Biographical radiation-induced defect formation as a method for the activation of red phosphorus in reactions with arylalkenes

Russian Chemical Bulletin -     

Synthesis of organic phosphines and phosphine oxides from elemental phosphorus and phosphine in the presence of strong bases

Data on the reactions of elemental phosphorus and phosphine with electrophilic reagents are described systematically and analyzed. These reactions occur in the presence of strong bases and yield primary, secondary, and tertiary phosphines and phosphine oxides. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1695–1702, September, 1998.     

A low-temperature synthesis-induced defect formation strategy for stable hierarchical porous metal-organic frameworks

A stable hierarchical porous metal-organic framework PCN-56 with abundant Lewis acid sites was synthesized by the low-temperature synthesis-induced defect formation method. It exhibits good adsorption capacity for dyes and high loading capacity toward macromolecular drugs.     

Novel C-H activation and C-S formation reactions on disulfide and diselenide ligands in dinuclear ruthenium complexes

The C-S bond formation reactions of the transition metal sulfides with organic molecules are collected and reviewed to understand the reactivity of the sulfide ligands supported by the transition metals. As an example of the role of the sulfide, the C-H bond activation is focused and discussed.     

A method for semi-continuous measurement of dissolved elemental mercury in industrial and natural waters

Mercury in aqueous systems can be present in different chemical forms. Of these, dissolved elemental Hg(0) (DEM) is of great importance because it can readily be partitioned between air and water. Analytical methods used for determining DEM are conventionally based on removal of Hg(0) by purging, pre-concentration on gold and detection by either cold vapour atomic absorption (CV-AAS) or atomic fluorescence spectrophotometry (CV-AFS). At present, there is no agreed protocol for the measurement of DEM in aqueous samples. A new method is described here, which is based on continuous stripping of DEM by mercury-free nitrogen in a flow injection mode and detection by CV-AAS. The partitioning of DEM between aqueous and gas phases is largely dependent on the composition of the former. Moreover, calibration using the standard addition method is not possible due to the reactivity of DEM introduced from calibration solutions. Calibration is therefore done by reference measurements using a manual method for DEM involving quantitative removal and CV-AFS detection. DEM is then determined in the water sample by applying the partitioning factor. The optimised method is precise, sensitive and linear over a wide concentration range. It has provided comparable results with the manual method when applied on board a research vessel in the Mediterranean Sea (0.02–0.05 ng L^?1) and during a pilot laboratory-scale experiment on industrial aqueous media from wet flue gas desulphurisation (WFGD) equipment (2–300 ng L^?1).     

Effect of heterovalent doping on photostimulated defect formation in CsPbBr3

Two series of CsPbBr₃ perovskites doped with Bi or Ag were synthesized and investigated for photostimulated defect formation. It was demonstrated that the type and concentration of dopants strongly affect the absorption spectra and kinetics of photostimulated defect formation.     

食品中磷的检测方法

磷是人体内的重要元素之一,对人体生命活动有十分重要的作用,如何快速、简便、准确、灵敏地检测食品中磷的含量已经引起了世界各国的重视.本文总结了前人的研究工作,概述了近年来食品中总磷及有机磷农药的检测研究进展,分析了各种检测方法的优势和局限性,展望了未来该领域研究的发展趋势.     

Intermediate carbene formation in the reaction of thioamides with phosphorus (III) derivatives: Quantum chemical investigation

The reactions of perfluoroalkyl thioamides with trimethyl phosphine, trimethyl phosphite, and tris(dimethylamino)phosphine have been analyzed by means of quantum chemical (DFT and MP2) calculations. The reaction seems to proceed via the nucleophilic attack of the electrophilic carbon atom by the phosphorus lone pair with the formation of cyclic or acyclic adducts. The latter releases the thiophosphate molecule forming perfluoroalkylaminocarbene as the short‐lived intermediate. The reaction of the carbene with the second molecule of trialkyl phosphite yields phosphorus ylide. The ylide undergoes a migration of fluorine from carbon to phosphorus. The reactions of perfluoroalkyl thioamides with phosphines and tris(dimethylamino)phosphine probably proceeds differently. Using alkyl thioamides or amides instead of perfluoroalkyl thioamides also makes the reaction less favorable. The only combination of perfluoroalkyl thioamides with trialkyl phosphite fulfills both the kinetic requirements (moderate activation energies and relative energies for intermediates) and the thermodynamic aspects (higher stabilities of the reaction products compared with the starting materials). © 2013 Wiley Periodicals, Inc.     

Ligand oxidation as a method for intramolecular activation of metal complexes

The results of investigations of organometallic and coordination compounds whose ligands contain redox fragments based on 2,6-di-tert-butylphenol and linked to the metal by various coordinating groups are summarized. The redox properties of -aryl, - and -allyl complexes, -diketonates, hydrazides, hydroxamates, glyoximates, and metalloporphyrins and metallophthalocyanines are considered. The possibility of changing the reactivity of organometallic and coordination compounds by changing the magnetic state due to oxidation of the redox-active phenolic group in the ligand is demonstrated. It is proposed to use ligand oxidation as a method for intramolecular activation of metal complexes.     

Optimisation of solid-state urea clathrate formation as a chemical separation method coupled to compound-specific stable carbon isotope analysis

Solid-state urea clathrate formation (SSUCF) as a chemical separation method prior to stable carbon isotope fingerprinting of diesel fuel contaminations was studied. The stable carbon isotope ratios (δ¹³C) of n-alkanes in diesel fuel can be used to trace the origin of a contamination. The accurate measurement of the stable isotopic composition of individual compounds requires baseline separation from any other co-eluting compounds. For this purpose silica gel column chromatography (SGCC) and SSUCF were applied. Detailed optimisation of SSUCF was performed: different activators, clathrate formation temperatures, activator volumes, clathrate formation times and sample capacity were investigated. The main benefits of the developed method are reduced clathrate formation time and increased recoveries for lower molecular weight n-alkanes. The recoveries of the developed SSUCF method ranged between 63 and 100% for C10–C24 n-alkanes with relative standard deviation no more than 7%. The precision of the gas chromatography-isotope ratio mass spectrometry measurement was acceptable with a standard deviation of the δ¹³C values ranging between 0.08 and 0.15‰. The absence of isotopic fractionation was also investigated.

The robustness of the method was tested within a model experiment. Nine different water samples including distilled water, tap water, river water, industrial wastewaters and groundwater samples were spiked with the same diesel fuel. The water samples were extracted with n-hexane and after purification with both SGCC and SSUCF n-alkanes were measured. The δ¹³C values of n-alkanes were found to be similar for all samples. The importance of sample purification prior to compound-specific isotope analysis (CSIA) was also demonstrated within this model experiment by analysing samples from different stages of the sample preparation.

Our results show that the proposed method can remarkably improve the precision of compound-specific stable carbon isotope analysis of n-alkanes originating from diesel contamination of the aquatic environment.     

Modification of the integral isoconversional method to account for variation in the activation energy

Integral isoconversional methods may give rise to noticeable systematic error in the activation energy when the latter strongly varies with the extent of conversion. This error is eliminated by using an integration technique that properly accounts for the variation in the activation energy. The technique is implemented as a modification of the earlier proposed advanced isoconversional method [Vyazovkin, S. J Comput Chem 1997, 18, 393]. The applications of the modified method are illustrated by simulations as well as by processing of data on the thermal decomposition of calcium oxalate monohydrate and ammonium nitrate. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 178–183, 2001     

A practical method for synthesis of stable phosphorus ylides in aqueous media

A convenient one-pot synthesis of stable phosphorus ylides by the condensation of triphenylphosphine with dialkyl acetylenedicarboxylate and CH acids, such as penta-2,4-dione or diethyl propane-1,3-dioate, in the presence of -cyclodextrin as a catalyst (to increase the solubility of the reactants in water) without using toxic organic solvents was proposed. This methodology is of interest due to the use of water as a solvent, thus minimizing such factors as the cost, operational hazards, and environmental pollution.     

Calculated bulk vacancy formation energy (Ev) for a Schottky defect in Al single crystals

In this paper the bulk vacancy formation energies (E_v) of Al single crystals (with different surface orientations (111), (100) and (110)) were calculated with the embedded atom method using the empirical many‐body potential of Sutton and Chen. These calculations indicate that there is a significant difference in the bulk vacancy formation energy underneath different surface orientations. The crystal with the (111) surface had the highest bulk vacancy formation energy and the crystal with the (110) surface had the lowest bulk vacancy formation energy. Copyright © 2003 John Wiley & Sons, Ltd.     

Investigation of activation energies for dissociation of host‐guest complexes in the gas phase using low‐energy collision induced dissociation

A low‐energy collision induced dissociation (CID) (low‐energy CID) approach that can determine both activation energy and activation entropy has been used to evaluate gas‐phase binding energies of host‐guest (H‐G) complexes of a heteroditopic hemicryptophane cage host (Zn (II)@1) with a series of biologically relevant guests. In order to use this approach, preliminary calibration of the effective temperature of ions undergoing resonance excitation is required. This was accomplished by employing blackbody infrared radiative dissociation (BIRD) which allows direct measurement of activation parameters. Activation energies and pre‐exponential factors were evaluated for more than 10 H‐G complexes via the use of low‐energy CID. The relatively long residence time of the ions inside the linear ion trap (maximum of 60 s) allowed the study of dissociations with rates below 1 s^?1. This possibility, along with the large size of the investigated ions, ensures the fulfilment of rapid energy exchange (REX) conditions and, as a consequence, accurate application of the Arrhenius equation. Compared with the BIRD technique, low‐energy CID allows access to higher effective temperatures, thereby permitting one to probe more endothermic decomposition pathways. Based on the measured activation parameters, guests bearing a phosphate (―OPO₃^2?) functional group were found to bind more strongly with the encapsulating cage than those having a sulfonate (―SO₃^?) group; however, the latter ones make stronger bonds than those with a carboxylate (―CO₂^?) group. In addition, it was observed that the presence of trimethylammonium (―N(CH₃)₃⁺) or phenyl groups in the guest's structure improves the strength of H‐G interactions. The use of this technique is very straightforward, and it does not require any instrumental modifications. Thus, it can be applied to other H‐G chemistry studies where comparison of bond dissociation energies is of paramount importance.     

Rate of phosphoantimonylmolybdenum blue complex formation in acidic persulfate digested sample matrix for total dissolved phosphorus determination: importance of post-digestion pH adjustment

Acidic persulfate oxidation is one of the most common procedures used to digest dissolved organic phosphorus compounds in water samples for total dissolved phosphorus determination. It has been reported that the rates of phosphoantimonylmolybdenum blue complex formation were significantly reduced in the digested sample matrix. This study revealed that the intermediate products of persulfate oxidation, not the slight change in pH, cause the slowdown of color formation. This effect can be remedied by adjusting digested samples pH to a near neural to decompose the intermediate products. No disturbing effects of chlorine on the phosphoantimonylmolybdenum blue formation in seawater were observed. It is noted that the modification of mixed reagent recipe cannot provide near neutral pH for the decomposition of the intermediate products of persulfate oxidation. This study provides experimental evidence not only to support the recommendation made in APHA standard methods that the pH of the digested sample must be adjusted to within a narrow range of sample, but also to improve the understanding of role of residue from persulfate decomposition on the subsequent phosphoantimonylmolybdenum blue formation.     

Acid dissolution of copper oxides as a method for the activation of Cu(0) wire catalyst for SET‐LRP

Here we reported the acid dissolution of copper oxides as a methodology for the activation of Cu(0) wire used as catalyst in single‐electron transfer living radical polymerization (SET‐LRP). In this method, the oxide layer on the surface of commercial Cu(0) wire was removed by dissolution in a concentrated acid such as nitric acid, glacial acetic acid and hydrochloric acid. SET‐LRP of methyl acrylate catalyzed with Cu(0) wire activated with acids showed comparable k value to that of the nonactivated Cu(0) wire‐catalyzed counterpart. However, the polymerizations catalyzed with activated Cu(0) wire proceeded with no initial induction period, predictable molecular weight evolution with conversion, and narrow molecular weight distribution. Regardless of the activation method, the chain end functionality of α,ω‐di(bromo) poly(methyl acrylate) (PMA) prepared from SET‐LRP initiated with a bifunctional initiator is extremely high, maintaining a 100% chain end functionality at ～90% monomer conversion. The degree of bimolecular termination increased as the polymerization exceeds 92% conversion. However, for binfunctional initiators this small amount of bimolecular termination at high conversion maintains a perfectly bifunctional polymer. Structural analysis by MALDI‐TOF upon thioetherification of α,ω‐di(bromo) PMA with thiophenol and 4‐fluorothiophenol confirmed the high fidelity of bromide chain ends. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A novel and unusual method for C-N bond formation in 1-substituted-pyrrolidin-2-ones

A novel 5-C-N bond forming reaction is reported, which involves heating 1-substituted-pyrrolidin-2-ones with cyclic amines in the presence of a base. This reaction provides a convenient method for the synthesis of 1,5-disubstituted-pyrrolidin-2-ones.     

掺稀土多孔硅中稀土光学活化的新方法: 微波热法

首次报道掺稀土多孔硅中稀土光学活化的一种新方法--微波热法.经微波加热处理后,掺稀土多孔硅样品外观均匀;室温下,分别观察到掺铒多孔硅在-1.5μm处、掺钕多孔硅在-1.06μm处强的光致发光.除起加热作用外,微波与样品之间的非热相互作用在稀土的光学活化方面与也起重要作用.     

Ferrocenyl bisoxazoline as an efficient non‐phosphorus ligand for palladium‐catalyzed copper‐free Sonogashira reaction in aqueous solution

Pd(OAc)₂‐catalyzed Sonogashira coupling reactions of alkynes and a variety of aryl halides with 1,3‐bis(5‐ferrocenylisoxazoline‐3‐yl)benzene as an efficient non‐phosphorus ligand under copper‐free conditions are presented. The main advantages over previous methodologies include low catalyst loading (0.2 mol% Pd(OAc)₂ and 0.4 mol% ferrocenyl bisoxazoline ligand are sufficient for these coupling reactions), less problematic reaction medium (water–dimethylformamide) and more convenient operation (no requirement for nitrogen protection).     

Metrological role of neutron activation analysis. II. Parametric INAA – an ideal back-up for INAA as a primary ratio method of measurement

In this paper, the second of this series, traceability and uncertainty of measurement results by k₀-INAA will be described. The role of k₀-INAA as a back-up to relative INAA will be discussed. Received: 19 March 2001 Accepted: 2 October 2001