Microwave assisted synthesis, spectroscopic studies and non linear optical properties of bis-chromophores

Article abstract of DOI:10.1016/j.saa.2014.08.065

Bis chromophores were synthesized by the terephthalaldehyde with (4-nitrophenyl) acetonitrile/(4-flurophenyl) acetonitrile under microwave irradiation. Bis-chromophores were obtained in good to excellent yields. The structures of bis-chromophores were est

Full text of DOI:10.1016/j.saa.2014.08.065

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Microwave assisted synthesis, spectroscopic studies and non linear
optical properties of bis-chromophores
b
b
Salman A. Khan a, , M.A.N. Razvi , Ahmed H. Bakry , S.M. Afzal b,d, Abdullah M. Asiri a,c, Samy A. El-Daly a
⇑
a Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
b Department of Physics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
c Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
d Department of Physics, Aligarh Muslim University, Aligarh, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
Synthesis of bis-chromophores by
microwave irradiation.
Absorption and emission spectra of
bis-chromophores in various non-
polar, polar aprotic and protic
solvents were studied.
-14.0
S1 - N2 (70 mW)
S2 - N2 (70 mW)
700
600
500
400
300
200
100
0
S1
2.5
-12.0
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
S2
EtOH
MeOH
DMSO
DMF
2.0
1.5
1.0
0.5
CHCl3
CH3CN
Dioxan
n-Heptane
ꢀ
Non linear optical properties of bis-
chromophores.
-40
-20
0
20
40
60
0
2
4
6
8
10
12
400
450
500
550
600
Z [mm]
Wavelength (nm)
Concentration [ mM ]
Emission spectra of 1 × 10-5 mol dm-3
Close aperture z-scan of S1 & S2
dyes
Variation of nonlinear refractive index n2
vs the concentration of S1 & S2 dyes
of dye S2 in different solvents
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 May 2014
Received in revised form 20 August 2014
Accepted 24 August 2014
Available online 6 September 2014
Bis chromophores were synthesized by the terephthalaldehyde with (4-nitrophenyl) acetonitrile/
(4-flurophenyl) acetonitrile under microwave irradiation. Bis-chromophores were obtained in good to
excellent yields. The structures of bis-chromophores were established by FT-IR, 1H NMR, 13C NMR, EI-MS
and elemental analyses. Physical chemical properties such as singlet absorption, extinction coefficient,
stokes shift, oscillator strength and dipole moment, were investigated by UV–Vis and fluorescence
spectroscopy measurements. Further we also measured the nonlinear refractive index and nonlinear
absorption coefficients of these compounds using the single beam z-scan technique with a cw argon
ion laser at 514.5 nm at different concentrations in DMSO solvent. The third order nonlinear susceptibil-
ity was estimated from these measurements and it shows high nonlinearity. The high negative refractive
index makes these compounds suitable for optical limiting application.
Keywords:
Bis-chromophore
Stokes shift
Oscillator strength
Dipole moment
Nonlinear absorption
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
fields such as optical limiting, molecular switching and frequency
doubling [4,5]. The most common design of molecules for the lin-
The design and synthesis of organic molecules with desirable
properties are of considerable importance in chemistry due to their
fundamental role in material science [1–3]. In previous studies, a
significant attempt has been focused on the development and the
synthesis of organic molecules with improved nonlinear optical
(NLO) properties because of their potential applications in different
ear optical properties with strong electron donors and acceptors
connected by p-conjugated system (donor–p–acceptor or
a
‘push–pull’ chromophores) [6]. In these donor–p–acceptor sys-
tems, the necessity of ground-state charge asymmetry is provided
by the donor and acceptor moieties, while as a trail for the rede-
ployment of electron density is provided by the p-conjugated
bridge under the influence of external electric fields [7,8]. High
molecular quadratic hyperpolarizability (a nonlinear-optical
property of a molecule) good thermal, chemical and photochemical
⇑
Corresponding author.
E-mail address: sahmad_phd@yahoo.co.in (S.A. Khan).
http://dx.doi.org/10.1016/j.saa.2014.08.065
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

S.A. Khan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
1101
stabilities are necessitated for the practical application of second-
order NLO materials [9,10]. By the substitution of an aromatic ring
with easily delocalizable heteroaromatics, excellent thermal and
photochemical stabilities of NLO chromophores with potted high
hyperpolarizabilities can be attained [11]. The design and the syn-
thesis of the materials demonstrating nonlinear optical (NLO)
properties is presently a most important chore in the field of
chemistry because of their numerous applications in the area of
opto-electronics and photonics [12,13]. By means of conjugated
bridge covalently connected through electron donor and acceptor
moieties, a molecular NLO-phores are conventionally constituted
[14]. On the other hand chromophores extensively used in field of
materials science due to their donor acceptor conjugation system,
such as, optical switching [15], electrochemical sensing [16], lang-
muir films and photoinitiated polymerization [17]. For determining
the behavior of compounds various physicochemical characteristics
for instance florescent quantum yield, photostability, oscillator
strength, solvatochromic, dipole moment and piezochromic are
included in the most important studies [18,19]. Because of these
numerous applications of chromophores, we are reporting the syn-
thesis of bis-chromophore and their non linear optical properties
with their physicochemical studies. We also report the results of
our studies on measurement of nonlinear refractive index and non-
linear optical absorption of these dyes using the z-scan technique
with a cw laser.
cell absorption spectra were collected. By using Shimadzu RF
5300 spectrofluorphotometer having a quartz cell of rectangular
shape with dimensions 0.2 cm ꢁ 1 cm for minimizing the reab-
sorption. Emission spectra were observed at right angle. Before
proceeding data analyses, all fluorescence spectra were blank
subtracted.
(2Z,20Z)-3,30-benzene-1,4-diylbis[2-(4-nitrophenyl)prop-2-enenitrile]
(S1)
A
mixture of 4-nitrophenyl-acetonitrile (0.0058 mol) and
terephthalaldehyde (0.0029 mol) in anhydrous ethanol (15 ml), in
the presence of few drops of pyridine. Inside the microwave oven
the reaction mixture was heated for 5 min. (at 210 W i.e., 30%
microwave power). When the reaction was completed, reaction
mixture was allowed to cool and recrystallized with ethanol and
chloroform. Mp. 199 °C; Yeild: 75%; IR (KBr)
v
max cmꢂ1: 3059
(CAH), 2930 (CAH), 2221 CACN), 1593 (C@C), 1535 (NAOasym),
1345 (NAOsym), 1167 (CAN); 1H NMR (CDCl3) d: 8.35 (s, 2H),
7.73 (s, 4H, CHaromatic), 8.09 (d, 2H, CHaromatic J = 7.8 Hz), 8.03
(d, CHaromatic), 7.90 (d, CHaromatic, J = 8.4 Hz), 7.26 (d, CHaro-
matic, J = 7.6 Hz); 13C NMR (CDCl3) d: 191.14, 148.35, 143.62,
139.80, 138.13, 137.74, 130.23, 130.14, 127.09, 124.50, 116.60,
112.67; GC–MS m/z (rel. int.%): 424 (72) [M + 1]+; anal. calc. for
C24H14N4O4: C, 68.24, H, 3.39, N, 13.26; found: C, 68.18, H, 3.32,
N, 13.21.
Experimental
(2Z,20Z)-3,30-benzene-1,4-diylbis[2-(4-fluorophenyl)prop-2-enenitrile
(S2)
Chemicals and reagents
Terephthalaldehyde, 4-nitrophenyl-acetonitrile and 4-flurophe-
nyl acetonitrile were acquired from Acros Organic. All solvents and
reagents (A.R.) were acquired commercially and utilized with no
additional purification, excluding dimethylformamide (DMF), eth-
anol and methanol.
A
mixture of 4-flurophenyl acetonitrile (0.0058 mol) and
terephthalaldehyde (0.0029 mol) in anhydrous ethanol (15 ml), in
the presence of few drops of pyridine. Inside the microwave oven
the reaction mixture was heated for 4 min (at 210 W i.e., 30%
microwave power). After the completion of the reaction, the reac-
tion mixture was let to cool and recrystallized with ethanol and
Apparatus
chloroform. Mp. 213 °C; Yeild: 78%; IR (KBr)
v
max cmꢂ1: 3052
Thomas Hoover capillary melting apparatus was used to record
the melting points of the synthesized compounds without any cor-
rection. Nicolet Magna 520 FT-IR spectrometer was utilized to
record the FT-IR spectra. Brucker DPX 600 MHz spectrometer with
tetramethyl silane as internal standard at room temperature was
used to perform the 1H NMR and 13C NMR experiments in CDCl3.
Shimadzu UV-160A spectrophotometer was utilized to gain the
UV–Vis electronic absorption data and by using a 10 mm quartz
(CAH), 2933 (CAH), 2208 (CACN), 1577 (C@C), 1156 (CAN); 1H
NMR (CDCl3) d: 8.00 (s, 2H), 7.77–7.15 (m, 12H, CHaromatic), 13C
NMR (CDCl3) d: 164.28, 162.61, 160.68, 159.01, 145.53, 140.51,
135.60, 135.41, 131.08, 130.34, 129.90, 128.08, 128.02, 124.85,
124.83, 122.58, 117.60, 116.76, 116.22, 112.08, 107.69, 107.68;
GC–MS m/z (rel. int.%): 370 (72) [M + 1]+; anal. calc. for
C
24H14N2F2: C, 78.25, H, 3.83, N, 7.60; found: C, 78.21, H, 3.75, N,
7.55.
Scheme 1. Synthesis of bis-chromophores (S1 and S2).

1102
S.A. Khan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
700
EtOH
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
MeOH
EtOH
600
500
400
300
200
100
0
DMSO
DMF
CHCl3
CH3CN
Dioxan
n-Heptane
MeOH
DMSO
DMF
CHCl3
CH3CN
Dioxan
n-Heptane
400
450
500
550
600
300
350
400
450
Wavelength (nm)
Wavelength (nm)
Fig. 2b. Emission spectra of 1 ꢁ 10ꢂ5 mol dmꢂ3 of compound S1 in different
Fig. 1a. Electronic absorption spectra of 1 ꢁ 10ꢂ5 mol dmꢂ3 of compound S1 in
solvents.
different solvent.
0.1 mm across the focal plane. The transmitted beam was passed
through a 2 mm circular iris aperture and detected by a photomul-
tiplier tube (McPherson) kept in the far field for the closed aperture
z-scans. For the open aperture z-scans, the iris diaphragm was fully
opened. The PMT signal was averaged, digitized and recorded by
the same computer.
300
EtOH
MeOH
250
DMSO
DMF
CHCl3
CH3CN
Dioxan
n-Heptane
200
150
100
50
Results and discussions
Chemistry
The synthesis of bis-chromophores is straight forward and the
compounds were isolated in good yield by the microwave irradia-
tion (Scheme 1) [20]. The acquired compounds are stable in both
solid as well as in the solution form. The structure of all the synthe-
sized compounds shown in experimental section was recognized
by comparing spectral data (IR, 1H NMR and 13C NMR, EI-MS) ele-
mental analyses. It is clear from the IR band positions that the for-
mation of bis-chromophores takes place. These compounds
0
350
400
450
500
550
600
Wavelength (nm)
Fig. 1b. Emission spectra of 1 ꢁ 10ꢂ5 mol dmꢂ3 of compound S1 in different
solvents.
0.5
demonstrated intense bands at 1577–1599 cmꢂ1 due to
v (C@C)
stretch, which proves the formation of bis-chromophores by Knoe-
venagel; condensation. Additional confirmation for the formation
of bis-chromophores was acquired from the 1H NMR spectra,
which offer diagnostic tools for the positional illumination of
the protons. Assignments of the signals are based on the chemi-
cal shifts and intensity patterns. The aromatic protons of bis-
chromophores are shown as s,d and dd in the range 8.09–7.15 ppm
for the compounds. A Singlet due to @CAH proton in the com-
pound S1 at 8.35 ppm and compound S2 at 8.00 ppm was observed
at respectively.
EtOH
0.4
MeOH
DMSO
DMF
0.3
CHCl3
CH3CN
Dioxan
n-Heptane
0.2
0.1
0.0
13C NMR (CDCl3) spectra of bis chromophores were recorded in
CDCl3 and spectral signals are in good agreement with the probable
structures details of 13C NMR spectra of both compound and those
data are given in the experimental section
300
350
400
450
Wavelength (nm)
Fig. 2a. Electronic absorption spectra of 1 ꢁ 10ꢂ5 mol dmꢂ3 of compound S1 in
Finally, characteristic peaks were observed in the mass spectra
of bis chromophores by the molecular ion peak. The mass spectrum
of compound S1 and S2 shows a molecular ion peak (M+) m/z 424
and 370.
different solvent.
z-Scan measurements
These measurements were carried out with a continuous wave
(cw) argon ion laser operating at 514.5 nm (CVI Melles Griot
Semrock) at 70 mW power. The laser beam was focused with a
5 cm focal length lens onto the quartz sample cuvette (1 mm path
Spectral behavior of bis-chromophores (S1 and S2)
Absorption and emission spectra of 1 ꢁ 10ꢂ5 mol dmꢂ3
compound S1 and S2 in various non-polar, polar aprotic and protic
solvents were studied (Figs. 1a–2b). Calculated physicochemical
parameters obtained from steady state absorption and
fluorescence spectra are summarized in Tables 1 and 2. A close
length, 400 lL) containing the dye solution in DMSO solvent at
concentrations from 1 mM to 10 mM. The sample cuvette was
mounted on a motorized and computer controlled translation
stage (Newmark Systems ET-200-11) and moved in steps of

S.A. Khan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
1103
Table 1
Spectral data of compound no. S1 in different solvents.
ꢂ1
ET (30) kcal molꢂ1
kab (nm)
kem (nm)
e
M ꢂ1 cmꢂ1
f
l12 debye
D
m
(cm )
ꢀ
Solvent
D
f
EtOH
0.305
0.308
0.266
0.263
0.217
0.274
0.148
0.0004
84.58
84.83
82.87
83.59
84.58
85.34
84.58
86.63
338
337
345
342
338
335
338
330
460
445
466
443
449
450
448
525
52,990
53,370
53,210
53,170
59,970
58,040
54,700
55,540
1.66
1.53
1.60
1.41
1.75
1.77
1.58
2.50
10.90
10.45
10.81
10.10
10.90
11.20
10.90
13.22
7846
7202
7526
6666
7314
7628
7264
11,256
MeOH
DMSO
DMF
CHCl3
CH3CN
Dioxan
n-Heptane
Table 2
Spectral data of compound no. S2 in different solvents.
ꢂ1
ET (30) kcal molꢂ1
kab (nm)
kem (nm)
e
M ꢂ1 cmꢂ1
f
l12 debye
D
m
(cm
)
ꢀ
Solvent
D
f
EtOH
0.305
0.308
0.266
0.263
0.217
0.274
0.148
0.0004
80.53
80.76
80.53
80.76
79.19
80.99
80.53
80.53
355
354
355
354
361
353
355
355
447
446
455
451
453
442
446
442
40,470
43,700
36,560
39,840
34,250
43,520
37,370
40,750
0.93
1.01
0.90
0.96
0.77
0.99
0.85
0.90
8.36
8.70
8.25
8.48
7.67
8.60
7.97
8.22
5798
5827
6199
6076
5625
5704
5748
5545
MeOH
DMSO
DMF
CHCl3
CH3CN
Dioxan
n-Heptane
S1
S2
2.5
1.06
S1 OPEN
FIT
2.0
1.5
1.0
0.5
1.04
1.02
1.00
0.98
-20
-10
0
10
20
-40
-20
0
20
40
60
Z [mm]
Z [mm]
Fig. 4. Open aperture z-scan of S1 dye. The solid line is a theoretical least square fit
of the observed data.
Fig. 3. Close aperture z-scan of S1 and S2 dyes (10 mM concentration solution in
DMSO) using Ar+ laser at 514.5 nm, 70 mW.
2
2ðle
ꢂ
lg
Þ
examination of Figs. 1a–2a displays that the polarity of solvent has
a slightly effected on absorption maxima, of the compound S1 and
S2 indicating a weak polar character the compounds S1 and S2 in
the ground state. However, the emission spectra of the compound
S1 is broad and red shifted as the solvent polarity decreases DMF to
n-heptane, as shown in Fig. 1b this indicates that the singlet
excited state is more polar than the singlet excited state because
of two NO2 group are present in bis-chromophore S1. The emission
spectra of the compound S2, showed broad and red shifted Fig. 2b,
as the solvent polarity increases. The red shift from 442 nm in n-
heptane to 466 nm in DMSO indicates that singlet excited state
of dye is more polar than the ground state because of two fluorine
group are presence in bis-chromophore S2.
ꢀ
D
D
mst
¼
D
f þ Const:
ð1Þ
hca3
D ꢂ 1
n2 ꢂ 1
f ¼
ꢂ
ð2Þ
2D þ 1 2n2 þ 1
ꢀ
where
D
mst is the Stokes-shift [23], which increases with increasing
the solvent polarity pointing to stronger stabilization of the excited
state in polar solvents, h denotes Planck’s constant, c refers to the
speed of light in vacuum and a is the Onsager cavity radius. Param-
eters D and n, in Eq. (2), correspond to the dielectric constant and
refractive index of the solvent, respectively. The Onsager cavity
radius was chosen to be 4.2 Å because this value is comparable to
the radius of a typical aromatic fluorophore [24]. Stokes shifts
ꢀ
ð mssÞ of compound S1 and S2 in different solvents were calculated,
D
as shown in Tables 1 and 2, using the following the equation [21]:
Determination of oscillator strength and transition dipole moment
ꢀ
mss
ꢀ
mex
ꢀ
mem
D
¼
ꢂ
ð3Þ
The solvatochromic behavior in bis-chromophores (S1 and S2)
allows one to determine the difference in the dipole moment
ꢀ
ꢀ
where mex and mem denote the wavenumbers of excitation and emis-
between the excited singlet and the ground state (
This difference can be obtained using the simplified Lippert–
D
l
=
le
ꢂ
l
g).
sion maxima (cmꢂ1), respectively. The change in dipole moment
(D
l
) for compound S1 is negative ꢂ0.95 value which indicates that
Mataga equation as follows [21,22]:
the ground state of these compounds is more polar than the singlet

1104
S.A. Khan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
Table 3
Nonlinear refractive index and nonlinear absorption at different concentration.
Dye
S1
S2
Concentration (mM)
n2 ꢁ 10ꢂ8 (cm2/W)
b ꢁ 10ꢂ3 (cm/W)
v(3) ꢁ 10ꢂ6 (esu)
n2 ꢁ 10ꢂ8 (cm2/W)
b ꢁ 10ꢂ3 (cm/W)
v(3) ꢁ 10ꢂ6 (esu)
1
2.5
5
7.5
10
ꢂ1.889
ꢂ4.447
ꢂ5.752
ꢂ9.254
ꢂ12.928
ꢂ0.41
ꢂ0.54
ꢂ1.54
ꢂ2.26
ꢂ5.35
9.3
12.4
34.8
51.2
120.8
ꢂ0.572
ꢂ0.717
ꢂ0.600
ꢂ1.762
ꢂ5.747
0.01
ꢂ0.05
ꢂ1.24
ꢂ2.24
ꢂ4.27
0.388
1.19
28.0
50.5
96.4
1.8
1.6
1.4
1.2
1.0
0.8
0.6
-14.0
-12.0
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
20 mW
30 mW
40 mW
50 mW
S1 - N2 (70 mW)
S2 - N2 (70 mW)
0.4
-40
-20
0
20
40
60
0
2
4
6
8
10
12
Z [mm]
Concentration [ mM ]
Fig. 5. Close aperture z-scan measurement of S1 dye (10 mM) at various laser
Fig. 6a. Variation of nonlinear refractive index n2 vs the concentration of S1 and S2
powers.
dyes at 70 mW laser power.
excited state. For compounds S2 the
Dl values are positive +2.9.2,
peak and a postfocal valley indicate the sign of the nonlinear
refractive index n2 is negative. The open aperture z-scan of S1
dye in Fig. 4 shows a reverse saturable absorption behavior indicat-
ing the nonlinear absorption coefficient b is also negative.
One can obtain the values of n2 and b by fitting the normalized
transmittance of close aperture (CA) scan data to the equation [29]:
indicating that the singlet excited is more polar than the ground state.
The effective number of electrons transition from the ground to
excited state is usually described by the oscillator strength, which
provides the absorption area in the electronic spectrum. The oscil-
lator strength, f, can be calculated using the following equation
[25]:
2ðꢂ
q
x2 þ 2x ꢂ 3
q
Þ
Z
T ðcloseÞ ¼ 1 þ
DU
f ¼ 4:32 ꢁ 10ꢂ9
eð
m m
Þd
ð4Þ
ðx2 þ 9Þðx2 þ 1Þ
ꢀ
ꢀ
D
W
where
q
¼
;
D
U
¼ kn2I0Leff and
DW
¼ bI0Leff =2 are the phase
is the extinction coefficient (L molꢂ1 cmꢂ1), and
repre-
ꢀ
m
U
shifts due toDnonlinear refraction and nonlinear absorption respec-
tively, and x = z/z0 is the dimensionless relative position from the
focus, z0 is the Rayleigh length, Leff is the effective thickness of the
where
e
sents the numerical value of wavenumber (cmꢂ1). Oscillator
strength values of compound S1 and S2 in different solvents are
reported in Tables 1 and 2. In addition, the transition dipole
sample; Leff = [1 ꢂ exp (ꢂ
a0L)]/a0, where a0 is the linear absorption
coefficient and I0 is the on-axis intensity of light at the focus. The
moment (l) for compound S1 and S2 from ground to excited state
in Debye was estimated in different solvents (Tables 1 and 2) using
the following relation [26]:
-5
-4
-3
-2
-1
0
S2 - BETA (70 mW)
S1 - BETA (70 mW)
f
l2
¼
ð5Þ
4:72 ꢁ 10ꢂ7 ꢁ Emax
where Emax is the maximum energy of absorption in cmꢂ1
The empirical Dimroth polarity parameter, ET (30), was also cal-
culated according to the following equation [27,28].
.
28591
kmax
ET ðsolventÞ ¼
ð6Þ
where kmax corresponds to the peak wavelength (nm) in the red
region of the intramolecular charge transfer absorption of all
compounds.
0
2
4
6
8
10
Nonlinear optical measurements
Concentration [mM]
A closed aperture z-scan of the two dyes S1 and S2 is shown in
Fig. 3 for a 10 mM solution with a laser power of 70 mW. A prefocal
Fig. 6b. Variation of nonlinear absorption coefficient b vs concentration at 70 mW
laser power.

S.A. Khan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1100–1105
1105
[6] A.M. Asiri, S.A. Khan, M.S. Al-Amodi, K.A. Alamry, Synthesis, characterization,
absorbance, fluorescence and non linear optical properties of some donor
acceptor chromophores, Bull. Korean Chem. Sci. 33 (2012) 1900–1906.
[7] A.M. Asiri, S.A. Khan, S.I. El-Hallag, Electrochemical studies of some carbazole
values of n2 and b are summarized in Table 3. We studied the var-
iation of normalized transmittance at different laser powers from
20 mW to 70 mW, the close aperture scans are shown in Fig. 5.
We also show a plot of n2 and b in Figs. 6a and 6b respectively as
a function of concentrations. It is clear from the figures that the
nonlinearity is getting enhanced, more or less linearly, with concen-
tration. This may be due to the thermal origin of the nonlinear
effect. The nonlinear absorption coefficient was also obtained from
the open aperture z-scan data by fitting it to the equation [30];
derivatives via cyclic voltammetry and convolution
– deconvolution
transforms, J. New Mater. Electron. Syst. 14 (2011) 251–258.
[8] M. Era, T. Kobayashi, K. Sakaguchi, E. Tsukamoto, Y. Oishi, Electric conduction
of PbBr-based layered perovskite organic–inorganic superlattice having
carbazole chromophore-linked ammonium molecule as an organic layer, Org.
Electron. 14 (2013) 1313–1317.
[9] C. Dragonetti, A. Colombo, D. Marinotto, S. Righetto, D. Roberto, A. Valore, M.
Escadeillas, V. Guerchais, H. Le Bozec, A. Boucekkine, C. Latouche,
Functionalized styryl iridium(III) complexes as active second-order NOL
chromophores and building blocks for SHG polymeric films, J. Organomet.
Chem. 751 (2014) 568–572.
[10] M. Bosch, C. Fischer, C. Cai, I. Liakatas, C. Bosshard, P. Gunter, Photochemical
stability of highly nonlinear optical bithiophene chromophores, Synth. Met.
124 (2001) 241–243.
[11] A.M. Asiri, S.A. Khan, Synthesis, characterization and optical properties of
mono- and bis-chalcone, Mater. Lett. 65 (2011) 1749–1752.
[12] M. Li, X. Zhang, Z. Shi, Y. Wan, L. Zhao, R. Jin, Y. Yu, M. Yi, Z. Cui, Synthesis of
novel two-dimensional spindle-type fluorinated nonlinear optical
chromophores, Opt. Mater. 34 (2012) 705–710.
[13] H. Xu, M. Zhang, A. Zhang, G. Deng, P. Si, H. Huang, C. Peng, M. Fu, J. Liu, L. Qiu,
Z. Zhen, S. Bo, X. Liu, Novel second-order nonlinear optical chromophores
containing multi-heteroatoms in donor moiety: design, synthesis, DFT studies
and electro-optic activities, Dyes Pigm. 102 (2014) 142–149.
[14] M.M.M. Raposo, A. Mauricio, C. Fonseca, M.C.R. Castro, M. Belsley, M.F.S. Cardoso,
L.M. Carvalho, P.J. Coelho, Synthesis and characterization of novel diazenes
bearing pyrrole, thiophene and thiazole heterocycles as efficient photochromic
and nonlinear optical (NLO) materials, Dyes Pigm. 91 (2011) 62–73.
[15] M.L. Rahman, G. Hegde, M. Azazpour, M.M. Yusoff, S. Kumar, Synthesis and
characterization of liquid crystalline azobenzene chromophores with
fluorobenzene terminal, J. Fluorine Chem. 156 (2013) 230–235.
[16] M. Ghaemy, M. Hassanzadeh, M. Taghavi, S.M.A. Nasab, Synthesis and
characterization of trifluoromethylated poly(ether–imidazole–imide)s based
on unsymmetrical diamine bearing carbazole and imidazole chromophores in
ionic liquids: Study of electrochemical properties by using nanocomposite
electrode, J. Fluorine Chem. 142 (2012) 29–40.
1
X
½ꢂq0ðzÞꢃ
T ðopenÞ ¼
1=2
m¼0 ðm þ 1Þ
ꢀ
ꢁ
z2
for q0(0) < 1 where q0ðzÞ ¼ bI0Leff = 1 þ . The values thus obtained
z02
match closely with the values of the closed aperture scan data.
The real and imaginary parts of third order nonlinear suscepti-
bility are calculated from the equations [31,32]:
ꢂ
ꢃ
e
0c2n2
cm2
W
Re vð3ÞðesuÞ ¼ 10ꢂ4
0 n2
p
ꢀ
ꢁ
e
0c2n20k cm
Im vð3ÞðesuÞ ¼ 10ꢂ2
b
4
p2
W
h
i
1=2
j
vð3Þj ¼ ðReðvð3ÞÞÞ2 þ ðImðvð3ÞÞÞ2
These are also presented in Table 3. The negative nonlinear
refraction indicates that the laser beam gets self defocused after
passing through the medium. This is particularly useful in applica-
tions like optical limiting to protect instruments/prevent damage
to the eye or tissues. The high value of nonlinearity makes these
compounds very useful materials in optical limiting applications.
[17] C. Carlini, F. Ciardelli, D. Donati, F. Gurzoni, Polymers containing side-chain
benzophenone chromophores: a new class of highly efficient polymerization
photoinitiators, Polymer 24 (1983) 599–606.
Conclusion
[18] H.M. Marwani, A.M. Asiri, S.A. Khan, Spectral, stoichiometric ratio,
physicochemical, polarity and photostability studies of newly synthesized
chalcone dye in organized media, J. Lumin. 136 (2013) 296–302.
[19] S.A. El-Daly, A.M. Asiri, A.Y. Obeid, S.A. Khan, K.A. Alamary, M.A. Hussien, A.G.
Al-Sehemi, Photophysical parameters and laser activity of 3(4-
dimethylamino-phenyl)-1-(2, 5-dimethyl-thiophen-3-yl)-propenone (DDTP):
a new potential laser dye, Opt. Laser Technol. 45 (2013) 605–612.
[20] S. Mallouk, K. Bougrin, A. Laghzizil, R. Benhida, Microwave-assisted and
efficient solvent-free knoevenagel condensation. a sustainable protocol using
porous calcium hydroxyapatite as catalyst, Molecules 15 (2010) 813–823.
[21] E. Lippert, Spectroscopic determinations of the dipole moment of aromatic
compounds in the first excited singlet state, Z. Electrochem. 61 (1957) 962–975.
[22] J.K. Dey, S.K. Dogra, Solvatochromism and prototropism in 2-(aminophenyl)
benzothiazoles, Bull. Chem. Soc. Jpn. 64 (1991) 3142–3152.
[23] W.E. Acree, D.C. Wilkins, S.A. Tucker, J.M. Griffin, J.R. Powell, Spectrochemical
investigations of preferential solvation. 2. Compatibility of thermodynamic
models versus spectrofluorometric probe methods for tautomeric solutes
dissolved in binary mixtures, J. Phys. Chem. 98 (1994) 2537–2544.
[24] S. Kumar, V.C. Rao, R.C. Rastogi, Excited-state dipole moments of some
hydroxycoumarin dyes using an efficient solvatochromic method based on the
solvent polarity parameter, ENT , Spectrochim. Acta A 57 (2001) 41–47.
[25] N.J. Turro, Molecular photochemistry (frontiers in chemistry), first ed., W.A.
Benjamin Inc, Reading, MA, 1965, p. 286.
Bis chromophores were synthesized by the terephthalaldehyde
with (4-nitrophenyl) acetonitrile/(4-flurophenyl)acetonitrile under
microwave irradiation. It is easier to perform, gives higher yields
and less time consuming. Physicochemical studies of these com-
pounds including singlet absorption, extinction coefficient, Stokes
shift, oscillator strength and dipole moment were investigated on
the basis of the polarity of solvent. The nonlinear optical measure-
ments show that these compounds offer high nonlinear refraction
and nonlinear absorption, and are well suited for device applica-
tions such as optical limiting.
Acknowledgment
This paper was funded by King Abdulaziz University, under
grant No. (D-004/431). The authors, therefore, acknowledge tech-
nical and financial support of KAU.
[26] B.J. Coe, J.A. Harris, I. Asselberghs, K. Clays, G. Olbrechts, A. Persoons, J.T. Hupp,
R.C. Johnson, S.J. Coles, M.B. Hursthouse, K. Nakatani, Quadratic nonlinear optical
properties of N-aryl stilbazolium dyes, Adv. Funct. Mater. 12 (2002) 110–116.
[27] M. Ravi, A. Samanta, T.P. Radhakrishnan, Excited state dipole moments from an
efficient analysis of solvatochromic stokes shift data, J. Phys. Chem. 98 (1994)
9133–9136.
References
[1] G.V.D. Tiers, C.V. Francis, Materials science of organic compounds Part 2.
thermal
studies
of
acentric
(second-harmonic-generative)
and
[28] M. Ravi, T. Soujanya, A. Samanta, T.P. Radhakrishnan, Excited-state dipole
moments of some coumarin dyes from a solvatochromic method using the
solventpolarity parameter, ENT , J. Chem. Soc. Faraday Trans. 91 (1995) 2739–2742.
[29] M. Sheik-Bahae, A.A. Said, T. Wei, D.T. Hagan, E.W. Van Stryland, Sensitive
measurement of optical nonlinearities using a single beam, IEEE J. Quant.
Electron. 26 (1990) 760–769.
[30] X. Liu, S. Guo, H. Wang, L. Hou, Theoretical study on the closed-aperture z-scan
curves in the materials with nonlinear refraction and strong nonlinear
absorption, Opt. Commun. 197 (2001) 431–437.
centrosymmetric crystals of achiral straight-chain para-nitrophenylcarbanyl
compounds, Thermochim. Acta 226 (1993) 311–316.
[2] X. Liu, Z. Guo, N.F. Roache, Experimental method development for estimating
solid-phase diffusion coefficients and material/air partition coefficients of
SVOCs, Atmos. Environ. 89 (2014) 76–84.
[3] S. Huang, J. Xiong, Y. Zhang, A rapid and accurate method, ventilated chamber
C-history method, of measuring the emission characteristic parameters of
formaldehyde/VOCs in building materials, J. Hazard. Mater. 261 (2013) 542–
549.
[31] C. Gayathri, A. Ramalingam, Z-scan determination of the third order optical
nonlinearities of an azo dye using diode pumped Nd:YAG laser, Optik 119
(2008) 409–414.
[32] S. Shettigar, G. Umesh, P. Poornesh, K.B. Manjunatha, A.M. Asiri, The third
order nonlinear optical properties of novel styryl dyes, Dyes Pigm. 83 (2009)
207–210.
[4] P. Lind, C. Lopes, K. Öberg, B. Eliasson, A QSPR study on optical limiting of
organic compounds, Chem. Phys. Lett. 387 (2004) 238–242.
[5] D. Bharath, S. Kalainathan, Optical studies on picoseconds response of optical
switching 2-{3-[2-(3-methyl-4-methoxyphenyl)vinyl]-5,5-dimethylcyclo-hex-
2-en-1-ylidene}malononitrile organic NLO material, Spectrochim. Acta, Part A
118 (2014) 1098–1105.