Effect Of Halogen Substitution Research Articles

Axial/Peripheral Halogen‐Substituted Phenoxy Boron Subphthalocyanines for Application as Electron Acceptors Materials for Organic Solar Cells and Hole Transport Materials for Perovskite Solar Cells: A DFT Approach

AbstractOrganic photovoltaic cells (OPVs) are a promising low‐cost renewable energy technology. Among various semiconductors studied for OPVs, boron subphthalocyanine chloride (Cl‐BsubPc) is one of the most explored. Phenoxy‐substituted BsubPc (PhO‐subPc) is an analogue of Cl‐BsubPc that introduces an axial phenoxy ligand in order to tune its electronic properties. In this paper, the effects of halogen substitution on the optoelectronic properties of PhO‐subPc are discussed in terms of the nature, number, and location of halogen atoms. DFT calculations show that the peripheral halogen substitutions significantly decrease the exciton binding energy value, increase the reorganization energy value, and also improve the light‐harvesting efficiency of the mentioned molecules. These modifications are symptoms of improved exciton separation and charge transport; hence, the peripherally halogenated PhO‐subPc are those that exhibit the best performances. However, the phenoxy‐substituted BsubPc do not enhance the performance of the boron subphthalocyanine chloride as far as the hole transport materials (HTM) of organic solar cells are concerned.

The Relationship Between Spin Crossover (SCO) Behaviors, Cation and Ligand Motions, and Intermolecular Interactions in a Series of Anionic SCO Fe(III) Complexes with Halogen-Substituted Azobisphenolate Ligands.

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5'-dihalogen substituents from fluorine to iodine were synthesized, and their anionic FeIII complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the FeIII complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C-H···X, C-H···N, and C-H···O hydrogen bonds, and C-H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity.

Halogen substitution effects in Chlorostannate(II) hybrid material: Insights from DFT study on 2(C4H4FN3O)·SnX6·2(H2O), (X = F, Cl, Br, I)

The development of new materials is crucial for advancing technologies in material science, energy, and biology. In this study, we investigate the effect of Halogen-substitution on the compound 2(C4H4FN3O)·SnX6·2(H2O) (where X = F, Cl, Br, and I). Using extensive theoretical analysis, we examined the impact of halogen substitution on the structural properties, band gap energy (Eg), and chemical behavior. Our results show that the Eg decreases with the increasing atomic number of halogens. The I-substituted compound is the most reactive and exhibits significant intramolecular charge transfer, enhancing its antioxidant properties. The spatial distribution of electron density in the Frontier Molecular Orbitals (FMOs) indicates that the HOMO is localized on the inorganic anion and the LUMO on the organic cation, a pattern consistent across all substituted compounds. These findings highlight the potential of these compounds in electron transfer reactions and provide insights for tailoring them for specific chemical and biochemical applications.

Halogenated-edge polymeric semiconductor for efficient spin transport.

Organic semiconductors (OSCs) are featured by weak spin-orbit coupling due to their light chemical element composition, which enables them to maintain spin orientation for a long spin lifetime and show significant potential in room-temperature spin transport. Carrier mobility and spin lifetime are the two main factors of the spin transport performance of OSCs, however, their ambiguous mechanisms with molecular structure make the development of spintronic materials really stagnant. Herein, the effects of halogen substitution in bay-annulated indigo-based polymers on carrier mobility and spin relaxation have been systematically investigated. The enhanced carrier mobility with an undiminished spin lifetime contributes to a 3.7-fold increase in spin diffusion length and a record-high magnetoresistance of 8.7% at room temperature. By analyzing the spin-orbit coupling and hyperfine interaction, it was found that the distance of the substitution site from the conjugated center and the nitrogen atoms in the molecules play crucial roles in spin relaxation. Based on the above results, we proposed a molecular design strategy of halogen substitution far from conjugate center to enhance spin transport efficiency, presenting a promising avenue for advancing the field of organic spintronics.

Covalent Organic Frameworks in Computational Design of Second-Harmonic Generation Materials: Role of Tetrel Atoms and Their Interactions.

Modern approaches to the design of nonlinear optical materials often rely on computational techniques. Here, we discuss the effects of the variation in the center tetrel atoms, Tt = C, Si, or Ge, in a series of covalent organic frameworks of the COF-102 family. The effects of halogen substitution, Hal = Cl, Br, or I on intramolecular tetrel bonding are also discussed. The characteristics of the calculated electron density have been implemented to describe the features of the electron distribution around the central fragment involving a tetrahedral tetrel atom. The effect of the central Tt atom leads to a dramatic change in the character of electron delocalization on the Tt-Car bond with aromatic rings. The location of the halogen atom at the ortho-position of the aromatic ring leads to the formation of tetrel bonds, halogen bonds, or other noncovalent interactions. The changes in the second-order electric susceptibility χ(2) have been studied in order to describe the strength of nonlinear optical properties within the periodic couple-perturbed Kohn-Sham approach. A counterintuitive trend for the χ(2) decrease is observed upon substitution of H > Cl > Br > I at the ortho-position of the phenyl ring. This is due to the corresponding elongation of the Tt-Car bond.

Computational study of substituent effects on molecular structure, vibrational and electronic properties of fluorene molecule using density functional theory

Density functional theory (DFT) provides a powerful tool for investigating the effects of halogen (F, Cl and Br) substitution on the electronic and structural properties of fluorene. The B3LYP/6-31G (d,p) protocol is a commonly used method in DFT calculations for the optimisation of molecular structures and the calculation of various molecular properties by Gaussian 09 W program. In the case of the fluorene molecule with halogen substitutions, (TD–DFT) calculations can be used to predict its UV–Vis spectrum. The B3LYP density functional model with a 6-31G(d,p) basis set is a common choice for performing (TD–DFT) calculations on molecules. The results showed a decrease in gap energies when electron-withdrawing groups were present in the molecule. A decrease in the gap energy indicates that the molecule is less stable and more reactive.

Halogen substitution effects on crystal structures and magnetic properties in nickel dithiolate molecular crystals

The substitution of halogens on distinct nickel dithiolene molecular crystals [Et3N(CH2)3X][Ni(mnt)2] has a noteworthy impact on the arrangement and magnetic behavior of [Ni(mnt)2]−.

The role of intermolecular interactions in [Fe(X-salEen)2]ClO4 spin crossover complexes.

Two new spin crossover (SCO) Fe(III) compounds were prepared, their structures were analysed and their magnetic properties were investigated. An exhaustive analysis of the effects of halogen substitution and aromatic ring functionalisation on the magnetic properties of non-solvated Fe(III) perchlorate complexes has been performed. Through comparative analysis, different magnetic profiles were found for the compounds studied, namely F (1), Cl (2), H (3), Br (4a, 4b), and I (5). Using tools like Hirshfeld analysis, the study revealed patterns in octahedral distortions and deviations from the ideal octahedral geometry. The SCO phenomenon as the conducting wire in this study, emphasises the influence of intermolecular interactions on the low spin (LS) to high spin (HS) transitions in these halogen-substituted complexes. The prevalence of H⋯H contributions has been demonstrated, albeit being the weakest and an inverse strength relationship in H⋯X interactions ranging from F to I. The findings not only interpret the intricate balance between halogen substitution, functionalisation, and intermolecular interactions in modulating magnetic properties but also direct future works in designing similar molecular systems.

Halogenation effects on the bridgehead position of the adamantane molecule

Halogen substitution effects on the bridgehead positioned carbon of adamantane molecule portraits many significant characteristics for the adamantane halides. As a result of the induction and electrostatic interaction caused by the substitution, large electron densities are formed around the halogens and a small positive electrostatic potential (σ-hole) is developed along the z-direction parallel to C-X bond axis. Computational study performed through EOM-CCSD method, B3LYP and WB97XD functionals of the density functional theory effectively supports this investigation in terms of molecular structure, vibrational properties, bonding behavior and electrostatic potential surfaces. Accordingly, substitution give rise to the change in the dipole moment and symmetry of the molecules. In addition, polarizabilities of the molecules along the C-X bond axis increases with respect to electron densities. HOMO-LUMO energy gap and positive σ-holes are found to decrease with the increase in the negative electron affinity. An anisotropic charge distribution developed upon substitution allows the adamantane halides to exhibit two different binding motifs like halogen and hydrogen bonding along the parallel and perpendicular directions of C-X bond. These characteristics feature of the halo adamantane finds applications in self-assembled monolayers, crystal engineering and biomedical applications.

Nonlinear optical properties of both sulfonated- and halogen-substituted phenyl porphyrins with the effect of mono or bis halogen substitution and of protonation at different pH values on picosecond pulse trains generation

We studied the nonlinear dynamical propagating of picosecond pulse trains in sulfonated porphyrins. The sulfonated porphyrins were synthesized with one or two halogens (fluorine or chlorine) in phenyl rings and macrocycle protonation. One pulse train contains 25 subpulses with 70 ps width and 13.2 ns spacing. The effects of protonation at different pH values on the optical limiting behaviours of sulfonated porphyrins were also studied in this work. The energy structures of porphyrins were simplified to five-level models and Crank-Nicholson numerical method was applied to solve rate equations coupled with two-dimensional paraxial field. The results show sulfonated porphyrins are terrific optical limiters. Two halogens in phenyl rings would improve the optical limiting effects of porphyrins compared to the case of only one halogen in phenyl rings. Besides, nonprotonated sulfonated porphyrins in neutral solution with pH=7.0 show the lowest energy transmittances. But when the intensity of pulse train is strong, protonated sulfonated porphyrins in acidic solution with pH=1.4 show extremely fast growing optical limiting behaviours.

Comparative cytotoxicity analyses of disinfection byproducts in drinking water using dimensionless parameter scaling method: Effect of halogen substitution type and number

Up to date, over 700 disinfection byproducts (DBPs) have been detected and identified in drinking water. It has been recognized that cytotoxicity of DBPs varied significantly among groups. Even within the same group, cytotoxicity of different DBP species was also different due to different halogen substitution types and numbers. However, it is still difficult to quantitatively determine the inter-group cytotoxicity relationships of DBPs under the effect of halogen substitution in different cell lines, especially when a large number of DBP groups and multiple cytotoxicity cell lines are involved. In this study, a powerful dimensionless parameter scaling method was adopted to quantitatively determine the relationship of halogen substitution and the cytotoxicity of various DBP groups in three cell lines (i.e., the human breast carcinoma (MVLN), Chinese hamster ovary (CHO), and human hepatoma (Hep G2) cell cytotoxicity) with no need to consider their absolute values and other influences. By introducing the dimensionless parameters Dx−orn−speciescellline and D¯x−orn−speciescellline, as well as their corresponding linear regression equation coefficients ktypeornumbercellline and k¯typeornumbercellline, the strength and trend of halogen substitution influences on the relative cytotoxic potency could be determined. It was found that the effect of halogen substitution type and number on the cytotoxicity of DBPs followed the same patterns in the three cell lines. The CHO cell cytotoxicity was the most sensitive cell line to evaluate the effect of halogen substitution on the aliphatic DBPs, whereas the MVLN cell cytotoxicity was the most sensitive cell line to evaluate the effect of halogen substitution on the cyclic DBPs. Notably, seven quantitative structure activity relationship (QSAR) models were established, which could not only predict the cytotoxicity data of DBPs, but also help to explain and verify the patterns of halogen substitution effect on cytotoxicity of DBPs.

Structural, electronic, optical, and mechanical properties of the all-inorganic lead-free metal halides double perovskites Cs2RbInX6 (X = Cl, Br, I): A first-principles based study

Lead-free metal halides double perovskite is an ideal alternative to lead-based perovskite and is poised to shine in the field of optoelectronics as a new and emerging photoelectric material. In this paper, we take as a starting point the halide double perovskite Cs2NaInCl6 which is a subject with well-established research results and determined the little-studied structure Cs2RbInCl6 by the replacement of the same-group element, and explore the effects of halogen substitution on the different properties, computational experiments and analyses of the Cs2RbInX6 (X = Cl, Br, I) have been carried out. Depending on the First-Principles studies, the band structure, density of states, optical and mechanical properties of this compound have all been systematically explored. The Materials Studio package's Castep code was used for all computational experiments. The tolerance factor (τ) reveal that Cs2RbInI6 is less stable than Cs2RbInCl6 and Cs2RbInBr6. The band gaps of all three compounds are direct. The light absorption is mainly attributed to the transition from the halogen X-p orbital to the In-s orbital. While Cs2RbInCl6 and Cs2RbInBr6 have no absorption occurring in the visible and infrared regions and possess a wide band gap, which considers them promising candidates for use in the ultraviolet detector. The replacement of halogen has noticeably enhanced the optical properties. The Cs2RbInX6 (X = Cl, Br, I) also meets the requirements for mechanical stability and is ductile, anisotropic, and toughness. Sequentially decreasing band gap values when the halogen from Cl to I, also obviously affects the placements of the threshold points and peaks in the various spectral figures and the macroscopic mechanical properties. The work presented in this paper sheds light on the electronic, optical, and mechanical characteristics of Cs2RbInX6 (X = Cl, Br, I), offering corresponding theoretical support for the related experimental research and promoting the possibility for the development of novel optoelectronic devices.

Complexes of carbon dioxide with methanol and its monohalogen-substituted: Beyond the tetrel bond

This work aims to investigate a significant change in the bonding feature of CO2 complexes that turns from the C∙∙∙O tetrel bond to the OH∙∙∙O hydrogen one due to the effect of halogen-substitution into methanol. The behavior and bonding nature of noncovalent interactions are thoroughly analyzed and discussed. The binding energies were calculated at various methods and extrapolated to the CCSD(T)/CBS. Among DFT-based methods, the B3LYP-D3 is incredibly effective in calculating the binding energy of CH2XOH-CO2 (X = F, Cl, Br) complexes. This work would provide insight into the effect of halogen substituents on the bonding characteristics of noncovalent interactions.

Effects of different halogen and chalcogen substitutions on the ESIPT process of benzoxazole derivatives: Theoretical research

2-(2-carbomethoxy-3,4-dichloro-6-hydroxyphenyl)benzoxazole (DCl-O) has been extensively studied due to its excited-state intramolecular proton transfer (ESIPT) characteristics. To obtain molecules with better luminescence properties, eight derivatives were designed by using different atomic (S, Se and F, Cl) substitution for further study the influence of electronegativity on ESIPT properties. The ESIPT process and photophysical characters of DCl-O and derivatives were studied with theoretical methods. The analysis indicates that hydrogen bonds were strengthened upon photo-excitation. Moreover, the ESIPT reaction is more facile to proceed in derivatives with the weak electronegativity of substitution and the substitution of chalcogen has better effect than that of halogen.

A quantum-chemical perspective on the laser-induced alignment and orientation dynamics of the CH3 X (X = F, Cl, Br, I) molecules.

Motivated by recent experiments, the laser‐induced alignment‐and‐orientation (A&O) dynamics of the prolate symmetric top CH3X (X = F, Cl, Br, I) molecules is investigated, with particular emphasis on the effect of halogen substitution on the rotational constants, dipole moments, and polarizabilities of these species, as these quantities determine the A&O dynamics. Insight into possible control schemes for preferred A&O dynamics of halogenated molecules and best practices for A&O simulations are provided, as well. It is shown that for accurate A&O ‐dynamics simulations it is necessary to employ large basis sets and high levels of electron correlation when computing the rotational constants, dipole moments, and polarizabilities. The benchmark‐quality values of these molecular parameters, corresponding to the equilibrium, as well as the vibrationally averaged structures are obtained with the help of the focal‐point analysis (FPA) technique and explicit electronic‐structure computations utilizing the gold‐standard CCSD(T) approach, basis sets up to quintuple‐zeta quality, core‐correlation contributions and, in particular, relativistic effects for CH3Br and CH3I. It is shown that the different A&O behavior of the CH3X molecules in the optical regime is mostly caused by the differences in their polarizability anisotropy, in other terms, the size of the halogen atom. In contrast, the A&O dynamics of the CH3X series induced by an intense few‐cycle THz pulse is mostly governed by changes in the rotational constants, due to the similar dipole moments of the CH3X molecules. The A&O dynamics is most sensitive to the B rotational constant: even the difference between its equilibrium and vibrationally‐averaged values results in noticeably different A&O dynamics. The contribution of rotational states having different symmetry, weighted by nuclear‐spin statistics, to the A&O dynamics is also studied.

Effects of Halogen Substitutions on Photoelectric Properties and Stability of Two-Dimensional Lead-Free Organic-Inorganic Hybrid Double Perovskite (C6h16n2)2agbix8.H2o(X=I, Br, Cl) with a Dion-Jacobson Structure

Effects of Halogen Substitutions on Photoelectric Properties and Stability of Two-Dimensional Lead-Free Organic-Inorganic Hybrid Double Perovskite (C6h16n2)2agbix8.H2o(X=I, Br, Cl) with a Dion-Jacobson Structure

Triplet exciton dynamics of pure organics with halogen substitution boosted two photon absorption and room temperature phosphorescence: A theoretical perspective

Organic room temperature phosphorescence (RTP) molecules have shown promising applications in organic light emitting diodes and vivo imaging. Thus, triplet exciton dynamics in solid phase should be revealed and the molecule should possess large two photon absorption (TPA) cross sections under near-infrared excitation. The effects of halogen substitution and intermolecular interaction on RTP and TPA properties are studied at molecular level for a series of derivatives. Surrounding environment in solid phase is considered by combined quantum mechanics and molecular mechanics method. Intermolecular interactions are evaluated by the independent gradient model and calculated through the molecular force field energy decomposition method. Minimum energy crossing point, Huang-Rhys factor and reorganization energy are discussed, triplet exciton dynamics are investigated by thermal vibration correlation function method. Results indicate that the largest TPA cross sections are found for molecule in water. The halogen substitution can enlarge the proportion of (π, π*) and facilitate the intersystem crossing process. Restricted intramolecular rotation motions of dihedral angle in low frequency regions are found for Br-Np-Cz-BF2 in solid phase. While enhanced vibrations of bond length and bond angle in high frequency regions are detected for I-Np-Cz-BF2. Effects of halogen substitution and intermolecular interaction on triplet exciton dynamics are highlighted.

Platinum(II) and Copper(II) complexes of asymmetric halogen-substituted [NNʹO] ligands: Synthesis, characterization, structural investigations and antiproliferative activity

In order to better understand the effect of structure, halogen substitution, metal ions and ligand flexibility on antiproliferative activity, eight Cu(II) complexes and eight Pt(II) complexes were obtained of 2,4-X1,X2-6-((pyridine-2-ylmethylamino)methyl)phenol and 2,4-X1,X2-6-((pyridine-2-ylmethylamino)ethyl)phenol (where X is Cl, Br, or I) ligands. The compounds were characterized with various techniques, such as FT-IR, NMR, elemental analysis and single-crystal X-ray diffraction (SCXRD). The X-ray structures showed that ligand acts as a bidentate and tridentate donor in Cu(II) and Pt(II) complexes, respectively. This difference in structures is due to the use or non-use of base in the preparation of complexes. Also, complexation of Cl2-H2L1 with CuCl2·2H2O gives two different types of structures: polymer (Cl2-H2L1-Cupolymer) and dimer (Cl2-H2L1-Cudimer), according to the crystal color. In addition, 1H NMR spectrum for platinum complexes display two set of signals that can be attributed to the presence of two isomers in solution.All complexes induced moderate to high reduction in A2780 and HCT116 cancer cell viability. However, only complexes bearing iodo- substituted in ligands exhibited significantly low cytotoxicity in normal fibroblasts when compared with cancer cell lines. The antiproliferative effect exhibited by I2-H2L2-Cu complex in A2780 cell line was due to induction of cell death mechanisms, namely by apoptosis and autophagy. I2-H2L2-Cu complex does not cause DNA cleavage but a slight delay in cell cycle was observed for the first 24 h of exposition. High cytotoxicity was related with the induction of intracellular ROS. This increase in intracellular ROS was not accompanied by destabilization of the mitochondrial membrane which is an indication that ROS are being triggered externally by I2-H2L2-Cu complex and in agreement with an extrinsic apoptosis activation. I2-H2L2-Cu complex has a pro-angiogenic effect, increasing the vascularization of the CAM in chicken embryos. This is also a very important characteristic in cancer treatment since the increased vascularization in tumors might facilitate the delivery of therapeutic drugs. Taken together, these results support the potential therapeutic of the I2-H2L2-Cu complex.

Synthesis and characterization of 4-Halobenzylidene malanonitriles for optical detection of Nickel (II) ions in aqueous solution

In this work, we have developed fluorescent detection techniques for the determination of Ni2+ ions in aqueous medium with sensitivity using metal coordinating fluorescent molecules namely 4-Halobenzylidene malanonitrile. The halogen substituted benzylidene malanonitile were synthesised Knoevenagel condensation reaction of various halogen substituted aromatic aldehydes with malanonitrile and products were characterised by IR and NMR spectroscopy. The obtained benzylidene malanonitiles and are exhibited a fluorescent emission with a peak of 430 nm, 440 nm and 448 nm for chloro, bromo and fluoro substituted compounds, respectively. The intensity of optical emission of the studied molecules is increased proportional to the addition of Ni2+ ions. The effect of different halogen substitution on the fluorescence behaviour of benylidene malononitrile has also been investigated. The synthesised title compounds showed a lowest detection limit of 10−20 M for the Nickel (II) ions in aqueous solution under UV–Vis absorption spectra. The molecule 4- Bromobenzylidene malanonitrile exhibited a lowest detection limit of 10−19 M for the Nickel (II) ions in, aqueous solution, photoluminescence analysis.

Straining to Put the Pieces Together: The Molecular Structure of (E)-1-Chloro-1,2-difluoroethylene-Acetylene from Microwave Spectroscopy.

The microwave, rotational spectrum between 5.6 and 19.7 GHz of the gas-phase heterodimer formed between acetylene and (E)-1-chloro-1,2-difluoroethylene is obtained using both broadband, chirped-pulse and narrow band, Balle-Flygare Fourier transform microwave spectrometers. The structure of the complex is determined from the rotational constants obtained via the analysis of the spectra for the normal isotopologue of the complex and three isotopically substituted species: the singly substituted 37Cl isotopologue, obtained in natural abundance, and two isotopologues singly substituted with 13C, obtained using an isotopically enriched HC13CH sample. The acetylene forms a hydrogen bond with the fluorine atom on singly halogenated carbon and a secondary interaction with the hydrogen atom on that same carbon. The angle strain induced in forming the secondary interaction is offset by the favorable electrostatics of the hydrogen bond to fluorine. Comparisons with acetylene complexes of 1,1,2-trifluoroethylene and cis-1,2-difluoroethylene show the effects of halogen substitution at the remote carbon on this bonding motif.