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Synthesis and characterization of a novel non-symmetrical bidentate Schiff base ligand and its Ni(II) complex: electrochemical and antioxidant studies

Imène Bougossa, Djouhra Aggoun, Ali Ourari, Raúl Berenguer, Sofiane Bouacida, and Emilia Morallon

Laboratoire d’Electrochimie, d’Ingénierie Moléculaire et de Catalyse Rédox (LEIMCR), Département Génie des Procédés, Faculté de Technologie, Université Ferhat ABBAS Sétif-1, Sétif, Algeria



Received: 5 November 2019  Accepted: 15 May 2020



This paper describes the synthesis and properties of a new nitro-substituted bidentate Schiff base ligand (HL) and its nickel complex (Ni(II)-2L). Its ligand was derived from the condensation of 2′-methoxyphenyl-2-ethylamine with 5-nitro-2-hydroxybenzaldehyde. This ligand and its nickel complex were characterized through elemental analysis, UV–Vis, IR, 1H NMR and 13C NMR. The molecular structure of the nickel complex was confirmed using single-crystal X-ray diffraction. This complex crystallizes in dichloromethane in triclinic system, space group of P-1 with a = 6.6803 (2), b = 9.6702 (2), c = 12.1836 (3) and 1 formula unit in the cell. The obtained data revealed that the Ni(II) center is tetra-coordinated by two oxygen and two nitrogen atoms involving two ligands. Cyclic voltammograms of the nickel complex, recorded in DMF solutions, showed one quasi-reversible redox couple related to the Ni(II)/Ni(I) couple, demonstrating its electro-activity. This indicates a slow redox transition and/or electron exchange process, which implies that this electrochemical process is mainly diffusion-controlled. The antioxidant activity of the synthesized compounds was evaluated from the reactivity with the free radical DPPH, showing IC50 values between 0.4 and 4.5 mg/mL.

Graphic abstract

Keywords: Bidentate Schiff base; Nickel(II) complex; X-ray diffraction; Electrochemical reduction; Antioxidant activity

Full paper is available at

DOI: 10.1007/s11696-020-01200-7


Chemical Papers 74 (11) 3825–3837 (2020)

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