Nitrogen adsorption on fluorinated activated carbon fiber

Nitrogen adsorption isotherms for fluorinated activated carbon fiber (F-ACF) and fluorinated carbon black (F-CB) were measured at 77 K. Surface structures of F-ACF and F-CB were examined by _s -plot analysis using the adsorption data on the nonporous carbon black (CB) and F-CB. The surface energy of F-ACF was lower than that of ACF. The micropore structure of ACF was preserved even after fluorination, although the limiting adsorption amount and the micropore width decreased with fluorination.     

Mechanism of nucleophilic fluorination promoted by bis‐tert‐alcohol‐functionalized crown‐6‐calix[4]arene

Theoretical calculations were performed to elucidate the ability of the recently reported bis‐tert‐alcohol‐functionalized crown‐6‐calix[4]arene (BACCA) molecule to promote nucleophilic fluorination of alkyl mesylates with cesium fluoride reagent. It was found that a similar structure, named BACCAt, can separate the cesium fluoride ion pair in tert‐butanol solution. This separation has a free energy cost, even considering the double hydrogen bonds with the fluoride ion. The solvent has an important effect on the stabilization of this complex, due to interaction with the high dipole moment of the separated ion pair. The observed rate acceleration effect involves a structure with double hydrogen bonds between the BACCAt and the centers of negative charges of the S_N2 transition state. The predicted free energy barrier of 27.3 kcal mol⁻¹ is in excellent agreement with the estimated experimental value of 26.2 kcal mol⁻¹.     

Late-stage fluorination of bridged scaffolds: Chemoselective generation of a CHF group at three positions of the bicyclo[3.3.1]nonane system

Monofluorobicyclo[3.3.1]nonane derivatives were prepared by late-stage fluorination, often proceeding with control of stereochemistry. Introduction of fluorine at the 3-, 6- or 7-position was achieved chemoselectively, the bicyclo system being constructed by a tandem one-pot Michael-aldol annulation. The major conformer was deduced for each of the fluorobicyclo compounds prepared, each possessing a unique CF orientation on a common rigid bridged scaffold that can be polysubstituted.     

Effect of Fluorination on the Photovoltaic Properties of Medium Bandgap Polymers for Polymer Solar Cells

Fluorination of conjugated polymers is one of the effective strategies to tune the molecular energy levels and morphology for high efficient polymer solar cells (PSCs). Herein, two novel donor‐acceptor conjugated polymers, PffBT and PBT, based on bis(3,5‐bis(hexyloxy)phenyl)benzo[1,2‐ b:4,5‐b']dithiophene and benzo[c][1,2,5]thiadiazole (BT) with or without fluorination, respectively, were synthesized, and their photovoltaic properties were compared. The polymer PffBT based on fluorinated BT showed lower frontier energy levels, improved polymer ordering, and a well‐developed fibril structure in the blend with PC₇₁BM. As a result, the PSCs based on PffBT/PC₇₁BM exhibit a superior power conversion efficiency (PCE) of 8.6% versus 4.4% for PBT‐based devices, due to a high space charge limit current (SCLC) hole mobility, mixed orientation of polymer crystals in the active layer, and low bimolecular recombination.     

Smectic behaviour of methyl 4-alkoxybenzoates with a partially fluorinated alkyl chain

A series of 4-alkoxybenzoic acids 1[m,n] and their methyl esters 2[m,n] containing a partially fluorinated alkyl chain was prepared and their physical properties were investigated by optical, thermal and powder X-ray diffraction (XRD) methods. The former exhibits an SmC phase, while the latter form an SmA phase. XRD analysis indicated liquid-like character of the linking alkyl chains, and showed a decreasing layer thermal expansion coefficient from positive to negative upon increasing the degree of fluorination. The new esters 2[m,n] expanded the series and permitted analysis of trends in thermal stability of the SmA phase. The results demonstrate that the SmA–I transition temperature increases by about +20 K per CF₂CF₂ unit, and is destabilised by –5.6 K upon extending the hydrocarbon part by each CH₂CH₂ group. Data for the expanded series 2[m,n] were used for comparative analysis of mesogenic behaviour in two other series of derivatives of 1[m,n]. Synthetic methods for 1[m,n] and 2[m,n] are reviewed.     

Selective C−H Halogenation with a Highly Fluorinated Manganese Porphyrin

The selective C?H functionalization of aliphatic molecules remains a challenge in organic synthesis. While radical chain halogenation reactions provide efficient access to many halogenated molecules, the use of typical protocols for the selective halogenation of electron‐deficient and strained aliphatic molecules is rare. Herein, we report selective C?H chlorination and fluorination reactions promoted by an electron‐deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for the aliphatic halogenation of recalcitrant, electron‐deficient, and strained substrates with unique regio‐ and stereoselectivity. UV/Vis analysis during the course of the reaction indicated that an oxo‐Mn^V species is responsible for hydrogen‐atom abstraction. The observed stereoselectivity results from steric interactions between the bulky porphyrin ligand and the intermediate substrate radical in the halogen rebound step.     

Continuous Heterogeneous Photocatalysis in Serial Micro‐Batch Reactors

Solid reagents, leaching catalysts, and heterogeneous photocatalysts are commonly employed in batch processes but are ill‐suited for continuous‐flow chemistry. Heterogeneous catalysts for thermal reactions are typically used in packed‐bed reactors, which cannot be penetrated by light and thus are not suitable for photocatalytic reactions involving solids. We demonstrate that serial micro‐batch reactors (SMBRs) allow for the continuous utilization of solid materials together with liquids and gases in flow. This technology was utilized to develop selective and efficient fluorination reactions using a modified graphitic carbon nitride heterogeneous catalyst instead of costly homogeneous metal polypyridyl complexes. The merger of this inexpensive, recyclable catalyst and the SMBR approach enables sustainable and scalable photocatalysis.     

Atomic fluorine in cobalt trifluoride thermolysis

The thermal decomposition of cobalt trifluoride was studied by High Temperature Mass Spectrometry (HTMS). It was ascertained that the rate of atomic fluorine evolution in the gas phase might be increased by adding small amounts of Ni(s) or CoF₂(s) to cobalt trifluoride. Scanning Electron Microscopy combined with Energy Dispersive X-ray spectroscopy (SEM/EDX) was used to determine the morphology and composition of the solid product surface layer formed under different rates of CoF₃(s) thermolysis.     

全氟烷基膦酸锂电解液的制备与性能研究

选取氯代二异丙基膦(C6H14PCl)为原料, 利用电化学氟化方法, 得到全氟烷基膦酸[(C3F7)2PF3], (C3F7)2PF3与氟化锂(LiF)反应得到全氟烷基膦酸锂(Li[(C3F7)2PF4]), 将其溶于碳酸乙烯酯(EC)和碳酸二甲酯(DMC)质量比为1∶1的混合溶剂中得到电解液, 考察电解液的电导率、抗水性及氧化分解电位. 以LiCoO2为正极, 锂片为负极组装两电极模拟电池体系, 测试得到电池的放电平台为3.7 V; 电池的首次放电比容量为107 mA•h•g－1; 当循环放电40次后, 容量衰减较快, 电池循环50周后, 效率仍保持102%. 交流阻抗图谱表明电解液放电时的阻抗约为140 Ω. 研究结果表明, 全氟烷基膦酸锂有望成为新型锂离子二次电池的电解质盐.     

Photoredox Activation of SF6 for Fluorination

We report the first practical use of SF₆ as a fluorinating reagent in organic synthesis. Photoredox catalysis enables the in situ conversion of SF₆, an inert gas, into an active fluorinating species by using visible light. Under these conditions, deoxyfluorination of allylic alcohols is effected with high chemoselectivity and is tolerant of a wide range of functional groups. Application of the methodology in a continuous‐flow setup achieves comparable yields to those obtained with a batch setup, while providing drastically increased material throughput of valuable allylic fluoride products.