Molecular structure optimization design of inhibitors based on frontier orbitals theory

Imidazoline derivatives with 7 levels of HOMO energy and imidazoline quaternary ammonium salts with 4 different LUMO energy levels were designed by adjusting the hydrophilic and hydrophobic groups of the imidazoline molecule. The changes in adsorption bonding and electron transfer of the imidazoline molecule on the metal surface were calculated by the density functional based tight binding method (DFTB+). It was found that when the HOMO and LUMO energy levels matched the iron Fermi level more closely, the imidazoline molecule could undergo more electron transfer with the iron substrate, thereby forming a stronger adsorption bond with the matrix. The corrosion inhibition performance of the imidazoline groups was further tested by electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). Finally, a clear correspondence between the frontier orbital energy level of the imidazoline molecule and its corrosion inhibition performance was discussed, which could provide an effective solution for designing high performance corrosion inhibitor molecules.