Many of the largest metal ions in the Periodic Table possess unique physical properties that can be harnessed for a variety of applications. The large alpha particle-emitting radiometals Ra-223, Ac-225, and Bi-213, for example, are currently under investigation for use in targeted cancer therapy, and the largest non-radioactive +2 metal ion, barium, has been employed for over a century in the form of insoluble barium sulfate for gastrointestinal imaging. Owing to the same physical properties, however, metals such as these also present health, environmental, and industrial hazards, requiring their decorporation or remediation. Therefore, the development of chelators that can effect both the delivery and removal of large metal ions is of global significance (Fig. 1). The selective and stable chelation of these large ions is challenging due to the predominance of electrostatic character in their ligand binding interactions, which become weaker with increasing ionic radius of the metal ion. Ligand design efforts in our lab for the chelation of large metal ions are focused on the development of expanded macrocycles bearing different pendent donor arms. This presentation will provide an overview of the synthesis of these ligands, their thermodynamic affinities for large s-, p-, and f-block metal ions, and the kinetic stabilities of the resulting metal-ligand complexes. Furthermore, we describe the implementation of these ligands for several medical and industrial applications.

Large and in charge: Development of expanded macrocycles for the chelation of large metal ions of therapeutic and industrial relevance

2019 Spring National Meeting

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