Mononuclear Manganese(III) Complexes as Building Blocks for the Design of Trinuclear Manganese Clusters: Study of the Ligand Influence on the Magnetic Properties of the [Mn33-O)]7+ Core

The synthesis, crystal structure, and magnetic properties of three new manganese(III) clusters are reported, [Mn33-O)(phpzH)3(MeOH)3(OAc)] (1), [Mn33-O)(phpzMe)3(MeOH)3(OAc)]·1.5MeOH (2), and [Mn33-O)(phpzH)3(MeOH)4(N3)]·MeOH (3) (H2phpzH = 3(5)-(2-hydroxyphenyl)-pyrazole and H2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole). Complexes 13 consist of a triangle of manganese(III) ions with an oxido-center bridge and three ligands, phpzR2− (R = H, Me) that form a plane with the metal ions. All the complexes contain the same core with the general formula [Mn33-O)(phpzR)3]+. Methanol molecules and additional bridging ligands, that is, acetate (complexes 1 and 2) and azide (complex 3), are at the terminal positions. Temperature dependent magnetic susceptibility studies indicate the presence of predominant antiferromagnetic intramolecular interactions between manganese(III) ions in 1 and 3, while both antiferromagnetic and ferromagnetic intramolecular interactions are operative in 2.