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 mu s 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 beta(110)=21.8(4) for 3,4,3-LI(1,2-HOPO) and log beta(120)=24.5(5) for 5-LIO(Me-3,2-HOPO)). The in vivo complex stability for both ligands was assessed by using Cm-248 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.