A Trinuclear Radical-Bridged Lanthanide Single-Molecule Magnet.

Assembly of the triangular, organic radical-bridged complexes Cp*₆Ln₃(μ₃-HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*₂Ln(BPh₄) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three Ln^III centers through the HAN^3−. radical ligand. Thorough investigation of the Dy^III congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of U_eff=51 cm⁻¹. Magnetic coupling in the Dy^III complex enables a large remnant magnetization at temperatures up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero-field up to 3.5 K. [ABSTRACT FROM AUTHOR]