2, 2 '-bipyrimidine as efficient sensitizer of the solid-state luminescence of lanthanide and uranyl ions from visible to near-infrared

Treatment of Ln(NO3)3.nH2O with 1 or 2 equiv 2, 2'-bipyrimidine (BPM) in dry THF readily afforded the mono-metallic complexes [Ln(NO3)3(BPM)2] (Ln = Eu, Gd, Dy, Tm) or [Ln(NO3)3(bpm)2].THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln = Ce, Nd, Sm) yielded one of two distinct mono-metallic complexes, depending on the recrystallization solvent: (Ln(NO3)3(BPM)2].THF (Ln=Nd, Sm) from THF, or [Ln(NO3)3(BPM)(MeOH)2].MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO2(NO3)2.6H2O with 1 equiv BPM in THF afforded the mono-adduct [UO2(NO3)2(BPM)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid-state luminescence measurements on these mono-metallic complexes showed that BPM is ail efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb(III) ion emitting in the near-IR. For Tb, Dv, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8%, respectively. All these complexes in the solid state were stable in air. (authors)