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1.
DFT method (B3LYP) with 6-31G * basis set was utilized in the computation of a fully optimized structure, net atomic charges and spin densities of the intermediate of cytochrome P-450-oxoiron(IV) porphyrin cation radical, compound I – in the presence of axial ligand such as thiolate (SMe −) imidazole (IM), phenoxide (OPh −), methoxide (OMe −) and chloride (Cl −). The results show doublet states in compound I are about 2–4 kcal/mol more stable than quartet states for all aforementioned ligands, and the doublet state is the ground state in all cases. However, electron donor ability of the ligands are in the order of SMe − > IM > OMe − > OPh − > Cl −. Also the active oxidant intermediate of cytochrome P-450 between different mesomeric structures select sulfur oxygen radical type structure and can be viewed as (RS ↓)Fe ↑(IV)(O ↑)(Por). In horseraddish peroxidase (HRP) and peroxidase with histidine axial ligand π cation radical character of porphyrin ring is preferred (Im)Fe ↑(IV)(O ↑)(Por ↓). For the ligands such as OMe −, OPh − and Cl − oxidation mainly took place on the iron and the active intermediate can be viewed as (L)Fe ↑(V)(O)(Por) with one unpaired electron localized on the iron. 相似文献
2.
Derivative photometric methods for trace analysis of Th(IV) and UO 2(II), and their simultaneous determination in mixtures using 5,8-dihydroxy-1,4-naphthoquinone in a micellar medium are reported. Molar absorptivity and Sandell's sensitivity of 1:2 Th(IV) and 1:1 UO 2(II) complexes at their λ max, 614.5 nm and 637.0 nm are, 1.19 × 10 4 1/mol/cm and 1.12 × 10 4 1/mol/cm and 1.95 × 10 −2 μg/cm 2 and 2.13 × 10 −2 μg/cm 2 μg/cm 2, respectively. Calibration graph is linear over the range 9.28 × 10 −2−18.56 μg/ml of Th(IV) and 9.52 × 10 −2−19.04 μg/ml of UO 2(II). Though presence of Th(IV) and UO 2(II) causes interference in each others determination, 9.28 × 10 −1−9.28 μg/ml Th(IV) and 9.52 × 10 −1−9.52 μg/ml UO 2(II) when present together, can be simultaneously determined using derivative spectra. 相似文献
3.
The optimum conditions for preparation of stable solutions of ruthenate and osmate, after alkaline fusion of ruthenium(IV) compounds, ruthenium metal and osmium metal in a silver crucible, have been determined. The molar absorptivities of ruthenate and osmate are 1.74 × 10 3 1. mole −1.cm −1 at 465 nm (Ru) and 2.75 × 10 3 1.mole −1.cm −1 at 340 nm (Os) in 2 M sodium hydroxide. A differential spectrophotometric method has been developed for determination of ruthenium in ruthenium dioxide, lead ruthenite and bismuth pyroruthenate. Simultaneous spectrophotometric determination is proposed for ruthenium and osmium. The other platinum metals interfere seriously only when present in> 1:1 w/w ratio to Ru. 相似文献
4.
The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet silylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction process of forming the silapolycyclic compound (P 2) for this reaction consists of four steps: (I) the two reactants first form a semi-cyclic intermediate INT1a through a barrier-free exothermic reaction of 32.5 kJ mol −1; (II) this intermediate then isomerizes to an active four-membered ring intermediate INT1 via a transition state TS1a with an energy barrier of 30.8 kJ mol −1; (III) INT1 further reacts with formaldehyde to form an intermediate INT2, which is also a barrier-free exothermic reaction of 30.1 kJ mol −1; (IV) INT2 isomerizes to a silapolycyclic compound P 2 via a transition state TS2 with a barrier of 50.6 kJ mol −1. Comparing this reaction path with other competitive reaction paths, we can see that this cycloaddition reaction has an excellent selectivity. 相似文献
5.
The synthesis, characterization, and thermal decomposition of the [Ni(SCN) 2(H +SCN) 2(4-mepy) 2] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm −1, 788; 773 cm −1 assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm −1. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm −1, ν(C---S) at 783; 770 cm −1, and δ(SCN) at 468; 477 cm −1. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l −1. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, 3A 2g→ 3T 1g and 3A 2g→ 3T 1g, for a symmetry close to O h. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H +SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed. 相似文献
6.
We present a molecular dynamics study of the solvation properties of large spherical ions S + and S − of same size, in water, chloroform and acetonitrile solutions, and at a water–chloroform interface. According to the “extrathermodynamic” TATB hypothesis, such ions have identical free energies of transfer from water to any solvent. We find that this is not the case, because S − interacts better than S + with water (by about 20 kcal mol −1), while S + is better solvated by acetonitrile (by about 2 kcal mol −1) and chloroform (about 8 kcal mol −1) solvents. The importance of “long-range” electrostatic interactions on the charge discrimination by solvent is demonstrated by the comparison of standard vs corrected methods to calculate: (i) the electrostatic potential at the centre of the solute; (ii) the interaction energies between the ions and the solvents; and (iii) the free energies of charging the neutral sphere S 0 to S + and S −, respectively. These conclusions are obtained with several solvent models and simulation conditions. The question of ion pairing for the S +S −, S +Cl − and S −Na + pairs is also examined in the three solvents. Finally, simulations at a liquid–liquid water–chloroform interface represented explicitly, show that S + and S − are highly surface active, although they do not possess, like classical surfactants, an amphiphilic topology. Adsorption at the interface is found with different methodologies and at different ion concentrations. These results are important in the context of the “TATB hypothesis”, and for our understanding of solvation of large hydrophobic ions in pure liquids or in heterogeneous liquid environments. 相似文献
7.
Metal parts and residues from machining processes are usually polluted with cutting or grinding oil and have to be cleaned before further use. Supercritical carbon dioxide can be used for extraction processes and precision cleaning of metal parts, as developed at Forschungszentrum Karlsruhe. For optimizing and efficiently conducting the extraction process, in-line analysis of oil concentration is desirable. Therefore, a monitoring method using fiber-optic NIR spectroscopy in combination with PLS calibration has been developed. In an earlier paper we have described the instrumental set-up and a calibration model using the model compound squalane in the spectral range of the CH combination bands from 4900 to 4200 cm −1. With this model only poor prediction results were obtained if applied to technical oil samples in supercritical CO 2. In this paper we describe a new calibration model, which was set up for the squalane/carbon dioxide system covering the 323–353 K temperature and the 16–35.6 MPa pressure range. Here, calibration data in the spectral range from 6100 to 5030 cm −1 have been used. This range includes the 5100 cm −1 CO 2 band of the Fermi triad as well as the hydrocarbon 1st overtone CH stretching bands, where spectral features of oil compounds and squalane are more similar to each other. The root mean-squared error of prediction obtained with this model is 4 mg cm−3 for carbon dioxide and 0.4 mg cm−3 for squalane, respectively. The utilizability of the newly developed PLS calibration model for predicting the oil concentration and CO2 density of solutions of technical oils in supercritical carbon dioxide has been tested. Three types of “real world” cutting and grinding oil formulations were used in these experiments. The calibration proved to be suitable for determining the technical oil concentration with an error of 1.1 mg cm−3 and the CO2 density with an error of 6 mg cm−3. Therefore, it seems possible to apply this in-line analytical approach on the basis of a cost-effective and time-saving model compound calibration for the surveillance of real world de-oiling and other extraction process based on supercritical carbon dioxide, and furthermore to establish an automated process termination criterion based on this technique. 相似文献
8.
A novel copper(II) thiocyanate complex [Cu(im) 2(NCS) 2] 1 (im=imidazole) has been prepared and characterized by spectroscopic analysis and crystallographic method. This supramolecular compound exhibits a three-dimensional solid state structure constituted by N–HS hydrogen bonds and π–π stacking interactions. The compound in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with absorption coefficient and refractive index 2=1.18×10 −11 mw −1, n2=−9.00×10 −16 m 2w −1, respectively, and third-order NLO susceptibility χ (3) of 7.00×10 −10 esu. 相似文献
9.
The “missing” fourth 35Cl NQR frequency postulated for NH 4ICl 4H 2O at room temperature has been observed. Four signals were also found for this compound at 195K, but the results at 77K were less clear-cut, with either five or (probably) six resonances detected. The occurrence of a phase transition between 77 and 195K seems likely. A structure is suggested for the ICl 4− ion at room temperature from the relationship found previously between NQR frequency and bond length in tetrachloroiodates. 相似文献
10.
The oxidation of Cp 2NbCl 2 with pure WF 6 in SO 2 solution yielded the cationic metallocene species [Cp 2NbCl 2] +[WF 6] − essentially in quantitative yield. The same reaction carried out in the presence of either equimolar amounts or a two-fold excess of HCN led to the preparation of the new niobocenium salt [Cp 2NbCl 2] 4+[WF 6] 2− which was studied by single crystal X-ray diffraction. This compound represents the first example of a structurally characterized metallocene-WF 6− complex, and crystallizes in the tetragonal system: space group, P4 12 12(No. 92), a = 11.083(8) Å, c = 48.285 (9) Å; Z = 8; R = 0.0759, RW = 0.0841. ab]Die Oxidation von Cp 2NbCl 2 mit reinem WF 6 führt in SO 2-Lösung zur Synthese von [Cp 2NbCl 2 ] +[WF 6] − in nahezu quantitativer Ausbeute. Die analoge Reaktion führt unter Anwesenheit der äquimolaren Menge oder eines zweifachen Überschusses an HCN zur Ausbildung des Niobocenium-Komplexsalzes [Cp 2NbCl 2] 4+ [WF 6] 2−[WCl 6] 2−, von dem eine Röntgenstrukturanalyse angefertigt wurde. Diese Verbindung repräsentiert den ersten structurell charakterisierten Vertreter eines Metallocen-WF 6−-Komplexes und kristallisiert im tetragonalen System: Raumgruppe P4 12 12 (Nr. 92), a = 11.083(8) Å, c = 48.285(9) Å; Z = 8; R = 0.0759, RW = 0.0841. kw]Niobium; X-ray diffraction; Oxidation; Metallocenes 相似文献
11.
The synthesis and electrochemical characterisation of octapentylthiophthalocyaninato manganese(III) acetate (4) and octapentylthiophthalocyaninato titanium(IV) oxide (5) complexes are reported. The complexes have an unusual purple (4) and red (5) colouration since the Q-band is shifted to the near infra red region with Q-band maxima at 893 nm and 808 nm in dichloromethane for 4 and 5, respectively. The structures of the complexes were confirmed by elemental analysis and interpretation of their spectroscopic data, including 2D NMR. The cyclic voltammetry (CV) of the Mn complex (4) showed four quasi reversible couples. The reduction processes are attributed to Mn IIIPc −2/Mn IIPc −2 and Mn IIPc −2/Mn IIPc −3 and the oxidation processes to Mn IVPc −2/Mn IIIPc −2 and Mn IVPc −1/Mn IVPc −2. The processes were confirmed by spectroelectrochemistry. A well-defined spectrum of the rare Mn IVPc −2 species is reported. The CV of the Ti complex (5) showed two well-resolved reduction processes due to Ti IVPc −2/Ti IIIPc −2 and Ti IIIPc −2/Ti IIPc −2. However, oxidation processes of the complex revealed adsorption behaviour and resulted in decomposition on electrolysis using spectroelectrochemistry. 相似文献
13.
The very sensitive, fairly selective direct spectrophotometric method for the determination of trace amount of vanadium (V) with 1,5-diphenylcarbohydrazide (1,5-diphenylcarbazide) has been developed. 1,5-diphenylcarbohydrazide (DPCH) reacts in slightly acidic (0.0001–0.001 M H 2SO 4 or pH 4.0–5.5) 50% acetonic media with vanadium (V) to give a red–violet chelate which has an absorption maximum at 531 nm. The average molar absorption coefficient and Sandell’s sensitivity were found to be 4.23×10 4 l mol −1 cm −1 and 10 ng cm −2 of V v, respectively. Linear calibration graph were obtained for 0.1–30 μg ml −1 of V v: the stoichiometric composition of the chelate is 1:3 (V: DPCH). The reaction is instantaneous and absorbance remain stable for 48 h. The interference from over 50 cations, anions and complexing agents has been studied at 1 μg ml −1 of V v. The method was successfully used in the determination of vanadium in several standard reference materials (alloys and steels), environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, solution containing both vanadium (V) and vanadium (IV) and complex synthetic mixtures. The method has high precision and accuracy (s=±0.01 for 0.5 μg ml −1). 相似文献
14.
The emission intensity at 517 nm from Pt 2(pop) 44− (pop = P 2O 5H 22−) is quenched by the addition of sulphur dioxide. The sulphur dioxide coordinates at the axial platinum(II) sites by a η 1-SO 2 bond. This coordination is supported by 31p NMR and Raman spectroscopy of aqueous solutions. The electronic spectrum of a sulphur dioxide saturated solution of Pt 2(pop) 44− shows an absorption at 428.5nm ( = 4.1 × 10 4). From the decrease in the chromophore for uncomplexed Pt 2(pop) 44− the equilibrium constant for SO 2 binding is estimated to be 1.74 M 2l −2. The effect of adding different quenchers to aqueous solutions of Pt 2(pop)44− is discussed. The compound Pt 2(pop) 44− will undergo 2-electron reduction with chromous ion. 相似文献
15.
A new method has been developed for ion-interaction chromatography with suppressed conductivity detection and a new graphitized carbon packing, which is sintered from carbonic material at a high temperature. Combinations of various eluting agents, tetrabutylammonium hydroxide (TBA) and acetonitrile have been investigated to optimize the separation of eight common anions (F −, Cl −, NO 2−, Br −, NO 3−, SO 42−, HPO 42− and I −). Calibration curves were linear from 0.5 to 10 μg/ml for F −, from 1.0 to 20 μg/ml for Cl −, NO 2− and NO 3−, from 2.5 to 50 μg/ml for Br − and SO 42− and from 5.0 to 100 μg/ml for HPO 42− and I − with a correlation coefficient ( r) of 0.999 or better. The relative standard deviations (R.S.D.s) of peak areas were between 0.2 and 0.9% for 10 repeated measurements. The application of this newly developed method was demonstrated by the determination of chloride, bromide and sulfate in pharmaceutical compounds using the direct injection method. The analytical results were within ±2% (relative) of the theoretical value, and thus in good agreement with the theoretical value for each sample. 相似文献
16.
Complexes having the formula [C 5Me 5Fe(CO)-η 4-diene] + BF 4− have been prepared by reaction of [C 5Me 5Fe(CO) 2THF] +BF 4− with a range of dienes. A Brönsted plot derived from the rates of addition of amine nucleophiles suggests an essentially “soft” nature for the complexes diene. 相似文献
17.
This paper describes a method for the simultaneous determination of As(III), Sb(III) and Se(IV) by combining hydride generation and gas phase molecular absorption spectrometry. A system for continuous hydride generation has been designed and developed, based on the use of a double process of gas-liquid separation, and optimal compromise operation conditions for the three compounds have been found. After generation, the hydrides are collected in a liquid nitrogen cryogenic trap, and then evaporated and driven to the flow cell of a diode array spectrophotometer, in which the transient signals over the 190–250 nm wavelength interval are measured. Under the recommended conditions (sample flow: 35 ml min −1, 0.5 M HCl; reductor flow: 4 ml min −1 of 4% NaBH 4, solution) linear response ranges above 50 μg 1 −1 for As(III), 30 μg 1 −1 for Sb(III) and 200 μg 1 −1 for Se(IV) are obtained with detection limits of 22 μg 1 −1, 15 μg 1 −1 and 65 μg 1 −1, respectively. Multiwavelength linear regression equations were used for the simultaneous determination of the three elements in different synthetic samples, with good precision and accuracy and to study simultaneously the interference from different chemical species for the three compounds. Results were similar to those obtained by other techniques using hydride generation. 相似文献
18.
In toluene as medium, tetra(cyclopentadienyl)niobium(IV), NbCp 4, has been prepared in satisfactory yields from the reaction of NaCp with: (a) Nb 2C1 10, (b) NbCl 4(THF) 2, or (c) NbCp 2Cl 2. Tetracyclopentadienylniobium(IV) has been characterized by X-ray diffraction. Crystal data: C 20H 20Nb, M=353.29 g mol −1, hexagonal, space group P6 5 (no. 170), a= b=9.396(2), c=31.23(3) Å, V=2388(2) Å 3, Z=6, dcalc=1.48 g cm −3, λ(Cu–K )=1.54184 Å, T=291 K, μ=62.04 cm −1, F(000)=1686. Two of the four cyclopentadienyl ligands are bonded to niobium in a pentahapto fashion, the other two being monohapto. NbCp 4 undergoes cyclopentadiene elimination in the presence of species containing active protons such as Ph 3SiOH or strong acids, the products being tris- or biscyclopentadienyl compounds depending on the molar ratio of the reagents. 相似文献
19.
The formation and extraction of the ion-associates of the vanadium(V)-3,5-dinitrocatechol (DNC) anionic chelate complex with various basic dyes have been studied and a new sensitive extraction—spectrophotometric method for the determination of vanadium based on the system V(V)-DNC-Brilliant Green has been developed. Beer's law is obeyed up to a vanadium concentration of 0.3 μg/ml and the molar absorptivity is 1.7 × 1O 5 l.mole −1. cm −1 at 630 nm. The molar ratios of the components and the form of the vanadium(V) cation in the extracted compound have been determined, and the formula [VO(OH)(DNC) 2−2][BG +] 2 is proposed. Titanium, molybdenum, tungsten, EDTA and thiocyanate interfere seriously. The method becomes specific after a preliminary separation of vanadium by its extraction as the BPHA complex from H 2SO 4-HF medium, and is 40 times more sensitive than the spectrophotometric BPHA method. The proposed method has been applied to determination of traces of vanadium (about 10 −5%) in alums. 相似文献
20.
The overall conformational order of the alkyl tail of the lyotropic lamellar phase of the dimethyldodecyl amineoxide, (CH 3) 2ON +(CH 2) 11CH 3 (DDAO)---H 2O system (75.7 wt.%) has been studied by using Fourier transform infrared spectroscopy. The spectral region 1000–1400 cm −1, covering the CH 2 wagging modes and the methyl umbrella modes of DDAO, has been recorded in the temperature interval 3–60°C and at different mole fractions of gramicidin-D with respect to DDAO ( Xg = 0.03, 0.05 and 0.1) for both DDAO-H 2O and DDAO-D 2O systems. It has been shown that the DDAO amphiphile molecules of the lamellar phase reorganise in a phase-like transition near 25–30°C. The DDAO-water system does not show any significant bands corresponding to a double gauche conformation at 1355 cm −1 nor to a gauche-transgauche (kinked) conformation at 1367 cm −1. These bands are probably present but hidden in the broad low-frequency side of the CH 3 umbrella band at 1377 cm −1. Upon incorporation of gramicidin into the lamellar phase both head group and acyl chain spectra of the lipid change in such a way as to indicate a decreased “ordering” of the molecules, as judged by comparison with spectra of the same molecule in a micellar environment, and with increased fluidity of the acyl chains. 相似文献
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