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

Abstract 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 interpenetrating α-polonium networks consisting of 1D chains of Cu–pyrazine units connected by [Au(CN) 2 ] bridges. The two networks are connected via weak aurophilic interactions (AuAu: 3.4729(2) A). Thermogravimetric analysis of all three compounds indicated the robust nature of these 3D systems, with decomposition beginning at 260 ( 1 ), 406 ( 2 ) and 360°C ( 3 ). The magnetic susceptibility of 1 shows a maximum in χ M at 5.0 K; these data could be fitted to the theoretical expressions for either a 1D or a 2D Heisenberg antiferromagnetic array ( J =−2.74 cm −1 , g =2.32 and J =−3.45 cm −1 , g =2.33, respectively). The magnetic susceptibility versus temperature 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 interactions between the [Au(CN) 2 ] units may positively influence both the formation of an interpenetrating structure and its subsequent thermal stability, the incorporation of anionic [Au(CN) 2 ] units into M(pyrazine) systems does not seem to significantly increase magnetic interactions.