Solution‐Phase Tuning of Emission of Divalent Europium

Abstract

The key to developing smart light-emitting systems lies in the ability to tune luminescence with only modest changes in the chemical environment. Divalent europium-based luminophores are unique materials that access emissions ranging from the blue to red regions of the visible spectrum. Early studies demonstrate the tunability of the emission of Eu II in solid-state host lattices, and recent research has shown that altering counter anions, solvents, and ligands also enables tuning of the emission of Eu II . These findings are supported by numerous publications, and mechanistic studies shed light on the underlying theories behind the tunable emissions of Eu II . The purpose of this article is to present the most recent hypotheses and understanding regarding the effect of counter anions, solvents, and ligands on luminescence properties of Eu II based systems.

Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures

“…This difference in the dependence of the luminescence of Eu II on the counterions between Eu II 1 and Eu II 2 is likely a consequence of the greater geometric flexibility of ligand 2 relative to ligand 1 , enabled by the acyclic nature of ligand 2 . The increased flexibility in 2 relative to 1 enables close interactions between counterions and Eu II , resulting in more pronounced differences in the extent of the splitting of 5d orbitals because the energies associated with the 5d–4f transitions depend on the extent of 5d splitting. , This greater tunability achieved by varying counterions in the presence of a suitable ligand (here, ligand 2 ) demonstrates the importance of studying the impact of counterions on the photophysical properties of divalent lanthanides, especially counterions other than the typical halides. In addition, this wide range of emission tunability of Eu II 2 makes Eu II 2 a potentially interesting family of lumiphores to study for applications such as light-emitting diodes.…”