Structural, vibrational and electronic spectroscopic study of 6-hydroxycoumarin using experimental and theoretical methods

Journal Pre-proof Structural, vibrational and electronic spectroscopic study of 6-hydroxycoumarin using experimental and theoretical methods

D. Vijay, Y. Sushma Priya, M. Satyavani, Asim Kumar Das, B.N. Rajasekhar, A. Veeraiah PII:

S1386-1425(19)31321-6

DOI:

https://doi.org/10.1016/j.saa.2019.117930

Reference:

SAA 117930

To appear in:

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Received date:

10 April 2019

Revised date:

4 December 2019

Accepted date:

6 December 2019

Please cite this article as: D. Vijay, Y.S. Priya, M. Satyavani, et al., Structural, vibrational and electronic spectroscopic study of 6-hydroxycoumarin using experimental and theoretical methods, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy(2019), https://doi.org/10.1016/j.saa.2019.117930

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© 2019 Published by Elsevier.

Structural, vibrational and electronic spectroscopic study of Journal Pre-proof 6-Hydroxycoumarin using experimental and theoretical methods

D.Vijay, 2Y.Sushma Priya 1M.Satyavani, ,3Asim Kumar Das,2B.N.Rajasekhar and 1†A.Veeraiah

1 1

Molecular Spectroscopy Laboratory, Department of Physics, D.N.R. College (A), Bhimavaram, India-534202 Department of Physics, Adikavi Nannaya University, Rajamahendravaram, A.P-533296 2 Atomic& Molecular Physics Division, BARC, Mumbai, India † Corresponding author:[email protected] (A.Veeraiah)

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Understanding the photochemical behavior of structural isomers of hydroxycoumarin (HC)having different properties of consequence in biological activities demand spectroscopic information of this class of compounds. Barring 6-Hydroxycoumarin (6-HC), other isomers of HC’s are well studied spectroscopically. To understand and compare the photochemical activity of 6-HC with other isomers, a detailed study of this molecule has been taken up. For this purpose, electronic, vibrational and structural properties of 6-HC have been studied using ultraviolet absorption and Infrared spectroscopy techniques. Quantum chemical calculations have been performed at DFT/B3LYP level of theory to get the optimized geometry and vibrational frequencies of normal modes to support and analyze experimental data. The detailed vibrational assignments were made on the basis of potential energy distributions. Chemical activity, molecular orbital energies, band gap and hyper-polarizability information have been computed from quantum chemical simulations. NBO analysis helped in understanding the stability of the molecule arising from hyperconjugative interaction and charge delocalization. UV-Visible spectrum of the compound was recorded in the region 300-600nm helped in obtaining band gap data of the compound. Molecular Electrostatic Potentials (MESP) were plotted and the respective centers of electrophilic and nucleophililc attacks were predicted with the help of Fukui functions calculations. Further, it was observed that the negative electrostatic potential regions are mainly localized over the oxygen atoms and the positive regions are localized over the benzene ring. Details of the results and analysis of experimental and theoretical spectroscopy studies are presented in this paper.

1.Introduction:

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Keywords: 6-hydroxycoumarin (6HC), TD-DFT, MESP, FT-IR, UV-Vis spectra.

Coumarins, otherwise called as benzopyrones, because of their chemical activity can interact with enzymes over a wide range of biological activities such as anticoagulant, anticancer, antioxidant, antiviral, anti-diabetics, anti-inflammatory, antibacterial, anti-fungal and anti-neurodegerative agents apart from fluorescent sensors [1]. Hydroxyl coumarins (HC) are found to be having biologically different importance [2] depending on the position of OH group substitution on the coumarin ring. For example 4hydroxycoumarin is a carcinogen, 7-Hydroxycoumarin has great significance as natural fragrances, whereas 6-Hydroxycoumarin (6-HC) is found to be used as an anticancer agent [3-5]. 6-HC have number of applications in medical, dyes, cosmetics, food additive applications apart from solid state lightning applications [6-10]. Most of the organic synthesis use 6-hydroxycoumarin as key material as it is shows unique photochemical and photo physical properties [11-12]. Though a detailed spectroscopic information

on other structural isomers of HC’S is available in Pre-proof literature [13-17], surprisingly the spectroscopic data Journal of 6-Hydroxycoumarin is very scarce. In this work, 6-HC has been studied experimentally using UV-Vis and Infrared techniques. Theoretical information obtained by simulations using density functional level of theory with hyper correlation function B3LYP at standard basis set 6-311++G (d, p)helped to consolidate structural geometry, vibrational frequencies, optical properties, HOMO-LUMO, NBO and Molecular Electrostatic Potentials (MESP). In this paper, UV-Vis and FT-IR data of 6-HC are reported for the first time. Details of the experimental and theoretical results and analysis of the results obtained are presented in this paper. 2.Computational Details:

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In these, quantum chemical calculations using hybrid function Becke’s parameter nonlocal

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hybrid exchange potential and the nonlocal correlation functional of Lee, Yang and Paar (B3LYP) with higher basis set 6-311++G(d, p) are performed using Gaussian09W package installed in PC

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series i3-4170 CPU @ 3.70GHz processor system[18-19] and the optimized structure is visualized by GaussView 5.0.9[20]. Definition of local-symmetry coordinates of the title compound have been

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performed by following the recommendations of P.Pulay et al [21]. Vibrational frequencies, natural

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bond orbital (NBO), UV-Vis, Infrared, first order polarizability, potential energy surface (PES), highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) of

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title compound were obtained from Gaussian09W package along with charge and multiplicity viz., in this case, 0 and 1 respectively. The scale factor calculation and characterization of the normal

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modes using potential energy distribution (PED) were performed using MOLVIB program version 7.0 written by Sundius[22-23]. Thermal properties, Mulliken atomic charge and Molecular

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Electrostatic Potentials (MESP) of the titled compound were obtained from the optimized structure at B3LYP/6-311++G(d, p). Quantum chemical simulations are very useful to predict properties and chemical activity without any wastage. Hence, we found very accurate results from this density functional theoretical study. 3.Experimental Details: 6-hydroxycoumarin (6HC) sample in the powder form was purchased from Sigma-Aldrich Chemical Company and was used as such without further purification. UV-Vis spectral studies were carried out at Photophysics beamline, Indus-1, RRCAT Indore, India using @450 MeV synchrotron radiation source. Absorption spectral studies are carried out from 174 nm to 1020 nm at frequency 50kHz and 1msec exposure time by using ANDOR spectral instrument (i DUS 401 series) for whole measurements. Sample is prepared by thin layer deposition method and spectral measurements (I) were recorded as a function of

wavelength with blank spectrum (I0) takenJournal as the reference and are further normalized with respect to the Pre-proof synchrotron beam current monitored simultaneously. Fourier transform Infrared spectrum (FT-IR) is carried out by Thermofisher Scientific/Nicolet 6700 FT-IR source employing XT-KBr beam splitter. In this experiment sample is prepared by KBr pellet method and spectrum is recorded using DTGS detector over the and scan range 4000cm-1 to 400cm-1 with 64 number of scans at resolution 4 cm-1. 4.Result and Discussion: 4.1 Molecular geometry: 6-hydroxycoumarin was optimized, the respective bond length, bond angles and dihedral angles were

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compared with experimental XRD data of a similar compound since the experimental XRD data of the titled compound hasn't been reported so far[24]. The molecular geometry of 6-HC was optimized using

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Gaussian09W, visualized by GaussView 5.0.9 and it is presented Fig. 1. Bond length, bond angles and

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dihedral angles of theoretical data along with experimental values were reported in Table 1. From Table 1, it can observed that the aromatic ring C-C bond lengths and C-C-C bond angles are closer to the

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experimental bond lengths. Potential energy surface scan is the exact method to find transition states as it helps to find exact stationary points [25]. The PES was performed by changing dihedral angle C1-C6-

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O18-H15 from 0° to 360° with an interval of 10°. The potential energy curve shows broad peak at stable energy (E= -572.3963Hartrees) corresponding to a dihedral angle of 180º. The potential energy surface

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curve is presented in the Fig. 2. Figure 2 , it shows the optimized geometry of molecule in equilibrium

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state.



Figure 1



Table 1



Figure 2

4.2 Vibrational analysis: The titled compound 6-HC is considered under C1 symmetry, contains 18 atoms. As a nonlinear molecule executes 3N-6 number of potentially observable active fundamental frequencies, 6-HC has 48 fundamental modes of vibrations. The internal coordinates as listed in supplementary material 1 were used to define local symmetry coordinates. The local-symmetry coordinates were defined by following the recommendations of Pulay et al.[26-27], values of corresponding scale factors used to correct the

B3LYP/6-311G++ (d, p) force field calculations arePre-proof presented in Table 2. The in-plane and out-of-plane Journal

symmetry vibrations are found by the formula, Γ3N−6 = 35A' (in − plane) + 13A" (out − of – plane)

(1)

The titled compound, 6-HC has C-C, C=O and O-H type of bonds. These bonds are involved in various stretching, bending and torsional vibrations. The calculated frequencies are scaled to achieve better match with the observed values. These vibrations along with the respective potential energy distribution percentages are tabulated in Table 3. The vibrational analysis of the respective modes is as

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 Table 2  Table 3  Figure 3

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follows.

4.2.1. C-C Vibrations:

singlet and doublet of C-C ring vibrational frequencies are

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In aromatic organic compounds,

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observed in the region 1400 cm-1 - 1650 cm-1[28]. In the present work, the scaled vibration at 1627 cm-1 was assigned to C-C stretching vibrations. This mode shows an excellent agreement with the observed value at 1621 cm-1. C-C-C in plane and out-of-plane deformation is observed between 766 - 542 cm-1.

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The scaled value at 731 cm-1 is assigned to C-C-C ring asymmetric deformation and the corresponding band is observed at 729 cm-1. This is in synchronous with the scaled value.

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4.2.2. Carbonyl functional group vibrations:

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Mostly, the dominant C=O in-plane stretching mode of vibration is located in the region 1600-1660 -1

cm [29]. In the present study, the band observed at 1585 cm-1 is assigned to C=O stretching vibration and the corresponding scaled value 1652 cm-1 shows a good agreement with the observed value as listed in the Table 3. Further, the C-O mode of vibrations is observed in the region 1000-1300 cm-1. According to scaled quantum mechanical (SQM) force field calculation, we found C-O modes of vibrations around 1094 and 1285 cm-1. COH in-plane bending is observed at 1198 cm-1 and its scaled value is 1161 cm-1. 4.2.3. O-H Vibrations: In general, the O-H functional group vibrations are present in the region 2500-4000 cm-1[30]. The experimental FT-IR spectra of 6-HC compound having O-H vibrations around 3434cm-1and corresponding theoretical peak was observed around 3438cm-1 as reported in Table 3. 4.3. NBO (Natural bond orbital) analysis:

Natural bond orbital analysis is used for molecularPre-proof atomic charge and orbital population[31-32]. Most of Journal NBO analysis is reported up to second order interactions. In the present work, the NBO calculations were performed on optimized structure of 6HC using NBO 6.0 which is embedded Gaussian09W program package. Here we observed second order perturbations and most of the bond interactions are occurring at lower population. Lone pair (LP) electrons are observed for O16, O17 and O18. The second order perturbations were studied to predict the donor-acceptor interaction in the natural bond orbital [33].

E

(2)

2

= - nσ

Fij2 σ|F|σ = - nσ ε σ* -ε σ ΔE

(2)

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The interactions of donor (i) -acceptor (j) were observed and the respective interactions of the titled

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compound were tabulated in Table 4. From the Table, largest stabilization energy is observed for C9(σ) – C3-O16 (σ*).

Table 4

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C11 (π) – C12-O17 (π*) at 20.97 kJ/mol and lowest stabilization is occurred at 0.69 kJ/mol for C2-C3

4.4. Frontier Molecular orbitals:

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Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) study is related to the ionization potential and chemical reactivity of the molecule[34]. The total energy, HOMO,

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LUMO, difference between HOMO and LUMO, Ionization potential (I), Electron Affinity (A), Chemical potential (μ), Electronegativity (χ), Chemical hardness(η), Electrofilicity index (ω), Global

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Softness (σ), Total energy change(ΔET), Dipole moment(D) for the investigated compound 6HC is

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studied by DFT method with higher basis set B3LYP/6-311++G(d,p) basis set and the values are tabulated in Table 5. From the table, it can be noticed that energy gap of HOMO-LUMO is 4.156813 eV and dipole moment

is 5.5990 Debye. Highest occupied and lowest unoccupied molecular orbital

(HOMO-LUMO) geometry along with negative and positive charge distribution surfaces are clearly shown in the Fig. 4. UV-Vis experimental result is provided as evidence of energy gap in spectral analysis. Some important relations are given below. 𝐶ℎ𝑒𝑚𝑖𝑐𝑎𝑙 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 (𝜇) =

𝐸𝐿𝑈𝑀𝑂 +𝐸𝐻𝑂𝑀𝑂

𝐸𝑙𝑒𝑐𝑡𝑟𝑜𝑛𝑎𝑔𝑎𝑡𝑖𝑣𝑖𝑡𝑦(𝜒) = −

𝐺𝑙𝑜𝑏𝑎𝑙 ℎ𝑎𝑟𝑑𝑛𝑒𝑠𝑠

=

2

𝐸𝐿𝑈𝑀𝑂 −𝐸𝐻𝑂𝑀𝑂 2

𝐸𝐿𝑈𝑀𝑂 −𝐸𝐻𝑂𝑀𝑂 2

(3)

(4)

(5)

Journal Pre-proof 𝜇2

𝐸𝑙𝑒𝑐𝑡𝑟𝑜𝑝ℎ𝑖𝑙𝑖𝑐𝑖𝑡𝑦(𝜔) = 2𝜂

(6)

1

𝑆𝑜𝑓𝑡𝑛𝑒𝑠𝑠(𝑠) = 𝜂

(7) 



Table 5 Figure 4

4.5 UV-Vis Spectrum: UV-Vis spectrums are recorded in the region 300-600 nm at Photophysics beamlineIndus-1, Indus-1, a 450 MeV synchrotron radiation source. Calibration of absorbance spectrum is presented with the help

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of -coefficient formula given in equation 2.The resultant spectrum is shown in Fig.5. From Uv-Vis

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spectrum, where UV light start absorption from 334 nm and there is a strong absorption peak observed at 374 nm. Predicted TD-DFT spectra were given same absorption. In addition to that the calculated I

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direct energy band gap was found at 3.9 eV. ( ∝ = ln h )

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Figure 5 4.6 NLO properties:

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Theoretical non liner optical (NLO) calculations gives information about the molecular electronic dipole moment (μ), the polarizability (α), and the first hyperpolarizability (β) which are difficult to calculate

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directly. Therefore, these three properties of the titled compound 6HC are calculated by using DFT method with higher basis set B3LYP/6-311++G(d, p) for the first time[35]. Polarizability and first order

following relations

   2x   2 y   2z o 

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hyperpolarizability of the investigated compound using X, Y, Z elements can be calculated by using the

(8)

 xx   yy   zz 3

(9)

  21/2 [( xx   yy ) 2  ( yy   xx ) 2  6 2 xx ]1/2

(10)

  (  2 x   2 y   2 z )1/2

(11)

and

 x   xxx   xyy   xzz

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(12)

 y   yyy   xxy   yzz

(13)

 z   zzz   xxz   yyz

(14)

The calculated values which are in atomic units (a.u) of the compound under investigation can be converted into electrostatic units (esu) and tabulated in Table 6. From the table calculated values of electronic dipole moment µ (D) is found to be 4.85246587, average polarizability (α): 1a.u= 47.72213318×10-24esu, first hyperpolarizability(β): 1 a.u = 3.566699×10-30 esu). Table 6

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4.7Molecular electrostatic potential (MESP):

Molecular electrostatic potential is used to determine theintermolecular interactions, nucleophilic and

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electrophilic attacks of the titled compound 6HC [36]. Most of recent studies on MESP analysis reported

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electronic distributions of molecule and visualizing electrophilic and nucleophililc attacks [37].The calculated 3D electrostatic potential contour map is shown in Fig. 6.The figure shows that oxygen atoms

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arenegatively charged and that is localized at red region. Positive charge localized at benzene ring is

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shown as blue region.

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Figure 6

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4.8Mullikan atomic charge population analysis: Mulliken atomic charge population is extracted from the optimized Gaussian output file. The titled

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compound has 18 atoms and their corresponding Mulliken charges along with ATP charges are tabulate in Table 7. From atomic charge population, oxygen atoms O16, O17 and O18 are having negative charged values. Optimized structure along with charge distribution number is shown in fig. 7. 

Table 7



Figure 7

5. Conclusions: In the present work, the basic structure of 6-hydroxycoumarin is optimized, vibrational spectroscopic (FTIR and UV-Vis), Non-linear optical properties, natural bonding orbital analysis, molecular electrostatic potential map and Mulliken atomic charge population analysis of 6HC molecule with DFT basis set B3LYP/6-311++G(d,p) have been investigated and reported for the first time. In this study, the detailed vibrational assignments are made on the basis of potential energy distribution. A good coherence between

the observed and calculated spectra is achieved. JournalElectrophilic Pre-proofand nucleophilic centers of the compound have been identified from molecular electrostatic potential map (MESP) maps. By proper tuning, the titled compound can be used as one of the potential sources of visible light. Chemical harness and softness of the titled compound have been predicted and reported. Acknowledgements: This work is funded byUGC-DAE, CRS project (Project code- CSR-IC-BL-56/CRS-173/2016-17/837) with the technical support by Photo physics beamline experimental station, Indus-1, RRCAT, India. The authors are highly grateful to IUC, Indore and D.N.R. College Association for providing necessary lab specialties. Further, the authors are highly grateful to Prof. T. Sundius for Molvib program.

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List of Figures

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Fig. 1: Optimized Molecular structure of 6-hydroxycoumarin along with numbering of atom. Fig. 2: Potential energy surface scan for dihedral angle C1-C6-O18-H15 of 6-hydroxycoumarin. Fig. 3: Visualization of the molecular orbital of 6-hydroxycoumarin [HOMO—MO:42 and LUMO—MO:43] Fig. 4: Theoretical and experimental FT-IR Spectrum of 6HC. Fig. 5: Theoretical and experimental Uv-Vis Spectrum of titled compound. Fig. 6:B3LYP/6-311++G(d,p) calculated 3D molecular electrostatic potential mapsof 6-hydroxycoumarin Fig. 7: Structural mulliken atomic charges of 6-hydroxycoumarin

List of tables

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Table 1: Optimized geometrical parameters of 6-hydroxycoumarin obtained by B3LYP/6-311++G** (d, p) density functional calculations Table 2: Definition of local-symmetry coordinates and the values of corresponding scale factors used to correct the B3LYP/6-311 G++ (d, p)force field calculations of 6-hydroxycoumarin Table3: Observed and calculated vibrational frequency of 6-hydroxycoumarin molecule at B3LYP method with 6311++G (d, p) basis set. Table 4: Second order perturbation theory analysis of fock matrix in NBO basis for 6-HC Table:The calculated quantum chemical parameters for6-hydroxycoumarin obtained by B3LYP/6-311++G**

calculations. Table 6: The electric dipole moment (D), average polarizability, first hyperpolarizability, etc., of 6-HC by quantum calculation Table 7: Atomic charges for optimized geometry of 6-HC at B3LYP/6-311++G(d, p) level

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Fig.1: Optimized Molecular structure of 6-hydroxycoumarin along with numbering of atom.

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Energy (Hartrees)

-572.404

B3LYP/6-311++G**

-572.402

-572.400

-572.398

0

60

120

180

of

-572.396 240

300

360

-p

ro

Dihedral Angle C1-C6-O18-H15 (º)

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Fig.2: Potential energy surface scan for dihedral angle C1-C6-O18-H15 of 6-hydroxycoumarin

Journal Pre-proof

+

566

1504 1473 1231 1161 1133 984

40

++ + + +

+ ++

2635

20

804

+

+

3438 3337

+

1642

0

0

(b).

B3LYP/6-311++G(d,p)

+

FT-IR Spectrum

1897 1841

80

+ +

+

ro

60

3500

3000

-p

100 4000

+ +

of

40

1621 1585 1455 1371 1339 1138

++ + +

20

2500

2000

1500

+

1000

+

+

729 609

(a).

948

100

1591

80

3434

Transmittance (%)

60

500

-1

lP

re

Wavenumber (cm )

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Fig. 3: (a) Theoretical FT-IR, (b) Experimental FT-IR Spectrum of 6-hydroxycoumarin.

lP

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Figure 4: Visualization of the molecular orbital of 6-hydroxycoumarin

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[HOMO—MO: 42 and LUMO—MO: 43]

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374

40

30

6-Hydroxy Coumarin

334

of

20

10

400

-p

350

450

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0 300

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*

500

550

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lP

Wavelength (nm)

ur

Fig. 5: Experimental UV-Vis Spectrum of titled compound.

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Absorbance (%)

*

600

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-p

Fig. 6: B3LYP/6-311++G(d, p) calculated 3D molecular electrostatic potential maps of hydroxycoumarin

6-

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Fig. 7: Mullikan atomic charges of 6-hydroxycoumarin

Table 1: Optimized geometrical parameters of 6-hydroxycoumarin obtained by Journal Pre-proof B3LYP/6-311++G(d, p) density functional calculations

ur see the reference [24]

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a

Dihedral Angle C1-C2-C3-C4 C2-C3-C4-C5 C3-C4-C5-C6 C4-C5-C6-C1 C5-C6-C1-C2 C6-C1-C2-C3 C3-O16-C12-C11 O16-C12-C11-C9 C12-C11-C9-C4 C11-C9-C4-C3 C9-C4-C3-O16 C4-C3-O16-C12 O18-C6-C5-C1 O17-C12-O16-C11 H7-C1-C2-C6 H8-C2-C3-C1 H10-C5-C4-C6 H14-C11-C9-C12 H13-C9-C11-C4 C1-C6-O18-H15 C5-C6-O18-H15

of

ro

-p

re

C1-C2-C3 C2-C3-C4 C3-C4-C5 C4-C5-C6 C5-C6-C1 C6-C1-C2 C3-O16-C12 O16-C12-C11 C12-C11-C9 C11-C9-C4 C9-C4-C3 C4-C3-O16 C5-C6-O18 C1-C6-O18 O16-C12-O17 C11-C12-O17 C6-C1-H7 C2-C1-H7 C1-C2-H8 C3-C2-H8 C4-C5-H10 C6-C5-H10 C12-C11-H14 C9-C11-H14 C11-C9-H13 C4-C9-H13 C6-O18-H15

na

C1-C2 C2-C3 C3-C4 C4-C5 C5-C6 C6-C1 C3-O16 O16-C12 C12-C11 C11-C9 C9-C4 C6-O18 C12-O17 C1-H7 C2-H8 C5-H10 C11-H14 C9-H13 O18-H15

Bond Angle

Value(°) 6Exp. a 311++G** 119.60 117.8 120.78 123.1 118.97 117.4 120.23 120.8 119.98 119.9 120.40 120.7 122.80 123.0 115.84 116.6 121.79 119.7 120.74 122.2 117.28 117.8 121.53 120.5 123.26 116.74 118.10 115.3 126.05 128.0 118.73 120.85 121.25 121.1 119.14 121.1 119.16 119.6 120.59 119.6 115.55 118.9 122.64 121.3 120.37 118.9 118.87 118.9 110.15 -

lP

Bond length

Value(Å) 6Exp. a 311++G** 1.384 1.391 1.394 1.382 1.401 1.394 1.407 1.408 1.386 1.370 1.403 1.406 1.367 1.372 1.392 1.391 1.459 1.460 1.349 1.357 1.440 1.442 1.365 1.353 1.203 1.201 1.082 0.950 1.082 0.950 1.086 0.950 1.081 0.950 1.085 0.950 0.962 -

Value(°) 6311++G** 0.002 -0.019 0.022 -0.010 -0.006 0.010 0.003 -0.013 0.020 -0.016 0.007 -0.001 179.994 179.996 179.951 179.974 179.998 179.995 179.988 -179.938 0.067

Table 2: Definition of local-symmetry coordinates and the Pre-proof values of corresponding scale factors used to correct the Journal B3LYP/6-311G++ (d, p) force field calculations of 6-hydroxycoumarin Where

Symbol a

No.(i) Stretching 1-6 7-11 12-13

Definition b

Scale factors

ν(C-C)(Ring1) ν(C-C)(Ring2) ν(C-O)sub

R1, R2, R3, R4, R5, R6 R7, R8, R9, R10, R11 R12, R13

0.992 0.702 0.778

14-16

ν(C-H)(Ring1)

R14, R15, R16

0.749

17-18

ν(C-H)(Ring2)

R17, R18

0.994

ν(O-H)(sub)

19

R19

0.800

In-Plane bending

βRasy βRsym

26-30

β(C-H)

31 32

β(C-O) β(C-OH)

ro

24-25

of

22-23

(γ 20-γ 21+ γ22-γ 23+ γ24-γ25)/√6, (γ 26-γ 27+ γ28-γ 29+ γ30-γ31)/√6 (2γ 20-γ 21- γ22+2γ23- γ24-γ25)/√12, (2γ 26-γ 27- γ28+2γ29- γ30-γ31)/√12 (γ 21- γ22+ γ24-γ25)/2, (γ 27- γ28+ γ30-γ31)/2 (γ32- γ33)/√2, (γ34-γ35)/√2, (γ36-γ37)/√2, (γ 38-γ39)/√2, (γ 40-γ41)/√2 (γ 42-γ43)/√2 γ 44 (γ 45-γ46)/√2

re

β(C-C-O) 33 Out of plane bending 34-38 ω (C-H) 39-40 ω (C-O)

ρ47, ρ48,ρ49, ρ50,ρ51 ρ52, ρ53

Torsion τ RING tri

43-44

τ RING asy

45-46

τ RING sym

(τ 54-τ55+τ56-τ57+τ58-τ59)/√6, (τ 60-τ61+τ62-τ63+τ64-τ65)/√6 (τ 54-τ56+τ57-τ59)/2, (τ 60-τ62+τ63-τ65)/2 (-τ54-2τ55-τ56+τ57+2τ58-τ59)√12, (-τ60-2τ61-τ62+τ63+2τ64-τ65)√12 (τ66-τ67)/2 ( τ68- τ69)/2

ur

na

41-42

τ BUTT τ CCOH

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47 48

-p

βRtri

lP

20-21

0.998, 0.958 0.998, 0.958 0.998, 0.958 0.979 0.783 0.948 0.995 0.950 0.912

0.884,0.921 0.884,0.921 0.884,0.921 0.992 0.913

a=cos1440, b=cos720. Abbreviations: ν, stretching;, in plane bending; ω, out of plane bending; τ, torsion, tri, trigonal deformation, sym, symmetrical deformation, asy, asymmetric deformation, butt, butterfly, sub, substitution. a These symbols are used for description of the normal modes by PED b The internal coordinates used here are defined in the table given in supplementary material 1

Journal Pre-proof

Table3: Detailed assignments of fundamental vibrations of 6-Hydroxycoumarin by normal mode analysis based on SQM force field calculations using B3LYP/6311++G(d,p)method. Mode no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

FT-IR Experimental frequencies (cm-1) Theoretical frequencies (cm-1) a scaled Unscaled 3434 (s) 3438 3838 3384 3214 3337 3206 2778 3193 1897 (w) 2735 3165 1841 (vs) 2724 3153 1642 1799 1621 (w) 1624 1668 1585 (s) 1591 1652 1504 1608 1455(w) 1473 1522 1407 1478 1371 (vw) 1372 1420 1339 (s) 1356 1376 1272 1311 1231 1285 1178 1275 1161 1198 1138 (vw) 1137 1194 1133 1176 1087 1135 984 1094 975 997 948 (s) 944 969 922 962 836 912 832 863 819 856 804 841 801 826 729 (s) 731 766 705 739 650 694

l a

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b

IR Intensity 74.329 0.247 8.623 0.676 0.791 12.786 84.796 47.139 640.957 113.838 76.298 29.816 3.895 10.167 0.620 65.526 101.162 157.989 31.447 71.253 2.879 73.498 0.285 0.649 12.767 65.249 18.488 20.934 18.521 126.610 23.264 3.618 1.489

c

122.112 151.777 89.326 172.182 68.458 89.300 61.555 16.570 175.338 11.563 83.753 36.644 3.598 179.160 0.890 76.215 2.412 11.850 68.530 12.243 69.755 30.106 2.359 0.132 14.845 0.142 7.285 0.007 0.251 8.371 16.468 0.606 0.763

Assignments (PED)

υ OH sub (100) υ CHR2 ( 99) υ CHR2( 99) υCHR1 ( 99) υCHR1 ( 99) υCHR1 ( 99) υ CCR1 ( 62), βCH ( 13) υ CCR1 ( 59) υ COsub ( 65), υ CCR1 ( 14) βCH ( 46), υ CCR1 ( 33) υ CCR1 ( 36), βCH ( 27) βCH ( 33), υ CCR2 ( 28), υ CCR1 ( 22) βCH ( 72), υ CCR2 ( 14) υ CCR1 ( 82) βCH ( 56), υ CCR1 ( 18) υ CCR1 ( 22), υ COsub ( 21), βR1tri ( 20) βCH ( 30), υ CCR2 ( 30), υ CCR1 ( 15) βCOH ( 39), υ CCR1 ( 24), βCH ( 18) βCH ( 47), υ CCR2 ( 23), υ CCR1 ( 14) βCH ( 51), υ CCR1 ( 19) υ CCR2 ( 29), βR1tri ( 26), βCH ( 20) υ CCR2 ( 49), βCO ( 16) ωCH ( 94) ωCH ( 89) υ CCR2 ( 22), υ CCR1 ( 22), βR1sym ( 16) ωCH ( 75) βR2tri ( 51), υ COsub ( 14) ωCH ( 81) ωCH ( 79) υ CCR2 ( 73) βR1asy ( 42), υCCR1 ( 21) τR2tri ( 41), ωCO ( 24), τR1tri ( 21) τR1tri ( 52), ωCO ( 28)

f o

o r p

e

r P

d

Raman Activity

Journal Pre-proof

34 35 36 37 38 39 40

41 42 43 44 45 46 47 48

609 (s) -

630 566 546 515 483 431 423 365 361 340 274 243 172 148 75

685 592 572 542 506 454 438 385 381 356 274 255 180 155 78

a

4.896 25.048 2.344 4.221 7.684 10.405 10.660 1.206 4.548 4.003 108.187 1.773 0.657 1.788 1.741

υ CCR2 ( 51) βR2asy ( 27), βR1asy ( 21) ωCO ( 50), τR1sym ( 25) βR2sym ( 34), βR1sym ( 25) βCO ( 29) τR1asy ( 42), τBUTT ( 28) βCCO ( 25), βR2asy ( 23), βCO ( 18) τR2asy ( 25), τR1asy ( 20), ωCH ( 17) βCCO ( 22), υ CCR2 ( 20), βR1sym ( 19) ωCH ( 27), τR2tri ( 21), τR2asy ( 17) τCCOH ( 86) υ CCR2 ( 22), βCCO ( 20), βR2sym ( 15) τR2tri( 30), τ R1sym ( 19), τ R2asy (16) τR2sym ( 33), τBUTT ( 20) τR2asy ( 32),τR2sym ( 24),τR2tri (21)

f o

o r p

e

r P

4.866 2.322 0.377 4.252 2.641 0.331 10.997 2.911 14.273 0.311 1.596 0.346 0.153 0.717 0.149

Scaling factor : 0.74 above 3000 cm−1 and 0.743 below 3000 cm−1 for B3LYP/6-311++G(d,p). Relative absorption intensities normalized with highest peak absorption equal to 100. c Relative Raman intensities normalized to 100. d Only PED contributions ≥10% are listed. e Abbreviations: υ, stretching; β, in plane bending; ω, out of planebending; τ, torsion, ss, symmetrical stretching, as, asymmetrical stretching, sc, scissoring, wa, wagging, twi, twisting, ro, rocking,ipb, inplanebending, opb, out-of -planebending; tri, trigonal deformation, sym, symmetrical deformation, asy, asymmetric deformation, butter, butterfly, ar, aromatic, sub, substitution, vs, verystrong; s, strong; ms, medium strong; w, weak; vw, very weak. b

l a

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Journal Pre-proof

Τable 4: Second order perturbation theory analysis of fock matrix in NBO basis for 6-HC

C4-C9 C5-C6 C5-C6 C5-H10 C6-O18 C9-C11 C9-C11 C9-H13 C11-C12 C11-H14 C12-O16 C12-O17 C12-O17 H15-O18 O16 O16 O17 O17 O18 C12-O16 a

1.96988 1.60914

1.99046 1.96802 1.97305 1.97849 1.69587 1.97826 1.99439 1.98132 1.82942 1.98016 1.98208 1.97622 1.99030 1.99447 1.98002 1.98726 1.96212 1.74253 1.98002 1.83174 1.97891 1.88239 0.12412

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

of

C3-O16 C4-C5

1.97469 1.97753

0.03296 0.02341 0.43406 0.36038 0.02441 0.02111 0.02441 0.02348 0.02478 0.03506 0.02111 0.02009 0.30915 0.36038 0.13452 0.02009 0.03506 0.02341 0.02009 0.01204 0.02478 0.30915 0.43406 0.03506 0.01064 0.02009 0.02348 0.43406 0.28318 0.05656 0.01526 0.02348 0.12412 0.02111 0.05656 0.13452 0.02478 0.03506 0.05656 0.43406 0.28318 0.05656 0.05656 0.12412 0.02441 0.36038 0.03296 0.01204

E(2)a (kcal/mol) 4.15 3.42 19.80 19.91 4.01 3.44 4.02 2.70 3.35 4.27 4.39 3.58 17.72 17.69 15.05 1.51 3.81 4.27 3.32 2.78 4.15 17.09 19.30 4.13 1.26 3.09 2.89 11.35 20.97 4.15 3.29 4.51 4.26 2.14 1.97 5.47 4.30 6.18 4.54 28.57 35.04 2.89 16.11 37.54 6.04 27.75 18.61 1.97

ro

C3-C4

1.97331 1.97801

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

-p

C3-C4

1.70807

C3-O16 C6-O18 C3-C4 C5-C6 C5-C6 C2-C3 C5-C6 C4-C9 C1-C6 C3-C4 C2-C3 C4-C5 C1-C2 C5-C6 C9-C11 C4-C5 C3-C4 C6-O18 C4-C5 C11-H14 C1-C6 C1-C2 C3-C4 C3-C4 C1-C2 C4-C5 C4-C9 C3-C4 C12-O17 C11-C12 C9-H13 C4-C9 C12-O16 C2-C3 C11-C12 C9-C11 C1-C6 C3-C4 C11-C12 C3-C4 C12-O17 C11-C12 C11-C12 C12-O16 C5-C6 C5-C6 C3-O16 C11-H14

Ed/e

re

C2-C3 C2-H8

1.97365

Type

lP

C1-C6 C1-H7

σ σ π π σ σ σ σ σ σ σ σ π π π σ σ σ σ σ σ π π σ σ σ σ π π σ σ σ σ σ σ π σ LP LP LP LP LP LP LP LP LP σ* σ*

Acceptor(j)

na

C1-C2

Ed/e

ur

C1-C2

Type

Jo

Donor(i)

E(j)-E(i)b (a.u) 1.06 1.05 0.28 0.28 1.27 1.08 1.09 1.21 1.07 1.07 1.27 1.26 0.29 0.29 0.29 1.47 1.25 1.04 1.24 1.13 1.27 0.30 0.29 1.09 1.51 1.31 1.26 0.30 0.30 0.99 1.11 1.03 0.85 1.44 1.53 0.40 1.29 1.09 0.99 0.35 0.35 1.13 0.70 0.56 1.18 0.35 0.03 0.12

f(i,j)c (a.u) 0.059 0.054 0.069 0.068 0.064 0.054 0.059 0.051 0.053 0.061 0.067 0.060 0.066 0.064 0.064 0.042 0.062 0.060 0.057 0.050 0.065 0.064 0.069 0.060 0.039 0.057 0.054 0.056 0.073 0.058 0.054 0.061 0.055 0.050 0.050 0.043 0.067 0.073 0.060 0.093 0.100 0.052 0.097 0.131 0.075 0.094 0.077 0.053

Journal Pre-proof

Table5: The calculated quantum chemical parameters for 6-hydroxycoumarin obtained by B3LYP/6311++G** calculations. 6-hydroxycoumarin

ro

of

-15575.858363 -6.4980821 -2.3412688 4.1568133 6.4980821 2.3412688 7.6687165 4.41967545 5.3274477 1.83329167 0.18770714 5.5990

Jo

ur

na

lP

re

-p

Property Total energy (eV) EHOMO(eV) ELUMO(eV) Energy gap (ΔE) (eV) Ionization potential (I) eV Electron Affinity (A) eV Electro-negativity (χ) eV Chemical Potential (μ) Chemical hardness(η) eV Electrofilicity index (ω) eV Global Softness (σ) eV Dipole moment (D)

Journal Pre-proof

Table 6: The electric dipole moment (D), average polarizability, first hyperpolarizability, etc., of 6-HC by quantum calculation

𝜷 components

17.57119×10-24

βxxx βxxy βxyy βyyy βxxz βxyz βyyz βxzz βyzz βzzz 47.72213318×10-24esu βtotal (esu)

of

1.6626 1.4450 0.0009 4.8524 181.9068 -4.2111 115.3935 0.0015 0.0026 58.3966

re lP na ur Jo

B3LYP/6-311++G**

ro

B3LYP/6311++G**

-p

µ and 𝛂 components µx µy µz µ(D) αxx αxy αyy αxz αyz αzz Δα 𝛼0 (esu)

-344.4361 112.4676 -51.3494 49.4611 0.0444 0.0114 -0.0245 22.7462 14.9624 -0.0133

3.566699×10-30

Table 7: Atomic charges for optimized geometry of 6-HC at B3LYP/6-311++G(d,p) level of theory Journal Pre-proof

re lP na ur Jo

Mulliken 0.051840 -0.466538 -2.312989 2.396587 0.236316 -0.459622 0.208543 0.213180 -0.113455 0.109668 -0.077670 0.194284 0.165705 0.220689 0.267699 -0.114415 -0.290918 -0.228905

of

ATP -0.038404 0.082820 0.282239 -0.124960 -0.014800 0.534493 0.000000 0.000000 0.354530 0.000000 -0.229475 1.224519 0.000000 0.000000 0.000000 -0.697322 -0.906587 -0.467053

ro

Atom C1 C2 C3 C4 C5 C6 H7 H8 C9 H10 C11 C12 H13 H14 H15 O16 O17 O18

-p

S.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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Graphical Abstract Journal Pre-proof

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6-hydroxycoumarin

Highlights Journal Pre-proof Title: Structural, vibrational and electronic spectroscopic study of

6-Hydroxycoumarin using experimental and theoretical methods

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FT-IR, UV Vis spectra of 6-Hydroxycoumarin Vibrational analysis NBO analysis NLO properties HOMO-LUMO analysis Molecular Electrostatic potentials Maps

Jo

     

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7