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Reported here is the preparation of azacrown ethers functionalized with catechol groups. The synthetic approach was (1st) novel in that it made use of the Mannich reaction and (2nd) valuable in that it provided an improved synthesis (in terms of practical deployment) of the known N,N′-bis(2,3-dihydroxybenzyl)-4,13-diaza-18-crown-6, H4ChaCha. Moreover, it demonstrated potential application of the synthetic method for accommodating a wide range of catecholate functionalities by using the synthetic strategy to prepare N,N′-bis(2,3-dihydroxy-5-tert-butylbenzyl)-4,13-diaza-18-crown-6 (H4tBu2ChaCha) for the first time. These H4ChaCha and H4tBu2ChaCha macrocycles offer exciting opportunity to expand redox chemistry for the f-elements. As “proof-of-principle,” we isolated the unusual tetrameric cluster [La2(tBuChaCha)2]2 from reactions between H4tBu2ChaCha and La[N(SiMe3)2]3. Characterization of [La2(tBuChaCha)2]2 by elemental analysis, single crystal X-ray diffraction, IR, and UV–vis–NIR spectroscopy suggested that the complex represented a rare example of an f-element semiquinone. It further demonstrated that the combination of La3+ and H4tBu2ChaCha provided access to one-electron oxidation chemistry within redox potential windows that were amenable to mild reaction conditions.

225 Ac is a valuable medical radionuclide for targeted α therapy, but 227 Ac is an undesirable byproduct of an accelerator-based synthesis method under investigation. Sufficient detector sensitivity is critical for quantifying the trace impurity of 227 Ac , with the 227 Ac / 225 Ac activity ratio predicted to be approximately 0.15% by end-of-bombardment (EOB). Superconducting transition edge sensor (TES) microcalorimeters offer high resolution energy spectroscopy using the normal-to-superconducting phase transition to measure small changes in temperature. By embedding 225 Ac production samples in a gold foil thermally coupled to a TES microcalorimeter we can measure the decay energies of the radionuclides embedded with high resolution and 100% detection efficiency. This technique, known as decay energy spectroscopy (DES), collapses several peaks from α decays into single Q-value peaks. In practice there are more complex factors in the interpretation of data using DES, which we will discuss herein. Using this technique we measured the EOB 227 Ac impurity to be (0.142 ± 0.005)% for a single production sample. This demonstration has shown that DES is a useful tool for quantitative measurements of complicated spectra.