THEORETICAL STUDY USING DFT CALCULATIONS ON INHIBITORY ACTION OF SOME PYRAZOLE DERIVATIVES ON STEEL

Abstract

The inhibition activity of two pyrazole derivatives, namely 1-{[benzyl-(2-cyano-ethyl)amino]methyl}-5-methyl-1H-pyrazole-3-carboxylic acid methyl ester (P1) and 1-{[benzyl-(2-cyano-ethyl)amino] methyl}-5-methyl-1H-pyrazole-3-carboxylic acid ethyl ester (P2) has been performed using density functional theory (DFT) at the B3LYP/6-31G(d,P) basis set level in order to elucidate the different inhibition efficiencies and reactive sites 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 pyrazole molecules to iron . The local reactivity has been analyzed through the condensed Fukui function and condensed softness indices using population analysis. The calculated % IE was found to be in agreement with experimental corrosion inhibition efficiencies.