Theoretical investigation on the crystal structure, spectral and optical properties of a novel organic optical material: (Acetoxy) (2-methylphenyl) methylacetate

Article abstract of DOI:10.1016/j.molstruc.2020.128579

An organic material (Acetoxy)(2-methylphenyl) methyl acetate (AMPMA) was synthesized at temperature and its chemical structure was analyzed by vibrational spectroscopic studies (FT-IR/FT-Raman) and NMR spectroscopy. HF and DFT/B3LYP theoretical methods were employed on AMPMA to investigate its molecular geometry, vibrational and bonding nature. The time-dependent HOMO-LUMO energy was found to be 6.0260 eV. The optical properties of the material were discussed through dipole moment and optical polarization. In this contest, the estimation of molecular dipole moment (μ) and linear polarizability (α) were studied by MP2, DFT and HF methods with different basis sets.

Full text of DOI:10.1016/j.molstruc.2020.128579

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Theoretical investigation on the crystal structure, spectral and optical properties of a
novel organic optical material: (Acetoxy) (2-methylphenyl) methylacetate
N. Sivakumar, J. Kanchanadevi, M. Govindarajan, R. Jayavel, G. Anbalagan
PII:
S0022-2860(20)30904-2
DOI:
https://doi.org/10.1016/j.molstruc.2020.128579
MOLSTR 128579
Reference:
To appear in: Journal of Molecular Structure
Received Date: 6 February 2020
Revised Date: 11 May 2020
Accepted Date: 31 May 2020
Please cite this article as: N. Sivakumar, J. Kanchanadevi, M. Govindarajan, R. Jayavel, G. Anbalagan,
Theoretical investigation on the crystal structure, spectral and optical properties of a novel organic
optical material: (Acetoxy) (2-methylphenyl) methylacetate, Journal of Molecular Structure (2020), doi:
https://doi.org/10.1016/j.molstruc.2020.128579.
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From
Dr.N. Sivakumar,
UGC-Postdoctoral Fellow,
Crystal Growth Centre,
Anna University, Chennai-25
nsivakumar1986@gmail.com
To
The Editor
Journal of Molecular Structure,
Elsevier Publishing Company.
Respected Sir,
Sub: Research article Credit statement–reg.
I hereby stating that the article entitled “Theoretical investigation on the crystal structure,
spectral and optical properties of a novel organic optical material: (Acetoxy) (2-methylphenyl)
methylacetate” submitted for the publication in Journal of Molecular Structure is the original,
and has been written by the stated authors who are all aware of its content and approve its
submission.
The credits to the authours in the present research work is as follows,
N. Sivakumar : Characterization and Investigation
J. Kanchanadevi : Synthesis and solved the structure
M. Govindarajan : Vibrational analysis
G. Anbalagan : Validation of the research work
R. Jayavel: Review and editing.
Thanking You,
Yours Sincerely,
Dr. N. Sivakumar

1
Theoretical investigation on the crystal structure, spectral and optical properties of a novel
organic optical material: (Acetoxy) (2-methylphenyl) methylacetate
a,b*
c
d
a
e,**
N. Sivakumar , J. Kanchanadevi , M. Govindarajan , R. Jayavel , G. Anbalagan
a
Crystal Growth Centre, Anna University, Chennai-600 025, India.
b
Department of Physics, Saveetha Schoolo of Engineering, Saveetha University, Chennai-602
1
05
b
Department of Physics, Presidency College, Chennai-600 005
c
Bharathidasan Government College for Women, Puducherry-605 003, India.
d
Department of Nuclear Physics, University of Madras, Chennai-600 005, India.
Corresponding Authors : *Dr. N. Sivakumar (E-mail: nsivakumar1986@gmail.com) and
*
*Dr. G. Anbalagn (E-mail: anbu24663@yahoo.co.in)
Abstract
An organic material (Acetoxy)(2-methylphenyl) methyl acetate (AMPMA) was
synthesized at temperature and its chemical structure was analyzed by vibrational spectroscopic
studies (FT-IR/FT-Raman) and NMR spectroscopy. HF and DFT/B3LYP theoretical methods
were employed on AMPMA to investigate its molecular geometry, vibrational and bonding
nature. The time-dependent HOMO-LUMO energy was found to be 6.0260 eV. The optical
properties of the material were discussed through dipole moment and optical polarization. In this
contest, the estimation of molecular dipole moment (µ) and linear polarizability (α) were studied
by MP2, DFT and HF methods with different basis sets.
Keywords: Optical properties; Crystal structure; Molecular Geometry; Vibrational analysis;
Energy gap.

2
1
. Introduction
In recent ages, the synthesis of acylals has been of great research because of its wide
variety of applications. The protecting groups are very much important in the synthesis of
organic materials and are being a key factor in the development of many synthetic materials [1].
The 1,1‐Diacetates are useful materials in asymmetric allylic alkylation, synthesis of natural
products, and synthesis of 1‐acetoxy dienes and 2,2‐dichlorovinyl acetates in Diels‐Alder
reactions [2, 3]. The acylal functions could be altered to other groups with appropriate
nucleophiles [4, 5] and 1,1‐diacetates are the cross‐linking agents for the cellulose in cotton and
as bleaching initiators in wine‐stained fabrics [6, 7]. (Acetoxy)(2-methylphenyl) methyl acetate
(AMPMA) is an acylal-organic material. Acrylals are 1,1diacetates which has a general structure
R-C(OOCR) , (where R represents an aromatic or aliphatic compound). The crystal structure of
2
the title compound was reported and in which acetoxy groups are oriented with the benzene ring
with an angle of 62.71 (6)° and 57.92 (5)° [8]. Centrosymmetric dimer has been developed via an
R22(16) ring motif by the intermolecular C—H…O interaction with two acetoxy groups. Shirin
and Khaligh conducted the acetylation of various alcohols, thiols, phenols, aldehydes and amines
with acetic anhydride under solvent-free conditions in the presence of a catalyst-succinimide-N-
sulfonic acid [9]. Most of the researchers concentrated only on the synthesis methods of acylals
using different catalysts [1-10].
Organic crystal, (Acetoxy) (2-methylphenyl) methylacetate is a newly syntheisized
material through the solvent evaporation method. In this material, there is a high degree of
electron delocalization in the benzene rings which are optically sensitive and show a fast optical
response. Therefore such kinds of organic materials are highly polarizable and show an excellent
nonlinearity. In the present research work, the very first time we are reporting the

3
physiochemical properties of the (Acetoxy) (2-methylphenyl) methylacetate material through the
chemical computational techniques to understand the details of various spectroscopic vibrations,
electronic properties like HOMO-LUMO energies, electrostatic potential, thermodynamic and
optical activities. Thus the properties explain the novelty or the originality of the titled material
in the forthcoming sections.
2
. Experimental
The precursor material, 2-methylbenzaldehyde and anhydrous indium bromide were taken
in the 1:1 molar ratio. Initially, 2-methylbenzaldehyde was completely dissolved in 25 ml of
acetic anhydride and indium bromide was gently added to the solution at room temperature.
The obtained mixture was stirred under a nitrogen atmosphere for 4 hours to get a homogenous
mixture. The product was washed well with the water and recrystallization processes were done
with methanol solvent to get a pure final product with a yield of 82%.
3
. Characterization
A Bruker kappa APEX II crystal X-ray diffractometer was used to collect the single
3
crystal data of AMPMA crystal. A defect-free single crystal (0.30 ×0.20 × 0.20 mm ) was
selected and X-ray diffraction data were recorded at 293 K on a three-circle X-ray diffractometer
fitted with Mo-Kα radiation of wavelength λ = 0.71073 Å. The ω: 2θ scan method was utilized to
obtained reflections. The data were rectified for absorption and polarization effects with an
empirical correction. The crystal structure of AMPMA was solved by SHELXL-97 method and
deposited at the Cambridge Crystallographic Data Centre (CCDC No. 841279). The data was
well-refined with full matrix (SHELXL-97) least square process by retaining 1856 reflections
2
which satisfy the condition, I >2σ(I). The results of consecutive refinements on F reveals the

4
low-reliability factor, R = 0.041 which reveals that the structure is more stable. The title crystal
belongs to the Monoclinic system with the centrosymmetric space group of C2/c. The unit cell
values were found to be a = 15.757(5)Å, b = 7.564(5)Å, c = 19.886(5)Å, β = 99.15(5)Å and
3
V = 2339.8(18) Å .
Powder X-ray diffraction study was carried out on the titled crystal using XPERT-PRO
equipment with Cu-Kα radiation of wavelength, 1.5406 Å. The XRD data were recorded in the
Bragg angle (2θ) range from 5 to 50⁰ with a step size of 0.02/sec. The IR spectrum was obtained
-1
in the wavenumber region (4000- 400 cm ) with the help of the Perkin Elmer spectrum one FT-
-1
IR spectrometer (of resolution 0.5 cm ) using KBr pellet method. Raman spectral analysis was
-1
done in the range 3500-50 cm with 500 scans using FT-Raman Bruker RFS 27:S Raman
-1
module (of resolution 2 cm ). Nd: YAG laser (1064 nm) with o/p power of 100 mW (air-cooled
diode pumped) was used in the Raman spectral equipment. Both IR and Raman identifies the
various chemical groups existing in the material. Further, the molecular structure was confirmed
by NMR spectra recorded at 22°C using Bruker Advance III 500 MHz spectrometer with CDCl
3
as a solvent.
3
.1. Quantum chemical calculations
Quantum chemical computations were performed at DFT (B3LYP) and ab-initio HF
methods with Gaussian 09 program [11]. The vibrational frequencies at the various theoretical
level and different basis sets with Cs point symmetry were calculated. In the optimized
geometry, all the modes are real frequency modes and thus a minimum potential energy surface
has been established on the molecule.
As a result, reduced masses, the unscaled estimated frequencies, force constants,
depolarization ratios, IR/Raman intensities and Raman activities were calculated. In this

5
estimation, a uniform scaling factor was applied to balance the systematic faults initiated by
vibrational anharmonicity, basis set incompleteness and neglect of electron correlation. Hence,
the calculation on vibrational frequencies at the HF level is scaled to 0.905 [12]. For B3LYP/6-
-1
-1
3
11++G(d,p), the wavenumbers above 1700 cm are scaled with 0.958 and below 1700 cm are
scaled with 0.983 [13, 14]. The visual animation and the normal mode assignments were verified
with the Gauss view program [15, 16]. DFT approach with B3LYP/6-311++G(d,p) level was
employed to obtain the simulated electronic absorption spectra. The investigation of reactive
sites of AMPMA was studied with MEP (molecular electrostatic potential) map. Moreover, the
thermodynamic parameters like heat capacity, entropy and enthalpy were examined from
vibrational frequency calculations at different temperatures.
3
. 2. Calculation of Raman intensities
According to Raman scattering intensity theory, the calculated Raman activities (S ) from
Ra
the Gaussian 09 program can be transformed into relative Raman intensities (I ) by the equation
Ra
[17, 18]
4
f
(
ν0 −νi
)
Si
Ii =
ν 1−exp −hcν / kT 
(
)

i

i
−
1
−1
where, ν is the exciting wavenumber in cm ( here, ν = 9398.5 cm and their corresponding
0
0
th
−1
wavelength is 1064 nm), ν is the i vibrational wavenumber in cm , S is the normal mode
i
i
−
12
Raman scattering activity and f(=10 ) is a constant normalization factor. Other symbols like h,
k, c and T are representing their usual meaning.

6
4
. Results and discussion
4
.1. X-ray diffraction analysis
From the single crystal X-ray diffraction analysis, it is confirmed that the AMPMA
crystal belongs to the monoclinic crystal system having a space group of C2/c. The
crystallographic data and their optimized geometrical parameters are given in Table 1 and Table
SM 1 (Supplementary Material) respectively. Table 2 provides information about an
intermolecular hydrogen bond in the AMPMA single crystal. ORTEP diagram (Fig. 1) shows an
intermolecular C—H···O interaction connecting acetoxy groups which develop a
centrosymmetric dimer. The recorded powder X-ray diffraction pattern of the AMPMA crystal
was compared with the simulated XRD pattern and is presented in Fig. 2. The simulated XRD
pattern was obtained from Mercury software (version 3.7) by using the CIF file. It is observed
from the XRD pattern that almost all the peak positions well coincided with the simulated
spectrum and thus confirms the single monoclinic phase of the titled crystal.
4
.2. Equilibrium geometry
Fig. 3 represents the optimized structure of the title molecule with B3LYP/6-
11++G(d,p). The global minimum energy and dipole moment of AMPMA were -766.8586
3
Hartrees and 2.8170 Debye respectively. The value of ZPVE called zero-point vibrational energy
-1
is estimated to be 150.3561 kcal mol . The elongation and contraction of bond lengths and bond
angles with the applied electric field would be responsible for the large polarizability of
AMPMA. For the title molecule, the calculated and investigational bond length values of C1–C2
and C1–C10 are 1.392 and 1.389 Å, respectively (Table SM 1 ). It is greater than other bond
lengths of C-C, in the benzene ring. The substitution of two methyl acetate groups to a toluene
ring is liable for the elongation of C1–C2 and contraction of C1–C10 bonds. C12-O26 and C17-

7
O28 bonds are not much deviated in the methyl acetate. There are four C-O bond lengths, in
which the bonds C11-O25 and C11-O27 are elongated more than the other two C12-O25 and
C17-O27 bond lengths. The bond angle (C1–C10–C11= 121°) of elongation and (C8–C10–C11=
1
18°) of contraction from the benzene ring angle of 120° show the substitution effect in the ring.
The acetic groups attached (C–C=O=125°) to the ring almost agreement with experimental
values. The calculated and experimental bond lengths of AMPMA can be understood from the
correlation graph which is given in Fig. SM 1 (Supplementary Material). The calculations
show good linear behavior of both the theoretical and investigational bond length values [8].
4
.3. Vibrational analysis
Vibrational spectra are helpful to elucidate the role of H-bonds in the molecular structure
displaying nonlinear optical activity in the crystal. The vibrational band assignments of
theoretical and experimental wavenumbers of AMPMA are listed in Table SM 2
(Supplementary Material). Vibrations that are present in both Raman and infrared spectrum are
active. The experimental and computer-generated FT-IR and that of FT-Raman spectra of
AMPMA are shown in Figs. 4 and 5 respectively.
4
.3.1. Aromatic C-H vibrations
The aromatic compound reveals C-H stretching, C-H in-plane and C-H out-of-plane
bending vibrations. C-H stretching vibrations of the aromatic compounds display multiple frail
-1
bands in wavenumber range 3100 to 3000 cm [19]. In the current study, AMPMA is a mono
switched aromatic system which describes the above three types of C-H stretching vibrations.
−
1
The C-H stretching vibration of AMPMA in the FTIR is observed at 3053 cm and in the
−
1
-1
FT-Raman at 3065 cm . This mode is estimated in the range 3068-3043 cm with B3LYP/6-
-
3
11++G(d,p). HF method estimated in the C-H stretching vibrations in the range 3053-3013 cm

8
1
.
All bands have medium and strong intensities and were found in the predictable region.
The C-H in-plane bending vibrational bands are commonly noted in the region 1000 to
-
1
-1
1
1
300 cm [20]. The in-plane bending vibrations are observed at 1135 cm in FT-Raman and
-1
119 cm in infrared. The theoretical vibrations well coincide with the experimental data.
The out-of-plane bending mode vibrations of C-H appears within the limit, 1000-700 cm
−
1
−
1
[
21]. The vibrations identified at 735, 710, 650 and 618 cm are allocated to C-H out-of-plane
−
1
bending vibrations of AMPMA. These modes were computed at 743, 712, 647 and 618 cm by
-1
the B3LYP/6-311++G(d,p) method and at 764, 730, 661 and 633 cm by HF/6-311++g(d,p).
These changes in vibrations confirm the complex formation.
4
.3.2. C-C vibrations
The C-C bands are more influential on aromatic ring modes. The aromatic ring C=C
-1
stretching modes generally present in the region, 1430–1625 cm [22]. The stretching vibrations
−
1
of C-C in an aromatic ring are anticipated within the wavenumber 1300-1000 cm [23, 24].
The maximum ring modes are changed by the substitution to the aromatic ring. In the
-1
present molecule, the IR peak observed at 1588 cm and Raman assignments at 1554 and 1468
−
1
-1
cm are attributed to C=C stretching mode of vibrations. These bands are estimated as 1624 cm
-1
-1
in DFT and 1582 cm in HF methods. The vibrations identified at 1265 & 1155 cm in FT-
-1
Raman and 1260 cm in infrared are attributed to C-C vibrations. The corresponding bands are
-1
calculated at 1281 and 1265 cm by HF and DFT methods respectively.
-1
The C–C–C aromatic cycle vibrations are noticed in the predictable region 750-1000 cm
-1
-1
[
25]. Experimental IR bands observed at 845 and 770 cm and Raman band at 828 cm are due
-1
to aromatic cycle vibrations. These bands have appeared at 927, 847, 824 and 768 cm in DFT
-1
and 971, 881, 830 and 775 cm in HF respectively.

9
4
3
.3.3. CH vibrations
The AMPMA possesses three CH groups. There are nine fundamentals, namely the CH
3
3
3
symmetrical stretching and CH asymmetric stretching, CH symmetrical deformation and CH
3
3
asymmetrical deformation modes; in-plane stretching and out-of-plane stretching modes; out-of-
plane rocking (CH opr), twisting (tCH ) modes and the CH in-plane rocking (ipr) for CH
3
3
3
3
vibrations. Methyl groups are stated as an electron donor substitution and the methyl C–H
−
1
stretching vibrations lie in the limit, 2975–2840 cm .
-1
-1
The IR and Raman modes observed at 1406 cm and 1409 cm are attributed to in-plane
CH bending vibrations. These fundamentals are better coincidence with the values calculated by
B3LYP and HF methods.
4
.3.4. C-O vibrations
The performance C-O vibrations can be studied through the oxygen lone pair electron.
These multiple bonded groups are highly polar and resulting in a strong IR absorption peak.
The intermolecular hydrogen bond across C and O diminishes the frequencies of C=O stretching
(abs.) due to the different electronegativity of carbon and oxygen as well as the unequal
distribution of the bond distance between the two atoms. The electron lone pair of oxygen
reveals the nature of the carbonyl group. The carboxylic acid, C=O band reveals a strong
-1
absorption within the limit,1700-1800 cm . C=O stretching modes of acid are stronger than
ketonic C=O bands.
-1
-1
The characteristic ketonic frequency of C=O appears at 1728 cm in FTIR and 1745 cm in
FT-Raman with very weak intensities. This C=O vibration observed is not altered by other
bands. The theoretically estimated frequencies by B3LYP (6-311++G(d,p)) for C=O are 1743

10
−
1
and 1726 cm which gives, strong support to the experimental data. However the HF method
gives this vibration at higher wavenumbers.
-1
The C–O stretching vibrations are observed at 1215 & 1056 cm in FT-Raman and FT-IR,
−
1
the corresponding bands (C–O stretching) are located at 1195, 1065 and 1040 cm . The
-1
computed values of C–O stretching are appeared at 1213, 1192, 1093 and 1035 cm in B3LYP
-1
(
6-311+G(d,p) and 1235, 1214, 1099 and 1075 cm in B3LYP (6-311+G(d,p) methods.
4
.4. NMR spectral analysis
1
13
NMR spectra provide efficient structural information and H/ C NMR spectra of AMPMA are
provided in Fig. SM 2 (Supplementary Material). Theoretically predicted and experimentally
1
13
identified NMR chemical shifts are shown in Table 3. The chemical shift of H and C were
estimated using IEFPCM/CDCl solution. CH and CH proton NMR values of AMPMA
3
3
2
appeared from 2 to 1 ppm except for H22. The H22 NMR value slightly deviates due to the
nearest oxygen (O28) atom. Methyl protons devoted to the carbonyl group produced their signals
at 2.112 ppm and hence they are chemically equivalent. The methyl protons devoted to the
phenyl ring give their signals at 2.45 ppm. The phenyl ring proton NMR appears in the range 8.5
to 6.5 ppm. In our compound, the NMR values of H3, H5, H7 and H9 confirm their position with
experimental values. One proton of acetoxy group produces its signal at 7.20 ppm. Chemical
shift observed at 7.83 ppm is attributed to meta protons of phenyl and at 7.51 ppm is due to
Orthoprotons of phenyl. The solvent (CDCl ) peak appears at 7.26 ppm.
3
1
3
C NMR spectrum gives the carbon environment in the molecule. Carbonyl carbon atoms
give their peak at 134.17 ppm. Acetoxy carbon gives its peak at 139.19 ppm. The carbon atom
attached to the acetoxy group is attributed to 129.68 ppm. Meta C-atoms of phenyl shows at
1
29.19 ppm and ortho C-atoms of phenyl ring shows at 126.44 ppm. The methyl group carbon

11
3
atom (CH ) attached to the phenyl ring gives its peak at 105.24 ppm. The medium peak at 14.56
ppm is attributed to the three equivalent CH groups. The triplet (77.49, 77.06 and 76.64 ppm) is
3
owing to the solvent (CDCl ) effect.
3
4
.5. Ultraviolet (UV) spectral analysis and Frontier molecular orbitals (FMOs)
UV spectral studies of AMPMA were demonstrated theoretically with DMSO, chloroform
and gas respectively. Low-lying excited levels of AMPMA were obtained by
TD-DFT/B3LYP/6-311++G(d,p) calculations with the use of fully optimized structure.
The theoretical values of oscillator strengths, electronic excitation energies and wavelength are
provided in Table 4. From the Table 4, it is noted that the estimated absorption maxima were
found to be 241.29, 218.93, 211.95, 210.58 and 206.99 nm for gas phase, 241.42, 219.24,
2
12.18, 210.78 and 207.42 nm for DMSO and 241.61, 219.64, 213.04, 211.65 and 207.55 nm
for chloroform at DFT/B3LYP/6-311++G(d,p) method. The maximum contribution to the
transitions was chosen with the help of a SWizard program [26]. The maximum absorption of
6
5% in all three media is due to the electron shift between HOMO and LUMO. The estimated
excitation energies, wavelength and oscillator strength with major assistances are provided in
Table 4.
The FMOs play an important part in quantum chemistry, optical and electrical analysis
[27]. Gauss-Sum 2.2 Program [28] was utilized to estimate the frontier orbital energy and the
energy gap of HOMO-LUMO which involved in the estimation of kinetic stability, chemical
reactivity, chemical hardness/softness of a molecule and optical polarizability. Chemical
hardness and softness are the tools in the clarification of thermodynamic characteristics of
chemical reactivity. The plot of the density of states is presented in Fig. 6. It gives the

12
information about the population study per orbital and establishes a modest molecular orbital
view in a definite energy range.
From the FMO energy states of the AMPMA, it is noticed that the respective electronic
transfer has occurred between HOMO and LUMO, HOMO-1 and LUMO+1 orbitals,
respectively. There are four significant molecular orbitals were found for AMPMA: the highest,
second highest occupied (HOMO, HOMO−1), the lowest unoccupied and the second lowest
unoccupied (LUMO and LUMO+1) orbitals were estimated using B3LYP/6-311++G(d,p) and
the estimated energy values are compiled in Table 5. The energy gap value is 6.0260, 6.0233 and
6
.0222 eV in gas, DMSO and chloroform respectively. Charge transfer interactions within the
molecule can be studied by the energy band gap value of HOMO–LUMO.
Fig. 7 shows the HOMO/LUMO 3D plot of AMPMA and from this figure, one can
understand that the highest occupied molecular orbital is localized the entire molecule,
particularly on the rings. LUMO is localized at the oxygen atom sites and the aromatic ring. The
positive and negative regions are indicated by the red and green colors respectively and the
electron density transfer can be identified by the HOMO→LUMO transition.
The values of electronegativity (4.0473 eV), chemical hardness (3.0310 eV), softness
(0.1659 eV) and electrophilicity index (1.5065 eV) in the gas stage are greater than that in
DMSO and chloroform phases. Larger the dipole moment indicates stronger the intermolecular
interactions in the compound. Table 5 reveals the estimated dipole moment values of the
molecule. It is observed from the table that the estimated dipole moment is higher for the gas
phase (3.7101 D) when compared to DMSO (3.6929 D) and Chloroform (3.4123 D) respectively.
4
.6.Thermodynamic properties
According to B3LYP/6-311++G(d,p) level, the statistical thermodynamic factors like heat

13
capacity (C), entropy (S) and enthalpy changes (ΔH) for AMPMA were calculated and are given
in Table 6. These thermodynamic parameters are increased in the temperature region, 100- 500
K. It is because, with the increase of temperature, the intensity of molecular vibrations is
increased [29].
The correlation equations connecting, enthalpy changes, entropies, heat capacities and
2
temperatures were close-fitting with the quadratic formulas. The respective fitting factors (R )
for the mentioned thermodynamic components are having the same value 0.9999.
The corresponding fitting equations are as follows and the correlation graphics are presented in
Fig. 8.
−
4
2
S=59.14269 +0.29269 T − 0.3303 x10 T
−
5
2
ΔH=− 0.25043+0.01448T + 7.75478 x10 T
−
5
2
C = 11.80259 + 0.16338 T −1.6857 x10 T
All the thermodynamic data provides sufficient details which could be helpful for further
analysis. They will be used for the other thermodynamic energy calculations within the
thermochemical field.
Note: All the thermodynamic estimations were analyzed by choosing the gas phase and are not
suitable for the solution phase.
4
.7. Electrostatic potential analysis of AMPMA
Fig. SM 3 (Supplementary Material) represents the 3D-photograph of ESP-electrostatic
potential, TED-total electron density and MEP-molecular electrostatic potential map of
AMPMA. The TED photograph of AMPMA molecule shows its identical distribution. However,
it is observed from the ESP that the yellowish blob represents the localization of ESP with the
oxygen atoms of the molecule. This is the expected result, since ESP associates with

14
electronegativity and limited charges.
Proton attraction by the high electron density reveals negative electrostatic potential which
is red on the ESP surface and the repulsion of the proton by the low electron density shows the
positive electrostatic potential and the shades of blue color exhibits the incomplete shielding of
nuclear charge. However, the color grading of MEP displays molecular shape, size, positive,
negative and neutral ESP regions respectively (Fig. SM 3) and thus the physiochemical
properties of the molecule can be easily studied [30-32]. Different color identifies the diverse
estimations of ESP at the molecular surface.
Potential increases in the order red < orange < yellow < green < blue. The color code of
these maps is in the range between -0.04671 a.u. (deep red) to 0.04671 a.u. (Deep Blue), where
the strong attraction and repulsion behavior of the molecule are indicated by blue and red colors
respectively. In the MEP map, the ring carbon and O-atoms of the molecule indicate the negative
potential region whereas the hydrogen atoms in the network indicate the positive potential. The
green colour of the methyl groups present dictates the neutral potential.
4
.8. Natural Bond Orbital( NBO) analysis
The NBO analysis evidenced to be an important measure of interpretation of intra and
intermolecular interaction. It is also used for examining conjugative contact or charge transfer
with the molecular system. Higher the energy of hyper conjugative interactions, the more severe
is the interface between electron donors and acceptors respectively.
The delocalization of electron density, intramolecular interactions and re-hybridization of
the molecule can be understood through NBO analysis. Fock-second order perturbation theory
examination on AMPMA molecule is provided in Table SM 3 (Supplementary Material).
The intramolecular interactions of the molecule could be owed to the orbital overlap of π(C6-C8)

15
*
*
over anti-bonding π (C1-C10) and π (C2-C4) with energies 18.12 kcal/mol and 21.6 kcal/mol,
*
π(C1-C10) and π(C2-C4) over π (C6-C8) with stabilization energies 21.81 kcal/mol and
*
1
8.61 kcal/mol. The molecule involves the interactions of σ of O25 with σ (C12-O26), σ of O26
*
*
*
with σ (C12-O25), σ of O27 with σ (C11-C28) and σ of O28 with σ (C17-C27) and has
stabilization energies 6.94 kcal/mol, 1.28 kcal/mol, 7.05 kcal/mol and 1.39 kcal/mol,
respectively.
4
4
.9. Optical properties
.9.1. Molecular dipole moment and polarizability calculations
Observation of optical activity in organic molecules provides the necessary key factors
for most of the optical properties like optical switching, optical modulation, optical logic and
signal processing etc., [33-36]. It is believed that in most of the organic materials, intramolecular
interactions are much tougher than the intermolecular chemical bonds. In such circumstances, the
molecular interactions of AMPMA were analyzed with different theoretical methods (MP2, DFT
and HF).
The optical activity of the materials significantly depends on large dipole moment and
polariability. The aromatic ring in the titled material is responsible for all the optical properties.
When an optical photons incident on the material, there is a transfer of energy to the electrons
and thus there is a development of the local electric field. Therefore, in this contest, the
calcualtion of the optical properties like molecular dipole moment (µ) and linear polarizability
(α) of AMPMA were studied by MP2, DFT and HF methods with different basis sets.
In the present research work, the axial components of molecular dipole moment (µ) and
polarizability (α) were calculated along the axial planes (x, y and z respectively). In addition to
these axial components, the methods were extended to describe the non axial components (xy, xz,

16
yz) of an applying electric field apart from the axial planes. The polarizability tensors were
estimated (α , α , α , α , α , α ) by using the Gaussian output file with an appropriate formula
xx
xy
yy
xz
yz
zz
[37] and the results based on DFT/B3LYP 6-311++g(d,p) method are recorded in Table 7.
The dipole moment (µ) and polarizability (α) of the AMPMA material are compared with the
reported materials and are presented in Table 8. The larger values of dipolemoment (µ) and
polarizability (α) indicate the substantial charge delocalization in the mentioned directions,
which shall responsible for the nonlinear optical activity.
4
.9.2. Basis sets analysis of DFT, MP2 and HF methods
It is noted from Fig. 9, the estimated electrostatic dipole moments from all the three
methods are having a similar trend. This reveals that the dipole moments were insensitive to
electrostatic correlation effect (EC) [41]. In all the three methods, 6-31+g(d,p) and 6-
3
1++g(d,p) basis set gives maximum dipole moment and the basis set of 6-311g(d,p) shows the
minimum dipole moment value. The results of MP2 method having 22% deviation from HF
method and it is 15% from DFT.
The polarizability behavior of the molecule can be understood from Fig. 10. The behavior
of the curves in all three methods revealed the molecular consistency in the estimation of linear
polarizability. Large the value of polarisability, more diffusion and polarization functions will be
considered [41]. In the DFT scheme, the obtained polarisability values are in the region from 19
-24
-24
x10 esu to 22 x10 esu. The 6-31+g(d,p) and 6-31++g(d,p) basis sets in DFT approach
showed maximum values of polarizabilities and hence these basis sets are suitable for theoretical
calculations.
5
. Conclusion

17
A complete chemical computational analysis of AMPMA was performed by HF and
DFT-B3LYP method at 6-311++G(d,p) basis level. An experimentally obtained and theoretically
generated spectra were well granted for the decent frequency fit with DFT B3LYP/6-
3
11++G(d,p) level. The structural and symmetrical properties of AMPMA were studied with
various quantum chemical calculations. UV-Vis. spectral studies of AMPMA were analyzed by
theoretical calculations. The electronic transitions of the material were completely studied by the
DFT method both with the gas phase and liquid phase (solvent-DMSO and Chloroform)
respectively. The MEP map explains the negative (oxygen and nitrogen atoms) and positive
(hydrogen atoms) potentials. Different theoretical approaches on different basis sets were used to
analyze the dipole moment and polarisability of the title molecule. The higher values of dipole
moment and polarisability components of the titled material dictates the considerable charge
delocalization which is accountable for its efficient optical property.
Acknowledgements
The author Dr. N. Sivakumar wish to acknowledge UGC (Dr.S.Kothari Postdoctoral
Research scheme. No.F.4-2/2006/(BSR)/PH/16-17/0109), New Delhi for proving the financial
assistance to carried out this research work.
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Table 1. Crystal data, Intensity data collection and Refinement for methyl acetate compound
AMPMA.
PARAMETERS
AMPMA
CRYSTAL DATA
Formula
Formula Weight
Crystal System
Space group
C H O
4
1
2
14
222.23
Monoclinic
C2/c
a, b, c [Å]
15.757(5)
7
1
.564(5)
9.886(5)
alpha, beta, gamma [deg]
90.00
9
9
9.17(5)
0.00
3
V [Å ]
2339.84(18)
Z
8
3
D(calc) [g/cm ]
1.2617
Radiation used
MoK
α
-1
Mu(MoK ) [ mm ]
0.095
α
Wavelength
F(000)
Crystal Size [mm]
0.71073
944
0.25×0.20×0.15
INTENSITY DATA COLLECTION
Diffractometer
Brucker Kappa APEXII CCD
Temperature (K)
295
Theta Min-Max [º]
Dataset
Reflection collected
Unique reflections
Reflection with
2.1, 26.5
-13:19; -9:8, -24:24
12571
2414
[
I > 0.02 σ(I)]
1856
0.027
R(int)
REFINEMENT
2
Refinement method
Full matrix least square on F
Parameters
149
2
GooF on F
1.045
0.041
0.1249
None
Final R indices,
2
wR
Extinction Correction
Min. and Max.
Resd. Dens. [e/Å ]
3
-0.19, 0.20

Table 2. Non-Bonded interactions and possible hydrogen bonds of AMPMA
D-H…A
D-H(Å)
0.9800
0.9800
H…A (Å)
2.2830
D…A (Å)
2.6641
D-H-A (°)
101.92
i
C7- H7…O2
ii
C9- H9A…O4
2.5410
2.656
85.85
Symmetry Code:(i) x, y, z; (ii) -x+1/2, y+1/2, -z+1/2

1
13
Table 3. Experimental and Calculated values of H and C NMR isotropic chemical shifts (with
respect to TMS and in CDCl
3
solution) of AMPMA
1
3
13
Atom
C NMR
Atom
H NMR
Experimental Calculated
B3LYP)
Experimental
Calculated
(B3LYP)
(
C12
C17
C1
1
1
1
1
1
1
1
1
77.4
76.6
44.7
40.5
34.8
34.7
33.1
30.7
H9
7.83
7.81
7.76
7.51
7.47
7.44
3.27
2.52
2.30
2.24
2.18
2.11
1.98
1.79
1.60
H30
H5
-
7.51
C10
C4
139.14
134.17
129.68
129.19
126.44
105.24
-
H7
7.49
H3
7.31
C2
H22
H24
H15
H20
H16
H23
H29
H14
H19
-
C8
2.45
C6
-
C11
C13
C18
C21
9
2.0
1.4
1.1
9.9
-
2
-
-
2
1
2.11
14.56
-
-
-

Table 4. Theoretical electronic absorption spectra of AMPMA (absorption wavelength λ (nm),
excitation energies E (eV) and oscillator strengths (f) using TD-DFT/B3LYP/6-311++G(d,p)
method in DMSO, chloroform and gas phase
-
1)
Phase
E(eV)
λ(nm)
F(cm
Major contribution%
HOMO->LUMO (65%)
H-1->LUMO (58%)
H-3->L+2 (-38%)
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
.138
.663
.849
.887
.990
.135
.655
.843
.882
.977
.131
.645
.819
.857
.978
241.29
218.93
211.95
210.58
206.99
241.42
219.24
212.18
210.78
207.42
241.61
219.64
213.04
211.65
207.55
0.0205
0.0818
0.0095
0.0005
0.0072
0.0219
0.0863
0.0098
0.0005
0.0067
0.0220
0.0842
0.0130
0.0007
0.0072
GAS
H-2->L+3 (-63%)
HOMO->L+2 (81%)
HOMO->LUMO (65%)
H-1->LUMO (58%)
H-3->L+2 (-36%)
DMSO
H-2->L+3 (-60%)
HOMO->L+2 (82%)
HOMO->LUMO (64%)
H-1->LUMO (56%)
H-3->L+2 (-37%)
CHCl3
H-2->L+3 (64%)
HOMO->L+2 (81%)