A novel triangular trinuclear mu(3)-CO3 ferromagnetic Cu-II compound prepared in situ from CO2 uptake in air. X-ray structure, spectroscopy and magnetism

The new trinuclear compound [Cu-3(bPY)(6)(mu(3)-CO3)]-(BF4)(4)(H2O)(2)(C2H6 O) (in which bpy = 2,2'-bipyridine) has been synthesized from Cu(BF4)(2) an d 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 = 13.6 91(7), c = 21.446(8) Angstrom, alpha = 82.87(4), beta = 73.57(4), gamma = 6 4.32(4)degrees, Z = 2. The three copper atoms are connected to each other t hrough the oxygen atoms from the bridging carbonate group, giving a triangu lar array of copper atoms. Each copper has a distorted square-pyramidal env ironment with a basal plane formed by three nitrogen atoms of the two chela ting bipyridine groups and the oxygen atom of the bridging carbonate group (Cu-N/O distances about 2.0 Angstrom). The apical position is formed at eac h copper by the fourth nitrogen atom of the bipyridines with distances vary ing from 2.120(5) to 2.188(5) Angstrom. A weak ferromagnetic interaction is observed between the copper(II) ions. All data were fitted using the Hamil tonian H = -J(12) (S-1.S-2) -J(13) (S-1.S-3) -J(23) (S-2.S-3). Observed par ameters are J = 10.6 cm(-1) and a very weak antiferromagnetic intercluster interaction with zj' = -1.2 cm(-1).