Cover Picture: Catalytic Enantioselective Protonation of Monofluorinated Silyl Enol Ethers towards Chiral α‐Fluoroketones (Chin. J. Chem. 8/2019)

The cover picture shows a highly enantioselective organocatalytic protonation of monofluorinated silyl enol ethers to α‐secondary α‐fluoroketones using water as proton source. Notably, in the presence of D₂O and MeOD, the facile access of chiral α‐deuterated α‐fluoroketones in excellent enantioselectivity is achieved. More details are discussed by Zhou et al. on page 799–806.

     

Smart Transformation of a Polyhedral Oligomeric Silsesquioxane Shell Controlled by Thiolate Silver(I) Nanocluster Core in Cluster@Clusters Dendrimers

Using polyhedral oligomeric silsesquioxane (POSS) modified by a thiol group as a protected ligand, atom‐precise multi‐heteorocluster‐based dendrimers Ag₁₂@POSS₆ ( 1 a and 1 b ) were assembled. Through the reactive ?SH groups, six POSS shell ligands stabilize the central 12‐core silver(I) cluster by diverse Ag?S interactions. When such Ag₁₂@POSS₆ complex was stimulated by different solvents (acetone or tetrahydrofuran), the core Ag₁₂ silver(I) cluster underwent reversible structural transformation between flattened cubo‐octahedral (in 1 a ) and normal cubo‐octahedral (in 1 b ); concomitantly shell POSS clusters rearranged from pseudo‐octahedral to quasi‐octahedral. Furthermore, the film matrix modified by 1 a or 1 b showed different hydrophobicity.     

Electrocatalytic Hydrogen Evolution by Water-Soluble Cobalt (II), Copper (II) and Iron (III) meso-Tetrakis(carboxyl)porphyrin

Three water-soluble carboxyl metalloporphyrins, cobalt (II), copper (II) and iron (III) meso-tetrakis (carboxyl) porphyrin were prepared and applied as homogeneous electrocatalysts for hydrogen evolution reaction (HER) with acetic acid, trifluoroacetic acid, p-toluene sulfonic acid and water as proton sources. Cyclic voltammetry (CV) results revealed the HER underwent different routes for these metalloporphyrins. Electrocatalysis tests in buffer solution of pH=7.0 showed the TOFs of cobalt (II), copper (II) and iron (III) meso-tetrakis (carboxyl) porphyrin were 184.78, 160.28 and 184.87 mol⁻¹ ⋅ h⁻¹ and the faradaic efficiency were 94.37 %, 93.01 % and 96.98 % at an overpotential of 788 mV, respectively. These results indicate the synthesized metal carboxyl porphyrins have good electrocatalytic activity for HER.     

Directional Potassium Transport through a Unimolecular Peptide Channel

Three unimolecular peptide channels have been designed and prepared by using the β‐helical conformation of gramicidin A (gA). The new peptides bear one to three NH₃⁺ groups at the N‐end and one to three CO₂^? groups at the C‐end. These zwitterionic peptides were inserted into lipid bilayers in an orientation‐selective manner. Conductance experiments on planar lipid bilayers showed that this orientation bias could lead to observable directional K⁺ transport under multi‐channel conditions. This directional transport behavior can further cause the generation of a current across a planar bilayer without applying a voltage. More importantly, in vesicles with identical external and internal KCl concentrations, the channels can pump K⁺ across the lipid bilayer and cause a membrane potential.     

The wax deposition rate of water-in-crude oil emulsions based on the laboratory flow loop experiment

This paper aims to develop a mathematical model to predict the wax deposition rate of waxy crude emulsions, combining heat and mass transfer mechanisms. According to the flow loop experimental results, the wax deposition rate increases with the decreasing average temperature of oil/wall in a manner of linear regularity, and shows a downtrend with the increase of water cut due to diffusion resistance. An applicable model is developed regarding emulsion properties, radial temperature gradient, shear stress, and wax diffusion coefficient. In model validation, the prediction results are in good agreement with experimental data with the relative errors within 28.87%.     

Beyond Clusters: Supramolecular Networks Self‐Assembled from Nanosized Silver Clusters and Inorganic Anions

Assembly of small clusters into rigid bodies with precise shape and symmetry has been witnessed by the significant advances in cluster‐based metal–organic frameworks (MOFs), however, nanosized silver cluster based MOFs remain largely unexplored. Herein, two anion‐templated silver clusters, CO₃@Ag₂₀ and SO₄@Ag₂₂, were ingeniously incorporated into a 2D sql lattice ( 1 , [CO₃@Ag₂₀(iPrS)₁₀(NO₃)₈(DMF)₂]_n) and an unprecedented 3D two‐fold interpenetrated dia network ( 2 , [SO₄@Ag₂₂(iPrS)₁₂(NO₃)₆ ? 2 NO₃]_n), respectively, under mild solvothermal conditions. Their atomically precise structures were confirmed by single‐crystal X‐ray diffraction analysis and further consolidated by IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Each drum‐like CO₃@Ag₂₀ cluster is extended by twelve NO₃^? ions to form the 2D sql lattice of 1 , whereas each ball‐shaped SO₄@Ag₂₂ cluster with a twisted truncated tetrahedral geometry is pillared by four [Ag₆(NO₃)₃] triangular prisms to form the 3D interpenetrated dia network of 2 . Notably, 2 is the first interpenetrated 3D MOF constructed from silver clusters. These results demonstrate the dual role of the anions, which not only internally act as anion templates to induce the formation of silver thiolate clusters but also externally extend the cluster units into the rigid networks. The photoluminescent and electrochemical properties of 2 are discussed in detail.