Reactivity and Fe complexation analysis of a series of quinoxaline derivatives used as steel corrosion inhibitors

The B3LYP/6-31G(d,p) calculations were conducted to establish a correlation between structural electronic properties and corrosion inhibition efficiencies of four quinoxaline derivatives. The Fukui functions reflecting the local reactivity centers were investigated to determine the Fe-complexes by the studied ligands. Three spin multiplicities were examined and the quintet complexes were the most stable. Five types of interactions between Fe and quinoxaline compounds were studied, i.e., Fe–2S, Fe–2O, Fe–ϕ, Fe–S, and Fe–O among 10 complexes. While the calculated binding energies of the chelating bidentate complexes Fe–2O/2S were the lowest, Fe–ϕ presented a higher energy value without loss of aromaticity.