Theoretical Investigation of Molecular Properties of 5-benzyl-6- methyl pyridazine-3-one and 5-benzyl-6-methyl pyridazine-3- thione and their Potentials for Corrosion Inhibition for Steel

摘要

The present study theoretically investigates the molecular properties of two pyridazine derivatives (5-benzyl-6-methyl pyridazine-3-one, PO and 5-benzyl-6-methyl pyridazine-3-thione, PS) using quantumchemical technique (Parameterization Method 3). It is also an attempt to offer a non-experimentalaccount while justifying the respective contributions of PO and PS molcules as corrosion inhibitors visà-vis their adsorption on corroding steel substrates. These molecular level computations were conductedusing semi-empirical molecular orbital (MO) technique in vacuo and 0 K for spatial molecular structuresof pyridazines molecules with full geometry optimization. This was accomplished using the popularPolar-Ribiere algorithm with a convergence set of 0.1 kcal/(? mol) RMS gradient. Also computed anddiscussed are the differences in molecular energies (EHOMO and ELUMO), Mulliken interatomic charge,dipole moments, bond lengths and angles, refractivity, polarizability and partition coefficients of bothcompounds. The obtained theoretical results align with previously reported experimental corrosionbehaviours of both compounds. Corrosion inhibition was attributed to the formation of inhibitor layerson steel surface and this further reduced steel corrosion due to electronic activities involving electrondonation via HOMO orbitals of these pyridazines to the empty 3d-orbitals of iron substrate. The computemagnitudes of Ebinding obtained from molecular dynamic (MD) simulations revealed a strong Fe-surfaceinteraction for PS compared to PO.