Molten salt matrices were used to evaluate outer-coordination sphere effects on lanthanide redox chemistry. Results were rationalized by correlating the polarization power of the outer-sphere cation with shifts in the Ln3+/Ln2+ reduction potentials.
Advances in targeted
α-therapies have increased the interest
in actinium (Ac), whose chemistry is poorly defined due to scarcity
and radiological hazards. Challenges associated with characterizing
Ac3+ chemistry are magnified by its 5f06d0 electronic configuration, which precludes the use of many
spectroscopic methods amenable to small amounts of material and low
concentrations (like EPR, UV–vis, fluorescence). In terms of
nuclear spectroscopy, many actinium isotopes (225Ac and 227Ac) are equally “unfriendly” because the actinium
α-, β-, and γ-emissions are difficult to resolve
from the actinium daughters. To address these issues, we developed
a method for isolating an actinium isotope (228Ac) whose
nuclear properties are well-suited for γ-spectroscopy. This
four-step procedure isolates 228Ra from naturally occurring 232Th. The relatively long-lived 228Ra (t
1/2 = 5.75(3) years) radioisotope subsequently
decays to 228Ac. Because the 228Ac decay rate
[t
1/2 = 6.15(2) h] is fast, 228Ac rapidly regenerates after being harvested from the 228Ra parent. The resulting 228Ac generator provides frequent
and long-term access (of many years) to the spectroscopically “friendly” 228Ac radionuclide. We have demonstrated that the 228Ac product can be routinely “milked” from this generator
on a daily basis, in chemically pure form, with high specific activity
and in excellent yield (∼95%). Hence, in the same way that
developing synthesis routes to new starting materials has advanced
coordination chemistry for many metals by broadening access, this 228Ac generator has the potential to broaden actinium access
for the inorganic community, facilitating the characterization of
actinium chemical behavior.
Increasing
access to the short-lived α-emitting radionuclide astatine-211
(211At) has the potential to advance targeted α-therapeutic
treatment of disease and to solve challenges facing the medical community.
For example, there are numerous technical needs associated with advancing
the use of 211At in targeted α-therapy, e.g., improving 211At chelates, developing more effective 211At
targeting, and characterizing in vivo
211At behavior. There is an insufficient understanding of astatine chemistry
to support these efforts. The chemistry of astatine is one of the
least developed of all elements on the periodic table, owing to its
limited supply and short half-life. Increasing access to 211At could help address these issues and advance understanding of 211At chemistry in general. We contribute here an extraction
chromatographic processing method that simplifies 211At
production in terms of purification. It utilizes the commercially
available Pre-Filter resin to rapidly (<1.5 h) isolate 211At from irradiated bismuth targets (Bi decontamination factors ≥876 000),
in reasonable yield (68–55%) and in a form that is compatible
for subsequent in vivo study. We are excited about
the potential of this procedure to address 211At supply
and processing/purification problems.
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