Theoretical studies of the interactions of 8-hydroxyquinoline derivatives with aluminum ; Etudes théoriques de dérivés (HqX) de la 8-hydroxyquinoléine : complexes Al(qX)3 et monocouches sur Al(111)

The 8-hydroxyquinoline (Hq) and its derivatives (chemically modified Hq) are known for their ability to chelate metallic cations. They are used in applications such as depollution, light emitting devices, medicine and inhibition of the corrosion of metallic surfaces. The properties of these molecules and of their metal-organic complexes depend on the chemical modifications made on Hq. In the present work, in addition to Hq, two derivatives are studied: the 5,7-dibromo-8-hydroxyquinoline (HqBr) and the 8-hydroxyquinoline-5-sulfonic acid (HqSH). Our investigation is carried out in the framework of the dispersion corrected Density Functional Theory (DFT-D), and focuses on the study of the interactions of Hq, HqBr and HqSH species with aluminum. First, we investigate the geometries of the complexes formed by deprotonated Hq, HqBr and HqSH with an aluminum cation, and characterize the bonds formed between the molecules and the cation from ELF and QTAIM topological analyses of the electronic structure of the complexes. The three molecules form similar iono-covalent bonds with the Al³ ion. We then focus on the interaction of the dehydrogenated Hq, HqBr and HqSH species with an Al(111) surface, in vacuum and in water, to get insight on the adsorption properties of the three molecules. While all three molecule can form stable and compact layers on Al(111), the adsorption a single molecule is different for Hq, which has been shown experimentally to be an efficient corrosion inhibitor of aluminum, than for HqBr and HqSH, which have shown no inhibition efficiency against aluminum corrosion. These different geometries could influence the dynamics of the layer formation, and thus the protection of the aluminum surface against corrosion. Finally, the formation of Hq complexes, noted Alq3, on Al(111) is investigated, using ab initio molecular dynamics to explore the conformation space of the system. The work shows a large amount of possible stable geometries that could coexist. The formation of a complex on the surface by the ...