Luminescent europium(iii) complexes based on tridentate isoquinoline ligands with extremely high quantum yield

Abstract

Here, we report two europium(III) complexes (Eu1 and Eu2) with high photoluminescence quantum yield, based on tridentate isoquinoline derivatives (HL1 and HL2). The single crystal structures of Eu1 and Eu2 show that three ligands coordinate with an Eu(III) ion through diphenylphosphoryl oxygen, pyridyl nitrogen and carboxyl oxygen atoms (O^N^O) with no solvent in the first coordination sphere. An appropriate triplet energy level (about 20 000 cm⁻¹) ensures efficient energy transfer from the ligands to the Eu(III) ion. As a result, the two complexes exhibited significantly high quantum yields in the solid state (94% and 87% for Eu1 and Eu2, respectively) with excitation bands extending to 350 nm.