Phase control of ferromagnetic copper(II) carbonate coordination polymers through reagent concentration

A significant degree of control over the dimensionality and magnetic connectivity of CuII carbonate coordination polymers is achieved through varying the concentration of ammonia in the reactant solution. Higher concentration leads to a two-dimensional ferromagnetic [Cu3(2,4′-bipy)6(CO3)2]n 2n+ kagome structure while lower concentration develops a ferromagnetic [Cu(2,4′-bipy)2(H2O)2][Cu(2,4′-bipy)2(CO3)2] chain (where 2,4′-bipy = 2,4′-bipyridine). The carbonate anion in the structures arises from the fixation of atmospheric CO2 by the basic ammonia solution. Modelling the magnetic susceptibility of 1 and 2 reveals ferromagnetic interactions with J/kB = +28.1 K for 1 and +13.99 K for 2. (H = –J). The use of a monodentate polypyridine ligand results in the suppression of the superexchange pathway between layers in 1, removing the metamagnetic behaviour seen in related compounds where a ditopic ligand presents the ability for the layer to couple antiferromagnetically. Attempts to substitute 2,4′-bipy for 4-(N,N-dimethylamino)pyridine (4-dmap) result in a discrete species [Cu(4-ampy)4](ClO4)2 (3).