Synthesis, photoluminescent behaviors, and theoretical studies of two novel ketocoumarin derivatives

Article abstract of DOI:10.1016/j.saa.2011.11.044

Two new coumarin derivatives, 3-[3-(4-formylphenyl)prop-2-enoyl]-coumarin (FEC) and 4-hydroxy-3-[3-(4-formylphenyl)prop-2-enoyl]-coumarin (HFEC), were synthesized and characterized by MS, ¹H NMR, FT-IR, and TG. The UV-vis absorption and photoluminescence (PL) of FEC and HFEC were also studied. Results show that the two compounds exhibit high fluorescence quantum yields, large Stokes shifts, and strong blue emissions. The molecular structures, the lowest energy transitions, the resonance frequencies, and the UV-vis spectra of FEC and HFEC were calculated using the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at the B3LYP/6-31G(d) level.

Full text of DOI:10.1016/j.saa.2011.11.044

Spectrochimica Acta Part A 88 (2012) 31–36
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, photoluminescent behaviors, and theoretical studies of two novel
ketocoumarin derivatives
∗
Jing Li, Xianggao Li , Shirong Wang
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 August 2011
Received in revised form
Two new coumarin derivatives, 3-[3-(4-formylphenyl)prop-2-enoyl]-coumarin (FEC) and 4-hydroxy-
-[3-(4-formylphenyl)prop-2-enoyl]-coumarin (HFEC), were synthesized and characterized by MS, 1
3
H
NMR, FT-IR, and TG. The UV–vis absorption and photoluminescence (PL) of FEC and HFEC were also
studied. Results show that the two compounds exhibit high fluorescence quantum yields, large Stokes
shifts, and strong blue emissions. The molecular structures, the lowest energy transitions, the resonance
frequencies, and the UV–vis spectra of FEC and HFEC were calculated using the density functional theory
1
3 November 2011
Accepted 18 November 2011
Keywords:
Coumarin
Synthesis
(DFT) and time-dependent density functional theory (TD-DFT) at the B3LYP/6-31G(d) level.
©
2011 Elsevier B.V. All rights reserved.
UV–vis
Photoluminescence
DFT studies
1
. Introduction
Coumarin and its derivatives have received considerable atten-
hydroxyl group at the 4-position of the coumarin ring compared
with FEC. The main purpose of the current investigation is to under-
stand the effect of substituents in the coumarin skeleton on the
photoluminescent properties of coumarin.
tion in the past few years not only for their versatile biological and
medical properties [1], such as antioxidant [2], anti-inflammatory
[
3], antibacterial [4], and anticancer activities [5], but also for their
2. Experimental
sufficient fluorescence in the visible light range [6], large Stokes
shifts [7], and high quantum yields [8], among others. In addition,
their photochemical and photophysical properties can be readily
modified by the introduction of substituents in the coumarin ring,
affording more flexibility that fit well in various applications. For
example, recent research suggests that the fusion of a chalcone
moiety to the coumarin ring is quite promising for the synthe-
sis of derivatives with an extended spectral range (270–600 nm
for the absorption band and 400–700 nm for the emission band)
2.1. Materials and methods
IR spectra (400–4000 cm−1) were measured on a Nicolet 380
spectrophotometer. 1H NMR spectra were obtained using a Varian
Inova 500 spectrometer (at 500 MHz). Mass spectra were recorded
on a micrOTOF-Q II mass spectrometer. Melting points were taken
using a RY-1 micro melting apparatus; the thermometer was uncor-
rected. Thermogravimetric (TG) analysis was carried out on a Q500
thermal analysis instrument. UV–vis absorption and emission spec-
tra were recorded using a Thermo Evolution 300 spectrometer and
a Cary Eclipse spectrometer, respectively. All the chemicals were
commercially available and used without further purification. All
the solvents were dried using standard methods before use.
[
6,9] and produce substances that can be used as blue, green,
and red dopants in organic light-emitting diodes (OLEDs). Many
ketocoumarin-based electroluminescent (EL) materials have been
and are currently being developed [10–12].
In the current work, we report the synthesis, photo-
physical property, and theoretical investigation of two novel
ketocoumarin derivatives, 3-[3-(4-formylphenyl)prop-2-enoyl]-
coumarin (FEC) and 4-hydroxy-3-[3-(4-formylphenyl)prop-2-
enoyl]-coumarin (HFEC). These derivatives exhibit strong blue
emissions under ultraviolet light excitation. HFEC has an additional
2.2. Synthesis and characterization of FEC and HFEC
The synthetic routes are shown in Scheme 1.
2.2.1. 3-Acetyl-coumarin (1)
Salicylaldehyde (10.6 mL, 0.1 mol), ethyl acetoacetate (12.6 mL,
∗ Corresponding author. Tel.: +86 22 27404208; fax: +86 22 27892279.
E-mail address: lixianggao@hotmail.com (X. Li).
0.1 mol), piperidine (2 mL), and ethanol (200 mL) were all placed
into a 500 mL round-bottomed flask. The resulting mixture was
1
386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.11.044

3
2
J. Li et al. / Spectrochimica Acta Part A 88 (2012) 31–36
Scheme 1. Synthetic routes to FEC and HFEC.
heated to reflux under magnetic stirring for 4 h, after which
the solution was cooled to room temperature and the separated
yellowish solid was filtered off. This was subsequently recrys-
tallized from ethanol to obtain the compound 1 (15.2 g, 80.6%).
and HFEC were calculated at the B3LYP/6-31G(d) level. The sol-
vent polarity effects were included by the polarizable continuum
model (PCM) [14]. The structure optimization and the energy and
frequency calculations were performed using the GAUSSIAN 03
program [15].
◦
1
m.p. 121–122 C. H NMR (CDCl , ı, ppm): 2.732 (s, 3H, CH ),
3
3
7
.333–7.679 (m, 4H, Aryl-H), 8.517 (s, 1H, 4-H).
3. Results and discussion
2.2.2. 3-Acetyl-4-hydroxy-coumarin (2)
Phosphorus oxychloride (25 mL, 0.1 mol) was added to a solu-
tion of 4-hydroxycoumarin (16.2 g, 0.1 mol) in glacial acetic acid
90 mL, 1.4 mol). The mixture was heated at reflux for 1 h. After
3
.1. Synthesis
(
Compound 1, compound 2, FEC, and HFEC were all prepared
cooling, the precipitate was collected and recrystallized from
ethanol to obtain compound 2 as white needles (15.3 g, 70.5%).
according to the method described earlier [16–18]. Knoevenagel
condensation of salicylaldehyde with ethyl acetoacetate yielded
compound 1. For the acetylation of 4-hydroxycoumarin to yield
compound 2, glacial acetic acid was used as acetylating agent in
the presence of POCl3. The Claisen–Schmidt condensation of com-
pounds 1 and 2 with benzene-1,4-dicarboxaldehyde yielded the
coumarin–chalcones FEC and HFEC, respectively.
The structure and purity of the resulting new compounds (i.e.,
FEC and HFEC) were confirmed by spectral data. In the IR spec-
tra of the two compounds, the strong bands at around 1720 and
◦
1
m.p. 139–140 C. H NMR (CDCl , ı, ppm): 2.790 (s, 3H, CH ),
3
3
7
.265–8.078 (m, 4H, Aryl-H).
2.2.3. FEC
A mixture of compound 1 (18.8 g, 0.1 mol), benzene-1,4-
dicarboxaldehyde (26.8 g, 0.2 mol), and piperidine (3 mL) in glacial
acetic acid (200 mL) was refluxed for 5 h and then cooled to room
temperature. Afterwards, the precipitate was filtered and dried.
The crude product was recrystallized from an ethanol/acetonitrile
−
1
1
730 cm , respectively, confirm the presence of a coumarin skele-
(
(
v:v = 1:1) mixture solvent to produce the pure product of FEC
22.8 g, 75.1%). m.p. 204–205 C. IR (KBr pellet cm ): 3040 (aryl-
◦
−1
ton. Note that for HFEC, no v–OH of the hydroxyl group appears in its
IR spectrum. This is due to the existence of a strong intra-molecular
hydrogen bond between the hydroxyl group and the ketonic oxy-
gen in its structure [16].
CH), 1720 (C O, lactone), 1690 (C O, formyl), 1670 (C O), 1560
C), 984 (C–O–C) cm−1
. H NMR (CDCl , ı, ppm): 10.049 (s, 1H),
3
1
(
C
8
.631 (s, 1H), 8.078 (d, J = 16.0 Hz, 1H), 7.927 (d, J = 8.0 Hz, 2H), 7.871
1
The structures of FEC and HFEC were also confirmed by H NMR
(
7
d, J = 15.5 Hz, 1H), 7.826 (d, J = 8.0 Hz, 2H), 7.686 (q, J = 13.3 Hz, 2H),
spectroscopy. The 1H NMR spectra of FEC show a clearly distin-
guishable intense singlet at ı = 8.631 ppm for H-4 of the coumarin
nucleus. Such a signal characterizes coumarin system protons [12].
Moreover, for FEC and HFEC, characteristic formyl proton singlets
+
.394 (m, 2H). HRMS (ESI ): m/z: calcd for C19H12O : 327.0628
4
+
[
M+Na ]; found: 327.0627.
2.2.4. HFEC
at ı = 10.049 and 10.060 ppm, respectively, are apparent in the 1
H
The preparation of HFEC was similar to that described for FEC.
NMR spectra.
The yield of the corresponding synthesis reaction was 80.1%. m.p.
◦
−1
2
09–210 C. IR (KBr pellet cm ): 3040 (aryl-CH), 1730 (C O, lac-
tone), 1700 (C O, formyl), 1630 (C O), 1540 (C C), 982 (C–O–C)
3
.2. Thermal properties of FEC and HFEC
−
1 1
cm
H), 8.108 (q, J = 7.8 Hz, 1H), 8.037 (d, J = 16.0 Hz, 1H), 7.947 (d,
J = 8.0 Hz, 2H), 7.866 (d, J = 8.0 Hz, 2H), 7.720 (m, 1H), 7.350 (m, 2H).
. H NMR (CDCl , ı, ppm): 10.060 (s, 1H), 8.544 (d, J = 15.5 Hz,
3
1
In order to investigate the thermal stabilities of FEC and HFEC,
the TG experiments were carried out in the temperature range of
30–800 C and a heating rate of 10 min in nitrogen atmosphere.
The resulting thermograph is shown in Fig. 1. The TG curves for FEC
and HFEC show a clear plateau, followed by a sharp decomposi-
tion curve. The loss in weight of the two compounds is rapid when
heated above 246 C. These results indicate that FEC and HFEC are
stable up to 246 C, after which they decompose rapidly and com-
pletely at a temperature above 363 C. This finding confirms that
the two compounds have similar and excellent thermal stabilities.
+
+
HRMS (ESI ): m/z: calcd for C19H12O5: 343.0577 [M+Na ]; found:
◦
◦
−1
3
43.0552.
2.3. Quantum chemical calculations
◦
◦
The structures of FEC and HFEC were optimized by the semiem-
pirical density functional theory (DFT) using a B3LYP/6-31G(d) [13]
basis set. The structural energies and resonance frequencies of FEC
◦

J. Li et al. / Spectrochimica Acta Part A 88 (2012) 31–36
33
1
20
00
1
0
0
0
.0
.8
.6
.4
1
FEC
1
HFEC
2
8
6
4
2
0
0
0
0
0
FEC
HFEC
0.2
0
.0
3
1
50
200
250
300
350
400
450
50
400
450
500
550
600
650
Temperature (ºC)
Wavelength (nm)
Fig. 1. TG curves of FEC and HFEC.
Fig. 3. Fluorescence emission spectra of compound 1(ꢀex = 341 nm), compound
(ꢀex = 324 nm), FEC(ꢀex = 333 nm), and HFEC(ꢀex = 370 nm) in dichloromethane at
2
−
5
Table 1
room temperature (C = 5.00 × 10 mol/L). (For interpretation of the references to
UV–vis absorption and fluorescence spectra data for compounds 1 and 2, FEC, and
HFEC.
color in this figure legend, the reader is referred to the web version of the article.)
Compound
ꢀa,max (nm)
ꢀe,max (nm)
Stake’s
shift (nm)
FEC and HFEC exhibit absorption spectral features that are quite
different from those of the corresponding starting compounds, i.e.,
compound 1 and compound 2, respectively. FEC and HFEC each
have only one intense absorption peak at 333 and 370 nm, respec-
tively. Due to the elongated conjugation in the FEC structure, the
absorption peak of the compound is red-shifted compared with that
of compound 1 at 300 nm. Similarly, the absorption peak of HFEC
is red-shifted compared with the sharp absorption peak of com-
pound 2. Note that the absorption peak of HFEC is red-shifted by
Compound 1
Compound 2
FEC
300, 341
300, 324
333
438
402
460
480
97
78
127
110
HFEC
370
3
.3. UV–vis absorption and fluorescence of compounds 1 and 2,
FEC, and HFEC
3
7 nm with respect to that of FEC. FEC and HFEC are typical intra-
UV–vis absorption and photoluminescence spectra of com-
pounds 1 and 2, FEC, and HFEC in dilute dichloromethane solutions
are given in Figs. 2 and 3, respectively, and the relevant data are
listed in Table 1. Compound 1 shows a sharp absorption peak at
molecular charge transfer compounds. Their molecules consist of
a typical D–␲–A structure, in which 3-carbonylcoumarinyl, styryl
and formyl groups are employed as donor (D), ␲-conjugated cen-
ter (␲) and acceptor (A) moieties, respectively. Thus, the reason for
the difference between the absorption features of FEC and HFEC
may be attributed to the increase of the electron-donating capa-
bility of the 3-carbonylcoumarinyl group and the greater strength
of the intra-molecular charge transfer upon the introduction of a
hydroxyl group to the 4-position of the coumarin ring.
The emission peak of compound 2 appears at around 402 nm,
which is blue-shifted by about 36 nm with respect to that of com-
pound 1 at 438 nm, due to the existence of the intermolecular
hydrogen bond in the structure of compound 2. In addition, the
emission peaks of FEC and HFEC appear at around 460 and 480 nm,
respectively; they are bathochromically shifted with respect to
those of the corresponding compounds, compound 1, and com-
pound 2. The emission peak of HFEC is red-shifted by about
3
00 nm, with a shoulder at 341 nm. Compound 2 shows a sharp
absorption peak at 300 nm, with a shoulder at 324 nm. The spec-
tral shape of compound 2 is similar to that of compound 1 because
of their highly similar structures. However, the shoulder peak at
3
24 nm of compound 2 is blue-shifted compared with that of com-
pound 1 (341 nm). It has been suggested that compound 2 has an
intra-molecular hydrogen bond between the hydroxyl group and
the ketonic oxygen in its chemical structure, thus weakening the
electron-withdrawing effect of the 3-acetyl group.
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
2
0 nm with respect to that of FEC, because of an electron repelling
1
hydroxyl group in the 4-position of the coumarin ring.
2
In Figs. 2 and 3, for FEC and HFEC, respectively, the Stokes shifts
between the absorption and the emission maximum are significant.
The efficient ␲-conjugation in the molecule is known to be respon-
sible for the charge-transfer nature of the emissive excited state
and for the observed relatively large Stokes shifts.
The 3-carbonylcoumarinyl group of the styrene-modified keto-
coumarins can also be used as an acceptor moiety. In FEC, for
example, when the p-formylphenyl moiety is replaced with a p-
N,N-diphenylaminophenyl group, the maximum absorption peak
is red-shifted to 465 nm because of the elongated conjugation in its
structure. However, the maximum emission peak is blue-shifted
to 430 nm [9] because the 3-carbonylcoumarinyl group acts as an
acceptor moiety, and the entire molecule adopts a typical A–␲–D
structure, which leads to the reversal of the intramolecular charge-
transfer route.
FEC
HFEC
2
50
300
350
400
450
500
Wavelength (nm)
Fig. 2. UV–vis absorption spectra of compound 1, compound 2, FEC, and HFEC in
−5
dichloromethane at room temperature (C = 5.00 × 10 mol/L). (For interpretation
of the references to color in this figure legend, the reader is referred to the web
version of the article.)

3
4
J. Li et al. / Spectrochimica Acta Part A 88 (2012) 31–36
Table 2
Mulliken charges (e) of FEC and HFEC obtained by the B3LYP/6-31G(d) method.
Molecules
FEC/HFEC
O(C–O–C)
O((O) C–O)
O(C O)
O(O C–H)
−0.519/−0.519
−0.436/−0.476
−0.440/−0.455
−0.400/−0.403
Table 3
The comparison of ꢀmax (nm) obtained by calculation and experiment.
3
.4. Fluorescence quantum yields of the compounds (˚S,FEC and
˚S,HFEC
)
Compound
Calc.a
Exp.b
The fluorescence quantum yields of FEC and HFEC in
dichloromethane solutions can be estimated from the following
equation [19]:
Without solvent
Dichloromethane
FEC
HFEC
320 (0.8553)
360 (0.8225)
334 (0.8239)
372 (0.8521)
333
370
a
Calculated oscillator strengths are given in parenthesis.
Solvent is dichloromethane.
ꢀ
AR FS nS
·
ꢁ
2
b
˚S = ˚R ·
FR AS nR
due to the presence of the hydroxyl group, enhancing the electron
density of the coumarin ring.
where ˚R is the quantum yield of the standard, A is the absorbance
at the wavelength of the excitation, F is the integrated intensity
of the emission spectra, n is the refractive index of the solution,
index (S) denotes the sample, and (R) denotes the reference. The
standard fluorophore for the quantum yield measurements is qui-
3.5. Quantum chemical calculations
To obtain further insight into the geometrical configuration and
photophysical properties of FEC and HFEC, DFT calculations were
performed at the B3LYP/6-31G(d) level for geometry optimization.
The optimized structures and electron distribution of the HOMO
and LUMO of FEC and HFEC are shown in Fig. 4.
−3
nine sulphate in 0.2 mol dm H SO (˚R = 0.51) [20]. In the current
2
4
research, the ˚ of FEC and HFEC are 0.55 and 0.70, respectively. The
S
typical D–␲–A structure in the two compounds leads to a high flu-
orescence quantum yield. Compared with ˚S,FEC, ˚S,HFEC increased
Fig. 4. Optimized structures and HOMO and LUMO electron distributions of FEC and HFEC.

J. Li et al. / Spectrochimica Acta Part A 88 (2012) 31–36
35
Table 4
Comparison of the calculated and experimental infrared data of FEC and HFEC.
No.
Exp. (FEC/HFEC)
Freq.a
Calcd. (FEC/HFEC)
Non scaled
Vibratory feature
Int. (IR)b
Scaledc
Int. (IR)
1
2
3
4
5
6
7
8
9
3040/3040
2820/2820
1720/1730
1690/1700
1670/1630
1610/1600
1560/1540
1180/1200
984/982
w/w
m/m
v/v
v/v
s/s
v/v
s/v
s/s
s/s
3181/3166
2915/2912
1839/1827
1799/1797
1742/1747
1673/1684
1614/1618
1232/1267
994/982
3058/3044
2803/2799
1768/1756
1729/1728
1675/1680
1608/1619
1552/1556
1184/1218
956/944
11.92/14.85
␯
␯
CH
165.74/173.41
514.70/536.41
305.39/315.57
196.95/364.04
120.46/220.80
83.06/104.58
256.22/176.13
130.07/177.22
56.70/32.10
CH(CHO)
␯C O(COO)
␯C O(CHO)
␯C O(CO)
␯C
␯C C(CH CH)
␯C
␯C–O–C
ı
ı
ı
C
C
1
1
1
0
1
2
822/829
752/764
577/588
m/m
m/m
m/m
863/870
774/761
594/580
830/836
744/732
571/557
CH
CH
CH
64.22/82.00
30.03/23.15
a
b
c
−1
Frequencies in cm
.
m: middle, s: strong, v: very strong, w: weak.
Scaling factor using 0.9613.
The chalcone skeleton is essentially planar, which is rotated
of the IR spectra of FEC and HFEC are given in Table 4. The value of
the calculated IR spectrum is slightly higher than the experimen-
tal value, which may be due to the fact that the result obtained
by the calculation is the harmonic oscillator frequency and that
the experimental value also contains the an harmonic oscillator
frequency. In addition, data of the IR spectra were modified using
0.9613 [22] as the frequency scaling factor. The resulting consis-
tent relation graph between the calculated and experimental data
of FEC and HFEC are shown in Fig. 5. The linear slope and inter-
cept of FEC are 1.0467 and −5.4282 for the non-scaled data, and
1.0063 and −5.2663 for the scaled data, respectively. For HFEC, the
corresponding non-scaled data are 1.0473 and −5.1105, and the
significantly out of the plane of the coumarin ring. This nonpla-
nar geometry structure can effectively prevent the aggregation of
molecules, causing FEC and HFEC to exhibit high fluorescence quan-
tum yields, as presented in Section 3.4. The HOMO and LUMO levels
of FEC are −6.5324 and −2.4364 eV, respectively, and the energy
gap between HOMO and LUMO is about 4.0960 eV. The correspond-
ing levels for HFEC are −6.6883 and −2.9930 eV, and the relative
energy gap is 3.6953 eV. The large HOMO–LUMO gaps of FEC and
HFEC demonstrate their high kinetic stabilities and low chemical
reactivities, given that the addition of electrons to a high-lying
LUMO or their extraction from a low-lying HOMO is energeti-
cally unfavorable [21]. For FEC and HFEC, the HOMO is located in
the electron-donating group and in the whole molecular skeleton,
respectively. For both FEC and HFEC, the LUMO is located in the
electron-withdrawing group through the ␲-spacer. Consequently,
the transition from HOMO to LUMO is easier in HFEC than in FEC.
This causes the value of the energy gap of HFEC to be lower than
that of FEC. In turn, this leads to the absorption peak of HFEC to be
bathochromically shifted compared with that of FEC, as shown in
Section 3.3.
Mulliken charges of FEC and HFEC were also obtained, and
the charges of oxygen atoms are listed in Table 2. Introducing a
hydroxyl group to the 4-position of the coumarin ring results in the
increase in the negative charges in the electron-attracting oxygen
atoms, especially in the lactone carbonyl oxygen atom. This is due
to the electron-repelling effect of the hydroxyl group conjugating
with the coumarin ring.
The UV–vis absorption spectra of FEC and HFEC were also cal-
culated by the time-dependent density functional theory (TD-DFT)
at the same level. The max absorption wavelengths correspond to
the S1 state. Table 3 lists the experimental and calculated ꢀmax
3
3
2
2
1
1
500
000
500
000
500
000
(
i)
Ynon-scaled = 1.0467X - 5.4282
Non-scaled
Scaled
Y
= 1.0063X - 5.2663
scaled
5
00
5
00
1000
1500
2000
2500
3000
3500
-1
Experimental wavenumber (cm )
3500
(
ii)
3
2
2
1
1
000
500
000
500
000
(
nm) values of the corresponding UV–vis absorption spectra for
Y
= 1.0473X - 5.1105
the S1 states of FEC and HFEC. Solvent effects were considered
in the PCM model, and the discrepancy between the theoretical
and experimental ꢀmax is reduced from 13 nm to 1 nm for FEC and
from 10 nm to 2 nm for HFEC. These results show the remarkable
increase in accuracy and are in very good agreement with the exper-
imental measurements when the solvent effects are taken into
account.
non-scaled
Non-scaled
Scaled
Y
= 1.0068X - 4.9127
scaled
The resonance frequency calculations of FEC and HFEC were car-
ried out at the B3LYP/6-31G(d) level to study the IR spectra of the
two structures. The calculation of resonance frequency is exten-
sively used in organic chemistry for the identification of functional
groups of organic compounds and for the study of molecular con-
formations, reaction kinetics, etc. The observed and calculated data
5
00
5
00
1000
1500
2000
2500
3000
3500
-1
Experimental wavenumber (cm )
Fig. 5. Consistency of the wavenumbers of the calculated and experimental IR spec-
tra main peaks of FEC (I) and HFEC (II).

3
6
J. Li et al. / Spectrochimica Acta Part A 88 (2012) 31–36
relative scaled data are 1.0068 and −4.9127, respectively. These
results indicate that the description error clearly decreases after
the introduction of the frequency-scaling factor, and the calculated
data are in good agreement with the experimental value.
[4] N. Hamdi, V. Passarelli, A. Romerosa, C. R. Chimie 14 (2011) 548.
[
5] M.E. Riveiro, N. De Kimpe, A. Moglioni, R. Vazquez, F. Monczor, C. Shayo, C.
Davio, Curr. Med. Chem. 17 (2010) 1325.
[
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1
[
[
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4
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[
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3
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successfully synthesized. Their photophysical properties have also
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(
460 and 480 nm) and large Stokes shifts. At the same time, the
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HOMO–LUMO levels and the IR and UV–vis spectra of FEC and HFEC
have been studied with the DFT and TD-DFT at the B3LYP/6-31G(d)
level. The results demonstrate that the calculation outcomes are in
good agreement with the experimental data. Based on the results,
FEC and HFEC are potential candidates for use in opto- or opto-
electronic blue-emitting devices. Their other characteristics will be
studied in the future.
Acknowledgement
This work was financially supported by National Natural Science
Foundation of China (21176180).
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