Light‐Driven C−H Oxygenation of Methane into Methanol and Formic Acid by Molecular Oxygen Using a Perfluorinated Solvent

The chlorine dioxide radical (ClO₂^.) was found to act as an efficient oxidizing agent in the aerobic oxygenation of methane to methanol and formic acid under photoirradiation. Photochemical oxygenation of methane occurred in a two‐phase system comprising perfluorohexane and water under ambient conditions (298 K, 1 atm). The yields of methanol and formic acid were 14 and 85 %, respectively, with a methane conversion of 99 % without formation of the further oxygenated products such as CO₂ and CO. Ethane was also photochemically converted into ethanol (19 %) and acetic acid (80 %). The methane oxygenation is initiated by the photochemical Cl?O bond cleavage of ClO₂^. to generate Cl^. and O₂. The produced Cl^. reacts with CH₄ to form a methyl radical (CH₃^.). Finally, the oxygenated products such as methanol and formic acid were given by the radical chain reaction. A fluorous solvent plays an important role of inhibiting the deactivation of reactive radical species such as Cl^. and CH₃^..     

Mesomorphic properties of cyanobiphenyl dimers with a central malonate unit

A series of cyanobiphenyl dimers attached via alkoxy spacers to a central malonate were prepared, and the mesomorphic behaviour was studied by differential scanning calorimetry (DSC), polarised optical microscopy and X-ray diffraction (Wide-angle X-ray scattering and Small-angle X-ray scattering). Depending on spacer lengths and substitution of the malonate, nematic and smectic A mesophases with pronounced odd–even effect were observed. C-2-unsubstituted malonates formed nematic phases for chain lengths C₆–C₁₄, while C₁₂ and C₁₄ homologues displayed additional smectic A phases. In contrast, malonates with fluorinated tails at C-2 displayed exclusively smectic A phases. Remarkably, the X-ray diffraction profile of the smectic A phase of the C-2-unsubstituted C₁₂ malonate showed a fundamental (001) and the corresponding third-order (003) diffraction peak, but no (002) reflection. Using Fourier analysis, the diffraction pattern was converted to an electron density profile, which was in good agreement with the proposed packing model of the SmA mesophase based on a horseshow- or hairpin-like conformation of the malonate.     

Evaluation of perfluorinated compounds in seven wastewater treatment plants in Beijing urban areas

The presence of perfluorinated compounds(PFCs)in seven major wastewater treatment plants(WWTPs)in Beijing was investigated in the current study.We detected nine PFCs in all the wastewater and sludge samples.Perfluorooctane acid(PFOA)is the dominant PFCs in influents and effluents,while perfluorooctane sulfonate(PFOS)is the major contaminant in sludge.The highest PFC concentration was found in plants at Qinghe and Jiuxianqiao WWTP,while the lowest was found at Fangzhuang WWTP.The total values of PFC range fr...     

High-Resolution Electronic Excitation and Emission Spectra of Pentacene and 6,13-Diazapentacene Monomers and Weakly Bound Dimers by Matrix-Isolation Spectroscopy

N-Heteropolycycles are among the most promising candidates for applications in organic devices. For this purpose, a profound understanding of the low-energy electronic absorbance and emission characteristics is of crucial importance. Herein, we report high-resolution absorbance and fluorescence spectra of pentacene ( PEN ) and 6,13-diazapentacene ( DAP ) in solid neon obtained using the matrix-isolation technique. Accompanying DFT calculations allow the assignment of specific vibrationally resolved signals to corresponding modes. Furthermore, we present for the first time evidence for the formation of van der Waals dimers of both substances. These dimers exhibit significantly different optical characteristics resulting from the change of electronic properties evoked by the incorporation of sp² nitrogen into the molecular backbone.     

Formation of Patches on 3D SAMs Driven by Thiols with Immiscible Chains Observed by ESR Spectroscopy

Beyond stripes : The extreme lipophobicity of perfluorinated chains attached to amphiphilic thiolates triggers the formation of “stars” (or patches) surrounded by amphiphilic alkylthiolates in three‐dimensional self‐assembled monolayers. This strategy led to the first example of a water‐soluble multicompartment monolayer wrapped around a gold core.

     

Design of Phase‐Vanishing Reactions

Phase‐vanishing reactions utilize a perfluorinated solvent as a liquid membrane to separate a substrate and a reagent. Since their introduction less than ten years ago, phase‐vanishing reactions have become a valuable alternative to reactions that require a slow addition of a reagent. A variety of experimental designs allow reactions to be carried out under anhydrous conditions, under photolytic conditions, under solvent‐free conditions, with a gas as a reagent, and under reflux.