Water-soluble Tb3+ and Eu3+ complexes based on task-specific ionic liquid ligands and their application in luminescent poly(vinyl alcohol) films

Novel water-soluble lanthanide complexes (Ln(IMI-DPA)3) have been synthesized using the task-specific ionic liquid consisting of a dipicolinic acid motif as the sensitizer of lanthanide luminescence. In Ln(IMI-DPA)3, Ln3+ ions are in 9-fold coordination through six carboxylate oxygen atoms and three nitrogen atoms in pyridine units, and the water molecule is excluded from the coordination sphere of the lanthanides. It is found that Ln(IMI-DPA)3 possess bright luminescence, long luminescence lifetime in aqueous solution, high thermal stability and good water solubility. Furthermore, these complexes can be incorporated into water-soluble poly(vinyl alcohol) (PVA) matrixes to obtain highly luminescent, transparent and flexible PVA composite films. The emission colors of the films can be tuned from red, orange, yellow, light green, green to white light by regulating the concentration of the various luminescent components.