A multiscale computational investigation for protection of carbon steel surface by pyrazolo-pyrimidine derivatives

The potential corrosion inhibition properties of pyrazolo-pyrimidine derivatives with extended π system for carbon steel in acidic medium were investigated through a combined DFT, Monte Carlo and molecular dynamic simulations to establish the relationship between electronic properties and adsorption behavior. Geometrical optimization, quantum chemical parameters, (FT-IR) and UV-Vis spectra were explored. The charge transfer and primary sites of adsorption corresponding to enhancement the corrosion inhibition were identified by NBO and Fukui analysis. The Pauli exchange repulsion effect was utilized for the examination of Localized Orbital Locator and Electron Localization Function. To identify bonding and anti-bonding interactions, a study of non-covalent interaction was conducted. Monte Carlo and molecular dynamic simulations predicted strong adsorption energies and explained the stability of inhibitor metal complexes. The ethyl ester substituted inhibitor showed the smallest energy gap (4.640 eV) and the highest negative adsorption energy (- 129.998 kcal·mol^-1), indicating superior adsorption capability and inhibition efficiency. These findings offer theoretical framework for designing efficient corrosion inhibitors with extended π systems for carbon steel protection.