Yb-to-Eu Cooperative Sensitization Upconversion in a Multifunctional Molecular Nonanuclear Lanthanide Cluster in Solution.

Lanthanide metal clusters excel in combining molecular and material chemistry properties. Here, we report an efficient cooperative sensitization UC phenomenon of a Eu 3+ /Yb 3+ nonanuclear lanthanide cluster in CD 3 OD. The synthesis and characterization of the heteronuclear cluster in the solid state and solution are described together with the UC phenomenon showing Eu 3+ luminescence in the visible region upon 980 nm NIR excitation of Yb 3+ at concentrations as low as 100 nM. Alongside being the Eu/Yb cluster to display UC (with a quantum yield value of 4.88 × 10 -8 upon 1.13 W cm -2 excitation at 980 nm), the cluster exhibits downshifted light emission of Yb 3+ in the NIR region upon 578 nm visible excitation of Eu 3+ , which is ascribed to sensitization pathways for Yb through the 5 D 0 energy levels of Eu 3+ . Additionally, a faint emission is also observed at ca. 500 nm upon 980 nm excitation, originating from the cooperative luminescence of Yb 3+ . The [Eu 8 Yb(BA) 16 (OH) 10 ]Cl cluster (BA = benzoylacetonate) is also a field-induced single-molecular magnet (SMM) under 4K with a modest U eff / k B of 8.48 K, thereby joining the coveted list of Yb-SMMs and emerging as a prototype system for next-generation devices, combining luminescence with single-molecular magnetism in a molecular cluster.