Accepted Manuscript A Combined Experimental and Theoretical studies on FT-IR, FT-Raman and UV-Vis Spectra of 2-chloro-3-quinolinecarboxaldehyde M.V.S. Prasad, N. Udaya Sri, V. Veeraiah PII: DOI: Reference:

S1386-1425(15)00420-5 http://dx.doi.org/10.1016/j.saa.2015.03.105 SAA 13520

To appear in:

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Received Date: Revised Date: Accepted Date:

18 September 2014 4 March 2015 27 March 2015

Please cite this article as: M.V.S. Prasad, N. Udaya Sri, V. Veeraiah, A Combined Experimental and Theoretical studies on FT-IR, FT-Raman and UV-Vis Spectra of 2-chloro-3-quinolinecarboxaldehyde, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2015), doi: http://dx.doi.org/10.1016/j.saa.2015.03.105

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A Combined Experimental and Theoretical studies on FT-IR, FT-Raman and UV-Vis Spectra of 2-chloro-3-quinolinecarboxaldehyde M. V. S. Prasada,1, N.Udaya Sria and V.Veeraiahb a

Department of Physics, D.N R. College, Bhimavaram, W.G. Dt, Andhra Pradesh, India-534202 b

Molecular Spectroscopy Laboratories, Department of Physics, Andhra University, Visakhapatnam, India

Abstract In the present study, the FT-IR and FT-Raman spectra of 2-chloro-3-quinolinecarboxaldehyde (2Cl3QC) have been recorded in the region 4000 - 400 cm-1 and 3500 - 50 cm-1, respectively. The fundamental modes of vibrational frequencies of 2Cl3QC are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of Density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO - LUMO energy gap reveals that

1

Corresponding Author e-mail : [email protected] 1

charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. The results show that charge in electron density (ED) in the π* antibonding orbitals and E(2) energies confirms the occurrence of ICT (Intra-molecular Charge Transfer) within the molecule. UV-visible spectrum of the title molecule has also been calculated using TD-DFT/CAM-B3LYP/6-31G(d,p) method. The calculated energy and oscillator strength almost exactly reproduces reported experimental data.

Keywords: 2-chloro-3-quinolinecarboxaldehyde, FT-IR, FT-Raman, UV-Vis, NBO, HOMOLUMO

2

1. Introduction Quinoline is a heterocyclic scaffold of vital importance to human race. The quinoline ring system occurs in various natural products, especially in alkaloids. Several quinoline derivatives isolated from natural resources or prepared synthetically are significant with respect to medicinal chemistry and biomedical use. Indeed quinoline derivatives are some of the oldest compounds which have been utilized for the treatment of a variety of diseases. In 1820, quinine was isolated as the active ingredient from the bark of Cinchona trees and successively replaced the crude bark for the treatment of malaria. The bark of Cinchona plant containing quinine was also utilized to treat palpitations [1], fevers and tertian’s since more than 200 years ago. Quinoline was first extracted from coal tar in 1834 by Friedlieb Ferdinand Runge [2]. Quinidine, a diastereoisomer of quinine was in the early 20th century acknowledged as the most potent of the antiarrhythmic compounds isolated from the Cinchona plant [3]. Compounds containing quinoline motif are most widely used as antimalarial [4], antibacterial [5], antifungal [6], anticancer agents [7] and HIV-1 Integrate Inhibitors [8]. Moreover, quinoline derivatives find use in the synthesis of fungicides, virucides, biocides, alkaloids, rubber chemicals and flavoring agents [9]. Despite its relatively low efficacy and tolerability, quinine still plays an important role in the treatment of multiresistant malaria [10]. This molecule has also played a historical role in organic chemistry as a target for structural determination and total synthesis [11] and recently both stereoselective [12] and enantioselective [13] total syntheses. They are also used as polymers, catalysts, corrosion inhibitors, preservatives, and as solvent for resins and terpenes. In addition, these compounds find applications in chemistry of transitionmetal catalyst for uniform polymerization and luminescence chemistry [14]. Quinoline derivatives also act as antifoaming agent in refineries [15]. Owing to such significance, the synthesis of substituted quinolines has been a

3

subject of great focus in organic chemistry. The first formal synthesis was reported by Skraup over a century ago [16]. 1,3,4-triphenyl-7-trifluoromethyl- 1H-pyrazolo[3,4-b]quinoline, shows fluorescence both in solution and in the solid state, and the electroluminescence is observed by Thomas et al.,[17-19] The precursor of to 8-hydroxyquinoline is a versatile chelating agent and precursor to pesticides and 2- and 4-methyl derivatives of quinoline are precursors to cyanine dyes. The title compound, 2-Chloro-3-quinolinecarbaldehyde and its derivatives were synthesized by Judit Toth et al.,[20] method proposed by Meth-Cohn et al. The molecular formula of parent compound i.e., quinoline is C6H7N, the density at 250C is 1.090, the melting and boiling points at atmospheric pressure are -150C and 237.640C respectively. It has strong absorption of light wavelengths greater than 290 nm. The monomer and intermolecular charge-transfer complexes of 13 different quinoline derivatives with di-iodine were studied using ab initio molecular orbital (MO) and density functional theory (DFT) methods by Kusama et al., [21] and showed that the interaction between the quinoline additives and iodine redox electrolyte is an important factor for controlling dye-sensitized solar cell performance. Mary,F.A., et al.,[22] studied luminescence and hydrogen bonding in quinoline and isoquinoline. Recently, quinoline conjugated derivatives have

generated

considerable

interest

as

blue-emitting

materials

[23].

π–conjugated

polyquinolines and related polyquinoxalines have demonstrated excellent electron-transport and electroluminescent properties in OLEDs [24,25]. Polyquinolines are emerging as very promising blue emitting materials due to their unique combination of high thermal stability, easy processability and high photoluminescence (PL) quantum yields [26]. Recently, a combined experimental and theoretical studies on the vibrational spectra of 2-, 3- and 6-

4

quinolinecarboxaldehyde have been reported by Kucuk et al.,[27-29]. Vibrational spectra and assignments for quinoline and isoquinoline were reported by Samuel et al., [30]. To our knowledge and literature survey reveals that, there are either no theoretical calculations

or

detailed

vibrational

analysis

have

been

performed

on

2-chloro-3-

quinolinecarboxaldehyde (2Cl3QC) molecule so far. A systematic study on the molecule geometry and vibrational spectra help in understanding the property of title molecule in depth insight. So, in the present investigation of title molecule has been performed using the scaled quantum mechanical (SQM) force field technique based on density functional theory (DFT) calculations. Vibrational spectra have been analyzed on the basis potential energy distribution (PED). The change in electron density (ED) in the antibonding orbital’s and stabilization energies E(2) of the molecule have been calculated by natural bond orbital (NBO) analysis to give clear evidence of stabilization. The UV spectroscopic studies along with HOMO, LUMO analysis have been used to elucidate information regarding charge transfer within the molecule.

2. Experimental The spectrochemically pure (>98%), 2-chloro-3-quinolinecarboxaldehyde is used as purchased from Sigma-Aldrich company, USA to record the FT-IR, FT-Raman and UV-vis. spectra. FT-IR measurements. The spectrum was recorded using Nicolet 6700 FT-IR spectrometer with an NXR FT-Raman module at room temperature. The spectrum was recorded on samples dispersed in KBr pellets in the range of 400–4000 cm−1. FT-IR spectrum was recorded at The Department of Pharmaceutical Sciences, Andhra University, Visakhapatnam.

5

FT-Raman measurements. Raman spectrum has been recorded on solid samples contained in standard NMR diameter tubes or on compressed samples contained in a gold-coated sample holder. FT-Raman spectra was recorded at Prof. Aswin Nangia’s Lab, School of chemistry, University of Hyderabad. UV-Visible measurements. The normal incidence optical absorption measurements of 2Cl3QC in solid form has been recorded in the range 200–800 nm at a scan speed of 120 nm/min and a slit width of 1 nm at room temperature using a JASCO,Version-570 spectrophotometer at the Department of Physics, IIT, Chennai.

3. Computational procedure Density functional calculations were performed using Gaussian 03W program package [31]. Gaussview program [32] is used to get visual animation and also for the verification of the normal modes assignment. The reliably accurate description of weak interactions generally needs a treatment of electron correlation. Hence, we used Density functional calculations with the popular Becke’s three parameter hybrid method using correlation function of Lee, Yang and Parr (B3LYP) [33,34] which is proved quite useful in this regard, for studying the system with weak interactions. In this functional, the exchange is a combination of 20% Hartree–Fock (exact) exchange, Slater functional, and Becke’s generalized gradient approximation (GGA) correction [35]. This method has been tested with different basis sets and has successfully been applied for several systems to estimate the preferred geometries. Density functional theory offers and electron correlation correction at a considerably lower computational cost. This significance of lower computational cost compared to other correlated methods allowed us to calculate the harmonic vibrational frequencies of the system studied here. Molecular geometries were fully 6

optimized by Berny’s optimization algorithm using redundant internal coordinates. All optimized structures were confirmed to be minimum energy conformations. Harmonic vibrational wavenumbers were calculated using analytic second derivatives to confirm the convergence to minima on the potential surface and to evaluate the zero-point vibrational energies (ZPVE). At the optimized structure of the 2Cl3QC, no imaginary frequency modes were obtained, proving that a true minimum on the potential energy surface was found. The optimum geometry was determined by minimizing the energy with respect to all geometrical parameters without imposing molecular symmetry constraints. The calculated harmonic force constants and wavenumbers are usually higher than the corresponding experimental quantities because of the combination of electron correlation effects and basis set deficiencies. Therefore, it is customary to scale down the calculated harmonic wavenumbers in order to improve the agreement with the experiment. The scaling of the force field was performed according to the scaled quantum mechanical (SQM) procedure [36,37] using selective scaling in the natural internal coordinate representation [38,39] to obtain a better agreement between the theory and the experiment. Normal coordinate analysis (NCA) has been performed in ordered to obtain the detailed interpretation of the fundamental modes using the MOLVIB program version7.0 written by Sundius [40,41]. The NBO calculations [42] were performed using NBO 3.1 program as carried out in the Gaussian 03W [31] package to understand the intra-molecular delocalization or hyperconjugation. Finally, the TD-DFT method was used to calculate energies, oscillator strengths of electronic singlet-singlet transitions and the absorption wavelengths. The Raman activities (SRa) calculated with the same program [31] were converted to relative Raman intensities (IRa) using the following relationship derived from the intensity theory of Raman scattering [43, 44]:

7

Ii = f (ν0 – νi)4 Si * {νi[1 − exp(−hcνi/kT)]}-1

(1)

where ν0 is the wavenumber of the exciting laser (in this work, we have used the excitation wavenumber ν0 = 9398.5 cm−1, which corresponds to the wavelength of 1064 nm of the Nd : YAG laser), νi is the vibrational wavenumber of the ith normal mode (in cm−1) and Si is the Raman scattering activity of the normal mode νi. f (a constant equal to 10−12) is a suitably chosen common normalization factor for all peak intensities. h, k, c and T are the Planck and Boltzmann constants, the speed of light and the temperature in Kelvin, respectively.

4. Results and Discussion 4.1. Molecular geometry The first task for a computational work is to determine the optimized geometry of 2Cl3QC. The optimized structure parameters calculated with DFT method are listed in Table 1 in accordance with the atom numbering scheme given in Fig. 1. The molecule belongs to the Cs point group with 19 atoms and expected to have 51 normal modes (35 in-plane and 16 out-ofplane) of vibrations. Our calculated results show that the aromatic ring in 2CL3QC is distorted from regular hexagon due to static and electronic effects of the electron donating and electron withdrawing substitutents. To the best of our knowledge, exact experimental data on the geometrical parameters of title molecule are not available in the literature. Therefore, we could not compare the calculation results given in Table.1 with the experimental data. Therefore, the crystal data of a closely related molecule such as 6-methoxy-2-naphthaldehyde [45] is compared with that of the title molecule. As seen from Table.1 most of the optimized bond lengths are slightly longer than the experimental values and the bond angles are slightly different from the experimental ones, because the molecular states are different during experimental and theoretical 8

processes. One isolated molecule is considered in gas phase in theoretical calculation, whereas many packed molecules are treated in condensed phase during the experimental measurement. However, the theoretical results obtained are almost comparable with the reported structural parameters of the parent molecules. The reported values of C-N bond lengths of different quinoline complexes are 1.307 – 1.362Å [46] and 1.359-1.456 Å.[47] In the present study, the CN bond length is calculated as 1.298-1.367Å, is shorter than the normal C–N single bond length of about 1.48 Å. The shortening of these C–N bonds reveals the effect of resonance in this part of the molecule. The C-Cl bond lengths given by calculations are in agreement with the C-Cl bond lengths given by Arslan et.al.[48] The substitution of chlorine in the ring shortens the C–C bond lengths of the quinoline complex. Chlorine is highly electronegative and tries to obtain additional electron density. It attempts to draw electron density from the neighboring atoms which as a result move closer together in order to share the electrons more easily. The C-Cl bond length observed [45] is 1.750 Å whereas the calculated value is found to be 1.770 Å. •

Figure 1

The calculated value of C=O bond length of the molecule is 1.217 Å show typical double bond characteristics. The calculated C-C bond length for the compound is observed in the range 1.377-1.488 Å. This is in agreement with the reported values [49] of the bond lengths similar quinoline complexes. The C-H bond length of the molecule is reported to be 0.948 - 0.951 Å and the calculated value of C-H bond length for the compound is 1.085 – 1.104 Å. For the present compound, the C C-C and C-C-N bond angles are between 116.4º - 124.8º and 118.8º -125.3º respectively. The reported values are of range 117.3º - 123.7º and 118.4º - 126.26º respectively [45]. It is evident from the observed data that, all the bond angles are in well agreement with the observed values. The bond angles at 2- and 3-position of the title molecule are showing much

9

more deviation than the other bond angles due to the substitution of heavy atoms at those positions. The reported C-C-H bond angle [45] between 118.8º - 120.2º for the quinoline complex and in the present study of 2Cl3QC, the ab initio calculations give the values in the range 118.0º - 122.0º. •

Table 1

A Potential energy surface (PES) of 2Cl3QC was scanned about the C2–C3–C4–C5 dihedral angle with an increment of 10º at the B3LYP/6-31G(d,p) level in order to localize the structure that corresponds to the energy minima. All the geometrical parameters were simultaneously relaxed during the calculations, while the C2–C3–C4–C5 dihedral angle was varied in steps of 10º. The resulting potential energy curve depicted in Fig. 2 shows that the minimum energy for this rotation is obtained at 0º hence, the 0º corresponds to the global minimum energy (-974.84 Hartrees). According to Kucuk et al., when the O atom of the aldehyde is farther away than the nitrogen atom of the quinoline, 2-quinolinecarboxaldehyde has the lowest possible energy, and thus is in its ground state [27]. •

Figure 2

4.2. Vibrational spectra The

detailed

vibrational

assignments

of

fundamental

modes

of

2-chloro-

3quinolinecarbaxaldehyde along with the PED are given in Table. 3. The molecular structure belongs to the Cs point group symmetry. The molecule consists of 19 atoms and expected to have 51 normal modes, dispersed among the symmetry species as 35A’ in plane and 16A’’ out of plane vibrations. Normal coordinate analyses were performed to provide a complete assignment of the fundamental vibrational wavenumbers of the molecule. For this purpose, the full set of 70 standard internal coordinates is defined as given in supplementary material 1. From these, a non-

10

redundant set of 51 local symmetry coordinates was constructed by suitable linear combinations of internal coordinates following the recommendations of Fogarasi and Pulay, [38,39] which are summarized in Table 2. The theoretically calculated DFT force fields were transformed to this latter set of vibrational coordinates and used in all subsequent calculations. The Potential energy distribution (PED) for each normal mode among the symmetry coordinates of the molecules was calculated. A complete assignment of the fundamentals was proposed based on the calculated PED values, FT-IR band intensities and FT-Raman activities. The unscaled vibrational wavenumbers are generally larger than the experimental value. The reason for the disagreement between calculated and observed vibrational wavenumbers is due to that, the calculations were made for a free molecule in vacuum, while experiments were performed for liquid sample. The reason is also partly due to the neglect of anharmonicity and partly due to approximate nature of the quantum mechanical methods. However, for reliable information on the vibrational properties the use of selective scaling is necessary. The calculated wavenumbers are scaled using the set of transferable scale factors recommended by Rauhut and Pulay.[50] •

Figure 3

•

Figure 4

The experimental and theoretical FT-IR and FT-Raman spectra are shown in Figs 3 and 4 for comparative purposes, where the calculated intensity and activity are plotted against the harmonic vibrational frequencies. The experimental wavenumbers, calculated wavenumbers and IR intensities and Raman scattering activities are given in Table 3. In the last column is given a detailed description of the normal modes based on the PED. All of the calculated modes are numbered from the biggest to the smallest frequency within each fundamental wavenumbers, in the first column of the Table 3.

11

•

Table 3

4.2.1. Carbon-hydrogen group vibrations In aromatic compounds, the C–H stretching wavenumbers appear in the range 3000–3100 cm−1, and the C–H in-plane and out-of-plane bending vibrations in the range 1000–1300 and 750–1000 cm−1, respectively [51,52]. This is the characteristic region for the identification of C-H stretching vibration. In this region the bands are not affected significantly by the nature of the substitutions. Accordingly, in the present study, the five adjacent hydrogen atoms left around the rings of 2Cl3QC give rise to six C–H stretching (ν1–ν5), five C–H in-plane bending (ν11,ν12,ν17,ν19,ν20) and five C–H out-of-plane bending (ν24,ν26,ν27,ν29,ν30) vibrations, which correspond to stretching modes of C4–H18, C2–H11, C7–H13, C3–H12, C1–H17,and C15–H19 units respectively. The aromatic C–H stretching of 2Cl3QCA give bands at 3059, 3042, 3013and 2872 cm−1 in the FT-IR spectrum and at 3060, 3045,2979 and 2875 cm−1 in the Raman spectrum. These modes are calculated from 3059 to 2872 cm−1 for 2Cl3QC. All the aromatic C–H stretching bands are found to be weak, and this is due to a decrease in the dipole moment caused by reduction of negative charge on the carbon atom. This reduction occurs because of the electron withdrawal on the carbon atom by the substituent due to the decrease in the inductive effect, which in turn is caused by the increase in the chain length of the substituent [53]. As expected, these six modes are pure stretching modes as is evident from PED column of Table 3, they almost contribute 100%. The C-H peaks were observed for quinoline-2carboxaldehyde in the range 3058-2813 cm-1 by Kucuk et.al. [27]. The in-plane aromatic C–H bending vibration occurs in the region of 1300–1000 cm−1; the bands are sharp but have weak to medium intensity. The C–H in-plane bending vibration observed at 1313, 1206, 1164, 1137 and 1134 cm−1 by the present method shows excellent

12

agreement with FT-IR bands at 1297, 1214, 1165, 1131 and 1002 cm−1 and at 1216, 1170 and 1147 cm-1 in the FT-Raman. The aromatic C–H out-of-plane bending vibrations occur at the region below 1000 cm-1. In the present study, the bands 937, 918, 901, 832 and 736 cm−1 are assigned to in the calculated spectrum belongs to the C-H out-of pane vibrations. These vibrations observed at 940, 912, 871, 807 and 749 cm-1 in the FT-IR spectrum and at 916, 811 and 754cm-1 in FT-Raman spectrum. The calculated results are in well agreement with the observed data [54,55]. 4.2.2. Carbon-Carbon vibrations The ring carbon–carbon stretching vibrations occur in the region of 1625–1430 cm−1. In general, the bands are of variable intensity and are observed at 1625–1590, 1590–1575, 1540– 1470, 1460–1430 and 1380–1280 cm−1 from the wavenumber ranges given by Varsanyi [56] for the five bands in the region. With heavy substituents, the bonds tend to shift to somewhat lower wavenumber and greater the number of substituents on the ring, broader the absorption regions. In the present work, the wavenumbers observed in the FT-IR spectrum at 1614, 1578, 1542, 1490, 1454, 1371, 1333, 1318, 1045 and 1002 cm−1 are assigned to C–C stretching vibrations. The same vibrations in the FT-Raman are at 1614, 1584, 1490, 1456, 1386, 1336, 1321, 1247 and 1020 cm−1. The ring-breathing mode at 777 cm−1 in FT-IR and the same vibration in FTRaman at 745 cm−1 as a medium band coincide with the B3LYP/6-31G(d,p) predicted value at 788 cm−1 for the most stable form. The PED of this vibration is a mixed mode, as evident from Table 3, mixing with the C–Cl stretching mode. The in-plane deformations are at higher wavenumbers than those of out-of-plane vibrations. Shimanouchi et al.[57]. gave the wavenumber data for this vibration for different benzene derivatives as a result of normal coordiante analysis. The bands at 969, 773, 524 and 424 cm−1 in both FT-IR and FT-Raman

13

spectrum are assigned to the C–C–C deformaton of the phenyl ring. The ring C–CHO stretching vibration occurs in the region 1230–1160 cm−1 [58]. Thus, the 1206 cm−1 band arises from the C–CHO stretching. 4.2.3. Carbon-nitrogen vibrations The C=N stretching skeletal bands [59-61] are observed in the range 1627–1566 cm−1. For the title compound the bands observed at 1578 and 1583 cm−1 in the FT-IR and FT-Raman spectrum respectively, are assigned to the C=N mode. The C-N stretching mode is observed at 1371 and 1386 cm-1 respectively in FT-IR and FT-Raman spectra, which is well agreed with calculated band at 1370 cm-1. For conjugated azines [62] the C=N mode is reported at 1553 cm−1. DFT calculations give these modes at 1566 and 1535 cm−1. 4.2.4. Aldehyde group vibrations The aldehyde CH stretching vibration can be distinctly observed in both IR and Raman spectra by its band position in the low wave number region, compared to other CH stretching vibrations. DFT calculation provides the CH stretching band position at 2855 cm-1. But the expected band is shifted to a higher wave number region, as a medium band in FT-IR at 2872 cm-1 and as a weak band in FT-Raman at 2875 cm-1. The shifting of band position can be attributed to the possible interaction of CH stretching mode with the overtone of CH in-plane bending, which reduces the intensity of CH stretching band via Fermi resonance [63].The overtone band expected below2796 cm-1 cannot be observed distinctly owing to low intensity. But, the doublet of Fermi resonance can be observed distinctly in solution spectrum. Aldehyde CH in-plane bending is expected around 1400 cm-1. DFT calculation predicts the aldehyde CH in-plane bending to be at 1429 cm-1.This vibration observed at 1418 cm-1 in the FT-IR and 1413 cm-1 in FT-Raman spectra. The CH in-plane bending vibration is mixed with C-C stretching

14

mode of the phenyl ring. Though the DFT computation gives the C=O stretching wave number to be 1717 cm-1, the conjugation of C=O bond with the phenyl ring and the electron-releasing effect due to intramolecular charge transfer are expected to lower the stretching wave number to 1685 cm-1, which is evident from the spectrum. The band position is further lowered to produce a very strong band in FT-Raman at 1683 cm-1 and a very strong FT-IR band at 1687 cm-1. Other intermolecular interactions of the aldehyde group are not strong enough to produce considerable influence on vibrational modes. The C-H out-of-plane bending vibration of the aldehyde group is observed at 970 cm-1 in both the FT-IR and FT-Raman spectra. 4.2.5. C-Cl vibrations The vibrations belonging to the bond between the ring and chlorine atoms are worth to discuss here since mixing of vibrations is possible due to the lowering of the molecular symmetry and the presence of heavy atoms on the periphery of the molecule [45]. Mooney [64,65] assigned vibrations of C–Cl, Br, and I in the wavenumber range of 1129–480 cm−1. The C-Cl stretching vibrations give generally strong bands in the region 710–505 cm−1. For simple organic chlorine compounds, C-Cl absorptions are in the region 750–700 cm−1. Sundaraganesan et al.[66] reported C-Cl stretching at 704 (IR), 705 (Raman), and 715 cm−1 (DFT) and the deformation bands at 250 and 160 cm−1. The aliphatic C-Cl bands absorb [67] at 830–560 cm−1 and putting more than one chlorine on a carbon atom raises the C-Cl wavenumber. Pazdera et al.[68,69] reported the C-Cl stretching mode at 890 cm−1. For 2- cyanophenylisocyanide dichloride the C-Cl stretching mode is reported at 870 cm−1 (IR), 877 cm−1 (Raman), and 882 cm−1 theoretically [70]. Arslan et al.[48] reported the C-Cl stretching mode at 683 (experimental), and at 711, 736, 687, and 697 cm−1 theoretically. The deformation bands of C-Cl are reported [48] at 431, 435, 441, and 441 cm−1. For the title compound, the band at 1045 cm−1

15

is assigned as C-Cl stretching mode. The deformation bands of C-Cl are also identified. This is in agreement with the literature data [71-73]. For 4-chlorophenylboronic acid, the CCl stretching and deformation bands are reported at 571 (DFT), and at 287 and 236 cm−1, respectively [74]. The C–Cl in-plane and out-of-plane bending vibrations are expected in the low-wavenumber region. The C–Cl in-plane bending vibrations predicted by theory at 218 cm−1 show good agreement with the FT-Raman spectral value at 190 cm−1 as a weak band. The PED corresponding to this mode almost contributes to 70%. The C–Cl out-of plane bending vibrations are assigned in the FT-IR and FTRaman spectra as a shoulder and strong band at 420 and 422 cm−1, respectively; they also show good agreement with the computed wavenumber at 419 cm−1.

5. First order hyperpolarizability The NLO activity give the key functions for frequency shifting, optical modulation, optical switching and optical logic for the developing technologies in areas such as communication, signal processing and optical interconnections [75,76]. Hyperpolarizabilities are very sensitive to basis sets and levels of theoretical computations employed [77,78] that the electron correlation can change the value of hyperpolarizability. In the present study, the first hyperpolarizability (β0) of this novel molecular system is calculated using DFT/6-31G(d,p) basis set, based on the finite field approach. In the presence of an applied electric field, the energy of a system is a function of the electric field. The first hyperpolarizability is a third-rank tensor that can be described by a 3 × 3 × 3 matrix. The 27 components of the 3D matrix can be reduced to 10 components because of the Kleinman symmetry [79]. The equations are supplied in the supplementary material 2.

16

The

calculated first hyperpolarizability of the title compound is 4.343 × 10-30 esu (Table 4),

which is comparable with the reported values of similar quinazoline derivatives but experimental evaluation of this data is not readily available. The total molecular dipole moment and average polarizability of 2Cl3QC are 1.469 Debye and 290.46 x 10-24 esu respectively shown in Table 4. The calculated first hyperpolarizability is about ~36 times greater than that of urea. The above results show that title compound is best material for NLO applications. We conclude that the title compound is an attractive object for future studies of nonlinear optical properties. •

Table 4

6. NBO analysis The NBO calculations [42] were performed using the NBO 3.1 program as implemented in the Gaussian 03W package in order to understand various second order interactions between the filled orbitals of one subsystem and vacant orbitals of another subsystem, which is a measure of the intermolecular delocalization or hyperconjugation. NBO analysis provides the most accurate possible ‘natural Lewis structure’ picture of j, because all orbital details are mathematically chosen to include the highest possible percentage of the electron density (ED). A useful aspect of the NBO method is that it gives information about interactions in both filled and virtual orbital spaces, which could enhance the analysis of intra- and intermolecular interactions. The second-order Fock matrix was carried out to evaluate the donor–acceptor interactions in the NBO basis [80]. The interactions result in a loss of occupancy from the localized NBO of the idealized Lewis structure into an empty non-Lewis orbital. For each donor (i) and acceptor (j), the stabilization energy E(2) associated with the delocalization E(2) = ∆Eij = qi F(i,j)2/( εj – εi)

i → j is estimated as (10)

17

where qi is the donor orbital occupancy, εi and εj are diagonal elements and F(i, j) is the offdiagonal NBO Fockmatrix element. The lowering of orbital energy due to the interaction between the doubly occupied orbitals and the unoccupied ones is a very convenient guide to interpret the molecular structure in the electronic point of view. In energetic terms, hyperconjugation is an important effect [81,82] in which an occupied Lewis-type NBO is stabilized by overlapping with a non-Lewistype orbital (either one-center Rydberg or two-center antibonding NBO). This electron delocalization can be described as a charge transfer from a Lewis valence orbital (donor), with a decrease in its occupancy, to a non-Lewis orbital (acceptor). Several other types of valuable data, such as directionality, hybridization, and partial charges, have been analyzed from the NBO results The most important interactions between Lewis-type NBOs and non-Lewis NBOs are reported in Table 5. •

Table 5

The intermolecular hyperconjugative interactions are formed by the orbital overlap between

π(C–C), π∗(C–C) and σ(C–C), σ∗(C–C) bond orbitals, which results in ICT, causing

stabilization of the system. These interactions are observed as an increase in the electron density (ED) in the C–C antibonding orbital that weakens the respective bonds. The ED at the conjugated σ bonds (∼1.96e) and σ ∗(0.02e) of the aromatic ring clearly demonstrates weak delocalization. The strong intramolecular hyperconjugation interaction of the π electrons from C6–C7 to the π∗ antibonding orbitals of C1–C2, C5-N10 and C8–C9 bond shows an ED of ~1.53e, leading to the stabilization of ∼23.55 kJ/mol. This enhanced π∗(C5–C6) NBO further conjugates with π∗(C2–C3), resulting in an enormous stabilization energy of 175.82 kJ/mol, as shown in Table 5.

18

The lone pair of Chlorine atom n3(Cl4) leads to a strong stabilization energy of 13.66 kJ/mol to π∗ (C8–C9) where as n1(Cl4) lead to a less stabilization energy ~1.2 kJ/mol to σ*(C8-C9) and σ*(C9-N10) bonds respectively. The other important aspects of the NBO analysis show that the π∗ (C8–C9) bonding conjugation with C6–C7 and C15-O16 lead to an enomorous stabilization energy of 125.38 and 112.64 kJ/mol respectively.

7.

UV-Visible spectra and HOMO-LUMO analysis On the basis of a fully optimized ground-state structure, the TD-DFT calculations have

been used to determine the low-lying excited states of 2Cl3QCA and are shown in Table 6. The calculated results involving the vertical excitation energies, oscillator strength (f) and wavelength are carried out and compared with measured experimental wavelength. Typically, according to the Frank–Condon principle, the maximum absorption peak (λmax) corresponds in a UV-visible spectrum to vertical excitation. The Calculations of molecular orbital geometry show that the visible absorption maxima of this molecule correspond to the electron transition between frontier orbitals, such as translation from HOMO to LUMO as can be seen from the UV–Vis spectrum absorption maxima values. The calculations predicts one intense electronic transition at (231 nm) with an oscillator strength f = 0.96, in good agreement with the measured experimental data (λexp = 234 nm) as shown in Fig. 5. This electronic absorption corresponds to the transition from the ground to the first excited state and is mainly described by one electron excitation from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). •

Table 6

•

Figure 5

19

Molecular electrostatic potential (MEP) mapping is very useful in the investigation of the molecular structure with its physiochemical property relationships [83]. The MEP is related to the electronic density and is a very useful descriptor in determining the sites for electrophilic and nucleophilic reactions. The molecular electrostatic potential surface MEP which is a plot of electrostatic potential mapped onto the iso-electron density surface simultaneously displays molecular shape, size and electrostatic potential values and has been plotted for both the molecules. The importance of MEP lies in the fact that it simultaneously displays molecular size, shape as well as positive, negative and neutral electrostatic potential regions in terms of color grading. The different values of the electrostatic potential are represented by different colors. Potential increases in the order red < orange < yellow < green < blue. To predict reactive sites for electrophilic and nucleophilic attack for the investigated molecule, the MEP at the B3LYP/631G(d,p) optimized geometry was calculated. The negative (red and yellow) regions of the MEP are related to electrophilic reactivity and the positive (blue) regions to nucleophilic reactivity, as shown in Fig.6. As can be seen from the Fig 6, this molecule has one possible site for electrophilic attack. Negative regions are mainly localized over the O and N atom. According to these calculated results, the MEP map shows that the negative potential sites are on electronegative O and N atoms as well as the positive potential sites are around the hydrogen atoms. The predominance of green region in the MEP surfaces corresponds to a potential halfway between the two extremes red and dark blue colour. These sites give information about the region from where the compound can have intermolecular interactions. •

Figure 6

The HOMO and LUMO energies and the energy gap for 2Cl3QC calculated at the B3LYP/6-31G(d,p) level are shown in Table 7. The Eigen values of LUMO and HOMO energies

20

and their energy gap reflect the chemical activity of the molecule. LUMO as an electron acceptor represents the ability to obtain an electron, while HOMO as an electron donor gives away an electron. The smaller the energy gap of LUMO and HOMO, the easier it is for the electrons of HOMO to be excited. The higher the energies of HOMO, the easier it is for HOMO to donate electrons; the lower the energies of LUMO, the easier it is for LUMO to accept electrons. The HUMO–LUMO orbitals are shown in Fig. 7 In the ground state, the charge density is mainly accumulated on the Cl and quinoline ring in the case of HOMO. From Table 7 the results show that the energy gap of title compound is 4.39249 eV, shows that there is a transfer of electrons from HOMO to LUMO. This study reveals that these molecular systems have large first static hyperpolarizabilities and have potential applications in the development of NLO devices. Furthermore, the decrease in the LUMO and HOMO energy gap explains the probable charge transfer taking place inside the complexes. •

Table 7

•

Figure 7

8. Thermodynamic properties On the basis of vibrational analysis at B3LYP/6-31G(d,p) level, the standard statistical thermodynamic functions such as heat capacities (Cp and Cv) entropy (S) and enthalpy changes (H) for the title compounds are obtained from the theoretical harmonic frequencies with the help of Moltran v.2.5 [84] (see Table 8 ) and, it can be observed that these thermodynamic functions are increasing with temperature ranging from 100 to 500 K due to the fact that the molecular vibrational intensities increase with temperature. In general, thermodynamic properties are important in the study of several molecular properties. Hence, we attempted to evaluate limited thermodynamic properties. We

21

have given the linear relation between the thermodynamic parameters and temperature in the present work by giving the fitting curves for each parameter. Relations mentioned below show the equations for fitting curves calculated for all the thermodynamic parameters in relation with temperature.

These parameters further are useful in calculating other quantum chemical

parameters. It can be observed that corresponding fitting factors are all beyond 0.999 for these thermodynamic properties. The corresponding fitting equations are given in the Table. 8. • 9.

Table 8

Mulliken population analysis Mulliken atomic charge calculation has an important role in the application of quantum

chemical calculation to molecular system, because atomic charges affect dipole moment, polarizability, electronic structure and much more properties of molecular systems. The charge distributions calculated by Mulliken method for the equilibrium geometry of the title molecule are listed in Table 9/ Supplimentary material 3. The charge distribution on the molecule has an important influence on vibrational spectra. The corresponding, Mulliken’s plots are shown in Fig. 8. The analysis shows that the presence of large electronegative atoms N10 creates more positive charge on C5 and C9 similarly, O16 creates more positive charge C8, C15, and H19. The atom N10 shows largest electro negativity (-0.497e) and C5 shows largest electro positivity (0.238e). Similarly, the atom O16 shows largest electro negativity (-0.400e) and C15 shows largest electro positivity (0.197e). This indicates the extensive charge delocalization in the molecule. The positive charges are localized on the hydrogen atoms. In the phenyl ring, all the carbon atoms have negative charges except C5, C6, C8, C9 and C15 which are attached with the nitrogen atom N10 and Oxygen atom O16. This suggests that the atoms C5 and C6 are acting as the centers for charge transfer between the substituent and the phenyl ring. Furthermore, the atom C5

22

(0.236e) delocalizes most of its charges to the ring when compared to the atom C6 (0.164e). The atom C1 shows more negative charge (-0.186e) than C7 (-0.180e). This confirms the above argument. The hydrogen atoms present in the ring shows less positive charge, while the one (H13) which is attached to Oxygen atom O16 shows more positive charge (0.183e) which confirms the more electro negativity of nitrogen atom.

• •

Table 9 Fig. 8

10. Conclusions In this paper we have reported complete structural, vibrational and electronic properties of the title compound by using experimental techniques (FT-IR, FT-Raman and UV-Vis absorption spectra) and theoretical method. The scaled vibrational frequencies are in good agreement with the experimental data. The vibrational modes of the experimental wavenumbers are assigned on the basis of potential energy distribution (PED). The calculated first hyperpolarizability of 2Cl3QC is about 20 times greater than that of urea. The above results show that title compound is best material for NLO applications. NBO analysis indicating the strong intramolecular hyperconjugative interaction within the molecule and stability of the molecule. In the UV-Vis absorption spectrum one intense electronic transition π→π* is observed at λmax = 344 nm. The Mulliken atomic charges of the title molecule have been studied by DFT method, it suggests that the atoms to O, N atoms and all H atoms are electron acceptor and charge transfer takes place from O and N to H. The calculated HOMO, LUMO energies show that charge transfer occurs within molecule. Furthermore, theoretical calculations give the thermodynamic properties (heat capacity, entropy and enthalpy) for the compound. It can be observed that these thermodynamic functions are increasing with temperature ranging from 100 23

to 500 K due to the fact that the molecular vibrational intensities increase with temperature. Therefore, we hope the results of this present study will facilitate researchers to explore and synthesize new compounds. Acknowledgements One of the authors M. V. S. PRASAD extends thanks to University Grants Commission (UGC), New Delhi, India for the award of Teacher fellowship under FDP scheme to complete the Ph.D degree. The authors highly grateful to Prof. T. Sundius for MOLVIB program.

24

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30

Figure Captions Figure. 1. Molecular structure of 2-Chloro-3-quinolinecarbaldehyde along with numbering of atom. Figure.2. Potential energy surface scan for dihedral angle C2-C3-C4-C5 of 2-Chloro-3quinolinecarbaldehyde. Figure.3. Experimental FT-IR and simulated FT-IR spectra of 2-Chloro-3-quinolinecarbaldehyde Figure.4. Experimental FT-Raman and simulated FT-Raman spectra of 2-Chloro-3quinolinecarbaldehyde. Figure.5. Experimental and calculated UV-visible spectra of 2-Chloro-3-quinolinecarbaldehyde. Figure.6. Molecular electrostatic potential energy surface (MEP) for 2-Chloro-3quinolinecarboxaldehyde. Figure.7. The atomic orbital components of the frontier molecular orbital of 2-Chloro-3quinolinecarbaldehyde. Figure. 8. Mulliken atomic charge distribution of 2Cl3QCA.

31

List of Tables Table 1: Optimized geometrical parameters of 2-Chloro-3-quinolinecarbaldehyde obtained by B3LYP/6-31G(d,p) density functional calculations. Table 2: Definition of local-symmetry coordinates and the values of corresponding scale factors used

to

correct

the

B3LYP/6-31G(d,p)

(refined)

force

field

of

2-Chloro-3-

quinolinecarbaldehyde. Table 3: Detailed assignments of fundamental vibrations of 2-Chloro-3-quinolinecarbaldehyde by normal mode analysis based on SQM force field calculations using B3LYP/6-31G(d,p ). Table 4:The electric dipole moment µ (D), the average polarizability α

tot

(x10-24 esu) and the

first hyperpolarizability β tot (x10-30 esu) of 2-Chloro-3-quinolinecarbaldehyde by HF/6-31G(d, p) method. Table 5: Second order perturbation theory analysis of fock matrix in NBO basis for 2-Chloro-3quinolinecarbaldehyde. Table

6:

The

UV-vis

excitation

energy

and

oscillator

strength

for

2-Chloro-3-

quinolinecarbaldehyde calculated by TDDFT/CAM-B3LYP/6-31G(d,p) method. Table 7: The calculated HOMO, LUMO energies and HOMO-LUMO energy gap for 2-Chloro3-quinolinecarboxaldehyde by using B3LYP/6-31G(d,p). Table 8: Thermodynamic properties for 2-Chloro-3-quinolinecarboxaldehyde obtained by B3LYP/6-31G(d,p) density functional calculations. Table 9: Mulliken atomic charges of 2-Chloro-3-quinolinecarboxaldehyde.

32

Supplementary material Supplementary

material-1:

Definition

of

internal

coordinates

of

2-Chloro-3-

quinolinecarbaldehyde Supplementary material-2: Theoretical Equations for hyperpolarizability calculations. Supplementary material-3: Mulliken atomic charges of 2-Chloro-3-quinolinecarboxaldehyde.

33

Fig.1. Molecular structure of 2-Chloro-3-quinolinecarboxaldehyde along with numbering of atom.

34

DFT/B3LYP/6-31G(d,p) -971.0 -971.5

Energy (a.u)

-972.0 -972.5 -973.0 -973.5 -974.0 -974.5 -975.0 -50

0

50

100

150

200

250

300

350

400

Dihedral angle/C2-C3-C4-C5

Fig.2. Potential energy surface scan for dihedral angle C2-C3-C4-C5 of 2-Chloro-3quinolinecarboxaldehyde.

35

0

788

1005

1566

50

736

1685 1614

3045

2855

1497

1135

B3LYP/6-31G(d,p)

1348

100

0.0 4000

592

485

912

1165

1687

Experimental FT-IR Sppectrum

760 777

1578

0.2

1045

0.4

1454 1371 1318

3042

0.6

2871

0.8

3735 3649

Transmittance (%)

1.0

3500

3000

2500

2000

1500

1000

500

-1

Wavenumber (cm )

Fig.3. Experimental FT-IR and simulated FT-IR spectra of 2-Chloro-3-quinolinecarboxaldehyde

36

Fig.4.

120

80

40

0

40

20

0

Experimental

3500 3000

FT-Raman

B3LYP/6-31G(d,p)

4000

Experimental

quinolinecarboxaldehyde

R am an intesity (arb.units)

3060

3045

2875

2855

2500 2000

simulated

1500

-1

FT-Raman

Wavenumber (cm )

and

37

1490 1336

spectra

1000

of

500

916

1614 1583

1685 1614 1566 1497 1547 1461 1428 1370 1313 1247 1164 1135 1029 977 1005

1683 1386

1143 1016 811

2-Chloro-3-

480 422 225

832

754

368

137

1348

788 736

586 480 419 360 290 218 178 133

348

100

230

344

234

4

Experimental

2

193

Absorbance(are.unit)

TDDFT/CAM-B3LYP/6-31G(d,p)

0 150

200

250

300

350

400

450

500

Wavelength (nm) Fig 5. Experimental and calculated UV-visible spectra of 2-Chloro-3-quinolinecarbaldehyde

38

Fig. 6 Molecular electrostatic potential energy surface (MEP) for 2-Chloro-3-quinolinecarboxaldehyde

39

Fig.7. The atomic orbital components of the frontier molecular orbitals of 2-Chloro-3quinolinecarboxaldehyde

40

Atoms

H H H O C Cl H H H N C C C C C C C C C -0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

Charge (e)

Fig. 8. Mulliken atomic charge distribution of 2Cl3QCA.

41

0.2

Table 1: Optimized geometrical parameters of 2-Chloro-3-quinolinecarboxaldehyde obtained by B3LYP/6-31G(d,p) density functional calculations.

Bond length (Å)a B3LYP/6-31G(d,p) 1.377 C1-C2 1.420 C1-C6 1.087 C1-H17 1.418 C2-C3 1.086 C2-H11 1.379 C3-C4 1.086 C3-H12 1.416 C4-C5 1.085 C4-H18 1.432 C5-C6 1.367 C5-N10 1.411 C6-C7 1.383 C7-C8 1.087 C7-H13 1.429 C8-C9 1.488 C8-C15 1.298 C9-N10 1.770 C9-Cl14 1.217 C15-O16 1.104 C15-H19

a

Expb 1.376 1.411 0.951 1.416 1.360 0.949 1.417 0.948 1.417 1.368 1.416 1.379 0.948 1.428 1.466 1.298 1.750 -

Bond angle (o)a B3LYP/6-31G(d,p) C2-C1-C6 120.2 C2-C1-H17 120.9 C1-C2-C3 120.3 C1-C2-H11 120.1 C6-C1-H17 119.0 C1-C6-C5 119.4 C1-C6-C7 123.6 C3-C2-H11 119.6 C2-C3-C4 120.9 C2-C3-H12 119.3 C4-C3-H12 119.8 C3-C4-C5 120.0 C3-C4-H18 122.0 C5-C4-H18 118.0 C4-C5-C6 119.3 C4-C5-N10 118.8 C6-C5-N10 122.0 C5-C6-C7 117.1 C5-N10-C9 118.4 C6-C7-C8 120.9 C6-C7-H13 121.1 C8-C7-H13 118.0 C7-C8-C9 116.4 C7-C8-C15 118.8 C9-C8-C15 124.8 C8-C9-N10 125.3 C8-C9-Cl14 119.0 C8-C15-O16 122.7 C8-C15-H19 116.2 N10-C9-Cl14 115.7 O16-C15-H19 121.1

For numbering of atoms refer to Fig. 1 See Ref. [45]

b

42

Expb 121.5 119.2 118.2 122.5 119.2 118.8 123.7 119.2 122.3 118.8 118.8 119.4 120.2 120.2 119.4 118.4 122.0 117.3 117.7 121.0 119.4 119.5 115.4 123.6 120.8 126.2 119.1 114.5 -

Table 2: Definition of local-symmetry coordinates and the values of corresponding scale factors used to correct the B3LYP/6-31G(d,p) (refined) force field of 2-Chloro-3-quinolinecarboxaldehyde

No.(i) Symbol a Definition b STRETCHING R1, R2, R3, R4, R5, R6,R7, R8, R9 , R10 1-10 νCC 11-15 νCH R11, R12, R13, R14, R15 16-17 νCN R16, R17 18 νCO R18 19 νCCl R19 20 νCHsub R20 IN PLANE BENDING (γ22- γ 23+ γ 24- γ 25+ γ 26- γ 27)/√6, (γ 28- γ 29+ γ 30- γ 31+ γ 32- γ 33)/√6, 21-22 Rtrid (γ 23- γ 24+ γ 26- γ 27)/2, (γ 29- γ 30+ γ 32- γ 33)/2 23-24 Rsym 25-26 Rasy (2 γ 22- γ 23- γ 24+2 γ 25- γ 26- γ 27)/√12, (2 γ 28- γ 29- γ 30+2 γ 31- γ 32- γ 33)/√12 (γ 34 – γ 35)/√2, (γ 36 – γ 37)/√2,( γ 38 – γ 39)/√2, (γ 40 – γ 41)/√2, (γ 42 – γ 43)/√2, 27-31 βCH (γ 44 – γ 45)/√2, 32 βCC (γ 46 – γ 47)/√2, 33 βCCl γ 48 34 βCO 35 βCHsub γ 49 OUT OF PLANE BENDING 36-41 ω50, ω51, ω52, ω53, ω54, ω55 ωCH ω56, 42 ωCC 43 ω57, ωCCl TORSIONS (τ58 - τ59 + τ60 - τ61+ τ62 - τ63)/√6, (τ64 - τ65 + τ66- τ67 + τ68 - τ69)/√6 44-45 τRtri (τ59- τ60 + τ62 - τ63)/2, (τ65 - τ66 + τ68 - τ69)/2 46-47 τRsym 48-49 τRasy (-τ58 + 2τ59 - τ60 - τ61 + 2τ62 - τ63)/√12, (-τ64 + 2τ65 - τ66 - τ67 + 2τ68 - τ69)/√12 (τ70 + τ71)/2, 50 τCO 51 BUTTER (τ72 - τ73)/2,

Scale factors

Abbreviations: v, stretching; ß, in plane bending; ω, out of plane bending; τ, torsion, sub, substitution, tri, trigonal deformation, sym, symmetric deformation, asy, asymmetric deformation, a These symbols are used for description of the normal modes by PED in Table 3 b The internal coordinates used here are defined in Supplementary material 1.

43

0.9275 0.9204 0.9283 0.9283 0.9220 0.9204 0.9589 0.9589 0.9589 0.9590 0.9300 0.9500 0.9300 0.9590 0.9500 0.9500 0.9500 0.9500 0.9500 0.9500 0.9500 0.8500

Table 3: Detailed assignments of fundamental vibrations of 2-Chloro-3-quinolinecarboxaldehyde by normal mode analysis based on SQM force field calculations using B3LYP/6-31G(d,p )

S. No

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Specie s

A’

Experimental (cm-1) ------------------------FT-IR FTRaman 3059ms 3060s

Scaled frequencies (cm-1)

Intensity IIRb IRAc

3057

A’

3042s

3045ms

3045

A’

-

-

3037

A’

-

-

3031

A’

3013vw

2979vw

3023

A’

2872s

2875s

2855

A’

1687vs

1683vs

1685

A’

1614ms

1614s

1614

A’

1578s

1583s

1566

A’

1542vw

-

1547

A’

1490ms

1490ms

1497

A’

1454ms

1456vw

1461

A’

1418vw

1413w

1429

A’

1371ms

1386vs

1370

A’

1333ms

1336w

1348

A’

1318vw

1321w

1320

0.0 6 0.1 1 0.0 5 0.0 5 0.0 2 0.3 8 0.8 5 0.1 9 1.0 0 0.4 2 0.1 6 0.1 6 0.0 6 0.5 0 0.1 9 0.3

44

Characterization of normal modes with PED (%)d

23.0

νCH(99)

27.3

νCH(99)

18.7

νCH(99)

18.0

νCH(99)

8.9

νCH(99)

14.0

νCHsub(99)

34.4

νCO(70), βCHsub (17)

33.3

νCC(62), βCH(22)

49.3

νCC(54), βCH(20), νCN(10)

31.6

νCC(57), βCH(13), νCN(12)

13.7

βCH(46), νCC(40)

5.7

βCH(50), νCC(31)

8.7

βCHsub (65), νCC(13)

59.0

νCC(47), βCH(15), νCN(14)

100. 0 18.8

νCC(74), νCN(12) νCC(33), νCN(32), βCH(29)

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

A’

1297vw

-

1313

A’

-

1247vw

1247

A’

1214w

1216vw

1206

A’

1165s

1170w

1164

A’

-

1147ms

1137

A’

1131ms

-

1134

A’

1045vs

1020ms

1029

A’

1002vw

-

1005

A”

970w

970vw

977

A”

940ms

-

937

A”

912ms

916vw

918

A”

-

-

907

A’

871w

-

901

A”

807s

811ms

832

A’

777s

754s

788

A”

760s

-

736

A”

749s

-

736

A’

678w

-

721

A”

621vw

-

638

A’

603

-

626

8 0.1 7 0.0 1 0.0 1 0.1 2 0.1 8 0.2 1 0.7 7 0.0 4 0.0 1 0.0 1 0.0 6 0.1 1 0.0 6 0.0 1 0.1 2 0.2 5 0.2 5 0.1 2 0.0 1 0.0

45

20.2

βCH(30), νCC(29), νCN(15), Rtri(12)

5.1

νCC(35), βCH(27), Rsym(18)

3.7

βCH(43), νCC(34), νCN(17)

9.3

βCH(41), νCC(40), νCN(10)

11.8

νCC(44), βCH(24), νCN(17)

11.9

νCC(46), βCH(36)

4.6

νCC(32), Rsym(22), Rtri(17), νCCl (12)

19.9

νCC(76), βCH(17)

8.3

ωCH(87)

0.5

τRtri(38), ωCH(37), τRasy(24)

1.3

ωCH(65), τRasy(22), τRtri(11)

2.9

Rtri(50), Rsym(13), νCC(12)

2.7

ωCH(83), τRasy(8)

4.6

τRasy(37), τRtri(32), ωCH(28)

23.2

νCC(36), βCO(14), νCCl (12), Rasy(11)

37.6

νCC(38), τRasy(24), Βco(11),

37.6

ωCH(47), τRtri(46)

8.2

τRasy(50), τRtri(41)

0.8

τRtri(50), τRasy(46)

1.8

Rsym(37), Rtri(35), Rasy(14), νCC(10)

37 38 39

A’

593w

-

593

A’

-

-

585

A”

-

-

502

A”

485s

480vw

480

A’

474ms

-

474

A”

420s

422vw

419

A’

366w

368vs

361

A’

344s

302vw

348

A”

-

264vw

290

A”

-

225w

244

A’

-

190w

218

A’

-

-

178

A”

-

137vs

134

A”

-

121s

100

A”

-

-

75

1 0.0 3 0.0 7 0.0 1 0.1 5

40 41 42 43 44 45 46 47 48 49 50 51

0.0 7 0.0 0 0.0 2 0.0 6 0.0 0 0.0 0 0.0 0 0.0 1 0.0 7 0.0 0 0.0 0

a

4.4

νCC(23), βCO(22), Rsym(13), Rasy(11), βCCl (10)

5.5

Rasy(44), Rsym(18), νCCl (17), νCC(11)

0.9

τRtri(53), τRasy(43)

9.6 5.5

Rsym(20), βCCl (17), νCC(16), βCC(11), Rtri(11), Rasy(10) BUTTER (35), τRtri(31), τRasy(17), ωCH(11)

4.9

τRtri(33), τRasy(23), ωCC(22)

34.4

νCC(28), Rtri(25), βCO(18), Rasy(16)

60.4

νCCl (49), Rasy(32)

13.6

τRsym(24), ωCC(20), ωCH(19), ωCCl (13)

3.0

τRasy(55), τRtri(28), τRsym(10)

16.8

βCCl (70), Rasy(12)

23.0

βCC(62), βCO(15)

18.9

τCO(53), τRtri(14), τRasy(10)

94.9

BUTTER (22), τRtri(21), τCO(15), ωCH(13), ωCCl (13)

-

τRasy(40), τRtri(29), τRsym(23)

Abbreviations: v, stretching; ß, in plane bending; ω, out of plane bending; τ, torsion,;tri, trigonal deformation, sym, symmetrical deformation, asy, asymmetric deformation, substitution,sub, vs, very strong; s, strong; ms, medium strong; w, weak; vw, very weak. b Relative absorption intensities normalized with highest peak absorption equal to 1. c Relative Raman intensities calculated by Eq. (1) and normalized to 100. d Only PED contributions ≥10% are listed

46

Table 4: The electric dipole moment µ(D), the average polarizability αtot (x10-24 esu) and the first hyperpolarizability β tot (x10-30 esu) of 2-Chloro-3-quinolinecarboxaldehyde by DFT/6-31G(d, p) method components μx μy μz μ(D) αxx αxy αyy αxz αyz αzz (esu)

DFT/6-31G(d, p) -0.8295 0.0005 1.2127 1.469 136.597 -0.019 41.517 -26.580 0.064 165.738 290.46 x 10-24

35

β components βxxx βxxy βxyy βyyy βxxz βxyz βyyz βxzz βyzz βzzz β total (esu)

DFT/6-31G(d, p) -177.550 0.044 2.794 -0.002 104.720 0.023 0.723 40.817 -0.311 -617.274 4.343 x 10-30

Table 5: Second order perturbation theory analysis of fock matrix in NBO basis for 2-Chloro-3quinolinecarboxaldehyde Donor (i)

C1 - C2

Type

ED/e

σ π

1.981 1.711

σ π

1.980 1.697

σ π

1.976 1.629

σ π

1.974 1.527

σ π

1.983 1.571

N10

σ π n1

1.996 1.976 1.909

Cl14

n1

1.993

Cl14

n2

1.961

Cl14

n3

1.913

O16

n1

1.898

C5 - N10

π*

0.506

C8 - C9

π*

0.479

C3 - C4 C5 - N10

C6 - C7

C8 - C9

C15 - O16

Acceptor (j)

Type

C6 - C7 C3 - C4 C6 - C7 C5 - N10 C1 - C2 C5 - N10 C9 -Cl14 C3 - C4 C6 - C7 C8 - C9 C5 - C6 C1 - C2 C5 - N10 C8 - C9 C7 - C8 C5 - N10 C6 - C7 C15 - O16 C8 - C9 C8 - C9 C4 - C5 C5 - C6 C8 - C9 C9 -Cl14 C8 - C9 C9 - N10 C8 - C9 C9 - N10 C15 - H19 C8 - C9 C8 - C15 C15 - H19 C8 - C9 C8 - C15 C15 - H19 C3 - C4 C6 - C7 C6 - C7 C15 - O16

σ* π* π* σ* π* π* σ* π* π* π* σ* π* π* π* σ* π* π* π* σ* π* σ* σ* σ* σ* σ* σ* σ* σ* σ* π* σ* σ* σ* σ* σ* π* π* π* π*

a

ED/e

0.506 0.252 0.364 0.021 0.254 0.505 0.056 0.252 0.364 0.479 0.045 0.255 0.506 0.479 0.020 0.506 0.364 0.097 0.041 0.479 0.024 0.045 0.041 0.056 0.041 0.028 0.041 0.028 0.048 0.479 0.060 0.048 0.041 0.060 0.048 0.252 0.364 0.364 0.097

E(2) means energy of hyper conjugative interaction (stabilization energy). Energy difference between donor and acceptor i and j NBO orbitals. c F(i,j) is the Fock matrix element between i and j NBO orbitals. b

35

E(2)a (kJ mol−1)

E(j)−E(i)b (a.u.)

3.39 19.37 18.57 3.91 18.61 25.89 3.96 14.02 12.50 26.16 3.51 21.98 29.41 19.26 3.09 14.62 20.98 16.82 1.52 5.52 1.86 10.38 9.01 4.47 1.57 0.86 4.04 6.09 0.83 13.66 1.33 0.93 0.52 19.43 18.44 112.30 175.82 125.38 112.64

1.26 0.29 0.28 1.21 0.28 0.26 0.94 0.32 0.31 0.29 1.26 0.28 0.26 0.25 1.29 0.28 0.30 0.29 1.57 0.37 0.90 0.88 0.85 0.46 1.44 1.41 0.84 0.81 0.78 0.31 1.13 1.15 0.78 0.70 0.71 0.03 0.02 0.03 0.02

F(i,j)c (a.u.)

0.058 0.067 0.066 0.061 0.065 0.077 0.055 0.062 0.056 0.079 0.060 0.075 0.078 0.062 0.056 0.058 0.072 0.068 0.044 0.046 0.037 0.086 0.079 0.041 0.043 0.031 0.052 0.063 0.023 0.065 0.035 0.029 0.018 0.105 0.104 0.081 0.082 0.083 0.070

Table 6: The UV-vis excitation energy and oscillator strength for 2-Chloro-3-quinolinecarboxaldehyde calculated by TDDFT/CAM-B3LYP/6-31G(d,p) method.

S. No.

1 2 3 4 5 6 7 8 9 10

Exp. Wavelength (nm) 344 257 234 -

TDDFT/CAM-B3LYP/6-31G(d,p) Energy Wavelength Osc. (cm-1) (nm) Strength 29058.7 344.1 0.0 32953.6 303.4 0.02 35346.6 282.9 0.00 35537.0 281.4 0.04 41550.7 240.6 0.00 43988.9 231.3 0.96 46708.7 214.1 0.27 46722.4 214.0 0.00 50513.2 197.9 0.00 52298.1 191.2 0.12

Symmetry

Major contribs

Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A Singlet-A

H-2->LUMO (61%), H-2->L+1 (14%) HOMO->LUMO (85%) H-3->LUMO (48%), H-2->L+1 (21%) H-1->LUMO (54%), HOMO->L+1 (33%) H-3->L+1 (35%), H-2->L+1 (33%) H-1->LUMO (35%), HOMO->L+1 (55%) H-1->L+1 (79%) H-3->L+1 (42%), H-2->L+1(20%) H-4->LUMO (66%) H-4->LUMO (15%), HOMO->L+2 (54%)

35

Table 7: The calculated HOMO, LUMO energies and HOMO-LUMO energy gap for 2-Chloro-3-quinolinecarboxaldehyde by using B3LYP/6-31G(d,p)

Property

2-Chloro-3quinolinecarboxaldehyde -974.85 -6.88 -2.48 4.39

Total energy (a.u) EHOMO (eV) ELUMO (eV) ∆E=EHOMO-ELUMO (eV)

35

Table 8: Thermodynamic properties for 2-Chloro-3-quinolinecarboxaldehyde obtained by B3LYP/6-31G(d,p) density functional calculations. Temperatur e K 100 200 300 400 500

CV J/K/mol 63.1 111.7 162.0 208.4 247.3

CP J/K/mol 71.5 120.1 170.3 216.8 255.7

U KJ/mol 359.8 368.5 382.2 400.8 423.7

H KJ/mol

S J/K/mol

360.6 370.2 384.7 404.1 427.8

293.5 357.8 416.0 471.5 524.2

Cv = 7.4292 + 0.56473 T - 1.66079x10-4 T2 Cp = 15.745 + 0.56472 T - 1.66064x10-4 T2 U = 355.6344 – 0.01791 T + 2.36829x10-4 T2 H = 355.6354 + 0.02622 T + 2.36836x10-4 T2 S = 227.1304 + 0.68621 T - 1.84921x10-4 T2 G = 358.546 - 0.24287 T - 2.8575x10-4 T2

35

G KJ/mol 331.3 298.6 259. 215.5 165.7

Table 9: Mulliken atomic charges of 2-Chloro-3-quinolinecarboxaldehyde. No. 1 2 3 4 5 6 7 8 9 10

Atom C C C C C C C C C N

Charge -0.186 -0.133 -0.131 -0.138 0.238 0.164 -0.180 0.069 0.062 -0.497

No. 11 12 13 14 15 16 17 18 19

Atom H H H Cl C O H H H

35

Charge 0.146 0.147 0.183 0.008 0.197 -0.400 0.149 0.158 0.141

A Combined Experimental and Theoretical studies on FT-IR, FT-Raman and UV-Vis Spectra of 2-chloro-3-quinolinecarboxaldehyde M. V. S. Prasada,2, N.Udaya Sria and V.Veeraiahb a

Department of Physics, D.N R. College, Bhimavaram, W.G. Dt, Andhra Pradesh, India-534202 b

Molecular Spectroscopy Laboratories, Department of Physics, Andhra University, Visakhapatnam, India

GRAPHICAL ABSTRACT The vibrational and electronic spectra of 2-Chloro-3-Quinolinecarbaxaldehyde (2Cl3QC) are reported and discussed. Using DFT employing B3LYP exchange correlation with the normal basis level 6-31G(d,p) the structural properties and vibrational frequencies of 2Cl3QC have been investigated. NLO, NBO and HOMO-LUMO analysis have been carried out. There is good agreement between experimental and theoretical results.

2

Corresponding Author e-mail : [email protected] 35

A Combined Experimental and Theoretical studies on FT-IR, FT-Raman and UV-Vis Spectra of 2-chloro-3-quinolinecarboxaldehyde M. V. S. Prasada,3, N.Udaya Sria and V.Veeraiahb a

Department of Physics, D.N R. College, Bhimavaram, W.G. Dt, Andhra Pradesh, India-534202 b

Molecular Spectroscopy Laboratories, Department of Physics, Andhra University, Visakhapatnam, India

Highlights


Vibrational spectra of is 2-chloro-3-quinolinecarboxaldehyde recorded and analyzed.
The optimized geometry and vibrational assignments with PED were compute using DFT method.
The MEP, NLO and HOMO, LUMO energy gap were theoretically predicted.
The redistribution of electron density (ED) in various bonding, antibonding orbitals and E(2) energies had been calculated by NBO.

3

Corresponding Author e-mail : [email protected] 35