A Novel Triangular Trinuclear μ3-CO3 Ferromagnetic CuII Compound Prepared in situ from CO2 Uptake in Air. X-ray Structure, Spectroscopy and Magnetism

Abstract

The new trinuclear compound [Cu3(bpy)6(μ3-CO3)](BF4)4(H2O)2(C2H6O) (in which bpy = 2,2′-bipyridine) has been synthesized from Cu(BF4)2 and bpy in aqueous ethanol by rapid uptake of atmospheric CO2. The structure of the compound has been determined by X-ray crystallography; it was found to crystallise in the triclinic space group P1¯ with a = 13.405(7), b = 13.691(7), c = 21.446(8) Å, α = 82.87(4), β = 73.57(4), γ = 64.32(4)°, Z = 2. The three copper atoms are connected to each other through the oxygen atoms from the bridging carbonato group, giving a triangular array of copper atoms. Each copper has a distorted square-pyramidal environment with a basal plane formed by three nitrogen atoms of the two chelating bipyridine groups and the oxygen atom of the bridging carbonato group (Cu−N/O distances about 2.0 Å). The apical position is formed at each copper by the fourth nitrogen atom of the bipyridines with distances varying from 2.120(5) to 2.188(5) Å. A weak ferromagnetic interaction is observed between the copper(II) ions. All data were fitted using the Hamiltonian H = −J12 (S1·S2) −J13 (S1·S3) −J23 (S2·S3). Observed parameters are J = 10.6 cm−1 and a very weak antiferromagnetic intercluster interaction with zj′ = −1.2 cm−1.