Préparation et caractérisation de complexes dérivés de nouvelles bases de Schiff et de ligand ferrocénique phosphine-carbène N-hétérocyclique

Abstract

In the first part of this thesis, new bidentate ferrocenyl phosphine/N-heterocyclic carbene (NHC) palladium complex rac-5, bearing a functionalized pendant arm for further grafting on a solid surface, has been synthesized in good yields and fully characterized. The molecular structure of proligand rac-4-BF4 and complex rac-5 were obtained by X-ray diffraction on single crystals. Kinetic studies demonstrated the good activity and stability of rac-5 in the Suzuki-Miyaura coupling of aryl bromides with arylboronic acids. The catalyst proved also to be active for the coupling of more challenging, bulky substrates such as 1-bromo-2-methylnaphthalene and naphthylboronic acid at relatively mild temperatures (40–70°C) and low loadings (0.1–0.5 mol%). Experiments carried out with various amounts of water highlighted the role of water on both activity and mechanism. In the second part, a series of new Schiff bases L1-L6 derived from benzimidazole were synthesized and their structures characterized by single-crystal X-ray diffraction analysis, NMR, IR and UV-Vis spectroscopy. L1, L2, L3, L4 et L6 react with Mercury ions to afford the corresponding complexes 1, 2, 3,4 et 6 in quantitative yield. The ligand L4 was also complexed win zinc ion to afford the corresponding complex 7. The in vitro measurement of the antioxidant activity of some compounds tested (L1, L2, L4, L6, 1, 2 and 7) against the free radical scavenger DPPH at low concentration (100 μg / mL), showed a moderate antioxidant activity (22%-35%), compared to the standard (Asc, 84%). To support experimental data, theoretical calculations including molecular geometry, electronic transitions and vibrational frequencies of the ligand 6 and the (Hg) complex 6 in the ground state were carried out using the global hybrid (B3LYP) density functional. In addition, a qualitative description of excited states and charge transfer character of electronic transitions states were carried out by plotting the Natural Transition Orbitals (NTOs) for main states. Theoretical calculations are in good agreement with experimental values.