Crown ether usually plays the role of macrocyclic host in supramolecular chemistry, but here the crown ether is also utilized as the stoppers in rotaxanes. In this work, we designed and synthesized two [3]rotaxanes containing four crown ether components by using an approach of template‐directed clipping reaction, of which, two crown ether components were employed as the macrocyclic hosts to assemble the mechanically interlocked framework while another two crown ether units located on the two ends of ammonium template acting as the stoppering groups of rotaxanes. Their self‐assembling process was monitored by the 1H NMR and one of the single crystal structures of [3]rotaxane was obtained. 相似文献
The cover picture shows an efficient one‐pot condensation of maleimide derivatives in the presence of acetic acid and water to afford a series of benzene triimides (BTIs). The structure, physicochemical properties and electrochemistry behavior of BTIs were systematically investigated. Owing to the planar structure and unique electron‐deficient nature, BTIs can self‐assemble into different motifs. More details are discussed by Wang et al. on page 684–688.
The cover picture shows a rapid detection of sildenafil drugs in liquid nutraceuticals based on surface‐enhanced Raman spectroscopy technology. A detailed attribution analysis by density functional theory (DFT) was used to guide specific experiments. The Raman signals were obtained from a silver colloid (Ag col) substrate, and they increased in the presence of the mineral salt, potassium iodide (KI). These methods detected sildenafil in aqueous solutions as low as 1 µg/mL with high signal uniformity (RSD = 3.77%). Raman technology detected low contents of sildenafil drugs in liquid nutraceuticals, not in solid samples. Therefore, SERS technology has great potential for on‐site and real‐time detection of illegal drugs in water and in liquid nutraceuticals. More details are discussed in the article by Hasi et al. on page 1522–1528.
The cover picture shows a new three‐dimensional non‐fullerene small molecular acceptor for solution‐processed organic solar cells. The acceptor was named SFTTIC using spiro‐bifluorene as the core unit linking with four thieno[3,2‐b ]thiophenes and end‐capped with 2‐(3‐oxo‐2,3‐dihydro‐1H ‐inden‐1‐ylidene)malononitrile. SFTTIC has a high absorption coefficient, good thermal stability and appropriate energy levels and the optimized power conversion efficiency (PCE) of 5.66% was achieved for the devices with PBDB‐T as donor material. These results indicate that the 3D non‐fullerene small molecule is potential for achieving high photovoltaic performance. More details are discussed in the article by Chen et al. on page 1687–1692.
The cover picture shows a new protocol for the NiCl2 ‐catalyzed cross‐electrophile coupling of aryl bromides with pyrimidin‐2‐yl tosylates to give the corresponding C2 ‐arylation pyrimidine derivatives. This study provides an improvement over previous methods by using pyrimidin‐2‐yl tosylates instead of halides as coupling partners that are stable and easily available. More details are discussed in the article by Wang et al. on page 1366–1370.
The cover picture shows a simple, inexpensive and robust method on defluorosilylation of diverse fluoroalkenes with silylboronates in the presence of alkoxy base to directly synthesize various silylated fluoroalkenes. Density functional theory calculations revealed that transient silyl anion complex undergoes SN2’ or SNV substitution, which is responsible for this base‐mediated defluorosilylation reaction, thus obviating the need for copper salts. More details are discussed in the article by Shi et al. on page 1009–1014.
The cover picture shows a series of Cp*Rh‐based molecular Borromean rings (BRs), which consist of three chemically independent rings that are locked in such a way that no two of the three rings are linked with each other. Interestingly, the structure of BRs is very similar to Kong Ming Lock (孔明锁), a kind of Chinese traditional six‐piece burr puzzle. In this work, some of as‐synthesized BRs display high stability in solution. The reason is related to the length ratio of the long‐arm linker and short‐arm linker, where smaller aspect ratios of the metallarectangles promote improved stability of the BRs in solution. Increasing the width of the metallaligand or pyridyl ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts. More details are discussed in the article by Jin et al. on page 106–111.
The control of stereoselectivity in radical reactions is of great importance, but remains a formidable challenge. The cover picture shows that the enantiomerically pure compounds can be prepared in radical transformations using chiral transition metal complexes as catalysts. Recent advances are summarized in the review by Kong et al. on page 247–256.
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