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)₂(OAc)­(salen)₂] (OAc: acetate anion, salen: <i>N,N</i>′-bis­(salicylidene)­ethylenediamine), brick-type [Eu₂(hfa)₄(OAc)₂(salbn)₂] (salbn: <i>N,N</i>′-bis­(salicylidene)-1,4-butanediamine), and polynuclear [Eu­(hfa)₂(OAc)­(salhen)]_<i>n</i> (salhen: <i>N,N</i>′-bis­(salicylidene)-1,6-hexanediamine) are reported for white light-emitting diode (LED) devices. Among these complexes, brick-type [Eu₂(hfa)₄(OAc)₂(salbn)₂] excited by blue light (460 nm) exhibits the photosensitized quantum yield (Φ_π–π* = 47%) and remarkably high efficiency of sensitization (η_sens = 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 [Eu₂(hfa)₄(OAc)₂(salbn)₂] was mounted on an InGaN blue LED chip