Electrochemically regulated luminescence of europium complexes with β-diketone in polyether matrices

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu³⁺ and Eu²⁺. Initially, the intrinsically stable Eu³⁺ complex showed intense red photoluminescence (PL) induced by f-f transitions. After the electrochemical reduction of Eu³⁺ to Eu²⁺, broad blue PL was observed attributed to the d-f transitions in the Eu²⁺ complex. This distinct blue luminescence from the Eu²⁺ complex was attributed to the effective stabilization of the Eu²⁺ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices.