Computational investigation of <i>Mesembryanthemum nodiflorum</i> as a copper corrosion inhibitor

Mesembrine (I), Mesembrenone (II), Mesembrenol (III), and Tortuosamine (IV), four compounds of
Mesembryanthemum nodiflorum
, were suggested as corrosion inhibitors on the surface of Cu (111) in an acidic solution. Using the 6-311G (d,p) basis set, theoretical investigations were conducted preferentially using density functional theory (DFT) at the B3LYP and M06 levels. To characterize the reactivity of each molecule, a variety of global and local reactivity descriptors were examined, including electronegativity (χ), hardness (η), frontier molecular orbital repartitions, E
HOMO
, E
LUMO
, and energy gap. However, in order to gain a deeper understanding of the adsorption behavior of the inhibitors under study, Monte Carlo simulations were examined on the Cu (111) surface. Additionally, the adsorption energies (E
ads
) were computed, which showed that the inhibitors are stable on the copper surface. From the comparative analysis, Mesembrenone (II) is identified as the most effective inhibitor, which is related to the smallest energy gap value and the highest binding energy. The results indicate that the presence of special π conjugated systems and oxygen heteroatoms has contributed to more effective charge transfer as well as more spontaneous adsorption on the Cu (111) surface. The order of ranking of the degree of inhibition efficiency is determined to be: II &gt; I &gt; III &gt; IV. This ranking order is mainly dominated by the presence of a conjugated carbonyl group in Mesembrenone (II), which reduces the band gap (ΔE) and thereby increases the amount of sharing of electrons with copper (111) surface, making its adsorption energy more negative.