A Rapid Solid-phase Synthesis to Soluble Oligothiophene Molecular Wires

A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity.     

Potentiometric determination of saccharin in dietary products using mercurous nitrate as titrant

A rapid, precise and low cost method for saccharin determination in dietary products is proposed. Saccharin in several samples is potentiometrically titrated with mercurous nitrate solution using a silver wire coated with a metallic mercury film as the working electrode, and the end point was found using a Gran's plot. The detection limit of sodium saccharin was 0.5 mg/ml and the best pH range was from 2.0 to 3.5. Sucrose, glucose, aspartame, sodium cyclamate, sorbitol, fructose, benzoic acid, salicylic acid and lactose do not interfere even in significant amounts. The interference due to the presence of chloride and/or phosphate ions can be eliminated by previous solvent extraction of this sweetener. Recovery of saccharin from various dietary products gave from 95.2 to 103.2% of the label claim.     

Biomass-derived dibasic acids to diesters with inorganic ligand-supported catalyst: synthesis,optimization, characterization

Research on Chemical Intermediates - Several attempts have been made to obtain aliphatic dicarboxylic diesters from esterification reaction to develop the biomass-derived platform molecules and...     

双金属MOFs及其衍生物在电化学储能领域中的应用

双金属有机骨架及其衍生物一方面具有单金属有机骨架孔道丰富、比表面积大、结构可调、活性位点丰富等特点,另一方面具有双组分与多孔结构之间的协同效应,因而受到了研究人员的密切关注,在储能、催化、分离、传感器、医药、气体存储等领域广泛应用。和单金属MOFs类似,双金属MOFs的导电性不佳、结构易坍塌,这极大地限制了其在电化学储能中的应用。通过对双金属MOFs进行热处理,易得到分布均匀的多孔碳@双金属氧化物/硫化物/磷化物/硒化物等衍生物,不仅保持了独特的多孔结构,而且提高了材料的导电性和结构稳定性,有利于在电化学储能中的应用。因此,本文从双金属MOFs中的主要金属离子入手,综述了双金属MOFs及其衍生物用于超级电容器、锂离子电池、钠离子电池、金属空气电池等电化学储能器件的最新应用进展。在此基础上,总结了双金属MOFs在电化学储能应用中的优势,并对其制备、作用机理和后处理研究提出了建议。     

[RhIII(Cp*)]‐Catalyzed ortho‐Selective Direct C(sp2)H Bond Amidation/Amination of Benzoic Acids by N‐Chlorocarbamates and N‐Chloromorpholines. A Versatile Synthesis of Functionalized Anthranilic Acids

A Rh^III‐catalyzed direct ortho‐C?H amidation/amination of benzoic acids with N‐chlorocarbamates/N‐chloromorpholines was achieved, giving anthranilic acids in up to 85 % yields with excellent ortho‐selectivity and functional‐group tolerance. Successful benzoic acid aminations were achieved with carbamates bearing various amide groups including NHCO₂Me, NHCbz, and NHTroc (Cbz=carbobenzyloxy; Troc=trichloroethylchloroformate), as well as secondary amines, such as morpholines, piperizines, and piperidines, furnishing highly functionalized anthranilic acids. A stoichiometric reaction of a cyclometallated rhodium(III) complex of benzo[h]quinoline with a silver salt of N‐chlorocarbamate afforded an amido–rhodium(III) complex, which was isolated and structurally characterized by X‐ray crystallography. This finding confirmed that the C?N bond formation results from the cross‐coupling of N‐chlorocarbamate with the aryl–rhodium(III) complex. Yet, the mechanistic details regarding the C?N bond formation remain unclear; pathways involving 1,2‐aryl migration and rhodium(V)– nitrene are plausible.     

Electrochemical Conversion of CO2 to Syngas with Controllable CO/H2 Ratios over Co and Ni Single‐Atom Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) to yield synthesis gas (syngas, CO and H₂) has been considered as a promising method to realize the net reduction in CO₂ emission. However, it is challenging to balance the CO₂RR activity and the CO/H₂ ratio. To address this issue, nitrogen‐doped carbon supported single‐atom catalysts are designed as electrocatalysts to produce syngas from CO₂RR. While Co and Ni single‐atom catalysts are selective in producing H₂ and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm^?2) with CO/H₂ ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single‐atom configurations for the H₂ and CO evolution. The results present a useful case on how non‐precious transition metal species can maintain high CO₂RR activity with tunable CO/H₂ ratios.     

Regioselective,Asymmetric Formal Hydroamination of Unactivated Internal Alkenes

We report the regioselective and enantioselective formal hydroamination of unsymmetrical internal alkenes catalyzed by a copper catalyst ligated by DTBM‐SEGPHOS. The regioselectivity of the reaction is controlled by the electronic effects of ether, ester, and sulfonamide groups in the homoallylic position. The observed selectivity underscores the influence of inductive effects of remote substituents on the selectivity of catalytic processes occurring at hydrocarbyl groups, and the method provides direct access to various 1,3‐aminoalcohol derivatives with high enantioselectivity.     

Radiochemical scheme for the quantitative isolation and gamma-spectrometric determination of La,Ga, Hf and Sc in neutron activation analysis of refractory materials

A new radiochemical scheme for the quantitative isolation of Ga, Sc, Hf and La, based on ion exchange and extraction chromatography, was devised, Ga and Sc were selectively retained on a Dowex 50WX2 [H⁺] column from 10 M HBr at 50°C. Ga was then eluted with ethyl acetate 0.25M in HBr, and scandium with 4M HBr. Hf was separated from 10M HBr at 75°C on a Kel-F column impregnated with tri-n-octylphosphine oxide (TOPO). The lanthamm fraction, after evaporation to dryness, was purified by ion-exchange chromatography in the system: Dowex 50WX8 [H⁺]−HCl. The effect of accompanying elements, and also the differences in the mechanism of uptake by the resin of various elements from concentrated HBr solution are briefly discussed. The scheme has been used for the determination of these four elements in refractory materials by activation analysis. As this procedure assured practically quantitative isolation of Ga, Sc, Hf and La, the addition of carriers and determination of chemical yield were unnecessary. The radiochemical purities of the respective fractions were as a rule high, and the measurements were performed by NaI(Tl) spectrometry. The detection limits were of the order of fractions of ppm, and could be considerably improved if necessary by increasing the counting time and sample weight.