On-Surface Decarboxylation Coupling Facilitated by Lock-to-Unlock Variation of Molecules upon the Reaction

TL;DR

This paper introduces a lock-to-unlock on-surface synthesis strategy that enhances molecular coupling efficiency and selectivity, enabling the formation of ordered macrocyclic networks with high yield and structural homogeneity.

Contribution

It presents a novel lock-to-unlock approach for on-surface synthesis, improving coupling selectivity and yield in macrocyclic compound formation.

Findings

High-yield synthesis of macrocyclic networks achieved

Selective coupling due to steric hindrance of maleimide group

Extended ordered networks formed exclusively from new macrocyclic compounds

Abstract

On-surface synthesis (OSS) involving relatively high energy barriers remains challenging due to a typical dilemma: firm molecular anchor is required to prevent molecular desorption upon the reaction, whereas sufficient lateral mobility is crucial for subsequent coupling and assembly. By locking the molecular precursors on the substrate then unlocking them during the reaction, we present a strategy to address this challenge. High-yield synthesis based on well-defined decarboxylation, intermediate transition and hexamerization is demonstrated, resulting in an extended and ordered network exclusively composed of the newly-synthesized macrocyclic compound. Thanks to the steric hindrance of its maleimide group, we attain a preferential selection of the coupling. This work unlocks a promising path to enrich the reaction types and improve the coupling selectivity hence the structual homogeneity of the final product for OSS.