Effect Of Halogen Research Articles

Computational insights into the photocyclization of diclofenac in solution: effects of halogen and hydrogen bonding.

The effects of noncovalent interactions, namely halogen and hydrogen bonding, on the photochemical conversion of the photosensitizing drug diclofenac (DCF) in solution were investigated computationally. Both explicit and implicit solvent effects were qualitatively and quantitatively assessed employing the DFT/6-31+G(d) and SQM(PM7) levels of theory. Full geometry optimizations were performed in solution for the reactant DCF, hypothesized radical-based intermediates, and the main product at both levels of theories. Notably, in good agreement with previous experimental results concerning the intermolecular halogen bonding of DCF, the SQM(PM7) method revealed different values for d(ClO, Å) and ∠(C-ClO, °) for the two chlorine-substituents of DCF, with values of 2.63 Å/162° and 3.13 Å/142° for the trans and cis orientations, respectively. Employing the DFT/6-31+G(d) method with implicit solvent effects was not conclusive; however, explicit solvent effects confirmed the key contribution of hydrogen and halogen bonding in stabilizing/destabilizing the reactant and hypothesized intermediates. Interestingly, the obtained results revealed that a protic solvent such as water can increase the rate of photocyclization of DCF not only through hydrogen bonding effects, but also through halogen bonding. Furthermore, the atomic charges of atoms majorly involved in the photocyclization of DCF were calculated using different methods, namely Mulliken, Hirshfeld, and natural bond orbital (NBO). The obtained results revealed that in all cases there is a notable nonequivalency in the noncovalent intermolecular interactions of the two chlorine substituents of DCF and the radical intermediates with the solvent, which in turn may account for the discrepancy of their reactivity in different media. These computational results provide insight into the importance of halogen and hydrogen bonding throughout the progression of the photochemical conversion of DCF in solution.

High-contrast mechanochromism and polymorphism-dependent fluorescence of difluoroboron β-diketonate complexes based on the effects of AIEE and halogen

A series of AIEE-active difluoroboron β-diketonate complexes derivatives exhibit high-contrast mechanochromism, polymorphism-dependent fluorescence, and extremely high fluorescent quantum yields which could be as promising stimuli-responsive materials.

Improvement of the high temperature oxidation resistance of Ti–50Al at 1000°C by anodizing in ethylene glycol/BmimPF6 solution

Abstract A compact Al-enriched and fluoride-containing surface layer can be fabricated on Ti–50Al by anodizing in ethylene glycol (EG) solution containing 1.8 vol.% ionic liquid named 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6). After high temperature oxidation, an Al2O3 layer is formed on the thin anodic oxide film (AOF) coated Ti–50Al, which efficiently inhibits the diffusion of oxygen and leads to excellent high temperature oxidation resistance. As a result, after oxidation in air at 1000 °C for 100 h, the anodized Ti–50Al shows a very low weight gain of 0.54 mg/cm2, while the weight gain of bare Ti–50Al is as high as 82.40 mg/cm2. The surface morphology and composition of AOF coated Ti–50Al before and after high temperature oxidation were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and glow discharge optical spectroscopy (GDOS). The results show that the excellent high temperature oxidation resistance of the AOF coated Ti–50Al can be ascribed to two aspects. One is the Al-enriched structure formed initially during anodization, which can inhibit the diffusion of oxygen into the substrate. The other one is the halogen effect. The fluorides introduced into the AOF during anodization promote a selective transport of aluminum from the substrate to the alumina scale/substrate interface through pores or micro-cracks due to the formation of gaseous aluminum fluorides. These aluminum fluorides are then oxidized to Al2O3 at the interface and within the alumina scale. Finally, a protective alumina scale is formed and provides excellent high temperature oxidation resistance.

Experimental study of REE, Ba, Sr, Mo and W partitioning between carbonatitic melt and aqueous fluid with implications for rare metal mineralization

Carbonatites host some unique ore deposits, especially rare earth elements (REE). Hydrothermal fluids have been proposed to play a significant role in the concentration and transport of REE and other rare metals in carbonatites, but experimental constraints on fluid–melt equilibria in carbonatitic systems are sparse. Here we present an experimental study of trace element (REE, Ba, Sr, Mo and W) partitioning between hydrous fluids and carbonatitic melts, bearing on potential hydrothermal activity associated with carbonatite ore-forming systems. The experiments were performed on mixtures of synthetic carbonate melts and aqueous fluids at 700–800 °C and 100–200 MPa using rapid-quench cold-seal pressure vessels and double-capsule assemblages with diamond traps for analyzing fluid precipitates in the outer capsule. Starting mixtures were composed of Ca, Mg and Na carbonates spiked with trace elements. Small amounts of F or Cl were added to some of the mixtures to study the effects of halogens on the element distribution. The results show that REE, Ba, Sr, Mo and W all preferentially partition into carbonatite melt and have fluid–melt distribution coefficients (D f/m) below unity. The REE partitioning is slightly dependent on the major element (Ca, Mg and Na) composition of the starting mixtures, and it is influenced by temperature, pressure, and the presence of halogens. The fluid–melt D values of individual REE vary from 0.02 to 0.15 with $$D_{\text{Lu}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ being larger than $$D_{\text{La}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ by a factor of 1.1–2. The halogens F and Cl have strong and opposite effects on the REE partitioning. Fluid–melt D REE are about three times higher in F-bearing compositions and ten times lower in Cl-bearing compositions than in halogen-free systems. $$D_{\text{W}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ and $$D_{\text{Mo}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ are the highest among the studied elements and vary between 0.6 and 0.7; $$D_{\text{Ba}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ is between 0.05 and 0.09, whereas $$D_{\text{Sr}}^{{{{\text{f}} \mathord{\left/ {\vphantom {{\text{f}} {\text{m}}}} \right. \kern-0pt} {\text{m}}}}}$$ is at about 0.01–0.02. The results imply that carbonatite-related REE deposits were probably formed by fractional crystallization of carbonatitic melts rather than from exsolved hydrothermal fluids. The same appears to be true for a carbonatite-related Mo deposit recently discovered in China.

Halogen and solvent effects on the conformational, vibrational and electronic properties of 1,4-diformylpiperazine: A combined experimental and DFT study

The molecular structure and properties of 1,4-diformylpiperazine (1,4-dfp, C6H[Formula: see text]N2O2) were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and density functional theory (DFT). The Becke-3-Lee–Yang–Parr (B3LYP) functional was used with the 6-31[Formula: see text]G(d,p) basis set. Total energy distribution (TED) analysis of normal modes was performed to identify characteristic frequencies by the scaled quantum mechanical (SQM) method. Halogeno-analogs of 1,4-dfp were studied to understand the halogen effect. Computations were focused on five conformational isomers of the compounds in the gas phase and in solutions. The computed and experimental frequencies of the C[Formula: see text]O stretching vibration of 1,4-dfp were correlated with the empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSER). The electronic properties of the compounds were also examined. The findings from the present work may be useful to understand systems involving the halogens and conformational changes analogous to the compounds investigated.

Core Halogenation as a Construction Principle in Tuning the Material Properties of Tetraazaperopyrenes.

A detailed study on the effects of core halogenation of tetraazaperopyrene (TAPP) derivatives is presented. Its impact on the solid structure, as well as the photophysical and electrochemical properties, has been probed by the means of X-ray crystallography, UV/Vis and fluorescence spectroscopy, high-resolution electron energy loss spectroscopy (HREELS), cyclic voltammetry (CV), and DFT modeling. The aim was to assess the potential of this approach as a construction principle for organic electron-conducting materials of the type studied in this work. Although halogenation leads to a stabilization of the LUMOs compared to the unsubstituted parent compound, the nature of the halide barely affects the LUMO energy while strongly influencing the HOMO energies. In terms of band-gap engineering, it was demonstrated that the HOMO-LUMO gap is decreased by substitution of the TAPP core with halides, the effect being found to be most pronounced for the iodinated derivative. The performance of the recently reported core-fluorinated and core-iodinated TAPP derivatives in organic thin-film transistors (TFTs) was investigated on both a glass substrate, as well as on a flexible plastic substrate (PEN). Field-effect mobilities of up to 0.17 cm(2) Vs(-1) and on/off current ratio of >10(6) were established.

Understanding the Halogenation Effects in Diketopyrrolopyrrole-Based Small Molecule Photovoltaics.

Two molecules containing a central diketopyrrolopyrrole and two oligothiophene units have been designed and synthesized. Comparisons between the molecules containing terminal F (FDPP) and Cl (CDPP) atoms allowed us to evaluate the effects of halogenation on the photovoltaic properties of the small molecule organic solar cells (OSCs). The OSCs devices employing FDPP:PC71BM films showed power conversion efficiencies up to 4.32%, suggesting that fluorination is an efficient method for constructing small molecules for OSCs.

Effect of Halogenation in Isoindigo-Based Polymers on the Phase Separation and Molecular Orientation of Bulk Heterojunction Solar Cells

Fluorinated and chlorinated isoindigo-based polymers, F-IIDT and Cl-IIDT, were developed as the donor materials for photovoltaic cells. Although showing similar frontier orbital energy levels, both polymers exhibited distinct solar cell device performance, for example, power conversion efficiency of 4.60% for Cl-IIDT and 1.19% for F-IIDT. The investigation of photophysical properties demonstrated that the strong preaggregation of F-IIDT was formed in solution due to increased noncovalent interactions between the backbones of the polymer. Therefore, large crystal domains in blended thin films with no preferred crystallographic orientation were obtained. On the other hand, the introduction of chlorine atoms increased the torsional angle of the polymer backbone, resulting in reduced crystallization tendency. Films with less crystallinity and face-on polymer orientation contributed to better device performance of Cl-IIDT. Our research proved that the effects of halogenation are far more than the tuning of fro...

Halogen effect on mixed-valence state of biosmocenium(II, IV) salts

The mixed-valence biosmocenium(II, IV)–Cl adduct [(C5H5)OsII(μ2-η5:η5-C10H8) (C5H5)OsIVCl]Y(1a:YPF6, 1b:YBF4) and biosmocenium-Br adduct [(C5H5)OsII(μ2-η5:η5-C10H8) (C5H5)OsIVBr]PF6(2) were prepared. The structures of 1b and 2 were determined by single crystal X-ray analysis, and it was found that Os-X bond was fixed on cis position to the other half of osmocenyl moiety. Although 1b and 2 had the trapped-valence state in solid state, valence-detrapping depending on temperature was observed in solution state by using variable-temperature 1H NMR spectroscopy. It was found that intramolecular electron exchange reaction OsII–OIV ⇄ OsIV–OsII occurred accompanied by halogen migration. The activation energy of the reaction was determined. The energy decreased in the order A > 2 > 1a depending on a kind of halogen ligand bonded to Os center, and the tendency can be explained by HSAB theory.

Structure of hypercoordinated monoorganodihalostannanes in solutions and in the solid state: the halogen effect

A series of hypercoordinated monoorganotin dibromides formed by glycolic acid amides, [RSnBr2(OCH2C(O)NR′2)]2 (2a, R=Et, NR′2=NMe2; 3a, R=n-Bu, NR′2=NMe2; 4b, R=Ph, NR′2=morpholin-4-yl), were obtained and investigated by X-ray analysis, multinuclear NMR spectroscopy in solutions (1H, 13C, 119Sn) and solid state (CP/MAS). It has been established that 2a, 3a and 4b in solid state are dimeric. For the solutions in coordinating solvents the slow monomer–dimer equilibrium has been observed. The structures of related solvated monomeric chlorides, RSnCl(DMSO)(OCH2C(O)NR′2), 5a·DMSO and 6a·DMSO, were also investigated by X-ray analysis.

Crystal structure, vibrational spectra and DFT simulations of 2-fluoro-4-bromobenzaldehyde

Molecular structure and properties of 2-fluoro-4-bromobenzaldehyde (FBB, C7H4BrFO) was experimentally investigated by X-ray diffraction technique and vibrational spectroscopy. Experimental results on the molecular structure of FBB were supported with computational studies using the density functional theory, with the Becke-3-Lee–Yang–Parr functional and the 6-311+G(3df,p) basis set. Molecular dimer formed by the intermolecular hydrogen bonding was investigated. Potential energy distribution analysis of normal modes was performed to identify characteristic frequencies. FBB crystallizes in orthorhombic space group P212121 with the O-trans conformation. In order to investigate halogen effect, the chloro- (CBB) and bromo- (BBB) analogs of FBB have also been studied theoretically. It is observed that all compounds prefer the stable O-trans conformation. Although the free energy difference between the O-cis and O-trans conformers is less than 2.5kcal/mol, the free energy rotational barrier is at least 7.4kcal/mol. There is a good agreement between the experimentally determined structural parameters, and vibrational frequencies of FBB and those predicted theoretically.

3-Iodobenzaldehyde: XRD, FT-IR, Raman and DFT studies

The structure of 3-iodobenzaldehyde (3IB) was characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 3IB were examined using density functional theory (DFT) method, with the Becke-3-Lee–Yang–Parr (B3LYP) functional and the 6-311+G(3df,p) basis set for all atoms except for iodine. The LANL2DZ effective core basis set was used for iodine. Potential energy distribution (PED) analysis of normal modes was performed to identify characteristic frequencies. 3IB crystallizes in monoclinic space group P21/c with the O-trans form. There is a good agreement between the theoretically predicted structural parameters, and vibrational frequencies and those obtained experimentally. In order to understand halogen effect, 3-halogenobenzaldehyde [XC6H4CHO; X=F, Cl and Br] was also studied theoretically. The free energy difference between the isomers is small but the rotational barrier is about 8kcal/mol. An atypical behavior of fluorine affecting conformational preference is observed.

Conformation stability, halogen and solvent effects on C[dbnd]O stretching of 4-chloro-3-halogenobenzaldehydes

The effects of halogen and solvent on the conformation and carbonyl stretching of 4-chloro-3-halogenobenzaldehydes [C7H4ClXO; X=F (CFB), Cl (CCB) or Br (CBB)] were investigated using the density functional theory (DFT) method. The B3LYP functional was used by the 6-311+G(3df,p) basis set in combination with the polarizable continuum model (PCM). Computations were focused on the cis and trans isomers of the compounds in 18 different polar or non-polar organic solvents. The theoretical frequencies of the solvent-induced CO stretching vibrations were correlated with the empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and the linear solvation energy relationships (LSER). The present work explores the effect of both the halogen and medium on the conformational preference and CO vibrational frequency. The findings of this work can be useful to those systems involving changes in the conformations analogous to the compounds studied.

Promotion of the Al2O3-Scale Formation on Ni–Cr–Al Alloys via the Fluorine Effect

The halogen effect, which involves the surface enrichment of an alloy with a halogen element to result in improved oxidation resistance, was assessed using model Ni-based Ni-Cr-Al alloys. The alloys studied varied in composition in a manner that produced sub-critical, borderline and protective intrinsic oxidation behaviours from the standpoint of being able to form a continuous Al2O3 scale. Fluorine-ion implantation allowed for a well-defined surface doping of the alloys. It was found that this doping could promote protective Al2O3-scale formation during oxidation at 900 and 1,000 C in both dry and steam-containing atmospheres. Specifically, the beneficial halogen effect was manifested by lowering the critical Al content in Ni-Cr-Al alloys needed for Al2O3-scale formation.

Construction of helical coordination polymers via flexible conformers of bis(3-pyridyl)cyclotetramethylenesilane: metal(ii) and halogen effects on luminescence, thermolysis and catalysis.

Infinite rectangular-tubular helices, [MX2L] (M = Zn(ii), Hg(ii); X(-) = Cl(-), Br(-); L = bis(3-pyridyl)cyclotetramethylenesilane), have been efficiently constructed via the combined effects of the potential flexible conformers of L and the tetrahedral geometry of M(ii) ions. This helical molecular system affords a racemic mixture of P- and M-helices in a crystal. The helical pitches (7.8934(4)-8.1560(2) Å) that are sensitive to the nature of M(ii) ions and halide anions are attributable to subtle change in the flexible dihedral angles between the two pyridyl groups around Si and the M(ii) hinges. Their photoluminescence intensities, correspondingly, are in the order [ZnCl2L] > [ZnBr2L] ≫ [HgCl2L] > [HgBr2L]. Zinc(ii) complexes show recyclable catalytic effects on the transesterification reaction in the order [ZnCl2L] > [ZnBr2L]. Calcination of [ZnCl2L] and [ZnBr2L] at 500 °C produces uniform hexagonal tubular spire crystals of 1.2 × 1.2 × 4.0 μm(3) dimensions and spheres, respectively.

Effect of side-chain halogenation on the interactions of conjugated polymers with SWNTs

Halogenation of polyfluorene side-chain ends with bromine or iodine causes significant differences in the nanotube species that are dispersed in solvent, indicating that subtle changes in polymer structure can affect polymer-nanotube interactions.

Conformation and NH stretching of 1,1-dihalogenoheptan-1-amines [CH3(CH2)5CX2NH2; X = F, Cl or Br]: Halogen and solvent effects

The effects of halogen and solvent on the conformation and NH stretching of 1,1-dihalogeno-heptan-1-amines [CH3(CH2)5CX2NH2; X=F, Cl or Br] were investigated using the density functional theory method. The functional used was B3LYP employing the 6-31++G(d,p) basis set for all atoms. Computations were carried out for ten possible conformational isomers of the compounds, in the gas phase and both in a non-polar solvent (benzene) and in a polar solvent (methanol). This research work indicates that both the halogen and the medium affect conformational preference, geometrical parameters and NH vibrational frequency. The findings of this work can be useful to those systems involving changes in the conformations analogous to the compounds studied.

Theoretical Study of Electronic Properties of X-Doped (X = F, Cl, Br, I) VO2 Nanoparticles for Thermochromic Energy-Saving Foils.

First-principles density functional theory (DFT) electronic structure calculations were carried out for the model halogen-doped VO2 (M1 phase) to evaluate the effect of halogen (X = F, Cl, Br, I) doping on the band edges. The model structures of X-doped VO2 with X at V site or O site were constructed on the basis of 96-atom 2 × 2 × 2 supercell of monoclinic M1 phase of VO2. Our results showed that the band gap Eg2 for Cl-doped VO2 at O1 site (0.51 eV) is smaller than that of F-doped VO2 at O1 site (0.61 eV) and that of pure VO2 (0.78 eV). We also investigated the substitution of chlorine, bromine, and iodine for vanadium in VO2, where the band gaps Eg2 are 0.40, 0.45, and 0.37 eV for Cl-, Br-, and I-doped VO2 at V site, respectively. The Cl-doped VO2 at V site is the best one for achieving good VO2 thermochromic energy-saving foils.

含卤有机化合物与甲状腺素转运蛋白相互作用的卤代效应

Thyroid disrupting chemicals (TDCs) can compete for the binding sites of transport proteins with thyroid hormones (THs) and alter the homeostasis of THs. The halogen moieties in TDCs play key role in determining the interactions between TDCs and transthyretin (TTR). Herein, the effects of halogenation on the binding interaction was investigated by analyzing the TTR crystal structures, the TDCs-TTR complex from molecular simulation, and the relative competing potency of a chemical with T 4 binding to hTTR (log RP ). We found that the halogen moieties in TDCs can affect the binding interactions by forming halogen bonds and halogen-hydrogen bonds with TTR and through inductive effects and hydrophobic effects. The halogen bonds (mainly halogen-oxygen bonds) and halogen-hydrogen bonds enhance the binding between organic halogenated compounds and TTR. Besides, for the halogenated phenolic compounds, the inductive effect is a main factor determining the log RP values. The hydrophobic effect is a critical factor governing the interactions between non-ionizable compounds (e.g. polybrominated diphenyl ethers) and TTR.

Host–Guest Chemistry of 1D Suprachannels and Dihalomethane Molecules: Metallacyclodimeric Ensembles Consisting of Zinc(II)-2,7-bis(nicotinoyloxy)naphthalene Complexes

Self-assembly of ZnX2 (X = Cl, Br, and I) with 2,7-bis(nicotinoyloxy)naphthalene (L) as a hemicircular bidentate ligand containing a chromophore moiety yields a systematic metallacyclodimeric unit, [ZnX2(L)]2. These basic skeletons constitute, via interdigitated π···π interactions, a unique columnar ensemble forming a suprachannel. This can then be employed as an unusual “diiodomethane within the suprachannel” host–guest system, CH2I2@[ZnX2(L)]2. Specifically, the suprachannel significantly stabilizes the CH2I2 molecules in the order [ZnI2(L)]2 > [ZnBr2(L)]2 > [ZnCl2(L)]2. This suprachannel has significant halogen effects on the photoluminescence (PL), thermal properties, and host–guest inclusion.