Designing water-quenching resistant highly luminescent europium complexes by regulating the orthogonal arrangement of bis-β-diketone ligands

Luminescent beta-diketone-based lanthanide complexes have been well explored as chemical sensor materials for biomedicine applications. Herein, three mononuclear Eu3+ complexes based on bis-beta-diketone ligands (L-1, L-2 and L-3) that can reduce luminescence quenching caused by water were developed. The ligands feature two beta-diketone units covalently bound at the 1,8-position of the derivatized anthracene (modified with tetracyanoethylene, TCNE). X-ray crystallographic analysis reveals that their self-assemblies with Ln(3+) ions in a 2 : 1 stoichiometric ratio form mononuclear anion complexes, [EuL2](-), in which two ligands coordinate to the metal center in a mutually orthogonal manner. This kind of arrangement together with the bulge of TCNE from the anthracene plane well protected the complexes from the quenching effects of water molecules in the second coordination. The photophysical measurements showed that the complexes not only had high luminescence quantum yields (QYs, up to 50-67%) but also presented excellent water-quenching resistant capability.

Automated summary

Three mononuclear Eu3+ complexes based on bis-beta-diketone ligands (L-1, L-2, and L-3) were developed to reduce luminescence quenching caused by water, with high luminescence quantum yields (QYs, up to 50-67%) and excellent water-quenching resistant capability. X-ray crystallographic analysis revealed their self-assemblies with Ln(3+) ions in a 2 : 1 stoichiometric ratio form mononuclear anion complexes, [EuL2](-), with two ligands coordinating to the metal center in a mutually orthogonal manner, effectively protecting the complexes from quenching effects of water molecules.