C5H14NO · ZnCl(HPO3), an unexpected product from an ionic-liquid synthesis

C₅H₁₄NO · ZnCl(HPO₃) arose from an unexpected reaction in which a component of the ionic liquid mixed solvent was incorporated into a hybrid structure in which cholinium (C₅H₁₄NO⁺) cations interact with [ZnCl(HPO₃)]⁻ macroanionic layers by way of O–H⋯O hydrogen bonds. The inorganic layers display a 4 · 8² topology.     

Two new β-octamolybdate supported rare earth metal complexes: [NH4]2[{Gd(DMF)7}2(β-Mo8O26)][β-Mo8O26] and [NH4][La(DMF)7(β-Mo8O26)]

Two novel β-octamolybdate supported rare earth metal complexes, [NH₄]₂[{Gd(DMF)₇(β-Mo₈O₂₆)}][β-Mo₈O₂₆] 1 and [NH₄][La(DMF)₇(β-Mo₈O₂₆)] 2, were obtained from the reaction of (NH₄)₆Mo₇O₂₄·4H₂O with LnCl₃ (Ln=Gd for 1 and La for 2) at low pH values in the mixed solvents of H₂O/DMF or H₂O/DMF/CH₃CN. The single X-ray diffraction studies reveal that 1 consists of discrete centrosymmetric heterometallic decanuclear [{Gd(DMF)₇}₂-β-Mo₈O₂₆]²⁺, [β-Mo₈O₂₆]⁴⁻ and two amino cations. In each decanuclear [{Gd(DMF)₇}₂-β-Mo₈O₂₆]²⁺ cation, the β-octamolybdate moiety is linked to two eight-coordinated Gd^III cations, which is coordinated by seven DMF ligands and one terminal oxygen atom of molybdenum center. Compound 2 is built up from DMF coordinated La^III fragment and β-octamolybdate unit joined together through two terminal oxygen atoms of two molybdenum atoms. Ferromagnetic behavior is observed for 1 from the magnetic measurement, which might result from the exchange interaction through the bridging β-[Mo₈O₂₆]⁴⁻ ligand or the presence of zero-field splitting.     

Decisive Interactions between the Heterocyclic Moiety and the Cluster Observed in Polyoxometalate-Surfactant Hybrid Crystals

Inorganic-organic hybrid crystals were successfully obtained as single crystals by using polyoxotungstate anion and cationic dodecylpyridazinium (C₁₂pda) and dodecylpyridinium (C₁₂py) surfactants. The decatungstate (W₁₀) anion was used as the inorganic component, and the crystal structures were compared. In the crystal comprising C₁₂pda (C₁₂pda-W₁₀), the heterocyclic moiety directly interacted with W₁₀, which contributed to a build-up of the crystal structure. On the other hand, the crystal consisting of C₁₂py (C₁₂py-W₁₀) had similar crystal packing and molecular arrangement to those in the W₁₀ crystal hybridized with other pyridinium surfactants. These results indicate the significance of the heterocyclic moiety of the surfactant to construct hybrid crystals with polyoxometalate anions.     

Crystal Structure and Physicochemical Properties of Two Supramolecular Compounds: (C4H8NH2)4[Mo8O26] and (NH4)Na2[AsIIIMo6O21(O2CCH2NH3)3]·8H2O

Two inorganic–organic hybrid supramolecular compounds based on polyoxometalates formulated as (C₄H₈NH₂)₄[Mo₈O₂₆] (1) and (NH₄)Na₂[As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]·8H₂O (2) have been synthesized by conventional solution method and characterized by infrared, UV–Vis and single-crystal X-ray diffraction analyses. Thermal analysis was performed to study their thermal stability. The atomic arrangement in compound (1) can be described as inorganic layers built by [Mo₈O₂₆]^4?, pyrrolidinium cations are embedded into layers. The fascinating structural feature of compound (2) is that the glycine molecules are bounded to two edge-sharing Mo centers via their carboxylate functionality leading to functionalized heteropolymolybdate [As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]^3?, extensive net hydrogen bonds between cations and anions contribute to the crystal packing. The electrochemical behavior of compound (2) has been studied.     

Shape-controlled fabrication of polypyrrole microstructures by replicating organic crystals through electrostatic interactions

Polypyrrole (PPy) microstructures with diverse shapes were synthesized in an aqueous inorganic salt medium including organic crystals and pyrrole (Py). A series of sulfobenzoic acid salt forms with various cations (K⁺, Na⁺, Li⁺, NH₄⁺) in different positions (para, meta, ortho) of the sulfonate group on the benzene ring were used to form organic crystals as sacrificial templates. Using these crystals, we produced five different shapes of PPy microstructures (hexagonal microplates, curled nanofibers, lozenge-shaped microplates, rigid rods, parallelogram microplates), which replicated the shapes of the organic crystal templates through electrostatic interaction between the anionic crystal surfaces and the cationic PPy chains. In contrast, PPy that was polymerized without crystals showed bulky agglomerates of 200-500 nm size. The electrical properties were dictated by the molecular structures of the organic salt molecules used. While the highest conductivity (200.3 Scm⁻¹) was observed in PPy using crystals of para-linked 4-sulfobenzoic acid monopotassium salt, the lowest conductivity (0.8 Scm⁻¹) was observed in PPy prepared in the presence of crystals of ortho-linked 2-sulfobenzoic acid monoammonium salt.     

Ionothermal synthesis and characterization of alkali metal polyoxometallates: Structural trends in the (emim)m[An(Mo8O26)] (emim = 1-ethyl-3-methylimidazolium; m = 2,3; n = 1,2; A = K,Rb, Cs) group of compounds

Three novel octamolybdates (emim)₃K(Mo₈O₂₆) (1), (emim)₃Rb(Mo₈O₂₆) (2) and (emim)₂Cs₂(Mo₈O₂₆) (3) (emim = 1-ethyl-3-methylimidazolium) have been prepared by ionothermal reactions using (emim)Br as a solvent. The structures contain octamolybdate anions [β-Mo₈O₂₆]^4–. In compounds 1 and 2, [β-Mo₈O₂₆]^4– units are linked by alkali metal cations to form 1D chain structures, while Cs cations in the compound 3 link to polyoxoanions to form a 2D layered structure.     

Potassium and nickel doped β-Mo2C catalysts for mixed alcohols synthesis via syngas

Potassium and nickel doped β-Mo₂C catalysts were prepared and their performances of CO hydrogenation were investigated. The main products over β-Mo₂C catalyst were hydrocarbons, and only few alcohols were obtained. The potassium promoter resulted in remarkable selectivity shift from hydrocarbons to alcohols over β-Mo₂C. Moreover, it was found that the potassium promoter enhanced the ability of chain propagation of β-Mo₂C catalyst and resulted in a higher selectivity to C₂₊OH. When doped by potassium and nickel, β-Mo₂C catalyst showed high activity and selectivity for mixed alcohols synthesis, the Ni promoter further enhanced the whole chain propagation to produce alcohols especially for the step of C₁OH–C₂OH. From the XPS analysis, it had been proved that the formation of higher alcohols might be attributable to the presence of Mo^IV species, whereas the formation of hydrocarbons was closely associated with the presence of Mo^II species on the surface of the catalysts.     

Oxidation of cyclopentene catalyzed by phosphotungstic quaternary ammonium salt catalysts

A series of phosphotungstic quaternary ammonium salts, Q₃ (PW₁₂O₄₀) and Q₃(PW₄O₁₆) [Q = (C₅H₅)N⁺(C₁₆H₃₃), (C₁₆H₃₃)N⁺(CH₃)₃, (C₄H₉)₄N⁺, and (CH₃)₄N⁺], were used as the catalysts in oxidation of cyclopentene. The catalysts [(C₅H₅)N(C₁₆H₃₃)]₃(PW₄O₁₆) and [(C₁₆H₃₃)N(CH₃)₃]₃(PW₄O₁₆) showed high catalytic activity in the selective oxidation of cyclopentene while using H₂O₂ (50%) as an oxidant and 2-propanol as a solvent. The oxidation products mainly consisted of glutaraldehyde, cis-1,2-cyclopentanediol and trans-1,2-cyclopentanediol. The above-mentioned two catalysts were dissolved completely in the reaction medium during the catalysis process and precipitated themselves from the reaction system after reaction, showing the characteristics of reaction-controlled phase-transfer catalysis. The types of quaternary ammonium cations and the phosphotungstic anions in phosphotungstic quaternary ammonium salts affected catalytic activity.     

Synthesis,structure and dielectric constant property of two novel complexes based on protonated 1-aminoadamantane

The reaction of 1-aminoadamantane hydrochloride and divalent metal chloride in concentrated hydrochloric acid medium yields two unusual complexes containing protonated 1-aminoadamantane, (C₁₀H₁₈N)¹⁺₂[ZnCl₄]^2? (1), (C₁₀H₁₈N)¹⁺₂[MnCl₄(H₂O)₂]^2? (2a) and (C₁₀H₁₈N)¹⁺₂[MnCl₄(D₂O)₂]^2? (2b). Their crystal structures have been determined by X-ray crystallography. Both complexes contain molecular network of (C₁₀H₁₈N)⁺ cations and divalent metal chloride polyhedral anions (Mn and Zn site symmetry 2/m). Dielectric constants of both two organic–inorganic hybrid salts were measured at different temperatures and frequencies. Different structures lead to large discrepancy in the dielectric property measurements. In addition, thermal analysis of complex 2 was studied.     

An experimental study of electroreduction of CO2 to HCOOH on SnO2/C in presence of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) and anions (HCO3−, Cl−, Br− and I−)

It is well-known that the electrolytes can influence the electrochemical reduction of carbon dioxide (ERCO₂) in aqueous media. In this work, we explore the effects of alkali metal cations and anions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, HCO₃⁻, Cl⁻, Br⁻, I⁻) on the current density and product selectivity for the ERCO₂ into formic acid (HCOOH) on the SnO₂/carbon paper (SnO₂/C) electrode. Results of the ERCO₂ experiments show that for the cations, the promotion effects on current density and faradaic efficiencies (FEs) are in the order of Li⁺ < Na⁺ < K⁺ < Cs⁺ < Rb⁺. For the anions, the current density values are in the order of NaHCO₃ < NaCl < NaBr < NaI and KHCO₃ < KCl ≈ KI < KBr, respectively, and that on the FEs for the formation of the HCOOH (FE_HCOOH) is HCO₃⁻ < Cl⁻ < Br⁻ < I⁻. Based on this result, the effects of alkali metal cations and anions on ERCO₂ are discussed.     

Mixed alcohols synthesis from carbon monoxide hydrogenation over potassium promoted β-Mo2C catalysts

Potassium-promoted β-Mo₂C catalysts were prepared and their performances in CO hydrogenation were investigated. The main products over β-Mo₂C catalyst were C₁-C₄ hydrocarbons, only ∼4 C-atom% alcohols were obtained. The products of hydrocarbons and alcohols obeyed traditional linear Anderson-Schultz-Flory (A-S-F) distribution. However, modification with K₂CO₃ resulted in a remarkable selectivity shift from hydrocarbons to alcohols. Moreover, it was found that potassium promoter enhanced the ability of chain propagation of β-Mo₂C catalysts and resulted in a higher selectivity to C₂₊OH. For K/β-Mo₂C catalysts, the hydrocarbon products also obeyed traditional linear A-S-F plots, whereas alcohols gave a unique linear A-S-F distribution with remarkable deviation of methanol compared with that on β-Mo₂C catalyst. It could be concluded that potassium promoter might exert a prominent function on the whole chain propagation to produce alcohols. A surface phase on the K/β-Mo₂C catalysts such as the “K-Mo-C” explained the higher value for C₂₊OH, especially could promote the step of C₁OH to C₂OH, or could have a role in producing directly C₂OH, but again this would be speculative. At the same time, the influence of the loadings of K₂CO₃ on the performances of β-Mo₂C catalyst was investigated and the results revealed that the maximum yield of alcohol was obtained at K/Mo molar ratio of 0.2.     

The effect of surface passivation on the preparation and stability of the graphite intercalation compounds containing tetra-n-alkylammonium cations

The kinetic stability of graphite intercalation compounds (GICs) is markedly increased by a surface passivation reaction that occurs under strong reducing conditions in the presence of long-chain tetra-n-alkylammonium cations. A simple alkylation model is proposed. Surface alkylation allows the formation of a stable, isolable, graphite intercalation compound of tetra-n-ethylammonium, (C₂H₅)₄N⁺ for the first time, by chemical surface passivation of [Na(en)_1.0]C₁₅ (en = ethylenediamine) with R₄N⁺, R = C₆H₁₃, C₇H₁₅ or C₈H₁₇, followed by an ion exchange reaction to displace the Na(en)⁺ complex with (C₂H₅)₄N⁺. One GIC thus obtained using dimethylsulfoxide (DMSO) as solvent has composition [(C₂H₅)₄N]C₅₇ 0.5DMSO, and is a stage-1 compound with a gallery expansion of 0.47 nm. This relatively small expansion indicates a monolayer of intercalate and additionally requires an unusually flattened cation conformation. Electrophoretic analyses indicate that the ion exchange within the graphene galleries goes to completion. Additionally, the passivated GIC surfaces afford a dramatic increase in the stability of GICs, in protic solvents, aqueous media, and the ambient environment.     

Synthesis and structure of a high-nuclearity oxomolybdenum(V) complex, [Mo12O28(OC2H5)4(C6H7N)8]

(PyH)[MoOBr₄(H₂O)]·2/3PyHBr (PyH⁺=pyridinium cation, C₅H₅NH⁺) yielded upon the solvothermal reaction with ethanol and 4-methylpyridine (4-MePy, C₆H₇N) a novel oxoethoxomolybdenum(V) cluster, [Mo₁₂O₂₈(OC₂H₅)₄(4-MePy)₈] 1. Molybdenum atoms are grouped into six Mo^V₂ pairs linked by single metal–metal bonds. Three crystallographically independent Mo–Mo distances are 2.5578(14), 2.5981(14) and 2.6489(16) Å.     

Comprehensive study of the structural and electronic properties of complexes formed by Mz+ (Li+, Na+, K+, Be2+, Mg2+, Ca2+) cation and thiophene and its derivatives

The interactions of metal cations (Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺) with thiophene and its derivatives have been investigated using MP2/6-311++G** and B3LYP/6-311++G** methods in the gas phase and the water solution. The following substituents are taken into considerations: F, Cl, Br, CH₃, OH and C₂H₃, which cover electron-withdrawing and electron-donating effects. The substituent, the metal cations and the solvent effects on the cation–π interactions are investigated. The physical properties such as dipole moment, chemical potential and chemical hardness of studied complexes have been systematically explored. Natural population analysis data, the electron density and Laplacian properties have been used to evaluate the cation–π interaction. The electron density (ρ) and Laplacian (?²ρ) properties, estimated by atoms-in-molecules calculations, indicate that the cation–π interactions possess low ρ and positive ?²ρ, which are in agreement with electrostatic character of the cation–π interactions. Charge transfer values are calculated using Mulliken charges and reveal that the electron charge transfer takes place from thiophene and its derivatives to the metal cation in the complexes under the study. To evaluate the aromaticity of the rings upon complexation, several well-established indices of aromaticity such as the nucleus-independent chemical shift and the harmonic oscillator model of aromaticity and the aromatic fluctuation index have been used. The molecular electrostatic potential is given the visual representation of the chemically active sites and comparative reactivity of atoms. Furthermore, the effects of interactions on NMR data have been used for more investigation of the analyzed complexes.     

Transitions and relaxations of copolypropylene molecules in copolypropylene–clay composites

Three commercial organoclays pretreated with C₁₈H₃₇N⁺H₃, C₁₈H₃₇N⁺(CH₃)₃ and (C₁₈H₃₇)₂N⁺(CH₃)₂, were used to prepare a series of copolypropylene (cPP)‐clay nancomposites by melt blending. Then, the effects of the clay content and pretreatment history on the transition and relaxation of cPP molecules in different composites were investigated in detail by dynamic mechanical analysis. The results show that the α‐relaxation, ascribed to the movement of polymer main chains within the crystalline regions of different cPP composites, is activated by the increase of clay content. The main β‐relaxation, assigned to the glass‐rubber transition of cPP segments in amorphous portions, is greatly limited by about 3–5 wt % clay loading, whereas drastically motivated with 7 wt % clay loading, which correlates closely with the dispersion order of clay layers in different composites. Lastly, the γ‐relaxation, associated with the motion of ethylene sequence of cPP chains, is restricted because of the increasing clay content. Additionally, it is found that the miscibility between cPP molecules and organoclay layers was strengthened as the clay premodifier varied from C₁₈H₃₇N⁺H₃ to C₁₈H₃₇N⁺(CH₃)₃, but somewhat weakened when the premodifier changed as (C₁₈H₃₇)₂N⁺(CH₃)₂. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrochemical properties of modified copper-thallium hexacyanoferrate electrode in the presence of different univalent cations

The preparation of copper(II) hexacyanoferrate (CuHCF) films on the surface of gold electrodes as well as their characterization in solutions of various alkali metal and NH₄⁺ cations and in the presence of thallium(I) are described. The electrochemical quartz crystal microbalance and cyclic voltammetric techniques were used. In 0.50 M lithium nitrate, even at submillimolar concentration of Tl(I), the formal potential of CuHCF was shifted to more positive values. At higher Tl(I) concentrations, the formal potential of the CuHCF redox reaction changed linearly with the logarithm of Tl(I) concentration (in the 0.50 M solution of lithium or another alkali metal nitrate). From such dependencies, selectivity coefficients K_Tl/M were calculated, and they show that the CuHCF film on the gold electrode interacts preferentially with Tl(I). High affinity of Tl(I) to copper hexacyanoferrate, that was observed in the presence of alkali metal cations, was explained by relatively strong donor-acceptor interactions of Tl(I) ions with nitrogen in CN groups of the CuHCF film.It was also shown for simple M₄[Fe(CN)₆] metal ferrocyanate salts (where M = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and Tl⁺) that there is a preferential interaction of Tl⁺ with CN group consistent with formation of a Tl-NC-Fe bridge.     

In situ X-ray diffraction of the intercalation of (C2H5)4N and BF4 into graphite from acetonitrile and propylene carbonate based supercapacitor electrolytes

The intercalation of (C₂H₅)₄N⁺ and BF₄⁻ from acetonitrile (AN) and propylene carbonate (PC) solutions into bound graphite electrodes during cyclic voltammetry was investigated by in situ X-ray diffraction (XRD) using synchrotron radiation. The disappearance of the 0 0 2 reflection of graphite in the XRD patterns upon intercalation of (C₂H₅)₄N⁺ indicates that the cations are accumulated between the graphene layers. For the intercalation of BF₄⁻, the appearance of 0 0 l reflexes in the intercalated state provides clear evidence of staging. In both cases, the in-plane periodicity was not significantly altered by the intercalation process apart from slight changes in the CC bond length. The intercalation of BF₄⁻ from the PC-based electrolyte was found to have the least destructive effect on the periodicity of the graphite structure during initial cycling in the anodic potential range along with the highest charge/discharge efficiency.     

Transport properties of organic vapours in silicone/clay nanocomposites

Poly(dimethylsiloxane) (PDMS)/clay nanocomposites have been synthesized using a novel ω-ammonium functionalized oligo-PDMS surfactant (PDMS-N⁺(CH₃)₃) and processed in membrane form. In order to relate the clay morphological structure to the degree of dispersion and physical properties of the membrane, the clay ion-exchanged by PDMS-N⁺(CH₃)₃ has been compared to a non-exchanged sodium MMT and to two organoclays organo-modified by using either non-functional alkyl ammonium cations (C₃₈H₈₀N⁺) or hydroxyalkyl ammonium (C₂₂H₄₈ON⁺) cations. Morphological analysis and transport properties (sorption, diffusion and permeability) have been investigated using two penetrants: acetone and n-hexane. The mechanical and rheological properties of the PDMS nanocomposite membranes have also been studied. It has been found a significant effect of the clay organo-modifier on the morphology, physical and barrier properties of the systems.     

Photoinduced non-oxidative coupling of methane over H-zeolites around room temperature

Photoinduced non-oxidative coupling of methane proceeded over H-form mordenite and ZSM-5. The major product was C₂H₆, and the stoichiometric formation of H₂ was also revealed. The effects of the pretreatment temperature, Al content and H⁺ exchange level upon the activity suggested that the active sites were highly isolated framework Al–O units interacting with no metal cations.     

Electrochemical and density functional theory study of bis(cyclopentadienyl) mono(β-diketonato) titanium(IV) cationic complexes

The electrochemical behaviour of fluorinated bis(cyclopentadienyl) mono(β-diketonato) titanium(IV) complexes, of general formula [Cp₂Ti(R′COCHCOR)]⁺ClO₄⁻ with Cp = cyclopentadienyl and R′, R = CF₃, C₄H₃S; CF₃, C₄H₃O; CF₃, Ph (C₆H₅); CF₃, CH₃; CH₃, CH₃; Ph, Ph and Ph, CH₃ is described. Both metal and ligand based redox processes are observed. The chemically and electrochemically reversible Ti^IV/Ti^III couple is followed by an irreversible ligand reduction at a considerably more negative (cathodic) potential. A comparison of the ligand reduction in its free and chelated state indicates that the β-diketonato ligand (R′COCHCOR)⁻ in [Cp₂Ti(R′COCHCOR)]⁺ClO₄⁻ is electroactive at more negative potentials. A theoretical density functional theory (DFT) study shows that a highly localized metal centred frontier orbital dominates the Ti^IV/Ti^III redox chemistry resulting in a non-linear relationship between the formal redox potential (E°′) and the sum of the group electronegativities of the R and R′ groups, χ_R + χ_R′, of the ligand. Linear relationships, however, are obtained between the DFT calculated electron affinity (EA) of the complexes and χ_R + χ_R′, the pK_a of the free β-diketones R′COCH₂COR and the carbonyl stretching frequency, v_CO, of the complexes. The DFT calculated electronic structure of the second reduced species [Cp₂Ti(β-diketonato)]⁻ shows that it is best described as Ti(III) coupled to a β-diketonato radical.