Effects of different substituted positions on the photophysical properties of pyrene-based sulfides

Article abstract of DOI:10.1016/j.molstruc.2019.07.021

A series of new pyrene-based sulfides were synthesized by the reaction between 4-methylbenzenethiol and R-bromopyrene (R = 1(1), 4(2), 2(3)). These compounds were structurally characterized and their properties were analyzed by spectroscopy, single crysta

Full text of DOI:10.1016/j.molstruc.2019.07.021

Journal of Molecular Structure 1197 (2019) 1e8
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Effects of different substituted positions on the photophysical
properties of pyrene-based sulfides
Hao Sun, Wen-Hao Sun, Li-Hua Xu, Ran Zhang, Jing Nie, Xiang-En Han, Zhong-Hai Ni*
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, 221116, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new pyrene-based sulfides were synthesized by the reaction between 4-methylbenzenethiol
and R-bromopyrene (R ¼ 1(1), 4(2), 2(3)). These compounds were structurally characterized and their
properties were analyzed by spectroscopy, single crystal X-ray diffraction, electrochemistry and theo-
retical studies. Significant effect of substituted positions on photophysical properties were observed. The
p-methylphenylthio group in 1- and 4-position significantly increases the absolute fluorescence quantum
Received 28 May 2019
Received in revised form
2 July 2019
Accepted 4 July 2019
Available online 7 July 2019
yield (
Ф
F) in solid state, decreases the ФF in solution and almost does not change the ФF in film state
F in solution, almost
compared to that of pyrene. However, this substituent in 2-position keeps the high
Ф
Keywords:
Aggregation-induced emission (AIE)
Pyrene
Different substituted positions
Photophysical properties
does not contribute to the ФF in solid state and significantly decreases the ФF in film state compared to
that of pyrene. Moreover, compounds 1, 2 and 3 exhibit typical aggregation-induced emission (AIE)
properties that were proved by time-resolved photoluminescence.
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
properties of 2- and 7- substituted pyrene due to the difficulty of
their synthesis. The 4-, 5-, 9-, and10-positions of pyrene are defined
Pyrene, the well-known polycyclic aromatic hydrocarbon chro-
mophore discovered by Laurent in 1837, has attracted extensive
attention of researchers from various scientific areas [1e9]. In the
past decades, pyrene-based derivatives have been widely applied in
the fields of organic light emitting diodes (OLEDs), organic photo-
voltaic cells (OPV), organic field-effect transistors (OFETs), fluo-
rescent probe and so on [10e17].
as the K-regions that are very interesting and important for the
preparation of extended aromatic systems [1,25e28]. However,
these positions are generally difficult to be functionalized just as in
the case of the 2- and 7-substituted pyrene. Although much efforts
have been devoted to the functionalization of pyrene, the systemic
studies about the effects of different substituted positions on the
photophysical properties of pyrene are rarely reported.
To date, most reported pyrene-based fluorescent materials are
functionalized by introducing substituents at the 1-, 3-, 6-, and 8-
positions known as the most active sites for electrophilic substi-
tution reactions [18e20]. The easy preparation and relatively sim-
ple purification of 1-substituted and 1-, 3-, 6-, and 8-
tetrasubstituted pyrene provide possibility of introducing pyrene
into interesting functional materials, which has attracted many
researchers’ interests. In addition, the development of 2- and 7-
substituted pyrene are generally challenging because the 2- and 7-
positions of pyrene are known as the molecular node sites [21e24].
The nodal plane in HOMO and LUMO passes through the 2- and 7-
positions and is perpendicular to the molecule (Scheme 1).
Consequently, little studies were carried out on the photophysical
Moreover, compounds exhibiting AIE property have drawn
extensive interesting since AIE phenomenon was discovered by
Tang's group in 2001 [29,30]. The parent nucleus of most AIE
compounds are non-fluorescent or weak fluorescent in dilute so-
lution or low water content solution, which will emit strong fluo-
rescence in aggregation sate. On the contrary, traditional
luminophores exhibit strong emission and suffer from the
aggregation-caused quenching (ACQ) in aggregation state. There-
fore, it is an interesting and important work to transform tradi-
tional ACQ luminophores into AIE compounds. In order to realize
this transformation, understanding the effects of different
substituted position on their photophysical properties in both so-
lution and solid state is of very importance. In addition, in recent
years, thioether linked compounds exhibiting AIE property have
received great attention [31]. However, the interesting effects of
thioether linked compounds on their own AIE phenomena have
rarely reported.
* Corresponding author.
E-mail address: nizhonghai@cumt.edu.cn (Z.-H. Ni).
https://doi.org/10.1016/j.molstruc.2019.07.021
0022-2860/© 2019 Elsevier B.V. All rights reserved.

2
H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
Scheme 1. Structure, HOMO and LUMO of pyrene (B3LYP).
In this work, a series of pyrene-based sulfide derivatives with
1898238, 1898241 and 1898242, respectively, and the data can be
obtained free of charge from the Cambridge Crystallographic Data
Centre (CCDC) or at www.ccdc.cam.ac.uk/conts/retrieving.html.
The ground state geometries of all molecules were fully optimized
using density functional theory (DFT) at the B3LYP/6-31G (d, p)
level, as implemented in Gaussian 09W software package.
different substituted position were synthesized, which exhibit
obviously different photophysical properties. In solution, 1- and 4-
substituted pyrene-based sulfides (1 and 2) exhibit similar spectral
properties. Both of them exhibit very weak emission (ФF, 7% and
3%) in dichloromethane (DCM) and relatively large red-shift in
absorption and photoluminescence (PL) spectra compared to that
of pyrene. However, 2-substituted pyrene-based sulfide (3) shows
similar spectral properties to pyrene in solution, which exhibits
2.2. Synthesis
very strong blue emission (
and 2 ( F, 75% and 79%) exhibit stronger emission than compound
3 ( F, 69%). These results indicate that p-methylphenylthio sub-
stituent in 1- and 4-position significantly increases the solid state
ФF and decreases the solution state F. However, p-methyl-
ФF, 29%). In solid state, compounds 1
2.2.1. Synthesis of pyren-1-yl(p-tolyl)sulfide (1)
Ф
1.69 g (12 mmol) 4-methylbenzenethiol, 2.81 g (10 mmol) 1-
bromopyrene and 50 mL DMF were added into a 100 ml round
bottom flask. The above mixture was stirred for 10 min in an ice
bath under the protection of N2. Then, 0.48 g (12 mmol) NaH (60%)
was slowly added into the above flask in batches and the mixture
was stirred for another 10 min. After all the generated hydrogen
was discharged, the mixture was refluxed for 10 h, poured into
water, extracted with DCM and washed with water for three times.
The organic phase was dried over MgSO4, filtered, and concen-
trated. The concentrated product was purified by silica gel flash
column chromatography using hexane as the eluent. Yield: 2.60 g,
Ф
Ф
phenylthio substituent in 2-position almost does not contribute to
the ФF in solid state. In film state, p-methylphenylthio substituent
in 1- and 4-position keeps a high ФF
that of pyrene, but this substituent in 2-position significantly
quenches the ФF F, 22%). In addition, compounds 1, 2 and 3 show
(ФF, 41% and 44%) compared to
(Ф
obvious AIE properties,. These results will provide important
guidance to relative studies and contribute to design and synthesis
of functionalized pyrene-based derivatives.
80%. Melting point, 101e102 ꢀC. 1H NMR (400 MHz, CDCl3),
d (TMS,
ppm):8.70e8.68 (d, 1H, J ¼ 8.69 Hz), 8.24e8.22 (d, 2H, J ¼ 8.23 Hz),
8.17e8.03 (m, 6H), 7.21e7.18 (m, 2H), 7.10e7.07 (m, 2H), 2.33 (s, 3H).
2. Experimental section
13C NMR (400 MHz, CDCl3),
d (TMS, ppm): 136.41, 133.49, 131.69,
131.37, 131.27, 131.20, 131.00, 129.98, 129.76, 129.44, 128.35, 127.89,
127.26, 126.26, 125.51, 125.50, 125.34, 125.15, 124.73, 124.47, 21.04.
2.1. Materials and instrumentation
MALDI-TOF MS (m/z): calcd for
Elemental analysis: anal. calcd for C23H16S: C, 85.15; H, 4.97; S,
9.88%. Found: C, 85.09; H, 4.99; S, 9.82%.
C23H16S 324.4, found 324.1.
Tetrahydrofuran (THF) was distilled from sodium and benzo-
phenone in a nitrogen atmosphere. All other reagents and solvents
were purchased commercially (AR grade) and used without further
purification unless otherwise noted. The THF/water mixtures with
different water fractions were prepared by slowly adding distilled
water into the THF solution of samples under ultrasound at room
temperature. The single crystals suitable for X-ray diffraction
analysis were obtained by the slow evaporation of dichloro-
methane/methyl alcohol. 1H NMR and 13C NMR spectra were
collected on a Bruker-400 MHz spectrometer in CDCl3 solution with
TMS as an internal standard. Mass spectra were obtained on a
MALDI-TOF MS. UV-vis spectra were recorded on Shimadzu UV-
3600 with a UV-VIS-NIR spectrophotometer. Emission spectra
were performed by a HITACHI fluorescence spectrometer (F-4600).
Crystal data of compounds 1, 2 and 3 were collected on a Bruker
2.2.2. Synthesis of pyren-4-yl(p-tolyl)sulfide (2)
The synthetic steps of 2 are the same as to the synthetic process
of 1. Yield: 2.49 g, 77%. Melting point, 116e117 ꢀC. 1H NMR
(400 MHz, CDCl3),
d
(TMS, ppm): 8.73e8.71 (dd, 1H, J ¼ 8.72 Hz),
8.25e8.21 (m, 3H), 8.14e8.09 (m, 3H), 8.06e7.99 (dt, 2H,
J ¼ 8.03 Hz), 7.34e7.31 (m, 2H), 7.14e7.11 (m, 2H), 2.35 (s, 3H). 13
C
NMR (400 MHz, CDCl3),
d (TMS, ppm): 136.78, 132.30, 132.03,
132.01, 131.44, 131.06, 130.88, 130.49, 130.34, 130.06, 127.64, 127.21,
126.19, 126.18, 125.77, 125.56, 125.27, 124.98, 124.21, 123.30, 21.10.
MALDI-TOF MS(m/z): calcd for
Elemental analysis: anal. calcd for C23H16S: C, 85.15; H, 4.97; S,
9.88%. Found: C, 85.09; H, 4.99; S, 9.86%.
C23H16S 324.4, found 324.1.
APEX II CCDC diffractometer with graphite monochromated Mo-K
a
radiation ( -scan technique. The
l
¼ 0.71073 Å) at 296 K using the
u
ФF was measured by a FS5 spectrofluorometer. Their crystal
structures were solved by direct methods with the SHELXS-2014
computer program, and refined by full matrix least-squares
methods (SHELXL-2014) on F2. Images were created by using DIA-
MOND program. CCDC number for compounds 1, 2 and 3 is
2.2.3. Synthesis of pyren-2-yl(p-tolyl) sulfide (3)
The synthetic steps of 3 are the same as to the synthetic process
of 1. Yield: 1.39 g, 43%. Melting point, 103e104 ꢀC. 1H NMR
(400 MHz, CDCl3),
8.10e8.05 (m, 4H), 8.03e7.95 (m, 3H), 7.44e7.35 (m, 2H), 7.22e7.08
d
(TMS, ppm): 8.24e8.17 (d, 2H, J ¼ 8.19 Hz),

H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
3
(m, 2H), 2.41 (s, 3H). 13C NMR (400 MHz, CDCl3),
d
(TMS,
shift of UV absorption. It is worth noting that the emission in-
tensities of compounds 1 and 2 are very weak, their F are only 7%
ppm):137.69, 134.66, 132.20, 131.83, 130.93, 130.21, 128.10, 126.80,
126.07, 125.95, 125.36, 124.45, 123.39, 21.20. MALDI-TOF MS (m/z):
calcd for C23H16S 324.4, found 324.1. Elemental analysis: anal. calcd
for C23H16S: C, 85.15; H, 4.97; S, 9.88%. Found: C, 85.09; H, 4.99; S,
9.90%.
Ф
and 2% in DCM, respectively. However, the emission intensity of
compound 3 is almost as strong as intensity of pyrene, the ФF
reaches up to 30%. This phenomenon can be explained by the
theory of restriction of intramolecular motion (RIM) proposed by
Tang et al. [29,30] As described above, 1- and 4-substituted pyrene
are effectively conjugate with abundant electron cloud density. In
dilute solution, molecules are isolated and pyrene ring and the
benzene ring can freely rotate around a single bond connected to
the sulfur atom, which will largely consume the excited state en-
ergy. Therefore, compounds 1 and 2 emit weak fluorescence.
However, 2-substituted pyrene is less conjugation and the lumi-
nescence behavior of the whole molecule is basically determined
by the pyrene ring. The energy of the excited state is all located on
pyrene ring and cannot be consumed by intramolecular rotation,
which may account for the strong emission of compound 3.
3. Results and discussion
3.1. Synthesis and characterization
The synthetic routs for compounds 1, 2 and 3 are illustrated in
Scheme 2. Compounds 1, 2 and 3 were structurally characterized by
1H NMR, 13C NMR, single crystal X-ray diffraction and mass spec-
trometer techniques.
3.2. Photophysical properties in solution
3.3. Photophysical properties in crystal, solid and film state
The UV-vis absorption and photoluminescence (PL) spectra of
compounds 1, 2 and 3 in DCM are shown in Fig. 1. As illustrated in
Fig.1A, compared to that of pyrene, the maximum absorption of 1, 2
and 3 red shifted 16, 10 and 6 nm, respectively. In addition, the
absorption peaks of the compounds 1 and 2 become wide and the
fine structures become unobvious. However, the absorption peak of
compound 3 is relatively sharp and the distinct fine structures are
observed, which is very similar to that of pyrene. This phenomenon
is obviously resulted from the difference of substituted position.
The electron cloud density of the 1-position and the 4-position of
pyrene are abundant and the electron-rich p-methylphenylthio
group can form an effective conjugate with the pyrene ring, which
will increase the degree of conjugation of the whole system. The
increased degree of conjugation thus results the red-shifted ab-
sorption. However, the electrons of p-methylphenylthio substituent
in 2-position is difficult to efficiently conjugate with the pyrene
ring due to the scarce electron cloud density of the 2-position.
Therefore, the absorption of the compound 3 is basically derived
from the pyrene ring, which may account for the similar absorption
to pyrene. As can be seen from Fig. 1B, the maximum emission peak
of compounds 1, 2 and 3 are observed at 415, 416 and 405 nm,
respectively. Their emission peaks exhibit slight red shift compared
to the emission peak of pyrene, which is consistent with the red
Fig. 2 presents the PL spectra of pyrene, 1, 2 and 3. The relevant
data are shown in Table 1. The crystal and powder of the compound
1 emit strong blue-green fluorescence with high
ФF (75% and 74%),
while its film emits green fluorescence with a relative low
Ф
F (41%).
The crystal emission peak of compound 1 at 468 nm almost co-
incides with the emission peak of its powder state, but the emission
peak of its film is red shifted to 489 nm. The large red-shifted
emission of its film may be caused by stronger
p-p interaction
between molecules in the amorphous state due to the lack of lattice
constraints. The luminescence phenomena of compounds 2 and 3
are similar to compound 1. Both crystals and powders of com-
pounds 2 and 3 emit blue-green fluorescence and the emission
peaks in both states almost coincide. The emission peaks of com-
pounds 2 and 3 exhibit little change compare to that of compound
1. However, their ФF exhibit obvious difference. It is worth noting
that the ФF of compound 2 (79% and 78%) is higher than com-
pounds 1 and 3. The
ФF of compound 3 is lowest (68% and 69%) and
ФF of its film state is only 22%. These results indicate that p-
methylphenylthio substituent in 1- and 4-position may signifi-
cantly increase the
ФF in solid state. However, p-methylphenylthio
substituent in 2-position almost does not contribute to the ФF in
solid state.
3.4. Crystal structure
The white crystals of 1, 2 and 3 were obtained by slow evapo-
ration of DCM/MeOH solution and the selected suitable single
crystals were analyzed by single crystal X-ray diffraction technique.
The crystal data are given in Table S1 and the crystal structures of 1,
2 and 3 are shown in Fig. S1. Fig. 3 presents the packing model of 1,
2 and 3. As illustrate, the pyrene rings in the molecule of com-
pounds 1, 2 and 3 are stacked in parallel with each other. Different
degrees of slip are observed for the two parallel pyrene rings. In
compound 1, the two parallel pyrene rings exhibit the least slip, and
the slip of compound 2 is larger than that of compound 1. The
distance between the parallel pyrene rings in 1 and 2 is 3.417 and
3.510 Å indicating strong
p-p interaction. Therefore, the p-p
interaction in compound 1 is stronger than that in compound 2,
which may account for the lower ФF of compound 1 than com-
pound 2. In compound 3, the two parallel pyrene rings are almost
stagger and only a very small fraction of them overlap, which
suggests the absence of p-p interaction. However, the ФF of 3 is still
low and close to ФF of pyrene. This phenomenon may result from
the scarce electron cloud density of the 2-position described above.
Scheme 2. Synthetic routes to compounds 1, 2 and 3.
In addition, there exist affluent intermolecular CeH$$$p interaction

4
H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
Fig. 1. (A) Absorption spectra of pyrene, 1, 2 and 3 in DCM. (B) PL spectra of pyrene, 1, 2 and 3 in DCM. Insets of (B): the emission images of 1, 2 and 3 DCM taken under 365 nm UV
illumination. For Absorption measurement, pyrene, 1, 2 and 3 concentrations: 10ꢁ5 M. For PL measurement, pyrene, 1, 2 and 3 concentrations: 10ꢁ4 M, excitation wavelength:
340 nm.
Fig. 2. PL spectra of pyrene, 1(A), 2 (B) and 3 (C) in crystal, powder and film state. (D): the emission images of 1, 2, 3 and pyrene. From left to right: crystal in daylight, crystal in 365
UV, powder in 365 UV, film in 365 UV. For PL measurement, excitation wavelength: 340 nm.

H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
5
Table 1
Data of UV-vis absorption and PL emission of compounds 1e3 and pyrene. (labs,max ¼ absorption maximum; lem,max ¼ emission maximum; Cry ¼ Crystal; Pow ¼ Powder.)
Compound
labs,max/nm
lem,max/nm
Stokes-shift/nm
ФF (%)
DCM
Cry
Pow
Film
DCM
Cry
Pow
Film
1
2
3
py
352
346
342
336
415
416
405
390
468
469
466
449
470
469
467
449
489
480
480
449
63
70
63
54
7
3
29
32
75
79
69
68
74
78
68
67
41
44
22
44
Fig. 3. Orthogonal projection of two parallel molecules in crystals (top) and crystal packing model of 1, 2 and 3 (bottom).
(from 2.649 to 2.854 Å) in the crystal structures of compounds 1e3,
which stabilizes the conformation of molecules and reduces the
non-radiative transition to some extent. Therefore, the ФF of solid
phase is higher than that in solution.
exhibits obvious effects of different substituted positions on pho-
tophysical properties.
In order to confirm the AIE nature, time-resolved single-photon
counting (TCSPC) technique was carried out (Fig. S2). As can be seen
from Fig. S3A-S3C, the luminescence decay curves of compounds 1,
2 and 3 in pure THF solution are well fitted with two-ordered
exponential decays. For compound 1, a shorter component with
3.5. AIE property
lifetime (t) of 0.51 ns and a longer species with a lifetime of 4.18 ns
The AIE properties of compounds 1 and 2 have further investi-
gated by dissolving them in THF and then adding water as bad
solvent. As is shown, compounds 1 and 2 are typical AIE-active
compounds (Fig. 4). As illustrated, when the water content is less
than 80%, only a weak emission peak around 400 nm is observed for
compound 1, which decreases with the increase of water content in
a whole. However, when the water content reaches 80%, a new
emission peak appears at about 490 nm and the emission peak at
400 nm is disappeared completely. With further increasing the
water content, the intensity of emission peak at 409 nm gradually
increases. Similar phenomenon is observed for compound 2.
However, the intensity of emission peak at 400 nm is lower than
that of compound 1, which is consistent with results in Table 1.
Interestingly, for compound 3, strong emission is observed both in
low and high water content solutions, which is obviously different
from that of compounds 1 and 2. This interesting phenomenon
were observed in THF solution. For compound 2 and 3, the lifetime
of shorter components are 0.77 ns and 0.51 ns, the lifetime of longer
whereas are 4.18 ns and 7.89 ns, respectively. According to previous
reports, the above longer components were explained by excimer
emission lifetime [32,33]. In addition, the emission lifetime of
aggregated state (water content ¼ 95%) of compounds 1, 2 and 3 are
22.62 ns (95.17%), 23.29 ns (96.49%) and 14.73 ns (96.24%), respec-
tively, which are longer than that of compounds 1, 2 and 3 in THF.
Therefore, the longer lifetime (22.62 ns, 23.29 ns and 14.73 ns) are
not resulted from excimer, which can be attributed to the emission
lifetime of aggregates.
3.6. Theoretical calculation
To further understand the relationship between structure and

6
H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
Fig. 4. PL spectra of compound 1 (A), 2 (B) and 3 (C) in H2O/THF mixtures with different water fractions. Insets: the emission images of 1, 2 and 3 in H2O/THF mixtures with different
water fractions taken under 365 nm UV and daylight illumination. For PL measurement, 1, 2 and 3 concentrations: 10ꢁ4 M, excitation wavelength: 365 nm.
physical properties, quantum mechanical computations on their
energy levels based on DFT/B3LYP/6-31G (d,p) using Gaussian 09
software were performed. The diagrams of the highest occupied
molecular orbital (HOMO) and lowest unoccupied molecular orbital
(LUMO) of 1, 2 and 3 are shown in Fig. 5. The HOMO of compound 1
is distributed on the molecule and LUMO is mainly located on
pyrene ring. The pyrene ring, sulfur atom and the benzene ring are
very effective conjugated indicating that the spectral properties of
compound 1 are determined by the electronic behavior of the
entire molecule. The HOMO and LUMO levels and energy gaps of
compound 1 are ꢁ5.675 eV, ꢁ2.070 eV and 3.605 eV, respectively,
compared to that of compound 1 and the LUMO distribution is
similar to that of compound 1. The HOMO and LUMO levels and
energy gaps are ꢁ5.708 eV, ꢁ1.970 eV and 3.738 eV, respectively.
Compared to that of compound 1, the HOMO level of compound 2 is
reduced but the LUMO level is increased, therefore, the energy gap
is increased. However, the energy gap of compound 2 is still smaller
than that of pyrene. Consequently, the wavelength of compound 2
is red-shifted than pyrene but degree of red-shifted wavelength is
smaller than compound 1. The HOMO and LUMO of compound 3
are all distributed on the pyrene ring suggesting that its spectral
properties are completely determined by pyrene ring and substit-
uent group at 2-position has a negligible effect on spectral prop-
erties. These results well explain the similar spectral properties of
compound 3 and pyrene.
which
is
decreased
compared
to
that
of
pyrene
(ꢁ5.338 eV, ꢁ1.497 eV and 3.841 eV). These results are consistent
with red-shifted spectral of compound 1 compared to that of pyr-
ene. The range of HOMO distribution of compound 2 is reduced
Fig. 5. Molecular orbital energy levels of the HOMO and LUMO of 1, 2 and 3 calculated by using the B3LYP/6-31G basis set.

H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
7
3.7. Electrochemical studies
These results indicate that p-methylphenylthio substituent in 1-
and 4-position significantly increases the ФF of pyrene-based
derivate in solid state and decreases the ФF in solution. However,
p-methylphenylthio substituent in 2-position almost does not
The electrochemical properties of compounds 1, 2 and 3 were
investigated using cyclic voltammetry (CV) method in anhydrous
DCM with the concentration of 1.0ⅹ10ꢁ3 M. Cyclic voltammetry
curves are illustrated in Fig. 6 and the obtained data are summa-
rized in Table 2. On the basis of the onset potentials of oxidation
(Eox onset), the HOMO energy levels of compounds 1, 2 and 3 were
calculated with the values of ꢁ5.09, ꢁ5.11 and ꢁ5.13 eV, respec-
tively, using the equation HOMO ¼ -eEonset ꢁ4.37 eV. These results
are slightly higher than that of pyrene (ꢁ4.92 eV). The band gaps of
compounds 1, 2 and 3 were derived from the absorption edge in the
absorption spectra with the values of 3.25, 3.46 and 3.56 eV
respectively. Although the calculated values are slightly higher than
the values estimated by CV, the trend is consistent with the order of
maximum absorption wavelength. The LUMO values of compounds
1, 2 and 3 can be estimated by subtraction of the optical band gap
energies from the HOMO energy levels (LUMO ¼ HOMO e Eg), the
obtained value is ꢁ1.84 for 1, -1.65 and ꢁ2.68 and ꢁ1.57 eV,
respectively.
contribute to
substituent in 1- and 4-position keeps a high ФF
compared to that of pyrene, but this substituent in 2-position
significantly quenches the ФF F, 22%). Besides, compounds 1, 2
Ф
F in solid state. In film state, the p-methylphenylthio
(Ф
F, 41% and 44%)
(Ф
and 3 exhibit typical AIE properties. The theoretical calculation
values agree well with the experimental data. These results will
provide important guidance to relative studies and contribute to
design and synthesis of functionalized pyrene-based derivatives.
Acknowledgements
This work was supported by the China Postdoctoral Science
Foundation (2019M652000 and 2019M652022) and the Priority
Academic Program Development of Jiangsu Higher Education
Institutions.
Appendix A. Supplementary data
4. Conclusions
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.molstruc.2019.07.021.
In conclusion, we have designed and synthesized a new series of
pyrene-based sulfides 1, 2 and 3. In solution, compounds 1 and 2 (1-
and 4-substituted pyrene-based sulfides) exhibit very weak emis-
References
sion (ФF, 7% and 3%) and relatively large red-shift in absorption and
PL spectra compared to that of pyrene. However, compound 3 (2-
substituted pyrene-based sulfide) exhibits very strong blue emis-
[1] T.M. Figueira-Duarte, K. Mullen, Pyrene-based materials for organic elec-
tronics, Chem. Rev. 111 (2011) 7260e7314.
[2] A.G. Crawford, Z. Liu, I.A. Mkhalid, M.H. Thibault, N. Schwarz, G. Alcaraz,
A. Steffen, J.C. Collings, A.S. Batsanov, J.A. Howard, T.B. Marder, Synthesis of 2-
and 2,7-functionalized pyrene derivatives: an application of selective C-H
borylation, Chem. Eur J. 18 (2012) 5022e5035.
sion (
Ф
F, 29%) in solution. In solid state, compounds 1 and 2 (ФF
,
75% and 79%) exhibit stronger emission than compound 3 (
ФF, 69%).
[3] A.G. Crawford, A.D. Dwyer, Z. Liu, A. Steffen, A. Beeby, L.O. Palsson, D.J. Tozer,
T.B. Marder, Experimental and theoretical studies of the photophysical
properties of 2- and 2,7-functionalized pyrene derivatives, J. Am. Chem. Soc.
133 (2011) 13349e13362.
[4] Y. Niko, S. Kawauchi, S. Otsu, K. Tokumaru, G. Konishi, Fluorescence
enhancement of pyrene chromophores induced by alkyl groups through
sigma-pi conjugation: systematic synthesis of primary, secondary, and tertiary
alkylated pyrenes at the 1, 3, 6, and 8 positions and their photophysical
properties, J. Org. Chem. 78 (2013) 3196e3207.
[5] H.M. Kim, Y.O. Lee, C.S. Lim, J.S. Kim, B.R. Cho, Two-photon absorption prop-
erties of alkynyl-conjugated pyrene derivatives, J. Org. Chem. 73 (2008)
5127e5130.
[6] J.A. Degheili, R.M. Moustafa, D. Patra, B.R. Kaafarani, Effect of chain length on
the photophysical properties of pyrene-based molecules substituted with
extended chains, J. Phys. Chem. A 113 (2009) 1244e1249.
[7] S. More, R. Bhosale, S. Choudhary, A. Mateo-Alonso, Versatile 2, 7-substituted
pyrene synthons for the synthesis of pyrene-fused azaacenes, Org. Lett. 14
(2012) 4170e4173.
[8] L. Zoephel, V. Enkelmann, K. Muellen, Tuning the HOMO-LUMO gap of pyrene
effectively via donor-acceptor substitution: positions 4, 5 versus 9, 10, Org.
Lett. 15 (2013) 804e807.
[9] S. Zhang, X. Qiao, Y. Chen, Y. Wang, R.M. Edkins, Z. Liu, H. Li, Q. Fang, Synthesis,
structure, and opto-electronic properties of regioisomeric pyrene-thienoa-
cenes, Org. Lett. 16 (2014) 342e345.
[10] R. Zhang, H. Sun, Y. Zhao, X.X. Tang, Z.H. Ni, Dipolar 1,3,6,8-tetrasubstituted
pyrene-based blue emitters containing electro-transporting benzimidazole
moieties: syntheses, structures, optical properties, electrochemistry and
electroluminescence, Dyes Pigments 152 (2018) 1e13.
Fig. 6. Plot of cyclic voltammetry for compounds 1e3 and pyrene.
[11] S. Kawata, Y.-J. Pu, C. Ohashi, K.-i. Nakayama, Z. Hong, J. Kido, A morphology
control layer of a pyrene dimer enhances the efficiency in small molecule
organic photovoltaic cells, J. Mater. Chem. C 2 (2014) 501e509.
[12] Y. Wang, H. Wang, Y. Liu, C.A. Di, Y. Sun, W. Wu, G. Yu, D. Zhang, D. Zhu, 1-
Imino nitroxide pyrene for high performance organic field-effect transistors
with low operating voltage, J. Am. Chem. Soc. 128 (2006) 13058e13059.
[13] R. Zhang, T.F. Zhang, L. Xu, F.F. Han, Y. Zhao, Z.H. Ni, A new series of short
axially symmetrically and asymmetrically 1,3,6,8-tetrasubstituted pyrenes
with two types of substituents: syntheses, structures, photophysical proper-
ties and electroluminescence, J. Mol. Struct. 1127 (2017) 237e246.
[14] X. Zhan, J. Zhang, S. Tang, Y. Lin, M. Zhao, J. Yang, H.L. Zhang, Q. Peng, G. Yu,
Z. Li, Pyrene fused perylene diimides: synthesis, characterization and appli-
cations in organic field-effect transistors and optical limiting with high per-
formance, Chem. Commun. 51 (2015) 7156e7159.
Table 2
Electrochemical properties of compounds 1, 2 and 3.
Compounds Eox onset(V) HOMO (eV)
LUMO (eV)
Exptl Calc.
ꢁ1.84 ꢁ2.070 3.25
Eg (eV)
Exptla Calcb
Exptl Calc.
1
2
3
Py
0.72
0.74
0.76
0.55
ꢁ5.09
3.605
3.738
3.787
3.841
ꢁ5.11 ꢁ5.708 ꢁ1.65 ꢁ1.970 3.46
ꢁ5.13 ꢁ5.621 ꢁ1.57 ꢁ1.834 3.56
ꢁ4.92 ꢁ5.338 ꢁ1.27 ꢁ1.497 3.65
a
Experimental value.
Calculated value.
b
[15] J. Nie, Y. Liu, J. Niu, Z.H. Ni, W.Y. Lin, A new pyrene-based fluorescent probe

8
H. Sun et al. / Journal of Molecular Structure 1197 (2019) 1e8
with large Stokes shift for detecting hydrogen peroxide in aqueous solution
and living cells, J. Photochem. Photobiol. A Chem. 348 (2017) 1e7.
[16] L.N. Wang, M.M. Yu, Z.T. Liu, W.Y. Zhao, Z.X. Li, Z.H. Ni, C.C. Li, L.H. Wei,
3395e3405.
[25] J. Hu, D. Zhang, F.W. Harris, Ruthenium (III) chloride catalyzed oxidation of
pyrene and 2, 7-disubstitued pyrenes: an efficient, one-step synthesis of
pyrene-4, 5-diones and pyrene-4, 5, 9, 10-tetraones, J. Org. Chem. 70 (2005)
707e708.
[26] F.G. Oberender, J.A. Dixon, Osmium and ruthenium tetroxide-catalyzed oxi-
dations of pyrene, J. Org. Chem. 24 (1959) 1226e1229.
A
visible light excitable “oneoff” and “greenered” fluorescent chemo-
dosimeter for Ni2þ/Pb2þ, New J. Chem. 36 (2012) 2176e2179.
[17] G. Xu, H. Wu, X. Liu, R. Feng, Z. Liu, A simple pyrene-pyridinium-based fluo-
rescent probe for colorimetric and ratiometric sensing of sulfite, Dyes Pig-
ments 120 (2015) 322e327.
[27] E.R. Young, R.L. Funk, A practical synthesis of pyrene-4, 5-dione, J. Org. Chem.
63 (1998) 9995e9996.
[18] H. Shimizu, K. Fujimoto, M. Furusyo, H. Maeda, Y. Nanai, K. Mizuno, M. Inouye,
Highly emissive
p
-conjugated alkynylpyrene oligomers: their synthesis and
[28] K. Medjanik, D. Chercka, P. Nagel, M. Merz, S. Schuppler, M. Baumgarten,
K. Mullen, S.A. Nepijko, H.J. Elmers, G. Schonhense, H.O. Jeschke, R. Valenti,
Orbital-resolved partial charge transfer from the methoxy groups of
substituted pyrenes in complexes with tetracyanoquinodimethane–a NEXAFS
study, J. Am. Chem. Soc. 134 (2012) 4694e4699.
[29] Y. Hong, J.W., Lam, B.Z. Tang, Aggregation-induced emission, Chem. Soc. Rev.
40 (2011) 5361e5388.
[30] J. Liu, J.W.Y. Lam, B.Z. Tang, Aggregation-induced emission of silole molecules
and polymers: fundamental and applications, J. Inorg. Organomet. Polym.
Mater. 19 (2009) 249e285.
[31] T.S. Reddy, S.H. Shin, M.S. Choi, Effects of molecular flexibility/rigidity on the
AIE/AIEE properties of aromatic thiolsesubstituted 1, 8enaphthalimides, Dyes
Pigments 160 (2019) 483e491.
[32] M. Shyamal, S. Maity, P. Mazumdar, G.P. Sahoo, R. Maity, A. Misra, Synthesis of
an efficient Pyrene based AIE active functional material for selective sensing of
2, 4, 6-trinitrophenol, J. Photochem. Photobiol. A Chem. 342 (2017) 1e14.
[33] J. Li, C. Yang, C. Huang, Y. Wan, W.Y. Lai, Tuning circularly polarized lumi-
nescence of an AIE-active pyrene luminogen from fluidic solution to solid thin
film, Tetrahedron Lett. 57 (2016) 1256e1260.
photophysical properties, J. Org. Chem. 72 (2007) 1530e1533.
[19] S. Yamaguchi, I. Yoshikawa, T. Mutai, K. Araki, Solid-state luminescence of
tetraphenylpyrene derivatives: mechano/vapochromic luminescence of
1,3,6,8-tetra(40-carboxyphenyl)pyrene, J. Mater. Chem. 22 (2012) 20065.
[20] T.M. Figueira-Duarte, S.C. Simon, M. Wagner, S.I. Druzhinin, K.A. Zachariasse,
K. Mullen, Polypyrene dendrimers, Angew. Chem. Int. Ed. 47 (2008)
10175e10178.
[21] C.E. Godinez, G. Zepeda, M.A. Garcia-Garibay, Molecular compasses and gy-
roscopes. II. Synthesis and characterization of molecular rotors with axially
substituted bis [2-(9-triptycyl) ethynyl] arenes, J. Am. Chem. Soc. 124 (2002)
4701e4707.
[22] S. Wan, J. Guo, J. Kim, H. Ihee, D. Jiang, A belt-shaped, blue luminescent, and
semiconducting covalent organic framework, Angew. Chem. Int. Ed. 47 (2008)
8826e8830.
[23] D. Rausch, C. Lambert, Synthesis and spectroscopic properties of a hexapyr-
enylbenzene derivative, Org. Lett. 8 (2006) 5037e5040.
[24] Y. Qiao, J. Zhang, W. Xu, D. Zhu, Novel 2,7-substituted pyrene derivatives:
syntheses, solid-state structures, and properties, Tetrahedron 67 (2011)