Density Functional Theory as a tool to identify the dominant magnetic interactions in the [Cu(hfac)2(N3TEMPO)]n chain

Density Functional Theory (DFT) was employed to investigate the dominant magnetic interactions in the [Cu(hfac)2N3TEMPO]n chain (hfac = hexafluoroacetylacetonate and N3TEMPO = 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl). This compound crystallizes with two copper(II) sites bridged coordinated in the axial positions by N3TEMPO radicals originating a chain. Short intermolecular contacts between nitroxide groups belonging to adjacent chains result in an effective pathway to magnetic interactions. DFT calculations show that intrachain magnetic interactions between the Cu2 center and the N3TEMPO radical are considerably weaker than intermolecular magnetic interactions between two N3TEMPO radicals. This result agrees with experimental data which show that the pathway for magnetic interaction does not coincide with the covalent skeleton, being indeed due to intermolecular contacts.