Synthesis, structure and magnetic properties of catena-diaqua-bis(pyridine-N-oxide)(μ-pyrazine)copper(II) perchlorate and the monomeric structure tetrakis(pyridine-N-oxide)copper(II) perchlorate

Reaction of copper(II) perchlorate with pyrazine and pyridine-N-oxide produced the coordination polymer catena-[diaqua-mu-pyrazine-bis(pyridine-N-oxide)copper(II)] perchlorate (1) which was characterized by single-crystal X-ray diffraction, EPR and variable temperature magnetic susceptibility measurements. The compound forms well-isolated linear chains, bridged by pyrazine. EPR studies show a rhombic structure with g(ave) = 2.15. The magnetic data are well described by the uniform Heisenberg chain model giving J/k(B) = -9.6(1) K and show no signs of inter-chain interactions down to 1.8 K [H = -J sigma S1S2 ]. In the course of the synthesis, the related [tetrakis(pyridine-N-oxide)copper(II)] perchlorate complex (2) was also isolated. X-Ray studies confirm the identity of the compound in comparison to the previous literature. EPR studies indicate a rhombic structure, similar to 1, but variable temperature magnetic susceptibility data show no significant magnetic exchange in agreement with the absence of a superexchange pathway in the crystal.