Multimeric oxo-hydroxo Al clusters function as models for common mineral structures and reactions. Cluster research, however, is often slowed by a lack of methods to prepare clusters in pure form and in large amounts. Herein, we report a facile synthesis of the little known cluster Al (OH) (H O) (SO ) (Al ) through a simple dissolution method. We confirm its structure by single-crystal X-ray diffraction and show by Al NMR spectroscopy, electrospray-ionization mass spectrometry, and small- and wide-angle X-ray scattering that it also exists in solution. We speculate that Al may form in natural water systems through the dissolution of aluminum-containing minerals in acidic sulfate solutions, such as those that could result from acid rain or mine drainage. Additionally, the dissolution method produces a discrete Al cluster on a scale suitable for studies and applications in materials science.

We describe a process to produce aqueous precursor solutions of the flat -Al 13 hydroxo cluster (Al13(μ3-OH)6(μ2-OH)18(H2O)24(NO3)15) via stoichiometric dissolution of bulk Al­(OH)3(s) in HNO3(aq). We highlight its facility by demonstrating high yields and large-scale synthesis. X-ray diffraction confirms formation of a single-phase product, and Raman spectra show characteristic O-Al-O vibrational modes, both techniques confirming the identity of the flat -Al 13 cluster in the bulk. 27Al NMR spectroscopy and dynamic light scattering also confirm the presence of the cluster in aqueous solution. We show the as-prepared solution produces smooth and continuous thin films via spin-coating. In capacitors, the films exhibit low leakage currents (near 10 nA/cm2) and dielectric constants expected for amorphous Al2O3. Because the precursor preparation requires no postsynthesis purification, it is readily scalable to large volumes.

Multimeric oxo-hydroxo Al clusters function as models for common mineral structures and reactions.C luster research, however,i so ften slowed by al acko fm ethods to prepare clusters in pure form and in large amounts.Herein, we report af acile synthesis of the little knownc luster Al 8 (OH) 14 -(H 2 O) 18 (SO 4 ) 5 (Al 8 )through asimple dissolution method. We confirm its structure by single-crystal X-rayd iffraction and show by 27 Al NMR spectroscopy, electrospray-ionization mass spectrometry,and small-and wide-angle X-ray scattering that it also exists in solution. We speculate that Al 8 may form in natural water systems through the dissolution of aluminumcontaining minerals in acidic sulfate solutions,s uch as those that could result from acid rain or mine drainage.Additionally, the dissolution method produces adiscrete Al cluster on ascale suitable for studies and applications in materials science.