Synthesis, optical characterization, and solvatochromism study of new two-photon absorption compounds

Article abstract of DOI:10.1016/j.tet.2016.03.030

The new donor-π-acceptor/acceptor-π-acceptor compounds (FQQ, KZQ, JYQ, and LVQ) were facilely synthesized and characterized by infrared, proton 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. The experiment results indicate that all these compounds exhibit relatively strong up-converted fluorescence and obvious solvatochromic effects. KZQ shows the largest σ value of 707 GM in THF upon 830 nm excitation. Its excellent optical properties provide a promising alternative as a polarity-sensitive two-photon fluorescent probe. Aided with the quantum chemical density functional theory calculations, the relationships between the structures and the properties were studied.

Full text of DOI:10.1016/j.tet.2016.03.030

Accepted Manuscript
Synthesis, optical characterization, and solvatochromism study of new two-photon
absorption compounds
Yan-Tao Zhou, Zhi-Bin Cai, Yu-Lu Pan, Li Bai, Guo-Chuang Zheng, Sheng -Li Li, Yu-
Peng Tian
PII:
S0040-4020(16)30163-6
10.1016/j.tet.2016.03.030
TET 27570
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 22 January 2016
Revised Date: 2 March 2016
Accepted Date: 8 March 2016
Please cite this article as: Zhou Y-T, Cai Z-B, Pan Y-L, Bai L, Zheng G-C, Li S-L, Tian Y-P, Synthesis,
optical characterization, and solvatochromism study of new two-photon absorption compounds,
Tetrahedron (2016), doi: 10.1016/j.tet.2016.03.030.
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ACCEPTED MANUSCRIPT
Graphical abstract
The new donor-π-acceptor / acceptor-π-acceptor compounds exhibit strong
up-converted fluorescence, obvious solvatochromic effects, and the largest σ value in
various solvents, which provide a promising alternative as a polarity-sensitive
two-photon fluorescent probe.

ACCEPTED MANUSCRIPT
Synthesis, optical characterization, and solvatochromism study of
new two-photon absorption compounds
a
Yan-Tao Zhou , Zhi-Bin Cai a,*, Yu-Lu Pan a, Li Bai a, Guo-Chuang Zheng a, Sheng
-Li Li b and Yu-Peng Tian b
a
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou
310014, PR China
b
Department of Chemistry, Anhui Province Key Laboratory of Functional Inorganic
Materials, Anhui University, Hefei 230039, PR China
Abstract
The new donor-π-acceptor / acceptor-π-acceptor compounds (FQQ, KZQ, JYQ,
and LVQ) were facilely synthesized and characterized by infrared, proton 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. The
experiment results indicate that all these compounds exhibit relatively strong
up-converted fluorescence and obvious solvatochromic effects. KZQ shows the
largest σ value of 707 GM in THF upon 830 nm excitation. Its excellent optical
properties provide a promising alternative as a polarity-sensitive two-photon
fluorescent probe. Aided with the quantum chemical density functional theory
calculations, the relationships between the structures and the properties were studied.
*Corresponding author. Tel. : +86 571 88320891.
E-mail address: caizbmail@126.com (Z.-B. Cai).
1

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Keywords: Optical property; Solvatochromism; Two-photon absorption compound;
Synthesis
1. Introduction
Two-photon absorption (TPA) is a third-order nonlinear optical process involving
simultaneous absorption of two photons to reach the excited state. TPA materials are
of interest in current research due to their potential applications in photodynamic
therapy1, scanning excitation microscopy2, up-converted lasing and three-dimensional
optical data storage3, etc. Especially, bioimaging techniques based on TPA methods
are superior to those based on one-photon absorption4 owing to their in-depth
penetration, less cell damage, and higher spatial resolution5. Therefore, to fully realize
these applications, great effort has been focused on the design and synthesis of
organic materials with high TPA cross-section (σ)6. Generally, there are several
factors on increasing σ values: (1) the efficiency of intramolecular charge transfer
(ICT)7; (2) the strength of the donor and acceptor8; (3) the character of the conjugated
bridge9; (4) the coplanarity of the molecule structure10; (5) the alternation of the
conjugation length11; (6) the dimensionality of the charge transfer network12. Up till
now, many organic materials have been synthesized with high σ as the following
structure types: dipolar D-π-A (A = acceptor, D = donor, and π = conjugated bridge)13,
quadrupolar D-π-D / A-π-A and D-π-A-π-D / A-π-D-π-A14, octupoles15, and TPA
oligomers / polymers16. Among them, organic molecules with D-π-A system are the
most extensively studied because their spectra and energy gaps can be tuned by
controlling the ICT from the conjugated electron donors to the electron acceptors,
which plays an important role in the determination of the photophysical properties.
However, as far as the practical applications be concerned, it is still a challenge by
now that how to design and facilely synthesize dipolar molecules with the low
molecular weight, the small molecular volume, and the large σ.
It is well-accepted that 9-ethyl-9H-carbazole and 10-ethyl-10H-phenothiazine, as a
class of large electron-rich heterocyclic structure, have strong electron-donating
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ability17, and methoxy is also a kind of effective electron-donating group18. Though
formyl has a relatively strong electron-withdrawing ability, a few examples that
formyl was studied as a type of electron acceptor in TPA materials have been reported.
We had previously synthesized a series of A-D-A molecules with a formyl moiety,
and it is proved that formyl can act as a good electron acceptor19. Herein, based on the
above considerations, we strategically designed three new D-π-A compounds (FQQ,
KZQ, and JYQ) and one new A-π-A (LVQ) counterpart, whose chemical structures
were illustrated in Scheme 1. Four new target compounds were facilely synthesized
by the following three-step reactions: (1) Arbuzov reaction; (2) solvent-free
Horner-Wadsworth-Emmons (HWE) reaction; (3) Mizoroki-Heck reaction. They
1
were characterized by IR, H NMR, MS, and elemental analysis. Their linear
photophysical characteristics were performed in different organic solvents and the
TPA properties were investigated by means of the two-photon fluorescence
spectroscopy. To well understand the underlying mechanisms of TPA properties, the
theoretical calculations were employed to investigate the structure-property
relationships of the target molecules by density functional theory (DFT) calculation
approaches20. Furthermore, four target compounds showed obvious solvatochromic
effects21 and large Stokes shifts upon increasing the polarity of solvents mainly due to
ICT. The optical characterization and investigation of TPA properties show that the
target compounds could provide promising alternatives as polarity-sensitive
two-photon fluorescent probes.
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Scheme 1. Molecular structures of the target compounds (FQQ, KZQ, JYQ, and
LVQ).
2. Results and discussion
2.1. Synthesis and characterization
The synthesis of the target compounds (FQQ, KZQ, JYQ, and LVQ) is relatively
straightforward as outlined in Scheme 2. The 10-ethyl-10H-phenothiazine-3-carboxal-
dehyde23 (1a) and 9-ethyl-9H-carbazole-3-carboxaldehyde24 (1b) were synthesized
efficiently by Vilsmeier reaction according to the references. Meanwhile, we used
[(4-ethenylphenyl)methyl]phosphonic acid diethyl ester as the starting material to
realize the synthesis of the phosphonate compound (LSZ) according to the literature25,
which was then reacted with the aromatic aldehydes (1a-1d) by the solvent-free HWE
reaction to form the trans-alkenes (2a-2d). Among these important intermediates, 2a
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was synthesized and reported for the first time by our research group. The solvent-free
HWE reaction is simple, safe, and environmentally friendly. And its additional
advantage of high E-selectivity make this method a candidate for not only laboratory
use but also widespread industrial applications. By following Mizoroki-Heck reaction,
1
the target compounds were accomplished in 61%-73% yields. In H NMR spectra,
one can see the chemical shifts (δ) of 2a-2d at 6.73-6.75 (J1 = 17.6-17.7 Hz, J2 =
10.9-11.0 Hz, 1H) , 5.84-5.87 (J = 17.6-17.7Hz, 1H), and 5.26-5.28 (J = 11.0-11.1 Hz,
1H) show the existence of the terminal carbon-carbon double bond. The
E-configurations of the carbon-carbon double bonds are certified by the coupling
constants J = 16.3-16.5 Hz for the olefinic AB spin systems. Meanwhile, the δ values
at 9.99-10.0 (s, 1H) indicate the existence of the formyl group. In the FT-IR spectra of
the target compounds, the characteristic absorption peaks appearing at 1693-1700
cm-1 are the stretch vibration absorption of the carbonyl group, and the characteristic
absorption peaks appearing at 1589-1597 cm-1 and 957-968 cm-1 illustrate the stretch
and bending vibration of the E-configurations of the carbon-carbon double bonds,
respectively.
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Scheme 1. Synthesis of the target compounds (FQQ, KZQ, JYQ, and LVQ).
2.2. One-photon absorption and fluorescence properties
The one-photon absorption and fluorescence properties of the target compounds in
four solvents of different polarity are listed in Table 1. To further investigate the
spectra relationships of the compounds, the corresponding one-photon absorption and
fluorescence spectra of the target compounds are depicted in Fig. 1, Fig. 2, and Fig. 3.
Table 1. Linear and nonlinear optical properties of the target compounds (FQQ,
KZQ, JYQ, and LVQ).
c
f
b
a
e
g
OPEF
λmax
TPEF
λmax
d
10−4ε
abs
max
λ
φ
σ
∆ν
(cm-1)
(nm)
(mol-1 L cm-1) (nm)
(GM)
(nm)
Compound Solvent
TOL
THF
405
407
2.15
4.80
3.58
510
520
527
5083
5339
5962
0.28
0.18
0.12
561
572
118
145
FQQ
CH2Cl2 401
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CH3CN 399
3.38
4.53
4.76
4.89
4.58
10.67
6.22
10.58
9.49
7.53
13.59
11.73
9.37
542
475
528
548
563
467
487
508
530
446
448
454
464
6612
3823
6123
6752
7619
4628
5851
6562
7728
4245
4560
4855
5257
0.09
0.88
0.48
0.29
0.08
0.97
0.51
0.43
0.33
0.68
0.63
0.65
0.60
TOL
THF
402
399
520
563
448
707
KZQ
JYQ
LVQ
CH2Cl2 400
CH3CN 394
TOL
THF
384
379
505
525
138
286
CH2Cl2 381
CH3CN 376
TOL
THF
374
372
489
493
55
85
CH2Cl2 372
CH3CN 373
a Maximum linear absorption wavelength, c = 1×10-5 mol L-1.
b Maximum molar absorption coefficient.
c Maximum one-photon excited fluorescence wavelength, c = 1×10-6 mol L-1.
d Stokes shift.
e
Fluorescence quantum yield, measured by using quinine sulfate in 0.5 mol L-1
sulfuric acid as the standard (
Φ
= 0.54626).
f Maximum two-photon excited fluorescence wavelength, c = 1×10-3 mol L-1.
g Two-photon absorption cross-section, 1 GM = 1×10-50 cm4 s photon-1.
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FQQ
KZQ
8

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JYQ
LVQ
Fig. 1. One-photon absorption spectra of the target compounds (FQQ, KZQ, JYQ,
and LVQ) in different solvents with a concentration of 1×10-5 mol L-1.
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Fig. 2. One-photon absorption spectra of the target compounds (FQQ, KZQ, JYQ,
and LVQ) in THF with a concentration of 1×10-5 mol L-1.
FQQ
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KZQ
JYQ
11

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LVQ
Fig. 3. One-photon fluorescence spectra of the target compounds (FQQ, KZQ, JYQ,
and LVQ) in different solvents with a concentration of 1×10-6 mol L-1.
As shown in Fig. 1, all of the compounds show two absorption bands in the range
of 290-360 nm and 372-407 nm. The low-energy band originates from the ICT
transition, while the high-energy band is assigned to the π-π* transition of the
phenothiazine ring (FQQ), the carbazole ring (KZQ), and the benzene ring (JYQ,
LVQ). With increasing solvent polarity from TOL to CH3CN, the absorption peak
positions ( abs ) of FQQ, KZQ, JYQ, and LVQ only have a little variation (< 8 nm).
λmax
abs
It can be seen from Fig. 2 that the
exhibits an obvious red shift from LVQ to
λ
max
FQQ (LVQ < JYQ < KZQ < FQQ). The reason for this characteristic is that
phenothiazine is a kind of nitrogen and sulfur-containing heterocyclic unit, and
carbazole is a kind of nitrogen-containing heterocyclic unit, which extend the
conjugation length of the system and lead to lower electronic transition energy
between the ground state and the excited state. Note that the maximum molar
absorptivities (εmax) of LVQ and JYQ are much larger than those of FQQ and KZQ,
which implies that the light absorbing ability of the compounds with heterocyclic
donors is relatively weak.
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As shown in Fig. 3 and listed in table 1, all the four compounds emit one-photon
excited fluorescence (OPEF) between 380 and 680 nm under the excitation at their
maximum absorption wavelengths. The compounds exhibit solvatochromic behavior
in different polar solvents. Upon increasing solvent polarity, the OPEF maxima
(
OPEF ) of FQQ, KZQ, JYQ, and LVQ show obvious bathochromic shifts. For
λmax
example, the OPEF of KZQ shows a red-shift by 88 nm that exhibits a greater
λmax
sensitivity to each solvent than the other compounds (FQQ, JYQ, and LVQ). The
Stokes shifts (∆ν) also show a tendency to monotonically increase with increasing the
polarity of solvents from TOL to CH3CN. These observations can be due to the
following reasons: the molecular polarity of the excited state is larger than that of the
ground state, as the enhanced dipole-dipole interactions caused by increasing the
polarity of the solutes and / or solvents will lead to a more significant energy level
decrease for the excited state. The fluorescence quantum yields (Φ) of the four
compounds in different solvents were determined by using quinine sulfate in 0.5 mol
L-1 sulfuric acid as the standard. In low-polarity TOL, the Φ show a sequence of JYQ
(0.97) > KZQ (0.88) > LVQ (0.68) > FQQ (0.28). Upon increasing solvent polarity,
the Φ of LVQ changes slightly, while the Φ of FQQ, KZQ, and JYQ decrease
consistently and significantly. Especially, the Φ of FQQ and KZQ are almost
quenched in highly polar CH3CN. The above results indicate that FQQ, KZQ, and
JYQ have much stronger ICT than LVQ.
The large values of ∆ν are observed for the target compounds in all four solvents
due to the strong solvent-solute dipole-dipole interactions, a manifestation of the large
dipole moments and orientation polarizability. As described above, the fluorescence
spectra show the large ∆ν which depend on the solvent polarity. The significant
solvatochromism is observed, suggesting a large change in the dipole moment
between the ground and the excited state. The Lippert-Mataga equation is the most
widely used equation to evaluate the dipole moment changes of the materials with
photoexcitation:27
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2∆f
∆ν =
∆f =
(
ꢀe
-
ꢀ
g) 2 + const
(1)
4
πε0hca3
ε
−1
n2 −1
−
(2)
2ε
+1 2n2 +1
in which ∆ν
=
νabs
-
νem stands for the Stokes shift,
ν
abs and
νem are the wave numbers
of the absorption and the emission, respectively. h is Planck’s constant, c is the speed
of light in vacuum, a is the Onsager radius. ꢀe and ꢀg are the permanent dipole
moments of the excited state and the ground state, respectively.
of the vacuum, is the static dielectric constant of the solvent, and n is the refractive
index, f is the orientation polarizability.
ε0 is the permittivity
ε
∆
Fig. 4. Lippert-Mataga plots of the target compounds (KZQ, FQQ, JYQ, and LVQ).
The plots of ∆ν as a function of
Lippert-Mataga equation, the slope of the best-fit line is related to the dipole moment
change between the ground state and the excited state (ꢀe g). The slopes of the four
lines are different: 4696, 13012, 9982, and 3201 cm-1 for FQQ
KZQ JYQ, and
LVQ, respectively. KZQ and JYQ have much larger slopes than FQQ and LVQ
∆f are shown in Fig. 4. According to the
-
ꢀ
,
,
,
which implies larger dipole moment changes for KZQ and JYQ with
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photoexcitation.28 The large ꢀe
- ꢀg values are beneficial to improving their TPA
properties.
2.3. Two-photon properties
The two-photon excited fluorescence (TPEF) spectra of the target compounds in
THF and TOL were recorded at different excitation wavelengths (690-950 nm) with a
pulse duration of 140 fs at 500 mW. The corresponding two-photon properties are
listed in Table 1. The representative TPEF spectra of KZQ in THF are shown in Fig.
5 and Fig. 6.
KZQ
Fig. 5. Two-photon excited fluorescence spectra of KZQ in THF (c = 1×
10-3 mol
L-1) pumped by femtosecond laser pulses at 500 mW under different excitation
wavelengths.
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(a)
KZQ
(b)
KZQ
Fig. 6. (a) Two-photon excited fluorescence spectra of KZQ in THF (c = 1
×
10-3
mol L-1) at 830 nm under different input powers. (b) Logarithmic plot of the output
fluorescence integral (Iout) of KZQ versus the input laser powers (Iin) .
The TPEF spectra of KZQ in THF pumped by femtosecond laser pulses at 500
mW under different excitation wavelengths are presented in Fig. 5. One can see that
the TPEF intensity is the largest under 830 nm excitation. The optimal excitation
wavelengths of the other compounds (FQQ, JYQ, and LVQ) are 830 nm, 790 nm,
and 790 nm, respectively. Fig. 6a and Fig. 6b show the fluorescence intensities of
KZQ under different pump powers and the logarithmic plot of the output
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fluorescence integral versus the input powers. As no linear absorption is observed in
the range from 500 nm to 1000 nm, the emission excited at 830 nm laser wavelength
should be attributed to the TPEF mechanism. The logarithmic plot has a slope of 2.01
as the input laser power is increased, confirming a two-photon excitation mechanism.
The other compounds (FQQ, JYQ, and LVQ) are also proved to have the same
excitation mechanism.
One can see from Table 1 that the TPEF maximum ( TPEF ) of KZQ in THF is 563
λmax
OPEF
max
nm, which is evidently red-shifted by 35 nm by comparing with its
(528 nm).
λ
The other compounds (FQQ, JYQ, and LVQ) also show 38-51 nm and 35-52 nm red
shifts in TOL and THF, respectively. This is attributed to the reabsorption effect28,
which can lead to the energy loss and the red-shift of emission wavelength.
The
presented in Fig. 7 and listed in Table 1. They all have larger
Obviously, the polarity of solvents has significantly influence on the
be explained by the stronger solute-solvent interaction in THF. The largest
σ
of the target compounds (FQQ
,
KZQ
,
JYQ, and LVQ) were calculated and
in THF than in TOL.
. It is also can
values
σ
σ
σ
in THF (TOL) are 145 GM (118 GM) for FQQ, 707 GM (448 GM) for KZQ, 286
GM (138 GM) for JYQ, and 85 GM (55 GM) for LVQ, respectively, which follow
the order: KZQ
> JYQ > FQQ > LVQ. To better understand the relationship
between the of the target compounds and the distribution of electron densities over
σ
the molecules, the density functional theory (DFT) calculations were carried out
using the Gaussian 09 program.30 The nonlocal density function of B3LYP with
6-31G basis sets was used for the calculations. The frontier molecular orbitals of the
target compounds were shown in Fig. 8. The HOMO-LUMO energy gaps (∆E) were
calculated and listed in Table 2. Upon excitation, the electron transition from the
HOMO to the LUMO is accompanied by the charge transfer from the terminal
phenothiazine ring, carbazole ring, and benzene ring to the formyl acceptor. The
of FQQ KZQ JYQ, and LVQ are 2.65, 2.89, 3.00 and 3.16 eV, respectively. The
value shows positive correlation with the ꢀe g, but negative correlation with the
∆
E
,
,
σ
-
ꢀ
∆E.
One can see that LVQ with A-π-A molecule structure has the smallest ꢀe - ꢀg (3201
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cm-1) and the largest
resulting in the smallest
among the target compounds, the ꢀe
∆
E (3.16 eV). Thus, the charge transfer degree is the weakest,
σ. Although the
∆E of FQQ is 2.65 eV, which is the smallest
-
ꢀg of FQQ is much smaller than those of KZQ
and JYQ. Furthermore, FQQ has a non-planar molecule structure (Fig. 9), which
may weaken the conjugation extension of the whole molecule and reduce the
intramolecular charge transfer. Based on the above factors, the
smaller than those of KZQ and JYQ. The of KZQ is nearly 2.5 times as large as
that of JYQ. This can be explained by the fact that not only the E of KZQ is
smaller than that of JYQ, but the ꢀe ꢀg of KZQ is larger than that of JYQ. The
intramolecule charges are almost completely transferred from the carbazole donor to
σ value of FQQ is
σ
∆
-
the formyl acceptor. Therefore, KZQ shows the largest
σ value.
(a)
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(b)
Fig. 7. Two-photon absorption cross-sections of the target compounds (KZQ
JYQ, and LVQ) in THF (a) and TOL (b) in the 690-950 nm regions.
, FQQ,
Compound
HOMO
LOMO
FQQ
KZQ
JYQ
LVQ
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Fig. 8. Frontier molecular orbitals of the target compounds (FQQ, KZQ, JYQ, and
LVQ).
Table 2. Calculated HOMO, LOMO energy and HOMO-LOMO energy gaps of the
target compounds (FQQ
,
KZQ
,
JYQ, and LVQ).
LOMO
(eV)
Compound
HOMO
HOMO-LOMO energy gaps
(eV)
(eV)
2.65
2.89
3.00
3.16
-4.86
-5.03
-5.19
-5.52
-2.21
FQQ
KZQ
JYQ
LVQ
-2.14
-2.18
-2.36
Compound
Top view
Front view
FQQ
KZQ
JYQ
LVQ
Fig. 9. Optimized geometries of the target compounds (FQQ, KZQ, JYQ, and
LVQ).
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3. Conclusion
In summary, the new donor-
KZQ JYQ, and LVQ) were facilely synthesized by Mizoroki-Heck reaction. The
important intermediates (2a 2d) were synthesized by the solvent-free HWE reaction
π-acceptor / acceptor-π-acceptor compounds (FQQ,
,
-
that is simple, safe, and environmentally friendly. Their linear and nonlinear optical
properties were systematically investigated in various solvents. The results show that
all of the target compounds exhibit obvious solvatochromism and large Stokes shifts.
KZQ exhibits the excellent optical properties and the
σ can be as large as 707 GM in
THF, which provide a promising alternative as a polarity-sensitive two-photon
fluorescent probe.
4. Experimental section
4.1. General experimental methods
122 1a23 1b24 LSZ25 were synthesized according to the literature procedures. DMF
, , ,
and Et3N were pre-dried over anhydrous magnesium sulfate for 20 h and distilled
before use. Other materials were commercially available and were used without
further purification. Unless otherwise specified, all the reactions were performed
1
under nitrogen atmosphere using standard Schlenk techniques. H NMR spectra were
recorded at room temperature on a Bruker AVANCEIII 500 spectrometer in CDCl3 or
DMSO-d6 solvent with tetramethylsilane (TMS) as internal standard. Chemical shifts
were reported in
δ scale and the standard abbreviations s, d, t, and q refer to singlet,
doublet, triplet, and quartet, respectively. Coupling constant (J) values are reported in
Hertz. FT-IR spectra were measured on KBr pellets with a Thermo Nicolet 6700
spectrometer. Mass spectra were taken on a Therm LCQ TM Deca XP plus ion trap
mass spectrometry instrument. Elemental analyses were conducted on a Thermo
Finnigan Flash EA 1112 apparatus. Melting points were measured on an X-4
micromelting point apparatus without correction. Column chromatography was
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carried out by using silica gel (200-300 mesh) as the stationary phase.
4.2. Optical measurements
The one-photon absorption (OPA) spectra were recorded by a Shimadzu UV-2550
UV-visible spectrometer. The OPEF spectra measurements were performed using a
RF-5301PC fluorescence spectrofluorometer with the maximum absorption
wavelengths as the excitation wavelengths. The OPA and OPEF spectra of the target
compounds (FQQ, KZQ, JYQ, and LVQ) were measured in four organic solvents of
different polarities. The OPA data were gotten at a concentration of 1×10-5 mol L-1,
while the OPEF were measured at a concentration of 1×10-6 mol L-1. The quartz
cuvettes used had a 1 cm path. The
mol L-1 H2SO4, = 0.546) as the reference according to the literature method.26 The
was corrected as follows:
Φ was determined by using quinine sulfate (in 0.5
Φ
Φ
Aref n2
A nr2ef
F
Φ
=
Φref
(3)
F
ref
where the ref subscript stands for the reference molecule, A is the absorbance at λexꢀ
n
is the refractive index of the solution, and F is the integrated area under the corrected
emission spectrum.
The
σ of the target compounds (FQQ, KZQ, JYQ, and LVQ) were obtained by the
TPEF method with a femtosecond laser pulse and a Ti : sapphire system (680-1080
nm, 80 MHz, 140 fs) as the light source. The samples were dissolved in THF and
TOL at a concentration of 1×10-3 mol L-1. The intensities of the TPEF spectra of the
reference and the samples were determined at their excitation wavelengths. Thus, the
σ
of the samples were determined by the following equation:
Φref nref cref
F
σ
=
σref
(4)
Φ
n
c F
ref
where the ref subscript stands for the reference molecule,
σ is the TPA cross-section
(here fluorescein in 0.1 mol L-1 sodium hydroxide solution at a concentration of
1×10-3 mol L-1 is used as reference,
σ
= 36 GM)31.
n is the refractive index of the
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solution,
c
is the concentration of the solution,
F
is the integrated area under the
corrected emission spectrum, and
Φ
is the fluorescence quantum yield.
4.3. General procedure for the preparation of 2a-2d
4.3.1 3-[(1E)-2-(4-ethenylphenyl)ethenyl]-10-ethyl-10H-phenothiazine (2a). LSZ
(2.54 g, 10 mmol), t-BuOK (2.24 g, 20 mmol) and 1a (3.83 g, 15 mmol) were placed
in a grinding jar and mixed. Then the grinding jar was placed in a planetary ball-mill
and stirred with a 7 mm stainless steel balls at 550 runs per minute during 2 h at room
temperature. Then 60 mL CH2Cl2 was added in the jar and the mixture was first
washed twice with 200 mL water, then saturated brine and dried over anhydrous
magnesium sulfate. The solvent was removed under reduced pressure and the residue
was purified by silica-gel column chromatography (VPE
:
VEA = 10 : 1) to afford 2a as
1
bright yellow needle crystals. Yield: 71.2% (2.52 g). m.p. 134-135
(DMSO-d6, 500 MHZ) : 7.55 (d, = 8.3 Hz, 2H), 7.47 (d,
J1 = 7.8 Hz, J2 = 1.9 Hz, 1H), 7.40 (s, 1H), 7.21 (t, = 7.8 Hz, 1H), 7.17 (d,
Hz, 1H), 7.15 (dd, J1 = 7.6 Hz, J2 = 1.4 Hz, 1H), 7.13 (d, = 16.5 Hz, 1H), 7.03 (d,
= 7.8 Hz, 1H), 7.01 (d, = 7.8 Hz, 1H), 6.95 (t, = 7.5 Hz, 1H), 6.73 (dd, J1 = 17.6
Hz, J2 = 11.0 Hz, 1H), 5.85 (d, = 17.7 Hz, 1H), 5.26 (d, = 11.1 Hz, 1H), 3.93 (q,
2H), 1.31 (t, = 6.8 Hz, 3H); FT-IR (KBr) : 3048, 2964, 2854, 1598, 1571, 1463,
ꢁ
; H NMR
δ
J
J
= 8.3 Hz, 2H), 7.41 (dd,
= 16.5
J
J
J
J
J
J
J
J
J
ν
1324, 1237, 1134, 964, 828, 745 cm-1; ESI-MS m/z: 356.1 [M+H]+; Anal. calcd for
C24H21NS: C 81.09, H 5.95, N 3.94; found C 81.36, H 6.08, N 4.13.
4.3.2 3-[(1E)-2-(4-ethenylphenyl)ethenyl]-9-ethyl-9H-carbazole (2b). The synthesis
of this compound was similar to 2a. Off-white crystalline powder. Yield: 74.4%
(2.40 g). m.p. 140-141
= 7.7 Hz, 1H), 7.76 (d,
ꢁ
; 1H NMR (DMSO-d6ꢀ500MHz)
δ
: 8.41 (s, 1H), 8.19 (d,
= 8.2 Hz, 2H), 7.61 (d, = 8.5 Hz,
= 16.4 Hz, 1H), 7.28
J
J
= 8.5 Hz, 1H), 7.62 (d,
J
J
2H), 7.50 (d,
(d, = 16.4 Hz, 1H), 7.23 (t,
1H), 5.86 (d, = 17.7 Hz, 1H), 5.26 (d,
7.1 Hz, 3H); FT-IR (KBr)
J
= 8.2 Hz, 2H), 7.48 (t,
J
= 7.5 Hz, 1H), 7.45 (d, J
J
J
= 7.4 Hz, 1H), 6.75 (dd, J1 = 17.6 Hz, J2 = 10.9 Hz,
= 11.0 Hz, 1H), 4.46 (q, 2H), 1.33 (t, J =
J
J
ν
: 3019, 2931, 2886, 1624, 1594, 1475, 1336, 1234, 1155,
23

ACCEPTED MANUSCRIPT
968, 826, 748, 608 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.
4.3.3 1-ethenyl-4-[(1E)-2-(4-methoxyphenyl)ethenyl]benzene (2c). The synthesis of
this compound was similar to 2a. Light yellow flaky crystal. Yield: 80.6% (1.91 g).
m.p. 149-151
= 8.3 Hz, 2H), 7.21 (d,
Hz, 2H), 6.73 (dd, J1 = 17.7 Hz, J2 = 11.0 Hz, 1H), 5.84 (dd, J1 = 17.7 Hz, J2 = 0.6
Hz, 1H), 5.26 (dd, J1 = 11.0 Hz, J2 = 0.6 Hz, 1H), 3.78 (s, 3H); FT-IR (KBr) : 3000,
ꢁ
; 1H NMR (DMSO-d6, 500MHz )
= 16.5 Hz, 1H), 7.09 (d,
δ
: 7.54 (d,
J
= 8.7 Hz, 4H), 7.46 (d,
J
J
J
= 16.5 Hz, 1H), 6.95 (d,
J
= 8.7
ν
2954, 2835, 1601, 1512, 1249, 1176, 1034, 968, 837, 535 cm-1; ESI-MS m/z: 237.3
[M+H]+; Anal. calcd for C17H16O: C 86.40, H 6.82; found C 86.69, H 6.97.
4.3.4 1-chloro-4-[(1E)-2-(4-ethenylphenyl)ethenyl]benzene (2d
this compound was similar to 2a. Light yellow flaky crystal. Yield: 74.8% (1.11 g).
m.p. 164-165 : 7.64 (d, = 8.5 Hz, 2H), 7.60 (d,
; 1H NMR (DMSO-d6, 500MHz)
= 8.3 Hz, 2H), 7.50 (d, = 8.3 Hz, 2H), 7.44 (d, = 8.5 Hz, 2H), 7.29 (s, 2H), 6.75
(dd, J1 = 17.6 Hz, J2 = 11.0 Hz, 1H), 5.87 (dd, J1 = 17.6 Hz, J2 = 0.7 Hz, 1H), 5.28
(dd, J1 = 11.0 Hz, J2 = 0.7 Hz, 1H); FT-IR (KBr) : 3017, 1626, 1509, 1488, 1408,
). The synthesis of
ꢁ
δ
J
J
J
J
ν
1094, 971, 839, 523 cm-1; ESI-MS m/z: 241.2 [M+H]+; Anal. calcd for C16H13Cl: C
79.83, H 5.44; found C 80.06, H 5.62.
4.4. General procedure for the preparation of the target compounds (FQQ, KZQ,
JYQ, and LVQ)
4.4.1
3-[(1E)-2-[4-[(1E)-2-(4-formylphenyl)ethenyl]phenyl]ethenyl]-10-ethyl-10H-phenoth
iazine (FQQ). A mixture of 2a (0.36 g, 1 mmol), 4-bromobenzaldehyde (0.18 g, 1
mmol), Pd(OAc)2 (0.007 g, 0.03 mmol), and tri-
in DMF / Et3N was stirred under N2 at 120
was poured into the ice water and filtered. The residue was purified by silica-gel
column chromatography (VPE VEA = 15 : 1) to afford FQQ as orange-red crystalline
powder. Yield: 60.5% (0.28 g). m.p. 204-206
; 1H NMR (DMSO-d6ꢀ500MHz)
= 8.3 Hz, 2H), 7.67 (d, = 8.3 Hz,
o
-tolylphosphine (0.04 g, 0.13 mmol)
ꢁ
for 20 h. After cooling, the mixture
:
ꢁ
δ:
9.99 (s, 1H), 7.92 (d,
J
= 8.3 Hz, 2H), 7.84 (d,
J
J
24

ACCEPTED MANUSCRIPT
2H), 7.61 (d,
2.0 Hz, 1H), 7.42 (s, 1H), 7.40 (d,
= 7.8 Hz, 1H), 7.17 (d,
7.03 (d, = 7.8 Hz, 1H), 7.02 (d,
2H), 1.32 (t, = 6.9 Hz, 3H); FT-IR (KBr)
J
= 8.3 Hz, 2H), 7.50 (d,
J
= 16.5 Hz, 1H), 7.43 (dd, J1 = 7.8 Hz, J2
=
J
= 16.5 Hz, 1H), 7.23 (d,
J
= 16.4 Hz, 1H), 7.21 (t,
J
J
= 16.4 Hz, 1H), 7.15 (dd, J1 = 7.6 Hz, J2 = 1.4 Hz, 1H),
= 7.8 Hz, 1H), 6.95 (t, = 7.4 Hz, 1H), 3.94 (q,
: 3022, 2924, 2853, 1693, 1594, 1570,
J
J
J
J
ν
1466, 1331, 1248, 1165, 964, 827, 751 cm-1; ESI-MS m/z: 460.4 [M+H]+; Anal. calcd
for C31H25NOS: C 81.01, H 5.48, N 3.05; found C 81.19, H 5.53, N 3.32.
4.4.2
3-[(1E)-2-[4-[(1E)-2-(4-formylphenyl)ethenyl]phenyl]ethenyl]-9-ethyl-9H-carbazole
(
KZQ). The synthesis of this compound was similar to FQQ. Yellow crystalline
powder. Yield : 67.2% (0.29 g). m.p. 222-224
; 1H NMR (DMSO-d6ꢀ500MHz)
10.00 (s, 1H), 8.43 (s, 1H), 8.20 (d, = 7.7 Hz, 1H), 7.93 (d,
= 8.3 Hz, 2H), 7.78 (d, = 8.6 Hz, 1H), 7.70 (d,
Hz, 2H), 7.64 (d, = 8.5 Hz, 1H), 7.63 (d,
7.51 (d, = 16.3 Hz, 1H), 7.48 (t, = 7.5 Hz, 1H), 7.41 (d,
= 16.3 Hz, 1H), 7.24 (t, = 7.4 Hz, 1H), 4.47 (q, 2H), 1.34 (t,
FT-IR (KBr) : 3023, 2930, 2889, 1696, 1623, 1588, 1473, 1335, 1234, 1166, 966,
ꢁ
δꢂ
J
J
= 8.3 Hz, 2H), 7.85 (d,
J
J
J
= 8.5 Hz, 2H), 7.67 (d, J = 8.5
J
J
= 8.2 Hz, 1H), 7.52 (d,
= 16.4 Hz, 1H), 7.31 (d,
= 7.1 Hz, 3H);
J = 16.4 Hz, 1H),
J
J
J
J
J
J
ν
824, 748, 611 cm-1; ESI-MS m/z: 428.3 [M+H]+; Anal. calcd for C31H25NO: C 87.09,
H 5.89, N 3.28; found C 87.24, H 5.92, N 3.47.
4.4.3 4-[(1E)-2-[4-[(1E)-2-(4-methoxyphenyl)ethenyl]phenyl]ethenyl]benzaldehyde
(JYQ). The synthesis of this compound was similar to FQQ. Yellow crystalline
1
powder. Yield: 72.8% (0.25 g). m.p. 254-256
9.99 (s, 1H), 7.92 (d, = 8.2 Hz, 2H), 7.84 (d,
2H), 7.62 (d, = 8.4 Hz, 2H), 7.57 (d, = 8.7 Hz, 2H), 7.50 (d,
7.40 (d, = 16.5 Hz, 1H), 7.28 (d, = 16.4 Hz, 1H), 7.13 (d, = 16.4 Hz, 1H), 6.97
(d, = 8.7 Hz, 2H), 3.79 (s, 3H); FT-IR (KBr) : 3021, 2919, 2848, 1698, 1589, 1512,
ꢁ
; H NMR (DMSO-d6, 500MHz)
δ
:
J
J
= 8.2 Hz, 2H), 7.67 (d,
J = 8.4 Hz,
J
J
J
= 16.5 Hz, 1H),
J
J
J
J
ν
1254, 1171, 1030, 967, 834, 548 cm-1; ESI-MS m/z: 341.2 [M+H]+; Anal. calcd for
C24H20O2: C 84.68, H 5.92; found C 84.75, H 6.02.
4.4.4
4-[(1E)-2-[4-[(1E)-2-(4-chlorophenyl)ethenyl]phenyl]ethenyl]benzaldehyde
(LVQ). The synthesis of this compound was similar to FQQ. Yellow crystalline
25

ACCEPTED MANUSCRIPT
powder. Yield: 70.6% (0.24 g). m.p. 248-250
10.00 (s, 1H), 7.93 (d, = 8.3 Hz, 2H), 7.85 (d,
2H), 7.66 (d, = 8.4 Hz, 2H), 7.65 (d, = 8.5 Hz, 2H), 7.51 (d,
7.46 (d, = 8.5 Hz, 2H), 7.42 (d, = 16.5 Hz, 1H), 7.33 (s, 2H); FT-IR (KBr) ν
ꢁ
; 1H NMR (DMSO-d6ꢀ500MHz)
= 8.3 Hz, 2H), 7.70 (d, = 8.4 Hz,
= 16.5 Hz, 1H),
: 3021,
δꢂ
J
J
J
J
J
J
J
J
1700, 1597, 1488, 1419, 1166, 1091, 968, 832, 545 cm-1; ESI-MS m/z: 345.3 [M+H]+;
Anal. calcd for C23H17ClO: C 80.11, H 4.97; found C 80.36, H 5.08.
Acknowledge
We are grateful to the Natural Science Foundation of Zhejiang province, China
(Grant No. LY15B030006) and the National Natural Science Foundation of China
(Grant No. 21103151) for financial support.
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