Monte Carlo simulation of adsorption of binary and quaternary alkane isomers mixtures in zeolites: Effect of pore size and structure

Grand canonical Monte Carlo and configurational bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of butane isomers and quaternary mixtures in nine zeolites at 300 K. For binary mixtures the results show there is a critical pore size, which is 10-membered-ring about 5.6 Å. The channel sizes of BEA, ISV, MOR and CFI are larger than this critical pore size, they prefer i-butane than n-butane, whereas TON with smaller channel size than critical pore size prefers n-butane than i-butane, but its selectivity decreases with pressure increasing. MFI, MEL and TER prefer i-butane than n-butane at low pressure, but with pressure increasing, the selectivity is reversed. BOG prefers i-butane than n-butane but the selectivity decreased with pressure increasing. It demonstrates that the adsorption and selectivity are controlled by both pore size and pore structure. The n-butane–i-butane–n-pentane–2-methylbutane quaternary mixtures adsorbed in these nine zeolites were studied, and the results show alkane chain length dependence at low pressure, but the adsorption is controlled by pore size and structure with pressure increasing in all the zeolites except for TON and BOG.     

Intramolecular C-N bond formation reactions catalyzed by ruthenium porphyrins: amidation of sulfamate esters and aziridination of unsaturated sulfonamides

Ruthenium porphyrins [Ru(F(20)-TPP)(CO)] (F(20)-TPP = 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato dianion) and [Ru(Por*)(CO)] (Por = 5,10,15,20-tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl]porphyrinato dianion) catalyzed intramolecular amidation of sulfamate esters p-X-C(6)H(4)(CH(2))(2)OSO(2)NH(2) (X = Cl, Me, MeO), XC(6)H(4)(CH(2))(3)OSO(2)NH(2) (X = p-F, p-MeO, m-MeO), and Ar(CH(2))(2)OSO(2)NH(2) (Ar = naphthalen-1-yl, naphthalen-2-yl) with PhI(OAc)(2) to afford the corresponding cyclic sulfamidates in up to 89% yield with up to 100% substrate conversion; up to 88% ee was attained in the asymmetric intramolecular amidation catalyzed by [Ru(Por)(CO)]. Reaction of [Ru(F(20)-TPP)(CO)] with PhI[double bond]NSO(2)OCH(2)CCl(3) (prepared by treating the sulfamate ester Cl(3)CCH(2)OSO(2)NH(2) with PhI(OAc)(2)) afforded a bis(imido)ruthenium(VI) porphyrin, [Ru(VI)(F(20)-TPP)(NSO(2)OCH(2)CCl(3))(2)], in 60% yield. A mechanism involving reactive imido ruthenium porphyrin intermediate was proposed for the ruthenium porphyrin-catalyzed intramolecular amidation of sulfamate esters. Complex [Ru(F(20)-TPP)(CO)] is an active catalyst for intramolecular aziridination of unsaturated sulfonamides with PhI(OAc)(2), producing corresponding bicyclic aziridines in up to 87% yield with up to 100% substrate conversion and high turnover (up to 2014).     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Synthesis and optical resolution of a series of inherently chiral calix[4]crowns with cone and partial cone conformations

A series of inherently chiral calix[4]arenes with cone and partial cone conformations and with crown ether moieties of variable size have been readily synthesized. By taking advantage of the carboxy appendage on the lower rim, these were condensed with the chiral auxiliary (S)-BINOL to form diastereomers which, in most cases, could be separated by preparative TLC, or more desirably, by column chromatography on silica gel (diastereomeric excess >99 % based on HPLC analysis). Seven enantiopure antipodes of inherently chiral calix[4]crowns were obtained after hydrolysis. It has been found that both the size of the crown moiety and alkylation of the last phenolic hydroxy group (accompanied with or without a change in the conformation) affect the separation of the diastereomers.     

Quantification of monohydroxy-PAH metabolites in urine by solid-phase extraction with isotope dilution-GC–MS

For measurement of biomarkers from polycyclic aromatic hydrocarbon (PAH) exposure, an analytical method is described quantifying hydroxylated PAH (OH-PAH) in urine samples. This method determined monohydroxy metabolites of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[c]phenanthrene, and benz[a]anthracene. The sample preparation consisted of enzymatic hydrolysis, solid-phase extraction and derivatization with a silylating reagent. Five carbon-13 labeled standards were used for isotope dilution. Analytes were separated by gas chromatography (GC) and quantified with high-resolution mass spectrometry (HRMS). This method produced good recoveries (41-70%), linearity, and specificity. Data were corrected for blank levels from the naphthalene, fluorene, and phenanthrene metabolites. Method detection limits ranged from 2 ng L(-1) for 1-hydroxypyrene to 43.5 ng L(-1) for 1-hydroxynaphthalene. Using quality control charts from two urine pools, the method can be readily applied to biomonitoring PAH exposure.     

Synthesis and reactions of some heterocyclic azacyanines

The one-step reaction of some amino-substituted heterocycles with diiodomethane to give azacyanines is reported. This useful reaction is of wider application than initially reported and includes the synthesis of new substituted pyrido-, isoquino-, benzimadazo-, and benzothiazoazacyanines 7. Furthermore, treatment of these azacyanines with base generally affects a facile opening of the dihydrotriazinium ring resulting in the formation of new heterocycles 10, 11, and 12, which would be difficult to prepare by other means. This reaction takes an additional direction in the case of halo-substituted azacyanines 7b/c/d where treatment with base gives rise to new interesting derivatives of dipyridotriazines 14b/c/d.     

Spectrophotometric determination of Fe(II) with 2,4,6-tri(2'-pyridyl)-1,3,5-triazine in the presence of large quantities of Fe(III) and complexing ions

A spectrophotometric method for the determination of Fe(II) in the presence of large amounts (up to 800 mg/l.) of Fe(III) is suggested. The Fe(III) is effectively masked by complexing with fluoride at pH 2.0-2.4 before development of the violet Fe(II) complex with 2,4,6-tri(2'-pyridyl)-1,3,5-triazine. The absorbance is measured at 595 nm. Various commonly occurring ions which complex with Fe(II) and/or Fe(III) do not interfere.     

二氯亚甲基锗烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.     

Determination of Human Alpha-Fetoprotein (AFP) by Solid Substrate Room Temperature Phosphorescence Enzyme-Linked Immune Response Using Luminescent Nanoparticles

Luminescent nanoparticles of silicon dioxide (SiO₂) containing fluorescein isothiocyanate (FITC) with a particle size of 20 nm were synthesized using the Sol–Gel method (abbreviated FITC–SiO₂). FITC–SiO₂ nanoparticles whose surfaces are modified (FITC–SiO₂–S–CH₂COOH) can emit strong and stable solid substrate room temperature phosphorescence (SS-RTP) on acetyl cellulose membranes. When the original color-producing agent (R) in the enzyme-linked immunosorbent assay (ELISA) kits for determination of alpha-fetoprotein (AFP) was substituted with (FITC–SiO₂–S–CH₂COOH), the system maintained good FITC–SiO₂ phosphorescence properties. Furthermore, the phosphorescence intensity enhanced markedly after the ELISA reaction. The relationship between the phosphorescence intensity and the content of AFP obeyed Beer’s law. Based on the facts stated above, a new method for the determination of human AFP by SS-RTP-ELISA (using the luminescent nanoparticle as marker) was established. The linear range of this method is 0.040–16.0 pg of human AFP per spot (sample volume: 0.40 μL spot⁻¹, corresponding concentration: 0.10–40.0 ng mL⁻¹). The regression equation of the working curve is ΔIp = −6.289+18.075 m_AFP (pg spot⁻¹) (r = 0.9960, n = 6). The detection limit (LD) of this method calculated by 3 S_b/k is 6.7 fg spot⁻¹ (corresponding concentration: 17 ng L⁻¹). Compared to the ELISA method using a traditional color-producing agent, the new method exhibited a 34.8 times higher sensitivity and a wider linear range. The method has been successfully applied to the determination of human AFP in serum.     

Novel vanadium(V) compounds with a layer structure: synthesis,crystal structures,and solid state NMR spectroscopy of [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))] x H(2)O (X = P and As)

A novel vanadium(V) phosphate and the arsenate analogue, [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))].H(2)O (X = P, As; bpy = bipyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are the first structurally characterized compounds in the vanadium(V)/4,4'-bpy/phosphate (or arsenate) systems. The two compounds are isostructural and crystallize in the triclinic space group P macro (No. 2) with a = 7.9063(3) A, b = 10.2201(4) A, c = 12.1336(5) A, alpha = 113.4652(7) degrees, beta = 95.7231(7) degrees, gamma = 94.4447(7) degrees, and Z = 2 for the phosphate, and a = 7.8843(6) A, b = 10.3686(7) A, c = 12.2606(9) A, alpha = 113.464(1) degrees, beta = 95.560(1) degrees, gamma = 94.585(1) degrees, and Z = 2 for the arsenate. The structure consists of phosphate-bridged vanadium(V) double chains linked through 4,4'-bpy ligands to form a sheet with the monoprotonated 4,4'-Hbpy(+) ligand being coordinated to the metal atom as a pendent group. The (1)H MAS NMR spectrum exhibits four resonances at 14.2, 9.5, 7.2, and 3.7 ppm with an intensity ratio close to 1:6:6:2, corresponding to three different types of protons in 4,4'-bpy and 4,4'-Hbpy(+) and one type of protons in H(2)O. The peak at 14.2 ppm can be assigned to the proton bonded to the pyridine nitrogen atom, which confirms the presence of 4,4'-Hbpy(+).