Towards the design of highly luminescent europium(III) complexes

We report on the synthesis, characterization, and photophysical investigation of a new nine-coordinate Eu3+ complex containing three tridentate ligands and exhibiting one of the highest emission quantum yields (Φ = 85 %) so far reported in solution. Ligand field theory (LFT) and semiempirical calculations were employed to predict the energies of the 7F JM J stark levels of the ion with the aim to find the best geometry of the complex on the basis of matching experimental data. The results from the LFT analysis corroborated the existence of a nine-coordinate Eu 3+ center and proved the transferability of the charge factors used in this theoretical model. Our findings contribute to the design and full characterization of highly luminescent Eu3+ complexes, and our approach could be extended to other trivalent lanthanide complexes. The synthesis of a tridentate ligand exhibiting appropriate spectral properties has led to the formation of a neutral, nine-coordinate Eu3+ complex that exhibits one of the largest emission quantum yields ever reported in solution, Φ = 85 %. Photophysical measurements and ligand field calculations were also made to characterize this highly luminescent complex.