Versatile pyridine-2,6-bis-tetrazolate scaffolds for the formation of highly luminescent lanthanide complexes
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(L-i)(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.