Solvothermal One-Pot Synthesis of a New Family of Chiral [Fe₄O₄]-Cubane Clusters with Redox Active Cores

Abstract

The two achiral ligands tris(1-methyl-1H-imidazol-2-yl)methanol ((mim)₃COH) and bis(1-methyl-1H-imidazol-2-yl)(3-methylpyridin-2-yl)methanol ((mim)₂(mpy)COH) form on reaction with Fe(BF₄)₂ ∙ 6 H₂O, the octahedral low-spin complexes [Fe((mim)₃COH)₂](BF₄)₂ ∙ MeCN (1) and [Fe((mim)₂(mpy)COH)₂](BF₄)₂ ∙ 0.5 MeCN (2). Both octahedral complexes immediately rearrange to the chiral [Fe₄O₄]-cubane clusters [Fe₄(mim)₃CO)₄](BF₄)₄ (3) and [Fe₄(mim)₃CO)₄](BF₄)₄∙CHCl₃ (4), whereas the highly symmetrical (3) crystallizes as racemate, (4) resolves based on the asymmetry introduced by the 2-methylpyridine moiety and crystallizes as an enantiomerically pure sample. Both clusters feature redox active [Fe₄O₄]-cubane cores with up to four individual accessible states, which directs towards a potential application as electron-shuttle.