An acyclic hexadentate diimine ligand, H₄L¹, was prepared in situ in methanol by the condensation of 1,4-diformyl-2,3-dihydroxybenzene (1) with 2-aminoethanol, and complexed directly with two equivalents of Mn^II(OAc)₂·4H₂O or Mn^III(OAc)₃·2H₂O, or with one equivalent of each. All three of these one-pot reactions gave the mixed-valent tetrametallic complex [Mn^II₂Mn^III₂(L¹)₂(OAc)₂(solvents)₄], [2(solvents)₄]. An X-ray crystal structure determination on [2(MeOH)₄]·2MeOH revealed a centre of inversion in the middle of the complex. The four metal ions are in an almost planar array, sandwiched by two offset ligands which provide all of the equatorial donors, with the axial sites occupied by acetate ions and methanol molecules. The two manganese(II) ions are seven coordinate and centrally located, whereas the two manganese(III) ions are Jahn–Teller elongated octahedra and are located in the outer sites. Magnetic analysis of an air-dried sample, [2(MeOH)₂(H₂O)₂]·3H₂O, showed that weak antiferromagnetic interactions between the manganese ions dominate, resulting in a low ground spin state.