Lanthanide Complexes with 4,4′‐Bis(2‐sulfonatostyryl)‐biphenyl: Crystal Structures and Luminescence Properties

A series of new tris(pyrazolyl)borate (Tp⁻) and tris(2‐pyridylpyrazolyl)borate (Tp^Py−) Eu³⁺, Gd³⁺, Tb³⁺ and Dy³⁺ complexes with the dianionic ligand 4,4′‐bis(2‐sulfonatostyryl)biphenyl (Ssp²⁻, a widely used fluorescent whitener) were synthesized and their luminescence properties were studied. The Gd³⁺, Tb³⁺ and Dy³⁺ compounds possess only ligand‐centered emission, arising from the Ssp²⁻ ligand, with quantum yields of up to 60 %. While the emission centers in these complexes are similar, the positions of the luminescence maxima, the emission quantum yields, and the lifetimes change in the order [(Tp₂Ln)₂Ssp]<[(Tp^PyLnSsp)₂]<[Ln₂Ssp₃]_n. Among the complexes studied, Eu³⁺‐centered emission was observed for only [(Tp₂Eu)₂Ssp]. In this compound, Tp⁻ plays the role of an antenna ligand for Eu³⁺‐radiation, though the quantum yield is only 5 %.