Crystal structures and magnetic properties of two-dimensional copper(II) complexes bridged with pyrazine-2-carboxamide

The crystal structures of [Cu(pyza)2](X)2 (X = BF4, ClO3, ClO4, PF6, AsF6) have been determined to be a quadratic copper(II) array with pyza bridges. Thus, facile preparation of an infinite copper-pyrazine grid with alternating Cu-N(ax) and N(eq)-Cu configurations is established. Contrary to the initial molecular design, the compounds showed antiferromagnetic couplings. The reason may reside in breakdown of orthogonality between the Cu2+ magnetic orbitals. The magnitude of J almost correlates with the Cu⋯Cu distance and also with the cell volume.