Transoid-to-Cisoid Conformation Changes of Single Molecules on Surfaces Triggered by Metal Coordination

TL;DR

This study demonstrates how metal coordination can induce irreversible conformational changes in single molecules adsorbed on surfaces, transforming their geometry from transoid to cisoid and affecting their chirality and supramolecular assembly.

Contribution

It reveals a novel method to control molecular conformation on surfaces via metal coordination, enabling manipulation of chirality and structure in surface-bound molecules.

Findings

Fe adatoms induce transoid-to-cisoid conformational change

Molecular structures become irreversibly achiral after coordination

Surface-dependent formation of enantiopure domains

Abstract

Conformational isomers are stereoisomers that can interconvert over low potential barriers by rotation around a single bond. However, such bond rotation is hampered by geometrical constraints when molecules are adsorbed on surfaces. Here we show that the adsorption of 4,4'-bis(4-carboxyphenyl)-6,6'-dimethyl-2,2'-bipyridine molecules on surfaces leads to the appearance of pro-chiral single-molecules on NiO(001) and to enantiopure supramolecular domains on Au(111) surfaces containing the $transoid$ molecule conformation. Upon additional Fe adatom deposition, molecules undergo a controlled interconversion from a $transoid$ to $cisoid$ conformation as a result of coordination of the Fe atoms to the 2,2'-bipyridine moieties. As confirmed by atomic force microscopy images and X-ray photoelectron spectroscopy measurements, the resulting molecular structures become irreversibly achiral.