Twisting, bending, stretching: strategies for making ferromagnetic [MnIII3] triangles

Abstract

The synthesis and characterisation of a large family of trimetallic [Mn^III₃] Single-Molecule Magnets is presented. The complexes reported can be divided into three categories with general formulae (type 1) [Mn^III₃O(R-sao)₃(X)(sol)_3-4] (where R = H, Me, ^tBu; X = ⁻O₂CR (R = H, Me, Ph etc); sol = py and/or H₂O), (type 2) [Mn^III₃O(R-sao)₃(X)(sol)_3-5] (where R = Me, Et, Ph, ^tBu; X = ⁻O₂CR (R = H, Me, Ph etc); sol = MeOH, EtOH and/or H₂O), and (type 3) [Mn^III₃O(R-sao)₃(sol)₃(XO₄)] (where R = H, Et, Ph, naphth; sol = py, MeOH, β-pic, Et-py, ^tBu-py; X = Cl, Re). We show that deliberate structural distortions of the molecule can be used to tune the observed magnetic properties. In the crystals the ferromagnetic triangles are involved in extensive inter-molecular H-bonding which is clearly manifested in the magnetic behaviour, producing exchange-biased SMMs. These interactions can be removed by ligand replacement to give “simpler” SMMs.