Fluorine Interaction Research Articles

Fluorinated covalent triazine frameworks as stationary phase for the separation of fluorinated compounds by capillary electrochromatography

Three covalent triazine frameworks (CTFs) named as H-CTF, TF50-CTF and TF-CTF, containing different numbers of fluorine atoms were constructed to serve as stationary phases for capillary electrochromatography (CEC), and fluorine interactions were investigated by changing the number of fluorine atoms in the stationary phases and separating the targeted analytes. The developed CEC column was used to separate fluoroquinolones (FQs), β-phenylalanine and trifluoromethyl β-phenylalanine analogs. Characterization of the materials and the electrochromatographic columns revealed that the materials were successfully synthesized and that the inner surfaces of the capillary columns were uniformly coated with CTFs. The evaluation of the TF-CTF-coated capillary column proved that it had good resolution and reproducibility. The intraday relative standard deviations (RSDs) of the retention time (n = 9) and peak area were 0.72 %-0.85 % and 1.19 %-2.60 %, respectively. The interday RSDs (n = 9) of the retention time and peak area were 0.85 %-1.06 % and 2.59 %-3.68 %, respectively. The column-to-column RSDs of the retention time (n = 9) and peak area were 0.54 %-0.69 % and 2.95 %-4.55 %, respectively. The interbatch RSDs of the retention time and peak area (n = 9) were 2.11 %-2.89 % and 2.74 %-6.46 %, respectively. A comparsion of the peak order of fluorinated compounds in the same stationary phase and the separation efficiency of three stationary phases relative to the same target substance, it demonstrated that fluorine interaction can improve the separation efficiency of CEC.

Effect of fluorine–fluorine repulsive coupling on charge transport in cyclopentadithiophene-based donor–acceptor-type conjugated copolymer films

This study elucidates the effect of fluorine–fluorine interactions on the charge transport properties of semiconductor channels in polymer-based field effect transistors (PFETs) in which both a donor–acceptor (D–A)-type conjugated polymer and a polymer dielectric material contain fluorinated units. The fluorinated units on the benzothiadiazole (BTZ) block of cyclopentadithiophene- alt -benzothiadiazole (CDT-BTZ) allow conformation locking via F⋯S nonbonding interactions, which increases the planarity of cyclopentadithiophene- alt -fluoro-2,1,3-benzothiadiazole (CDT-FBTZ). Thus, the CDT-FBTZ copolymer films are highly crystalline and adopt the edge-on orientation, resulting in an eight-fold increase in the field-effect mobility for CDT-FBTZ-based PFETs coated with a poly(methyl methacrylate) (PMMA) dielectric layer compared with PMMA-coated CDT-BTZ-based PFETs. Meanwhile, the field-effect mobility of CDT-BTZ-based PFETs containing a fluorinated dielectric polymer (CYTOP) is double that of PMMA-coated CDT-BTZ-based PFETs. These enhanced electrical properties are attributed to surface polarization doping at the interface between the conjugated polymer and the fluorinated polymer dielectric. However, despite the effect of surface polarization doping, the electrical properties of CDT-FBTZ-based PFETs deteriorate when combined with the fluorinated CYTOP dielectric. Charge transport analyses based on the Gaussian disorder model reveal that, for CDT-based D–A-type conjugated copolymer PFETs, very few localized states in the semiconducting channel of PFET devices in which fluorine–fluorine interaction effects occur at the interface switch to delocalized states as the gate-bias increases. In contrast, the localized charge states in PFET channels without fluorine–fluorine interactions depend strongly on the applied gate-bias and become delocalized upon applying a gate-bias. Thus, it is inferred that the fluorine–fluorine repulsive coupling in D–A-type conjugated copolymers containing fluorinated functional moieties that interface with fluorinated polymer dielectric layers hinders the delocalization of charges induced by the gate-bias, thereby degrading the device performance. • Effect of fluorine–fluorine interactions on charge transport in polymer transistors investigated. • High-performance polymer field effect transistor obtained using fluorinated polymer. • Temperature-variable current-voltage analyses of the devices conducted. • Electrical degradation of polymer transistor caused by the fluorine–fluorine interactions.

The Effect of Deoxyfluorination on Intermolecular Interactions in the Crystal Structures of 1,6-Anhydro-2,3-epimino-hexopyranoses.

The effect of substitution on intermolecular interactions was investigated in a series of 1,6-anhydro-2,3-epimino-hexopyranoses. The study focused on the qualitative evaluation of intermolecular interactions using DFT calculations and the comparison of molecular arrangements in the crystal lattice. Altogether, ten crystal structures were compared, including two structures of C4-deoxygenated, four C4-deoxyfluorinated and four parent epimino pyranoses. It was found that the substitution of the original hydroxy group by hydrogen or fluorine leads to a weakening of the intermolecular interaction by approximately 4 kcal/mol. The strength of the intermolecular interactions was found to be in the following descending order: hydrogen bonding of hydroxy groups, hydrogen bonding of the amino group, interactions with fluorine and weak electrostatic interactions. The intermolecular interactions that involved fluorine atom were rather weak; however, they were often supported by other weak interactions. The fluorine atom was not able to substitute the role of the hydroxy group in molecular packing and the fluorine atoms interacted only weakly with the hydrogen atoms located at electropositive regions of the carbohydrate molecules. However, the fluorine interaction was not restricted to a single molecule but was spread over at least three other molecules. This feature is a base for similar molecule arrangements in the structures of related compounds, as we found for the C4-Fax and C4-Feq epimines presented here.

A novel analytical strategy for the determination of perfluoroalkyl acids in various food matrices using a home-made functionalized fluorine interaction SPME in combination with LC-MS/MS

In this study, a fluorine-fluorine interaction approach through fluoridating boron nitride nanosheets (BNNs) for sensing perfluoroalkyl acids (PFAAs) in multiple food matrices was developed. Through a facile hydrothermal fluorination modification, the BNNs were transferred into homogeneous fluorinated boron nitride nanoparticles (F-BNNs) with robust networks and specific surface area. After morphological modification, the particles displayed strong adsorption and sensing capabilities on PFAAs in both solid and liquid food matrix. Under the evaluation of mass spectrometry, F-BNNs based microextraction approach exhibited low method detection limits (MDLs) in the ranges of 0.9–3.9 pg mL−1 and 3.6–15.8 pg g−1 for milk and meat matrices, respectively, with satisfactory repeatability (RSD% <13.5%) and recoveries (77.7–110.5%). This work not only depicted a facile approach for preparing F-BNNs based SPME fiber, but also provided a routine analysis protocol for monitoring PFAAs in food systems.

Fluorine as a Lewis acid: A symmetry-adapted perturbation theory based on density functional theory and interacting quantum atoms study of noncovalent interactions in the NCF⋯NH3 complex.

Different computational methods are used to investigate the nature of interaction in the NCF⋯NH3 model complex, in which the fluorine atom acts as a Lewis acid and forms a noncovalent bond with the ammonia (Lewis base). Symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)) indicates that the noncovalent interaction in the NCF⋯NH3 complex is mainly electrostatics. However, dispersion and induction terms also play important roles. Although fluorine noncovalent interactions are typically classified as halogen bonds, they are somewhat different from the well-known halogen bonds of iodine, bromine, and chlorine. The halogen bonds of NCCl⋯NH3 and NCBr⋯NH3 are directional and the C  X  N (X = Cl or Br) angle tends to be linear. In contrast, the fluorine interaction in NCF⋯NH3 is not directional; the interaction energy shows no sensitivity to the angular (C  F  N) distortions, and the energy profile is flat over a wide angular range (from 180° to about 140°). However, for the angles less than 130°, the energy curve shows a clear angular dependence and the interaction between NCF and NH3 becomes stronger as the C  F  N angle decreases. It seems that at the tighter angles, a tetrel-bonded NCF⋯NH3 complex is preferred. Moreover, interacting quantum atoms (IQA) analysis shows that the competition between different intra-atomic and interatomic interactions determines the geometry of NCF⋯NH3 complex.

Impact of Noncovalent Sulfur–Fluorine Interaction Position on Properties, Structures, and Photovoltaic Performance in Naphthobisthiadiazole‐Based Semiconducting Polymers

AbstractControlling the energetics and backbone order of semiconducting polymers is essential for the performance improvement of polymer‐based solar cells. The use of fluorine as the substituent for the backbone is known to effectively deepen the molecular orbital energy levels and coplanarize the backbone by noncovalent interactions with sulfur of the thiophene ring. In this work, novel semiconducting polymers are designed and synthesized based on difluoronaphthobisthiadiazole (FNTz) as a new family of naphthobisthiadiazole (NTz)–quaterthiophene copolymer systems, which are one of the highest performing polymers in solar cells. The effect of the fluorination position on the energetics and backbone order is systematically studied. It is found that the dependence of the solar cell fill factor on the active layer thickness is very sensitive to the fluorination position. It is thus further investigated and discussed how the structural features of the polymers influence the photovoltaic parameters as well as the diode characteristics and bimolecular recombination. Further, the polymer with fluorine on both the naphthobisthiadiazole and quaterthiophene moieties exhibits a quite high power conversion efficiency of 10.8% in solar cells in combination with a fullerene. It is believed that the results would offer new insights into the development of semiconducting polymers.

Precise Synthesis of Ultra‐High‐Molecular‐Weight Fluoropolymers Enabled by Chain‐Transfer‐Agent Differentiation under Visible‐Light Irradiation

AbstractUltra‐high‐molecular‐weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible‐deactivation radical polymerization based on the strong and selective fluorine–fluorine interaction, allowing chain‐transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (Đ≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible‐light irradiation. In situ chain‐end extensions from UHMW polymers facilitated the synthesis of well‐defined block copolymers, revealing the excellent chain‐end fidelity achieved by this method.

Interaction of Single-Crystalline Metal Fluorides with Titanium-Containing Melts

The wetting of solid titanium substrates with liquid lithium and magnesium fluorides was studied by the sessile drop method in 1 · 10–3 Pa vacuum at 1173 and 1553 K, respectively. Titanium and fluorine were found to actively interact in the systems to change the titanium substrate surface profile, leading to a ‘crater’ in the contact area. The ‘solid titanium–liquid magnesium fluoride’ interfacial geometry was examined and confirmed the potential to form gaseous products in the titanium–fluorine interaction. Such gaseous compounds prevent the wetting of alkaline-earth metal fluorides with titanium-containing melts at temperatures above 1400 K. This allows the materials made of alkaline-earth metal fluorides to be used as refractories for high-temperature melting, longterm homogenization, and casting of alloys with a high content of Ti, Zr, Hf, Nb, and V.

Electronic, Magnetic, and Theoretical Characterization of (NH4)4UF8, a Simple Molecular Uranium(IV) Fluoride.

The simple system of tetraammonium octafluorouranate is employed to derive a fundamental understanding of the uranium-fluorine interaction. The structure is composed of isolated molecules, enabling a detailed examination of the U4+ ( f2) ion. Characterization of single-crystals by X-ray diffraction, absorption spectroscopy, and magnetic analysis up to 45 T is combined with extensive theoretical treatment by CASSCF. The influence of different active spaces and representations of the structure is examined in the context of the experimental evidence. The Interacting Quantum Atoms method (IQA) is used to examine the nature of the U-F bond, concluding that there is a non-negligible degree of covalent character (9% of the total bond energy) in [UF8]4-. For the structural and theoretical reasons discussed herein, it is proposed that the structure of (NH4)4UF8 may be appropriately employed as a benchmark compound for future theoretical characterization of U(IV).

Galectin-3: studying role of fluorine interaction to achieve high affinity and selectivity

Galectin-3: studying role of fluorine interaction to achieve high affinity and selectivity

The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6···(HF)1–4 complexes

ABSTRACTThe effect of the hydrogen fluoride chain ((HF)n) on the aromaticity and π character of C–C bonds of C6H6 in the C6H6···(HF)n (n = 1–4) complexes were investigated using density functional theory employing RM05 functional. It was found that the binding energy between C6H6 and different (HF)n chains showed a maximum at n = 3 (C6H6···(HF)3). Also, the π–hydrogen interaction (πHI) and the bifurcated fluorine interaction (BFI) increased and decreased the π character of the C–C bond of C6H6, respectively. In addition, the change of aromaticity of the C6H6 due to the interaction with the HF chains was also studied using three different aspects such as aromatic fluctuation index (FLU), average two centre index (ATI) and proton nuclear magnetic resonance (HNMR) spectrum. The most change in the aromaticity happens when the C6H6 interacts with (HF)3 chain. The variation of aromaticity with the binding energy and the summation of two-body terms were investigated and very good linear correlations were observed.

Fluorine and carbon fluoride interaction with a diamond surface: Quantum-chemical modeling

Our study provides the results of quantum-chemical calculations of the interaction of fluorine atoms F, as well as CF2 and CF3 particles, with the ordered and defective C(100)-(2×1) diamond surfaces. We discuss the possible degree of fluorine coating for an ordered C(100)-(2×1) surface. It is shown that difluoride states on an ordered diamond surface are single complexes surrounded by monofluoride states. This paper includes the estimated values of activation energies of the particle adsorption and desorption, which determine the surface chemical etching mechanism. It is shown that fluorine atoms in the gas phase, along with vacancies on the surface, reduce the activation energy of difluoride state formation and increase the etching rate, while the CF2 and CF3 fragments in the gas mixture impede atomic fluorine etching of the surface.

Investigation into Rhenium Fluorination Process

The process of rhenium and fluorine interaction in the interval of temperatures from 200 °C up to 600 °C has been investigated. Influence of fluorine charge, fluorination square and temperatures on the process efficiency and fluorine use efficiency have been determined. Presence of two areas of process behavior, namely kinetic and diffusion has been demonstrated. It was shown that in the course of fluorination a mixture of hexafluorides and heptafluorides was formed. Dependence of rhenium fluorides composition on temperature has been determined

Fluorine interaction with defects on graphite surface by a first-principles study

The interaction between fluorine atom and graphite surface has been investigated in the framework of density functional theory. Due to the consideration of molten salt reactor system, only carbon adatoms and vacancies are chemical reactive for fluorine atoms. Fluorine adsorption on carbon adatom will enhance the mobility of carbon adatom. Carbon adatom can also be removed easily from graphite surface in form of CF2 molecule, explaining the formation mechanism of CF2 molecule in previous experiment. For the interaction between fluorine and vacancy, we find that fluorine atoms which adsorb at vacancy can hardly escape. Both pristine surface and vacancy are impossible for fluorine to penetrate due to the high penetration barrier. We believe our result is helpful to understand the compatibility between graphite and fluorine molten salt in molten salt reactor system.

Theoretical anharmonic Raman and infrared spectra with vibrational assignments and NBO analysis for 2,3,4,5,6-pentafluoroaniline

2,3,4,5,6-Pentafluoroaniline (PFA) is a very attractive object to theoretical study of fluorine interaction with an aromatic ring. Two major opposite effects are observed in PFA: interaction of the σ–π electron donating amino group, promoting electrophilic substitution at the ortho/para position by increasing the electron density at the ortho/para carbons versus fluorine substituents. This very strongly withdraws electron density from the aromatic system through the σ bond (inductive effect) and donates electron density through the π system (resonance effect). The stability of PFA arising from hyper conjugative interaction is investigated with natural bond orbital (NBO) analysis. The influences of the fluorine atoms on the geometrical and electronic properties as well as the detailed interpretation of vibrational spectra and potential energy distribution (PED) are also reported. The assignment of fundamental frequencies is confirmed by the qualitative agreement between the observed and calculated wavenumbers.

Fluorine interaction controlled AIEE phenomenon in an expanded calixbenzophyrin and its vapoluminescent response: turn on emission with volatile ketones and esters

Fluorine interaction assisted AIEE characteristic in an expanded calixbenzophyrin is presented by single-crystal X-ray-diffraction analysis and molecular modelling approaches. Selective exposure to volatile organic compounds such as ketones and esters results in the breaking of fluorine interaction, leading to enhanced monomer emission.

Preparation of a photoresponsive molecularly imprinted polymer containing fluorine-substituted azobenzene chromophores

The primary objective of this work is to explore the photoresponsive molecular recognition directed by fluorine–fluorine interaction. A new kind of fluorine-substituted photoresponsive functional monomer, (4-methacryloyloxy) nonafluoroazobenzene (MANFAB), was designed and synthesized, and a photoresponsive molecularly imprinted polymer containing a fluorine-substituted azobenzene chromophore (MIPF) was then fabricated using MANFAB as the monomer and 2,3,4,5,7,8,9,10-octafluorophenazine (PAF) as the model template. The photoisomerization process of MIPF materials is reversible. The release and uptake of PAF from toluene is photoregulated by alternate irradiation at 315 nm and 440 nm, indicating that photoresponsive molecular recognition directed by fluorine–fluorine interaction is possible. The binding strength of the imprinted receptor sites in MIPF for PAF is 4.67 × 10 4 M −1. The density of receptor sites in the MIPF material is 1.26 μmol/g-MIPF.

Intermolecular Hydrogen–Fluorine Interaction in Dimolybdenum Triply Bonded Complexes Modified by Fluorinated Formamidine Ligands for the Construction of 2D‐ and 3D‐Networks

AbstractThe formamidines ArNHC(H)=N–Ar [Ar = Ph (2a), 4‐F‐Ph (2b), 3,5‐F2Ph (2c) and 2,6‐F2Ph (2d) and R = 2,3,5‐F3Ph (2e), 3,4,5‐F3Ph (2f), F5Ph (2g) and 4‐CF3Ph (2h)] were synthesized and the influence of the introduction of a fluorine or a trifluoromethyl group into the aryl unit on the solid‐state structures was investigated. On comparing the experimental data, only marginal differences in the geometrical and electronic features of the diverse substituted species were detected. DFT calculations and X‐ray crystallography of 2d–2g revealed that the E‐syn‐configuration corresponded to the thermodynamically most stable motif of all of the examined formamidines. However, in their solid‐state, these ligands showed a range of H···F interactions, which varied depending on the number and position of the fluorine atoms on the aryl group and thus led to interesting solid‐state structures. Moreover, compounds 2 were used for the synthesis of the new heteroleptic dimolybdenum triply‐bonded complexes, Mo2[(2a–2c; 2e–f)–H]2(OtBu)4 (3a–3c; 3e–3f). X‐ray crystallography of complexes 3c and 3f revealed two different isomers in the solid state: in trans‐3c the two formamidines are in one plane, while in cis‐3c and cis‐3f they are next to each other. The DFT calculations showed only a small distinction in energy between the configurations, which led us to assume that the different configurations were induced by the crystal packing. The specific H···F interactions provided by the different formamidines led to a two‐dimensional arrangement for trans‐3c and a three‐dimensional network for cis‐3c and cis‐3f.

Synthesis of stable arsonium and sulfur ylides from perfluoroalkanesulfonyl diazocarbonyl compounds and their X-ray diffraction analysis

A series of stable fluorine-containing arsonium ylides and sulfur ylides were simply synthesized from perfluoroalkanesulfonyl diazocarbonyl compounds in the presence of rhodium catalyst. The ylide products are fairly stable due to the strong electron-withdrawing properties of perfluoroalkanesulfonyl group and carbonyl group. They are fully confirmed by spectral methods and the structures of 3ba and 3cd are also established by X-ray single crystal diffraction analysis. Several interesting features about the ylide structures and some weak fluorine interaction between them are described here.

Group additivity values for enthalpies of formation (298 K), entropies (298 K), and molar heat capacities (300 K < T < 1500 K) of gaseous fluorocarbons

A group additivity method was developed to estimate standard enthalpies of formation and standard entropies at 298 K of linear radical and closed-shell, gaseous fluorocarbon neutrals containing four or more carbon atoms. The method can also be used to estimate constant pressure molar heat capacities of the same compounds over the temperature range 300 K to 1500 K. Seventeen groups and seven fluorine–fluorine interaction terms were defined from 12 fluorocarbon molecules. Interaction term values from Yamada and Bozzelli [T. Yamada, J.W. Bozzelli, J. Phys. Chem. A 103 (1999) 7373–7379] were utilized. The enthalpy of formation group values were derived from G3MP2 calculations by Bauschlicher and Ricca [C.W. Bauschlicher, A. Ricca, J. Phys. Chem. A 104 (2000) 4581–4585]. Standard entropy and molar heat capacity group values were estimated from ab initio geometry optimization and frequency calculations at the Hartree–Fock level using the 6-31G(d) basis set. Enthalpies of formation for larger fluorocarbons estimated from the group additivity method compare well to enthalpies of formation found in the literature.