Ultrahigh-yield on-surface synthesis and assembly of circumcoronene into a chiral electronic Kagome-honeycomb lattice

Abstract

On-surface synthesis has revealed remarkable potential in the fabrication of atomically precise nanographenes. However, surface-assisted synthesis often involves multiple-step cascade reactions with competing pathways, leading to a limited yield of target nanographene products. Here, we devise a strategy for the ultrahigh-yield synthesis of circumcoronene molecules on Cu(111) via surface-assisted intramolecular dehydrogenation of the rationally designed precursor, followed by methyl radical-radical coupling and aromatization. An elegant electrostatic interaction between circumcoronenes and metallic surface drives their self-organization into an extended superlattice, as revealed by bond-resolved scanning probe microscopy measurements. Density functional theory and tight-binding calculations reveal that unique hexagonal zigzag topology of circumcoronenes, along with their periodic electrostatic landscape, confines two-dimensional electron gas in Cu(111) into a chiral electronic Kagome-honeycomb lattice with two emergent electronic flat bands. Our findings open up a new route for the high-yield fabrication of elusive nanographenes with zigzag topologies and their superlattices with possible nontrivial electronic properties.

Machine Vision Automated Chiral Molecule Detection and Classification in Molecular Imaging

“…The synthetic procedures of the HPB and F-HPB compounds have been reported in previous studies. , A Knudsen cell was used to deposit the HPB and F-HPB precursor molecules (at 160 and 180 °C, respectively) onto a Ag(111) surface held at room temperature. The STM experiments were performed in ultrahigh vacuum conditions (base pressure of >5 × 10 –11 mbar) at 4.4 K using a commercial Omicron low temperature STM system.…”

Exploring Intramolecular Methyl–Methyl Coupling on a Metal Surface for Edge-Extended Graphene Nanoribbons

“…As visualized by STM and nc-AFM, the coupling of methyl groups proceeded when heated to 350°C, mainly forming the ethanediyl bridges alongside fully conjugated six-membered rings. Considering the success of intramolecular methyl-methyl coupling in circumcoronene synthesis from dodecamethyl hexa-perihexabenzocoronene, 33 we envision that the preplanarization might allow more efficient aromatization. Besides, a more reactive surface like Cu(111) is expected to achieve more sp 2 -hybridized carbons from the intramolecular methyl-methyl coupling.…”

“…[30][31][32] Recently, intramolecular methyl-methyl coupling has been achieved to construct circumcoronene, a hexagonal NG with six zigzag edges. 33 However, the intramolecular coupling between two benzylic methyl groups has never been explored in GNRs, although it could potentially be developed as a powerful edge functionalization approach for structure engineering.…”

Scanning probe microscopy in probing low-dimensional carbon-based nanostructures and nanomaterials

“…cyclodehydrogenation reactions on Au (111). In addition, a rationally designed synthetic route via the dehydrogenative coupling of adjacent methyl groups led to the ultrahigh-yield fabrication of circumcoronene on Cu (111) [41]. Furthermore, by a combination of STM/nc-AFM imaging and density functional theory (DFT) calculations, Zhong et al reported the onsurface synthesis of dibenzoperihexacenes (with and without tert-butyl (tBu) groups) and dibenzoperioctacene (with tBu groups, as shown in figure 3(a)) on Au (111) starting from tetranaphthyl-p-terphenyl and tetra-anthryl-p-terphenyl precursors, respectively [42].…”