Mixed Phenanthroline–Bipyridine Europium and Ytterbium Cryptates─Bright Luminophores with Small Radiative Lifetimes

New phenanthroline-based tris (biaryl) europium (III) and ytterbium (III) cryptates with great luminescence efficiencies in solution are reported. 1, 10-Phenantroline, in combination with 2, 2′-bipyridine-N, N′-dioxide, delivers cryptates with high rigidity, efficient lanthanoid (III) sensitization (ηₒ₄₍ₒ) and small radiative lifetimes τrad for Eu and Yb. The powerful synergy of both bidentate chelating units results in excellent absolute quantum yields of up to 20% for the europium complexes in aqueous solution, which indicates an impressive improvement compared to other well-known tris (bipyridyl) -based Eu (III) cryptates.