Continuous process for singlet oxygenation of hydrophobic substrates in microemulsion using a pervaporation membrane

Chemically generated singlet oxygen (1O2, 1Deltag) is able to oxidize a great deal of hydrophobic substrates from molybdate-catalyzed hydrogen peroxide decomposition, provided a suitable reaction medium such as a microemulsion system is used. However, high substrate concentrations or poorly reactive organics require large amounts of H2O2 that generate high amounts of water and thus destabilize the system. We report results obtained on combining dark singlet oxygenation of hydrophobic substrates in microemulsions with a pervaporation membrane process. To avoid composition alterations after addition of H2O2 during the peroxidation, the reaction mixture circulates through a ceramic membrane module that enables a partial and selective dewatering of the microemulsion. Optimization phase diagrams of sodium molybdate/water/alcohol/anionic surfactant/organic solvent have been elaborated to maximize the catalyst concentration and therefore the reaction rate. The membrane selectivity towards the mixture constituents has been investigated showing that a high retention is observed for the catalyst, for organic solvents and hydrophobic substrates, but not for n-propanol (cosurfactant) and water. The efficiency of such a process is illustrated with the peroxidation of a poorly reactive substrate, viz., beta-pinene.     

Synthesis and structure of Ag(6)[(UO(2))(3)O(MoO(4))(5)]: a novel sheet of triuranyl clusters and MoO(4) tetrahedra

The new uranyl molybdate Ag(6)[(UO(2))(3)O(MoO(4))(5)] (1) with an unprecedented uranyl molybdate sheet has been synthesized at 650 degrees C. The structure (monoclinic, C2/c, a = 16.4508(14) A, b = 11.3236(14) A, c = 12.4718(13) A, beta = 100.014(4)(o), V = 2337.4(4) A(3), Z = 4) contains [(UO(2))(3)O(MoO(4))(5)] sheets composed of triuranyl [(UO(2))(3)O] clusters that are connected by MoO(4) tetrahedra. The topology of the uranyl molybdate sheet in 1 represents a major departure from sheets observed in other uranyl compounds. Of the approximately 120 known inorganic uranyl compounds containing sheets of polyhedra, 1 is the only structure that contains trimers of uranyl pentagonal bipyramids that are connected only by the sharing of vertexes with other polyhedra. The sheets are parallel to (001) and are linked by Ag cations.     

N-heterocycle chelated oxomolybdenum(VI and V) complexes with bidentate citrate

A 1,10-phenanthroline (phen) chelated molybdenum(VI) citrate, [(MoO2)2O(H2cit)(phen)(H2O)2] x H2O (1) (H4cit = citric acid), is isolated from the reaction of citric acid, ammonium molybdate and phen in acidic media (pH 0.5-1.0). A citrato oxomolybdenum(V) complex, [(MoO)2O(H2cit)2(bpy)2] x 4H2O (2), is synthesized by the reduction of citrato molybdate with hydrazine hydrochloride in the presence of 2,2'-bipyridine (bpy), and a monomeric molybdenum(VI) citrate [MoO2(H2cit)(bpy)] x H2O (6) is also isolated and characterized structurally. The citrate ligand in the three neutral compounds uses the alpha-alkoxy and alpha-carboxy groups to chelate as a bidentate leaving the two beta-carboxylic acid groups free, that is different from the tridentate chelated mode in the citrato molybdate(VI and V) complexes. 1 and in solution show obvious dissociation based on 13C NMR studies.     

Directed synthesis of noncentrosymmetric molybdates using composition space analysis

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.     

Syntheses, spectroscopies and structures of molybdenum(VI) complexes with homocitrate

Initial investigations into the possible role of homocitric acid in iron molybdenum cofactor (FeMo-co) of nitrogenase lead us to isolate and characterize two tetrameric molybdate(VI) species. The complexes K2(NH4)2[(MoO2)4O3(R,S-Hhomocit)2].6H2O (1) and K5[(MoO2)4O3(R,S-Hhomocit)2]Cl.5H2O (2) (homocitric acid = H4homocit, C7H10O7) are prepared from the reactions of acyclic homocitric acid and molybdates, which represent the first synthetic structural examples of molybdenum homocitrate complexes. The homocitrate ligand trapped by tetranuclear molybdate coordinates to the molybdenum(VI) atom through alpha-alkoxy and alpha-, beta-carboxy groups. The physical properties, structural parameters, and their possible biological relevances are discussed.     

Solid-state coordination chemistry: influences of (M(terpyridyl))(M = Fe(III), Cu(II), Ni(II)) subunits on molybdenum oxide structures

The hydrothermal reactions of Na2MoO4 x 2H2O and 2,2':6',2"-terpyridine with appropriate salts of Fe(II), Cu(II), and Zn(II) yield a variety of mixed metal oxide phases. The Cu(II) system affords the molecular cluster [Cu(terpy)MoO4].3H2O (MOXI-40 x 3H2O), as well as a one-dimensional material [Cu(terpy)Mo2O7](MOXI-41) which is constructed from (Mo4O14)4- clusters linked through (Cu(terpy))2+ units. In constrast, the Zn(II) phase of stoichiometry identical to that of MOXI-41, [Zn(terpy)Mo2O7](MOXI-42), exhibits a one-dimensional structure characterized by a (Mo2O7)n2n- chain decorated with peripheral (Zn(terpy))2+ subunits. The iron species [(Fe(terpy))2Mo4O12](MOXI-43) is also one-dimensional but exhibits [(Fe(terpy))2(MoO4)2]2+ rings linked through (MoO4)2- tetrahedra. A persistent structural motif which appears in MOXI-40, MOXI-41, and MOXI-43 is the [(M(terpy))2(MoO4)2]n cluster with a cyclic )(M2Mo2O4) core. In general, the secondary metal sites M(II, III) are effective bridging groups between molybdate subunits of varying degrees of aggregation. Furthermore, the ligands passivate the bimetallic oxide from spatial extension in two or three dimensions and provide a routine entree into low-dimensional structural types of the molybdenum oxide family of materials.     

Stabilization of a monomethyl orthomolybdate in the binding pocket of a dinuclear cobalt complex

The ability of the dinuclear Co(II) complex [(L(Me))Co(II)2(mu-Cl)]+ [1; (L(Me))2- = 3,6,9,17,20,23-hexamethyl-3,6,9,17,20,23-hexaaza-29,30-dithiol-13,27-di-tert-butyltricyclo[23.3.1(11.15)]triaconta-1(28),11,13,15(30),25,26-hexaene] to bind tetrahedral oxoanions of the transition metal has been investigated. Two new complexes, [(L(Me))Co(II)2(mu-MoO4)] (2) and [(L(Me))Co(II)2(mu-MoO3(OMe))]2[Mo4O10(OMe)6] (3), were prepared by substitution reactions of 1 with (n-Bu4N)2MoO4 in MeCN or with MoO3 x 2 H2O/NEt3 in MeOH. Both compounds were characterized by X-ray crystallography. The dioctahedral complex 2 features a mu(1,3)-bridging MoO4(2-) unit, whereas the cation in 3 hosts an unprecedented mu(1,3)-MoO3(OMe)- motif, demonstrating that four-coordinate molybdate esters can be stabilized in the binding pocket of the bowl-shaped [(L(Me))Co(II)2]2+ complex. The results of IR, UV/vis, and cyclic voltammetry measurements are also reported.     

Reactivity, chemoselectivity, and diastereoselectivity of the oxyfunctionalization of chiral allylic alcohols and derivatives in microemulsions: comparison of the chemical oxidation by the hydrogen peroxide/sodium molybdate system with the photooxygenation

The chiral allylic alcohols 1a-d and their acetate (1e) and silyl ether (1f) derivatives have been oxidized by the H2O2/MoO4(2)- system, a convenient and efficient chemical source of singlet oxygen. This chemical peroxidation (formation of the allylic hydroperoxides 2) has been conducted in various media, which include aqueous solutions, organic solvents, and microemulsions. The reactivity, chemoselectivity, and diastereoselectivity of this chemical oxidation are compared to those of the sensitized photooxygenation, with the emphasis on preparative applications in microemulsion media. While a similar threo diastereoselectivity is observed for both modes of peroxidation, the chemoselectivity differs significantly, since in the chemical oxidation with the H2O2/MoO4(2)- system the undesirable epoxidation by the intermediary peroxomolybdate competes efficiently with the desirable peroxidation by the in situ generated singlet oxygen. A proper choice of the type of microemulsion and the reaction conditions furnishes a high chemoselectivity (up to 97%) in favor of threo-diastereoselective (up to 92%) peroxidation.     

Hydrothermal Synthesis and Crystal Structure of [（CH3CH2）4N]4[（La12（OH）12MoO29）],A Novel Cluster Compound with a MoO5 Hexahedron Center surrounded by La—O Octahedron

IntroductionRecently,the molecular designs of polyox-ometalates( POM) with basic oxometal clusterbuilding blocks are of great interest[1,2 ] . Hy-drothermal synthesis,with the characteristic ofone- pot reaction,provides a convenient method toobtain novel structures of POM compounds[3— 6] . Inthe Ln/Mo/O system ( Ln=rare earth) ,somecompounds containing La and Mo elements havebeen reported[7— 17] . However,these compoundshave all been synthesized under the highly restrict-ed synthetic co…     

Studies on Organo-Phosphorus, -Arsenic and -Antimony Polytungstates and Polymolybdates(IX )——Preparation and Properties of o-Aminophenylarsenic Polymolybdates

In order to investigate the influence of organic groups on the types of organoarsenic polymolybdates, o-nitrophenylarsonic acid was reduced to o- aminophenylarsonic acid and then it reacted with sodium molybdate at pH = 3~5. Three new salts were prepared and characterized:( 1 ) (CN3H6)4[(o-NH2C6H4As)2Mo6O24], ( 2 ) Cs4[(o-NH2C6H4As)2Mo6O24], (3) [(CH3)4N]4[(o-NH2C6H4As)2Mo6O24].2H2O. The IR, UV spectra, thermal properties and electrochemical behaviors are reported. It is strange enough that when the o-nitro group was reduced to o-amino group, [(RAs)2Mo6O24]4- type of complexes was formed.     

Phase behavior and solubilization of microemulsion systems containing Gemini imidazoliums and their monomeric analogues

The Gemini imidazolium surfactants with a four-methylene spacer group [C_n(Bim)₂-2Br, n?=?12, 14, 16] and their corresponding monomers [C_nmimBr, n?=?12, 14, 16] were synthesized and characterized. The phase behavior and solubilization of microemulsion systems containing C_n(Bim)₂-2Br/butan-1-ol/octane/brine as well as microemulsion systems containing C_nmimBr/butan-1-ol/octane/brine were studied and compared. The C_n(Bim)₂-2Br-based microemulsion systems have greater solubilization ability than that of the corresponding mono surfactants C_nmimBr-based systems. As the carbon chain lengths of the surfactants [C_n(Bim)₂-2Br and C_nmimBr] increase, the mass fraction of the alcohol in the interfacial layer A ^S would decrease, whereas the solubilization ability (SP*) would increase. The maximum solubilization ability (SP*) of the two microemulsion systems was attained when the oil/water mass ratio (α) approaches 0.5. The solubilization ability of both microemulsion systems would increase with increasing NaCl concentrations in aqueous phase. In C_n(Bim)₂-2Br-based microemulsion systems, the alcohol is significantly more soluble in aqueous phase than in the oleic phase. And it was noted that the alcohol is more soluble in C_n(Bim)₂-2Br-based systems than in C_nmimBr-based systems in both aqueous and oleic phases.     

New coordination modes at molybdenum for 2-diphenylphosphinoaniline derived ligands

The complexes [MoCl3(1-N,2-Ph2P-C6H4)2] (1) and {MoCl(Nt-Bu)[1-micro(N),2-(Ph2P)C6H4]}2 (2) have been obtained from the reaction of 2-diphenylphosphinoaniline [1,2(NH2)(Ph2P)C6H4] with either sodium molybdate [Na2MoO4] (in the presence of Et3N and Me3SiCl) or [MoCl2(Nt-Bu)2(DME)]; the crystal structure of 1 reveals a novel MoNC2PN six-membered conjugated ring system derived from a P-N coupling reaction between two ligands, whilst that of 2 reveals bridging imido/terminal phosphine ligation.     

Enzymatic Hydrolysis of Penicillin for 6-APA Production in Three-Liquid-Phase System

A dodecane/thermosensitive polymer/water three-liquid-phase system was introduced for enzymatic hydrolysis of penicillin G (Pen G) for 6-aminopenicillanic acid (6-APA). The enzyme was covalently attached to the terminal of PEO–PPO–PEO polymer (L63), which would be transferred into a polymer coacervate phase at high temperature above its “cloud point”. 6-APA was primarily resided in the aqueous phase due to its zwitterionic nature. More than 70% phenylacetic acid (PAA) was transferred into the organic phase using trioctylmethylammonium hydroxide and trihexyl-(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate ionic liquids (Cyphos IL-104) mixture at pH 5.5, while most of Pen G resided in water. As a result, high operational pH was permitted in three-liquid-phase system, which leads to higher enzymatic activity (120 IU at 40°C) and stability (enzymatic half-time up to 55 h at 60°C) in comparison with the value in butyl acetate/water two-phase system. On the other hand, two products in three-liquid-phase system might be automatically separated from the enzyme sphere into different phases at the same time, which facilitated the reaction equilibrium towards the product’s side with 6-APA productivity of 80% at 42°C, pH 5.5. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ligand influences of the structures of molybdenum oxide networks

The influence of organonitrogen ligands on the network structure of molybdenum oxides was examined by preparing three new molybdenum oxide phases [MoO3(4,4'-bpy)0.5] (MOXI-8), [HxMoO3(4,4'-bpy)0.5] (MOXI-9), and [MoO3(triazole)0.5] (MOXI-32). The structure of [MoO3(4,4'-bpy)0.5) consists of layers of corner-sharing MoO5N octahedra, buttressed by bridging 4,4'-bipyridyl ligands into a three-dimensional covalently bonded organic-inorganic composite material. Partial reduction of [MoO3(4,4'-bpy)0.5] yields the mixed-valence material [HxMoO3(4,4'-bpy)0.5] (x approximately 0.5). The most apparent structural change upon reduction is found in the Mo-ligand bond lengths of the MoO5N octahedra, which exhibit the usual (2 + 2 + 2) pattern in [MoO3(4,4'-bpy)0.5] and a more regular (5 + 1) pattern in [HxMoO3(4,4'-bpy)0.5]. Substitution of triazole for 4,4'-bipyridine yields [MoO3(triazole)0.5], which retains the layer motif of corner-sharing MoO5N octahedra but with distinct sinusoidal ruffling in contrast to planar layers of [MoO3(4,4'-bpy)0.5] and [HxMoO3(4,4'-bpy)0.5]. The folding reflects the ligand constraints imposed by the triazole ligand that bridges adjacent Mo sites within a layer. MOXI-8, C5H4NMoO3: monoclinic P2(1)/c, a = 7.5727(6) A, b = 7.3675(7) A, c = 22.433(3) A, beta = 90.396(8) degrees, Z = 8. MOXI-9, C5H4.5NMoO3: monoclinic I2/m, a = 5.2644(4) A, b = 5.2642(4) A, c = 22.730(2) A, beta = 90.035(1) degrees, Z = 4. MOXI-32, C2H3N3Mo2O6: orthorhombic Pbcm, a = 3.9289(5) A, b = 13.850(2) A, c = 13.366(2) A, Z = 4.     

Surfactant-mixing effects on the interfacial tension and the microemulsion formation in water/supercritical CO2 system

The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.     

Solid and Solution Structural Studies of Dimeric and Tetrameric Molybdenum(Ⅵ) Malate Complexes

Reactions of potassium molybdate with racemic malic acid (H3mal = C4H6O5) result in the isolation of two mesomeric molybdenum malate complexes Ks[(MoO2)2O(R-mal)2][(MoO2)2O(S- mal)2]·4H2O 1 and (Him)2K6[(MoO2)4O3(R-mal)2][(MoO2)4O3(S-mal)2]·8H2O 2. Complex 1 belongs to the monoclinic system, space group C2/c with a = 14.8637(3), b = 6.9544(1), c = 19.6783(5) A, β = 100.081(2)°, V= 2002.70(7)A3, Mr = 1452.88, Z= 2, F(000) = 1416, T= 173 K, Dc = 2.409 g/cm3, μ(MoKa) = 2.167, R = 0.0283 and wR = 0.0733.2 is of triclinic system, space group P1 with a = 8.7707(2), b = 9.3310(3), c = 17.9093(7) A, α = 83.781(3), β = 85.626(2), γ= 84.822(2)°, V = 1447.84(8) A3, Mr = 2160.68, Z = 1, F(000) = 1048, T= 173 K, Dc = 2.478 g/cm3, μ(MoKα) = 2.230, R = 0.0234 and wR = 0.0584.1 is the first isolated dinuclear molybdenum(Ⅵ) malato complex in 1:1 molar ratio. The molybdenum atoms in the two complexes are six-coordinated in an approximately octahedral geometry. Two malates coordinate tridentately with the Mo atom via their α-alkoxy, α-carboxy and α-carboxy groups in 1 and 2. β-Carboxy group in 2 further links with the other two Mo atoms to give a tetrameric unit. The solution 1H and 13C NMR spectra indicate that dimeric malate molybdenum in 1 dissociates partly in solution and exists in an equilibrium with tetrameric species, while 2 is stable and retains its tetrameric structure without any dissociation.     

羧甲基纤维素系列高分子表面活性剂形成微乳液的研究

采用紫外光谱、相图、动态激光光散射、同位素示踪、光学显微镜、电导率等研究了羧甲基纤维素系列高分子表面活性剂与甲苯-水-异丙醇体系微乳液的形成过程,发现微乳液粒子大小均一,形态一致,其尺寸比低分子表面活性剂所形成的微乳液粒子大得多.醇分子插入到油水界面,改变了两相界面结构,促使微乳液的生成.电导率测定表明所形成的微乳液区均为水包油结构,即使在富含甲苯区域,亦不会有油包水的反相胶束形成.     

Formation of fluorinated nonionic surfactant microemulsions in hydrofluorocarbon 134a (HFC 134a)

A structurally related series of fluorinated nonionic oxyethylene glycol surfactants of the type C(m)F(2m+1)(CH(2))(n)O[(CH(2)CH(2)O)(p)H], denoted C(m.n)E(p) (where m=4, 6, or 7, m=1 or 2, and p=4 or 6) were synthesized and their surface behavior in aqueous solution was characterized. The ability of these surfactants to form water-in-hydrofluorocarbon (HFC) propellant 134a microemulsions suitable for use in the aerosolized delivery of water-soluble drugs has been investigated. Phase studies showed that, regardless of the composition used, clear one-phase systems could not be prepared if a fluorinated nonionic surfactant was used alone, or in combination with a short or medium fluorocarbon alcohol cosurfactant. Clear one-phase systems could, however, be prepared if a short-chain hydrocarbon alcohol, such as ethanol, n-propanol, or n-pentanol, was used as cosurfactant, with the extent of the one-phase region increasing with decreased chain length of the alcohol cosurfactant. Light-scattering studies on a number of the hydrocarbon-alcoholcontaining systems in the propellant-rich part of the phase diagram showed that only systems prepared with C(4.2)E(6) and propanol contained microemulsion droplets (all other systems investigated were considered to be cosolvent systems).     

The Effect of Fatty Alcohols and Valeric Acid on the Regions of Existence of a Three-Phase System Containing Water, Oil, and Surfactant

For different water–oil–surfactant systems with added aliphatic alcohols and valeric acid, conditions for the formation of the microemulsion (third) phase containing approximately equal amounts of oil and water were determined. It was established that the microemulsion phases are formed in the initial two-phase system (oil-in-water microemulsion–oil) on adding alcohols or the acid, which can be more hydrophilic or more hydrophobic than micelle-forming surfactants. Concentrations of alcohols necessary for the transformation of the three-phase system into the two-phase one were determined. The influence of energy parameters of surfactants and structural characteristics of the alcohol and basic micelle-forming surfactant on the stability of the three-phase system is discussed.     

基于Dy_2(MoO_4)_3-AuNPs复合纳米材料的葡萄糖生物传感器

采用水热法合成了纳米材料钼酸镝[Dy_2(MoO_4)_3],并制备了Dy_2(MoO_4)_3-AuNPs复合材料,利用该复合材料固定葡萄糖氧化酶(GOD)构建了葡萄糖生物传感器.通过透射电子显微镜(TEM)、紫外-可见光谱(UV-Vis)和能谱分析(EDS)等手段对所制备的材料进行了表征,并利用电化学阻抗谱(EIS)和循环伏安(CV)曲线研究了该传感器的电化学性能.结果表明,Dy_2(MoO_4)_3-AuNPs复合材料具有较好的生物相容性,能增强固定化的GOD的生物活性,并促进GOD在电极表面的电子传递速率;该传感器在葡萄糖浓度为0.01~1.0 mmol/L范围内葡萄糖浓度与响应电流呈较好的线性关系,最低检出限为3.33μmol/L(S/N=3),该生物传感器还具有较好的稳定性和重现性.