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

A new 1D coordination polymer comprised of [Mn(III)(6)O(2)(Et-sao)(6)(EtOH)(4)(H(2)O)(2)](2+) units and bithiophene dicarboxylato was synthesized by mixing EtsaoH(2) (salicylaldoxime), H(2)btda (2,2'-bithiophene-5,5'-dicarboxylic acid) and Mn(ClO(4))(2)·6H(2)O in the presence of NEt(4)OH. 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) approximately 50 K and tau(0) approximately 2.2 10(-10) s. The magnetic measurements do not show any noticeable interaction between the Mn(6) clusters through the bithiophene dicarboxylato bridges.