Triply Chalcogenophenolato-Bridged Erbium-Cyclooctatetraenyl Complexes: Syntheses and Single-Molecule Magnetic Properties

Lanthanide-containing molecular magnets have dominated the research of single-molecule magnets (SMMs) in the past two decades. To explore the effects of bridging ligands on the properties of dinulcear lanthanide SMMs, we report herein three closely related yet systematically altered dinuclear erbium-cyclooctatetraenyl complexes of the general formulaThe complex cations feature a common core of two half-sandwich Er-COT complex units being bridged by three PhE -ligands. The transverse component of the dipolar fields effectively diminishes due to the unique head-to-tail alignment of the magnetic easy axes of the Er(III) ions, leading to the emergence of open magnetic hysteresis loops at low temperatures. As the bridging atoms change from O to S and Se, a decrease of the intramolecular dipolar interactions (1.76 cm -1 (1), 1.17 cm -1 (2), 1.06 cm -1 (3)) was observed, which is accompanied by an increase of their effective energy barriers (113(3) cm -1 (1), 134(4) cm -1 (2), 141(2) cm -1 (3)). Because of the opposite impact of changing the bridging atoms, these complexes exhibit comparable magnetic blocking behaviors below 6 K. This work suggests that multinuclear lanthanide-SMMs with optimized properties can be achieved using judiciously selected bridging atoms.