Red Luminescent Eu(III) Coordination Bricks Excited on Blue LED Chip.

Three types of red luminescent Eu(III) complexes with Schiff base and hfa ligands (hfa: hexafluoroacetylacetonate), mononuclear [Eu(hfa)(OAc)(salen)] (OAc: acetate anion, salen: N,N'-bis(salicylidene)ethylenediamine), brick-type [Eu(hfa)(OAc)(salbn)] (salbn: N,N'-bis(salicylidene)-1,4-butanediamine), and polynuclear [Eu(hfa)(OAc)(salhen)] (salhen: N,N'-bis(salicylidene)-1,6-hexanediamine) are reported for white light-emitting diode (LED) devices. Among these complexes, brick-type [Eu(hfa)(OAc)(salbn)] excited by blue light (460 nm) exhibits the photosensitized quantum yield (Φ = 47%) and remarkably high efficiency of sensitization (η = 96%). The efficiency of sensitization is caused by the excited state based on ligand-ligand interaction between the Schiff base and hfa ligands in Eu(III) complexes. To fabricate LED devices, the red luminescent [Eu(hfa)(OAc)(salbn)] was mounted on an InGaN blue LED chip.