Showing papers on "Fluorine published in 2023"

LiNaB6O9F2: A Promising UV NLO Crystal Having Fluorine‐Directed Optimal Performances and Double Interpenetrating 3[B6O9F2]∞ Networks

Abstract: A long‐lasting challenge in ultraviolet (UV) nonlinear optical (NLO) materials design is to combine conflicting and harsh properties into one structure, including wide UV transparency, strong NLO efficiency, and moderate birefringence to realize phase‐matching at short wavelength. A fluorine‐directed material design strategy is adopted to accelerate the process of finding NLO materials with optimal performances. In this work, taking LiB3O5 (LBO) as a maternal structure, one O atom with two F atoms is substituted and LiNaB6O9F2 which possesses novel double interpenetrating 3[B6O9F2]∞ networks and fluorine‐directed optimal performances including enhanced birefringence and phase‐matching capacity is successfully obtained. The perfect balance among deep‐UV cutoff edge, large second‐harmonic generation (SHG) response (1.1 × KDP), and moderate birefringence (0.067 at 1064 nm) of LiNaB6O9F2 makes it a promising UV NLO crystal.

Significantly Enhanced Electrocatalytic Reduction of Chloramphenicol from Water Mediated by Fe–F–N Co-doped Carbon Materials

Abstract: Chloramphenicol (CAP) is a widely used antibiotic drug and poses a great threat to human health and the ecosystem. In this work, an iron–fluorine–nitrogen (Fe–F–N) co-doped porous carbon material was innovatively prepared and applied for the electrocatalytic reduction of CAP from water, and excellent treatment performance was achieved. For an initial CAP concentration of 10 mg/L, after 60 min operation, almost 100% of CAP was removed. The active Fe(II) sites and the F-doping-induced electronic structure of Fe-FNC facilitated the electrocatalytic reductive degradation of CAP by promoting electron transfer, rather than the H*-mediated indirect reduction process. Therefore, a better treatment performance was obtained by Fe-FNC compared to other catalysts such as Fe-NC and FNC. The reaction pathways for CAP reduction were elucidated, and the ecotoxicity of the reaction products was assessed. The toxicity of the intermediate products was found to be significantly reduced, indicative of the good prospect of this method for CAP-containing wastewater pretreatment.

The First UV Nonlinear Optical Selenite Material: Fluorination Control in CaYF(SeO3)2 and Y3F(SeO3)4.

Abstract: It is a great challenge to develop UV nonlinear optical (NLO) material due to the demanding conditions of strong second harmonic generation (SHG) intensity and wide band gap. The first ultraviolet NLO selenite material, Y3F(SeO3)4, has been obtained by control of the fluorine content in a centrosymmetric CaYF(SeO3)2. The two new compounds represent similar 3D structures composed of 3D yttrium open frameworks strengthened by selenite groups. CaYF(SeO3)2 has a large birefringence (0.138@532 nm and 0.127@1064 nm) and a wide optical bandgap (5.06 eV). The non-centrosymmetric Y3F(SeO3)4 can exhibit strong SHG intensity (5.5×KDP@1064 nm), wide band gap (5.03 eV), short UV cut-off edge (204 nm) and high thermal stability (690 ℃). So, Y3F(SeO3)4 is a new UV NLO material with excellent comprehensive properties. Our work shows that it is an effective method to develop new UV NLO selenite material by fluorination control of the centrosymmetric compounds.

24.64%‐Efficiency MA‐Free Perovskite Solar Cell with Voc of 1.19 V Enabled by a Hinge‐Type Fluorine‐Rich Complex

Abstract: High density of defects at interface severely affects the performance of perovskite solar cells (PSCs). Herein, cobalt (II) hexafluoro‐2,4‐pentanedionat (CoFAc), a hinge‐type fluorine‐rich complex, is introduced onto the surface of formamidinium cesium lead iodide (FACsPbI3) film to address the issues of perovskite/Spiro‐OMeTAD interface. The existence of CoFAc passivates both organic cation and halide anion vacancies by establishing powerful hydrogen bonds with HC(NH2)2+ (FA+) and strong ionic bonds with Pb2+ in perovskite films. In addition, CoFAc serves as a connecting link to enhance interfacial hole‐transport kinetics via interacting with Spiro‐OMeTAD. Consequently, FACsPbI3 PSCs with CoFAc modification display a champion power conversion efficiency (PCE) of 24.64% with a charming open‐circuit voltage (VOC) of 1.191 V, which is the record VOC among all the reported organic‐inorganic hybrid PSCs with TiO2 as electron transport layer. Furthermore, CoFAc‐modified devices exhibit an outstanding long‐term stability, which can maintain 95% of their initial PCEs after exposure to ambient atmosphere for 1500 h without any encapsulation.

Prediction of stable radon fluoride molecules and geometry optimization using first-principles calculations

Abstract: Abstract Noble gases possess extremely low reactivity because their valence shells are closed. However, previous studies have suggested that these gases can form molecules when they combine with other elements with high electron affinity, such as fluorine. Radon is a naturally occurring radioactive noble gas, and the formation of radon-fluorine molecules is of significant interest owing to its potential application in future technologies that address environmental radioactivity. Nevertheless, because all isotopes of radon are radioactive and the longest radon half-life is only 3.82 days, experiments on radon chemistry have been limited. Here, we study the formation of radon molecules using first-principles calculations; additionally, possible compositions of radon fluorides are predicted using a crystal structure prediction approach. Similar to xenon fluorides, di-, tetra-, and hexafluorides are found to be stabilized. Coupled-cluster calculations reveal that RnF 6 stabilizes with O h point symmetry, unlike XeF 6 with C 3v symmetry. Moreover, we provide the vibrational spectra of our predicted radon fluorides as a reference. The molecular stability of radon di-, tetra-, and hexafluoride obtained through calculations may lead to advances in radon chemistry.

4′-Fluoro-nucleosides and nucleotides: from nucleocidin to an emerging class of therapeutics

Abstract: The history and development of 4'-fluoro-nucleosides is discussed in this review. This is a class of nucleosides which have their origin in the discovery of the rare fluorine containing natural product nucleocidin. Nucleocidin contains a fluorine atom located at the 4'-position of its ribose ring. From its early isolation as an unexpected natural product, to its total synthesis and bioactivity assessment, nucleocidin has played a role in inspiring the exploration of 4'-fluoro-nucleosides as a privileged motif for nucleoside-based therapeutics.

The Substituent Effect on the Ligand-centered Electrocatalytic Hydrogen Evolution of Phosphorus Corroles.

Abstract: There have been few reports of the substituent effect on the main group element corrole complexes as ligand-centered homogeneous electrocatalysts for the Hydrogen evolution reaction (HER). The key to comprehend the catalytic mechanism and develop efficient catalysts is the elucidation of the effects of electronic structure on the performance of energy-related small molecules. In this work, the "push-pull" electronic effect of the substituents on electrocatalytic HER of phosphorus corroles was investigated by using 1-4P complexes bearing hydroxyl axial ligands and different numbers of fluorine atoms on the meso-aryl substituents. The results revealed that the catalytic HER activity of phosphorus corroles decreased with the increasing of fluorine atom numbers, it follows an order of 1P > 2P > 3P > 4P. Density Functional Theory (DFT) calculations shows the corrole 1P has the lowest free energy barrier in catalytic HER.

Frontispiece: Activating Lattice Oxygen in Spinel ZnCo2O4 through Filling Oxygen Vacancies with Fluorine for Electrocatalytic Oxygen Evolution

Abstract: Electrocatalysis. In their Research Article (e202301408), Zhao-Qing Liu et al. report the activation of lattice oxygen in spinel ZnCo2O4 through filling oxygen vacancies with fluorine, thus resulting in a highly active catalyst for electrocatalytic oxygen evolution.

Quantitative imaging of fluorine in human teeth by cryogenic laser ionization time-of-flight mass spectrometry

Abstract: The scarcity of technology to visualize the fluorine (F) distribution hinders the comprehensive understanding of the role of anti-caries fluorides. In this study, the liquid nitrogen cooling device was introduced...

Design and synthesis of novel poly (aryl ether ketones) containing trifluoromethyl and trifluoromethoxy groups

Abstract: ABSTRACT The high-frequency and high-speed communication in the 5 G era puts forward requirements for the dielectric properties of polymers. Introducing fluorine into poly(ary ether ketone) can improve its dielectric properties. In this work, by introducing the fluorine group strategy, we successfully designed and synthesized three novel trifluoromethyl (−CF3) or trifluoromethoxy (−OCF3)-containing bisphenol monomers and their F-substitution PEK-based polymers (PEK-Ins). All these PEK-Ins exhibited good thermal, mechanical and dielectric properties. The T d5% of the three polymers is all higher than 520℃. The free volume fraction of novel polymers increased from 3.75% to 5.72%. Among the three polymers, exhibited the lowest dielectric constant of the films is 2.839, and the dielectric loss is 0.0048, ascribing to the increasing free volume. The Young’s modulus of the polymer film is as high as 2.9 GPa and the tensile strength is as high as 84 MPa. PEK-Ins reduced the dielectric constant by introducing a low fluorine content. This study provides a new way to design PEK to synthesize low dielectric constant polymers.

Phase Transition Induced Enhanced Performance of Sodium-Rich Na1.2Mn0.8O2–yFy (y = 0–0.5) Cathodes

Abstract: Increasing capacity and cycle stability is key to successfully commercializing sodium battery technologies. Currently, cation-rich cathodes are well suited for this trend owing to superior overall performance through fluorine substitution in the cation. However, the exact effects and synergy due to fluorine substitution as anions are still unknown. Understanding such synergistic effects can significantly facilitate increasing the capacity, leading to maximum performance at optimum conditions. In this work, the systematic addition of F into sodium-layered oxide and its corresponding changes in the crystal structure or phase formation are extensively studied. More specifically, the effect of fluorine substitution in the anion site on Na diffusion and the Na–Tm polyhedral are extensively studied using X-ray diffraction and subsequent Rietveld analysis. In addition, the effects of F on transition metals (i.e., Mn) and its valence states are also analyzed using X-ray absorption spectroscopy. Na1.2Mn0.8O1.5F0.5 not only showed superior capacity of approximately 172 mAh g–1 and capacity retention but also remarkable cycling stability for up to 300 cycles at higher current densities. Improvements in the performance due to distortion induced by F substitution are also presented. This study provides insight into the transition of cathode material properties from F doping (y = 0–0.2) to F substitution (y ≥ 0.3) and the associated structural changes and capacity improvements.

Control of the diastereoselectivity at C(20) in the formation of C(21)-fluorinated thevinols.

Abstract: A method is reported to control the stereoselectivity at C(20) in the syntheses of 20-R-21,21,21-trifluorothevinols (12), the opioid ligands incorporating fluorine atoms within the pharmacophore associated with the surroundings of the C(20) carbon atom. The C(20)-alcohols 12 can be prepared either by reaction of 21,21,21-trifluorothevinone (9) with RM (R = alkyl; M = Li, MgX) or by reaction of thevinone (2) and related non-fluorinated ketones with CF3SiMe3. In general, alcohols 12 were formed as mixtures of the C(20)-epimers, with the major epimers of the alcohols obtained from the aforementioned reactions exploiting RLi vs. CF3SiMe3 with opposite absolute configurations at C(20). Some individual C(20)-epimers of the fluorinated alcohols 12 were isolated from the reaction mixtures in pure form by trivial crystallization. The reactions of the ketones with RMgX (R ≠ Me) and RLi (R = tertiary or secondary alkyl) resulted in the reduction of the carbonyl function to produce the secondary alcohols 11a,b rather than the tertiary alcohols 12. The additives of the salts were found to affect the composition of the products in the reactions of 9 with alkyl organomagnesium and organolithium reagents.

Nontarget analysis and fluorine atom balances of transformation products from UV/sulfite degradation of perfluoroalkyl contaminants.

Abstract: Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of highly fluorinated, anthropogenic compounds that are used in a wide variety of consumer applications. Due to their widespread use and high persistence, PFAS are ubiquitous in drinking water, which is of concern due to the threats these compounds pose to human health. Reduction via the hydrated electron is a promising technology for PFAS remediation and has been well-studied. However, since previous work rarely reports fluorine atom balances and often relies on suspect screening, some transformation products are likely unaccounted for. Therefore, we performed non-target analysis using high-resolution mass spectrometry on solutions of perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate (PFBS), perfluorooctanoate (PFOA), and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate (GenX) that had been treated with UV/sulfite to produce hydrated electrons. We determined fluorine atom balances for all compounds studied, finding high fluorine atom balances for PFOS and PFBS. PFOA and GenX had lower overall fluorine atom balances, likely due to the production of volatile or very polar transformation products that were not measured by our methods. Transformation products identified by our analysis were consistent with literature, with a few exceptions. Namely, shorter-chain perfluorosulfonates (PFSA) and their H/F substituted counterparts were also detected from PFOS. This is an unexpected result based on literature, as no documented pathway exists for the formation of shorter-chain PFSA during UV/sulfite treatment. Furthermore, the nontarget approach we employed allowed for identification of novel, unsaturated products from the hydrated electron treatment of perfluorooctanesulfonate (PFOS) that warrant further investigation.

Syntheses, structures, and applications of inorganic materials functionalized by fluorine

Abstract: 「Fluorine, a small atom with a big ego」という言葉に表されるように，フッ素は小さいながら個性の強い元素である。含フッ素化合物は高い熱的化学的安定性，撥水撥油性などの様々な優れた特長を有し，その応用分野は多岐にわたる。本学位論文では，無機材料である炭素材料とイオン液体に関連して，含フッ素材料の新規合成法の開発やその構造解析，電気化学的応用について調べた。

Visible-Light Photoredox Catalysis for the Synthesis of Fluorinated Aromatic Compounds

Abstract: Fluorine-containing functional groups are important motifs influencing physical and biological properties of organic compounds. Visible-light photoredox catalysis as a powerful strategy for the activation of small molecules contributed significantly to the rapid progress of new synthetic procedures allowing introduction of fluorine atoms into organic substrates. In this review, we highlight the distinct strategies for transition metal- and organic-photocatalytic fluorination of arenes and heteroarenes by a broad range of fluorinating compounds. The presented procedures are divided into two groups. The first group involves the reactions enabling a direct attachment of CF3-, CnFm-, F-, CF3O-, CF3S-, and SO2F- substituents to various aromatic compounds. The second group presents the tandem reactions where the formation of the aromatic system occurs after installation of the fluorine-containing group on the non-aromatic fragment of the molecule.