Magnet-like behaviour, in the form of slow relaxation of the magnetization, was observed for a monometallic cerium(III) sandwich complex. The use of trimethylsilyl substituted COT ligands (COT'') led to the formation of a staggered COT'' arrangement in the cerocene-type sandwich complex with a well-defined oxidation state of +3 for the Ce ion.

We report the synthesis of 1,3-bis[(2′-tertbutyl)hydroxyaminophenyl]benzene (H2arene-diNOx) and its metal complexes, Ce(arene-diNOx)2 (1) and [(py)2K(18-crown-6)][La(arene-diNOx)2] (2). Electrochemical studies demonstrated that the H2arene-diNOx, bidentate nitroxide ligands significantly stabilized the Ce(IV/III) redox couple to −1.74 V versus Fc/Fc(+). Moreover, a reversible oxidation wave was observed for 1 at −0.37 V, leading to a novel, stable redox-active nitroxide ligand. DFT calculations confirmed that the observed oxidation is assignable to one of the nitroxide groups.