Synthesis, crystal structures and magnetic properties of two tetranuclear lanthanide-hydroxo cubane clusters

• Two tetranuclear Er3+ and Yb3+-hydroxo clusters were synthesized.
• They consist of a Ln4(μ3-OH)48+ cluster core showing cubane-like geometry.
• Their magnetic and optical properties were elucidated.

Two tetranuclear Lanthanide-hydroxo cubane clusters of composition [Ln4(μ3-OH)4{(μ-O)-η2-acac}4(η2-acac)4]·C7H8 (Ln = Er 1 and Yb 2, acac = acetylacetonate) have been prepared and characterized by elemental analyses, FTIR spectroscopy and X-ray crystallography. Single crystal X-ray analyses of 1 and 2 revealed that they are isostructural with the Ln4(μ3-OH)48+ cluster core showing cubane-like geometry. Each cluster consists of four lanthanide atoms, four μ3-O atoms, and eight acac ligands making up the peripheral part of the cluster. Two types of the coordination modes [η2- and (μ-O)-η2-] of the acac ligands in 1 and 2 are observed. Investigations on the magnetic properties of 1 and 2 indicate that both complexes do not exhibit frequency-dependent in-phase (χ′) and out-of-phase (χ′′) signals in the alternating current (ac) magnetic susceptibilities of 1 and 2. In particular, unlike most documented lanthanide β-diketonate mono- or multinuclear complexes exhibiting near-infrared (NIR) emission property, 1 and 2 do not show any detectable NIR emission at any temperature range and the reason of nonluminescence for 1 and 2 is further elucidated in this work.