Synthesis, photophysical and electrochemical properties of novel D-π-D and D-π-a triphenylamino-chalcones and β-arylchalcones

Article abstract of DOI:10.21577/0103-5053.20180156

A series of triphenylamino (TPA)-chalcones and triphenylamino-β-arylchalcones, displaying either D-π-D or D-π-A architecture, were synthesized through aldol condensations and Heck reactions. The chalcone derivatives display intense absorption bands rangin

Full text of DOI:10.21577/0103-5053.20180156

http://dx.doi.org/10.21577/0103-5053.20180156
J. Braz. Chem. Soc., Vol. 30, No. 1, 81-89, 2019
Article
Printed in Brazil - ©2019 Sociedade Brasileira de Química
Synthesis, Photophysical and Electrochemical Properties of Novel D-π-D and D-π-A
Triphenylamino-Chalcones and β-Arylchalcones
a
a
a
Rafaela G. M. da Costa, Francisco R. L. Farias, Luis Maqueira,
a
a
a
Carlos Castanho Neto, Leonardo S. A. Carneiro, Joseany M. S. Almeida,
a
a
,a
Camilla D. Buarque, Ricardo Q. Aucélio and Jones Limberger *
a
Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro,
Rua Marquês de São Vicente, 225, Gávea, 22451-900 Rio de Janeiro-RJ, Brazil
A series of triphenylamino (TPA)-chalcones and triphenylamino-β-arylchalcones, displaying
either D-π-D or D-π-A architecture, were synthesized through aldol condensations and Heck
reactions. The chalcone derivatives display intense absorption bands ranging from 389 to 432 nm
5
-1
-1
and molar extinction coefficients of ca. 10 L mol cm corresponding to π-π* electronic transitions.
The photoluminescence emissions are peaked between 470 and 563 nm with large Stokes shifts
(80-131 nm), attributed to charge transfer in the excited state. The dyes present low fluorescence
quantum yields, which is attributed to radiationless excited state deactivation related to aryl rings
rotation. Spectroscopic and electrochemical methods were used to determine the highest occupied
molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels. Both
optical and electrochemical properties of the TPA-chalcone derivatives are considerably affected by
the substitution pattern of the chalcones aryl rings and also by the β-arylation of the olefin moiety.
Keywords: fluorescence, chalcone, β-arylchalcone, Heck reaction, triphenylamine
Introduction
Triphenylamine (TPA) is one of the most applied donor
group in the design of organic dipolar chromophores.
Moreover, TPA derivatives have been extensively applied
The chalcone backbone can be considered a privileged
template for the synthesis of highly conjugated compounds.
The careful choice of groups attached to both aryl rings
allow the modulation of chalcones properties, providing
derivatives with a wide range of applications, for
1
2,13
as photovoltaic and hole-transporting materials.
The
incorporation of the TPA group on chalcone structure has
been performed and the photophysical and electrochemical
7,14
properties of TPA-chalcone derivatives have been studied.
1
-4
5
instance, in medicinal chemistry, analytical chemistry
These chromophores display interesting features and
depending on the structure, can be applied, for instance,
6
,7
and light technology. Concerning photochemical
applications, two architectures have been used in the
design of conjugated chalcone-based dyes: D-π-D
compounds, with both aryl rings possessing electron-
donating groups, and D-π-A derivatives, which have one
electron-rich and one electron-poor aryl ring. Chalcone
derivatives with such structural features generally display
intramolecular charge transfer (ICT) in the excited state
and are highly emissive compounds. Chalcone-based
compounds with these properties have been applied as
15
as fluorescent sensor for picric acid, as additive in dye
6
sensitized solar cell, as color conversion materials for
16
white light-emitting diodes (LEDs), as photosensitizer for
production of singlet oxygen, among others. In this context,
for the development of novel useful chromophores, the
synthesis and photophysical/electrochemical characterization
of novel TPA-chalcones derivatives is important.
In this paper, a series of novel D-π-D and D-π-A
chalcones and β-arylchalcones substituted with TPA
moiety have been synthesized and characterized. Optical,
electrochemical and theoretical properties of these
compounds were studied. In addition, the influence of
chalcone substitution pattern on the electronic properties
was evaluated and compared to the theoretical results
calculated using density functional theory (DFT).
5
fluorescent probes for detection of anions and enzymatic
8
9
acivities, as water content sensor, as electrochromic
1
0
11
materials, as non-linear optical materials, among other
applications.
*e-mail: limberger@puc-rio.br

8
2
Synthesis, Photophysical and Electrochemical Properties of Novel D-p-D and D-p-A Triphenylamino-Chalcones
J. Braz. Chem. Soc.
Results and Discussion
Taking into consideration the widespread application of
carbazole core in the structure of luminescent compounds,
we also designed a TPA-chalcone with architecture D-π-D,
possessing the triarylamino and carbazole as donating
groups. For the synthesis of this dye, in the first step, an
Ullmann coupling between carbazole (6) and 4-bromo-
benzaldehyde (7) was performed with a system based on
CuI, 18-crown-6, K CO and o-dichlorobenzene. Under
For the synthesis of the TPA-chalcone dyes, initially,
4-aminoacetophenone (1) was reacted with 4-iodoanisole (2)
in an Ullmann protocol (Scheme 1). A system composed
of CuI, phenanthroline and K CO was applied and
2
3
provided the TPA-acetophenone 3 in 75% yield. Next,
was reacted with various arylaldehydes in the presence
3
2
3
of KOH in order to afford the aldol products. By using
ethanol as solvent, chalcone formation was not observed
after 4 h at room temperature. This result was attributed to
the low solubility of 3 in the alcoholic solvent. Therefore,
a mixture of tetrahydrofuran (THF) and EtOH (1:1) was
used as reaction media, affording the desired TPA-chalcone
dyes 4a-d in 38-78% yields. It is worth mentioning that
aldehydes substituted with either electron-donating or
electron-withdrawing groups were employed in these
reactions, in order to obtain compounds with D-π-D
or D-π-A architecture. Recently, we reported a useful
methodology to arylate α- and β-positions of chalcones via
these conditions, the intermediate 8 was isolated in 69%
yield. Next, 8 was reacted with 4 in optimized condensation
conditions, affording the target dye 9 in 44% yield.
Photophysical properties of 4a-d, 5a-b and 9 were
studied by means of absorption and emission spectra.
Initially, in order to evaluate both the solvatochromic
effect and the influence of TPA-chalcones substitution
pattern on UV-Vis absorption profiles, spectra were
recorded in isopropanol, acetonitrile, dichloromethane,
toluene and cyclohexane (Figure 1). The relevant
UV-Vis data as well as the calculated oscillator strength
0
18
(f ) and radiative rate constants (k ) are depicted in
e
e
17
Heck or Suzuki couplings. In order to obtain β-aryl-TPA-
chalcones, the Heck protocol (Pd(OAc) , P(o-Tol) , K CO ,
Table 1. For all derivatives, intense absorption bands
5
-1
-1
(ε ca. 10 L mol cm ) peaked between 381 and 435 nm
2
3
2
3
dimethylformamide (DMF)) was applied to the compounds
b and 4c, with iodobenzene or iodoanisole as coupling
partner. In these conditions, the desired β-arylated dyes 5a
and 5b were obtained in 48 and 77% yields, respectively.
were observed. These ε values in conjunction with the
0
4
calculated radiative rate constant (k ) indicate spin and
e
1
symmetry allowed π-π* transitions. The optical band-gaps
were calculated from the absorption spectra and values
o
Scheme 1. Synthesis of the TPA-chalcone and β-arylchalcone derivatives. Reaction conditions: (a) CuI, phenantroline, K CO , 120 C, 20 h; (b) EtOH/
2
3
o
o
THF (1:1), KOH, r.t., 6 h; (c) Pd(OAc) , P(o-Tol) , K CO , 120 C, 24 h; and (d) CuI, 18-crown-6, K CO , o-dichlorobenzene, 180 C, 48 h.
2
3
2
3
2
3

Vol. 30, No. 1, 2019
da Costa et al.
83
varied from 2.25 to 2.76 eV.A considerable solvatochromic
effect was observed in the ground state (∆λabs from 8 to
TPA-chalcone structure caused bathochromic shifts in
comparison with the non-substituted derivative 4a. In
opposition, the insertion of additional aryl groups on olefin
β-position (5a and 5b) produced a small hypsochromic
effect. These blue shifts can be attributed to the non-
planarity of β-arylated chalcones derivatives, since a
considerable torsion angle between the β-aryl groups and
1
7 nm) for all TPA-chalcone derivatives. This effect was
attributed to the electron delocalization between the TPA
moiety and the α,β-unsaturated carbonyl system.
As expected, the insertion of both auxochrome group
NMe (4c) and chromophore group NO (4d) to the
2
2
Figure 1. UV-Vis spectra of the TPA-chalcone derivatives in (a) isopropanol, (b) acetonitrile, (c) dichloromethane, (d) toluene and (e) cyclohexane.
-
1
Concentration of 50 µmol L .

8
4
Synthesis, Photophysical and Electrochemical Properties of Novel D-p-D and D-p-A Triphenylamino-Chalcones
J. Braz. Chem. Soc.
Table 1. Relevant absorption data of compounds 4a-d, 5a-b and 9
4
-1
-1
0
8
-1
Dye
Solvent
i-PrOH
MeCN
CH Cl
λabs / nm
410
392
404
402
402
407
390
400
400
396
431
418
424
415
410
435
416
433
431
432
396
382
390
382
389
400
382
392
381
392
408
394
407
400
397
ε / (10 L mol cm )
2.46
∆Eopt / eV
2.53
2.68
2.54
2.67
2.67
2.59
2.72
2.66
2.68
2.70
2.52
2.62
2.54
2.65
2.62
2.34
2.47
2.25
2.38
2.41
2.57
2.75
2.56
2.74
2.70
2.63
2.76
2.67
2.74
2.70
2.51
2.66
2.49
2.61
2.61
fe
ke / (10 s )
2.19
0.75
2.39
0.46
2.96
2.16
1.26
2.09
0.93
1.69
3.02
0.54
3.47
0.46
3.29
1.17
0.73
1.38
0.59
1.12
2.06
0.45
3.31
0.30
1.68
1.62
0.42
1.21
0.30
2.01
0.74
0.67
3.83
0.53
0.87
0.55
0.17
0.58
0.11
0.51
0.53
0.29
0.50
0.22
0.40
0.84
0.14
0.93
0.12
0.83
0.33
0.16
0.39
0.13
0.31
0.48
0.12
0.75
0.08
0.38
0.39
0.10
0.28
0.07
0.46
0.19
0.15
0.95
0.12
0.20
2.71
4
4
4
4
5
5
9
a
b
c
2.56
2
2
PhMe
cyclohexane
i-PrOH
2.13
2.31
2.45
MeCN
2.80
CH Cl
2.06
2
2
PhMe
cyclohexane
i-PrOH
2.31
2.01
3.02
MeCN
3.01
CH Cl
3.15
2
2
PhMe
cyclohexane
i-PrOH
2.91
3.02
1.56
MeCN
1.64
d
a
b
CH Cl
1.58
2
2
PhMe
cyclohexane
i-PrOH
1.41
1.41
1.70
MeCN
1.65
CH Cl
2.28
2
2
PhMe
cyclohexane
i-PrOH
1.65
1.58
1.48
MeCN
1.54
CH Cl
1.34
2
2
PhMe
cyclohexane
i-PrOH
1.32
1.69
2.29
MeCN
2.05
CH Cl
2.76
2
2
PhMe
2.23
cyclohexane
0.70
0
e
λabs: absorption maximum; ε: molar absorptivity; ∆E : optical band-gap; f : calculated oscillator strength; k : calculated radioactive rate constant.
opt
e
the enone conjugated system was observed on previously
in Figure 2 and in Table 2. The TPA-chalcone derivatives
displayed emission maxima between 470 and 563 nm.
When dissolved in more polar solvents, significant decrease
in the fluorescence intensities along with a considerable red
shift were observed (Figure S1, Supplementary Information
(SI) section). These results suggest that these molecules
present high dipolar moments becoming well solvated in
17
described β-arylated chalcones. The substitution pattern
also affected the extinction coefficient, since hypochromic
effects were observed with the D-π-A compound 4d and
with the β-aryl derivatives 5a and 5b.
The fluorescence spectra of the dyes were recorded in
-1
cyclohexane (5 µmol L ) and the emission data are shown

Vol. 30, No. 1, 2019
da Costa et al.
85
the excited (S1) state. The high polar S1 state in conjunction
with high Stokes shifts (80 to 131 nm in cyclohexane)
suggest a charge transfer character in excited state.
(Φ = 0.93), as a comparison standard. Low Φ values were
observed (1-2%), indicating predominant participation of
f
f
radiationless relaxation for these dyes. The low Φ observed
f
for some chalcone derivatives has been attributed to the
lack of rigidity of their structure, with the dissipation of
electronic energy proceeding through rotation of the aryl
7,21
rings.
In order to study the electrochemical behavior
of the compounds, cyclic voltammograms from
TPA-chalcones 4a-d and β-arylchalcone 5a were
obtained in dichloromethane using tetrabutylammonium
hexafluorophosphate (TBAPF ) as supporting electrolyte
6
(
Figure 3). A glassy carbon electrode (electroactive area
2
of about 0.019 cm ) was used as the working electrode.
An Ag/AgCl(KCl ) electrode was used as the reference
sat
and a platinum wire was used as auxiliary electrode. For
4
a, 4b, 4d and 5a two oxidation peaks were observed
in the positive potential range. An apparently reversible
redox pair can be observed for all of the compounds
with a further oxidation (not reversible) event at higher
potentials. The reversible peak can be attributed to
reversible oxidation of the TPA moiety, also detected in
Figure 2. Fluorescence emission spectra of the TPA-chalcone derivatives
in cyclohexane (concentration of 5 µmol L ).
-
1
Table 2. Relevant data of steady-state fluorescence of compounds 4a-d,
5a-b and 9
1
0
previously described TPA-chalcones. For the compound
c only one non-reversible oxidation peak was detected,
a
b
Compound
λemis / nm
Stokes shift / nm
Φ / %
f
4
4
4
4
4
5
5
a
b
c
517
503
490
563
470
–
118
108
80
1
1
2
–
–
–
2
which can be related to simultaneous oxidation of both
amino groups.
d
a
b
131
81
–
9
504
107
a
-1
Determined in cyclohexane solutions (concentration of 5 µmol L );
b
19
determined in cyclohexane solutions, using the comparative method and
-
1
20
fluorescein sodium salt in 0.1 mol L NaOH (Φ = 93%) as standard.
f
λemis: emission maximum; Φ : fluorescence quantum yield.
f
The influence of substituents on the emission properties
of the TPA-chalcones could be evaluated through the
relative fluorescence intensities (Figure 2). The most
emissive compound was 4c, possessing two strong donating
amino groups. By comparing 4b, 4c and 9 with 4d, it can
be seen that the architecture D-π-D led to compounds
with higher fluorescence than the compound with a D-π-A
design. Another interesting finding was the decrease in
the fluorescence intensity observed when an additional
aryl group was added to the olefin β-position (4a and 4b
vs. 5a and 5b). This result can also be attributed to the
diminished conjugation caused by the lack of planarity
Figure 3. Cyclic voltammetry of 4a-d and 5a dissolved in CH Cl .
2
2
The highest occupied molecular orbital (HOMO) level of
the TPA-chalcones were calculated from the onset potential
using the relation
,
where is the ferrocene/ferrocenium redox couple
17
observed in β-arylchalcones. The fluorescence quantum
yields of the compounds 4a-c and 9 were determined in
cyclohexane using fluorescein, in alkaline aqueous media
potential. Values ranging from –5.17 to –5.04 eV were
observed and the compound with smaller ionization
potential was 4c. By combining the HOMO values with

8
6
Synthesis, Photophysical and Electrochemical Properties of Novel D-p-D and D-p-A Triphenylamino-Chalcones
J. Braz. Chem. Soc.
the optical band-gaps, the lowest unoccupied molecular
orbital (LUMO) level was also estimated (Table 3). Values
from –2.92 to –2.48 eV were observed and the D-π-A
chalcone 4d displayed the lower energy level, indicating
the high electron affinity of this compound.
aryl groups. For the D-π-A dye 4d the orbital is extended
over the nitro group.
Conclusions
In summary, seven novel TPA-chalcone derivatives
were synthesized and characterized. The compounds
display intense absorption bands, moderate fluorescence
intensity and band-gaps in appropriate range for application
in electroluminescent devices. The chalcone substitution
pattern plays a crucial role in the properties of the dyes.
Among the compounds, 4a presented featured properties,
including higher extinction coefficient, higher fluorescence
quantum yield and lower ionization potential. These
features were attributed to the presence of a more electron-
donating aryl group (4-dimethylaminophenyl) bonded to
the acceptor α,β-conjugated carbonyl system.
Table 3. HOMO, Egap and LUMO obtained by cyclic voltammetry
a
b
c
Compound
Eonset / V
0.79
EHOMO / eV
Egap / eV
ELUMO / eV
4
4
4
4
5
a
b
c
–5.15
–5.14
–5.04
–5.17
–5.13
2.54
2.66
2.54
2.25
2.56
–2.61
–2.48
–2.50
–2.92
–2.57
0.78
0.68
d
a
0.81
0.77
a
+
.
The oxidation potential of Fc/Fc
-
2
against Ag/AgCl was recorded in CH Cl -Bu NPF (5 × 10 M)
2
2
4
6
b
solution as 0.49 V; optical band-gap obtained from absorption spectra
c
in dichloromethane; E
(eV) = EHOMO + Egap. Eonset: onset potential.
LUMO
Experimental
Computational calculations using DFT method
were performed in order to rationalize the experimental
properties of the TPA-chalcone dyes. Becke, three-
parameter, Lee-Yang-Parr (B3LYP) exchange correlation
functional with 6-31G** basis set was used for the structure
Materials and instruments
All solvents used (isopropanol, dichloromethane,
cyclohexane, toluene, dichlorobenzene and DMF) were of
analytical grade and purchased from Merck. Fluorescein
sodium salt was from Fluka, and NaOH was from Merck.
When used in Ullmann and Heck reactions, toluene, DMF
2
2
optimization. Theoretical studies have been performed
2
3
using ORCA 3.0.3 program package. The obtained
LUMO and HOMO energy levels, as well as the orbital
distribution, are depicted in Figure 4. For all compounds,
the HOMO is located mainly over the TPA moiety. For 4c a
slight HOMO orbital density can also be observed over the
diarylamino unit. This finding can be related to the charge
transfer feature observed for this compound in the ground
state and also to the higher fluorescence of this compound
in comparison with other synthesized TPA-chalcones.
Concerning the LUMO coefficient, for all compounds, the
orbital is concentrated over the enone and vinyl-substituted
and dichlorobenzene were deaerated with N before the
reactions.
2
UV-VisabsorptionspectrawereacquiredonaPerkinElmer
Lambda 35 spectrophotometer using scan velocity of
-1
1200 nm min , spectral bandpass of 10 nm and 1 cm path
length quartz cuvettes. Photoluminescence spectra and steady
state photoluminescence measurements were performed on
a Horiba model FluoroMax 4 spectrophotometer. Scanning
-1
was made at 1500 nm min with solutions placed in 1 cm
optical path length quartz cuvettes (four optically clear faces).
Nuclear resonance magnetic (NMR) spectra were recorded
in a Bruker model Advance III HD 400 MHz spectrometer.
Electron spray ionization high-resolution mass spectrometric
(ESI(+)-HRMS) analyses were performed on a Micromass
Q-ToF mass spectrometer (Waters). The infrared spectra
were recorded with a PerkinElmer Spectrum 2 spectrometer
-1
in the range 3500-500 cm .
Synthesis and characterization
Synthesis of 1-(4-(bis(4-methoxyphenyl)amino)phenyl)
ethanone (3)
An oven-dried resealable Schlenk flask was filled with
4-aminoacetophenone (270 mg, 2.0 mmol), CuI (76 mg,
Figure 4. Energy levels and orbital distribution for HOMO and LUMO
obtained from DFT calculations at the B3LYP/6-31G** level.

Vol. 30, No. 1, 2019
da Costa et al.
87
-
1
0
.4 mmol) and phenanthroline (83 mg, 0.5 mmol), evacuated
ν / cm 2930, 2834, 1653, 1588, 1504, 1421, 1290, 1240,
1
and back-filled with nitrogen. Then, 4-iodoanisole (1.2 g,
1223; H NMR (400 MHz, CDCl ) d 7.87 (d, J 8.8 Hz,
3
5
.0 mmol), KOH (840 mg, 15 mmol) and toluene (8 mL)
2H), 7.78 (d, J 15.6 Hz, 1H), 7.65-7.60 (m, 2H), 7.53 (d,
J 15.6 Hz, 1H), 7.40 (d, J 7.1 Hz, 3H), 7.13 (d, J 8.8 Hz,
4H), 6.88 (t, J 8.3 Hz, 6H), 3.82 (s, 6H); C NMR
o
were added and the reaction was stirred at 100 C for 12 h.
After, the mixture was allowed to attain room temperature,
filtered and concentrated in rotatory evaporator. The crude
product was purified through column chromatography in
1
3
(100 MHz, CDCl ) d 188.0, 157.1, 152.9, 143.2, 139.3,
3
135.4, 130.3, 130.1, 129.0, 128.9, 128.3, 127.9, 122.1,
silica gel (hexane/ethyl acetate) providing the compound 3
117.1, 115.0, 55.6; HRMS (ESI) m/z calcd. for C H NO
3
[M + H] : 436.1916; found: 436.1896.
2
9
26
1
+
in 75% yield as a white solid. H NMR (400 MHz, CDCl )
3
d 7.75 (d, J 9.0 Hz, 2H), 7.11 (d, J 9.0 Hz, 4H), 6.88 (d,
J 9.0 Hz, 4H), 6.81 (d, J 9.0 Hz, 2H), 3.81 (s, 6H), 2.50 (s,
(E)-1-(4-(bis(4-Methoxyphenyl)amino)phenyl)-3-(4-methoxy-
phenyl)prop-2-en-1-one (4b)
1
3
3
H); C NMR (100 MHz, CDCl ) d 196.4, 157.0, 152.9,
3
o
-1
1
39.2, 130.0, 128.2, 127.9, 116.8, 115.0, 55.5, 26.2.
Yellow solid; 62% yield; mp 85 C; IR (ATR) ν / cm
3
039, 2932, 2835, 1653, 1586, 1503, 1449, 1336, 1284,
1
Synthesis of 4-(9H-carbazol-9-yl)benzaldehyde (8)
The compound 8 was synthesized as described in
1249, 1032; H NMR (400 MHz, CDCl ) d 7.87 (d,
3
J 8.8 Hz, 2H), 7.76 (d, 1H), 7.58 (d, J 8.7 Hz, 2H), 7.40 (d,
24
literature. In a typical reaction, 249.4 mg (1.5 mmol) of
H-carbazole, 283.2 mg (1.5mmol) of 4-bromobenzaldehyde,
8.0 mg (0.22 mmol) of 18-crown-6, 303.9 mg (2.2 mmol)
of K CO , 42.3 mg (15 mmol%) CuI and 1.5 mL of
1H), 7.17-7.07 (m, 4H), 6.89 (m, 8H), 3.85 (s, 3H), 3.82 (s,
13
9
5
6H); C NMR (101 MHz, CDCl ) d 188.0, 161.3, 157.0,
3
152.7, 143.0, 139.3, 130.1, 130.0, 129.3, 128.1, 127.8,
119.7, 117.2, 115.0, 114.3, 65.9, 55.5; HRMS (ESI) m/z
2
3
+
o-dichlorobenzene were added to a 10 mL Schlenk tube. The
calcd. for C H NO [M + H] : 466.2018; found: 466.2031.
30
28
4
o
mixture was refluxed under nitrogen atmosphere at 180 C for
4
8 h.After, the reaction was quenched with aqueous 20% HCl
(E)-1-(4-(bis(4-Methoxyphenyl)amino)phenyl)-3-(4-(dimethyl-
amino)phenyl)prop-2-en-1-one (4c)
and extracted with chloroform. The organic phase was dried
with anhydrous Na SO and concentrated under vacuum. The
product was purified by silica flash column chromatography
o
Reddish-brown solid; 40% yield; mp 149-151 C; IR
2
4
-1
(ATR) ν / cm 3027, 2906, 2836, 1645, 1590, 1500, 1432,
1
(mobile phase: ethyl acetate/hexane 5%). The compound 8was
1338, 1229, 1028; H NMR (400 MHz, CDCl ) d 7.86 (d,
3
1
obtained as a white solid in 69% yield. H NMR (400 MHz,
DMSO-d ) d 10.14 (s, 1H), 8.28 (d, J 7.67 Hz, 2H), 8.21 (d,
J 8.9 Hz, 2H), 7.77 (d, J 15.4 Hz, 1H), 7.53 (d, J 8.9 Hz,
2H), 7.34 (d, J 15.5 Hz, 1H), 7.12 (d, J 8.9 Hz, 4H), 6.89-
6
J 8.35 Hz, 2H), 7.92 (d, J 8.32 Hz, 2H), 7.53 (d, J 8.32 Hz,
6.86 (m, 6H), 6.69 (d, J 8.9 Hz, 2H), 3.82 (s, 6H), 3.03 (s,
13
13
2H), 7.47 (t, J 7.63 Hz, 2H), 7.34 (t, J 7.38 Hz, 2H); C NMR
6H); C NMR (101 MHz, CDCl ) d 188.3, 156.9, 152.4,
3
(
1
100 MHz, DMSO-d ) d 193.1, 143.1, 140.4, 135.5, 132.3,
151.8, 144.1, 139.5, 130.1, 130.0, 127.7, 123.1, 117.3,
116.8, 114.9, 111.9, 55.5, 40.2.
6
27.6, 127.4, 124.2, 121.7, 121.6, 110.8; infrared (IR)
-1
(attenuated total reflectance, ATR) ν / cm 3050, 2824, 2743,
1
702, 1595, 1510, 1479, 1450, 1361, 1336, 1198, 1161, 1123,
(E)-1-(4-(bis(4-Methoxyphenyl)amino)phenyl)-3-(4-nitro-
phenyl)prop-2-en-1-one (4d)
1103, 916, 830, 749, 720, 633, 620, 567, 529, 502.
o
Reddish-brown solid; 38% yield; mp 106-108 C; IR
-1
Typical procedure for synthesis of the TPA-chalcones
A mixture of 3 (347 mg, 1.0 mmol), the respective
arylaldehyde (1.6 mmol), NaOH (48 mg, 1.2 mmol), ethanol
(ATR) ν / cm 2929, 2837, 1655, 1586, 1505, 1339, 1241;
1
H NMR (400 MHz, CDCl ) d 8.26 (d, J 8.9 Hz, 2H),
3
7.87 (d, J 8.9 Hz, 2H), 7.78 (d, J 15.8 Hz, 1H), 7.75 (d,
J 11.9 Hz, 2H), 7.63 (d, J 15.8 Hz, 1H), 7.14 (d, J 8.9 Hz,
(4 mL) and THF (4 mL) was stirred at room temperature for
13
18 h. Then, the solvent was evaporated in rotatory evaporator,
4H), 6.91-6.85 (m, 6H), 3.82 (s, 6H); C NMR (100 MHz,
the crude product was dissolved in 30 mL of dichloromethane
and washed with water (3 × 10 mL). The organic solution
was dried over sodium sulfate, filtered and concentrated in
rotatory evaporator. The crude product was purified through
column chromatography in silica gel (hexane/ethyl acetate).
CDCl ) d 186.8, 157.3, 153.3, 148.3, 141.6, 140.1, 138.9,
3
130.5, 128.7, 128.2, 128.0, 125.9, 124.2, 116.8, 115.0,
+
55.5; HRMS (ESI) m/z calcd. for C H N O [M + H] :
29
25
2
5
481.1763; found: 481.1785.
(
E)-1-(4-(bis(4-Methoxyphenyl)amino)phenyl)-
(
E)-1-(4-(bis(4-Methoxyphenyl)amino)phenyl)-
-phenylprop-2-en-1-one (4a)
3-(4-(9H-carbazol-9-yl)phenyl)prop-2-en-1-one (9)
o
3
Yellow solid; 44% yield; mp 173-175 C; IR (ATR)
o
-1
Yellow solid; 78% yield; mp 115-117 C; IR (ATR)
ν / cm 2931, 2836, 1652, 1595, 1505, 1450, 1335, 1241,

8
8
Synthesis, Photophysical and Electrochemical Properties of Novel D-p-D and D-p-A Triphenylamino-Chalcones
J. Braz. Chem. Soc.
1
1
225, 1171, 1028; H NMR (400 MHz, CDCl ) d 8.15
Theoretical calculation software
3
(
d, J 7.7 Hz, 2H), 7.92 (d, J 8.9 Hz, 2H), 7.88-7.84 (m,
2
2
6
1
1
1
H), 7.66-7.58 (m, 3H), 7.49-7.41 (m, 4H), 7.35-7.28 (m,
Theoretical calculations were performed using ORCA
2
3
H), 7.15 (d, J 8.9 Hz, 2H), 6.95-6.82 (m, 6H), 3.83 (s,
3.0.3 program package. Structures optimization were
carried out by the DFT method using B3LYP exchange-
1
3
H); C NMR (101 MHz, CDCl ) d 187.7, 157.1, 153.0,
3
22
42.0, 140.5, 139.2, 139.2, 134.2, 130.3, 129.7, 128.9,
27.9, 127.1, 126.1, 123.6, 122.5, 120.4, 120.3, 117.0,
15.0, 109.8, 55.5; HRMS (ESI) m/z calcd. for C H N O
3
correlation functional with the 6-31G** basis set. Solvent
effect (cyclohexane) was taken into account via the
COSMO solvation method (ORCA package).
41
33
2
+
[
M + H] : 601.2491; found: 601.2499.
Determination of fluorescence quantum yields
Typical procedure for the synthesis of β-arylchalcones 5a
and 5b
The fluorescence quantum yield of chalcones were
19
An oven-dried resealable Schlenk flask was filled
determinedbyastandardcomparativemethod usingequation
1. All chalcone solutions were prepared in cyclohexane at a
with 4b or 4c (1.0 mmol), Pd(OAc) (4.4 mg, 0.02 mmol)
2
-7
-6
-1
and P(o-Tol) (12.2 mg, 0.04 mmol), evacuated and
concentration range between 3.0 × 10 -1.1 × 10 mol L .
Fluorescein sodium salt solution was prepared in NaOH
3
back-filled with nitrogen. Then, aryl iodide (1.5 mmol),
K CO (276 mg, 2.0 mmol) and DMF (4 mL) were added
-1
(0.1 mol L ) and employed as the standard solution with
2
3
o
20
and the reaction was stirred at 120 C for 24 h. After, the
mixture was allowed to attain room temperature, water
fluorescence quantum efficiency (f ) of 0.93.
st
(
15 mL) was added and the product was extracted with
ethyl acetate (3 × 15 mL). The combined organic layers
were dried over sodium sulfate, filtered and concentrated in
rotatory evaporator. The crude product was purified through
column chromatography in silica gel (hexane/ethyl acetate)
providing the β-arylchalcones 5a and 5b in 48 and 77%
yields, respectively.
(1)
where
and
is the
integrated area of the fluorescence spectra of standard
(x = st) or chalcone (x = ch) and n is the refractive index
of solvents.
1
3
- ( 4 - ( b i s ( 4 - M e t h ox y p h e ny l ) a m i n o ) p h e ny l ) -
,3-diphenylprop-2-en-1-one (5a)
Orange oil; 48% yield; IR (ATR) ν / cm 2932, 2835,
Cyclic voltammetry
-1
1
1647, 1588, 1502, 1443, 1329, 1267, 1239, 1163; H NMR
Cyclic voltammetry was performed on an Ivium Compact
Stat potentiostat. The measurements were performed in a
system of three-electrode setup: (i) a glassy carbon working
electrode; (ii) an Ag/AgCl(KCl(sat)) reference electrode; and
(iii) a Pt auxiliary electrode. Solutions of the compounds 4a-d
(
400 MHz, CDCl ) d 7.72 (d, J 8.9 Hz, 2H), 7.35 (s, 5H),
3
7
5
6
1
1
5
5
.28 (d, J 7.2 Hz, 3H), 7.21-7.16 (m, 2H), 7.10-7.04 (m,
H), 6.86 (d, J 9.0 Hz, 4H), 6.75 (d, J 8.9 Hz, 2H), 3.80 (s,
H); C NMR (101 MHz, CDCl ) d 190.8, 157.0, 152.9,
1
3
3
-3
-1
52.7, 141.8, 139.4, 139.3, 130.5, 129.8, 129.3, 129.0,
28.5, 128.4, 128.1, 128.0, 127.7, 124.8, 117.1, 114.9,
and 5a with concentration of 2 × 10 mol L were prepared
in dichloromethane. TBAPF was used as supporting
6
+
25
5.5; HRMS (ESI) m/z calcd. for C H NO [M + H] :
electrolyte. An electrochemical cell without the chalcone
35
30
3
12.2226; found: 512.2245.
derivatives was used for reference and the pair ferrocene/
ferrocenium was used for calibration. The cyclic
voltammetry experiments were performed in a range of 0 to
2.0V with a step of 50 mV s and these measurements were
repeated 5 times. The HOMO energy levels were obtained
2
6
1
3
- ( 4 - ( b i s ( 4 - M e t h ox y p h e ny l ) a m i n o ) p h e ny l ) -
-1
,3-bis(4-methoxyphenyl)prop-2-en-1-one (5b)
1
Orange oil; 77% yield; H NMR (400 MHz, CDCl )
3
d 7.72 (d, J 8.9 Hz, 2H), 7.33-7.28 (m, 2H), 7.14-7.09 (m,
through the equation
.
2
6
H), 7.09-7.04 (m, 4H), 6.93 (s, 1H), 6.89-6.83 (m, 5H),
.82-6.78 (m, 2H), 6.75 (d, J 8.9 Hz, 2H), 3.83 (s, 6H), 3.81
13
(s, 6H); C NMR (101 MHz, CDCl ) d 190.9, 160.5, 159.6,
3
1
1
5
56.9, 153.2, 152.4, 139.5, 134.7, 131.9, 131.4, 130.4,
30.1, 129.8, 127.6, 122.3, 117.2, 114.9, 113.7, 113.3,
5.5, 55.4, 55.2; HRMS (ESI) m/z calcd. for C H NO
5
Supplementary Information
Supplementary information is available free of charge
at http://jbcs.sbq.org.br as PDF file.
37
34
+
[
M + H] : 572.2437; found: 572.2410.

Vol. 30, No. 1, 2019
da Costa et al.
89
Acknowledgments
11. Poornesh, P.; Shettigar, S.; Umesh, G.; Manjunatha, K. B.;
Prakash Kamath, K.; Sarojini, B. K.; Narayana, B.; Opt. Mater.
2009, 31, 854.
The authors would like to thank VRAC/PUC-Rio
and FAPERJ for partial financial support. Authors also
acknowledge FAPERJ (R. Q. A., F. R. L. F.), CAPES (L.
M.) and CNPq (R. Q. A., J. M. S. A., L. S. A. C., R. G.
M. C.) for the granted scholarships. The authors are also
grateful to CAPLH-PUC-Rio for the use of NMR facilities,
to Prof Marco Cremona for the use of IR facilities and to
Prof Jairton Dupont for the use of the HRMS facilities.
12. Planells, M.; Abate, A.; Hollman, D. J.; Stranks, S. D.; Bharti,
V.; Gaur, J.; Mohanty, D.; Chand, S.; Snaith, H. J.; Robertson,
N.; J. Mater. Chem. A 2013, 1, 6949.
13. Kochapradist, P.; Prachumrak, N.; Tarsang, R.; Keawin, T.;
Jungsuttiwong, S.; Sudyoadsuk, T.; Promarak, V.; Tetrahedron
Lett. 2013, 54, 3683.
14. Liang, Z.-Q.; Wang, X.-M.; Dai, G.-L.;Ye, C.-Q.; Zhou,Y.-Y.;
Tao, X.-T.; New J. Chem. 2015, 39, 8874.
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Submitted: May 29, 2018
2
Published online: August 17, 2018
This is an open-access article distributed under the terms of the Creative Commons Attribution License.