Monte Carlo Simulation Study on Enamine Derivatives

Abstract

A thorough understanding of molecular-level processes at the metal-electrolyte boundary is necessary for the design of highly effective, environmentally friendly organic inhibitors. The interfacial adsorption thermodynamics, spatial orientation mechanisms, and corrosion inhibition efficacy of seven enamine derivatives (L1–L7) on the Fe(110) substrate were examined in this work using Advanced Monte Carlo (MC) simulations. Highly negative adsorption energies (Eads) ranging from -551.33 to -954.50 kJ mol-1 were shown by simulated annealing protocols (30,000 steps over three cycles) with the COMPASSIII force field, indicating energetically favorable adsorption and strong inhibitor–surface interactions. The hierarchical order is strictly followed by the computational binding affinity: L5 > L7 > L4 > L6 >> L1 > L3 > L2. Important mechanistic insights into molecular spatial adaptation were obtained by deconvolution of Eads into rigid adsorption (Erigid) and structural deformation (Edeformation) components. Strong charge-transfer interactions involving heteroatoms (N, O), delocalized π-electrons, and unoccupied Fe d-orbitals are displayed by the best-performing cluster (L4–L7, Eads < -918 kJ mol-1); side-view analysis showed different equilibrium separation distances (deq) for L2 and L7. Interestingly, L7 adopts a parallel aromatic alignment to maximize surface coverage footprint, thereby overcoming a severe geometric deformation penalty (-637.14 kJ mol-1). Stable adsorption configurations derived from the Monte Carlo calculations are consistent with the strong numerical agreement between Eads and differential adsorption energy (dEads/dNi). These findings support the idea that enamine architectures, particularly L5 and L7, are good candidates for cutting-edge corrosion prevention techniques for mild steel.