The Mn(II) complexes of a set of linear tridentate ligands with pyridyl and aminophenolate donors (L) formed under inert gas react with O2 in methanol to give Mn(III) complexes of two types: in one type(MnL2.ClO4)two ligand molecules coordinate in trans-facial tridentate modes and in another type (Mn(L)2(CH3OH)2(ClO4))the two ligand molecules each coordinate as bidentates through the amine N, the phenolate O and two methanol molecules coordinate axially leaving the pyridyl groups uncoordinated and dangling. In cyclic voltammetry, quazi-reversible Mn(III)/Mn(IV) and Mn(III)/Mn(II) redox processes are displayed by complexes of the Schiff base type ligands whereas irreversible oxidations (to Mn(IV) and reductions (to Mn(II)are displayed with larege separations in potentials and also show additional weak peaks attributed to dimeric species. The UV-Visible absorption spectra obtained as a function of time during the reaction, in acetonitrile solvent, of the Mn(II) complexes with O2 and the reaction of the Mn(III) complexes with aqueous H2O2, suggest the formation of a common intermediate (Mn(III)-(�-O2)�Mn(III)) suggesting that a common pathway is likely followed in the oxidation of the Mn(II) by O2 and the reduction of the Mn(II) complexes by H2O2. In acetonitrile solution, the Mn(III) complexes catalyze the epoxidation of cyclohexene by H2O2 with a turnover of about 72.