Guapsidial A and Guadials B and C: Three New Meroterpenoids with Unusual Skeletons from the Leaves of Psidium guajava

A novel sesquiterpene‐based Psidium meroterpenoid, possessing an unusual coupling pattern, and two new monoterpene‐based meroterpenoids with unprecedented skeletons were isolated from the leaves of Psidium guajava. Their structures and absolute configurations were elucidated by spectroscopic, X‐ray diffraction, and computational methods. The plausible biosynthetic pathway of these meroterpenoids as well as their cytotoxicities toward HepG2 and HepG2/ADM cells were also discussed.     

Highly Segregated Lamello‐Columnar Mesophase Organizations and Fast Charge Carrier Mobility in New Discotic Donor–Acceptor Triads

Four new donor–acceptor triads (D–A–D) based on discotic and arylene mesogens have been synthesized by using Sonogashira coupling and cyclization reactions. This family of triads consists of two side‐on pending triphenylene mesogens, acting as the electron‐donating groups (D), laterally connected through short lipophilic spacers to a central perylenediimide (PI), benzo[ghi]perylenediimide (BI), or coronenediimide (CI) molecular unit, respectively, playing the role of the electron acceptor (A). All D–A–D triads self‐organize to form a lamello‐columnar oblique mesophase, with a highly segregated donor–acceptor (D–A) heterojunction organization, consequent to efficient molecular self‐sorting. The structure consists in the regular alternation of two disrupted rows of triphenylene columns and a continuous row of diimine species. High‐resolution STM images demonstrate that PI‐TP2 forms stable 2D self‐assembly nanostructures with some various degrees of regularity, whereas the other triads do not self‐organize into ordered architectures. The electron‐transport mobility of CI‐TP2, measured by time‐of‐flight at 200 °C in the mesophase, is one order of magnitude higher than the hole mobility. By means of this specific molecular designing idea, we realized and demonstrated for the first time the so‐called p–n heterojunction at the molecular level in which the electron‐rich triphenylene columns act as the hole transient pathways, and the coronenediimide stacks form the electron‐transport channels.     

On the Extreme Oxidation States of Iridium

It has recently been suggested that the oxidation states of Ir run from the putative ?III in the synthesized solid Na₃[Ir(CO)₃] to the well‐documented +IX in the species IrO₄⁺. Furthermore, [Ir(CO)₃]^3? was identified as an 18‐electron species. A closer DFT study now finds support for this picture: The orbitals spanned by the 6s,6p,5d orbitals of the iridium are all occupied. Although some have considerable ligand character, the deviations from 18 e leave the orbital symmetries unchanged. The isoelectronic systems from Os^?IV to Au^?I behave similarly, suggesting further possible species. To paraphrase Richard P. Feynmann “there is plenty of room at the bottom”.     

Monodisperse AgSbS2 Nanocrystals: Size‐Control Strategy,Large‐Scale Synthesis,and Photoelectrochemistry

We report an efficient approach to the synthesis of AgSbS₂ nanocrystals (NCs) by colloidal chemistry. The size of the AgSbS₂ NCs can be tuned from 5.3 to 58.3 nm with narrow size distributions by selection of appropriate precursors and fine control of the experimental conditions. Over 15 g of high‐quality AgSbS₂ NCs can be obtained from one single reaction, indicative of the up‐scalability of the present synthesis. The resulting NCs display strong absorptions in the visible‐to‐NIR range and exceptional air stability. The photoelectrochemical measurements indicate that, although the pristine AgSbS₂ NC electrodes generate a cathodic photocurrent with a relatively small photocurrent density and poor stability, both of them can be significantly improved subject to CdS surface modification, showing promise in solar energy conversion applications.     

Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li‐Ion Storage

MoS₂ nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100–150 nm in diameter and constructed from MoS₂ nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m² g^?1. The MoS₂@C nanofibers are treated at 450 °C in H₂ and comparison samples annealed at 800 °C in N₂. The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H₂ contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H₂ deliver an extraordinary capacity of 1022 mA h g^?1 and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g^?1, as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS₂@C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS₂, and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass‐ and charge‐transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge‐transfer reaction and the diffusivity of the MoS₂@C mesoporous nanofibers. It is believed that the integration of MoS₂ nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li‐ion battery market.     

Selective Probing of Gaseous Ammonia Using Red‐Emitting Carbon Dots Based on an Interfacial Response Mechanism

Solid‐state fluorescence sensing is one of the most appealing detection techniques because of its simplicity and convenience in practical operation. Herein, we report the development of a red‐emitting carbon dots (RCDs)‐based material as a solid‐state fluorescence sensor for the selective probing of gaseous ammonia. The RCDs were prepared by a low‐cost, one‐step carbonization method using sugar cane bagasse as the carbon precursor. The pristine RCDs were then directly coated on polyvinylidene fluoride membrane to produce a new fluorescence sensor capable of selectively distinguishing toxic gaseous ammonia from other analyte vapors through sensitive fluorescence quenching with a low detection limit. More importantly, the interfacial response mechanism occurring on the surface of the RCDs has been studied by X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, and Raman measurements. The results indicate that fluorescence quenching in the RCDs might result from ammonia‐induced Michael addition through insertion of N into the C?C group and deprotonation of the carboxyl group. To the best of our knowledge, this is the first report that provides clear insight into the mechanism of surface chemistry on CDs in the solid state.     

超分子水凝胶作为胰岛素缓释体系的研究

利用α-环糊精(α-CD)与含有聚乙二醇(PEG)链段的聚合物Pluronic F127的超分子作用制备水凝胶.该物理交联水凝胶的交联点包括α-CD与PEG链包合物堆积形成的微晶区和聚合物疏水链段聚集区.优化水凝胶组分,得到具有较低固含量和较短凝胶化时间的体系用于胰岛素的负载和释放研究.通过X射线衍射(XRD),扫描显微镜(SEM)对水凝胶结构进行表征.通过紫外分光光度计监测胰岛素的释放过程,结果表明,水凝胶释药时间约为65 h,且释放曲线较为平缓.细胞毒性实验结果表明该水凝胶材料对细胞生长无明显抑制作用.小鼠体内释药实验结果表明该水凝胶载体对延长胰岛素的释药时间有一定效果,可作为多肽类药物的缓释体系.     

二种求算晶体平面间距d_(hkl)的数学方法

用数学方法推导出结构化学晶体学中晶面间距的一般通式,并在此基础上推导出其他晶系的晶面间距(d(hkl))的计算表达式。     

Enantioselective synthesis of (1S,4R)-N-(benzylcarbamoyl)-4-aminocyclopent-2-en-1-ol by Candida antarctica lipase B

An efficient biocatalytic process has been developed to obtain optically pure (1S,4R)-N-(benzylcarbamoyl)- 4-aminocyclopent-2-en-1-ol which can be used as the key intermediate of ticagrelor. In this research, several N-(benzylcarbamoyl)-4-aminocyclopent-2-en-1-ol derivatives have been investigated in which Candida antarctica lipase B (CALB) was used to catalyze the asymmetric hydrolysis reaction. As expected, some of these substrates successfully gave (1S,4R)-N-(benzylcarbamoyl)-4-aminocyclopent- 2-en-1-ol in >98% enantiomeric excess (ee) with conversion yields up to 45%.     

Facile synthesis of 1-naphthols through a copper-catalyzed arylation of methyl ketones with o-bromoacetophenones

The coupling reactions of simple methyl ketones with o-bromoacetophenones and subsquential cyclization reactions were realized to produce a range of 1-naphthols. These cascade reactions were initiated by a rare Cu-catalyzed arylation reaction of methyl ketones with aromatic bromides.