Site-Selective Supramolecular Complexation Activates Catalytic Ethane Oxidation by a Nitrido-Bridged Iron Porphyrinoid Dimer

Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 ⁵⁺, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 ⁵⁺ catalyzed ethane oxidation in the presence of H₂O₂ at a relatively low temperature. The site-selective complexation of 3 ⁵⁺ with an additional anionic porphyrin (TPPS⁴⁻) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 ⁵⁺ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS⁴⁻ to 3 ⁵⁺ enhanced the catalytic activity.     

Cyanide-Free One-Pot Synthesis of Methacrylic Esters from Acetone

Methacrylic esters, represented by methyl methacrylate (MMA), are widely used as commodity chemicals. Here, the one-pot synthesis of methacrylic esters from acetone, a haloform and alcohols in the presence of an organic base is described. Using DBU as the organic base for the reaction of acetone, chloroform and methanol in acetonitrile afforded MMA in 66 % yield. When the solvent was replaced by benzonitrile, the product MMA was successfully purified by distillation. Applicability of this process to various alcohols was also investigated to show ethyl, phenyl, CF₃CH₂, and n-C₆F₁₃CH₂CH₂ esters were obtained in moderate yields. The use of bromoform instead of chloroform resulted in the improvement of the yield, for example, methyl and n-C₆F₁₃CH₂CH₂ esters up to 81 and 70 %, respectively. The reaction with deuterated starting materials acetone-d₆ and MeOH-d₄, with DBU in acetonitrile afforded deuterated MMA (MMA-d₈) in 70 % yield.     

Palladium complexes bearing an N‐heterocyclic carbene–sulfonamide ligand for cooligomerization of ethylene and polar monomers

Herein, we report the synthesis of palladium complexes bearing an N‐heterocyclic carbene (NHC)‐sulfonamide bidentate ligand and their application in ethylene oligomerization and ethylene/polar monomer cooligomerization. These catalysts could smoothly catalyze ethylene oligomerization and ethylene/methyl acrylate cooligomerization albeit the performance was lower compared to that of a NHC–phenoxide catalyst. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 474–477     

Significant Effect of the Flexibility of Bridging Alkyl Chains on the Proximity of Stacked Porphyrin and Phthalocyanine Conjugated with a Fourfold Rotaxane Linkage

Spatial distance is an important factor in controlling the functional interactions between molecular units in a conjugate; therefore, the bridging unit has been closely examined. Here, we examined the effect of the flexibility of bridging alkyl chains on the proximity of stacked porphyrin and phthalocyanine conjugated with a fourfold rotaxane linkage. We found that closely stacking two π systems requires bridging alkyl chains above a certain length, and the shorter bridges hinder stacking because of their lower flexibility. The stacking distance between porphyrin and phthalocyanine in the conjugate with decyl (C₁₀) chains was estimated to be 4.03 Å and showed a unique physical character arising from short-distance interactions. The longer alkyl chains minimized steric restriction inside the fourfold rotaxane and allowed efficient communication between the porphyrin and phthalocyanine units. This is due to the flexibility of the side chains.     

Study on transport of molecules in gel by surface-enhanced Raman spectroscopy

Cellulose - Surface-enhanced Raman spectroscopy (SERS)-based biosensors have recently been extensively developed because of their high sensitivity and nondestructive nature. Conventional SERS...     

α-Trifluoromethyl Chalcones as Potent Anticancer Agents for Androgen Receptor-Independent Prostate Cancer

α-Trifluoromethyl chalcones were prepared and evaluated for their antiproliferative activities against androgen-independent prostate cancer cell lines as well as five additional types of human tumor cell lines. The most potent chalcone 5 showed superior antitumor activity in vivo with both oral and intraperitoneal administration at 3 mg/kg. Cell-based mechanism of action studies demonstrated that 5 induced cell accumulation at sub-G1 and G2/M phases without interfering with microtubule polymerization. Furthermore, several cancer cell growth-related proteins were identified by using chalcone 5 as a bait for the affinity purification of binding proteins.     

Upper limit of enhancement of boiling heat transfer in a narrow vertical rectangular channel due to passing bubbles

An experimental study has been made of saturated boiling heat transfer for water and R113 in a narrow vertical rectangular channel (2 mm space, 20 mm wide, and 200 mm long) at atmospheric pressure, in which the vertical heated surface (10 mm long and 20 mm wide) is located on one side at a position of 150 mm from its entrance and bubbles are forcibly passed through it at a designated period from 0.33 to 1.0 sec. The experiment shows that the heat transfer coefficients are increased by the bubble passing through the heated surface for the value of thermal diffusivity,a, times period, T₀, of the passing bubbles above about 6×10^–9 m² (a T ₀>6×10^–9 m²) while fora T ₀< 6×10^–9 m², the heat transfer coefficients become independent of the period and the effectiveness of the enhancement of the heat transfer owing to the passing bubble disappears.

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Die obere Grenze der Verbesserung des Wärmeübergangs beim Sieden in einem vertikalen, rechteckigen Kanal infolge von aufsteigenden Blasen

Zusammenfassung Es wurden Experimente über den Wärmeübergang beim Sättigungssieden mit Wasser und R113 in einem engen, vertikalen, rechteckigen Kanal (2 mm Abstand, 20 mm Breite und 200 mm Länge) bei Umgebungsdruck durchgeführt, wobei die vertikale, beheizte Oberfläche (10 mm lang und 20 mm breit) auf der einen Seite in einem Abstand von 150 mm vom Eintritt angeordnet ist und die Blasen zwangsweise durch den Kanal sich mit einem Periodenabstand von 0,033 bis 1,0 s bewegen. Das Experiment zeigt, daß die Wärmeübergangskoeffizienten durch das Vorbeistreichen der Blasen an der beheizten Oberfläche verbessert werden, wenn das Produkt aus Temperaturleitfähigkeit,a, mal der Periode, T₀, der vorbeistreichenden Blasen größer als 6×10^–9 m² liegt, während unterhalb dieses Wertes der Wärmeübergangskoeffizient unabhängig von der Blasenperiode ist und die Effektivität der Wärmeübergangsverbesserung infolge der Blasenströmung verschwindet.

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Nomenclature a thermal diffusivity of liquid - ¯h time-averaged heat transfer coefficient - q _w heat flux at wall - T ₀ period of passing bubble - T _w(t) temperature of heated surface - T _w amplitude of heated surface temperature Greek symbols thermal conductivity - thickness of liquid film     

Fixation of a cholesteric helical structure by the photopolymerization of a cholesteryl derived monomer

A cholesteryl derived monomer was synthesized according to a conventional synthetic route; it exhibits a cholesteric phase above 129°C, and shows a red colour due to selective reflection in the cholesteric phase. Photopolymerization of the monomer was carried out at 135°C in the cholesteric phase. The helical structure of the cholesteric phase of the monomer was frozen by photopolymerization. A peak based on the selective reflection of the cholesteric phase was detected at 615 nm in the transmittance UV-Vis spectrum. Mixtures of the monomer with a binaphthyl derivative were prepared to control the selective reflection wavelength; they all also exhibited a cholesteric phase. The selective reflection wavelength of the mixture was dependent upon the ratio of the binaphthyl derivative in the mixture. This wavelength became shorter with increasing ratio of the binaphthyl derivative. The polymer films obtained by photopolymerization displayed almost the same selective reflection wavelength as the corresponding mixtures before photopolymerization. The selective reflection wavelength of the polymer films did not change up to about 250°C.