Versatile pyridine-2,6-bis-tetrazolate scaffolds for the formation of highly luminescent lanthanide complexes

Abstract

Here we report the straightforward synthesis of the ligands L^tz, L^tzC8, L^tzPEG, L^tzAnis and L^Anis presenting the same pyridine-bistetrazolate (pytz, L) chelating scaffold but different substituents on the para position of the pyridine ring. Its substitution allows the tuning of the solubility of the Ln^III complexes [Ln(Lⁱ)₃]³⁻. These new ligands form homoleptic nona-coordinated Ln^III complexes of analogous structure and comparable stability in water and methanol. The derivatization of the para position with triazole and substituted triazole groups does not lead to a significant shift of the absorption window, but a shift of 40 nm is observed in ligand L^Anis due to the presence of the p-ethynyl anisole fragment. The L^tzX series sensitize well, both the Eu and the Tb ions with quantum yields up to 98% for Tb and 43% for Eu, while the ligand L^Anis sensitizes well Eu (QY of 48%) but cannot sensitize Tb due to the position of its triplet state.