Chalcogen Chemistry Research Articles

Enabling Argyrodite Sulfides as Superb Solid‐State Electrolyte with Remarkable Interfacial Stability Against Electrodes

While argyrodite sulfides are getting more and more attention as highly promising solid‐state electrolytes (SSEs) for solid batteries, they also suffer from the typical sulfide setbacks such as poor electrochemical compatibility with Li anode and high‐voltage cathodes and serious sensitivity to humid air, which hinders their practical applications. Herein, we have devised an effective strategy to overcome these challenging shortcomings through modification of chalcogen chemistry under the guidance of theoretical modeling. The resultant Li6.25PS4O1.25Cl0.75 delivered excellent electrochemical compatibility with both pure Li anode and high‐voltage LiCoO2 cathode, without compromising the superb ionic conductivity of the pristine sulfide. Furthermore, the current SSE also exhibited highly improved stability to oxygen and humidity, with further advantage being more insulating to electrons. The remarkably enhanced compatibility with electrodes is attributed to in situ formation of helpful electrolyte–electrode interphases. The formation of in situ anode–electrolyte interphase (AEI) enabled stable Li plating/stripping in the Li|Li6.25PS4O1.25Cl0.75|Li symmetric cells at a high current density up to 1 mA cm−2 over 200 h and 2 mA cm−2 for another 100 h. The in situ amorphous nano‐film cathode–electrolyte interphase (CEI) facilitated protection of the SSE from decomposition at elevated voltage. Consequently, the synergistic effect of AEI and CEI helped the LiCoO2|Li6.25PS4O1.25Cl0.75|Li full‐battery cell to achieve markedly better cycling stability than that using the pristine Li6PS5Cl as SSE, at a high area loading of the active cathode material (4 mg cm−2) in type‐2032 coin cells. This work is to add a desirable SSE in the argyrodite sulfide family, so that high‐performance solid battery cells could be fabricated without the usual need of strict control of the ambient atmosphere.

Miklós Bodanszky Award Lecture: Selective chalcogen chemistry to study protein science.

In recent decades, chemical protein synthesis and the development of chemoselective reactions-including ligation reactions-have led to significant breakthroughs in protein science. Among them are a better understanding of protein structure-function relationships, the study of protein posttranslational modifications, exploration of protein design, unnatural amino acid incorporation, and the study of therapeutic proteins and protein folding. Chalcogen chemistry, especially that of sulfur and selenium, is quite rich, and we have witnessed continuous progress in this field in recent years. In this short review, we will instead summarize three stories that we have recently presented on chalcogen chemistry and its impact on protein science, which was presented in the Miklós Bodanszky Award Lecture at the 35th European Peptide Society Meeting in Dublin, Ireland, 26 August 2018.

Selenium- and tellurium-containing fluorescent molecular probes for the detection of biologically important analytes.

As scientists in recent decades have discovered, selenium is an important trace element in life. The element is now known to play an important role in biology as an enzymatic antioxidant. In this case, it sits at the active site and converts biological hydrogen peroxides to water. Mimicking this reaction, chemists have synthesized several organoselenium compounds that undergo redox transformations. As such, these types of compounds are important in the future of both medicinal and materials chemistry. One main challenge for organochalcogen chemists has been to synthesize molecular probes that are soluble in water where a selenium or tellurium center can best modify electronics of the molecule based on a chemical oxidation or reduction event. In this Account, we discuss chemists' recent efforts to create chalcogen-based chemosensors through synthetic means and current photophysical understanding. Our work has focused on small chromophoric or fluorophoric molecules, in which we incorporate discrete organochalcogen atoms (e.g., R-Se-R, R-Te-R) in predesigned sites. These synthetic molecules, involving rational synthetic pathways, allow us to chemoselectively oxidize compounds and to study the level of analyte selectivity by way of their optical responses. All the reports we discussed here deal with well-defined and small synthetic molecular systems. With a large number of reports published over the last few years, many have notably originated from the laboratory of K. Han (P. R. China). This growing body of research has given chemists new ideas for the previously untenable reversible reactive oxygen species detection. While reversibility of the probe is technically important from the stand-point of the chalcogen center, facile regenerability of the probe using a secondary analyte to recover the initial probe is a very promising avenue. This is because (bio)chalcogen chemistry is extremely rich and bioinspired and continues to yield important developments across many scientific fields. Organochalcogen (R-E-R) chemistry in such chemical recognition and supramolecular pursuits is a fundamental tool to allow chemists to explore stable organic-based probe modalities of interest to develop better spectroscopic tools for (neuro)biological applications. Chalcogen donor sites also provide sites where metals can coordinate, and facile oxidation may extend to the sulfone analogues (R-EO2-R) or beyond. Consequently, chemists can then make use of reliable reversible chemical probing platforms based on the chemical redox properties valence state switching principally from 2 to 4 (and back to 2) of selenium and tellurium atoms. The main organic molecular skeletons have involved chemical frames including boron-dipyrromethene (BODIPY) systems, extended cyanine groups, naphthalimide, rhodamine, and fluorescein cores, and isoselenazolone, pyrene, coumarin, benzoselenadiazole, and selenoguanine systems. Our group has tested many such molecular probe systems in cellular milieu and under a series of conditions and competitive environments. We have found that the most important analytes have been reactive oxygen species (ROS) such as superoxide and hypochlorite. Reactive nitrogen species (RNS) such as peroxynitrite are also potential targets. In addition, we have also considered Fenton chemistry systems. Our research and that of others shows that the action of ROS is often reversible with H2S or biothiols such as glutathione (GSH). We have also found that a second class of analytes are the thiols (RSH), in particular, biothiols. Here, the target group might involve an R-Se-Se-R group. The study of analytes also extends to metal ions, for example, Hg(2+), and anions such as fluoride (F(-)), and we have developed NIR-based systems as well. These work through various photomechanisms, including photoinduced electron transfer (PET), twisted internal charge transfer (TICT), and internal charge transfer (ICT). The growing understanding of this class of probe suggests that there is much room for creative thinking regarding modular designs or unexpected organic chemical synthesis designs, interplay between analytes, new analyte selectivity, biological targeting, and chemical switching, which can also serve to further the neurological probing and molecular logic gating frontiers.

Common Aspects of Boronic Acids and Chalcogen Chemistry

This review presents the organic compounds and reactions in which boronic acids are featured together with chalcogens. Structurally varied sulfur-, selenium- and tellurium-containing boronic acids are described. Survey of their preparation methods as well as the scope of applications in organic, medicinal, analytical and supramolecular chemistry is provided. Reactions involving both the boronic acids and chalcogen-containing compounds are discussed, with emphasis placed on the role of the chalcogen atom in these transformations. Keywords: Boron, Boronic acid, Chalcogen, Cross-coupling, Heteroatoms, Selenium, Sulfur, Tellurium, phenylboronic, boronic

Hybrid passivated colloidal quantum dot solids

Colloidal quantum dot (CQD) films allow large-area solution processing and bandgap tuning through the quantum size effect. However, the high ratio of surface area to volume makes CQD films prone to high trap state densities if surfaces are imperfectly passivated, promoting recombination of charge carriers that is detrimental to device performance. Recent advances have replaced the long insulating ligands that enable colloidal stability following synthesis with shorter organic linkers or halide anions, leading to improved passivation and higher packing densities. Although this substitution has been performed using solid-state ligand exchange, a solution-based approach is preferable because it enables increased control over the balance of charges on the surface of the quantum dot, which is essential for eliminating midgap trap states. Furthermore, the solution-based approach leverages recent progress in metal:chalcogen chemistry in the liquid phase. Here, we quantify the density of midgap trap states in CQD solids and show that the performance of CQD-based photovoltaics is now limited by electron-hole recombination due to these states. Next, using density functional theory and optoelectronic device modelling, we show that to improve this performance it is essential to bind a suitable ligand to each potential trap site on the surface of the quantum dot. We then develop a robust hybrid passivation scheme that involves introducing halide anions during the end stages of the synthesis process, which can passivate trap sites that are inaccessible to much larger organic ligands. An organic crosslinking strategy is then used to form the film. Finally, we use our hybrid passivated CQD solid to fabricate a solar cell with a certified efficiency of 7.0%, which is a record for a CQD photovoltaic device.

Oxygen, Sulfur, Selenium and Tellurium

AbstractFor Abstract see ChemInform Abstract in Full Text.

8 Oxygen, sulfur, selenium and tellurium

This chapter reviews original highlights in the chemistry of the Group 16 elements reported during 2003. The bulk of the review focuses on the chemistry/interaction of the chalcogens with other p-block elements. Due to the vast abundance and diversity of research into chalcogen chemistry, the report has been limited to materials with discrete molecular structure, either as novel products or reagents, or obtained by new synthetic strategies. The most important advances in 2003 include the isolation of hitherto unknown functionalities or bonding modes, unusual, unique or unexpected structures and a fascinating ferromagnet.

New Oxonium Halochalcogenates(IV) and -(II)

The reported novel compounds [H3O·(dibenzo-18-crown-6)][Te2Br9], [H5O2][Te2Cl9]·2C4H8O2 and [H5O2·(bis-dibromo-dibenzo-24-crown-8)]2[Se3Br8] highlight the large structural and chemical variety of halogen chalcogen chemistry. Both [Te2X9]− anions (X = Cl, Br) consist of one square pyramidal TeX5 fragment connected to a TeX6 octahedron by a common edge. The linear [Se3Br8]2− anion is built by three square planar SeBr4-fragments. The three counterions offer a convenient possibility for controlled synthesis of supramolecular oxonium systems.

Methods in chalcogen chemistry : V. A new reagent for the synthesis of aromatic tellurium compounds

It has been discovered that the combination of tellurium tetrachloride with more than one molar equivalent of aluminium chloride constitute an efficient reagent for the introduction of tellurium into aromatic molecules. Kinetics control of the reaction with benzene (a substance inert to TeCl 4 alone) selectively yielded the products of successive substitution on tellurium as follows: diphenyl ditelluride (via reductive workup from phenyltellurium trichloride), diphenyltellurium dichloride and triphenyltelluronium chloride after evolution of 1,2 and 3 equivalent HCl, respectively. Extension of this simple reaction to the preparation of numerous other aromatic tellurium compounds appears feasible.

Chalcogen chemistry. VII. Preparation of compounds containing the phenyldibromoselenate(II) ion

Chalcogen chemistry. VII. Preparation of compounds containing the phenyldibromoselenate(II) ion

Chalcogen chemistry. Part VIII. Complexes of arylselenium and aryltellurium trichlorides with pyridine, 4-picoline, and 4-picoline N-oxide

Arylselenium and aryltellurium trichlorides form crystalline 1 : 1 adducts with pyridine (py), 4-picoline (pic), and picoline N-oxide (pico). The selenium complexes are pale yellow and moderately sensitive to atmospheric moisture while the tellurium analogues are colourless and fairly stable to moist air. In contrast to p-MeOC6H4TeCl3-(tmtu)(tmtu = tetramethylthiourea) which is molecular in solution land a weak electrolyte, ArTeCl3(py) and ArTeCl3(pic) behave as 1 : 1 electrolytes in solution. The behaviour of ArSeCl3(py), ArSeCl3(pic), and ArTeCl3-(pico) in solution is intermediate to the above. It is likely that square pyramidal ArMCl3(:B) molecules exist in the solid state, but available i.r. data do not allow an unambiguous conclusion in this regard.

Chalcogen chemistry. V. Complexes of organotellurium trihalides with tetramethylthiourea

Chalcogen chemistry. V. Complexes of organotellurium trihalides with tetramethylthiourea