Magnetic properties of a metal-organic porous network [Ni2(BODC)2(TED)]

A new material [Ni(2)(BODC)(2)(TED)], (BODC=4,4(')-bicyclo[2.2.2]octane dicarboxylate and TED=triethylene-4,4(')-diamine), which is a guest-free, porous metal-organic coordination network, has been successfully synthesized. The crystal structure of this compound is tetragonal with the space group P4/mmm. It is a three-dimensional network that can be deconstructed into rectangular gridlike layers along ab planes. These planes are formed by BODC and Zn(2)O(4) paddle-wheel-like clusters, and the TED ligands from the axial directions of the paddle-wheels connect the layers into a three-dimesional structure. There are no guest molecules found in the pores. The shortest Ni-Ni distance within the paddle wheel is found to be 2.613 A. Magnetic susceptibility chi(T)=M(T)/H and isothermal magnetization M(H) measurements have been measured on powder samples of this compound. The results of chi(T) show that there is a rapid increase in the susceptibility below 20 K due to a spontaneous ordering of the Ni(2+) moments. The effective moment mu(eff) of Ni(2+) is about 2.20 mu(B) at room temperature. The M(H) result at 1.8 K shows a clear hysteresis with a coercivity of H(coe)approximate to 1700 G. The behavior of this compound is discussed in terms of Ni-Ni coupling within the Ni dimers and dimer chains. (c) 2008 American Institute of Physics.