Functional\nGroup Effects on the Interfacial Adsorption\nof Arylquinoline-3-Carbonitriles on Iron: A DFT-D3 Investigation of\nSurface Interaction Mechanisms

Reliable corrosion inhibition systems are crucial for\nextending\nthe lifespan of industrial metal structures. Quinolines, with their\nhigh adsorption capacity and protective efficiency, are promising\nnext-generation inhibitors. However, the impact of substitutions on\ntheir coordination with iron surfaces requires deeper understanding.\nHerein, we investigate the influence of various functional groups\non the adsorption behavior of three 2-amino-4-arylquinoline-3-carbonitriles\n(AACs) on iron surfaces using first-principles density functional\ntheory calculations. Results reveal that nitrophenyl and hydroxyphenyl\nsignificantly enhance the adsorption strength of AACs on the Fe(110)\nsurface, facilitated by donor–acceptor interactions. Neutral\nmolecules were more stable than their protonated counterparts. Key\nresults show strong adsorption energies, with values ranging from\n−2.005 to −1.809 eV for the AACs, along with significant\nelectron gains across carbon atoms as indicated by Bader charge analysis.\nThese strong interactions result in notable charge redistribution\nand bond formation, as shown by projected density of states and electron\ndensity difference iso-surfaces. Furthermore, electron localization\nfunction analysis indicates that van der Waals interactions, influenced\nby multiple nitrogen atoms, play a crucial role in stabilizing the\nadsorbed molecules. Stronger adsorption through electron donation\nand retro-donation mechanisms suggests enhanced corrosion protection\nefficiency of these substituted quinolines. The conductor-like screening\nmodel for real solvents analysis provides complementary insights into\nthe solvation characteristics. Overall, the findings demonstrate the\nspecific role functional groups play in the coordination of arylquinoline-3-carbonitriles\nwith iron surfaces.