Effect Of Halogen Research Articles

Investigating the effect of halogens on the electronic and optical properties of lead‐free double halide perovskites based on CuBi

AbstractIn recent years, three‐dimensional (3D) lead‐free double halide perovskites have been considered promising candidates for photovoltaic applications due to their high stability and the use of non‐toxic materials, and the absence of organic materials in their structure. The structural, electronic, and optical properties of 3D double Halide perovskites and were investigated in this paper using first‐principles density functional theory (DFT) simulation with BLYP approximation. The results showed that structures and have an indirect band gap, high absorption coefficient, low reflection, and high conductivity. A redshift of absorption edge and band gap shrinkage has been observed in the structure with an increase in the ionic radius of the halogen, which indicates the unique features of structure for photovoltaic applications, LED, laser, and other optoelectronic devices.

Effects of Halogenation on Quinoline-Malononitrile based AIEgens: Photophysical Properties Investigation and Wash-Free Imaging.

Developing halogen-functionalized fluorescent dyes with intriguing photophysical properties, including enhanced photostability, is particularly important for bioimaging. In this work, we synthesized two new halogen-functionalized aggregation-induced emission (AIE)-active molecules, DQMF-OH and DQMCl-OH, based on the quinoline-malononitrile chromophore. The halogen effect on the photophysical characteristics was detailedly studied by absorption and fluorescence spectroscopy, density functional theory calculations, and crystal structures. Compared with non-halogen substituted AIE luminogen (AIEgen) DQM-OH, the halogen substituted DQMF-OH and DQMCl-OH exhibited red-shifted absorptions and emissions in the solution and solid state. In addition, DQMF-OH and DQMCl-OH also possessed enhanced fluorescence toward viscosity changes. These AIEgens served as remarkable imaging tools for cell tracking in a wash-free manner. Furthermore, DQMF-OH and DQMCl-OH showed much more excellent photobleaching resistance than DQM-OH. Our work sheds new light on developing fluorescent halogenated dyes with enhanced photophysical performances for biological applications.

Effect of Halogen at the Divalent Sulfur Atom on the Properties of Complexes with a Chalcogen and Hydrogen Bond

Effect of Halogen at the Divalent Sulfur Atom on the Properties of Complexes with a Chalcogen and Hydrogen Bond

Effect of Halogen at the Divalent Sulfur Atom on the Properties of Complexes with a Chalcogen and Hydrogen Bond

Binary complexes with a chalcogen (A complexes) and hydrogen (B complexes) bond formed by SHX molecules (X = F, Cl, Br, OH) of divalent sulfur and a water molecule have been calculated by the MP2/aug-cc-pVTZ quantum chemical method. An NBO analysis was performed for complexes of both types along with the topological analysis of electron density and decomposition of the binding energy into components. The quantum chemical calculations showed that the binding energies, interorbital interaction energies of monomers, and electron densities at the critical point (3, –1) of intermolecular contact are close in the A and B complexes. The main contribution to stabilization of the complexes is made by the electrostatic interaction; in the B complexes, however, the contribution of the charge transfer component is also significant. The dispersion energy plays a significant role in the binding of monomers in complexes of both types. According to the calculations, the interconversion of A and B complexes occurs with a very low activation barrier.

Series of Halogen Engineered Ni(OH)2 Nanosheet for Pseudocapacitive Energy Storage with High Energy Density.

Ni(OH)2 nanosheet, acting as a potential active material for supercapacitors, commonly suffers from sluggish reaction kinetics and low intrinsic conductivity, which results in suboptimal energy density and long cycle life. Herein, a convenient electrochemical halogen functionalization strategy is applied for the preparation of mono/bihalogen engineered Ni(OH)2 electrode materials. The theoretical calculations and experimental results found that thanks to the extraordinarily high electronegativity, optimal reversibility, electronic conductivity, and reaction kinetics could be achieved through F functionalization . However, benefiting from the largest ionic radius, INi(OH)2 contributes the best specific capacity and morphology transformation, which is a new finding that distinguishes it from previous reports in the literature. The exploration of the interaction effect of halogens (F, INi(OH)2 , F, BrNi(OH)2 , and Cl, INi(OH)2 ) manifests that F, INi(OH)2 delivers a higher specific capacity of 200.6 mAh g-1 and an excellent rate capability of 58.2% due to the weaker electrostatic repulsion, abundant defect structure, and large layer spacing. Moreover, the F, INi(OH)2 //FeOOH@NrGO device achieves a high energy density of 97.4Wh kg-1 and an extremely high power density of 32426.7W kg-1 , as well as good cycling stability. This work develops a pioneering tactic for designing energy storage materials to meet various demands.

Effects of Halogenation on Cyclopentadithiophenevinylene-Based Acceptors with Excellent Responses in Binary Organic Solar Cells.

In recent years, non-fused non-fullerene acceptors (NFAs) have attracted increasing consideration due to several advantages, which include simple preparation, superior yield, and low cost. In the work reported here, we designed and synthesized three new NFAs with the same cyclopentadithiophenevinylene (CPDTV) trimer as the electron-donating unit and different terminal units (IC for FG10, IC-4F for FG8, and IC-4Cl for FG6). Both halogenated NFAs, i.e., FG6 and FG8, show red-shifted absorption spectra and higher electron mobilities (more pronounced for FG6) in comparison with FG10. Moreover, the dielectric constants of these materials also increased upon halogenation of the IC terminal units, thus leading to a reduction in the exciton binding energy, which is favorable for dissociation of excitons and subsequent charge transfer despite the driving force (highest occupied molecular orbital and lowest unoccupied molecular orbital offsets) being very small. The organic solar cells (OSCs) constructed using these acceptors and PBDB-T, as the donor, showed PCE values of 15.08, 12.56, and 9.04% for FG6, FG8, and FG10, respectively. The energy loss for the FG6-based device was the lowest (0.45 eV) of all the devices, and this may be attributed to it having the highest dielectric constant, which leads to a reduction in the binding energy of exciton and a small driving force for hole transfer from FG6 to PBDB-T. The results indicate that the NFA containing the CPDTV oligomer core and halogenated terminal units can efficiently spread the absorption spectrum to the NIR zone. Non-fused NFAs have a bright future in the quest to obtain efficient OSCs with low cost for marketable purposes.

A near-infrared ratiometric fluorescent probe for hydrazine and its application for gaseous sensing and cell imaging

Hydrazine (N2H4) is a widely used raw material in the chemical industry, but at the same time hydrazine has extremely high toxicity. Therefore, the development of efficient detection methods is crucial for monitoring hydrazine in the environment and evaluating the biological toxicity of hydrazine. This study reports a near-infrared ratiometric fluorescent probe (DCPBCl2-Hz) for the detection of hydrazine by coupling a chlorine-substituted D-π-A fluorophore (DCPBCl2) to the recognition group acetyl. Due to the halogen effect of chlorine substitution, the fluorophore has an elevated fluorescence efficiency and a lowered pKa value and is suitable for physiological pH conditions. Hydrazine can specifically react with the acetyl group of the fluorescent probe to release the fluorophore DCPBCl2, so the fluorescence emission of the probe system significantly shifted from 490 nm to 660 nm. The fluorescent probe has many advantages, such as good selectivity, high sensitivity, large Stokes shift, and wide applicable pH range. The probe-loaded silica plates can realize convenient sensing gaseous hydrazine with content down to 1 ppm (mg/m3). Subsequently, DCPBCl2-Hz was successfully applied to detect hydrazine in soils. In addition, the probe can also penetrate living cells and allow the visualization of intracellular hydrazine. It can be anticipated that probe DCPBCl2-Hz will be a useful tool for sensing hydrazine in biological and environmental applications.

Effects of Halogenation of Small‐Molecule and Polymeric Acceptors for Efficient Organic Solar Cells

AbstractTuning the properties of non‐fullerene acceptors (NFAs) through halogenation, including fluorination and chlorination, represents one of the most promising strategies to boost the performance of organic solar cells (OSCs). However, it remains unclear how the F and Cl choice influences the molecular packing and performance between small‐molecule and polymeric acceptors. Here, a series of small‐molecule and polymeric acceptors with different amounts and types of halogenation is synthesized, and the effects of fluorination and chlorination between small‐molecule and polymeric acceptors are investigated. It is found that chlorinated small‐molecule acceptors lead to longer exciton diffusion length and better performance compared to the corresponding fluorinated ones, which attributes to their stronger intermolecular packing mode. For polymer acceptors, in contrast, the fluorinated polymers achieve a denser packing mode and better performance, because chlorinated polymers exhibit reduced intrachain conjugation between end group moieties and linker units. This study demonstrates different halogenation effects on the packing modes and performances for small‐molecule and polymeric acceptors, which provides important guidance for the molecule design of high‐performance acceptors for OSCs.

Asymmetric Organocatalyzed Cascade Reactions─Merging the pseudo-Halogen and Halogen Effect with Dienamine Catalysis

The combination of asymmetric organocatalysis with the (pseudo)-halogen effect enables the formation of chiral norcarane scaffolds in high yields and selectivities (up to 92% yield, >99% ee, and >95:5 d.r.). This was achieved by reacting (pseudo)-halogenated 3-vinyl chromones with in situ generated chiral dienamines in an inverse electron demand [4 + 2] cycloaddition followed by an intramolecular SN2 reaction. These scaffolds could easily undergo photoinduced rearrangements or lactonization to form intricate chiral ring structures.

Elevated nitrate promoted photodegradation of PAHs in aqueous phase: Implications for the increased nutrient discharge.

Polycyclic aromatic hydrocarbons (PAHs) are frequently released in aqueous phase by oil spill or from other sources, and photochemical oxidation is one of their major weathering processes. In this study, the photochemical behavior of phenanthrene (PHE, as a representative PAH) were studied and the effects of nitrogenous compounds were evaluated. The results showed that nitrate was an effective photosensitizer for improving the photodegradation of PHE, but the promoting effect was less effective in seawater due to the presence of halogen ions; the ammonia played a negligible role on PHE degradation. The photochemical ionization was a key process for PHE degradation, it can be retarded due to the quenching of triplet excited state by dissolved oxygen, and the inhibition was most prominent in fresh water. The presence of nitrate increased the steady state concentration of •OH from 2.08×10-15 M to 1.04×10-14 M in fresh water, and from 1.5×10-16 M to 2.08×10-15 M in seawater. The secondary-order reaction rate constant between PHE and •OH (k•OH,PHE) was determined as 5.70 × 109 M-1 s-1. Similar trend was observed for 1O2. The contribution of •OH to PHE removal was more prominent in fresh water than in seawater due to the quenching effects of halogen, and the increasing of nitrate enlarged the contribution of •OH. Two possible PHE degradation pathways were proposed based on GC-MS analysis and DFT calculation. The Quantitative Structure-activity Relationship (QSAR) evaluation showed that some degradation intermediates were more toxic than PHE, but the total environmental risk was still diminished due to the low percentage of toxic intermediates. This study provided theoretical and experimental insights into the influence of nitrogenous compounds on the photodegradation of PHAs in water environment.

Effects of Mixed Halogenation on the Performance of Nonfullerene Acceptors in All‐Small Molecule Organic Solar Cells

Mixed halogen substitution on the end groups of organic photovoltaic materials has been proven to be an effective way to generate materials with enhanced performance. A systematic comparison of the mixed halogen atom types can provide comprehensive information on this strategy; however, this is usually limited by the lack of a facile synthesis route. Herein, a new class of end groups featuring mixed halogenation, easily obtained via two steps with excellent yields, is reported. The new end groups are applied in synthesizing acceptor materials, and their performance is compared in organic solar cell devices. Combined with the small molecule donor BTR‐Cl, the best‐performing acceptor BTP‐FCl‐FCl achieves a power conversion efficiency of 15.27% and a high fill factor (FF) of 75.94%. Systematic studies of the mixed halogenation analogues in devices reveal that the higher FF is consistent with the longer carrier lifetime, faster charge extraction, weaker bimolecular recombination, and is associated with the favorable BTR‐Cl:BTP‐FC1‐FC1 domain size and molecular packing, all of which are derived from the different halogen atoms. The results demonstrate that selecting suitable halogen atoms is vital in achieving high‐performance organic solar cells.

Synthesis and Characterization of New o‐Carboranes‐Based Aggregation‐Induced Emission Molecules with Ultra‐Large Stokes Shift

AbstractFour o‐carborane‐based aggregation‐induced emission molecules with ultra‐large Stokes shifts were designed and synthesized. To explore the origin of the ultra‐large Stokes shifts (Δλ ≈ 268–294 nm) of the four target molecules, a new molecule named CZ‐Ph‐PO was synthesized by replacing the o‐carborane unit in CZ‐CB‐PO with a benzene ring. It was found that the ultra‐large Stokes shift was the result of the combined action of diphenylphosphinyl and o‐carborane, in which o‐carborane was the key group. In addition, combined with the single crystal structure analysis, the effect of halogens on molecular photophysical properties was investigated. Our work provides a reference for the design and synthesis of o‐carborane‐based fluorescent molecules with ultra‐large Stokes shifts.

Narrowing the band gap and suppressing electron-hole recombination in β-Fe2O3 by chlorine doping.

The effects of halogen (F, Cl, Br, I, and At) doping in the direct-band-gap β-Fe2O3 semiconductor on its band structures and electron-hole recombination have been investigated by density functional theory. Doping Br, I, and At in β-Fe2O3 leads to transformation from a direct-band-gap semiconductor to an indirect-band-gap semiconductor because their atomic radii are too large; however, F- and Cl-doped β-Fe2O3 remain as direct-band-gap semiconductors. Due to the deep impurity states of the F dopant, this study focuses on the effects of the Cl dopant on the band structures of β-Fe2O3. Two impurity levels are introduced when Cl is doped into β-Fe2O3, which narrows the band gap by approximately 0.3 eV. After doping Cl, the light-absorption edge of β-Fe2O3 redshifts from 650 to 776 nm, indicating that its theoretical solar to hydrogen efficiency for solar water splitting increases from 20.6% to 31.4%. In addition, the effective mass of the holes in halogen-doped β-Fe2O3 becomes significantly larger than that in undoped β-Fe2O3, which may suppress electron-hole recombination.

Role of halogen effects and cyclic imide groups in constructing red and near-infrared room temperature phosphorescence molecules: theoretical perspective and molecular design.

Organic room temperature phosphorescence (RTP) has been widely investigated to realize long-lifetime luminescent materials and improvement in their efficiency is a key focus of research, especially for red and near-infrared (NIR) RTP molecules. However, due to the lack of systematic studies on the relationship between basic molecular structures and luminescence properties, both the species and amounts of red and NIR RTP molecules remain far from meeting the requirements of practical applications. Herein, based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, the photophysical properties of seven red and NIR RTP molecules in tetrahydrofuran (THF) and in the solid phase were theoretically studied. The excited state dynamic processes were investigated by calculating the intersystem crossing and reverse intersystem crossing rates considering the surrounding environmental effects in THF and in the solid phase using a polarizable continuum model (PCM) and quantum mechanics and molecular mechanics (QM/MM) method, respectively. The basic geometric and electronic data were obtained, Huang-Rhys factors and reorganization energies were analyzed, and natural atomic orbital was used to calculate the orbital information of the excited states. Simultaneously, the electrostatic potential distribution on molecular surfaces was analyzed. Further, intermolecular interactions were visualized using the molecular planarity binding independent gradient model based on Hirshfeld partition (IGMH). The results showed that the unique molecular configuration has the potential to achieve red and NIR RTP emission. Not only did the substitutions of halogen and sulfur make the emission wavelength red-shifted, but also linking the two cyclic imide groups could further make the emission wavelength longer. Moreover, we found that the emission characteristics of molecules in THF had a similar trend as in the solid phase. Based on this point, two new RTP molecules with long emission wavelengths (645 nm and 816 nm) are theoretically proposed and their photophysical properties are fully analyzed. Our investigation provides a wise strategy to design efficient and long-emission RTP molecules with an unconventional luminescence group.

Halogen effect in photomechanical molecular crystals

Halogen-involved intermolecular interactions affect the stacking of photo-responsive chromophores and the photochemical reactions in crystals. This review highlights the halogen effect in photomechanical crystals.

Investigation of enhanced Am selectivity for Eu in solvent extraction using a BTPhen ligand substituted with halogen.

The effect of bromine (Br) on the separation of Am/Eu using BTPhen was investigated using DFT calculations. The simulated results agreed well with the reported experimental result of Br substitution. It is concluded that the contribution of the d orbital becomes less important by increasing the number of Br atoms, that is, the relative contribution of the f orbital becomes important. The Am f orbital contributed to both bonding and antibonding interactions with the ligand, whereas the Eu f orbital contributed to the antibonding interaction with the ligand. To study the halogen effect systematically, we introduced a series of new halogen atoms (chlorine, fluorine, iodine) into BTPhen. When the electronegativity of the halogen atom increases, the ΔG for complex formation shifts to the positive direction, and the ΔΔG which shows the difference in ΔG between Am and Eu becomes a large negative value, suggesting that the Am selectivity is larger. This is due to the increased Δρ BCP (= ρ BCP(Am) - ρ BCP(Eu)) between the metal and the ligating nitrogen atom with an increase of electronegativity of the halogen atom.

Formation of halogenated macromolecular organics induced by Br− and I− during plasma oxidation/chlorination of DOM: Highlighting competitive mechanisms

Understanding the effects of halogens on the production of macromolecular disinfection byproducts (DBPs) is critical for drinking water safety. The effects of Br− and I− on the chemical diversity of dissolved organic matter (DOM) during plasma preoxidation and the subsequent formation of macromolecular halogenated DBPs after chlorination were deciphered. Plasma preoxidation changed DOM diversity from aromatic component-oriented to lignin and tannin component-oriented, resulting in 62.0% and 21.2% decreases in N-DBPs (CkHnOmNzClx formulas) and C-DBPs (CkHnOmClx formulas) after chlorination, respectively. Br− could induce the formation of organobromine compounds (OBrCs) during plasma oxidation; however, the intensities of OBrCs decreased by 56.3% (CHO formulas) and 75.2% (CHON formulas) after further chlorination. OBrCs still accounted for 79.8% of the total organohalogen compounds (OXCs, X=Cl or Br) due to the higher substitutability of bromine. I−promoted OIC production in the DOM preoxidation process, and OICs acted as intermediates to form OClCs during chlorination. When Br−and I−coexisted, Br− promoted OIC production in the DOM preoxidation process; therefore, more OBrCs and OClCs were generated due to intermediates of OICs in subsequent chlorination. Connections between OXCs and their precursors were established using network computation. The precursors of OClCs were located in the aromatic structure region (0.2 < H/C ≤ 0.7; O/C ≤ 0.67); those of OBrCs and OICs were located in the lignin (0.7 < H/C ≤ 1.5; 0.1 < O/C < 0.67) and tannin (0.6 ≤ H/C ≤ 1.5, 0.67 < O/C < 1.0) regions with relatively greater H/C and O/C ratios, respectively.

Exploring the Effect of Halogenation in a Series of Potent and Selective A2B Adenosine Receptor Antagonists.

The modulation of the A2B adenosine receptor is a promising strategy in cancer (immuno) therapy, with A2BAR antagonists emerging as immune checkpoint inhibitors. Herein, we report a systematic assessment of the impact of (di- and mono-)halogenation at positions 7 and/or 8 on both A2BAR affinity and pharmacokinetic properties of a collection of A2BAR antagonists and its study with structure-based free energy perturbation simulations. Monohalogenation at position 8 produced potent A2BAR ligands irrespective of the nature of the halogen. In contrast, halogenation at position 7 and dihalogenation produced a halogen-size-dependent decay in affinity. Eight novel A2BAR ligands exhibited remarkable affinity (Ki < 10 nM), exquisite subtype selectivity, and enantioselective recognition, with some eutomers eliciting sub-nanomolar affinity. The pharmacokinetic profile of representative derivatives showed enhanced solubility and microsomal stability. Finally, two compounds showed the capacity of reversing the antiproliferative effect of adenosine in activated primary human peripheral blood mononuclear cells.

Combined Experimental and Theoretical Investigation into the Photophysical Properties of Halogenated Coelenteramide Analogs.

Marine Coelenterazine is one of the most well-known chemi-/bioluminescent systems, and in which reaction the chemi-/bioluminophore (Coelenteramide) is generated and chemiexcited to singlet excited states (leading to light emission). Recent studies have shown that the bromination of compounds associated with the marine Coelenterazine system can provide them with new properties, such as anticancer activity and enhanced emission. Given this, our objective is to characterize the photophysical properties of a previously reported brominated Coelenteramide analog, by employing a combined experimental and theoretical approach. To better analyze the potential halogen effect, we have also synthesized and characterized, for the first time, two new fluorinated and chlorinated Coelenteramide analogs. These compounds show similar emission spectra in aqueous solution, but with different fluorescence quantum yields, in a trend that can be correlated with the heavy-atom effect (F > Cl > Br). A blue shift in emission in other solvents is also verified with the F−Cl−Br trend. More relevantly, the fluorescence quantum yield of the brominated analog is particularly sensitive to changes in solvent, which indicates that this compound has potential use as a microenvironment fluorescence probe. Theoretical calculations indicate that the observed excited state transitions result from local excitations involving the pyrazine ring. The obtained information should be useful for the further exploration of halogenated Coelenteramides and their luminescent properties.

Selectively Halogenated Flavonolignans—Preparation and Antibacterial Activity

A library of previously unknown halogenated derivatives of flavonolignans (silybins A and B, 2,3-dehydrosilybin, silychristin A, and 2,3-dehydrosilychristin A) was prepared. The effect of halogenation on the biological activity of flavonolignans was investigated. Halogenated derivatives had a significant effect on bacteria. All prepared derivatives inhibited the AI-2 type of bacterial communication (quorum sensing) at concentrations below 10 µM. All prepared compounds also inhibited the adhesion of bacteria (Staphyloccocus aureus and Pseudomonas aeruginosa) to the surface, preventing biofilm formation. These two effects indicate that the halogenated derivatives are promising antibacterial agents. Moreover, these derivatives acted synergistically with antibiotics and reduced the viability of antibiotic-resistant S. aureus. Some flavonolignans were able to reverse the resistant phenotype to a sensitive one, implying that they modulate antibiotic resistance.