K.V. Basavarajappa et al. / Journal of Molecular Structure 1199 (2020) 126946
3
ꢂ
ꢀ1
1
Noran 7) and the surface morphology and crystalline structure
were obtained by scanning electron microscopy (SEM) (ZEISS EVO
LS15).
yield having mp 148e150 C was obtained. IR (KBr, v, cm ): 1710
(lactone C¼O), 1642 (ketone C¼O), 3026 (Ar C-H). H NMR
3 3
(400 MHz, CDCl ) d (ppm):1.213e1.249 (t, 6H, CH ), 3.419e3.473 (q,
2
4H, -CH ), 6.494e6.500 (d, 1H, Ar), 6.593e6.622 (dd, 1H, Ar),
2.2.6. Calculation of HOMO and LUMO energy levels
7.334e7.357 (d, 1H, Ar), 7.415e7.453 (t, 2H, Ar), 7.524e7.542 (d, 1H,
The energies of HOMO and LUMO were calculated using the
Ar),7.792e7.813 (t, 2H, Ar) and 8.076 (s, 1H, Ar). MS-APþ (m/z)
þ
formula: EHOMO ¼ -(Eonsetox þ5.1) eV and ELUMO ¼ -(Eonsetred þ5.1)
eV where Eonsetox is the onset oxidation potential in V, Eonsetred is
the onset reduction potential in V and 5.1 eV is the assumed elec-
calculated for C20
H
19NO
3
: 321.1359, found: 322.1457 (MþH)
1
(Supporting information S7 for IR, S8 for HNMR and S9 for Mass
spectra).
þ
trochemical potential of ferrocene/ferrocenium (Fc/Fc ) vs. vacuum
[
21].
2.3.2. Representative procedure for 2,4-dinitrophenylhydrazones of
substituted 3-benzoyl coumarins (DNP1ꢀDNP3)
2
2
.3. Synthesis
Substituted 3-benzoyl coumarins (2abꢀ2cb) (0.576 g,
2.23 mmol) were added to a solution of 2,4-dinitrophenylhydrazine
.3.1. General procedure for solvent free synthesis of 3-benzoyl
(0.5 g, 2.52 mmol) in dimethylformamide (5 mL) contained in a
50 mL beaker and the mixtures were swirled to get homogenous
solutions, added two drops of con. HCl and kept for 30 min at room
temperature. The obtained solid products were filtered, washed
with 20 mL of 2N hydrochloric acid followed by 30 mL water and
30 mL cold 95% aqueous ethanol. The crude product was dried and
recrystallized from 1,4-dioxane to get pure hydrazones (40e74%) as
orange-yellow powder. The synthesized compounds were
coumarin derivatives (2 abꢀ2 cb)
Out of various methods available in the literature, solvent free
method was selected for the synthesis of 3-benzoyl coumarins via
Knoevenagel condensation [22]. The advantages of utilizing this
method involve simple operation, waste minimization and easier
product work-up. The synthetic procedure involves an equivalent
mixture of derivatives of salicylaldehyde (1a-1c, 10.0 mmol), ethyl
benzoyl acetate (10.0 mmol) and a few drops of piperidine were
mixed and ground well for 5 min at room temperature (rt). The
reaction mixtures were neutralized with dil. HCl and then, the so
obtained substituted 3-benzoyl coumarins (2 abꢀ2 cb) were iso-
1
confirmed by their IR, H NMR and Mass spectral data. The syn-
thetic pathway is as shown in Scheme 2.
The yield and physical data of the synthesized compounds are
tabulated in Table 1. The structures of synthesized compounds were
in good agreement with their IR, NMR and Mass spectral data
(Table 2).
1
lated by filtration. The IR, H NMR and Mass spectral analysis were
used for structural confirmation of the synthesized molecules. The
synthetic pathway is as shown in Scheme 1.
2.3.3. Synthesis of ZnO nanoparticles
2.3.1.1. 3-Benzoyl-2H-chromen-2-one (2ab). After recrystallization
In order to test the synthesized coumarin dye molecules as
in alcohol a shiny cream powder with 71.16% yield having mp.
photosenitizer, the cone shaped ZnO nanoparticles were prepared
by microwave combustion method using reported procedure [23].
A 3 g of ZnNO ,6H O was taken in a dry beaker and 2e3 drops of
3 2
ꢂ
ꢀ1
1
34e136 C was obtained. IR (KBr, v, cm ): 1723 (lactone C¼O),
1
1
660 (ketone C¼O), 3044 (Ar C-H). H NMR (400 MHz, CDCl
3
)
d
(ppm): 7.325e7.363 (m, 1H, Ar), 7.388e7.409 (d, 1H, Ar),
.453e7.492 (m, 2H, Ar), 7.585e7.661 (m, 3H, Ar), 7.861e7.883 (m,
ethylene glycol was added and kept in a microwave oven for 6 s.
Then the above solution was heated in a domestic microwave oven
7
ꢂ
2
2
H, Ar), 8.071 (s, 1H, Ar). MS-APþ (m/z) calculated for C16
H
10
O
3
:
for 6 min. Later, white porous powder of ZnO was calcined at 500 C
þ
50.0624, found: 251.0139 (MþH) (Supporting information S1 for
in a muffle furnace, to get the ZnO nanocones. The elemental
analysis and the surface morphology data were obtained by energy
dispersive analyzer using X-rays (EDAX) and scanning electron
microscopy (SEM) techniques. The X-ray diffractometer (XRD) was
used for the analysis of crystalline structure (Fig. 2).
1
IR, S2 for H NMR and S3 for Mass spectra).
2.3.1.2. 2-Benzoyl-3H-benzo[f]chromen-3-one (2bb). After recrys-
tallization in alcohol a yellow powder with 65.99% yield having mp.
ꢂ
ꢀ1
2
1
d
06e208 C was obtained. IR (KBr, v, cm ): 1708 (lactone C¼O),
1
657 (ketone C¼O), 3058 (Ar C-H). H NMR (400 MHz, CDCl
3
)
3. Result and discussion
(ppm): 7.482e7.539 (q, 3H, Ar), 7.616e7.634 (t, 2H, Ar),
.707e7.728 (t, 1H, Ar), 7.912e7.963 (m, 3H, Ar), 8.102e8.124 (m,
7
3.1. Organic synthesis (spectral analysis)
2
H, Ar), 8.258e8.280 (d, 1H, Ar) and 8.928 (s, 1H, Ar). MS-APþ (m/z)
þ
calculated for C20
H
12
O
3
: 300.0781, found: 300.9746 (MþH) .
The compounds of Scheme 1 involve the Knoevenagel conden-
sation followed by cyclization leads to the formation of coumarin
skeleton, which was confirmed by appearance of strong IR peaks at
1
(
Supporting information S4 for IR, S5 for HNMR and S6 for Mass
spectra).
ꢀ
1
1
708 ꢀ 1723 cm (supporting information S1, S4 and S7). The
ꢀ1
2.3.1.3. 3-Benzoyl-7-(diethylamino)-2H-chromen-2-one
(2cb).
peaks around 1642 ꢀ 1660 cm corresponds to the ketonic group
After recrystallization in alcohol a creamy powder with 60.73%
present between coumarin ring and a benzene ring of 2abe2cb. The
Scheme 1.. Synthesis of 3-benzoyl coumarin derivatives (2 ab-2cb).