Strain-induced skeletal rearrangement of a polycyclic aromatic hydrocarbon on a copper surface

Abstract

Controlling the structural deformation of organic molecules can drive unique reactions that cannot be induced only by thermal, optical or electrochemical procedures. However, in conventional organic synthesis, including mechanochemical procedures, it is difficult to control skeletal rearrangement in polycyclic aromatic hydrocarbons (PAHs). Here, we demonstrate a reaction scheme for the skeletal rearrangement of PAHs on a metal surface using high-resolution noncontact atomic force microscopy. By a combination of organic synthesis and on-surface cyclodehydrogenation, we produce a well-designed PAH—diazuleno[1,2,3-cd:1′,2′,3′-fg]pyrene—adsorbed flatly onto Cu(001), in which two azuleno moieties are highly strained by their mutual proximity. This local strain drives the rearrangement of one of the azuleno moieties into a fulvaleno moiety, which has never been reported so far. Our proposed thermally driven, strain-induced synthesis on surfaces will pave the way for the production of a new class of nanocarbon materials that conventional synthetic techniques cannot attain.

The Macrocycle versus Chain Competition in On‐Surface Polymerization: Insights from Reactions of 1,3‐Dibromoazulene on Cu(111)

“…Azulene is a building block with a prototypical non‐alternant aromatic π‐electron system, which has recently attracted attention in surface chemistry, organic electronics, and related areas . Non‐alternant aromatic π‐electron systems typically contain odd‐numbered rings such as pentagons and heptagons.…”

Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

“…As an alternative to standard mechanochemical methods, internal strain in molecular systems induced by interactions with a substrate could be used to mimic external mechanical stimuli. Recent studies have shown that substrate‐induced structural distortion of molecular systems can facilitate their intra‐ and intermolecular cyclodehydrogenation as well as skeletal rearrangements . Treirer et al.…”

“…Furthermore, Shiotari et al. found that the adsorption of a non‐planar polycyclic hydrocarbon on Cu(100) induces the accumulation of internal strain, and that the relief of this strain at elevated temperatures promotes diverse skeletal rearrangements . It has also been reported that the substrate‐binding affinity of equivalent chemical groups in organic molecules varies depending on their local adsorption geometries, enabling site‐selective bond functionalization …”

Nanoribbons with Non-Alternant Topology from Fusion of Polyazulene: Carbon Allotropes Beyond Graphene

“…Related carbon rearrangements have also been reported for a polycyclic aromatic hydrocarbon with azulene moieties on a Cu(001) surface. 34 Lateral fusion of polyazulene chains into non-alternant carbon nanoribbons. At this stage (after heating to 730 K, see Fig.2d) also pairwise lateral dehydrogenative fusion of the polyazulene chains is induced, leading to the formation of wider nanoribbons as presented by Fig.…”