The Quantum Chemical Investigation on the Structure-Activity Relationship of a Schiff Base Corrosion Inhibitor

This study investigated the relationship between the molecular structure and the corrosion inhibition efficiency of three corrosion inhibitors for steel in acidic media using the DFT method. First, the molecular conformations of the three compounds were optimized and the populations of charges and frontier orbitals were obtained at the B3LYP/6-311G level. Quantum chemical parameters were also obtained by calculations, including the highest occupied molecular orbital energy (EHOMO), the energy gap (ELUMO−EHOMO), the total energy of the molecule, the dipole moment and the number of electrons transferred (ΔN). The results of the correlation between quantum chemical parameters and inhibition efficiencies demonstrated that the inhibition efficiency of the inhibitors increased with the decrease of ELUMO-EHOMO and the increase of ΔN. The regions with nitrogen and oxygen atoms are the sites most likely to bond with iron atoms by donating electrons.