An unusual 3D-topology and dominant ferromagnetic couplings in two Cu(ii)–azide coordination polymers

Abstract

The coordination polymers [(Cu(N₃)₂)₂Cu(N₃)₂(methylpyrazine)₂]_n1 and [Cu(4-bromopyridine)(N₃)₂]_n2, were prepared from NaN₃, Cu(NO₃)₂·3H₂O and nitrogen-containing heterocycles. 1 contains a three- and four-connected 3D (4.10²)₂(4².10⁴)-dmd-net based on tetrahedral and trigonal planar nodes, whereas 2 is a sheet-structure formed by a uninodal three-connected 8².4 2D-net with additional Br⋯Br (mean 3.903(2) Å) and Br⋯N(azide) (3.035(5) Å) contacts. Both compounds contain end-on-type azide bridges, and 2 has in addition one end-to-end bridge as well. The corresponding magnetic interactions are J_1,2 = +14.9(6) cm⁻¹ for the end-on azido interactions in 1 with an additional −1.7 cm⁻¹ coupling through the pyrazine, and J₁ = 36(6) cm⁻¹ for the end-on azido interactions and J₂ = 2.5(1) cm⁻¹ for the orthogonal end-to-end azido interactions found in 2.