Ionic liquids-metal surface interactions: Effect of alkyl chain length on coordination capabilities and orientations

The present study describes the interaction of fifteen ionic liquids differing in alkyl chain length and halide ions with the iron (steel) surface using computational methods such as density functional theory (DFT), Monte Carlo (MC), and molecular dynamics (MD) simulations. Various reactivity parameters were derived to describe their reactivity towards anticorrosive and metal decontamination applications. DFT analysis suggests that all fifteen ionic liquids acquire a strong tendency to interact with the metal surface and an increase in the length of alkyl chain length improves their bonding performance. Along with frontier molecular orbital pictures, numerous reactivity indices were derived for the ionic liquids to describe their interactions with the metallic substrate. Through DFT analyses, it was assessed that the binding tendency of the ionic liquids greatly enhanced with the rise in the length of hydrocarbon chain length. Monte Carlo (MC) and molecular dynamics (MD) simulations indicated that all tested ionic liquids adsorb on the metallic surface spontaneously through planar orientation. Based on DFT, MD, and MC, simulations studies, it can be concluded that the binding tendency of ionic liquids with the metal surface and therefore their anticorrosive and metal decontamination tendency increase on extending the length of hydrocarbon chain length.