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We report the first bottom‐up synthesis of NBN‐doped zigzag‐edged GNRs (NBN‐ZGNR1 and NBN‐ZGNR2) through surface‐assisted polymerization and cyclodehydrogenation based on two U‐shaped molecular precursors with an NBN unit preinstalled at the zigzag edge. The resultant zigzag‐edge topologies of GNRs are elucidated by high‐resolution scanning tunneling microscopy (STM) in combination with noncontact atomic force microscopy (nc‐AFM). Scanning tunneling spectroscopy (STS) measurements and density functional theory (DFT) calculations reveal that the electronic structures of NBN‐ZGNR1 and NBN‐ZGNR2 are significantly different from those of their corresponding pristine fully‐carbon‐based ZGNRs. Additionally, DFT calculations predict that the electronic structures of NBN‐ZGNRs can be further tailored to be gapless and metallic through one‐electron oxidation of each NBN unit into the corresponding radical cations. This work reported herein provides a feasible strategy for the synthesis of GNRs with stable zigzag edges yet tunable electronic properties., Close to the edge: Two novel NBN‐doped zigzag‐edged graphene nanoribbons (ZGNRs) are derived through surface‐assisted synthesis. Experiments and calculations reveal the importance of the NBN units in modulating the electronic structures of the ZGNRs. Moreover, theoretical calculations predict that the electronic structures of NBN‐ZGNRs can be further tailored through one‐electron oxidation of each NBN unit into the corresponding radical cations.

A two-dimensional (2D) sp2 -carbon-linked conjugated polymer framework (2D CCP-HATN) has a nitrogen-doped skeleton, a periodical dual-pore structure and high chemical stability. The polymer backbone consists of hexaazatrinaphthalene (HATN) and cyanovinylene units linked entirely by carbon-carbon double bonds. Profiting from the shape-persistent framework of 2D CCP-HATN integrated with the electrochemical redox-active HATN and the robust sp2 carbon-carbon linkage, 2D CCP-HATN hybridized with carbon nanotubes shows a high capacity of 116 mA h g-1 , with high utilization of its redox-active sites and superb cycling stability (91 % after 1000 cycles) and rate capability (82 %, 1.0 A g-1 vs. 0.1 A g-1 ) as an organic cathode material for lithium-ion batteries.

Polycyclic aromatic azomethine ylides (PAMYs) are powerful building blocks in the bottom-up synthesis of internally nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) through 1,3-cycloaddition reactions. In this work, the cycloaddition reaction of PAMYs to asymmetric ortho-quinones is presented, which, in contrast to the addition to symmetric para-quinones, facilitates subsequent condensation reactions and allows the synthesis of three helical N-PAHs with ullazine-quinoxaline (UQ-1-3) backbones. UQ-1 and UQ-2 possess two helical centers; however, single-crystal X-ray analysis together with the computational modeling of UQ-3 elucidate the formation of only the thermodynamically most stable geometry with four helical centers in a (P,P,M,M) configuration. For the series UQ-1-3, the number of redox steps is directly correlated with the number of ullazine or quinoxaline units incorporated into the targeted molecular backbones. A detailed investigation of the spectroscopic and magnetic properties of the radical cation and anion as well as the dication and dianion species by in situ EPR/UV/Vis-NIR spectroelectrochemistry is provided. The excellent optical and redox properties combined with helical geometries render them possibly applicable as chiral emitter or ambipolar charge transport material in organic electronics.

Herein, we report the design and synthesis of a series of novel cationic nitrogen-doped nanographenes (CNDNs) with nonplanar geometry and axial chirality. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the frontier orbitals of the CNDNs are energetically lower lying, with a reduced optical energy gap and greater electron-accepting behavior. Cyclic voltammetry shows all the derivatives to undergo quasireversible reductions. In situ spectroelectrochemical studies prove that, depending on the number of nitrogen dopants, either neutral radicals (one nitrogen dopant) or radical cations (two nitrogen dopants) are formed upon reduction. The concept of cationic nitrogen doping and introducing helicity into nanographenes paves the way for the design and synthesis of expanded nanographenes or even graphene nanoribbons with cationic nitrogen dopants.

Wir berichten uber Design und Synthese einer Serie von neuen kationischen stickstoffdotierten Nanographenen (CNDN) mit einer nichtplanaren Geometrie und axialer Chiralitat. Einkristall-Rontgendiffraktometrie beweist deren helikale und teils “Cove”-terminierte Struktur. Verglichen mit den reinen Kohlenstoffanalogen liegen die Grenzorbitale der CNDN energetisch tiefer, was zu einer verringerten optischen Energielucke und einer erhohten Elektronenaffinitat fuhrt. Alle Derivate zeigen in cyclovoltammetrischen Untersuchungen quasireversibles Reduktionsverhalten. Abhangig von der Zahl an Stickstoffdotanden ist es moglich, neutrale Radikale (bei einem Stickstoffdotanden) oder Radikalkationen (bei zwei Stickstoffdotanden) wahrend des Reduktionsprozesses uber In-situ-Spektroelektrochemie zu analysieren. Kationische Stickstoffdotierung kombiniert mit Helizitat erschliest neue Wege fur das Design und die Synthese von ausgedehnten Nanographenen und Nanographenstreifen.

Covalent organic frameworks (COFs) have aroused immense scientific interest as an exhilarating class of porous materials due to their structure tunability and diverse properties. However, understanding of their response towards laser induced nonlinear optical (NLO) applications is in its infancy and demands prompt attention. Herein, we report three novel regioregular porphyrin based porous COFs, Por‐COF‐HH and its dual metalated congeners (Por‐COF‐ZnCu and Por‐COF‐ZnNi) with excellent NLO properties. Notably, intensity dependent NLO switching behavior was observed for these Por‐COFs, which is highly desirable for optical switching and optical limiting devices. Moreover, the efficient π‐conjugation and charge transfer transition in ZnCu‐Por‐COF enable a high nonlinear absorption coefficient (β=4470 cm/GW) and figure of merit (FOM = σ1/σo, 3565) values compared to other state‐of‐art materials including molecular porphyrins (β=~100‐400 cm/GW), metal‐organic frameworks (MOFs; β=~0.3‐0.5 cm/GW) and graphene (β=900 cm/GW).

A two‐dimensional (2D) sp2‐carbon‐linked conjugated polymer framework (2D CCP‐HATN) has a nitrogen‐doped skeleton, a periodical dual‐pore structure and high chemical stability. The polymer backbone consists of hexaazatrinaphthalene (HATN) and cyanovinylene units linked entirely by carbon–carbon double bonds. Profiting from the shape‐persistent framework of 2D CCP‐HATN integrated with the electrochemical redox‐active HATN and the robust sp2 carbon‐carbon linkage, 2D CCP‐HATN hybridized with carbon nanotubes shows a high capacity of 116 mA h g−1, with high utilization of its redox‐active sites and superb cycling stability (91 % after 1000 cycles) and rate capability (82 %, 1.0 A g−1 vs. 0.1 A g−1) as an organic cathode material for lithium‐ion batteries.

Eine Bottom-up-Methode zur Synthese stabiler und monodisperser Graphensegmente mit Stickstoff-dotierten Zickzackkanten wird vorgestellt. Auf Grundlage des bisher unbeschriebenen Dibenzo-9a-azaphenalens (DBAPhen) als molekularer Baustein wird ein allgemein anwendbares Konzept zur Synthese ausgedehnter Nanographene und Nanographenstreifen mit Stickstoff-dotierten Zickzackkanten eingefuhrt.

Organic electrode materials are of long-standing interest for next-generation sustainable lithium-ion batteries (LIBs). As a promising cathode candidate, imide compounds have attracted extensive attention due to their low cost, high theoretical capacity, high working voltage, and fast redox reaction. However, the redox active site utilization of imide electrodes remains challenging for them to fulfill their potential applications. Herein, the synthesis of a highly stable, crystalline 2D polyarylimide (2D-PAI) integrated with carbon nanotube (CNT) is demonstrated for the use as cathode material in LIBs. The synthesized polyarylimide hybrid (2D-PAI@CNT) is featured with abundant π-conjugated redox-active naphthalene diimide units, a robust cyclic imide linkage, high surface area, and well-defined accessible pores, which render the efficient utilization of redox active sites (82.9%), excellent structural stability, and fast ion diffusion. As a consequence, high rate capability and ultrastable cycle stability (100% capacity retention after 8000 cycles) are achieved in the 2D-PAI@CNT cathode, which far exceeds the state-of-the-art polyimide electrodes. This work may inspire the development of novel organic electrodes for sustainable and durable rechargeable batteries.

The Taylor-Couette flow of viscous and viscoelastic second-order fluids is examined by a low-dimensional truncated expansion of trigonometric functions. Tie influence of gap width between the cylinders is included up to second order. By comparing the results for the critical Taylor number, obtained from the series expansion, with numerical results from linear stability calculation the truncation is validated with an error of less than two percent. The dynamics of the truncated system of ordinary differential equations describe well the transition from laminar to Taylor-vortex flow, but no further bifurcations to more complex flows are found. The reason for this behaviour is assumed to be due to the omission of non-axisymmetric disturbances.