DFT Study of Interaction of Azoles with Cu(111) and Al(111) Surfaces: Role of Azole Nitrogen Atoms and Dipole–Dipole Interactions

Azoles and their derivatives are among the often used organic corrosion inhibitors for copper. For this reason, the adsorption of four azole molecules—imidazole, 1,2,3-triazole, tetrazole, and pentazole—on Cu(111) and Al(111) surfaces has been studied and characterized using density functional theory (DFT) calculations. We find that the molecules weakly adsorb in an upright geometry onto the top site of Cu(111) via single nitrogen atom; except for triazole the bonding with two nitrogen atoms to a bridge site becomes slightly preferred at very low coverage. Molecular electronic structure is only weakly perturbed upon adsorption and the molecule–surface interaction involves the hybridization between molecular σ orbitals and metal states, yet the main contribution to bonding comes from the electrostatic dipole interactions due to a large dipole moment of azole molecules. Also, the lateral intermolecular repulsion can be significant and very long ranged. With increasing the number of nitrogen atoms in azole ring the molecular electronegativity and chemical hardness linearly increase. The harder the molecule the more difficult the hybridization with metal states, which can explain why with the increasing number of nitrogen atoms in azole ring the molecule–Cu(111) bond strength decreases linearly, being 0.69, 0.55, 0.43, and 0.22 eV for imidazole, 1,2,3–triazole, tetrazole, and pentazole, respectively. The same bonding trend with very similar adsorption energies is also found on Al(111).