Synthesis and Optical Properties of Ln2Ln′2‐Tetranuclear Lanthanide(III) Complexes
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A series of new heterotetranuclear lanthanide complexes (Ln2Ln′2) is synthesized to study Ln-to-Ln′ energy transfer. Using stable dinuclear precursors, Tb2Yb2 and Nd2Tb2 are prepared and show visible/NIR emission. Reduced Tb3+ lifetimes suggest energy transfer to Yb3+ or Nd3+, offering a modular route to mixed-lanthanide systems.
A set of structurally related heterotetranuclear lanthanide(III) (Ln) complexes containing Ln1 2Ln2 2 cores has been synthesized as potential downshifting materials for solar applications. The Ln1 2Ln2 2 complexes can be regarded as intermediate model systems between classical doped systems and dinuclear molecular systems. The choice of Ln1 and Ln2 is based on commonly used codoped solid-state systems to evaluate the effect of energy transfer in the tetranuclear unit. The complexes are obtained by a new systematic approach involving the reactions of stable, solvent-free dinuclear homometallic precursors (Ln1 2 + Ln2 2 →Ln1 2 + Ln2 2). The new complexes Tb2Yb2q6(hfac)4(μ3-OH)2 (Tb 2 Yb 2 ) and Nd2Tb2q6(hfac)4(μ3-OH)2 (Nd 2 Tb 2 ) (q− = 8-hydroxyquinolate; hfac− = hexafluoroacetylacetonate), show emission both in the visible and near-IR regions. In both Nd 2 Tb 2 and Tb 2 Yb 2 , a reduction in the excited-state lifetime of the donor, Tb3+ is observed relative to the acceptor-free complex, Tb2Y2q6(hfac)4(μ3-OH)2 (Tb 2 Y 2 ), thus, signifying an energy transfer to the acceptors, Nd3+ or Yb3+, respectively. Overall, this work provides a versatile approach to controlling the aggregation and composition of mixed-lanthanide complexes while introducing new building blocks for exploring Ln-to-Ln′ energy transfer in discrete heteropolynuclear systems.
