DFT theoretical studies of antipyrine Schiff bases as corrosion inhibitors



The anti-corrosive properties of some antipyrine Schiff bases (benzylidine amino)antipyrine (a), 4-hydroxy 3-(benzylidine amino)antipyrine (b), 2-hydroxy 3-(benzylidine amino)antipyrine (c), and 2-hydroxy 3-(naphthylidine amino)antipyrine (d) are studied using density functional theory at the B3LYP/6-31G level. The computational calculations are performed to find a relation between their electronic and structural properties and the inhibition efficiency. The calculated quantum chemical parameters correlated to the inhibition efficiency are, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the separation energy (ΔE), the dipole moment (µ), the softness (σ), the total negative charge on the whole molecule (TNC), the total charge on the azomethine moiety, the molecular volume (Vi), and the total energy (TE). A good correlation between the quantum chemical parameters and the experimental inhibition efficiency is found.