Rigid, Perdeuterated Lanthanoid Cryptates: Extraordinarily Bright Near-IR Luminophores.

Near-IR emissive lanthanoid cryptates have been developed with the lanthanoids Yb, Nd, Er, and Pr by designing a fully deuterated ligand environment that greatly suppresses multiphonon nonradiative deactivation pathways through avoidance of high-energy oscillators and rigidification of the ligand backbone. Strong luminescence is observed in CD3CN for all four lanthanoids. Luminescence lifetimes in CD3CN are among the highest values for molecular complexes in solution reported so far (Yb, τobs = 79 μs; Nd, τobs = 3.3 μs). For the ytterbium cryptate, the highest luminescence lifetime can be obtained using CD3OD (τobs = 91 μs) and even in nondeuterated CH3CN the lifetime is still unusually high (τobs = 53 μs). X-ray crystallography and 1H NMR analysis of the corresponding nondeuterated lutetium cryptate suggest that the inner coordination sphere in solution is completely saturated by the octadentate cryptand and one chloride counterion. All lanthanoid cryptates remarkably show complete stability during reversed-phase HPLC measurements under strongly acidic conditions.