Syntheses, experimental and theoretical studies on absorption/emission properties of pyrazoline-containing aryl/methoxynaphthyl substituents

Article abstract of DOI:10.21577/0103-5053.20170216

5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine. The compounds were characterized by¹H and¹³C nuclear mag

Full text of DOI:10.21577/0103-5053.20170216

http://dx.doi.org/10.21577/0103-5053.20170216
J. Braz. Chem. Soc., Vol. 29, No. 6, 1210-1217, 2018
Printed in Brazil - ©2018 Sociedade Brasileira de Química
Article
Syntheses, Experimental and Theoretical Studies on Absorption/Emission
Properties of Pyrazoline-Containing Aryl/Methoxynaphthyl Substituents
Jorge Trilleras,*,a Edwin González-López,a Jhair León-Jaramillo,a
Alfredo Pérez-Gamboa,a Esneyder Puello-Polo,b Pablo Romo,c
Alejandro Ortízc,d andJairo Quirogac,d
aGrupo/Semillero de Investigación en Compuestos Heterocíclicos, Programa de Química-Ciencias Básicas,
Universidad del Atlántico, km 7 Via Puerto, Atlántico, Colombia
bGrupo de Investigación en Oxi/Hidrotratamiento Catalítico y Nuevos Materiales,
Programa de Química-Ciencias Básicas, Universidad del Atlántico, km 7 Via Puerto, Atlántico, Colombia
cGrupo de Investigación de Compuestos Heterocíclicos, Departamento de Química,
Universidad del Valle, A. A. 25360 Cali, Colombia
dCentre for Bioinformatics and Photonics, CIBioFI,
Calle 13 No. 100-00, Edificio 320, No. 1069, 760032 Cali, Colombia
5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized
starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine.
The compounds were characterized by 1H and 13C nuclear magnetic resonance (NMR), elemental
analyses and mass spectrometry. Some compounds showed promising luminescence properties
in solution and in solid state; the absorption and emission characteristics were measured and
the fluorescence quantum yield of two of the derivatives [4,5-dihydro-3-(2-methoxynaphthalen-
6-yl)-5-(3,4,5-trimethoxyphenyl)-1-phenyl-1H-pyrazoline and 5-(4-chlorophenyl)-4,5-dihydro-
3-(2-methoxynaphthalen-6-yl)-1-phenyl-1H-pyrazoline] were found to have excellent values
compared to rhodamine B standard. Theoretical calculations at time-dependent density functional
theory (TD-DFT) level are in agreement with the experimental measurements and are helpful to
explain the electronic behavior.
Keywords: luminescence, 1-naphthalenylpropenone, TD-DFT, triaryl pyrazoline derivatives
Introduction
versatile synthetic auxiliaries in classical organic synthesis.
Reports in the literature15-18 have attributed an increase
in the biological properties of pyrazoline derivatives
to the combined effect of ERG, aryl substituents and
π-extended configuration. These electronic and structural
characteristics of compounds containing the pyrazole
nucleus are also widely used in electroluminescence fields.
Reports in the literature include studies on solvatochromic
effect and electrochemical, photophysical, optical and
nonlinear optical properties.5-8,19-22 Following our research
on the synthesis and evaluation of potential applications
of pyrazole derivatives,23,24 and the growing interest in
the development of luminescence small molecules as
emitting materials and biology research,5-8,19-25 we report a
series of pyrazoline derivatives incorporating methoxyl, an
electron donor group, naphthyl and phenyl substituents as
chromophores, on the π-conjugated structure and analysis
of absorption/emission properties of these compounds.
The properties and applications of pyrazoline and
their analogues are numerous and known, not only in the
biological and medical field,1-4 but also for their potential
and practical applications as materials with luminescent
and nonlinear optical properties.5-8
The building of these N-heterocycles systems, from
simple reactions, using small molecules and compatible
with multicomponent, regioselective, eco-friendly and
efficient synthetic procedures, which include variations
to conventional methods, allows to incorporate specific
structural characteristics.9-14
Substituents of different nature, electron withdrawing
group (EWG) and electron releasing group (ERG), in
aromatic aldehydes, ketones and hydrazines, make them
*e-mail: jorgetrilleras@mail.uniatlantico.edu.co

Vol. 29, No. 6, 2018
Trilleras et al.
1211
Results and Discussion
of the reaction and easy isolation of the solid formed. The
results inducing the reaction by ultrasound radiation were
not satisfactory. In the molecular structure of derivatives
4, it is remarkable the presence of a cyclic hydrazine
core, although this phenomenon diminishes the electronic
conjugation respect to derivatives 3, the mentioned fact
does not allow the isomerization of the double bond C=N.
This feature allows favored processes of photoinduced
electronic transfer (PET) and so a strong influence in the
luminescent properties29-31 as this behavior can be seen in
the computational detail below.
The yields (see Table 1) of compounds 3 and 4 were
determined by stoichiometric analysis of the starting
materials and the final weight of product obtained
after purified and complete drying (compared to the
stoichiometric expected quantity). Despite the difference
in electronegativity of the substituents on chalcone and
pyrazoline derivatives, no influence was observed on the
final yield of the compounds.
All compounds were characterized by nuclear
magnetic resonance (NMR), elemental analyses and mass
spectrometry (MS) analysis. The 1H NMR spectra of all the
derivatives show the characteristic signals. In the case of
compounds 3, signals are observed in the aromatic region
with multiplicity of doublets, corresponding to the Hα and
Hβ protons of the unsaturated system, with J > 15 Hz. The
compound 4 have two methylene protons (Ha and Hb) and
one methine proton (Hx), evidenced in the spectrum by
Synthesis and characterization of the chalcones 3 and
pyrazoline 4 derivatives
Pyrazoline derivatives were obtained by a conventional
method, outlined in Scheme 1. Chalcones 3 were
prepared by the classical method of Claisen-Schmidt
condensation between 1-(2-methoxynaphthalen-6-yl)
ethanone and aromatic aldehydes.26 The ultrasound-
promoted reaction, unlike conventional heating, results
in improved yields, shorter reaction times, easy work-up
and milder conditions, compared with data reported in the
literature for chalcones 3a, 3b and 3g.27
Due to the availability of commercial reagents
(aldehydes and ketones), and different types of reactions
involved, the α,β-unsaturated derivatives are versatile
precursors for the construction of substituted heterocyclic.
Specifically, in the incorporation of ERG and core
recognized as chromophores-a 2-methoxynaphthalen-6-yl
group in the 3-position and 5-aryl pyrazoline moiety, both
linked from the starting chalcone 3.28 The preparation of
the pyrazoline derivatives 4a-g was made using Michael
cyclocondensation reaction. By varying the reaction
parameters (solvent, acid and molar ratio of reactants), the
reaction conditions suitable were established to prepare the
pyrazoline derivatives in less time and higher yield. An
acetic acid/water mixture allows visualizing the progress
Scheme 1. Reaction sequence for the synthesis of (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-ones (3a-g) and 5-aryl-3-(2-methoxynaphthalen-
6-yl)-1-phenylpyrazolines (4a-g).
Table 1. Reaction time (tr), melting point (Tf) and yield for compounds 3 and 4
Compound 3
Tf / °C
Compound 4
Tf / °C
entry
Aryl
tr / min
10
Yield / %
80a
tr / h
4.5
3
Yield / %
a
b
c
d
e
f
4-CH3C6H4
4-H3COC6H4
3,4,5-tri-H3COC6H2
3,4-OCH2C6H3
2-H3COC11H6
4-ClC6H4
166-169
131-134
126-129
170-173
210-213
166-169
198-201
228-231
214-217
186-189
238-241
245-248
219-222
222-225
75
70
70
70
70
73
75
5
81a
10
78
3
10
76
4
10
77
3.5
3
5
80
g
4-NO2C6H4
15
65a
3.5
aReported in the literature.26

1212
Syntheses, Experimental and Theoretical Studies on Absorption/Emission Properties
J. Braz. Chem. Soc.
Table 2. Absorption and emission data of compounds 3c, 3f, 4c and 4f
c
Compound
λ1 / nm
229
λ2 / nm
262
264
−
λmaxa / nm
317
ε / (M-1 cm-1)
1.19 × 104
1.66 × 104
1.39 × 104
λemb (F ) / nm
3c
3f
4c
4f
372 (6.72 × 10-3)
370 (1.15 × 10-3)
449 (0.593)
231
319
239
359
239
–
361
1.84 × 104
448 (0.740)
b
c
aSolutions concentrations: (1 × 10-5 M); emission spectra measured at λmax for excitation for each compound; emission quantum yield with respect to
rhodamine B as standard.
three doublets of doublets corresponding to the Ha, Hb and
Hx atoms of the pyrazoline ring, respectively.
Absorption and emission properties
The electronic properties of compounds 3c, 3f, 4c and 4f
in acetonitrile were studied by absorption and fluorescence
spectroscopy because of their outstanding emission
properties in solution and solid state. In the absorption
spectra of all compounds, a strong band around 229-239 nm
associated to π-π* transition is observed; compounds 3c and
3f show an additional π-π* transition around 262-264 nm as
a shoulder; the n-π* transitions for 3c and 3f are shifted to
Figure 1.Absorption spectra of compounds 3c, 3f, 4c and 4f in acetonitrile
at room temperature.
higher energy values than the same transitions for 4c and 4f
due to the presence of nitrogen atoms in the pyrazoline ring
of the latter (Figure 1). Table 2 summarizes the absorption
and emission data.
The emission spectra of compounds 3c, 3f, 4c and 4f
(Figure 1) were measured in acetonitrile as solvent at λmax
as excitation wavelength. This value is also near to the
excitation wavelength of rhodamine B as standard.
In this way, a broad emission band can be seen
at 370-449 nm (λem) for all compounds (Figure 2);
additionally, compound 3c exhibits a second emission band
at 483 nm, an indication that the deactivation emission
pathways are the same for compounds 3f, 4c and 4f. On
the other hand, the shapes between the absorption and
fluorescence spectra of compound 3c are quite different,
which indicate different exciton structures between the
ground and excited states in such molecule, according to
the Kasha model.32,33
The fluorescence quantum yields (F) were calculated
from equation 1 using rhodamine B in acetonitrile as the
standard.
(1)
Figure 2. (a) Emission spectra of compounds 3c, 3f, 4c and 4f in acetonitrile at room temperature; (b) normalized emission spectra of compounds 3c, 3f,
4c and 4f.

Vol. 29, No. 6, 2018
Trilleras et al.
1213
where F and Fstd are the areas under the fluorescence curves
of the compounds and the standard, respectively; A and
Astd are the absorbance peaks of the sample and standard
at the excitation wavelengths, respectively; I and Istd are the
relative intensities of the exciting lights of the samples and
the standard, respectively; and n2 and n2std are the refractive
indices of the solvents used for the sample and standard,
respectively.
According to equation 1, the experimental quantum
yields (F) of compounds 4c and 4f are higher (0.593-0.740)
than those of compounds 3c and 3f (1.15 × 10-3-6.72 × 10-3),
even higher than rhodamine B, due to the lowest unoccupied
molecular orbital (LUMO) stabilization of pyrazoline
ring, this fact indicates the ease of the excitonic states
deactivation. As shown in Figure 2, the areas under the
fluorescence curves of compounds 4c and 4f are higher
than the rhodamine B. This phenomenon is favored by the
reduction of the emission energy gap of the compounds
mentioned above, which is due to the introduction of the
nitrogen atoms of the heterocyclic ring.
Frontier orbital diagram for photophysic process for 4f
(Figure 3) can be used to explain the experimental features
in the absorption and emission spectra measured.According
to the observed experimental data and their relationship to
those found computationally, the highest energy occupied
molecular orbital (HOMO) to LUMO transition generates
(PET behavior) a first excited state (S1) with an additional
transition between HOMO-1 and LUMO to generate the
excited state (S2); the emission process can be ascribed to
a LUMO to HOMO (among some of his vibrational states)
decay; in this way, the LUMO to HOMO-1 decay is slightly
promoted with several non-radiative decay processes.
We made theoretical calculations at time-dependent
density functional theory (TD-DFT) level, using B3LYP
as hybrid functional and 6-31G++ as basis set to determine
the minimum energy geometry. In addition, we used the
polarization continuum method (PCM) model to simulate
the electronic excited state properties in the presence of
acetonitrile as solvent, in order to explain the absorption
behaviors of the obtained compounds 3c, 3f, 4c and 4f. The
theoretical data for electronic excited states are summarized
in Table 3. Importantly, the calculated transition energies
are close in regard to the experimental transition energies
(see Table 3), although it is clear that the theoretical
method used in this work underestimates the energy values
for both electronic transitions; this trend is usual in DFT
calculations.
Figure 3. Energy levels diagram for photo-physic process of 4f (absorption
and emission).
Conclusions
We synthesized seven pyrazoline derivatives, four
new and three already reported in the literature, through
a simple synthetic sequence with low environmental
impact. The characteristic of this work is the variation
in the conditions of classical reactions and incorporation
of recognized chromophores in the target structure.
Compounds 4c and 4f may represent a new alternative
as materials in luminescence applications due to the
interesting π-π* and n-π* bands exhibited in the absorption
spectra with remarkable ε values between 1.39 × 104 and
1.84 × 104 M-1 cm-1. Furthermore, the fluorescence quantum
yields (0.593-0.740) are in the range of the analytical and
biological qualitative and quantitative probes.
Table 3. Theoretical data for electronic excited states of compounds 3c,
3f, 4c and 4f
Oscillator
Compound
Excited state
Energy / eV
strength
0.6476
0.2796
0.2702
0.4048
0.6530
0.2857
0.8954
0.7375
0.8972
0.4165
S1 (HOMO→LUMO)
S2 (HOMO-1→LUMO)
S3 (HOMO-2→LUMO+3)
S1 (HOMO→LUMO)
S2 (HOMO-2→LUMO)
S3 (HOMO-3→LUMO)
S1 (HOMO→LUMO)
S2 (HOMO-1→LUMO+1)
S1 (HOMO→LUMO)
S2 (HOMO-1→LUMO)
3.0054
3.3034
4.4727
2.9649
3.5798
3.8339
3.1861
4.7825
2.7985
4.7448
3c
3f
Experimental
4c
4f
All materials, reagents and solvents reagent grade
are commercial (Merck or Aldrich Chemical Company).
Melting points were determined using a Thermo Scientific

1214
Syntheses, Experimental and Theoretical Studies on Absorption/Emission Properties
J. Braz. Chem. Soc.
Fluke 51 II, model IA 9100 melting point apparatus and are
reported uncorrected. 1H NMR (400 MHz) and 13C NMR
(100 MHz) spectra of compounds (in dimethyl sulfoxide,
DMSO-d6) were recorded at room temperature on a Bruker
Ultra Shield 400. Peak multiplicities were designed as:
s, singlet; d, doublet; t, triplet; m, multiplet; dd, double
doublet. Chemical shifts were reported as d (ppm) relative
tetramethylsilane (TMS) as internal standard and coupling
constants (J) were reported in hertz (Hz). The EI-MS were
run on a Shimadzu GC-MS 2010 spectrometer, which was
operating at 70 eV. The elemental analyses were performed
on a LECO CHNS-900 elemental analyzer and the values
are within 0.4% of theoretical values.
Ultrasonic irradiation was performed by using a
Branson ultrasonic cleaner bath, model 1510, 115v, 1.9 L
with mechanical timer (60 min with continuous hold) and
heater switch, 47 kHz. Progress of reaction was monitored
by thin-layer chromatography (TLC) on F254 silica-gel pre
coated sheets (Merck, Darmstadt, Germany), revealed
under UV light (254 and 365 nm), with ethyl acetate:hexane
(3:7 v/v) as solvent systems. The resulting solid was filtered
and purified by recrystallization from methanol or ethanol/
hexane mixture.
DMSO-d6) d 8.83 (s, 1H), 8.11 (d, 1H), 8.07 (d, 1H),
7.97 (d, 1H, J 15.7, Hβ), 7.94 (d, 1H), 7.89 (d, 2H, J 8.8,
Ho), 7.76 (d, 1H, J 15.7, Hα), 7.45 (s, 1H), 7.29 (d, 1H),
7.05 (d, 2H, J 8.8, Hm), 3.92 (s, 1H, OCH3), 3.83 (s, 1H,
OCH3); 13C NMR (100 MHz, DMSO-d6) d 188.3 (C=O),
161.3 (Cp), 159.4, 143.4 (Cβ), 136.8, 133.1, 131.2, 130.7
(Co), 130.1 (Ci), 127.6, 127.5, 127.2, 124.8, 119.6 (Cα),
119.5, 114.4 (Cm), 106.1, 55.4 (OCH3), 55.3 (OCH3); MS
(ESI, positive scan 70 eV) m/z, 318 [M+]; anal. calcd. for
C21H18O3: C 79.22, H 5.77, found: C 79.23, H 5.73.
(E)-1-(2-Methoxynaphthalen-6-yl)-3-(3,4,5-trimethoxy-
phenyl)prop-2-en-1-one (3c)
1
Yield 78%; mp 126-129 °C; H NMR (400 MHz,
DMSO-d6) d 8.80 (s, 1H), 8.60 (s, 1H), 8.06 (d, 1H), 8.01
(d, 1H, J 15.6, Hβ), 7.96 (d, 1H), 7.92 (d, 1H), 7.85 (d, 1H),
7.72 (d, 1H, J 15.6, Hα), 6.65 (s, 2H, H aryl), 3.92-3.88
(m, 12H, OCH3); 13C NMR (100 MHz, DMSO-d6) d 198.8
(C=O), 188.8, 159.6, 153.4, 152.8, 144.3, 137.1, 136.2,
131.4, 130.1, 127.7, 127.3, 125.2, 124.5, 121.6, 119.8, 106.8,
106.3, 105.3, 56.5 (OCH3), 56.1 (OCH3), 55.7 (OCH3); MS
(ESI, positive scan 70 eV) m/z, 378 [M+]; anal. calcd. for
C23H22O5: C 73.00, H 5.86, found: C 73.03, H 5.89.
General procedure for synthesis of (E)-1-(3-aryl)-
(2-methoxynaphthalen-6-yl)-prop-2-en-1-one (3a-g)
(E)-3-(Benzo[d][1,3]dioxol-5-yl)-1-(2-methoxynaphthalen-
6-yl)prop-2-en-1-one (3d)
1
Yield 76%; mp 170-173 °C; H MNR (400 MHz,
A mixture of 1-(2-methoxynaphthalen-6-yl)ethanone
(1 mmol), NaOH 40% (1 mL) and methanol (3 mL), was
sonicated for 30 s in the water bath of an ultrasonic cleaner
bath. Then, the respective aromatic aldehyde was added
(1.5 mmol) and the sonication continued. The precipitate
was filtered and recrystallized from methanol.
DMSO-d6) d 8.85 (s, 1H), 8.10 (d, 1H), 8.04 (d, 1H), 7.96
(d, 1H, J 15.2, Hβ), 7.91 (d, 1H), 7.70 (d, 1H, J 15.2, Hα),
7.69 (s, 1H, naphtyl), 7.42 (s, 1H, aryl), 7.34 (d, 1H), 7.27
(d, 1H), 7.00 (d, 1H), 6.12 (s, 2H, CH2), 3.92 (s, 3H, CH3);
13C NMR (100 MHz, DMSO-d6) d 188.3 (C=O), 159.4,
149.5, 148.1, 143.5 (Cβ), 136.9, 133.0, 131.2, 130.2, 129.4,
127.6, 127.2, 125.8 (Cα), 124.8, 120.0, 119.5, 108.6, 106.9,
106.1, 101.7 (CH2), 55.4 (OCH3); MS (ESI, positive scan
70 eV) m/z, 332 [M+]; anal. calcd. for C21H16O4: C 75.89,
H 4.85, found: C 75.87, H 4.82.
(E)-1-(2-Methoxynaphthalen-6-yl)-3-p-tolylprop-2-en-1-one
(3a)
1
Yield 80%; mp 166-169 °C; H NMR (400 MHz,
DMSO-d6) d 8.87 (s, 1H), 8.11 (d, 1H), 8.10 (s, 1H), 8.06
(d, 1H), 7.94 (d, 1H), 7.82 (d, 2H, J 8.0, Ho), 7.76 (d, 1H,
J 15.7, Hα), 7.45 (s, 1H), 7.32-7.29 (m, 1H, Hm), 3.94
(E)-1,3-bis(2-Methoxynaphthalen-6-yl)prop-2-en-1-one (3e)
1
Yield 77%; mp 210-213 °C; H NMR (400 MHz,
13
(s, 3H, OCH3), 2.38 (s, 3H, CH3); C NMR (100 MHz,
DMSO-d6) d 8.90 (s, 1H), 8.28 (s, 1H), 8.20-8.08 (m, 4H),
7.97-7.90 (m, 4H), 7.40 (d, 2H), 7.29 (d, 1H), 7.22 (d, 1H),
3.93-39.1 (s, 6H, OCH3); 13C NMR (100 MHz, DMSO-d6) d
188.5 (C=O), 158.7, 143.9, 137.0, 136.1, 133.0, 131.4, 130.7,
130.3, 128.5, 127.5, 125.2, 121.4, 119.8, 119.4, 106.4, 63.2,
55.5; MS (ESI, positive scan 70 eV) m/z, 368 [M+]; anal.
calcd. for C25H20O3: C 81.50, H 5.47, found: C 81.54, H 5.46.
DMSO-d6) d 188.4 (C=O), 159.4, 143.5 (Cβ), 140.6 (Cp),
136.9, 132.9, 132.1, 131.2, 130.3, 129.5 (Cm), 128.9 (Co),
127.6, 127.2, 124.8, 121.0 (Cα), 119.5, 106.1, 55.4 (OCH3),
21.1 (CH3); MS (ESI, positive scan 70 eV) m/z, 302 [M+];
anal. calcd. for C21H18O2: C 83.42, H 6.00, found: C 83.41,
H 6.03.
(E)-1-(2-Methoxynaphthalen-6-yl)-3-(4-methoxyphenyl)
prop-2-en-1-one (3b)
(E)-3-(4-Chlorophenyl)-1-(2-methoxynaphthalen-6-yl)prop-
2-en-1-one (3f)
1
1
Yield 81%; mp 131-134 °C; H NMR (400 MHz,
Yield 80%; mp 166-169 °C; H NMR (400 MHz,

Vol. 29, No. 6, 2018
Trilleras et al.
1215
DMSO-d6) d 8.86 (s, 1H), 8.10 (d, 1H), 8.05 (d, 1H),
7.97-7.93 (t, 3H), 7.76 (s, 1H), 7.53 (d, 2H, J 8.6, Ho),
7.43-7.41 (m, 2H), 7.28 (d, 1H), 3.92 (s, 3H, OCH3);
13C NMR (100 MHz, DMSO-d6) d 188.3 (C=O), 159.5,
141.8, 137.0 (Cp), 135.0, 133.8, 132.7, 131.2, 130.5
(Co), 128.9 (Cm), 127.5, 127.2, 124.7, 119.5, 106.1, 55.4
(OCH3); MS (ESI, positive scan 70 eV) m/z, 322 [M+]; anal.
calcd. for C20H15ClO2: C 74.41, H 4.68, found: C 74.42,
H 4.66.
(s, 1H), 7.21 (d, 2H, J 8.3), 7.19-7.14 (m, 3H), 7.03 (d,
2H, J 8.3), 6.88 (d, 2H), 6.69 (t, Hp-phenyl), 5.42 (dd, 1H,
CH-pyrazoline), 3.91 (dd, 1H, CH-pyrazoline), 3.88 (s, 3H,
OCH3), 3.70 (s, 3H, OCH3), 3.14 (dd, 1H, CH-pyrazoline);
13C NMR (100 MHz, DMSO-d6) d 158.5, 157.8, 147.5
(C-pyrazoline), 144.3, 134.5, 134.4, 129.7, 128.8, 127.8,
127.1, 127.0, 125.3, 123.6, 118.9, 118.4, 114.3, 113.0,
106.3, 62.6 (CH-pyrazoline), 55.5 (OCH3), 55.0 (OCH3),
43.0 (CH2); MS (ESI, positive scan 70 eV) m/z, 408 [M+];
anal. calcd. for C27H24N2O2: C 79.38, H 5.92, N 6.85, found:
C 79.39, H 5.89, N 6.83.
(E)-1-(2-Methoxynaphthalen-6-yl)-3-(4-nitrophenyl)prop-
2-en-1-one (3g)
1
Yield 65%; mp 198-201 °C; H NMR (400 MHz,
4,5-Dihydro-3-(2-methoxynaphthalen-6-yl)-5-(3,4,5-trimethoxy-
DMSO-d6) d 8.88 (s, 1H), 8.30-8.26 (m, 3H), 8.17 (d, 2H,
J 8.4, Ho), 8.10 (d, 1H), 8.05 (d, 1H), 7.93 (d, 1H), 7.82
(d, 1H, J 15.7, Hα), 7.43 (s, 1H), 7.28 (d, 1H), 3.92 (s, 3H,
OCH3); 13C NMR (100 MHz, DMSO-d6) d 188.5 (C=O),
159.9, 148.3 (Cp), 141.6 (Cβ), 140.8, 137.4, 131.6, 131.1,
130.0 (Co), 127.6, 126.4, 124.9 (Cα), 124.2 (Cm), 119.8,
106.5, 55.7 (OCH3); MS (ESI, positive scan 70 eV) m/z,
333 [M+]; anal. calcd. for C20H15NO4: C 72.06, H 4.54,
N 4.20, found: C 72.02, H 4.56, N 4.16.
phenyl)-1-phenyl-1H-pyrazoline (4c)
1
Yield 70%; mp 186-189 °C; H NMR (400 MHz,
DMSO-d6) d 8.05 (d, 1H), 7.98 (s, 1H), 7.83 (d, 1H),
7.35 (s, 1H), 7.22-7.18 (m, 4H), 7.05 (t, 2H), 6.74 (t, 1H),
6.64 (s, 2H), 5.35 (dd, 1H, CH-pyrazoline), 3.97 (dd,
1H, CH-pyrazoline), 3.89 (s, 3H, OCH3), 3.70 (s, 6H,
OCH3), 3.63 (s, 3H, OCH3), 3.21 (dd, 1H, CH-pyrazoline);
13C NMR (100 MHz, DMSO-d6) d 157.8, 153.3, 147.8,
144.8, 138.5, 136.5, 134.4, 129.7, 128.9, 128.2, 127.6,
127.0, 125.4, 123.7, 118.9, 118.7, 113.1, 106.3, 102.9, 63.8
(CH-pyrazoline), 59.9 (OCH3), 55.8 (OCH3), 55.2 (OCH3),
43.2 (CH2); MS (ESI, positive scan 70 eV) m/z, 468 [M+];
anal. calcd. for C29H28N2O4: C 74.33, H 6.02, N 5.97, found:
C 74.34, H 6.04, N 5.99.
General procedure for synthesis of 5-aryl-3-(2-methoxy-
naphthalen-6-yl)-1-phenylpyrazoline (4a-g)
A mixture of (E)-1-(3-aryl)-(2-methoxynaphthalen-
6-yl)-prop-2-en-1-ones (3a-g, 1 mmol), phenylhydrazine
(3 mmol) in CH3COOH/H2O 7:3 (3 mL) was refluxed for
3-4.5 h. After completion, the reaction mixture was cooled
to room temperature and the precipitate was filtered, dried
and recrystallized from ethanol/hexane mixture.
5-(Benzo[d][1,3]dioxol-5-yl)-4,5-dihydro-3-(2-methoxy-
naphthalen-6-yl)-1-phenyl-1H-pyrazoline (4d)
1
Yield 70%; mp 238-241 °C; H NMR (400 MHz,
DMSO-d6) d 8.06 (d, 1H), 7.99 (s, 1H), 7.85 (d, 2H, J 8.8),
7.37 (s, 1H), 7.20 (m, 3H), 7.09 (t, 2H, J 8.7, Hm-phenyl),
6.90-6.73 (m, 3H), 6.66 (s, 1H), 5.99 (s, 2H, OCH2O), 5.44
(dd, 1H, CH-pyrazoline), 3.94 (dd, 1H, CH-pyrazoline),
3.91 (s, 3H, OCH3), 3.19 (dd, 1H, CH-pyrazoline);
13C NMR (100 MHz, DMSO-d6) d 158.4, 153.8, 148.2,
146.9, 145.3, 144.7, 137.0, 134.9, 130.2, 129.4, 128.8,
127.5, 119.5, 113.5, 109.1, 106.8, 103.4, 63.4 (OCH3),
60.4 (CH-pyrazoline), 55.8, 43.5 (CH2); MS (ESI, positive
scan 70 eV) m/z, 422 [M+]; anal. calcd. for C27H22N2O3:
C 76.73, H 5.28, N 6.68, found: C 76.76, H 5.25,
N 6.63.
4,5-Dihydro-3-(2-methoxynaphthalen-6-yl)-1-phenyl-
5-p-tolyl-1H-pyrazoline (4a)
1
Yield 75%; mp 228-231 °C; H NMR (400 MHz,
DMSO-d6) d 8.04 (d, 1H), 7.97 (s, 1H), 7.82 (dd, 2H), 7.35
(s, 1H), 7.21-7.13 (m, 7H), 7.02 (d, 2H, J 7.7, Hm-aryl),
6.71 (t, 1H, J 7.2, Hp), 5.45 (dd, 1H, CH-pyrazoline), 3.95
(dd, 1H, CH-pyrazoline), 3.89 (s, 3H, OCH3), 3.15 (dd,
1H, CH-pyrazoline), 2.25 (s, 3H, CH3-aryl); 13C NMR
(100 MHz, DMSO-d6) d 129.3, 128.6, 125.6, 123.3, 118.7,
118.2, 112.7, 62.8 (C-pyrazoline), 58.1, 55.0 (OCH3), 42.9
(CH2), 20.3 (CH3-aryl); MS (ESI, positive scan 70 eV) m/z,
392 [M+]; anal. calcd. for C27H24N2O: C 82.63, H 6.16,
N 7.13, found: C 82.60, H 6.13, N 7.09.
4,5-Dihydro-3,5-bis(2-methoxynaphthalen-6-yl)-1-phenyl-
1H-pyrazoline (4e)
1
Yield 70%; mp 245-248 °C; H NMR (400 MHz,
4,5-Dihydro-3-(2-methoxynaphthalen-6-yl)-5-(4-methoxy-
DMSO-d6) d 8.08 (d, 1H), 8.04 (d, 1H), 7.97 (s, 2H), 7.87-
7.78 (m, 6H), 7.20-7.08 (m, 4H), 7.02 (d, 2H), 6.72 (t, 1H),
5.53 (dd, 1H, CH-pyrazoline), 3.96 (dd, 1H, CH2), 3.89
(s, 6H, OCH3), 3.19 (dd, 1H, CH2); 13C NMR (100 MHz,
phenyl)-1-phenyl-1H-pyrazoline (4b)
1
Yield 70%; mp 214-217 °C; H NMR (400 MHz,
DMSO-d6) d 8.04 (d, 1H), 7.95 (s, 1H), 7.82 (d, 2H), 7.34

1216
Syntheses, Experimental and Theoretical Studies on Absorption/Emission Properties
J. Braz. Chem. Soc.
DMSO-d6) d 157.8, 147.6 (Ci), 141.5, 141.4, 134.4, 131.9,
129.7, 129.0, 128.9, 128.2, 127.8, 127.5, 127.0, 125.4,
123.6, 119.0, 118.7, 112.9, 106.3, 62.3 (C-pyrazoline),
55.2 (OCH3), 42.7 (CH2); MS (ESI, positive scan 70 eV)
m/z, 458 [M+]; anal. calcd. for C31H26N2O2: C 81.16, H 5.71,
N 6.11, found: C 81.20, H 5.72, N 6.09.
Computational detail
The theoretical calculations were performed using the
Gaussian09package34 withaDFTmethod, ahybridfunctional
type B3LYP and 6-31G++ basis set. The 3c, 3f, 4c and 4f
geometry optimization was carried out in ground state and the
excited states were performed by a SCF-TD with polarization
continuum method (PCM) in acetonitrile as solvent.
5-(4-Chlorophenyl)-4,5-dihydro-3-(2-methoxynaphthalen-
6-yl)-1-phenyl-1H-pyrazoline (4f)
1
Yield 73%; mp 219-222 °C; H NMR (400 MHz,
Supplementary Information
DMSO-d6) d 8.08 (d, 1H), 7.99 (s, 1H), 7.87 (d, 1H), 7.84
(d, 1H), 7.41 (d, 2H, J 8.7, Hm-aryl), 7.37-7.34 (m, 1H,
Ho-aryl), 7.22-7.19 (m, 1H, Hm-phenyl), 7.04 (d, 2H, J 8.1,
Ho-phenyl), 6.75 (t, 1H, J 7.3, Hp-phenyl), 5.58 (dd, 1H,
CH-pyrazoline), 4.01 (dd, 1H, CH-pyrazoline), 3.91 (s, 3H,
OCH3), 3.25 (dd, 1H, CH-pyrazoline); 13C NMR (100 MHz,
DMSO-d6) d 158.0, 147.7, 144.2, 141.6, 134.5, 132.0,
129.8, 129.1, 129.0, 128.3, 128.0, 127.6, 127.2, 125.5,
123.7, 119.1, 118.8, 113.0, 106.4, 62.5 (CH-pyrazoline),
55.4 (OCH3), 42.9 (CH2); MS (ESI, positive scan 70 eV)
m/z, 412 [M+]; anal. calcd. for C26H21ClN2O: C 75.65,
H 5.12, N 6.74, found: C 75.63, H 5.13, N 6.78.
Supplementary information (MS, H and 13C NMR
spectra for 3 and 4) is available free of charge at
http://jbcs.sbq.org.br as PDF file.
1
Acknowledgments
J. T., A. P. and E. P. P. thank the Universidad del
Atlántico for its 7th internal call: Fortalecimiento a Grupos
de Investigación de la Universidad del Atlántico-Cb36-
Fgi2016. A. O. and J. Q. thank Universidad del Valle and
the Science, Technology and Innovation Fund-General
Royalties System (FCTeI-SGR) under contract BPIN
2013000100007 for financial support.
4,5-Dihydro-3-(2-methoxynaphthalen-6-yl)-5-(4-nitro-
phenyl)-1-phenyl-1H-pyrazoline (4g)
1
Yield 75%; mp 222-225 °C; H NMR (400 MHz,
References
DMSO-d6) d 8.23 (d, 2H, J 8.5, Hm-aryl), 8.07 (d, 1H),
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J 8.5, Ho-aryl), 7.37 (s, 1H), 7.21 (m, 3H), 7.04 (d, 2H,
J 8.3, Ho-phenyl), 6.77 (t, Hp-phenyl), 5.71 (dd, 1H,
CH-pyrazoline), 4.04 (dd, 1H, CH-pyrazoline), 3.90 (s,
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anal. calcd. for C26H21N3O3: C 73.79, H 4.97, N 9.90, found:
C 73.75, H 5.00, N 9.92.
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Submitted: August 9, 2017
Published online: December 4, 2017
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