Highly luminescent Tb(III) macrocyclic complex based on a DO3A hosting unit and an appended carboxylated N,C-pyrazolylpyridine antenna

The synthesis of a new ligand based on a DO3A moiety (DO3A = 1,4,7,10 tetraaza cyclododecane -1,4,7-triacetic acid) as a hosting agent for the lanthanide ions and an appended chromophoric unit N,C-pyrazolylpyridine core functionalized by a carboxylic acid in the 3-position of the pyrazole ring was reported. The luminescence properties of the 1/1 Eu(III) and Tb(III) corresponding complexes were investigated in air-equilibrated water and deuterated water (Tris buffer, pH 7.4) at 298 and 77 K. High luminescence lifetime (τ = 2.30 ms), quantum yield (Φ = 45%) and efficiency for the sensitized emission (ηsens = 60%) were observed for the terbium complex. A detailed study of the steps originating from light absorption at the chromophore unit and leading to lanthanide-centred emission was reported.