New coordination polymer based on a triply bridged dicarboxylate ligand: Synthesis, structure, and magnetic properties of the adipato complex [Cu 4(bpy) 4(adip) 3](tcnoet) 2 · 2H 2O {bpy = C 10H 8N 2; adip 2− = [O 2C(CH 2) 4CO 2] 2−; tcnoet − = [(NC) 2CC(OEt)C(CN) 2] −}

Abstract

One-pot reaction of copper(II) chloride dihydrate CuCl 2 · 2H 2O with 2,2′-bipyridyl (bpy = C 10H 8N 2) in the presence of sodium adipate Na 2adip (adip 2− = [O 2C(CH 2) 4CO 2] 2−) and potassium 1,1,3,3-tetracyano-2-ethoxypropenide (tcnoet − = [(NC) 2CC(OEt)C(CN) 2] −) gives the new compound [Cu 4(bpy) 4(adip) 3](tcnoet) 2 · 2H 2O ( 1), which was characterized by single crystal X-ray diffraction analysis. The Cu(II) metal ion presents an elongated square pyramidal CuN 2O 3 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 and by an almost symmetrical OCO unit with a bidentate syn– syn bridging mode. Each Cu 2 dinuclear unit is triply bonded by aliphatic chains of the three adipate ligands to generate a ladder-like infinite chain. Magnetic measurements exhibit a maximum in the χ m versus T plot (at ∼5.0 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 −3.26(1) cm −1 (the Hamiltonian is written as H = −2 JS a S b ).