R.M. Kamel et al.
Journal of Photochemistry & Photobiology, A: Chemistry 411 (2021) 113218
Stock solution of 1-amino-3-arylidene-2(3 H)-pyrrolone (AAP) was
prepared by dissolving 8.70 mg in 25 mL DMF. Buffer solution pH 2.0,
2.4.2. Binding constant calculation
The binding constant (K) calculated using Benesi-Hildebrand equa-
tion, where K result from the intercept to the slope ratio [31].
4
.0, 6.0, 8.0 and 10.0 was prepared using KCl / HCl, acetic acid / sodium
acetate tri-hydrate, acetic acid / sodium acetate tri-hydrate, disodium
hydrogen phosphate / HCl, disodium hydrogen phosphate / and KCl /
NaOH respectively. Aqueous solutions of all cationic compounds of
◦
F
∝
1
= ∝ + K
[
], ∝ =
(1)
F ꢀ F◦
3+
F
L
ꢀ F◦
Fe
2
+
2+
2+
2+
3+
2+
2+
Zn , Cd , Mn , Cu , Fe , Co and Ni ions, were purchased from
Aldrich and used as received were prepared from their chlorate or ni-
trates salts.
Where [Fe] is Fe ions concentration, Fo and F are the fluorescence
3+
3+
intensity in the absence and presence of Fe ions, respectively, and F
the limiting intensity of fluorescence.
L
is
2
.2. Apparatus
2
.4.3. Molar ratio method
The stoichiometry of AAP sensor with Fe3 ions is evaluated using
+
A Shimadzu-UV Probe Version 2.33 and JASCO FP-8300 were used
fluorescence measurements by using various concentrations of AAP
for UV–vis. and fluorescence measurements respectively. Flame atomic
absorption spectrophotometer was (FAAS; Perkin Elmer A Analyst 100)
3+
sensor while the Fe ions is kept constant, then recording the intensity
of the emission peak at 470 nm.
2
.3. Synthesis of 5-(4-(dimethylamino)phenyl)-4-(2-(4-methoxy-3-
2
.4.4. Calculation quantum yield and brightness for AAP sensor
methylphenyl)-2-oxoethyl)-1H-pyrazol-3(2 H)-one (AAP) sensor
The quantum yield (QY) of AAP sensor was determined in DMF using
ꢀ 1
the following equation at concentration 10 mol L . The QY was
μ
2
.3.1. Synthesis of 5-[4-methoxy-3-methylphenyl]-2(3 H)-furanone (2)
calculated with coumarin 6 in ethanol (QY = 0.78) as the reference [32]:
A mixture of 4-[4-methoxy-3-methylphenyl]-4-oxobutanoic acid (1)
A
A
R
.I
.I
X
.n2
.n
X
R
(
0.01 mol) and acetic anhydride (3 mL) in20 mL toluene was heated
Q
X
= Q
R
(2)
2
under reflux for 1 h, the reaction was then cooled, the solid product
obtained after cooling was collected by filtration and recrystallized from
ethanol to give 5-[4-methoxy-3-methylphenyl]-2(3 H)-furanone (2) as
orange crystals.
X
R
Where Q is the quantum yield, A is the absorbance value at the excita-
tion wavelength, I is the integrated area of the emission spectra, n is the
refractive index of the responding solvent and subscripts R and X denote
the of the reference and AAP sensor, respectively. While the brightness
2
3
.3.2. Synthesis of 3-(4-(dimethylamino)benzylidene)-5-(4-methoxy-
methylphenyl)-2(3 H)-furanone (3)
was determined by multiplying molar absorbance (
ε
) and quantum yield
(
Q) of AAP sensor.
To a solution of compound (2) (0.01 mol) in acetic anhydride
(
10 mL), we added the 4-(dimethylamino)benzaldehyde (0.01 mol) and
anhydrous sodium acetate (0.01 mol). The reaction mixture was heated
under reflux for 2 h, the solid compound was filtered after cooling then
crystallized from the ethanol to give 3-arylidene-2(3 H)-furanone (3) as
yellow crystals [30].
3. Results & discussion
3.1. Characterization of 5-(4-(dimethylamino)phenyl)-4-(2-(4-methoxy-
3-methylphenyl)-2-oxoethyl)-1H-pyrazol-3(2 H)-one (AAP) sensor
2
.3.3. Formation of 2-(4-(dimethylamino)benzylidene)-4-
The starting 5-[4-methoxy-3-methylphenyl]-2(3 H)-furanone (2),
was synthesized by Friedel-Crafts acylation of o-cresyl methyl ether with
succininc anhydride in the presence of anhydrous aluminium chloride,
and subsequent cyclization of the intermediate,4-(4-methoxy-3-meth-
ylphenyl)-4-oxo-butanoic acid (1) with acetic anhydride.
oxobutanhydrazide (4)
Hydrazine hydrate (0.02 mol) was added to a solution of compound
(
3) (0.01 mol) in ethanol (40 mL), after stirring for 4 h at room tem-
perature and kept overnight. The resultant white solid was filtered and
washed with diluted ethanol. The hydrazide was used directly in the
next reaction.
3-(4-(Dimethylamino)benzylidene)-5-(4-methoxy-3-methylphenyl)-
2(3 H)-furanone (3) was synthesised from the condensation reaction of
5
-[4-methoxy-3-methyl phenyl]-2(3 H)-furanone with 4-(dimethyla-
2
.3.4. Formation of 5-(4-(dimethylamino)phenyl)-4-(2-(4-methoxy-3-
mino)benzaldehyde in the presence of anhydrous sodium acetate under
perkin reaction conditions.
methylphenyl)-2-oxoethyl)-1H-pyrazol-3(2 H)-one (5)
A solution of the hydrazides (4) (0.01 mol) in ethanol (30 mL) was
heated under reflux for 4 h. After cooling, the solid compound was
filtered, dried and crystallized from the ethanol to give orange crystals of
The synthesis of hydrazide (4), was accomplished by stirring of a
mixture of 5-[4-methoxy-3-methylphenyl]-3-substituted-2(3 H)-fur-
anone (3) and hydrazine hydrate. The reaction was carried out by stir-
ring the reaction mixture in ethanol on cold.
ꢀ 1
pyrazolone (5), m.p. 160, yield 63.7 %. IR (ATR, ʋ, cm ): 1686(C = O),
1
3
309 and 3208 (2 NH). H NMR (400 MHz, DMSO) δ 12.96 (s, 1 H), 7.76
Heating the hydrazide (4) in refluxing ethanol provided mainly the
pyrazolone (5). The formation of the pyrazolone (5) was assumed to
proceed via the intramolecular Michael addition according to the reac-
tion mechanism outlined in (Scheme 1), where the nitrogen atom of NH2
group could attack onto the β-carbon of the unsaturated carbonyl group
followed by dehydrogenation with the formation of the corresponding
pyrazolone.
(
(
s, 1 H), 7.59 (dd, J = 12.0, 3.5 Hz, 2 H), 7.16 (d, J =8.7 Hz, 2 H), 7.01
d, J =8.6 Hz, 1 H), 6.67 (d, J =8.7 Hz, 2 H), 3.83 (s, 3 H), 3.72 (s, 2 H),
2
7
1
23 3 2
.85 (s, 6 H), 2.20 (s, 3 H). Anal. Calcd (%) for C21H N O (349.43): C,
2.18; H, 6.63; N, 12.03; Found C, 71.97; H, 6.49; N, 12.25 (SI: Scheme
).
2
2
.4. Spectrofluorimetric measurements
The structure of pyrazolone (5) (AAP sensor) was confirmed by IR
1
and H-NMR (SI: Figs. 1and 2). The IR spectrum revealed the presence of
.4.1. Fluorescence determination of Fe3 ions
To obtain the optimum sensing condition of Fe3 ions, the fluoro-
+
two absorption bands corresponding to the 2NH groups at 3309 cm
ꢀ 1
+
-1
and 3208 cm . The absorption band of carbonyl group appeared at
-
1
metric measurements were conducted at room temperature over a wide
range of pH solutions from 2 to 10 using standard buffer solutions. The
1686 cm .
1
The H-NMR spectrum (DMSO-d
presence of four singlets in the aliphatic region at 2.20, 2.85, 3.72 and
3.83 ppm corresponding to Arꢀ CH , CH of side chain, N(CH , and
Arꢀ OCH , respectively. The signals of the aromatic protons were
6
) of the pyrazolone (5) showed the
3
+
spectrofluorometric sensing of Fe ions via AAP sensor was performed
over a different concentration of Fe3 ions adjusted at pH 4.0 at exci-
tation and emission wavelength 370 nm and 470 nm respectively.
+
3
2
3 2
)
3
2