Solution structural characterization of an array of nanoscale aqueous inorganic Ga13–xInx (0 ≤ x ≤ 6) clusters by 1H-NMR and QM computations† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc00776c

NMR spectroscopy is the go-to technique for determining the solution structures of organic, organometallic, and even macromolecular species. However, structure determination of nanoscale aqueous inorganic clusters by NMR spectroscopy remains an unexplored territory. The few hydroxobridged inorganic species well characterized by H Nuclear Magnetic Resonance spectroscopy (H-NMR) do not provide enough information for signal assignment and prediction of new samples. H-NMR and quantum mechanical (QM) computations were used to characterize the NMR spectra of the entire array of inorganic flat-Ga13 xInx (0 # x # 6) nanoscale clusters in solution. A brief review of the known signals for m2-OH and m3-OH bridges gives expected ranges for certain types of protons, but does not give enough information for exact peak assignment. Integration values and NOESY data were used to assign the peaks of several cluster species with simple H-NMR spectra. Computations agree with these hydroxide signal assignments and allow for assignment of the complex spectra arising from the remaining cluster species. This work shows that H-NMR spectroscopy provides a variety of information about the solution behavior of inorganic species previously thought to be inaccessible by NMR due to fast ligand and/or proton exchange in wet solvents.