Latest ArticlesFive hybrid tetrapeptides, each consisting a central dipeptide segment of α-amino acid residues flanked by two aromatic γ-amino acid residues, are found to fold into well-defined β-hairpin conformations as shown by NMR, computational study, and X-ray structures. The turn loop of this β-hairpin motif accommodates different two-residue α-amino acid sequences from the highly flexible Gly-Gly, to the more restricted d-Pro-Gly. The presence of α-amino acid side chains enhances the stabilities of the β-hairpins with the exception of d-Pro-Gly-which results in destabilization. Based on this hairpin/turn motif, a variety of different dipeptide sequences of α-amino acids which rarely occur in β-turns can be introduced and presented as two-residue loops.
Over the past few decades, supramolecular chemistry has entered the field of scientific research and attracted extensive attention. Among supramolecular macrocycles, cyclodextrins (CDs) are widely applied in the field of adsorption due to their unique structure and properties. This review focuses on the important role of cyclodextrin polymers (CDPs) as adsorbents in the adsorption of different substances. It covers the category of CDPs adsorbents (including crosslinked CDPs, grafted CDPs, CD-based polyrotaxanes/pseudo-polyrotaxanes, and imprinted CDPs), their adsorption mechanism and applications in the adsorption of inorganic metal ions, organic pollutants, and biomacromolecules. Finally, the challenges and future perspectives in relative research fields are discussed.
We have developed a metal-free radical cascade reaction of N-substituted 2-aryl indoles with readily available sulfonyl hydrazides for the rapid construction of arylsulfonyl-substituted indolo[2,1-a]isoquinolin-6(5H)-one derivatives. With the TBAI–TBHP catalytic system, a broad series of structurally diverse indolo[2,1-a]isoquinolin-6(5H)-one derivatives were obtained in moderate to excellent yields. The reaction features mild reaction conditions, operationally easiness, scaled-up feasibility, and high functional-group-tolerance.
A new micro-spherical conjugated macrocycle polymer (P[5]-TFB-CMP) was prepared by the condensation reaction between dihydrazide functionalized pillar[5]arene and 1, 3, 5-triformylbenzene under ambient conditions. P[5]-TFB-CMP exhibits large surface area with excellent thermal stability and has been used as additive to prepare composite PMMA film of photochromic naphthopyrans. The results showed that the addition of P[5]-TFB-CMP could dramatically accelerate the thermal fading rate of the photochromic composite film by up to 12 times. This is a new strategy to overcome the drawback of the matrix effect.
Electronic tuning by para substitutions was explored to achieve a highly active manganese N-heterocyclic carbene pincer complex for the selective electrocatalytic reduction of CO2 to CO. [MnCNCOMe]BF4 (L2-Mn) bearing an electron-donating group (-OMe) showed high activity with 63×catalytic current enhancement, average Faradaic efficiency of 104%, and a TOFmax value of 26, 127 s-1, which is 127 times higher than that of unsubstituted [MnCNCH]Br (L1-Mn) reported previously. In contrast, the electron-withdrawing group (-COOMe) in [MnCNCCOOMe]PF6 (L3-Mn) inhibited the electrocatalytic activity. Ambient Brønstic acid, however, suppressed the activity of L2-Mn probably due to the protonation of the -OMe group. These findings indicate a potential electronic tuning strategy to improved manganese N-heterocyclic carbene catalysts for CO2 reduction.
We describe a janusarene derivative PyJ, which forms micrometer-scale one-dimensional metallo-supramolecular polymer through coordination driven self-assembly. PyJ is a well-preorganized dodecatopic pyridyl ligand built on a hexaphenylbenzene platform. The two-face structural feature of PyJ allows for a delicate control over multiple Py-Ag+-Py coordination interactions, leading to assembled structure of PyJ-Ag, which was characterized by dynamic light scattering, atomic force microscopy, and transmission electron microscopy.
A facile access to mono-C-alkynyl-o-carboranes from o-carboranes and arylsulfonylacetylenes was developed. This facile process tolerates a wide variety of functional groups, occurs at mild conditions in one-pot procedure with short reaction time. The obtained mono-C-alkynyl-o-carboranes can be easily derivatized to synthesize 1, 2-difunctionalized o-carboranes. This work provides a useful tool for the functionalization of o-carboranes.
The synthesis, structure, and properties of pyrene-based conformationally adaptive macrocycles are described. This new type of conformationally adaptive macrocycle was constructed through Perkin reaction, followed by imidization. By changing the condensation partner as the linking unit, a family of conjugated macrocycles with different sizes of the cavity was synthesized, which provide a simple and modular synthetic strategy towards the conformationally adaptive macrocycles. Furthermore, the macrocycles provide two well-defined conformations through flipping pyrene subunit, which were unambiguously determined by single-crystal X-ray diffraction analysis. The conformational interconversion barrier was determined by density functional theory (DFT) calculations. This new macrocycle also demonstrated unique properties, such as vapochromic behavior and aggregation emission enhancement effect. Furthermore, we have also investigated the effect of the linker on the shape and photophysical properties of the resulting macrocyclic products.
As an essential part in the toolbox of super-resolution microscopy, stimulated emission depletion (STED) nanoscopy has been widely explored in revealing the substructure and bioactivities in fluorescence imaging. Among the applied STED fluorophores, silicon-substituted rhodamines (SiRs) belong to one of the most extensively employed fluorophores. The carboxy-SiR was favored in STED bioimaging with many advantages, including reliable photostability, cell permeability, tunable fluorogenicity, feasible structural decoration and so on. We reviewed the research of carboxy-SiR in the STED nanoscopy and hopefully this can inspire more efforts in the design and application of STED fluorophores.
Glutathione thiol-reactive pillar[6]arene (TWP6) is designed and synthesized as the first example of reducing agent-reactive host molecule. TWP6 shows high affinity binding towards suitable anti-tumor drugs and guests. Doxorubicin-based acid-labile prodrugs and TWP6 are used to construct supramolecular vesicles, which are also loaded with camptothecin. The supramolecular vesicles loaded with two drugs demonstrate glutathione- and acid-responsive drug release as well as sequential release to both stimuli types. Supramolecular vesicles show combination therapeutic effect towards tumor cells in vitro.
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