Solid-State ⁶⁹Ga and ⁷¹Ga NMR Study of the Nanoscale Inorganic Cluster [Ga₁₃(μ₃-OH)₆(μ₂-OH)₁₈(H₂O)₂₄](NO₃)₁₅

Abstract

Solid-state 71Ga and 69Ga NMR was used to probe the structure of the hydroxo-aquo cluster, [Ga13(μ3-OH)6(μ2-OH)18(H2O)24]­(NO3)15, envisioned as a solution-processable material for thin film electronics. This species, termed Ga13, is made up of three types of 6-coordinate gallium sites, with bridging OH groups and H2O species decorating the outer edges. Solid-state NMR at two magnetic fields (13.9 and 21.1 T) of these quadrupolar nuclei, in conjunction with modeling, demonstrates that these sites are best represented as distorted octahedra, exhibiting a wide range of distinct quadrupolar couplings and asymmetry parameters. This information is critical for analyses of the local coordination environment for gallium in related gallium-oxide films, and this work adds to the growing body of evidence that gallium solid-state NMR is a useful tool for structural analyses.

An overview of selected current approaches to the characterization of aqueous inorganic clusters

“…NMR chemical shifts of nuclei due to properties including molecular geometry or effects related to the electronegativity of nearby atoms can be used to determine more detailed structural features of a molecule. 18,19 NMR methods have also proven key for establishing the dynamics for reaction of these clusters, including ligand-exchange and isomerization rates. 15 NMR was first described 75 years ago and has been used extensively in organic chemistry for some time.…”

“…An excellent example is provided by Ohlin, et al (2009) 44 who followed the 18 O substitution into a manganese-cubane oxide cluster and could resolve rate data into all four oxygens. The magnitude of the shift not only shows the efficacy of isotopic substitution but if the stoichiometry of substitution is understood, it also allows one to assign charge to the fragment and to compared fitted and measured spectra.…”

“…We have reported the synthesis of a family of f-M 13 clusters, including the gallium hydroxo-aquo cluster, [Ga 13 (µ 3 -OH) 6 -(µ 2 -OH) 18 (H 2 O) 24 ](NO 3 ) 15 (f-Ga 13 , Fig. 1B), 5,63 and we recently reported its solid-state NMR characterization.…”

Structural study by solid-state71Ga NMR of thin film transistor precursors

“…The clusters studied here are Ga 7 In 6 , Ga 8 In 5 , Ga 10 In 3 , Ga 11 In 2 , and Ga 12 In 1 . The structure of Ga 13 has been studied by ssNMR spectroscopy previously, 12 and we depict it here as a guide to the gallium sites that are present. These heterometallic clusters share a common motif (Fig.…”

“…Ga NMR experimental parameters at 21.1 T from Dmfit used for the simulation of NMR lineshapes for the various Ga 13−x In a Parameters are reproduced from reference Ma et al12 …”