One dimensional assembly of Mn_6 single molecule magnets linked by oligothiophene bridges

摘要

A new 1D coordination polymer comprised of [Mn~(III)_6O_2(Et-sao)_6(EtOH)_4(H _2O)_2]~(2+) units and bithiophene dicarboxylato was synthesized by mixing EtsaoH_2 (salicylaldoxime), H_2btda (2,2′-bithiophene-5,5′-dicarboxylic acid) and Mn(ClO _4)_2·6H_2O in the presence of NEt _4OH. The crystal structure was determined and consists of Mn _6 clusters bridged by the bithiophene dicarboxylato ligands coordinated to two of the Mn~(III) ions of the Mn_6 polynuclear complex. Direct current magnetic measurements show an overall ferromagnetic interaction between the Mn~(III) ions within the Mn _6 cluster leading to an S = 12 ground state for the Mn_6 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 τ_0≈ 2.2 10~(-10) s. The magnetic measurements do not show any noticeable interaction between the Mn_6 clusters through the bithiophene dicarboxylato bridges.