A method for controlling the synthesis of stable twisted two-dimensional conjugated molecules

Pathway to Polyradicals: A Planar and Fully π-Conjugated Organic Tetraradical(oid)

In this work, we provide a general strategy to stabilize the ground state of polyradical(oid)s and make higher spin states thermally accessible. As a proof of concept, we propose to merge two planar fully π-conjugated diradical(oid)s to obtain a planar and cross-conjugated tetraradical(oid). Using multireference quantum chemistry methods, we show that the designed tetraradical(oid) is stabilized by aromaticity and delozalization in the π-system and has six thermally accessible spin states within 1.72 kcal/mol. Analysis of the electronic structure of these six states of the tetraradical(oid) shows that its frontier π-system consists of two weakly interacting subsystems: aromatic cycles and four unpaired electrons. Conjugation between unpaired electrons, which favors closed-shell structures, is mitigated by delocalization and the aromaticity of the bridging groups, leading to the synergistic cross-coupling between two diradical(oid) subunits to stabilize the tetraradical(oid) electronic structure.

Alcohol imination catalyzed by carbon nanostructures synthesized by C(sp2)-C(sp3) free radical coupling

Imines are important intermediates for synthesizing various fine chemicals, with the disadvantage of requiring the use of expensive metal-containing catalysts. We report that the dehydrogenative cross-coupling of phenylmethanol and benzylamine (or aniline) directly forms the corresponding imine with a yield of up to 98%, and water as the sole by-product, in the presence of a stoichiometric base, using carbon nanostructures as the "green" metal-free carbon catalysts with high spin concentrations, which is synthesized by C(sp2)-C(sp3) free radical coupling reactions. The catalytic mechanism is attributed to the unpaired electrons of carbon catalysts to reduce O2 to O2·-, which triggers the oxidative coupling reaction to form imines, whereas the holes in the carbon catalysts receive electrons from the amine to restore the spin states. This is supported by density functional theory calculations. This work will open up an avenue for synthesizing carbon catalysts and offer great potential for industrial applications.

Organic radicals stabilization above 300 °C in Eu-based coordination polymers for solar steam generation

Organic radicals feature unpaired electrons, and these compounds may have applications in biomedical technology and as materials for solar energy conversion. However, unpaired electrons tend to pair up (to form chemical bonds), making radicals unstable and hampering their applications. Here we report an organic radical system that is stable even at 350 °C, surpassing the upper temperature limit (200 °C) observed for other organic radicals. The system reported herein features a sulfur-rich organic linker that facilitates the formation of the radical centers; on the solid-state level, the molecules are crystallized with Eu(III) ions to form a 3D framework featuring stacks of linker molecules. The stacking is, however, somewhat loose and allows the molecules to wiggle and transform into sulfur-stabilized radicals at higher temperatures. In addition, the resulting solid framework remains crystalline, and it is stable to water and air. Moreover, it is black and features strong broad absorption in the visible and near IR region, thereby enhancing both photothermal conversion and solar-driven water evaporation.

Organic radicals have potential applications in a variety of fields, including energy conversion. Here, the authors report Eu-based coordination polymers that enable the stabilization of organic radicals up to 350 °C; these systems can be used to enhance solar steam generation.

Core-Twist Reduces the Triplet Formation Efficiency in Brominated Perylene Diimides

Bromination is a recent approach to achieve intersystem crossing (ISC) in perylene diimides (PDIs). Herein, we explore the triplet formation dynamics in two tetrabrominated PDI (PDI-Br₄) positional isomers with planar (P-PDI) and twisted (T-PDI) π-conjugated frameworks. In contrast to the known effect where the planar geometry favors fluorescence, T-PDI shows higher fluorescence (ϕ_f = 0.64) than the planar counterpart P-PDI (ϕ_f = 0.42). P-PDI possesses near-degenerate S₁ and T₃/T₄ states and a larger spin-orbit coupling (SOC). Core-twisting has a pronounced effect on the absorption spectra due to symmetry breaking and would open up multiple ISC pathways, albeit with a lower SOC. Low-energy singlet-triplet state crossings within the Franck-Condon region would facilitate ultrafast triplet generation via the S₁-T₃/T₄ ISC pathway in P-PDI. In comparison, such crossings occur at relatively higher energy, reducing the triplet formation efficiency in T-PDI.

Controlled Growth and Self-Assembly of Multiscale Organic Semiconductor

Currently, organic semiconductors (OSs) are widely used as active components in practical devices related to energy storage and conversion, optoelectronics, catalysis, and biological sensors, etc. To satisfy the actual requirements of different types of devices, chemical structure design and self-assembly process control have been synergistically performed. The morphology and other basic properties of multiscale OS components are governed on a broad scale from nanometers to macroscopic micrometers. Herein, the up-to-date design strategies for fabricating multiscale OSs are comprehensively reviewed. Related representative works are introduced, applications in practical devices are discussed, and future research directions are presented. Design strategies combining the advances in organic synthetic chemistry and supramolecular assembly technology perform an integral role in the development of a new generation of multiscale OSs.

Molecular tetrominoes: selective masking of the donor π-face to control the configuration of donor-acceptor complexes

Understanding the doping mechanism in organic semiconductors and generating molecular design rules to control the doping process are crucial for improving the performance of organic electronics. Even though controlling the location and orientation of the dopant along the semiconductor backbone is an important step in the doping mechanism, studies in this direction are scarce as it is a challenging task. To address this, herein, we incorporated π-face masked (strapped) units in 1,4-bis(phenylethynylene)benzene (donor) to control the acceptor (dopant) location along the trimer, donor-acceptor binding strength, and acceptor ionization. Two strapped trimers, PCP and CPC, are synthesized with control over the location of the strapped repeat unit in the trimer. The trimers are complexed with the 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) acceptor in solution. DFT calculations show that DDQ residing on the non-strapped repeat unit (the percentage of this configuration is at least ca. 73%) has the highest binding energy for both PCP and CPC. The percentage of dopant ionization is higher in the case of strapped trimers (PCP and CPC) compared to that of linear control trimers (PLP and LPL) and the completely non-strapped (PPP) trimer. The percentage of dopant ionization increased by 15 and 59% in the case of PCP and CPC respectively compared to that of PPP.

Multiple [n]helicenes with various aromatic cores

Usually, multiple [n]helicene molecules have a characteristic aromatic core, such as benzene, naphthalene, pyrene, perylene, hexabenzocoronene, corannulene, or azacorannulene.

Benzodithiophene-Fused Cyclopentannulated Aromatics via a Palladium-Catalyzed Cyclopentannulation and Scholl Cyclodehydrogenation Strategy

We report the synthesis of a new class of cyclopenta-fused polyaromatic hydrocarbon (CP-PAH) incorporating fused benzodithiophene subunits. These CP-PAHs were prepared utilizing a two-step process involving a palladium catalyzed cyclopentannulation followed by a Scholl cyclodehydrogenation. This work broadens the scope of annulation chemistry by employing 1,2-bis(5-hexylthiophen-3-yl)ethyne and dibromoaryl derivatives based on anthracene, pyrene, and perylene to give 4,4',4'',4'''-(cyclopenta[hi]aceanthrylene-1,2,6,7-tetrayl)tetrakis(2-hexylthiophene), 4,4',4'',4'''-(dicyclopenta[cd,jk]pyrene-1,2,6,7-tetrayl)tetrakis(2-hexylthiophene), and 1,2,7,8-tetrakis(5-hexylthiophen-3-yl)-1,2,7,8-tetrahydrodicyclopenta[cd,lm]perylene. Scholl cyclodehydrogenation of the pendant thiophene units provided access to the π-extended polyaromatic systems 2,5,11,14-tetrahexylrubiceno[5,4-b:6,7-b':12,11-b'':13,14-b''']tetrathiophene, 2,5,11,14-tetrahexyldithieno-[4,5:6,7]indeno[1,2,3-cd]dithieno[4,5:6,7]indeno-[1,2,3-jk]pyrenes, and 2,9,12,19-tetrahexyldithieno[4,5:6,7]indaceno[1,2,3-cd]dithieno[4,5:6,7]indaceno[1,2,3-lm]perylene that possess helicene-like fragments. The anthracene-based CP-PAH was contorted owing to [5]helicene-like arrangements, while the pyrene- and perylene-based systems were essentially planar. The fully conjugated small molecules give low optical gaps (1.7-2.1 eV) with broad light absorption. The HOMO and LUMO energies of the CP-PAHs were found to be in the range of -5.48 to -5.05 eV and -3.48 to -3.14 eV, respectively. Finally, the anthracene-based CP-PAH was found to be a p-type semiconductor when tested in an organic field effect transistor.

Pentagon-Containing π-Expanded Systems: Synthesis and Photophysical Properties

We have designed and synthesized three novel twistacene-modified enlarged pentagon-containing π-systems (6 and 9) with mismatched structures. The introduction of electron-withdrawing cyclopenta rings in the parent skeleton effectively stabilizes the electron-rich arenes. Their optoelectronic properties were studied via ultraviolet-visible (UV-vis) absorption spectra, fluorescence spectra, cyclic voltammetry, and density functional theory (DFT) calculation. In addition, chemical oxidation of the as-prepared compounds with nitrosonium hexafluoroantimonate could form the corresponding cationic radicals.

Carbon Origami via an Alumina-Assisted Cyclodehydrofluorination Strategy

The synthesis of pristine non-planar nanographenes (NGs) via a cyclodehydrofluorination strategy is reported and the creation of highly strained systems via alumina-assisted C-F bond activation is shown. Steric hindrance could execute an alternative coupling program leading to rare octagon formation offering access to elusive non-classical NGs. The combination of two alternative ways of folding could lead to the formation of various 3D NG objects, resembling the Japanese art of origami. The power of the presented "origami" approach is proved by the assembly of 12 challenging nanographenes that are π-isoelectronic to planar hexabenzocoronene but forced out of planarity.

Synthesis and derivatization of hetera-buckybowls

Buckybowls have concave and convex surfaces with distinct π-electron cloud distribution, and consequently they show unique structural and electronic features as compared to planar aromatic polycycles. Doping the π-framework of buckybowls with heteroatoms is an efficient scheme to tailor inherent properties, because the nature of heteroatoms plays a pivotal role in the structural and electronic characteristics of the resulting hetera-buckybowls. The design, synthesis, and derivatization of hetera-buckybowls open an avenue for obtaining fascinating organic entities not only of fundamental importance but also of promising applications in optoelectronics. In this review, we summarize the advances in hetera-buckybowl chemistry, particularly the synthetic strategies toward these scaffolds.

A Data-Mining Approach for the Quantitative Assessment of Physicochemical Properties of Molecular Compounds in the Skin Flux

This paper aimed to provide an insight into the mechanism of transdermal penetration of drug molecules with respect to their physicochemical properties, such as solubility (S), the presence of enantiomer (ET) and logarithm of octanol-water partition coefficient (log P), molecular weight (MW), and melting point (MP). Propionic acid derivatives were evaluated for their flux through full-thickness skin excised from hairless mice upon being delivered from silicone-based pressure-sensitive adhesive (PSA) matrices in the presence or absence of various enhancers. The skin fluxes of model compounds were calculated based on the data obtained using the method engaged with the diffusion cell system. The statistical design of experiments (DoE) based on the factorial approach was used to find variables that have a significant impact on the outcomes. For the prediction of skin flux, a quantitative equation was derived using the data-mining approach on the relationship between skin permeation of model compounds (~125 mg/ml) and involved physicochemical variables. The most influential variables for the skin flux of propionic acid derivatives were the melting point (0.97) followed by the presence of enantiomer (0.95), molecular mass (0.93), log P values (0.86), and aqueous solubility (0.80). It was concluded that the skin flux of molecular compounds can be predicted based on the relationship between their physicochemical properties and the interaction with cofactors including additives and enhancers in the vehicles.

Of Twists and Curves: Electronics, Photophysics, and Upcoming Applications of Non-Planar Conjugated Organic Molecules

Non-planar conjugated organic molecules (NPCOMs) contain π-conjugation across their length and also exhibit asymmetry in their conformation. In other words, certain molecular fragments in NPCOMs are either twisted or curved out of planarity. This conformational asymmetry in NPCOMs leads to non-uniform charge-distribution across the molecule, with important photophysical and electronic consequences such as altered thermodynamic stability, chemical reactivity, as well as materials properties. Majorly, NPCOMs can be classified as having either Fused or Rotatable architectures. NPCOMs have been the focus of significant scientific attention in the recent past due to their exciting photophysical behavior that includes intramolecular charge-transfer (ICT), thermally activated delayed fluorescence (TADF) and long-lived charge-separated states. In addition, they also have many useful materials characteristics such as biradical character, semi-conductivity, dynamic conformations, and mechanochromism. As a result, rational design of NPCOMs and mapping their structure-property correlations has become imperative. Researchers have executed conformational changes in NPCOMs through a variety of external stimuli such as pH, temperature, anions-cations, solvent, electric potential, and mechanical force in order to tailor their photophysical, optoelectronic and magnetic properties. Converging to these points, this review highlights the lucrative electronic features, photophysical traits and upcoming applications of NPCOMs by a selective survey of the recent scientific literature.

Cove-Edged Nanographenes with Localized Double Bonds

The efficient synthesis and electronic properties of two large-size cove-edged nanographenes (NGs), CN1 and CN2, are presented. X-ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1) or six (for CN2) localized C=C double bonds embedded in nine (for CN1) or twelve (for CN2) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations. Furthermore, Raman spectra exhibit a band associated with the longitudinal CC stretching mode of olefinic double bonds. Owing to the existence of the additional olefinic bonds, both compounds show a small band gap (1.84 eV for CN1 and 1.37 eV for CN2). They also display moderate fluorescence quantum yield (35 % for CN1 and 50 % for CN2) owing to the contorted geometry, which can suppress aggregation in solution.

β-Strand inspired bifacial π-conjugated polymers

Access to diverse, relatively high molecular weight soluble linear polymers without pendant solubilizing chains is the key to solution state synthesis of structurally diverse nanoribbons of conjugated materials. However, realizing soluble 1D-π-conjugated polymers without pendant solubilizing chains is a daunting task. Herein, inspired from the polypeptide β-strand architecture, we have designed and developed novel bifacial π-conjugated polymers (M n: ca. 24 kDa) that are soluble (ca. 70 to >250 mM) despite the absence of pendant solubilizing chains. The impact of varying the bifacial monomer height on polymer solubility, optical properties, and interactions with small molecules is reported.

X-Shaped Polycyclic Aromatic Hydrocarbons: Optical Properties and Tunable Assembly Ability

Although a number of synthetic methodologies have been developed to prepare stable polycyclic aromatic hydrocarbons (PAHs), much less research has been devoted to functionalizing the peripheries of molecules to tune the self-assembly ability or introduce functional groups without altering their photophysical properties. Herein, we report twisted "X"-shaped molecules prepared through annulation of hexacene with benzoanthracene on the zigzag edge, and an investigation of their photophysical properties and self-assembly properties. The shape-complementary "X"-shaped molecules prefer to dimerize, while the π-extension would lead to one-dimensional π-stacking. Our findings give some insights into the design of stable PAHs without disturbing the electronic structures.

Graphdiyne-Supported NiFe Layered Double Hydroxide Nanosheets as Functional Electrocatalysts for Oxygen Evolution

Graphdiyne (GDY), a novel two-dimensional full-carbon material, has attracted lots of attention because of its high conjugated system comprising sp² and sp-hybridized carbons. The distinctive structure characteristics endow it unique electronic structure, uniform distributed pores and excellent chemical stability. A novel GDY-supported NiFe layered double hydroxide (LDH) composite was successfully prepared for the first time. By taking advantage of the increased surface active areas and improved conductivity, the designed hierarchical GDY@NiFe composite exhibits outstanding catalytic activity that only required a small overpotential about 260 mV to achieve the current density of 10 mA cm^-2. The nanocomposite shows excellent durability in alkaline medium implying a superior OER electrocatalytic activity. It is anticipated that the as-prepared GDY@NiFe composite electrocatalyst provide new insights in designing graphdiyne-supported electrocatalyst materials for oxygen evolution application.

Impact of morphology, side-chains, and crystallinity on charge-transport properties of π-extended double helicenes

We report a computational study on the effect of side-chain substitution, heteroaromatic substitution and unique crystal packing on the charge transport and mobility of three double helicene molecules. These double helicene (DH) molecules, having curved π-conjugation, are structural hybrids of non-planar [6]helicene and planar tribenzo[b,n,pqr]perylene (TBP). We find that side-chain substitution has only a effect on intrinsic electronic properties in DHs but dramatically impacts the packing arrangement, morphologies and transport network, exhibited in calculated charge transport parameters. Interestingly, the dimensionality of the transport evolves from one dimensional to three dimensional with side-chain substitution (DH2) and heteroaromatic substitution (DH3). Using two different well-known transport models, we have established a direct link between the morphology, transport connectivity, and hole mobilities. While both unsubstituted and substituted DHs exhibit high hole mobilities in the ordered phase, the results show that with inclusion of positional disorder, the mobilities of disordered DH1 and DH3 are lower while the mobility of DH2 remain nearly unchanged. We relate this effect to the dimensionality of their unique transport networks. These DH molecules are promising organic semiconductors with high mobilities in ordered and disordered phases, with predicted values that lie in the range of ∼1 to 10 cm2 V-1 s-1.

Regioselective arene homologation through rhenium-catalyzed deoxygenative aromatization of 7-oxabicyclo[2.2.1]hepta-2,5-dienes

A facile approach to PAHs with an arm-chair edge via regioselective bromination, Diels–Alder reaction, and rhenium-catalyzed deoxygenative aromatization is described.

Dehydrative π-extension to nanographenes with zig-zag edges

Zig-zag nanographenes are promising candidates for the applications in organic electronics due to the electronic properties induced by their periphery. However, the synthetic access to these compounds remains virtually unexplored. There is a lack in efficient and mild strategies origins in the reduced stability, increased reactivity, and low solubility of these compounds. Herein we report a facile access to pristine zig-zag nanographenes, utilizing an acid-promoted intramolecular reductive cyclization of arylaldehydes, and demonstrate a three-step route to nanographenes constituted of angularly fused tetracenes or pentacenes. The mild conditions are scalable to gram quantities and give insoluble nanostructures in close to quantitative yields. The strategy allows the synthesis of elusive low bandgap nanographenes, with values as low as 1.62 eV. Compared to their linear homologues, the structures have an increased stability in the solid-state, even though computational analyses show distinct diradical character. The structures were confirmed by X-ray diffraction or scanning tunneling microscopy.

Highly Regioselective Domino Benzannulation Reaction of Buta-1,3-diynes To Construct Irregular Nanographenes

The properties of nanographenes can be tuned by changing their shapes, therefore the development of new methods suitable for the synthesis of various nanographenes is highly desirable. Described herein is an intramolecular InCl₃ /AgNTf₂ -catalyzed regioselective domino benzannulation reaction of buta-1,3-diynes to build irregular nanographenes. Different nanographene compounds were easily obtained in moderate to high yields through careful design of the precursor compounds. This new domino reaction was successfully applied to a fourfold alkyne benzannulation of dimethoxy-1,1'-binaphthalene derivatives to arrive at novel chiral butterfly ligand precursors. The regioselectivity of the benzannulation reaction was unambiguously confirmed by X-ray crystallography. Moreover, this new method enables us to synthesize different nanographene isomers and study their optical properties as a function of shape.

Expanding the scope of peropyrenes and teropyrenes through a facile InCl3-catalyzed multifold alkyne benzannulation

Synthesizing a broad scope of peropyrenes and teropyrenes with tunable bandgaps is now possible via an InCl₃-catalyzed one-pot multifold alkyne benzannulation reaction.

Cyclopentannulation and cyclodehydrogenation of isomerically pure 5,11-dibromo-anthradithiophenes leading to contorted aromatics

Isomerically pure 5,11-dibromo-ADT was used to create contorted aromatics with large splay angles, low band gaps, and low LUMOs.

Pyridine-ring containing twisttetraazaacene: Synthesis, physical properties, crystal structure and picric acid sensing

Novel pyridine-ring containing twisttetraazaacene 9,14-diphenylpyreno[4,5-g]isoquinoline (1) and its full-carbon derivative 9,14-diphenyldibenzo[de,qr]tetracene (2) have been synthesized and fully characterized. Studies showed that compound 1 could identify picric acid (PA) over other common nitro compounds with high selectivity and sensitivity. Upon the addition of PA, the emission peak of compound 1 in CH₃CN was red shifted from 447 to 555nm with a fluorescence quenching efficiency as high as 95%, the detection limit was calculated to be 2.42μM, while its full-carbon derivative (2) could not exhibit this kind of performance. The possible mechanism with the enhanced PA detection efficiency in pyridine-ring containing twisttetraazaacene (1) than its full-carbon derivative (2) was also investigated.

Ultrathin two-dimensional porous organic nanosheets with molecular rotors for chemical sensing

Molecular rotors have played an important role in recent materials chemistry. Although several studies on functional materials containing molecular rotors have been reported for fluorescence sensing, this concept has yet to be realized in two-dimensional (2D) materials. Here we report the preparation of all-carbon, π-conjugated 2D porous organic nanosheets, named NUS-24, which contain flexible tetraphenylethylene (TPE) units as the molecular rotors. NUS-24 nanosheets exhibit high stability, large lateral size, and ultrathin thickness (2-5 nm). The dynamic TPE rotors exposed on the surface of NUS-24 nanosheets can be restricted in the aggregated state with different water fractions, which is reminiscent of the aggregation-induced emission mechanism, thereby leading to the size-selective turn-on fluorescence by volatile organic compounds. Significantly, the ultrathin 2D nanosheets and its composite membranes show much higher sensitivity and selectivity toward Fe³⁺ ions and nitro-containing compounds sensing, suggesting their potential applications in explosive detection and environmental monitoring.

Rapid Access to Nanographenes and Fused Heteroaromatics by Palladium-Catalyzed Annulative π-Extension Reaction of Unfunctionalized Aromatics with Diiodobiaryls

Efficient and rapid access to nanographenes and π-extended fused heteroaromatics is important in materials science. Herein, we report a palladium-catalyzed efficient one-step annulative π-extension (APEX) reaction of polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics, producing various π-extended aromatics. In the presence of a cationic Pd complex, triflic acid, silver pivalate, and diiodobiaryls, diverse unfunctionalized PAHs and heteroaromatics were directly transformed into larger PAHs, nanographenes, and π-extended fused heteroaromatics in a single step. In the reactions that afford [5]helicene substructures, simultaneous dehydrogenative ring closures occur at the fjord regions to form unprecedented larger nanographenes. This successive APEX reaction is notable as it stiches five aryl-aryl bonds by C-H functionalization in a single operation. Moreover, the unique molecular structures, crystal-packing structures, photophysical properties, and frontier molecular orbitals of the thus-formed nanographenes were elucidated.

Conformational behavior and stacking interactions of contorted polycyclic aromatics

Computational studies of non-covalent dimers of saddle-shaped molecules unveil widely varying conformations and stacking configurations.

Enhanced intersystem crossing in core-twisted aromatics

Core-twisted aromatics exhibit enhanced intersystem crossing upon photoexcitation when compared to their planar analogs.

We describe the design, bottom-up synthesis and X-ray single crystal structure of systematically twisted aromatics 1c and 2d for efficient intersystem crossing. Steric congestion at the cove region creates a nonplanar geometry that induces a significant yield of triplet excited states in the electron-poor core-twisted aromatics 1c and 2d. A systematic increase in the number of twisted regions in 1c and 2d results in a concomitant enhancement in the rate and yield of intersystem crossing, monitored using femtosecond and nanosecond transient absorption spectroscopy. Time-resolved absorption spectroscopic measurements display enhanced triplet quantum yields (Φ_T = 10 ± 1% for 1c and Φ_T = 30 ± 2% for 2d) in the twisted aromatics when compared to a negligible Φ_T (<1%) in the planar analog 3c. Twist-induced spin–orbit coupling via activated out-of-plane C–H/C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C vibrations can facilitate the formation of triplet excited states in twisted aromatics 1c and 2d, in contrast to the negligible intersystem crossing in the planar analog 3c. The ease of synthesis, high solubility, access to triplet excited states and strong electron affinity make such imide functionalized core-twisted aromatics desirable materials for organic electronics such as solar cells.

Extraordinarily Durable Graphdiyne-Supported Electrocatalyst with High Activity for Hydrogen Production at All Values of pH

We have used a scalable and inexpensive method to prepare a catalyst comprising graphdiyne nanosheet-supported cobalt nanoparticles wrapped by N-doped carbon (CoNC/GD); this unprecedentedly durable electrocatalyst mediated the hydrogen evolution reaction (HER) with highly catalytic activity over all values of pH. The durability of the CoNC/GD structure was evidenced by the catalytic performance being preserved over 36 000, 38 000, and 9000 cycles under basic, acidic, and neutral conditions, respectively-behavior superior to that of commercial Pt/C (10 wt %) under respective conditions. Such long-term durability has rarely been reported previously for HER catalysts. In addition, this electrode displayed excellent catalytic activity because the improved physical/chemical properties facilitated electron transfer in the composite. The combination of high durability and high activity at all values of pH for this nonprecious metal catalyst suggests great suitability for practical water splitting.

Synthesis, Crystal Analyses, Physical Properties, and Electroluminescent Behavior of Unsymmetrical Heterotwistacenes

Four novel unsymmetrical heteroacenes containing five-membered heterocycles (OPyN, TPyN, TPyC, TPyO) have been synthesized and characterized. The formed molecules exhibited twisted structures, determined by crystal analysis and showed blue/green fluorescence in dichloromethane and in thin film. Compounds OPyN and TPyN were selectively used as active ingredients, and the fabricated devices displayed promising electroluminescent performance.