A series of [NaMnIII3MnII] clusters constructed using a multidentate Schiff-base ligand and decorated with different auxiliary ligands

Abstract

Four new polynuclear clusters [NaMn^III₃Mn^II(HL)₃(μ₄-O)(μ_1,1-N₃)₃]ClO₄·CH₃CH₂OH·(H₂O)₃ (1), [NaMn^III₃Mn^II(HL)₃(μ₄-O)(μ_1,1-N₃)₂(μ_1,3-N₃)]ClO₄·CH₃CH₂OH·H₂O (2), [NaMn^III₃Mn^II(HL)₃(μ₄-O)(HCOO)₃]ClO₄·(H₂O)₄ (3) and [NaMn^III₃Mn^II(HL)₃(μ₄-O)(PhCOO)(H₂O)₂](ClO₄)₂·H₂O·PhCOO·PhCOOH·CH₃OH (4) have been obtained via self-assembly between 3-((2-hydroxy-3-methoxybenzylidene)amino)propane-1,2-diol (H₃L: condensed from o-vanillin and 3-amino-1,2-propanediol) and the auxiliary bridges (N₃⁻, HCOO⁻, PhCOO⁻, H₂O) with Mn(ClO₄)₂·6H₂O in the air-exposed methanol solution. The structures of 1–4 all contain [NaMn^III₃Mn^II] units and show a very similar trigonal propeller-like shape. The valences of the metal ions were determined by detection of the Jahn–Teller distortion visible for Mn^II,III, and confirmed by bond-valence sum (BVS) calculations. Three Mn^III ions and one Mn^II ion take the shape of a super-tetrahedron with the Mn^II ion lying above the triangular [Mn₃O] plane constructed from three Mn^III ions linked by a central μ₄-O atom. The Na^I ion which lies below the [Mn₃O] plane is linked with Mn^III ions through the oxygen atoms from Schiff base ligands. The main structural difference in the four clusters is caused by the different bridging modes among Mn^III ions. A structural comparison of 1–4 demonstrates that the auxiliary ligands play a key role in governing the coordination motifs. Moreover, the magnetic properties of these clusters exhibit dominating antiferromagnetic exchange interaction between spin carriers of Mn^II,III.