MnBr2 Research Articles

Syntheses, Crystal Structures, and Optical Properties of the Hexagonal Perovskites Variants ABX3 (B = Ni, A = Gu, FA, MA, X = Cl, Br; B = Mn, A = MA, X = Br)

Herein we report on our systematic investigations on the solution processed synthesis and characterization of transition metal halides (guanidinium, formamidinium, and methylammonium nickel bromides and chlorides as well as methylammonium manganese bromide) with the composition ABX3 (A = organic cation; B = Mn, Ni; X = Cl, Br). The investigations were carried out with respect to possible applications of 3d transition metal compounds for the perovskite solar cell. All the compounds represent different variants of the hexagonal perovskite structure (2H). Crystal structures and symmetry relations are discussed. Additionally, (CH3NH3)2MnI4, which consists of tetrahedral coordinated Mn2+, and the water containing compounds (CH3NH3)MnBr3·2H2O, which forms chains of edge sharing octahedra, as well as (CH3NH3)NiCl3·2H2O, which consists of dimers of octahedra, are presented. Investigations on the crystal structures are supported by vibrational and optical spectroscopy.

Pyridine-Modulated Mn Ion Emission Properties of C10H12N2MnBr4 and C5H6NMnBr3 Single Crystals

Pb-free inorganic–organic perovskite materials - C10H12N2MnBr4 (compound 1) and C5H6NMnBr3 (compound 2) - with different structures were obtained by using pyridine and manganese bromide as raw materials. The single-crystal X-ray diffraction analyses revealed their different lattices in space groups. Compound 1 - Mn tetra-Br-coordinated with two pyridines - presented an isolated mononuclear structure. Its temperature-dependent photoluminescence spectra exhibited an emission band at 523 nm from the lowest d–d crystal field transition of Mn and a higher energy emission at 493 nm from its vibronic state at low temperature. Compound 2 - Mn octahedra-Br-coordinated with a minor pyridine - face-shares with linear chains, which were separated by pyridine molecules. Its emission peak occurred at around 650 nm, in which ferromagnetism was observed. The lifetimes of d–d transition for a single manganese ion and the Mn cluster were presented.

In situ TEM observation of novel chemical evolution of MnBr2 catalyzed by Cu under electron beam irradiation

Manganese bromide has attracted enormous attention for its applications in the syntheses of organic-inorganic hybrid compounds. A complete understanding of structural and chemical stabilities of MnBr2 is important for controlling its properties. Here, we focus on the irradiation resistance of MnBr2. The chief purpose of this research is reached by in situ transmission electron microscopy. It is demonstrated that the deliquescent MnBr2 powder is prone to adsorb the vapor in air, and the hydrous MnBr2 can be decomposed under its continuous exposure to electron beam, indicated by a transmission electron microscope via the catalysis of Cu grid at room temperature.

Electronic properties of single-walled carbon nanotubes filled with manganese halogenides

In this work, single-walled carbon nanotubes (SWCNTs) were filled with manganese chloride and manganese bromide by a capillary filling method. The electronic properties of the filled SWCNTs were investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. It was found that the encapsulated manganese halogenides led to hole doping of the SWCNTs due to the charge transfer from the nanotubes to the encapsulated compounds. The embedded MnCl2 had stronger doping effect on the SWCNTs than MnBr2.

Re-manufacture of cobalt-manganese-bromide as a liquid catalyst from spent catalyst containing cobalt generated from petrochemical processes via hydrometallurgy

Cobalt and manganese have been the subject of individual separation studies because their fields of application are different. However, this study shows that high-value products can be manufactured in the form of a cobalt-manganese-bromide (CMB) liquid catalyst by simultaneously recovering cobalt and manganese. Na-bis-(2,4,4-tri-methyl-pentyl)phosphinic acid was employed in order to manufacture the CMB liquid catalyst from the spent catalyst generated from petroleum chemistry processes. The pH-isotherm, degree of saponification of solvent and separation factor values were investigated. ΔpH50 and separation factor values show that Co and Mn can be separated from impurities such as Mg and Ca. Further, the extraction stages and organic/aqueous ratio isotherms were investigated using counter-current simulation extraction batch tests. To prepare CMB from a loaded organic phase obtained in a stripping study using hydrogen bromide, the Co and Mn were completely stripped and concentrated by a factor of 6 using a 2M hydrogen bromide solution. When compared with manufactured and commercial CMB, the CMB liquid catalyst could be produced by supplying a shortage of Mn in the form of manganese bromide. Finally, the method of manufacture of CMB was subjected to a real pilot plant test.

Manganese-Catalyzed Borylation of Unactivated Alkyl Chlorides.

The use of low-cost manganese(II) bromide (MnBr2) and tetramethylethylenediamine (TMEDA) catalyzes the cross coupling of (bis)pinacolatodiboron with a wide range of alkyl halides, demonstrating the first manganese-catalyzed coupling with alkyl electrophiles. This method allows access to primary, secondary, and tertiary boronic esters from the parent chlorides, which were previously inaccessible as coupling partners. The reaction proceeds in high yield with as little as 1000 ppm catalyst loading, while 5 mol % can provide high yields in as little as 30 min. Finally, radical-clock experiments revealed that at 0 °C direct borylation outcompetes alternative radical processes, thereby providing synthetically useful, temperature-controlled reaction outcomes.

Magnetic behavior of manganese bromide hydrates including deuteration effects

The magnetic properties of previously unexamined MnBr2·2H2O, MnBr2·H2O, MnBr2·2D2O and MnBr2·D2O are studied. Curie–Weiss fits to high temperature data yield θ of −13.1, −3.9, −8.2 and −5.0K, respectively, in χM=C/(T−θ). The net antiferromagnetic exchange yields susceptibility maxima at 6.34, 3.20, 2.10, and 3.40K, with χmax of 0.197, 0.357, 0.465 and 0.348emu/mol, respectively. Noteworthy is the contrast between dideuterate and dihydrate, the largest deuteration effect observed for hydrated transition metal halides. Antiferromagnetic ordering is estimated to occur at 5.91, 2.65, 2.00 and 2.50K, respectively. The ratio Tc/Tmax is 0.93, 0.83, 0.95 and 0.74 in the same order, implying low dimensional magnetism for monohydrate and monodeuterate. Heisenberg model fits to susceptibilities yield primary and secondary exchange interactions. Magnetization data at moderate fields and different temperatures are presented for each substance, and high field data to 70kG at 2.00K. Spin-flop transitions are estimated to occur at 45, 33 and 30kG, respectively, for dihydrate, monohydrate and monodeuterate, but are not observable for MnBr2·2D2O. The results are analyzed from various perspectives. A different monoclinic unit cell is determined for MnBr2·2D2O than for MnBr2·2H2O, with 1.3% larger volume, providing some rationale for the difference in magnetic properties.

MnBr₂/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield.

The reaction of manganese(ii) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80-130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn(2+) cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn(2+) coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)](+) cation - with Mn(2+) coordinated by six oxygen atoms and Br - and a [MnBr(18-crown-6)MnBr4](-) anion. In this anion, Mn(2+) is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn(2+) cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination.

The investigation of liquid phase reaction of 4-aminotoluene with ozone in the presence of manganese bromide catalyst

A new catalytic system Mn(ІІ)- KBr-H 2 SO 4 -Ас 2 О to obtain 4-aminobenzaldehyde treatment by ozonation of 4-aminotoluene is developed. It has been shown that injection of potassium bromide significantly increases the depth, speed and selectivity of substrate oxidation, the main reaction product is 4-acetylaminobenzylidendiacetate with the discharge of 84.5%. Active particles responsible for the inclusion of 4-aminotoluene oxidation by a methyl group in the presence of manganese (II) acetate and potassium bromide is manganese bromide radical-ion (Mn (II) Br •), which is more active than Mn (III) and because of the higher rate of initiating oxidation by a methyl group. It is proposed the mechanism of the process by which the substrate oxidation is carried out by ion-radical unchain mechanism in which manganese-bromide radical is generated mainly in reaction with ozone. The main functions of sulfuric acid in the system are determined. It affects the main stages of the catalytic cycle: reduces the rate of manganese bromide complex reaction with ozone, significantly increases the rate of substrate oxidation by a methyl group and catalyzes the acylation reaction. These data are the basis for laying the foundations of technology of 4- aminotoluene oxidation by ozone to 4-aminobenzaldehyde and development of preparative and industrial methods for obtaining of aromatic aldehydes.

Recovery of Co metal and Electrolytic Manganese Dioxide (EMD) from Co–Mn sludge

A process flow sheet has been developed to produce cobalt metal and Electrolytic Manganese Dioxide (EMD) from Cobalt–Manganese Bromide (CMB) spent catalyst sludge. The Co–Mn sludge was leached in sulphuric acid media followed by the removal of organic matter from the leach liquor through adsorption by activated charcoal. Co–Mn separation was carried out by precipitating cobalt as mixed cobalt sulphide. The cobalt mixed sulphide was roasted and then leached in sulphuric acid to produce cobalt sulphate solution. Co metal and EMD were electrodeposited from their respective sulphate solutions. The optimal conditions during sludge leaching, Co–Mn separation, roasting of Co mixed sulphide, dissolution of the roasted material, electrodeposition of Co metal and EMD have been studied. The EMD was characterized for its suitability for the use in batteries and a tentative flow sheet for processing Co–Mn sludge is presented.

Supramolecular Assembly of Bis(benzimidazole)pyridine: An Extended Anisotropic Ligand For Highly Birefringent Materials

Four new bis(benzimidazole)pyridine (BBP)-containing compounds Zn(BBP)Cl[Au(CN)2], Mn(BBP)[Au(CN)2]2·H2O, Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH have been synthesized and structurally characterized and their birefringence values (Δn) determined. The structure of Zn(BBP)Cl[Au(CN)2] contains a hydrogen-bonded dimer of Zn(BBP)Cl[Au(CN)2] units which propagate into a 1D chain through Au-Au interactions, although the crystals are of poor optical quality. The supramolecular structure of Mn(BBP)[Au(CN)2]2·H2 O forms a 1D coordination polymer through chains of Mn(BBP)[Au(CN)2]2 units, each containing one bridging Au(CN)2 and one forming a 2D sheet through Au-Au interactions. The supramolecular structures of Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH are very similar, consisting of a complex hydrogen-bonded network between NH imidazole, methanol and halide groups to align BBP building blocks. In the plane of the primary crystal growth direction, the birefringence values of the three Mn-containing materials were Δn=0.08(1), 0.538(3) and 0.69(3), respectively. The latter two birefringence values are larger than in the related 2,2';6'2''-terpyridine systems, placing them among the most birefringent solids reported. These compounds illustrate the utility of extending the π-system of the building block and incorporating hydrogen-bonding sites as design elements for highly birefringent materials and also illustrates the effect on the measurable birefringence of the crystal quality, growth direction and structural alignment of the anisotropic BBP building blocks.

ChemInform Abstract: Models for Intrinsic and Extrinsic Fracto‐mechanoluminescence of Solids

AbstractReview: 162 refs.

РіДИННОФАЗНЕ КАТАЛіТИЧНЕ ОКИСНЕННЯ ТОЛУОЛУ ОЗОНОПОВіТРЯНОЮ СУМіШШЮ

The article presents the results of the study of kinetic patterns of the reaction of ozone with toluene in acetic anhydride. It was shown that an effective method of control of the depth of ozone oxidation of toluene at the methyl group is carrying out the reaction in a solution of acetic anhydride with sulfuric acid, where the labile intermediates in the moment of formation turn into the forms resistant to ozone - benzyl acetate and benzylidene diacetate. The use of manganese-bromide catalyst increases the rate and depth of oxidation of toluene: the main products of the reaction are benzaldehyde (72.5% in acylated and 10% in non acylated forms and 7.5% of benzyl acetate. It was determined that the implication of toluene to the oxidation at the methyl group passes according to the reaction with the oxidized form of the metal, which is formed in result of the reaction with ozone. A scheme for catalysis was suggested in the article. In these conditions, the oxidation is carried out by molecular oxygen, and ozone acts as an initiator of oxidation. The kinetics of the main stages of the catalytic cycle was studied, the mechanism of oxidation-reduction catalysis, which conforms to the experimental data obtained was suggested

Models for intrinsic and extrinsic fracto-mechanoluminescence of solids

A large number of noncentric and centric organic and inorganic crystals exhibit intrinsic and extrinsic fracto-mechanoluminescence (ML) due to the electron bombardment and electron-trapping mechanisms, and only a few crystals show ML due to the chemically induced fracto-ML and other possible mechanisms. The charged surfaces produced during fracture of solids owing to piezoelectrification, defective-phase piezoelectrification, movement of charged dislocations, baro-diffusion of defects near the crack-tip, and many other processes may cause production of very high electric field near the charged surfaces. In the case of non-photoluminescent and non-cathodoluminescent materials, the high energy electrons may be emitted from the charged surfaces and the electron bombardment (EB) mechanism may excite the molecules of surrounding gases and subsequently the gas discharge ML may be produced. In photoluminescent and cathodoluminescent solids, the electron bombardment may cause cathodoluminescence. In certain photoluminescent crystals, the light of gas discharge may excite photoluminescence. In many solids, the free electrons produced at fracture may be captured in the traps and consequently the electron-trapping (ET) mechanism may give rise to the light emission. Few solids may exhibit chemiluminescence because of the chemical reactions at the newly created surfaces. Some solids may exhibit black body radiations because of the high temperature produced near the tip of the moving cracks. Infrared radiation may also be emitted during the fracture of certain crystals. In certain solids, the gas discharge fracto-ML and the photoluminescence excited by the gas discharge disappear when the solids are fractured inside liquids; however, in certain solids the solid state fracto-ML appears even inside the liquids if they are not based on the processes involving gas discharge. Overall, depending on the prevailing conditions the ML spectra consist of either the gas discharge spectra or solid state luminescence spectra or the combination of the both. The fracto-ML of SrAl2O4:Eu, europium tetrakis (dibenzoyl methide) triethyl ammonium, ditriphenylphosphine oxide manganese bromide, freshly grown impure saccharin, etc. is so intense that it can be seen in day light with naked eye. The understanding of the mechanism of fracto-ML may be useful in preparing suitable fracto-mechanoluminescent materials and it may be helpful in designing the fracto-ML based devices such as fracture sensor, impact sensor, damage sensor, safety management monitoring system, fuse system for army warheads, etc.

Facile Metalation of Silicon and Germanium Analogues of Thiocarboxylic Acids with a Manganese(II) Hydride Precursor

Synthesis and characterization of the first manganese(II)-containing heavier thiocarboxylate analogues, [L(Dip)Si(=S)OMnL(Dep)] (4; L(Dip)=CH[C(Me)N(2,6-iPr(2)C(6)H(3))](2), L(Dep)=CH[C(Me)N(2,6-Et(2)C(6)H(3))](2)) and [L(Dip)Ge(=S)OMnL(Dep)] (5) are described. They are accessible through reaction of the silicon and germanium analogues of the respective thiocarboxylic acids [L(Dip)E(=S)OH] (E=Si, Ge) with the β-diketiminato (nacnac) manganese(II) hydride precursor [(L(Dep)Mn)(2)(μ-H)(2)] (3) in high yield. The first Mn nacnac hydride 3 has been prepared by the reaction of manganese bromide [(L(Dep)Mn)(2)(μ-Br)(2)] (2) with KBEt(3)H. Compounds 4 and 5 represent the first transition-metal heavier thiocarboxylates with the Si=S and Ge=S functionalities. All new compounds are paramagnetic and were characterized by elemental analysis, IR spectroscopy, MS (EI), and single-crystal X-ray diffraction analyses. Due to the N→E (E=Si, Ge) and E=S→Mn donor-acceptor interaction as well as the carboxylate-like π-electron delocalization within the E(S)O moieties, the E=S double bonds in these compounds are resonance stabilized.

5-[(1H-Benzimidazol-1-yl)methyl]benzene-1,3-dicarboxylic acid

Crystals of the title compound, C16H12N2O4, were obtained accidentally from a hydro­thermal reaction of 5-[(1H-benzimidazol-1-yl)meth­yl]isophthalic acid with manganese bromide in the presence of N,N′-dimethyl­formamide. In the title mol­ecule, the benzimidazole ring system is almost planar, with a maximum deviation from the mean plane of 0.010 (2) Å. The benzimidazole and central benzene rings are inclined at a dihedral angle of 71.7 (6)°. The crystal structure is stabilized by O—H⋯N and O—H⋯O hydrogen bonds.

Second monoclinic polymorph of 4-[(1H-benzimidazol-1-yl)methyl]benzoic acid

Recently, we reported the first monoclinic [Kuai & Cheng (2011). Acta Cryst., E67, o2787] and the ortho­rhom­bic polymorph [Kuai & Cheng (2011). Acta Cryst., E67, o3014] of the title compound, C15H12N2O2. Another monoclinic polymorph was obtained accidentally by the hydro­thermal reaction of the title compound with manganese chloride in the presence of potassium hydroxide at 413 K. The asymmetric unit consists of four independent mol­ecules. In the crystal, O—H⋯N hydrogen bonds link the independent mol­ecules into four separate chains parallel to the b axis.

Monoclinic polymorph of 4-[(1H-benzimidazol-1-yl)methyl]benzoic acid

Three polymorphs of the title compound, C15H12N2O2, were obtained accidentally as single crystals in the hydro­thermal reaction of the title compound with manganese bromide in the presence of N,N′-dimethyl­formamide at 373 K. Here we report the structure of the first polymorph. The benzimidazole ring is almost planar, the maximum deviation from the mean plane being 0.016 (1) Å. The benzimidazole and benzene rings are approximately perpendicular, making a dihedral angle 85.56 (7)°, which is a reflection of the axial rotation of the flexible benzimidazolyl arm. In the crystal, adjacent mol­ecules are connected through O—H⋯N hydrogen bonds into a chain along [100], and neighboring chains are further linked by via weak C—H⋯O hydrogen-bonding inter­actions, forming a two-dimensional network.

Selective aerobic oxidation of para-xylene in sub- and supercritical water. Part 1. Comparison with ortho-xylene and the role of the catalyst

The selective, continuous, aerobic oxidations of para-xylene (pX) and ortho-xylene (oX) were performed in an identical fashion in supercritical water. The xylenes were oxidized without a catalyst and with hydrobromic acid, cobalt(II) and manganese(II) bromide catalysts. The conversions and yields to phthalic acid (OA) from oX were always significantly higher than those for terephthalic acid (TA) from pX. The formation of CO2 was significantly higher for pX than oX despite the higher conversions to oX. These results are unexpected because the literature teaches that thermal and catalytic decarboxylation is much higher for OA than TA. The superior yields from oX are consistent with a lower steady-state concentration of hydroxyl radicals, OH˙ due to the internal, concerted attack of the peroxides with the oX methyl group. This mechanism forms the phthalide directly from o-tolualdehyde (oTOL) which is consistent with the observation that ortho-toluic acid (OTA) is much lower in oX than para-toluic acid, PTA, in pX oxidation. This mechanism also lowers the steady-state concentration of aromatic acids consistent with the observed lower benzoic acid and CO2 yields. Overall, the results suggest that the metal catalysts can play more than one role, thereby opening up the opportunity for discovering new catalytic synergies which are explored in our next paper, Part 2 of this series.

The dissociative excitation of doublet and sextet manganese atom levels in collisions of electrons with manganese dibromide molecules

Inelastic collisions of electrons with manganese dibromide molecules were studied by the method of extended crossing beams. These collisions cause the formation of excited manganese atoms in doublet and sextet states. At an exciting electron energy of 100 eV, 52 dissociative excitation cross sections were measured. At electron energies 0–100 eV, three optical excitation functions were recorded. The ratio between excitation cross sections in electron-molecular and electron-atomic collisions is considered.