Allopurinol, oxypurinol, and thiopurinol expired drugs as corrosion inhibitors toward Al (111) surface: a DFT and FPMD simulation study

By means of density functional theory and first-principle molecular dynamics (FPMD) simulations, the corrosion inhibition potential of allopurinol (Allo), oxypurinol (Oxy), and thiopurinol (Thio) expired drugs toward the aluminium (Al) (111) surface was thoroughly examined. ESP maps and FMOs analysis indicated the electron-donating nature of the studied drugs. From global reactivity descriptors, the potential of the Allo, Oxy, and Thio drugs in gas and aqueous phases as corrosion inhibitors was confirmed. Thio drug showed lower IP and higher EA values than the other investigated drugs, illustrating its higher reactivity. Further, the lowest value of ƞ and the highest value of σ were found for the Thio drug, indicating its high potential as a corrosion inhibitor. Employing FPMD simulations, the most stable configurations of the drug∙∙∙Al (111) complexes were determined, and the corresponding interaction and binding energies were estimated. According to the energetic affirmations, the Thio drug demonstrated the largest affinity to inhibit the Al (111) surface with an interaction energy (E_int) value of − 25.12 kcal/mol. The findings of the charge transfer (Q_t) were in line with the E_int, in which the Q_t of the drug∙∙∙Al (111) complexes decreased in the order Thio∙∙∙ > Allo∙∙∙ > Oxy∙∙∙Al (111) with values of − 0.5119, − 0.2737, and − 0.2471 e, respectively. The obtained results would provide fundamental insights into the promising application of Allo, Oxy, and Thio expired drugs as corrosion inhibitors, especially for aluminium surface.

Graphical abstract