O‐oxazolinyl‐ and O‐thiazolinylphenol As Antennae in Luminescent EuIII and TbIII Complexes

Europium(III) and terbium(III) complexes have been prepared using the ligands 2-(4,5-dihydro-1,3-oxazol-2-yl)phenol (HL1) and 2-(4,5-dihydro-1,3-thiazol-2-yl)phenol (HL2) in yields ranging between 74 and 100%. Metal-to-ligand ratios of 1:3 and 1:4 can be achieved, giving rise to compounds with the formulae [Ln(2)(L)(6)] and NR4[Ln(L)(4)], Ln = Eu, Tb. Recrystallisation of the complexes from DMSO resulted in the formation of octanuclear complexes [Na-2(Ln(L1)(3))(2)(CO3)(DMSO)(2)](2) held tightly together by carbonate ions that have been formed from CO2 from the atmosphere. Five structures have been determined, showing a bidentate binding mode of the ligand through the phenolate oxygen and the nitrogen atom of the five-membered ring. Most terbium compounds show bright luminescence upon excitation with near-UV radiation, with quantum yields of 16% to 79%. Strong emission is observed for NBu4[Eu(L1)(4)] and NEt4[Eu(L2)(4)] with quantum yields of 43% and 20%, respectively.