A new series of two-photon blue/violet fluorescent trans-alkenes: Green synthesis and optical properties

Article abstract of DOI:10.1016/j.saa.2015.10.034

A new series of trans-alkenes (3a-3e) containing different electron-donating groups were synthesized by the solvent-free Horner-Wadsworth-Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their UV-visible absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in different solvents. Experimental results show different trends in linear and nonlinear optical properties with different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.

Full text of DOI:10.1016/j.saa.2015.10.034

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
journal homepage: www.elsevier.com/locate/saa
A new series of two-photon blue/violet fluorescent trans-alkenes: Green
synthesis and optical properties
a
a,
a
b
b
Jiu-Qiang Huang , Zhi-Bin Cai ⁎, Fan Jin , Sheng-Li Li , Yu-Peng Tian
a
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, PR China
Department of Chemistry, Anhui Province Key Laboratory of Functional Inorganic Materials, Anhui University, Hefei 230039, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 June 2015
Received in revised form 19 August 2015
Accepted 22 October 2015
Available online 24 October 2015
A new series of trans-alkenes (3a–3e) containing different electron-donating groups were synthesized by the
solvent-free Horner–Wadsworth–Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic
resonance, mass spectrometry and elemental analysis. Their UV–visible absorption, one-photon excited fluores-
cence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in differ-
ent solvents. Experimental results show different trends in linear and nonlinear optical properties with
different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue
up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Trans-alkene
Solvent-free
Optical property
Synthesis
1
. Introduction
In recent years, two-photon excitation (TPE) has drawn great atten-
prepared using solvents. The solvent-free HWE reaction [23–26] has
the advantages of simplicity, safety, environment-friendliness, and in-
expensiveness, so it is of great importance in green synthesis.
In this paper, we conveniently synthesized a new series of trans-
alkenes (3a–3e) by the solvent-free HWE reaction. Their linear
photophysical characteristics were performed in different organic sol-
vents and two-photon absorption (TPA) properties were investigated
by means of two-photon fluorescence spectroscopy. The structure–
property relationships were systematically discussed.
tion because of its potential applications such as two-photon up-
converted lasing [1,2], three-dimensional fluorescence imaging [3–6],
optical data storage [7–9], microfabrication [10,11], optical power limit-
ing [12], bioimaging [13–15], photodynamic therapy [16,17], and so on.
The majority of these applications are based on the fluorescence proper-
ties of the two-photon excited molecules. However, the wavelengths of
two-photon excited fluorescence (TPEF) are mostly in the green-to-red
(
500–700 nm) light region. The molecules emitting blue/violet TPEF are
2. Experimental
fairly lacking, which restricts some specific applications. For example,
this kind of molecule can be used to reduce the autofluorescence back-
ground from green and red proteins [18]. So the study of new high-
performance organic blue/violet TPEF emitters is extremely necessary.
In our design for blue/violet TPEF molecules, three strategies have
been considered. Firstly, trans-styrene has been adopted as the π-
bridge because trans-styrene is a good electron channel and efficient
fluorophore. Secondly, in order to achieve short wavelength emission,
the target compounds have the relatively short conjugation, which
can suppress redshift of the emission wavelength. Thirdly, the efficient
electron donors have been introduced. The electron-rich arylamine
and heterocycle have been chosen as the electron donors, which can en-
hance intramolecular charge transfer, and finally enlarge the polariz-
ability of the molecules.
2.1. Materials and instruments
1a [27], 1b [28], 1c [29], and 1d [30] were synthesized according to
the literature procedures. Other materials were commercially available
and were used without further purification.
Melting points were measured on an X-4 micromelting point appa-
1
ratus without correction. H NMR spectra were collected on a Bruker
AVANCE III 500 apparatus, with TMS as internal standard and DMSO-
d or CDCl as solvent. FT-IR spectra were recorded on a Thermo Nicolet
6 3
6700 spectrometer using KBr pellets. Mass spectra were taken on a
Therm LCQ TM Deca XP plus ion trap mass spectrometry instrument. El-
emental analyses were conducted on a Thermo Finnigan Flash EA 1112
apparatus.
Horner–Wadsworth–Emmons (HWE) reaction [19–22] is a com-
monly used method to synthesize trans-alkenes, most of which were
The linear absorption spectra were measured on a Shimadzu UV-
2550 UV–visible spectrophotometer. The one-photon excited fluores-
cence (OPEF) spectra measurements were performed using a RF-
5301PC fluorescence spectrophotometer with the maximum absorption
⁎
Corresponding author.
http://dx.doi.org/10.1016/j.saa.2015.10.034
386-1425/© 2015 Elsevier B.V. All rights reserved.
1

J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
165
Scheme 1. Synthesis of the target trans-alkenes (3a–3e).
wavelengths as the excitation wavelengths. The fluorescence quantum
5.73(d, J = 17.6 Hz, 1 H), 5.22(d, J = 10.8 Hz, 1 H), 3.92–4.11(m, 4 H),
3.14(s, 1 H), 3.09(s, 1 H), 1.23(t, J = 7.2 Hz, 6 H).
−
1
yields were determined using quinine sulfate in 0.5 mol L
sulfuric
acid as the standard. The TPEF spectra were measured using a femtosec-
ond laser pulse and Ti: sapphire system (680–1080 nm, 80 MHz, 140 fs)
as the light source.
2.3. Synthesis of 4-[(1E)-2-(4-ethenylphenyl)ethenyl]-N,N-
diphenylbenzenamine (3a)
2
.2. Synthesis of [(4-ethenylphenyl)methyl] phosphonic acid diethyl ester
In a grinding jar, 4-(diphenylamino)benzaldehyde (0.015 mol,
4.10 g) were combined with [(4-ethenylphenyl)methyl] phosphonic
acid diethyl ester (0.01 mol, 2.53 g), t-BuOK (0.02 mol, 2.76 g) and the
7 mm stainless steel balls. The grinding jar was placed in a planetary
ball-mill and stirred at 550 runs per minute during 2 h at room temper-
ature. Then 60 mL DCM was added in the jar and the mixture was
washed twice with 200 mL water. The organic layer was dried over
(2)
4
-(Chloromethyl)styrene (3.02 g, 0.02 mol) and triethyl phosphite
(
6.65 g, 0.04 mol) were added to a dry four-necked flask with a reflux
condenser. The mixture was stirred at 120 °C for 15 h. The excess of
triethyl phosphite was removed by vacuum distillation. The residue liq-
uid was isolated by column chromatography on silica gel using petro-
4
MgSO , concentrated under vacuum. The residue was isolated by col-
leum ether/ethyl acetate (1:1) as eluent to afford 4.60 g light yellow
umn chromatography on silica gel using petroleum ether/ethyl acetate
1
oil. Yield 90.6%. H NMR (CDCl
3
, 500 MHz) δ: 7.36 (d, J = 8.0 Hz, 2 H),
= 17.6 Hz, J = 10.8 Hz, 1 H),
(10:1) to afford 3.06 g of the titled compound as a light yellow needle
1
7
.25(d, J = 8.0 Hz, 2 H), 6.69(dd, J
1
2
crystal. Yield 80.2%. m.p. 192–193 °C; H NMR (DMSO-d
6
, 500 MHz) δ:

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J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
7
2
1
.55 (d, J = 8.3 Hz, 2 H), 7.52 (d, J = 8.7 Hz, 2 H), 7.47 (d, J = 8.3 Hz,
H), 7.33 (dd, J = 8.3 Hz, J = 7.6 Hz, 4 H), 7.22 (d, J = 16.4 Hz,
H), 7.12 (d, J = 16.4 Hz, 1 H), 7.08 (t, J = 7.4 Hz, 2 H), 7.05 (dd,
= 8.5 Hz, J = 0.9 Hz, 4 H), 6.96 (d, J = 8.6 Hz, 2 H), 6.73 (dd, J
7.7 Hz, J = 11.0 Hz, 1 H), 5.85 (d, J = 17.9 Hz, 1 H), 5.26 (d, J =
1.3 Hz, 1 H), FT-IR (KBr) ν: 3025, 1623, 1588, 1493, 1334, 1282, 839,
Table 1
One-photon absorption and emission properties of 3a–3e.
1
2
absa
10−4
b
OPEFc
d
e
Compound
Solvent
λmax
nm
ε
λmax
nm
Δυ
ϕ
mol L cm−1
−
1
cm
−1
J
1
2
1
=
1
1
7
2
3a
3b
3c
TOL
380
376
379
377
354
349
351
350
350
345
349
346
350
349
348
345
345
343
341
340
8.50
8.64
8.75
8.36
4.02
4.18
4.22
3.53
8.18
8.30
8.42
7.76
2.11
2.47
2.63
2.05
4.34
4.56
4.91
4.19
432
457
470
481
435
459
472
486
424
430
438
441
432
435
437
441
395
398
401
405
3167.6
4713.9
5108.6
5735.2
5260.1
6866.8
7303.6
7995.3
4986.5
5729.7
5822.2
6226.0
5423.3
5664.8
5852.3
6309.8
3669.0
4028.9
4387.9
4720.4
0.50
0.53
0.60
0.39
0.25
0.27
0.32
0.16
0.23
0.26
0.29
0.11
0.07
0.12
0.15
0.03
0.10
0.13
0.17
0.04
THF
DCM
ACN
TOL
THF
DCM
ACN
TOL
THF
DCM
ACN
TOL
THF
DCM
ACN
TOL
−
1
+
53, 696 cm ; ESI-MS m/z: 374.4 [M + H] ; Anal. calcd for C28H23N:
C 90.04, H 6.21, N 3.75; found C 90.16, H 6.23, N 3.79.
2
.4. Synthesis of 1-piperidinyl-4-[(1E)-2-(4-ethenylphenyl)ethenyl]
benzene (3b)
The synthesis of this compound was similar to 3a. Light yellow crys-
talline power. Yield 80.0%. m.p. 177–179 °C; 1H NMR (DMSO-d
00 MHz) δ: 7.46 (d, J = 8.3 Hz, 2 H), 7.43 (d, J = 8.7 Hz, 2 H), 7.40
d, J = 8.3 Hz, 2 H), 7.06 (d, J = 16.3 Hz, 1 H), 6.95 (d, J = 16.2 Hz,
H), 6.93 (d, J = 8.7 Hz, 2 H), 6.73 (dd, J = 17.6 Hz, J = 10.9 Hz,
6
,
3d
5
(
1
1
5
1
1
2
3e
H), 5.76 (d, J = 17.6 Hz, 1 H), 5.23 (d, J = 11.0 Hz, 1 H), 3.23 (t, J =
.3 Hz, 4 H), 1.61–1.64 (m, 6 H); FT-IR (KBr) ν: 3020, 2932, 2852,
623, 1596, 1516, 1238, 1127, 968, 835 cm ; ESI-MS m/z: 290.3
THF
DCM
ACN
−
1
+
a
b
c
Maximum absorption peak position in nm (1 × 10 mol L−1).
−5
[
M + H] ; Anal. calcd for C21H23N: C 87.15, H 8.01, N 4.84; found C
−1
L cm−1
Maximum molar absorption coefficient in mol
.
8
7.21, H 8.12, N 4.92.
Maximum peak position of one-photon excited fluorescence in nm (1 × 10 mol L−1),
−6
excited at the absorption maximum.
d
e
−1
Stokes shift in cm
.
−1
2
.5. Synthesis of 3-[(1E)-2-(4-ethenylphenyl)ethenyl]-9-ethyl-9
Fluorescence quantum yield, determined by using quinine sulfate in 0.5 mol L sul-
H-carbazole (3c)
furic acid as the standard (Φ = 0.546 [31].)
3. Results and discussion
The synthesis of this compound was similar to 3a. Off-white crystal-
line power. Yield 74.4%. m.p. 140–141 °C; H NMR (DMSO-d
1
6
, 500 MHz)
δ: 8.41 (s, 1 H), 8.19 (d, J = 7.7 Hz, 1 H), 7.76 (d, J = 8.5 Hz, 1 H), 7.62 (d,
J = 8.2 Hz, 2 H), 7.61 (d, J = 8.5 Hz, 2 H), 7.50 (d, J = 8.2 Hz, 2 H), 7.48 (t,
J = 7.5 Hz, 1 H), 7.45 (d, J = 16.4 Hz, 1 H), 7.28 (d, J = 16.4 Hz, 1 H), 7.23
3.1. Synthesis and characterization
The new series of target compounds (3a–3e) were synthesized
according to Scheme 1. [(4-Ethenylphenyl)methyl] phosphonic
acid diethyl ester (2) was obtained by Arbuzov reaction of 4-
(chloromethyl)styrene and triethyl phosphite. In our experiments, ball
milling was adopted to do the solvent-free HWE reaction, which can
be achieved conveniently by milling highly π-conjugated aldehyde
(
t, J = 7.4 Hz, 1 H), 6.75 (dd, J
1
2
= 17.6 Hz, J = 10.9 Hz, 1 H), 5.86 (d, J =
1
3
1
7.7 Hz, 1 H), 5.26 (d, J = 11.0 Hz, 1 H), 4.46 (q, 2 H), 1.33 (t, J = 7.1 Hz,
H); FT-IR (KBr) ν: 3019, 2931, 2886, 1624, 1594, 1475, 1336, 1234,
155, 968, 826, 748 cm−1; ESI-MS m/z: 324.3 [M + H] ; Anal. calcd
+
for C24H21N: C 89.12, H 6.54, N 4.33; found C 89.25, H 6.58, N 4.42.
(1a–1e) with 2 using t-BuOK. The phosphonate anions of 2 were strong-
ly nucleophilic and react readily with 1a–1e to form 3a–3e in relatively
1
2.6. Synthesis of 2-[(1E)-2-(4-ethenylphenyl)ethenyl]-1-methyl-1 H-pyrrole
high yields. Their yields are 73.8%–80.2%. In H NMR spectra, the (E)-
(3d)
configurations of the C–C double bonds were certified by the coupling
constants J (H, H) = 16.1–16.4 Hz for the olefinic AB spin systems.
3
The Synthesis of this compound was similar to 3a. Yellow crystalline
1
power. Yield 73.8%. m.p. 74–76 °C; H NMR (DMSO-d
d, J = 8.4 Hz, 2 H), 7.39 (d, J = 8.4 Hz, 2 H), 6.98 (d, J = 16.2 Hz, 1 H),
.86 (d, J = 16.1 Hz, 1 H), 6.72 (dd, J = 17.6 Hz, J = 10.9 Hz, 1 H), 6.66
t, J = 2.0 Hz, 1 H), 6.51 (dd, J = 3.7 Hz, J = 1.4 Hz, 1 H), 6.17 (t, J =
.2 Hz, 1 H), 5.76 (d, J = 17.7 Hz, 1 H), 5.24 (d, J = 11.0 Hz, 1 H); FT-IR
6
, 500 MHz) δ: 7.43
(
6
(
3
1
2
1
2
(
1
KBr) ν: 3026, 2941, 2816, 1698, 1667, 1624, 1598, 1470, 1425, 1300,
−
1
+
060, 958, 821, 712 cm ; ESI-MS m/z: 210.3 [M + H] ; Anal. calcd
15N: C 86.08, H 7.22, N 6.69; found C 86.24, H 7.37, N 6.84.
for C15
H
2
.7. Synthesis of 2-[(1E)-2-(4-ethenylphenyl)ethenyl]thiophene (3e)
The Synthesis of this compound was similar to 3a. Off-white flaky
1
crystal. Yield 76.6%. m.p. 129–131 °C; H NMR (DMSO-d
6
, 500 MHz) δ:
7
1
5
1
5
2
2
7
.45 (d, J = 8.4 Hz, 2 H), 7.41 (d, J = 8.4 Hz, 2 H), 7.25 (d, J = 16.1 Hz,
H), 7.21 (d, J = 5.1 Hz, 1 H), 7.09 (d, J = 3.4 Hz, 1 H), 7.02 (dd, J
.1 Hz, J = 3.5 Hz, 1 H), 6.93 (d, J = 16.1 Hz, 1 H), 6.73 (dd, J
7.6 Hz, J = 10.9 Hz, 1 H),5.79 (dd, J = 17.5 Hz, J
.27 (dd, J = 10.8 Hz, J = 0.6 Hz, 1 H); FT-IR (KBr) ν: 3067, 2972,
848, 1622, 1505, 1406, 1228, 1178, 960, 832, 691 cm ; ESI-MS m/z:
1
=
2
1
=
2
1
2
= 0.6 Hz, 1 H),
1
2
−
1
+
13.1 [M + H] ; Anal. calcd for C14
9.38, H 5.82.
H12S: C 79.20, H 5.70; found C
Fig. 1. One-photon absorption spectra of 3a–3e in DCM with a concentration of
1 × 10− mol L
5
−1
.

J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
167
3
.2. One-photon absorption and emission properties
The linear photophysical data of 3a–3e are listed in Table 1. The one-
photon absorption (OPA) and OPEF were measured in four different sol-
−
5
−1
vents. The OPA data were got at a concentration of 1 × 10 mol L
,
while the OPEF were measured at a concentration of 1 × 10 mol L−1.
−6
Fig. 2 (continued).
The OPA and OPEF spectra of 3a–3e are shown in Figs. 1 and 2. The fluo-
rescence photos of 3a–3e in DCM are shown in Fig. 3.
As shown in Fig. 1, 3a–3e all exhibit two major absorption bands, the
⁎
latter of which is localized in styrene π–π transition. As shown in
abs
Table 1, in various solvents, the OPA peak positions (λmax ) of 3a–3e
are 376–380 nm, 349–354 nm, 345–350 nm, 345–350 nm, and 340–
3
45 nm, respectively, which indicate the solvent polarity has little
effect on the OPA wavelength. Compared among 3a–3e, 3a has the
abs
largest λmax
due to the increase of its π-conjugated system. And the
molar absorption coefficients (ε) change following the order:
3a ≈ 3c N 3b ≈ 3e N 3d.
As shown in Fig. 3, all the five target compounds emit blue/violet
fluorescence excited under their maximum absorption wavelengths.
OPEF
The OPEF peak positions (λmax
4
) of 3a–3e in DCM are 470 nm,
OPEF
72 nm, 438 nm, 437 nm, and 401 nm, respectively. The λmax
show an increasing tendency as the solvent polarity increases following
the order: Toluene (TOL) b Tetrahydrofuran (THF) b Dichloromethane
(
DCM) b Acetonitrile (ACN). The Stokes shifts (Δν) also show monoton-
ically increasing tendency with the increase of solvent polarity. These
can be explained by the stronger solute/solvent interaction at the excit-
ed state comparing with that at the ground state, which indicates that
the polarity of the excited state increases. The energy level can be
lowered greatly by increasing dipole-dipole interaction between the
solute and solvent. On the other hand, the quantum yields (Φ) change
Fig. 2. One-photon excited fluorescence spectra of 3a–3e in various solvents with a con-
centration of 1 × 10− mol L
6
−1
.

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J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
following the order: 3a N 3b ≈ 3c N 3d ≈ 3e, which shows that
triphenylamine is an efficient fluorophore. The Φ of 3a–3e do not vary
significantly in low polarity (TOL) and medium polarity (THF, DCM),
while decreasing in highly polar ACN. This result indicates that 3a–3e
have strong intramolecular charge transfer.
Table 2
Two-photon absorption and emission properties of 3a–3e.
TPEFa
b
Compound
Solvent
λmax
σmax
3
3
3
a
b
c
DCM
THF
DCM
THF
DCM
THF
DCM
THF
496
481
502
491
463
459
461
458
425
420
218
112
144
69
42
18
3
.3. Two-photon absorption properties
The nonlinear photophysical data of 3a–3e are listed in Table 2,
16
3d
which were measured in DCM and THF at a concentration of
0.8
9
0.1
−
3
−1
1
× 10
mol L . The TPA cross-section (σ) spectra of 3a–3e are
3e
DCM
THF
shown in Fig. 4. The representative TPEF spectra of 3a are shown in
Fig. 5.
a
Maximum peak position of two-photon excited fluorescence in nm (1 × 10−3 mol L−1),
pumped by femtosecond laser pulses.
The σ is an important parameter in evaluating TPA properties of ma-
terials. There are many methods to get it such as nonlinear transmission
method, Z-scan technology, two-photon induced fluorescence method
and so on. In this paper, the two-photon induced fluorescence method
is used to get σ of the target compounds and fluorescein in
b
Two-photon absorption cross-section in GM (1GM = 1 × 10−50 cm4 s photon−1).
induced emission measurements, we used dilute solutions (1 ×
−
6
−1
10
mol L ), thus the reabsorption of the fluorescence within the
−
1
−3
−1
0
.1 mol L sodium hydroxide (c = 1 × 10 mol L ) is selected as
compounds is negligible. In the case of two-photon excitation, concen-
−
3
−1
standard solution (σ = 36 GM [32]). The σ was obtained referring to
the following equation [33]:
trated solutions (1 × 10 mol L ) were used. Since the laser beam
can pass through the whole solution without linear depletion, the fluo-
rescence emission is not only from the surface layer, but also from inside
the solution. As a result, the reabsorption of the shorter wavelength
Fs ϕ nr cr
r
σs ¼
σr:
ð1Þ
Fr ϕ ns cs
s
In this equation, s and r stand for the sample and the reference com-
pound, n for the refractive index, c for the concentration, F for the inte-
gral fluorescence intensity, and Φ for the quantum yield.
As shown in Table 2 and Fig. 4, all the five trans-alkenes display TPA
activities in the range of 700–900 nm. The largest values σ of 3a–3e
appear at 780 nm, 740 nm, 740 nm, 700 nm, and 700 nm, respectively.
And they all have larger σ in DCM than in THF. Obviously, the polarity of
the solvent has significant influence on the σ. It is also can be explained
by the stronger solute/solvent interaction in DCM. The σ values of 3a–3e
show the sequence of σ3a N σ3b N σ3c N σ3d N σ3e in DCM, showing the
same sequence in THF. It is exactly consistent with the electron-
donating abilities of their electron donors except 3a. 3a has the largest
σ value of 218 GM compared with the other four target compounds
(3b–3e), though its electron-donating ability is less than that of 3b. It
may be explained that triphenylamine contains the nitrogen center
linked to three electron-rich phenyl groups in a propeller-like geometry,
which may be delocalized onto the conjugated system of the molecule
and increase intramolecular charge-transfer.
As shown in Tables 1 and 2, the TPEF wavelengths of 3a–3e are evi-
dently red-shifted by 22–32 nm by comparing with those of OPEF,
which can be explained by the reabsorption effect. For one-photon
Fig. 4. (a) Two-photon absorption cross-sections of 3a–3e in DCM in 700–900 nm regions.
(b) Two-photon absorption cross-section of 3a in DCM and THF.
Fig. 3. The fluorescence photos of 3a–3e in DCM.

J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
169
Fig. 5. (a) Two-photon excited fluorescence spectra of 3a in DCM pumped by femtosecond laser pulses at 0.5 w at different excitation wavelength. (b) Two-photon excited fluorescence
spectra of 3a in DCM under different pumped powers at 780 nm, inset contains the logarithmic plots of the fluorescence integral (Iout) of 3a versus different excitation intensities (Iin).
fluorescence by the concentrated solutions can no longer be neglected.
The short wavelength side of the two-photon fluorescence was
reabsorbed by the solution and red shifts of the fluorescence spectra
were readily observed [34].
Fig. 5b shows TPEF spectra of 3a under different pumped intensities
at 780 nm, and the inset shows logarithmic plots of the fluorescence
integral versus pumped powers with a slope of 1.98 when the input
laser power is increasing, suggesting a two-photon excitation mecha-
nism. As no linear absorption was observed in the range from 450 nm
to 1000 nm, so the emission excited by 780 nm laser wavelength can
be attributed to the TPEF mechanism.
have promising applications for probing or tagging some specific cellu-
lar components.
Acknowledgements
We are grateful to the Natural Science Foundation of Zhejiang Prov-
ince, China (Grant No. LY15B030006) and the National Natural Science
Foundation of China (Grant No. 21103151) for the financial support.
References
4
. Conclusion
[1] Q. Chen, C.F. Zhang, B. Jiang, X.Y. Wang, Y.J. Liu, Y. Cao, M. Xiao, Opt. Express 20
(2012) 9135–9143.
[
2] F. Todescato, I. Fortunati, S. Gardin, E. Garbin, E. Collini, R. Bozio, J.J. Jasieniak, G. Della
Giustina, G. Brusatin, S. Toffanin, R. Signorini, Adv. Funct. Mater. 22 (2012) 337–344.
In conclusion, a new series of trans-alkenes containing different
electron donors were synthesized by the solvent-free HWE reaction.
Their linear and nonlinear optical properties were systematically inves-
tigated in various solvents. The results show that the donor units and
the solvent polarity can result in different trends in optical properties.
[3] C. Kanony, B. Akerman, E. Tuite, J. Am. Chem. Soc. 123 (2001) 7985–7995.
[
[
[
[
4] R. Dahl, S. Larsen, T.L. Dohlmann, K. Qvortrup, J.W. Helge, F. Dela, C. Prats, Acta Phys-
iol. 213 (2015) 145–155.
5] T. Lukes, P. Krizek, Z. Svindrych, J. Benda, M. Ovesny, K. Fliegel, M. Klima, G.M.
Hagen, Opt. Express 22 (2014) 29805–29817.
6] P. Verboven, E. Herremans, L. Helfen, Q.T. Ho, M. Abera, T. Baumbach, M. Wevers,
B.M. Nicolai, Plant J. 81 (2015) 169–182.
7] K.D. Belfield, Y. Liu, R.A. Negres, M. Fan, G. Pan, D.J. Hagan, F.E. Hernandez, Chem.
Mater. 14 (2002) 3663–3667.
3
a with triphenylamine donor exhibits the best optical properties. It
emits strong blue up-converted fluorescence, and the two-photon ab-
sorption cross-section can be as large as 218 GM in DCM, which may

170
J.-Q. Huang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 154 (2016) 164–170
[
[
8] A.S. Dvornikov, E.P. Walker, P.M. Rentzepis, J. Phys. Chem.
3633–13644.
9] K. Iliopoulos, O. Krupka, D. Gindre, M. Salle, J. Am. Chem. Soc. 132 (2010)
4343–14345.
A
113 (2009)
[20] S. Sano, T. Matsumoto, M. Nakao, Tetrahedron Lett. 55 (2014) 4480–4483.
[21] Q.Q. Zhao, J. Sun, B.J. Liu, J.X. He, Dyes Pigments 99 (2013) 339–347.
[22] M. Shimizu, M. Tateishi, I. Mizota, Chem. Lett. 43 (2014) 1752–1754.
[23] K. Ando, K. Yamada, Tetrahedron Lett. 51 (2010) 3297–3299.
[24] K. Ando, K. Yamada, Green Chem. 13 (2011) 1143–1146.
[25] A. Ranoux, L. Lemiegre, M. Benoit, J.P. Guegan, T. Benvegnu, Eur. J. Org. Chem. (2010)
1314–1323.
1
1
[
[
10] K.S. Lee, R.H. Kim, D.Y. Yang, S.H. Park, Prog. Polym. Sci. 33 (2008) 631–681.
11] B. Tan, K. Venkatakrishnan, A. Makaronets, Des. Monomers Polym. 16 (2013)
145–150.
[
[
[
[
12] P. Chantharasupawong, R. Philip, N.T. Narayanan, P.M. Sudeep, A. Mathkar, P.M.
Ajayan, J. Thomas, J. Phys. Chem. C 116 (2012) 25955–25961.
13] F. Jin, D.L. Xu, H.Z. Zhu, Y. Yan, J. Zheng, J. Zhang, H.P. Zhou, J.Y. Wu, Y.P. Tian, Dyes
Pigments 109 (2014) 42–53.
[26] H. Valizadeh, A. Shockravi, Synth. Commun. 39 (2009) 4341–4349.
[27] H. Tian, X. Yang, R. Chen, R. Zhang, A. Hagfeldt, L. Sun, J. Phys. Chem. C 112 (2008)
11023–11033.
[28] P. Mateus, R. Delgado, P. Groves, S.R. Campos, A.n.M. Baptista, P. Brandão, V. Félix, J.
14] W. Li, M.D. Yang, L.P. Wang, W.J. Zhu, L.N. Ye, J.Y. Wu, Y.P. Tian, H.P. Zhou, Dyes Pig-
Org. Chem. 77 (2012) 6816–6824.
ments 107 (2014) 133–139.
15] Y.B. Zhang, F.J. Huo, C.X. Yin, Y.K. Yue, J.S. Hao, J.B. Chao, D.S. Liu, Sensors Actuators B
Chem. 207 (2015) 59–65.
[29] G. Bai, J. Li, D. Li, C. Dong, X. Han, P. Lin, Dyes Pigments 75 (2007) 93–98.
[30] W.E. Noland, N.P. Lanzatella, L. Venkatraman, N.F. Anderson, G.C. Gullickson, J.
Heterocycl. Chem. 46 (2009) 1154–1176.
[
[
16] T. Luo, B.C. Wilson, Q.B. Lu, J. Photochem. Photobiol. B 132 (2014) 102–110.
17] O. Mongin, M. Sankar, M. Charlot, Y. Mir, M. Blanchard-Desce, Tetrahedron Lett. 54
[31] J. Demas, G.A. Crosby, J. Phys. Chem. C 75 (1971) 991–1024.
[32] M.A. Albota, C. Xu, W.W. Webb, Appl. Opt. 37 (1998) 7352.
[33] C. Xu, W.W. Webb, J. Opt. Soc. Am. B 13 (1996) 481–491.
[34] F. Xu, Z. Wang, Q. Gong, Opt. Mater. 29 (2007) 723–727.
(2013) 6474–6478.
[
[
18] J. Bhawalkar, A. Shih, S. Pan, W. Liou, J. Swiatkiewicz, B. Reinhardt, P. Prasad, P.
Cheng, Bioimaging 4 (1996) 168–178.
19] M. Chalal, D. Vervandier-Fasseur, P. Meunier, H. Cattey, J.C. Hierso, Tetrahedron 68
(2012) 3899–3907.