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

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.

Desilylative Coupling Involving C(sp2)–Si Bond Cleavage on Metal Surfaces

“…Figure a shows that the 1,4-BTN molecule adopted stereoscopic adsorption configuration attributable to steric hindrance provided by TMS groups on both sides, as well as a small amount of electron transfer with substrate as demonstrated by electron density difference (EDD) results. Generally, when relatively high-energy barriers are involved, a firmly anchored adsorption is necessary for maintaining the molecules on the surface sufficiently long to overcome the reaction barrier . Instead, the adsorption energy (1.48 eV) that is significantly lower than the reaction energy barrier (2.55 eV) implies that the 1,4-BTN molecule would desorb rather than react during annealing (Figure S18).…”

Subsurface‐Carbon‐Induced Local Charge of Copper for an On‐Surface Displacement Reaction

“…Very interestingly, although the deprotonation of the CA groups is expected to occur on pristine Cu(111) at elevated temperature according to the literature, [26] Z2 structure is not observed up to the temperature at which the adsorbates completely desorb from the surface [15] . The influence of subsurface C‐induced local charge of Cu on the reaction was then explored further, by comparing the deprotonation process for a model system of a single benzyl acid molecule on pristine Cu(111) with that on the 4 C‐Cu δ+ surface (details in SI).…”

Steric hindrance in the on-surface synthesis of diethynyl-linked anthracene polymers

“…18,19,21 Nonetheless, the choice of the precursor was demonstrated to be the primary aspect in the control of the on-surface synthesis process. 22,23 The rational design of the precursor molecules allows one -for example -to exploit their side functionality to control the order and symmetry of the polymers, and the steric hindrance of chemical groups to steer the molecular assembly. [24][25][26] Topologically non-trivial properties have been unveiled on p-conjugated polymers made by laterally assembling acene monomers, as a function of the number of the aromatic rings.…”