Adsorption and inhibition behavior of purine based drugs on mild steel corrosion in hydrochloric acid solution: DFT study

The adsorption behavior of three purine based chemical medicines (drugs) namely, 2-amino-9-((2-hydroxyethoxy)methyl)-3H-purin-6(9H)-one (Acyclovir; Acy), ((1S,4R)-4-(2-amino-6-(cyclopropylamino)-9H-purin-9-yl)cyclopent-2-en-1-yl)methanol (Abacavir; Aba) and (R)-(((1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)phosphonic acid (Tenofovir; Ten) on mild steel corrosion in acidic solution has been investigated using DFT based quantum chemical calculations. An attempt has been made to established correlation between experimentally determined inhibition efficiency and DFT based quantum chemical calculations. Several computational parameters such as energies of highest occupied and lowest unoccupied frontier molecular orbitals (E_HOMO and E_LUMO), energy band gap (ΔE), electronegativity (χ), global harness (η) and global softness (σ), fraction of electron transfer (ΔN), and dipole moment (µ) were derived in order to describe the relative adsorption tendency of these drugs on the mild steel surface. Among the tested drugs, abacavir exhibited the maximum adsorption tendency. The adsorption tendency of these drugs follows the order: abacavir>acyclovir>tenofovir. The DFT based quantum chemical calculations was carried out for neutral as well as protonated forms of the drug molecules.