Solution-Based,Anion-Doping of Li4Ti5O12 Nanoflowers for Lithium-Ion Battery Applications

Solution-based, anionic doping represents a convenient strategy with which to improve upon the conductivity of candidate anode materials such as Li₄Ti₅O₁₂ (LTO). As such, novel synthetic hydrothermally-inspired protocols have primarily been devised herein, aimed at the large-scale production of unique halogen-doped, micron-scale, three-dimensional, hierarchical LTO flower-like motifs. Although fluorine (F) doping has been explored, the use of chlorine (Cl) dopants is the primary focus here. Several experimental variables, such as dopant amount, lithium hydroxide concentration, and titanium butoxide purity, were probed and perfected. Furthermore, the Cl doping process did not damage the intrinsic LTO morphology. The analysis, based on interpreting a compilation of SEM, XRD, XPS, and TEM-EDS results, was used to determine an optimized dopant concentration of Cl. Electrochemical tests demonstrated an increased capacity via cycling of 12 % for a Cl-doped sample as compared with pristine LTO. Moreover, the Cl-doped LTO sample described in this study exhibited the highest discharge capacity yet reported at an observed rate of 2C for this material at 143mAh g⁻¹. Overall, these data suggest that the Cl dopant likely enhances not only the ion transport capabilities, but also the overall electrical conductivity of our as-prepared structures. To help explain these favorable findings, theoretical DFT calculations were used to postulate that the electronic conductivity and Li diffusion were likely improved by the presence of increased Ti³⁺ ion concentration coupled with widening of the Li migration channel.     

Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

Pincer complexes featuring readily tunable tridentate ligand frameworks comprise one of the most actively studied classes of organometallic and metal–organic compounds and find extensive use in catalysis, organic synthesis, materials science, and other fields of chemistry and allied disciplines. Currently growing attention is devoted to non‐classical ligand scaffolds, such as functionalized carboxamides, which offer multiple options for directed structural modifications. In this study, the reactions of (methylsulfanyl)acetyl and propanoyl chlorides with 2‐(aminomethyl)pyridine, 2‐(2‐aminoethyl)pyridine, 8‐aminoquinoline and 2‐(diphenylthiophosphoryl)aniline afford a series of new pincer‐type ligands based on functionalized carboxamides. The ligands obtained readily undergo direct cyclopalladation under the action of PdCl₂(NCPh)₂ in dichloromethane at room temperature, resulting in Pd(II) pincer complexes with N,N,S‐ and S,N,S‐donor sets. Importantly, some of the cyclopalladated derivatives can also be produced efficiently under solvent‐free conditions according to the approach recently developed by our group. The complexes obtained have been tested for cytotoxicity against several human cancer cell lines and catalytic activity in the model Suzuki reaction. The results have been compared to those for the related Pd(II) pincer complexes to define the main structure–activity relationships and to outline the most promising structures for further investigations.     

Interplay of thermochemistry and Structural Chemistry,the journal (volume 29, 2018, issues 3–4) and the discipline

The contents of issues 3 and 4 of Structural Chemistry from the calendar year 2018 are summarized in the present review. A brief thermochemical commentary and recommendations for future research have been added to the summary of each paper.

     

Crystal structures of two isostructural compounds: a second polymorph of dipotassium hydrogen citrate,K2HC6H5O7, and potassium rubidium hydrogen citrate,KRbHC6H5O7

The crystal structures of a new polymorph of dipotassium hydrogen citrate, 2K⁺·HC₆H₅O₇^2?, and potassium rubidium hydrogen citrate, K⁺·Rb⁺·HC₆H₅O₇^2?, have been solved and refined using laboratory powder X‐ray diffraction and optimized using density functional techniques. In the new polymorph of the dipotassium salt, KO₇ and KO₈ coordination polyhedra share corners and edges to form a three‐dimensional framework with channels parallel to the a axis and [111]. The hydrophobic methylene groups face each other in the channels. The un‐ionized carboxylic acid group forms a strong charge‐assisted hydrogen bond to the central ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to a different central carboxylate group. In the potassium rubidium salt, the K⁺ and Rb⁺ cations are disordered over two sites, in approximately 0.72:0.28 and 0.28:0.72 ratios. KO₈ and RbO₉ coordination polyhedra share corners and edges to form a three‐dimensional framework with channels parallel to the a axis. The un‐ionized carboxylic acid group forms a strong charge‐assisted hydrogen bond to an ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to the central carboxylate group. Density functional theory (DFT) calculations on the ordered cation structures suggest that interchange of K⁺ and Rb⁺ at the two cation sites changes the energy insignificantly.     

Direct Synthesis of Anatase Films with ~100% (001) Facets and [001] Preferred Orientation

Anatase films exhibiting ~100% (001) reactive facets at the surface were grown hydrothermally on gold substrate from a homogeneous solution of TiF(4) and NaF. In addition to NaF, it was found that TiO(2) films with very similar properties could be prepared with the fluoride salts LiF, CsF, HF, NH(4)F, and N(CH(2)CH(3))(4)F. The polycrystalline anatase films are continuous, approximately 1 μm thick, and evenly coat the substrate. The surface grain size is ~400 nm. Grazing angle XRD measurements show that the films exhibit a high degree of preferred orientation with the c-axis normal to the substrate surface. SEM images reveal that the grains span the thickness of the films. Annealing the films at 500 °C removes fluorine and causes crystallites within the grains to restructure as shown by SEM, XRD, and Raman spectroscopy. Supported anatase films grown from this one-pot method may serve as oxidative photocatalysts and electrodes for photoelectrochemical applications such as solar cells and hydrogen evolution.     

Optimization and validation of organochlorine compounds in adipose tissue by SPE‐gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C₁₈‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP₁₈ SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C₁₈‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of amidoammonium calix[4]resorcinarenes on methyl orange protolytic equilibrium: supramolecular indicator systems

Here, we report on the study of cationic amidoammonium calix[4]resorcinarenes 1–5 of various lipophilicity capable of binding acid–base indicator methyl orange (MO). We identified the contributions of macrocycle aggregation and conformational mobility in the binding of MO. The effective pK_a values of bound MO systematically decrease as the size and the packing density of the aggregates increase with an increase in calixresorcinarene lipophilicity. Consideration of a series of macrocycles clearly shows that large aggregates form most stable complexes, binding guests not on individual level but as aggregates. It was found that the most stable MO complex with 5 is formed due to electrostatic binding with ammonium groups of the macrocycle and incapsulation of MO in a hydrophobic layer of the aggregates. We have shown that competitive binding of MO and cationic surfactants by aggregates of 5 is suitable for visual/spectrophotometric detection of colourless anionic substrates.