One dimensional assembly of Mn6 single molecule magnets linked by oligothiophene bridges

Abstract

A new 1D coordination polymer comprised of [Mn^III₆O₂(Et-sao)₆(EtOH)₄(H₂O)₂]²⁺ units and bithiophene dicarboxylato was synthesized by mixing EtsaoH₂ (salicylaldoxime), H₂btda (2,2′-bithiophene-5,5′-dicarboxylic acid) and Mn(ClO₄)₂·6H₂O in the presence of NEt₄OH. The crystal structure was determined and consists of Mn₆ clusters bridged by the bithiophene dicarboxylato ligands coordinated to two of the Mn^III ions of the Mn₆ polynuclear complex. Direct current magnetic measurements show an overall ferromagnetic interaction between the Mn^III ions within the Mn₆ cluster leading to an S = 12 ground state for the Mn₆ unit. Furthermore, this compound presents single-molecule magnet behaviour. Slow relaxation of the magnetization is observed at low temperature following a thermal activated regime with U_eff≈ 50 K and τ₀≈ 2.2 10⁻¹⁰ s. The magnetic measurements do not show any noticeable interaction between the Mn₆ clusters through the bithiophene dicarboxylato bridges.