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Molecular structure and charge transfer contributions to nonlinear optical property of 2-Methyl-4-nitroaniline: A DFT study
Accepted Manuscript Molecular structure and Charge transfer contributions to nonlinear optical property of 2-Methyl-4-Nitroaniline: A DFT Study G.Femina Jasmine, M. Amalanathan, S.Dawn Dharma Roy PII:
S0022-2860(16)30107-7
DOI:
10.1016/j.molstruc.2016.02.013
Reference:
MOLSTR 22222
To appear in:
Journal of Molecular Structure
Received Date: 16 November 2015 Revised Date:
3 February 2016
Accepted Date: 3 February 2016
Please cite this article as: G.F. Jasmine, M. Amalanathan, S.D.D. Roy, Molecular structure and Charge transfer contributions to nonlinear optical property of 2-Methyl-4-Nitroaniline: A DFT Study, Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.02.013. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Molecular structure and Charge transfer contributions to nonlinear optical property of 2-Methyl-4-Nitroaniline: A DFT Study G.Femina Jasminea, M. Amalanathanb* and S.Dawn Dharma Royc Department of Physics , Bethlahem Institute of Engineering, Kanyakumari District, Tamil Nadu.
b
Department of Physics, Annai Velankanni College, Tholayavattam- 629157, Tamil Nadu. C
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a
Department of Physics. NMCC, Marthandom - 629 165Tamil Nadu.
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Abstract
The Charge transfer contributions to the second-order nonlinear optical properties of 2-
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Methyl-4-nitroaniline have been performed by means of DFT computation. The vibrational contribution studies of 2-Methyl-4-nitroaniline have also been performed using FTIR, FTRaman analysis. More support on the experimental findings were added from the quantum chemical studies performed with DFT (B3LYP) method using 6-311++G(d,p)basis sets.
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Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. The HOMO and LUMO analysis reveals the possibility of charge transfer within the molecule. The first order hyperpolarizability (α0) and related
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properties (β,α0 and ∆α) of 2-Methyl-4-nitroaniline were calculated. In addition, molecular electrostatic potential (MEP), charge analysis also were investigated using theoretical
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calculations.
Keywords: Charge transfer contribution; DFT; Polarizability ; Hyperpolarizabilities; NBO; HOMO-LUMO Energy.
*Corresponding author: M.AMALANATHAN; Department of Physics, Annai Velankanni College, Tholayavattam- 629157, Tamil Nadu. Tel: +91-9940347178 E-mail: [email protected]
ACCEPTED MANUSCRIPT Introduction Materials having large second-order nonlinear optic (NLO) properties are in demand due to their potential applications in photonic devices and optical information processing[1-3]. Organic NLO materials have drawn much attention because of their attractive potential
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applications in optical data transmission and optical information processing[5]. Compared with traditional inorganic and semiconductor materials, the organic NLO materials have many advantages such as larger nonlinear optical coefficients, simpler preparation and lower cost [6].
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At a fundamental level, organic push pull NLO chromophores contain electron-donor and electron-acceptor groups at opposite ends of a p-conjugated spacer[4], and the vast majority of
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known organic NLO compounds utilize aromatic linkers in the p-conjugated bridge. [6]. Generally, the nonlinear optical (NLO) chromophore molecules possessing a dipolar D-π-A type structure is the core component in such materials, which turned the design and preparation of NLO chromophores into a research hotspot in the area of organic NLO materials[7,8]. Many
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great attentions have been paid to the rational design of chromophores with not only high firstorder hyperpolarizability but also good thermal and photochemical stabilities. In recent years much work on poly conjugated systems has been done using vibrational spectroscopy and DFT
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computation in order to find structure–property correlations. In particular, Infrared and Raman spectroscopy have enabled us to obtain information on the molecular structure of conjugated
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molecules and on their NLO behaviour [9]. Spectroscopic studies on aniline and its derivatives have been studied extensively
[10,12], since they are widely used in commercial and industrial purposes, including pesticide, pharmaceuticals manufacturing and chemical dye industries. Nitro anilines share the common feature of having an electron-rich (donor, –NH2) and an electron-deficient (acceptor, –NO2) substituent, connected by a conjugated π-electron system. Nitro anilines belong to push–pull molecules due to the intra-molecular charge transfer (ICT) from the electron-donor group
ACCEPTED MANUSCRIPT through the phenyl ring to the electron-acceptor group. Aniline derivatives can form inter- and intra-molecular hydrogen bonding in solid state which imparts innovative properties in compounds. Inter- and intramolecular hydrogen bonding interactions [13,14] and these can be
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lead to increase the NLO activity of the materials. Currently, quantum mechanical calculations are very popular because of their efficiency and accuracy with respect to the evaluation of a number of molecular properties. In the present investigation, the growth of 2M4NA single crystals and the detailed vibrational
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spectral analysis of the molecule in the crystalline state is taken up to understand the correlation
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of the charge transfer interactions and NLO activity of the molecule. The structure activity relation supported by the NBO calculation and HOMO-LUMO energy calculation. 2. Experimental 2.1. Synthesis
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The title compound 2-Methyl-4-nitroaniline was synthesized by mixing in methanol solution. The mixture was stirred at room temperature for 3 hours and 2M4NA salt was
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obtained as precipitate. The product was purified by re crystallization using mixed solvent, methanol and acetone. The purified salt was mixed with the methanol solution and it is allowed
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to evaporate at room temperature, After 2 weeks tiny 2M4NA crystals were obtained. 2.2. IR and Raman measurements The FT-IR spectrum of 2M4NA was recorded using Perkin–Elmer RXI spectrometer in
the region 4000–400 cm-1 , with samples in the KBr. The resolution of the spectrum is 4 cm -1. The NIR-FT Raman spectrum of 2M4NA crystal was obtained in the range 3500–10 cm-1 using Bruker RFS 100/S FT Raman spectrophotometer with a 1064 nm Nd:YAG laser source of 100 mW power. Liquid nitrogen cooled Ge-diode was used as a detector.
ACCEPTED MANUSCRIPT 2.3 Powder SHG Powder second harmonic generation efficiency of the grown crystal was determined using modified Kurtz and Perry method. Q-switched mode locked Nd:YAG laser was used as a
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optical source. The crystals were grained into powder and densely packed between two glass slides. The input energy was measured using power meter and it is 4.6mJ/s. 3. Computational Techniques
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All the electronic structure calculations have been carried out using Gaussian ‘09 program package [15]. The geometry is fully optimized at the Becke3–Lee–Yang–Parr
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(B3LYP) level with standard 6-311++G(d,p)basis set[16]. The computed wavenumbers were scaled by an empirical scaling factor of 0.97[17] to fit with the experimental wavenumbers, which accounts for systematic errors caused by basis set incompleteness, neglect of electron correlation and vibrational anharmonicity. Since the electron correlation effects have been
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extensively considered in DFT method, a precisely predicted structure of the molecule can be evolved. The Raman activities (Si) calculated by Gaussian ‘09 are converted to relative Raman
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intensities (Ii) using the relation derived from the basic theory of Raman scattering[18,19].
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f (ν o − ν i ) 4 S i Ii = − hcν i ν i 1 − exp kT
................. (1)
where νo is the exciting frequency ( in cm-1 units), νi is the vibrational wavenumber
of the ith normal mode, h, c and k are universal constants, and ƒ is the suitably chosen common scaling factor for all the peak intensities.The natural bonding orbital calculations were done at the B3LYP method in order to investigate the optimized geometry corresponding to charge transfer interaction. The hyperconjugative interaction energy was deduced from the second-
ACCEPTED MANUSCRIPT order perturbation approach [20]. The frontier molecular orbital’s and the HOMO–LUMO energy gap has been computed. 4. Result and Discussion
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4.1 Optimized Geometry From the single crystal XRD data[21] it is found that, the 2M4NA crystal belongs to orthorhombic system with the following cell dimensions: a=7.6113 Å, b=11.6304 Å, c =
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8.2286 Å, α = 90° β = 94.05 γ =90°. For doing theoretical calculations, the initial parameters are taken from [21] and structural optimizations have been done. The ground state optimized
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structure of the 2M4NA molecule is presented in Figure 1. The optimized and experimental structures of the molecule are compared. The agreement between the optimized and experimental crystal structure is quite good, which shows that the geometry optimization almost exactly reproduces the experimental conformation. The Optimized structure of 2M4NA,
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which is determined by using DFT method, is shown in Figure.1. The optimized geometrical parameters are summarized in Table 1. Our calculated structural parameters using B3LYP show a comparable agreement with the experimental ones. From the theoretical values, one can
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find that most of the optimized bond lengths are larger than the experimental values, because
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the theoretical calculations refer to isolated molecules in the gaseous phase and the experimental results are for molecules in the solid state. The C–H bond lengths obtained from the experimental value [21] range from 0.95 to 0.98 Å; while of theoretical values ranges between 1.08 and 1.09 Å. This larger deviation of C–H bond lengths may be due to the low scattering factors of hydrogen atoms in X-ray diffraction experiments which are not included in the theoretical calculations.
ACCEPTED MANUSCRIPT 4.2 Natural Bond Orbital analysis The natural bond orbital (NBO) calculation [21] of the title compound was performed using NBO 5.0 program implemented in the Gaussian 09 package at the B3LYP/6-311+G(d,p)
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level. Natural bond orbital analysis is an essential tool for studying intra and intermolecular bonding interaction of 2M4NA. It also provides a convenient basis for investigating charge transfer or conjugative interaction in molecular systems. Some electron donor orbital, acceptor orbital and the interacting stabilization energy resulting from the second–order micro
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disturbance theory is reported [23,24]. The hyper-conjugative interaction energy was deduced
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from the second-order perturbation approach.
Fij2 σ Fσ E (2) = −nσ = −nσ εσ* − εσ ∆E 2
……….(2)
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where 〈σ|F|σ〉2, or F2ij is the Fock matrix element between i and j NBO orbitals, εσ and εσ∗ are the energies of σ and σ* NBO's and nσ is the population of the donor σ orbital. Table 2
energies E(2).
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shows some of the significant donor–acceptor interactions and their second order perturbation
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The interactions formed by the orbital overlap between π (C – C) -π* (C – C), LP(1)-
π*(C – C), LP(1)- σ*(C – C) bond orbital which results in intermolecular charge transfer (ICT) causing stabilization of the system. These charge transfer interaction are possible to increase the induce large nonlinearity of the molecule. The larger the E(2) values, the more intensive is the interaction between electron donors
and electron acceptors. The intramolecular
hyperconjugative interactions are formed by the orbital overlap between π(C–C) and π*(C–C) bond orbital’s which results in intramolecular charge transfer (ICT) causing stabilization of the system. These interactions are observed as an increase in electron density (ED) in C–C
ACCEPTED MANUSCRIPT antibonding orbital that weakens the respective bonds. The ED at the eight conjugated π bonds (1.56-1.71 e) and π* bonds (~0.30-0.42 e) of the phenyl ring clearly demonstrates the strong delocalization of electron leading to stabilization of (~21-28 kJ/mol) energy. This intramolecular charge transfer leads the NLO activity of the molecule. The maximum energy
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transfer from lone pair (O1o) to π*(N15AO17) (159.04 kJ/mol), clearly demonstrates the intermolecular hyper conjugative interaction between the lone pair atoms of the molecule to other part are strong in the ground state and listed in Table 2. It is also evident from the
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decreasing of electron density in lone pair oxygen and increasing of electron density in the π*(N15-O17) bonding. These charge transfer interactions of 2M4NA are also responsible for N
4.3 Non linear optical analysis
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LO properties. Other possible interactions of 2M4NA are listed in table.
Density functional theory has been used as an effective method to investigate the
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organic non-linear optical (NLO) materials. Recent research works have illustrated that the organic non-linear optical materials are having high optical non-linearity than inorganic materials [25]. In the presence of an applied electric field, the energy of a system is a function
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of the electric field. Polarizabilities and hyperpolarizabilities characterize the response of a system in an applied electric field [26]. They determine not only the strength of molecular
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interactions but also the cross sections of different scattering and collision processes, as well as the NLO properties of the system [27,29]. For this subject, in this study the electronic dipole moment, molecular polarizability, anisotropy of polarizability and molecular first hyperpolarizability of present compound were investigated. The electric dipole moment µ polarizability α, the hyper polarizability β and first order hyperpolarizability γ of the of title compound are calculated by finite field method using B3LYP/6-311++G(d,p) basis set available in Gaussian 09 package.
ACCEPTED MANUSCRIPT In the presence of an applied electric field, the energy of a system is a function of the electric field and the first hyperpolarizability is a third rank tensor that can be described by a 3 x 3 x 3 matrix. The 27 components of the 3D matrix can be reduced to 10 components because of the Kleinman symmetry [28]. The matrix can be given in the lower tetrahedral format. It is
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obvious that the lower part of the 3x 3 x 3 matrices is a tetrahedral. The components of b are defined as the coefficients in the Taylor series expansion of the energy in the external electric field. When the external electric field is weak and homogeneous, this expansion is given below:
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E = Eº- µi Fi – ½ α ij FiFj – 1/6 βijk FiFj Fk - 1/24 γijkl FiFj Fk Fl + …….
(3)
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where Eo is the energy of the unperturbed molecules, Fi is the field at the origin µiα ij , βijk and γijkl are the components of dipole moment, polarizabiltiy, first and second order hyperpolarizability respectively. These studies led to the fact that ab initio calculations of polarizabilities and hyperpolarizabilities have become available through the strong theoretical
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basis for analyzing molecular interactions. They made possible the determination of the elements of these tensors from derivatives of the dipole moment with respect to the electric field.
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The total static dipole moment µ, the mean polarizability α0, the anisotropy of the polarizability ∆α and the mean first hyperpolarizability βo, using the x-, y- and z- components
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are defined as
µ = ( µ x2 + µ y2 + µ z2 )
1
2
The dipole moment µ, NLO material Urea, KDP and 2M4NA crystal are calculated
using
DFT level. The three dipole moment component of NLO material Urea and KDP and
2M4NA crystal are given in Table 3 and the total dipole moment is found to be1.527 Debye, 3.008 Debye and 5.911 Debye respectively.
α 0 = (α xx + α yy + α zz ) 3
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−1
2
1
[(α xx − α yy ) 2 + (α yy − α zz ) 2 + (α zz − α xx ) 2 + 6α xz2 ] 2 …… (4)
The other components of the polarizability (αxy, αxz,etc.) are not needed to obtain the isotropic quantity. The polarizability components of
Urea, KDP and 2M4NA are given in Urea, KDP and
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Table 4. From the polarizability component the static polarizabilities of
2M4NA are calculated, which is found to be 5.664 x 10-24 e.s.u , 7.289 x 10-24 e.s.u and 17.024 x 10-24 e.s.u respectively. The dynamic polarizabilities are found to be 6.304x 10-24 e.s.u,
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12.656 x 10-24 e.s.u, 22.698 x 10-24 e.s.u respectively. From the above result the static and dynamic polarizability of 2M4NA material is comparatively larger than the NLO reference
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material Urea and KDP. It confirms that the strong electron donor’s acceptor molecules increase their linear polarizabilities are became larger than other. The addition of large end groups –NO2, leads to an increase of mean polarizability and also leads to an increase of longitudinal polarizability αxx. From these results, it is inferred that strong charge transfer
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substitutions are the good candidates for systems with large polarizabilities [29,30]. The first order hyperpolarizability β was also calculated using the finite field approach theory. The components of First hyperpolarizability can be calculated using the following
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equation
(
)
1 ∑ βijj + β jij + β jji , ( i ≠ j ) 3
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β i = β iii +
Using the x,y and z components, the magnitude of the first hyperpolarizability tensor can be calculated using
βtot = ( β x2 + β y2 + β z2 )
1
2
……………
(5)
The complete equation for calculating the magnitude of the first hyperpolarizability from Gaussian 09 output is as follows.
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(
β = β xxx + β xyy + β xzz
) + (β 2
yyy
+ β yzz + β yxx
) + (β 2
zzz
+ β zxx + β zyy
)
1
2
2 ……. (6)
The ten hyperpolarizability components of Urea, KDP and 2M4NA are given in Table 5. The first order hyperpolarizability of Urea, KDP and 2M4NA are calculated at DFT level
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and is found to be 0.781 x 10-30 e.s.u., 7.390 x 10-30 e.s.u and 13.956 x 10-30 e.s.u. respectively. The above result shows that the NLO activity of 2M4NA is 17.8 times that of urea and 9.6 times that of KDP. The β values are large for 2M4NA compared to Urea and KDP. The result
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indicates also that the magnitude of first hyperpolarizability β of molecules is dependent upon the availability of the lone pair of electrons on the nitrogen atom to conjugate with the Phenyl
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ring. The dramatic increase of first hyperpolarizability has been observed when the lone pair on the nitrogen atom of the donor groups is forced to conjugate with the phenyl ring, upon substitution on nitrogen of –NH2 group with other groups such as methyl[31]. From the above result it confirms that the increase of polarizability increase the NLO activity of the molecule.
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The increase of polarizability is due to the increasing of charge transfer interaction inside the molecule, which leads the greater NLO activity of 2M4NA than Urea and KDP.
(
1 γ xxxx + γ yyyy + γ zzzz + 2γ xxyy + 2γ xxzz + 2γ yyzz 5
)
……………. (7)
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γ =
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The equation for average second hyperpolrizability is
The theoretical second order hyperpolarizability was calculated using Gaussian 09
software [31]. The components of second order hyperpolarizability are given in Table 6. The calculated average second order hyperpolarizability of Urea, KDP and 2M4NA are found to be 7.301 x 10-39 e.s.u, 8.937 x 10-39 e.s.u and 8.762 x 10-39 e.s.u respectively.
ACCEPTED MANUSCRIPT 4.4 Second harmonic generation (SHG) test In order to confirm nonlinear optical (NLO) property, microcrystalline form of pure and urea-doped 2M4NA were packed separately between two transparent glass slides (sample cell).
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A fundamental laser beam of 1064 nm from a Nd:YAG laser was made to fall on the sample cell and Second Harmonic Generation (SHG) was confirmed by emission of green light (λ=532 nm). The green output (532nm) was collected by a photomultiplier tube and finally measured on the storage oscilloscope (CRO) as output voltage. Output signal of 22 mV is obtained for the
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titled compound while the KDP is 15 mV. It is concluded that title compound is 1.2 times
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greater than that of reference KDP and 6.2 times of Urea. Output SHG intensities of Urea, KDP, 2M4NA and the comparative SHG outputs are given in Table 7.
4.5 Frontier Molecular Orbital Energy:
The highest occupied molecular orbital’s (HOMO) and the lowest-lying unoccupied
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molecular orbital’s (LUMO) are named as frontier molecular orbital’s (FMO). The FMO plays an important role in the optical and electric properties, as well as in quantum chemistry [32]. The HOMO represents the ability to donate an electron, LUMO as an electron acceptor,
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represents the ability to obtain an electron. The energy gap between HOMO and LUMO
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determines the kinetic stability, chemical reactivity, optical polarizability and chemical hardness–softness of a molecule [33,34]. The hard molecules are not more polarizable than the soft ones because they need big energy to excitation. In order to evaluate the energetic behavior of the title compound, we carried out calculations in 2M4NA in gas phase. This study reveals that these novel molecular systems have very large first static hyperpolarizabilities and may have potential applications in the development of NLO materials due to the possibility of charge transfer interaction. Molecular HOMOs and LUMOs have been computed using Gaussian 09 software program. The HOMO and LUMO plots are given in Figure 2. From the
ACCEPTED MANUSCRIPT figure the HOMO largely localized on ring with π bond and LUMO is delocalized on in NH2 group through ring with σ bond. The energy of HOMO and LUMO are calculated, because the HOMO–LUMO gap (∆E) is an important parameter for predicting the nonlinear optical properties (NLO) of molecular systems. A low ∆E value indicates more ease of electronic
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transition and hence better NLO properties of a molecule. We make comparison with urea, a well known molecule used for comparative purpose to predict the NLO of molecular systems [35]. The ∆E value of the 2M4NA crystal is calculated as 4.4091 eV, which is lower than that
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of urea (7.431 eV) and KDP (6.835). From this point of view, the calculations predicted that the
SHG also (Table 8).
4.6 Molecular Electrostatic Potential
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studied compound have better NLO properties than urea and KDP, which is confirmed by NLO
The MEP which is a plot of electrostatic potential mapped onto the constant electron
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density surface. The MEP is an useful property to study about reactivity. It is given that an approaching electrophile will be attracted to negative regions (where the electron distribution effect is dominant). In the majority of the MEP, the maximum negative region with preferred
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site for electrophilic attack indicates as red color, and the maximum positive region with preferred site for nucleophilic attack indicates as blue color. The importance of MEP lies in the
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fact that it simultaneously displays molecular size, shape as well as positive, negative and neutral electrostatic potential regions in terms of color grading (Figure 3) and is very useful in research of molecular structure with its physiochemical property relationship [36–39]. The resulting surface simultaneously displays molecular size and shape and electrostatic potential value. The different values of the electrostatic potential at the MEP surface are represented by different colours; red, blue and green which represent the regions of most negative, most positive and zero electrostatic potential, respectively. The colour code of these maps is in the range between -6.23 e a.u. (deepest red) to 6.23 e a.u. (deepest blue) in compound, where blue
ACCEPTED MANUSCRIPT indicates the strongest attraction and red indicates the strongest repulsion. From the figure the positive and negative charges are located at the ends of 2M4NA molecular system, and so the charges are transferred from positive to negative through the phenyl ring in the NLO chromophore 2M4NA. This leads the charge transfer interaction and increasing of the NLO
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activity of the molecules.
4.7 Mulliken and Natural atomic charges
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The reactive atomic charges [40] play an important role in the application of quantum chemical calculation to molecular system, because the atomic charges affects dipole moment,
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polarizability, electronic structure and more properties of molecular system. The total atomic charge values are obtained by Mulliken population analysis by optimized geometry and natural charges are obtained by natural bond orbital analysis (NBO) and are listed in Table S1 (Supplementary material). The two methods predict the same tendencies. The results show that
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all the hydrogen atoms have a net positive charge. Mulliken and Natural atomic charges calculated by B3LYP/6-311++G(d,p) and the charge plots are shown in Figure 4. From the Mullikken charge analysis, it is found that, C2 and C5 atoms exhibit positive charges, while
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C1, C3, C4, C6 and C10 negative charges and C1 atom has maximum negative charge values of about -1.5711 e. The maximum positive atomic charge obtained for C2 is 1.696 e. The
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charge on H18 atom has the maximum magnitude of 0.244 e among the hydrogen atoms present in the molecule. The presence of large negative charge on C2 and net positive charge on H atom may suggest the formation of intramolecular interaction in solid forms [41].
4.8 Vibrational Contribution to charge transfer interaction The vibrational spectroscopy method is used to identify the charge transfer contribution and the NLO activity of the material. . In recent years much work on polyconjugated systems has been done using vibrational spectroscopy in order to find structure–property correlations. In
ACCEPTED MANUSCRIPT particular, infrared and Raman spectroscopy have enabled us to obtain information on the molecular structure of conjugated molecules and on their NLO behavior [30].The computed vibrational wavenumbers, their IR and Raman activities, and the atomic displacements corresponding to the different normal modes have been used to identify the vibrational modes
band shapes
with a band width of
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unambiguously. The simulated IR and Raman spectra have been plotted using pure Lorentzian full wave half maximum (FWHM) of 10cm-1. The
vibrational modes were assigned on the basis of Total Energy distribution (TED) analysis using
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VEDA program [42]. The calculated vibrational wavenumbers, measured infrared and Raman band positions and their tentative assignments are given in Table S2. The experimental FT-IR
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and ft-Raman spectra are shown in Figure 5 and 6.
The allowed tangential C–C stretching modes are 8a, 8b, 19a, 19b and 14 for the disubstituted benzene derivatives[43,44]. The degenerate vibrational pair 8a (1570-1628 1
cm-
) is expected to be larger than 8b (1552-1605 cm-1). The observed band in IR is at 1584 cm-1
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and in Raman is at 1581 cm-1 is assigned to the C-C stretching mode 8a of phenyl ring. With donor substituent’s the ring mode 19a appears in the region 1460-1530 cm-1 and 19b appears in
1
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the region1370-1470cm−1. Mode 19a of phenyl ring is observed as weak band in IR at 1473 cmand in Raman at 1467 cm-1. From the above vibration the simultaneous activation of C-C
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stretching are present in modes 8a and 19a. This simultaneous activation provides evidences for the possibility of charge transfer interaction [43] in 2M4NA. The simultaneous occurrence of 8a and 19a provides evidence for the charge-transfer interaction, which are responsible for hyperpolarizability enhancement and hence NLO activity of the molecule. The charge transfer interaction is supported using Natural bond orbital analysis. The other modes of vibrations are given in Table 3.
ACCEPTED MANUSCRIPT 5. Conclusions The understanding of the structure–property correlation of organic NLO chromophore materials is important for the development of photonic materials. The 2M4NA crystal was
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grown in slow evaporation technique. The structural features of the highly efficient electrooptic crystal 2M4NA as well as the vibrational spectral investigations have been carried out from the NIR FT-Raman and FT-IR spectra aided by the DFT computations. The agreement between the optimized and experimental crystal structure is quite good, which shows that the
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geometry optimization almost exactly reproduces the experimental conformation. The NBO
present in the grown crystal.
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analysis confirms the hyperconjugative interaction and the intramolecular charge interaction
The dipole moment static polarizability, poalrizability, hyperpolarizability and the first order hyperpolarizability of the grown crystal were calculated and it was compared with the
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reference materials Urea and KDP. The result shows that the values are higher than the reference materials. It evidences the increasing NLO activity of the molecule. The experimental NLO activity is also measured using Second Harmonic Generation analysis and it confirms the
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NLO activity of the grown crystal. The NLO efficiency of the grown crystal is 1.2 times greater than that of reference KDP and 6.2 times of Urea . It shows that the grown NLO chromophore
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crystal is a better entrant material to the Photonic application. The vibrational spectral analysis gives the simultaneous activation of 8a and 19a modes. This simultaneous activation provides evidences for the possibility of charge transfer interaction and possibility of increase the NLO activity of the molecule. The molecular electrostatic potential and charges are also calculated. The result supports the charge transfer interactions of the grown 2M4NA crystal.
Acknowledgement:
ACCEPTED MANUSCRIPT The authors thank Dr.I.Hubert Joe, Associate Professor, Centre for Molecular and Bio Physics Research, Mar Ivanios College, Nalanchira, Trivandrum for helping to do the Gaussian09 based Calculation.
Reference:
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[1]. A. Kay, A. Woolhouse, Y. Zhao, K. Clays, J. Mat. Chem. 14 (2004) 1321.
[2]. M. Bass, J.M. Enoch, E.W.V. Stryland, W.L. Wolfe, Handbook of optics IV, fibre
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optics and nonlinear optics, New York, Academic Press, 2001.
[3]. P.N. Prasad, D.R. Ulrich, Nonlinear optical and electroactive polymers, New York,
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Plenum, 1988.
[4]. D.M. Burland, R.D. Miller, C.A. Walsh, Second-order nonlinearity in poledpolymer systems, Chem. Rev. 94 (1994) 31.
Springer, 2003.
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[5]. F. Kajzar, K.S. Lee, A.Y. Jen, Polymers for photonicsapplications II, Berlin Heidelberg,
[6]. M. Hochberg, T. Baehr-Jones, G. Wang, M. Shearn, K. Harvard, J. Luo, et al., Nat
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Mater 5(9) (2006) 703.
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[7]. H. Kang, A. Facchetti, P. Zhu, H. Jiang, Y. Yang, E. Cariati, et al., Angew. Chem. Int. Ed. 44(48) (2005) 7922.
[8]. C. Zhang, L.R. Dalton, M.C. Oh, H. Zhang, W.H. Steie., Chem. Mater. 13(9) (2001) 3043.
[9]. C. Ravikumar, I. Hubert Joe, V.S. Jayakumar Chemical Physics Letters 460 (2008) 552. [10]. J. Whysner, L. Vera, G.M. Williams, Pharmacol. Ther. 71 (1996) 107. [11]. P.J. Krueger, Tetrahedron 26 (1970) 4753.
ACCEPTED MANUSCRIPT [12]. M.A. Palafox, M. Gill, J.L. Nunez, Vibr. Spectrosc. 6 (1993) 95. [13]. J.J. Novoa Fernando Mota, Chem. Phys. Lett. 318 (2000) 345. [14]. P. Tarakeshwar, H.S. Choi, K.S. Kim, J. Am. Chem. Soc. 123 (2001) 3321.
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[15]. M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg,
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M.Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F.
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Ogliaro,M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R.
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Cammi, C.Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,J.V. Ortiz, J. Cioslowski, D.J. Fox, GAUSSIAN 09, Gaussian, Inc.,
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Wallingford CT,2009.
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[16]. A. C Costa Jr1, G.F. Ondar, O. Versiane, J.M. Ramos, T.G. Santos, A.A. Martin, L.Raniero, G.G. Bussi, C.A. Tellez Soto, Spectrochim. Acta A Mol. Biomol.Spectrosc. 105 (2013) 251.
[17]. G. Keresztury, S. Holly, J. Varga, G. Besenyei, A.Y. Wang, J.R. Durig, Spectrochim.Acta A 49 (1993) 2007.
ACCEPTED MANUSCRIPT [18]. G. Keresztury, Raman spectroscopy theory, in: J.M. Chalmers, P.R. Griffith(Eds.), Handbook of Vibrational Spectroscopy, vol. 1, John Wiley & Sons Inc.,Chichester,
2002..
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[19]. J. Chocholousova, V. Spirko, P. Hobza, Phys. Chem. Chem. Phys. 6 (2004) 37. [20]. E.D. Glendening, J.K. Badenhoop, A.E. Reed, J.E. Carpenter, J.A. Bohmann, C.M. Morales, F. Weinhold, NBO 5.0, Theoretical Chemistry Institute, University of
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Wisconsin, Madison, 2001.
C57 (2001) 315
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[21]. G. Ferguson, C. Glidewell, J. N. Low, J. M. S. Skakle and J. L. Wardell Acta Cryst.
[22]. C. James, A. Amal Raj, R. Reghunathan, I. Hubert Joe, V.S. Jayakumar, J. Raman Spectrosc. 37 (2006) 1381.
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[23]. Jun-na Liu, Zhi-Rang Chen, Shen-Fang Yuan, J. Zhejiang Univ. Sci. 6B (2005) 584. [24]. C.R. Zhang, H.S. Chen, G.H. Wang, Chem. Res. Chin. U 20 (2004) 640.
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[25]. Y. Sun, X. Chen, L. Sun, X. Guo, W. Lu, Chem. Phys. Lett. 381 (2003) 397.
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[26]. O. Christiansen, J. Gauss, J.F. Stanton, Chem. Phys. Lett. 305 (1999) 147. [27]. D.A. Kleinman, Phys. Rev. 126 (1977) 1962. [28]. N.S. Labidia,, A. Djebaili, Materials Science and Engineering B169 (2010) 28. [29]. T. Vijayakumar, I. Hubert Joe, C.P. Reghunadhan Nair, V.S. Jayakumar, Chem. Phys. 343 (2008) 83. [30]. N.S. Labidi, A. Djebaili , I. Rouina Journal of Saudi Chemical Society 15 (2011) 29.
ACCEPTED MANUSCRIPT [31]. D. Young, Computational Chemistry: A Practical Guide for Applying Techniques to Real World Problems, John Wiley & Sons, New York, 2001. [32]. I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London,
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1976. [33]. A.M. Asiri, M. Karabacak, M. Kurt, K.A. Alamry, Spectrochim. Acta A 82 (2011) 444.
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[35]. L.S. Pu, ACS Symp. Ser. 455 (1991) 331.
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[34]. B. Kosar, C. Albayrak, Spectrochim. Acta A 78 (2011) 160.
[36]. J.S. Murray, K. Sen, Molecular Electrostatic Potentials, Concepts and 399 Applications, Elsevier, Amsterdam, 1996.
[37]. E. Scrocco, J. Tomasi, in: P. Lowdin (Ed.), Advances in Quantum Chemistry,
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Academic Press, New York, 1978.
[38]. F.J. Luque, M. Orozco, P.K. Bhadane, S.R. Gadre, J. Phys. Chem. 97 (1993) 9380.
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[39]. J. Sponer, P. Hobza, Int. J. Quant. Chem. 57 (1996) 959. [40]. V.K. Rastogi, M.A. Palafox, L. Mittai, N. Perica, W. Kiefer, K. Lang, P. Ohja,
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J.Raman Spectrosc. 38 (2007) 1227.
[41]. L. Xiao-Hong, Z. Xian-Zhou, Comput. Theor. Chem. 969 (2011) 27. [42]. M. H. Jamroz , Vibrational energy distribution analysis VEDA 4, Warsaw,
2004.
[43]. M. Amalanathan, T.S. Xavier, I. Hubert Joe, V.K. Rastogi, Spectrochimica Acta Part A: 116 (2013) 574. [44]. C.Ravikumar, I.Hubert Joe, Phys. Chem. Chem. Phys. 12 (2010) 94542.
ACCEPTED MANUSCRIPT Figure Captions: Figure 1. Optimized structure of 2M4NA calculated at DFT level Figure 2. HOMO and LUMO pot of 2M4NA crystal Figure 3. Molecular electrostatic potential plot of 2M4NA
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Figure 4. Mulliken and Natural charge plots of 2M4NA crystal Figure 5.FT-IR spectra of 2M4NA crystal in the range 4000-400 cm-1
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Figure 6. FT-Raman spectra of 2M4NA crystal in the range 4000-50 cm-1
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119.1 120.2 121.3 121.1 119.5 120.0 120.0 119.4 109.5 109.5 109.5 120.0 120.2 119.7 118.5 120.9 119.4
C1 – C2 –C3 – C4 C2 – C3 –C4 – C5 C3 – C4 –C5 – C6 C5 – C6 –C1 – N7 C6 – C1 –N7 – H8 C6 – C1 –N7 – H9 C6 – C1 –C2 – C10 C1 – C2 –C10 – H11 C1 – C2 –C10 – H12 C1 – C2 –C10 – H13 C1 – C2 –C3 – H14 C2 – C3 –C4 – N15 C3 – C4 –H15 – O16 C3 – C4 –H15 – O17 C3 – C4 –C5 – H18 C4 – C5 –C6 – H19
-0.17 -0.03 0.13 -177.85 -16.06 -161.81 -1.78 58.89 -61.45 178.93 179.91 179.93 -0.07 179.96 180.0 -179.9
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118.6 120.8 121 118.9 120.0 117.9 118.7 120.4 111.8 110.9 110.9 120.4 119.4 118.0 117.9 119.7 119.7
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C1 – C2 – C3 C2 – C3 – C4 C3 – C4 – C5 C4 – C5 – C6 C6 – C1 – N7 C1 – N7 – H8 C1 – N7 – H9 C1 – C2 – C10 C2 – C10 – H11 C2 – C10 – H12 C2 – C10 – H13 C2 – C3 – H14 C3 – C4 – N15 C4 – H15 – O16 C4 – H15 – O17 C4 – C5 – H18 C5 – C6 – H19
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1.415 1.381 1.399 1.387 1.378 1.358 0.86 0.86 1.505 0.96 0.96 0.96 0.93 1.433 1.233 1.231 0.93 0.93
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1.418 1.388 1.394 1.393 1.383 1.38 1.008 1.007 1.507 1.096 1.090 1.090 1.082 1.462 1.230 1.229 1.081 1.085
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C1 – C2 C2 – C3 C3 – C4 C4 – C5 C5 – C6 C1 – N7 N7 – H8 N7 – H9 C2 – C10 C10 – H11 C10 – H12 C10 – H13 C3 – H14 C4 – N15 N15 – O16 N15 – O17 C5 – H18 C6 – H19
Values (/º) Exp Cal.
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Table 1:The DFT level calculated optimized geometrical parameters. Value (Å) Values (/º) Bond Dihedral Angles Exp Exp Cal. Cal. Length Angles
0.42 -0.96 0.90 -179.40 179.67 -0.1 0.14 65.85 -54.12 -174.16 -179.58 179.63 0.68 -179.72 -179.09 179.65
ACCEPTED MANUSCRIPT Table 2:Second order perturbation theory analysis of Fock matrix in NBO basis. ED(i)
ED(j)
b E(j)– E(i) a.u
c F (ij) a.u
π* (C3 – C4)
0.42542
28.15
0.28
0.079
π* (C5 – C6)
0.30621
15.07
0.28
0.060
π* (C1 – C2)
0.42023
16.08
0.29
0.061
π* (C5 – C6)
0.30621
23.17
0.29
0.074
π* (C1 – C2)
0.42023
21.97
0.28
0.073
π* (C3 – C4)
0.42542
15.62
0.28
0.061
1.64617
π* (N15 – O17)
0.64636
32.14
0.14
0.065
LP(1) N7
1.80196
π* (C1 – C2)
32.54
0.32
0.096
LP(2) O16
1.90209
σ* (C4 – N15)
11.43
0.58
0.073
LP(2) O16
1.90209
σ* (N15 – O17)
0.05481
18.92
0.72
0.105
LP(3) O16
1.46723
π* (N15 – O17)
0.64636
159.04
0.14
0.137
LP(2) O17
1.90186
σ*(C4 – N15)
11.45
0.58
0.073
LP(2) O17
1.90186
σ* (N15 – O16)
18.93
0.72
0.105
1.64617
π (C5 – C6)
1.71230
π (C3 – C4)
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π (C3 – C4)
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1.56543
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π (C1 – C2)
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(e)
Acceptor NBO (j)
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(e)
a E (2) KJ/mol
Donor NBO (i)
0.42023
0.09739
0.09739
0.05506
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Urea
KDP
2M4NA -2.673
1.282
2.114
µy
0.264
0.00004
-0.254
µz
-1.354
-0.830
-5.514
Total
3.008 Debye
1.527 Debye
5.911 Debye
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Dipole moment µx
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Table 3: Calculated Dipole moment and total dipole moment of 2M4NA, Urea and KDP at DFT level
ACCEPTED MANUSCRIPT Table 4: Calculated Polarizabilities Static Polarizabilities and Total Polarizabilities moment of 2M4NA, Urea and KDP at DFT level 2M4NA 159.631
Urea 39.260
αxy
0.027
0.2947
KDP 46.619 0.459
αyy
60.352
24.690
46.805
αxz
17.712
-1.159
0.778
αyz
0.180
0.454
αzz
124.646
38.219
17.024 x 10-24 e.s.u
5.664 x 10-24 e.s.u
7.289 x 10-24 e.s.u
22.698 x 10-24 e.s.u
6.304 x 10-24 e.s.u
12.656 x 10-24 e.s.u
Static Polarizability (α0)
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Total Polarizability (∆α)
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Polarizabilities αxx
-0.790
54.1384
ACCEPTED MANUSCRIPT Table 5: Calculated First order Polarizabilities and Total First order Polarizabilities moment of 2M4NA, Urea and KDP at DFT level Urea
KDP
2M4NA 1143.903
24.729
βxxy
14.408
-0.499
132.383 -5.841
βxyy
-81.109
31.817
63.361
βyyy
9.555
0.0066
βxxz
785.197
-61.443
βxyz
4.9009
-0.225
βyyz
-49.718
-20.593
βxzz
355.405
19.374
βyzz
7.762
0.5057
βzzz
37.449
32.896
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First order Polarizabilities βxxx
-26.762
-43.435 -1.802
-118.569
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110.151 13.681
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-636.568
0.781 x 10-30 e.s.u
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13.956 x 10-30 e.s.u
7.390 x 10-30 e.s.u
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Urea
KDP
2M4NA 2.31375
-4.95
γxxxx
-0.2351917 -1.28532
-4.789
γxxyy
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-1.8785
9.747
3.5990723 γyyyy
2.1137123
0.235
-1.81515 γyyzz
1.2790763
5.361
2.55444 γzzzz
2.6165167 1.9762432 7.301 x 10-39 e.s.u
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8.762 x 10-39 e.s.u
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3.914
3.19399 γzzzz
8.937 x 10-39 e.s.u
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Urea
3.5
KDP
15
2M4NA
22
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Specimen
ACCEPTED MANUSCRIPT Table 8:The Frontier Molecular orbital energies and HOMO-LUMO energy gap of 2M4NA, Urea and KDP at DFT Level 2M4NA Urea KDP (eV) (eV) (eV) -6.503 -9.739 -9.5759 -2.412 -2.307 -2.741 4.091 7.431 6.835
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MO’s HOMO LUMO HOMO-LUMO gap
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DFT calculations have been performed on the NLO crystal 2-Methyl-4-Nitroaniline (2M4nA) Calculation
such
as
Optimized
geometry,
Hyperpolarizabilities were calculated The IR and Raman spectra of the compound were analyzed.
NBO,
The NLO activity of the crystal was confirmed by SHG analysis.
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HOMO and LUMO analysis were also performed by DFT approach.
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charge
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Theoretical
and
S0022-2860(16)30107-7
DOI:
10.1016/j.molstruc.2016.02.013
Reference:
MOLSTR 22222
To appear in:
Journal of Molecular Structure
Received Date: 16 November 2015 Revised Date:
3 February 2016
Accepted Date: 3 February 2016
Please cite this article as: G.F. Jasmine, M. Amalanathan, S.D.D. Roy, Molecular structure and Charge transfer contributions to nonlinear optical property of 2-Methyl-4-Nitroaniline: A DFT Study, Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.02.013. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Molecular structure and Charge transfer contributions to nonlinear optical property of 2-Methyl-4-Nitroaniline: A DFT Study G.Femina Jasminea, M. Amalanathanb* and S.Dawn Dharma Royc Department of Physics , Bethlahem Institute of Engineering, Kanyakumari District, Tamil Nadu.
b
Department of Physics, Annai Velankanni College, Tholayavattam- 629157, Tamil Nadu. C
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a
Department of Physics. NMCC, Marthandom - 629 165Tamil Nadu.
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Abstract
The Charge transfer contributions to the second-order nonlinear optical properties of 2-
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Methyl-4-nitroaniline have been performed by means of DFT computation. The vibrational contribution studies of 2-Methyl-4-nitroaniline have also been performed using FTIR, FTRaman analysis. More support on the experimental findings were added from the quantum chemical studies performed with DFT (B3LYP) method using 6-311++G(d,p)basis sets.
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Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. The HOMO and LUMO analysis reveals the possibility of charge transfer within the molecule. The first order hyperpolarizability (α0) and related
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properties (β,α0 and ∆α) of 2-Methyl-4-nitroaniline were calculated. In addition, molecular electrostatic potential (MEP), charge analysis also were investigated using theoretical
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calculations.
Keywords: Charge transfer contribution; DFT; Polarizability ; Hyperpolarizabilities; NBO; HOMO-LUMO Energy.
*Corresponding author: M.AMALANATHAN; Department of Physics, Annai Velankanni College, Tholayavattam- 629157, Tamil Nadu. Tel: +91-9940347178 E-mail: [email protected]
ACCEPTED MANUSCRIPT Introduction Materials having large second-order nonlinear optic (NLO) properties are in demand due to their potential applications in photonic devices and optical information processing[1-3]. Organic NLO materials have drawn much attention because of their attractive potential
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applications in optical data transmission and optical information processing[5]. Compared with traditional inorganic and semiconductor materials, the organic NLO materials have many advantages such as larger nonlinear optical coefficients, simpler preparation and lower cost [6].
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At a fundamental level, organic push pull NLO chromophores contain electron-donor and electron-acceptor groups at opposite ends of a p-conjugated spacer[4], and the vast majority of
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known organic NLO compounds utilize aromatic linkers in the p-conjugated bridge. [6]. Generally, the nonlinear optical (NLO) chromophore molecules possessing a dipolar D-π-A type structure is the core component in such materials, which turned the design and preparation of NLO chromophores into a research hotspot in the area of organic NLO materials[7,8]. Many
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great attentions have been paid to the rational design of chromophores with not only high firstorder hyperpolarizability but also good thermal and photochemical stabilities. In recent years much work on poly conjugated systems has been done using vibrational spectroscopy and DFT
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computation in order to find structure–property correlations. In particular, Infrared and Raman spectroscopy have enabled us to obtain information on the molecular structure of conjugated
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molecules and on their NLO behaviour [9]. Spectroscopic studies on aniline and its derivatives have been studied extensively
[10,12], since they are widely used in commercial and industrial purposes, including pesticide, pharmaceuticals manufacturing and chemical dye industries. Nitro anilines share the common feature of having an electron-rich (donor, –NH2) and an electron-deficient (acceptor, –NO2) substituent, connected by a conjugated π-electron system. Nitro anilines belong to push–pull molecules due to the intra-molecular charge transfer (ICT) from the electron-donor group
ACCEPTED MANUSCRIPT through the phenyl ring to the electron-acceptor group. Aniline derivatives can form inter- and intra-molecular hydrogen bonding in solid state which imparts innovative properties in compounds. Inter- and intramolecular hydrogen bonding interactions [13,14] and these can be
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lead to increase the NLO activity of the materials. Currently, quantum mechanical calculations are very popular because of their efficiency and accuracy with respect to the evaluation of a number of molecular properties. In the present investigation, the growth of 2M4NA single crystals and the detailed vibrational
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spectral analysis of the molecule in the crystalline state is taken up to understand the correlation
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of the charge transfer interactions and NLO activity of the molecule. The structure activity relation supported by the NBO calculation and HOMO-LUMO energy calculation. 2. Experimental 2.1. Synthesis
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The title compound 2-Methyl-4-nitroaniline was synthesized by mixing in methanol solution. The mixture was stirred at room temperature for 3 hours and 2M4NA salt was
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obtained as precipitate. The product was purified by re crystallization using mixed solvent, methanol and acetone. The purified salt was mixed with the methanol solution and it is allowed
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to evaporate at room temperature, After 2 weeks tiny 2M4NA crystals were obtained. 2.2. IR and Raman measurements The FT-IR spectrum of 2M4NA was recorded using Perkin–Elmer RXI spectrometer in
the region 4000–400 cm-1 , with samples in the KBr. The resolution of the spectrum is 4 cm -1. The NIR-FT Raman spectrum of 2M4NA crystal was obtained in the range 3500–10 cm-1 using Bruker RFS 100/S FT Raman spectrophotometer with a 1064 nm Nd:YAG laser source of 100 mW power. Liquid nitrogen cooled Ge-diode was used as a detector.
ACCEPTED MANUSCRIPT 2.3 Powder SHG Powder second harmonic generation efficiency of the grown crystal was determined using modified Kurtz and Perry method. Q-switched mode locked Nd:YAG laser was used as a
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optical source. The crystals were grained into powder and densely packed between two glass slides. The input energy was measured using power meter and it is 4.6mJ/s. 3. Computational Techniques
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All the electronic structure calculations have been carried out using Gaussian ‘09 program package [15]. The geometry is fully optimized at the Becke3–Lee–Yang–Parr
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(B3LYP) level with standard 6-311++G(d,p)basis set[16]. The computed wavenumbers were scaled by an empirical scaling factor of 0.97[17] to fit with the experimental wavenumbers, which accounts for systematic errors caused by basis set incompleteness, neglect of electron correlation and vibrational anharmonicity. Since the electron correlation effects have been
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extensively considered in DFT method, a precisely predicted structure of the molecule can be evolved. The Raman activities (Si) calculated by Gaussian ‘09 are converted to relative Raman
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intensities (Ii) using the relation derived from the basic theory of Raman scattering[18,19].
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f (ν o − ν i ) 4 S i Ii = − hcν i ν i 1 − exp kT
................. (1)
where νo is the exciting frequency ( in cm-1 units), νi is the vibrational wavenumber
of the ith normal mode, h, c and k are universal constants, and ƒ is the suitably chosen common scaling factor for all the peak intensities.The natural bonding orbital calculations were done at the B3LYP method in order to investigate the optimized geometry corresponding to charge transfer interaction. The hyperconjugative interaction energy was deduced from the second-
ACCEPTED MANUSCRIPT order perturbation approach [20]. The frontier molecular orbital’s and the HOMO–LUMO energy gap has been computed. 4. Result and Discussion
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4.1 Optimized Geometry From the single crystal XRD data[21] it is found that, the 2M4NA crystal belongs to orthorhombic system with the following cell dimensions: a=7.6113 Å, b=11.6304 Å, c =
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8.2286 Å, α = 90° β = 94.05 γ =90°. For doing theoretical calculations, the initial parameters are taken from [21] and structural optimizations have been done. The ground state optimized
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structure of the 2M4NA molecule is presented in Figure 1. The optimized and experimental structures of the molecule are compared. The agreement between the optimized and experimental crystal structure is quite good, which shows that the geometry optimization almost exactly reproduces the experimental conformation. The Optimized structure of 2M4NA,
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which is determined by using DFT method, is shown in Figure.1. The optimized geometrical parameters are summarized in Table 1. Our calculated structural parameters using B3LYP show a comparable agreement with the experimental ones. From the theoretical values, one can
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find that most of the optimized bond lengths are larger than the experimental values, because
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the theoretical calculations refer to isolated molecules in the gaseous phase and the experimental results are for molecules in the solid state. The C–H bond lengths obtained from the experimental value [21] range from 0.95 to 0.98 Å; while of theoretical values ranges between 1.08 and 1.09 Å. This larger deviation of C–H bond lengths may be due to the low scattering factors of hydrogen atoms in X-ray diffraction experiments which are not included in the theoretical calculations.
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level. Natural bond orbital analysis is an essential tool for studying intra and intermolecular bonding interaction of 2M4NA. It also provides a convenient basis for investigating charge transfer or conjugative interaction in molecular systems. Some electron donor orbital, acceptor orbital and the interacting stabilization energy resulting from the second–order micro
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disturbance theory is reported [23,24]. The hyper-conjugative interaction energy was deduced
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Fij2 σ Fσ E (2) = −nσ = −nσ εσ* − εσ ∆E 2
……….(2)
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where 〈σ|F|σ〉2, or F2ij is the Fock matrix element between i and j NBO orbitals, εσ and εσ∗ are the energies of σ and σ* NBO's and nσ is the population of the donor σ orbital. Table 2
energies E(2).
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shows some of the significant donor–acceptor interactions and their second order perturbation
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The interactions formed by the orbital overlap between π (C – C) -π* (C – C), LP(1)-
π*(C – C), LP(1)- σ*(C – C) bond orbital which results in intermolecular charge transfer (ICT) causing stabilization of the system. These charge transfer interaction are possible to increase the induce large nonlinearity of the molecule. The larger the E(2) values, the more intensive is the interaction between electron donors
and electron acceptors. The intramolecular
hyperconjugative interactions are formed by the orbital overlap between π(C–C) and π*(C–C) bond orbital’s which results in intramolecular charge transfer (ICT) causing stabilization of the system. These interactions are observed as an increase in electron density (ED) in C–C
ACCEPTED MANUSCRIPT antibonding orbital that weakens the respective bonds. The ED at the eight conjugated π bonds (1.56-1.71 e) and π* bonds (~0.30-0.42 e) of the phenyl ring clearly demonstrates the strong delocalization of electron leading to stabilization of (~21-28 kJ/mol) energy. This intramolecular charge transfer leads the NLO activity of the molecule. The maximum energy
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transfer from lone pair (O1o) to π*(N15AO17) (159.04 kJ/mol), clearly demonstrates the intermolecular hyper conjugative interaction between the lone pair atoms of the molecule to other part are strong in the ground state and listed in Table 2. It is also evident from the
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decreasing of electron density in lone pair oxygen and increasing of electron density in the π*(N15-O17) bonding. These charge transfer interactions of 2M4NA are also responsible for N
4.3 Non linear optical analysis
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LO properties. Other possible interactions of 2M4NA are listed in table.
Density functional theory has been used as an effective method to investigate the
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organic non-linear optical (NLO) materials. Recent research works have illustrated that the organic non-linear optical materials are having high optical non-linearity than inorganic materials [25]. In the presence of an applied electric field, the energy of a system is a function
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of the electric field. Polarizabilities and hyperpolarizabilities characterize the response of a system in an applied electric field [26]. They determine not only the strength of molecular
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interactions but also the cross sections of different scattering and collision processes, as well as the NLO properties of the system [27,29]. For this subject, in this study the electronic dipole moment, molecular polarizability, anisotropy of polarizability and molecular first hyperpolarizability of present compound were investigated. The electric dipole moment µ polarizability α, the hyper polarizability β and first order hyperpolarizability γ of the of title compound are calculated by finite field method using B3LYP/6-311++G(d,p) basis set available in Gaussian 09 package.
ACCEPTED MANUSCRIPT In the presence of an applied electric field, the energy of a system is a function of the electric field and the first hyperpolarizability is a third rank tensor that can be described by a 3 x 3 x 3 matrix. The 27 components of the 3D matrix can be reduced to 10 components because of the Kleinman symmetry [28]. The matrix can be given in the lower tetrahedral format. It is
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obvious that the lower part of the 3x 3 x 3 matrices is a tetrahedral. The components of b are defined as the coefficients in the Taylor series expansion of the energy in the external electric field. When the external electric field is weak and homogeneous, this expansion is given below:
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E = Eº- µi Fi – ½ α ij FiFj – 1/6 βijk FiFj Fk - 1/24 γijkl FiFj Fk Fl + …….
(3)
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where Eo is the energy of the unperturbed molecules, Fi is the field at the origin µiα ij , βijk and γijkl are the components of dipole moment, polarizabiltiy, first and second order hyperpolarizability respectively. These studies led to the fact that ab initio calculations of polarizabilities and hyperpolarizabilities have become available through the strong theoretical
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basis for analyzing molecular interactions. They made possible the determination of the elements of these tensors from derivatives of the dipole moment with respect to the electric field.
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The total static dipole moment µ, the mean polarizability α0, the anisotropy of the polarizability ∆α and the mean first hyperpolarizability βo, using the x-, y- and z- components
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are defined as
µ = ( µ x2 + µ y2 + µ z2 )
1
2
The dipole moment µ, NLO material Urea, KDP and 2M4NA crystal are calculated
using
DFT level. The three dipole moment component of NLO material Urea and KDP and
2M4NA crystal are given in Table 3 and the total dipole moment is found to be1.527 Debye, 3.008 Debye and 5.911 Debye respectively.
α 0 = (α xx + α yy + α zz ) 3
ACCEPTED MANUSCRIPT ∆α = 2
−1
2
1
[(α xx − α yy ) 2 + (α yy − α zz ) 2 + (α zz − α xx ) 2 + 6α xz2 ] 2 …… (4)
The other components of the polarizability (αxy, αxz,etc.) are not needed to obtain the isotropic quantity. The polarizability components of
Urea, KDP and 2M4NA are given in Urea, KDP and
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Table 4. From the polarizability component the static polarizabilities of
2M4NA are calculated, which is found to be 5.664 x 10-24 e.s.u , 7.289 x 10-24 e.s.u and 17.024 x 10-24 e.s.u respectively. The dynamic polarizabilities are found to be 6.304x 10-24 e.s.u,
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12.656 x 10-24 e.s.u, 22.698 x 10-24 e.s.u respectively. From the above result the static and dynamic polarizability of 2M4NA material is comparatively larger than the NLO reference
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material Urea and KDP. It confirms that the strong electron donor’s acceptor molecules increase their linear polarizabilities are became larger than other. The addition of large end groups –NO2, leads to an increase of mean polarizability and also leads to an increase of longitudinal polarizability αxx. From these results, it is inferred that strong charge transfer
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substitutions are the good candidates for systems with large polarizabilities [29,30]. The first order hyperpolarizability β was also calculated using the finite field approach theory. The components of First hyperpolarizability can be calculated using the following
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equation
(
)
1 ∑ βijj + β jij + β jji , ( i ≠ j ) 3
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β i = β iii +
Using the x,y and z components, the magnitude of the first hyperpolarizability tensor can be calculated using
βtot = ( β x2 + β y2 + β z2 )
1
2
……………
(5)
The complete equation for calculating the magnitude of the first hyperpolarizability from Gaussian 09 output is as follows.
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(
β = β xxx + β xyy + β xzz
) + (β 2
yyy
+ β yzz + β yxx
) + (β 2
zzz
+ β zxx + β zyy
)
1
2
2 ……. (6)
The ten hyperpolarizability components of Urea, KDP and 2M4NA are given in Table 5. The first order hyperpolarizability of Urea, KDP and 2M4NA are calculated at DFT level
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and is found to be 0.781 x 10-30 e.s.u., 7.390 x 10-30 e.s.u and 13.956 x 10-30 e.s.u. respectively. The above result shows that the NLO activity of 2M4NA is 17.8 times that of urea and 9.6 times that of KDP. The β values are large for 2M4NA compared to Urea and KDP. The result
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indicates also that the magnitude of first hyperpolarizability β of molecules is dependent upon the availability of the lone pair of electrons on the nitrogen atom to conjugate with the Phenyl
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ring. The dramatic increase of first hyperpolarizability has been observed when the lone pair on the nitrogen atom of the donor groups is forced to conjugate with the phenyl ring, upon substitution on nitrogen of –NH2 group with other groups such as methyl[31]. From the above result it confirms that the increase of polarizability increase the NLO activity of the molecule.
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The increase of polarizability is due to the increasing of charge transfer interaction inside the molecule, which leads the greater NLO activity of 2M4NA than Urea and KDP.
(
1 γ xxxx + γ yyyy + γ zzzz + 2γ xxyy + 2γ xxzz + 2γ yyzz 5
)
……………. (7)
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γ =
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The equation for average second hyperpolrizability is
The theoretical second order hyperpolarizability was calculated using Gaussian 09
software [31]. The components of second order hyperpolarizability are given in Table 6. The calculated average second order hyperpolarizability of Urea, KDP and 2M4NA are found to be 7.301 x 10-39 e.s.u, 8.937 x 10-39 e.s.u and 8.762 x 10-39 e.s.u respectively.
ACCEPTED MANUSCRIPT 4.4 Second harmonic generation (SHG) test In order to confirm nonlinear optical (NLO) property, microcrystalline form of pure and urea-doped 2M4NA were packed separately between two transparent glass slides (sample cell).
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A fundamental laser beam of 1064 nm from a Nd:YAG laser was made to fall on the sample cell and Second Harmonic Generation (SHG) was confirmed by emission of green light (λ=532 nm). The green output (532nm) was collected by a photomultiplier tube and finally measured on the storage oscilloscope (CRO) as output voltage. Output signal of 22 mV is obtained for the
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titled compound while the KDP is 15 mV. It is concluded that title compound is 1.2 times
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greater than that of reference KDP and 6.2 times of Urea. Output SHG intensities of Urea, KDP, 2M4NA and the comparative SHG outputs are given in Table 7.
4.5 Frontier Molecular Orbital Energy:
The highest occupied molecular orbital’s (HOMO) and the lowest-lying unoccupied
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molecular orbital’s (LUMO) are named as frontier molecular orbital’s (FMO). The FMO plays an important role in the optical and electric properties, as well as in quantum chemistry [32]. The HOMO represents the ability to donate an electron, LUMO as an electron acceptor,
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represents the ability to obtain an electron. The energy gap between HOMO and LUMO
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determines the kinetic stability, chemical reactivity, optical polarizability and chemical hardness–softness of a molecule [33,34]. The hard molecules are not more polarizable than the soft ones because they need big energy to excitation. In order to evaluate the energetic behavior of the title compound, we carried out calculations in 2M4NA in gas phase. This study reveals that these novel molecular systems have very large first static hyperpolarizabilities and may have potential applications in the development of NLO materials due to the possibility of charge transfer interaction. Molecular HOMOs and LUMOs have been computed using Gaussian 09 software program. The HOMO and LUMO plots are given in Figure 2. From the
ACCEPTED MANUSCRIPT figure the HOMO largely localized on ring with π bond and LUMO is delocalized on in NH2 group through ring with σ bond. The energy of HOMO and LUMO are calculated, because the HOMO–LUMO gap (∆E) is an important parameter for predicting the nonlinear optical properties (NLO) of molecular systems. A low ∆E value indicates more ease of electronic
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transition and hence better NLO properties of a molecule. We make comparison with urea, a well known molecule used for comparative purpose to predict the NLO of molecular systems [35]. The ∆E value of the 2M4NA crystal is calculated as 4.4091 eV, which is lower than that
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of urea (7.431 eV) and KDP (6.835). From this point of view, the calculations predicted that the
SHG also (Table 8).
4.6 Molecular Electrostatic Potential
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studied compound have better NLO properties than urea and KDP, which is confirmed by NLO
The MEP which is a plot of electrostatic potential mapped onto the constant electron
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density surface. The MEP is an useful property to study about reactivity. It is given that an approaching electrophile will be attracted to negative regions (where the electron distribution effect is dominant). In the majority of the MEP, the maximum negative region with preferred
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site for electrophilic attack indicates as red color, and the maximum positive region with preferred site for nucleophilic attack indicates as blue color. The importance of MEP lies in the
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fact that it simultaneously displays molecular size, shape as well as positive, negative and neutral electrostatic potential regions in terms of color grading (Figure 3) and is very useful in research of molecular structure with its physiochemical property relationship [36–39]. The resulting surface simultaneously displays molecular size and shape and electrostatic potential value. The different values of the electrostatic potential at the MEP surface are represented by different colours; red, blue and green which represent the regions of most negative, most positive and zero electrostatic potential, respectively. The colour code of these maps is in the range between -6.23 e a.u. (deepest red) to 6.23 e a.u. (deepest blue) in compound, where blue
ACCEPTED MANUSCRIPT indicates the strongest attraction and red indicates the strongest repulsion. From the figure the positive and negative charges are located at the ends of 2M4NA molecular system, and so the charges are transferred from positive to negative through the phenyl ring in the NLO chromophore 2M4NA. This leads the charge transfer interaction and increasing of the NLO
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activity of the molecules.
4.7 Mulliken and Natural atomic charges
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The reactive atomic charges [40] play an important role in the application of quantum chemical calculation to molecular system, because the atomic charges affects dipole moment,
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polarizability, electronic structure and more properties of molecular system. The total atomic charge values are obtained by Mulliken population analysis by optimized geometry and natural charges are obtained by natural bond orbital analysis (NBO) and are listed in Table S1 (Supplementary material). The two methods predict the same tendencies. The results show that
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all the hydrogen atoms have a net positive charge. Mulliken and Natural atomic charges calculated by B3LYP/6-311++G(d,p) and the charge plots are shown in Figure 4. From the Mullikken charge analysis, it is found that, C2 and C5 atoms exhibit positive charges, while
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C1, C3, C4, C6 and C10 negative charges and C1 atom has maximum negative charge values of about -1.5711 e. The maximum positive atomic charge obtained for C2 is 1.696 e. The
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charge on H18 atom has the maximum magnitude of 0.244 e among the hydrogen atoms present in the molecule. The presence of large negative charge on C2 and net positive charge on H atom may suggest the formation of intramolecular interaction in solid forms [41].
4.8 Vibrational Contribution to charge transfer interaction The vibrational spectroscopy method is used to identify the charge transfer contribution and the NLO activity of the material. . In recent years much work on polyconjugated systems has been done using vibrational spectroscopy in order to find structure–property correlations. In
ACCEPTED MANUSCRIPT particular, infrared and Raman spectroscopy have enabled us to obtain information on the molecular structure of conjugated molecules and on their NLO behavior [30].The computed vibrational wavenumbers, their IR and Raman activities, and the atomic displacements corresponding to the different normal modes have been used to identify the vibrational modes
band shapes
with a band width of
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unambiguously. The simulated IR and Raman spectra have been plotted using pure Lorentzian full wave half maximum (FWHM) of 10cm-1. The
vibrational modes were assigned on the basis of Total Energy distribution (TED) analysis using
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VEDA program [42]. The calculated vibrational wavenumbers, measured infrared and Raman band positions and their tentative assignments are given in Table S2. The experimental FT-IR
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and ft-Raman spectra are shown in Figure 5 and 6.
The allowed tangential C–C stretching modes are 8a, 8b, 19a, 19b and 14 for the disubstituted benzene derivatives[43,44]. The degenerate vibrational pair 8a (1570-1628 1
cm-
) is expected to be larger than 8b (1552-1605 cm-1). The observed band in IR is at 1584 cm-1
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and in Raman is at 1581 cm-1 is assigned to the C-C stretching mode 8a of phenyl ring. With donor substituent’s the ring mode 19a appears in the region 1460-1530 cm-1 and 19b appears in
1
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the region1370-1470cm−1. Mode 19a of phenyl ring is observed as weak band in IR at 1473 cmand in Raman at 1467 cm-1. From the above vibration the simultaneous activation of C-C
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stretching are present in modes 8a and 19a. This simultaneous activation provides evidences for the possibility of charge transfer interaction [43] in 2M4NA. The simultaneous occurrence of 8a and 19a provides evidence for the charge-transfer interaction, which are responsible for hyperpolarizability enhancement and hence NLO activity of the molecule. The charge transfer interaction is supported using Natural bond orbital analysis. The other modes of vibrations are given in Table 3.
ACCEPTED MANUSCRIPT 5. Conclusions The understanding of the structure–property correlation of organic NLO chromophore materials is important for the development of photonic materials. The 2M4NA crystal was
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grown in slow evaporation technique. The structural features of the highly efficient electrooptic crystal 2M4NA as well as the vibrational spectral investigations have been carried out from the NIR FT-Raman and FT-IR spectra aided by the DFT computations. The agreement between the optimized and experimental crystal structure is quite good, which shows that the
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geometry optimization almost exactly reproduces the experimental conformation. The NBO
present in the grown crystal.
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analysis confirms the hyperconjugative interaction and the intramolecular charge interaction
The dipole moment static polarizability, poalrizability, hyperpolarizability and the first order hyperpolarizability of the grown crystal were calculated and it was compared with the
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reference materials Urea and KDP. The result shows that the values are higher than the reference materials. It evidences the increasing NLO activity of the molecule. The experimental NLO activity is also measured using Second Harmonic Generation analysis and it confirms the
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NLO activity of the grown crystal. The NLO efficiency of the grown crystal is 1.2 times greater than that of reference KDP and 6.2 times of Urea . It shows that the grown NLO chromophore
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crystal is a better entrant material to the Photonic application. The vibrational spectral analysis gives the simultaneous activation of 8a and 19a modes. This simultaneous activation provides evidences for the possibility of charge transfer interaction and possibility of increase the NLO activity of the molecule. The molecular electrostatic potential and charges are also calculated. The result supports the charge transfer interactions of the grown 2M4NA crystal.
Acknowledgement:
ACCEPTED MANUSCRIPT The authors thank Dr.I.Hubert Joe, Associate Professor, Centre for Molecular and Bio Physics Research, Mar Ivanios College, Nalanchira, Trivandrum for helping to do the Gaussian09 based Calculation.
Reference:
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[1]. A. Kay, A. Woolhouse, Y. Zhao, K. Clays, J. Mat. Chem. 14 (2004) 1321.
[2]. M. Bass, J.M. Enoch, E.W.V. Stryland, W.L. Wolfe, Handbook of optics IV, fibre
SC
optics and nonlinear optics, New York, Academic Press, 2001.
[3]. P.N. Prasad, D.R. Ulrich, Nonlinear optical and electroactive polymers, New York,
M AN U
Plenum, 1988.
[4]. D.M. Burland, R.D. Miller, C.A. Walsh, Second-order nonlinearity in poledpolymer systems, Chem. Rev. 94 (1994) 31.
Springer, 2003.
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[5]. F. Kajzar, K.S. Lee, A.Y. Jen, Polymers for photonicsapplications II, Berlin Heidelberg,
[6]. M. Hochberg, T. Baehr-Jones, G. Wang, M. Shearn, K. Harvard, J. Luo, et al., Nat
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Mater 5(9) (2006) 703.
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[7]. H. Kang, A. Facchetti, P. Zhu, H. Jiang, Y. Yang, E. Cariati, et al., Angew. Chem. Int. Ed. 44(48) (2005) 7922.
[8]. C. Zhang, L.R. Dalton, M.C. Oh, H. Zhang, W.H. Steie., Chem. Mater. 13(9) (2001) 3043.
[9]. C. Ravikumar, I. Hubert Joe, V.S. Jayakumar Chemical Physics Letters 460 (2008) 552. [10]. J. Whysner, L. Vera, G.M. Williams, Pharmacol. Ther. 71 (1996) 107. [11]. P.J. Krueger, Tetrahedron 26 (1970) 4753.
ACCEPTED MANUSCRIPT [12]. M.A. Palafox, M. Gill, J.L. Nunez, Vibr. Spectrosc. 6 (1993) 95. [13]. J.J. Novoa Fernando Mota, Chem. Phys. Lett. 318 (2000) 345. [14]. P. Tarakeshwar, H.S. Choi, K.S. Kim, J. Am. Chem. Soc. 123 (2001) 3321.
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[15]. M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg,
SC
M.Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F.
M AN U
Ogliaro,M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R.
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Cammi, C.Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,J.V. Ortiz, J. Cioslowski, D.J. Fox, GAUSSIAN 09, Gaussian, Inc.,
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Wallingford CT,2009.
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[16]. A. C Costa Jr1, G.F. Ondar, O. Versiane, J.M. Ramos, T.G. Santos, A.A. Martin, L.Raniero, G.G. Bussi, C.A. Tellez Soto, Spectrochim. Acta A Mol. Biomol.Spectrosc. 105 (2013) 251.
[17]. G. Keresztury, S. Holly, J. Varga, G. Besenyei, A.Y. Wang, J.R. Durig, Spectrochim.Acta A 49 (1993) 2007.
ACCEPTED MANUSCRIPT [18]. G. Keresztury, Raman spectroscopy theory, in: J.M. Chalmers, P.R. Griffith(Eds.), Handbook of Vibrational Spectroscopy, vol. 1, John Wiley & Sons Inc.,Chichester,
2002..
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[19]. J. Chocholousova, V. Spirko, P. Hobza, Phys. Chem. Chem. Phys. 6 (2004) 37. [20]. E.D. Glendening, J.K. Badenhoop, A.E. Reed, J.E. Carpenter, J.A. Bohmann, C.M. Morales, F. Weinhold, NBO 5.0, Theoretical Chemistry Institute, University of
SC
Wisconsin, Madison, 2001.
C57 (2001) 315
M AN U
[21]. G. Ferguson, C. Glidewell, J. N. Low, J. M. S. Skakle and J. L. Wardell Acta Cryst.
[22]. C. James, A. Amal Raj, R. Reghunathan, I. Hubert Joe, V.S. Jayakumar, J. Raman Spectrosc. 37 (2006) 1381.
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[23]. Jun-na Liu, Zhi-Rang Chen, Shen-Fang Yuan, J. Zhejiang Univ. Sci. 6B (2005) 584. [24]. C.R. Zhang, H.S. Chen, G.H. Wang, Chem. Res. Chin. U 20 (2004) 640.
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[25]. Y. Sun, X. Chen, L. Sun, X. Guo, W. Lu, Chem. Phys. Lett. 381 (2003) 397.
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[26]. O. Christiansen, J. Gauss, J.F. Stanton, Chem. Phys. Lett. 305 (1999) 147. [27]. D.A. Kleinman, Phys. Rev. 126 (1977) 1962. [28]. N.S. Labidia,, A. Djebaili, Materials Science and Engineering B169 (2010) 28. [29]. T. Vijayakumar, I. Hubert Joe, C.P. Reghunadhan Nair, V.S. Jayakumar, Chem. Phys. 343 (2008) 83. [30]. N.S. Labidi, A. Djebaili , I. Rouina Journal of Saudi Chemical Society 15 (2011) 29.
ACCEPTED MANUSCRIPT [31]. D. Young, Computational Chemistry: A Practical Guide for Applying Techniques to Real World Problems, John Wiley & Sons, New York, 2001. [32]. I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London,
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1976. [33]. A.M. Asiri, M. Karabacak, M. Kurt, K.A. Alamry, Spectrochim. Acta A 82 (2011) 444.
M AN U
[35]. L.S. Pu, ACS Symp. Ser. 455 (1991) 331.
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[34]. B. Kosar, C. Albayrak, Spectrochim. Acta A 78 (2011) 160.
[36]. J.S. Murray, K. Sen, Molecular Electrostatic Potentials, Concepts and 399 Applications, Elsevier, Amsterdam, 1996.
[37]. E. Scrocco, J. Tomasi, in: P. Lowdin (Ed.), Advances in Quantum Chemistry,
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Academic Press, New York, 1978.
[38]. F.J. Luque, M. Orozco, P.K. Bhadane, S.R. Gadre, J. Phys. Chem. 97 (1993) 9380.
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[39]. J. Sponer, P. Hobza, Int. J. Quant. Chem. 57 (1996) 959. [40]. V.K. Rastogi, M.A. Palafox, L. Mittai, N. Perica, W. Kiefer, K. Lang, P. Ohja,
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J.Raman Spectrosc. 38 (2007) 1227.
[41]. L. Xiao-Hong, Z. Xian-Zhou, Comput. Theor. Chem. 969 (2011) 27. [42]. M. H. Jamroz , Vibrational energy distribution analysis VEDA 4, Warsaw,
2004.
[43]. M. Amalanathan, T.S. Xavier, I. Hubert Joe, V.K. Rastogi, Spectrochimica Acta Part A: 116 (2013) 574. [44]. C.Ravikumar, I.Hubert Joe, Phys. Chem. Chem. Phys. 12 (2010) 94542.
ACCEPTED MANUSCRIPT Figure Captions: Figure 1. Optimized structure of 2M4NA calculated at DFT level Figure 2. HOMO and LUMO pot of 2M4NA crystal Figure 3. Molecular electrostatic potential plot of 2M4NA
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Figure 4. Mulliken and Natural charge plots of 2M4NA crystal Figure 5.FT-IR spectra of 2M4NA crystal in the range 4000-400 cm-1
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Figure 6. FT-Raman spectra of 2M4NA crystal in the range 4000-50 cm-1
ACCEPTED MANUSCRIPT
119.1 120.2 121.3 121.1 119.5 120.0 120.0 119.4 109.5 109.5 109.5 120.0 120.2 119.7 118.5 120.9 119.4
C1 – C2 –C3 – C4 C2 – C3 –C4 – C5 C3 – C4 –C5 – C6 C5 – C6 –C1 – N7 C6 – C1 –N7 – H8 C6 – C1 –N7 – H9 C6 – C1 –C2 – C10 C1 – C2 –C10 – H11 C1 – C2 –C10 – H12 C1 – C2 –C10 – H13 C1 – C2 –C3 – H14 C2 – C3 –C4 – N15 C3 – C4 –H15 – O16 C3 – C4 –H15 – O17 C3 – C4 –C5 – H18 C4 – C5 –C6 – H19
-0.17 -0.03 0.13 -177.85 -16.06 -161.81 -1.78 58.89 -61.45 178.93 179.91 179.93 -0.07 179.96 180.0 -179.9
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118.6 120.8 121 118.9 120.0 117.9 118.7 120.4 111.8 110.9 110.9 120.4 119.4 118.0 117.9 119.7 119.7
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C1 – C2 – C3 C2 – C3 – C4 C3 – C4 – C5 C4 – C5 – C6 C6 – C1 – N7 C1 – N7 – H8 C1 – N7 – H9 C1 – C2 – C10 C2 – C10 – H11 C2 – C10 – H12 C2 – C10 – H13 C2 – C3 – H14 C3 – C4 – N15 C4 – H15 – O16 C4 – H15 – O17 C4 – C5 – H18 C5 – C6 – H19
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1.415 1.381 1.399 1.387 1.378 1.358 0.86 0.86 1.505 0.96 0.96 0.96 0.93 1.433 1.233 1.231 0.93 0.93
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1.418 1.388 1.394 1.393 1.383 1.38 1.008 1.007 1.507 1.096 1.090 1.090 1.082 1.462 1.230 1.229 1.081 1.085
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C1 – C2 C2 – C3 C3 – C4 C4 – C5 C5 – C6 C1 – N7 N7 – H8 N7 – H9 C2 – C10 C10 – H11 C10 – H12 C10 – H13 C3 – H14 C4 – N15 N15 – O16 N15 – O17 C5 – H18 C6 – H19
Values (/º) Exp Cal.
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Table 1:The DFT level calculated optimized geometrical parameters. Value (Å) Values (/º) Bond Dihedral Angles Exp Exp Cal. Cal. Length Angles
0.42 -0.96 0.90 -179.40 179.67 -0.1 0.14 65.85 -54.12 -174.16 -179.58 179.63 0.68 -179.72 -179.09 179.65
ACCEPTED MANUSCRIPT Table 2:Second order perturbation theory analysis of Fock matrix in NBO basis. ED(i)
ED(j)
b E(j)– E(i) a.u
c F (ij) a.u
π* (C3 – C4)
0.42542
28.15
0.28
0.079
π* (C5 – C6)
0.30621
15.07
0.28
0.060
π* (C1 – C2)
0.42023
16.08
0.29
0.061
π* (C5 – C6)
0.30621
23.17
0.29
0.074
π* (C1 – C2)
0.42023
21.97
0.28
0.073
π* (C3 – C4)
0.42542
15.62
0.28
0.061
1.64617
π* (N15 – O17)
0.64636
32.14
0.14
0.065
LP(1) N7
1.80196
π* (C1 – C2)
32.54
0.32
0.096
LP(2) O16
1.90209
σ* (C4 – N15)
11.43
0.58
0.073
LP(2) O16
1.90209
σ* (N15 – O17)
0.05481
18.92
0.72
0.105
LP(3) O16
1.46723
π* (N15 – O17)
0.64636
159.04
0.14
0.137
LP(2) O17
1.90186
σ*(C4 – N15)
11.45
0.58
0.073
LP(2) O17
1.90186
σ* (N15 – O16)
18.93
0.72
0.105
1.64617
π (C5 – C6)
1.71230
π (C3 – C4)
SC
π (C3 – C4)
M AN U
1.56543
TE D
π (C1 – C2)
AC C
EP
(e)
Acceptor NBO (j)
RI PT
(e)
a E (2) KJ/mol
Donor NBO (i)
0.42023
0.09739
0.09739
0.05506
ACCEPTED MANUSCRIPT
Urea
KDP
2M4NA -2.673
1.282
2.114
µy
0.264
0.00004
-0.254
µz
-1.354
-0.830
-5.514
Total
3.008 Debye
1.527 Debye
5.911 Debye
AC C
EP
TE D
M AN U
SC
Dipole moment µx
RI PT
Table 3: Calculated Dipole moment and total dipole moment of 2M4NA, Urea and KDP at DFT level
ACCEPTED MANUSCRIPT Table 4: Calculated Polarizabilities Static Polarizabilities and Total Polarizabilities moment of 2M4NA, Urea and KDP at DFT level 2M4NA 159.631
Urea 39.260
αxy
0.027
0.2947
KDP 46.619 0.459
αyy
60.352
24.690
46.805
αxz
17.712
-1.159
0.778
αyz
0.180
0.454
αzz
124.646
38.219
17.024 x 10-24 e.s.u
5.664 x 10-24 e.s.u
7.289 x 10-24 e.s.u
22.698 x 10-24 e.s.u
6.304 x 10-24 e.s.u
12.656 x 10-24 e.s.u
Static Polarizability (α0)
AC C
EP
TE D
M AN U
SC
Total Polarizability (∆α)
RI PT
Polarizabilities αxx
-0.790
54.1384
ACCEPTED MANUSCRIPT Table 5: Calculated First order Polarizabilities and Total First order Polarizabilities moment of 2M4NA, Urea and KDP at DFT level Urea
KDP
2M4NA 1143.903
24.729
βxxy
14.408
-0.499
132.383 -5.841
βxyy
-81.109
31.817
63.361
βyyy
9.555
0.0066
βxxz
785.197
-61.443
βxyz
4.9009
-0.225
βyyz
-49.718
-20.593
βxzz
355.405
19.374
βyzz
7.762
0.5057
βzzz
37.449
32.896
RI PT
First order Polarizabilities βxxx
-26.762
-43.435 -1.802
-118.569
SC
110.151 13.681
M AN U
-636.568
0.781 x 10-30 e.s.u
AC C
EP
TE D
13.956 x 10-30 e.s.u
7.390 x 10-30 e.s.u
ACCEPTED MANUSCRIPT Table 6: Calculated Second order Polarizabilities and Total Secondorder Polarizabilities moment of 2M4NA, Urea and KDP at DFT level Second order Polarizability
Urea
KDP
2M4NA 2.31375
-4.95
γxxxx
-0.2351917 -1.28532
-4.789
γxxyy
RI PT
-1.8785
9.747
3.5990723 γyyyy
2.1137123
0.235
-1.81515 γyyzz
1.2790763
5.361
2.55444 γzzzz
2.6165167 1.9762432 7.301 x 10-39 e.s.u
AC C
EP
TE D
M AN U
8.762 x 10-39 e.s.u
SC
3.914
3.19399 γzzzz
8.937 x 10-39 e.s.u
ACCEPTED MANUSCRIPT Table 7: The relative second harmonic generation (SHG) output and the conversion efficiency SHG output (mV)
Urea
3.5
KDP
15
2M4NA
22
AC C
EP
TE D
M AN U
SC
RI PT
Specimen
ACCEPTED MANUSCRIPT Table 8:The Frontier Molecular orbital energies and HOMO-LUMO energy gap of 2M4NA, Urea and KDP at DFT Level 2M4NA Urea KDP (eV) (eV) (eV) -6.503 -9.739 -9.5759 -2.412 -2.307 -2.741 4.091 7.431 6.835
AC C
EP
TE D
M AN U
SC
RI PT
MO’s HOMO LUMO HOMO-LUMO gap
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
ACCEPTED MANUSCRIPT
DFT calculations have been performed on the NLO crystal 2-Methyl-4-Nitroaniline (2M4nA) Calculation
such
as
Optimized
geometry,
Hyperpolarizabilities were calculated The IR and Raman spectra of the compound were analyzed.
NBO,
The NLO activity of the crystal was confirmed by SHG analysis.
EP
TE D
M AN U
SC
HOMO and LUMO analysis were also performed by DFT approach.
AC C
charge
RI PT
Theoretical
and