Theoretical Insights into the Anti-Corrosion Effectiveness of Indole-Based Compounds on Surfaces of Iron: An Integrated DFT Along with Monte Carlo Simulations Studies

Corrosion of metal surfaces remains a persistent challenge across industrial environments, necessitating the exploration of efficient and eco-friendly inhibitors. The aim and novelty of present study is the comprehensive theoretical investigation of ten indole-based derivatives ( ST1–ST10 ) as corrosion inhibitors efficiency for Fe surfaces. Using DFT at the B3LYP/6–311 ++ G(2d,p), we computed key electronic properties such as HOMO–LUMO energies, dipole moments, to assess molecular stability and reactivity. Natural Bond Orbital (NBO) analysis identified strong π → π*, σ → σ*, and LP → π* delocalization, confirming notable electron mobility within molecular frameworks. To sum, the chemical softness values show that the title compounds ST8 and ST10 preferentially exchange their associated electron clouds with the surrounding environment. These findings offer a robust multiscale framework for designing advanced indole-based inhibitors for corrosion protection in aggressive environments.