An Inherently Chiral Au-24 Framework with Double-Helical Hexagold Strands

2,3-bis(diphenylphosphino)butane enantiomers (chiraphos, L) used as chiral auxiliaries results in the preferential formation of an unprecedented Au-24 framework with inherent chirality. The crystal structure of [Au24L6Cl4](2+)(1) has a square antiprism-like octagold core twinned by two helicene-like hexagold motifs, where the inherent chirality is associated with the helical arrangement. The clusters carrying (R,R)- and (S,S)- diphosphines had right- and left-handed strands, respectively. Circular dichroism spectra showed peaks in the visible to near-IR region, sonic of which did not coincide with absorption bands, suggesting the enantiomeric Au-24 frameworks possess unique chiroptical properties. The Au-24 frameworks were thermally robust, which could be attributed to the superatomic concept (18e(-) system) and the steric constraint effects of the bridging ligand units.