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Homo-dinuclear VO2+and Ni2+dihydrazone complexes: Synthesis, characterization, catalytic activity and CO2-corrosion inhibition under sustainable conditions

2019; Elsevier BV; Volume: 499; Linguagem: Inglês

10.1016/j.ica.2019.119212

1873-3255

Mohamed Shaker S. Adam, Kamal A. Soliman, Hany M. Abd El‐Lateef,

Oxidative Organic Chemistry Reactions

• VO 2+ and Ni 2+ complexes were synthesized and fully characterized. • Ligand, VO 2+ and Ni 2+ complexes have an inhibition effect on M-steel in CO 2 -saturated brine. • Both complexes are effective catalysts for 1,2-cyclohexene (ep)oxidation and Suzuki-Miyaura reactions. • Theoretical results were convenient with the obtained catalytic and corrosion inhibition progresses. VO 2+ and Ni 2+ complexes (VOPHL and NiPHL) were prepared by complexation of terephthaloyl salicylidene dihydrazone (H 2 PHL) with VO 2+ or Ni 2+ ions. The chemical structures were estimated by various spectroscopic methods. Their sustainable corrosion inhibition on mild steel in NaCl solutions saturated with CO 2 was investigated using potentiodynamic polarization (PDP), open circuit potential and electrochemical impedance spectroscopy (EIS) methods. H 2 PHL, NiPHL and VOPHL showed maximum capacity within 89.57, 97.25 and 98.22%, respectively. The PDP study refers to that they could act as mixed-type inhibitors i.e. retarded both cathodic and anodic reactions. Metal complexes displayed better inhibition than their coordinated ligand. H 2 PHL and its M-complexes adsorbed on C-steel surface via chemical adsorption with obeying the Langmuir model. The post-exposure investigation, for the inhibited and uninhibited C-steel surface, was elucidated using SEM /EDS. The homogeneous catalytic behavior of NiPHL and VOPHL was studied in the (ep)oxidation of unsaturated cycloalkene (1,2-cyclohexene) and Suzuki-Miyaura cross-coupling. VOPHL shows better catalytic potential in (ep)oxidation processes. NiPHL has higher catalytic efficiency towards cross-couplings. The aqueous hydrolysis of epoxy selective product could be reduced in low temperature of the (ep)oxidation processes. DFT studies were performed on H 2 PHL, NiPHL and VOPHL. Electronic representatives E LUMO , E HOMO, energy gap (Δ E ), hardness, softness and electronegativity were computed. Theoretical values are in good accordance with corrosive and catalytic experimental results.