X-ray crystal structures of uranyl(VI) peroxide clusters contain 4-, 5- and 6-membered rings, where the uranyl units are linked by peroxide and hydroxide bridges. The clusters are formed by crystallization from aqueous solution, but the nature of the assembly process is far from clear. In a number of publications we have shown that 4-and 5-membered rings are formed in solution and that these might be precursors to cluster formation. We have also shown that alkali- and tetramethylammonium ions play a role in the ring formation reactions, suggesting a similar role as in the synthesis of crown-ethers. The experimental studies (using potentiometry, spectrophotometry, calorimetry and NMR methods) demonstrate that the reactions are labile, in contrast to the formation of crown-ethers. By using quantum chemical methods we have explored possible structures in solution, reaction thermodynamics (Gibbs energy, enthalpy and entropy of reaction) and the nature of the peroxide bridges. There is a strong similarity between the alkali ion complexes of the peroxide rings and similar crown-ether complexes.<br/><br/>[1] P. L. Zanonato, P. Di Bernardo, V. Vallet, Z. Szabó and I. Grenthe, Dalton Trans., 2014, DOI:10.1039/C4DT02104E.<br/>[2] ibid. in preparation.

Experimental and quantum chemical studies of alkali-ion promoted formation of uranyl(VI) peroxide rings and a comparison with similar reactions in12-crown-5 and 15-crown-5 systems

249th National Meeting (2015)

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