DFT and PM3 calculation Studies on Pyrrole Oligomers as Corrosion Inhibitors of Aluminum

Résumé

Theoretical Quantum chemical studies was performed on Pyrrole oligomers as corrosion inhibitors of Aluminum, using density functional theory(DFT) at the B3LYP/6-31 G level (d) and semi-empirical methods(PM3) to search the correlation between the molecular structure and corrosion inhibitor efficiency. The calculated energy of highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and energy gap (ΔE = EHOMO- ELUMO) for Pyrrole oligomers (1 to 10) were calculated. Quantum chemical parameters such as , the inhibitor to metallic surface, electrophilicity (electrons transfer from metals to the anti π- orbitals of the inhibitors), chemical softness (σ) and chemical hardness (η) of Pyrrole oligomers were reported. The interactions of these frontier molecular orbital's (ELUMOinh- EHOMOAl and ELUMOAl- EHOMOinh) with Aluminum reveal that charge transfer mechanism may be responsible for the binding or adsorption of these compounds onto the metal surface. It was found that the corrosion inhibitor efficiencies of Pyrrole oligomers increase with an increasing the number of Pyrrole units in Pyrrole oligomers structure, which is in agreement with the previous published experiment