RETRACTED ARTICLE: Living annulative π-extension polymerization for graphene nanoribbon synthesis

Several distance and degree-based molecular structural attributes of cove-edged graphene nanoribbons

A carbon-based material with a broad scope of favourable developments is called graphene. Recently, a graphene nanoribbon with cove-edged was integrated by utilizing a bottom-up liquid-phase procedure, and it can be geometrically viewed as a hybrid of the armchair and the zigzag edges. It is indeed a type of nanoribbon containing asymmetric edges made up of sequential hexagons with impressive mechanical and electrical characteristics. Topological indices are numerical values associated with the structure of a chemical graph and are used to predict various physical, chemical, and biological properties of molecules. They are derived from the graph representation of molecules, where atoms are represented as vertices and bonds as edges. In this article, we derived the exact topological expressions of cove-edged graphene nanoribbons based on the graph-theoretical structural measures that help reduce the number of repetitive laboratory tasks necessary for studying the physicochemical characteristics of graphene nanoribbons with curved edges.

Molecular Engineering of Rylene Diimides via Sila-Annulation Toward High-Mobility Organic Semiconductors

The continuous innovation of captivating new organic semiconducting materials remains pivotal in the development of high-performance organic electronic devices. Herein, a molecular engineering by combining sila-annulation with the vertical extension of rylene diimides (RDIs) toward high-mobility organic semiconductors is presented. The unilateral and bilateral sila-annulated quaterrylene diimides (Si-QDI and 2Si-QDI) are designed and synthesized. In particular, the symmetrical bilateral 2Si-QDI exhibits a compact, 1D slipped π-π stacking arrangement through the synergistic combination of a sizable π-conjugated core and intercalating alkyl chains. Combining the appreciable elevated HOMO levels and reduced energy gaps, the single-crystalline organic field-effect transistors (SC-OFETs) based on 2Si-QDI demonstrate exceptional ambipolar transport characteristics with an impressive hole mobility of 3.0 cm2 V-1 s-1 and an electron mobility of 0.03 cm2 V-1 s-1 , representing the best ampibolar SC-OFETs based on RDIs. Detailed theoretical calculations rationalize that the larger transfer integral along the π-π stacking direction is responsible for the achievement of the superior charge transport. This study showcases the remarkable potential of sila-annulation in optimizing carrier transport performances of polycyclic aromatic hydrocarbons (PAHs).

Diaryliodonium Salts Enabled Arylation, Arylocyclization, and Aryl-Migration

Our research interest focusing on synthetic methodology with diaryliodonium salts, is summarized in this account. Besides employing a dual activation strategy of C-I and ortho C-H bonds, we have introduced vicinal functional groups at ortho-positions of diaryliodonium salts, in which their unique reactivities have been explored in various processes, including arylation, diarylation, cascade annulation, benzocyclization, arylocyclization, and intramolecular aryl migration. The variety of mechanisms of these reactions that involves either transition metals, especially palladium in organometallic catalysis, or transition-metal free conditions, were discussed in the context.

Distinct armchair and zigzag charge transport through single polycyclic aromatics

In aromatic systems with large π-conjugated structures, armchair and zigzag configurations can affect each material's electronic properties, determining their performance and generating certain quantum effects. Here, we explore the intrinsic effect of armchair and zigzag pathways on charge transport through single hexabenzocoronene molecules. Theoretical calculations and systematic experimental results from static carbon-based single-molecule junctions and dynamic scanning tunneling microscope break junctions show that charge carriers are preferentially transported along the hexabenzocoronene armchair pathway, and thus, the corresponding current through this pathway is approximately one order of magnitude higher than that through the zigzag pathway. In addition, the molecule with the zigzag pathway has a smaller energy gap. In combination with its lower off-state conductance, it shows a better field-effect performance because of its higher on-off ratio in electrical measurements. This study on charge transport pathways offers a useful perspective for understanding the electronic properties of π-conjugated systems and realizing high-performance molecular nanocircuits toward practical applications.

A one-dimensional conductive metal-organic framework with extended π-d conjugated nanoribbon layers

Conductive metal-organic frameworks (MOFs) have performed well in the fields of energy and catalysis, among which two-dimensional (2D) and three-dimensional (3D) MOFs are well-known. Here, we have synthesized a one-dimensional (1D) conductive metal-organic framework (MOF) in which hexacoordinated 1,5-Diamino-4,8-dihydroxy-9,10-anthraceneedione (DDA) ligands are connected by double Cu ions, resulting in nanoribbon layers with 1D π-d conjugated nanoribbon plane and out-of-plane π-π stacking, which facilitates charge transport along two dimensions. The DDA-Cu as a highly conductive n-type MOF has high crystalline quality with a conductivity of ~ 9.4 S·m^-1, which is at least two orders of magnitude higher than that of conventional 1D MOFs. Its electrical band gap (E_g) and exciton binding energy (E_b) are approximately 0.49 eV and 0.3 eV, respectively. When utilized as electrode material in a supercapacitor, the DDA-Cu exhibits good charge storage capacity and cycle stability. Meanwhile, as thse active semiconductor layer, it successfully simulates the artificial visual perception system with excellent bending resistance and air stability as a MOF-based flexible optoelectronic synaptic case. The controllable preparation of high-quality 1D DDA-Cu MOF may enable new architectural designs and various applications in the future.

Molecular Carbon Imides

The creation and development of new forms of nanocarbons have fundamentally transformed the scientific landscape in the past three decades. As new members of the nanocarbon family with accurate size, shape, and edge structure, molecular carbon imides (MCIs) have shown unexpected and unique properties. Particularly, the imide functionalization strategy has endowed these rylene-based molecular carbons with fascinating characteristics involving flexible syntheses, tailor-made structures, diverse properties, excellent processability, and good stability. This Perspective elaborates molecular design evolution to functional landscapes, and illustrative examples are given, including a promising library of multi-size and multi-dimensional MCIs with rigidly conjugated π-architectures, ranging from 1D nanoribbon imides and 2D nanographene imides to cross-dimensional MCIs. Although researchers have achieved substantial progress in using MCIs as functional components for exploration of charge transport, photoelectric conversion, and chiral luminescence performances, they are far from unleashing their full potential. Developing highly efficient and regioselective coupling/ring-closure reactions involving the formation of multiple C-C bonds and the annulation of electron-deficient aromatic units is crucial. Prediction by theory with the help of machine learning and artificial intelligence research along with reliable nanotechnology characterization will give an impetus to the blossom of related fields. Future investigations will also have to advance toward─or even focus on─the emerging potential functions, especially in the fields of chiral electronics and spin electronics, which are expected to open new avenues.

Chain-Growth Sulfur(VI) Fluoride Exchange Polycondensation: Molecular Weight Control and Synthesis of Degradable Polysulfates

Sulfur(VI) fluoride exchange (SuFEx) click chemistry has offered a facile and reliable approach to produce polysulfates and polysulfonates. However, the current SuFEx polymerization methods lack precise control of target molecular weight and dispersity. Herein, we report the first chain-growth SuFEx polycondensation process by exploiting the unique reactivity and selectivity of S-F bonds under SuFEx catalysis. Given the higher reactivity of iminosulfur oxydifluoride versus fluorosulfate, the chain-growth SuFEx polycondensation is realized by using an iminosulfur oxydifluoride-containing compound as the reactive chain initiator and deactivated AB-type aryl silyl ether-fluorosulfates bearing an electron-withdrawing group as monomers. When 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was utilized as the polymerization catalyst, precise control over the polymer molecular weight and polydispersity was achieved. The resulting polymers possess great thermal stability but are easily degradable under mild acidic and basic conditions.

Promising Graphene-Based Nanomaterials and Their Biomedical Applications and Potential Risks: A Comprehensive Review

Graphene-based nanomaterials (GBNs) have been the subject of research focus in the scientific community because of their excellent physical, chemical, electrical, mechanical, thermal, and optical properties. Several studies have been conducted on GBNs, and they have provided a detailed review and summary of various applications. However, comprehensive comments on biomedical applications and potential risks and strategies to reduce toxicity are limited. In this review, we systematically summarized the following aspects of GBNs in order to fill the gaps: (1) the history, synthesis methods, structural characteristics, and surface modification; (2) the latest advances in biomedical applications (including drug/gene delivery, biosensors, bioimaging, tissue engineering, phototherapy, and antibacterial activity); and (3) biocompatibility, potential risks (toxicity in vivo/vitro and effects on human health and the environment), and strategies to reduce toxicity. Moreover, we have analyzed the challenges to be overcome in order to enhance application of GBNs in the biomedical field.

Cleaving arene rings for acyclic alkenylnitrile synthesis

Synthetic chemistry is built around the formation of carbon-carbon bonds. However, the development of methods for selective carbon-carbon bond cleavage is a largely unmet challenge^1-6. Such methods will have promising applications in synthesis, coal liquefaction, petroleum cracking, polymer degradation and biomass conversion. For example, aromatic rings are ubiquitous skeletal features in inert chemical feedstocks, but are inert to many reaction conditions owing to their aromaticity and low polarity. Over the past century, only a few methods under harsh conditions have achieved direct arene-ring modifications involving the cleavage of inert aromatic carbon-carbon bonds^7,8, and arene-ring-cleavage reactions using stoichiometric transition-metal complexes or enzymes in bacteria are still limited^9-11. Here we report a copper-catalysed selective arene-ring-opening reaction strategy. Our aerobic oxidative copper catalyst converts anilines, arylboronic acids, aryl azides, aryl halides, aryl triflates, aryl trimethylsiloxanes, aryl hydroxamic acids and aryl diazonium salts into alkenyl nitriles through selective carbon-carbon bond cleavage of arene rings. This chemistry was applied to the modification of polycyclic aromatics and the preparation of industrially important hexamethylenediamine and adipic acid derivatives. Several examples of the late-stage modification of complex molecules and fused ring compounds further support the potential broad utility of this methodology.

Halogen Functionalization in the 2D Material Flatland: Strategies, Properties, and Applications

Given the electronegativity and bonding environment of halogen elements, halogenation (i.e., fluorination, chlorination, bromination, and iodination) serves as a versatile strategy for chemical modifications of materials. The combination of halogens and 2D materials has triggered extensive interests since the first report on graphene fluorination in 2008. Subsequently, scholars consistently conduct pre-, in-process, or posthalogenation modifications of emerging 2D materials to achieve desired properties and broad device applications. They also continuously explore the role of halogens in 2D material functionalization. The multiple advantages introduced by halogen decoration make 2D materials outstanding from each subclass. In this review, an overall retrospect is provided on the research advances in the area of 2D material halogenation, including experimental halogenation strategies, halogen-triggered novel physics and properties, and advanced applications across the studied objects. Future research directions in this area are also proposed.

Materials Science Challenges to Graphene Nanoribbon Electronics

Graphene nanoribbons (GNRs) have recently emerged as promising candidates for channel materials in future nanoelectronic devices due to their exceptional electronic, thermal, and mechanical properties and chemical inertness. However, the adoption of GNRs in commercial technologies is currently hampered by materials science and integration challenges pertaining to synthesis and devices. In this Review, we present an overview of the current status of challenges, recent breakthroughs toward overcoming these challenges, and possible future directions for the field of GNR electronics. We motivate the need for exploration of scalable synthetic techniques that yield atomically precise, placed, registered, and oriented GNRs on CMOS-compatible substrates and stimulate ideas for contact and dielectric engineering to realize experimental performance close to theoretically predicted metrics. We also briefly discuss unconventional device architectures that could be experimentally investigated to harness the maximum potential of GNRs in future spintronic and quantum information technologies.

On-surface Synthesis of a Chiral Graphene Nanoribbon with Mixed Edge Structure

Chiral graphene nanoribbons represent an important class of graphene nanomaterials with varying combinations of armchair and zigzag edges conferring them unique structure-dependent electronic properties. Here, we describe the on-surface synthesis of an unprecedented cove-edge chiral GNR with a benzo-fused backbone on a Au(111) surface using 2,6-dibromo-1,5-diphenylnaphthalene as precursor. The initial precursor self-assembly and the formation of the chiral GNRs upon annealing are revealed, along with a relatively small electronic bandgap of approximately 1.6 eV, by scanning tunnelling microscopy and spectroscopy.

Graphene Nanoribbons: On-Surface Synthesis and Integration into Electronic Devices

Graphene nanoribbons (GNRs) are quasi-1D graphene strips, which have attracted attention as a novel class of semiconducting materials for various applications in electronics and optoelectronics. GNRs exhibit unique electronic and optical properties, which sensitively depend on their chemical structures, especially the width and edge configuration. Therefore, precision synthesis of GNRs with chemically defined structures is crucial for their fundamental studies as well as device applications. In contrast to top-down methods, bottom-up chemical synthesis using tailor-made molecular precursors can achieve atomically precise GNRs. Here, the synthesis of GNRs on metal surfaces under ultrahigh vacuum (UHV) and chemical vapor deposition (CVD) conditions is the main focus, and the recent progress in the field is summarized. The UHV method leads to successful unambiguous visualization of atomically precise structures of various GNRs with different edge configurations. The CVD protocol, in contrast, achieves simpler and industry-viable fabrication of GNRs, allowing for the scale up and efficient integration of the as-grown GNRs into devices. The recent updates in device studies are also addressed using GNRs synthesized by both the UHV method and CVD, mainly for transistor applications. Furthermore, views on the next steps and challenges in the field of on-surface synthesized GNRs are provided.

Fjord-Edge Graphene Nanoribbons with Site-Specific Nitrogen Substitution

The synthesis of graphene nanoribbons (GNRs) that contain site-specifically substituted backbone heteroatoms is one of the essential goals that must be achieved in order to control the electronic properties of these next generation organic materials. We have exploited our recently reported solid-state topochemical polymerization/cyclization-aromatization strategy to convert the simple 1,4-bis(3-pyridyl)butadiynes 3a,b into the fjord-edge nitrogen-doped graphene nanoribbon structures 1a,b (fjord-edge N₂[8]GNRs). Structural assignments are confirmed by CP/MAS ¹³C NMR, Raman, and XPS spectroscopy. The fjord-edge N₂[8]GNRs 1a,b are promising precursors for the novel backbone nitrogen-substituted N₂[8]_AGNRs 2a,b. Geometry and band calculations on N₂[8]_AGNR 2c indicate that this class of nanoribbons should have unusual bonding topology and metallicity.

Bottom-Up, On-Surface-Synthesized Armchair Graphene Nanoribbons for Ultra-High-Power Micro-Supercapacitors

Bottom-up-synthesized graphene nanoribbons (GNRs) with excellent electronic properties are promising materials for energy storage systems. Herein, we report bottom-up-synthesized GNR films employed as electrode materials for micro-supercapacitors (MSCs). The micro-device delivers an excellent volumetric capacitance and an ultra-high power density. The electrochemical performance of MSCs could be correlated with the charge carrier mobility within the differently employed GNRs, as determined by pump-probe terahertz spectroscopy studies.

On-Surface Synthesis of All-cis Standing Phenanthrene Polymers upon Selective C-H Bond Activation

On-surface synthesis has emerged as a powerful approach to the atomically precise fabrication of molecular architectures with potential applications in nanotechnology. However, it is challenging to synthesize molecular structures that can protrude from the surface such as polymer chains forming by the molecules with upright conformations, since most of the on-surface reaction products, particularly the conjugated structures, prefer to adsorb parallel on the surface to maximize the molecule-substrate interaction. Here, we show an up-standing phenanthrene polymer chain with an all-cis configuration obtained by on-surface synthesis upon highly selective C-H activation. Using bond-resolved nc-AFM imaging, the reaction route of polymers from an in-plane to an all-cis upright conformation is fully characterized, and the reaction mechanism is further revealed in combination with first principles calculations. Our results on this selective dehydrogenation induced upright-oriented polymer chains that will enrich the toolbox for the on-surface synthesis of novel molecular structures and may provide new insights on designing optimized precursors for preparing three-dimensional molecular frameworks through on-surface synthesis.

From spin-labelled fused polyaromatic compounds to magnetically active graphene nanostructures

Molecular design of magnetically active graphene nanoscale structures is an emerging field of research. The key goal of this research is to produce graphene nanoribbons and graphene quantum dots with specified electronic, optical and magnetic properties. The review considers methods for the synthesis of spin-labelled polycyclic aromatic hydrocarbons, which are homologous precursors of graphene nanostructures, and discusses the advances and prospects of the design of magnetically active graphene materials.

The bibliography includes 134 references.

Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy

Presented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of Tb^III and Cd^II ions and two to five phthalocyaninato ligands, which are stabilized by electron‐donating n‐butoxy groups. From X‐ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl‐shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic ¹H NMR studies on the resulting series of triple, quadruple and quintuple‐decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple‐decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single‐molecule magnet properties, which are controlled by the multi‐step redox induced structural changes.

Twofold π-Extension of Polyarenes via Double and Triple Radical Alkyne peri-Annulations: Radical Cascades Converging on the Same Aromatic Core

A versatile synthetic route to distannyl-substituted polyarenes was developed via double radical peri-annulations. The cyclization precursors were equipped with propargylic OMe traceless directing groups (TDGs) for regioselective Sn-radical attack at the triple bonds. The two peri-annulations converge at a variety of polycyclic cores to yield expanded difunctionalized polycyclic aromatic hydrocarbons (PAHs). This approach can be extended to triple peri-annulations, where annulations are coupled with a radical cascade that connects two preexisting aromatic cores via a formal C-H activation step. The installed Bu₃Sn groups serve as chemical handles for further functionalization via direct cross-coupling, iodination, or protodestannylation and increase solubility of the products in organic solvents. Photophysical studies reveal that the Bu₃Sn-substituted PAHs are moderately fluorescent, and their protodestannylation results in an up to 10-fold fluorescence quantum yield enhancement. DFT calculations identified the most likely possible mechanism of this complex chemical transformation involving two independent peri-cyclizations at the central core.

Scalable and Precise Synthesis of Armchair-Edge Graphene Nanoribbon in Metal-Organic Framework

Graphene nanoribbons (GNRs), narrow and straight-edged stripes of graphene, attract a great deal of attention because of their excellent electronic and magnetic properties. As of yet, there is no fabrication method for GNRs to satisfy both precision at the atomic scale and scalability, which is critical for fundamental research and future technological development. Here, we report a methodology for bulk-scale synthesis of GNRs with atomic precision utilizing a metal-organic framework (MOF). The GNR was synthesized by the polymerization of perylene (PER) or its derivative within the nanochannels of the MOF. Molecular dynamics simulations showed that PER was uniaxially aligned along the nanochannels of the MOF through host-guest interactions, which allowed for regulated growth of the nanoribbons. A series of characterizations of the GNR, including NMR, UV/vis/NIR, and Raman spectroscopy measurements, confirmed the formation of the GNR with well-controlled edge structure and width.

Synthesis of Nitrogen-Containing Polyaromatics by Aza-Annulative π-Extension of Unfunctionalized Aromatics

Nitrogen-containing polycyclic aromatic compounds (N-PACs) are an important class of compounds in materials science. Reported here is a new aza-annulative π-extension (aza-APEX) reaction that allows rapid access to a range of N-PACs in 11-84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow-up oxidative treatment with p-chloranil affords structurally diverse N-PACs, which are very difficult to synthesize. DFT calculations reveal that the aza-APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N-PACs into nitrogen-doped nanographenes and their photophysical properties are also described.

Air-stable, long-length, solution-based graphene nanoribbons

Within the context of nanoelectronics, general strategies for the development of electronically tunable and air stable graphene nanoribbons are crucial. Previous studies towards the goal of processable nanoribbons have been complicated by ambient condition instability, insolubility arising from aggregation, or poor cyclization yield due to electron deficiency. Herein, we present a general strategy for the elongation of smaller graphene nanoribbon fragments into air-stable, easily processed, and electronically tunable nanoribbons. This strategy is facilitated by the incorporation of electron-rich donor units between electron-poor acceptor perylene diimide oligomeric units. The ribbons are processed in solution via a visible-light flow photocyclization using LEDs. The resulting long nanoribbons can be solution-cast and imaged, which are necessary characteristics for device fabrication. The ribbons become conductive after thermolysis of the pendent side-chains. The electron-accepting character of these nanoribbons in solution is reversible, and the conductivity of the thermolyzed species as a solid remains stable. This work highlights our general strategy for the mild and reliable fabrication of tunable and ambient-stable graphene nanoribbons, and charts a straightforward route for facile device incorporation.

A strategy is shown for the elongation of graphene nanoribbon (GNR) fragments into air-stable, solution processable and electronically tunable GNRs, aided by incorporating electron-rich donor units between electron-poor oligomeric acceptor units.

Switching of the conformational flexibility of a diazacyclooctane-containing ladder polymer by coordination and elimination of a Lewis acid

We report the first system of ladder polymers capable of interconversion between rigid and flexible conformations by coordination and elimination of a Lewis acid (BPh₂Cl) on diazacyclooctane units in the main chain.

Selective synthesis of diazacyclooctane -containing flexible ladder polymers with symmetrically or unsymmetrically substituted side chains

We report a versatile synthetic method for selectively obtaining symmetrical or unsymmetrical N,N′-dialkylated DACO-containing flexible ladder polymers with various functionalities.

Low-temperature synthesis of sp2 carbon nanomaterials

sp² carbon nanomaterials are mainly composed of sp²-hybridized carbon atoms in the form of a hexagonal network. Due to the π bonds formed by unpaired electrons, sp² carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years. As the advanced sp² carbon nanomaterials, graphene and carbon nanotubes (CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature, expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp² carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.

Topologically Unique Molecular Nanocarbons

As new forms of carbon are unearthed, they invariably transform the scientific landscape. Numerous researchers have been inspired to discover the unique characteristics of these fascinating materials, consistently leading to the development of important technological innovations in materials science. Recently, studies on the preparation of molecular nanocarbons (small molecule analogues of larger carbon nanostructures) by precision organic synthesis have attracted much attention. Cycloparaphenylene (CPP), the substructure of carbon nanotubes (CNTs), is the oldest of such organic molecules, and since 2008 the successful synthesis of CPP dramatically advanced the synthetic chemistry of molecular nanocarbons. In fact, as pioneering research, we succeeded in producing carbon nanotubes using seed CPP molecules in 2013. This method represented an important landmark in the quest for controlling the diameter of CNTs via utilization of a well-defined small molecule as a template. Other avenues of research on graphene nanoribbons and partial structures of fullerenes such as corannulene and sumanene are also highly active at the current time. On the other hand, carbon forms with nontrivial topologies, i.e., topological nanocarbons, are virtually unexplored. In addition to the 3D network structures represented by the Mackay crystal, many topologically complex structures have been envisioned. To date, there is no rational approach toward the bottom-up synthesis of these carbon structures. As with the case of fullerenes and CNTs, access to these unique carbon structures should undoubtedly revolutionize a wide range of sciences. This Account highlights our efforts toward the synthesis of topologically unique molecular nanocarbons. Starting from CPP as the topologically simple subunit, we have successfully created novel molecular nanocarbons that have more complexed topologies. The first topic is carbon nanobelts, fully fused cylinder-shaped molecular nanocarbons representing the segment structure of armchair-type CNTs. The second topic is carbon nanocages, molecular nanocarbons having a "three-holed" topology representing the joint unit of branched CNTs. The third and fourth topics are all-benzene catenanes consisting of two CPP rings and an all-benzene trefoil knot topologically related to a carbon nanotorus. The world of nanocarbon molecules is only limited by our imagination and creativity. As history has proved, the synthesis of new forms of carbon and topologically complex molecules has always subsequently led to new fields and applications associated with their unforeseen properties and functions.

Two-in-One Strategy for the Pd(II)-Catalyzed Tandem C-H Arylation/Decarboxylative Annulation Involved with Cyclic Diaryliodonium Salts

We report here a two-in-one strategy for the Pd(II)-catalyzed tandem C-H arylation/decarboxylative annulation between readily available cyclic diaryliodonium salts and benzoic acids. The carboxylic acid functionality can be used as both a directing group for the ortho-C-H arylation and the reactive group for the tandem decarboxylative annulation. By a step-economical double cross-coupling annulation procedure, the privileged triphenylene frameworks were efficiently constructed, which have potential applications in material chemistry.

TriQuinoline

The bottom-up synthesis of structurally well-defined motifs of graphitic materials is crucial to understanding their physicochemical properties and to elicit new functions. Herein, we report the design and synthesis of TriQuinoline (TQ) as a molecular model for pyridinic-nitrogen defects in graphene sheets. TQ is a trimer of quinoline units concatenated at the 2- and 8-positions in a head-to-tail fashion, whose structure leads to unusual aromatisation behaviour at the final stage of the synthesis. The central atomic-sized void endows TQ with high proton affinity, which was confirmed empirically and computationally. TQ•H⁺ is a two-dimensional cationic molecule that displays both π-π and CH-π contact modes, culminating in the formation of the ternary complex ([12]cycloparaphenylene(CPP) ⊃ (TQ•H⁺/coronene)) that consists of TQ•H⁺, coronene (flat), and [12]cycloparaphenylene ([12]CPP) (ring). The water-miscibility of TQ•H⁺ allows it to serve as an efficient DNA intercalator for e.g. the inhibition of topoisomerase I activity.