Bidentate nitroxide ligands stable toward oxidative redox cycling and their complexes with cerium and lanthanum

We report the synthesis of 1,3-bis[(20-tertbutyl) hydroxyaminophenyl]-benzene (H(2)arene-diNOx) and its metal complexes, Ce(arene-diNOx)(2) (1) and [(py)(2)K(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.