Quantum chemical studies on the inhibition of corrosion of copper surface by substituted uracils

The inhibitive effect of some substituted uracils, dithiouracil (DTUr), thiouracil (TUr), uracil (Ur) and dihydrouracil (DHUr) against the corrosion of neutral copper surface is studied by means of density functional approach B3LYP/6-31G calculations. It is found that the DTUr inhibitor has the highest inhibition efficiency among the investigated inhibitors. The calculated quantum chemical parameters correlated to the inhibition efficiency are, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the separation energy (DE), the dipole moment (m), the softness (sigma), the fraction of the electrons transferred from the inhibitor to the metal surface (Delta N), the total negative charge (TNC), the molecular volume (upsilon(i)) and the total energy (TE). Also, the study of adsorption of the inhibitors on the neutral copper surface shows that the adsorption through the thiocarbonyl functional (C-S) group is more favored than the carbonyl group which agrees well with the experimental observations. (C) 2008 Elsevier B. V. All rights reserved.