Solution structural characterization of an array of nanoscale aqueous inorganic Ga13-x In x (0 ≤ x ≤ 6) clusters by 1H-NMR and QM computations.

Abstract

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 hydroxo-bridged inorganic species well characterized by 1H Nuclear Magnetic Resonance spectroscopy (1H-NMR) do not provide enough information for signal assignment and prediction of new samples. 1H-NMR and quantum mechanical (QM) computations were used to characterize the NMR spectra of the entire array of inorganic flat-Ga13-x In x (0 ≤ x ≤ 6) nanoscale clusters in solution. A brief review of the known signals for μ2-OH and μ3-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 1H-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 1H-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.