On-Surface Synthesis and Characterization of [7]Triangulene Quantum Ring

Abstract

The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for nextgeneration molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronenelike antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.

Recent progresses of quantum confinement in graphene quantum dots

“…Based on the bottom-up on surface synthetic approach and STM/AFM measurements, many other different nanographenes with special structures are also formed and investigated besides the above triangular zigzag nanographenes, such as Clar's goblet [214] and [7]triangulene quantum rings [215]. The Clar's goblet shows a rubost antiferromagnetic order with the exchangecoupling strenght about 23 meV, which is comparable to the reported values in previous researches of graphene nanoribbon junctions [216] and triangulene dimer [20].…”

Manifold dynamic non-covalent interactions for steering molecular assembly and cyclization

“…Competition between thermal diffusion and intermolecular reactions during thermal annealing of the self-assembled structures plays an important role in the on-surface synthesis. [42] Random diffusion of the precursor molecules with multiple reaction pathways usually leads to the yield of undesired by-products, such as uncontrolled graphene nanoribbon junctions, [43] and unexpected molecular oligomers, [44] which thus severely limits the yield of desired products. To this end, taking advantage of non-covalent interactions between the precursor reactants may provide a promising approach for steering the reaction pathways towards the desired products.…”

Manifold Dynamic Non-Covalent Interactions for Steering Molecular Assembly and Cyclization

“…Competition between thermal diffusion and intermolecular reactions during thermal annealing of the selfassembled structures plays an important role in the on-surface synthesis. [39] Random diffusion of the precursor molecules with multiple reaction pathways usually leads to the yield of undesired by-products, such as uncontrolled graphene nanoribbon junctions, [40] and unexpected molecular oligomers, [41] which thus severely limits the yield of desired products. To this end, taking advantage of non-covalent interactions between the precursor reactants may provide a promising approach for steering the reaction pathways towards the desired products.…”