Pentagon‐Embedded Cycloarylenes with Cylindrical Shapes

Cylinder‐shaped graphitic networks in carbon nanotubes have attracted interest from scientists in various disciplines. The chemical synthesis of segments thereof is considered as a challenging and appealing subject in chemistry, and deepens our understanding of curved and conjugated arrays of hexagons. We herein report the synthesis of cylinder‐shaped molecules containing non‐hexagon bridges in their conjugated systems. Multiple pentagon units were embedded in the cylinder‐shaped discrete molecules, and the stereoisomerism originating from their helical carbon arrangements was studied. Structural analysis by NMR, UV/Vis absorption spectroscopy, and single‐crystal X‐ray diffraction provided fundamental experimental information on the curved systems with conjugation across the pentagons. This study provides the first experimental guide for further explorations of anomalous non‐hexagon arrays of graphitic carbon materials with cylindrical shapes.     

Resonance Raman contribution to the D band of carbon materials: modeling defects with quantum chemistry

Polycyclic aromatic hydrocarbons (PAHs) are employed to model the Raman features that are generally associated with sp(2) nanostructures in carbon materials or with disorder and defects in graphitic materials. To this end molecular parameters (geometry changes upon electronic excitation, vibrational normal modes, and displacement parameters) are computed with semiempirical quantum-chemical methods for a series of PAHs ranging from 6 to 384 carbon atoms, and Raman intensities are evaluated according to Albrecht's formalism restricted to the A term. The computed preresonance and resonance Raman intensities are compared with available experimental data for hexa-peri-hexabenzocoronene and for pyrene. For the latter compound, simulations carried out at semiempirical and ab initio levels of theory are shown to be of comparable quality. Finally, the collection of displacement parameters computed for the sample of conjugated molecules is used to model the effect of disorder and defects in the Raman response of a carbon material containing sp(2) islands. It is shown that the computed D-band frequency dispersion, with respect to excitation wavelength, reproduces closely the experimental data measured for sp(2) hybridized carbon materials.     

Synthesis of π‐Functional Molecules through Oxidation of Aromatic Amines

In this review, we focus on the synthesis of π‐conjugated functional molecules by the oxidation of aromatic amines, which is one of the most effective methods for the construction of C?C, C?N, and N?N bonds between two π‐conjugated molecular units, and consider their characteristics and applications. Polyanilines are the most common products of the oxidation of aromatic amines; however, azobenzenes, phenazines, and 1,1′‐binaphthyl‐2,2′‐diamines may be produced in this manner also, depending on the reaction conditions. Recent advances in the methodology of aniline oxidation have led to the development of high‐regioselectivity industrial‐scale syntheses of optically or electroactive π‐functional dyes containing nitrogen atoms. In particular, the regioselective fusion of π‐extended aromatic amines can be used to prepare distorted π‐conjugated molecules under mild reaction conditions, allowing the construction of unprecedented curved nitrogen‐containing π‐conjugated molecules.     

A DNA-Gated and Self-Protected Bioorthogonal Catalyst for Nanozyme-Assisted Safe Cancer Therapy

Transition metal catalysts (TMCs) mediated bioorthogonal uncaging catalysis has sparked increasing interest in prodrug activation. However, due to their “always-on” catalytic activity as well as the complex and catalytic-detrimental intracellular environment, the biosafety and therapeutic efficiency of TMCs are unsatisfactory. Herein, a DNA-gated and self-protected bioorthogonal catalyst has been designed by modifying nanozyme-Pd⁰ with highly programmable nucleic acid (DNA) molecules to achieve efficient intracellular drug synthesis for cancer therapy. Monolayer DNA molecules could endow the catalyst with targeting and perform as a gatekeeper to achieve selective prodrug activation within cancer cells. Meanwhile, the prepared graphitic nitrogen-doped carbon nanozyme with glutathione peroxidase (GPx) and catalase (CAT)-like activities could improve the catalytic-detrimental intracellular environment to prevent the catalyst from being inactivated and sensitize the subsequent chemotherapy. Overall, we believe that our work will promote the development of secure and efficient bioorthogonal catalytic systems and provide new insights into novel antineoplastic platforms.     

Bowl-shaped conjugated polycycles

The conjugated polycycles show excellent optical and electrical properties that are suitable for application in various organic electronics.While most of attentions have been paid to polycycles having planar π-conjugated system,the curved polycycles seem amazing due to their unique physical and chemical features.The non-planar conjugated polycycles have been created with the geometries of bracelet,saddle,bowl,Mobius band,helicenes,etc.Among them,the bowl-shaped one is of growing interest owing to the multidiscipline applications such as synthetic intermediates for end-cap of carbon nanotube,coordination with metal ions,encapsulation of fullerenes,and fabrication of electronic devices.In this paper,we summarize the recent advances on the chemistry of the bowl-shaped conjugated polycycles,particularly on their synthesis and the further chemical modifications toward organic functional materials.     

Review of Acetic Acid Synthesis from Various Feedstocks Through Different Catalytic Processes

Acetic acid (AA) has been largely used with a wide range of applications such as a raw material for a synthesis of vinyl acetate monomer, cellulose acetate or acetate anhydrate, acetate ester and a solvent for a synthesis of terephthalic acid and so on. The present paper briefly summarizes the commercialized chemical processes with their Rh or Ir-based catalytic systems in a liquid-phase carbonylation reaction such as Monsanto, Cativa and Acetica processes. In addition, some alternative catalytic systems such as heterogeneous catalysts to produce AA by direct oxidation or indirect carbonylation of dimethyl ether through BP-SaaBre process in a gas-phase reaction to solve some problems such as a difficult separation of homogeneous catalysts in a corrosive reaction medium. Some home-made heterogeneous catalysts such as a rhodium incorporated graphitic carbon nitride (Rh-g-C₃N₄) and some heterogenized homogeneous catalysts using the supports of tungsten carbide, iron oxide or graphitic carbon nitride containing rhodium complexes were also introduced for the synthesis of AA through a liquid-phase methanol carbonylation reaction to effectively solve the leaching problem of active rhodium metal as well as to mitigate the separation problem of homogeneous catalysts.     

DFT investigation for NH3 adsorption behavior on Fe,Ru, and Os-embedded graphitic carbon nitride: promising candidates for ammonia adsorbent

Journal of the Iranian Chemical Society - The adsorption of NH3 molecules on the pristine graphitic carbon nitride (gCN) and TM-embedded gCN systems (TM = Fe, Ru, and Os atoms) was...     

Synthesis, self-assembly, and characterization of supramolecular polymers from electroactive dendron rodcoil molecules

We report here the synthesis and self-assembly of a series of three molecules with dendron rodcoil architecture that contain conjugated segments of oligo(thiophene), oligo(phenylene-vinylene), and oligo(phenylene). Despite their structural differences, all three molecules yield similar self-assembled structures. Electron and atomic force microscopy reveals the self-assembly of the molecules into high aspect ratio ribbon-like nanostructures which at low concentrations induce gelation in nonpolar solvent. Self-assembly results in a blue-shifted absorption spectrum and a red-shifted, quenched fluorescence spectrum, indicating aggregation of the conjugated segments within the ribbon-like structures. The assembly of these molecules into one-dimensional nanostructures is a route to pi-pi stacked supramolecular polymers for organic electronic functions. In the oligo(thiophene) derivative, self-assembly leads to a 3 orders of magnitude increase in the conductivity of iodine-doped films due to self-assembly. We also found that electric field alignment of these supramolecular assemblies can be used to create arrays of self-assembled nanowires on a device substrate.     

Finetuning hierarchical energy material microstructure via high temperature material synthesis route

Hierarchical energy materials such as graphite are a backbone of various scientifically and commercially important emerging technologies including high-energy density energy storage systems with fast charging capability, multifunctional catalyst systems, selective membrane separation systems, and next-generation nuclear material systems. Consequently, it is extremely crucial to develop an efficient and cost-effective route of bulk hierarchical material synthesis (e.g., carbonaceous materials with a well-controlled fraction of the graphitic content) to cater the extraordinary operational and energy material requirements in a very complex coupled thermophysicochemical environment. Here we present a fabrication of Polyacrylonitrile (PAN) derived carbon films and fibers (~with linear dimension ~100 nm) via electrospinning and spin coating methods ensued by a heat-treatment in the range of 1000–3000 °C under inert atmospheric conditions. Intriguingly, we observed at least a two orders of magnitude enhancement (~134%) in length of graphitic plane accompanied by 36% more graphitization when the carbonization temperature increased from 1000 °C to 3000 °C. Such significant enhancements were attributed to the differences in the fundamental nanomorphology of initial carbonaceous materials and their subsequent kinetic evolution as it was more favorable for underlying graphene layers in films to stack and bond to the adjacent ones without strong rotations as compared to fibers, which were further evident from fewer voids and cracks in the films. The covalent cross-links, substrate effect and physical entanglements of carbon domains in PAN-derived carbon films contributed to a higher graphitic length owing to more shear stress between the graphene layers, compared to fibers and undergoes an enormous transformation from turbostratic structures to ordered state along with nitrogen removing over high temperature heating. This morphology dependent graphitization was also investigated from computational approach and concluded in the similar thoughts. The outcomes from this systematic study can be beneficial to the carbon research community focusing in the morphology dependent applications, for instance catalysis, energy storage, sensors etc.     

Recent advances of folded tetraphenylethene derivatives featuring through-space conjugation

Through-space conjugated molecules are interesting building blocks for the construction of functional materials that allow multi-dimensional transport of carrier and energy. However, the well explored through-space conjugated molecules are quite limited, which defers their structure-property correlation establishment and wide-scale application. In this review, we introduce a kind of newly-emerging folded tetraphenylethene derivatives featuring through-space conjugation. Their synthesis, crystal and electronic structures, and optical properties are described, and their representative applications as bipolar charge-transporting materials in organic light-emitting diodes and as single-molecule wires in molecular devices are presented, which are anticipated to provide guidance for the further expansion of through-space conjugated systems.     

Chemically Functionalized Two‐Dimensional Carbon Materials

Nanographenes (NGs), also known as graphene quantum dots, have recently been developed as nanoscale graphene fragments. These nanocarbon species can be excited with UV light and emit light from the UV‐to‐visible region. This photoemission has received great attraction across multiple scientific fields. NGs can be produced by cutting off carbon sources or fusing small organic molecules to grow graphitic structures. Furthermore, the organic synthesis of NGs has been intensely studied. Recently, the number of research papers on postsynthetic modification of NGs has gradually increased. Installed organic groups can tune the properties of NGs and provide new functionalities, opening the door for the development of sophisticated carbon‐based functional materials. This review sheds light on recent progress in the postsynthetic modification of NGs and provides a brief summary of their production methods.     

The adsorption of hetero- and alicyclic thiophene derivatives from water-acetonitrile solutions on the surface of porous graphitic carbon under high-performance liquid chromatography conditions

The adsorption of hetero- and alicyclic thiophene derivatives synthesized for the first time from water-acetonitrile solutions with various compositions on the surface of porous graphitic carbon was studied by the high-performance liquid chromatography method. The retention factor and Henry adsorption constant values and equilibrium constants of quasi-chemical reactions of the adsorption and solvation of the heterocyclic compounds studied were calculated using the Lanin-Nikitin equation. The influence of the structure of hetero- and alicyclic thiophene derivative molecules on their adsorption on the surface of porous graphitic carbon and solvation in water-acetonitrile solutions was discussed. The Lanin-Nikitin model was found to be more informative in the interpretation of the adsorption-chromatographic experiment data compared with the Snyder-Soczewinski and Scott-Kucera models.     

Transition to organic materials science. Passive, active, and hybrid nanotechnologies

This article covers the author's transition from small molecule organic synthesis into polymeric materials and nanotechnology which led to receipt of the Arthur C. Cope Scholar Award in 2007. This includes his start in organometallic reaction development, synthesis of precisely controlled oligomers, conjugated polymers, planar conjugated polymers, and his work on fullerenes. Also mentioned are the people of influence in his life during that formative period. The meaning of nanotechnology is explained in light of bottom-up vs top-down construction and then more specifically related to the passive, active, and hybrid sides of nanotechnology research. These three areas are explained using examples from the author's laboratory: from the passive side, functionalization of carbon nanotubes and their use in composites; from the active side, molecular electronics and nanocars; and finally, the hybrid side, complementing silicon with molecules.     

Functionalized Carbon Nanomaterials Derived from Carbohydrates

A tremendous growth in the field of carbon nanomaterials has led to the emergence of carbon nanotubes, fullerenes, mesoporous carbon and more recently graphene. Some of these materials have found applications in electronics, sensors, catalysis, drug delivery, composites, and so forth. The high temperatures and hydrocarbon precursors involved in their synthesis usually yield highly inert graphitic surfaces. As some of the applications require functionalization of their inert graphitic surface with groups like ? COOH, ? OH, and ? NH₂, treatment of these materials in oxidizing agents and concentrated acids become inevitable. More recent works have involved using precursors like carbohydrates to produce carbon nanostructures rich in functional groups in a single‐step under hydrothermal conditions. These carbon nanostructures have already found many applications in composites, drug delivery, materials synthesis, and Li ion batteries. The review aims to highlight some of the recent developments in the application of carbohydrate derived carbon nanostructures and also provide an outlook of their future prospects.     

Hydrazone-Linked Heptazine Polymeric Carbon Nitrides for Synergistic Visible-Light-Driven Catalysis

Heptazine-based conjugated polymeric carbon nitrides (PCNs) are promising metal-free photocatalysts, yet their synthesis is challenging due to the electron-deficiency and insolubility of heptazine units. Indeed, heptazine-containing polymers have only been prepared through nucleophilic substitution with amines by using toxic cyameluric chloride as the starting material. Herein, we report the novel and environmentally friendly method for preparing heptazine-based mesoporous PCNs with hydrazone links formed through a simple Schiff base condensation of melem-NH₂ and aldehydes. Unlike cyameluric chloride, melem-NH₂ is non-toxic, stable, and can be readily obtained from melem and hydrazine in solution. We demonstrate that the hydrazone linkages and the heptazine units synergistically enhance the photocatalytic activity of PCNs in visible-light-driven aerobic oxidation of benzyl alcohol to benzaldehyde. In particular, the polymer constructed from melem-NH₂ and p-phthalaldehyde shows 17 times more activity than graphitic carbon nitride (g-C₃N₄).     

Separation and detection of the isomeric equine conjugated estrogens, equilin sulfate and delta8,9-dehydroestrone sulfate, by liquid chromatography--electrospray-mass spectrometry using carbon-coated zirconia and porous graphitic carbon stationary phases

Equilin-3-sulfate and delta8,9-dehydroestrone-3-sulfate are two isomers found in equine conjugated estrogens that differ in structure only by the position of a double bond in the steroid B-ring. These geometric isomers were not resolved on a C18 column during the analysis of conjugated estrogen drug products by LC-MS using acetonitrile-ammonium acetate buffer as the mobile phase. While no separations of these two isomers were observed on C18 or other alkyl-bonded silica based phases using a variety of mobile phase conditions, partial separations were achieved on phenyl bonded silica phases with a resolution of 1.5 on a diphenyl phase, and baseline separations were readily achieved on two carbonaceous phases with resolutions routinely exceeding three on graphitic carbon-coated zirconia (Zr-CARB) and resolutions as high as 19 on porous graphitic carbon (Hypercarb). An examination of a selected few conjugated estrogens in the complex drug substance by LC-MS on Hypercarb is presented.     

Marked adsorption irreversibility of graphitic nanoribbons for CO2 and H2O

Graphene and graphitic nanoribbons possess different types of carbon hybridizations exhibiting different chemical activity. In particular, the basal plane of the honeycomb lattice of nanoribbons consisting of sp(2)-hybridized carbon atoms is chemically inert. Interestingly, their bare edges could be more reactive as a result of the presence of extra unpaired electrons, and for multilayer graphene nanoribbons, the presence of terraces and ripples could introduce additional chemical activity. In this study, a remarkable irreversibility in adsorption of CO(2) and H(2)O on graphitic nanoribbons was observed at ambient temperature, which is distinctly different from the behavior of nanoporous carbon and carbon blacks. We also noted that N(2) molecules strongly interact with the basal planes at 77 K in comparison with edges. The irreversible adsorptions of both CO(2) and H(2)O are due to the large number of sp(3)-hybridized carbon atoms located at the edges. The observed irreversible adsorptivity of the edge surfaces of graphitic nanoribbons for CO(2) and H(2)O indicates a high potential in the fabrication of novel types of catalysts and highly selective gas sensors.     

Selective Synthesis of Conjugated Chiral Macrocycles: Sidewall Segments of (−)/(+)‐(12,4) Carbon Nanotubes with Strong Circularly Polarized Luminescence

Carbon nanotubes (CNTs) have unusual physical properties that are valuable for nanotechnology and electronics, but the chemical synthesis of chirality‐ and diameter‐specific CNTs and π‐conjugated CNT segments is still a great challenge. Reported here are the selective syntheses, isolations, characterizations, and photophysical properties of two novel chiral conjugated macrocycles ([4]cyclo‐2,6‐anthracene; [4]CAn_2,6 ), as (?)/(+)‐(12,4) carbon nanotube segments. These conjugated macrocyclic molecules were obtained using a bottom‐up assembly approach and subsequent reductive elimination reaction. The hoop‐shaped molecules can be directly viewed by a STM technique. In addition, chiral enantiomers with (?)/(+) helicity of the [4]CAn_2,6 were successfully isolated by HPLC. The new tubular CNT segments exhibit large absorption and photoluminescence redshifts compared to the monomer unit. The carbon enantiomers are also observed to show strong circularly polarized luminescence (g_lum≈0.1). The results reported here expand the scope of materials design for bottom‐up synthesis of chiral macrocycles and enrich existing knowledge of their optoelectronic properties.     

Synthesis,properties and molecular modeling of functional hyperbranched polymers and dendrimers

The design, synthesis, properties and molecular modeling of fully conjugated dendritic molecules and conjugated hyperbranched polymers are described. It has been shown that conjugated hyperbranched molecules are much more soluble than their linear analogues while maintaining all the properties characteristic of conjugated polymers. It was found that the use of polymeric solid support in hyperbranched polymerization allows to control molecular weight and degree of branching (DB). The molecular modeling of hyperbranched conjugated molecules reveals that hyperbranched structure of conjugated molecules affects significantly neither their stability nor the conjugation. On the other hand the terminal groups affect appreciably the electronic structure of conjugated hyperbranched molecules.