Quantum chemical and QSPR studies of bis-benzimidazole derivatives as corrosion inhibitors by using electronic and lipophilic descriptors

The inhibition ability of six bis-benzimidazole derivatives against corrosion of mild steel in acidic medium was modeled by the electronic and lipophilic descriptors such as: the energy of the highest occupied molecular orbital (E HOMO), the energy of the lowest unoccupied molecular orbital (E LUMO), the dipole moment (mu), the molecular critical volume (V-c), the inhibitor concentration (C-i), the logarithm of the partition coefficient (log P), and the molecular mass (M), by means of quantitative structure property relationships (QSPR). To do so, the structure electronic properties of these molecules were investigated by using three quantum methods: a semi-empirical method (AM1), the Hartree-Fock method (HF) and the density functional theory method (DFT), at B3LYP/6-311G level of theory. The correlation was developed by three mathematical models, based-QSPR approaches: the multiple linear regression (MLR), the multiple polynomial regression (MPR) and the partial least squares regression (PLS). A very good determination coefficient (R-2 = 0.99), adjusted determination coefficient (R-adj(2) = 0.99) and predicted determination coefficient (R-pred(2) = 0.97), were obtained. The calculated inhibition efficiency increased in the order OBBI > HBBI > BBI > MBBI> BBBI > EBBI, was in good agreement with experimental results.