Condensation and asymmetric amplification of chirality in achiral molecules adsorbed on an achiral surface

The origin of homochirality in nature is an important but open question. Here, the authors provide insight into the physicochemical origin of homochirality through surface adsorption on the model of adlayers of achiral carbon monoxide molecules on an achiral Au(111) surface. The origin of homochirality in nature is an important but open question. Here, we demonstrate a simple organizational chiral system constructed by achiral carbon monoxide (CO) molecules adsorbed on an achiral Au(111) substrate. Combining scanning tunneling microscope (STM) measurements with density-functional-theory (DFT) calculations, two dissymmetric cluster phases consisting of chiral CO heptamers are revealed. By applied high bias voltage, the stable racemic cluster phase can be transformed into a metastable uniform phase consisting of CO monomers. Further, during the recondensation of a cluster phase after lowering down bias voltage, an enantiomeric excess and its chiral amplification occur, resulting in a homochirality. Such asymmetry amplification is found to be both kinetically feasible and thermodynamically favorable. Our observations provide insight into the physicochemical origin of homochirality through surface adsorption and suggest a general phenomenon that can influence enantioselective chemical processes such as chiral separations and heterogeneous asymmetric catalysis.

Automated summary

The physicochemical origin of the phenomenon of homochirality is explored through the adsorption of achiral carbon monoxide molecules on an achiral gold surface. The researchers observe dissymmetric cluster phases consisting of chiral CO heptamers and demonstrate chiral amplification during the recondensation of a cluster phase. These findings provide insight into the origin of homochirality and have implications for enantioselective chemical processes.