Direct Observation of Three Chiral Conformers of an Atomically Precise Metal Nanoparticle

Atomically precise nanoclusters (NCs) have attracted a lot of attention owing to their many interesting properties and applications. Although such clusters could be considered small molecules due to their discrete atomic compositions, their size and complexity push them into a distinct regime where the line between molecule and material is blurred. On the fundamental side, they can provide a testbed for understanding structure-property relationships in nanomaterials. Hence, their isomerism is of intrinsic significance. In this work, we report the atomically precise structure of three Cu14 NC conformers, i.e., NCs with the same chemical formula and atomic connectivity but with varying bond angles and distances, obtained through X-ray crystallography. Interestingly, all three conformers exhibit chirality and co-crystallize in the same lattice structure. Since interconversion of each conformer and its chiral counterpart is possible without breaking and remaking bonds, these NCs constitute a set of atropisomers. The structure of our Cu14 NC highlights the various sources of isomerism one can observe at the nanoscale. These subtle yet identifiable differences represent something like a minimal unit of structural change, facilitating future investigation of structure-property relationships.