Synthesis and Stability of Actinium-225 Endohedral Fullerenes, ²²⁵Ac@C₆₀

Abstract

We report the first synthesis of 225 Ac ( t 1/2 = 10 days) endohedral fullerenes, 225 Ac@C 60 . The 225 Ac@C 60 was produced with a 12 ± 2% efficiency by applying an electrical arc discharge between a source of α-particle emitter 225 Ac (∼1 mCi, electroplated on a Pt disk) and a thin coat of “preformed” C 60 on an Al disk (C 60 thickness of ∼0.25 mg/cm 2 ). After formation by electrical arc discharge, the resulting radiofullerenes on the Al disk were dissolved in toluene under anaerobic conditions and converted to a malonate derivative using the Bingel reaction. Subsequent to repeated washings of the organic phase with dilute acidic solutions to remove exohedral 225 Ac, ∼45% of 225 Ac activity was retained in the organic phase, which resisted extraction into the aqueous phase. Failure to extract the 225 Ac from the organic phase provided definitive evidence that the 225 Ac is located inside of the fullerene. The formation of 225 Ac@C 60 was further confirmed using a classical hot-atom chemistry technique in which the organic phase containing purified endohedral 225 Ac@C 60 malonate was contacted with fresh dilute acid to repeatedly extract the ionic 4.8 m 221 Fr and 45.6 m 213 Bi activities (decay daughters of 225 Ac), which were released by molecular disruption due to nuclear recoil. The result from the extraction experiments was further supported by a series of thin-layer chromatography and high-pressure liquid chromatography analysis of the organic phase containing 225 Ac@C 60 or 225 Ac@C 60 malonate. Taken together, studies show that, like polydentate chelators, single-wall fullerenes are not capable of retaining the 225 Ac decay daughters.

C60 and Derivatives Boost Electrocatalysis and Photocatalysis: Electron Buffers to Heterojunctions

“…Stability of catalysts might be improved, however, using C 60 as a carbon-based carrier model for loading of single-atom catalysts (SACs) because these reportedly appear to exhibit a boosted performance over typical SACs. [215][216][217][218]…”

Electronic Structure, Aromaticity, and Magnetism of Minimum-Sized Regular Dodecahedral Endohedral Metallofullerenes Encapsulating Rare Earth Atoms

“…Fullerene superatoms can serve as special building blocks for constructing nanomaterials due to their ability to encapsulate atoms or molecules. − In 1985, Heath et al discovered the first stable embedded metal complex, LaC 60 , which was named metallofullerene . Since then, a rich variety of endohedral metallofullerenes (EMFs) with different cage sizes and embedded atoms have been extensively studied. − Compared to larger-sized fullerenes, small fullerenes are relatively unstable due to increased curvature, causing strain within the cage and weakening π-conjugation. − Especially for the smallest fullerene C 20 , which has all pentagonal faces, the bonds tend to be sp 3 bonds rather than the sp 2 bonds that are dominant in large fullerenes . Through metal doping, it is possible to increase the stability of smaller fullerenes and change their electronic properties. − T. Guo et al reported in 1992 that the experiment of MC 28 confirmed that the 5f feature of U in the photoemission spectra of UC 28 existing in sublimed films is consistent with the formal 4 + valence state of U.…”