Synthesis, structure and magnetic properties of 3D interpenetrating nets of M(pyrazine)[Au(CN)(2)](2) (M = Cu, Ni, Co) supported by aurophilic interactions

New inorganic coordination polymers of the form M(pyrazine)[Au(CN)(2)](2) ( M = Cu (1); Ni (2); Co (3)) have been prepared and the copper(II) analogue structurally characterised. The X-ray analysis revealed two 3D interpenetra ting alpha -polonium networks consisting of 1D chains of Cu-pyrazine units connected by [Au(CN)(2)] bridges. The two networks are connected via weak a urophilic interactions (Au-Au: 3.4729(2) Angstrom). Thermogravimetric analy sis of all three compounds indicated the robust nature of these 3D systems, with decomposition beginning at 260 (1), 406 (2) and 360 degreesC (3). The magnetic susceptibility of 1 shows a maximum in chi (M) at 5.0 K; these da ta could be fitted to the theoretical expressions for either a 1D or a 2D H eisenberg antiferromagnetic array (J = -2.74 cm(-1), g = 2.32 acid J = -3.4 5 cm(-1), g = 2.33, respectively). The magnetic susceptibility versus tempe rature data for 2 and 3 showed effects primarily associated with single-ion zero-field splitting; any weak antiferromagnetic coupling in these systems is very weak and hence was not quantified. Although the aurophilic interac tions between the [Au(CN)(2)] units may positively influence both the forma tion of an interpenetrating structure and its subsequent thermal stability, the incorporation of anionic [Au(CN)(2)] units into M(pyrazine) systems do es not seem to significantly increase magnetic interactions. (C) 2001 Elsev ier Science Ltd. All rights reserved.