Anhydrous Metal Research Articles

Mono-β-diketiminate supported cerium(III) complex: Synthesis, characterization and reactivity

Mono-β-diketiminate cerium(III) complex 1 was easily accessible from the anhydrous metal tribromide and LNa (L = N,N-2,6-diisopropylphenyl-2,4-pentanediimine anion) in THF at room temperature. Interaction of 1 with 1,2-dimethoxyethane, pyridine and 4-dimethylaminopyridine gave the ligand substitution products 2, 3 and 4 in good yield. All of those complexes exhibited molecular structure similar to that of 1, and the coordination environment around cerium center was the distorted octahedral geometry. The reaction of 1 with 2,6-dimethylphenyl isocyanide gave dinuclear complex 5 with an unusual triple bromine bridge in the molecule. It was worth noting that the reaction of 1 with one equivalent of cyclopentadienylsodium (CpNa) did not afford the mixed-ligand complex but the undesirable ligand redistributed product Cp2CeL (6). Treatment of 1 with arylamido lithium reagent whereas obtained the dissociated product 7. All the complexes were well characterized and further broadened the utility of β-diketiminate ligands.

A three-dimensional terbium metal − organic framework fluorescent sensor for efficient detection of chloroquine phosphate in serum

A novel three-dimensional (3D) anionic anhydrous metal − organic framework (MOF), {[NH2(CH3)2]·[Tb(pdca)2]}n (Tb-MOF; H2pdca = 2,5-pyridinedicarboxylic acid) has been triumphantly fabricated and structurally characterized. The obtained Tb-MOF displays good stability in some common solvent systems and high temperature environments. The luminescence properties of Tb-MOF are investigated by fluorescence spectra, and the results exhibit superb characteristic emission of Tb3+ ions, which lay a foundation for exploring the fluorescence sensing application of the material. More importantly, based on competitive absorption and dynamic quenching, Tb-MOF can be applied to detect chloroquine phosphate (CQ) used for the treatment of COVID-19 and malaria, showing high sensitivity and fast response speed in the sensing process. Notably, the specific quenchingeffect between Tb-MOF and CQ in the serum system without interference from other components, demonstrating the practical application potential of Tb-MOF.

Neptunium Alkoxide Chemistry: Expanding Alkoxides to the Transuranium Elements.

Two oxo-containing neptunium(IV) tert-butoxides, [Np3O(OtBu)10] (1) and [K4Np2O(OtBu)10] (2), were synthesized using the ligand substitution between neptunium(IV) silylamides and HOtBu, whereas the salt metathesis between [NpCl4(DME)2] (DME = dimethoxyethane) and various amounts of LiOtBu resulted in the formation of oxo-free alkoxides [Np(OtBu)4(py)2] (3; py = pyridine) and [Li(THF)]2[Np(OtBu)6] (4; THF = tetrahydrofuran). These complexes are the first structurally characterized neptunium(IV) alkoxides using single-crystal X-ray diffraction and solid-state absorption spectroscopy, which provide data for the development of anhydrous metal-organic neptunium chemistry.

Facile Solvent-Free Synthesis of Metal Thiophosphates and Their Examination as Hydrogen Evolution Electrocatalysts.

The facile solvent-free synthesis of several known metal thiophosphates was accomplished by a chemical exchange reaction between anhydrous metal chlorides and elemental phosphorus with sulfur, or combinations of phosphorus with molecular P2S5 at moderate 500 °C temperatures. The crystalline products obtained from this synthetic approach include MPS3 (M = Fe, Co, Ni) and Cu3PS4. The successful reactions benefit from thermochemically favorable PCl3 elimination. This solvent-free route performed at moderate temperatures leads to mixed anion products with complex heteroatomic anions, such as P2S64−. The MPS3 phases are thermally metastable relative to the thermodynamically preferred separate MPx/ MSy and more metal-rich MPxSy phases. The micrometer-sized M-P-S products exhibit room-temperature optical and magnetic properties consistent with isolated metal ion structural arrangements and semiconducting band gaps. The MPS3 materials were examined as electrocatalysts in hydrogen evolution reactions (HER) under acidic conditions. In terms of HER activity at lower applied potentials, the MPS3 materials show the trend of Co > Ni >> Fe. Extended time constant potential HER experiments show reasonable HER stability of ionic and semiconducting MPS3 (M = Co, Ni) structures under acidic reducing conditions.

Tungsten(II) chloride hydrates with high solubility in chloroaluminate ionic liquids for the electrodeposition of Al–W alloy films

• Tungsten(II) chloride hydrates showed high solubility in AlCl 3 -based ionic liquids. • Al–W alloy films with high W contents were obtained at high current densities. • Current efficiencies close to 100% were achieved even in the baths with hydrates. • Spectroscopic techniques were used to identify the chemical species in the bath. The electrodeposition of Al alloys using chloroaluminate ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium chloride (EMIC)–AlCl 3 , has been of significant interest as a surface coating technology. To minimize the contamination of the ILs with water, which can inhibit Al deposition, anhydrous metal chlorides were generally used as metal precursors in the previous studies on Al alloy electrodeposition. However, many anhydrous transition metal chlorides have limited solubility in ILs, making it difficult to obtain Al-based alloy films with a high alloy content at a high current density. This article describes the electrodeposition of Al–W alloy films using W(II) chloride hydrates, W 6 Cl 12 ·2H 2 O and (H 3 O) 2 [W 6 Cl 14 ]·7H 2 O, as W precursors. These hydrated salts were found to have much higher solubilities in EMIC–AlCl 3 ILs than anhydrous W 6 Cl 12 . Therefore, owing to the high solubility of the hydrated salts, Al–W alloy films with a high W content could be electrodeposited even at high current densities. Furthermore, the use of hydrated salts had no negative effect on the quality of the electrodeposited films or the current efficiency. A chemical speciation of the Al and W ions in the ILs was carried out using Raman spectroscopy, Fourier-transform infrared spectroscopy, extended X-ray absorption fine structure spectroscopy, and UV-visible spectroscopy. The spectral data conclusively indicated that the dissolved species derived from the hydrated salts were different compared to those derived from the anhydrous salt. The high solubility of the hydrated W salts and the success of Al–W alloy electrodeposition encourage the use of hydrated salts in chloroaluminate ILs.

New polymorph for Cd(II) chloro‑bridged coordination polymer based on 3-aminopyrazin-2-carboxylic acid: Synthesis, structural characterization, Hirshfeld surface analysis, thermal properties and molecular docking study on the antifungal activity

A new polymorph of cadmium (II) coordination polymers, namely poly[[(3-aminopyrazin-4-ium-2-carboxylate-k2N1,O)di-μ-chlorido-cadmium(II)] monohydrate], {[CdCl2(C5H5N3O2)]-H2O}n, (PM2), is synthesized from the reaction of cadmium(II) chloride and 3-aminopyrazine-2-carboxylic acid (Hapca). The first P-1 polymorphic (PM1) has already been isolated; it was synthesized by the reaction of Hapca with the hydrated cadmium salt. Meanwhile, for the preparation of the new Pccn polymorph (PM2), the anhydrous metal salt was used. The two polymorphic Cd-based coordination polymers are synthesized in aqueous acidic media. To identify the potential protonation sites in the organic ligand Hapca and determine its coordinating ability, the ionization constants pKa are predicted using ACD/pKa and ChemAxon calculators. The new polymorph is characterized by single-crystal X-ray diffraction and show chloro-bridged zigzag chains with octahedrally coordinated metal ions where Hapca acts as a bidentate N/O chelating ligand. The chains are further interconnected via noncovalent interactions into three dimensional supramolecular networks. The dominant H···O and H···Cl interactions for both polymorphs were quantified using Hirshfeld surface analysis. The thermal properties of the two isolated polymorphic coordination polymers are also discussed. The antifungal activity of the two polymorphs PM1, PM2 and the organic free ligand Hapca against the yeast Candida albicans was screened by the molecular docking approach. The enzyme exo-β- (1,3)-glucanase (Exg) was chosen as a target. The drug-likeness activity and ADMET properties were also evaluated.

Green synthesis, X-ray crystal structure, evaluation as in vitro cytotoxic and antibacterial agents of a new Zn(II) complex containing dipicolinic acid

• A novel complex of Zn(II) has been synthesized through a one-pot reaction and without using chemical solvents • The structure of the complex was characterized by X-ray crystallography • In vitro cytotoxicity of the compounds was studied against four cancer cell lines and a normal cell line • Effect of the complex was assayed on production of ROS and decrease of MMP in A375 and HT29 cells • In vitro antimicrobial activity of the compounds was tested A zinc(II) complex formulated as (4-apyH) 2 [Zn(pydc)(pydcH)] 2 .(pydcH 2 ) 2 .10H 2 O was prepared through a one-pot reaction of pyridine-2,6- dicarboxylic acid, 4-aminopyridine, and zinc chloride anhydrous metal salt. In all the steps, only distilled water was used as the solvent. The compound was fully characterized by single-crystal X-ray diffraction and disordered octahedral geometry was recognized for it. The cytotoxicity of the complex and its ligands was evaluated by MTT method against A375, LN229, DLD1, HT29, and HFF cell lines. The strongest anti-proliferative effect of the complex was exhibited toward HT29 (IC 50 =10 µM, Viability inhibition =78.23%) cells. The apoptosis was proposed as the main pathway for the death of the cells according to the product of ROS high value and reduction of MMP. The antibacterial effect of compounds was studied against two Gram-positive bacteria namely Staphylococcus aureus , and Staphylococcus epidermidis, and also three Gram-negative bacteria namely Escherichia coli, Pseudomonas aeruginosa, and Proteus vulgaris . The established antibacterial tests were including the broth microdilution method and the agar well diffusion method. S. aureus (MIC=16 µg/mL, IZD=30 mm) and S. epidermidis (MIC=32 µg/mL, IZD=22 mm) were considered as the most susceptible bacteria following treatment of the complex. A new Zn(II) complex was synthesized without using chemical solvents and was characterized by single-crystal X-ray diffraction. Anticancer activity of the complex, ligands, and zinc chloride anhydrous metal salt was evaluated by MTT assay toward A375, LN229, DLD1, HT29, and HFF cells. The strongest cytotoxic effect was indicated by the complex toward A375 and HT29 cells, in vitro . Accordingly, these two cell lines were selected to evaluate MMP and ROS. Also, the antimicrobial activity of the compounds was investigated against 5 strains of Gram-negative and Gram-positive bacteria. S. aureus and S. epidermidis were realized as the most susceptible bacteria following the treatment of the complex.

Methanol electrooxidation at NiCl2–FeCl3–graphite intercalation compound affected by ozone treatment

A graphite intercalation compound (GIC) incorporating nickel(II) and iron(III) chlorides (NiCl2–FeCl3–GIC) has been prepared, and the effect of ozone treatment on its catalytic activity towards methanol electrooxidation has been examined. The NiCl2–FeCl3–GIC was synthesized by a molten salt method, combining purified flaky graphite with the anhydrous metal chlorides. The obtained product was then modified with gaseous ozone. The crystalline structures and morphologies of the investigated compounds have been characterized by XRD and SEM/TEM techniques, respectively, and the results of these analyses have shown that ozone treatment of NiCl2–FeCl3–GIC contributes to changes in its structure and morphology. The process of methanol oxidation at both original and ozone-modified NiCl2–FeCl3–GIC electrodes has been examined in an alkaline electrolyte by means of cyclic voltammetry and a potentiostatic method. Electrochemical results have revealed that NiCl2–FeCl3–GIC exhibits activity towards the process of methanol electrooxidation. Furthermore, it has been proved that the electroactivity and durability of NiCl2–FeCl3–GIC are significantly increased following its ozone modification.

Hydrogen Adsorption/Desorption Properties of Anhydrous Metal Oxalates; Metal = Mg2+ and Ca2+

Abstract Hydrogen adsorption/desorption properties of magnesium oxalate and calcium oxalate (M(ox); M = Mg2+ and Ca2+) were measured at selected temperatures between 77 K and 200 K. The hydrogen uptake amounts were 0.037 wt% for Mg(ox) and 0.147 wt% for Ca(ox) at 87 K, 0.15 MPa. Hydrogen adsorption enthalpy for Ca(ox) was estimated as −16 ∼ −13 kJ/mol-H2, which indicated the contribution of charge-transfer interaction between Ca2+ and H2 molecule. Limited hydrogen uptake for both Mg(ox) and Ca(ox) were attributed to the intermolecular interaction between M2+ and oxygen atoms of surrounding M(ox) molecules.

Synthesis and QCM gas-sensing properties of 3,4-dialkoxyphenyl tosylamino-substituted phthalocyanines

Octa-substituted metallophthalocyanines [M = Ni(II), Zn(II), Co(II), and Cu(II)] carrying 3,4-dialkoxyphenyl tosylamino groups at the peripheral positions have been synthesized from 1,2-dicyano-4,5-bis[(3,4-dialkoxyphenyl-tosylamino)methyl]benzene in the presence of the corresponding anhydrous metal salt. Next to the metal ion center, the length of the alkyl chains in the dialkoxyphenyl moiety ([Formula: see text], 5, 6, and 12) was varied. In total, sixteen soluble phthalocyanines have been characterized by elemental analysis, FT-IR and [Formula: see text]H-NMR spectroscopy as well as mass spectrometry. Furthermore, the gas sensing properties of these new compounds have been studied using quartz crystal microbalance transducers. The sensing properties are described on the basis of sensor responses to nine different test analytes comprising volatile organic compounds, toxic gases, and chemical warfare agent simulants. The influence of the metal ion center and substituents on sensor selectivity and sensitivity is discussed. The compounds show good performance in the gas-sensing experiments with diverse responses to the analytes. Phthalocyanine species with pronounced selectivity for polar analytes, hydrocarbons or amines have been identified among the set of sensors with the help of multivariate data exploration methods. The results reveal that quite a high diversity in terms of selectivity is introduced through the minute variations to the phthalocyanine structure.

The synthesis of binary and ternary cobalt based metal borides by inorganic molten salt technique

Crystalline metal boride powders were synthesized via low temperature method in inorganic molten salt medium, and binary and ternary metal boride composite powders were investigated using anhydrous metal chlorides and sodium borohydride powder mixtures. The reactions were carried out in an aluminum crucible placed in a silica tube under argon which was put in a vertical tube furnace. At the end of the reaction, the resulting powder mixture was leached with hot water to remove any undesirable chloride phases. In order to improve crystalline properties, some of pure powders were selected and annealed at 1100°C. Characterization of synthesized and annealed powders was carried out using X-ray diffractometer (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM / EDX) and dynamic light scattering technique (DLS). The results showed the positive effect of inorganic molten salt technique (LiCl/KCl eutectic mixture) on the formation of phases during the reaction between CoCl2, NiCl2 and NaBH4 powder mixtures. Following the reactions at between 750-950 °C, the binary and ternary metal boride powders consisting of CoB-Ni2B-CoBx, CoB-Ni4B3 ve CoB-NiB-Ni2Co0.67B0.33 phases were obtained. The measured particle size of the final particles had an average of 60 nm.

Synthesis, characterization, aggregation and electrochemical properties of peripheral octa-2-{[4-(2-benzylphenoxy]benzyl]thio} ethoxy group substituted cobalt(II) phthalocyanine

We were reported here, the synthesis, characterization, aggregation and electrochemical properties of 4,5-bis(2-{[4-(2- benzyl)phenoxy)benzyl]thio}ethoxy)phthalonitrile and 2,3,9,16, 17,23,24-octa[(2-{[4-(2-benzyl)phenoxy)benzyl]thio}ethoxy)] phthalociyaninatocobalt(II). CoPc were prepared by the reaction of 4,5-bis(2-{[4-(2-benzyl)phenoxy)benzyl]thio}ethoxy) phthalonitrile with the corresponding anhydrous metal salt in n-pentanol and DBU. The structures of the original compounds were identified by using elemental analysis, 1 H-NMR, 13C-NMR, IR, mass and UVvis spectroscopic data. Electrochemical redox characteristics of the compounds were determined by electroanalytical techniques such as cyclic voltammetry, square wave voltammetry. The aggregation tendencies and electrochemical redox properties of all phthalocyanines were investigated on the basis of central metal, solvent medium and substituent effects, using UV-Vis spectral.

Impact of 2-Aminonicotinic Acid and/or β-Cyclodextrin on the Morphology of Metal Carbonates (M = Ca2+ and Sr2+) Crystallization

We examined the crystallization impact of the surfactant, 2-aminonicotinic acid and/or β-cyclodextrin on the formation of two anhydrous metal carbonates, MCO3 (M = Ca2+ and Sr2+), from their respective calcium chloride and strontium chloride salts along with NaHCO3 at room temperature. By varying the concentrations of this hybrid surfactant to the concentrations of MCO3 during the preparations and examined their particle sizes by PXRD, FTIR, TGA and SEM. The characterization on these newly formed anhydrous metal carbonates clearly indicated that CaCO3 formed with three different shapes such as truncated calcite, hexagonal calcite and rod shaped aragonite. Whereas, SrCO3 formed with two different shapes such as hexagonal poles and bloom scale bars by varying concentrations of the surfactants. The mixed surfactant certainly made an impact on the metal carbonates formations with different shapes and sizes by varying surfactants concentrations and conditions.

Extreme negative mechanical phenomena in the zinc and cadmium anhydrous metal oxalates and lead oxalate dihydrate

The crystal structures and elastic properties of the anhydrous zinc and cadmium oxalates and lead oxalate dihydrate are determined using rigorous first-principles solid-state methods. The three materials are shown to display negative Poisson’s ratios (NPR) and to exhibit the negative linear compressibility (NLC) phenomenon. Anhydrous zinc and cadmium oxalates display NLC for a very wide range of external pressures applied in the direction of minimum compressibility in the ranges − 1.3 to 5.5 GPa and − 1.2 to 2.7 GPa, respectively. The increase of volume in both materials is substantial for pressures larger than 3.6 and 1.8 GPa, and the compressibilities become − 70.1 and − 67.0 TPa−1 for pressures of 5.2 and 2.6 GPa, respectively. The increase of volume is so drastic that these materials become unstable for pressures larger than 5.5 and 2.7 GPa. Lead oxalate dihydrate also displays NLC along the direction of minimum Poisson’s ratio for negative pressures in the range − 0.05 to − 0.08 GPa and undergoes a pressure-induced phase transition for relatively low external pressures of the order of 0.1 GPa. The presence of NPR and NLC phenomena in these three materials together with the previous finding of these phenomena for silver oxalate strongly suggests that other metal oxalate materials could also exhibit an extremely anomalous mechanical behavior.

Exploring Main Group Metal Borosulfates: Similarities and Differences of Two New Borosulfates M[B2O(SO4)3] (M = Sr, Pb)

The first strontium borosulfate Sr[B2O(SO4)3] and a novel lead borosulfate Pb[B2O(SO4)3] were obtained by solvothermal reaction of the respective anhydrous metal chlorides MCl2 (M = Sr, Pb) with H[B(HSO4)4] at 300 °C. The crystal structure of Sr[B2O(SO4)3] [Pnma, Z = 4, a = 1657.38(27) pm, b = 1203.68(19) pm, c = 439.484(8) pm] is isotypic with Ba[B2O(SO4)3] and consists of chains, built up by three membered rings of two borate tetrahedra and a sulfate tetrahedron. These rings are further connected via corner‐sharing sulfate tetrahedra and hence can be classified as loop branched zweier double chains. Pb[B2O(SO4)3] crystallizes in a new structure type [P21/m, Z = 2, a = 440.00(2) pm, b = 1210.19(5) pm, c = 860.43(4) pm, β = 103.587(2) °] closely related to Sr[B2O(SO4)3]. Both structures share the common supergroup Pnmm and basically differ by the orientation of adjacent anionic chains. The coordination surrounding of Pb2+ indicates a lone pair activity and DFT calculations confirmed a weak polarizability. Moreover, the compounds were characterized by electrostatic calculations, vibrational spectroscopy and thermal analysis and broaden the structural and chemical diversity of borosulfates.

Electrochemical, spectroelectrochemical and electrocatalytic properties of newly synthesized phthalocyanine compounds with 1,1′-thiobis(2-naphthol) groups

In this work, the synthesis and characterization of new phthalocyanine compounds containing 1,1′-thiobis(2-napthol) units have been reported. The metal-free phthalocyanine, H2Pc 3 was synthesized by the cyclotetramerization of dinitrile derivative 2 in dry n-pentanol by a classical method. Metal phthalocyanines complexes, ZnPc 4 and CoPc 5 were prepared by the reaction of 2 with the corresponding anhydrous metal salts in n-pentanol and DBU. The structures of the original compounds were identified by using elemental analysis, 1H NMR, 13C NMR, IR, mass and UV–vis spectroscopic data. Electrochemical redox characteristics of the compounds were determined by electroanalytical techniques such as cyclic voltammetry, square wave voltammetry, and chronocoulometry. Extra support for the precise nomination of the electron transfer processes were also maintained with in situ spectroelectrochemical measurements. The compounds usually showed one-electron metal- and/or ligand-based reversible or quasi-reversible reduction and oxidation processes. The processes were found to be accompanied by distinct colour changes, indicating the possibility of the use of the compounds as electrochromic material. Electrocatalytic oxygen reducing performances of the compounds were also tested by dynamic voltammetry in a medium similar to fuel-cell working conditions. The CoPc compound showed high performance for electrocatalytic reduction of dioxygen to water through a process involving the transfer of totally 4 electrons per molecule in two different ways.

Phosphorus-Rich Metal Phosphides: Direct and Tin Flux-Assisted Synthesis and Evaluation as Hydrogen Evolution Electrocatalysts.

Metal phosphides from the 3d period exhibit a range of structures and compositions. Many metal-rich phosphides and monophosphides function as heterogeneous electrocatalysts in the hydrogen evolution reaction. This paper describes the direct and tin flux-assisted synthesis of phosphorus-rich metal phosphides with MP2 or MP3 compositions. The facile synthesis of FeP2, CoP3, NiP2, and CuP2 is thermochemically driven by PCl3 formation from reactions of anhydrous metal halides and P4 vapor at 500 °C. Well-crystallized micrometer-sized particles result from these solvent-free reactions. A tin flux leads to more complete reactions at lower temperature for FeP2 and enables synthesis of a monoclinic polymorph of NiP2 rather than the kinetic cubic product formed by direct reaction. These crystalline metal phosphides are investigated as electrocatalyts for hydrogen evolution in acidic and buffered aqueous solutions. All phosphorus-rich products show very good stability in strongly acidic media. The catalytic activity for hydrogen evolution ordered by higher current at a fixed electrode geometric area and low onset potential is CoP3 > NiP2 (cubic and monoclinic) > FeP2 ≫ CuP2. At high applied potentials, CuP2 undergoes surface reactions and roughening that improve its electrocatalytic activity. Correlations of the observed electrocatalytic activity with electrochemically active surface area, particle size, metallic versus semiconducting properties, and local metal coordination environment are noted for these phosphorus-rich 3d metal phosphides.

Synthesis, characterization and Judd-Ofelt analysis of Sm3+-doped anhydrous Yttrium trimesate MOFs and their Y2O3:Sm3+ low temperature calcination products

Abstract The luminescence quenching in RE3+-containing materials (RE: rare earth) has a close dependence with the water content on the first coordination sphere around the activator ions. The hydration content of [RE(TMA)] systems (TMA = 1,3,5-benzenetricarboxylic acid) is dependent on the RE3+ ionic radius, leading to elements smaller than Gd3+ to form anhydrous matrixes. It is noteworthy that [Sm(TMA)·6(H2O)] is hexahydrate, while [Y(TMA)] is anhydrous. In this work, we report the synthesis, characterization and the luminescent properties of [Y(TMA)] anhydrous metal organic frameworks (MOFs) serving as hosts for Sm3+ ions. The materials are synthesized by a quick and easy coprecipitation procedure in aqueous solution. Under calcination at mild conditions (starting at 500 °C, benzenecarboxylate method), the precursor complexes are converted into Y2O3:Sm3+ with strong Sm3+ photoluminescence. The compounds were characterized by different techniques (elemental analyses, infrared spectroscopy, thermogravimetry, powder X ray diffraction and photoluminescence). The phenomenological intensity parameters (Ω2,4,6) of Sm3+ were determined by a least squares procedure based on the Judd-Ofelt theory.

(Invited) Electrochemical Synthesis of Ammonia Using Ion Conducting Membranes

Ammonia offers potential as a carbon-free energy carrier with a high hydrogen content and if fully oxidized, the products nitrogen and water are environmentally benign. It also serves as the major feedstock for fertilizer production and a building block for nitrogen containing chemicals and polymers. Ammonia is readily liquefied and conveniently stored in low cost steel tanks. It may function as a high energy density storage medium for hydrogen produced by renewable energy derived electricity. Ammonia synthesis is currently carried out in a few very large Haber-Bosch plants, mostly fueled from natural gas. The current large-scale Haber-Bosch (H-B) technology needs to run at constant inputs of energy and reactants. The economics dictate very large process reactors and separation systems, consequently the technology does not downscale well to small sized plants, nor does it work with interruptible energy supplies. Even though the ammonia synthesis efficiency can be considered low at ~70%, these efficiencies are only obtained in large-scale integrated facilities. Highly efficient ammonia synthesis in small-scale H-B systems does not exist, thus stimulating research towards a low temperature and pressure processes. Electrosynthetic pathways for NH3 production theoretically offer higher efficiency and scalability but, the challenges are quite foreboding as the dinitrogen triple bound is extremely stable and most known nitrogen dissociation catalysts are deactivated by oxygen or water [1]. We are currently engaged in a DOE ARPA-e funded program to develop electrochemical methods for ammonia synthesis. We are developing and evaluating intermediate NH3 synthesis processes, one based on the spontaneous electro-reduction of nitrogen in lithium ion systems where the potential for lithium is close to metal deposition and the subsequent formation of lithium nitride. The other utilizes proton conducting, anhydrous metal pyrophosphate/polymer composite membranes for protonation of nitrogen [2]. The advantage of the lithium process is the reaction is autocatalytic, however the reaction of Li3N with water to form NH3 and LiOH is exothermic, with an amount of enthalpy of -581.62 kJ mol-1 and thus presents challenges for the design of an energy efficient process. The direct protonation process is thermodynamically favorable at modest potentials near hydrogen evolution potentials, however it requires suitable electrocatalysts that dissociate dinitrogen but inhibit the parasitic hydrogen evolution reaction (HER). Using proprietary Li ion solid electrolytes, we have demonstrated lithium nitride formation at high coulombic efficiency and ammonia evolution upon hydrolysis. We have also demonstrated intermittent ammonia production at >8% efficiency using Pt catalysts, however the coulombic efficiency is limited by HER. We are exploring the use of carbon supported Ru, MoxC and Ru/MoxC catalysts to limit current efficiency losses due to HER.

New peripherally tetra-[trans-3,7-dimethyl-2,6-octadien-1-ol] substituted metallophthalocyanines: synthesis, characterization and catalytic activity studies on the oxidation of phenolic compounds

In this paper, we elucidated the synthesis, characterization, and investigation of catalytic activity studies of new metallophthalocyanines 4 and 5 as the catalyst for phenolic compounds oxidation by trying different types of oxygen sources. The structural characterization of the products was made by a combination of elemental analysis, FT-IR, LC-MS/MS (for phthalonitrile derivative 3), MALDI-TOF mass spectral data (for metallophthalocyanines 4–7), UV–vis spectroscopy (for metallophthalocyanines 4–7), 1H NMR and 13C NMR spectroscopies (for compounds 3 and 6). The synthetic routes for the (trans-3,7-dimethyl-2,6-octadien-1-ol) substituted phthalonitrile derivative 3 and corresponding metallophthalocyanines 4–7 are outlined in Scheme 1. The MPc complexes 4–7 were synthesized via cyclotetramerization of compound 3 in the presence of the corresponding anhydrous metal salts (CoCl2 for 4, CuCl2 for 5, Zn(CH3COO)2 for 6 and MnCl2 for 7) in dry n-pentanol as solvent and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as strong base at reflux temperature under nitrogen gas. Phthalocyanines and their metal complexes, in general, display poor solubility in most of the organic solvents, however, the synthesized metallophthalocyanine complexes 4–7 were highly soluble in common organic solvents because of the introduction of the methyl groups on alkyl chains of peripheral arms. The catalytic activity of compounds 4 and 5 was evaluated for the oxidation of phenolic compounds such as 4-nitrophenol, o-chlorophenol, 2,3-dichlorophenol, and p-methoxyphenol. CoPc 4 displayed good catalytic performance with a full oxidation of 4-nitrophenol into the corresponding benzoquinone and hydroquinone with the highest TON and TOF values within 3 h.