A Combined DFT and Molecular Simulation Study of Pyrazolo-Pyrimidine Derivatives as Carbon Steel Corrosion Inhibitors

Abstract A combined density functional theory, Monte Carlo (MC) and molecular dynamics simulation approach was employed to explain the corrosion inhibition potential of three pyrazolo-pyrimidine derivatives with extended π conjugation on Fe (110) carbon steel in an acidic medium. Optimized geometries and quantum chemical descriptors provided fundamental insights into electronic properties and molecular reactivity, supported by Fourier transform infrared and UV-visible spectral analyses. Molecular electrostatic potential mapping, Fukui function indices and natural bond orbital analysis identified oxygen and nitrogen centres as preferential adsorption centres, reinforced by strong donor–acceptor interactions. The Pauli repulsion effect was analysed using localized orbital locator and electron localization function methods. Non-covalent interaction highlighted weak interactions such as hydrogen bonding, van der Waals forces, π–π stacking and steric repulsion by identifying attractive and repulsive regions based on electron density. MC and molecular dynamics simulations confirmed strong adsorption energies and demonstrated the stability of the inhibitor metal complexes. The outcomes of these computational analyses are expected to offer valuable guidance for the future development and practical use of pyrazolo-pyrimidine derivatives as effective compounds for carbon steel corrosion protection.