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

A variety of [Cu(pyza)(2)](X)(2) (X = BF4 (1), ClO3 (2), ClO4 (3), PF6 (4), AsF6 (5)) were synthesized (pyza = pyrazine-2-carboxamide). The crystal structures of 1-5 have been determined to be isomorphous to that of known 3 in a monoclinic P2(1)/c space group. They form a quadratic copper(II) array with pyza bridges. The 1- and 4-nitrogen atoms in the pyrazine ring are coordinated to copper ions at equatorial and axial positions, respectively. Complexes 1-5 showed very weak antiferromagnetic interactions with J/k(B) = -0.439(6), -0.321(5), -0.304(1), -0.209(3), and -0.264(5) K, respectively, analyzed on the basis of an antiferromagnetic two-dimensional model. The magnitude of J almost correlates with the Cu center dot center dot center dot Cu distance and the cell volume. (C) 2013 Elsevier Ltd. All rights reserved.