Lanthanide complexes based on a C₃ symmetric tripodal ligand and potential application as fluorescent probe of Fe³⁺

Based on a novel C₃ symmetric tripodal ligand 1,1′,1′′-[(2,4,6-trimethyl-1,3,5-benzenetriyl)tris(methylene)]tris[2(1H)-pyridinone], eight isostructural lanthanide coordination complexes have been constructed. The one-dimensional ladder-like chain structures in these complexes are packed together through the interaction of hydrogen bonding and π-π stacking, leading to the formation of a three-dimensional structure with one-dimensional channels. A systematic study on Ln-O bond lengths in this family of complexes revealed that Ln-O distances exhibited a trend according to the lanthanide contraction. And the torsion angles that define the ligand conformation are different for the pyridone groups on distinct side of the plane of the central phenyl ring. Selected complex from the family shows highly selective and sensitive fluorescence quenching by Fe³⁺ ion, which is not affected by other common metal ions. The Stern–Volmer curve regarding the fluorescence quenching of Fe³⁺ toward the complex exhibits perfect linearity for a variety of concentrations, demonstrating the complex to be a good candidate as highly selective, efficient, and quantitative fluorescent probe for Fe³⁺.