Structural Changes during the Growth of Atomically Precise Metal Oxido Nanoclusters from Combined Pair Distribution Function and Small-Angle X-ray Scattering Analysis.

The combination of in situ Pair Distribution Function (PDF) analysis and Small-Angle X-ray Scattering (SAXS) allows to analyze the formation mechanism of metal oxido nanoclusters and cluster-solvent interactions as they take place. Here, we demonstrate the method for the formation of clusters with a [Bi 38 O 45 ] core. Upon dissolution of crystalline [Bi 6 O 5 (OH) 3 (NO 3 ) 5 ]·3H 2 O in DMSO, an intermediate rapidly forms, which slowly grows to stable [Bi 38 O 45 ] clusters. To identify the intermediate, we developed an automated modelling method, where smaller [Bi x O y ] structures, based on the [Bi 38 O 45 ] framework, are tested against the data. [Bi 22 O 26 ] was identified as the main intermediate species, illustrating how combined PDF and SAXS analysis is a powerful tool to provide insights into nucleation on an atomic scale. In addition, we use PDF to provide information on the interaction between nanoclusters and solvent, which is shown to depend on the nature of the ligands on the cluster surface.