Metal-radical chains based on polychlorotriphenylmethyl radicals: synthesis, structure, and magnetic properties

We report the synthesis, crystal structures, and magnetic properties of two new metal-radical chains built up from a new class of organic radical-based ligands, the polychlorinated triphenylmethyl (PTM) radicals. Crystal structures of two new 1D coordination polymers, [Cu(2)(PTMDC)(2)(py)(5)(EtOH)].3EtOH (1) and [Co(2)(PTMDC)(2)(DMF)(2)(H(2)O)(6)].5DMF (2) (where PTMDC is a PTM radical functionalized with two carboxylic groups), show similar chain-like structures, in which each of the PTMDC radicals are connecting two Cu(II) or Co(II) metal ions. Therefore, from a magnetic point of view, both structures describe a magnetic chain model based on the PTMDC-M(II) unit. In this manuscript, the magnetic exchange coupling constants between both metal ions and the bridging PTM radicals have been determined. In both cases, the temperature dependence of the magnetic susceptibility reveals antiferromagnetic exchange coupling constants between the PTMDC radicals and Cu(II) (J/k(B) = -42 K) and Co(II) (J/k(B) = -14.6 K) ions based on the exchange Hamiltonian H = -J sum S(A(i))S(A(i+1)).