Tailoring of ionic supramolecular assemblies based on ammonium carboxylates toward liquid‐crystalline micellar cubic mesophases

Ionic liquid crystals based on ionic complexation of tris(2‐aminoethyl)amine (1) with 3,4,5‐tris(7,7,8,8,9,9,10,10,11,11,12,12,12‐tridecafluorododecyloxy)benzoic acid (2) and with 3,4,5‐tris(2‐octyldodecyloxy)benzoic acid (3) were investigated. The ionic complex with the partially fluorinated alkyl chains (1·2) exhibited a morphological transition from a hexagonal columnar mesophase to a Pm3n micellar cubic phase upon increasing the molar ratio of 2 to 1. For the complex with the branched alkyl chains (1·3) a micellar cubic mesophase was exclusively generated at appropriate composite ratios. The generation of the micellar cubic mesophases is attributed to the introduction of the laterally expanded volume of the alkyl chains compared with the corresponding normal dodecyl chains. Their thermal stabilities were most enhanced at a specific molar ratio of 1:5 for 1·2 and 1:4 for 1·3. This result corresponds to the most suitable chain volume for the stable micellar cubic mesophase.     

Non‐Heme Dioxygenase Catalyzes Atypical Oxidations of 6,7‐Bicyclic Systems To Form the 6,6‐Quinolone Core of Viridicatin‐Type Fungal Alkaloids

The 6,6‐quinolone scaffold of the viridicatin‐type of fungal alkaloids are found in various quinolone alkaloids which often exhibit useful biological activities. Thus, it is of interest to identify viridicatin‐forming enzymes and understand how such alkaloids are biosynthesized. Here an Aspergillal gene cluster responsible for the biosynthesis of 4′‐methoxyviridicatin was identified. Detailed in vitro studies led to the discovery of the dioxygenase AsqJ which performs two distinct oxidations: first desaturation to form a double bond and then monooxygenation of the double bond to install an epoxide. Interestingly, the epoxidation promotes non‐enzymatic rearrangement of the 6,7‐bicyclic core of 4′‐methoxycyclopenin into the 6,6‐quinolone viridicatin scaffold to yield 4′‐methoxyviridicatin. The finding provides new insight into the biosynthesis of the viridicatin scaffold and suggests dioxygenase as a potential tool for 6,6‐quinolone synthesis by epoxidation of benzodiazepinediones.     

Swinging and tumbling of fluid vesicles in shear flow

The dynamics of fluid vesicles in simple shear flow is studied using mesoscale simulations of dynamically triangulated surfaces, as well as a theoretical approach based on two variables: a shape parameter and the inclination angle, which has no adjustable parameters. We show that, between the well-known tank-treading and tumbling states, a new "swinging" state can appear. We predict the dynamic phase diagram as a function of the shear rate, the viscosities of the membrane and the internal fluid, and the reduced vesicle volume. Our results agree well with recent experiments.     

Catalytic Alkynylation of Polyfluoroarenes by Amide Base Generated In Situ

We herein demonstrate that the amide base generated in situ from CsF and N(TMS)₃ catalyzes the deprotonative coupling reactions of terminal alkynes with polyfluoroarenes, wherein mono- and dialkynylations occur efficiently for penta- and hexafluorobenzenes, respectively. Tetraalkynylated products could also be synthesized from dialkynylated compounds.     

Molecular Insights into the Ligand-Based Six-Proton- and Six-Electron-Transfer Processes Between Tris-ortho-Phenylenediamines and Tris-ortho-Benzoquinodiimines

The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H₂) important. A high-spin (hs) Fe^II complex with o-phenylenediamine (opda) ligands, [Fe^II(opda)₃]²⁺ (hs- [6R] ²⁺), was reported showing photochemical H₂ evolution. In addition, a low-spin (ls) [Fe^II(bqdi)₃]²⁺ (bqdi: o-benzoquinodiimine) (ls- [0R] ²⁺) formation by O₂ oxidation of hs- [6R] ²⁺, accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls- [0R] [PF₆]₂ can be reduced by hydrazine giving ls-[Fe^II(opda)(bqdi)₂][PF₆]₂ (ls- [2R] [PF₆]₂) and ls-[Fe^II(opda)₂(bqdi)][PF₆]₂ (ls- [4R] [PF₆]₂) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials.     

Hydrogen-induced magnetic and structural transformations of GdCu

The magnetization of GdCu induced by hydrogen uptake was measured within the temperature range of 4.2 to 300 K, occurring phase changes were followed by X-ray diffraction measurements at ambient temperature. The prepared GdCu powder of CsCl-type structure readily absorbed hydrogen at ambient temperature, where hydrogen pressure was below 100 kPa. Hydrogenation changed the magnetism of GdCu in a complex manner from an antiferromagnetic-like type to a paramagnetic-like one. The changes in magnetic properties of GdCu by hydrogenation are governed by hydrogen-induced disproportionation. Within the composition range 0<[H]/[GdCu]<1, GdCu disproportionated according to 2GdCu+H₂→GdH₂+GdCu₂ . The magnetization was evaluated by the expression χ_total=(1-x)χ_GdCu+(x/2)(χ_GdH2+χ_GdCu2). GdCu hydride was not observed. Hydrogenation beyond [H]/[GdCu]>1 gave rise to the disproportionation of GdCu₂ causing the change in magnetization.     

The Heat Kernel on Hyperbolic Space

The purpose of this note is to provide a new proof for the explicitformulas of the heat kernel on hyperbolic space. By definition,the hyperbolic space Hⁿ is a (unique) simply connected completen-dimensional Riemannian manifold with a constant negative sectionalcurvature –1. 1991 Mathematics Subject Classification58G32, 58G11.     

Structural and superconductivity study on α-FeSex

We have successfully synthesized the α-FeSe_x binary tetragonal superconductors with nominal composition of FeSe_x (x=0.6-1.0) via conventional solid state reactions between Fe and Se sealed in quartz tubes. Fe and β-FeSe are the most commonly seen impurities in this binary system. A low-temperature annealing at 400 °C is found to be crucial to remove β-FeSe, which is the thermodynamic stable phase with hexagonal symmetry. For all the samples of FeSe_x, superconductivity is confirmed by magnetic measurements as well as resistivity measurements with their T_c at around 8 K. We noticed that their T_c does not vary with the different nominal Se amount. High-resolution synchrotron X-ray diffraction analysis revealed that the unit cell parameters of all these samples do not change within the error range, and their structure only tolerate the same very small amount of Se deficiency. Based on this study, we concluded that the α-FeSe_x superconductor only exist in a very narrow deficiency range.