Synthesis, Isolation, and Study of Heterobimetallic Uranyl Crown Ether Complexes

• Published in: Journal of the American Chemical Society 2024-04, Vol.146 (14), p.9597-9604
• Main Authors: Golwankar, Riddhi R., Ervin, Alexander C., Makoś, Małgorzata Z., Mikeska, Emily R., Glezakou, Vassiliki-Alexandra, Blakemore, James D.
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c12075

Although crown ethers can selectively bind many metal cations, little is known regarding the solution properties of crown ether complexes of the uranyl dication, UO2 2+. Here, the synthesis and characterization of isolable complexes in which the uranyl dication is bound in an 18-crown-6-like moiety are reported. A tailored macrocyclic ligand, templated with a Pt­(II) center, captures UO2 2+ in the crown moiety, as demonstrated by results from single-crystal X-ray diffraction analysis. The U­(V) oxidation state becomes accessible at a quite positive potential (E 1/2) of −0.18 V vs Fc+/0 upon complexation, representing the most positive UVI/UV potential yet reported for the UO2 n+ core. Isolation and characterization of the U­(V) form of the crown complex are also reported here; there are no prior reports of reduced uranyl crown ether complexes, but U­(V) is clearly stabilized by crown chelation. Joint computational studies show that the electronic structure of the U­(V) form results in significant weakening of U–Ooxo bonding despite the quite positive reduction potential at which this species can be accessed, underscoring that crown-ligated uranyl species could demonstrate unique reactivity under only modestly reducing conditions.