Effects of substituents on absorption and fluorescence properties of trimethylsilylethynyl- and tert-butylethynyl-pyrenes

Article abstract of DOI:10.1016/j.jphotochem.2020.112428

Effects of substituents introduced at 1-position of trimethylsilylethynyl- and tert-butylethynyl-pyrenes on absorption and fluorescence properties were investigated. Fluorescence intensities of 1.0 × 10^–5 M CH₂Cl₂ solutions of these pyrene derivatives were significantly larger than that of pyrene. Absorption of a silyl derivative having a formyl group shifted to longer wavelengths as the solvent polarity increased, whereas that of the carbon analog shifted to shorter wavelengths. On the other hand, in the solvent dependence of fluorescence, both fluorescence of them shifted to longer wavelengths as the polarity of the solvent increased. Fluorescence spectra of pyrene derivatives synthesized in this study at saturated concentrations in CH₂Cl₂ exhibited excimer emissions in the longer wavelength regions compared to that of unsubstituted pyrene. Fluorescence quantum yields of silicon analogs were higher than that of the corresponding carbon analogs in both solution and solid states. From the results of molecular orbital calculations, it was clarified that the effects of the substituents at the 1-position on the pyrene ring on the absorption and fluorescence properties can be explained by the properties of the molecular orbitals corresponding to the respective electron transitions.

Full text of DOI:10.1016/j.jphotochem.2020.112428

JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
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Journal of Photochemistry & Photobiology A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Effects of substituents on absorption and fluorescence properties of
trimethylsilylethynyl- and tert-butylethynyl-pyrenes
Hajime Maedaa,*, Ryota Uenoa, Taniyuki Furuyamaa,b, Masahito Segia
a Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan
b Japan Science and Technology Agency (JST)-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords:
Effects of substituents introduced at 1-position of trimethylsilylethynyl- and tert-butylethynyl-pyrenes on ab-
sorption and fluorescence properties were investigated. Fluorescence intensities of 1.0 × 10–5 M CH2Cl2 solu-
tions of these pyrene derivatives were significantly larger than that of pyrene. Absorption of a silyl derivative
having a formyl group shifted to longer wavelengths as the solvent polarity increased, whereas that of the carbon
analog shifted to shorter wavelengths. On the other hand, in the solvent dependence of fluorescence, both
fluorescence of them shifted to longer wavelengths as the polarity of the solvent increased. Fluorescence spectra
of pyrene derivatives synthesized in this study at saturated concentrations in CH2Cl2 exhibited excimer emissions
in the longer wavelength regions compared to that of unsubstituted pyrene. Fluorescence quantum yields of
silicon analogs were higher than that of the corresponding carbon analogs in both solution and solid states. From
the results of molecular orbital calculations, it was clarified that the effects of the substituents at the 1-position
on the pyrene ring on the absorption and fluorescence properties can be explained by the properties of the
molecular orbitals corresponding to the respective electron transitions.
Pyrene
Silylethynyl group
Absorption
Fluorescence
Excimer
1. Introduction
with carbon analogs, we synthesized trimethylsilylethynylpyrenes and
the corresponding tert-butylethynylpyrenes with various substituents
Pyrene and its derivatives are often used as fluorescent substances
because it has fluorescent duality (monomer and excimer), high fluor-
escence quantum yield, and photostability [1–8]. To date, various
synthetic methods of pyrene derivatives have been developed and their
photophysical properties have been investigated [9–12]. In particular,
ethynyl-substituted pyrenes are used as fluorescent probes for detecting
biomolecules because of their high fluorescence quantum yields
[13–17].
introduced on the pyrene ring, and examined the effects of these sub-
stituents on the absorption and fluorescence properties. Investigation
was carried out by using absorption and fluorescence spectroscopic data
and molecular orbital calculations.
2. Results and discussion
The synthesis of compounds 1-10 to be investigated is shown in
Scheme 1. Cyano, formyl, and methoxy groups were introduced into the
1-position of pyrene, respectively, and the 3, 6 and 8 positions were
tribrominated. Then, silyl derivatives 2-5 were synthesized by Sono-
gashira reaction with trimethylsilylacetylene, and carbon analogs 7-9
were prepared by the reaction with 3,3-dimethyl-1-butyne. Tetrakis
(trimethylsilylethynyl)pyrene 6 and tetrakis(tert-butylethynyl)pyrene
10 were synthesized by Sonogashira reaction of tetrabromopyrene with
trimethylsilylacetylene or 3,3-dimethyl-1-butyne.
The photophysical properties of compounds in which silyl groups
are introduced into aromatic hydrocarbons such as naphthalene
[18–29], anthracene [23–26,30–42], tetracene [40], pentacene
[41,43–45], phenanthrene [23,46,47], triphenylene [48], pyrene
[23,49–55], and perylene [56] have been well studied, and it has often
been discussed that the fluorescence intensity increases by the in-
troduction of silyl groups. In our previous studies, we have reported
that the fluorescence quantum yields are increased by introducing tri-
methylsilyl [57–59] and trimethylsilylethynyl [58,60–62] groups into
pyrene, and the effect of substituents on silicon on the absorption and
fluorescence properties [63,64]. In this study, with the aim of in-
vestigating the effect of substituents on the pyrene ring and comparison
The absorption spectra of compounds 1-10 were measured at a
concentration of 1.0 × 10–5 M using CH2Cl2 as a solvent (Fig. 1,
Table 1). The absorption bands based on the π-π* transition of the
compounds 2-10 appeared at the longer wavelengths compared to
⁎ Corresponding author.
E-mail address: maeda-h@se.kanazawa-u.ac.jp (H. Maeda).
https://doi.org/10.1016/j.jphotochem.2020.112428
Received 10 December 2019; Received in revised form 11 January 2020; Accepted 29 January 2020
Availableonline30January2020
1010-6030/©2020ElsevierB.V.Allrightsreserved.

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
unsubstituted pyrene (1) and reached the visible light region. The ab-
sorption maxima shifted to longer wavelengths in the order of
2 < 3 < 6 < 5 < 4 for the silicon analogs and 9 < 10 < 7 < 8 for the
carbon analogs. The compounds with the longest wavelength shift were
4 and 8 having a formyl group. The bathochromic shift of the pyrene
absorption bands due to the introduction of a formyl group has also
been observed for other pyrene derivatives due to modulation of the
molecular band gap [66]. The molar absorption coefficients of 1-10
showed values on the order of 104 to 105.
The fluorescence spectra of 1.0 × 10–5 M CH2Cl2 solutions of com-
pounds 1-10 are displayed in Fig. 2. The fluorescence wavelengths of
compounds 2-10 appeared on the longer wavelength region compared
to 1, and reached the visible light region. The Stokes shifts of com-
pounds 2, 6 and 10 with the same substituents introduced at the 1,3,6-
or 1,3,6,8-positions were 5−6 nm, whereas those of compounds 3-5
and 7-9 having a polar substituent at the 1-position showed large values
of 12−25 nm.
The fluorescence intensities of 2-10 were significantly higher than
that of pyrene (1), and the fluorescence intensity was greatly different
depending on the type of substituent on the pyrene ring. In particular, it
was found that 4 and 8 substituted with a formyl group had lower
fluorescence intensity than other compounds and had the maximum
fluorescence wavelength on the longest wavelength region.
The fluorescence quantum yields determined by using cyclohexane
solutions that were freeze-degassed to eliminate the influence of di-
oxygen are shown in Table 1. The fluorescence quantum yields were
affected by the substituents at the 1-position of the pyrene ring, and
increased in the order of 4 < 2 < 5 < 3 ∼ 6 for silicon analogs and
8 < 9 < 7 < 10 for carbon analogs. The fluorescence quantum yields of
the formyl derivatives were found to be the smallest in each family.
Comparing the fluorescence quantum yields of silicon compounds and
their carbon analogs, it was found that compounds with silicon func-
tional groups showed higher values in all cases.
Pyrene is known to exhibit excimer emission in concentrated solu-
tions (> 10–2 M) [67–70]. Fig. 3 shows the fluorescence spectra of
CH2Cl2 solutions of compounds 1-10 at saturated concentrations. Re-
markable excimer fluorescence with an emission maximum at
546−592 nm was observed from compounds 2-10, which is longer
wavelengths than that of excimer fluorescence of unsubstituted pyrene
1 (472 nm). The maximum wavelengths of the excimer emission shifted
in the order of 1 < 2 < 9 < 10 < 3 < 7 < 6 < 5 < 4 < 8. In parti-
cular, excimer emission of 4 and 8 having a formyl group appeared on
the longest wavelength regions in both silicon and carbon analogs.
Based on the results thus far, we considered that compounds with
formyl groups have different properties from those with other sub-
stituents, and investigated solvatochromism to elucidate the lumines-
cence mechanism. Absorption and fluorescence spectra of 4 were
measured in various solvents at a concentration of 1.0 × 10–5 M (Fig. 4,
Table 2). As a result, long wavelength shifts were observed at both the
absorption and fluorescence wavelengths as the polarity of the solvent
increased. In contrast, when the absorption and fluorescence spectra of
carbon analog 8 were measured under the same conditions (Fig. 5,
Table 2), unlike the case of 4, the fluorescence shifts longer wave-
lengths but the absorption shifts shorter wavelengths as the polarity of
the solvent increases. Inspection of the solvent dependence of fluores-
cence of 6 without a formyl group showed that almost no difference was
observed in the spectral shapes and wavelengths (Fig. S1, Table 2). As a
result of Lippert-Mataga plot [72–75] by using the solvent dependence
data of 4 and 8, the slopes of 4 and 8 were found to be 1.47 × 103 and
3.31 × 103, respectively (Table S1, Fig. S2). These results indicate that
the difference between the dipole moments in the ground and excited
states (Δμ) is larger in 8 than in 4.
Scheme 1. Synthesis of pyrene derivatives 2-10.
Next, fluorescence of these compounds in the solid state was ex-
plored. Fig. 6 shows fluorescence photographs of solids of 3-10 irra-
diated with UV (365 nm) and the absolute fluorescence quantum yields
(Φf) in the solid state. The solids exhibited green to red fluorescence,
Fig. 1. UV–vis absorption spectra of (a) 1-6 and (b) 1, 7-10, 1.0 × 10–5 M in
aerated CH2Cl2.
2

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
Table 1
Photophysical properties of 1-10.
Compound
Absorptiona
Fluorescence
λabs
logε
λem (monomer)a
Φf (solution)b
λem (excimer)c
(nm)
(nm)
pyrene (1)
337
416
434
453
437
437
432
452
423
428
4.69
4.97
4.91
4.67
5.00
5.13
4.72
4.53
4.57
4.79
370
422
447
472
442
442
442
477
437
433
0.32d
0.80e
0.99
0.63
0.92
0.99e
0.88
0.53
0.74
0.90
472
546
556
583
564
563
558
592
552
553
2 (M = Si, R = H)
3 (M = Si, R = CN)
4 (M = Si, R = CHO)
5 (M = Si, R = OMe)
6 (M = Si, R = C ≡ CSiMe3)
7 (M = C, R = CN)
8 (M = C, R = CHO)
9 (M = C, R = OMe)
10 (M = C, R = C ≡ CCMe3)
a
b
c
d
e
[1-10] = 1.0 × 10–5 M in CH2Cl2.
Degassed by freeze-pump-thaw method, [1-10] = 1.0 × 10–6 M in cyclohexane.
[1-10] = saturated concentration in CH2Cl2.
Data from reference [65] in cyclohexane.
Data from reference [60] in EtOH.
Fig. 2. Fluorescence spectra of (a) 1-6 and (b) 1, 7-10, 1.0×10–5 M in aerated
CH2Cl2, λex = λabs in Table 1.
Fig. 4. Solvent dependence of (a) UV–vis absorption and (b) fluorescence
spectra of 4, 1.0 × 10–5 M, λex = λabs in Table 2.
and like in the solution state, and it was found that if the substituent at
the 1-position on pyrene is the same, the silicon analogs have higher
fluorescence quantum yields than those of the carbon analogs.
The energy levels of HOMO and LUMO and their energy gaps, the
charge densities of M (M = Si or C), those of methyl groups on M, and
their sum obtained by molecular orbital calculation are shown in
Table 3. The introduction of electron-withdrawing cyano and formyl
groups on the pyrene ring decreased the energy levels of HOMO and
LUMO, and the introduction of electron-releasing methoxy groups in-
creased the energy levels of HOMO and LUMO. The energy gaps be-
tween HOMO and LUMO of pyrene derivatives 2-10 decreased com-
pared with pyrene (1), and are in good agreement with experimental
absorption spectroscopic results. This is a consequence of expansion of
the π-conjugated system by introduction of substituents. As an inter-
pretation of the fact that the absorption bands of the formyl derivatives
appeared on the longest wavelength regions, calculations showed that
Fig. 3. Fluorescence spectra of 1-10, saturated concentration in aerated CH2Cl2,
λex = λabs in Table 1.
3

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
Table 2
Solvent dependence of specroscopic properties of 4, 8, and 6.
Solvent
ET(30)a 4 (M = Si,
8 (M = C,
6 (M = Si,
R = CHO)
R = CHO)
R = C ≡ CSiMe3)
b
b
b
b
b
λabs
λem
λabs
λem
λabsb (nm) λem (nm)
(nm)
(nm)
(nm)
(nm)
cyclohexane 30.9
451
454
452
447
455
452
455d
455d
455
463
464
462
475
472
467d
476d
452
457
434
439
c
c
c
c
CCl4
32.4
33.9
37.4
39.1
40.7
45.6
51.9
–
–
–
–
toluene
THF
453
454
453
449
447d
446d
467
466
481
477
473d
485d
438
436
438
437
434d
433
444
441
444
442
439d
438
CHCl3
CH2Cl2
CH3CN
EtOH
a
b
c
Data from reference [71].
1.0 × 10–5 M.
Not measured.
d
Saturated concentration.
Fig. 6. Fluorescence and absolute fluorescence quantum yields (Φf) in the solid
state of 3-10. The photos were taken under UV irradiation (λex =365 nm).
found that the absorption bands near 315 nm of 4 and 8 having a formyl
group also contain the n-π* transition.
The selected MO diagrams for 6 and 4 is shown in Fig. 8. The red
and green lobes represent the charge distribution in each molecular
orbital. Since the charge distribution of the orbitals involved in the
transitions of both molecules extends to the silicon part, the influence of
silicon on these interorbital transitions was confirmed [76–83].
Since the molecular symmetry of 6 is high, the charge distribution of
all four substituents is symmetric, and all orbitals on silicon, ethynyl
moiety, and pyrene ring are on a plane. Calculations of 6 also revealed
that only π-π* transitions were observed. On the other hand, in com-
pound 4, the formyl group acts as an electron withdrawing group, and
the negative charge is biased to the formyl group. Also, in HOMO-6 of
4, the two nonbonding orbitals of the carbonyl oxygen lone pair are
coplanar with the π orbital on the pyrene ring. Therefore, 4 includes not
only π-π* transitions but also n-π* transitions.
Fig. 5. Solvent dependence of (a) UV–vis absorption and (b) fluorescence
spectra of 8, 1.0 × 10–5 M, λex = λabs in Table 2.
In the π-π* transition state often seen in aromatic compounds, the
excited state is largely stabilized compared with the ground state as the
solvent polarity increases, causing a long wavelength shift in absorp-
tion. On the other hand, in the n-π* transition state derived from a lone
pair such as a carbonyl group, the ground state is greatly stabilized
compared with the excited state as the solvent polarity increases, and a
short wavelength shift of absorption occurs. Since the carbonyl group of
1-formylpyrene (PyCHO) can be conjugated with the pyrene π system,
it is easy to cause intersystem crossing by the El-Sayed rule [84,85], and
the fluorescence intensity decreases. The fluorescence quantum yield of
PyCHO is less than 0.01 in aprotic solvents, but in protic solvents, the
energy of n-π* transition is increased by hydrogen bonding, and the
fluorescence quantum yield increases [86–88]. It is known that the
introduction of a donor substituent into PyCHO enhances the properties
of intramolecular charge transfer (ICT) in the excited state, increases
the fluorescence quantum yield, and exhibits solvatofluorochromism
[66,89,90]. Also in this study, compound 4 showed a relatively high
fluorescence quantum yield of 0.63 in CH2Cl2 and 0.48 in the solid
state.
the level of LUMO is falling because formyl is an electron withdrawing
group, but the level of HOMO is not so lowered. Regarding the charge
density, it was found that the substituents on the pyrene ring have little
effect on the charge density of the silicon and carbon functional groups.
Moreover, it turned out that the density of the positive charge of a
SiMe3 group is high compared with a tert-butyl group. Since silicon has
a lower electronegativity than carbon, SiMe3 group has a high electron-
donating property and functions as an electron-donating group for the
ethynyl moiety.
Fig. 7 shows UV–vis absorption spectra of compounds 6 and 4, the
theoretical absorption spectra obtained by TD-SCF calculation, and the
transitions in each theoretical absorption. All data for compounds 2-9
are shown in Fig. S3-S11. Compound 6 in which all 1,3,6,8-positions of
pyrene are substituted with trimethylsilylethynyl groups has two the-
oretical absorption peaks with an intensity of about 0.9 and three
transitions. On the other hand, compound 4 contains four theoretical
absorption peaks with different intensities and mixed six transitions. All
the absorption bands are based on the π-π* transitions, however, it was
In solvatochromism in the absorption of 4, the wavelength shifted to
the longer wavelength region as the polarity of the solvent increased. In
4

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
Table 3
Calculated data of 1-10.a
Compound
HOMO (eV)
LUMO (eV)
Energy gap (eV)
Charge densityb
M
Me3
MMe3
pyrene (1)
–5.326
–5.219
–5.543
–5.480
–4.942
–5.190
–5.296
–5.223
–4.717
–4.862
–1.480
–2.207
–2.660
–2.652
–2.424
–2.357
–2.357
–2.382
–1.742
–1.956
3.846
3.013
2.883
2.828
2.514
2.834
2.921
2.848
2.974
2.906
–
–
–
2 (M = Si, R = H)
0.654
0.655
0.655
0.654
0.655
–0.033
–0.032
–0.031
–0.031
–0.478
–0.468
–0.474
–0.479
–0.477
0.065
0.063
0.057
0.067
0.176
0.187
0.181
0.175
0.178
0.033
0.031
0.026
0.036
3 (M = Si, R = CN)
4 (M = Si, R = CHO)
5 (M = Si, R = OMe)
6 (M = Si, R = C ≡ CSiMe3)
7 (M = C, R = CN)
8 (M = C, R = CHO)
9 (M = C, R = OMe)
10 (M = C, R = C ≡ CCMe3)
a
b
Calculated by B3LYP/6-31G.
Mülliken charge.
Fig. 8. Selected molecular orbital (MO) diagrams of (a) 6 and (b) 4.
ethynyl moiety. Because of these factors, the contribution of the π-π*
transition is larger in 4 than in 8, and 4 may have shown solvato-
chromism opposite to 8. The high electron-donating ability of the si-
licon atom increases the ground-state dipole moment of the silyl deri-
vative 4 compared to the carbon analog 8, so the Δμ of 4 may have
appeared to be smaller than that of 8. The fact that the silyl derivatives
showed larger fluorescence intensities than the carbon analogs may
indicate that these effects affected on the energy levels of S1 and Tn and
the ratios of the rate constants of fluorescence emission to the rate
constants of other relaxation processes such as intersystem crossing and
non-radiative deactivation [27,59,63,64].
Fig. 7. UV–vis absorption spectra (1.0 × 10–5 M aerated CH2Cl2) and oscillator
strengths (calculated by TD-SCF/B3LYP/6-31 G) of (a) 6 and (b) 4.
contrast, a short wavelength shift was observed in solvatochromism in
the absorption of 8. This is because the ground and excited state
structures of 4 and 8 depend on the polarity of the solvent, with the
silicon analog 4 contributing the π-π* transition and the carbon analog
8 contributing the n-π* transition. The silicon functional group has
stronger σ(*)-π(*) interaction with the ethynyl moiety than the carbon
functional group, and the π-conjugated system is expanded. Also, since
silicon is an electropositive element having a lower electronegativity
than carbon, the Me3Si group acts as an electron donating group for the
3. Conclusion
In this study, we investigated the effect of substituents on the ab-
sorption and fluorescence properties of silylethynyl- and tert-buty-
lethynyl-pyrenes. In the UV–vis absorption spectra of compounds 2-10
in CH2Cl2 at a concentration of 1.0 × 10–5 M, the absorption bands
based on the π-π* transition appeared on the longer wavelength regions
5

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
compared to pyrene (1), and showed molar absorption coefficients on
the order of 104 to 105. The experimental maximum absorption wave-
lengths correspond well to the theoretical absorption spectra obtained
from TD-SCF calculations. As the polarity of the solvent increased, the
absorption of 4 having a formyl group shifted to longer wavelengths,
whereas the absorption of its carbon analog 8 shifted to shorter wa-
velengths. From molecular orbital calculations, it was found that the
transitions of the formyl derivatives had a larger contribution of π-π*
transition in 4 while 8 had a larger contribution of n-π* transition.
In the fluorescence spectra of 2-10 at a concentration of 1.0 × 10–5
M in CH2Cl2, the intensities of the monomer fluorescence were sig-
nificantly increased compared to pyrene (1). In particular, the fluor-
escence of the formyl derivatives 4 and 8 appeared on the longer wa-
velength region as the polarity of the solvent increased. In the
fluorescence spectra of 2-10 at saturated concentrations in CH2Cl2,
typical excimer emissions were observed. The silicon analogs were
found to have higher fluorescence quantum yields in both the solution
state and the solid state than the carbon analogs.
A mixture of 1,3,6-tribromopyrene (0.87 g, 2.0 mmol), trimethylsi-
lylacetylene (0.844 g, 8.6 mmol), PdCl2(PPh3)2 (0.071 g, 0.10 mmol),
CuI (0.033 g, 0.17 mmol), and PPh3 (0.068 g, 0.26 mmol) in THF
(30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under an
argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1,3,6-tris(trimethylsilylethynyl)pyrene (2, 0.16 g, 16 %
yield, pale yellow solid). Lit [60].
4.3. Preparation of 3
To a stirred CCl4 (250 mL) solution of pyrene (1, 10.55 g, 50 mmol)
was added dropwise CCl4 (30 mL) solution of Br2 (2.0 mL, 40 mmol),
and the resulting solution was stirred at 80 °C for 12 h. After cooling to
room temperature, conc. NaOH aq (20 mL) was added to quench excess
Br2. Sat. NaCl aq (100 mL) was added and then the solution was ex-
tracted with CHCl3 (200 mL). The organic layer was dried over Na2SO4,
filtered, and concentrated in vacuo to give 1-bromopyrene (9.7 g, 70 %
yield, gray solid). Lit [92].
The results of theoretical calculations showed that the Me3Si group
has a higher electron donating property for the tetraethynylpyrene
moiety than the tert-butyl group. In addition, the silyl group has a
greater σ(*)-π(*) interaction with the ethynyl moiety than the carbon
functional group, and has a greater effect of expanding the π-con-
jugated system. It is considered that the electron donating property of
the silyl group and the effect of conjugate expansion contributed to the
increase in fluorescence intensities. Thus, it has been clarified that the
effect of the substituents at the 1-position on the pyrene ring on the
absorption and fluorescence properties can be attributed to molecular
orbitals and electronic transitions.
A mixture of 1-bromopyrene (1.4 g, 5.0 mmol) and CuCN (2.2 g,
24.6 mmol) in N-methyl-2-pyrrolidone (15 mL) was stirred at 190 °C for
4 h [93]. After cooling to room temperature, NH3 aq (23 mL) was
added. The formed solid was removed by filtration with CHCl3. The
filtrate was extracted with CHCl3 (200 mL) and sat. NaCl aq (100 mL).
The organic layer was separated, dried over Na2SO4, filtered, and
concentrated in vacuo, giving a residue that was subjected to silica gel
column chromatography (eluent: CHCl3:hexane = 2:1) to give 1-cya-
nopyrene (0.96 g, 84 % yield, yellow solid). Lit [94].
To a stirred nitrobenzene (120 mL) solution of 1-cyanopyrene
(0.45 g, 2.0 mmol) was added dropwise nitrobenzene (40 mL) solution
of Br2 (0.4 mL, 7.2 mmol), and the resulting solution was stirred at 80 °C
for 12 h. After cooling to room temperature, conc. NaOH aq (10 mL)
was added to quench excess Br2. The formed solid was washed with
CHCl3 (100 mL) and collected by filtration to give 1,3,6-tribromo-8-
cyanopyrene (0.86 g, 93 % yield, yellow solid).
4. Experimental section
4.1. Materials and equipments
THF was distilled from CaH2 and then from Na/Ph2C = O. CCl4 and
CH2Cl2 were distilled from CaH2. Spectral grade of CHCl3 and CH2Cl2
were purchased and used for spectroscopic studies without further
purification. Most other chemical substances were used after purifica-
tion by distillation or recrystallization. 1H and 13C NMR spectra were
recorded using a JEOL JMN LA-400 (400 MHz and 100 MHz, respec-
tively) or a JEOL ECA-500 (500 MHz and 125 MHz, respectively)
spectrometer with Me4Si as an internal standard. IR spectra were de-
termined using a Shimadzu FTIR-8300 spectrometer. Low- and high-
resolution mass spectra were taken on a JEOL JMS-700 and a JEOL
JMS-SM102A instrument, respectively. UV–vis spectra were recorded
using a Hitachi U-2900 spectrophotometer. Fluorescence spectra were
recorded using a JASCO FP-8500 spectrophotometer. HPLC separations
were performed on a recycling preparative HPLC instrument (Japan
Analytical Industry Co. Ltd., LC-908 equipped with a JAIGEL-H (GPC)
column). Column chromatography was conducted by using Kanto
Chemical Co. Ltd., silica gel 60 N (spherical, neutral, 0.04-0.05 mm).
Thin-layer chromatography was performed with Merck Kiesel gel 60
F254 plates, and spots were detected by using UV light and a phos-
phomolybdic acid ethanol solution with heating. Theoretical calcula-
tions were performed by using a Gaussian 09 software package.
A mixture of 1,3,6-tribromo-8-cyanopyrene (0.92 g, 2.0 mmol), tri-
methylsilylacetylene (0.844 g, 8.6 mmol), PdCl2(PPh3)2 (0.071 g,
0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3 (0.068 g, 0.26 mmol)
in THF (30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under
an argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1-cyano-3,6,8-tris(trimethylsilylethynyl)pyrene (3,
0.29 g, 28 % yield). Yellow solid; mp > 280 °C; 1H NMR (400 MHz,
CDCl3) δ 0.37 (s, 9 H), 0.38 (s, 9 H), 0.40 (s, 9 H), 7.65 (s, 1 H), 8.27 (s,
1 H), 8.41 (d, J =9.3 Hz, 1 H), 8.47 (d, J =9.3 Hz, 1 H), 8.51 (d, J
=9.3 Hz, 1 H), 8.52 (d, J =9.3 Hz, 1 H) ppm; 13C NMR (100 MHz,
CDCl3) δ 0.01, 0.01, 0.03, 101.4, 101.9, 102.0, 102.8, 102.9, 103.1,
117.7, 120.7, 120.2, 122.8, 123.1, 125.1, 126.5, 127.2, 127.8, 127.9,
128.8, 129.1, 131.2, 131.4, 132.2, 134.0, 134.6, 134.9 ppm; IR (KBr)
845, 883, 1096, 1250, 2152, 2222, 2958 cm–1; MS (CI) m/z (relative
intensity, %) = 18 (6), 73 (10), 149 (8), 243 (17), 500 (30), 515 (M+
100); HRMS (EI) calcd for C32H33NSi3: 515.1921, found: 515.1910.
,
4.4. Preparation of 4
4.2. Preparation of 2
To a stirred CH2Cl2 (100 mL) solution of pyrene (2.02 g, 10 mmol)
was added dichloromethyl methyl ether (1.2 mL, 13 mmol) at 0 °C
under an argon atmosphere. To the solution was added dropwise
CH2Cl2 (10 mL) solution of TiCl4 (2.0 mL, 18 mmol) at 0 °C, and the
resulting solution was stirred at 0 °C for 1.5 h and then at room tem-
perature for 1.5 h. The solution was poured into ice water (150 mL),
and the mixture was stirred for 30 min. The mixture was extracted with
CHCl3 (100 mL) and sat. NaCl aq (50 mL). The organic layer was
To a stirred nitrobenzene (120 mL) solution of pyrene (1, 0.40 g,
2.0 mmol) was added dropwise nitrobenzene (40 mL) solution of Br2
(0.4 mL, 7.2 mmol), and the resulting solution was stirred at 80 °C for
12 h. After cooling to room temperature, conc. NaOH aq (10 mL) was
added to quench excess Br2. The formed solid was washed with CHCl3
(100 mL) and collected by filtration to give 1,3,6-tribromopyrene
(0.76 g, 87 % yield, white solid). Lit [91].
6

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
separated, dried over Na2SO4, filtered, and concentrated in vacuo to
give 1-formylpyrene (2.1 g, 91 % yield, yellow solid). Lit [95].
To a stirred nitrobenzene (120 mL) solution of 1-formylpyrene
(0.46 g, 2.0 mmol) was added dropwise nitrobenzene (40 mL) solution
of Br2 (0.4 mL, 7.2 mmol), and the resulting solution was stirred at 80 °C
for 12 h. After cooling to room temperature, conc. NaOH aq (10 mL)
was added to quench excess Br2. The formed solid was washed with
CHCl3 (100 mL) and collected by filtration to give 1,3,6-tribromo-8-
formylpyrene (0.94 g, 100 % yield, orange solid). Lit [66].
0.24 g, 23 % yield). Yellow solid; mp 288 °C; 1H NMR (400 MHz, CDCl3)
δ 0.37 (s, 9 H), 0.38 (s, 9 H), 0.40 (s, 9 H), 4.18 (s, 3 H), 7.66 (s, 1 H),
8.27 (s, 1 H), 8.42 (d, J =9.3 Hz, 1 H), 8.48 (d, J =9.3 Hz, 1 H), 8.52 (d,
J =9.3 Hz, 1 H), 8.53 (d, J =9.3 Hz, 1 H) ppm; 13C NMR (100 MHz,
CDCl3) δ 0.0, 0.0, 0.0, 56.2, 100.3, 101.0, 103.0, 103.0, 103.5, 111.8,
111.8, 116.8, 117.0, 119.2, 121.1, 122.5, 123.8, 123.9, 124.7, 125.0,
126.6, 127.0, 132.5, 132.5, 134.3, 134.3, 153.5 ppm; IR (KBr) 887,
1119, 1250, 2152, 2360, 2959 cm–1; MS (CI) m/z (relative intensity,
%) = 75 (100), 245 (12), 448 (14), 520 (M+, 85); HRMS (EI) calcd for
A mixture of 1,3,6-tribromo-8-formylpyrene (0.93 g, 2.0 mmol),
trimethylsilylacetylene (0.844 g, 8.6 mmol), PdCl2(PPh3)2 (0.071 g,
0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3 (0.068 g, 0.26 mmol)
in THF (30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under
an argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1-formyl-3,6,8-tris(trimethylsilylethynyl)pyrene (4,
0.27 g, 26 % yield). Orange solid; mp > 340 °C; 1H NMR (400 MHz,
CDCl3) δ 0.400 (s, 9 H), 0.402 (s, 9 H), 0.42 (s, 9 H), 8.34 (s, 1 H), 8.58
(s, 1 H), 8.63 (d, J =9.3 Hz, 1 H), 8.69 (d, J =9.3 Hz, 1 H), 8.71 (d, J
=9.3 Hz, 1 H), 9.43 (d, J =9.3 Hz, 1 H) 10.69 (s, 1 H) ppm; 13C NMR
(100 MHz, CDCl3) δ 0.10, 0.12, 0.15, 102.4, 102.5, 102.5, 102.7, 118.7,
120.0, 120.2, 124.0, 124.5, 126.9, 127.5, 129.2, 129.3, 130.5, 131.3,
134.6, 134.8, 135.7, 136.4, 136.5, 192.4 ppm; IR (KBr) 845, 887, 1250,
1693, 2152, 2959 cm–1; MS (CI) m/z (relative intensity, %) = 183 (11),
244 (22), 262 (17), 422 (6), 503 (25), 518 (M+, 100); HRMS (EI) calcd
for C32H34OSi3: 518.1918, found: 518.1910.
C32H36OSi3: 520.1316, found: 520.2074.
4.6. Preparation of 6
A mixture of 1,3,6,8-tetrabromopyrene [98] (1.04 g, 2.0 mmol),
trimethylsilylacetylene (0.971 g, 9.9 mmol), PdCl2(PPh3)2 (0.082 g,
0.12 mmol), CuI (0.038 g, 0.20 mmol), and PPh3 (0.078 g, 0.30 mmol)
in THF (30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under
an argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1,3,6,8-tetrakis(trimethylsilylethynyl)pyrene (6, 0.91 g,
78 % yield, red solid). Lit [60].
4.7. Preparation of 7
A mixture of 1,3,6-tribromo-8-cyanopyrene (0.92 g, 2.0 mmol, see
preparation of 3), 3,3-dimethyl-1-butyne (0.657 g, 8.0 mmol),
PdCl2(PPh3)2 (0.071 g, 0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3
(0.068 g, 0.26 mmol) in THF (30 mL) and i-Pr2NH (25 mL) was stirred at
80 °C for 12 h under an argon atmosphere. The resulting mixture was
concentrated in vacuo, giving a residue that was subjected to silica gel
column chromatography (eluent: hexane) followed by recycling pre-
parative HPLC (GPC, eluent: CHCl3) to give 1,3,6-tris(3,3-dimethylbut-
4.5. Preparation of 5
A
mixture of 1-formylpyrene (see preparation of 4, 0.69 g,
3.0 mmol) and m-CPBA (1.04 g, 6.0 mmol) in CH2Cl2 (50 mL) was
stirred at reflux for 24 h under an argon atmosphere. To the solution
were added THF (5 mL), MeOH (10 mL), and 25 % KOH aq (0.6 mL),
and the resulting solution was stirred at room temperature for 3 h. The
solution was concentrated in vacuo to give a black residue. The residue
was extracted with CH2Cl2 (100 mL) and sat. NaCl aq (50 mL). The
organic layer was separated, dried over Na2SO4, filtered, and con-
centrated in vacuo, giving a residue that was subjected to silica gel
column chromatography (eluent: CHCl3) to give 1-hydroxypyrene
(0.36 g, 55 % yield, pink solid). Lit [96].
1-yn-1-yl)-8-cyanopyrene (7, 0.67 g, 73
% yield). Yellow solid;
mp > 340 °C; 1H NMR (400 MHz, CDCl3) δ 1.496 (s, 9 H), 1.500 (s,
9 H), 1.506 (s, 9 H), 8.21 (s, 1 H), 8.30 (s, 1 H), 8.38 (d, J =9.4 Hz, 1 H),
8.50 (d, J =9.4 Hz, 1 H), 8.61 (d, J =9.4 Hz, 1 H), 8.63 (d, J =9.4 Hz,
1 H) ppm; 13C NMR (100 MHz, CDCl3) δ 28.6, 31.05, 31.09, 31.13,
31.17, 76.5, 77.1, 105.8, 106.3, 106.4, 106.5, 118.1, 119.4, 121.0,
121.1, 123.2, 123.5, 124.3, 124.4, 125.68, 125.75, 125.77, 128.5,
128.6, 128.9, 130.4, 130.5, 131.9, 133.4, 133.5, 134.1, 134.2,
134.5 ppm; IR (KBr) 833, 891, 1203, 1269, 1308, 1601, 2222, 2970
cm–1; MS (CI) m/z (relative intensity, %) = 137 (12), 387 (8), 452 (33),
467 (M+, 100); HRMS (EI) calcd for C35H33N: 467.2613, found:
467.2617.
A mixture of 1-hydroxypyrene (0.17 g, 0.77 mmol), NaOH (0.5 g,
5.0 mmol), Me2SO4 (0.26 g, 2.1 mmol) in H2O (15 mL) and THF (10 mL)
was stirred at room temperature for 12 h. The mixture was extracted
with AcOEt (100 mL) and then Et2O (100 mL). The combined organic
layers were washed with sat. NaCl aq (50 mL), dried over Na2SO4, fil-
tered, and concentrated in vacuo, giving a residue that was subjected to
silica gel column chromatography (eluent: CHCl3) to give 1-methox-
ypyrene (0.080 g, 45 % yield, brown solid). Lit [97].
4.8. Preparation of 8
A mixture of 1,3,6-tribromo-8-formylpyrene (0.93 g, 2.0 mmol, see
preparation of 4), 3,3-dimethyl-1-butyne (0.657 g, 8.0 mmol),
PdCl2(PPh3)2 (0.071 g, 0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3
(0.068 g, 0.26 mmol) in THF (30 mL) and i-Pr2NH (25 mL) was stirred at
80 °C for 12 h under an argon atmosphere. The resulting mixture was
concentrated in vacuo, giving a residue that was subjected to silica gel
column chromatography (eluent: hexane) followed by recycling pre-
parative HPLC (GPC, eluent: CHCl3) to give 1,3,6-tris(3,3-dimethylbut-
1-yn-1-yl)-8-formylpyrene (8, 0.68 g, 73 % yield). Orange solid; mp
336 °C; 1H NMR (400 MHz, CDCl3) δ 1.49 (s, 9 H), 1.50 (s, 9 H), 1.52 (s,
9 H), 8.20 (s, 1 H), 8.50 (s, 1 H), 8.57 (d, J =9.3 Hz, 1 H), 8.66 (d, J
=9.5 Hz, 1 H), 8.67 (d, J =9.3 Hz, 1 H), 9.39 (d, J =9.5 Hz, 1 H), 10.70
(s, 1 H) ppm; 13C NMR (100 MHz, CDCl3) δ 28.7, 31.21, 31.25, 31.27,
77.1, 105.9, 106.1, 106.3, 119.3, 120.9, 121.1, 123.5, 124.3, 126.1,
127.1, 129.0, 129.2, 130.2, 130.4, 130.8, 130.9, 133.8, 135.7, 135.8,
To a stirred nitrobenzene (120 mL) solution of 1-methoxypyrene
(0.46 g, 2.0 mmol) was added dropwise nitrobenzene (40 mL) solution
of Br2 (0.4 mL, 7.2 mmol), and the resulting solution was stirred at 80 °C
for 12 h. After cooling to room temperature, conc. NaOH aq (10 mL)
was added to quench excess Br2. The formed solid was washed with
CHCl3 (100 mL) and collected by filtration to give 1,3,6-tribromo-8-
methoxypyrene (0.85 g, 91 % yield, yellow solid).
A mixture of 1,3,6-tribromo-8-methoxypyrene (0.93 g, 2.0 mmol),
trimethylsilylacetylene (0.844 g, 8.6 mmol), PdCl2(PPh3)2 (0.071 g,
0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3 (0.068 g, 0.26 mmol)
in THF (30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under
an argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1-methoxy-3,6,8-tris(trimethylsilylethynyl)pyrene (5,
192.7 ppm; IR (KBr) 833, 891, 1204, 1454, 1690, 2222, 2966 cm–1
.
7

H. Maeda, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
4.9. Preparation of 9
Declaration of Competing Interest
A mixture of 1,3,6-tribromo-8-methoxypyrene (0.93 g, 2.0 mmol,
see preparation of 5), 3,3-dimethyl-1-butyne (0.657 g, 8.0 mmol),
PdCl2(PPh3)2 (0.071 g, 0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3
(0.068 g, 0.26 mmol) in THF (30 mL) and i-Pr2NH (25 mL) was stirred at
80 °C for 12 h under an argon atmosphere. The resulting mixture was
concentrated in vacuo, giving a residue that was subjected to silica gel
column chromatography (eluent: hexane) followed by recycling pre-
parative HPLC (GPC, eluent: CHCl3) to give 1,3,6-tris(3,3-dimethylbut-
1-yn-1-yl)-8-methoxypyrene (9, 0.66 g, 71 % yield). Yellow solid; mp
243 °C; 1H NMR (400 MHz, CDCl3) δ 1.47 (s, 9 H), 1.48 (s, 9 H), 1.50 (s,
9 H), 4.17 (s, 3 H), 7.57 (s, 1 H), 8.12 (s, 1 H), 8.35 (d, J =9.2 Hz, 1 H),
8.42 (d, J =9.2 Hz, 1 H), 8.45 (d, J =9.2 Hz, 1 H), 8.45 (d, J =9.2 Hz,
1 H) ppm; 13C NMR(100 MHz, CDCl3) δ 28.5, 28.6, 31.2, 31.3, 56.1,
77.6, 77.7, 78.1, 104.3, 104.9, 111.5, 111.6, 117.8, 118.0, 119.8,
120.6, 121.7, 123.7, 124.4, 124.8, 125.2, 126.3, 126.4, 131.7, 131.8,
133.5, 133.6, 153.3 ppm; IR (KBr) 826, 1119, 1250, 1601, 2218, 2966
cm–1; MS (CI) m/z (relative intensity, %) = 427 (5), 442 (5), 457 (28),
472 (M+, 100); HRMS (EI) calcd for C35H36O: 472.2766, found:
472.2765.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Acknowledgements
This study was financially supported by a Grant-in-Aid for Scientific
Research (C) (20550049, 23550047, 26410040, 17K05777) from the
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
of Japan. This work was also supported by the Collaborative Research
Program of the Institute for Chemical Research, Kyoto University (grant
#2013-5, #2014-20). H.M. is also grateful for financial support from
The Mazda Foundation, The Murata Science Foundation, Izumi Science
and Technology Foundation, Shibuya Science Culture and Sports
Foundation, A-STEP (Adaptable and Seamless Technology Transfer
Program through target-driven R&D, JST, Japan), and Kanazawa
University SAKIGAKE Project. We thank Professor Tsuyoshi Asakawa,
Associate Professor Akio Ohta, Professor Tadaaki Yamagishi, and
Professor Tomoki Ogoshi at Kanazawa University for permission to use
UV–vis absorption and fluorescence spectrophotometers. We thank
Professor Tetsuya Taima at Kanazawa University for permission to use
an absolute fluorescence quantum yield spectrometer with an in-
tegrating sphere.
4.10. Preparation of 10
A mixture of 1,3,6,8-tetrabromopyrene [98] (1.04 g, 2.0 mmol), 3,3-
dimethyl-1-butyne (0.756 g, 9.2 mmol), PdCl2(PPh3)2 (0.071 g,
0.10 mmol), CuI (0.033 g, 0.17 mmol), and PPh3 (0.068 g, 0.26 mmol)
in THF (30 mL) and i-Pr2NH (25 mL) was stirred at 80 °C for 12 h under
an argon atmosphere. The resulting mixture was concentrated in vacuo,
giving a residue that was subjected to silica gel column chromatography
(eluent: hexane) followed by recycling preparative HPLC (GPC, eluent:
CHCl3) to give 1,3,6,8-tetrakis(3,3-dimethylbut-1-yn-1-yl)pyrene (10,
0.81 g, 78 % yield). Lit [60].
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2020.
112428.
References
[1] F.M. Winnik, Chem. Rev. 93 (1993) 587–614.
[2] S. Karuppannan, J.-C. Chambron, Chem. Asian J. 6 (2011) 964–984.
[3] M.E. Østergaard, P.J. Hrdlicka, Chem. Soc. Rev. 40 (2011) 5771–5788.
[4] G. Bains, A.B. Patel, V. Narayanaswami, Molecules 16 (2011) 7909–7935.
[5] E. Manandhar, K.J. Wallace, Inorg. Chim. Acta 381 (2012) 15–43.
[6] J. Duhamel, Langmuir 28 (2012) 6527–6538.
4.11. Fluorescence quantum yields
Fluorescence quantum yields in solutions (Table 1) were obtained
by relative methods [99]. Cyclohexane solutions of 2-10 (1.0 × 10−6
M) were degassed by using freeze-pump-thaw cycles. Fluorescence
spectra were recorded at 298 K using a 1 cm path length cell. Fluores-
cence quantum yields (Φfs) of 2-10 were determined by using 6 as a
standard with a known Φf of 0.99 in EtOH [60]. The Φfs were calculated
employing the equation
[7] J.J. Bryant, U.H.F. Bunz, Chem. Asian J. 8 (2013) 1354–1367.
[8] O.A. Krasheninina, D.S. Novopashina, E.K. Apartsin, A.G. Venyaminova, Molecules
22 (2017) 2108.
[9] T.M. Figueira-Duarte, K. Müllen, Chem. Rev. 111 (2011) 7260–7314.
[10] J.M. Casas-Solvas, J.D. Howgego, A.P. Davis, Org. Biomol. Chem. 12 (2014)
212–232.
[11] X. Feng, J.-Y. Hu, C. Redshaw, T. Yamato, Chem. Eur. J. 22 (2016) 11898–11916.
[12] D. Zych, Molecules 24 (2019) 2551.
[13] J. Fujimoto, T. Bando, M. Minoshima, S. Uchida, M. Iwasaki, K. Shinohara,
H. Sugiyama, Bioorg. Med. Chem. 16 (2008) 5899–5907.
Φf(spl) = Φf(std) × [A(std)/A(spl)] × [I(spl)/I(std)]
× [n(spl)/n(std)]2
[14] V.V. Filichev, I.V. Astakhova, A.D. Malakhov, V.A. Korshun, E.B. Pedersen, Chem.
Eur. J. 14 (2008) 9968–9980.
where Φf(spl) and Φf(std) are the fluorescence quantum yields of the
sample and standard, respectively, A(spl), I(spl), and n(spl) are the
absorbance at excitation wavelength (λex), integrated fluorescence in-
tensities obtained from spectra in which the horizontal axis is converted
from wavelength to wavenumber, and refractive index of solvents.
A(std), I(std), and n(std) are those of the standard. Excitation wave-
lengths (λex =309 nm) and concentrations of solutions of sample and
standard (1.0 × 10−6 M) were identical in each determination.
Fluorescence quantum yields in the solid state (Fig. 6) were de-
termined by using a JASCO FP-6600 spectrophotometer and an abso-
lute fluorescence quantum yield measurement unit ILF-533 with an
integrating sphere.
[15] I.V. Astakhova, V.A. Korshun, J. Wengel, Chem. Eur. J. 14 (2008) 11010–11026.
[16] U. Förster, C. Grünewald, J.W. Engels, J. Wachtveitl, J. Phys, Chem. B 114 (2010)
11638–11645.
[17] K. Astakhova, A.V. Golovin, I.A. Prokhorenko, A.V. Ustinov, I.A. Stepanova,
T.S. Zatsepin, V.A. Korshun, Tetrahedron 73 (2017) 3220–3230.
[18] F. Gerson, J. Heinzer, H. Bock, H. Alt, H. Seidl, Helv. Chim. Acta 51 (1968)
707–718.
[19] A.L. Allred, L.W. Bush, J. Am. Chem. Soc. 90 (1968) 3352–3360.
[20] A.G. Evans, B. Jerome, N.H. Rees, J. Chem, Soc. Perkin Trans. 2 (1973) 2091–2093.
[21] H.J. Sipe Jr, R. West, J. Organomet. Chem. 70 (1974) 353–366.
[22] W. Kaim, H. Tesmann, H. Bock, Chem. Ber. 113 (1980) 3221–3234.
[23] H. Shizuka, Y. Sato, Y. Ueki, M. Ishikawa, M. Kumada, J. Chem, Soc. Faraday Trans.
1 (80) (1984) 341–357.
[24] T. Karatsu, T. Shibata, A. Nishigaki, K. Fukui, A. Kitamura, Chem. Lett. 30 (2001)
994–995.
[25] T. Karatsu, T. Shibata, A. Nishigaki, A. Kitamura, Y. Hatanaka, Y. Nishimura,
S. Sato, I. Yamazaki, J. Phys, Chem. B 107 (2003) 12184–12191.
[26] T. Karatsu, M. Terasawa, S. Yagai, A. Kitamura, T. Nakamura, Y. Nishimura,
I. Yamazaki, J. Organomet, Chemistry 689 (2004) 1029–1035.
[27] H. Maeda, T. Maeda, K. Mizuno, Molecules 17 (2012) 5108–5125.
[28] M. Yamaji, H. Maeda, K. Minamida, T. Maeda, K. Asai, G.-I. Konishi, K. Mizuno, Res.
Chem. Intermed. 39 (2013) 321–345.
CRediT authorship contribution statement
Hajime Maeda: Conceptualization, Project administration. Ryota
Ueno: Investigation. Taniyuki Furuyama: Supervision. Masahito
Segi: Supervision.
[29] H. Maeda, T. Fujii, K. Minamida, K. Mizuno, J. Photochem, Photobiol. A: Chem. 342
8

H. Maeda, et al.
(2017) 153–160.
JournalofPhotochemistry&PhotobiologyA:Chemistry392(2020)112428
[60] H. Maeda, T. Maeda, K. Mizuno, K. Fujimoto, H. Shimizu, M. Inouye, Chem. Eur. J.
[30] G. Felix, R. Lapouyade, H. Bouas-Laurent, B. Clin, Tetrahedron Lett. 17 (1976)
2277–2278.
12 (2006) 824–831.
[61] T. Tamai, M. Watanabe, H. Maeda, K. Mizuno, J. Polym. Sci. A: Polym. Chem. 46
(2008) 1470–1475.
[31] H. Sakurai, K. Sakamoto, A. Nakamura, M. Kira, Chem. Lett. 14 (1985) 497–498.
[32] M. Daney, C. Vanucci, J.-P. Desvergne, A. Castellan, H. Bouas-Laurent, Tetrahedron
Lett. 26 (1985) 1505–1508.
[62] M. Yamaji, H. Maeda, Y. Nanai, K. Mizuno, ISRN Phys. Chem. (2012) 103817.
[63] H. Maeda, T. Shoji, M. Segi, Tetrahedron Lett. 58 (2017) 4372–4376.
[64] H. Maeda, T. Suzuki, M. Segi, Photochem. Photobiol. Sci. 17 (2018) 781–792.
[65] I.B. Berlman (Ed.), Handbook of Fluorescence Spectra of Aromatic Molecules, 2nd
ed., Academic Press, New York and London, 1971.
[33] J.-P. Desvergne, N. Bitit, A. Castellan, M. Webb, H. Bouas-Laurent, J. Chem. Soc.
Perkin Trans. 2 (1988) 1885–1894.
[34] K.J. Shea, D.A. Loy, O. Webster, J. Am. Chem. Soc. 114 (1992) 6700–6710.
[35] H. Suzuki, S. Satoh, Y. Kimata, A. Kuriyama, Chem. Lett. 24 (1995) 451–452.
[36] S. Kyushin, M. Ikarugi, M. Goto, H. Hiratsuka, H. Matsumoto, Organometallics 15
(1996) 1067–1070.
[66] Y. Niko, S. Sasaki, K. Narushima, D.K. Sharma, M. Vacha, G. Konishi, J. Org. Chem.
80 (2015) 10794–10805.
[67] J.B. Birks, Acta Phys. Pol. 34 (1968) 603–617.
[37] S. Yamaguchi, S. Akiyama, K. Tamao, Organometallics 17 (1998) 4347–4352.
[38] J.-P. Desvergne, R. Bonneau, G. Dörr, H. Bouas-Laurent, Photochem. Photobiol. Sci.
2 (2003) 289–296.
[68] Th. Förster, Angew. Chem. Int. Ed. 8 (1969) 333–343.
[69] K. Zachariasse, W. Kühnle, Z. Phys. Chem. 101 (1976) 267–276.
[70] F.C. De Schryver, P. Collart, J. Vandendriessche, R. Goedeweeck, A.M. Swinnen,
M. Van der Auweraer, Acc. Chem. Res. 20 (1987) 159–166.
[71] C. Reichardt, Chem. Rev. 94 (1994) 2319–2358.
[39] T. Karatsu, R. Hazuku, D. Nishioka, S. Yagai, N. Kobayashi, A. Kitamura, J.
Photopolym. Sci. Tech. 18 (2005) 65–68.
[40] S. Kyushin, Y. Ishikita, H. Matsumoto, H. Horiuchi, H. Hiratsuka, Chem. Lett. 35
(2006) 64–65.
[72] N. Mataga, Y. Kaifu, M. Koizumi, Bull. Chem. Soc. Jpn. 28 (1955) 690–691.
[73] Von F. Schneider, E. Lippert, Ber. Bunsenges. Phys. Chem. 72 (1968) 1155–1160.
[74] N. Mataga, Y. Kaifu, M. Koizumi, Bull. Chem. Soc. Jpn. 29 (1956) 465–470.
[75] D. Chitnis, N.T. Kalyani, S. Dhoble, Luminescence 33 (2018) 968–980.
[76] J.C. Giordan, J. Am. Chem. Soc. 105 (1983) 6544–6546.
[77] H. Sakurai, Pure Appl. Chem. 59 (1987) 1637–1646.
[78] S. Yamaguchi, K. Tamao, Bull. Chem. Soc. Jpn. 69 (1996) 2327–2334.
[79] D.-D.H. Yang, N.C. Yang, I.M. Steele, H. Li, Y.-Z. Ma, G.R. Fleming, J. Am. Chem.
Soc. 125 (2003) 5107–5110.
[41] J.E. Anthony, Chem. Rev. 106 (2006) 5028–5048.
[42] T. Karatsu, R. Hazuku, M. Asuke, A. Nishigaki, S. Yagai, Y. Suzuri, H. Kita,
A. Kitamura, Org. Electron. 8 (2007) 357–366.
[43] J.E. Anthony, J.S. Brooks, D.L. Eaton, S.R. Parkin, J. Am. Chem. Soc. 123 (2001)
9482–9483.
[44] M.-A. Tehfe, J. Lalevée, F. Morlet-Savary, B. Graff, N. Blanchard, J.-P. Fouassier,
Macromolecules 45 (2012) 1746–1752.
[45] S.N. Sanders, E. Kumarasamy, A.B. Pun, K. Appavoo, M.L. Steigerwald,
L.M. Campos, M.Y. Sfeir, J. Am. Chem. Soc. 138 (2016) 7289–7297.
[46] C. Eaborn, Z. Lasocki, J.A. Sperry, J. Organomet, Chemistry 35 (1972) 245–252.
[47] Y. Hakoda, M. Aoyagi, K. Irisawa, S. Kato, Y. Nakamura, M. Yamaji, Photochem.
Photobiol. Sci. 15 (2016) 1586–1593.
[80] T. Shyamala, S. Sankararaman, A.K. Mishra, Chem. Phys. 330 (2006) 469–477.
[81] S. Kyushin, T. Matsuura, H. Matsumoto, Organometallics 25 (2006) 2761–2765.
[82] H. Lu, Q. Wang, Z. Li, G. Lai, J. Jiang, Z. Shen, Org. Biomol. Chem. 9 (2011)
4558–4562.
[83] Y. Niko, S. Kawauchi, S. Otsu, K. Tokumaru, G. Konishi, J. Org. Chem. 78 (2013)
3196–3207.
[48] S. Kyushin, N. Takemasa, H. Matsumoto, H. Horiuchi, H. Hiratsuka, Chem. Lett. 32
(2003) 1048–1049.
[84] S.K. Lower, M.A. El-Sayed, Chem. Rev. 66 (1966) 199–241.
[85] M. Baba, J. Phys. Chem. A 115 (2011) 9514–9519.
[49] D. Declercq, F.C. De Schryver, R.D. Miller, Chem. Phys. Lett. 186 (1991) 467–473.
[50] D. Declercq, P. Delbeke, F.C. De Schryver, L. Van Meervelt, R.D. Miller, J. Am.
Chem. Soc. 115 (1993) 5702–5708.
[86] N.J. Turro, T. Okubo, J. Phys. Chem. 86 (1982) 159–161.
[87] Ch.V. Kumar, S.K. Chattopadhyay, P.K. Das, Photochem. Photobiol. 38 (1983)
141–152.
[51] L. Gherghel, M. Baumgarten, D. Declerq, F.C. De Schryver, Chem. Phys. Lett. 232
(1995) 567–570.
[88] Y. Niko, Y. Hiroshige, S. Kawauchi, G. Konishi, Tetrahedron 68 (2012) 6177–6185.
[89] Y. Niko, S. Kawauchi, G. Konishi, Chem. Eur. J. 19 (2013) 9760–9765.
[90] Y. Niko, S. Sasaki, S. Kawauchi, K. Tokumaru, G. Konishi, Chem. Asian J. 9 (2014)
1797–1807.
[52] S. Kondo, Y. Bie, M. Yamamura, Org. Lett. 15 (2013) 520–523.
[53] S. Kondo, Y. Taguchi, Y. Bie, RSC Adv. 5 (2015) 5846–5849.
[54] F. Xu, T. Nishida, K. Shinohara, L. Peng, M. Takezaki, T. Kamada, H. Akashi,
H. Nakamura, K. Sugiyama, K. Ohta, A. Orita, J. Otera, Organometallics 36 (2017)
556–563.
[91] J. Grimshaw, J. Trocha-Grimshaw, J. Chem. Soc. Perkin Trans. 1 (1972)
1622–1623.
[55] S. Koga, S. Ueki, M. Shimada, R. Ishii, Y. Kurihara, Y. Yamanoi, J. Yuasa, T. Kawai,
T. Uchida, M. Iwamura, K. Nozaki, H. Nishihara, J. Org. Chem. 82 (2017)
6108–6117.
[92] W.H. Gumprecht, Org. Synth. Collect. 5 (1973) 147–148.
[93] K.W. Rosenmund, E. Struck, Ber. Dtsch. Chem. Ges. 52 (1919) 1749–1756.
[94] K. Okamoto, N. Sakata, K. Ohe, Org. Lett. 17 (2015) 4670–4673.
[95] H. Maeda, T. Akai, M. Segi, Tetrahedron Lett. 58 (2017) 4377–4380.
[96] R.K. Sehgal, S. Kumar, Org. Prep. Proc. Int. 21 (1989) 223–225.
[97] Y. Zhou, F. Wang, Y. Kim, S.-J. Kim, J. Yoon, Org. Lett. 11 (2009) 4442–4445.
[98] K. Ogino, S. Iwashima, H. Inokuchi, Y. Harada, Bull. Chem. Soc. Jpn. 38 (1965)
473–477.
[56] M. Yamaji, H. Maeda, Y. Nanai, K. Mizuno, Chem. Phys. Lett. 536 (2012) 72–76.
[57] H. Maeda, Y. Inoue, H. Ishida, K. Mizuno, Chem. Lett. 30 (2001) 1224–1225.
[58] A.M. Ara, T. Iimori, T. Nakabayashi, H. Maeda, K. Mizuno, N. Ohta, J. Phys. Chem.
B 111 (2007) 10687–10696.
[59] H. Maeda, H. Ishida, Y. Inoue, A. Merpuge, T. Maeda, K. Mizuno, Res. Chem.
Intermed. 35 (2009) 939–948.
[99] D.F. Eaton, Pure Appl. Chem. 60 (1988) 1107–1114.
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