Synthesis and photochemical properties of luminescent Eu(III) complexes with macrocyclic and macropolycyclic ligands incorporating 3,3'-biisoquinoline-2,2-dioxide units

Three novel ligands incorporating two, or three 3,3'-biisoquinoline-2,2'-dioxide units have been synthesized using modified standard methods of cyclization. These ligands formed photoactive mononuclear complexes with a Eu(III) cation. The ligand with two photoactive units displayed a better quantum yield for the Eu(III) emission (0.064) upon UV excitation than the other two complexes incorporating three units, whose luminescence quantum yields have been estimated to be below 0.01. The luminescence of the Eu(III) complex with two sensitizing units was not stable in aqueous solution, whereas with the two other complexes, their luminescence in solution remained for a couple of days.