Remarkable high efficiency of red emitters using Eu(iii) ternary complexesElectronic supplementary information (ESI) available: Instruments, experimental procedure, characterization of compounds, XRD and PXRD analyses, cytotoxicity study and confocal microscopy, solubility study and OLEDs. CCDC 1818246 and 1818247. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8cc02930j

We have synthesized Eu( iii ) ternary complexes possessing record photoluminescence yields up to 90%. This high luminescence performance resulted from the absence of quenching moieties in the Eu coordination environment and an efficient energy transfer between ligands, combined with a particular symmetry of the coordination environment. We have synthesized Eu( iii ) ternary complexes possessing record photoluminescence yields up to 90%.