Type Of Halogen Research Articles

Targeted Metabolomic Assessment of the Sub-Lethal Toxicity of Halogenated Acetic Acids (HAAs) to Daphnia magna.

Halogenated acetic acids (HAAs) are amongst the most frequently detected disinfection by-products in aquatic environments. Despite this, little is known about their toxicity, especially at the molecular level. The model organism Daphnia magna, which is an indicator species for freshwater ecosystems, was exposed to sub-lethal concentrations of dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA) for 48 h. Polar metabolites extracted from Daphnia were analyzed using liquid chromatography hyphened to a triple quadrupole mass spectrometer (LC-MS/MS). Multivariate analyses identified shifts in the metabolic profile with exposure and pathway analysis was used to identify which metabolites and associated pathways were disrupted. Exposure to all three HAAs led to significant downregulation in the nucleosides: adenosine, guanosine and inosine. Pathway analyses identified perturbations in the citric acid cycle and the purine metabolism pathways. Interestingly, chlorinated and brominated acetic acids demonstrated similar modes of action after sub-lethal acute exposure, suggesting that HAAs cause a contaminant class-based response which is independent of the type or number of halogens. As such, the identified metabolites that responded to acute HAA exposure may serve as suitable bioindicators for freshwater monitoring programs.

Molecular engineering of α and β peripherally tri-halogenated substituted boron subphthalocyanines as mixed alloys to control physical and electrochemical properties for organic photovoltaic applications

The relative impact of position and type of halogens on the boron subphthalocyanine periphery has been established as well as their ability to form mixed alloys and the impact on organic electronic properties utilizing organic solar cell base data.

Spin State Modulation in Cobalt(II) Terpyridine Complexes by Co-Crystallization with 1,3,5-Triiodo-2,4,6-trifluorobenzene

Abstract Reversible water molecule-induced spin state inter-conversion for the mononuclear cobalt(II) complex [Co(terpy)2]I2·2H2O (1, terpy = 2,2′:6′,2′′-terpyridine) is reported along with its co-crystallization with 1,3,5-triiodo-2,4,6-trifluorobenzene (TITFB) to yield three types of halogen bonded frameworks, [Co(terpy)2][(TITFB)I2] (2), [Co(terpy)2][(TITFB)2I2] (3) and [Co(terpy)2][(TITFB)4(MeOH)I2] (4) (TITFB = 1,3,5-triiodo-2,4,6-trifluorobenzene). The magnetic properties of 1–4 have been investigated. While 1 exhibits gradual spin crossover (SCO) behavior, de-solvated [Co(terpy)2]I2 (1′) exhibits abrupt SCO behavior (T1/2 = 120 K) attributed to a change in its intermolecular interactions on dehydration. The crystal structures as well as the magnetic properties of 1 and 1′ can be switched reversibly via single-crystal to single-crystal (SCSC) transformations via hydration/dehydration processes. Co-crystallization of [Co(terpy)2]I2 with TITFB resulted in three types of halogen-bonded frameworks (2–4). While 2 exhibits incomplete abrupt spin transition (T1/2 = 56 K), 3 and 4 show incomplete gradual SCO behavior (attributed to stabilization of the LS state). The observed SCO behaviors are in accord with the structural distortions occurring in the respective [Co(terpy)2]2+ cations and resulting from their intermolecular interactions with the surrounding frameworks. These results illustrate the manner by which co-crystallization leading to halogen-bonded co-crystals in the present study can result in spin state modulation in SCO complexes.

Chlorine substituents and linker topology as factors of 5-HT6R activity for novel highly active 1,3,5-triazine derivatives with procognitive properties in vivo

In the light of recent lines of evidence, 5-HT6R ligands are a promising tool for future treatment of memory impairment. Hence, this study has supplied highly potent 5-HT6R agents with procognitive effects, which represent an original chemical class of 1,3,5-triazines, different from widely studied sulfone and indole-like 5-HT6R ligands. The new compounds were rationally designed as modifications of lead, 4-(1-(2-chlorophenoxy)ethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (1), involving an introduction of: (i) two chlorines at benzene ring and (ii) varied linkers joining the triazine ring to aromatic ethers. Synthesis, in vitro and in vivo biological tests and computer-aided SAR analysis for 19 new compounds were carried out. Most of the new triazines displayed high affinity (Ki < 100 nM) and selectivity towards 5-HT6R, with respect to 5-HT2AR, 5-HT7R and D2R. The crystallography-supported docking studies, including quantum-polarized ligand docking (QPLD), indicated that chlorine atoms may be involved in different type of halogen bonding, however, the linker properties seem to predominately affect the 5-HT6R affinity. 4-[1-(2,5-Dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (9), which displayed: the highest affinity (Ki = 6 nM), very strong 5-HT6R antagonistic action (KB = 27 pM), procognitive effects in vivo in novel object recognition (NOR) test in rats, a very good permeability in PAMPA model and satisfying safety in vitro, was identified as the most potent 1,3,5-triazine agent so far, useful as a new lead for further research.

HETEROCYCLIZATION OF 3-PROPARGYLSULFANYL-5 PHENYL-1,2,4-TRIAZINE: TANDEM REACTIONS WITH BROMINE LEADING TO NEW DERIVATIVES OF 7 PHENYL[1,3]THIAZOLO[3,2-B][1,2,4]TRIAZINIUM

Derivatives of 1,2,4-triazine-3-thione exhibit biological activity in a wide range. They have optoelectronic properties and can be used as synthons in synthesis of various pyridines by the Diels-Alder reaction. 1,2,4-Triazines are of the greatest interest, for organic synthesis in particular. In the present study we have established that the interaction of 3-propargylsulfanyl-5-phenyl-1,2,4-triazine, obtained by alkylation of 5-phenyl-2,3-dihydro-1,2,4-triazine-3-thione with 3-bromopropyne in acetone in the presence of triethylamine, with halogens leads to annelation of thiazole cycle. At that, [1,3]thiazolo[3,2-b][1,2,4]triazinium systems contain either endo- or exocyclic double bond in their structure, depending on the halogen type. By way of example, iodine acting on propargyl sulfide forms a dark precipitate of (3Z)-3-iodomethylene-7-phenyl-2,3-dihydro-[1,3]thiazolo[3,2-b][1,2,4]triazinium triiodide, the structure of which has been confirmed by 1H and 13C NMR spectroscopy, including two-dimensional 2D 1H-13C HSQC, HMBC and 1H-1H NOESY experiments. Treatment of the obtained triiodide by sodium iodide in acetone leads to synthesis of the corresponding monoiodide, which precipitates from the reaction mixture as a dark red precipitate. Reaction with bromine, as distinct from heterocyclization under iodine action, comprises an unusual cascade reaction including the stages of electrophile heterocyclization, bromine addition, and hydrogen bromide elimination, which leads to formation of 3-dibromomethyl-7-phenyl[1,3]thiazolo[3,2-b][1,2,4]triazinium bromide. It should be pointed out that the identifying feature of 3-propargylsulfanyl-5-phenyl-1,2,4-triazine heterocyclization under iodine and bromine action is the signal bias of the aromatic proton in a triazine ring towards weak field in the 1H NMR spectrum of the reaction products. This is presumably associated with formation of the positively charged nitrogen atom.

Effect of deep eutectic solvents hydrogen bond acceptor on the anhydrous proton conductivity of Nafion membrane for fuel cell applications

This study intended to assess the role of halogens on proton conductivity of polymer electrolyte membranes (PEMs) for fuel cell applications. For this purpose, the halogens were used as hydrogen bond acceptors (HBA) to form deep eutectic solvents (DES) which were later used as electrolyte in Nafion membrane. The prepared DESs were initially characterized in terms of rheology, thermal behavior, and ionic conductivity. Then, Nafion/DES composite membranes were prepared and their electrochemical reactions, thermal stabilities and proton conductivities were characterized. Interestingly, the bromide containing DESs provided super proton conductivity in Nafion/DES composites so that a proton conductivity of 337 mS/cm was achieved at 100 °Cat anhydrous condition which was about 120% higher than the iodide based Nafion/DES membranes and about 1200 % higher than other Nafion/ionic liquid PEMs at anhydrous condition. An upper bound concept was introduced for the Nafion/DES composite membranes which was compared with those obtained for conventional Nafion/ionic liquid composite membranes at anhydrous conditions. Furthermore, fuel cell performance of Nafion/DES composite membrane showed that DESs can be considered as proper electrolytes for anhydrous PEMs, and their properties can be justified by halogen type.

Computational insight into the halogen bonded self-assembly of hexa-coordinated metalloporphyrins.

We demonstrate herein a computational study probing the influence of metalloporphyrins on intermolecular halogen bonding (XB) during supramolecular self-assembly. The results demonstrate that porphyrin aromatic rings can activate or deactivate halogen bonding interactions, especially those on axial ligands, and further influence the preference type of halogen···halogen bonding during the supramolecular self-assembly. Calculations show that the halogen atom present at the equatorial position has a higher sigma hole potential (VS,max) than that at the axial position. The computational analysis and our observations from the X-ray structure analysis are in good agreement. From structural analysis it is clear that equatorial halogen atoms prefer to participate in Type-II XB interactions whereas the axial halogen atoms either participate in Type-I XB interaction or reluctant to participate in XB interactions due to the decrease of their sigma hole potential. Thus, we demonstrate, herein, for the first time a computational study probing the direct influence of the porphyrin's ring current on the sigma hole potential (VS,max) of the halogen atoms and subsequently the effects of the supramolecular self-assembly.

Classifying the Electronic and Optical Properties of Janus Monolayers.

Inspired by the recent synthesis of monolayer MoSSe, we conduct a first-principles high-throughput investigation of 216 MXY Janus monolayers consisting of a middle layer of metal atoms (M) sandwiched between different types of chalcogen, halogen, or pnictogen atoms (X,Y). Using density functional theory and many-body perturbation theory, we perform an exhaustive computational characterization of the 70 most stable semiconducting monolayers. These are found to exhibit diverse and fascinating properties including finite out-of-plane dipoles, giant Rashba-splittings, direct and indirect band gaps ranging from 0.7 to 3.0 eV, large exciton binding energies, and very strong light-matter interactions. The data have been generated using the workflow behind the Computational 2D Materials Database and are freely available online. Our work expands the class of known Janus monolayers and points to several potentially synthesizable structures, which could be interesting candidates for valley- or optoelectronic applications or for generating out-of-plane electric fields to control charge transfer, charge separation, or band alignments in van der Waals heterostructures.

Evidence-based analysis on the toxicity of disinfection byproducts in vivo and in vitro for disinfection selection

Disinfection is a key step in drinking water treatment process to prevent water-borne infections. However, reactions between chlorine, one of the most common disinfectants, and natural organic matter (NOM) often lead to the formation of hazardous disinfection byproducts (DBPs). However, the cytotoxicity of some DBPs is still poorly understood. Such knowledge is critical for proper selection of disinfection processes. We investigated the effects of DBPs on mouse acute liver injury. The exacerbation of liver damage increased with the DBPs concentrations, likely due to the increased hepatic macrophages. Haloacetonitriles (HANs) and haloketones (HKs) are more toxic to Human Hepatocellular (Hep3B) cells than trihalomethanes (THMs). Cytotoxicity of DBPs were governed by the halogen type (brominated DBPs > chlorinated DBPs) and the numbers of halogen atoms per molecule. Then, we used the pilot-scale WDS to study the best conditions for reducing the formation of DBPs. The result showed that the formation of DBPs followed the order: stainless-steel (SS) > ductile iron (DI) > polyethylene (PE) pipe. Higher flowrate promoted the formation of DBPs in all three pipes. The results suggest that the formation of DBPs in chlorine disinfection can be reduced by using PE pipes and low flow rate in water distribution systems (WDS).

Spectroscopic Measurement of a Halogen Bond Energy.

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br- anions is reported. The XB strength between the positively-charged σ-hole on the Br atom of the bromotrichloromethane (CCl3 Br) molecule and the Br- anion was found to be 0.63 eV (14.5 kcal mol-1 ). In the neutral complexes, Br(CCl3 Br)1,2 , the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl3 Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol-1 ) and 0.12 eV (2.8 kcal mol-1 ).

Spectroscopic Measurement of a Halogen Bond Energy

AbstractHalogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br− anions is reported. The XB strength between the positively‐charged σ‐hole on the Br atom of the bromotrichloromethane (CCl3Br) molecule and the Br− anion was found to be 0.63 eV (14.5 kcal mol−1). In the neutral complexes, Br(CCl3Br)1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl3Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol−1) and 0.12 eV (2.8 kcal mol−1).

Activation of the Cyano Group at Imidazole via Copper Stimulated Alcoholysis

Reactions of 4,5-dicyano-1-methylimidazole with CuX2 (X = Cl, Br) in alcohol solvents (ethanol and methanol) resulted in the formation of Cu(II) carboximidate complexes [CuCl2(5- cyano-4-C(OEt)N-1-methylimidazole)(EtOH)] (1), [Cu2(µ-Cl)2Cl2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (2), [Cu2(µ-Br)2Br2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (3), and [Cu2(µ-Br)2Br2(5-cyano-4-C(OEt)N-1-methylimidazole)2] (4). The structures were determined by the X-ray crystallographic method, and further spectroscopic and computational methods were employed to explain the structural features. The solvent contributed to the alcoholysis reaction of the cyano group, as the result of which the ligand coordinated to the metal center in bidentate mode forming a five-membered chelating ring. In 1, the solvent also acts as an additional ligand, which coordinates to the metal center of a monomeric complex. In compounds 2–4, two halogen ligands link the metal atoms forming dihalo-bridged copper dimers. The infrared absorption characteristics were verified by simulation of the infrared spectra at the density functional theory level. In addition, the electronic absorption characteristics were explained by simulation of the UV–Vis spectra using the TD-DFT method. Molecular modelling at the DFT level was performed to study the effects of halogen type and steric hindrance of the alkoxy groups in forming the copper(II) complexes.

Electrochemical Characterization and Voltammetric Determination of Benzoyl Derivatives of Phenobarbital Using Glassy Carbon Electrode

AbstractThe electrochemical behavior of a number of benzoyl barbiturates was studied using a glassy carbon electrode (GCE). The kinetics of the electrode process is determined, the contribution of physical adsorption to the electrochemical process is estimated, and the mechanism of the possible electrochemical reaction is proposed. It is shown that the electrochemical reduction potentials of benzoyl phenobarbital derivatives are determined by the LUMO energies, calculated by the B3LYP 6‐311+G method. It is established that the process is quasi‐reversible, complicated by adverse reactions. The influence of halogen type and its position in the benzoyl residue of the studied substances on the analytical signal is established. The effective values of the dissociation constants of various forms of benzoyl derivatives were calculated using the example of halonal, for which the values 3.16 ⋅ 10−8 and 6.31 ⋅ 10−12, respectively, were found.

Metal–Organic Framework Supported Palladium Nanoparticles: Applications and Mechanisms

AbstractHeterogeneous palladium (Pd)‐based catalysts are extensively applied to improve the catalytic performance and/or expand the reaction scope in many catalytic processes, involving the cross‐coupling, hydrogenation, reduction, and oxidation reactions. Among them, metal–organic framework (MOF)‐supported Pd nanoparticles (Pd NPs) are becoming the most popular one for their excellent catalytic performance and reusable property. To motivate the development of this technology, the applications of MOF‐supported Pd NPs (Pd NPs/MOFs) in heterogeneous catalysis are critically summarized herein, including the hydrogenation reduction of nitro‐ and polyunsaturated compounds, synthesis of carbon–carbon (CC) bonds compounds, chromium (Cr(VI)) reduction, dehalogenation, alcohol oxidation, CO2 conversion, and CO oxidation. The influences of base, solvents, electron character of substitutes, and type of halogen on the catalytic performance are comprehensively discussed. Finally, the application prospects of Pd NPs/MOFs and existing shortcomings in the catalytic field are proposed.

Frequency dependent linear and nonlinear optical properties of compositionally tuned inorganic CsSnX (X = Br, I) composites

Structural, electronic and optical properties of CsSnX (X = Br, I) system have been thoroughly investigated by means of an unbiased crystal structure screening, density functional theory and perturbation approach. Crystallography of known parent structures, CsI and CsBr were well replicated compared to experimental observations. Experimentally verified cubic Cs2SnI6 phase was operatively reproduced. Its computed crystal class and simulated XRD pattern match the available experimental data, hence signifying the robustness of methodology applied. Other energetically and dynamically stable structures include cubic Cs2SnBr6, triclinic Cs2Sn2Br6 and Cs2Sn2I6. These phases are direct semiconductors which exhibit non-monotonic association between GW corrected band gap and halogen type or atomic mass. Instead, their energy gap is determined by the structure of CsSn halide compounds, and span an energy range from mid infrared to near ultraviolet region. The GW-raised gap was incorporated as scissor shift to ensure good reliability of optical calculations. Dynamical dielectric function, adsorption coefficient, energy-loss and refractive index spectrum of aforementioned phases were acquired. Both novel Cs2Sn2Br6 and Cs2Sn2I6 phases have impressive zero limit second-order susceptibility ranging from 3.1 p.m. V−1 to 22.8 p.m. V−1.

Halogen-hydrogen bonds: A general synthetic approach for highly photoactive carbon nitride with tunable properties

The design of the chemical, photo-physical, and catalytic properties of graphitic carbon nitride (g-CN) is highly challenging due to the harsh solid-state reaction. Here we report a template-free, large-scale synthesis of highly photoactive and stable g-CN with a unique dot-like morphology by using melamine-halogen complexes as starting precursor. The supramolecular structures are synthesized by sequential treatment of melamine with different acids. Experimental results together with theoretical calculations reveal that different halogens result in different interactions with melamine. We found that bromide reacts with the inner melamine aggregates while chloride is present mainly in the outer shell. Upon calcination, the delicate design results in porous carbon nitride with controlled morphologies and optical properties as well as improved charge separation under illumination and excellent photoactivity and stability for hydrogen production. Our results indicate that the type of halogen can significantly affect different properties in the final g-CN. This work provides new opportunities for template-free facile synthesis of highly photoactive carbon nitride and other carbon-nitrogen based materials with controllable chemical, optical, and catalytic properties for sustainable energy-related applications owing to the utilization of hydrogen-halogen based assemblies as well as the elucidation of their unique interaction.

Kinetics of oxidation of a hemicellulose model compound by chlorine dioxide in bleaching

Kinetics of the oxidation of D-xylose, a hemicellulose model compound, by chlorine dioxide was studied under simulated bleaching conditions. The final reaction product, chloroacetic acid, which is a type of adsorbable organic halogen (AOX), was detected by gas chromatography-mass spectrometer (GC-MS). The kinetic equation was expressed as dW/dt = 2.36e-560/T[H+]0.05[ClO2]0.11X0.92. The reaction exhibited first-order kinetics, with a good agreement between the experimental and modelling data. The reaction activation energy was 4.66 kJ.mol-1. Thus, the process is not controlled by a chemical reaction, but rather, it is controlled by hemicellulose properties. These results might have potential for resolving the major problems of environmental pollution in elemental chlorine-free (ECF) bleaching of pulp.

Tailoring topological states in silicene using different halogen-passivated Si(111) substrates

We investigate the band structure and topological phases of silicene embedded on halogenated Si(111) surface, by virtue of density functional theory and tight-binding calculations.Our results show that the Dirac character of low energy excitations in silicene is almost preserved in the presence of silicon substrate passivated by various halogens. Nevertheless, the combined effects of charge transfer into the substrate, stretching of bonds between silicon atoms, and symmetry breaking which originates from van der Waals interaction, result in a gap $E_{g1}$ in the spectrum of the embedded silicene. We further take the spin-orbit interaction into account and obtain its strength and the resulting enhancement in the gap $E_{g2}=2\lambda$. Both $E_{g1}$ and $E_{g2}$ which contribute to the total gap, vary significantly when different halogen atoms are used for the passivation of the Si surface and for the case of iodine, they have very large values of $70$ and $23$ meV, respectively. To examine the topological properties, we calculate the projected band structure of silicene from which the tight binding parameters of the low-energy effective Hamiltonian are obtained by fitting. Our results based on Berry curvature and $\mathbb{Z}_2$ invariant reveals that silicene on halogenated Si substrates has a topological insulating state which can survive even at room temperature for the substrate with iodine and bromine at the surface. Similar to the free standing silicene, by applying a perpendicular electric field and at a certain critical value which again depends on the type of halogens, the gap closes and silicene undergoes a transition to a trivial insulating state. As a key finding, we see that the presence of halogenated substrate except for the case of fluorine enhances the robustness of the topological phases against the vertical electric field and most probably other external perturbations.

Halogen type as a selectivity switch in catalysed alkane oxyhalogenation

The type of halogen enables a powerful selectivity control ranging from olefins in oxychlorination to alkyl bromides in oxybromination over europium oxyhalide catalysts.

Peptide selectivity between the PDZ domains of human pregnancy-related serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) can be reshaped by different halogen probes.

The human HtrA family of serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) are the key enzymes associated with pregnancy and closely related to the development and progression of many pathological events. Previously, it was found that halogen substitution at the indole moiety of peptide Trp-1 residue can form a geometrically satisfactory halogen bond with the Drosophila discs large, zona occludens-1 (PDZ) domain of HtrA proteases. Here, we attempt to systematically investigate the effect of substitution with 4 halogen types and 2 indole positions on the binding affinity and specificity of peptide ligands to the 4 HtrA PDZ domains. The complex structures, interaction energies, halogen-bonding strength, and binding affinity of domain-peptide systems were modeled, analyzed, and measured via computational modeling and fluorescence-based assay. It is revealed that there is a compromise between the local rearrangement of halogen bond involving different halogen atoms and the global optimization of domain-peptide interaction; the substitution position is fundamentally important for peptide-binding affinity, while the halogen type can effectively shift peptide selectivity between the 4 domains. The HtrA1-PDZ and HtrA4-PDZ as well as HtrA2-PDZ and HtrA3-PDZ respond similarly to different halogen substitutions of peptide; -Br substitution at R2-position and -I substitution at R4-position are most effective in improving peptide selectivity for HtrA1-PDZ/HtrA4-PDZ and HtrA2-PDZ/HtrA3-PDZ, respectively; -F substitution would not address substantial effect on peptide selectivity for all the 4 domains. Consequently, the binding affinities of a native peptide ligand DSRIWWV-COOH as well as its 4 R2-halogenated counterparts were determined as 1.9, 1.4, 0.5, 0.27, and 0.92μM, which are basically consistent with computational analysis. This study would help to rationally design selective peptide inhibitors of HtrA family members by using different halogen substitutions.