Substitution Of Bromide Research Articles

Halogenated Phenylpyridines Possessing Chemo-Selectivity for Diverse Molecular Architectures.

Pentafluoropyridine was used as a molecular building block for the installation of aryl bromides, affording a series of multisubstituted halogenated arenes. This operationally simplistic methodology offers precise regioselectivity, ease of scalability, and high purity. 19F Nuclear magnetic resonance (NMR) served as a key diagnostic tool for structural characterization, given the sensitivity with various aryl bromine substitutions on the fluorinated pyridine ring. Furthermore, molecular modeling simulations offered insight into this new class of halogenated phenylpyridines and their unique electronic and reactive properties. This study also demonstrates examples of efficient chemo-selectivity upon either metal-catalyzed aryl-aryl coupling or nucleophilic aromatic substitution of the aryl bromide or fluorinated pyridine scaffold, respectively. A diverse pool of polyarylene structures with high degree of complexity, functionalized linear polymers, and controlled network architectures were achieved from this simple methodology.

Exploring the Influence of Cation and Halide Substitution in the Structure and Optical Properties of CH3NH3NiCl3 Perovskite.

This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.

A new method for synthesis of modified cellulose‐graft‐poly(acrylic acid) copolymer using 4‐cyano‐4‐[(phenylcarbothioyl)solfanyl]pentanoic acid to serve as RAFT agent

AbstractIn this study, cellulose was first treated with 4‐cyano‐4‐((phenyl carbonothioyl)solfanyl) pentanoic acid to serve as the reversible addition‐fragmentation chain transfer polymerization (RAFT) agent, then the controlled grafting polymerization of acrylic acid was successfully performed. A well‐defined, cellulose‐graft‐acrylic acid copolymer (Cell‐g‐PAA), has been prepared by RAFT polymerization technique using three different approaches: RAFT agent was prepared by substitution of dithiobenzoate magnesium bromide with 4,4'‐azobis(4‐cyanopentanoic acid) in ethyl acetate as a solvent, mediated cellulose (Cell) block as the macromolecular Cell‐RAFT agent and (cellulose‐co‐acrylic acid) copolymer with alternating sequence. The resulting (Cell‐RAFT) for “living” free radical polymerization was then heated in the adjacent acrylic acid monomer for the development of the controlled graft copolymer onto cellulose. The structures of the intermediate, graft copolymer were investigated by FT‐IR, DSC, 1H NMR, scanning electron microscopy, and thermo gravimetric. The results demonstrate that the preparation of graft copolymers was successfully confirmed. This approach would provide an extensive classification of molecular designs to obtain modern types of tailored hybrid materials derived from natural polysaccharides and synthetic polymers. Also, using a macro‐initiator is an excellent method for synthesizing new materials.

One-pot nucleophilic substitution-double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives.

The nucleophilic substitution of benzylic bromides with sodium azide was combined with a subsequent copper-catalyzed (3 + 2) cycloaddition with terminal alkynes. This one-pot process was developed with a simple model alkyne, but then applied to more complex alkynes bearing enantiopure 1,2-oxazinyl substituents. Hence, the precursor compounds 1,2-, 1,3- or 1,4-bis(bromomethyl)benzene furnished geometrically differing bis(1,2,3-triazole) derivatives. The use of tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) as ligand for the click step turned out to be very advantageous. The compounds with 1,2-oxazinyl end groups can potentially serve as precursors of divalent carbohydrate mimetics, but the reductive cleavage of the 1,2-oxazine rings to aminopyran moieties did not proceed cleanly with these compounds.

Exploring the Relationship Between Halide Substitution, Structural Disorder, and Lithium Distribution in Lithium Argyrodites (Li6-xPS5-xBr1+x).

Lithium argyrodite superionic conductors have recently gained significant attention as potential solid electrolytes for all-solid-state batteries because of their high ionic conductivity and ease of processing. Promising aspects of these materials are the ability to introduce halides (Li6-xPS5-xHal1+x, Hal = Cl and Br) into the crystal structure, which can greatly impact the lithium distribution over the wide range of accessible sites and the structural disorder between the S2- and Hal- anion on the Wyckoff 4d site, both of which strongly influence the ionic conductivity. However, the complex relationship among halide substitution, structural disorder, and lithium distribution is not fully understood, impeding optimal material design. In this study, we investigate the effect of bromide substitution on lithium argyrodite (Li6-xPS5-xBr1+x, in the range 0.0 ≤ x ≤ 0.5) and engineer structural disorder by changing the synthesis protocol. We reveal the correlation between the lithium substructure and ionic transport using neutron diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy. We find that a higher ionic conductivity is correlated with a lower average negative charge on the 4d site, located in the center of the Li+ "cage", as a result of the partial replacement of S2- by Br-. This leads to weaker interactions within the Li+ "cage", promoting Li-ion diffusivity across the unit cell. We also identify an additional T4 Li+ site, which enables an alternative jump route (T5-T4-T5) with a lower migration energy barrier. The resulting expansion of the Li+ cages and increased connections between cages lead to a maximum ionic conductivity of 8.55 mS/cm for quenched Li5.5PS4.5Br1.5 having the highest degree of structural disorder, an 11-fold improvement compared to slow-cooled Li6PS5Br having the lowest degree of structural disorder. Thereby, this work advances the understanding of the structure-transport correlations in lithium argyrodites, specifically how structural disorder and halide substitution impact the lithium substructure and transport properties and how this can be realized effectively through the synthesis method and tuning of the composition.

Structure-based virtual screening of new antitumor natural berberines: Bioactivity against pancreas cancer by HIF1 inhibition effect

Despite medical and technological advances to contain the proliferation of pancreatic cancer, many diagnoses are late due to the high specificity of this type of cancer. Because it is asymptomatic cancer until the most advanced or terminal state, the efficiency of therapeutic actions can be reduced. HIF-1α is the factor that regulates crucial genes involved in tumor proliferation and metastasis. In this study, a virtual structure-based screening was carried out to evaluate the alignment between pharmacokinetics and pharmacodynamics against the anti-cancer mechanism of the pancreas via HIF-1α of new derivatives of the natural product berberine, a natural alkaloid based on protic isoquinoline whose antitumor effect is reported in the literature. Here, a multiparametric optimization system is used to estimate, quantitatively and topologically, the alignment between the pharmacokinetic attributes of these analogs, where it was possible to observe that the less lipophilic analogs, that is, the 1a-b derivatives, showed better ADME viability. Furthermore, the substitution of alkyl bromide promotes an inductive electron-withdrawing effect that increases the probability of demethylation in analog 1b and reduces the number of O-dealkylation sites, increasing the metabolic stability of the compound. The results of molecular docking suggest that the ligands with better viability of ADME also present a great affinity and specificity for the HIF-1α receptor, mainly in interactions in common with the residue of Thr 196, present in the binding site of the OGA inhibitor, constituting promising ligands in the treatment of pancreatic cancer.

How chloride functions to enable proton conduction in photosynthetic water oxidation: Time-resolved kinetics of intermediates (S-states) in vivo and bromide substitution

Chloride (Cl−) is essential for O2 evolution during photosynthetic water oxidation. Two chlorides near the water-oxidizing complex (WOC) in Photosystem II (PSII) structures from Thermosynechococcus elongatus (and T. vulcanus) have been postulated to transfer protons generated from water oxidation. We monitored four criteria: primary charge separation flash yield (P* → P+QA−), rates of water oxidation steps (S-states), rate of proton evolution, and flash O2 yield oscillations by measuring chlorophyll variable fluorescence (P* quenching), pH-sensitive dye changes, and oximetry. Br-substitution slows and destabilizes cellular growth, resulting from lower light-saturated O2 evolution rate (−20 %) and proton release (−36 % ΔpH gradient). The latter implies less ATP production. In Br- cultures, protonogenic S-state transitions (S2 → S3 → S0’) slow with increasing light intensity and during O2/water exchange (S0’ → S0 → S1), while the non-protonogenic S1 → S2 transition is kinetically unaffected. As flash rate increases in Cl− cultures, both rate and extent of acidification of the lumen increase, while charge recombination is suppressed relative to Br−. The Cl− advantage in rapid proton escape from the WOC to lumen is attributed to correlated ion-pair movement of H3O+Cl− in dry water channels vs. separated Br− and H+ ion movement through different regions (>200-fold difference in Bronsted acidities). By contrast, at low flash rates a previously unreported reversal occurs that favors Br− cultures for both proton evolution and less PSII charge recombination. In Br− cultures, slower proton transfer rate is attributed to stronger ion-pairing of Br− with AA residues lining the water channels. Both anions charge-neutralize protons and shepherd them to the lumen using dry aqueous channels.

Catalytic SNAr Hexafluoroisopropoxylation of Aryl Chlorides and Bromides.

Fluoroalkyl aryl ethers are valuable structural motifs in pharmaceuticals because compounds with these motifs are more metabolically stable and more lipophilic than their nonfluorinated analogues. However, hexafluoroisopropyl aryl ethers have not been extensively studied, presumably because of the lack of efficient synthetic methods. Herein, we describe a rhodium-catalyzed nucleophilic aromatic substitution of aryl chlorides or bromides, which act as the limiting reagents, with weakly nucleophilic hexafluoro-2-propanol under mild reaction conditions. This method provides diverse hexafluoroisopropyl aryl ethers. We demonstrated the generality of this method by carrying out reactions of a large array of unactivated aryl halides, and we found that the success of the reactions relied on arene activation by means of η6-coordination.

Catalytic SNAr Hexafluoroisopropoxylation of Aryl Chlorides and Bromides

AbstractFluoroalkyl aryl ethers are valuable structural motifs in pharmaceuticals because compounds with these motifs are more metabolically stable and more lipophilic than their nonfluorinated analogues. However, hexafluoroisopropyl aryl ethers have not been extensively studied, presumably because of the lack of efficient synthetic methods. Herein, we describe a rhodium‐catalyzed nucleophilic aromatic substitution of aryl chlorides or bromides, which act as the limiting reagents, with weakly nucleophilic hexafluoro‐2‐propanol under mild reaction conditions. This method provides diverse hexafluoroisopropyl aryl ethers. We demonstrated the generality of this method by carrying out reactions of a large array of unactivated aryl halides, and we found that the success of the reactions relied on arene activation by means of η6‐coordination.

Halometabolites isolated from the marine-derived fungi with potent pharmacological activities.

Halometabolites, usually produced in marine environment, are an important group of natural halogenated compounds with rich biological functionality and drugability and thus play a crucial role in pharmaceutical and/or agricultural applications. In the exploration of novel halometabolites from marine microorganisms, the growing number of halogenated compounds makes it necessary to fully present these metabolites with diverse structures and considerable bioactivities. This review particularly focuses on the chemodiversity and bioactivities of halometabolites from marine-derived fungi. As a result, a total of 145 naturally halogenated compounds, including 118 chlorinated, 23 brominated, and four iodinated compounds, were isolated from 17 genera of marine-derived fungi. Interestingly, many of halometabolites, especially for the brominated and iodinated compounds, are generated by the substitution of bromide and iodide ions for the chloride ion in cultivation process. In addition, these compounds possess diverse structural types, which are classified into polyketides (62.7%), phenols (16.6%), alkaloids (14.5%), and terpenoids (6.2%). Their cytotoxic, antibacterial, and anti-inflammatory activities indicate the high potential of these halogenated compounds as lead compounds for drug discovery.

Controllable Access to Furans and Dihydrofurans through Cyclization/Coupling of Internal Acetylenic β‐Ketoesters with Aryl Bromides

AbstractPd‐catalyzed tandem cyclization/coupling of internal β‐propargylic‐β‐ketoesters with (hetero)aryl bromides is described. Two protocols are established which selectively lead to 2‐benzylidene‐dihydrofurans, when isomerization is inhibited under mild conditions (temp. ≤40 °C and weak base – K2CO3), or to 2‐benzyl‐furans when base‐induced aromatization is enabled. A catalytic cycle involving oxidative addition, substitution of bromide with alkyne, rate limiting anti‐selective 5‐exo‐dig oxocyclization followed by fast deprotonation of the oxonium intermediate, and reductive elimination is proposed based on detailed experimental and theoretical studies.magnified image

Enhancement of Superionic Conductivity by Halide Substitution in Strongly Stacking Faulted Li3HoBr6–xIx Phases

Ternary lithium halide-based solid electrolytes have attracted broad scientific interest due to their high ionic conductivities in conjunction with good electrochemical stabilities against high-voltage cathode materials. Here, we analyze the structure of the rare earth halide solid solution series Li3HoBr6–xIx and quantify structural defects such as intralayer cation disorder and stacking faults. Almost all members of the solid solution series show strong stacking fault disorder, whereas the intralayer cation disorder systematically increases with increasing iodide content. The substitution of bromide by iodide in Li3HoBr6–xIx leads to an increasing lattice softness and therefore to a higher ionic conductivity and to a lower activation energy. This is counteracted by the increased cation disorder, which also has a strong influence on the ionic conductivity of the solid solution series. Thus, a decrease in ionic conductivity by one order of magnitude is observed when the iodine content exceeds an optimum value. Stacking faults on the other hand do not have a significant impact on the ionic conductivity as the connectivity between neighboring lithium halide octahedra and hence the energy landscape of their migration pathways is not affected for equivalent stacking vectors. The competing factors above give rise to an optimum ionic conductivity at x ≈ 3 with 2.7 × 10–3 S cm–1 at 20 °C and an activation energy of 0.21 eV. While thermal annealing reduces the structural disorder of Li3HoBr6–xIx, the self-healing properties are significantly impeded by mechanical sample treatment, demonstrating the complex interplay between thermal and mechanical effects on the microstructure and, hence, ionic conductivity of layered superionic conductors.

HCF2Se/HCF2S Installation by Tandem Substitutions from Alkyl Bromides.

Herein we describe an efficient construction of HCF2Se and HCF2S groups by tandem substitutions between alkyl bromides and a reagent system consisting of MSeCN (or MSCN) and Ph3P+CF2H Br-. The tandem process occurs via the first nucleophilic substitution of alkyl bromides by -SeCN (or -SCN) and the subsequent nucleophilic difluoromethylation.

Exploring the Stability of Mixed-Halide Vacancy-Ordered Quadruple Perovskites

The structural and optical properties of the halide substitutions of Br– and I– into Cs4MIIMIII2Cl12 (MII = Cd2+, Mn2+; MIII = Bi3+, Sb3+) have been investigated. All compositions adopt the ⟨111⟩ layered vacancy-ordered quadruple perovskite structure with R3̅m space group symmetry. Through incremental halide substitution reactions, we show that significant bromide incorporation is possible (>25% for Cd2+-containing structures). The larger halide ions (Br– or I–) preferentially occupy the anion sites adjacent to the cation-vacancy layer. In those compositions where MII is Cd2+, incorporation of bromide ions leads to substantial MII/vacancy antisite disorder, which is accompanied by a more even distribution of bromide substitution over the two chemically distinct anion sites. The Cs4CdMIII2Cl12 compounds can incorporate over twice the amount of bromide as analogous Mn2+-containing compounds, with a maximum of 29(2)% bromide substitution found for Cs4CdSb2Cl12. Iodide incorporation is more limited, with a maximum of ∼6% halide substitution for Cs4CdBi2Cl12. The incorporation of the heavier, less electronegative Br– and I– ions results in a red shift of the onset of optical absorption in a Vegard’s Law type fashion. The effect is largest for Cs4CdBi2Cl12–zXz, where the absorption onset shifts from 3.20(1) eV to 2.99(1) eV as the composition changes from Cs4CdBi2Cl12 to Cs4CdBi2Cl8.9Br3.1. As discussed in the paper, these results offer some insights into the factors that stabilize the vacancy-ordered quadruple perovskite structure.

Disinfection byproduct formation from algal organic matters after ozonation or ozone combined with activated carbon treatment with subsequent chlorination

Algal organic matter (AOM), including extracellular organic matter (EOM) and intracellular organic matter (IOM) from algal blooms, is widely accepted as essential precursors of disinfection byproducts (DBPs). This study evaluated the effect of ozonation or ozone combined with activated carbon (O3-AC) treatment on characteristic alternation and DBP formation with subsequent chlorination of Chlorella sp.. The effects of pH and bromide concentration on DBP formation by ozonation or O3-AC treatment were also investigated. Results showed that the potential formation of DBPs might be attributed to ozonation, but these DBP precursors could be further removed by activated carbon (AC) treatment. Moreover, the formation of target DBPs was controlled at acidic pH by alleviating the reactions between chlorine and AOM. Besides, the bromide substitution factor (BSF) value of trihalomethanes (THMs) from EOM and IOM remained constant after AC treatment. However, THM precursors could be significantly decreased by AC treatment. The above results indicated that O3-AC was a feasible treatment method for algal-impacted water.

Structure and Optical Properties of Layered Perovskite (MA)2PbI2-xBrx(SCN)2 (0 ≤ x < 1.6).

The layered perovskite (MA)2PbI2(SCN)2 (MA = CH3NH3+) is a member of an emerging series of compounds derived from hybrid organic-inorganic perovskites. Here, we successfully synthesized (MA)2PbI2-xBrx(SCN)2 (0 ≤ x < 1.6) by using a solid-state reaction. Despite smaller bromide substitution for iodine, 1% linear expansion along the a axis was observed at x ∼ 0.4 due to a change of the orientation of the SCN- anions. Diffuse reflectance spectra reveal that the optical band gap increases by the bromide substitution, which is supported by the DFT calculations. Curiously, bromine-rich compounds where x ≥ 0.8 are light sensitive, leading to partial decomposition after ∼24 h. This study demonstrates that the layered perovskite (MA)2PbI2(SCN)2 tolerates a wide range of bromide substitution toward tuning the band gap energy.

Photo-Effect on Ion Transport in Mixed Cation and Halide Perovskites and Implications for Photo-Demixing*.

Lead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo‐decomposition and photo‐demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo‐ionic effect, following our previous study on CH3NH3PbI3, where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo‐demixing in mixed halide compositions.

Photo‐Effect on Ion Transport in Mixed Cation and Halide Perovskites and Implications for Photo‐Demixing**

AbstractLead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo‐decomposition and photo‐demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo‐ionic effect, following our previous study on CH3NH3PbI3, where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo‐demixing in mixed halide compositions.

Electrochemical Ring Expansion to Synthesize Medium-Sized Lactams Through C–C Bond Cleavage

Medium-sized nitrogen heterocycles are prevalent motifs in many kinds of bioactive molecules and natural products. Owing to the unfavorable enthalpic and entropic barriers during the transition sta...

SYNTHESIS AND CHARACTERIZATION OF NEW 1,2,3-TRIAZOLYL Α-AMINOPHOSPHONATE DERIVATIVES, THROUGH 1,3-DIPOLAR CYCLOADDITION REACTION

A series of novel biheterocyclic α-aminophosphonate N-protected derivatives have been synthesized through 1,3-dipolar cycloaddition reaction between the diethyl α-azido-αaminophosphonate and heterocyclic alkynes which were prepared by nucleophilic substitution of propargyl bromide by different heterocycles.