An unsymmetrical bidentate Schiff base ligand, ethane 2-(4-methox-yphenyl)-1-iminosalicylidene, and its novel two mononuclear complexes, Nickel(II) [Ni(II)-2L] and Manganese(III) [Mn(III)Cl-2L] where L represents the ligand, have been synthesized and characterized by various physicochemical methods. The Ni(II) ion is coordinated by two nitrogen and two oxygen atoms with both the bidentate Schiff base ligands in an approximately square planar coordination geometry, while the manganese complex, the Mn(III) ion, is involved in an additional contact with one chloride anion for which the coordination sphere appears as a square pyramidal arrangement. The thermogravimetric analyses of the synthesized compounds revealed three different stages of decomposition for NONO bis-biden-tate manganese and nickel complexes. The cyclic voltammetry studies of these complexes in N,N-dimethylformamide showed a redox couple for each one of them, such as Ni(II)/Ni(I) and Mn(III)/Mn(II), which are quasi-reversible. Their catalytic behaviors were tested showing that the nickel complex is an effective electrocatalyst in the reduction of bromocyclopentane. Regarding the manganese complex, it was revealed that it is an efficient catalyst in the activation of molecular dioxygen, & Brahim Bouzerafa