Astatine partitioning between nitric acid and conventional solvents: indication of covalency in ketone complexation of AtO+

Abstract

Astatine-211 has been produced at Texas A&M University on the K150 cyclotron, with a yield of 890 ± 80 MBq through the ²⁰⁹Bi(α,2n)²¹¹At reaction via an 8 h bombardment with a beam current of 4–8 μA and an α-particle beam energy of 28.8 MeV. The target was then dissolved in HNO₃ and the extraction of ²¹¹At was investigated into a variety of organic solvents in 1–3 M HNO₃. Extraction of ²¹¹At with distribution ratios as high as 11.3 ± 0.6, 12.3 ± 0.8, 42.2 ± 2.2, 69 ± 4, and 95 ± 6 were observed for diisopropyl ether, 1-decanol, 1-octanol, 3-octanone, and methyl isobutyl ketone, respectively, while the distribution ratios for ²⁰⁷Bi were ≤0.05 in all cases. The extraction of ²¹¹At into both methyl isobutyl ketone and 3-octanone showed a strong, linear dependence on the HNO₃ initial aqueous concentration and better extraction than other solvents. DFT calculations show stronger binding between the carbonyl oxygen of the ketone and the At metal center.