Thorium(IV) and uranium(VI) compounds with cucurbit[10]uril: from one-dimensional nanotube to supramolecular framework

Cucurbit[10]uril {Q[10]} has the largest portal size and cavity in the series of Q[n]s (n = 5-10) molecules. In contrast to its rich host-guest chemistry, its coordination chemistry is under developed with only limited metal ions being investigated so far. In this work, we initiated the study of Q[10] complexes with Th(IV) and U(VI) ions in HCl solutions via a self-assembly approach. The coordination of Th(IV) ions with Q[10] led to the formation of a compound, {Th4(Cl)16(H2O)20(Q[10])}·nH2O (Q[10]-Th), with a unique nano-tubular structure while U(VI) ions facilitated the formation of a compound, [(UO2)2(Cl)4(H2O)6]·(Q[10])2·HCl·nH2O (Q[10]-U), with a Q[10]-based supramolecular framework structure via intermolecular out-surface and second-shell interactions. The structural and spectroscopic aspects of the two compounds together with their optical and thermal properties have been investigated. The successful preparation and characterization of the first two Q[10] compounds with Th(IV)/U(VI) ions highlighted the potential for further exploration of Q[10] coordination chemistry with actinide ions.