Ligand-induced distortion of a tetranuclear manganese butterfly complex

Abstract

The reaction of the pentadentate Schiff-base ligand 1,3-bis(salicylideneamino)-2-propanol (salproH₃) with [Mn₃O(O₂CR)₆(py)₃] (R = Me, Et, Bu^t) gives the corresponding tetranuclear manganese product [Mn₄O₂(O₂CR)₅(salpro)] (4Mn^III). The syntheses, structure and magnetochemical characterization of these complexes are reported. The structure of the [Mn₄(µ₃-O)₂]⁸⁺ is butterfly-like much more closed than in previous complexes with this core as a result of the alkoxide oxygen of the salpro ligand bridging the two wingtip Mn atoms. Variable-temperature, solid-state magnetic susceptibility studies reveal that these complexes possess S = 0 ground state spins. Fitting of the magnetic susceptibility data to the theoretical χ_MTvs. T expression derived for a C_2v symmetry complex, assuming an isotropic Heisenberg spin-Hamiltonian and using the Van Vleck equation, revealed that the various exchange parameters are all antiferromagnetic, and the core thus experiences spin frustration effects.