DFT–based QSAR Study of Substituted Pyridine–Pyrazole Derivatives as Corrosion inhibitors in Molar Hydrochloric Acid

Abstract

Quantum chemical calculations, based on DFT methods at B3LYP/6-31G** level of theory, were performed, by means of the G03 set of programs, on four pyridine-pyrazole compounds. The objective of this work was to attempt to find relationships between the intrinsic electronic properties and inhibiting efficiencies of two pyridine-pyrazole derivatives, denoted H-PP and Br-PP, which have been previously studied experimentally as mild steel corrosion inhibitors in acidic medium. Based on these results, the Quantitative Structure–Activity Relationships (QSAR) studies allowed us to calculate the inhibitive efficiencies for the former and for two other pyridine-pyrazole derivatives, Cl-PP and Me-PP, of which the experimental study, was not yet made. The structural electronic properties of the whole pyridine-pyrazole molecules were investigated by means of number of global and local theoretical reactivity descriptors. The results showed that the electronic effect of the substituent at the meta of the pyridine ringmarkedly influenced the performance of the studied inhibitors. TheQSAR’s quadratic model results, representing the best fitting, showed that the Cl-PP and Me-PP will probably have the same corrosion inhibitory performance as Br -PP and H-PP, respectively especially at higher concentrations.