An efficient route to pyridine and 2,2′-bipyridine macrocycles incorporating a triethylenetetraminetetraacetic acid core as ligand for lanthanide ions

Two novel macrocyclic chelators L1 and L2 incorporating an intracyclic pyridine or 2,2′-bipyridine unit and a triethylenetetraminetetraacetic acid core (TTTA) were synthesized with the aim of forming lanthanide complexes suitable as efficient long-lived luminophores. For this goal, an efficient methodology for the preparation of TTTA derivatives using prealkylated precursors is described. Starting from commercially available compounds, the target ligands were obtained in seven (L1) and nine (L2) steps in 40% and 20% overall yields, respectively. Stable Tb(III) complexes were prepared and displayed interesting luminescence properties.