Switchable photoluminescence of europium(III) complexes with chromonylhydrazones

Abstract

Europium(III) complexes bearing 4-hydroxy- or 4-methyl-N’-((6-methyl-4-oxo-4H-chromen-3-yl)methylene)benzohydrazide (HL¹ or HL²) showed characteristic Eu^III5D₀ → ⁷F_J (J = 0–4) luminescence both in acetonitrile and in solid states with relatively high Φ_tot values. The luminescence was quenched not only by adding triethylamine in acetonitrile, but also by heating the solid sample, and recovered by adding perchloric acid in solution or by diffusion of HCl vapor to the resulting solid sample.