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.