Influence Of Fluorine Atoms Research Articles

Mesomorphic thermal stabilities and nonlinear optical properties of fluorine containing liquid crystals

H-bonded liquid crystals (HBLCs) are newly synthesized with PyBF viz., (4-pyridyl)-benzylidene-4′-fluoro aniline as the proton acceptor which is non-mesogenic and alkyloxy benzoic acids viz., nOBAs (n = 3, 12) as the mesogenic proton donors. The H-bond formed is confirmed by FTIR spectroscopy. Polarizing Optical Microscopy confirmed the H-bonded compound’s mesomorphic textures, and the thermal analysis is carried out using a Differential Scanning Calorimeter. The influence of fluorine atom on mesomorphic stability is studied. The nonlinear optical properties of the H-bonded compound is studied using DFT theoretical approach. This work supports the SDG-9 of the United Nations.Graphical abstract

Influence of fluorine atoms on reactive oxygen species-mediated degradation of ophthalmic fluoroquinolones. Kinetic and cytotoxicity studies

Fluoroquinolones have been attractive broad-spectrum antibiotics for ophthalmic application. However, they have shown phototoxicity as a significant side effect, which is strongly dependent on fluoroquinolone structure and some environment conditions. Beyond their photo-reactivity, an indirect light-induced process deserves to be considered. The photosensitized action of molecules present in the ocular organ, such as Riboflavin, may produce reactive oxygen species (ROS) that could degrade fluoroquinolones. As a consequence, the antibiotics may lose their therapeutic action and/or produce degradation products with harmful effects on health.In this contribution, a kinetic analysis of ROS-mediated degradation processes of ophthalmic quinolones is addressed. Further, considering the evidence towards the structure-modulated phototoxicity, we evaluated the influence of structural fluorine atoms on these processes. The non-fluorinated precursor Nalidixic Acid and the fluoroquinolones (Ciprofloxacin, Norfloxacin and Lomefloxacin) were selected for this study. Cytotoxicity experiments in Vero cells were performed in order to investigate the potential toxicity of the ROS-mediated degradation products.Our results suggest that quinolones may be degraded by ROS and these processes are regulated by the ionization state of quinolone and the presence of fluorine atoms in their structure. Both effects increase the electron donor ability of the quinolones, which favor electron transfer processes and increase their reactivity towards species with an electrophilic character. Interestingly, this fluorine-dominated effect has been recently called “fluoromaticity”.Cytotoxicity assays indicated that neither the Qs nor their ROS-mediated degradation products presented injury on Vero cells under the current experimental conditions.

Pyrrolidine-Derived Phenanthroline Diamides: An Influence of Fluorine Atoms on the Coordination of Lu(III) and Some Other f-Elements and Their Solvent Extraction.

Three pyrrolidine-derived phenanthroline diamides were studied as ligands for lutetium trinitrate. The structural features of the complexes have been studied using various spectral methods and X-ray. The presence of halogen atoms in the structure of phenanthroline ligands has a significant impact on both the coordination number of lutetium and the number of solvate water molecules in the internal coordination sphere. The stability constants of complexes with La(NO3)3, Nd(NO3)3, Eu(NO3)3, and Lu(NO3)3 were measured to demonstrate higher efficiency of fluorinated ligands. NMR titration was performed for this ligand, and it was found that complexation with lutetium leads to an approximately 13 ppm shift of the corresponding signal in the 19F NMR spectrum. The possibility of formation of a polymeric oxo-complex of this ligand with lutetium nitrate was demonstrated. Experiments on the liquid-liquid extraction of Am(III) and Ln(III) nitrates were carried out to demonstrate advantageous features of chlorinated and fluorinated pyrrolidine diamides.

Porphyrin sensitizers involving a fluorine-substituted benzothiadiazole as auxiliary acceptor and thiophene as π bridge for use in dye-sensitized solar cells (DSSCs)

Three ‘donor–acceptor–π bridge–acceptor’ (D–A–π–A) type zinc porphyrin sensitizers TH-0F, TH-1F and TH-2F with a benzothiadiazole (BTD) unit bearing no fluorine, one fluorine and two fluorine atoms, respectively, as the auxiliary acceptor and thiophene as the π bridge were designed and synthesized for use in dye-sensitized solar cells (DSSCs). The influence of fluorine atom and thiophene unit on the photophysical and photochemical properties of the sensitizers was investigated. It was shown that the photon to current conversion efficiencies (PCE) of three sensitizer-based devices increased in the order of TH-2F > TH-1F > TH-0F, with the highest PCE of 6.98% achieved for the TH-2F-based device. To further understand the molecular structure of the TH series of dyes, a density functional (DFT) calculation was performed. The result suggests that the strong electron-withdrawing ability of the fluorine atom, along with the intramolecular interaction between the auxiliary acceptor and thiophene, optimized the electronic configuration, thereby facilitating the intramolecular charge transfer efficiency and ultimately improving the performance of the corresponding device.

Properties of binary mixtures derived from hydrogen bonded liquid crystals

Linear supra-molecular liquid crystals, 4-(octyloxy) benzoic acid (8OBA) and 4-(octyloxy)-3-fluoro benzoic acid (8OBAF), have been synthesized. The structure of these compounds was investigated by NMR and FTIR. The thermal and phase behavior of these compounds were studied by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and dielectric spectroscopy. The influence of fluorine atom in benzene ring core compounds and on electro-optical and optical properties has been studied as well. The binary mixtures of these compounds are well-established and the phase diagram (temperature-concentration) is plotted in heating as well as in cooling mode. The substituted mesogen exhibits rich phase variance compared to the 80BA. From the experimental observations, smectic-G phase appeared in the complexes.

Identification of 3-substituted-6-(1-(1H-[1,2,3]triazolo[4,5-b]pyrazin-1-yl)ethyl)quinoline derivatives as highly potent and selective mesenchymal-epithelial transition factor (c-Met) inhibitors via metabolite profiling-based structural optimization

c-Met/HGF signaling pathway plays an important role in cancer progression, and it was considered to be related to poor prognosis and drug resistance. Based on metabolite profiling of (S)-7-fluoro-6-(1-(6-(1-methyl-1H-pyrazol-4-yl)-1H-imidazo[4,5-b]pyrazin-1-yl)ethyl)quinoline (1), a series of 2-substituted or 3-substituted-6-(1-(1H-[1,2,3]triazolo[4,5-b]pyrazin-1-yl)ethyl)quinoline derivatives was rationally designed and evaluated. Most of the 3-substituted derivatives not only exhibited potent activities in both enzymatic and cellular assays, but also were stable in liver microsomes among different species (human, rat and monkey). SAR investigation revealed that introducing of N-methyl-1H-pyrazol-4-yl group at the 3-position of quinoline moiety is beneficial to improve the inhibitory potency, especially in the cellular assays. The influence of fluorine atom at 7-position or 5, 7-position of quinoline moiety and substituents at the 6-position of triazolo[4,5-b]pyrazine core on overall activity is not very significant. Racemate 14, an extremely potent and exquisitely selective c-Met inhibitor, demonstrated favorable pharmacokinetic properties in rats, no significant AO metabolism, and effective tumor growth inhibition in c-Met overexpressed NSCLC (H1993 cell line) and gastric cancer (SNU-5 cell line) xenograft models. Docking analysis indicated that besides the typical interactions of most selective c-Met inhibitors, the intramolecular halogen bond and additional hydrogen bond interactions with kinase are beneficial to the binding. These results may provide deep insight into potential structural modifications for developing potent c-Met inhibitors.

Small but strong: The influence of fluorine atoms on formation and performance of graphene quantum dots using a gradient F-sacrifice strategy

Fluorinated graphene quantum dots (FGQDs) have distinctive charge distribution in structure and unique chemical bonds in composition, corresponding to novel performance different from common quantum dots. However, their synthesis is a challenge due to chemically inert CF bonds and hydrophobic nature, and the fluorine influence on FGQDs remains scarce and to be studied. Herein, we first design a gradient fluorine-sacrificing strategy to synthesize FGQDs with controllable sizes and tunable fluorine contents from bulk fluorinated graphite. It is found that although fluorine atom is the second-smallest in periodic table, it not only greatly affects the size formation process, but also endows FGQDs with pH-independent luminescence without any additional surface passivation. And it is for the first time to experimentally observed that point defects in FGQDs induced by fluorine can greatly increase paramagnetism, which is 5 times higher than unfluorinated ones. Moreover, cytotoxicity experiments clearly reveal FGQDs show good biocompatibility, and it is the chemical surface rather than size that influences the cell viability. This work realizes fine control over both structure and chemistry of FGQDs, and thus allows a better insight into the fluorine effects on formation and performance of graphene quantum dots.

Effect of Fluorination on Molecular Orientation of Conjugated Polymers in High Performance Field-Effect Transistors

Fluorinated conjugated polymers have been widely used in high performance polymer solar cells, but they showed limited application in field-effect transistors (FETs). In this paper, we focus on the influence of fluorine atoms upon charge transport of conjugated polymers in FET devices. Two series of conjugated polymers without or with fluorine atoms were designed and applied into FETs. Nonfluorinated conjugated polymers show high hole mobilties up to 11.16 cm2 V–1 s–1, while fluorinated polymers exhibit low hole mobilities below 1.80 cm2 V–1 s–1. Further investigation by differential scanning calorimetry (DSC) and 2D grazing-incidence wide-angle X-ray scattering (2D-GIWAXS) reveal that fluorinated conjugated polymers show low crystallinity and “face-on” orientation in thin films, explaining their poor hole mobilities in FET devices. Our results clearly show how the chemical structures influence the charge transport properties, which can be used to design new conjugated polymers toward high performance FETs.

A series of fluorinated phenylpyridine-based electron-transporters for blue phosphorescent OLEDs

A series of fluorinated phenylpyridine-based electron-transport materials were developed and the influence of fluorine atom(s) on molecular orientation and mobility was investigated.

Influence of Fluorine Atoms and Aromatic Rings on the Acidity of Ethanol

Absolute gas-phase acidities Delta(acid)G(0)(OH) and Delta(acid)G(0)(CH) were calculated at the B3LYP and MP2 levels using six different standard basis sets for the OH and CH heterolytic bond cleavage of ethanol and twelve derivatives of the type CH(3-n)F(n)CHX(r)OH, where n ranges from zero to three and represents the number of fluorine atoms and r represents hydrogen and the type of aromatic ring, namely: X(0) = hydrogen, X(1) = phenyl, X(2) = 1-naphthyl, and X(3) = 9-anthryl. The similarity between calculated and experimental Delta(acid)G(0)(OH) values for ethanol (1a), 2-fluoroethanol (1b), 2,2-difluoroethanol (1c), 2,2,2-trifluoroethanol (1d), and 1-phenylethanol (2a) was used to validate the right theoretical method for this study. Substituent partial contributions to hydroxyl-, methylene-, and methine-hydrogen acidities were evaluated by linear combination. Good parameter fittings of the primary and secondary alcohols were obtained and interpreted as additive contribution of the substituent effects. The nonlinear contributions were identified. Calculations prove that fluoroalcohols exhibit C-H acidity, which is usually lower than O-H acidity. In principle, the inversion of this acidity order is possible by the introduction of a large aromatic ring instead to increase the number of fluorine atoms.

Low Frequency Dielectric Relaxation, Spontaneous Polarization, Optical Tilt Angle and Response Time Investigations in a Flourinated Ferroelectric Liquid Crystal, N125F2(R*)

Experimental investigations of thermal microscopy, low frequency dielectric relaxation, spontaneous polarization P s (T), optical tilt angle θ(T) and response times τ s (T) are carried out in a fluorinated ferroelectric liquid crystal, N125F2(R*) exhibiting smectic-A and smectic-C* phases. Dielectric loss in the smectic-A phase exhibits single Debye's relaxation in the MHz region. The smectic-C* phase exhibits two relaxations, viz., a Goldstone mode at ∼500 Hz and another at a much higher frequency, ∼5 MHz. The Arrhenius shift of Smectic-A relaxation frequency (f R ) gives an activation energy of 1.5 eV. The influence of temperature and applied voltage on the smectic-C* Goldstone mode relaxation is studied. In the smectic-C* high frequency relaxation mode, the relaxation frequency (relevant to the tilt) is found to increase with decreasing temperature. The temperature variation of the reciprocal of the dielectric strength (1/Δϵ s ) above the smectic-A—smectic-C* phase transition qualitatively supports the Curie-Weiss law. Temperature variation of primary (tilt) and secondary (P s ) order parameters are presented. The temperature variation of τ s in the smectic-C* phase studied through square wave technique is presented. The influence of fluorine atoms on the rigid core part of the present ferroelectric liquid crystal on the physical properties exhibited in it's smectic-C* phase is discussed.

AIM study on the influence of fluorine atoms on the alkyl chain

Abstract A topological analysis of HF/6-31++G**//HF/6-31G* electron distributions on diverse conformers of 36 linear fluoroalkanes of formula CH n F 3− n (CH 2 ) m CH 3 was carried out within the atoms in molecules (AIMs) formalism. Group energy additivity of molecular energies was found in spite of lack of energy transferability. Cooperative effects due to stepwise fluorination on carbon 1 that appear to be around to 90 kJ mol −1 according to traditional analysis based upon fitted group energies, exceed 370 kJ mol −1 when obtained from AIMs energies. Mean values of atomic properties and empirical relationships between concrete atomic properties lead to a definition of transferable fragments. It was found that the effect of fluorine atom on the chain is appreciable at further carbons for trans than for gauche arrangements, whereas effects on the hydrogen atoms give rise to an oscillatory behaviour (related to F–H interatomic distances) displayed along the whole chain.

Acceleration of Organic Contaminant Adsorption Onto Silicon Surfaces in the Presence of Residual Fluorine

ABSTRACTThe influence of fluorine atoms remaining after HF treatment on the adsorption of organic contaminants onto the surface of silicon wafers was investigated by analyzing the organic contaminants with gas chromatography-mass spectrometry following thermodesorption (TDGC/MS), and the surface composition with X-ray photoelectron spectroscopy (XPS). It has been found that residual fluorine on silicon surfaces after cleaning of the silicon wafers with either aqueous HF or anhydrous HF accelerates the adsorption of organic contamination onto the silicon surfaces. This would be due to the electrostatic force of attraction between the polar groups of organic compounds and the residual fluorine on the silicon surface.

Influence of fluorine atoms on the electron impact and chemical ionization mass spectrometric fragmentation of methyl x‐deoxy‐x‐fluoro‐per‐O‐methyl‐β‐D‐galactopyranosides

AbstractFully methylated methyl x‐deoxy‐x‐fluoro‐β‐D‐galactopyranosides were studied using electron impact (EI) and chemical ionization (CI) mass spectrometry and by gas chromatography (GC)/mass spectrometry. Metastable daughter‐ and parent‐ion measurements and high‐resolution measurements were used to evaluate the fragmentation schemes. Both the presence and the position of the electronegative fluorine atom influences the fragmentation pathways of the permethylated compounds. The individual methyl x‐deoxy‐x‐fluoro‐per‐O‐methyl‐β‐D‐ galactopy‐ranosides have different GC retention times. This, together with the characteristic differences present in the EI or CI (methane or isobutane) mass spectra, allows the location of fluorine in these substances to be unambiguously determined.

General method for the asymmetric synthesis of fluorine-containing amino acids

Several recent developments in our laboratories have made it possible to elaborate a general method for preparing optically pure fluorine containing α-amino acids starting from a Ni(II)-complex ( 1) of a Schiff's base derived from (S)-o-[(benzylpropyl)amino]-benzophenone (BBP) and glycine or alanine. ▪ Alkylation of ( 1) with fluorine-substituted benzyl halides and aldehyde condensation result, respectively, in fluorine-containing S-Phe and its α-methyl derivatives, 2R,3S-, 2S,3R-, 2R,3R-PhSer and 2S,3S-β-perfluoroalkyl Ser in good chemical and optical yields. Simplicity of the synthetic procedure, ease of recovery of the chiral auxiliary (BBP), and the possibility of obtaining optically pure fluorine containing amino acids make this method attractive. The influence of fluorine atoms or fluorine containing groups and reaction conditions on the stereochemical results in the reactions of this type will be discussed.

N-(polyfluoroaryl)-hydroxylamines. Synthesis and properties

Fluorine-containing N-arylhydroxylamines have been obtained by the action of hydroxylamine or its N- and O-derivatives on polyfluorinated benzenes and pentafluoropyridine. The influence of fluorine atoms on the reactivity of hydroxylamino group has been investigated. The reaction of N-polyfluoroarylhydroxylamines with aldehydes has been shown not to occur, whereas their reaction with nitrosobenzenes leads to azoxybenzenes and with Lewis acids leads to corresponding nitrosobenzenes, azoxybenzenes and anilines. The action of acids on 2,3,5,6-tetrafluorophenylhydroxylamine leads to the acid-catalyzed rearrangement of the latter into 4-amino-2,3,5,6-tetrafluorophenol. C,N-Diarylnitrones have been obtained by the oxidation with MnO 2 of fluorine-containing arylhydroxylamines possessing the CH-fragment in an α-position.

Influence of fluorine atoms on intensity of aromatic ring vibrations in raman spectra of fluorobenzenes and pentafluoro-substituted derivatives of benzene

1. The changes in frequency and intensity of the benzene ring vibrations in the 1600–1660 cm1 interval upon introduction of F atoms into the ring are not related to any change in form of the vibrations. 2. The regularities observed in change of intensity of ν8 vibrations in the Raman spectra of polyfluoroaromatic compounds under the influence of substituents (including those with multiple bonds) are analogous to what is observed for other substituted benzenes, but the changes are less pronounced.

Raman studies of conjugation in polyfluoroaromatic compounds

Influence of the aromatic fluorine atoms in compounds of the type ArYAr ( Y = -NN-, -NN(O)-,-CN- ) and ArNSO on frequencies and intensities of stretching vibrations of functional groups in Raman spectra has been studied. The stretching frequencies of groups -NN-, -NN(O)-, -CHN-, -NSO are shown to be practically independent of position and number of fluorine atoms, but the intensities do depend. This is attributed to the changed effectivity of conjugation of nitrogen non-bonding electron pair with the aromatic π -system caused by the influence of fluorine atoms.

Spectroscopic investigation of the intramolecular effects in the hydrazides of fluoro-substituted carboxylic acids

1. The introduction of a phenyl or alkyl substituent at the β-nitrogen atom in the hydrazides of carboxylic acids and their fluorinated analogs leads to a trans orientation of the unshared pairs of electrons on the nitrogen atoms. 2. The influence of fluorine atoms on the electronic state of the C=O group in molecules of 1-acyl-2-alkylhydrazines and 1-acyl-2-phenylhydrazines is due to the inductive effect of the substituent R and to the possibility of stabilization by the intramolecular NH...F hydrogen bond. 3. The greatest electronic effect of a fluoroalkyl substituent on a hydrazide fragment is realized in the acylhydrazines and 1-acyl-2-phenylhydrazines.