Coupling strategies to enhance single-molecule magnet properties of erbium-cyclooctatetraenyl complexes

Two different coupling strategies were employed to create ErIII single-molecule magnets (SMMs) using high blocking temperature mononuclear precursors. The magnetic properties of three lanthanide–COT complexes, [ErIII2(COT′′)3] (1) (COT′′ = 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion) and K2(THF)4[LnIII2(COT)4] (Ln = Gd (2), Er (3); THF = tetrahydrofuran, COT = cyclooctatetraenyl dianion), are reported. Both ErIII complexes behave as SMMs and exhibit magnetic hysteresis at 12 K in solid state. In solution compound 1 exhibits hysteresis up to 14 K. Ac susceptibility data indicates a 100 s blocking temperature of 12.5 and 12.9 K for [ErIII2(COT′′)3] and K2(THF)4[ErIII2(COT)4], respectively. Both ErIII dimers display enhanced SMM properties over their mononuclear analogues due to their linear structure and strictly axial anisotropy. A 4 K increase in the magnetic blocking temperature of [ErIII2(COT′′)3] over the double-decker analogue is attributed to an additional mechanism of magnetization blocking arising from exchange coupling between ErIII ions