New manganese(II) and nickel(II) coordination compounds with N,O-polydentate ligands obtained from pyridoxal and tripodal units

• Manganese(II) and Nickel(II) Schiff bases complexes derived from condensation of pyridoxal and tris(2-aminoethyl)amine.
• The cyclization of the ligand in the mononuclear nickel(II) complex providing a hemiacetal substituent.
• The mononuclear manganese(II) complex showed a mimetic superoxide dismutase activity.

We have reported the synthesis involving the condensation of pyridoxal with tris(2-aminoethyl)amine obtained a tripodal ligand, as well as its subsequent complexation with the manganese(II) and nickel(II) ions. The structural analysis revealed, in the case of complex 1, the formation of a monomeric complex with Mn(II) species. In the complex 2, with Ni(II) metal ion, we describe the probable mechanism for the formation of hemiacetal in these complexes. Only the complex 1 catalyze the dismutation of superoxide efficiently with IC50 equal to 3.38 μM, evaluated through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. Density functional theory calculations are done to characterize and compare the molecular frontier orbitals of the Mn(II) and Ni(II) complexes.

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