Substitution Of Fluorine Atom Research Articles

BODIPY Compounds Substituted on Boron.

BODIPY compounds are important organic dyes with exceptional spectral and photophysical properties and numerous applications in different scientific fields. Their widespread applications have flourished due to their easy structural modifications, which enable the preparation of different molecular structures with tunable spectral and photophysical properties. To date, researchers have mostly devoted their efforts to modifying BODIPY meso-position or pyrrole rings, whereas the substitution of fluorine atoms remains largely unexplored. However, chemistry of the boron atom is possible, and it enables tuning of the photophysical properties of the dyes, without tackling their spectral properties. Furthermore, modifications of boron affect the solubility and aggregation propensity of the molecules. This review article highlights methods for the preparation of 4-substituted compounds and the most important reactions on the boron of the BODIPY dyes. They were divided into reactions promoted by Lewis acid (AlCl3 or BCl3), or bases such as alkoxides and organometallic reagents. By using these two methodologies, it is possible to cleave B-F bonds and substitute them with B-C, B-N, or B-O bonds from different nucleophiles. A special emphasis in this review is given to still underdeveloped photochemical reactions of the boron atom of BODIPY dyes. These reactions have the potential to be used in the development of a new line of BODIPY photo-cleavable protective groups (also known as photocages) with bio-medicinal and photo-pharmacological applications, such as drug delivery.

Adsorbtive removal of HF toxic gas via tinsulfide monolayer modification: A molecular perspective

Hydrofluoric Acid (HF) is considered one of the most hazardous chemicals used in industrial plants. Even small exposures to HF can have fatal consequences if not promptly and properly treated. Various research teams have presented numerous substances with the objective of capturing or detecting toxic HF gas. In this study, we explore the impact of HF gas on a single layer of SnS by employing density functional theory (DFT). The interaction nature between the gas molecule and the adsorbent is elucidated by analyzing the related adsorption energy, electronic structure properties and differential charge transfer. The findings indicate that HF is physically adsorbed on the pristine SnS with an adsorption energy value of −0.63 eV. By introducing a Sn mono vacancy defect, the modification of SnS enhances the adsorption energy to −1.26 eV, resulting in a chemisorption process. Molecular fluorine (F2) was discovered to undergo a barrierless reaction with SnS, resulting in the formation of fluorine-substituted SnS. It has been discovered that the substitution of fluorine atoms enhances the reactivity of SnS towards hydro-gen fluoride gas. The adsorption potential of the studied structures towards HF gas was determined to be in the following order: F2SnS > VSn–SnS > VS-SnS ∼ SnS. The current study is anticipated to offer new molecular insights that could lead to the creation of innovative devices for detecting or eliminating HF toxic gas from a specific atmosphere.

SYNTHESIS, CHARACTERIZATION & BIOLOGICAL EVALUATION OF SOME FLUOROQUINOLONE DERIVATIVES AS ANTIMICROBIAL AGENTS

Fluoroquinolones, a class of synthetic antibacterial agents, have gained significant attention due to their broad-spectrum activity against various bacterial pathogens. However, the emergence of resistance to conventional fluoroquinolones underscores the necessity for novel derivatives with enhanced efficacy and reduced resistance profiles. The synthesis of fluoroquinolone derivatives involves structural modifications aimed at improving antimicrobial activity, pharmacokinetic properties, and minimizing adverse effects. Various synthetic routes, including modification of the quinolone core structure, substitution of fluorine atoms, and introduction of diverse functional groups, have been explored to tailor the properties of these derivatives. Characterization techniques such as infrared spectroscopy (IR) has been employed to elucidate the chemical structures and confirm the purity of synthesized compounds. Biological evaluation encompasses in vitro and in vivo studies to assess the antimicrobial activity, cytotoxicity, and pharmacological profiles of fluoroquinolone derivatives. These evaluations provide crucial insights into the therapeutic potential, mechanism of action, and safety profile of novel compounds.

Where do the Fluorine Atoms Go in Inorganic‐Oxide Fluorinations? A Fluorooxoborate Illustration under Terahertz Light

AbstractThe substitution of fluorine atoms for oxygen atoms/hydroxyl groups has emerged as a promising strategy to enhance the physical and chemical properties of oxides/hydroxides in fluorine chemistry. However, distinguishing fluorine from oxygen/hydroxyl in the reaction products poses a significant challenge in existing characterization methods. In this study, we illustrate that terahertz (THz) spectroscopy provides a powerful tool for addressing this challenge. To this end, we investigated two fluorination reactions of boric acid, utilizing MHF2 (M=Na, C(NH2)3) as fluorine reagents. Through an interplay between THz spectroscopy and solid‐state density functional theory, we have conclusively demonstrated that fluorine atoms exclusively bind with the sp3‐boron but not with the sp2‐boron in the reaction products of Na[B(OH)3][B3O3F2(OH)2] (NaBOFH) and [C(NH2)3]2B3O3F4OH (GBF2). Based on this evidence, we have proposed a reaction pathway for the fluorinations under investigation, a process previously hindered due to structural ambiguity. This work represents a step forward in gaining a deeper understanding of the precise structures and reaction mechanisms involved in the fluorination of oxides/hydroxides, illuminated by the insights provided by THz spectroscopy.

Where do the Fluorine Atoms Go in Inorganic-Oxide Fluorinations? A Fluorooxoborate Illustration under Terahertz Light.

The substitution of fluorine atoms for oxygen atoms/hydroxyl groups has emerged as a promising strategy to enhance the physical and chemical properties of oxides/hydroxides in fluorine chemistry. However, distinguishing fluorine from oxygen/hydroxyl in the reaction products poses a significant challenge in existing characterization methods. In this study, we illustrate that terahertz (THz) spectroscopy provides a powerful tool for addressing this challenge. To this end, we investigated two fluorination reactions of boric acid, utilizing MHF2 (M=Na, C(NH2)3) as fluorine reagents. Through an interplay between THz spectroscopy and solid-state density functional theory, we have conclusively demonstrated that fluorine atoms exclusively bind with the sp3-boron but not with the sp2-boron in the reaction products of Na[B(OH)3][B3O3F2(OH)2] (NaBOFH) and [C(NH2)3]2B3O3F4OH (GBF2). Based on this evidence, we have proposed a reaction pathway for the fluorinations under investigation, a process previously hindered due to structural ambiguity. This work represents a step forward in gaining a deeper understanding of the precise structures and reaction mechanisms involved in the fluorination of oxides/hydroxides, illuminated by the insights provided by THz spectroscopy.

Ab initio anharmonic analysis of complex vibrational spectra of phenylacetylene and fluorophenylacetylenes in the acetylenic and aromatic C-H stretching region.

Vibrational spectra in the acetylenic and aromatic C-H stretching regions of phenylacetylene and fluorophenylacetylenes, viz., 2-fluorophenylacetylene, 3-fluorophenylacetylene, and 4-fluorophenylacetylene, were measured using the IR-UV double resonance spectroscopic method. The spectra, in both acetylenic and aromatic C-H stretching regions, were complex exhibiting multiple bands. Ab-initio anharmonic calculations with quartic potential using B97D3/6-311++G(d,p) and vibrational configuration interaction were able to capture all important spectral features in both the regions of the experimentally observed spectra for all four molecules considered in the present work. Interestingly, for phenylacetylene, the spectrum in the acetylenic C-H stretching region emerges due to anharmonic coupling of modes localized on the acetylenic moiety along with the other ring modes, which also involve displacements on the acetylenic group, which is in contrast to what has been proposed and propagated in the literature. In general, this coupling scheme is invariant to the fluorine atom substitution. For the aromatic C-H stretching region, the observed spectrum emerges due to the coupling of the C-H stretching with C-C stretching and C-H in-plane bending modes.

Conformational landscapes of symmetrically fluorine-substituted benzoic acids I: Microwave spectroscopic and theoretical studies on 3,5-difluorobenzoic acid

We report our combined theoretical and spectroscopic studies on 3,5-difluorobenzoic acid. Using a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer, we recorded and analyzed the rotational spectrum spanning the frequency range of 6 – 12.5 GHz. Quantum chemical calculations were employed to analyze the conformational changes and landscapes of 3,5-difluorobenzoic acid. These calculations focused on studying the potential energy surfaces along the CCCO and OCOH dihedral angles at the B3LYP/6-311G level. Based on the computational results, we identified the global minimum conformer 1 as well as the local minimum conformer 2. We discussed and interpreted the geometric structures of the relevant conformations, with a particular emphasis on the interactions between the carboxylic group and the substituted fluorine atoms. Furthermore, these findings were compared to benzoic acid in internal strains. In our spectral analysis, we successfully identified conformer 1 and its seven 13C singly substituted isotopologues. We derived highly accurate rotational constants for 3,5-difluorobenzoic acid, displaying good agreement with computational results. We established the effective structure of its ground vibrational state using Kraitchman’s equations. Similar to benzoic acid, the global minimum conformation of 3,5-difluorobenzoic acid adopts a planar structure, corroborating our computational outcomes.

Growth and Structure of Rare-Earth Molybdate Crystals Na0.65La4.35Mo3O15.81±δF0.07±ε

Rare-earth sodium- and fluorine-substituted molybdates with the Na0.65La4.35Mo3O15.81±δF0.07±ε composition were synthesized for the first time as single crystals. An accurate X-ray diffraction analysis of three samples at room temperature showed that the obtained crystals are isostructural to undoped cubic compounds of the Ln5Mo3O16+δ family (space group Pn3¯n). Sodium cations partially occupy one of the two lanthanum positions and center the more distorted LaO8 polyhedra, while fluorine anions occupy over-stoichiometric oxygen positions in the vast interstices (cavities) of the structure. The partial substitution of fluorine atoms for oxygen ones affects the transport characteristics of compounds by activating the oxygen atoms in the anionic subsystem due to the effect of supplementary electrostatic repulsion between anions of different types.

Terahertz spectroscopy analysis of L-Phenylalanine and its fluorinated derivatives

3-Fluoro-L-Phenylalanine (3-F-L-Phe) and 4-Fluoro-L-Phenylalanine (4-F-L-Phe) are fluorinated derivatives of L-Phenylalanine (L-Phe) that hold significant medical applications. To investigate the impact of introducing fluorine atoms on the structure of L-Phe, this study employed terahertz (THz) spectroscopy to distinguish three crystal structure differences. A comparative analysis of the absorption peaks of 3-F-L-Phe and 4-F-L-Phe with that of L-Phe revealed varying degrees of red shift and blue shift. The dielectric loss analysis demonstrated that the substitution of fluorine atoms in different positions of the benzene ring changes the crystal structure and electric dipole moment. By combining lattice network and vibration mode comparative analysis, the study concluded that the differences in the spectrum could be attributed to variations in the hydrogen bond network and changes in the unit cell volume. These findings highlight the effectiveness of using terahertz time domain spectroscopy (THz-TDS) and solid-state density functional theory (DFT) as a new method for the qualitative analysis of fluorinated amino acid derivatives.

Thienoindolizines and their Benzo-Fused Derivatives: Synthesis and Physical Properties.

A series of thienoindolizine structural isomers have been synthesized in a one-pot, two-step procedure starting from easily accessible gem-difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2-g]-, thieno[3,4-g]- and thieno[2,3-g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29% to 95%. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures.

Synthesis of Thiophene-Based Derivatives and the Effects of Their Molecular Structure on the Mesomorphic Behavior and Temperature Range of Liquid-Crystalline Blue Phases

The development of blue-phase liquid crystal (BPLC) materials with a wide temperature range is of great significance for practical applications in the optoelectronic field. In the study, bent-core derivatives with a 3-hexyl-2,5-disubstituted thiophene central ring in the λ-shaped molecular structure were designed and synthesized. Their mesomorphic behavior and effect on the blue-phase (BP) temperature range were investigated. Interestingly, a BP was achieved both during the heating and cooling processes by doping with a proper concentration of chiral compound into the thiophene bent-shaped molecule with high rigidity, while derivatives with fluorine atom substitution only exhibited cholesteric phase no matter how many chiral compounds were added. This result proved that BP is highly sensitive to the molecular structures of bent-shaped molecules. Moreover, the BP temperature range was broadened when adding these molecules into a BPLC host, which thus improved the BP temperature range from the initial value, no more than 4 °C, to as much as 24 °C. The experimental phenomena were reasonably explained through molecular simulation calculations. The study may provide some experimental basis and theoretical guidance for the design of novel bent-shaped molecules and BPLC material with a wide temperature range.

Structure-Electrochemical Property Relationship of F vs 2F Substituents in Low Bandgap Conjugated Polymers

Two alternating copolymers bearing fluorinated benzothiadiazole as a strong acceptor unit and dithienopyrrole as a strong donor unit were designed and synthesized to discuss the effect of the number of fluorine atom substitution. The polymers were characterized via cyclic voltammetry, spectroelectrochemistry, electrochemical impedance spectroscopy and galvanostatic charge discharge studies. Besides a red shift in absorption spectra, an anodic shift was also observed in the oxidation potentials when number of fluorine atom increases in the polymer backbone. Galvanostatic charge-discharge (GCD) studies revealed that difluorinated polymer exhibited enhanced area specific capacitance compared to mono fluorinated polymer.

Asymmetric Polymer Additive for Morphological Regulation and Thermally Stable Organic Solar Cells.

High thermal stability is crucial for the commercialization of organic solar cells (OSCs). The thermal stability of OSCs has been improved using the tailoring blend morphology of bulk heterojunctions (BHJs). Herein, we demonstrated thermally stable OSCs in a ternary blended system containing low-crystalline semiconducting polymers (asy-PNDI1FTVT and PTB7-Th) and a non-fullerene acceptor (Y6). The asymmetric n-type semiconducting polymer (asy-PNDI1FTVT) differed from general symmetric semiconducting polymers as it randomly substituted fluorine atoms at the donor moiety (TVT), resulting in significantly lower crystallinity. asy-PNDI1FTVT in PTB7-Th:Y6 exhibited a well-mixed morphology at the BHJ and efficiently facilitated the charge dissociation process with an enhanced fill factor and power conversion efficiency. Furthermore, the ternary system of PTB7-Th:Y6:asy-PNDI1FTVT suppressed phase separation with negligible burn-in loss and performance degradation under thermal stress. The experiments showed that our devices without encapsulation retained over 90% of their initial efficiencies after 100 h at 65 °C. These results show significant potential for the development of thermally stable OSCs with reasonable efficiency.

Efficient Small‐Molecule Organic Solar Cells by Modulating Fluorine Substitution Position of Donor Material

Comprehensive SummaryThe fluorine substitution position in organic semiconductors is critical in improving device performance for organic solar cells (OSCs). Herein, two similar small‐molecule donors, B3T‐PoF and B3T‐PmF, are designed and synthesized, which only differ on the fluorine substitution position on the pendent benzene unit. Although both small‐molecule donors exhibit similar absorption profiles and molecular energy levels, B3T‐PmF has stronger crystallinity and lower energetic disorder than B3T‐PoF. After blending with the non‐fullerene acceptor of BO‐4Cl, B3T‐PmF shows better phase separation and more ordered molecular packing in blend film. As a result, the B3T‐PoF:BO‐4Cl‐based OSC shows a power conversion efficiency (PCE) of 12.3%. In contrast, the B3T‐PmF:BO‐4Cl‐based cell demonstrates obviously increased JSC and FF values, thus yielding an excellent PCE of 14.7%. This study indicates that reasonable selection of fluorine atom substitution position in conjugated side chains is one of the promising strategies for achieving high‐performance SM‐OSCs.

Placing CF2 in the Center: Major Physicochemical Changes Upon a Minor Structural Alteration in Gem-Difunctional Compounds.

Fluorine atoms play an important role in all branches of chemistry and accordingly, it is very important to study their unique and varied effects systematically, in particular, the structure-physicochemical properties relationship. The present study describes exceptional physicochemical effects resulting from a H/F exchange at the methylene bridge of gem-difunctional compounds. The Δlog P(CF2-CH2) values, that is, the change in lipophilicity, observed for the CH2 /CF2 replacement in various α,α-phenoxy- and thiophenoxy-esters/amides, diketones, benzodioxoles and more, fall in the range of 0.6-1.4 units, which for most cases, is far above the values expected for such a replacement. Moreover, for compounds holding more than one such gem-difunctional moiety, the effect is nearly additive, so one can switch from a hydrophilic compound to a lipophilic one in a limited number of H/F exchanges. DFT studies of some of these systems revealed that polarity, conformational preference as well as charge distributions are strongly affected by such hydrogen to fluorine atom substitution. The pronounced effects described, are a result of the interplay between changes in polarity, H-bond basicity and molecular volume, which were obtained with a very low 'cost' in terms of molecular weight or steric effects and may have a great potential for implementation in various fields of chemical sciences.

Synthetic approaches to fluorinated derivatives of 4-(vinylthio)pyridine

An effective strategy for the synthesis of new polyfluoropyridine derivatives, which are valuable building blocks in the synthesis of potentially biologically active fluorine-containing compounds, has been developed. A series of fluorinated derivatives of 4-(vinylthio)pyridine have been synthesized, starting from pentafluoropyridine and 2-mercaptoethanol via aromatic nucleophilic substitution of fluorine atoms and elimination process. The obtained derivatives with NHAlk-substituents at position 2-, are of interest as new heteroaryl vinyl sulfide components that can be used in the synthesis of more complex fluorine-containing structures. The possibility of oxidation of tetrafluoro-4-(vinylthio)pyridine to the corresponding heteroaryl vinyl sulfone has been demonstrated. It was found that the resulting tetrafluoro-4-(vinylsulfonyl)pyridine reacted with cycloheptanamine under basic conditions to form a heterocyclic framework containing fragments of pyridine and 3,4-dihydro-2H-1,4-thiazine 1,1-dioxide.

Two-in-one combination therapy of fluoronucleoside analogues and triplex forming oligonucleotides

Antigene technology based on triplex-forming oligonucleotide (TFO) has been widely used in gene-specific regulation, serving as a potential gene therapy method. The optimization of TFO backbone and base can significantly improve the formation and stability of the triplex DNA. Fluorination is widely used in small molecule drug development, but its application in TFO optimization has not been well characterized. Herein, we developed a ‘in silico-in vitro-in vivo’ screening strategy to optimize fluorine atom (F) substitution of TFO. Molecular dynamics simulations are applied to screen single-site F substitutions in the TFO bases that retained stable triplex formation ability with the Ets2-targeted duplex DNA. Combining existing nucleotide analogue floxuridine, the synergistic effect is realized via a two-in-one chemo-TFO including gene regulation and chemotherapeutic functions, which is verified through in vitro and in vivo anti-tumor experiments.

Exploring the fluorination effect mechanism on charge transport in organic solar cells

The fluorination in organic solar cells (OSCs) impacts the photoelectric properties of conjugated polymers. Here, two benzo [1,2-c:4,5-c’] dithiophene-4,8-dione (T1) based donor polymers with different numbers of fluorine substitutions (F1 and F2) have been investigated. Through density functional theory (DFT), optimized structures, frontier molecular orbitals (FMOs), energy gaps, electron affinity energies (EAs) and ionization potentials (IPs) of the fluorinated polymers were studied. Simultaneously, one used time-dependent density functional theory (TD-DFT) to simulate the absorption spectra of F1 and F2 polymer molecules. The impact mechanism of F atoms for the above parameters was explained in depth. Then, through constructing the molecular dimer model, the hole mobility based on Marcus’ theory was calculated for two systems, suggesting that the hole mobility of F1 (with two fluorine atoms introduced in the specific para position of the benzene unit) was greater than that of F2. Finally, the ideal photovoltaic parameters of donor–acceptor compounds were theoretically investigated, and the reasons for performance differences were analyzed from the micro level. The research helps understand the influence of specific fluorine atom substitution on the structure, spectrum, electrochemical parameters, charge transfer and photovoltaic properties, and provides a theoretical guideline for the molecular fluorination modification strategy of excellent OSCs.

Effect of fluorine substitution on the photobiological and electronic properties of resveratrol crystal structure: A first- principles study

The electrical and optical properties of pure resveratrol (RS) and RS derivatives from substituted fluorine atom at hydrogen sites (fluorine is bonded to an oxygen or a carbon atom) are investigated by first-principles calculations. It is shown that RS is a semiconductor with an indirect bandgap of 2.47 eV. The substitution of hydrogen atoms by fluorine atoms that is bonded to oxygen atom changes the bandgap value and affect significantly on optical properties of RS. For other derivatives, the hydrogen substitution by fluorine does not change the bandgap value sensibility. The nature of band gap change from indirect to direct at F3 structure. Optical spectra of F3 to F8 derivatives are very similar to RS. Birefringenceis observed in all RS derivatives. The results show that fluorine atoms play key role in photo biological applications of RS derivatives.

Experimental and theoretical investigation of the substitution effects on N-substituted carbazole derivatives functionalized with azomethine bonds

Examining the structural, spectroscopic, and electronic properties of molecules using both theoretical and experimental methods allow to reveal their structure-property relationship. In this study, the structural and electrochemical properties of the newly synthesized N-substituted carbazole monomers with aniline (ACA), p-methylaniline (ACMA) and pentafloroaniline (ACFA) by using a combination of experimental and computational methods have been comparatively presented. Theoretically optimized molecular structures of newly synthesized monomers have been determined by Density Functional Theory (DFT) method with 6-31G(d,p) basis set. The structural, spectroscopic, and electronic characterizations of monomers have been performed by various techniques including 1H NMR, FT-IR, and UV–Visible spectroscopy. Electrochemical polymerizations of monomers were carried out in a 0.1 M LiClO4/DCM/ACN (5:95, V: V) system. Compared to other monomers, the substitution of fluorine atoms has led to an anodic shift of the oxidation potential of the ACFA. Electrochemical and electrochromic properties of the obtained conductive polymers have been comparatively investigated by cyclic voltammetry and spectroelectrochemistry techniques. It has been observed that the poly(E)-N-(4-(9H-carbazol-9-yl) benzylidene) aniline (PACA) polymer film shows higher optical contrast, fast response time, and good electrochemical stability compared to the poly (E) N - (4- (9H-carbazol-9-yl) benzylidene) -4-methylaniline (PACMA) polymer film.