First coordination compounds based on a bis(imino nitroxide) biradical and 4f metal ions: Synthesis, crystal structures and magnetic properties

The synthesis, crystal structures and magnetic properties of two families of heterospin complexes containing lanthanide ions and a bis(imino nitroxide) biradical (IPhIN = 1-iodo-3,5-bis(4 ’,4’,5’,5’-tetramethyl-4’,5’-dihydro-1H-imidazole-1’-oxyl)benzene) are reported: in [Ln2(hfac)6(IPhIN)(H2O)2] compounds, twolanthanide ions [Ln = GdIII(1) and DyIII(2)] are coordinated to the biradical, and in [Ln(hfac)3(IPhIN)(H2O)]compounds, one lanthanide ion (Ln = TbIII(3), GdIII(4 )or DyIII(5)) is coordinated to the biradical. Ferro-magnetic intramolecular magnetic interactions between GdIIIand the biradical were found for 1 and 4, while intramolecular magnetic interactions between the radicals were ferro- and antiferromagnetic, respectively. Compound 2 shows a field induced slow relaxation of magnetization, which (under an external applied field of 2 kOe) exhibits an activation energy barrier of ΔE/kB= 27 K and a pre-exponential factor of 1.4 × 10−8s. To support the magnetic characterization of compound 3 ab initio calculations were also performed.