Slow magnetic relaxation in O–Se–O bridged manganese(iii) Schiff base complexes

Abstract

Two new chain complexes consisting of a Mn(salen) building block bridged by O–Se–O units, [Mn₂(salen)₂(L)](ClO₄) (1) and {[Mn(salen)]₂(L)₂}·Y (2) (salen = N,N′-bis(salicylidene)-ethylenediamine, L = 3,4,5-trifluorobenzeneseleninic acid, Y = salicylaldehyde) have been synthesized and characterized structurally and magnetically. In the two complexes above, the 3,4,5-trifluorobenzeneseleninic acid ligand adopts a syn–anti bridging coordination mode and all the Mn^III ions show a distorted octahedral geometry. In complex 1, the [Mn₂(salen)₂]²⁺ dimers are connected alternatively by the bridging ligands into an infinite zigzag chain, while the [Mn(salen)]⁺ monomers are connected alternatively in complex 2. The magnetic measurements reveal that both complexes exhibit slow magnetic relaxation behaviours with an effective energy barrier U_eff = 31.2 K for 1 and U_eff = 35.1 K for 2, respectively. These compounds are rare examples of a small number of aromatic selenite based magnetic materials.