Mn Br Research Articles

Electronic and magnetic properties of Mn-doped and Mn-X (F, Cl, Br, I) co-doped modulated monolayer SnSe2

The density functional theory is employed for learning the modulation of the electronic structure and magnetic properties of monolayer SnSe2 by an Mn atom and by co-doping an Mn atom with a halogen atom. It is found that intrinsic SnSe2 is nonmagnetic, which is consistent with the properties of semiconductors. Following Mn atom doping, the doped system is magnetic and the magnetic moments are primarily responsible for the Mn atom. After co-doping the Mn atom with halogen atoms, the doped system's total magnetic moments are decreased. The examination of the electronic structure demonstrates that the doping of the Mn atom and the co-doping of the Mn atom with halogen atoms lead to the introduction of impurity energy levels into the doped system, which appear only in the spin-up part and do not cross the Fermi energy level. There is asymmetry between the spin-up and spin-down energy bands and the doped system exhibits magnetic semiconductor properties. The hybridization of the p-orbitals of the halogen atoms and the 3d orbitals of the Mn atom is primarily responsible for the introduction of impurity energy levels in the energy bands of the doped system. In the Mn-doped system, ionic bonds were shaped between Mn and Se. In the co-doped system, strong ionic bonds were shaped between the Mn atom and F, Cl atoms, and covalent bonds were shaped between the Mn atom and Br, I atoms.

The experimental study on the air oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with Co–Mn–Br system

Abstract 2,5-Furandicarboxylic acid (FDCA), an eco-friendly biomass resource capable of replacing petroleum-based fuels, is gaining increasing popularity. In this article, 2,5-FDCA was prepared by liquid-phase oxidation of the sustainable precursor 5-hydroxymethylfurfural using the Co–Mn–Br catalyst system. The effects of catalyst concentration, catalyst ratio, reaction temperature, reaction time, reaction pressure, and solvent ratio on the reaction of FDCA were investigated. The products are subjected to qualitative and quantitative analyses using high-performance liquid chromatography, infrared spectroscopy, and hydrogen nuclear magnetic spectroscopy. Moreover, considering the loss of catalytic liquid, the suitable reaction conditions were determined as follows: n(Co)/n(Mn)/n(Br) = 1/0.04/0.5, n(HMF)/n(HAC) = 0.05, reaction temperature of 170°C, reaction pressure of 2 MPa, reaction time 40 min, and airflow rate 1.0 L·min−1. Under these conditions, the yield of the product is 86.01%, the purity is 97.53%, and the loss of the catalytic liquid is about 5.63%, which is at an ideal level and provides a good basis for the recovery of the subsequent catalytic liquid and multiple cycle reactions. Through the optimization of the existing process, the use of noble metal catalysts has been reduced, and the recycling of catalytic liquid has also reduced the consumption of catalysts. This advancement marks a significant stride toward sustainable development in the green chemical industry.

Ozonation of 4-aminotoluene as a new method of synthesis of 4-aminobenzaldehyde – an intermediate for the production of anti-tuberculosis drugs

Solutizon is an original anti-TB drug that is effective in resisting mycobacteria to other anti-TB drugs, which is obtained by the interaction of thiosemicarbazone 4-aminobenzaldehyde and sodium oxymethylene sulfonate. 4-Aminobenzaldehyde is synthesized by redox conversion of 4-nitrotoluene in the presence of sodium polysulfide. The reaction is carried out in boiling alcohol, and 4-aminobenzaldehyde is separated after steam distillation with a yield of 40–50 %. However, today this method loses its practical, environmental and economic attractiveness, as it has significant disadvantages – low product yield, high reaction temperature (80–120 °C), the formation of sulfur-containing wastewater. Therefore, the development of low-temperature, environmentally friendly methods for obtaining 4-aminobenzaldehyde is an urgent task. The aim of the work is to study the kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene to create a new low-temperature, environmentally friendly method for the synthesis of 4-aminobenzaldehyde. Materials and methods. Sigma acetic anhydride of сh.р. qualification was used for the experiments. 4-Aminotoluene company “Sinbias” qualification “сh.р.”; 4-Acetamidotoluene and its derivatives were used chromatographically pure. Acetates of metals of qualification “сh.р.”, potassium bromide of qualification “pharmacopoeial” were used without additional purification. Continuous control of the current ozone concentration and recording the results in the form of a kinetic curve was carried out when passing ozone-containing gas through the container of the spectrophotometer “SF-46 LOMO” at a certain wavelength of a monochromatic light source. The results of the analysis were recorded using the KSP-4 potentiometer included in the spectrophotometer optical density reference circuit. This device automatically compensated the photocurrent by recording its value. The scale KSP-4 was calibrated in units of optical density, and the conversion into absolute ozone concentration was carried out according to the Lambert-Ber equation using molar extinction coefficients. Relative analysis error ≤5 %. At the optical stroke length of the container 10 ÷ 100 mm, the sensitivity of the device was ~10-7mol·l-1 ozone. Results. The kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene have been studied. It is shown that the developed catalytic system Mn(II)-KBr-H2SO4-Ac2O significantly increases the depth, rate, and selectivity of oxidation of 4-aminotoluene and the main reaction product is 4-aminobenzaldehyde in the form of the corresponding benzylidenediacetate with a yield of 69.5 %. The active particle responsible for the inclusion of the substrate in the oxidation of the methyl group in the presence of manganese (II) acetate and potassium bromide is manganese bromide ion radical (Mn(II)Br•), which is more active than Mn (III) and therefore more high-speed initiates oxidation by the methyl group. Conclusions. Catalytic systems have been developed that allow the oxidation of ozone to be directed mainly to the methyl group of 4-aminotoluene and to stop the reaction at different oxidation depths. It was found that manganese (II) acetate, which has a relatively low redox potential, in the system Ac2O-ArCH3-H2SO4-O3 at a temperature of 20 °C has a high substrate selectivity in the reactions of formation of 4-aminobenzyl alcohol. Manganese (II) acetate in the presence of potassium bromide forms a manganese bromide complex with increased catalytic activity, which under the same conditions contributes to the predominant production of 4-aminobenzaldehyde.

Pressure‐Treated Engineering to Harvest Enhanced Green Emission in Mn‐Based Organic–Inorganic Metal Halides at Ambient Conditions

AbstractIn the pressure‐induced emission enhancement paradigms, harvesting enhanced emission on the basis of original color is still largely hampered due to the recovery or decrement of emission intensity upon decompression. Here, a pressure‐treated strategy is reported to achieve the remarkable green emission enhancement of organic–inorganic metal halide (OIMH) [PP14]2[MnBr4] (N‐butyl‐N‐methylpiperidinium [PP14]+) at ambient conditions. After a cycle of 1 atm to 15.2 GPa, the [PP14]2[MnBr4] shows a 1.67‐fold enhancement in the photoluminescence quantum yield from 54.5% to 90.8%, and green emission monochromaticity is unexpectedly retained. The restriction of motion freedom of [MnBr4]2− by increased Br···H interactions is highly responsible for the intense emission. Furthermore, [PP14]2[MnBr4] exhibits significant piezochromism that shifts from green to red, and an ultrabroad tunability of 185 nm is observed below 12.5 GPa. The enhancement of the crystal field splitting energy and the reduction of the relaxation from the low‐energy excited state 4T1 to the ground state 6A1 that is caused by the shrinkage of MnBr bond result in the red shift of emission. This work sheds light on the effects of pressure treatment in boosting emission enhancement and facilitates the design of new OIMHs with the desired emission properties.

Deciphering the Mechanistic Details of Manganese-Catalyzed Formic Acid Dehydrogenation: Insights from DFT Calculations.

A comprehensive density functional theory investigation has been carried out to unravel the complete mechanistic landscape of aqueous-phase formic acid dehydrogenation (FAD) catalyzed by a pyridyl-imidazoline-based Mn(I) catalyst [Mn(PY-NHIM)(CO)3Br], which was recently reported by Beller and co-workers. The computed free energy profiles show that for the production of a Mn-formate intermediate [Mn(HCO2-)], a stepwise mechanism is both kinetically and thermodynamically favorable compared to the concerted mechanism. This stepwise mechanism involves the dissociation of a Br- ion from a Mn-bromide complex [Mn(Br)] to create a vacant site and coordination of water solvent to this vacant site, followed by the dissociative exchange of the aqua ligand with the formate ion to form Mn(HCO2-). Non-covalent interaction analysis revealed that the steric hindrance at the transition state is the cardinal reason for the preference to a stepwise mechanism. The β-hydride elimination process was estimated to be the rate-determining step with a barrier of 19.0 kcal/mol. This confirms the experimental observation. The generation of a dihydrogen-bound complex was found to occur through the protonation of Mn-hydride by a hydronium ion instead of formic acid. The mechanistic details and insights presented in this work would promote future catalytic designing and exploration of earth-abundant Mn-based catalytic systems for potential applications toward FAD.

Isophthalic acid production catalyzed by Co(II) together with phosphotungstic acid loaded on carbon modified with tartaric acid

AbstractBackgroundIsophthalic acid (IPA) is commercially produced using the Co–Mn–Br catalyst system, which suffers from the shortcomings of the discharge of CH3Br and corrosion of equipment. It is necessary to develop a technology to avoid the pollution caused by bromide. The production of IPA from the oxidation of m‐xylene (MX) by air is realized under catalysis with H3PW12O40 (HPW) loaded on carbon and cobalt.ResultsTartaric acid has been used to improve the catalytic activity of the HPW@C catalyst. Experiments indicate that the best modification condition is calcining the carbon at 450 °C for 4 h after being soaked in a 2.0 mol L−1 tartaric acid solution for 10 h. Surface characterization reveals that the tartaric acid modification leads to an increase in the acid groups and a reduction in the basic groups on the carbon surface.ConclusionsThe MX conversion obtained using the HPW@C catalyst prepared from modified carbon is 6.77% over that obtained using the HPW@C catalyst prepared from the original carbon. The IPA generated using the former is 71.1% over that generated using the latter. The catalytic activity of the HPW@C catalyst relies on its surface chemical characteristics and physical properties. The surface chemistry plays a more important role than the physical properties. © 2020 Society of Chemical Industry

Synthesis and Characterization of the Manganese Hydroxide Halides Mn(OH)X (X = Br, I) and Crystal Structure of trans‐MnBr2·4H2O

The pale‐pink, hygroscopic compounds Mn(OH)X (X = Br, I) were obtained by high‐pressure synthesis in a Walker‐type multianvil apparatus. They crystallize in the space group P21/c with a = 640.48(3), b = 698.80(3), c = 615.54(2) pm, β = 110.30(1)° at 183(1) K (X = Br), and a = 686.18(3), b = 713.08(3), c = 637.18(3) pm, β = 109.51(1)° at 150(1) K (X = I). The crystal structures are isotypic to Cu(OH)Cl and consist of edge‐sharing distorted Mn(OH)3X3 octahedra arranged in sheets parallel to the bc‐plane. Spin‐polarized scalar‐relativistic DFT+U calculations predict an intrinsic magnetic insulating state (ca. 3.5 eV bandgap) that is proximate to frustration. Calculated effective magnetic moments equal to 4.34 μB/f.u. for Mn(OH)Br and 4.33 μB/f.u. for Mn(OH)I. FT‐IR spectroscopy confirmed interlayer hydrogen bonding. As a side result of the experiments, the compound trans‐MnBr2·4H2O was obtained. It crystallizes in the space group Cmcm with a = 438.64(2), b = 1167.84(6), and c = 730.95(4) pm.

Asymmetric Transfer Hydrogenation of Ketones with Well-Defined Manganese(I) PNN and PNNP Complexes

Three new manganese complexes trans-[Mn(P–NH–NH–P)(CO)2][Br], (14) P–NH–NH–P = (S,S)-PPh2CH2CH2NH–CHPhCHPhNHCH2CH2PPh2), fac-[Mn(P′–NH–NH2)(CO)3][Br], (15) P′–NH–NH2 = (S,S)-PPh2(C6H4)NHCHPhCHPhNH2, and syn-mer-Mn(P–NH–NH2)(CO)2Br, (16) P–NH–NH2 = (S,S)-PPh2CH2CH2NHCHPhCHPhNH2 were synthesized and tested for the asymmetric transfer hydrogenation (ATH) of acetophenone in 2-PrOH. The ligands have stereogenic centers derived from the starting diamine, (S,S)-DPEN. Complex 16 was shown by NOE NMR experiments to have Mn–Br syn to the N–H of the secondary amine. Only the precatalyst 16, upon reaction with potassium tert-butoxide (KOtBu) in 2-PrOH, generated an active system at 80 °C for the ATH of acetophenone to 1-phenylethanol in an enantiomeric excess (ee) of 42% and thus was selected for further investigation into the mechanism of transfer hydrogenation. The corresponding amido complex Mn(P–N–NH2)(CO)2 (17), a borohydride complex syn-mer-Mn(P–NH–NH2)(CO)2(BH4) (18), and an ethoxide complex anti-mer-Mn(P–NH–N...

Direct Hot-Injection Synthesis of Mn-Doped CsPbBr3 Nanocrystals

We report the direct hot-injection synthesis of Mn-doped cesium lead bromide (CsPbBr3) perovskite nanocrystals. In contrast to Mn-doped CsPbCl3 nanocrystals, where doping of Mn under typical hot-injection synthesis condition has been relatively straightforward, extending the same approach to CsPbBr3 has been very difficult. Here, we achieved the synthesis of Mn-doped CsPbBr3 nanocrystals via the formation of an intermediate structure (L2[Pb1–xMnx]Br4, L = ligand) before the hot-injection of the Cs precursor, which contains the same Mn–Br coordination present in Mn-doped CsPbBr3 nanocrystals. A strong correlation was observed between the Mn luminescence intensities of L2[Pb1–xMnx]Br4 and Mn-doped CsPbBr3 nanocrystals, suggesting the possible role of L2[Pb1–xMnx]Br4 as the structural precursor to Mn-doped CsPbBr3 nanocrystals. The successful Mn doping in CsPbBr3 nanocrystal host, which has significantly better optical characteristics than CsPbCl3 nanocrystals, will expand the range of useful properties of M...

Enantioselective Transfer Hydrogenation of Ketones Catalyzed by a Manganese Complex Containing an Unsymmetrical Chiral PNP′ Tridentate Ligand

AbstractManganese complexes of the types [Mn(PNP′)(Br)(CO)2] and [Mn(PNP′)(H)(CO)2] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantioselective transfer hydrogenations of 13 ketones. The catalytic reactions proceeded with conversions up to 96 % and ee values up to 86 %. The absolute configuration of all products was determined to be (S). Notably, the presence of dihydrogen (up to 20 bar) did not affect the reduction. On the basis of DFT calculations, preliminary mechanistic details including the origin of the (S) selectivity are presented. The molecular structure of [Mn(PNP′)(Br)(CO)2] was studied by X‐ray diffraction.

New mechanistic insight into the aerobic oxidation of methylaromatic compounds catalyzed by Co–Mn–Br and its applications

The mechanism for aerobic oxidation of methylaromatic compounds using Co(CH3COO)2–Mn(CH3COO)2–KBr was further studied. The experimental results suggested that the intermediates (aromatic alcohols) are unexpectedly inert to direct oxidation via Co–Mn–Br catalysts under moderate conditions. In addition, it is found that both aromatic and aliphatic alcohols can inhibit the oxidation of the substrates and other intermediates (aromatic esters, aromatic aldehydes). UV–vis spectra indicated that oxidation from Co(II) to Co(III) would be interrupted in the presence of a given amount of alcohol. A plausible mechanism was also proposed. The intermediates analyzed by LC–MS and control experiments showed that aromatic alcohols prefer to undergo esterification rather than being directly oxidized as described in previous studies, and aromatic acetates are subsequently oxidized to corresponding aldehydes. According to the new mechanism, a strategy of highly selectively synthesizing aromatic alcohols and aldehydes from corresponding methylaromatic compounds was designed. The selectivities of aromatic alcohols and aldehydes could also be tuned by the added amount of CH3COOK.

Experimental Study and Modeling of Homogenous Catalytic Oxidation of m-Xylene to Isophthalic Acid

The homogeneous oxidation of m-xylene (MX) to isophthalic acid (IPA) with acetic acid as solvent catalyzed by Co–Mn–Br catalyst was investigated at temperatures from 448.2 to 466.2 K by semicontinuous and continuous experiments. Based on the free radical chain reaction mechanism of hydrocarbon, one simplified kinetic model of MX oxidation with six parameters was developed involving MX, IPA, and important intermediates. The kinetic model fitted experimental data well, in which there was only one adjustable parameter, i.e., chain initiation rate constant corresponding to various temperatures, while other parameters were kept constant. It was found that the oxidation rate constants concerning the methyl on the benzene ring of MX was well consistent with the predictions by the Hammett structure–reactivity relationship. Through reasonable assumptions, the well-mixed reactor model of MX oxidation was further developed, by which successful predictions of the continuous MX oxidation process under different operating conditions were performed. Hopefully the kinetic experiments and related models may bring fundamental data and some valuable insights to industrial MX oxidation.

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.

Bulk and molecular compressibilities of organic-inorganic hybrids [(CH₃)₄N]₂MnX₄ (X = Cl, Br); role of intermolecular interactions.

This work reports an X-ray diffraction, X-ray absorption, and Raman spectroscopy study of [(CH₃)₄N]₂MnX₄ (X = Cl, Br) under pressure. We show that both compounds share a similar phase diagram with pressure. A P2₁/c monoclinic structure describes precisely the [(CH₃)₄N]₂MnCl₄ crystal in the 0.1-6 GPa range, prior to crystal decomposition and amorphization, while [(CH₃)₄N]₂MnBr₄ can be described by a Pmcn orthorhombic structure in its stability pressure range of 0-3 GPa. These materials are attractive systems for pressure studies since they are readily compressible through the weak interaction between organic/inorganic [(CH₃)₄N⁺/MnX₄²⁻] tetrahedra through hydrogen bonds and contrast with the small compressibility of both tetrahedra. Here we determine the equation-of-state (EOS) of each crystal and compare it with the corresponding local EOS of the MnX₄²⁻ and (CH₃)₄N⁺ tetrahedra, the compressibility of which is an order and 2 orders of magnitude smaller than the crystal compressibility, respectively, in both chloride and bromide. The variations of the Mn-Cl bond distance obtained by extended X-ray absorption fine structure and the frequency of the totally symmetric ν₁(A₁) Raman mode of MnCl₄²⁻ with pressure in [(CH₃)₄N]₂MnCl₄ allowed us to determine the associated Grüneisen parameter (γ(loc) = 1.15) and hence an accurate local EOS. On the basis of a local compressibility model, we obtained the Grüneisen parameters and corresponding variations of the intramolecular Mn–Br and C–N bond distances of MnBr₄²⁻ (γ(loc) = 1.45) and (CH₃)₄N⁺ (γ(loc) = 3.0) in [(CH₃)₄N]₂MnBr₄.

The molecular structure of high-spin (S = 5/2) manganese(II) phthalocyanine in tetrabutylammonium bromido(phthalocyaninato)manganese(II).

The title complex salt, (C16H36N)[MnBr(C32H16N8)] or (TBA)[Mn(II)Br(Pc)] (TBA is tetrabutylammonium and Pc is phthalocyaninate), has been obtained as single crystals by the diffusion technique and its crystal structure was determined using X-ray diffraction. The high-spin (S = 5/2) [Mn(II)Br(Pc)](-) macrocycle has a concave conformation, with an average equatorial Mn-N(Pc) bond length of 2.1187 (19) Å, an axial Mn-Br bond length of 2.5493 (7) Å and with the Mn(II) cation displaced out of the 24-atom Pc plane by 0.894 (2) Å. The geometry of the Mn(II)N4 fragment in [Mn(II)Br(Pc)](-) is similar to that of the high-spin (S = 5/2) manganese(II) tetraphenylporphyrin (TPP) in [Mn(II)(1-MeIm)(TPP)] (1-MeIm is 1-methylimidazole).

Synthesis, solution properties, and solid-state structural analysis of [Mn(κ4-N,N,S,N-dpktsc)Br]2·nCH3CN (n = 1 or 0 and dpktsc = di-2-pyridyl ketone thiosemicarbazone)

Ultrasonic radiation of a mixture of [Mn(CO)5Br], [dpktsc], and CH3CN gave [Mn(κ4-N,N,S,N-dpktsc)Br]2·nCH3CN (n = 0 or 1). Under reflux, a mixture of [Mn(CO)5Br], [dpktsc], and CH3CN gave [Mn(κ3-N,N,S-dpktsc-H)2]·2H2O. Crystals of [Mn(κ4-N,N,S,N-dpktsc)Br]2 were obtained by the evaporation of CH3CN from crystals of [Mn(κ4-N,N,S,N-dpktsc)Br]2·CH3CN. The solid-state structures of [Mn(κ4-N,N,S,N-dpktsc)Br]2·nCH3CN (n = 0 or 1) reveal two independent centrosymmetric dimers in the unit cell of each crystal and one CH3CN in the case of solvated crystal. Crystals of [Mn(κ4-N,N,S,N-dpktsc)Br]2·nCH3CN are stabilized by a network of non-covalent interactions that include hydrogen bonds and π–π interactions. Spectroscopic measurements reveal sensitivity of protophilic solutions of [Mn(κ4-N,N,S,N-dpktsc)Br]2 and [Mn(κ3-N,N,S-dpktsc-H)2]·2H2O to changes in their surroundings, as manifested by changes in the intensity of electronic absorption spectral properties in the presence and absence of external stimulus (acid or base). Electrochemical measurements in DMF reveal two closely spaced reduction/oxidation couples due to MnI → Mn0 and MnI → MnII of the dimer. In the case of [Mn(κ3-N,N,S-dpktsc-H)2]·2H2O, two well-separated reductions appeared due to MnII → MnI and MnI → Mn0. Electrochemical reactions of [Mn(κ4-N,N,S,N-dpktsc)Br]2 and [Mn(κ3-N,N,S-dpktsc-H)2]·2H2O show the monomer to be more active toward CO2 than the dimer.

Metal complexes of 2-aza-2-benzyloxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrin: M(2-NCH2COOCH2C6H5NCTPP) (M = Ni2+, Pd2+) and Mn(2-NCH2COOCH2C6H5NCTPP)Br (NCTPP = N-confused 5,10,15,20-tetraphenylporphyrinate)

The crystal structures of (2-aza-2-benzyloxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″)nickel(II) [Ni(2-NCH2COOCH2C6H5NCTPP); 5], (2-aza-2-benzyloxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″)palladium(II) toluene solvate [Pd(2-NCH2COOCH2C6H5NCTPP)·C6H5CH3; 6·C6H5CH3] and bromo(2-aza-2-benzyloxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″)manganese(III) ethyl acetate solvate [Mn(2-NCH2COOCH2C6H5NCTPP)Br·EtOAc; 7·EtOAc] have been established. The coordination sphere around the Ni2+ ion in 5 (or Pd2+ ion in 6·C6H5CH3) is distorted square planar (DSP), whereas for Mn3+ in 7·EtOAc, it is square-based pyramidal with the Br atom lying in the axial site. The g value of 10.98 measured from the parallel polarization of the X-band ESR spectrum at 4K is consistent with a high spin mononuclear manganese(III) centre (S=2) in 7. The magnitude of the axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) centre in 7 was determined to be approximately 0.52cm−1 by paramagnetic susceptibility measurements. The 13C [C(19)] and 1H [H(19)] chemical shifts of the N+CH(Ar) fragment at 20°C in CDCl3 are located at δ 152.5±0.5 and 8.21±0.04ppm respectively for the iminium ion of the dipolar form in complexes 5–7. From the X-ray diffraction data, the N(4)–C(19) bond length of 1.312±0.013Å indicates the existence of the dipolar form for 5–7.

Production of isophthalic acid from m-xylene oxidation under the catalysis of the H3PW12O40/carbon and cobalt catalytic system

Isophthalic acid (IPA) is commercially produced from m-xylene oxidation with the catalysis of the homogeneous Co–Mn–Br catalyst system. In this study, a catalytic system consisting of HPW/C and Co(II) has been put forward to oxidize m-xylene (MX) to IPA. The experimental results prove that the HPW/C and Co catalytic system is capable of catalyzing the oxidation of MX to IPA, which can obtain a higher MX conversion and IPA concentration than the homogeneous H3PW12O40/Co(OAc)2/Mn(OAc)2 catalytic system. The heterogeneous catalytic system is also advantageous over the homogeneous catalytic system in the inhibition of the oxidation of acetic acid and IPA. The optimal amount of phosphotungstic acid supported on carbon is 7.5% (wt). The best dosage of HPW/C is 15gl−1. The optimum Co(II) concentration in the catalytic system for IPA production is 0.064% (wt). The best HPW/C activation temperature is 220°C.

Indoleninemeso-Substituted Dibenzotetraaza[14]annulene and Its Coordination Chemistry toward the Transition Metal Ions MnIII, FeIII, CoII, NiII, CuII, and PdII

A new dibenzotetraaza[14]annulene bearing two 3,3-dimethylindolenine fragments at the meso positions (LH(2)), has been synthesized through a nontemplate method. X-ray crystallography shows that the whole molecule is planar. The basicity of the indolenine ring permits the macrocycle to be protonated external to the core and form LH(4)(2+)·2Cl(-). Yet another structural modification having strong C-H···π interactions was found in the chloroform solvate of LH(2). The latter two modifications are accompanied by a degree of nonplanar distortion. The antiaromatic core of the macrocycle can accommodate a number of metal ions, Mn(III), Fe(III), Co(II), Ni(II) and Cu(II), to form complexes of [Mn(L)Br], [Mn(L)Cl], [Fe(LH(2))Cl(2)](+)·Cl(-), [Co(L)], [Ni(L)], and [Cu(L)]. In addition, the reaction of LH(2) with the larger Pd(II) ion leads to the formation of [Pd(2)(LH(2))(2)(OAc)(4)] wherein the macrocycle acts as a semiflexible ditopic ligand to coordinate pairs of metal ions via its indolenine N atoms into dinuclear metallocycles. The compounds LH(2), [Co(L)], and [Ni(L)] are isostructural and feature close π-stacking as well as linear chain arrangements in the case of the metal complexes. Variable temperature magnetic susceptibility measurements showed thermally induced paramagnetism in [Ni(L)].

Dianion N1,N4-bis(salicylidene)-S-allyl-thiosemicarbazide complexes: Synthesis, structure, spectroscopy and thermal behavior

The products with the general formulas VO(Salits) 1, Mn(Salits)Br 2, Fe(Salits)Cl 3 and UO2(Salits)(MeOH) 4 (Salits=N1,N4-bis(salicylidene)-S-allyl-thiosemicarbazide) are prepared by the reaction of salicylaldehyde-S-allyl-thiosemicarbazone (H2L) and salicylaldehyde with VOSO4·3H2O, Mn(CH3COO)2·4H2O, FeCl3·6H2O and UO2(CH3COO)2·2H2O, respectively. Complexes 1–4 were characterized by elemental analysis, spectroscopic (FT-IR and UV–Vis) and TGA techniques. Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction. The results revealed that the complexes 1, 2 and 3 contain a dideprotonated tetradentate form of Salits coordinated via N2O2 donors along with oxido, bromido or chlorido ligands, respectively, and they have distorted square pyramidal geometries. However, the complex 4 adopts a severely distorted pentagonal bipyramidal geometry consisting of N2O2 coordination of Salits, a methanol ligand and two oxygens of the uranyl moiety. TG analysis showed that complex 3 is more stable than the others.