Synthesis, photophysical and DFT studies of naphthyl chalcone and nicotinonitrile derivatives

Article abstract of DOI:10.1016/j.jphotochem.2019.112222

Chalcone and cyanopyridine derivatives have emerged as attractive light sensitive materials, with potential use in cell probing and optoelectronic applications. They are highly fluorescent both in solution and solid state and thus well-suited for OLED applications. Herein, we report the synthesis of a chalcone derivative (CP1) using the Claisen Schmidt condensation of 2-acetyl thiophene and 2-methoxy naphthaldehyde followed by the heterocyclization to yield the novel cyanopyridine derivative (NP1). Synthesized molecules were characterized using elemental analysis, FTIR and NMR spectra. Density functional theory (DFT) calculations were performed on the molecules, in order to understand their absorption and emission properties. The orbital picture of all the excitations involved in these transitions were identified as π- > π*. The, experimentally obtained FTIR spectra were in excellent agreement with DFT calculated infrared spectrum. The steady state fluorescence spectra of CP1 showed dual emission in the blue and green regions while a single band, orange emission was observed for the other molecule NC1. NC1 showed the solid-state emission in orange region inferring its suitability for the OLED application.

Full text of DOI:10.1016/j.jphotochem.2019.112222

Journal Pre-proof
Synthesis, photophysical and DFT studies of naphthyl chalcone and
nicotinonitrile derivatives
Hemant Hegde, Rajeev K. Sinha, Suresh D. Kulkarni, Nitinkumar S.
Shetty
PII:
S1010-6030(19)31333-4
DOI:
https://doi.org/10.1016/j.jphotochem.2019.112222
JPC 112222
Reference:
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5 November 2019
Please cite this article as: Hegde H, Sinha RK, Kulkarni SD, Shetty NS, Synthesis,
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Synthesis, photophysical and DFT studies of naphthyl chalcone and
nicotinonitrile derivatives
Hemant Hegdea, Rajeev K. Sinhab, Suresh D. Kulkarnib and Nitinkumar S. Shettya*
a Department of Chemistry, Manipal Institute of Technology, Manipal Academy of Higher Education,
Manipal, Karnataka, India-576104.
b Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal,
Karnataka, India-576104.
*nitin.shetty@manipal.edu
Graphical abstract

Highlights:
 Synthesis & characterization of naphthyl chalcone and cyanopyridine are reported
 Absorption & emission properties calculated by density functional theory
 Orbital picture of all excitations were identified as π->π*
 Cyanopyridine emits blue & green while naphthyl chalcone showed orange emission
 Naphthyl chalcone showed orange emission in solid-state & well-suited for OLEDs
Abstract:
Chalcone and cyanopyridine derivatives have emerged as attractive light sensitive materials, with
potential use in cell probing and optoelectronic applications. They are highly fluorescent both in
solution and solid state and thus well-suited for OLED applications. Herein, we report the synthesis of a
chalcone derivative (CP1) using the Claisen Schmidt condensation of 2-acetyl thiophene and 2-
methoxy naphthaldehyde followed by the heterocyclization to yield the novel cyanopyridine derivative
(NP1). Synthesized molecules were characterized using elemental analysis, FTIR and NMR spectra.
Density functional theory (DFT) calculations were performed on the molecules, in order to understand
their absorption and emission properties. The orbital picture of all the excitations involved in these
transitions were identified as π->π*. The, experimentally obtained FTIR spectra were in excellent
agreement with DFT calculated infrared spectrum. The steady state fluorescence spectra of CP1
showed dual emission in the blue and green regions while a single band, orange emission was observed
for the other molecule NC1. NC1 showed the solid-state emission in orange region inferring its
suitability for the OLED application.
Keywords: Chalcone, cyanopyridine, DFT, fluorescence.

1. Introduction
Besides being suitable for promising biological activities such as anticancer, antimicrobial,
antidepressant, immunosuppressive, anti-inflammatory, etc. [1-7], chalcone and its derivatives have
displayed numerous other properties like optical [8], photochemical [9, 10] and NLO properties, and
have been used as fluorescent dyes, in light emitting diodes, fluorescent sensors and as fluorescent
probes [11].
As a member of the π-conjugated system, the optical properties of chalcone and its derivatives, have
received considerable attention owing to its nonlinear optical and fluorescence property, due to the
delocalization of electronic charge and overlapping π orbitals. Furthermore, as a family of traditional
luminogenic materials, chalcone and its derivatives often possess strong emissions in the solution state,
but their luminescence gets quenched at high-concentrations or/and solid states [12, 13]. However, their
optical properties are easily controlled by introducing electron donor or acceptor groups to aromatic
rings. Fluorescence of chalcones have been utilized for many applications such as cell probe in a mouse
embryonic stem cell [14]. Therefore, the fluorescent study of chalcones has been area of interest in
photochemistry.
In view of the considerable importance and adjustable structure of chalcone and its derivatives,
designing and synthesizing a chalcone that can emit strong fluorescence in solid state is possible. On
the other hand, heterocyclisation of chalcone derivative has produced worthwhile compounds with
widespread applications. Therefore, several reports are available for the synthesis of nicotinonitrile
(cyanopyridines) via chalcones, which produces highly substituted cyanopyridine derivatives [15-21].
Owing to the recent development in the field of organic based optoelectronic materials, study of
photophysical properties of diverse organic frameworks has become a major interest in the field of
organic chemistry [22, 23].
Cyanopyridines were first reported for their optoelectronic properties by Ahipa et al. [24]. The
fluorescence spectra of cyanopyridine derivatives were studied both in solution and in liquid crystalline
film state. The compounds were found to exhibit good quantum yields (ϕf = 28–49 %) in the solution
state and satisfactory quantum yields (ϕf = 10–22 %) in the film state also. These results support the
optoelectronic properties of 2-(4, 6-disubstituted aryl-3-cyanopyridyl) oxy acetohydrazones and also, as
an active photo-responsive and electron-transporting material for device applications.

Later, Ershov et al. [25] reported 5- or/and 6- aryl substituted cyanopyridine derivative found to
possess a solid-state emission with various intensities. The fluorescent maxima of the studied
cyanopyridine was found to be in blue region of the spectrum (410-535 nm). Therefore, the
cyanopyridine derivatives reported to show high fluorescence intensity which is a basic need of modern
light sensitive materials [26]. In agreement with the reported data, the target molecules are designed to
possess significant optoelectronic behavior in the solution phase as well as in solid state. This would
help in the development of new cyanopyridine derivatives for OLED applications.
Being inspired by the photochemical applications of chalcones and pyridine derivatives, in the present
work, we are reporting the synthesis of chalcone derivatives from naphthaldehyde and new
nicotinonitrile derivative from there on. The synthesis is followed by (i) structural characterization
using Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared (FTIR) spectroscopy and
Density Functional Theory (DFT) calculations and (ii) investigation of emissive property using
Fluorescence spectroscopy.
2. Material and methods:
2.1 Synthesis of molecular systems
Required chemicals were procured commercially and were used as such without further purification.
Thin layer chromatographic technique (TLC) was used to monitor progress of the reaction. Pre-coated
aluminum sheets (alichrosep) silica gel-60/UV254 was used as stationary phase with I2 and UV light as
visualizing agents. Melting point was checked using Thiele’s tube in open capillary tube and was
uncorrected. IR spectra were taken on Shimadzu Infrared spectrometer-8400s using KBr as background
1
in pellet form. H and 13C NMR spectra were recorded on Bruker NMR-400 MHz and 100 MHz
respectively using TMS as an internal standard. Elemental analysis was performed by using Perkin
Elmer 2400 CHN elemental analyzer.

Scheme 1: Synthesis of 2-methoxy-4-(2-methoxynaphthalen-1-yl)-6-(thiophen-2-yl) nicotinonitrile, 5.
Synthesis of chalcone derivatives (NC1), 3:
Chalcone derivative of 2-methoxy-1-naphthaldehyde and 2-acetyl thiophene was prepared as earlier
reported procedure [27]. The method begins with the generation of enolate ion, by dissolving 2-acetyl
thiophene (2.52 g, 20 mmol) in minimum quantity of sodium hydroxide solutions (30 %). To the above
solution, 2-methoxy-1-naphthaldehyde (3.72 g, 20 mmol) dissolved in ethanol (2 mL) was added and
the reaction mixture was stirred at room temperature to obtain a homogeneous mixture. Stirring was
continued at room temperature for 16-18 h. On completion of the reaction (checked by thin layer
chromatography), reaction mixture was then poured into the beaker containing crushed ice and
neutralized using dil. HCl. Precipitate formed was then filtered and washed with distilled water.
3-(2-methoxynaphthalen-1-yl)-1-(thiophen-2-yl)prop-2-en-1-one (NC1), 3:
Greenish yellow amorphous solid; yield, 5.42 g (92.4 %); m.p.: 122-124 °C; IR spectrum (Fig. S1 in
1
ESI) (γ-max, cm-1): 3080 (Ar-H), 2933 (C-H), 1631 (C=O), 1593(C=C), 1575; H NMR (Fig. S2 in
ESI) (400 MHz, DMSO-d6) δ: 8.14-8.15(d, 1H, ), 8.07-8.09 (d, 1H, J= 8 Hz, thiophene-H), 8.19-8.21(d,
1H, J= 8 Hz, thiophene-H), 7.91-7.96 (m, 4H, Ar-H), 7.87, 7.61-7.63 (d, 1H, J= 8 Hz, Ar-H), 7.56-7.59,
13
7.43-7.46 (dd, J= 4 Hz, 2 Hz) 7.30-7.32 (d, 1H, J= 8 Hz, Ar-H), 4.07 (s, 3H, OCH3) ppm; C NMR
(Fig. S3 in ESI) (100 MHz, DMSO-d6) δ: 56.2, 113.8, 118.9, 123.9, 124.0, 127.1, 128.6, 128.68, 129.0,

130.2, 131.7, 133.3, 135.2, 135.4, 145.2, 153.8, 184.0 ppm; Elemental analysis: calctd. for C18H14O2S;
C, 73.44; H, 4.79. Found: C, 73.48; H, 4.83.
Synthesis of cyanopyridine derivatives (CP1), 5:
Compound 3 (2.94 g, 10 mmol) was dissolved in 5 mL of methanol and 2.5 mL of sodium methoxide
(0.54 g, 10 mmol) solution in methanol was added with constant stirring and the reaction mixture was
stirred for 8-9 h at room temperature. The precipitate was filtered and washed with methanol and dried
to afford Creamy yellow colored product. The crude product was recrystallised using ethyl acetate.
2-methoxy-4-(2-methoxynaphthalen-1-yl)-6-(thiophen-2-yl)nicotinonitrile (CP1), 5:
Creamy yellow crystalline solid; yield, 3.25 g (87.5 %); m. p.: 234-235 °C; IR spectrum (Fig. S4 in
ESI) (γ-max, cm-1): 3090 (Ar-H), 2945 (C-H), 2220 (CN), 1624 (C=N), 1610 (C=C); 1H NMR (Fig. S5
in ESI) (400MHz, DMSO-d6) δ: 8.16-8.18 (d, 1H, J= 8 Hz, thiophene-H), 7.84-8.04 (m, 5H, Ar-H),
7.65-7.67 (d, 1H, J= 8 Hz, Ar-H), 7.46-7.49 (dd, 2H, J= 4 Hz, Ar-H), 7.42-7.44 (d, 1H, J= 8 Hz, Ar-H)
13
7.20-7.22 (d, 1H, J= 8 Hz, Ar-H), 4.1 (s, 3H, OCH3), 3.91(s, 3H, OCH3) ppm; C NMR (Fig. S6 in
ESI) (100 MHz, DMSO-d6) δ: 54.9, 56.9, 95.4, 114.1, 114.7, 115.3, 118.5, 123.9, 124.4, 128.1, 128.3,
128.8, 129.1, 129.5, 131.5, 131.9, 143.0, 153.4, 153.6, 154.0, 164.3 ppm; Elemental analysis: calctd.
for C22H16N2O2S; C, 70.95; H, 4.33; N, 7.52. Found: C, 70.91; H, 4.36; N, 7.57.
2.2 FTIR and fluorescence spectral analysis
FTIR spectral studies were done for the functional group identification of the titled compounds.
Samples were prepared by mixing 1:10 synthetic compound and KBr. The mixture was ground to fine
powder and pressed to pellets using hydraulic press. Fluorescence spectra were recorded at room
temperature using Jasco FP8300 Fluorescence spectrophotometer with 450 W xenon lamp. The
compounds were dissolved in acetonitrile to make 0.1 mM, 0.2 mM, 1.0 mM and 10.0 mM solutions.
2.3 Density Functional Theory (DFT) calculations
Density functional theory (DFT) calculations were performed on the molecules of interest in the ground
state using Becke-3-Lee-Yang-Parr (B3LYP) theory and Gaussian type basis set 6-311++G(d,p). For
the excited state calculations, time dependent (TD) B3LYP method was used. The Ground state
geometry optimization was followed by harmonic frequency calculation to ensure the structure to be in

global minimum of the potential energy surface. The UV-Visible spectrum was calculated utilizing
vertical excitation from the ground state optimized geometry. The emission spectrum was calculated as
adiabatic energy difference between the first excited state and the ground state. All calculations were
performed with GAMESS (US) program package [28].
3. Results and discussion
In this work, targeted molecule 5 was synthesized by the reaction between 3-(2-methoxynaphthalen-1-
yl)-1-(thiophen-2-yl)prop-2-en-1-one (NC1), 3 and malononitrile in the presence of sodium methoxide
as base catalyst [19, 20]. Chalcone was synthesized as precursor molecules by using conventional
Claisen Schmidt condensation using 2-methoxy-1-naphthaldehyde and 2-acetyl thiophene in presence
of NaOH at room temperature [27].
IR and NMR spectroscopic analysis confirmed the chemical structure of desired products. FTIR
spectrum of compound 3 showed characteristic peaks for C=O and C=C of chalcone at around 1631
cm-1 and 1593 cm-1 respectively. We can observe the absence of these peaks in the cyanopyridine (CP1)
5, which clearly shows the cyclisation of chalcone to form the corresponding cyanopyridine derivative.
The FTIR spectrum of the compound 5 also showed a peak at 2220 cm-1 corresponding to -CN group of
pyridine which is also evident from 13C NMR spectrum as it showed characteristic signal at δ 95.4 ppm.
3.1 Structural study (FTIR and DFT):
Figure 1(a) and (b) shows the structure of molecules NC1 and CP1 respectively in the ground electronic
state, calculated with B3LYP/6-311++G(d,p) level of theory. As it can be seen in the Figure 1(a), in the
molecule NC1, the naphthalene and thiophene rings are nearly coplanar. The thiophene ring is bent
relative to the naphthalene ring by ~16.9 degrees. In the molecule CP1, shown in Figure 1(b), the
pyridine and thiophene aromatic rings are coplanar whereas the plane of pyridine and thiophene rings is
bent relative to the naphthalene ring by 109.4 degrees. The xyz coordinates of the optimized structure
of NC1 and CP1 molecules are provided in the supplementary Table S1 and S2.

(a) NC1
(b) CP1
Figure 1: Ground state optimized structure of molecules NC1 and CP1 calculated with B3LYP/6-
311++G(d,p) level of theory.
FTIR spectrum of molecules NC1 and CP1 are shown in Figure 2(a) and (c) respectively. The spectral
position of bands observed in the FTIR spectrum for NC1 and CP1 are shown in supplementary Figure
S1 and S4 respectively. The calculated structures of the both NC1 and CP1 are ascertained with the
calculated harmonic infrared frequencies shown in Figure 2(b) and (d) respectively. The calculated
infrared spectra are scaled with a factor of 0.956. As it is evident from the Figure 2, the calculated
spectra are in excellent agreement with the FTIR spectra of two molecules both in terms of position and
intensity.

Figure 2: (a) FTIR spectrum of NC1 (b) calculated infrared spectrum of NC1 (c) FTIR spectrum of
CP1 and (d) Calculated infrared spectrum of CP1. The calculated spectra were obtained with B3LYP/6-
311++G(d,p) theory level. The calculated harmonic frequencies are scaled with a factor of 0.956.
3.2 Fluorescence spectroscopic study

Fig. 3: Fluorescence excitation emission matrix of 0.1 mM NC1.
3000
0.1 mM
0.2 mM
1.0mM
2500
10.0mM
2000
1500
1000
500
0
500
600
700
800
900
Wavelength (nm)
Fig. 4: Fluorescence spectra of NC1 at different concentrations (Excitation wavelength-470 nm)
537em
1000
800
600
400
200
0
150
200
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 5: Excitation spectra of NC1 (emission wavelength-537 nm)
The excitation and emission matrix for NC1 (Fig. 3) showed predominantly one emission centered
around 537 nm. The fluorescence spectra of NC1 (Fig. 4) showed an emission band which is slightly
asymmetric. The corresponding excitation spectrum is shown in Fig. 5. The intensity was maximum for
0.2 mM concentration and gradually the FWHM of the peak reduced with intensity. The shoulder,
poorly visible at lower concentrations was clearly distinguishable at 494 nm at higher (10.0 mM)
concentration.

(A)
(B)
Fig. 6: A) Excitation-emission matrix
B) CIE coordinates of NC1 in the Solid-state
The solid-state emission of NC1 is shown in Fig. 6a. The excitation emission matrix shows that the
emission of NC1 is centered around ~570 nm which has excitation band situated at ~500 nm. The
corresponding CIE (Commission Internationale de l'Elcairage) colour coordinates (Fig. 6b) shows that
the materials emit strongly in the orange region. The solid-state emission can be useful in solid-state
lighting applications as the material can be easily excited with visible light.
(A)
(B)
Fig. 7: A) Fluorescence excitation emission matrix B) CIE coordinates of 0.1 mM CP1

1000
800
600
400
200
0
0.1 mM
0.2 mM
1.0mM
10.0mM
400
500
600
700
800
900
Wavelength (nm)
Fig. 8: Fluorescence spectra of CP1 at different concentrations (Excitation wavelength-370 nm)
1000
800
600
400
200
0
200
250
300
350
400
450
Wavelength (nm)
Fig. 9: Excitation spectra of CP1 0.1mM (Emission wavelength-460 nm)
The excitation emission matrix of CP1 (Fig. 7a) shows the presence of two excitation bands for the
same emission. The corresponding CIE colour coordinates (Fig. 7b) show that the material exhibits
strong blue emission under UV excitation. The fluorescence spectra of CP1 (Fig. 8) showed that the
main emission band is centered around 460 nm while the other emission band is a weak shoulder

around 530 nm. Increase in concentration of CP1 led to decreased fluorescence intensity due to
concentration quenching [29]. The excitation spectra (Fig. 9) revealed that the excitation band in the
230 nm - 340 nm was intense only for 0.1 mM and gradually vanished with increasing CP1
concentration. However, the excitation band at 370 nm was observed for all concentrations though their
intensity reduced at higher CP1 concentration.
3.3 Excited state calculations
In order to understand the absorption and emission properties of synthesized molecules NC1 and CP1,
excited state density functional theory calculations were performed using time-dependent (TD) B3LYP
method. Figure 10 (a) and (b) shows the structure of NC1 and CP1 respectively, in their lowest excited
electronic state. The optimized xyz coordinates of two molecules are given in the supplementary Table
S3 and S4. Remarkable structural change is observed for NC1 compared to its ground state structure
(shown in Figure 1(a)). As it has been discussed earlier, in the ground state, the naphthalene and
thiophene ring in the molecule NC1 are nearly planar which changes dramatically in the first excited
state. The plane of thiophene ring has changed its orientation and is nearly perpendicular to the
naphthalene ring. The angle between two ring planes are 113.96 degrees compared to 16.9 degrees in
the ground state. Structural changes were also observed in the molecule CP1. In this molecule, the
angle between naphthalene ring and pyridine ring is 96.6 degree compared to 109.4 degree in the
ground state. The pyridine and thiophene rings are coplanar as it was observed in the ground state.
(a)
(b)
Figure 10: First electronic excited state structure of (a) NC1 and (b) CP1 obtained using TD-
B3LYP/6-311++G(d,p) level of theory.
The origin of this change in structure can be understood from the HOMOLUMO transitions for first
excited states of molecules under consideration. Figure 11(a)-(d) shows HOMO and LUMO for NC1

and CP1 molecules. As it is evident form Figure 11(a) and (b), in case of NC1, HOMO is a π orbital
where electron density is localized on C=C bonds of naphthalene and linear chain. Excitation of an
electron from HOMO(π) to LUMO(π*) changes the electron density to C-C bonds of linear chain. Such
a strong shift of electron density can possibly change the intra-molecular interactions such as
hyperconjugation and steric interactions leading to twist of the C=C bond to make the molecule non-
planar in its first excited state. The molecule CP1 has more rigid frame compared to NC1, with pyridine
ring directly connected to the naphthalene ring. In this molecule also, HOMO(π) shows the
accumulation of electron density on C=C bands of naphthalene whereas LUMO(π*) shows the electron
density on pyridine and thiophene rings. Although this also represents strong migration of electron
density in HOMOLUMO transition for the first excited state, the rigid molecular frame prevent the
very large modulation in the structure, as it is seen in the case of NC1.
(a) NC1: HOMO
(b) NC1: LUMO
(c) CP1: HOMO
(d) CP1: LUMO
Figure 11: HOMO and LUMO orbitals for molecules NC1 and CP1.
To obtain the UV-Vis absorption spectrum through DFT calculations, six lowest singlet excited states
were calculated by using the vertical excitation from the ground state optimized geometry as shown in
Figure 1(a) and (b). Various orbital interactions involved excited state 1 to excited state 6 for NC1 and
CP1 are listed in supplementary Table S5 and S6. The corresponding orbitals are shown in
supplementary Figure S7 and S8. The calculated UV-Vis spectrum of NC1 is shown in Figure 12. As it
can be seen, for NC1, the first excited state is due to HOMOLUMO transition, and it is the most
prominent ππ* transition with oscillator strength 0.4253. The corresponding vertical absorption is at
402.56 nm. The second excited state has fifty times lower oscillator strength (0.0086) and corresponds
to nπ* transition between HOMO-3LUMO. The vertical absorption for excited state 3 to 6 in the

spectral region 295-325 nm are due to ππ* transitions with moderate oscillator strength of 0.0615 –
0.0963.
Figure 12: UV-Vis absorption spectrum of NC1. Six lowest singlet excited states are shown as stick
and convolution.
The experimentally obtained UV-Vis spectrum of NC1 in DMSO is shown in Figure 13. As it is seen in
the Figure 13, three prominent peaks appeared at 272, 324 and 356 nm. The band at 356 nm could be
due to the first excited state. It is however lower by 52 nm relative to the calculated vertical excitation
wavelength. It has to be noted that the calculations were made in gas phase. Moreover the structure of
NC1 in first excited state obtained adiabatically shows a strong twisting of C-C bond. The observed
shift in the first excited state could be due to structural modulation in the process of excitation.

Figure 13: UV-Vis spectrum of NC1 obtained with 0.2mM concentration in DMSO. Strong absorption
in 200-230 nm spectral range could be due to the solvent.
In usual condition, the adiabatically calculated energy for singlet excited state closely corresponds to
the emission energy. The plot of adiabatic energy for the molecule NC1 in the first excited state is
shown in Figure 14. This first excited state shows transition centered at 517.1 nm. The observed band
in the fluorescence spectrum at 537 nm resembles very closely this calculated energy and thus the
observed fluorescence spectrum is due to ππ* transition between first excited state and ground state.
The observed asymmetry in the fluorescence bands could be due to the emission from higher excited
state.
Figure 14: Emission spectrum of NC1 obtained from excitation of lowest excited state.
The calculated UV-Vis spectrum of CP1 is shown in Figure 15. In this molecule, the first excited state
is HOMOLUMO characterized as ππ* at 399.4 nm with oscillator strength 0.0449. The second
excited state is the most prominent feature at 336.8 nm in the calculated spectrum which is another
ππ* transition between HOMO-1LUMO with oscillator strength 0.5641. Excited state 3-6 are also
ππ* with lower oscillator strength appears between 289-313 nm.
Experimental UV-Vis absorption spectrum of CP1 (0.1mM in DMSO) is shown in the Figure 16. The
spectrum shows strong and broad absorption peak at 277 and 348 nm. The band at 348 nm possibly
corresponding to the calculated second excited state and is of ππ* characteristic. The less prominent
band at 277 nm could be corresponding to calculated excited state 3-6.

Figure 15: UV-Vis absorption spectrum of CP1. Six lowest singlet excited states are shown as stick
and convolution.
Figure 16: Emission spectrum of CP1 obtained from excitation of lowest excited state.
Figure 17 shows the adiabatic energy for the first excited state of CP1. In the adiabatic calculation of
first excited state, the emission from the first excited state (π π*) was found to be located at 501.08
nm showing the Stoke shift of ~113 nm. In the fluorescence spectrum a band at 530 nm is observed
which possibly is due to emission from the first excited state and is of π π* nature. The 460 nm band
observed in the fluorescence spectrum could be due to the emission from second excited state. The
higher intensity of band at 460 nm is possibly due to higher absorption to second excited state as shown
in Figure 15.

Figure 17: Emission spectrum of CP1 obtained from excitation of lowest excited state.
4. Conclusion:
The Claisen Schmidt condensation between acetyl thiophene and 2-methoxy-1-naphthaldehyde under
basic condition followed by the heterocyclization can be used for the synthesis of targeted
cyanopyridine derivatives in good yield. Resulted α, β-unsaturated ketone was heterocyclised to form
cyanopyridines using malononitrile in the presence of sodium methoxide as a catalyst. Structures of the
1
13
resulted compounds were established using FTIR, H NMR and C NMR studies. The photochemical
behavior of the target molecules was investigated and have shown few interesting results. The chalcone
(NC1) showed one major emission around 537 nm whereas the cyanopyridine derivative (CP1) has
shown two emission bands at 460 and 530 nm in solution phase. The solid-state emission of chalcone
derivative is observed in orange region which makes it suitable for the OLED application. The DFT
calculation of cyanopyridine for the excited state revealed the change in the angle between naphthalene
and pyridine plane which can ascertained for the HOMO to LUMO excitation. This property would
make these molecules considerable for the optical materials.
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