A Tetranuclear Mixed-Valence Manganese Complex of a Diimine Ligand Derived from 1,4-Diformyl-2,3-dihydroxybenzene: Synthesis, Structure, and Magnetic Properties

Abstract

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 MnII(OAc)2·4H2O or MnIII(OAc)3·2H2O, or with one equivalent of each. All three of these one-pot reactions gave the mixed-valent tetrametallic complex [MnII2MnIII2(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.