Metal-Free Phosphination and Continued Functionalization of Pyridine: A Theoretical Study

This study investigates the mechanism of metal-free pyridine phosphination with P(OEt)₃, PPh₃, and PAr₂CF₃ using density functional theory calculations. The results show that the reaction mechanism and rate-determining step vary depending on the phosphine and additive used. For example, phosphination of pyridine with P(OEt)₃ occurs in five stages, and ethyl abstraction is the rate-determining step. Meanwhile, 2-Ph-pyridine phosphination with PPh₃ is a four-step reaction with proton abstraction as the rate-limiting step. Energy decomposition analysis of the transition states reveals that steric hindrance in the phosphine molecule plays a key role in the site-selective formation of the phosphonium salt. The mechanism of 2-Ph-pyridine phosphination with PAr₂CF₃ is similar to that with PPh₃, and analyses of the effects of substituents show that electron-withdrawing groups decreased the nucleophilicity of the phosphine, whereas aryl electron-donating groups increased it. Finally, TfO⁻ plays an important role in the C–H fluoroalkylation of pyridine, as it brings weak interactions.     

ESR study of free radicals formed upon UV irradiation of nitropentafluoroacetone in various solvents

The formation of CF₃C(O)CF₂N(O^.)O₂CF₂C(O)CF₃ free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO₂ anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF₃COCFN(O^–)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF₃COCF₂N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993.     

Kinetic regularities of the heat release during the reactions of aliphatic hydrocarbons with aqueous HNO3

The kinetics of the heat release during the reactions of aqueous HNO₃ withn-heptane andn-octadecane was studied. The kinetic regularities of the reactions of hydrocarbons C₇H₁₆−C₁₈H₃₈ with HNO₃ and the heats of the reactions were described. At all stages, except initial, the hydrocarbon reacts with NO₂ and nitric acid reproduces NO₂ in the reaction with NO. The accumulation of NO₂ results in the acceleration of the process. When the pressure of the hydrocarbon vapor is equilibrium, its reaction with NO₂ can also proceed in the gas phase. The contribution of this reaction to the total heat release was estimated. The additives of aromatic and unsaturated hydrocarbons to aliphatic hydrocarbons increase strongly the initial rate of the heat release and changes slightly the subsequent stages of the process. Naphthenic hydrocarbons have almost no effect on the kinetic parameters of the process. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–40, January, 1998.     

Direct AAS determination of Co, Cr, Cu, Mn and Ni in U3O8 by electrothermal atomization

Summary An atomic absorption spectrometric method has been developed for the determination of chromium, cobalt, copper, manganese and nickel in U₃O₈ by electrothermal atomization of 5 mg powder samples. Nanogram amounts of all the elements can be estimated with a precision ranging between 7–12%. The non-specific absorption due to U₃O₈ for these measurements is negligible. The use of graphite powder with U₃O₈ in equal or double the sample amount improves sensitivity for the analyte element and prolongs the life of the atomizer.

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Direkte AAS-Bestimmung von Co, Cr, Cu, Mn und Ni in U₃O₈ durch elektrothermische Atomisierung

Zusammenfassung Das entwickelte AAS-Verfahren geht von pulverförmigen 5mg-Proben aus. Nanogramm-Mengen der genannten Elemente können mit einer Genauigkeit im Bereich von 7–12% bestimmt werden. Die durch U₃O₈ verursachte unspezifische Absorption ist zu vernachlässigen. Durch Graphitzusatz (in der gleichen oder doppelten Menge der Probe) wird die Empfindlichkeit der Bestimmung verbessert und die Lebensdauer des Atomizers verlängert.

     

Alternativ-Liganden. XXVI [1]. M(CO)4L-Komplexe (M  Cr,Mo, W) der Chelatliganden Me2ESiMe2(CH2)2E′Me2 (Me  CH3; E  P,As; E′  N,P, As)

Alternative Ligands. XXVI. M(CO)₄ L-Complexes (M ? Cr, Mo, W) of the Chelating Ligands Me₂ESiMe₂(CH₂)₂E′ Me₂ (Me ? CH₃; E ? P, As; E′ ? N, P, As) The reaction of M(CO)₄NBD (NBD = norbornadiene; M ? Cr, Mo, W) with the ligands Me₂ESiMe₂(CH₂)₂E′ Me₂ yields the chelate complexes (CO)₄M[Me₂ESiMe₂]) for E,E′ ? P, As, but not for E and /or E′ ? N. The NSi group is not suited for coordination because of strong (p-d)π-interaction. In the case of the ligands with E ? P or As and E′ ? N chelate complexes can be detected in the reaction mixture, but isolable products are complexes with two ligands coordinated via the E donor group. The new compounds are characterized by analytical and spectroscopic (IR, NMR, MS) investigations. The spectroscopic data are also used to deduce the coordinating properties of the ligands. X-ray diffraction studies of the molybdenum complexes (CO)₄Mo[Me₂ESiMe₂(CH₂)₂AsMe ₂] (E ? P, As) in accord with the observed coordination effects show only small differences between SiE and CE donor functions. Attempts to use the ligands Me₂ESiMe₂(CH₂)₂AsMe₂ (E ? P, As) for the preparation of Fe(CO)₃L complexes result in the fission of the SiE bonds and the formation of the binuclear systems Fe₂(CO)₆(EMe₂)₂ (E ? P, As) together with the disilane derivative [Me₂Si(CH₂)₂AsMe₂]₂.     

Molecular and electronic structure of several heterofullerene BNC58 and B2N2C56 oligomers and [B2N2C56] n macromolecule

Molecular and electronic structure of heterofullerene BNC₅₈ (C _s) and B₂N₂C₅₆ (C _2h) monomers, B₂N₂C₁₁₆ and B₄N₄C₁₁₂ dimers, and B₆N₆C₁₆₈ trimer (the last three molecules withC _2h symmetry) was simulated by the MNDO method. Clusters BNC₅₈ and B₂N₂C₅₆ are formed by replacement of carbon atoms participating in one or two of the most distant oppositely lying (6,6)-type C−C bonds in fullerene C₆₀ by B and N atoms. In one of the two studied isomers of the B₂N₂C₁₁₆ dimer, the monomers are linked by the four-membered carbon cycle, while the heteroatoms form the most distant oppositely lying bonds of the dimer. In the other isomer of the B₂N₂C₁₁₆ dimer, as well as in the B₄N₄C₁₁₂ dimer and B₆N₆C₁₆₈ trimer, the monomers are linked by four-membered B₂N₂ cycles with alternation of the atoms. For all the systems studied, the optimum geometric parameters, heats of formation, ionization potentials, and atomic charges were calculated. Dimerization energies of heterofullerenes BNC₅₈ and B₂N₂C₅₆ lie in the range from 33 to 49 kcal mol⁻¹. It was found that the B₂N₂C₁₁₆ dimer, in which the monomers are linked by the four-mernbered carbon cycle, is the most stable system. In the case of B₂N₂C₅₆ trimerization, the energy gain (compared to the triple monomer energy) is about twice as large as the dimerization energy. Molecular structure of the quasi-linear [B₂N₂C₅₆) _n macromolecule was simulated, and extended Hückel calculations of its energy band structure by the crystal orbital method were performed. It was found that the electron energy spectrum is of semiconducting type (the band gap is equal to 1.27 eV. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 431–435, March, 1999.     

Proteomic and Bioinformatic Investigation of Altered Pathways in Neuroglobin-Deficient Breast Cancer Cells

Neuroglobin (NGB) is a myoglobin-like monomeric globin that is involved in several processes, displaying a pivotal redox-dependent protective role in neuronal and extra-neuronal cells. NGB remarkably exerts its function upon upregulation by NGB inducers, such as 17β-estradiol (E2) and H₂O₂. However, the molecular bases of NGB’s functions remain undefined, mainly in non-neuronal cancer cells. Human MCF-7 breast cancer cells with a knocked-out (KO) NGB gene obtained using CRISPR/Cas9 technology were analyzed using shotgun label-free quantitative proteomics in comparison with control cells. The differential proteomics experiments were also performed after treatment with E2, H₂O₂, and E2 + H₂O₂. All the runs acquired using liquid chromatography–tandem mass spectrometry were elaborated within the same MaxQuant analysis, leading to the quantification of 1872 proteins in the global proteomic dataset. Then, a differentially regulated protein dataset was obtained for each specific treatment. After the proteomic study, multiple bioinformatics analyses were performed to highlight unbalanced pathways and processes. Here, we report the proteomic and bioinformatic investigations concerning the effects on cellular processes of NGB deficiency and cell treatments. Globally, the main processes that were affected were related to the response to stress, cytoskeleton dynamics, apoptosis, and mitochondria-driven pathways.     

密度泛函理论及光谱对CuCl2溶液中微团簇的研究

利用密度泛函理论和拉曼光谱对氯化铜溶液第一溶剂化层中的微团簇进行了研究。采用B3LYP方法对溶液中可能存在的团簇构型进行优化,从动力学和热力学方面分析得出溶液中团簇结构信息。理论拉曼光谱在100~500 cm~(-1)主要为Cu—O的伸缩振动峰,3400~4000 cm~(-1)范围内为O—H的对称和不对称伸缩振动。实验光谱在200~340 cm~(-1)出现明显新峰,位于2500~4000 cm-1的O—H伸缩振动峰随着溶液浓度的增加,峰的强度逐渐减小,峰形有明显变化。实验光谱和理论光谱验证和比对,表明溶液的实验光谱中产生的新峰为Cu—O振动,CuCl_2水溶液中产生短程离子相互作用及溶剂化现象,且随着溶液浓度的增加,溶剂化数目减小。     

ChemInform Abstract: Bonding in Clusters. Part 9. The closo-nido Relationship; an MNDO Computational Study.

On the basis of the MNDO results, the role of the four bridging hydrogens in the cluster bonding of B₅H₉ is compared with that of S in SB₅H₅, CH- in (CB₅H₆)-, and BH₂^- in (B₆H₆)₂-.     

Nitro Fatty Acids (NO2-FAs): An Emerging Class of Bioactive Fatty Acids

Unsaturated nitro fatty acids (NO₂-FAs) constitute a category of molecules that may be formed endogenously by the reaction of unsaturated fatty acids (UFAs) with secondary species of nitrogen monoxide and nitrite anions. The warhead of NO₂-FAs is a nitroalkene moiety, which is a potent Michael acceptor and can undergo nucleophilic attack from thiol groups of biologically relevant proteins, showcasing the value of these molecules regarding their therapeutic potential against many diseases. In general, NO₂-FAs inhibit nuclear factorκ-B (NF-κB), and simultaneously they activate nuclear factor (erythroid derived)-like 2 (Nrf2), which activates an antioxidant signaling pathway. NO₂-FAs can be synthesized not only endogenously in the organism, but in a synthetic laboratory as well, either by a step-by-step synthesis or by a direct nitration of UFAs. The step-by-step synthesis requires specific precursor compounds and is in position to afford the desired NO₂-FAs with a certain position of the nitro group. On the contrary, the direct nitration of UFAs is not a selective methodology; thus, it affords a mixture of all possible nitro isomers.     

Organo–Phosphorus–Sulfur Heterocycles by Reactions of Phenylphosphine with Ketones

Abstract

The reaction of phenylphosphine (PhPH₂) with ketones showed conversion into a 5-membered heterocyclic ring of the type P₂SOC if 2–2.5 equivalents of sulfur (S₈) were used. X-Ray data and ³¹P, ¹³C, ¹H NMR spectra proved the formation of the (Z) diastereomer of 1,3,2,4-oxathiadiphospholane 1 ((PhPS)₂SOCMe₂) if acetone is used. Mechanistic studies displayed that small changes in the reaction pathway lead toward the formation and characterization of intermediates including 1,3,2,4,5-dithiatriphospholane, 2,4,5-triphenyl-2-sulfide (PhP)₃S₃ and 1,3,2,4-oxathiadiphospholane, and 5,5-dimethyl-2,4-diphenyl-2-sulfide ((PhPS)(PhP)SOCMe₂), which undergo reactions with acetone, subsequently yielding the abovementioned heterocyclic ring.     

Zur Kenntnis eines Barium-Kupfer-Orthoarsenats: BaCu2(AsO4)2

On the Crystal Structure of Barium-Copper-Orthoarsenate BaCu₂(AsO₄)₂ Single crystals of BaCu₂(AsO₄)₂ were prepared above 1 000°C by CO₂-LASER technique and investigated by X-ray structure determination. The light blue crystals show monoclinic symmetry, space group C? P2₁/n, a = 4.752; b = 8.506; c = 8.945 Å; β = 93.49°, Z = 2. BaCu₂(AsO₄)₂ represents a hitherto unknown structure type with Cu²⁺ in trigonal bipyramidal coordination. Ba²⁺ shows an 8 + 2 surrounding by O^2? and As⁵⁺ is tetrahedrally coordinated. The crystal structure is discussed with respect to related orthophosphates and vanadates.     

Isolation of a Nitromethane Anion in the Calix-Shaped Inorganic Cage

A calix-shaped polyoxometalate, [V₁₂O₃₂]⁴⁻ (V12), stabilizes an anion moiety in its central cavity. This molecule-sized container has the potential to control the reactivity of an anion. The highly-reactive cyanate is smoothly trapped by V12 to form [V₁₂O₃₂(CN)]⁵⁻. In the CH₃NO₂ solution, cyanate abstracts protons from CH₃NO₂, and the resultant CH₂NO₂⁻ is stabilized in V12 to form [V₁₂O₃₂(CH₂NO₂)]⁵⁻ (V12(CH₂NO₂)). A crystallographic analysis revealed the double-bond characteristic short bond distance of 1.248 Å between the carbon and nitrogen atoms in the nitromethane anion in V12. ¹H and ¹³C NMR studies showed that the nitromethane anion in V12 must not be exchanged with the nitromethane solvent. Thus, the V12 container restrains the reactivity of anionic species.     

Poly(ethylene oxide) electrolytes containing mixed salts

An unusual conductivity enhancement occurs in PEO-based ZnBr₂/LiBr electrolytes of composition, [xZnBr₂ + (1 ? x)LiBr](PEO)₁₆ with x = 0.00, 0.05, 0.50, 0.75, 1.00. The conductivity of the mixed-salt electrolytes is higher than that of either pure salt electrolyte. The highest conductivity, observed for x = 0.5, is two orders of magnitude higher than that of pure LiBr(PEO)₁₆ and one order higher than ZnBr₂(PEO)₁₆. In contrast, the conductivity of mixed Mg (CIO₄)₂/LiCIO₄ electrolytes, [xMg(CIO₄)₂ + (1 ? x) LiCIO₄](PEO)₁₆ where x = 0.00, 0.20, 0.50, 0.80, 1.00, increases monotonically with the mole fraction of the higher conductivity component, LiCIO₄(PEO)₁₆. The conductivity and differential scanning calorimetry (DSC) results suggest that the conductivity enhancement in the ZnBr₂/LiBr electrolytes results from a change in charge carrier type and concentration, whereas the conductivity change in the Mg(CIO₄)₂/LiCIO₄ electrolytes arises from a change in the microscopic viscosity of the electrolytes. © 1993 John Wiley & Sons, Inc.     

Synthese und Kristallstruktur von Ba25Cu142+Cu43+Zn4O49

Synthesis and Crystal Structure of Ba₂₅Cu₁₄²⁺Cu₄³⁺Zn₄O₄₉ Single crystals of Ba₂₅Cu₁₄²⁺Cu₄³⁺Zn₄O₄₉ were prepared with solid state and flux reactions. X-ray investigations show tetragonal symmetry, space group D⁷_4th–P4/nmm, a = 18.2146, c = 9.3230 Å, Z = 2. The hitherto unknown structure type shows copper in square pyramids and planar polygones, connected to six member rings or Cu₅O₂₀ groups. Slightly bent Cu₅O₁₂ groups produced by edge connection of five CuO₄ polygones are connected with ZnO₄ tetrahedra forming Cu₅Zn₄O₂₀ units. The complicated structure is shown step by step.     

钳形酰腙类阴离子受体的合成及识别性质研究

设计合成了基于吲哚酰腙单元的钳形阴离子受体(1),UV-Vis滴定实验表明,它在含1%DMSO的CH3CN溶液中能选择性识别具有重要生物学意义的F-、Ac O-和H2PO4-(结合比均为1∶1且Ka104L/mol),但对Cl-、Br-、I-、NO3-、N3-、HSO4-和Cl O4-无识别作用。与它相比,端基为苯并呋喃的参照化合物2在同样溶剂中对上述3种阴离子的亲和性减弱,尤其是对H2PO4-。核磁滴定实验表明,受体1中的吲哚环NH和酰胺NH能产生协同效应,从而对阴离子产生了强效键合作用。     

ChemInform Abstract: Identification of Diborane(4) with Bridging B—H—B Bonds.

Photolysis of B₂H₆ dispersed in solid neon with far‐UV light (120—220 nm) at 3 K leads to the formation of B₂H₄, which is characterized by IR spectroscopy and B3LYP quantum chemical computations.     

New Experimental Conditions for Diels–Alder and Friedel-Crafts Alquilation Reactions with Thiophene: A New Selenocyanate with Potent Activity against Cancer

The reactivity of thiophene in Diels-Alder reactions is investigated with different maleimide derivatives. In this paper, we have synthesized for the first time the Diels–Alder adducts of thiophene at room temperature and atmospheric pressure. Maleimido–thiophene adducts were promoted by AlCl₃. The effects of solvent, time, temperature and the use of different Lewis acids were studied, showing dramatic effects for solvent and Lewis acid. Furthermore, the catalysis with AlCl₃ is highly stereoselective, preferably providing the exo form of the adduct. Additionally, we also discovered the ability of AlCl₃ to catalyze the arylation of maleimides to yield 3-aryl succinimides in a straightforward manner following a Friedel–Crafts-type addition. The inclusion of a selenocyanate group contributes to the cytotoxic activity of the adduct. This derivatization (from compound 7 to compound 15) results in an average GI₅₀ value of 1.98 µM in the DTP (NCI-60) cell panel, resulting in being especially active in renal cancer cells.     

Cinnamal Sensing and Luminescence Color Tuning in a Series of Rare-Earth Metal−Organic Frameworks with Trans-1,4-cyclohexanedicarboxylate

Three isostructural metal–organic frameworks ([Ln₂(phen)₂(NO₃)₂(chdc)₂]·2DMF (Ln³⁺ = Y³⁺ for 1, Eu³⁺ for 2 or Tb³⁺ for 3; phen = 1,10-phenanthroline; H₂chdc = trans-1,4-cyclohexanedicarboxylic acid) were synthesized and characterized. The compounds are based on a binuclear block {M₂(phen)₂(NO₃)₂(OOCR)₄} assembled into a two-dime nsional square-grid network containing tetragonal channels with 26% total solvent-accessible volume. Yttrium (1)-, europium (2)- and terbium (3)-based structures emit in the blue, red and green regions, respectively, representing the basic colors of the standard RGB matrix. A doping of Eu³⁺ and/or Tb³⁺ centers into the Y³⁺-based phase led to mixed-metal compositions with tunable emission color and high quantum yields (QY) up to 84%. The bright luminescence of a suspension of microcrystalline 3 in DMF (QY = 78%) is effectively quenched by diluted cinnamaldehyde (cinnamal) solutions at millimolar concentrations, suggesting a convenient and analytically viable sensing method for this important chemical.     

Phosphaniminato-Komplexe des Zinks mit Hydrido-, Alkinylo-, Alkenylo- und Amido-Liganden

Phosphoraneiminato Complexes of Zinc with Hydrido, Alkynylo, Alkenylo, and Amido Ligands Synthesis and properties of the phosphoraneiminato complexes [ZnCl(NPMe₃)]₄ ( 1 ), [ZnH(NPMe₃)]₄ ( 2 ) as well as of the alkynylo derivatives [Zn(C≡C–SiMe₃)(NPMe₃)]₄ ( 3 ), [Zn(C≡C–C≡C–SiMe₃)(NPR₃)]₄ [R = Me ( 4 a ), R = Et ( 4 b )], [Zn(C≡C–Ph)(NPMe₃)]₄ ( 5 ) and of the alkenylozinc complexes [Zn(CH=CHMe)(NPR₃)]₄ [R = Me ( 6 a ), R = Et ( 6 b )] are described. According to crystal structure analyses of 1 , 3 , and 4 b these complexes possess heterocubane structures with only slightly distorted Zn₄N₄ cubic skeletons. Experiments to substitute the terminal ligands at the zinc atoms by bis(trimethylsilyl)amido groups lead to disintegration of the heterocubanes and formation of the dimeric complex [Zn(μ₂-NPEt₃){N(SiMe₃)₂}]₂ ( 7 ) and of the trinuclear derivative [Zn₃(μ₂-NPMe₃)₄{N(SiMe₃)₂}₂] ( 8 ), in which the central zinc atom is surrounded by the four N atoms of the NPEt₃^– groups in a spiro-cyclic fashion. 7 and 8 are also characterized by crystal structure analyses.