Luminescence of Salen Lanthanide Bimetallic Complexes: Dual Emission and Energy Transfer

The luminescence properties of the tetranuclear bimetallic lanthanide complexes Sm 2 Eu 2 ( 1 ) and Eu 2 Tb 2 ( 2 ), were compared with those of the analogous homometallic complexes [Sm 4 (μ 3 ‐OH) 2 (salen) 2 (acac) 6 (CH 3 OH) 2 ] · CH 3 OH ( 3 ) and [Eu 4 (μ 3 ‐OH) 2 (salen) 2 (acac) 6 (CH 3 OH) 2 ] ( 4 ) [H 2 salen = N, N ′‐ethylenebis(salicylideneimine), Hacac = acetylacetonate]. X‐ray crystallographic analysis reveals that complexes 3 and 4 have planar tetranuclear structures. For the Eu 2 Tb 2 configurational isomer, the Tb III ion in complex 2 mainly serves as a sensitizer. The quantum yields and lifetime measurements for 2 support the premise that Ln / Ln energy transfer occurs in such lanthanide bimetallic complexes, along with the usual ligand‐to‐metal triplet energy pathways. Complexes 3 and 4 exhibit the characteristic metal‐centered emission.