Presence Of Metal Halides Research Articles

Constructing Stable and Potentially High-Performance Hybrid Organic-Inorganic Perovskites with "Unstable" Cations.

A new family of functional hybrid organic-inorganic perovskites (HOIPs) is theoretically designed based on the following chemical insights: when a proton is adhered to molecules like water or ethanol, the newly formed larger-sized cations (e.g., H5O2+, C2H5OH2+, and CH3SH+) entail low electron affinities mimicking superalkalis; they are conjugated acids of weak bases that cannot survive in solution, while their chemistry behavior in the HOIP frameworks, however, may be markedly different due to greatly enhanced cohesive energies of the proton, which facilitate the formation of new HOIPs. First-principles computations show that the putative formation reactions for these newly designed HOIPs typically release much more energy compared with the prevailing HOIP MAPbI3, suggesting the likelihood of facile solution-based fabrications, while the suppression of reverse formation suggests that the humidity stability may be markedly enhanced. During their formations, halide acids are unlikely to react with ethanol or methanethiol without the presence of metal halides, a condition further favoring their stability. The proposed structure of (H5O2)PbI3 may also clarify the origin of the long-speculated existence of HPbI3. Importantly, density functional theory computations suggest that many of these HOIPs possess not only direct bandgaps with values within the optimal range for solar light absorbing but also more desirable optical absorption spectra than that of MAPbI3, where their ferroelectric polarizations also benefit photovoltaics. The stability and photovoltaic efficiency may be even further improved for the newly designed two-dimensional (2D) HOIPs and 2D/3D hybrid HOIP structures.

Highly stereoselective metal-mediated domino aldol reactions of propiophenone enolates with heteroaromatic, aliphatic, and unsaturated aldehydes

The one-pot reaction of propiophenone with heteroaromatic, aliphatic, and unsaturated aldehydes in the presence of metal halides furnishes racemic tetrahydro-2H-pyran-2,4-diols in a highly diastereo-selective manner. The mechanism for the stereoselective product formation as well as the surprising formation of a side product was explained on the basis of DFT computations.

Kinetic study of wood pyrolysis in presence of metal halides

Abstract The purpose of this work was to study the kinetics of wood pyrolysis in the presence of inorganic salts, representatives of classes of alkali and alkaline earth metal halides (NaCl, KCl, KBr, CaCl2, BaCl2·2H2O) and Lewis acids (AlCl3·6H2O, FeCl3·6H2O, CuCl2, CuBr2, ZnCl2·1.5H2O, NiCl2·6H2O, SnCl2·2H2O) using TG-DSC. The activity of these catalysts was estimated by the temperature of the beginning of pyrolysis, charcoal yield and kinetic parameters, such as energy of activation and reaction order. Using the Lewis acids as catalysts for pyrolysis leads to a decrease in the temperature of the process beginning and the activation energy. In the presence of other catalysts activation energy does not significantly change. The increase of a seeming reaction order in the presence of Lewis acids possibly is a consequence of complication of the thermodestruction mechanism, with the appearance of new parallel competing stages.

Photodegradation of an azo dye with reusable SrF2–TiO2 under UV light and influence of operational parameters

SrF2 loaded TiO2 (SrF2–TiO2), prepared by sol–gel method, was characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), atomic force microscopy (AFM) and BET surface area measurements. TEM images reveal that the sizes of SrF2–TiO2 particles are in the range of 3–20nm. Presence of metal halide (SrF2) in the catalyst was confirmed by FT-IR, XRD, XPS and CV measurements. SrF2 loading increases the absorption of UV and visible light. AFM images show a cavity which increases the surface area and photocatalytic activity of the catalyst. 3wt% SrF2 loaded TiO2 was found to be more photoactive than bare TiO2 in Reactive Yellow 84 (RY 84) dye degradation. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photomineralization by SrF2–TiO2 have been analyzed. The optimum pH and catalyst amount for efficient removal of dye are found to be 5 and 4gL−1, respectively. The intermediates identified by GC–MS analysis during photodegradation, are 2-amino-4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]phenol (1), 6-chloro-N-phenyl-1,3,5-triazin-2,4-diamine (2), 2,4-diaminophenol (3) and 1,3,5-triazin-2,4-diamine (4) based on their molecular ion and mass spectrometric fragmentation peaks. The mineralization of RY 84 has also been confirmed by CV and chemical oxygen demand (COD) measurements. Mechanism of dye degradation by SrF2–TiO2 is proposed on the basis of hole trapping property of SrF2. The catalyst was found to be stable and reusable.

ChemInform Abstract: Rational Addition of Capping Groups to the Phosphomolybdate Keggin Anion [PMo12O40]3‐ by Mild, Non‐Aqueous Reductive Aggregation.

AbstractControlled reductive assembly of capped Keggin‐type polyoxometalates is achieved by mild, non‐aqueous reduction of [PMo12O40]3‐ with sodium‐mercury amalgam in the presence of metal halides.

About allyl methacrylate polymerization in the presence of PdCl2

Allyl (meth)acrylates are known to be polymerized in a nitrogen atmosphere upon material initiation or UV irradiation. In the initial reaction stages, soluble polymers are formed, which are converted to insoluble form as polymerization goes to high degrees of conver� sion [1–3]. Examples of initiation of radical polymer� ization of acrylates by some metal halides, for exam� ple, ZnCl2 , are known [4]; however, no data on PdCl 2 � induced polymerization are available. No information on allyl methacrylate polymerization in the presence of metal halides is available. The purpose of this work was an attempt to poly� merize allyl methacrylate in the presence of PdCl2. Investigations showed that allyl methacrylate (AMA)

Structures, IR, NMR Spectra and Thermodynamics Properties of Halogenated Compounds X‐1‐ZB11H10 (ZO, S, Se; XF, Cl, Br): A DFT Study

AbstractThe halogenated compounds of twelve‐vertex closo‐1‐ZB11H11(Z=O, S, Se; X=F, Cl, Br) have unusual stability. The structures of halogenated isomers obtained by DFT method indicate that the halogen atoms are more likely to attack the meta vertexes. The chemical thermodynamic properties show that the halogenations are spontaneous and exothermic. The result that both the optimized and experimental cages of closo‐thiaborane have not changed after chlorination indicates that the substitution of a chlorine atom for a hydrogen atom of closo‐thiaborane happens at outer of the cage. The calculated electronic structures show that the three‐dimensioned aromaticity of cage would like positive chlorine atoms to attack. The halogenations by elemental halogen in the presence of metal halides were proved to belong to the electrophilic substitutions and the mechanism was discussed in details. The suggested transition state interpreted the experiments. The thermal rearrangement which was supposed early according to experiments was verified by the thermodynamic properties of chlorination theoretically. The IR and 11B/1H NMR isotropic chemical shifts were calculated and compared with the experimental data to reconfirm the structures of chlorinated closo‐thiaborane. Furthermore, the predictions on the halogenated closo‐oxaborane and closo‐selenaborane are significant for the syntheses.

All-Carbon-Substituted Vinylsilane Stable to TBAF: Synthesis of Allyldimethylvinylsilane and Its Pd-Catalyzed Cross-Coupling under Mild Conditions

[reaction: see text] Allyldimethylvinylsilanes 3 are easily synthesized by the reaction of silylallylmetals, generated from 1 by n-BuLi/t-BuOK, with carbonyl compounds in the absence or presence of metal halides. They can tolerate 2 equiv of TBAF in THF at room temperature for at least 6 h but can be easily activated in the presence of a palladium catalyst and TBAF to perform the cross-coupling reaction with aryl iodides at room temperature.

Modelling current transfer to cathodes in metal halide plasmas

This work is concerned with investigation of the main features of current transfer to cathodes under conditions characteristic of metal halide (MH) lamps. It is found that the presence of MHs in the gas phase results in a small decrease of the cathode surface temperature and of the near-cathode voltage drop in the diffuse mode of current transfer; the range of stability of the diffuse mode expands. Effects caused by a variation of the work function of the cathode surface owing to formation of a monolayer of alkali metal atoms on the surface are studied for particular cases where the monolayer is composed of sodium or caesium. It is found that the formation of the sodium monolayer affects the diffuse mode of current transfer only moderately and in the same direction that the presence of metal atoms in the gas phase affects it. Formation of the caesium monolayer produces a dramatic effect: the cathode surface temperature decreases very strongly, the diffuse-mode current–voltage characteristic becomes N–S-shaped.

Effects of Ions on Two-Step Phase Separation of Poly(vinyl methyl ether) in Water As Studied by IR and Raman Spectroscopy

Thermosensitive phase separation of aqueous solutions of poly(vinyl methyl ether) (PVME) has been investigated by infrared and Raman spectroscopy and differential scanning calorimetry (DSC) in the presence of metal halides as added salts. DSC measurements showed that the phase separation of PVME proceeds in two successive steps, that is, the first broad endothermic peak starting at Tp1 followed by the second sharp one at Tp2. KF, KBr, and KCl reduced Tp1 and Tp2 as well as the heat of phase transition, whereas KI raised these values. IR spectra showed that the C−H stretching (ν(C−H)) band exhibited a red shift and the C−O stretching band (ν(C−O)) exhibited a blue shift during the phase separation. Although addition of the salts altered Tp1 andTp2, the profiles of the ν(C−H) and ν(C−O) bands measured in the presence of them were similar to those measured without salts. Confocal Raman microscopy reveled that droplets that are rich in polymer are formed above Tp1. The droplets showed a sharp decrease in PVME concentration at Tp2 and a gradual decrease between Tp2 and Tp1 at a cooling process. The temperature region where the CH2 stretching Raman band measured in the polymer-rich phase exhibited a positional change was lower than the region where the CH3 stretching band exhibited a positional change, suggesting that the main chain of PVME is dehydrated at a lower temperature than the methyl side chains. So-called type III phase separation of aqueous PVME solution proposed by Schäfer-Soenen et al. (Macromolecules 1997, 30, 410) was supported by IR and Raman spectroscopic measurements.

Change in Hydration State during the Coil−Globule Transition of Aqueous Solutions of Poly(N-isopropylacrylamide) as Evidenced by FTIR Spectroscopy

Coil−globule transition of poly(N-isopropylacrylamide) (PIPA), followed by intermolecular association in H2O and D2O, was investigated by Fourier transform infrared (FTIR) spectroscopy. IR spectra of the solutions were measured as a function of temperature, and spectral changes induced by the transition were observed. The intensities of the difference IR bands due to the vibrational modes of isopropyl and amide groups critically increased at the lower critical solution temperature (LCST). Heating of the PIPA solutions above the LCST led shifts of the amide II, C−H-stretching, and C−H-bending bands to lower wavenumbers during a shift of the amide I band to a higher wavenumber. The amide I band of the PIPA observed below the LCST could be fitted with a single component centered at 1625 cm-1, whereas two components (1625 and 1650 cm-1) were necessary to fit the band above the LCST. These components may be assigned to the CO group which is bound to water molecules as the solvent (1625 cm-1) and to the N−H in the side chain (1650 cm-1) via hydrogen bonding. About 13% of the CO group is estimated to form the intra- or interchain hydrogen bonding, and the remaining CO group forms a hydrogen bond with water in the globule state. Red shifts of the antisymmetric and symmetric C−H-stretching bands for the isopropyl group also indicate dehydration of the hydrophobic moiety during the transition. A mechanistic hypothesis of the coil−globule transition, insisting that above the LCST the polymer chain is dehydrated and hydrophobic interaction between isopropyl groups induces the collapse of the chain, is strongly supported. Though the presence of metal halides (NaCl, KCl, KBr, KI) lowered the LCST, the profiles of IR difference spectra of the PIPA in those solutions were similar to those measured in pure water. Specific interactions between the amide groups on the polymer chain and the ions were unlikely. Importance of the structure and properties of water in the solution to determine the LCST of the polymer solutions is suggested.

Electrochemical oxidative dimerization of acetoacetic and benzoylacetic esters in the presence of metal halides

Acetoacetic and benzoylacetic esters dimerize on electrolysis in the presence of metal halide mediators to form 2,5-dioxohexane-3,4-dicarboxylic and 1,4-dioxo-1, 4-diphenylbutane-2,3-dicarboxylic esters in yields up to 90%. Primarily the meso-form of the dimer is produced (up to 90%) under optimal conditions (NaI, −20°C) in acetone and acetonitrile. Diastereomers of the dimer are produced in comparable amounts in methanol and ethanol.

ChemInform Abstract: Oxidation of Secondary Cycloalkanoles with the System Lead Tetraacetate/ Metal Halide.

AbstractCyclopentanol (I) is oxidized with lead(IV) acetate in the presence of metal halides or the rhodanide (IV) to give the aldehydes (II) or (V), together with no or minor amounts of cyclopentanone (III).

Electrothermal atomization of chromium in the presence of metal halides: enhancement effects arising from thermal pretreatment processes

Chlorine generated by thermal dissociation of matrix halides is a potential interferent in furnace atomic absorption analysis of elements such as Cr which form volatile chlorides or oxychlorides at low temperatures. This interference is countered by thermal pretreatment of the analyte to form a carbide which is not reactive with chlorine below 1200 K. A strong depression of the Cr atomic absorption signal by CuCl 2 is reversed by thermal pretreatment of chromium oxides at 1850K; a strong signal enhancement results. MnCl 2 does not induce enhancement but its interfering action is diminished by thermal pretreatment. Similar effects are observed when the analyte is atomized from the furnace wall with halides introduced from a pyrolytic graphite platform. Analyte atomization involves two steps, namely condensation onto the cooler platform followed by halogen (matrix) assisted volatilization.

Hydrogenation of liddell vitrinite: Effects of metal halide catalysts in the temperature range 200–480°C

A vitrinite concentrate prepared from the Liddell Seam (high volatile bituminous coal, NSW, Australia) has been hydrogenated in an unstirred 50 cm 3, batch autoclave at reaction temperatures between 200 and 480°C in the presence of metal halides (SnCl 1 or ZnCl 1) and/or alumina (α-Al 1O 3). A vehicle was not used. The influence of reaction temperature, metal halide and alumina on the composition of the products was studied by gas chromatography (GC), gel permeation chromatography (gpc), 1H solution and 13C solid-state cross polarization (CP) nuclear magnetic resonance (nmr) spectroscopy and optical microscopy. The metal halides lower the temperature at which softening and agglomeration of vitrinite takes place. The resultant plastic isotropic material forms mesophase at temperatures above 400°C unless an inert diluent, i.e. alumina, is added. The alumina inhibits reactions involved in the formation of mesophase which would otherwise compete with hydrogenation reactions that yield hexane soluble material (oil). Above 400°C carbon monoxide, carbon dioxide and C 1-C 5 alkanes are the principal gaseous products. At lower temperatures, in the presence of alumina, ethylene is formed in the catalysed experiments; the ethylene is converted to ethane at higher temperatures. The structure of the hexane soluble products derived from vitrinite is also temperature dependent. Above 420°C much of the aliphatic component decomposes to yield further quantities of hydrocarbon gases. Tin(II) chloride and zinc chloride produce hexane soluble products of similar molecular composition, which suggests that they operate through a similar mechanism. The addition of alumina to the reaction mixture results in a more aromatic liquid product with shorter aliphatic carbon chains. Whether or not alumina is present, the aromaticity of the solid residues increases with increase in hydrogenation temperature. Thus the increased aromaticity of the liquid products is not caused by the extraction of a greater proportion of aromatic material from the coal with increase in the hydrogenation temperature. It follows that with increase in hydrogenation temperature an increasing proportion of the aliphatic material becomes transformed into aromatic compounds and/or gas. In summary, the results show that over a wide range of temperatures (200–480°C) the structure of the hexane soluble product depends on the thermal stability of the products and the degree of competition from reactions leading to mesophase formation, and not on the nature of the halide catalyst.

Synthesis of 3-(dialkylamino)indolizines. Reaction of 3-(2-pyridyl)-2-propenals with secondary amines.

Reaction of 2-or 3-substituted 3-(2-pyridyl)-2-propenals (3a-f) with secondary amines afforded 2-or 1-substituted 3-(dialkylamino) indolizines (2a-1) in the presence of metal halides. It was found that titanium tetrachloride was the best catalyst.

Polymerization of coordinated monomers. XVI. Stereoregulation in the alternating copolymerization of methyl methacrylate with styrene in the presence of metal halides

AbstractTriad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of 1H‐ and 13C‐NMR. The cotacticities from 1H‐NMR spectra are obtained accurately by using α‐d‐styrene in the place of styrene and by measuring the spectra on the copolymer in o‐dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis‐Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the 1H‐ and 13C‐NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C1 carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f2Y ‐ 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C1 carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first‐order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex.

Polymerization of coordinated monomers. XIV. Systematic deviations from alternating regulation in copolymerization of methyl methacrylate with styrene in the presence of metal halides

Polymerization of coordinated monomers. XIV. Systematic deviations from alternating regulation in copolymerization of methyl methacrylate with styrene in the presence of metal halides

Polymerization of coordinated monomers. XIV. Systematic deviations from alternating regulation in copolymerization of methyl methacrylate with styrene in the presence of metal halides

AbstractMethyl methacrylate (MMA) and styrene (St) copolymerize in the presence of zinc chloride at 3°C under photoirradiation. The contents of methyl methacrylate in the copolymers obtained at a [ZnCl2]/[MMA] molar ratio of 0.4 are systematically larger than 53 mole %, which is the limiting value at a small feed ratio of methyl methacrylate. The resulting copolymers are confirmed as the sole products and not the mixtures by thin layer chromatography. The effect of dilution of the monomer feed mixture with toluene on copolymer composition suggests that it depends chiefly on the feed concentration of styrene and hardly at all on monomer feed ratios. Copolymerizations are also conducted in the presence of stannic chloride at −17°C under photoirradiation and in the presence of ethylaluminium sesquichloride at 0°C with spontaneous initiation. The contents of methyl methacrylate in both copolymers obtained at feed ratios lower than 60 mole % almost correspond to the 1:1 alternating copolymer and increase systematically with higher feed ratios. The systematic deviations of copolymer composition obtained in the presence of metal halides are reasonably interpreted by the participation of the binary molecular complex composed of metal halide and methyl methacrylate in the polymerization of the ternary molecular complex composed of metal halide, methyl methacrylate, and styrene.

Addition of Chloromethyl Methyl Ether to Isoprene and the Prepation of Isogeranyl Methyl Ether

The cationic addition of chloromethyl methyl ether to isoprene in the presence of metal halides was investigated in order to obtain the 1, 4-adduct, 1-chloro-3-methyl-5-methoxypentene-2. It was found that the addition of small amounts of ethyl alcohol caused a large increase in the yield of the adduct, especially in the case of stannic chloride catalyst. Aliphatic glycols and esters as well as alcohols were found to be effective cocatalysts. A reaction mechanism of the cationic telomerization was discussed and the effects of the additives were attributed to the intramolecular chloride transfer in the reaction intermediate, [CH3OCH2 (C5H8)] + [SnCl5] - [ROH] x. The Grignard coupling of 1-chloro-3-methyl-5-methoxypentene-2 with methallyl chloride afforded α-isogeranyl methyl ether, a useful component of mixed perfumes.