[M(N-3)(2)(H2O)(2)]center dot(bpeado): Unusual Antiferromagnetic Heisenberg Chain (M = Mn) and Ferromagnetic Ising Chain (M = Co) with Large Coercivity and Magnetic Relaxation (bpeado=1,2-Bis(4-pyridyl)ethane-N,N '-dioxide)

We present here the structures and magnetism of two isostructural magnetic metal-azido chain compounds of the type [M(N-3)(2)(H2O)(2)]center dot(bpeado) (1, M = Mn; 2, M = Co; bpeado 1,2-bis(4-pyridyl)ethane-N,N'-dioxide), prepared by utilizing the long spacer bpeado. The structure is composed of [M(N-3)(2)(H2O)(2)](n) metal-azido chains, in which metal lions are bridged by two end-on azido ligands, and the chains are further supported by H-bonding interactions between the coordination water of the chain and the lattice bpeado in a three-dimensional (3D) threefold interpenerated H-bonded framework. Within the structure, the metal-azido chains are seperated quite well. Investigation has revealed that the Mn compound 1 is an isotropic Heisenberg chain with unusual antiferromagnetic coupling between the Mn2+ ions linked by double end-on azide anions. The Co compound 2 shows a strong anisotropic Ising-type ferromagnetic chain within the material. Detailed magnetic studies on both polycrystalline and single-crystal samples of 2 have revealed a large coercivity of up to 37.5 kOe (along the crystallographic b-axis), multi-magnetic transitions, and single-chain-magnet-like magnetic relaxation behavior.