A Trinuclear Radical-Bridged Lanthanide Single-Molecule Magnet.

Assembly of the triangular, organic radical-bridged complexes Cp*6 Ln3 (μ3 -HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*2 Ln(BPh4 ) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three LnIII centers through the HAN3-. radical ligand. Thorough investigation of the DyIII congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of Ueff =51 cm-1 . Magnetic coupling in the DyIII 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.