Investigation of the substitution impacts on 2-mercaptobenzothiazole (2-MBT) derivatives as volatile corrosion inhibitor: A DFT study

Corrosion is a primary concern in industrial environments because of its economic impact. This study provides a novel investigation of substitution effects on the anticorrosion performance of two tautomeric forms of mercaptobenzothiazole (MBT), examining the adsorption of these molecules on the copper (1 1 1) surface using the DFT and Conductor-like Screening Model (COSMO) methods. Adsorption behavior was studied in both gas and liquid phases (implicit and explicit solvent models) across three orientations, including parallel, perpendicular-S, and perpendicular-N. Each MBT derivative was designed with a single substituent, located either at position 4 or at position 7 of the ring, with the studied groups including electron-donating (OCH₃, CH₃) and electron-withdrawing (Cl, F, CN, NO₂). Significant quantum chemical descriptors, such as adsorption energy, HOMO and LUMO energy, and their energy gap, fraction of electron transfer, softness, hardness, and reactivity parameters like the Fukui function, Mulliken atomic charge, and Density of States, were calculated to assess reactivity and inhibition efficiency. According to outcomes, between the two tautomeric forms, the thione form exhibits stronger adsorption on the copper surface compared to the thiol form. Also, both strong electron-donating and electron-withdrawing groups enhance the adsorption strength and inhibition efficiency. In line with findings, the thione tautomer containing a methoxy (OCH₃) group in perpendicular-s mode exhibited the strongest adsorption among all derivatives and modes, with an adsorption energy of –53.42 kcal/mol. Ultimately, these computational insights provide the scientific community with specific chemical guidelines for designing highly efficient MBT derivatives. • MBT derivatives effectively protect copper against corrosion. • Strong electron-donating and electron-withdrawing groups enhance inhibition efficiency. • Electron-donating groups increase electron transfer to copper. • Local H 2 O-inhibitor interactions stabilize the inhibitors' adsorption on copper. • The electrostatic effect of water reduces the inhibitors' stability on copper.