The reaction between [2-(MeOCH₂)C₆H₄]MgBr and SnCl₄ yielded the highly crowded stannanes [2-(MeOCH₂)C₆H₄)]₃SnBr (1), [2-(MeOCH₂)C₆H₄)]₂SnX₂ (2, X₂=Br₂ (a) and BrCl (b)), together with trace amounts of the distannane [{2-(MeOCH₂)C₆H₄}₃Sn]₂ (3), and a distannoxane [2-{(MeOCH₂)C₆H₄)}₂SnBr]₂O (4). The new compounds 1–4 were characterized by single crystal X-ray crystallography showing that 1, 2a and 4 exhibit significant Sn…O secondary bonding interactions that persist in solution for 1.

Abstract

The reaction between the Grignard reagent formed from Mg and 2-bromobenzylmethyl ether and SnCl₄ produced four products: [2-(MeOCH₂)C₆H₄]₃SnBr (1), [2-(MeOCH₂)C₆H₄]₂SnX₂ (2, X₂=Br₂ (a) and BrCl (b)), [{2-(MeOCH₂)C₆H₄}₃Sn]₂ (3), and [{2-(MeOCH₂)C₆H₄}₂SnBr]₂O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O−Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2a the resulting hexacoordinate structure exhibits two very short O−Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O−Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn−O−Sn bond angle of 148.1(2)° which is larger compared to other distannoxane structures. The intermolecular interactions between Sn−O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms. The various ¹¹⁹Sn_, ¹³C and ¹H NMR spectra are in accord with their structural analysis for 1 and 2, and in the solid state ¹³C NMR spectrum of 1 the dangling methylene group is observable whereas is solution there is a rapid dynamic equilibrium resulting in a single resonance for all methylene groups.

A CISC@S/CNTs graded composite electrode with C−O, C−N, and C−S bonds stabilization and CNTs coating protection was prepared using the organic waste chestnut inner shell. It can effectively suppress the shuttling effect of sulfur and polysulfide ions, enhance the charge and electrolyte transfer kinetics, and provide an effective way to commercialize lithium-sulfur batteries.

Abstract

The shuttle effect of lithium-sulfur (Li−S) batteries and the poor conductivity of sulfur (S) and lithium polysulfide severely limit their practical applications. Currently, compounding carbon materials with S is one of the effective ways to solve this problem. Therefore, green, low-cost chestnut inner shell biochar (CISC) with graded porous structure was used as the S carrier in this experiment, and carbon nanotubes (CNTs) coating was employed as the S protective layer to improve the electrical conductivity and inhibit the shuttle effect. The results showed that the CISC prepared in this experiment had a relatively high specific surface area (1135.11 m² g⁻¹), and the S loading rate was as high as 65.72 %. The graded porous structure and high specific surface area of CISC can increase the loading rate of S and thus increase the battery capacity. Meanwhile, the naturally contained O and N elements can improve the chemisorption of S. The initial discharge capacity of the CISC@S/CNTs battery at 0.1 C is 967.3 mAh g⁻¹, and the capacity retention rate is 74.3 % after 500 cycles. The unique composite structure improves the battery‘s electrical conductivity, reduces the dissolution of polysulfides, and enhances the battery cycle stability.

Chiral carbon dots can be widely used in various fields such as chiral recognition, chiral catalysis and biomedicine because of their unique optical properties, low toxicity and good biocompatibility. In addition, chiral carbon dots with circularly polarized luminescence (CPL) can be synthesized, thus broadening the prospects of chiral carbon dots applications. Since the research on chiral carbon dots is still in its infancy, this paper reviews the chiral origin, formation mechanism, chiral evolution, synthesis and emerging applications of chiral carbon dots, with a special focus on chiral carbon dots with CPL activity. It is hoped that it will provide some reference to solve the current problems faced by chiral carbon dots. Finally, the opportunities and challenges of the current research on chiral carbon dots are described, and their future development trends have also been prospected.