From Racemic Metal Nanoparticles to Optically Pure Enantiomers in One Pot

Abstract

A general strategy, using mixed ligands, is utilized to synthesize atomically precise, intrinsically chiral nanocluster [Ag₇₈(DPPP)₆(SR)₄₂] (Ag₇₈) where DPPP is the achiral 1,3-bis(diphenyphosphino)propane and SR = SPhCF₃. Ag₇₈ crystallizes as racemates in a centric space group. Using chiral diphosphines BDPP = 2,4-bis(diphenylphosphino)pentane, the enantiomeric pair [Ag₇₈(R/S-BDPP)₆(SR)₄₂] can be prepared with 100% optical purity. The chiral diphosphines gives rise to, separately, two asymmetric surface coordination motifs composed of tetrahedral R₃PAg(SR)₃ moieties. The flexible nature of C-C-C angles between the two phosphorus atoms restricts the relative orientation of the tetrahedral R₃PAg(SR)₃ moieties, thereby resulting in the enantiomeric selection of the intrinsic chiral metal core. This proof-of-concept strategy raises the prospect of enantioselectively synthesizing optically pure, atomically precise chiral noble metal nanoclusters for specific applications.