The Structure and Magnetic Properties of the Two-Dimensional Di-Pyrazine Bridged Polymers M(pz)2Br2 (M = FeII, CoII, NiII)

Abstract

The polymeric compounds M(pyrazine)₂Br₂ [M = Fe (1), Co (2), and Ni (3)] have been synthesized by the addition of a solution of pyrazine in methanol to a methanolic solution of the anhydrous metal bromide. The crystal structures of (1)-(3) were determined using powder synchrotron and neutron diffraction data and were found to be isostructural. The structures consist of pseudo-octahedral units, doubly linked by pyrazine ligands to form two-dimensional sheets. Magnetic susceptibility data were recorded for each complex down to 5 K and reveal paramagnetic behaviour at high temperatures and antiferromagnetic interactions at low temperatures. Comparison of the structures and magnetism of these and other M(pz)₂X₂ compounds highlight the relative importance of the canting of the pyrazine ligands on the strength of the magnetic exchange.