Structural and Photophysical Studies on Geometric (Er₂Yb₂/Yb₂Er₂) and Configurational (EuTb₃/Eu₃Tb) Isomers of Heterotetranuclear Lanthanide(III) Complexes

Heterotetranuclear geometrical (Er₂Yb₂/Yb₂Er₂) and configuational (EuTb₃/Eu₃Tb) isomeric lanthanide­(III) complexes have been synthesized and characterized by spectroscopy as well as X-ray crystallography. The geometric Er₂Yb₂/Yb₂Er₂ isomers exhibit dual emissions from both erbium­(III) and ytterbium­(III) ions. For the EuTb₃/Eu₃Tb configurational isomers, the Tb^III subunits transfer energy to the Eu^III centers in the EuTb₃ complex, whereas the Tb^III ion in the TbEu₃ complex serves mainly as a structural stabilizer.