Highly Luminescent and Stable Hydroxypyridinonate Complexes: A Step Towards New Curium Decontamination Strategies

The photophysical properties, solution thermodynamics, and in vivo complex stabilities of Cm^III complexes formed with multidentate hydroxypyridinonate ligands, 3,4,3‐LI(1,2‐HOPO) and 5‐LIO(Me‐3,2‐HOPO), are reported. Both chelators were investigated for their ability to act as antenna chromophores for Cm^III, leading to highly sensitized luminescence emission of the metal upon complexation, with long lifetimes (383 and 196 μs for 3,4,3‐LI(1,2‐HOPO) and 5‐LIO(Me‐3,2‐HOPO), respectively) and remarkable quantum yields (45 % and 16 %, respectively) in aqueous solution. The bright emission peaks were used to probe the electronic structure of the 5f complexes and gain insight into ligand field effects; they were also exploited to determine the high (and proton‐independent) stabilities of the corresponding Cm^III complexes (log β₁₁₀=21.8(4) for 3,4,3‐LI(1,2‐HOPO) and log β₁₂₀=24.5(5) for 5‐LIO(Me‐3,2‐HOPO)). The in vivo complex stability for both ligands was assessed by using ²⁴⁸Cm as a tracer in a rodent model, which provided a direct comparison with the in vitro thermodynamic results and demonstrated the great potential of 3,4,3‐LI(1,2‐HOPO) as a therapeutic Cm^III decontamination agent.