Ac2SO43

Ac2SO43 is a theoretical or experimentally unconfirmed anionic species composed of two actinium atoms bound to a sulfate group, bearing an overall charge of –3. Its formula is sometimes written Ac2(SO4)3–, implying that each actinium contributes a +3 charge while the sulfate (SO4^2–) shares its charge in a complex cluster. The ion has not been observed in solution or as a solid crystal and remains a computational curiosity rather than an empirically characterized compound.

Actinium (Ac) is the first element of the actinide series and is only found in trace amounts from the natural decay chain of uranium. Because of its radioactivity and scarcity, actinium chemistry is limited; only a handful of inorganic compounds have been isolated, most notably AcCl3, AcF3, and Ac(NO3)3. Solid–state characterization of actinium salts is challenging, and spectroscopic studies are impeded by self‑irradiation damage. Consequently, the sulfate chemistry of actinium remains largely unexplored, and no definitive structures for Ac2SO43 have been reported.

Computational studies on actinium sulfates suggest that large, multinuclear anions may form under non‑equilibrium conditions, but these predictions have not yet been verified experimentally. If synthesized, Ac2SO43 would likely exhibit high radioactivity and a short half‑life, complicating detailed analysis. Future work in the chemistry of the actinides may clarify whether such anions can exist and what properties they would possess.