Synthesis, structure, electrochemistry, and electrochemiluminescence of thienyltriazoles

Four blue-emitting thienyltriazoles with desired N and O coordination atoms were prepared in high yield via click chemistry for potential incorporation into metal complexes. Three of their crystal structures were determined by X-ray crystallography. The electrochemical properties, electronic structures of these thienyltriazoles, 1-4, and their correlations were studied using cyclic voltammetry and differential pulse voltammetry techniques along with density function theory (DFT) calculations. All of the compounds underwent irreversible redox reactions, leading to unstable electrogenerated radical cations and anions. Electrochemical gaps determined from the differences between first formal reduction and oxidation reactions were correlated to HOMO-LUMO energy gaps obtained from UV-vis spectroscopy and the DFT calculations as well as energies of excited states measured from photoluminescence spectroscopy. We observed weak electrochemiluminescence (ECL) from annihilation of these thienyltriazole radicals in acetonitrile containing 0.1 M tetra-n-butylammonium perchlorate as electrolyte. An enhancement in ECL efficiency ranging from 0.16 to 0.50% was observed upon addition of benzoyl peroxide as a coreactant in the above electrolyte solutions. The generation of excimers in solutions of 1-4 was observed as seen by the red-shift in ECL maxima relative to their corresponding photoluminescence peak wavelengths. Our work is of importance for the development of efficient blue-emitting fluorophores via click chemistry that could be potential luminophores in metal complexes.     

Simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals in organometallic compounds

A method for the simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals which combines features of the known intermediate storage technique in organic microanalysis and formation of the metal-oxine complex, is described. Carbon and hydrogen are determined gravimetrically as usual. Sulfur and halogens are absorbed and stored on electrolytic silver. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulfur as sulfur dioxide and halogens as hydrogen halides and regenerates the silver layer. The liberated gases can be easily absorbed by dilute hydrogen peroxide and determined titrimetrically. The metal oxide, remaining in the platinum boat, is dissolved in a mixture of nitric-perchloric acids in a test tube and the metal content is determined gravimetrically and titrimetrically using 8-hydroxyquinoline.     

Synthesis,Structure, Photophysical Properties,and Photostability of Benzodipyrenes

This work explores the syntheses, structures, photophysical properties, and photostability of benzodipyrenes (BDPs). BDPs were synthesized through an InCl₃-AgNTf₂-catalyzed, four-fold alkyne benzannulation reaction. The structures of BDP 4 a and its corresponding endoperoxide product were unambiguously confirmed by X-ray crystallography. The BDPs reported here can also be recognized as peri- and cata-benzannulated pentacenes with a non-functionalized central ring. Unlike the previous reported pentacene-based polycyclic aromatic hydrocarbons, the absorbances of the BDPs were blueshifted by ca. 40 nm relative to pentacene, even after extension of π-conjugation. The newly synthesized BDP products exhibit relatively good stability with half-lives as high as 4612 min in THF.     

Synthesis of new pyrazoles,oxadiazoles, triazoles,pyrrolotriazines, and pyrrolotriazepines as potential cytotoxic agents

4-Oxo-4-phenylbutanehydrazide (1) reacted with many active methylene reagents such as acetylacetone, diethylmalonate, ethylacetoacetate, ethylcyanoacetate, benzoyl-acetonitrile, and malononitrile under neat conditions to afford the corresponding pyrazoles (2–7) , also, treatment of butanehydrazide (1) with electrophilic reagents as triethylorthoformate, dimethylformamide-dimethylacetal, acetic anhydride, and carbon disulfide to give 1,3,4-oxadiazoles (8,10,11) and N′-acetyl-butanehydrazide (9) . Reacted of butanehydrazide (1) with potassium thiocyanate gave 1,2,4-triazoles (12) . Similarly, treatment of (1) with chloroacetamide gave 1,2,4-triazinones (13) . The pyrrolotriazinones (14) was obtained by cyclization of (13) . Also, butanehydrazide ( 1 ) was utilized as a starting material for the synthesized of new Schiff bases as N′-(4-sub-benzylidene)-phenylbutane-hydrazide (15a-c) , which are used as an initiative to prepare new compounds such as 1,2,4-triazepinones (16a-c) , pyrrolotriazepinones (17a-c) , 1,2,4-triazines (18a-c) , and pyrrolotriazines (19a-c) by reacted of (15a-c) with each chloroacetamide or formamide. The chemical structure of the newly prepared compounds was determined through the spectrum data, including IR, NMR, and MS. The prepared compounds were tested for their in vitro antitumor activities. The compounds 17a-c , 16a-c , and 19a-c displayed activity against several types of cancer cell lines.     

Field-flow fractionation of proteins, polysaccharides, synthetic polymers, and supramolecular assemblies

This review summarizes developments and applications of flow and thermal field-flow fractionation (FFF) in the areas of macromolecules and supramolecular assemblies. In the past 10 years, the use of these FFF techniques has extended beyond determining diffusion coefficients, hydrodynamic diameters, and molecular weights of standards. Complex samples as diverse as polysaccharides, prion particles, and block copolymers have been characterized and processes such as aggregation, stability, and infectivity have been monitored. The open channel design used in FFF makes it a gentle separation technique for high- and ultrahigh-molecular weight macromolecules, aggregates, and self-assembled complexes. Coupling FFF with other techniques such as multiangle light scattering and MS provides additional invaluable information about conformation, branching, and identity.     

Reduced ion mobilities of aspartame,cortisone, betamethasone,butylparaben, propylparaben and vanillin

Electrospray ionization IMS coupled to quadrupole mass spectrometry was used to calculate the reduced ion mobilities of aspartame, cortisone, betamethasone, butylparaben, propylparaben and vanillin, a set of organic compounds used as drugs or food additives using 2,6-ditert-butylpyridine (DTBP) as a chemical standard. The K_0’S of these compounds in the literature are either unavailable or unreliable. The importance of using chemical standards to calibrate the ion mobility scale and the use of correct experimental temperatures to calculate ion mobilities are stressed.     

含O-, S-, N-和C-2,3-不饱和糖苷的合成

以3,4,6-三-O-乙酰基-D-葡萄烯糖为原料,(NH₄)₂S₂O₈为催化剂,利用Ferrier重排反应制得一系列含O-, S-,N-和C-2,3-不饱和糖苷,其结构经¹H NMR, IR和MS（ESI）确证。考察了催化剂及其用量,溶剂和温度对产率的影响。结果表明：在最优条件［反应温度80 ℃,乙腈为溶剂,(NH₄)₂S₂O₈为催化剂(1 eq.)］下,3a产率高达83%。     

The certification of the contents of Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl and Cr in a city waste incineration ash

Summary The analysis of ashes being of increasing importance, a reference material was prepared from fly ash of a city waste incinerator. The procedures of preparation, homogeneity and stability testing are described as well as the way of certification of elements of major importance: Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se and Tl.

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Zertifizierung der Gehalte an Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl und Cr in einer Stadtmüll-Verbrennungsasche

Zusammenfassung Da die Analyse von Aschen zunehmend an Bedeutung gewinnt, wurde von der Flugasche einer Stadtmüll-Verbrennungsanlage ein Referenzmaterial hergestellt. Die Methoden der Herstellung sowie der Homogenitätsund Stabilitätsprüfung werden beschrieben und die Art der Zertifizierung der Elemente von hauptsächlicher Bedeutung aufgezeigt (Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl).

     

Preconcentration of gold,silver, palladium,platinum, and ruthenium with organophosphorus extractants

Extraction of noble metals in acid media with new tertiary phosphines and phosphine chalcogenides was examined. Tristyrylphosphine, tristyrylphosphine sulfide tris(2-phenylethyl)phosphine oxide, tris-(2-phenylethyl)phosphine sulfide, bis(2-phenylethyl)[2-(propylthio)ethyl]phosphine oxide, bis(2-phenylethyl)-[2-(butylthio)ethyl]phosphine oxide, and tris[2-(butylthio)ethyl]phosphine oxide were used as extractants. The suitability of the extractants for determination of Au, Ag, and Pd in rock and ore samples was elucidated.     

Synthesis,Structure, Composition,and Properties of Rolivsans

Novel thermosetting resins Rolivsans were prepared, and their structure, composition, and properties were studied. The structural parameters of Rolivsans as influenced by the synthesis conditions were determined.     

Enthalpies of formation, bond dissociation energies, and molecular structures of the n-aldehydes (acetaldehyde, propanal, butanal, pentanal, hexanal, and heptanal) and their radicals

Aldehydes are important intermediates and products in a variety of combustion and gas-phase oxidation processes, such as in low-temperature combustion, in the atmosphere, and in interstellar media. Despite their importance, the enthalpies of formation and bond dissociation energies (BDEs) for the aldehydes are not accurately known. We have determined enthalpies of formation for acetaldehyde, propanal, and butanal from thermodynamic cycles, using experimentally measured reaction and formation enthalpies. All enthalpy values used for reference molecules and reactions were first verified to be accurate to within around 1 kcal mol-1 using high-level ab initio calculations. Enthalpies of formation were found to be -39.72 +/- 0.16 kcal mol-1 for acetaldehyde, -45.18 +/- 1.1 kcal mol-1 for propanal, and -49.27 +/- 0.16 kcal mol-1 for butanal. Enthalpies of formation for these three aldehydes, as well as for pentanal, hexanal, and heptanal, were calculated using the G3, G3B3, and CBS-APNO theoretical methods, in conjunction with bond-isodesmic work reactions. On the basis of the results of our thermodynamic cycles, theoretical calculations using isodesmic work reactions, and existing experimental measurements, we suggest that the best available formation enthalpies for the aldehydes acetaldehyde, propanal, butanal, pentanal, hexanal, and heptanal are -39.72, -45.18, -50.0, -54.61, -59.37, and -64.2 kcal mol-1, respectively. Our calculations also identify that the literature enthalpy of formation of crotonaldehyde is in error by as much as 1 kcal mol-1, and we suggest a value of -25.1 kcal mol-1, which we calculate using isodesmic work reactions. Bond energies for each of the bonds in the aldehydes up to pentanal were calculated at the CBS-APNO level. Analysis of the BDEs reveals the R-CH(2)CH=O to be the weakest bond in all aldehydes larger than acetaldehyde, due to formation of the resonantly stabilized vinoxy radical (vinyloxy radical/formyl methyl radical). It is proposed that the vinoxy radical as well as the more commonly considered formyl and acetyl radicals are important products of aldehyde combustion and oxidation, and the reaction pathways of the vinoxy, formyl, and acetyl radicals are discussed. Group additivity values for the carbon-oxygen-hydrogen groups common to the aldehydes are also determined. Internal rotor profiles and electrostatic potential surfaces are used to study the dipole induced dipole-dipole interaction in the synperiplanar conformation of propanal. It is proposed that the loss of this dipole-dipole interaction in RC(.-)HCH(2)CH=O radicals causes a ca. 1-2 kcal mol-1 decrease in the aldehyde C-H and C-C bond energies corresponding to RC(.-)HCH(2)CH=O radical formation.     

Comparison of small metal clusters: Ni, Pd, Pt, Cu, Ag, Au

Structures of small clusters of Ni, Pd, Pt, Cu, Ag, and Au with n=2–34 and n=55 atoms are calculated as functions of number of atoms and temperature by the simulated annealing Monte Carlo method using an embedded atom potential.     

Assimilation, dissimilation, and detoxification of formaldehyde, a central metabolic intermediate of methylotrophic metabolism

Methanol is a valuable raw material used in the manufacture of useful chemicals as well as a potential source of energy to replace coal and petroleum. Biotechnological interest in the microbial utilization of methanol has increased because it is an ideal carbon source and can be produced from renewable biomass. Formaldehyde, a cytotoxic compound, is a central metabolic intermediate in methanol metabolism. Therefore, microorganisms utilizing methanol have adopted several metabolic strategies to cope with the toxicity of formaldehyde. Formaldehyde is initially detoxified through trapping by some cofactors, such as glutathione, mycothiol, tetrahydrofolate, and tetrahydromethanopterin, before being oxidized to CO2. Alternatively, free formaldehyde can be trapped by sugar phosphates as the first reaction in the C1 assimilation pathways: the xylulose monophosphate pathway for yeasts and the ribulose monophosphate (RuMP) pathway for bacteria. In yeasts, although formaldehyde generation and consumption takes place in the peroxisome, the cytosolic formaldehyde oxidation pathway also plays a role in formaldehyde detoxification as well as energy formation. The key enzymes of the RuMP pathway are found in a variety of microorganisms including bacteria and archaea. Regulation of the genes encoding these enzymes and their catalytic mechanisms depend on the physiological traits of these organisms during evolution.     

Pigmentation of White,Brown, and Green Chicken Eggshells Analyzed by Reflectance,Transmittance, and Fluorescence Spectroscopy

We report on the reflectance, transmittance and fluorescence spectra (λ=200–1200 nm) of four types of chicken eggshells (white, brown, light green, dark green) measured in situ without pretreatment and after ablation of 20–100 μm of the outer shell regions. The color pigment protoporphyrin IX (PPIX) is embedded in the protein phase of all four shell types as highly fluorescent monomers, in the white and light green shells additionally as non-fluorescent dimers, and in the brown and dark green shells mainly as non-fluorescent poly-aggregates. The green shell colors are formed from an approximately equimolar mixture of PPIX and biliverdin. The axial distribution of protein and colorpigments were evaluated from the combined reflectances of both the outer and inner shell surfaces, as well as from the transmittances. For the data generation we used the radiative transfer model in the random walk and Kubelka-Munk approaches.     

High frequency t1tration and estimation of ions: Determination of barium,lead, thallium,calcium, cerium,copper and silver

Solutions of potassium chromate, ammonium oxalate and ferrocyanide are used as titrants for the high frequency titration of metal ions. Lead and barium, up to 20 mg, and thallium, up to 50 mg, are estimated with chromate und yield good results. Similarly, ammonium oxalate behaves satisfactorily when the concentration of calcium is not more than 10 mg and that of cerium is between 10 and 40 mg. Copper and silver can be titrated by ferrocyanide only up to a concentration of 10 and 20 mg, respectively. In all cases, the pH of the solution should preferably be between 6.0 and 6.5, though it can be extended in some cases to as low as 5.0.     

Thin-layer chromatographic separation of aldrin,dieldrin, γ-hexachlorocyclohexane,malathion, ethyl-parathion,pentachlorophenol, and of chlordane,dieldrin, γ-hexachlorocyclohexane,malathion, ethyl-parathion,and pentachlorophenol from each other

A thin-layer chromatographic method is reported for the separation of aldrin (or chlordane), dieldrin, γ-hexachlorocyclohexane, malathion, ethyl-parathion, and pentachlorophenol from each other. The procedure, however, does not separate aldrin and chlordane from each other although it does separate either pesticide from the other components. The method employs alumina plates with n-hexane:xylene:benzene:toluene:cyclohexane:methyl cyclohexane (50:50:50:50:50:50:) as developing solvent.     

In silico modeling of p450 substrates, inhibitors, activators, and inducers

Cytochrome P450 enzymes are the predominant mediators of phase I metabolism of exogenous small molecules. As a result of their extensive role in metabolism of xenobiotics, drug compounds, and endogenous compounds, as well as their wide tissue distribution, significant drug discovery resources are spent to avoid interacting with this class of enzymes. Here we review historical and recent in silico modeling of 7 cytochrome P450 enzymes of particular interest, specifically CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. For each we provide a brief biological background including known inhibitors, substrates, and inducers, as well as details of computational modeling efforts and advances in structural biology. We also provide similar details for 3 nuclear receptors known to regulate gene expression of these enzyme families.     

Synthesis, Analgesic, and Antiparkinsonian Profiles of Some Pyridine, Pyrazoline, and Thiopyrimidine Derivatives

Summary. A series of substituted pyridine, pyrazoline, and thiopyrimidine derivatives were synthesized from 3-acetylpyridine, which was prepared from nicotinic acid as a naturally starting material. The pharmacological screening showed that many of these compounds have good analgesic and antiparkinsonian activities comparable to Voltarene^? and Benzatropine^? as reference drugs. The structure assignment of the new compounds is based on chemical and spectroscopic evidence. The detailed synthesis, spectroscopic data, and pharmacological properties for synthesized compounds are reported.     

Inorganic,Organometallic, and Organic Analogues of Carbenes

This review deals with inorganic, organometallic, and organic compounds, as well as with elements, that on the basis of their electronic structure and their reactions can be regarded formally as analogues of carbenes. These “carbene analogues” include in particular the compounds of monovalent boron, aluminum, nitrogen, and phosphorus; those of divalent silicon, germanium, tin, and lead; atomic oxygen; atomic sulfur; and atomic selenium. The preparation and chemical properties of the carbenes and their analogues are compared.