The atomic absorption determination of antimony,arsenic, bismuth, cadmium, lead, and tin in iron, copper,and zinc alloys with the graphite furnace

Antimony, arsenic, bismuth, cadmium, lead, and tin can be determined in metallurgical samples by flame atomic absorption spectrometry at levels of 0.005 wt%, but lower concentrations frequently necessitate preconcentration. The graphite furnace allows determination of these elements at concentrations 1–2 orders of magnitude lower than is possible with flame techniques. All six elements have detection limits at or below 1μg g⁻¹ in a variety of alloys. Calibration for antimony and load was done with standards containing the principal component of the alloy as a synthetic matrix. Bismuth, cadmium, and tin could be determined accurately only by the standard addition method. Arsenic could be determined in iron alloys with synthetic standards, but standard additions were required for copper alloys.     

Calcium, strontium, barium, and ytterbium complexes with cyclooctatetraenyl or cyclononatetraenyl ligands

Neutral triple-decker complexes of the heavy alkaline earth metals and ytterbium with tetraisopropylcyclopentadienide anions as terminal ligands and a cyclooctatetraene dianion as a middle deck have been synthesized from tetraisopropylcyclopentadienyl metal halide precursors and disodium cyclooctatetraenide. The pentaisopropylcyclopentadienyl analogue [{(C5iPr5)Yb}2(C8H8)] was prepared from ytterbium metal, cyclooctatetraene, and the free pentaisopropylcyclopentadienyl radical. X-ray crystal structure determinations for the barium and the calcium derivative show an almost linear arrangement of ring centers and metal atoms in both cases with metal-ring center distances of 2.33 A (Ca-Cp), 1.99/1.98 A (Ca-COT) and 2.71 A (Ba-Cp), 2.40 A (Ba-COT). The geometrical features of these molecules could be modeled quite accurately with density functional calculations. With potassium cyclononatetraenide, sparingly soluble bis(cyclononatetraenyl)barium could be prepared and characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Cyclononatetraenyl(tetraisopropylcyclopentadienyl)barium was obtained from [(C5HiPr4)BaI(THF)2]2 and KC9H9 as a 1:1 mixture with octaisopropylbarocene. Density functional calculations predict sandwich structures with parallel rings and a 2.37 A Ba-ring distance for [Ba(C9H9)2] and a 174 bending with metal-ring distances of 2.72 A (Ba-Cp) and 2.35 A (Ba-CNT) for [(C5HiPr4)Ba(C9H9)]. All alkaline earth sandwich and triple-decker complexes mentioned above have been heated to 250 degrees C without decomposition and have been sublimed in oil pump vacuum.     

3-O-Methl-6-desoxy-L-talose,Synthese und Identifizierung mit L-Acovenose. Desoxyzucker, 43. Mitteilung

3-O-methly-6-deoxy-L -talose has been synthesized starting from 1, 2–5, 6-di-O-isopropylidene-α-D -allose ( 1 ). Methylation, selective acidic hydrolysis, sodium periodate oxidation and GRIGNARD reaction with CH₃MgBr gave a mixture of the 1, 2-isopropylidene derivatives of 3-O-methyl-6-deoxy-D -allose and 3-O-methyl-6-deoxy-D -allose ( 7 ) and 3-O-methyl-6-deoxy-L -talose ( 8 ) (L -acovenose) could be obtained. Oxidation of the latter gave the corresponding crystalline lactone, which could be indentified with a sample obtained from natural L -acovenose.     

PdYn±(n=0, 1, 2, 3)分子离子的结构与稳定性

在Pd和Y原子相对论有效原子实势和基函数SDD下, 使用密度泛函理论B3LYP方法对PdYn±(n=0, 1, 2, 3)分子离子的势能曲线与稳定性进行计算研究, 结果表明, PdY分子和PdY−, PdY2−, PdY3−与PdY+分子离子的基态电子状态分别为X2Σ、X1Σ、X2Σ、X1Σ、X1Σ, 能稳定存在, 势能函数可用Murrell-Sorbie函数表达, 并计算得到相应的力常数与光谱数据; PdY2+和PdY3+分子离子的基态分别为X2Σ和X1Σ, 是亚稳定态, PdY3+分子离子的三重态是排斥态, 不能稳定存在.     

Chloropupukeananin, the first chlorinated pupukeanane derivative, and its precursors from Pestalotiopsis fici

Chloropupukeananin (1), the first pupukeanane chloride with highly functionalized tricyclo-[4.3.1.03,7]-decane skeleton and its possible biosynthetic precursors iso-A82775C (2) and pestheic acid (3), have been isolated from the plant endophyte Pestalotiopsis fici. The structure of 1 was determined by NMR spectroscopy and X-ray crystallography. Biogenetically, 1 could be derived from the Diels-Alder adduct of 2 and 3.     

Vibrational Stark Effects on Carbonyl, Nitrile, and Nitrosyl Compounds Including Heme Ligands, CO, CN, and NO, Studied with Density Functional Theory

Changes in the matrix electric field in a protein, due for example to mutations or structural fluctuations, can be correlated with changes in the vibrational transition frequencies of suitable chromophores measured by IR spectroscopy through the Stark tuning rate. To make this correlation, the Stark tuning rate must be known from experiment or theory. In this paper, density functional theory at the B3LYP/TZV level of theory is used to compute the Stark tuning rate of adducts of heme porphyrin, namely, -CO, -CN, and -NO+ compounds. The results are compared with the corresponding vibrational frequencies-field dependencies from vibrational Stark spectroscopy of heme-proteins. The zero-field computed Stark tuning rate of 1.3 cm-1/MV/cm for heme-CO is in agreement with experiment, where typically the rate is 2.4/f cm-1/MV/cm for myoglobin, where f is a local field correction between 1.1 and 1.4. Several small nitrile, carbonyl, and dinitrile molecules were studied to rationalize the findings for the heme-adducted models. Here, the higher B3LYP/6-311++G(2d,2p) level of theory could be used so the agreement with recent experimental results is even better than for heme-adducted groups.     

Vibrational spectra and structures of H2O-NO, HDO-NO, and D2O-NO complexes. An IR matrix isolation and DFT study

The IR spectra of H2O+NO, HDO+NO, and D2O+NO, isolated in solid neon at low temperature have been investigated. Concentration effects and detailed vibrational analysis of deuterated and partially deuterated species allowed identification of three 1:1 HDO-NO species, two 1:1 D2O-NO species, and only one 1:1 H2O-NO complex. From comparison between the experimental spectra and the results of DFT calculations, it appeared that two different types of weakly bound complexes between water and nitric oxide can be formed in a neon matrix. The first species is a 1:1 complex where bonding occurs between water hydrogen and nitric oxide nitrogen, in which OH-N and OD-N intermolecular bonds are engaged. For this complex only DOD-NO, HOD-NO, and DOH-NO isotopic species have been experimentally detected and no IR bands of HOH-NO were observed. This result could be explained by the fact that the dissociation energy of HOH-NO is lower than those of DOD-NO, HOD-NO and DOH-NO. For the second detected 1:1 H2O-NO complex and its isotopic variants, the H2O-NO potential surface was explored systematically at the B3LYP level, but no stable species corresponding to the complex could be calculated. The structure of the second observed 1:1 H2O-NO complex results from columbic attractions between water and nitric oxide and could be stabilized only in matrix, probably by interaction between NO, water and (Ne)n.     

Alizarin-s,a reagent for thorium. a gravimetric,colorimetric, and spectrophotometric study

The claim of Beck in the use of alizarin-S for separating cerite earths from thorium could not be substantiated. Detailed conditions for estimating from 0.0095 to 6.3 mg of thorium dioxide in 50 ml of solution by the method of Rao and Murthy are described. The absorption characteristics of alizarin-S and its-thorium complex have been studied in their dependance on pH. The thorium complex has been shown by adopting different optical methods to correspond to Th-Al-S (a stoichiometric ratio of 1:1) which is also confirmed from gravimetric analyses. The dissociation coefficient of the complex at pH 2.7 has been computed to be less than 1.10^-8.     

莲子草假隔链格孢毒素的分离纯化与结构鉴定

从莲子草假隔链格孢(Nimbya alternantherae)中分离纯化了一种毒素物质, 并对其进行了结构鉴定, 为研究其致病机理及进一步的化学合成奠定了基础.     

Thin-layer chromatographic screening method for the tranquillizers azaperone, propiopromazine and carazolol in pig tissues

A procedure is described for the detection of azaperone, propiopromazine and carazolol in pig muscle, liver and kidney tissue. The method comprises extraction from an alkaline tissue homogenate with diethyl ether, followed by cleaning up and concentration of the extract on a silica gel solid-phase extraction column. Two-dimensional thin-layer chromatography on a silica plate was used for the detection of the tranquillizers. Detection levels were 25 micrograms kg-1 for propiopromazine, 50 micrograms kg-1 for azaperone (or its metabolite azaperol) and 125 micrograms kg-1 for carazolol. In pigs treated with the usual doses the presence of propiopromazine and azaperol could be established in kidney tissue 8 h after administration, whilst in injection sites all three tranquillizers could be detected.     

Hydroxy-1-aminoindans and derivatives: preparation, stability, and reactivity

The chemical stability and reactivity of hydroxy-1-aminoindans and their N-propargyl derivatives are strongly affected by the position of the OH group and its orientation relative to that of the amino moiety. Thus, the 4- and 6-OH regioisomers were found to be stable, while the 5-OH analogues were found to be inherently unstable as the free bases. The latter, having a para orientation between the OH and the amino moieties, could be isolated only as their hydrochloride salts. 7-Hydroxy-1-aminoindans and 7-hydroxy-1-propargylaminoindans represent an intermediate case; while sufficiently stable even as free bases, they exhibit, under certain experimental conditions, unexpected reactivity. The instability of the 5- and 7-hydroxy-aminoindans is attributed to their facile conversion to the corresponding, reactive quinone methide (QM) intermediates. The o-QM obtained from 7-hydroxy-aminoindans was successfully trapped with ethyl vinyl ether via a Diels-Alder reaction to give tricyclic acetals 32a,b.     

Single crystals of L-O-serine phosphate X-irradiated at low temperatures: EPR, ENDOR, EIE, and DFT studies

Single crystals of the phosphorylated amino acid L-O-serine phosphate were X-irradiated and studied at 10 K and at 77 K using EPR, ENDOR, and EIE techniques. Two radicals, R1(10 K) and R1(77 K), were detected and characterized as two different geometrical conformations of the protonated reduction product >CH-C(OH)(2). R1(10 K) is only observed after irradiation at 10 K, and upon heating to 40 K, R1(10 K) transforms rapidly and irreversibly into R1(77 K). The transition from R1(10 K) to R1(77 K) strongly increases the isotropic hyperfine coupling of the C-CH(beta) coupling (Delta = 32 MHz) and the major C-OH(beta) coupling (Delta = 47 MHz), in sharp contrast to the their much reduced anisotropic hyperfine couplings after the transition. An umbrella-like inversion of the carboxylic acid center, accompanied by minor geometrical adjustments, explains the changes of these observed isotropic and anisotropic couplings. DFT calculations were done on the reduced and protonated L-O-serine phosphate radical at the B3LYP/6-311+G(2df,p)//B3LYP/6-31+G(d) level of theory in order to support the experimental observations. Two different conformations of the anion radical, related by an inversion at the carboxylic center, could be found within the single molecule partial energy-optimization scheme. These two conformations reproduce the experimental hyperfine couplings from radicals R1(10 K) and R1(77 K). A third radical, radical R2, was observed experimentally at both 10 and 77 K and was shown to be due to the decarboxylated L-O-serine phosphate oxidation product, a conclusion fully supported from the DFT calculations. Upon thermal annealing from 77 to 295 K, radicals R1(77 K) and R2 disappeared and all three previously observed room-temperature radicals could be observed. No phosphate-centered radicals could be observed at any temperatures, indicating that the phosphate-ester bond break for one of the room-temperature radicals does not occur by dissociative electron capture at the phosphate group.     

Synthesis, characterization, physicochemical, and photophysical studies of redox switchable NIR dye derived from a ruthenium-dioxolene-porphyrin system

Newly synthesized semi-quinone derivatives of the ruthenium polypyridyl, covalently linked to a porphyrin core, show very high epsilon values (59,000-83,500 M(-1)cm(-1)) for the absorption band in the near infrared (NIR) region of the spectrum. Further, complexes 1-4 show an interesting reversible electrochromic behavior as a function of the redox state of the coordinated dioxolene functionality, and a switching phenomenon between bleaching and the restoration of the NIR peak could be achieved electrochemically. Thus, complexes 1-4 could be ideal candidate materials for NIR-active electrochromic devices. Ultrafast studies on 1 and its mononuclear components, 5-(3,4-dihydroxyphenyl)-10,15,20-triphenyl-21H,23H-porphyrin (H2L1) and Ru(bpy)2(bsq)+, reveal that there is no electron or energy transfer from the porphyrin to the Ru(bpy)2sq+ (bpy is 2,2'-bipyridine and sq is the deprotonated species of a substituted semi-quinone fragment) fragment or vice versa in 1. The observed decrease in the luminescence quantum yield for 1 compared to that of H2L1 can be ascribed to the increased nonradiative pathway due to higher vibronic coupling because of the direct linkage of the metal center to the porphyrin moiety.     

Magnesium sulfate aerosols studied by FTIR spectroscopy: hygroscopic properties, supersaturated structures, and implications for seawater aerosols

Supersaturated MgSO4 aerosols and dilute MgSO4 solutions were studied by FTIR spectroscopic techniques (i.e., aerosol flow tube (AFT) and attenuated total reflection (ATR)). The hygroscopic properties of MgSO4 aerosols were investigated with results in good agreement with previous measurements by a scanning electrodynamic balance (SEDB). Well-defined spectral evolutions with changing relative humidity (RH) for the v3 band of SO4(2-) and the water O-H stretching envelope could be directly related to the observed hygroscopic properties of MgSO4 aerosols. When the RH decreased from approximately 55 to approximately 40%, the v1 band of SO4(2-) in supersaturated MgSO4 aerosols was observed to transform from a sharp peak at approximately 983 cm(-1) into a wide band at approximately 1005 cm(-1). The sharp peak at approximately 983 cm(-1) was mainly assigned to such associated complexes of Mg2+ and SO4(2-) as double solvent-separated ion pairs (2SIPs), solvent-shared ion pairs (SIPs), and simple contact ion pairs (CIPs) in supersaturated MgSO4 aerosols, while the wide band at approximately 1005 cm(-1) was due to polymeric CIPs chains, probably the main component of gels formed in MgSO4 aerosols at low RHs. Relating to this v1 band transformation, the peak position of the v(3) band was first shown to be a sensitive indicator of CIPs formation, spanning across approximately 40 cm(-1) on the formation of polymeric CIPs chains, which could also be supported by aerosol composition analysis in the form of water-to-solute molar ratios (WSR). In the water O-H stretching envelope, the absorbance intensities at 3371 and 3251 cm(-1) were selected to represent contributions from weak and strong hydrogen bonds, respectively. The absorbance intensity ratio changing with RH of 3371 to 3251 cm(-1) could be related to the previous observations with the v1 and v3 bands of SO4(2-). As a result, the formation of CIPs with various structures in large amounts was supposed to significantly weaken hydrogen bonds in supersaturated MgSO4 aerosols, while 2SIPs and SIPs were not expected to have similar effects even when occurring in abundance. In comparison with MgSO4 aerosols, the peak positions of the v3 band of SO4(2-) in artificial seawater aerosols implied that the MgSO4 component should be contained as gels or concentrated solutions in the fissures of microcrystals of sea salts for freshly formed seawater aerosols at low RHs.     

Heterocycle-substituted stable thioaminyl radicals: isolation, ESR spectra, and magnetic properties(1)

N-[(2-Benzothiazolyl)thio]- (1), N-[(2-benzoxazolyl)thio]- (2), and N-(2-pyrimidylthio)-2,4,6-trisubstituted-phenylaminyls (3) were generated by oxidation of the corresponding amines. Although 2 and 3 were not sufficiently persistent to be isolated, 1 was very persistent and could be isolated as radical crystals. The ESR spectra of nondeuterated and partially deuterated 1-3 radicals were measured, and the spin density distributions were estimated from the hyperfine coupling constants. Ab initio molecular orbital calculations were made for 1 to discuss the spin density distribution in more detail. Single-crystal X-ray crystallographic analysis was performed for one radical. Magnetic properties were measured for isolated four radicals with a SQUID. Two radicals showed ferromagnetic interaction, and analyses of chiT vs T plots with the one-dimensional regular Heisenberg model gave 2J/k(B) = 5.8 and 8.6 K. The remaining two radicals showed antiferromagnetic interaction. Analyses of the chiT vs T plots with the Curie-Weiss law or dimer model gave theta = -1.4 K and 2J/k(B) = -1370 K. The strong antiferromagnetic interaction could be explained in terms of the X-ray crystallographic results.     

Synthesis, characterization, and catalytic application of PbS nanoparticles for the synthesis of amidoalkyl naphthols under solvent-free conditions

A simple one-pot synthesis has been developed for the synthesis of amidoalkyl naphthols using an efficient and recyclable nanocrystalline PbS catalyst under solvent-free condition. Using this nanocrystalline solid catalyst, the reactions could be carried out under mild reaction conditions with very good yield (85–95 %). This catalyst could be recycled very easily, which makes this methodology environmentally benign. The biologically active drug-like molecule 1-aminomethyl-2-naphthol derivatives can be easily obtained from 1-amidomethyl-2-naphthol by amide hydrolysis reaction in the presence of PbS nanoparticles. Characterization of the catalyst was performed by X-ray diffraction, transmission electron microscopy, and adsorption/desorption analysis (BET).     

Biradicals/zwitterions from thermolysis of enyne-isocyanates. Application to the synthesis of 2(1H)-pyridones, benzofuro[3,2-c]pyridin-1(2H)-ones, 2,5-dihydro-1H-pyrido[4,3-b]indol-1-ones, and related compounds

Thermolysis of benzannulated enyne-isocyanates 13 and enyne-isocyanates 36 and 37 promoted the cycloaromatization reactions to generate in situ O,4-didehydro-2-hydroxyquinolines and O,4-didehydro-2-hydroxypyridines, respectively, as reactive intermediates. These cycloaromatized intermediates could be captured either as biradicals and/or as zwitterions depending on the nature of the substituent at the alkynyl terminus. The intermediate derived from cycloaromatization of 13a bearing a phenyl substituent could be regarded as biradical 14, which then abstracts hydrogen atoms from gamma-terpinene leading to 2(1H)-quinolinone 15. Alternatively, the same intermediate could also be regarded as zwitterion 14', which then undergoes an initial hydride abstraction from gamma-terpinene followed by protonation to produce 15. The presence of a 2-phenylethyl substituent in 13b and 37a or a 2-methylphenyl substituent in 37b also allowed the resulting intermediates to be captured intramolecularly either as biradicals or as zwitterions, producing 2(1H)-quinolinone 19, 2(1H)-pyridone 39, and benzopyranopyridine 43, respectively. On the other hand, with a 2-methoxyphenyl, a 2-(dimethylamino)phenyl, or a 3-methoxypropyl substituent, the chemical behavior of the cycloaromatized adduct could be best accounted for in terms of a zwitterionic intermediate leading to benzofuro[3,2-c]quinolin-6(5H)-one (20), 5,11-dihydro-11-methyl-6H-indolo[3,2-c]quinolin-6-one (25), benzofuro[3,2-c]pyridin-1(2H)-one 44, 2,5-dihydro-2,5-dimethyl-1H-pyrido[4,3-b]indol-1-one 46, and related compounds. Interestingly, thermolysis of 37f bearing a 2-(methoxymethyl)phenyl substituent at the alkynyl terminus produced the unexpected benzopyranopyridine 56 as the major product in a process involving the cleavage of the bond between the methoxyl oxygen and the adjacent methylene carbon. The efficiency and selectivity of the cycloaromatization reaction could also be enhanced by the introduction of 1.1 to 10 equiv of dimethylphenylsilyl chloride to the reaction mixture to capture the resulting zwitterion.     

Novel stereochemistry, reactivity, and stability of an arsenic heterocycle in a metal-promoted asymmetric cycloaddition reaction

The organopalladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]phenylene as the chiral auxiliary has been used as the chiral template to promote the asymmetric cycloaddition reaction between diphenylvinylphosphine and 3,4-dimethyl-1-phenylarsole. A diphenylphosphino-substituted asymmetrical heterobidentate arsanorbornene (As-P) ligand was obtained stereoselectively on the chiral palladium template in moderate yield. The chiral benzylamine auxiliary could be removed chemoselectively from the template by treatment with HCl to produce the neutral complex [(As-P)PdCl2]. In contrast to their reported P-P analogue, the arsenic donor in the dichloro complex could be eliminated stereospecifically under mild reaction conditions to generate the corresponding 1-(diphenylphosphino)-3,4-dimethyl-2,4-cyclohexadiene, which remained as a bidentate ligand at the PdCl2 unit via phosphorus and the eta2-C4-C5 double bond. The arsenic-elimination process was found to be influenced by the halo ligand in [(As-P)PdX2]. A similar process was observed with the analogous dibromo complex, but the corresponding diiodo species did not show similar reactivity. All of the novel As-Pd complexes have been characterized by X-ray crystallography.     

Synthesis,structural characterization,and immunological properties of carbon nanotubes functionalized with peptides

Carbon nanotubes (NTs) are becoming highly attractive molecules for applications in medicinal chemistry. The main problem of insolubility in aqueous media has been solved by developing a synthetic protocol that allows highly water-soluble carbon NTs to be obtained. As a result, biologically active peptides can be easily linked through a stable covalent bond to carbon NTs. We have demonstrated that a bound peptide from the foot-and-mouth disease virus, corresponding to the 141-159 region of the viral envelope protein VP1, retained the structural integrity and was recognized by monoclonal and polyclonal antibodies. In addition, this peptide-NT conjugate is immunogenic, eliciting antibody responses of the right specificity. Such a system could be greatly advantageous for diagnostic purposes and could find future applications in vaccine delivery.     

Chromatographic and electrophoretic studies of immune complexes in non-A, non-B hepatitis

Immune complexes isolated from two patients with chronic non-A, non-B hepatitis, one patient with acute non-A, non-B hepatitis and one patient with juvenile rheumatoid arthritis were examined by means of a combined chromatographic and electrophoretic method. Both analyses showed the presence of complexes consisting of IgG, IgM, complement c1q factor and albumin; no antigen constituents were detected. The IgG-to-IgM ratio varied from 1:1 to 4:1, suggesting that one could be dealing with complexes of both IgG-IgM and IgG-IgG types. Moreover, the detectable presence of c1q factor might indicate that such complexes were capable of activating complement.