Vibrational Spectra of 1,3-bis-acto-5-substituted methyl Benzimidazoline-2-thiones: An Antiviral and Antifungal Drug

INTRODUCTION

1,3-bis-acto-5-substituted benzimidazoline-2-thionesis a chemically active compound that shows the property of Antiviral and Antifungal Drugs. Benzimidazole derivatives are being explored in pharmaceutical industries and substituted benzimidazole derivatives have also been found in the diverse therapeutic applications such as in anti-ulcers, antihypertensive, anti-viral, anti-fungal, anti-cancers and anti-histaminics. On the other hand, such benzimidazole derivatives are condensed with other heterocycles like pyrazole, thiadiazole, triazole, thiazole, coumarin and 2- azetidinone moieties which have shown diverse pharmacological activities. compound.Benzimidazoles have different activities as they can act as bacteriostats or bactericides, anticarcinogens, etc. They are often bioactive.Bezimidazole fungicides are commercialized. They act by binding to the fungal microtubules and stopping hyphal growth. They are applied to cereals, fruits, vegetables and vines, and are also used in post-harvest handling of crops. The solubility of Bezimidazole fungicides is low at physiological pH and becomes high at low ph. Since 1952 the antiviral activity of benzimidazole has been studied extensively. A major stimulus during this work has been the central finding that virus-inhibiting activity and cell toxicity of chemical derivatives of benzimidazole may vary independently. The introduction of 1,3-bis-acto-5-substituted benzimidazoline-2-thiones as an antiviral and antifungal agent marked a most important step of the investigations on selective inhibition of viral and fungal replication. Benzimidazoles are also known as benziminazoles and 1,3-benzodiazoles.1,2 They possess both acidic and basic characteristics. The NH group present in benzimidazoles is relatively strongly acidic and also weakly basic. Another characteristic of benzimidazoles is that they have the capacity to form salts. Benzimidazoles with unsubstituted–NH- groups exhibit fast prototropic tautomerism, which leads to equilibrium mixtures of asymmetrically substituted compounds. The molecular geometry optimization, energy and Vibrational frequency calculations have been performed for 1,3-bis-acto-5-substituted benzimidazoline-2-thiones using Gauss view

investigate the structural, magnetic and electronic properties of molecules, materials and defects DFT calculations allow the prediction and calculation of material behaviour on the basis of quantum mechanical considerations, without requiring higher order parameters such as fundamental material properties. DFT computational methods are applied for the study of systems to synthesis and processing parameters. In such systems, experimental studies are often encumbered by inconsistent results and non-equilibrium conditions.

The optimized geometry, frequency and intensity of the vibrational bands of 1, 3-bis-acto-5-substituted benzimidazoline-2-thiones were obtained by the Restricted Hartree-Fock (RHF) density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G basis set. The harmonic vibrational frequencies for 1,3-bis-acto-5-substituted benzimidazoline-2-thiones were calculated and the scaled values have been compared with experimental values of FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The harmonic vibrational wave numbers and intensities of vibrational bands of 1,3-bis-acto-5-substituted benzimidazoline-2-thiones with its cation and anion were calculated and compared with the neutral 1,3-bis-acto-5-substituted benzimidazoline-2-thiones. The DFT calculated HOMO and LUMO energies shows that charge transfer occurs within the molecule. DFT calculations allow the prediction and calculation of material behavior on the basis of quantum mechanical considerations, without requiring higher order parameters such as fundamental material properties. Optimized geometrical structure of 1,3-bis-acto-5-substituted benzimidazoline-2-thiones;

spectra of optimized geometrical structure of chemical compound1,3-bis-acto-5-substituted benzimidazoline-2-thioneswere also evaluate from the calculation of intensities. Then the followingfigures show the calculated IR and Raman spectra of Optimized geometrical structure1,3-bis-acto-5-substituted benzimidazoline-2-thiones .These calculations were done by using B3LYP/6˗31G methods.

Bond dipole moment of Optimized geometrical structural compound is the measurement of polarity of a chemical bond and also known as the mathematical product of the separation of the ends of a dipole and the magnitude of the charges. The dipole moment creates by unequal sharing of electron in optimized geometrical molecules by their atoms. Dipole moment and energy of the medically active compound 1,3-bis-acto-5-substituted benzimidazoline-2-thionesis shown in following table:- (1 Debye = 3.34*10-30 cm.) (1 a.u. of energy = 1hartree = 4.360 × 10−18 J. = 27.211eV = 2625kJ/mol = 627.5kcal/mol.)

The most important orbitals in a molecule are the frontier molecular orbitals, called highest occupied molecular orbital (HOMO) and lowest unoccupied chemical reactivity and kinetic stability of the molecule. A molecule with a small frontier orbital gap is more polarizable and is generally associated with a high chemical reactivity, low kinetic stability and is also termed as soft molecule. HOMO and LUMO are types of molecular orbitals. The acronyms stand for "highest occupied molecular orbital" and "lowest unoccupied molecular orbital", respectively. The energy difference between the HOMO and LUMO is termed the HOMO–LUMOgap. HOMO and LUMO are sometimes called frontier orbitalsin frontier molecular orbital theory. The difference in energy between these two frontier orbitals can be used to predict the strength and stability of transition metal complexes, as well as the colors they produce in solution. Energy levels of the frontier molecular orbital‘s especially HOMO, LUMO as well as their spatial distributions are important parameters for determining the optoelectronic properties. The density plot of the HOMO and LUMO of 1,3-bis-acto-5-substituted benzimidazoline-2-thionesis calculated at B3LYP/6-31G level of theory and are shown in Figure;

The energy gap between HOMO and LUMO has been used to prove the bioactivity from intermolecular charge transfer. The energy gap measures the kinetic stability of the molecules. The HOMO and LUMO energy gap show the charge transfer interaction taking place within the molecule. The HOMO and LUMO energy calculated by B3LYP /6-31G method as shown below in table:-

In molecular geometry, bond length or bond distance is the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest of the molecule. Molecular geometries can be specified in terms of bondlengths, bond angles and torsional angles. The bond length is defined to be the average distance between the nuclei of two atoms bonded together in any given molecule. A bond angleis the angle formed between three atoms across at least two bonds. The such as bond lengths, bond angle are the optimized structural parameters , so these parameters were determined at B3LYP level theory with 6-31G basis set and they are presented in a table, which is given below –

H22-C21 1.09124 O16-C14 1.36054 N12-C7 1.43565

O15-C17 1.46862 C17-H20 1.09178 C3-H8 1.07994 C1-C6 1.39283 H9-C5 1.08227 C5-C4 1.40513 C4-O26 1.38954 O26-C27 1.45165 C27-H29 1.08921 H30-C27 1.09641

H22-C12-H24 111.268 H23-C21-O16 107.593 O16-C14-N12 107.413 N12-C7-S25 126.203 C7-N11-C2 109.547 C7-N11-C13 133.889 O15-C13-C17 33.630 H18-C17-H20 111.506 H19-C17-O15 107.120 C2-C1-N12 107.020 C1-C6-C5 118.131 H9-C5-C4 120.628 H8-C3-C4 121.360 C27-O26-C4 118.990 H30-C27-O26 111.294 H28-C27-H29 109.725

substituted benzimidazoline-2-thionesis on progress. It will be reported very soon.

I would like to thank my parents, who push me towards good education.I wish to thank my teachers, They made me enjoy learning new things and take new heights in life. We are very grateful to the DSMNR University Lucknow for the facility provided.

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Micromolecular and Biophysics Laboratory, Department of Physics, Dr. Shakuntala Mishra National and Rehabilitation University, Mohan Road, Lucknow