16 research outputs found
Topological design and synthesis of high-spin aza-triangulenes without Jahn-Teller distortions
The atomic doping of open-shell nanographenes enables the precise tuning of
their electronic and magnetic state, which is crucial for their promising
potential applications in optoelectronics and spintronics. Among this
intriguing class of molecules, triangulenes stand out with their size-dependent
electronic properties and spin states, which can also be influenced by the
presence of dopant atoms and functional groups. However, the occurrence of
Jahn-Teller distortions in such systems can have a crucial impact on their
total spin and requires further theoretical and experimental investigation. In
this study, we examine the nitrogen-doped aza-triangulene series via a
combination of density functional theory and on-surface synthesis. We identify
a general trend in the calculated spin states of aza-[n]triangulenes of various
sizes, separating them into two symmetry classes, one of which features
molecules that are predicted to undergo Jahn-Teller distortions that reduce
their symmetry and thus their total spin. We link this behavior to the location
of the central nitrogen atom relative to the two underlying carbon sublattices
of the molecules. Consequently, our findings reveal that centrally-doped
aza-triangulenes have one less radical than their undoped counterparts,
irrespective of their predicted symmetry. We follow this by demonstrating the
on-surface synthesis of {\pi}-extended aza-[5]triangulene, a large member of
the higher symmetry class without Jahn-Teller distortions, via a simple
one-step annealing process on Cu(111) and Au(111). Using scanning probe
microscopy and spectroscopy combined with theoretical calculations, we prove
that the molecule is positively charged on the Au(111) substrate, with a
high-spin quintet state of S = 2, the same total spin as undoped neutral
[5]triangulene.Comment: Main paper 18 pages, 5 figures. Removed hyphen from author name,
addded funding information for one autho
新規炭素ナノリボンの表面合成に関する研究
京都大学0048新制・課程博士博士(エネルギー科学)甲第20728号エネ博第356号新制||エネ||70(附属図書館)京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻(主査)教授 坂口 浩司, 教授 萩原 理加, 教授 佐川 尚学位規則第4条第1項該当Doctor of Energy ScienceKyoto UniversityDFA
Substrate induced strain for on-surface transformation and synthesis
10.1039/d0nr01270jNanoscale12147500-750
Ultrahigh-yield on-surface synthesis and assembly of circumcoronene into a chiral electronic Kagome-honeycomb lattice
On-surface Synthesis of [7]triangulene Quantum Ring via Antidot Engineering
The ability to engineer geometrically well-defined antidots in large triangulene homologues
allows for creating an entire family of triangulene quantum ring (TQR) structures with tunable high-spin
ground state and magnetic ordering, crucial for next-generation 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
coronene-like antidot in the molecular centre. 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 (� = 3) on Au(111). This work demonstrates a new route for
the design of high-spin graphene quantum rings as the key components for future quantum devices
Tailoring Long-Range Superlattice Chirality in the Molecular Selfassemblies via Weak Fluorine-Mediated Interactions
Controllable
fabrication of the enantiospecific molecular superlattices is a matter of
imminent scientific and technological interest. Herein, we demonstrate that long-range
superlattice chirality in molecular self-assemblies can be tailored by tuning the
interplay of weak intermolecular non-covalent interactions. Different chiral
recognition patterns are achieved in the two molecular self-assemblies comprised
by two molecular enantiomers with identical steric conformations, derived from the
hexaphenylbenzene – the smallest star-shaped polyphenylene. By means of high-resolution
scanning tunneling microscopy measurements, we demonstrate that functionalization
of star-shaped polyphenylene with fluorine (F) atoms leads to the formation of molecular
self-assemblies with the distinct long-range chiral recognition patterns. We employed
the density functional theory calculations to quantify F-mediated
lone pair F ···π, C-H··· F, F···F interactions attributed to the tunable enantiospecific
molecular self-organizations. Our findings underpin a viable route to tailor long-range chiral recognition
patterns in supramolecular assemblies by engineering the weak non-covalent intermolecular interactions
Ultra-high Yield On-surface Synthesis and Assembly of Circumcoronene into Chiral Electronic Kagome-honeycomb Lattice
On-surface synthesis has revealed remarkable potential in the fabrication of a plethora of
elusive nanographenes with tailored structural, electronic and magnetic properties
unattainable by conventional wet-chemistry synthesis. Unfortunately, surface-assisted
synthesis often involves multiple-step cascade reactions with competing pathways, leading
to the formation of a diversity of products with limited yield, which reduces its feasibility
towards the large-scale production for future technological applications. Here, we devise a
new on-surface synthetic strategy for the ultra-high yield synthesis of a hexagonal
nanographene with six zigzag edges, namely circumcoronene on Cu(111) via surfaceassisted intramolecular dehydrogenation of the rationally-designed precursor molecule,
followed by methyl radical-radical coupling and aromatization. An elegant electrostatic
interaction between circumcoronene and Cu(111) drives their self-organization into an
extended superlattice, as revealed by bond-resolved low-temperature scanning probe
microscopy and spectroscopy 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 (2D) electron gas in Cu(111)
surface into 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 novel 2D superlattices with possible nontrivial electronic properties towards their future technological applications
Highly-Entangled Polyradical Nanographene with Coexisting Strong Correlation and Topological Frustration
Open-shell benzenoid polycyclic aromatic hydrocarbons, known as magnetic nanographenes, exhibit unconventional π-magnetism arising from topological frustration or strong electronic-electron interaction. Imprinting multiple strongly entangled spins into polyradical nanographenes creates a major paradigm shift in realizing non-trivial collective quantum behaviors and exotic quantum phases in organic quantum materials. However, conventional design approaches are limited by a single magnetic origin, which can restrict the number of correlated spins or the type of magnetic ordering in open-shell nanographenes. Here, we present a novel design strategy combing topological frustration and electron-electron interactions to fabricate the largest fully-fused open-shell nanographene reported to date, a 'butterfly'-shaped tetraradical on Au(111). We employed bond-resolved scanning tunneling microscopy and spin excitation spectroscopy to unambiguously resolve the molecular backbone and reveal the strongly correlated open-shell character, respectively. This nanographene contains four unpaired electrons with both ferromagnetic and anti-ferromagnetic interactions, harboring a many-body singlet ground state and strong multi-spin entanglement, which can be well described by many-body calculations. Furthermore, we demonstrate that the nickelocene magnetic probe can sense highly-correlated spin states in nanographene. The ability to imprint and characterize many-body strongly correlated spins in polyradical nanographenes not only presents exciting opportunities for realizing non-trivial quantum magnetism and phases in organic materials but also paves the way toward high-density ultrafast spintronic devices and quantum information technologies
Visualizing designer quantum states in stable macrocycle quantum corrals
10.1038/s41467-021-26198-8Nature Communications121589