Invited for the cover of this issue are Anna Oliveri from Southern Oregon University, USA, and co-workers. The cover image shows the outer surface of a nanoscale U28 cage cluster.

The conformational dynamics of nanometer-sized actinide ions are exceptionally sensitive to the choice of counter-cations. A new means of following these dynamics in solution is presented that follows 1H NMR signals. The direct bond between hydrogen and phosphorus atoms in the bridging phosphonic groups of the [(UO2)28(O2)20(PHO3)24(H2O)12]32– (U28) cluster allows unparalleled recording of the orientations of these bridges in situ. The µ3-PHO3 bridges are organized into two supersets of conformers (facing inward vs. outward from the cluster), but each of these supersets additionally have four subsets that can be identified based upon orientations of the lone pairs of electrons in the associated oxygen atoms. The ensemble of these subsets changes over days or weeks depending upon bulk solution chemistry, temperature, and pressure. They also reflect cations trapped within the molecule. The 1H NMR spectra at room temperature indicate that the molecular orientation of this enormous ion tunes itself in response to solution composition, which suggests a strategy for selecting host–guest combinations.

The solution chemistry of aluminum has long interested scientists due to its relevance to materials chemistry and geochemistry. The dynamic behavior of large aluminum-oxo-hydroxo clusters, specifically [Al₁₃ O₄ (OH)₂₄ (H₂ O)₁₂ ]⁷⁺ (Al₁₃ ), is the focus of this paper. ²⁷ Al NMR, ¹ H NMR, and ¹ H DOSY techniques were used to follow the isomerization of the ϵ-Al₁₃ in the presence of glycine and Ca²⁺ at 90 °C. Although the conversion of ϵ-Al₁₃ to new clusters and/or Baker-Figgis-Keggin isomers has been studied previously, new ¹ H NMR and ¹ H DOSY analyses provided information about the role of glycine, the ligated intermediates, and the mechanism of isomerization. New ¹ H NMR data suggest that glycine plays a critical role in the isomerization. Surprisingly, glycine does not bind to Al₃₀ clusters, which were previously proposed as an intermediate in the isomerization. Additionally, a highly symmetric tetrahedral signal (δ=72 ppm) appeared during the isomerization process, which evidence suggests corresponds to the long-sought α-Al₁₃ isomer in solution.

Invited for the cover of this issue is a group of researchers from the University of California Davis, Colgate–Palmolive Company, and Oregon State University. The image depicts aluminum ions as silver spheres, oxygen atoms as red spheres, carbon as black spheres, and nitrogen as green spheres. Hydrogen atoms were omitted for clarity. Read the full text of the article, which also includes insight on the other aluminum clusters that glycine stabilizes, at 10.1002/chem.201604640.