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

Abstract

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.

Surface-Assisted Selective Air Oxidation of Phosphines Adsorbed on Activated Carbon

“…In this contribution, phosphines P n Bu 3 (1), PEt 3 (2), P n Oct 3 (3), PMe t Bu 2 (4), PCy 3 (5), and PPh 3 (6) were used to demonstrate the ability of the AC surface to assist in their clean oxidation to the corresponding phosphine oxides 1 ox −6 ox . All oxidations could be accomplished at room temperature and with air as the oxidant.…”

“…10 To test the general nature of the dynamic phenomena and probe the interactions with a surface different from the silica used previously, we applied activated carbon (AC) as the adsorbent. Since PPh 3 (6) is solid, inexpensive, not air sensitive, and therefore easy to handle, we started adsorbing this phosphine on AC.…”

“…Adsorption of molecules on surfaces is a crucially important process with wide-ranging applications in academia and industry. Therefore, new developments in the separation sciences, as well as physical and analytical chemistry, appear frequently in the chemical literature. − Volatile adsorbates can be removed in vacuo, while washing with favorable solvents removes nonvolatile adsorbates.…”

“…Therefore, new developments in the separation sciences, as well as physical and analytical chemistry, appear frequently in the chemical literature. 1 − 6 Volatile adsorbates can be removed in vacuo, while washing with favorable solvents removes nonvolatile adsorbates.…”

Modulation of the assembly fashion among metal–organic frameworks for enantioretentive epoxide activation

“…1–3 Thanks to vigorous advances of chiral science made in biomedicines, 4 pesticides, 5,6 fine chemicals, 7 chiroptics, 8 and so on, 9 the increasing demand for various types of chiral substances in high enantiopurity has been an urgent task in chiral synthesis and asymmetric catalysis. 10–13 For instance, the enantioretentive alcoholysis of epoxide substrates is an important way to synthesize chiral β-alkoxy alcohols with 1,2-disynthons introduced, which are multifunctional chiral intermediates irreplaceable in preparations of chiral polyurethane elastomers, anticancer eugenol β-amino alcohols and derivatives. 14 However, owing to the poor nucleophilicity of alcohols, this reaction generally requires harsh conditions like high temperature, long reaction time and strong acid to get satisfactory conversions of epoxides.…”