Spectroscopic Study of Cobalt(III) β-Aminoethylate Complexes

Aqueous solutions of fac- and mer-isomers of [Co(NH₂C₂H₄O)₃] · 3H₂O were investigated by the ¹³C NMR spectroscopy method. The spectrum of the fac-isomer exhibited only two signals with 47.08 (C_N) and 63.87 (C_O) ppm, which points to a high symmetry of the compound and to the presence of a complex in the solution (unlike the crystal) with one type of polyhedron (probably, of a trigonal-prismatic type). The spectrum of the mer-isomer solution is more complicated: the C_Nand C_Osignals are split into three components with 48.81, 47.18, and 46.11 ppm and 64.70, 64.45, and 64.23 ppm, respectively. This fact confirms deterioration of the symmetry of the coordination polyhedron due to nonequivalence of -aminoethylate ions bound to the central atom. The successive protonation of the complexes does not affect either the symmetry of the coordination sphere of the fac-isomer or the asymmetry of the coordination sphere of the mer-isomer. The ¹H, ¹³C, ⁵⁹Co NMR and IR spectroscopy data made it possible to suggest that both fac-[Co(NH₂C₂H₄O)₃] fragments in the binuclear fac-[H₃(Co(NH₂C₂H₄O)₃)₂](NO₃)₃complex are linked together by three symmetrical hydrogen bridges.     

Nonelectrolyte Solvation in Aqueous Dimethyl Sulfoxide—A Calorimetric and Infrared Spectroscopic Study

We report enthalpies of solution of formamide, N,N-dimethylformamide,N,N-dimethylacetamide, acetic acid, methyl acetate, and acetonitrile in water +dimethylsulfoxide mixed solvents. These, along with literature data for additional solutes,are analyzed in terms of the extended coordination model of solvation. We alsoanalyze infrared data for several of these solutes. These analyses show thatN,N-dimethylformamide and N,N-dimethylacetamide are preferentially hydrated,while the other solutes appear to be preferentially solvated by dimethylsulfoxide.In all cases, the extent of preferential solvation is relatively small. It is also foundthat the degrees of preferential solvation recovered from analyses of the enthalpydata correspond closely to those recovered from the infrared data, although thelatter refer only to the polar chromophores on the solute molecules. It is foundthat the extent to which the solutes disrupt the solvent-solvent interactions variessystematically with the area of the nonpolar surfaces of the solute molecules.     

X-Ray Photoelectron Spectroscopic Study on the Synthesis of Copper Sulphide in LB Films( Ⅱ )

The present paper covers the formation process of copper sulphide in copper stearate Langmuir-Blodgett films studied carefully by XPS. The further identification of sulfur species and the examination of its change in the reaction have been made. Also the formation mechanism of sulfur species in the special microenvironment-LB films is discussed.     

Chiral-at-Molybdenum – A Computational Study on N-Substituted cis-MoO2(nacnac)2

Cis-MoO₂(nacnac)₂ (nacnac=β-diketiminate) can be a viable chiral-at-metal catalyst when its two β-diketiminate (nacnac) ligands are N-substituted to prevent Λ⇌Δ racemization. Even simple methyl groups raise the barriers for racemization significantly for the Bailar, Rây-Dutt, Conte-Hippler, and Dhimba-Muller-Lammertsma (DML) twists to a respectable 28.5, 37.8, 30.5, and 25.1 kcal/mol, respectively, at ωB97X-D/6-311+G(2d,p) (LANL2DZ for Mo) including acetonitrile solvation. The lowest energy DML barrier increases to ΔG^o=27.4 kcal/mol with N-substituted t-butyl groups. The nacnac ligands’ electronic and steric components to the racemization barriers are discussed.     

Alternating Diene Metathesis Polycondensation (ALTMET) – Opitimizing Catalyst Loading

Summary: Olefin metathesis polymerization is a flexible and easy way to prepare highly functionalized macromolecules with high precision. Within this context, the efficiency of a series of ruthenium based catalysts in the polycondensation of dienes with diacrylates yielding alternating copolymers is studied. Previous works with Grubbs 2^nd generation catalyst are compared with Hoveyda 2^nd generation catalyst that was found to be much more efficient in these reactions giving reasonable conversions and thus high molecular weights at low catalyst loading. Additionally the performance of several other Hoveyda type catalysts has been studied.     

Polymerization of α-methylstyrene in the solid (frozen) state

Russian Chemical Bulletin -     

High Trans-1,4(Co)Polymerization of β-Myrcene and Isoprene with an Iminophosphonamide Lanthanum Catalyst

β-Iminophosphonamide ligated lanthanum bis(benzyl) complex(NPNDipp)La(CH2Ph-4-Me)2(THF)(NPNDipp = Ph2P(NC6H3iPr2-2,6)2), upon activation of Al Et3 and [Ph3C][B(C6F5)4], exhibited high catalytic activity and high trans-1,4 stereoselectivity for the polymerization of bio-sourced b-myrcene(MY). Based on which, a series of novel trans-1,4 regulated elastomers could be generated by random/block copolymerization of MY and isoprene(IP).     

Infrared Spectroscopic and Gravimetric Studies on the Dicyclopentylaminemetal(II) Tetracyanonickellate(II) Host–Aromatic Guest Systems

The host complexes M(Cyclopentylamine)₂Ni(CN)₄ (M=Co or Cd) havebeen prepared in powder form. The spectral data suggest that the structures of thesecompounds are similar to those of the Hofmann-dma-type hosts. The absorptionand the liberation processes of the aromatic guests (benzene, toluene, 1,2-, 1,3-,1,4-dichlorobenzene, 1,4-dibromobenzene o-, m-, p-xylene, naphthalene)in these hosts have been examined at room temperature by gravimetric and spectroscopicmeasurements. The desorption of the benzene guest against time has been measured. Thehost structures do not change on inclusion and liberation of the guests. The host compoundshave been suggested as sorbents for isomeric separations.     

A Study of Rectification and Liquid-Vapor Phase Equilibrium in Systems Phenol-Water-Hydroxyacetone and Phenol-Water-α-Methylstyrene

Distillation processes and the liquid-vapor phase equilibrium in the systems phenol-water-hydroxyacetone and phenol-water--methylstyrene at atmospheric pressure were studied. The direction of the distillation lines was established and the possibility of preparing pure phenol and concentrating other components, i.e., impurities, in various regions of distillation of the systems was determined.     

The Mechanism of Acid-Catalyzed Nucleophilic Substitution in Decahydro-closo-Decaborate(2–) Anions

The reactions of salts formed by the B₁₀H^2– ₁₀anion with carboxylic acids were studied. From the model systems Cat₂B₁₀H₁₀+ HCOOH (Cat = Et₄N⁺, Bu₄N⁺, Ph₄P⁺, Ph₄As⁺), several intermediates were isolated and characterized. A mechanism was proposed for the replacement of the exo-polyhedral hydrogen atoms in B₁₀H^2– ₁₀by carboxylate groups in the reactions of Cat₂B₁₀H₁₀with carboxylic acids.     

Influence of Backbone and Axial Substituent of Catalyst on α-Imino-ketone Nickel Mediated Ethylene (Co)Polymerization

Chinese Journal of Polymer Science - The α-imino-ketone nickel catalyst is an emerging versatile platform that is easy to prepare and allows for the production of branched high molecular...     

Shifting From Ziegler–Natta to Philips‐Type Catalyst? A Simple and Safe Access to Reduced Titanium Systems for Ethylene Polymerization

Silica‐supported titanium(IV) chloride is readily reduced by Mashima and co‐workers' reagent (1‐methyl‐3,6‐bis(trimethylsilyl)‐1,4‐cyclohexadiene) to afford materials active in ethylene polymerisation without need of aluminum alkyl cocatalyst.     

Raman Spectroscopic Study of the Conformation and Melting of Poly(dG) · Poly(dC) and Poly(dG-dC) · Poly(dG-dC) in Aqueous Solution

Raman spectroscopic measurements on aqueous solutions of poly(dG) · poly(dC)indicate that the conformation of the polynucleotides in this double helicalcomplex are distributed between the A and B types at room temperature, the Aform being predominant at –15°C and decreasing progressively upon raising thetemperature to 65°C. A reversible pretransition has been found in this complexnear 70°C. Modifications in the spectra at this temperature indicate no majorconformational changes, but rather suggest altered base pairing and hydration ofthe carbonyl groups, accompanied by a slight distortion of the double helix,resulting in a slightly reduced stacking of the cytosine bases. Measurements inself-pressurized solutions of the complex at high temperature show that it meltsat 103°C in 0.1M NaCl solution (107°C in 0.5M NaCl). These values are somewhatlower than those we have determined in the same manner for the complexpoly(dG-dC) · poly(dG-dC): 117°C in 0.1M MgCl₂ and 113°C or higher in 0.1MNaCl solution.     

A Study of Heteropoly Complexes of Rare Earths as Catalyst Promoter in the Synthesis of Ethyl Acetate

Ethyl acetate(EA) is a kind of important materials in chemistry industry. The synthesis of EA is catalyzed by the oil of vitriol (H2SO4) in the industry. The preparation method of EA from acetic acid and alcohol using the large quantity of H2SO4 has many shortages of environment pollution, equipment erosion and low yield 1. Recently heteropoly acids were used as catalysts 1,2. Because most of the heteropoly acids are in liquid state and need to have the solid supporting materials 3. …     

Metal–Organic Framework (MOF)-Derived Carbon-Mediated Interfacial Reaction for the Synthesis of CeO2−MnO2 Catalysts

CeO₂-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO₂ and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO₄ to synthesize CeO₂−MnO₂, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO₂ crystallites under a high calcination temperature and, more importantly, intimate contact within CeO₂/C is conveyed to CeO₂/MnO₂ after the interfacial reaction; this is responsible for the high catalytic activity of CeO₂−MnO₂ towards CO oxidation.     

A New Model for Correlating the Solubility of Solids in SupercriticalCo_2 and Study on Some Systems (I): The New Model

Manyresearchershavesuggestedthatthereexistsolvent-soluteclustersinsupercriticalfluid(SCF)-solutesystems.'-'TocorrelatethephaseequilibriaofSCF-solidbinarysystems,weproposeamodelwhichisbasedonthefoIlowingfactsandassumptions.l.TheSCFphaseconsistsofsolventmolecules,freesolutemolecuIes,andthesolvent-soluteclusterswithonesolutemoleculeandanumberofthesolventmolecules.2.Thenumberofthesolventmoleculesineachclusterisassumedtobeindependentofpressure.ThisassumptionisthesameasthatusedbyChrastillinhism…     

Synthesis and Study of Spectroscopic Properties of Imidazole Porphyrin and Its Zn(Ⅱ) Complex

A novel sensitizer with imidazole zinc porphyrin as electron donor has been synthesized. The structure has been characterized by UV-Vis, elemental analyses and 1 H NMR.UV-Vis and fluorescence spectra show that it has good light absorbing properties in the range of visible light and suggests that it has potential applications in dye-sensitized solar cells.     

Spectroscopic and Structural Study of the 1:2 Aluminium(III) Complex of Quercetin

Quercetin (3, 3’, 4’, 5, 7-pentahydroxyflavone) is one of the most common flavonols present in nature. The complexation of Al(III) by various flavonoids has been suggested to reduce the overload of aluminum in the diet, a metal which has been implicated…     

A New Model for Correlating the Solubility of Solids in Supercritical CO_2 and Study on Some Systems(Ⅱ): Correlation and Prediction

Inthepreviouspaper',wedevelopedanewmodelforcorrelatingandpredictingthesolubilitiesofsolidsinsupercriticalfluids(SCFs),whichcanbegiveninthefollowingformin[yi/(l-"y,)]=njnon(RTdr)-'dp-inP BP C(l)wherethecoefficientofthepressuretermisgivenbyB=-n(RTd,')-,(2)InEqs(1)and(2),yZisthemolefractionofthesoluteinSCFphase,d.thebulkdensityofthesolvent,d,'thelocaldensityofthesolventsurroundingthesolute,Tabsollltetemperatllre,Ppressure,Rgasconstallt,andCconstant.Thevalidityofamodelshouldbeverifiedbycor…