Addition Of Heteroatoms Research Articles

Molecular-Scale Geometric Design: Zigzag-Structured Intrinsically Stretchable Polymer Semiconductors.

Orienting intelligence and multifunction, stretchable semiconductors are of great significance in constructing next-generation human-friendly wearable electronic devices. Nevertheless, rendering semiconducting polymers mechanical stretchability without compromising intrinsic electrical performance remains a major challenge. Combining geometry-innovated inorganic systems and structure-tailored organic semiconductors, a molecular-scale geometric design strategy is proposed to obtain high-performance intrinsically stretchable polymer semiconductors. Originating from the linear regioregular conjugated polymer and corresponding para-modified near-linear counterpart, a series of zigzag-structured semiconducting polymers are developed with diverse ortho-type and meta-type kinking units quantitatively incorporated. They showcase huge edges in realizing stretchability enhancement for conformational transition, likewise with long-range π-aggregation and short-range torsion disorder taking effect. Assisted by additional heteroatom embedment and flexible alkyl-chain attachment, mechanical stretchability and carrier mobility could afford a two-way promotion. Among zigzag-structured species, o-OC8-5% with the initial field-effect mobility up to 1.92 cm2 V-1 s-1 still delivers 1.43 and 1.37 cm2 V-1 s-1 under 100% strain with charge transport parallel and perpendicular to the stretching direction, respectively, accompanied by outstanding performance retention and cyclic stability. This molecular design strategy contributes to an in-depth exploration of prospective intrinsically stretchable semiconductors for cutting-edge electronic devices.

Synthesis Route to Single-Walled Zeolite Nanotubes Enabled by Tetrabutylammonium Hydroxide.

Single-walled zeolite nanotubes (ZNT) were recently synthesized in a narrow compositional window. ZNT structural features-thin zeolitic walls and large mesopores-can allow for easy access of small molecules to zeolite micropores, but they also impart processing limitations for these materials, such as challenges with conventional aqueous ion-exchange conditions. Conventional solid- and liquid-phase ion exchange of calcined NaOH-derived ZNT (NaH-ZNT) results in structural degradation to either 2D sheet-like phases, 3D nanocrystals, or amorphous phases, motivating different direct synthesis routes and unconventional ion-exchange procedures of uncalcined ZNT precursors. Here, a modified synthesis route for ZNT synthesis is introduced that facilitates facile ion exchange as well as incorporation of additional non-Al heteroatoms in the zeolite framework. Tetrabutylammonium hydroxide (TBAOH) is used as a hydroxide source and co-OSDA, enabling synthesis of new compositions of ZNT, otherwise unachievable by post-modification of previously reported NaH-ZNT. By varying the gel composition, synthesis temperature, crystallization time, hydroxide source, silicon source, and aluminum source, productive conditions for the new TBAOH synthesis are developed, leading to increased strong acid site density in the ZNT. The collected results demonstrate the sensitivity of the ZNT synthesis to many key parameters and show that the ZNT forms only when Si/(Al + T) ∼ 30 in these synthesis gels and with specific Si and Al sources, and always in the presence of trace Na+. Catalytic testing, via the tandem CO2 hydrogenation to methanol and methanol to aromatics reaction, shows that ZNTs provide adequate catalytic activity (acidity), relative to their conventional 3D counterparts in converting methanol to aromatic compounds.

Early Preclinical Studies of Ergosterol Peroxide and Biological Evaluation of Its Derivatives.

Ganoderma lucidum is a medicinal mushroom that produces various pharmacological compounds, including triterpenoids. A major bioactive component of G. lucidum is ergosterol peroxide (EP), which is attributed to its anticancer effects. The current study focuses on the in vitro ADME (absorption, distribution, metabolism, and elimination), in vivo efficacy and toxicity of EP, and the synthesis of new EP derivatives to improve aqueous solubility. It was found that EP is metabolically stable in liver microsomes and plasma. In vivo studies showed that EP inhibits tumor growth in murine cancer models, and it is well tolerated by mice. The maximum tolerated dose was investigated in mice at escalating doses with a defined maximum amount of 500 mg/kg, which indicated no signs of toxicity, confirmed by plasma chemistry and analysis of harvested tissues. Complementary organ toxicity assays including cardio and hepatotoxicity assays of EP demonstrated no inhibitory effects. Next, a focused library of EP derivatives was developed to investigate the iterative addition of heteroatoms to improve the aqueous solubility properties of EP. Significant solubility improvement was observed by the introduction of hydrogen bonding promoting groups, particularly the sulfate group. Superior aqueous solubility properties are directly correlated with the biological activity of the compound against triple-negative breast cancer cellular (TNBC) models. The EP derivatives maintain ample therapeutic index at the tested concentrations, indicating they engage with the same biological target(s) as the parental compound (EP). The combined studies indicate that EP and its derivatives are selective TNBC cell death inducers, while sparing noncancerous tissue.

Crystalline 1D Linear Conjugated Polymers with a Quinoidal Unit As Metal‐Free Electrocatalysts for Oxygen Reduction

AbstractCrystalline and soluble 1D linear conjugated polymers (LCPs) have garnered considerable interest as cost‐effective and efficient metal‐free electrocatalysts for the oxygen reduction reaction (ORR) due to their high exposure of catalytic sites and ease of processing. However, difficulties remain in achieving excellent ORR performance for 1D LCPs by conventional molecular design. Herein, it is demonstrated the utilization of quinoidal units as a promising strategy to develop 1D LCPs for ORR. The incorporation of quinoidal unit not only results in polymers with strong inter‐ and intra‐molecular interactions and low‐lying LUMO (lowest unoccupied molecular orbital) energy levels, but also provides polymers with good crystallinity and commendable charge carrier mobilities. The electronic properties of these polymers are fine‐tuned through the introduction of additional heteroatoms and/or substituents in the monomers and comonomers to understand and optimize their ORR catalytic activity. Evaluation of their catalytic performances reveals a remarkable half‐wave potential and limiting current density of up to 0.74 V (vs reversible hydrogen electrod) and 7.50 mA cm−2, respectively. Notably, these performances are achieved without the addition of carbon nanomaterials as support. This study offers a new insight into the design of highly efficient metal‐free organic electrocatalysts.

Theoretical investigation on the second order nonlinear optical properties of heptagon bridged bi-porphyrin derivatives

Porphyrins and their derivatives have drawn extensive attention as promising nonlinear optical (NLO) materials especially for biological applications owing to its large aromatic conjugation and special biological activity and compatibility. However, it is still critical to strategically design porphyrin derivatives materials with high performance in second order NLO applications and disclose the structure property correlation. In the present work, a series of dual-metallic-porphyrin derivatives are designed by incorporating a heptagon between two porphyrins with further addition of heteroatoms and metals. The doping of B and N along the dipole direction induces large static first hyperpolarizability, and strong charge transfer occurs with further introduction of Mg, thus ultimately achieving excellent second order NLO properties including strong sum frequency generation and difference frequency generations under external fields. The doping of heteroatoms and metals synergistically tunes the electronic structure of porphyrin-based derivatives and brings about high performance in biological nonlinear optics.

Hierarchical porous carbon with abundant N/O doping as an anode for zinc ion hybrid supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZISCs) known for their affordability, stability, and high energy density represent innovative energy storage devices. Porous carbon is usually used as the cathode material of ZISCs, and its structure significantly affects the dual performance of high power density and energy density of ZISCs. Herein, a one-pot carbonization strategy is proposed, eliminating the need for templates, additional heteroatom compounds, and activation processes. By precisely controlling the temperature to optimize the structure and electrochemical performance of carbon materials, we successfully synthesized hierarchical porous carbon materials (NOPC-800) with a high specific surface area of 1545.7 mg, featuring dual doping of 12.3 at% nitrogen and 13.35 at% oxygen. The self-doping of abundant nitrogen and oxygen atoms facilitates the chemical adsorption of ions and accelerates pseudocapacitive reaction kinetics. Leveraging these advantages, ZISCs were assembled using NOPC-800 as the positive electrode and zinc as the negative electrode, showcasing remarkable performance: a specific capacity of up to 121.9 mAh g, an energy density of 97.5 Wh kg, and a power density of up to 16000 W kg. Remarkably, NOPC-800 maintained an excellent capacity retention of 94.9% after 10,000 cycles at a current density of 10 A g. This research paves an innovative and feasible path for the design and advancement of novel heteroatom-rich carbon cathodes.

Synergistic effects of fluorine and nitrogen dopants in fluorine/nitrogen-coordinated iron-co-doped carbon catalysts for enhanced oxygen reduction in alkaline media

The expensiveness of oxygen reduction reaction (ORR) catalyst materials especially Pt has hindered the commercialization of next-generation energy conversion devices including metal–air batteries and polymer electrolyte membrane fuel cells. Fe–N–C has drawn attention as a nonprecious metal catalyst owing to its high but commercially unsatisfactory ORR performance; nevertheless, additional heteroatom co-doping could help augment its ORR activity. Here we report nitrogen/fluorine-coordinated iron-co-doped carbon (Fe@NFC) catalysts with improved ORR performance in alkaline media. The annealing temperature affects the nitrogen/fluorine doping and functional group formation, as ascertained by an analysis of control samples annealed at various temperatures. To assess the synergy between the doped fluorine and nitrogen-coordinated iron, we compare the catalyst annealed at 700 °C (Fe@NFC700) with control samples containing different heteroatom dopants but annealed at 700 °C (Fe@NC, Fe@FC). Fe@NFC700 shows improved ORR kinetics and onset potential than those of Fe@NC and commercial Pt/C, respectively, in alkaline media.

Hydrothermal synthesis of B, S, and N-doped carbon quantum dots for colorimetric sensing of heavy metal ions.

In this study, glucose was used as the carbon source to synthesize carbon quantum dots (CQDs) and also aimed to synthesize CQDs doped with heteroatoms such as sulphur, nitrogen, and boron to enhance their functionality. The obtained material has been characterized by several techniques. According to FL analysis, the highest peaks for CQD, N-CQD, B-CQD, and S-CQD were determined as 432 nm (ex 350), 425 (ex 350), 430 nm (ex 340 nm), and 436 nm (ex 340 nm), respectively. FTIR spectra showed different characteristic peaks for CQD, and the FTIR results show that CQDs have a unique structure. According to TEM analysis, the morphology of all CQDs was found to be spherical and monodisperse with average sizes in the range of 5-7 nm. The characterization results of CQDs show that the addition of heteroatoms changes the properties of CQDs. The synthesized CQDs were also tested as colorimetric sensors for the detection of heavy metals. It was observed that CQDs detected Fe3+ metal ions, B-CQD and S-CQD detected Fe3+ and Ag+ metal ions, and N-CQDs detected Ca2+ metal ions. Sensor studies were performed for all CQDs and linear plots were obtained against metal concentrations in the range of 0.06-1.23 μM. LOD values for CQD, N-CQD, S-CQD, and B-CQD were calculated as 0.187 μM (Fe3+), 0.391 μM (Ca2+), 0.224 μM (Fe3+)-0.442 μM (Ag+), and 0.182 μM (Fe3+)-0.174 μM (Ag+), respectively. The results show that the addition of B, N, and S atoms to CQDs plays a role in the improvement and modification of colorimetric sensor properties and has the potential to be used in sensor applications for the detection of heavy metals in areas such as the environment and health.

Hydrogen-Bonded Organic Framework Derived 2D N, O Co-Doped Carbon Nanobelt with Tunable Pseudocapacitive Contribution for Efficient Capacitive Deionization.

Defect engineering is recognized as an attractive method for modulating the electronic structure and physicochemical characteristics of carbon materials. Exploiting heteroatom-doped porous carbon with copious active sites has attracted great attention for capacitive deionization (CDI). However, traditional methods often rely on the utilization of additional heteroatom sources and strong corrosive activators, suffering from low doping efficiency, insufficient doping level, and potential biotoxicity. Herein, hydrogen-bonded organic frameworks (HOFs) are employed as precursors to synthesize N, O co-doped porous carbon via a simple and green reverse defect engineering strategy, achieving controllable heavy doping of heteroatoms. The N, O co-doping triggers significant pseudocapacitive contribution and the surface pore structure supports the formation of the electric double layer. Therefore, when HOF-derived N, O co-doped carbon is used as CDI electrodes, a superior salt adsorption capacity of 32.29±1.42mgg-1 and an outstanding maximum salt adsorption rate of 10.58±0.46mgg-1min-1 at 1.6V in 500mgL-1 NaCl solution are achieved, which are comparable to those of state-of-the-art carbonaceous electrodes. This work exemplifies the effectiveness of the reverse nitrogen-heavy doping strategy on improving the carbon structure, shedding light on the further development of rational designed electrode materials for CDI.

Fluorometric carbon-dots nanosensor for the detection of hexavalent chromium in water

The detection of trace residues of hexavalent chromium (Cr(VI)) in water is crucial for assessing ecological hazards due to its high cytotoxicity and carcinogenic properties. In this study, we have developed a selective and sensitive fluorescent sensor utilizing carbon dots (CDs) with an average size of 2 nm. The CDs is synthesized via a low-cost and facile one-step method without the need for additional heteroatoms. The CDs-based sensor exhibits superior selectivity, even in the presence of environmentally relevant cations, and can detect Cr(VI) over a concentration range of 1–1000 μM (with a linear range of 1 – 125 μM and R2≥ 0.998). The detection limit of the sensor is found to be 0.6 μM (equivalent to 31 μg L−1), which is below the value of 50 μg L−1 for drinking water guide-lined by the World Health Organization. This performance can be attributed to the combination of inner filter effect with the static quenching effect between the as-synthesized CDs and Cr(VI). Furthermore, we demonstrate the applicability of the CDs-based sensor for Cr(VI) detection in real samples of drinking water and tap water.

DFT and electrochemical studies of new superplasticizers on the corrosion inhibition of 316L stainless steel in neutral medium: A comparative study

In this study, new corrosion inhibitors such as polycarboxylate ether (PCE), sulfonated naphthalene formaldehyde (SNF), modified lignosulphonate (MLS), and sulfonated melamine formaldehyde (SMF) are utilized for 316L stainless steel in a 3.5% NaCl medium. ATR-IR and UV–Vis spectroscopy were used to study the superplasticizers' structural characterization. Based on the ATR-IR and UV–Vis results, all of the spectrum information for PCE, SNF, MLS, and SMF are closely matched to the findings of the significant superplasticizers described in the literature. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) measurements and the weight loss method were used to investigate the corrosion inhibition efficacy of new superplasticizers on 316L stainless steel in a 3.5% NaCl solution. According to the EIS, PDP, and weight loss results, SMF has the highest inhibitory efficiency of all the inhibitors examined. These could be attributed to the presence of additional heteroatoms (N, O, and S) in the SMF than in the other three inhibitors. The inhibition efficiencies were in the order of SMF > MLS > SNF > PCE, with the maximum inhibition efficiency of 88.8% for the SMF inhibitor at 0.00012 mol L−1 concentration. The adsorption of all inhibitors, including PCE, SNF, MLS, and SMF, is well-fitted and follows the Langmuir isotherm model. SEM and EDX analyses were used to study the corrosion mechanism of the adsorbed inhibitor molecules PCE, SNF, MLS, and SMF and their elemental composition on the metal surface. The SEM and EDX result reveals that the SMF inhibitor is substantially adsorbed onto the 316L SS surface as a protective layer. Quantum chemical calculations were utilized to give further evidence of the mechanism of inhibition action of all corrosion inhibitors such as PCE, SNF, MLS, and SMF. All the DFT studies demonstrate that sulfonated melamine formaldehyde (SMF) has outstanding inhibitory capabilities on 316L stainless steel in a 3.5% NaCl solution at room temperature out of the four proficient superplasticizers studied.

(Invited) Synthesis, Characterization and Quality Control of Heteroatom-Doped Graphene

Heteroatom doped graphene materials have gained attention as promising candidates for a variety of energy-related applications. Addition of heteroatoms in the graphene lattice is a powerful tool to modify their electronic, electrochemical, and catalytic properties. This presentation focusses on N-doped reduced graphene oxide and summarizes strategies to engineer the structure and properties of the material through control of the synthetic conditions. The produced N-doped graphene materials are characterized to determine their chemical composition, nitrogen content, degree of graphitization, surface area, electronic and electro-chemical properties. The scalability and manufacturability of the N-doped graphene materials are assessed and various examples of their current and future applications in batteries and supercapacitors are discussed.

Unraveling the Origin of Enhanced K+ Storage of Carbonaceous Anodes Enabled by Nitrogen/Sulfur Co‐Doping

AbstractN‐doped carbons, as promising anode materials for energy storage, are generally modified by the additional heteroatoms (B, P, and S) doping to further promote the electrochemical performance. However, the promotion mechanism by such additional doping, especially its interplay with N‐containing species, remains unclear. Herein, by adopting N/S co‐doped carbon as a model system, it is found that S‐doping can significantly improve the content of pyridinic‐N, i.e., the most energetically favorable N type for K+ storage. Theoretical calculations reveal that such S‐induced pyridinic‐N improvement possibly originates from its catalytic effect that can facilitate the transition from edge quaternary‐N to pyridinic‐N. The resultant high content of pyridinic‐N, together with the additional S species, ensures abundant active sites for K+ storage. Accordingly, the N/S co‐doped carbon anode delivers both a high reversible capacity (422.9 mA h g−1 at 0.05 A g−1) and an impressive cyclic stability (249.6 mA h g−1 at 1 A g−1 over 4000 cycles). Moreover, in/ex situ characterizations further verify the merits of N/S co‐doped carbon from the perspective of compositional evolution and structural stability. This study unravels the origin of enhanced K+ storage by N/S co‐doping, which also helps to understand the synergistic effects of other heteroatoms co‐doping systems.

A Consideration of the Extent That Tertiary Amines Can Form N-Nitroso Dialkylamines in Pharmaceutical Products

Most secondary amines have the potential to undergo nitrosation in the presence of nitrite under certain conditions, particularly at low pH, to generate N-nitrosamines. Tertiary amines are generally considered to be less prone to nitrosamine formation as they require an additional dealkylation step. A review of the published literature combined with recently generated experimental data from nitrosation experiments carried out on several trialkyl amines further informs on the extent that tertiary amines can form N-nitrosamines by reaction with trace levels of nitrite, which may be present during drug substance or drug product manufacture. Simple trialkylamines, amines containing no additional heteroatoms, have been demonstrated to react via a nitrosative dealkylation mechanism that slowly generates a dialkylamine, which in turn nitrosates. This sequence of reactions to generate a N-nitrosamine is approximately 1000-fold slower than the simple nitrosation of a secondary amine of comparable pKa. Therefore, the formation of N-nitrosamines from simple trialkylamines in pharmaceutical products is typically not considered to be a risk. Dialkylanilines are able to access alternative reaction mechanisms and may undergo dealkylative nitrosation with greater ease than simple trialkylamines and therefore require a more focused risk assessment. Finally, certain structurally complex tertiary amines may contain functional groups that can facilitate the formation of N-nitrosamines through resonance and/or inductive electronic effects. Therefore, structures containing highly functionalized tertiary amines require a thorough, compound-specific assessment to determine the level of risk of nitrosamine generation. Note that in situations where higher amounts of nitrosating agents are present, such as when nitrosation chemistry is used during the drug substance manufacturing process, simple trialkylamines should be considered for N-nitrosamine generation during the risk assessment.

Design, Synthesis, and Biological Evaluation of Pyrimidine Dihydroquinoxalinone Derivatives as Tubulin Colchicine Site-Binding Agents That Displayed Potent Anticancer Activity Both In Vitro and In Vivo.

Polymerization of tubulin dimers to form microtubules is one of the key events in cell proliferation. The inhibition of this event has long been recognized as a potential treatment option for various types of cancer. Compound 1e was previously developed by our team as a potent inhibitor of tubulin polymerization that binds to the colchicine site. To further improve the potency and therapeutic properties of compound 1e, we hypothesized based on the X-ray crystal structure that modification of the pyrimidine dihydroquinoxalinone scaffold with additional hetero-atom (N, O, and S) substituents could allow the resulting new compounds to bind more tightly to the colchicine site and display greater efficacy in cancer therapy. We therefore synthesized a series of new pyrimidine dihydroquinoxalinone derivatives, compounds 10, 12b-c, 12e, 12h, and 12j-l, and evaluated their cytotoxicity and relative ability to inhibit proliferation, resulting in the discovery of new tubulin-polymerization inhibitors. Among these, the most potent new inhibitor was compound 12k, which exhibited high cytotoxic activity in vitro, a longer half-life than the parental compound in liver microsomes (IC50 = 0.2 nM, t 1/2 = >300 min), and significant potency against a wide range of cancer cell lines including those from melanoma and breast, pancreatic, and prostate cancers. High-resolution X-ray crystal structures of the best compounds in this scaffold series, 12e, 12j, and 12k, confirmed their direct binding to the colchicine site of tubulin and revealed their detailed molecular interactions. Further evaluation of 12k in vivo using a highly taxane-resistant prostate cancer xenograft model, PC-3/TxR, demonstrated the strong tumor growth inhibition at the low dose of 2.5 mg/kg (i.v., twice per week). Collectively, these results strongly support further preclinical evaluations of 12k as a potential candidate for development.

Safety and efficacy of the feed additives 2-acetylfuran [13.054] and 2-pentylfuran [13.059] belonging to chemical group 14 for animal species (FEFANA asbl).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of 2-acetylfuran [13.054] and 2-pentylfuran [13.059] belonging to chemical group 14 (furfuryl and furan derivatives with and without additional side-chain substituents and heteroatoms), when used as sensory additives (flavourings) in feed for all animal species. 2-Acetylfuran [13.054] was tested in tolerance studies in chickens for fattening, weaned piglets and cattle for fattening. No adverse effects were observed in the tolerance studies at 10-fold the intended use level. The FEEDAP Panel concluded that 2-acetylfuran [13.054] is safe for these species at the proposed use level of 0.5mg/kg and conclusions were extrapolated to all animal species. For 2-pentylfuran [13.059], the Panel concluded that it is safe at the proposed maximum use level in feed of 0.5mg/kg. No safety concern would arise for the consumer from the use of 2-acetylfuran [13.054] and 2-pentylfuran [13.059] up to the proposed maximum use level in feed as flavourings. The additives should be considered as irritant to skin and eyes and the respiratory tract, and as dermal and respiratory sensitisers. The use of 2-acetylfuran [13.054] and 2-pentylfuran [13.059] as flavours in animal feed was not expected to pose a risk for the environment. Since the compounds under assessment are used in food as flavourings and their function in feed is essentially the same as that in food, no further demonstration of efficacy was considered necessary.

Synthesis of N–C Fused Bicyclic 1,3,5-Triazinane-2,4-dione Derivatives from Saturated Ring-Fused Urazoles

AbstractA synthesis of novel bicyclic 1,3,5-triazinane-2,4-diones has been accomplished through base-promoted fragmentation followed by cyclization. Various saturated ring-fused bicyclic urazoles were prepared by two complementary methods: by the reaction of N,N′-bis(2-chloroethyl)urazoles with various nucleophiles or by using 4-substituted urazoles and dibromoalkanes. Treatment of these symmetrical urazole derivatives with LDA at –78 °C to 25 °C resulted in fragmentation of the N–N bond to form an imine that underwent intramolecular cyclization, resulting in moderate yields of nonsymmetric heterocycle derivatives with an asymmetric (racemic) center and various ring sizes. The utility of these transformations was extended to syntheses of a tricyclic system and bicyclic systems containing additional heteroatoms.

Signatures of Room-Temperature Quantum Interference in Molecular Junctions.

ConspectusDuring the past decade or so, research groups around the globe have sought to answer the question: "How does electricity flow through single molecules?" In seeking the answer to this question, a series of joint theory and experimental studies have demonstrated that electrons passing through single-molecule junctions exhibit exquisite quantum interference (QI) effects, which have no classical analogues in conventional circuits. These signatures of QI appear even at room temperature and can be described by simple quantum circuit rules and a rather intuitive magic ratio theory. The latter describes the effect of varying the connectivity of electrodes to a molecular core and how electrical conductance can be controlled by the addition of heteroatoms to molecular cores. The former describes how individual moieties contribute to the overall conductance of a molecule and how the overall conductance can change when the connectivities between different moieties are varied. Related circuit rules have been derived and demonstrated, which describe the effects of connectivity on Seebeck coefficients of organic molecules. This simplicity arises because when a molecule is placed between two electrodes, charge transfer between the molecule and electrodes causes the molecular energy levels to adjust, such that the Fermi energy (EF) of the electrodes lies within the energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital. Consequently, when electrons of energy EF pass through a molecule, their phase is protected and transport takes place via phase-coherent tunneling. Remarkably, these effects have been scaled up to self-assembled monolayers of molecules, thereby creating two-dimensional materials, whose room temperature transport properties are controlled by QI. This leads to new molecular design strategies for increasing the on/off conductance ratio of molecular switches and to improving the performance of organic thermoelectric materials. In particular, destructive quantum interference has been shown to improve the Seebeck coefficient of organic molecules and increase their on/off ratio under the influence of electrochemical gating. The aim of this Account is to introduce the novice reader to these signatures of QI in molecules, many of which have been identified in joint studies involving our theory group in Lancaster University and experimental group in Bern University.

A novel isocyanide/Ag2CO3-promoted addition of heteroatoms to alkynes under mild conditions

A silver(i) isocyanide complex was used as a catalyst to activate alkynes rapidly and carry out intramolecular electrophilic addition of alkynes to synthesize various different-sized rings in excellent yields under mild conditions.

Electrochemical Features of Low Pt Electrocatalysts Deposited Over Doped Carbon Nanotubes

Carbon nanotubes (CNT) are being utilized in PEM fuel cells electrocatalysts, due to their physical and chemical characteristics. Diverse studies have been reported on their use as support of Pt to improve the metal particles dispersion, as well as to provide a higher mechanical and electrochemical stability. As it is known, the development of highly efficient electrocatalysts with low platinum loading is crucial in order to achieve the massive application of PEM fuel cells. The electronic properties of CNT can still be improved, since they play an important role in the electrochemical performance. Recently, it has been reported that the incorporation of heteroatoms to the CNT structure (i.e. N, B, F, S, Si, etc.) can change positively their properties such as stability. Also, it is expected the dopant to have an effect on the Pt nanoparticles dispersion, affecting the electrochemical activity. The bonds form with the heteroatoms, as well as their concentration within the volumetric structure of the carbon, generally influence the properties of the material and change its structural geometry. The morphology and characteristics of the materials differ for each type of doping. For example, N-doping creates hollow sections separated by one or a few graphitic layers, while S-doping produces branched morphologies. Hence, it is of great interest to take advantage of the defects created by addition of heteroatoms to the CNT structure. In this research work low-Pt over doped CNT systems were obtained and evaluated. The doped carbon nanotubes were synthesized using a modified chemical vapor deposition (M-CVD) system in a high-temperature argon flow furnace. Toluene was used as a carbon source, ferrocene as a catalytic agent, adding different precursors of the heteroatoms. Low Pt loadings were deposited over pristine and doped CNT using a colloidal methodology. The structure of the obtained materials was analyzed by X-ray diffraction and Raman spectroscopy. Also, energy dispersive X-ray spectroscopy and scanning electron microscopy studies were done in order to obtain the chemical properties and the morphology. Electrochemical impedance spectroscopy (EIS) studies were done in the presence of 0.5 M H2SO4 and at an amplitude of 10 mV at different potentials vs AgAgCl (KCl sat), within a frequency range of 100 mHz to 100 KHz, in order to analyze the conductivity of the doped CNT used as support. In addition, electrochemical evaluation was performed by cyclic and lineal voltammetry in a conventional three electrode cell, in acidic electrolyte and using Ag/AgCl (KCl sat) as reference electrode, and Pt wire as a counter. In addition, in order to compare the same analyzes were carried out on reference materials such as vulcan carbon and nanotubes without dopant (pristine). The results of an extensive physical and chemical characterization confirmed the growth of doped CNT with different heteroatoms. It was possible to establish that the morphological characteristics of the obtained doped carbon nanotubes varied, depending on the dopant. Differences on the diameter, length, as well as the graphitization degree of the structure were found. Also, it was possible to confirm the low Pt loading over the supports. The evaluation of the electrochemical properties yielded interesting differences. Hence, results obtained of low-Pt loading over doped CNT electrochemical systems, will be presented and discussed at the conference.Acknowledgments: We thank the Fund "CONACyT-SENER-Sustainability Energy" (No. 254667) for the support provided for the development of this project.