Stabilization of Cu7 clusters in azide networks: syntheses, structures and magnetic behaviour

Abstract

Two new azide bridged copper(II) coordination polymer compounds, [Cu₇(N₃)₁₄(C₃H₁₀N₂)(C₄H₁₃N₃)]_n (I) and [Cu₇(N₃)₁₄(C₃H₁₀N₂)(C₅H₁₅N₃)₂]_n (II) [where C₃H₁₀N₂ = 1,2-diaminopropane (1,2-DAP); C₄H₁₃N₃ = diethylenetriamine (DETA); C₅H₁₅N₃ = N-2-aminoethyl-1,3-propanediamine (AEDAP)] were prepared by employing a room temperature diffusion technique involving three layers. Single crystal studies reveal that both compounds I and II, have similar connectivity forming Cu₇ clusters through end-on (EO) bonding of the azide. The Cu₇ clusters are connected through end-to-end (EE) connectivity of the azides forming three-dimensional structures. Magnetic studies confirmed the ferromagnetic interactions within the Cu₇ units and revealed the occurrence of concomitant ferro- and antiferro-magnetic interactions between these clusters. As a result I behaves as a weak-ferromagnet with T_C = 10 K.