Two-photon optical properties of novel branched conjugated derivatives carrying benzophenone moiety with various electron donor-acceptor substituent groups

Article abstract of DOI:10.1007/s10895-010-0728-8

This paper presents a range of novel new branched conjugated dyes containing benzophenone moiety. As compared with those of 4-(p-benzoyl-styrene) yl-4′-(styrene)yl-triphenylamine (C1) and 4-(p-benzoyl-styrene)yl- 4′-3,4,5-trimethoxyl-styrene)yl-triphenylamine (C2), the maximal linear absorption and emission wavelength of 4-(p-benzoyl-styrene)yl-4′- (p′-nitro-styrene)yl-triphenylamine (C3) displays red-shifted remarkably, While the fluorescence quantum yields of C3 are lower than those of C1 and C2 in various solvents. The fluorescence lifetimes of the derivatives were measured, and radiative and non-radiative transition constants of the derivatives were calculated. Two-photon absorption (TPA) optical data of the derivatives were measured by Ti:sapphire femtosecond laser tuning from 720 to 880 nm at intervals of 20 nm. TPA induced fluorescence emission of C3 is red-shifted with respected to that of C1 and C2. TPA cross sections of C3 are larger than those of C1 and C2 in various excited laser frequencies. TPA cross section of C2 and C3 are much larger than those of 3,4,5-(trimethoxylstyrene)yl-triphenylamine (C4) and 4-(p-nitrostyrene)yl-triphenylamine (C5) respectively under various near-IR Ti:sapphire femtosecond laser wavelength. C1 and C2 show similar one- and two- photon optical nature. Geometry optimization with ab initio method confirms that C3 has different electron density distribution, the energy levels in frontier orbitals, the dipole moment changes, the absorption and emission spectroscopy from those of C1 and C2. The cyclic voltammograms of the derivatives were detected in methylene chloride at various scan rates, and the energy of frontier orbials were estimated further from the redox potentials.

Full text of DOI:10.1007/s10895-010-0728-8

J Fluoresc (2011) 21:393–407
DOI 10.1007/s10895-010-0728-8
ORIGINAL PAPER
Two-Photon Optical Properties of Novel Branched
Conjugated Derivatives Carrying Benzophenone Moiety
with Various Electron Donor-Acceptor Substituent Groups
Hongru Li & Long Yang & Jian Liu & Chunfeng Wang &
Fang Gao & Shengtao Zhang
Received: 12 June 2010 /Accepted: 8 September 2010 /Published online: 1 October 2010
#
Springer Science+Business Media, LLC 2010
Abstract This paper presents a range of novel new
branched conjugated dyes containing benzophenone moie-
ty. As compared with those of 4-(p-benzoyl-styrene)yl-4′-
(styrene)yl-triphenylamine (C1) and 4-(p-benzoyl-styrene)
yl-4′-3,4,5-trimethoxyl-styrene)yl-triphenylamine (C2), the
maximal linear absorption and emission wavelength of 4-
(p-benzoyl-styrene)yl-4′-(p′-nitro-styrene)yl-triphenylamine
(C3) displays red-shifted remarkably, While the fluores-
cence quantum yields of C3 are lower than those of C1 and
C2 in various solvents. The fluorescence lifetimes of the
derivatives were measured, and radiative and non-radiative
transition constants of the derivatives were calculated. Two-
photon absorption (TPA) optical data of the derivatives
were measured by Ti:sapphire femtosecond laser tuning
from 720 to 880 nm at intervals of 20 nm. TPA induced
fluorescence emission of C3 is red-shifted with respected to
that of C1 and C2. TPA cross sections of C3 are larger than
those of C1 and C2 in various excited laser frequencies.
TPA cross section of C2 and C3 are much larger than those
of 3,4,5-(trimethoxylstyrene)yl-triphenylamine (C4) and 4-
(p-nitrostyrene)yl-triphenylamine (C5) respectively under
various near-IR Ti:sapphire femtosecond laser wavelength.
C1 and C2 show similar one- and two- photon optical
nature. Geometry optimization with ab initio method
confirms that C3 has different electron density distribution,
the energy levels in frontier orbitals, the dipole moment
changes, the absorption and emission spectroscopy from
those of C1 and C2. The cyclic voltammograms of the
derivatives were detected in methylene chloride at various
scan rates, and the energy of frontier orbials were estimated
further from the redox potentials.
.
.
Keywords Optical properties Conjugated derivative
.
.
Benzophenone moiety Subsitutent group effect
Cyclic voltammograms
Introduction
The application potentials of highly fluorescent and two-
photon absorption dyes in a wide range of fields, such as
two-photon fluorescence sensors [1–3], two-photon fluo-
rescence excitation microscopy [4–7], three-dimensional
optical data storage and microfabrication [8, 9], optical
limiting materials [10, 11], and two-photon photodynamic
therapy [12–14], has stimulated the survey of new
conjugated dyes. In looking for high quality organic dyes
with ideal optical nature, the chemical structures of the dyes
have been shown to a strong relationship with the optical
characteristics. Consequently, the investigation of the
relationship between molecular structure and optical prop-
erties of two-photon dyes receives considerable attention.
Since Marder and coauthors have discovered that some
bis(styryl)benzene derivatives with D-π-D, D-π-A and D-
A-D structural motifs showed excellent two-photon
optical properties [15, 16], a substantial number of
scientists have explored the investigation of such deriva-
tives [17–22], and two factors was found to play crucial
role on the regulation of the optical properties: (1) the
:
:
:
:
:
H. Li (*) L. Yang J. Liu C. Wang F. Gao (*) S. Zhang
College of Chemistry and Chemical Engineering,
Chongqing University,
Chongqing 400044, China
e-mail: hongrli1972@gmail.com
F. Gao
e-mail: fanggao1971@gmail.com

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J Fluoresc (2011) 21:393–407
conjugated length of the molecules, which could be
increased by the insertion of phenylene-vinylene or
phenylene-butadienylene groups. (2) the extent of the
symmetrical charge transfer from the ends of the mole-
cules to the middle, or vice versa. This indicates that the
electron density distribution of frontier orbitals of the
derivatives could be mediated well via the enhancement of
number of branches and the variation of substituent
groups, and thus the optical character could be regulated.
Although some endeavors have been made to investigate the
optical properties of conjugated triphenylamine-cored deriv-
atives containing electron-donating substituent groups [22,
23], while the comparable studies on the optical properties of
such derivatives bearing with various electron-donating and
electron-withdrawing groups are seldomly reported.
Benzophenone is a well-known photoactive compound
and is used extensively in material and biomedical fields
[24, 25]. We could imagine that if a two-photon chromophore
is linked with benzophenone via conjugated double bond, the
new derivatives have great application potentials in various
fields. Furthermore, benzophenone unit could play acceptor-
donor role because of electron-withdrawing effect of carbonyl
group. Herein, we employed various push-pull substituent
groups, including nitro and methoxy groups, to tune the
electron density distribution of the frontier orbitals of
branched conjugated derivatives containing benzophenone
moiety with the purpose to reveal the effect of the substituent
group on one- and two- photon optical properties of the
derivatives. We describe new branched conjugated derivatives
carrying benzophenone part, including 4-(p-benzoylstyrene)
yl-4′-(styrene)yl-triphenylamine (C1), 4-(p-benzoylstyrene)
yl-4′-3,4,5-trimethoxylstyrene)yl-triphenylamine (C2), 4-(p-
benzoyl styrene)yl-4′-(p′-nitrostyrene)yl-triphenylamine (C3)
in this paper. As shown in Fig. 1, the substituent group is in
one branch, and benzophenone part locates at the other
branch. Each branch forms a π conjugated structure and the
overall conjugation of the derivatives are efficiently extend-
ed. So, two-photon absorption nature could be enhanced,
and the effect of substituent group on the optical properties
of such derivatives could be observed. In order to confirm the
effect of benzopheonone branch on the TPA nature of the
derivatives, we further compared TPA properties of C2 and
C3 with those of 3,4,5-trimethoxylstyrene)yl-triphenylamine
(C4), 4-(p-nitrostyrene)yl-triphenylamine (C5) in this man-
uscript. We also determined the fluorescence lifetime and the
cyclic voltammograms of the derivatives, and performed
Fig. 1 Chemical structures of
C1, C2 and C3
O
O
O
N
N
N
H3CO
OCH3
OCH3
NO2
C1
C3
C2
N
N
H3CO
OCH3
OCH3
NO2
C4
C5

J Fluoresc (2011) 21:393–407
395
molecular geometry optimization calculations to understand
deeply the interrelationship between the chemical structures
and the optical characteristics,
the area of the fluorescence bands for the reference and
sample, respectively.
Two-photon excited fluorescence spectra, pumped by Ti:
sapphire femto-second laser (Spectra-Physics Ltd., Tsunami
mode-locked, 80 MHz, <130 f s, average power ≤700 mW)
tuned by step of 20 nm in the range of 700~880 nm, were
recorded on Ocean Optics USB2000 CCD camera with
detecting range of 180~880 nm. Two-photon absorption
(TPA) cross-section (σ) was determined by up-conversion
fluorescence method using 5×10-4 mol/L fluorescein in
0.1 mol/L solution of NaOH as reference sample [31]. The
sample was bubbled with N2 for 15 min to eliminate O2
before the detection. Two-photon absorption crossing
sections of the compounds were determined by the
following equations [31, 32]:
Experimental
Reagents and Materials
Organic solvents were obtained from Chongqing Medi-
cal and Chemical Corporation. Other chemicals and
reagents were purchased from Aldrich unless otherwise
specified. The organic solvents were dried using stan-
dard laboratory techniques according to well-known
methods [26]. The starting materials were further purified
with redistillation or recrystallization before use. C1 to
C3 (Fig. 1) were prepared in our laboratory. Synthesis of
reference TPA compounds C4 and C5 will be reported
elsewhere [27].
sTPE
6F
s ¼
ð2Þ
TPE ccal ncal
S
sTPE ¼ scal
ð3Þ
c
n
Scal
One- and Two-Photon Optical Measurement
and Structural Characterization
Wherein σ is two-photon absorption section, σTPE repre-
sents as two-photon excited crossing section, c is concen-
tration of reference and sample molecules, n shows
refractive index of the solvent, and S is two-photon up-
conversion fluorescence intensity, cal denotes as reference.
In order to eliminate saturation photophysical processes
and ensure the two-photon excited fluorescence intensity
being quadratically dependent on excitation intensity, the
excitation powers in our TPA cross-section measurements
were limited below 130 mW.
The UV/visible absorption spectra (1×10−5 mol/L) were
recorded with a Cintra spectrophotometer. The emission
spectra (1×10−6 mol/L) were checked with Shimadzu RF-
531PC spectrofluorophotonmeter. Rodamin 6G in ethanol
(Φ=0.94, 1×10−6–1×10−5 mol/L [28]) was used as
reference to determine the fluorescence quantum yields of
the compounds herein. To avoid self-quenching of fluores-
cence emission, low concentration of the compounds (1×
10−6 mol/L) was prepared for the survey of fluorescence
quantum yields. The melting point was determined using
a Beijing Fukai melting point apparatus. Nuclear mag-
netic resonance (NMR) spectroscopy was conducted at
room temperature on a Bruker 500 MHz apparatus with
tetramethylsilane (TMS) as an internal standard and
CDCl3 as solvent. Elemental analysis was performed by
a CE440 elemental analysis meter from Exeter Analytical
Inc. FT-IR spectra were recorded on a Nicolet Magna-IR
550-II in the region of 4,000–400 cm−1 using KBr pellets
spectrophotometer.
One-Photon Fluorescence Lifetimes
One-photon fluorescence lifetimes of the derivatives were
determined using a Horiba NAES-1100 time-corrected
single photon counting unit. Lifetimes were calculated
from the decay curves using a least-square method.
Molecular Geometry Optimization
The calculations were performed by means of the Gaussian
03 program package. The geometry optimization of enol
and keto forms for the ground electronic state (S0) was
carried out with HF (Hartree-Fock) method using the
B3LYP method both [33–35], while the CIS (Configuration
Interaction Singles-excitation) has been employed to opti-
mize the geometries of the first singlet excited state (S1) of
the derivatives. Although the CIS method has been shown
to produce basically reliable geometries and force-fields, it
predicts much too high excitation energies (by ca. 1 eV)
[33]. To correct the errors and introduce the dynamic
The fluorescence quantum yields of the compounds in
solvents with different polarities were measured based on
the following equation [29, 30]:
R
n20A0 If ðlf Þdlf
Φf ¼ Φ0f
ð1Þ
R
n2A If0ðlf Þdlf
wherein n0 and n are the refractive indices of the solvents,
A0 and A are the optical densities at excitation wavelength,
Φf and Φf0 are the quantum yields, and the integrals denote

396
J Fluoresc (2011) 21:393–407
electron correlation, TDDFT (time-dependent DFT) was
performed to predict energies at the HF and CIS optimized
geometries for S0 and S1 state respectively, namely
TDDFT//HF or TDDFT//CIS (denoted as single-point
calculation//optimization method) [36], the latter was used
to analyze the fluorescence properties of the derivatives in
the excited state. While the TDDFT//HF and was used for
the calculation of absorption spectra.
Scheme 1 Synthesis of C1, C2
and C3
O
O
O
O
P(OCH2CH3)3
130-1600C
NBS/CCl4
reflux
CH2P(OC2H5)2
Br
Ph3P, toluene
reflux
CH2Ph3PBr
+
Ph3P
Br
CHO
CHO
N
CH2Ph3PBr
N
N
POCl3/DMF
90-1000C
KOBtu, THF, 800C.
C6
CHO
O
O
CH2P(OC2H5)2 CH3ONa, THF.
C1
H3CO
H3CO
H3CO
H3CO
PBr3
H3CO
NaBH4
CH3OH
H3CO
H3CO
CHO
CH2OH
THF/reflux
Br
H3CO
H3CO
130-1600C P(OCH2CH3)3
H3CO
H3CO
H3CO
O
CH2P(OC2H5)2
CHO
CHO
H3CO
H3CO
H3CO
N
O
CH2P(OC2H5)2
N
N
POCl3/DMF
90-1000C
CH3ONa/THF
C7
CHO
H3CO
OCH3
OCH3
O
O
CH2P(OC2H5)2 CH3ONa, THF.
C2

J Fluoresc (2011) 21:393–407
Scheme 1 (continued)
397
CHO
CHO
N
N
N
p-nitro-phenylacetic acid
piperidine, 100-1300C
POCl3/DMF
90-1000C
C8
CHO
NO2
O
O
CH2P(OC2H5)2 CH3ONa, THF.
C3
Electrochemistry
Ar-OCH3). Bromide of 3,4,5-trimethoxyl-benzyl alco-
hol was carried out in THF using phosphorus tribromide
as bromine reagent under reflux. The solvent and excess
phosphorus tribromide were removed in vacuum. The
crude product was washed by distilled water for 5 times.
3, 4, 5-trimethoxyl-benzyl bromide was purified with
recrystallization in benzene/cyclohexane (3:1). 1H NMR
(CDCl3,500 MHz) δ (ppm): 6.35 (s, 2H, Ar-H), 4.10(s,
2H, CH2), 3.77(s, 3H, Ar-OCH3), 3.31(s, 6H, Ar-
OCH3)
Electrochemical measurement was carried out using a
Shanghai Chenhua working station. Two Pt work electrodes
and an Ag/Ag+ reference electrode, namely three electrodes
system, were included in a cell. Typically, a 0.05 mol/L
solution of tetra-n-butylammonium hexaflorophosphate in
methylene chloride containing of dyes was bubbled with
argon for 15 min before the measurement.
Synthesis
5-Trimethoxyl-benzylbromide reacted with triethyl
phosphate under 130–160 °C for 6 h. After excess
triethyl phosphite was removed in vacuum, the crude 3′
4′5-trimethoxyl-4-benzylphosphonate was obtained,
which directly went to the next step without further
purification.
4, 4′-Diformyl-triphenylamine was prepared according to
well-known procedures with modified procedure. The
synthesis of the derivatives was depicted in Scheme 1.
(1) 4-Bromomethylbenzophenone, which was prepared
via bromide of 4-methylbenzophenone with N-
bromosuccinimide [37], reacted with triethyl phos-
phate at 130–160 °C. After removed the excess
triethyl phosphate under vacuum, the crude 4-
phosphonate benzopheonone was obtained, which
was used in the next step without further purification.
(2) Benzylbromidetriphenylphosphine salt was obtained
from benzyl bromide and triphenylphosphine in
toluene under reflux and purified with recrystallization
in anhydrous ethanol.
(3) 3, 4, 5-Trimethoxyl-benzaldehyde was reduced with
sodium borohydride in methyl alcohol. The reaction
was preformed at room temperature under argon for 2 h.
After the reaction, the solvent was removed in vacuum
after the solid materials were filtered. The crude product
was washed by water for five times. 3, 4, 5-Trimethoxyl-
benzyl alcohol was purified with column chromatogra-
phy using benzene as eluent. 1H-NMR(CDCl3,500 MHz)
δ (ppm): 6.42 (s, 2H, Ar-H), 5.10 (s, 1H, Ar-CH2-OH),
4.52 (s, 2H, CH2), 3.95 (s, 3H, Ar-OCH3), 3.83 (s, 6H,
(4) 4-Formyl-4′-(styrene)yl-triphenylamine (C6) was pre-
pared from the reaction of benzylbromidetriphenyl-
phosphine salt and 4,4′-diformyl-triphenylamine using
1.2
triphenylamine
red shift
C1
C2
C3
1.0
0.8
0.6
0.4
0.2
0.0
300
350
400
450
500
550
600
275
Wavelength (nm)
Fig. 2 UV/visible Normalized absorption spectroscopy of C1, C2 and
C3 in benzene (c: 1×10−5 mol/L)

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J Fluoresc (2011) 21:393–407
Table 1 Maximal absorption
wavelength (λa: nm) and the
molar extinction coefficients (ε)
of the derivatives in various
solvents
Compounds
Solvents
Benzene
THF
EtOAc
CH2Cl2
CH3CN
C1
C2
C3
10−5ε
λa,max
10−5ε
λa,max
10−5ε
λa,max
0.397
406
0.437
405
0.463
407
0.438
410
0.394
404
0.440
406
0.498
406
0.512
407
0.494
411
0.522
404
0.416
432
0.484
431
0.504
431
0.462
432
0.516
427
ε mol−1 ·l·cm−1
tert-butoxide as base at room temperature. It was
further purified with column chromophgraphy using
benzene/ethyl acetate (v: v=4:1) mixed solvents as
eluent and used in the next step. Yellow solid, yield:
40%, m.p.: 115–116 °C.1H-NMR(CDCl3, 500 MHz) δ
(ppm): 9.82(s, 1H, Ar-CHO), 7.680–7.707(d, 2H, J=
9.0 Hz, Ar-H), 7.513–7.515(d, 2H, J=7.5 Hz, Ar-H),
7.463–7.489 (d, 2H, J=9.0 Hz, Ar-H), 7.334–7.373(m,
4H, Ar-H), 7.245–7.260(t, 1H, Ar-H), 7.179–7.196(m,
3H, Ar-H), 7.146–7.177(d, 2H, J=8.5 Hz, Ar-CH=
CH), 7.069–7.073(t, 4H, J=4.5 Hz, Ar-H). 13C-NMR
(CDCl3,125 MHz):119.901, 125.267, 126.011,
126.368, 126.494, 127.688, 127.730, 127.744,
128.531, 128.749, 129.438, 129.818, 131.343,
134.042, 137.287, 145.536, 146.052, 153.117,
190.458.
128.427, 128.943, 129.831, 130.163, 130.915,
130.957, 131.720, 131.991, 132.873, 136.734,
137.978, 138.653, 141.804, 147.311, 147.776,
148.119,195.120. Anal. Calcd for C41H31NO, C,
88.94, H, 5.64, N, 2.53, O, 2.89, Found, C, 88.87, H,
5.71, N, 2.59. IR (KBr) cm−1: 3055.1, 3025.8, 2922.8
(=C–H), 1654.2(C=O), 1589.7, 1507.6(Ar-), 842.7
(trans-CH=CH-).
(6) 4-Formyl-4′-(3,4,5-trimethoxystyrene)yl-triphenylamine
(C7) was firstly prepared from the reaction of 4-
benzylphosphonate-(3,4,5-trimethoxybenzene) and
4,4′-diformyl-triphenylamine employing sodium meth-
oxide as base at room temperature. It was purified with
column chromophgraphy using benzene/ethyl acetate
(v: v=45:1) mixed solvents as eluent and used in the
next step. Yellow solid, yield: 50%, m.p.: 61–63 °C.
1HNMR (CDCl3,500 MHz) δ: 9.827 (s, 1H, Ar-CHO),
7.691–7.709 (d, 2H, J=8.5 Hz, Ar-H), 7.457–7.474 (d,
2H, J=8.5 Hz, Ar-H), 7.342–7.374 (t, 2H, J=8.0 Hz,
Ar-H), 7.183–7.204 (m, 3H, Ar-H), 7.136–7.153 (d,
2H, J=8.0 Hz, Ar-CH=CH), 7.060–7.078 (d, 2H, J=
8.5 Hz, Ar-H), 6.986 (s, 2H, Ar-H), 6.735 (s, 2H, Ar-
H), 3.92 (s, 6H, Ar-OCH3), 3.87 (s, 3H, Ar-OCH3).
13C-NMR (CDCl3, 125 MHz): 56.165, 60.990,
(5) 4-(p-Benzoyl-styrene)yl-4′-(styrene)yl-triphenylamine
(C1)
C1 was obtained from the reaction of 4-formyl-
4′-(styrene)yl-triphenylamine (0.80 g, 2.13 mmol)
and 4-benzylphosphonate benzopheonone (1.72 g,
3.20 mmol) in THF using sodium methoxide (0.35 g,
6.40 mmol) as base at room temperature. After the
filtration of solid materials and the evaporation of
THF in vacuum, the reactant mixture was dissolved in
chloroform and washed by water. The organic layer
was dried over magnesium sulphate. After evaporated
in vacuum, C1 was purified with column chromophg-
raphy using benzene/petroether (v: v=5:1) mixed
solvents as eluent. C1, yield: 58%, color, yellow,
1.2
red shift
C1
1.0
0.8
0.6
0.4
0.2
0.0
C2
C3
1
m.p., 126–127 °C, H-NMR (d6-benzene, 500 MHz,
δppm): 7.781–7.829(m, 4H, Ar-H), 7.344–7.361(d,J=
8.5 Hz, 2H, Ar-H), 7.240–7.279(m, 6H, Ar-H), 7.193–
7.223(t, J=7.5 Hz, 2H, Ar-H), 7.138–7.143(d, J=
2.5 Hz, 2H, Ar-CH=CH), 7.121–7.125(d, J=2.0 Hz,
2H, Ar-CH=CH), 7.085–7.110(m, 4H, Ar-H), 7.054–
7.083(d, J=14.5 Hz, 2H, Ar-H), 7.008–7.041(t, J=
8.25 Hz, 2H, Ar-H), 6.989–7.000(t, J=2.75 Hz, 2H,
Ar-H), 6.956(s, 1H, Ar-H), 6.891–6.911(m, 2H, Ar-H).
13C-NMR(d-benzene,125 MHz):123.910, 124.001,
124.662, 125.309, 126.392, 126.419, 126.830,
127.675, 128.071, 128.294, 128.324, 128.398,
425
450
500
550
600
650
700
750
Wavelength (nm)
Fig. 3 Normalized fluorescence spectra of C1, C2 and C3 in benzene
(c: 5×10−5 mol/L)

J Fluoresc (2011) 21:393–407
399
Table 2 Maximal fluorescence
emission wavelength (λe: nm)
and the fluorescence quantum
yields (Φ) of the derivatives
Compounds
Solvents
Benzene
THF
EtOAc
CH2Cl2
CH3CN
C1
C2
C3
φ
0.97
493
0.93
494
0.44
542
0.45
535
0.52
527
0.10
549
0.0034
541
λf,max
φ
0.23
535
0.29
529
0.029
549
0.0024
541
λf,max
φ
0.0055
596
0.0025
590
λf,max
103.576, 119.922, 125.263, 125.981, 126.358, 127.193,
127.622, 128.419, 129.441, 129.805, 131.324, 133.022,
133.876, 145.509, 146.029, 153.099, 153.451, 190.449.
(7) 4-(p-Benzoyl-styrene)yl-4′-3,4,5-trimethoxyl-styrene)
yl-triphenylamine (C2)
(8) The crude 4-formyl-4′- (p-nitrostyrene)yl-triphenyl-
amine (C8) was prepared from the reaction of p-nitro-
phenylacetic acid with 4,4′-diformyl-triphenylamine at
temperature of 100–130 °C (at 100 °C for 2 h, and then
at 130 °C for 1 h till no production of CO2). The
compound was further purified with column chroma-
tography with benzene/ethyl acetate (v: v=45:1) mixed
solvents as eluent. Red solid, yield: 45%, m.p.: 172–
173 °C. 1HNMR(CDCl3, 500 MHz) δ: 9.84 (s, 1H, Ar-
CHO), 8.21 (d, 2H, J=9.0 Hz, Ar-H), 7.72 (d, 2H, J=
9.0 Hz, Ar-H), 7.62 (d, 2H, J=9.0 Hz, Ar-H), 7.50 (d,
2H, J=8.5 Hz, Ar-H), 7.37 (t, 2H, J=6.8 Hz, Ar-H), 7.26
(d, 1H, J=3.0 Hz, Ar-CH=CH), 7.22 (d, 1H, 6.0 Hz,
Ar-CH=CH), 7.17 (t, 5H, J=11.0 Hz, Ar-H), 7.10 (d,
2H, J=8.5 Hz, Ar-H). 13C-NMR(CDCl3,125 MHz):
120.522, 124.198, 125.496, 125.529, 125.738,
126.525, 126.770, 128.314, 128.355, 129.866,
129.924, 131.334, 132.373, 132.410, 143.898,
145.925, 146.676, 146.781, 190.445.
4-Formyl-4′-(3,4,5-trimethoxystyrene)yl-triphenylamine
(1.20 g, 2.58 mmol) reacted with 4-benzylphosphonate
benzopheonone (2.07 g, 3.87 mmol) using sodium
methoxide (0.42 g, 7.74 mmol) as base at room
temperature to prepare C2, which was purified with
column chromophgraphy using benzene/ethyl acetate
(v: v=45:1) mixed solvents as eluent. C2, yield: 65%,
colour, orange, m.p., 80–82 °C. 1H-NMR
(CDCl3,500 MHz, δppm):7.79–7.824(t, J=6.8 Hz,3H,
Ar-H),7.713–7.728(d, J=7.5 Hz,1H, Ar-H), 7.575–
7.591(d, J=8.0 Hz, 2H, Ar-H), 7.458–7.505 (t, J=
6.5 Hz, 2H, Ar-H), 7.360–7.444(m, 4H, Ar-H), 7.271–
7.311(m, 2H, Ar-H),7.146–7.254(t, J=7.8 Hz, 3H, Ar-
H), 7.001–7.130(m, 5H, Ar-H), 6.942–6.968(m, 2H,
Ar-H), 6.718–6.729(d, J=12.6 Hz, 2H, Ar-CH = CH),
6.537–6.648(d, J=12.0 Hz, 2H, Ar-CH = CH), 3.917(s,
6H, OCH3), 3.870(s, 3H, OCH3). 13C-NMR
(CDCl3,125 MHz):56.172, 61.017, 103.438, 123.591,
123.677, 124.242, 125.026, 125.889, 126.032,
127.399, 127.570, 127.927, 127.814, 128.305,
129.475, 129.952, 130.299, 130.832, 131.792,
132.042, 133.328, 135.972, 137.742, 137.947,
141.883, 146.846, 147.134, 147.696, 153.454,
196.101. Anal. Calcd for C44H37NO4, C, 82.09, H,
5.79, N, 2.18, O, 9.94, Found, C, 81.99, H, 5.83, N,
2.11. IR (KBr) cm−1: 3055.1, 3026.8, 2933.2(=C–H),
2833.6(−OCH3), 1652.9(C = O), 1589.3, 1057.9(Ar-),
833.9(trans-CH = CH-).
(9) 4-(p-benzoyl-styrene)yl-4′-(p′-nitro-styrene)yl-triphe-
nylamine (C3)
C3 was obtained from Wittig-Horner reaction of 4-
benzylphosphonate benzopheonone (1.93 g, 3.61 mmol)
and 4-formyl-4′-(p-nitrostyrene)yl-triphenylamine
(1.00 g, 2.40 mmol) in THF (60 ml) using sodium
methoxide (0.39 g, 7.21 mmol) as base at room
temperature. After the filtration of solid materials and
the evaporation of THF in vacuum, the reactant mixture
was dissolved in chloroform and washed by water. The
organic layer was dried over magnesium sulphate. After
the evaporation of solvent in vacuum, C3 was purified
with column chromophgraphy using benzene/petroether
(5:1) mixed solvents as eluent. C3, yield: 57%, color,
Table 3 Fluorescence lifetimes
Compounds
Benzene
EtOAc
radiative transition constants
and non-radiative transition
constants of the derivatives
7 −1
7 −1
7 −1
7 −1
τ/ns
Kr/10
Knr/10
τ/ns
Kr/10
Knr/10
s
s
s
s
C1
C2
C3
2.039
2.184
3.055
47.57
1.470
2.248
1.482
–
23.130
19.56
21.350
47.910
τ: Fluorescence lifetimes (ns).
42.58
14.40
3.210
Kr, radiative transition constants
7
(
−1 ) Knr, non-radiative
10
s
18.330
–
–
7
−1
transition constants (10
)
s

400
J Fluoresc (2011) 21:393–407
7000
6000
5000
4000
3000
2000
1000
0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
red shift
C1
C2
C3
C1
C2
0
0.05
0.1
0.15
0.2
0.25
0.3
Orientation polarizability (Δ f)
400
450
500
550
600
650
700
750
800
Wavelength (nm)
Fig. 4 Relationship between Stokes’ shifts of the derivatives C1 and
C2 and the orientation polarizability (Δƒ) of solvents respectively
Fig. 5 Normalized TPA emission of the derivatives in benzene in
800 nm laser excitation (c: 5×10−4 mol/L)
red, m.p. 91-93 °C, 1H-NMR(CDCl3, 500 MHz, δppm):
8.183–8.200(d, J=8.5 Hz, 2H, Ar-H), 7.795–7.820(t, J=
6.8 Hz, 4H, Ar-H), 7.575–7.589(d, J=7.0 Hz, 5H, Ar-
H), 7.423–7.500(m, 6H, Ar-H), 7.295–7.325(t, J=
7.5 Hz, 2H, Ar-H), 7.216–7.243(t, J=6.75 Hz, 1H, Ar-
CH=CH), 7.184–7.198(d, J=7.0 Hz, 1H, Ar- CH =
CH), 7.147–7.163(d, J=8.0 Hz, 2H, Ar- CH = CH),
7.076–7.111(t, J=8.5 Hz, 6H, Ar-CH),7.006–7.040(d,
J=17.0 Hz, 1H, Ar-H). 13C-NMR(CDCl3, 125 MHz):
123.412, 124.057, 124.153, 124.546, 125.322,
126.025, 126.155, 126.531, 127.840, 128.064,
128.262, 128.320, 129.540, 129.900, 130.421,
130.659, 130.778, 131.527, 132.238, 132.695,
136.002, 137.859, 141.713, 144.462, 146.415,
146.816, 147.283, 148.006, 153.454, 196.000, Anal.
Calcd for C41H30N2O3, C, 82.25, H, 5.05, N, 4.68, O,
8.02, Found, C, 82.17, H, 5.11, N, 4.62. IR (KBr) cm−1:
3055.1, 3028.7, 2922.1(=C–H), 1650.4(C = O), 1628.0
(nitro-), 1583.9, 1507.6(Ar-), 842.0(trans-CH = CH-).
egies. The branch without benzophenone part was attached
to core firstly. For C1, this branch was constructed by
Wittig reaction, and for C2, this branch was synthesized by
Wittig-Horner reaction. While for C3, this branch was built
by heating condensation. Owing to the electron-
withdrawing effect of nitro group and the electron-
donating of N core, the heating condensation reaction are
able to occur between p-nitro-phenylacetic acid and 4,4′-
diformyl-triphenylamine in weak base such as piperidine,
and then C-C double bond is formed as carbon dioxide is
produced. At the end, benzophenone part was coupled as
the other branch of the derivatives by Wittig-Horner
reaction. The target compounds could be purified easily
through column chromophgraphy with the approximate
60% yield.
One-Photon Absorption and Emission Spectroscopy
Figure 2 shows that the derivatives exhibit double absorp-
tion peaks in 275–600 nm in benzene. The first absorption
bands of the derivatives are similar to that of triphenyl-
amine, which means that it may arise from the localized
electronic transition of core. The absorption maxima of C3
are larger than those of C1 and C2, which could be ascribed
to internal charge transfer character of (π, π*) transition and
C3 has a larger intramolecular charge transfer [38]. Table 1
Results and Discussion
Synthesis
As shown in Scheme 1, conjugated double bonds in
derivatives were constructed with different synthetic strat-
Table 4 Two-photon optical data of compounds C1, C2 and C3 in various solvents
Solvents
C1
C2
C3
λmax (TPA)
σ
TPA/GM
λmax (TPA)
σTPA/GM
λmax (TPA)
σTPA/GM
Benzene
495
544
181
147
497
544
241
142
548
640
1,443
1,687
Ethyl acetate
λmax (TPA) nm, the maximal up-conversion fluorescence wavelength; σ two-photon crossing section (GM, 1GM=10−50 cm·s·photo−1
)

J Fluoresc (2011) 21:393–407
401
1600
1400
1200
1000
800
600
400
200
0
presents the linear absorption optical parameters in various
solvents, including the maximal absorption and the molar
extinction coefficients of the derivatives. The data show
that the maximal absorption maxima of C3 are approximate
30 nm red-shifted with respect to those of C1 and C2 in
various solvents. Table 1 also shows that the derivatives
have similar molar extinction coefficients because they
have the same number of branches.
Figure 3 shows that the emission maxima of C3 are red-
shifted with respected to those of C1 and C2 in benzene.
Table 2 lists the maximal emission wavelength and the
fluorescence quantum yields of the derivatives. The
emission of the derivatives exhibits more pronounced to
solvent polarity than absorption, which results from larger
intramolecular charge transfer in the excited states. As
shown in Table 2, the maximal emission wavelength of C3
is 40–60 nm longer than those of C1 and C2, while C1 and
C2 have much larger fluorescence quantum yields than C3,
in various solvents. This could be ascribed to larger internal
charge transfer and larger internal conversion in the excited
state of C3 due to electron-accepting effect of nitro group
and the emission is thus prohibited.
C1
C2
C3
700
720
740
760
780
800
820
840
860
880
900
Wavelength (nm)
Fig. 7 TPA cross sections (σTPA) of C1, C2 and C3 in benzene in
various laser wavelength (c: 5×10−4 mol/L)
C3 has larger non-radiative transition constants and smaller
radiative transition constants, and C1 and C2 have similar
radiative transition constants and non-radiative transition
constants. This could explain why the emission of C3 is
(a)
300
C4
C2
The radiative transition constants and non-radiative
transition constants of the derivatives are calculated
according to the following equations:
250
200
150
100
50
6F
Kr ¼
ð4Þ
t
1 ꢀ 6F
Knr ¼
ð5Þ
t
0
wherein ΦF is fluorescence quantum yield, τ represents as
fluorescence lifetime, Kr is radiative transition constant, Knr
is non-radiative transition constant. Table 3 suggests that
680 700 720 740 760 780 800 820 840 860 880
Wavelength (nm)
(b)
1400
560
550
540
C3
C5
1200
1000
800
600
400
200
C1
C2
C3
530
520
510
500
490
680 700 720 740 760 780 800 820 840 860 880
Wavelength (nm)
680 700 720 740 760 780 800 820 840 860 880 900
Wavelength (nm)
Fig. 8 Comparison of TPA cross sections (σTPA) of C2, C3, C4 and
C5 in benzene in various laser frequencies (c: 5×10−4 mol/L) (a)
HOMO and LUMO orbitals of the ground state (S0) (b) HOMO and
LUMO orbitals of the excited singlet state (S1)
Fig. 6 Maximal TPA emission wavelengths of the derivatives in
benzene excited by different laser wavelength

402
J Fluoresc (2011) 21:393–407
lower than those of C1 and C2, and C1 and C2 have
similar emission nature. We notice that the nonradiative
transition constants of the derivatives are increased remark-
ably in polar solvents, which could be mainly ascribed to
the enhancement of molecular geometric twist and extent of
the internal charge transfer of (π, π*) transition, and
accordingly nonradiative deactivation of the excited state
is increased.
Wherein h represents as Planck’s constant, c is the speed of
light, and Δƒ is called the orientation polarizability. υabs,
υem are the wavenumbers of the absorption and emission
respectively, n is the refractive index, and ε is the relative
low-frequency dielectric constant of the solvents. Lippert
equation describes a solvent effect of the index of refraction
and relative dielicetric constant. Because C3 exhibit too
weak photoluminescence in polar solvents, we did not
perform Lippert equation for it. It is expected that C1 and
C2 have similar dipole moment changes between the
excited state and ground state.
We have employed further Lippert equation to estimate
the dipole moment changes of the derivatives as [39, 40]:
ꢀ
ꢁ
2
Figure 4 plots the Stokes shift as a function of the
solvent orientation polarizability (Δƒ) for the C1 and C2.
The linear correlations between Stokes shift and orienta-
tional polarizability indicates the dipolar solvent effects.
The dipole moment changes between the excited state and
the ground state are calculated from the slopes of lines:
2 me ꢀ mg
hcðnabs ꢀ nemÞ ¼
Δf þ const
ð6Þ
4pe0a3
ꢂ
ꢃ
e ꢀ 1
n2 ꢀ 1
Δf ¼
ꢀ
ð7Þ
2e þ 1 2n2 þ 1
C1 : Y ¼ 8940:6X þ 4141; C2 : Y ¼ 8858:1X þ 4105:1
Fig. 9 Electron density
distributions of frontier orbitals
of C1 C2 and C3 in the S0
and S1
HOMO
LUMO
C1
C2
C3
(a) HOMO and LUMO orbitals of the ground state (S0)

J Fluoresc (2011) 21:393–407
Fig. 9 (continued)
403
HOMO
LUMO
C1
C2
C3
(a) HOMO and LUMO orbitals of the ground state (S0)
The similar slopes from the lines imply similar solvent
effects for the derivatives C1 and C2, and close dipole
moment changes are obtained as 6.00 and 6.48 Derby for
C1 and C2 respectively, which could further account for the
similar linear optical properties for C1 and C2.
C2 in benzene. Seen from Table 4, C3 has not only red-
shifted TPA emission, but a larger cross section. We further
determine TPA emission by tuning laser frequencies from
700 nm to 880 nm at intervals of 20 nm. It is interesting to
observe that the maximal TPA emission of the derivatives is
almost identical to one-photon emission wavelength and is
almost irrelevant to that of excitation laser wavelength
(Fig. 5), indicating the both emission could be from a
similar excited state. TPA cross sections of C3 are larger
than those of C1 and C2 in benzene in various laser
TPA Emission
Figure 5 presents that the maximal TPA emission wave-
length of C3 is red-shifted with respect to those of C1 and
Table 5 Energy gaps of HOMO
and LUMO obtained from theo-
C1
C2
C3
retical calculations in the ground
state (S0) and the excited state
S0
S1
S0
S1
S0
S1
(S1)
EHOMO(ev)
LUMO(ev)
Energy gap (ev)
−4.789
−2.047
2.741
−4.951
−1.751
3.200
−4.767
−2.035
2.732
−4.919
−1.743
3.177
−5.062
−2.446
2.616
−5.177
−2.252
2.925
E

404
J Fluoresc (2011) 21:393–407
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
C1(Absorption)
C2(Absorption)
C3(Absorption)
C1(Fluorescence)
C2(Fluorescence)
C3(Fluorescence)
red shift
red shift
4.0
3.0
0.05 V/S
0.10 V/S
0.15 V/S
0.20 V/S
2.0
1.0
0.0
300
400
500
600
700 750
Wavelength (nm)
-1.0
Fig. 10 Normalized calculated absorption spectra (obtained from
TDDFT//HF), fluorescence spectra (obtained from TDDFT//CIS) of
the derivatives
-2.0
-3.0
C1
-1.75
-1.5
1.75
1.5
1.0
0.5
0.0
-0.5
-1.0
Potential / V
frequencies (Fig. 6), which could be due to larger dipole
moment change of C3 between the excited state and the
ground state. The relationship of TPA intensities of the
derivatives and the pumped powers follows well the square
law in the excitation laser frequency 800 nm. The slopes of
1.98, 1.96 and 2.03 for C1, C2 and C3 respectively
demonstrate that the derivatives have excellent two-photon
absorption nature (Fig. 7).
3.0
2.0
0.05 V/S
0.10 V/S
0.15 V/S
0.20 V/S
1.0
0.0
Prasad and coauthors reported that two-photon cross
section of C3 was much larger than that of C5 [41],
indicating that benzophenone branch makes a contribution
to TPA emission of the derivatives. We further prepared C4
and C5 and determined TPA cross sections of C4 and C5
under various near-IR Ti:sapphire femtosecond laser wave-
length to compare. As shown in Fig. 8, TPA cross section
of C2 and C3 are much larger than those of C4 and C5
under various near-IR laser wavelength excitation, which
demonstartes that benzophenone branch has a significant
effect on the enhancement of TPA emission of the
derivatives containing benzophenone groups.
-1.0
-2.0
-3.0
C2
1.75
-1.75
-1.5
1.5
1.0
0.5
0.0
-0.5
-1.0
Potential / V
4.0
3.0
2.0
1.0
0.0
0.05 V/S
0.10 V/S
0.15 V/S
Molecular Geometry Optimization
The HOMO and LUMO orbitals in the ground and excite
states were further analyzed. Figure 9 presents the electron
density distribution of frontier orbitals of the derivatives.
Obvious (π, π*) transition with internal charge transfer
occurs for the derivatives. In S0 and S1 states, the electron
density distribution is mainly distributed around tripheyl-
amine core in HOMO of the derivatives, and benzophenone
branches of C1 and C2 have major electron contribution in
LUMO orbital which confirms its donor-acceptor role.
While for C3, the electron density contribution is mainly
located in nitro branch of LUMO. Accordingly, C1 and C2
have similar electron density distribution, while it is
-1.0
-2.0
-3.0
-4.0
C3
1.75
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5 -1.75
Potential / V
Fig. 11 Cyclic voltammetries of C1, C2 and C3 in methylene
chloride at various scan rates

J Fluoresc (2011) 21:393–407
405
different from that of C3. We calculated dipole moment
difference of the derivatives between the excited state and
ground state. Remarkably, as our expectation, C3 has a
larger dipole moment change (2.33 D) than C1 (1.43D) and
C2 (1.63D) in vacuum. Both experimental estimation and
theoretical calculation demonstrate that C1 and C2 have
similar dipole moment changes. Furthermore, HOMO-
LUMO energy gaps in S0 and S1 of the derivatives were
calculated and the results are shown in Table 5. C3 has
smaller HOMO-LUOMO energy gaps than C1 and C2 in
both S0 and S1, while C1 and C2 have close HOMO-
LUMO gaps. The above calculations well explains that the
linear absorption, emission and TPA emission of C3 is red-
shifted and TPA cross section of C3 is larger. The data also
interpret why the derivatives C1 and C2 have similar linear
and two-photon optical properties.
Figure 10 presents the calculated linear absorption
spectra and fluorescence spectra of the derivatives, which
were obtained with the Lorenz broadening of the anterior
twenty excitation energies and corresponding oscillator
strengths with Swizard program [42, 43] peak wavelength
of the spectrum is equal to the corresponding singlet-
singlet strongest transition energy. The values of absorp-
tion refer to the vertical transition from the S0 states to the
Franck-Condon S1 states, while the value from the S1
states to the corresponding Franck-Condon S0 state yields
an assignment to fluorescence [44]. The calculated
absorption and emission maxima of C3 are red-shifted
with respect to those of C1 and C2, and the derivatives
C1 and C2 exhibit similar absorption and emission
nature, which are well consistent with the experimental
observation.
scan rates indicates that the redox processes of the
derivatives are well dominated by the diffusion-controlled
electron transfer reactions [49]. C3 has a larger oxidation
potential (0.889 V) than those of C1 (0.701 V) and C2
(0.832 V). On the other hand, the reductive peak potentials
of C3 (−0.501 V, −0.148 V) is much lower than those of C1
(−0.285, 0.548 V) and C2 (−0.208, 0.686 V). This could be
ascribed to strong electron-withdrawing effect of nitro
group, which could lower the reductive potentials, and
increase oxidative potentials. We further estimated HOMO-
LUMO energies from the optical band gap (Eg), which was
calculated from the onset of the longest absorption
wavelength at 10% of the maximal UV peak. Table 6
shows clearly that LUMO energy of C3 is lower than those of
C1 and C2, but its HOMO is higher than those of C1 and
C2. As a consequence, C3 has the lowest HOMO-LUMO
gaps in these derivatives, which is in accordance with that of
calculated result. This suggests that both HOMO and LUMO
energies and HOMO-LUMO gaps of the derivatives could
be affected by electro-withdrawing group.
Conclusions
This article presents some novel branched conjugated
derivatives containing benzophenone group. One- and
two- photon optical properties of the derivatives are much
related to the chemical structures. We show strong
evidences that benzopheonone branch does play significant
role on the improvement of TPA nature of the derivatives
carrying benzophenone moiety. Furthermore, the experi-
mental and calculated results demonstrate that the electron
density distribution, the energies and the energy gaps of the
frontier orbitals of the derivatives are remarkably affected
by electro-withdrawing substituent group, which results in
large difference in internal charge transfer. These could be
the deep reasons on the effect of substituent group on the
optical properties of the derivatives. The results presented
in this report would be of great interest in the development
of new organic dyes carrying benzophenone moiety with
ideal optical characteristics.
Cyclic Voltammograms
Figure 11 shows the cyclic voltammograms of the deriva-
tives at the scan rates from 50 to 200 mV·s−1. No
corresponding redox potentials demonstrate that redox
processes of the derivatives dyes are characterized with
irreversible nature under all sweeping rates. Furthermore,
the linear increasing of peak currents with the square root of
Table 6 Estimated HOMO and LUMO energies of the derivatives from redox potentials
Derivatives
λonset/nm
Gap/eV
EOX
ELUMO/eV
EHOMO/eV
C1
C2
C3
460.0
461.6
503.2
2.70
2.69
2.46
0.70
0.83
0.89
−5.04
−5.17
−5.23
−7.74
−7.86
−7.69
Eg=1,240/λ, LUMO (eV)=- EOX −4.34, [45, 46]. HOMO (eV)=LUMO - Eg, λonset:the longest absorption wavelength at 10% of the maximal UV peak
[47, 48]

406
J Fluoresc (2011) 21:393–407
Acknowledgements The authors appreciate financial support from
National Natural Science Foundation of China (Nos. 20776165,
20702065, 20872184). We would thank “the Foundation of Chongqing
Science and Technology Commission” (CSTC2008BA4020,
CSTC2009BB4216). H. Li thanks “A Foundation for the Author of
National Excellent Doctoral Dissertation of PR China (200735)”, and
thanks the support from the Key Laboratory of Functional Crystals and
Laser Technology, TIPC, Chinese Academy of Sciences. We also thank
“Innovative Talent Training Project, the Third State of “211 Project, S-
09103”, Chongqing University.
13. Belfield KD, Corredor CC, Morales AR, Dessources MA,
Hernandez FE (2006) Synthesis and characterization of new
fluorene-based singlet oxygen sensitizers. J Fluoresc 16(1):105–
110
14. Karotki A, Khurana M, Lepock JR, Wilson BC (2006) Simulta-
neous two-photon excitation of photofrin in relation to photody-
namic therapy. Photochem Photobiol 82(2):443–452
15. Pond SJK, Rumi M, Levin MD, Parker TC, Beljonne D, Day
MW, Brédas J, Marder SR, Perry JW (2002) One- and two-photon
spectroscopy of donor - acceptor - donor distyrylbenzene
derivatives: effect of cyano substitution and distortion from
planarity. J Phys Chem A 106(47):11470–11480
16. Rumi M, Ehrlich JE, Heikal AA, Perry JW, Barlow S, Hu Z,
McCord-Maughon D, Parker TC, Röckel H, Thayumanavan S,
Marder SR, Beljonne D, Brédas J (2000) Structure–Property
relationships for two-photon absorbing chromophores: bis-donor
diphenylpolyene and Bis(styryl)benzene derivatives. J Am Chem
Soc 122(39):9500–9510
17. Lee S, Yang W, Choi JJ, Kim CH, Jeon SJ, Cho BR (2005) 2, 6-
Bis[4-(p-dihexylaminostyryl)styryl]anthracene derivatives with
large two-photon cross sections. Org Lett 7(2):323–326
18. Cho BR, Chajara K, Oh HJ, Son KH, Jeon SJ (2002) Synthesis
and nonlinear optical properties of 1, 3, 5-Methoxy-2, 4, 6-tris
(styryl)benzene derivatives. Org Lett 4(10):1703–1706
19. Mongin O, Porrès L, Moreaux L, Mertz J, Blanchard-Desce M
(2002) Synthesis and photophysical properties of new conjugated
fluorophores designed for two-photon-excited fluorescence. Org
Lett 4(5):719–722
20. Pawlicki M, Collins HA, Denning RG, Anderson HL (2009) Two-
photon absorption and the design of two-photon dyes. Angew
Chem Int Ed 48(18):3244–3266
21. Bordeau G, Lartia R, Metge G, Fiorini-Debuisschert C, Charra F,
Teulade-Fichou MP (2008) Trinaphthylamines as robust organic
materials for two-photon-induced fluorescence. J Am Chem Soc
130(50):16836–16837
22. Fang Z, Teo TL, Cai LP, Lai YH, Samoc A, Samoc M (2009)
Bridged triphenylamine-based dendrimers: tuning enhanced two-
photon absorption performance with locked molecular planarity.
Org Lett 11(1):1–4
23. Wei P, Bi XD, Wu Z, Xu Z (2005) Synthesis of triphenylamine-
cored dendritic two-photon absorbing chromophores. Org Lett 7
(15):3199–3202
24. Chan EW, Chattopadhaya S, Panicker RC, Huang X, Yao SQ
(2004) Developing photo-active affinity probes for proteomic
profiling: hydroxamate-based probes for metalloproteases. J Am
Chem Soc 126(44):14435–14446
25. Konry T, Novoa A, Shemer-Avni Y, Hanuka N, Cosnier S,
Lepellec A, Marks RS (2005) Optical fiber immunosensor based
on a Poly(pyrrole − benzophenone) film for the detection of
antibodies to viral antigen. Anal Chem 77(6):1771–1779
26. Perrin D, Armarego W, Perrin D (1966) Purification of laboratory
chemicals. Pergamon, New York
References
1. Farruggia G, Iotti S, Prodi L, Montalti M, Zaccheroni N, Savage
PB, Trapani V, Sale P, Wolf FI (2006) 8-Hydroxyquinoline
derivatives as fluorescent sensors for magnesium in living cells.
J Am Chem Soc 128(1):344–350
2. Sumalekshmy S, Henary MM, Siegel N, Lawson PV, Wu YG,
Schmidt K, Brédas JL, Perry JW, Fahrni CJ (2007) Design of
emission ratiometric metal-ion sensors with enhanced two-photon
cross-section and brightness. J Am Chem Soc 129(39):11888–11889
3. Taki M, Wolford JL, O’Halloran TV (2004) Emission ratiometric
imaging of intracellular zinc: design of a benzoxazole fluorescent
sensor and its application in two-photon microscopy. J Am Chem
Soc 126(3):712–713
4. Denk W, Strickler JH, Webb WW (1990) Two-photon laser
scanning fluorescence microscopy. Science 248(4951):73–76
5. Picot A, D’Aléo A, Baldeck PL, Grichine A, Duperray A,
Andraud C, Maury O (2008) Long-lived two-photon excited
luminescence of water-soluble europium complex: applications in
biological imaging using two-photon scanning microscopy. J Am
Chem Soc 130(5):1532–1533
6. Tokar VP, Losytskyy MY, Ohulchanskyy TY, Kryvorotenko DV,
Kovalska VB, Balanda AO, Dmytruk IM, Prokopets VM,
Yarmoluk SM, Yashchuk VM (2010) Styryl dyes as two-photon
excited fluorescent probes for DNA detection and two-photon
laser scanning fluorescence microscopy of living cells. J Fluoresc
20(4):865–872
7. Chang CJ, Nolan EM, Jaworski J, Okamoto K, Hayashi Y, Sheng
M, Lippard SJ (2004) ZP8, a neuronal zinc sensor with improved
dynamic range; imaging zinc in hippocampal slices with two-
photon microscopy. Inorg Chem 43(21):6774–6779
8. Claeyssens F, Hasan EA, Gaidukeviciute A, Achilleos DS,
Ranella A, Reinhardt C, Ovsianikov A, Shizhou X, Fotakis C,
Vamvakaki M, Chichkov BN, Farsari M (2009) Three-
dimensional biodegradable structures fabricated by two-photon
polymerization. Langmuir 25(5):3219–3223
9. Lee KS, Kim RH, Yang D, Park SH (2008) Advances in 3D
Nano/Microfabrication using two-photon initiated polymerization.
Prog Polym Sci 33(6):631–681
27. Gao F, Liu J, Yang L, Wang Q, Li H, Zhang S (2010) Chin J
Chem 28(6):950–960
10. Sun W, Zhu H, Barron PM (2006) Binuclear cyclometalated
Platinum(II) 4, 6-Diphenyl-2, 2′-bipyridine complexes: interesting
photoluminescent and optical limiting materials. Chem Mater 18
(10):2602–2610
11. Vestberg R, Westlund R, Eriksson A, Lopes C, Carlsson M,
Eliasson B, Glimsdal E, Lindgren M, Malmström E (2006)
Dendron decorated Platinum(II) acetylides for optical power
limiting. Macromolecules 39(6):2238–2246
12. Kim S, Ohulchanskyy TY, Pudavar HE, Pandey RK, Prasad PN
(2007) Organically modified silica nanoparticles co-encapsulating
photosensitizing drug and aggregation-enhanced two-photon
absorbing fluorescent dye aggregates for two-photon photody-
namic therapy. J Am Chem Soc 129(9):2669–2675
28. Fischer M, Georges J (1996) Fluorescence quantum yield of
rhodamine 6G in ethanol as a function of concentration using
thermal lens spectrometry. Chem Phys Lett 260(1–2):115–118
29. Maus M, Rettig W (1999) Photoinduced intramolecular charge
transfer in a series of differently twisted donor-acceptor biphenyls
as revealed by fluorescence. J Phys Chem A 103(18):3388–3401
30. Lukeman M, Veal D, Wan P, Ranjit V, Munasinghe N, Corrie JET
(2004) Photogeneration of 1, 5-Naphthoquinone methides via
excited-state (formal) intramolecular proton transfer (ESIPT) and
photodehydration of 1-naphthol derivatives in aqueous solution.
Can J Chem 82(2):240–253

J Fluoresc (2011) 21:393–407
407
31. Xu C, Webb WW (1996) Measurement of two-photon excitation
cross sections of molecular fluorophores with data from 690 to
1050 nm. J Opt Soc Am B 13(3):481–491
32. Albota MA, Xu C, Webb WW (1998) Two-photon fluorescence
excitation cross sections of biomolecular probes from 690 to
960 nm. Appl Opt 37(31):7352–7356
33. Zgiershi MZ, Grabowska A (2000) Photochromism of Salicylide-
neaniline (SA). How the photochromic transient is created: a
theoretical approach. J Chem Phys 12(14):6329–6338
34. Yi PG, Liang YH, Cao CZ (2005) Intramolecular proton or
hydrogen-atom transfer in the ground and excited-states of 2-
hydroxybenzophenone: a theoretical study. Chem Phys 315
(3):297–302
40. Lakowicz JR (1999) Principles of fluorescence spectroscopy.
Kluwer Academic, New York
41. Lin TC, He GS, Prasad PN, Tan LS (2004) Degenerate nonlinear
absorption and optical power limiting properties of asymmetrically
substituted stilbenoid chromophores. J Mater Chem 14(6):982–991
42. Gaenko AV, Devarajan A, Tselinskii IV, Ryde U (2006) Structural
and photoluminescence properties of excited state intramolecular
proton transfer capable compounds-potential emissive and elec-
tron transport materials. J Phys Chem A 110(25):7935–7942
43. Gorelsky SI, Swizard program, revision XX, http://www.sg-chem.net/
44. Wang YL, Wu GS (2008) Electronic structure characteristics of
ESIPT and TICT fluorescence emissions and calculations of
emitting energies. Acta Phys Chim Sin 24(4):552–560
35. Liang YH, Yi PG (2007) Theoretical studies on structure,
energetic and intramolecular proton transfer of Alkannin. Chem
Phys Lett 438(4–6):173–177
36. Yang ZN, Yang SY, Zhang JP (2007) Ground-and excited-state
proton transfer and rotamerism in 2-(2-Hydroxyphenyl)-5-Phenyl-
1, 3, 4-Oxadiazole and its O/″NH or S″-substituted derivatives. J
Phys Chem A 111(28):6354–6360
37. Itoh T, Hall HK (1990) 7-Chloro-7-Phenyl-8, 8-Dicyanoquinodimethane.
A novel initiator for cationic polymerizations. Macromolecules
23(22):4879–4881
38. Wang S, Kim SH (2009) Photophysical and electrochemical
properties of D–π–A type solvatofluorchromic isophorone dye for
pH molecular switch. Current Appl Phys 9(4):783–787
39. Lippert E (1957) Spektroskopische Bistimmung Des Dipolmo-
mentes Aromatischer Verbindungen im Ersten Angeregten Singu-
lettzustand. Z Electrochem 61:962
45. Liu J, Tu GL, Zhou QG, Cheng YX, Geng Y, Wang LX, Ma DG, Jing
XB, Wang FS (2006) Highly efficient green light emitting polyfluorene
incorporated with 4-Diphenylamino-1, 8-Naphthalimide as green
dopant. J Mater Chem 16(15):1431–1438
46. Bard AJ, Faulkner LA (1984) Electrochemical methods-
fundamentals and applications. Wiley, New York
47. Domagalska BW, Wilk KA, Wysocki S (2003) Experimental and
theoretical studies on solvent effects of amphiphilic conjugated
polyenals. Phys Chem Chem Phys 5(4):696–702
48. Ndaykengurukiye H, Jacobs S, Tachelet W, Looy JVD, Pollars A,
Geise HJ, Claeys M, Kauffmann JM, Janietz S (1997) Alkoxy-
lated p-Phenylenevinylene oligomers: synthesis and spectroscopic
and electrochemical properties. Tetrahedron 53(40):13811
49. Aoki K, Guo Y, Chen JY (2009) Diffusion-controlled currents in
viscous solutions of polyethylene glycols. J Electroanal Chem 629
(1–2):73–77