A copper(II) coordination polymer based on flexible spacer ligands: Synthesis, crystal structure, and magnetic properties of the adipato complex [Cu4(bpy)4(adip)3](tcnp)2 [bpy = C10H8N2; image; image]

One-pot reaction of copper(II) chloride dihydrate CuCl2 · 2H2O with sodium adipate Na2adip View the MathML source(adip2-=O2C(CH2)4CO22-) in the presence of 2,2′-bipyridyl (bpy = C10H8N2) and potassium 1,1,3,3-tetracyano-2-ethoxypropenide View the MathML source(tcnp-=(NC)2CC(OEt)C(CN)2-) gives the new compound [Cu4(bpy)4(adip)3](tcnp)2 (1), which was characterized by single crystal X-ray diffraction analysis. Each metal ion presents an elongated square pyramidal CuN2O3 environment, with an oxygen atom in apical position and a base plane involving almost equivalent bond lengths. The structure can be described as a pseudo dinuclear species in which two Cu(bpy) units are triply bridged by two unsymmetrical bridging oxygen atoms of two carboxylate groups with a κ-μ-bridging mode and by an almost symmetrical OCO unit with a bidentate syn–syn κ:κ–μ-bridging mode. Such coordination modes generate the tetranuclear Cu2(adip)2Cu2 units which are bound by a symmetrical adipate ligand through a κ-μ-bridging mode to lead to infinite chains involving a succession of Cu2 units alternatively bridged by one or two aliphatic chains of adipate ligands. Magnetic measurements exhibit a maximum in the χm versus T plot (at ∼15.2 K), which is characteristic of weak antiferromagnetic exchange interactions between the Cu(II) ions bridged by the carboxylate groups. Fit of the magnetic data with appropriate model led to J value of −7.74 cm−1 (the Hamiltonian is written as H = −2JSaSb).