Effect of the Introduction of Zn ^II and Cd ^II Ions on Eu ^III and Tb ^III Emission in M ₂ Ln ₂ Heterometallic Molecules With 2‐Furoic Acid Anions

ABSTRACT Heterometallic d‐4f coordination complexes are of paramount interest in modern coordination chemistry because of their potential applications in organic light‐emitting devices and spintronic materials. Here we report the synthesis and thorough investigation of Ln and MLn (M = Zn, Cd; Ln = Sm, Eu, Gd, Tb) molecular complexes based on 2‐furancarboxylic acid anion (Hfur): [Ln 2 (NO 3 ) 2 (fur) 4 (DME) 2 ] (Ln = Eu, Gd, Tb; DME is dimethoxyethane) and [M 2 Ln 2 (NO 3 ) 2 (fur) 8 (bpy) 2 ] (M = Zn, Cd; Ln = Eu, Gd, Tb, Sm; bpy is 2,2′‐bipyridyl). The structure and isostructural nature of compounds were determined based on the single‐crystal and powder X‐ray diffraction data. The photophysical properties of the obtained compounds were studied in detail: The energies of the triplet levels of the furoate anion and d‐blocks {M(fur) 2 (bpy)} (M = Zn, Cd), the relaxation times of the excited states, and the quantum yields were determined. Critical step from Ln complexes to ZnLn and CdLn (Ln = Eu, Tb) is accompanied by an increase in quantum yields, which correlates with a change in the energy of the triplet level of the aromatic part of the complexes and with the results of quantum chemical calculations indicating different schemes for the origination of triplet levels in MLn compounds.