Twisting, bending, stretching: strategies for making ferromagnetic [Mn-3(III)] triangles

The synthesis and characterisation of a large family of trimetallic [Mn-3(III)] Single-Molecule Magnets is presented. The complexes reported can be divided into three categories with general formulae (type 1) [(Mn3O)-O-III(R-sao)(3)(X)(sol)(3-4)] (where R = H, Me, Bu-t; X = -O2CR (R = H, Me, Ph etc); sol = py and/or H2O), (type 2) [(Mn3O)-O-III(R-sao)(3)(X)(sol)(3-5)] (where R = Me, Et, Ph, Bu-t; X = -O2CR (R = H, Me, Ph etc); sol = MeOH, EtOH and/or H2O), and (type 3) [(Mn3O)-O-III(R-sao)(3)(sol)(3)(XO4)] (where R = H, Et, Ph, naphth; sol = py, MeOH, beta-pic, Et-py, Bu-t-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.