Tuning the magnetic behaviors in [FeIII12LnIII4] clusters with aromatic carboxylate ligands

Abstract

A family of Fe₁₂Ln₄ clusters based on thiophene-3-carboxylic acid (3-TCA) or 3-methoxybenzoic acid (m-MOBA) were synthesized with a step-by-step strategy, namely [Fe₁₂Ln₄(μ₄-O)₆(μ₃-O)₄(μ₃-OH)₄(3-TCA)₂₄] (Ln = La (1), Gd (3) and Dy (4)), {[Fe₂₄Sm₈(μ₄-O)₁₂(μ₃-O)₈(μ₃-OH)₈(3-TCA)₄₆(NO₃)₂]·4CH₃CN} (2), [Fe₁₂La₄(μ₄-O)₆(μ₃-O)₄(μ₃-OH)₄(m-MOBA)₂₄] (5) and {[Fe₁₂Sm₄(μ₄-O)₆(μ₃-O)₄(μ₃-OH)₄(m-MOBA)₂₄]·4CH₃CN} (6). For each of the six complexes, two Fe₄O₂(OH)₂ cubane units “sandwich” four Fe^III centers to form Fe₁₂O₁₀(OH)₄, and it is further connected to four Ln^III ions through six μ₄-O²⁻ bridges to obtain a Fe₁₂Ln₄ core. Magnetic analyses indicate that 1–6 show different magnetic properties, and 2 and 6 show SMM-like behaviors, due to the differences in lanthanide ions and aromatic monocarboxylate ligands. Note that Sm^III-containing 3d–4f clusters exhibiting SMM-like behavior are still rare in the documented cases.