Sensitization of europium(III) luminescence in bis(bipyridine) DTPA and DTTA-based ligands: effect of the deletion of amide groups

Two new ligands containing two 2,2′-bipyridine groups and derived from diethylenetriaminepentaacetic acid (DTPA) (1) or diethylenetriaminetriacetic acid (DTTA) (2) were synthesized and the luminescent properties of their europium(III) complexes were investigated in aqueous solutions. In the two systems, the 2,2′-bipyridine chromophores act as antenna for the sensitization of the lanthanide ion and are not coordinated to the metal. It is shown that the change in ligand structure from 1 to 2 creates a higher antenna-to-metal energy transfer, and consequently a better luminescence quantum yield.