Computational Studies for Inhibitory Action of 2-Mercapto-1-Methylimidazole Tautomers on Steel Using of Density Functional Theory Method (DFT)

Tappa Vinod Kumar

doi:10.11648/j.ijctc.20160401.11

Abstract

The inhibition activity of thione–thiol tautomers of 2-mercapto-1-methylimidazole (MMI), namely 1-methyl-1H-imidazole-2 (3H)-thione (M1) and 1-methyl-1H-imidazole-2-thiol (M2) has been performed using density functional theory (DFT) B3LYP/6-311G (d, P) basis set level in order to elucidate the different inhibition efficiencies of these compounds as corrosion inhibitors. The calculated structural parameters correlated to the inhibition efficiency are the frontier molecular orbital energies EHOMO (Highest occupied molecular orbital energy), ELUMO (Lowest unoccupied molecular orbital energy), energy gap (ΔE), dipole moment (μ), hardness (η), softness (S), the absolute electronegativity (χ), the electrophilicity index (ω) and the fractions of electrons transferred (ΔN) from thione–thiol tautomer molecules to iron. The highest value of EHOMO is -5.30241 (eV) of M1 indicates the better inhibition efficiency than the other inhibitor M2. In our study, the trend for the (ΔEg gap) values follows the order M1>M2, which suggests that inhibitor M1 has the highest reactivity in comparison to M2 and would therefore likely interact strongly with the metal surface. The parameters like hardness (η), Softness (S), dipole moment (μ), electron affinity (EA) ionization potential (IE), electronegativity (χ) and the fraction of electron transferred (ΔN) confirms the inhibition efficiency in the order of M1>M2.

Highlights

Methimazole (MMI) (2-mercapto-1-methylimidazole) is known to have several chemotherapeutic applications, in the treatment of thyroid disorders
Grave's disease is the most common cause of hyperthyroidism. It is an autoimmune disease resulting from antibodies that attach to receptors on thyroid hormone producing cells in the thyroid gland and trigger over production of thyroid hormone
The geometries for thione and thiol forms of MMI molecule were fully optimized at density functional theory (DFT) level of theory using a B3LYP functional together with 6-311G (d, p) basis set in Thione (M1) Bond angle C2, C1, N5 C2, C1, H8 N5, C1, H8 C1, C2, N3 C1, C2, H9 N3, C2, H9 C2, N3, C4 C2, N3, C6 C4, N3, C6 N3, C4, C5 N3, C4, S7 N5, C4, S7 C1, N5, C4 C1, N5, H10 C4, N5, H10 N3, C6, H11 N3, C6, H12 N3, C6, H13 H11, C6, H12 H11, C6, H13 H12, C6, H13 Bond C1-C2 C1-N5 C1-H8 C2-N3 C2-H9 N3-C4 N3-C6 C4-N5 C4-S7 N5-H10 C6-H11 C6-H12 C6-H13

Summary

Introduction

Methimazole (MMI) (2-mercapto-1-methylimidazole) is known to have several chemotherapeutic applications, in the treatment of thyroid disorders. The reactions and coordination ability of S, N-containing heterocyclic ligands such as MMI have been of considerable interest both from the structural point of view and pharmacological importance [1] It is taken before thyroid surgery or radioactive iodine therapy. MMI prevents iodine and peroxidase from their normal interactions with thyroglobulin to form T4 and T3 Due to the enormous complexity of this type of studies which need to consider the metallic surface, inhibitor and solvent molecules, theoretical calculations of the corrosion inhibition processes cannot be achieved in a rigorous way from the viewpoint of quantum chemistry

Computational Details

Molecular Geometry

Global Molecular Reactivity

Conclusion