The investigation of corrosion inhibition efficiency on some benzaldehyde thiosemicarbazones and their thiole tautomers: Computational study

• Quantum chemical calculations are performed on three benzaldehyde thiosemicarbazones inhibitors.
• NBO charges, proton affinities and Fukui functions are used to determine the active sites.
• Inhibition efficiency follows the order: 4DMBTSC > BTSC > PClBTSC.
• Inhibition efficiencies of thione tautomers are higher than their thiole tautomers.
• Correlation constant between experimental and theoretical inhibition efficiencies are calculated as 0.999 and this result is a good and acceptable.

Quantum chemical calculations using three methods, Hartree–Fock (HF), Møller–Plesset (MP) and density functional theory (DFT/B3LYP) method with SDD, 6−31G(d,p) and 6−31++G(d,p) basis sets are performed some benzaldehyde thiosemicarbazones and their thiole tautomers. The results of the quantum chemical calculations and experimental IE% which are belong to thione tautomers are subjected to correlation analysis and indicate that their inhibition effect are closely related to some quantum chemical parameters. The active sites are determined by using MEP diagrams, proton affinities and Fukui functions. The theoretically obtained results are found to be consistent with the experimental data which are reported for thione tautomers.