The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand HBPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)·2HO, , in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand HBPClNOL, a phenoxide and an alkoxide group. In the solid state, this mixed valence dinuclear unit is connected to its neighbors through chloro bridges. Magnetic measurements indicated the presence of ferromagnetic [ = +0.076(13) cm] and antiferromagnetic [ = -5.224(13) cm] interactions. The compound promotes O dismutation in aqueous solution (IC = 0.370 μmol dm, = 3.6x10 M s). EPR studies revealed that a high-valent Mn(III)-O-Mn(IV) species is involved in the superoxide dismutation catalytic cycle. Complex shows catalase activity only in the presence of a base, e.g., piperazine or triethylamine. Kinetic studies were carried out in the presence of piperazine and employing two different methods, resulting in values of 0.58 ± 0.03 s (detection of O production employing a Clark electrode) and 2.59 ± 0.12 s (HO consuption recorded via UV-Vis). EPR and ESI-(+)-MS studies indicate that piperazine induces the oxidation of , resulting in the formation of the catalytically active Mn(III)-O-Mn(IV) species.