2013; E-mail: iyamaguchi@riko.shimane-u.ac.jp
1-(4-Methoxyphenyl)pyrene (PyrPhOMe(1)), 1,3,6,8-tetrakis(4-methoxyphenyl)pyrene (PyrPhOMe(4)), 1-(4-meth-
oxyphenylethynyl)pyrene (PyrC¸CPhOMe(1)), 1,3,6,8-tetrakis(4-methoxyphenylethynyl)pyrene (PyrC¸CPhOMe(4)),
1-(4-hydroxyphenylethynyl)pyrene (PyrC¸CPhOH(1)), and 1,3,6,8-tetrakis(4-hydroxyphenylethynyl)pyrene (PyrC¸
CPhOH(4)) were synthesized via organometallic complex catalysis. Deprotection of the methoxy groups of PyrPhOMe(1)
and PyrPhOMe(4) was conducted by treatment with BBr3. Deprotonation of the OH groups of PyrPhOH(1), PyrPhOH(4),
PyrC¸CPhOH(1), and PyrC¸CPhOH(4) through treatment with NaH caused a bathochromic shift in the absorption and
photoluminescence (PL) peaks. The bathochromic shift of the deprotonated species increased with the donor number
(DN) of the solvents. These observations can be explained as the consequence of intramolecular charge transfer (ICT)
from the ONa groups to the pyrene core.
Oligo(p-phenylene)s (OPs) are an important class of ³-
conjugated oligomer because they are useful as luminophores
for light-emitting materials,1-6 as semiconductors for field-
effect transistors,7 as rigid-rod cores for liquid crystalline mate-
rials,8-10 and as amphiphilic materials for biological applica-
tions.11-17 We have recently reported on OPs with an OH group
located at either one end or at both ends, namely, OP(n)-OH
(where n is the number of benzene rings; n = 3-5) and HO-
ArPh(n)-OH species (Ar: 9,9-dihexylfluorene-2,7-diyl and 2,5-
dioctyloxybenzene-1,4-diyl), respectively.18,19 These OP(n)-
OH and HO-ArPh(n)-OH compounds exhibited significant
solvatochromism where deprotonation of the OH groups, when
treated with NaH, caused bathochromic shifts of -max and -em
that increased with the DN of the solvent. The solvatochrom-
ism exhibited by OP(n)-ONa and NaO-ArPh(n)-ONa was
attributed to an intramolecular charge transfer (ICT) from the
ONa group(s) to the adjacent rings.19,20 The degree of batho-
chromic shift in the deprotonated species increased with an
increase in the chain length that corresponds to the expansion
of the ³-conjugation system. Thus, Ph-ONa substituted by a
fused aromatic ring with a large ³-conjugation system will
exhibit significant bathochromic behavior.
Pyrene derivatives (Pyrs) are an important class of fused
aromatic compound in materials science because they can
be useful materials for electroluminescence and photovoltaic
devices.20-24 Pyrs are also used as luminescent probes for
sensing of biomolecules.25-28 In this study, the optical properties
of Pyrs with 4-hydroxyphenyl groups (PyrPhOHs) were inves-
tigated before and after deprotonation of the OH groups. The
³-conjugated system of the PyrPhOHs is somewhat restricted
by the presence of steric hindrance between the phenyl and Pyr
rings. We herein therefore also studied PyrC¸CPhOHs which
have ethynyl spacing groups, and subsequently investigated
their solvatochromic behavior. It has been reported that Pyrs
with arylethynyl groups (PyrC¸CArs) exhibit unique optical
properties such as two-photon absorption and electrogenerated
chemiluminescence.29-32 These properties are based on the fact
that PyrC¸CArs have a more extended coplanar structure,
which thus enables extended ³-conjugation and improves
their carrier mobilities compared to Pyr-Ars. The large carrier
mobility in PyrC¸CPhONa is suited to the development of
new solvatochromic materials based on ICT. The investigation
into the optical properties of PyrPhOHs and PyrC¸CPhOHs
will afford information pertinent to the development of new
solvatochromic materials. It is noteworthy that PyrPhOHs and
PyrC¸CPhOHs are expected to be useful starting materials
for the synthesis of new Pyrs through reactions using the OH
groups.
We herein report on the synthesis of Pyrs with 4-hydroxy-
phenyl and 4-hydroxyphenylethynyl and their optical proper-
ties before and after the deprotonation of the OH groups.
Results and Discussion
Synthesis and Characterization.
Pyr derivatives with
4-methoxyphenyl, 4-hydroxyphenyl, 4-methoxyphenylethynyl,
and 4-hydroxyphenylethynyl groups were synthesized by the
methods shown in Scheme 1. The Suzuki coupling reaction
of 4-methoxyphenylboronic acid with 1-bromopyrene and
1,3,6,8-tetrabromopyrene yielded 1-(4-methoxyphenyl)pyrene
(PyrPhOMe(1)) and 1,3,6,8-tetrakis(4-methoxyphenyl)pyrene
(PyrPhOMe(4)), respectively (Scheme 1a). The deprotection of
the OMe groups of PyrPhOMe(1) and PyrPhOMe(4) with BBr3
resulted in the production of PyrPhOH(1) and PyrPhOH(4),
respectively. The Sonogashira coupling reaction of 4-ethy-
nylanisole with 1-bromopyrene and 1,3,6,8-tetrabromo-
pyrene yielded 1-(4-methoxyphenylethynyl)pyrene (PyrC¸
CPhOMe(1)) and 1,3,6,8-tetrakis(4-methoxyphenylethynyl)-
pyrene (PyrC¸CPhOMe(4)), respectively (Scheme 1b). How-
Published on the web October 15, 2013; doi:10.1246/bcsj.20130144

I. Yamaguchi et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013) 1175
OMe OH
O
O
Ar
Ar
R
(a)
Br
R
Ar'
MeO
B
(i)
(ii)
Ar
Ar'
Ar'
R
PyrPhOMe(1); Ar = H
PyrPhOMe(4); Ar = 4-C6H4OMe
R = H
Br
PyrPhOH(1); Ar' = H
PyrPhOH(4); Ar' = 4-C6H4OH
OMe
Ar
R
Br
R
MeO
(b)
(iii)
Ar
Ar
R
PyrC≡CPhOMe(1); Ar = H
PyrC≡CPhOMe(4); Ar = 4-C CC6H4OMe
R = H
Br
OH
Ar
R
I
OH
(c)
(iii)
Ar
Ar
R
R
R = H
PyrC≡CPhOH(1); Ar = H
PyrC≡CPhOH(4); Ar = 4-C CC6H4OH
C CH
Scheme 1. Synthesis of Pyr derivatives. i) [Pd(PPh3)4], K2CO3(aq), reflux, THF; ii) BBr3, CH2Cl2, 20 °C, 30 h; iii) [PdCl2(PPh3)2],
CuI, NEt3, rt.
ever, PyrC¸CPhOMe(1) and PyrC¸CPhOMe(4) could not
be deprotected by using BBr3; hence, PyrC¸CPhOH(1) and
PyrC¸CPhOH(4) were synthesized by the reaction of 4-
iodophenol with 1-bromopyrene and 1,3,6,8-tetrabromopyrene,
respectively (Scheme 1c).
and the 3-position of the benzene ring of PyrC¸CPhOMe(1) to
be observed at lower magnetic field positions than those of
PyrPhOMe(1).
The IR spectra of PyrPhOMe(4), PyrPhOH(4), PyrC¸
CPhOMe(4), and PyrC¸CPhOH(4) are shown in Figure S1.
The main features of the IR spectra of PyrPhOMe(1) and
PyrPhOMe(4) were identical, with absorption peaks resulting
from C-O stretching, the presence of a phenyl ring, and out-
of-plane C-H bending vibrations of p-phenylene observed at
approximately 1241, 1519, and 839 cm¹1, respectively. Simi-
larly, the main features of the IR spectra of PyrC¸CPhOMe(1)
and PyrC¸CPhOMe(4) were identical, with the absorption
peaks resulting from C¸C and C-O stretching, the presence
of a phenyl ring, and out-of-plane C-H bending vibrations of
p-phenylene observed at approximately 2200, 1246, 1512, and
833 cm¹1, respectively. The observation of a broad absorp-
The structures of the newly synthesized compounds were
determined by 1H and 13C NMR spectroscopy and elemen-
tal analysis. The solubilities of the obtained compounds
are summarized in Table S1. PyrPhOMe(1), PyrPhOMe(4),
PyrPhOH(1), PyrC¸CPhOMe(1), and PyrC¸CPhOMe(4) were
soluble in polar organic solvents such as 1,4-dioxane, tetra-
hydrofuran (THF), N,N-dimethylformamide (DMF), and di-
methyl sulfoxide (DMSO) as well as in less polar organic
solvents such as chloroform and dichloromethane. However,
PyrPhOH(4) and PyrC¸CPhOH(4) were partly soluble in DMF
and DMSO but insoluble in dichloromethane and chloroform
because of the presence of four hydrophilic OH groups.
¹1
tion due to the OH group at 3341 cm and disappearance
1
1H NMR and IR Spectra. Figure 1 shows the H NMR
of absorption peaks due to C-O stretching and C-H stretch-
ing vibrations of the methoxy group in the IR spectrum of
PyrPhOH(4) confirmed occurrence of the deprotection reaction.
Deprotonation of the OH groups of PyrPhOH(1),
PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸CPhOH(4) was
carried out through treatment with an excess amount of NaH
in DMSO-d6. The result is that the signal corresponding to the
spectra of PyrPhOMe(1), PyrPhOH(1), PyrC¸CPhOMe(1),
1
and PyrC¸CPhOH(1). The H NMR spectra of PyrPhOMe(1)
and PyrC¸CPhOMe(1) exhibited a peak corresponding to
the methoxy groups at ¤ 3.94 and 3.88, respectively. These
1
peaks disappeared in the H NMR spectra of the correspond-
ing demethylated species, thus suggesting that the deprotection
reaction proceeded to completion. The electron-withdrawing
ethynyl groups on the pyrene and phenylene protons caused the
peaks due to the H-atoms at the 10-position of the pyrene ring
1
OH group disappeared from the H NMR spectra for solutions
of these compounds in the presence of NaH, indicating that
the deprotonation proceeded quantitatively.

1176 Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013)
Synthesis and Solvatochromic Behavior of Pyrene Derivatives
groups in PyrC¸CPhOMe(1) and PyrC¸CPhOMe(4) which
reduces the bond twisting between the pyrene and benzene
rings. Whereas the absorption wavelengths due to the electronic
transition directed along the y axis of PyrC¸CPhOMe(1) and
PyrC¸CPhOMe(4) are comparable to those of PyrPhOMe(1)
and PyrPhOMe(4). The absorption peaks of PyrPhOMe(4),
PyrPhOH(4), PyrC¸CPhOMe(4), and PyrC¸CPhOH(4) are
observed at longer wavelengths than those of PyrPhOMe(1),
PyrPhOH(1), PyrC¸CPhOMe(1), and PyrC¸CPhOH(1), re-
spectively. This observation is attributed to the fact that the ³-
conjugated system of the tetrasubstituted compounds is larger
than that of the monosubstituted compounds because of the
presence of the ethynyl spacing group.
PyrPhOMe(1)
solv.
OMe
OMe
12
11
10
4
9
5
8
6
2
7
H2~H10
3
H12
H11
PyrPhOH(1)
OH
PyrC¸CPhOMe(1) and PyrC¸CPhOMe(4) exhibit two
couples of absorption peaks at approximately 370 and 390
nm and 460 and 490 nm due to the electronic transition directed
along the z axis, respectively. The two couples of absorption
peaks can be assigned to the C-C stretching modes of vibration
of the ground electronic state of the pyrene moiety. Two similar
couples of absorption peaks are observed in the UV-vis spectra
of pyrene and pyrenes with arylethynyl substituent(s).31 The
disappearance of coupled absorption peaks in PyrPhOMe(1)
and PyrPhOMe(4) is ascribed to the assumption that the
hydroxyphenyl group bonded to the pyrene core affects the
C-C stretching vibration of the pyrene core because of the
presence of steric hindrance between the 4-hydroxyphenyl
group and the pyrene core. The ethynyl spacing group of
PyrC¸CPhOMe(1) and PyrC¸CPhOMe(4) reduces the steric
hindrance between the hydroxyphenyl group and the pyrene
core, which enables the C-C stretching of the pyrene moiety
in the ground electronic state.
H2~H10
H11 H12
12
11
9 10
8
OH
7
2
6
3
5
4
OMe
PyrC CPhOMe(1)
OMe
12
11
9 10
8
6
2
7
3
H12
H11
H2~H9
5
4
H10
Figure 4 shows the UV-vis spectra of PyrPhOH(1),
PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸CPhOH(4) before
and after the treatment with NaH in DMF. The treatment
of the DMF solutions of PyrPhOH(1), PyrPhOH(4), PyrC¸
OH
H12
H11
H2~H9
OH
12
11
H10
9 10
8
CPhOH(1), and PyrC¸CPhOH(4) with NaH causes
a
2
7
bathochromic shift in absorption bands. The formation of
PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1), and PyrC¸
CPhONa(4) was mainly responsible for the shift in absorption
toward a longer wavelength. To prove that these observations
were due to the deprotonation of the OH groups after treat-
ment with NaH, we confirmed that there was no change in the
absorption spectra of the compounds with the OMe groups
upon the addition of NaH. The degree of bathochromic shift
(¦-) in the peak that corresponds to the electric transition
along the z axis was the largest of the three described. This
result suggests that ICT from the ONa group to the pyrene core
was preferred through the benzene and phenylethynyl groups.
The ¦- values for PyrC¸CPhONa(1) and PyrC¸CPhONa(4)
were larger than those for PyrPhONa(1) and PyrPhONa(4).
These results correspond to the assumption that the ICT
from the ONa group to the pyrene core occurred more easily
in PyrC¸CPhONa(1) and PyrC¸CPhONa(4) because of less
steric hindrance between the PhONa group and the pyrene core.
The bathochromic shift attributable to deprotonation is
dependent on the DN of the solvent used. As shown in
Figure 5, the -z values for PyrPhOH(1), PyrPhOH(4), PyrC¸
CPhOH(1), PyrC¸CPhOH(4), and their deprotonated species
shifted to longer wavelengths as the DN of the solvent was
3
6
5
4
PyrC CPhOH(1)
8
7
6
5
4
/ ppm
Figure 1. 1H NMR spectra of PyrPhOMe(1), PyrPhOH(1),
PyrC¸CPhOMe(1), and PyrC¸CPhOH(1) in CDCl3.
UV-vis Spectra. The optical data of the pyrene derivatives
obtained in this study are summarized in Tables 1-4. The UV-
vis spectra of the pyrene derivatives can be divided into three
distinguishable parts. These three regions appear to be separate
states of electronic transition, as shown in Figure 2.
Figure 3 shows the UV-vis spectra of PyrPhOMe(1), PyrC¸
CPhOMe(1), PyrPhOMe(4), and PyrC¸CPhOMe(4) in di-
chloromethane. The absorption peaks in the ranges of 240-260,
275-360, and 340-490 nm in the UV-vis spectra of the com-
pounds are probably results of the electronic transitions direct-
ed along the y, x, z axes, respectively, as shown in Figure 2.
The absorption wavelengths (-z’s) due to the electronic tran-
sitions directed along the z axis of PyrC¸CPhOMe(1) and
PyrC¸CPhOMe(4) are longer than those of PyrPhOMe(1) and
PyrPhOMe(4) because of the presence of the ethynyl spacing

I. Yamaguchi et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013) 1177
Table 1. Optical Data of PyrPhOMe(1), PyrPhOH(1), and PyrPhONa(1)
PyrPhOMe(1)
DNa)
PyrPhOH(1)
Absorption/nmb) Emission/nmc)
PyrPhONa(1)
Absorption/nmb) Emission/nmc)
Absorption/nmb)
Emission/nmc)
CH2Cl2
0
245 (4.62), 280 (4.48), 389, 406 (349)
345 (4.48)
1,4-dioxane 14.8 246 (4.70), 278 (4.48), 388, 405 (349)
245 (4.72), 280 (4.64), 389, 406 (350)
345 (4.50)
212 (4.31), 245 (4.53), 392, 406 (348)
278 (4.56), 345 (4.21)
244 (4.76), 278 (4.66), 392, 404d) (348) 244, 268, 373
345 (4.28)
240, 349
489 (378)
488 (378)
501 (373)
219, 271, 346
344 (4.45)
THF
20 278 (4.65), 344 (4.57) 389, 406 (347)
26.6 280 (4.45), 345 (4.45) 405 (352)
29.8 280 (4.59), 348 (4.45) 392d), 406 (349)
e)
DMF
DMSO
273 (4.48), 278 (4.50), 409 (351)
347 (4.34)
275, 341, 441
®
e)
281, 349 (4.24)
411 (353)
278, 337, 443
®
a) DN: Donor number. b) log ¾ values are shown in the parenthesis. c) Excitation wavelengths are shown in parenthesis. d) Shoulder
peak. e) Not observed.
Table 2. Optical Data of PyrPhOMe(4), PyrPhOH(4), and PyrPhONa(4)
PyrPhOMe(4)
Absorption/nmb) Emission/nmc)
PyrPhOH(4)
Absorption/nmb) Emission/nmc)
PyrPhONa(4)
Absorption/nmb) Emission/nmc)
DNa)
0
d)
d)
d)
d)
CH2Cl2
269, 393
432 (393)
430 (391)
431 (393)
436 (397)
439 (399)
®
®
®
272, 378, 424
270, 443
274, 376, 484
369, 490
®
1,4-dioxane 14.8 263, 301, 391
313, 396
306, 393
272, 399
275, 403
430 (382)
432 (384)
438 (389)
442 (395)
506 (378)
497 (363)
551 (376)
549 (370)
THF
DMF
DMSO
20
258, 304, 393
26.6 273, 397
29.8 273, 399
a) DN: Donor number. b) log ¾ value was not estimated due to low solubility. c) Excitation wavelengths are shown in parenthesis.
d) Not measured due to low solubility.
Table 3. Optical Data of PyrC¸CPhOMe(1), PyrC¸CPhOH(1), and PyrC¸CPhONa(1)
PyrC¸CPhOMe(1)
Absorption/nmb) Emission/nmd) Absorption/nmb)
PyrC¸CPhOH(1)
PyrC¸CPhONa(1)
Emission/nmd)
DNa)
0
Emission/nmd) Absorption/nmb)
CH2Cl2
285 (5.24), 299 (4.91)c), 405, 409c)
351 (4.49), 366 (4.72),
390 (4.70)
285 (4.58), 297 (4.58), 401, 410 (366) 286 (4.19), 297 (4.20), 506 (410)
348 (4.46)c), 366 (4.69),
388 (4.67)
367 (4.30), 388 (4.29)
1,4-dioxane 14.8 285 (5.29), 299 (4.95)c), 400, 419
349 (4.46), 366 (4.68),
285 (4.60), 298 (4.52), 402, 414 (366) 284 (4.47), 322 (4.34), 522 (422)
351 (4.46)c), 366 (4.69),
389 (4.64)
285 (4.55), 299 (4.45), 409 (367)
352 (4.40)c), 367 (4.63),
389 (4.60)
286 (4.77), 298 (4.64), 430 (369)
355 (4.48)c), 369 (4.72),
391 (4.69)
344 (4.22), 393 (4.38),
422 (4.44)
283 (4.58), 389 (4.39), 545 (447)
437 (4.31)
390 (4.64)
THF
20 284 (4.77), 298 (4.66), 402, 409c)
352 (4.43)c), 366 (4.66),
389 (4.63)
DMF
DMSO
26.6 286 (5.08), 299 (4.91), 413, 418c)
353 (4.52)c), 368 (4.76),
390 (4.75)
281 (4.98), 338 (4.67), ®e)
390 (4.22), 479 (4.53)
29.8 286 (4.77), 300 (4.65), 421
352 (4.44)c), 372 (4.68),
394 (4.68)
287 (4.53), 301 (4.43), 439 (370)
355 (4.33)c), 370 (4.60),
394 (4.56)
282 (4.56), 338 (4.43), ®e)
494 (4.41)
a) DN: Donor number. b) log ¾ values are shown in the parenthesis. c) Shoulder peak. d) Excitation wavelengths are shown in
parenthesis. e) Not observed.
increased. In contrast to the small bathochromic shift for
PyrPhOH(1), PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸
CPhOH(4), with an increase in the DN of the solvent, the
-z values of PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1),
and PyrC¸CPhONa(4) were larger than those of PyrPhOH(1),
PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸CPhOH(4). For
example, the -z values of PyrPhONa(1) and PyrPhONa(4) vary
from 349 and 424 nm in 1,4-dioxane (DN = 14.8) to 443 and
490 nm in DMSO (DN = 29.8), through to values of 373 and
443 nm in THF (DN = 20.0), respectively. Similarly, those of
PyrC¸CPhONa(1) and PyrC¸CPhONa(4) vary from 422 and
501 nm 1,4-dioxane (DN = 14.8) to 494 and 610 nm in DMSO
(DN = 29.8). The large ¦- values can be attributed to the fact
that solvents with a high DN effectively solvate with Na+
to stabilize the deprotonated species in the solutions. Similar
solvatochromic behavior was observed in the cases of OP(n)-
OH (n = 4 and 5) and OP(n)-ONa (n = 4 and 5), as reported
earlier.18,19 The fact that the ¦- values for PyrC¸CPhONa(1)
and PyrC¸CPhONa(4) were larger than those for PyrPhONa(1)
and PyrPhONa(4) corresponds to the increased length of ³-

1178 Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013)
Synthesis and Solvatochromic Behavior of Pyrene Derivatives
Table 4. Optical Data of PyrC¸CPhOMe(4), PyrC¸CPhOH(4), and PyrC¸CPhONa(4)
PyrC¸CPhOMe(4)
Absorption/nmb) Emission/nmc)
254, 352, 451, 482 497, 529 (355)
493, 526 (354)
262, 354, 451, 478 495, 527 (356)
PyrC¸CPhOH(4)
Absorption/nmb) Emission/nmc)
PyrC¸CPhONa(4)
Absorption/nmb) Emission/nmc)
DNa)
0
d)
d)
d)
d)
CH2Cl2
®
®
®
283, 398, 501
®
589 (403)
1,4-dioxane 14.8 351, 449, 477
255, 350, 449, 476 493, 526 (356)
257, 355, 452, 480 497, 530 (355)
268, 340, 456, 485 505, 537 (358)
264, 363, 456, 490 511, 541 (365)
THF
DMF
DMSO
20
273, 414, 496, 554 599 (404)
26.6 268, 355, 455, 482 501, 533 (359)
29.8 262, 359, 458, 487 505, 538 (362)
338, 448, 523, 599 595 (447)
e)
296, 451, 535, 610
®
a) DN: Donor number. b) log ¾ value was not estimated due to low solubility. c) Excitation wavelengths are shown in parenthesis.
d) Not measured due to low solubility. e) Not observed.
550
500
450
400
350
Figure 2. Electronic transition directions in pyrene deriva-
tives.
300
0
10
DN of solvent
20
30
650
600
0.7
0.6
0.5
0.4
0.3
550
500
450
400
350
0.2
0.1
0
200
300
400
Wavelength/ nm
500
0
10
DN of solvent
20
30
Figure 3. UV-vis spectra of the dichloromethane solutions
of PyrPhOMe(1) (black curve), PyrC¸CPhOMe(1) (red
curve), PyrPhOMe(4) (blue curve), and PyrC¸CPhOMe(4)
(green curve).
Figure 4. Dependence of -z of PyrPhOH(1) (black line),
PyrPhONa(1) (black dashed line), PyrC¸CPhOH(1) (red
line), PyrC¸CPhONa(1) (red dashed line), PyrPhOH(4)
(blue line), PyrPhONa(4) (blue dashed line), PyrC¸
CPhOH(4) (green line), and PyrC¸CPhONa(4) (green
dashed line) on the DNs of solvents.
conjugation in PyrC¸CPhONa(1) and PyrC¸CPhONa(4) that
arises from the presence of the ethynyl spacing groups.
Photoluminescence Spectra. The compounds obtained in
this study and their deprotonated species are photolumines-
cent in solution. Figure 6 shows the photoluminescence (PL)
spectra of PyrPhOH(1), PyrPhOH(4), PyrC¸CPhOH(1),
PyrC¸CPhOH(4), and their deprotonated species in THF.
The PL data are summarized in Tables 1-4. The observation
that the PL peak positions for PyrPhOH(4) and PyrC¸
CPhOH(4) were longer than those for PyrPhOH(1) and PyrC¸
CPhOH(1) is comparable to the result that the -max wave-
lengths for PyrPhOH(4) and PyrC¸CPhOH(4) were longer
than those for PyrPhOH(1) and PyrC¸CPhOH(1).
wavelengths after deprotonation with NaH. This shift is
comparable to the bathochromic shift observed in the UV-
vis spectra of these compounds. The emission peak positions
for PyrPhOH(1), PyrPhOH(4), PyrC¸CPhOH(1), PyrC¸
CPhOH(4), and their deprotonated species depended on the
DN of the solvent; therefore, the emission color can be tuned
by changing the solvent. For example, PyrPhONa(4) exhibited
blue, green, and yellow emissions after it was irradiated with
UV light in 1,4-dioxane (DN = 14.8), THF (DN = 20.0), and
DMF (DN = 26.6), respectively, as shown in Figure 7.
As shown in Figure 8, by varying solvents such as CH2Cl2
and 1,4-dioxane, which have small DN values, with those such
as DMF and DMSO, which have large DN values, it is observed
The PL peak positions for PyrPhOH(1), PyrPhOH(4),
PyrC¸CPhOH(1), and PyrC¸CPhOH(4) shifted to longer

I. Yamaguchi et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013) 1179
PyrPhONa(4) in
1.0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1,4-dioxane THF
DMF
(DN = 14.8) (DN = 20.0) (DN = 26.6)
0
250
300
350
400
450
500
Wavelength/ nm
1.2
1.0
0.8
0.6
0.4
0.2
0
Figure 7. Photographs of PyrPhONa(4) when it was irra-
diated with UV light in 1,4-dioxane (DN = 14.8), THF
(DN = 20.0), and DMF (DN = 26.6).
600
550
500
450
400
250 300 350 400 450 500 550 600 650
Wavelength/ nm
Figure 5. UV-vis spectra of PyrPhOH(1) (black curve),
PyrPhONa(1) (black dashed curve), PyrC¸CPhOH(1)
(red curve), PyrC¸CPhONa(1) (red dashed curve),
PyrPhOH(4) (blue curve), PyrPhONa(4) (blue dashed
curve), PyrC¸CPhOH(4) (green curve), and PyrC¸
CPhOH(4) (green dashed curve) in DMF.
0
10
20
30
DN of solvent
600
550
500
450
400
0
10
20
30
DN of solvent
Figure 8. Dependence of -em of PyrPhOH(1) (black line),
PyrPhONa(1) (black dashed line), PyrC¸CPhOH(1) (red
line), PyrC¸CPhONa(1) (red dashed line), PyrPhOH(4)
(blue line), PyrPhONa(4) (blue dashed line), PyrC¸
CPhOH(4) (green line), and PyrC¸CPhONa(4) (green
dashed line) on the DNs of solvents. When two emission
peaks were observed, the longer wavelength was adopted
for the data point.
350
400
450
500
550
600
650
700
Wavelength/ nm
Figure 6. PL spectra of PyrPhOH(1) (black solid curve),
PyrPhOH(4) (red solid curve), PyrC¸CPhOH(1) (blue
solid curve), PyrC¸CPhOH(4) (green solid curve), and
their deprotonated species (respective dashed curve) in
THF.
peaks for PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1),
and PyrC¸CPhONa(4) occurred as the DN of the solvent was
increased. These observations are consistent with the observa-
tion that with an increase in the DN of the solvent, -max of
PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1), and PyrC¸
CPhONa(4) in solution shifts to a longer wavelength than that
that the emission peak positions for PyrPhOH(1), PyrPhOH(4),
PyrC¸CPhOH(1), and PyrC¸CPhOH(4) shift by only 4-29
nm. However, a significantly large shift in the emission

1180 Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013)
Synthesis and Solvatochromic Behavior of Pyrene Derivatives
of PyrPhOH(1), PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸
CPhOH(4). The remarkable solvatochromic shift of the PL peak
position of PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1),
and PyrC¸CPhONa(4) may be due to the shift in charge
from the phenolate group to the adjacent rings. In addition to
the effect of charge shift, a large amount of stabilization energy
produced by the solvation of PyrPhONa(1), PyrPhONa(4),
PyrC¸CPhONa(1), and PyrC¸CPhONa(4) may contribute
to the solvatochromic red shift as the DN of the solvent
is increased. There was no change in the PL spectra of
PyrPhOMe(1), PyrPhOMe(4), PyrC¸CPhOMe(1), and PyrC¸
CPhOMe(4) upon the addition of NaH, which suggests that
the solvatochromism in PyrPhONa(1), PyrPhONa(4), PyrC¸
CPhONa(1), and PyrC¸CPhONa(4) can be attributed to the
deprotonation of the OH group after treatment with NaH.
The quantum yields of the PLs of the THF solutions of
PyrPhOH(1), PyrPhOH(4), PyrC¸CPhOH(1), and PyrC¸
CPhOH(4) were 19, 38, 43, and 31%, respectively, while
those of PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1), and
PyrC¸CPhONa(4) were 0.02, 3, 0.1, and 0.01%, respectively.
The fact that the quantum yields of the PLs of PyrPhONa(1),
PyrPhONa(4), PyrC¸CPhONa(1), and PyrC¸CPhONa(4)
are lower than those of PyrPhOH(1), PyrPhOH(4), PyrC¸
CPhOH(1), and PyrC¸CPhOH(4) is attributed to the ICT in
PyrPhONa(1), PyrPhONa(4), PyrC¸CPhONa(1), and PyrC¸
CPhONa(4). It has been reported that the ICT in ³-conjugated
molecules reduces their PL emission efficiencies.7
dissolved in 20 mL of dry toluene under N2. To the solution
were added K2CO3(aq) (2.0 M, 10 mL; N2 bubbled before use),
[Pd(PPh3)4] (0.30 g, 0.26 mmol), and several drops of the
phase-transfer catalyst (Aliquat336). After the mixture was
refluxed for 48 h, the precipitate from the reaction solution
was removed by filtration, and the filtrate was extracted with
chloroform and washed with brine. The solvent was removed
under vacuum to give a light yellow solid, which was purified
by silica gel column chromatography (eluent: CHCl3/hexane;
v/v = 3/2). The solvent was removed by evaporation and the
resulting solid was dried in vacuo to give PyrPhOMe(1) as
a light yellow powder (0.64 g, 42%). 1H NMR (400 MHz,
CDCl3): ¤ 8.22-7.96 (m, 9H), 7.57 (d, J = 8.8 Hz, 2H, H of
m-position of MeOPh ring), 7.11 (d, J = 8.8 Hz, 2H, H of
o-position of MeOPh ring), 3.94 (s, 3H, CH3). 13C NMR
(125 MHz, CDCl3): ¤ 159.0, 137.4, 133.5, 131.6, 131.5, 131.0,
130.3, 128.6, 127.7, 127.4, 127.3, 127.2, 125.9, 125.4, 125.0,
124.9, 124.7, 124.6, 113.8, 55.4 (CH3). IR (KBr, cm¹1): 3040,
2996, 2954, 2899, 2832, 1604, 1519, 1497, 1458, 1438, 1283,
1241, 1175, 1105, 1034, 828, 839. Anal. Calcd for C16H14O2:
C, 80.65; H, 5.92%. Found: C, 80.88; H, 6.10%.
Synthesis of PyrPhOMe(4): PyrPhOMe(4) was synthe-
sized by the reaction of 4-methoxyphenylboronic acid with
1
1,3,6,8-tetrabromopyrene analogously. Yield = 53%. H NMR
(400 MHz, CDCl3): ¤ 8.16 (s, 4H, H at 4,5,9,10-positions of
pyrene ring), 7.96 (s, 2H, H at 2,7-positions of pyrene ring),
7.60 (d, J = 8.4 Hz, 8H, H of m-position of MeOPh ring), 7.08
(d, J = 8.8 Hz, 8H, H of o-position of MeOPh ring), 3.92
(s, 12H, CH3). 13C NMR (125 MHz, CDCl3): ¤ 159.1 (C at
2,7-positions of pyrene ring), 136.8, 131.8 (C of m-position
of MeOPh ring), 129.7, 128.1, 126.2, 125.2 (C at 4,5,9,10-
positions of pyrene ring), 113.9 (C of o-position of MeOPh
ring), 55.5 (CH3). IR (KBr, cm¹1): 3033, 3000, 2952, 2930,
2833, 1607, 1514, 1495, 1461, 1287, 1247, 1175, 1034, 755.
Anal. Calcd for C44H34O4: C, 84.32; H, 5.47%. Found: C,
83.96; H, 5.23%.
PyrC¸CPhOMe(1): 4-Ethynylanisole (0.84 g, 6.4 mmol)
and 1-bromopyrene (1.41 g, 5.0 mmol) were dissolved in a
mixture of dry toluene (5 mL) and triethylamine (5 mL) under
N2. To the solution were added [PdCl2(PPh3)2] (0.044 g, 0.063
mmol) and CuI (0.017 g, 0.090 mmol). After the reaction
solution was stirred at 70 °C for 86 h, the solvent was removed
under vacuum to give a light yellow solid, which was purified
by silica gel column chromatography (eluent: CHCl3/hexane;
v/v = 1/2). The solvent was removed by evaporation and a
resulting solid was dried in vacuo to give PyrC¸CPhOMe(1)
as a yellow powder (0.59 g, 35%). 1H NMR (400 MHz, CDCl3):
¤ 8.67 (d, J = 9.2 Hz, 1H, H at 10-position of pyrene ring),
8.24-8.01 (m, 8H), 7.66 (d, J = 8.8 Hz, 2H, H of m-position
of MeOPh ring), 6.97 (d, J = 8.8 Hz, 2H, H of o-position of
MeOPh ring), 3.88 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3):
¤ 159.8, 133.2, 131.7, 131.3, 131.1, 131.0, 129.4, 128.2, 128.0,
127.3, 126.2, 125.6, 125.51, 125.46, 124.5, 124.4, 118.2,
115.7, 114.2, 95.2 (PyrC¸CPh), 87.4 (PyrC¸CPh), 55.4 (CH3).
IR (KBr, cm¹1): 3039, 2958, 2927, 2838, 2202, 1597, 1512,
1450, 1288, 1246, 1176, 1036, 755. Anal. Calcd for C25H16O:
C, 90.33; H, 4.85%. Found: C, 90.67; H, 5.06%.
Conclusion
Pyrene derivatives with 4-hydroxyphenyl and 4-hydroxy-
phenylethynyl groups were obtained by using reactions with
transition-metal complexes. The treatment of these compounds
with a base produced corresponding deprotonated species,
whose absorption and PL peak positions in solution shifted
toward longer wavelengths with an increase in the DN of the
solvent. The optical properties of the pyrene derivatives were
significantly affected by bond twisting between the 4-hydroxy-
phenyl group and the central pyrene core. The introduction of an
ethynyl spacing group between the 4-hydroxyphenyl group and
the pyrene core enhanced its solvatochromic behavior. The
results obtained in this study will be useful in providing infor-
mation for the development of new solvatochromic materials.
Experimental
General. Solvents were dried, distilled, and stored under
nitrogen. 1-Ethynylpyrene and 1,3,6,8-tetraethynylpyrene were
synthesized according to the literature.31,32 Other reagents were
purchased and used without further purification. Reactions were
carried out with standard Schlenk techniques under nitrogen.
IR and NMR spectra were recorded on a JASCO FT/IR-660
PLUS spectrophotometer and JEOL AL-400 and ECX-500
spectrometers, respectively. Elemental analysis was performed
on a Yanagimoto MT-5 CHN corder. UV-vis and PL spec-
tra were obtained with a JASCO V-560 spectrometer and a
JASCO FP-6200 spectrofluorometer, respectively. Quantum
yields were calculated by using a diluted ethanol solution of
7-dimethylamino-4-methylcoumarin as the standard.
Synthesis. PyrPhOMe(1): 4-Methoxyphenylboronic acid
(0.79 g, 5.2 mmol) and 1-bromopyrene (1.40 g, 5.0 mmol) were
PyrC¸CPhOMe(4): PyrC¸CPhOMe(4) was synthesized
using a procedure similar to that used for PyrC¸CPhOMe(1).

I. Yamaguchi et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 10 (2013) 1181
1
Yield = 3%. H NMR (400 MHz, CDCl3): ¤ 8.75 (s, 4H, H
PyrC¸CPhOH(4):
1,3,6,8-Tetraethynylpyrene (0.16 g,
0.54 mmol), 4-iodophenol (0.87 g, 4.0 mmol), [PdCl2(PPh)2]
(0.051 g, 0.072 mmol), and CuI (0.027 g, 0.14 mmol) were
added to triethylamine (8 mL) at ¹4 °C. After the suspension
was stirred at 20 °C for 47 h, the solvent was removed under
vacuum. The resulting solid was washed with chloroform and
water, collected by filtration, and dried under vacuum to give
PyrC¸CPhOH(4) as a yellowish green powder (0.074 g, 21%).
1H NMR (400 MHz, DMSO-d6): ¤ 10.09 (s, 4H, OH), 8.78
(s, 4H, H at 4,5,9,10-positions of pyrene ring), 8.41 (s, 2H,
H at 2,7-positions of pyrene ring), 7.66 (d, J = 8.4 Hz, 8H,
H of m-position of HOPh ring), 6.91 (d, J = 8.8 Hz, 8H,
H of o-position of HOPh ring). 13C NMR measurement was not
obtained due to the low solubility of this compound. IR (KBr,
cm¹1): 3389, 3196, 1594, 1512, 1264, 1166, 831. Anal. Calcd
for C48H26O4¢0.5H2O: C, 85.32; H, 4.03%. Found: C, 85.65;
H, 4.42%.
at 4,5,9,10-positions of pyrene ring), 8.41 (s, 2H, H at 2,7-
positions of pyrene ring), 7.67 (d, J = 8.8 Hz, 8H, H of
m-position of MeOPh ring), 6.98 (d, J = 8.8 Hz, 8H, H of
o-position of MeOPh ring), 3.89 (s, 12H, CH3). 13C NMR
measurement was not acquired due to the low solubility of
this compound. IR (KBr, cm¹1): 2999, 2934, 2834, 2199,
1595, 1511, 1287, 1248, 1173, 1031, 833. Anal. Calcd for
C52H34O4¢0.3H2O: C, 85.76; H, 4.79%. Found: C, 85.74; H,
5.00%.
PyrPhOH(1): After a dichloromethane solution (5 mL) of
BBr3 (1.0 mL, 10 mmol) was added dropwise to a dichloro-
methane solution (20 mL) of PyrPhOMe(1) (0.256 g, 0.83
mmol) at ¹78 °C, the reaction solution was stirred at 20 °C for
3 h and quenched with KOH(aq) (5 M, 5 mL). The resulting
precipitate was removed by filtration, extracted with chloro-
form, and dried under vacuum to give PyrPhOH(1) as a light
brown solid (0.24 g, 98%). 1H NMR (400 MHz, CDCl3): ¤
8.22-7.95 (m, 9H), 7.52 (d, J = 8.8 Hz, 2H, H of m-position of
HOPh ring), 7.04 (d, J = 8.8 Hz, 2H, H of o-position of HOPh
ring), 4.83 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): ¤ 154.9,
137.4, 133.8, 131.8, 131.5, 131.0, 128.6, 127.7, 127.43,
127.36, 127.29, 126.0, 125.3, 125.03, 125.01, 124.9, 124.8,
124.6, 115.3 (C of o-position of HOPh ring). IR (KBr, cm¹1):
3244, 3043, 1609, 1523, 1498, 1448, 1434, 848, 837, 758, 721.
Anal. Calcd for C22H14O¢0.2H2O: C, 88.68; H, 4.87%. Found:
C, 88.57; H, 4.90%.
This work was performed under the Cooperative Research
Program of “Network Joint Research Center for Materials and
Devices” (No. 2012192).
Supporting Information
1
Solubilities, IR, H, and 13C NMR spectra of the obtained
compounds. This material is available free of charge on the
web at http://www.csj.jp/journals/bcsj/.
PyrPhOH(4):
PyrPhOH(4) was synthesized using a
References
procedure similar to that used for PyrPhOH(1). Yield = 60%.
1H NMR (400 MHz, DMSO-d6): ¤ 9.65 (s, 4H, OH), 8.12
(s, 4H, H at 4,5,9,10-positions of pyrene ring), 7.85 (s, 2H, H
at 2,7-positions of pyrene ring), 7.49 (d, J = 8.4 Hz, 8H, H
of m-position of HOPh ring), 6.98 (d, J = 8.4 Hz, 8H, H of
o-position of HOPh ring). 13C NMR (125 MHz, DMSO-d6): ¤
156.9, 136.8, 131.7, 130.9, 129.5, 127.1, 125.8, 124.8, 115.5
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0.7H2O: C, 82.37; H, 4.74%. Found: C, 82.59; H, 4.93%.
PyrC¸CPhOH(1): 1-Ethynylpyrene (0.44 g, 1.9 mmol), 4-
iodophenol (0.53 g, 2.4 mmol), [PdCl2(PPh3)2] (0.042 g, 0.060
mmol), and CuI (0.024 g, 0.13 mmol) were added to triethyl-
amine (5 mL) at ¹4 °C. After the suspension was stirred at
20 °C for 24 h, the solvent was removed under vacuum. The
resulting solid was purified by silica gel column chromatog-
raphy (eluent: CHCl3/acetone; v/v = 10/1). The solvent was
removed by evaporation and the resulting solid was extracted
with hexane. After the solvent was removed under vacuum,
the resulting solid was dried under vacuum to give PyrC¸
1
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CPhOH(1) as a yellow powder (0.065 g, 11%). H NMR (400
MHz, CDCl3): ¤ 8.66 (d, J = 9.2 Hz, 1H, H at 10-position
of pyrene ring), 8.24-8.01 (m, 8H), 7.63 (d, J = 8.8 Hz, 2H, H
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