Ferromagnetic coupling in a chloride-bridged erbium single-molecule magnet

We present the first ferromagnetically-coupled Er3+ complex with linked, high-anisotropy Er-COT (COT2- = cyclooctatetraene dianion) subunits. The dinuclear complex, [Er(mu(2)-Cl)(COT)(THF)](2), demonstrates single-molecule magnetism with a single, zero-field magnetization relaxation barrier of U-eff = 113 cm(-1). This system offers evidence that anisotropy can be preserved in the presence of ferromagnetic linking of the Er-COT subunits, providing a rational means to build strong molecular magnets of tunable dimensionality.