2-methyl-4-oxo-N-(4-oxo-2-phenyl substituted-1,3-thiazolidin-3-yl)-3,4- dihydroquinazoline-5-carboxamides - A new range of fluorescent whiteners: Synthesis and photophysical characterization

Article abstract of DOI:10.1007/s10895-014-1387-y

Fluorescent quinazolinones were synthesized form ethyl 2-methyl-4-oxo-3,4- dihydroquinazoline -5-carboxylate intermediate. The photophysical properties of the compounds were evaluated in DMF solvent. The experimental absorption and emission of the compoun

Full text of DOI:10.1007/s10895-014-1387-y

J Fluoresc
DOI 10.1007/s10895-014-1387-y
ORIGINAL PAPER
2
3
-Methyl-4-oxo-N-(4-oxo-2-phenyl substituted-1,
-thiazolidin-3-yl)-3,4-dihydroquinazoline-5-carboxamides—
A New Range of Fluorescent Whiteners: Synthesis
and Photophysical Characterization
Vikas S. Patil & Vikas S. Padalkar & Nagaiyan Sekar
Received: 14 October 2013 /Accepted: 7 April 2014
#
Springer Science+Business Media New York 2014
Abstract Fluorescent quinazolinones were synthesized form
ethyl 2-methyl-4-oxo-3,4-dihydroquinazoline −5-carboxylate
intermediate. The photophysical properties of the compounds
were evaluated in DMF solvent. The experimental absorption
and emission of the compounds were compared with the
vertical excitation and emission obtained Density Functional
Theory (DFT) and Time Dependent Density Functional The-
ory (TD-DFT) computation. Application of the fluorescent
compounds as a fluorescent brightening agent was tested on
polyester fiber. Changes in the electronic transition, energy
levels, and orbital diagrams of quinazolin-4(3H)-one ana-
logues were investigated using the DFT computations and
were correlated with the experimental spectral data. The ex-
perimental absorption and emission wavelengths are in good
agreement with those predicted using the DFT and TD-DFT.
are widely used as coloring materials in dyestuff industry [2,
3]. The azo colorants based on quinazolinone have industrial
importance [3, 4]. The substituted quinazolinone are reported
as fluorescent compounds for different applications [5–10].
Quinazolinone derivatives are known to be fluorescent bright-
ening agents [2, 3, 8]. Optical whiteners are characterized by a
strong absorption below 400 nm with well separated intense
emission beyond 400 nm [11]. The optical bleaching agents
are chemicals that increase the whiteness when applied on the
natural and synthetic textile materials [12]. The surface of
textile materials therefore appear whiter to the human eye
[13]. Fluorescent brighteners are substances which normally
have a system of conjugated double bonds and electron-
donating groups to show high fluorescence [14, 15].
Fluorescent brightening agents (FBAs) are used in textile
industry to enhance the whiteness and brightness of textile
substrates; they also significantly increase the UV-blocking
properties of the medium to which they are applied [16, 17].
They are also used in pulp and paper industries for the im-
provement of brightness [18]. In addition to the above
mentioned applications they are also used in pH
chemosensing materials [19], chemosensors [20], photo-
induced electron transfer sensors [21], light emitting
diodes [22], biological staining [23] and polyurethane
fluorescent brightener dispersions [24].
.
.
.
.
Keywords Quinazoline DFT TD-DFT Absorption
.
Emission Photophysical properties
Introduction
A large number of alkaloids contain quinazolinone nucleus
and they are known to have biological activities [1]. In addi-
tion to pharmaceutical applications, quinazolinone derivatives
Fluorescent whitening agents are derivatives of triazine
[
25], stilbene [26], pyrazole [27], naphthalimide [28], quino-
line [29], iso-quinoline [30], quinoxaline [31], oxadiazole
32], triazole [33], benzoxazole [34], benzotriazole [35] and
:
:
V. S. Patil V. S. Padalkar N. Sekar (*)
Tinctorial Chemistry Group, Institute of Chemical Technology
Formerly UDCT), N. P. Marg, Matunga, Mumbai 400
[
(
tinopol-CBX [36] based compounds. The fluorescent
quinazolinone are also reported as fluorescent brightening
agents for polyester fibers [2, 3]. A fluorescent brightener
should present a high quality of whiteness and fastness. How-
ever, as the fluorescent brightener is exposed to the sunlight,
its whiteness is diminished [3]. This happens because the
0
19, Maharashtra, India
e-mail: n.sekar@ictmumbai.edu.in
V. S. Patil
e-mail: vikasudct@gmail.com
V. S. Padalkar
e-mail: vikaspadalkar@gmail.com

J Fluoresc
chemical structure of fluorescent brightener is destroyed by
the autoxidation from free radical generated from the sunlight
phase using (DFT) [37]. The functional used in this study
was B3LYP [38, 39]. The basis set used for all atoms
was 6-31G(d) [40–42]. The vibrational frequencies of the
optimized structures were computed using the same
method to verify that the optimized structures correspond
to local minima on the potential energy surface. The
vertical excitation energies at the ground-state equilibri-
um geometries were calculated with TD-DFT [43–45].
[3]. Fluorescent whiteners with enhanced chemical, thermal
and photostability are needed today for high performance
textile substrates.
Reported quinazolinone derivatives are 2 and 6-substituted
in which the electron donor is at the 2-position and the
acceptor at the 6- position [2, 3]. A study of the literature
reveals that, electron donor substitution at the 2-position along
with an acceptor at the 6-position gives red shifted absorption
and hence red shifted emission, because such a substitution
pattern leads to an effective donor acceptor chromophore [9].
To achieve blue shifted emission it is necessary to reduce the
donor strength.
In this paper, attempts have been made to synthesize fluo-
rescent quinazolinone thiazolidines. The synthesized
quinazolinone derivatives contain electron donor at the 2-
position and an acceptor at the 5-position. The photophysical
properties like absorption, emission and quantum yields of the
compounds were recorded in the solvent dimethylformamide
The low-lying first singlet excited state (S ) of each
1
tautomer was relaxed using the TD-DFT to obtain its
minimum energy geometry. The difference between the
energies of the optimized geometries in the first singlet
excited state and the ground state was used in computing
the emissions [46–52]. All electronic structure computa-
tions were carried out using the Gaussian 09 program
[53].
Relative Quantum Yield Calculations
The quantum yields of compounds 7a–7e in DMF were
evaluated. Anthracene was used as the standard. Quan-
tum yields were calculated using the comparative method
[54, 55]. The absorption and emission characteristics of
the standards and for the compounds in polar solvents
were measured at different concentrations (1, 2, 3, 4, and
5 ppm level). The emission intensity values were plotted
against absorbance values and linear plots were obtained.
The gradients were calculated for the compounds in each
solvent and for the standards. All the measurements were
done by keeping the parameters such as solvent and slit
width constant. The relative quantum yields of the syn-
thesized compounds in different solvents were calculated
by using the Eq. 1 [54, 55].
(
DMF). Fluorescent compounds were used for whitening
polyester fiber for optical brightening study. The changes in
the electronic transition, energy levels, and orbital diagrams of
the quinazolinone derivatives were studied by TD-DFT com-
putation. The computational results were correlated with the
experimental photophysical properties.
Methodology
Materials and Methods
All the commercial reagents and solvents were purchased
from S. D. Fine Chemicals Pvt. Ltd. and they were used
without purification and all the solvents were of spectro-
scopic grade. The absorption spectra of the dyes were
recorded on a Spectronic Genesys 2 UV-Visible spectro-
photometer, and emission spectra were recorded on
Varian Cary Eclipse fluorescence spectrophotometer
using freshly prepared solutions in solvents of different
2
Gradx
η
x
ϕx ¼ Φst Â
 η
ð1Þ
2
Gradst
st
Where:
−
6
−1
Φ
x
Quantum yield of compound
polarities at the concentration of 1×10 mol L . The
excitation wavelength used for the fluorescence measure-
ments was absorption maxima of the compounds in re-
Φst
Quantum yield of standard sample
Gradx Gradient of compound
Gradst Gradient of standard sample
spective solvents. The FT-IR spectra were recorded on a
1
η
x
Refractive index of solvent used for synthesized
compound
Perkin-Elmer Spectrum 100 FT-IR Spectrometer.
H
NMR spectra were recorded on VXR 400 MHz instru-
ment using TMS as an internal standard. Mass spectra
were recorded on Finnigan mass spectrometer.
ηst
Refractive index of solvent used for standard sample
General Procedure of Dyeing
Computational Methods
Dyeing of polyester fabric was carried out using high temper-
ature high pressure method in Rossari Labtech Flexi Dyer
dyeing machine at a material to liquor ratio of 1:20. 2 %
The ground state geometries of the compounds 7a–7e in their
C symmetry were optimized using the tight criteria in the gas
1

J Fluoresc
Fluorescent compounds were used for the dying (calculated
on weight of the fabric). All the synthesized fluorescent com-
pounds are having less solubility in water. Initially the com-
pounds were dissolved in 5 mL DMF and diluted with 15 mL
buffered solution of pH 5 made by using sodium acetate and
acetic acid in water. The mixture was ultrasonicated for
2-Methyl-N′-[(Z)-(4-nitrophenyl)methylidene]
-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 6b
2-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
(1 g, 4.58 mmol) was reacted with p-nitro benzaldehyde
(0.69 g, 4.58 mmol) in methanol in the presences of catalytic
amount of sulfuric acid at reflux condition for 6 h to give 2-
methyl-N′-[(Z)-(4-nitrophenyl) methylidene]-4-oxo-3,4-
dihydroquinazoline-5-carbohydrazide 6b.
1
5 min to obtain a fine dispersion. Metamol was used as a
dispersant. The polyester fabric was dyed using the above
solution and metamol as the dispersing agent. The dye bath
−1
temperature was raised at a rate of 3 °C min to 130 °C,
maintained at this temperature for 60 min, and rapidly cooled
to room temperature as shown in Fig. 1. The dyed fabrics were
rinsed with cold water and allowed to dry in the open air.
Yield: 87 %, Melting point => 300 °C.
1
H-NMR (CD ) SO: δ 2.23 (s, 3H), 7.34 (d, 2H, J=
3
2
7.7 Hz), 7.62 (d, 2H, J=7.7 Hz), 7.75 (dd, 2H, J=7.7,
9.1 Hz), 8.15 (d, 2H, J=13.2 Hz), 8.3 (d, 1H, J=13.2 Hz),
11.75 (s,1H).
FT-IR (KBr): 2965, 2900, 2644, 1691, 1665, 1584, 1478,
−1
Experimental
1406, 1309, 1264, 908, 740, 711. cm .
Mass: m/z 349 (M-2).
Synthesis Details
N′-(anthracen-9-ylmethylidene)
Ethyl 2-methyl-4-oxo-3,4-dihydroquinazoline-5-carboxylate 4
-2-methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide
6c
The intermediate 4 was prepared according to the known
procedure [56].
2-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
1 g, 4.58 mmol) was reacted with anthracene 9-
(
2
-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
carbaldehyde (0.94 g, 4.58 mmol) in methanol in the pres-
ences of catalytic amount of sulfuric acid at reflux condition
for 4 h to give N′-(anthracen-9-ylmethylidene)-2-methyl-4-
oxo-3,4-dihydroquinazoline-5-carbohydrazide 6c.
Yield: 83 %, Melting point => 300 °C.
Ethyl-2-methyl-4-oxo-3,4-dihydroquinazoline-5-carboxylate
5 g) on reaction with hydrazine hydrate (15 mL) for 2 h under
(
r e f l u x c o n d i t i o n g a v e 2 - m e t h y l - 4 - o x o - 3 , 4 -
dihydroquinazoline-5-carbohydrazide 5.
1
H-NMR (CD ) SO: δ 2.24 (s, 3H), 7.34 (d, 1H, J=
3
2
Yield: 89 %, Melting point => 300 °C.
7.7 Hz), 7.59 (d, 1H, J=7.0 Hz), 7.62 (dd, 4H, J=8.1,
7.9 Hz), 7.76 (d, 4H, J=8.1, 9.7 Hz), 7.73 (s, 1H), 9.25 (s,
1H), 11.72 (s, 1H).
1
H-NMR (CD ) SO: δ 2.20 (s, 3H), 5.26 (s, 2H), 7.72 (d,
3
2
1
2
H, J=22.00 Hz), 7.79 (d, 1H, J=6.7 Hz), 7.82 (dd, 1H, J=
2.00, 6.7 Hz).
−1
FT-IR (KBr): 2991, 1778, 1623, 1637, 1557, 967, 656 cm .
+
FT-IR (KBr): 3165, 3103, 2981, 2917, 2871, 1665, 1607,
562, 1478, 1383, 1325, 1261, 1193, 1158, 1103, 1041, 843,
Mass: m/z 407 (M ).
1
7
−1
88, 721, 663 cm .
2-Methyl-N′-[(Z)-(4-N, N-diethyl, 2-hydroxy)methylidene]
-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 6d
2
-Methyl-4-oxo-N′-[(Z)-phenylmethylidene]
-
3,4-dihydroquinazoline-5-carbohydrazide 6a
2-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
1 g, 4.58 mmol) was reacted with 4-(diethylamino)-2-
(
2
(
4
-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
1 g, 4.58 mmol) was reacted with benzaldehyde (0.46 g,
.58 mmol) in methanol in presences of catalytic amount of
hydroxybenzaldehyde (0.88 g, 4.58 mmol) in methanol in
the presences of catalytic amount of sulfuric acid at reflux
condition for 7 h to give 2-methyl-N′-[(Z)-(4-N, N-diethyl, 2-
hydroxy)methylidene]-4-oxo-3,4-dihydroquinazoline-5-
carbohydrazide 6d.
sulfuric acid at reflux condition for 2 h to give 2-methyl-4-
oxo-N′-[(Z)-phenylmethylidene]-3,4-dihydroquinazoline-5-
carbohydrazide 6a.
Yield: 79 %, Melting point => 300 °C.
1
Yield: 67 %, Melting point => 300 °C.
H-NMR (CD ) SO: δ 2.21 (s, 3H), 2,48 (t, 3H, J=
3
2
1
H-NMR (CD ) SO: δ 2.36 (s, 3H), 2.50 (s, 1H), 3.16 (s,
7.0 Hz), 3.35 (d, 2H, J=7.0 Hz), 7.30 (d, 1H, J=8.1 Hz),
7.60 (d, 1H, J=7.7 Hz), 7.74 (dd, 1H, J=9.8, 7.7 Hz), 8.81 (m,
3H, J=9.8, 6.9 Hz), 12.21 (s, 1H), 10.39 (s, 1H),
3
2
1
5
H), 7.45 (d, 2H, J=7.7 Hz), 7.78 (d, 1H, J=8.5 Hz), 7.86 (m,
H, J=8.0, 11.09 Hz), 12.01 (s, 1H)
−1
FT-IR (KBr): 3011, 1678, 1613, 1567, 987, 673 cm .
FT-IR (KBr): 3027, 1781, 1622, 1645, 1534, 2511, 978,
+
−1
Mass: m/z 307 (M ).
656 cm .

J Fluoresc
Fig. 1 Dyeing profile of
polyester used
+
1
Mass: m/z 395 (M ).
H-NMR (CD ) SO: δ 2.5 (s, 3H), 2.65 (s, 9H), 7.30 (d,
3
2
1
7
H, J=8.1 Hz), 7.60 (d, 1H, J=7.7 Hz), 7.74 (dd, 1H, J=8.1,
.7 Hz), 11.72 (s, 1H).
N′-[(Z)-(1-Tert-butyl-4-chloro-1H-pyrazol-5-yl)methylidene]
FT-IR (KBr): 3014, 1771, 1643, 1655, 1521, 1456, 1378,
−1
-
2-methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide
1218, 978, 698, 651 cm .
+
6
e
Mass: m/z 388 (M ).
2
-Methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 5
(
1 g, 4.58 mmol) was reacted with 2-tert-butyl-5-chloro-1H-
2-Methyl-4-oxo-N-(4-oxo-2-phenyl-1,3-thiazolidin-3-yl)
-3,4-dihydroquinazoline-5-carboxamide 7a
imidazole-4-carbaldehyde (0.85 g, 4.58 mmol) in methanol in
the presences of catalytic amount of sulfuric acid at reflux
condition for 4 h to give N′-[(Z)-(1-tert-butyl-4-chloro-1H-
pyrazol-5-yl)methylidene]-2-methyl-4-oxo-3,4-
dihydroquinazoline-5-carbohydrazide 6e.
2-Methyl-4-oxo-N′-[(Z)-phenylmethylidene]-3,4-
dihydroquinazoline-5-carbohydrazide 6a (1.42 mmol) was
reacted with thioglyconic acid (1.42 mmol) in tetrahydrofuran
(THF) at reflux condition for 6 h to give 2-methyl-4-oxo-N-(4-
Yield: 85 %, Melting point => 300 °C.
COOEt
COOH
COOH
COOEt
COOEt
COOEt
EtOH
PTSA
H2
Pd/C
Dry HCl
CH CN
O
COOEt
3
N
NH
NO2
NO2
2
NH2
3
1
4
Ar
O
O
S
O
COOEt
NH2
N
Ar
NH
NH
N
NH
O
O
8
0 % NH NH2
HS CH COOH
2
O
Ar CHO
MeOH
O
2
O
THF, PTSA
N
NH
N
NH
N
NH
N
NH
4
5
6a - 6e
7a - 7e
6a, 7a : Ar :
6b, 6b : Ar :
6
c, 7c : Ar :
NO2
OH
N
t-Bu
6d, 7d : Ar :
6e, 7e : Ar :
N
H
Cl
Scheme 1 Synthesis of 2-methyl-4-oxo-N-(4-oxo-2-phenyl substituted-1,3-thiazolidin-3-yl)-3,4-dihydroquinazoline-5-carboxamides

J Fluoresc
a
a
b
b
Fig. 3 Absorption and emission spectra of compounds 7a–7e. a Absorp-
tion spectra of compounds 7a–7e in DMF. b Emission spectra of com-
pounds 7a–7e in DMF
Fig. 2 Absorption and emission spectra of compounds 6a–6e. a Absorp-
tion spectra of compounds 6a–6e. b Emission spectra of compounds 6a–6e
condition for 12 h to give 2-methyl-N-[2-(4-nitrophenyl)-4-
oxo-1,3-thiazolidin-3-yl]-4-oxo-3,4-dihydroquinazoline-5-
carboxamide 7b.
oxo-2-phenyl-1,3-thiazolidin-3-yl)-3,4-dihydroquinazoline-
5
-carboxamide 7a.
Yield: 61 %, Melting point => 300 °C.
H-NMR (CD ) SO: δ 2.28 (s,1H), 2.50 (s, 1H), 3.65
3 2
1
Yield: 69 %, Melting point => 300 °C.
1
H-NMR (CD ) SO: δ 2.25 (s, 3H), 2.5 (s, 2H), 3.45
(s, 1H), 7.37 (d, 1H, J=7.7 Hz), 7.69 (d, 1H, J=7.7 Hz),
7.69 (d, 1H, J=7.7 Hz), 7.76 (dd, 1H, J=8.1, 7.3 Hz),
8.16 (d, 2H, J=8.8 Hz), 8.37 (d, 2H, J=8.8 Hz), 9.71 (s,
1H), 11.85 (s, 1H)
3
2
(
s, 1H), 7.33 (d, 1H, J=7.7 Hz), 7.63 (d, 1H, J=7.7 Hz),
7
8
8
.74 (dd, 1H, J=8.1, 7.3 Hz), 7.80–7.88 (m, 3H, J=8,
.1, 7.7 Hz), 8.15 (d, 1H, J=8.1 Hz), 8.36 (d, 1H, J=
Hz), 9.71 (s, 1H), 11.78(s, 1H)
FT-IR (KBr): 2981, 2823, 2761, 1629, 1558, 1478, 1419,
−1
FT-IR (KBr): 2978, 1789, 1768, 1628, 1667, 1581, 1458,
1338, 1167, 1089, 1044, 876, 779, 698 cm .
−1
+
1
335, 1267, 1211, 970, 689, 651 cm .
Mass: m/z 427 (M ).
+
Mass: m/z 388 (M ).
2-Methyl-4-oxo-N-(4-oxo-2-anthracene-1,3-thiazolidin-3-yl)
2
-Methyl-N-[2-(4-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]
-3,4-dihydroquinazoline-5-carboxamide 7c
-
4-oxo-3,4-dihydroquinazoline-5-carboxamide 7b
N′-(Anthracen-9-ylmethylidene)-2-methyl-4-oxo-3,4-
dihydroquinazoline-5-carbohydrazide 6c (1.42 mmol) was
reacted with thioglyconic acid (1.42 mmol) in THF at reflux
condition for 14 h to give 2-methyl-4-oxo-N-(4-oxo-2-
2
-Methyl-N′-[(Z)-(4-nitrophenyl)methylidene]-4-oxo-3,4-
dihydroquinazoline-5-carbohydrazide 6b (1.42 mmol) was
reacted with thioglyconic acid (1.42 mmol) in THF at reflux

J Fluoresc
Table 1 Observed UV-visible absorption, emission and computed vertical excitation and emission of compounds 7a -7e in DMF
Expt
Expt
DFT
Em
a
b
Comp
λ
(
max(nm)
TD-DFT
vertical excitation
f
%
D
λ
Em (nm)
λ
%
D
Stokes shift
Δλ
Φ
nm)
–
1
(cm )
nm
eV
7
7
7
7
7
a
b
c
d
e
300
341
354
342
312
307
362
402
383
303
4.029
3.417
3.083
3.233
4.083
0.120
0.003
0.010
0.0003
0.007
2
431
432
464
431
428
345
426
440
473
470
19
1
10131
6177
6696
6037
8686
0.002
0.017
0.021
0.102
0.253
6
13
11
2
4
9
9
a
–1
Stokes shift in cm
Quantum yield
b
Analyses were carried out at room temperature (25 °C); experimentally observed λmax
%
(
D) % Deviation between vertical excitation and experimental absorption and experimental emission and computed (TD-DFT) emission
f: Oscillator strength
anthracene-1,3-thiazolidin-3-yl)-3,4-dihydroquinazoline-5-
carboxamide 7c.
N-(4-oxo-2-(4-(diethylamino)2-phenol-1,3-thiazolidin-3-yl)-
3,4-dihydroquinazoline-5-carboxamide 7b.
Yield: 71 %, Melting point => 300 °C.
Yield: 69 %, Melting point => 300 °C.
1
1
H-NMR (CD ) SO: δ 2.28 (s, 3H), 2.50 (s, 2H), 3.65 (s,
H-NMR (CD ) SO: δ 2.43 (s, 3H), 2.51 (6H, t, J=
3
2
3 2
1
7
H), 7.37 (d, 1H, J=7.7 Hz), 7.67 (d, 1H, J=7.7 Hz), 7.70–
.82 (m, 12H, J=18.6, 7.7, 8.0 Hz), 11.85 (s, 1H).
14.3 Hz), 2.64 (2H, s), 3.36 (1H, s), 3.92 (q, 4H, J=
14.3 Hz), 6.92 (s, 1H), 7.63 (d 1H, J=7.7 Hz), 7.72 (d, 1H,
J=8.1), 7.92 (dd, 1H, J=7.7, 8.1 Hz), 8.03 (d, 1H, J=9.3 Hz),
8.23 (d, 1H, J=7.9 Hz), 8.88 (dd, 1H, J=9.3, 7.9 Hz), 10.39
(s, 1H), 12.25 (s, 1H), 12.51 (s, 1H).
FT-IR (KBr): 3018, 1801, 1757, 1625, 1681, 1580, 1448,
−1
1
345, 1255, 1210, 978, 667, 644 cm .
+
Mass: m/z 488 (M ).
FT-IR (KBr): 3028, 1777, 1759, 1631, 1667, 1568, 1440,
−1
1
320, 1245, 1264, 957, 678, 621 cm .
Mass: m/z 469 (M ).
+
2
2
-Methyl-4-oxo-N-(4-oxo-2-(4-(diethylamino)
-phenol-1,3-thiazolidin-3-yl)
-
3,4-dihydroquinazoline-5-carboxamide 7d
2-Methyl-4-oxo-N-(4-oxo-2-1-tert-butyl-4-chloro-1
H-pyrazole-1,3-thiazolidin-3-yl)
2
4
-Methyl-N′-[(Z)-(4-N, N-diethyl, 2-hydroxy)methylidene]-
-oxo-3,4-dihydroquinazoline-5-carbohydrazide 6d
-3,4-dihydroquinazoline-5-carboxamide 7e
(
1.42 mmol) was reacted with thioglyconic acid (1.42 mmol)
N′-[(Z)-(1-Tert-butyl-4-chloro-1H-pyrazol-5-yl)methylidene]-
2-methyl-4-oxo-3,4-dihydroquinazoline-5-carbohydrazide 6e
in THF at reflux condition for 10 h to give 2-methyl-4-oxo-
Graph 1 HOMO-LUMO
energies of compounds 7a–7e in
different solvents

J Fluoresc
Table 2 Frontier molecular orbitals of compounds 7a-7e
(1.42 mmol) was reacted with thioglyconic acid (1.42 mmol)
Compounds
HOMO
LUMO
in THF at reflux condition for 18 h to give 2-methyl-4-oxo-
N-(4-oxo-2-1-tert-butyl-4-chloro-1H-pyrazole-1,3-
thiazolidin-3-yl)-3,4-dihydroquinazoline-5-carboxamide 7e
Yield: 61 %, Melting point => 300 °C.
7
a
1
H-NMR (CD ) SO: δ 2.22 (s, 3H), 2.48 (s, 9H), 3.16 (s,
3
2
1
8
H), 3.35 (s, 1H), 7.30 (d, 1H, J=8.7 Hz), 7.61 (d, 1H, J=
.7 Hz), 7.74 (dd, 1H, J=6.1, 8.7 Hz), 11.72 (1H, s)
FT-IR (KBr): 3034, 1759, 1721, 1645, 1621, 1545, 1435,
−1
1
341, 1257, 1222, 950, 669, 602 cm
Mass: m/z 462 (M ).
.
+
7
b
Result and Discussion
Chemistry
7c
Synthesis of 2-methyl-4-oxo-3,4-dihydroquinazoline-5-
carbohydrazide 5 was performed by reacting ethyl-2-methyl-
4-oxo-3,4-dihydroquinazoline-5-carboxylate with 98 % hy-
drazine hydrate under reflux condition for 2 h. Initially
ethyl-2-methyl-4-oxo-3,4-dihydroquinazoline-5-carboxylate
was insoluble in hydrazine hydrate at room temperature and it
gets solubilized after heating at reflux condition. The product
was separated from the reaction mass as the reaction goes to
completion. On completion of the reaction the reaction mix-
ture was cooled, the product was separated by filtration,
washed with cold water, and dried.
7
d
The intermediate 2-methyl-4-oxo-3,4-dihydroquinazoline-
5-carbohydrazide 5 was reacted with different aldehydes in
methanol at reflux condition to give the corresponding Schiff
base 2-methyl-4-oxo-N′-[(Z)-phenyl substituted
methylidene]-3,4-dihydroquinazoline-5-carbohydrazide (6a–
7e
6e). In this step the formation of Schiff base requires nearly
2
to 7 h. The reaction was initiated in the presence of catalytic
amount of H SO . On completion of the reaction the reaction
2
4
Fig. 4 TGA of compounds 7a,
b, 7c and 7e
7

J Fluoresc
mixture was cooled, and neutralized with Na CO at low
conjugation between quinazolone and thiazolyl units. This is
also supported by the fact that the compound 6a–6e and 7a–7e
have similar photophysical properties. The compounds 6a–6e
absorb at 300 nm except the compound 6c which absorbs at
354 nm in DMF. The experimental absorption properties of
the compounds are well in agreement with the computed
energy difference between HOMO and LUMO Graph 1. In
the case of the compound 6c the energy difference between
HOMO and LUMO is less as compared to the other com-
pounds and it shows a red shifted absorption. The analo-
gous behavior is observed for the compounds 7a–7e. The
compounds 6a–6e emit at 430 nm except the compound 6c
which emits at 470 nm in DMF. The emission properties of
the compound 6a–6e and the compounds 7a–7e are almost
the same in DMF. This clearly indicates that the quinazolone
unit is responsible for the absorption as well as the emission
properties. The compounds 7b and 7c show dual absorption.
The short wavelength absorption is in the range 274–294 nm
and the long wavelength absorption is at 350 nm. In the case
of the emission spectra of the compound 7a–7e a single
intense emission was observed. The quantum yields of the
compounds are in range of 0.002 to 0.353. The compound 7e
shows a higher quantum yield as compared to the compounds
7a–7d in DMF.
2
3
temperature to precipitate the products. The products were
filtered and dried. The yields of the compounds 6a–6e range
from 67 to 87 %.
2
-Methyl-4-oxo-N-(4-oxo-2-phenyl substituted −1,3-
thiazolidin-3-yl)-3,4-dihydroquinazoline-5-carboxamide
7a–7b) was prepared by reacting the Schiff base 2-methyl-4-
(
oxo-N′-[(Z)-phenyl substituted methylidene]-3,4-
dihydroquinazoline-5-carbohydrazide (6a–6e) with
thioglyconic acid in THF in the presence of catalytic amount
of PTSA. The reaction details are summarized in the experi-
mental procedure and the synthetic strategy is presented in
Scheme 1.
Photophysical Properties
The absorption and emission properties of the compounds 6a–
6
e and 7a–7e were studied in the solvent DMF. All the
absorption-emission studies were performed at room temper-
−6
ature using solutions of concentration 1×10 M. The synthe-
sised compounds are fluorescent in solution under irradiation
of UV light. The absorption and emission spectra of the
compounds 6a–6e and 7a–7e are presented in Figs. 2 and 3
respectively. The effect of electron donor and electron accep-
tor groups on the absorption and the emission properties of the
compounds were studied. All the compounds absorb in the
ultraviolet region and emit in the visible region. The absorp-
tion and the emission properties of the compounds show that
they are well suitable to function as fluorescent brightening
agents. In other words they absorb in the ultra-violet region
and emit in the visible region. The observed photophysical
properties of the compounds are compared with the computa-
tional results obtained by DFTand TD-DFTand the results are
summarised in Table 1.
Computational Study
The observed experimental absorption properties of the com-
pounds were compared with the vertical excitation data ob-
tained computationally and they are in good agreement with
each other. The maximum difference is observed for the
compounds 7c and 7d. In the case of the compounds 7a, 7b
and 7e the experimental absorption and the vertical excitation
are almost the same. In the case of the emission a large
difference was observed between the experimental emission
and the calculated emission for the compound 7a (19 %) and a
The absorption and emission properties of the compounds
depend on the quinazolone unit as there is no direct
Table 3 Color properties of compounds 7a-7e
Standard blank polyester
7a
7b
7c
7d
48.921
7e
X
48.025
50.82
56.532
59.421
56.284
81.522
0.525
51.414
54.689
55.871
78.862
−1.111
2.687
57.805
61.766
61.848
82.789
−1.797
3.915
53.635
56.874
57.327
80.109
−0.696
3.451
Y
51.823
54.815
77.175
−0.54
Z
54.138
76.57
L*
a*
−0.396
0.416
b*
6.879
0.799
C*
0.574
6.899
2.908
4.308
0.964
3.52
H*
133.608
0.2515
85.601
0.5506
112.491
0.3152
114.682
0.5626
124.075
0.2739
−16.865
73.158
63.791
101.434
0.4152
K/S
Berger whiteness
Stensbay whiteness
Taube whiteness
−299.914
62.46
−145.533
67.468
−275.681
65.653
−168.12
67.668
46.873
59.417
62.094
58.686

J Fluoresc
larger difference was observed for the compounds 7d and 7e.
In the case of the compounds 7c and 7d the experimental
emission and the calculated emission are very close to each
other. A large Stokes shift was observed for the compounds 7c
and 7e. The % deviation between the experimental
photophysical properties and the calculated photophysical
properties and oscillator strength obtained by DFT computa-
tion are summarised in Table 1.
The most probable electronic transitions occurring in
the molecules were understood using the frontier molec-
ular orbitals (HOMO and LUMO) generated using
Gaussview 05 program for compounds 7a–7e in the sol-
vent DMF Table 2. All the compounds may be
considered to be consisting of three cores—quinazolinone,
thiazolidine and aromatic cores. The electron density for
the compounds 7a–7e is concentrated on the thiazolidine
core, but the LUMO energy distribution pattern is not
linear. In the case of compounds 7a, 7d and 7e the
electron density is spread over quinazolinone unit. The
electron distribution is on the aromatic system of the
thiazolidine for compounds 7c and 7b. The electron
distribution patterns of compounds 7a–7e indicates that
the thiazolidine core acts as donor and quinazolinone and
aromatic cores of the compound 7c and 7b act as acceptor
units.
Conclusion
Fluorescent compounds are synthesised from the intermediate
ethyl 2-methyl-4-oxo-3, 4-hydroquinazoline-5-carboxylate.
Photophysical properties of the compounds in DMF were
evaluated experimentally and the results are compared with
the theoretical data. The experimental results are in good
agreements with the theoretical results. The % deviation be-
tween the experimental absorption and the emission is in the
range between 1 and 19 %. The fluorescent compounds show
good brightness on polyester fibres and have good thermal
stability.
Acknowledgments Vikas Patil and Vikas Padalkar are thankful to
Institute of Chemical Technology and they have contributed equally.
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