Reactions of Chalcogenide β-Diiminate Nickel Complexes with Samarium Bis(pentamethylcyclopentadienide)

The reactions of [(L^iPrNi)₂(μ-η²:η²-S₄)] (I) and [(L^iPrNi)₂(μ-η²:η²-Se₂)] (II) (L^iPr = CH[C(Me)N(2,6- ⁱ Pr₂C₆H₃)]₂) with decamethylsamarocene [Sm(Cp*)₂(Тhf)₂] (Cp* = η⁵-C₅Me₅) are studied. It is assumed that the reactions afford hetero-d/f-metal complexes. However, these complexes are not observed but the transfer of chalcogens from Ni to Sm and the formation of [(Sm(Cp*)₂(Тhf))₂(μ-S)] (III) and [(Sm(Cp*)₂(Тhf))₂(μ-Se)] (IV) occur. The second reaction products are [(L^iPrNi)₂(μ-η²:η²-S₂)] (V) in the case of sulfur and [(L^iPrNi^I)₂(μ-η⁶:η⁶-C₇H₈)₂] (VI) in the case of selenium. All reaction products have been described previously, but compounds III and V are isolated as new crystalline phase, the structures of which are determined by X-ray diffraction analysis (CIF files CCDC nos. 1559045 (V) and 1559046 (III)).     

Synthesis of isotactic polystyrene-block-polyethylene by the combination of sequential monomer addition and hydrogenation of 1,4-<Emphasis Type="Italic">trans</Emphasis>-polybutadiene block

Herein, we demonstrate the synthesis of a well-defined diblock copolymer consisting of isotactic polystyrene (iPS) and linear polyethylene, isotactic polystyrene-block-polyethylene (iPS-b-PE), by the combination of sequential monomer addition and hydrogenation. Isospecific living polymerization of styrene and living trans-1,4-polymerization of 1,3-butadiene were catalyzed by 1,4-dithiabutandiyl-2,2′-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by triisobutyl aluminum modified methylaluminoxane (MMAO) at room temperature to provide highly isotactic polystyrene (iPS) and 1,4-trans-polybutadiene (1,4-trans-PBD) with narrow molecular weight distribution. Furthermore, the iPS-b-1,4-trans-PBD was synthesized via sequential monomer addition in the presence of complex 1 and MMAO. The hydrogenation of the 1,4-trans-PBD block was promoted by RuCl₂(PPh₃)₃ used as a catalyst to produce iPS-b-PE.     

Thermal polymerization of styrene: New data on the conversion dependence of the initiation rate

With the aid of new acceptors of free radicals usable at high temperatures (T > 100°C), the rate of initiation w _i has been measured experimentally for the thermal polymerization of styrene at 122.5°C in a wide range of conversions C = 0–80%. It has been shown that the value of w _i tends to increase in the course of polymerization transformation in agreement with the w _i = f(C) relationship calculated from the kinetic data on the thermal polymerization of styrene in the absence of counters of free radicals. Hypothetical reasons for this non-trivial tendency have been formulated. The experimental dependence w _i = f(C) has been measured for the first time and has been invoked to refine currently available mathematical models for the thermal polymerization of styrene that assume that w _i remains invariable in the course of polymerization transformation.     

Vapor pressure and heat capacities of perfluoro-<Emphasis Type="Italic">N</Emphasis>-(4-methylcyclohexyl)piperidine

Heat capacities of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) have been measured by low-temperature adiabatic calorimetry. The purity of the compound, its triple-point temperature, and its enthalpy and entropy of fusion have been determined. The saturated vapor pressure was determined by comparative ebulliometry as a function of temperature in the 6.2–101.6 kPa pressure range and 374.2–460.9 K temperature range. The calorimetric enthalpy of vaporization at T = 298.15 K has been measured. The following thermodynamic properties were calculated for PMCP: normal boiling temperature, enthalpy of vaporization Δ_vap H _m ⁰ (T) as a function of temperature, and critical parameters. The enthalpies of vaporization at 298.15 K obtained experimentally and by calculation methods match within their error limits, which validates their adequacy and the adequacy of the Δ_vap H _m ⁰ = f(T) equation as an extrapolation.     

Why is ‘amount of substance’ so poorly understood? The mysterious Avogadro constant is the culprit!

The base quantity ‘amount of substance’ is poorly understood and the name and symbol usually avoided. This is because of its formal interpretation as the number of entities multiplied by the reciprocal of the mysterious Avogadro constant, N _A. If X signifies the kind of entities involved, the number of entities in a sample, N(X), is easily comprehended, and if m _av(X) is the sample-average entity mass, the total mass, m(X) = N(X)m _av(X)—an aggregate of N(X) average entity masses—is also conceptually straightforward. However, the corresponding amount of substance, n(X) = N(X)(1/N _A)—an aggregate of N(X) ‘reciprocal Avogadro constants’—is incomprehensible unless some physical meaning can be attached to 1/N _A. By contrast, the base unit, mole, is thought of by chemists as an aggregate of a particular number of entities: mol = \( {\mathcal N}_{\rm{Avo}} \) ent, where \( {\mathcal N}_{\rm{Avo}} \) is the Avogadro number (equal to g/Da) and ent represents one entity. It makes sense, therefore, to interpret amount of substance as an aggregate of a general number of entities: n(X) = N(X) ent—an easily grasped concept. A ‘reciprocal Avogadro constant’ is thus seen to actually be exactly one entity. One mole then corresponds to setting N(X) = \( {\mathcal N}_{\rm{Avo}} \), for which the total mass is the relative entity mass in grams—conforming to the original mole concept.     

Concentration,temperature, and isotopy effects on the heat capacity of aqueous urea

Relations for the apparent molar heat capacity ?_c of urea in an aqueous solution depending on the molality m and temperature were obtained. A transition to the relations ?_c(m,T) for D₂O-(ND₂)₂CO and T₂O-(NT₂)₂CO systems was effected by temperature scaling. At low temperatures, the isotherms of the molar heat capacity C _p(m) of the protium and deuterium systems have minima shifted to more dilute solutions at elevated temperatures. At m = 1, C _p of a solution does not depend on temperature in both systems. The dependences C _p(T) also have minima at constant concentrations. The temperature of the minimum heat capacity is most effectively lowered by small additions of urea. For m = 0.25, T _min is 7.5 K lower than T _min of pure water, and its heat capacity is 0.08 J/(mol K) higher. A transition from m = 1.5 to m = 2 lowers the temperature of the minimum heat capacity by 3.6 K; thus, the heat capacity of solutions differs by 0.02 J/(mol K) only.     

General conditions and experimental design of sustained frontal photopolymerization in photopolymerizable liquid compositions

It has been shown that, in order to accomplish frontal photopolymerization in the mode of a self-sustained travelling wave, it is necessary to use compositions that are optically transparent behind the front and experience the onset of gelling at a minimal degree of polymerization, e.g., systems based on oligoether (meth)acrylates. With the use of a composition containing oligocarbonate methacrylate and the o-benzoquinone-amine photoinitiator system, frontal photopolymerization in a layer of more than 100 mm in thickness was experimentally revealed. It was shown that the photoinitiator and monomer conversion fronts synchronously propagate into the layer. It was found that the coordinate of the leading edge of the monomer conversion front h is related to the irradiated time τ by the equations h = A ₁ log τ ? B and h = A ₂ τ ? B at the first and the second step of frontal polymerization, respectively. It was found that the thickness of the area of the formulation layer in which the condition h = A ₁ logτ ? B is fulfilled is equal to the width of the photoinitiator and monomer conversion front. A general equation of motion of the coordinate of the photoinitiator conversion label in the layer of a liquid photopolymerizable composition during sustained frontal photopolymerization was proposed for describing experimental data.     

The doubly thermo-responsive triblock copolymer nanoparticles prepared through seeded RAFT polymerization

The doubly thermo-responsive triblock copolymer nanoparticles of polystyrene-block-poly(N-isopropylacrylamide)-block-poly[N,N-(dimethylamino) ethyl methacrylate] (PS-b-PNIPAM-b-PDMAEMA) are successfully prepared through the seeded RAFT polymerization in situ by using the PS-b-PNIPAM-TTC diblock copolymer nanoparticles as the seed. The seeded RAFT polymerization undergoes a pseudo-first-order kinetics procedure, and the molecular weight increases with the monomer conversion linearly. The hydrodynamic diameter (D _h) of the triblock copolymer nanoparticles increases with the extension of the PDMAEMA block. In addition, the double thermo-response behavior of the PS-b-PNIPAM-b-PDMAEMA nanoparticles is detected by turbidity analysis, temperature-dependent 1H-NMR analysis, and DLS analysis. The seeded RAFT polymerization is believed as a valid method to prepare triblock copolymer nanoparticles containing two thermo-responsive blocks.     

Specific Features of <Emphasis Type="Italic">N</Emphasis>-Morpholinoethyl Methacrylate Synthesis

Methods for synthesis of N-morpholinoethyl methacrylate were compared. It was shown that the monomer produced by acylation of N-morpholinoethanol with methacrylic acid anhydride or methacryloyl chloride spontaneously polymerizes in storage. The possible reasons for the spontaneous polymerization of N-morpholinoethyl methacrylate produced by the acylation method were considered. The conditions in which a stable-in-storage monomer can be obtained in 86–88% yield by the method of re-esterification of methyl methacrylate with N-morpholinoethanol were determined.     

Density,Viscosity, and Glass Transition of an Ethylenediamine–Ethylene Glycol Binary System

Densities ρ and viscosities η were measured for the binary mixtures of ethylenediamine (EDA) and ethylene glycol (EG) in the temperature range 288.15–323.15 K for ρ and at 273.15–323.15 K for η, both of which are broader temperature ranges than those reported previously. The value of ρ monotonously decreases against the mole fraction of EDA, x _EDA, and increasing temperature. The concentration dependence of η exhibits a maximum in the intermediate concentration range at all temperatures measured. The glass transition temperature, T _g, for samples with x _EDA < 0.7 was measured using differential scanning calorimetry. The measured T _g values show a peak in the intermediate concentration range, which is a behavior similar to that of η; however, the peak concentrations for η and T _g did not precisely align because of a deviation in the maximum hydrogen-bond density. The partial molar volumes for EDA and EG and the thermal expansivities, α, were obtained from ρ. Results in the present study are discussed in terms of the extensively increasing hydrogen-bond density for polyamine–polyhydric alcohol systems.     

Microbial Transformation of Curcumin to Its Derivatives with a Novel <Emphasis Type="Italic">Pichia kudriavzevii</Emphasis> ZJPH0802 Strain

Curcumin, a polyphenolic compound, has shown a wide range of pharmacological activities and has been widely used as a food additive. However, the clinical use of curcumin is limited to some extent because of its poor water solubility and low bioavailability. To overcome these problems, many approaches have been attempted and structural modification of curcumin by microbial transformation has been proven to be an alternative. In this study, we isolated a novel yeast strain Pichia kudriavzevii ZJPH0802 from a soil sample, which is capable of converting curcumin to its derivatives. The transformed products by this strain were evaluated by HPLC, (+) electrospray ionization (ESI)-MSⁿ, and ¹H nuclear magnetic resonance methods. Compared with controls, two new peaks of the transformed broth appeared at retention times of 26 min (I) and 62 min (II) by HPLC analysis. The two transformed products were then further identified by (+) ESI-MSⁿ. The spectrum showed that compound I had an accurate [M+H+NH₃]⁺ ion at m/z 392, [M+H]⁺ ion at m/z 375, [M+H–H₂O]⁺ ion at m/z 357, and (+) ESI-MS³ spectrum showed that ion at m/z 357 could further form fragment ions at m/z 339, 177, and 163; compound II had an accurate [M+H]⁺ ion at m/z 373, [M+H–H₂O]⁺ ion at m/z 355, and (+) ESI-MS³ spectrum showed that ion at m/z 355 could further form fragment ions at m/z 219, 179, 177, 163, and 137. These two transformed products thereby were confirmed as hexahydrocurcumin (I) and tetrahydrocurcumin (II).     

Ro-vibrating energy states of a diatomic molecule in an empirical potential

An approximate analytical solution of the Schrödinger equation is obtained to represent the rotational–vibrational (ro-vibrating) motion of a diatomic molecule. The ro-vibrating energy states arise from a systematical solution of the Schrödinger equation for an empirical potential (EP) V _±(r) = D _e {1 ? (?/δ)[coth (ηr)]^±1/1 ? (?/δ)}² are determined by means of a mathematical method so-called the Nikiforov–Uvarov (NU). The effect of the potential parameters on the ro-vibrating energy states is discussed in several values of the vibrational and rotational quantum numbers. Moreover, the validity of the method is tested with previous models called the semiclassical (SC) procedure and the quantum mechanical (QM) method. The obtained results are applied to the molecules H₂ and Ar₂.     

Molecular structure of ErCl<Subscript>3</Subscript> and YbCl<Subscript>3</Subscript> according to the data of the simultaneous electron diffraction and mass spectrometric experiment

The saturated vapors of ErCl₃ and YbCl₃ were studied in a simultaneous electron diffraction and mass spectrometric experiment at 1165 K and 1170 K, respectively. In the vapors of these compounds, we found up to 3 mol.% dimers along with the monomers. The parameters of the r _g effective configuration of the monomer molecules were determined. For ErCl₃ and YbCl₃, the internuclear distances r _g(Ln-Cl) were 2.436(5) Å and 2.416(5) Å, and the bond angles ∠_g(Cl-Ln-Cl) were 117.0(10)° and 117.2(10)°, respectively. The equilibrium configurations and vibration frequencies of the monomer and dimer molecules were calculated by the HF, B3LYP, and MP2 methods using the combination of the ECP_D energy-consistent quasirelativistic core potential, including 4f electrons [Kr4d ¹⁰4f ⁿ ], and the contracted [5s4p3d] valence basis set for Er and Yb atoms and the MIDIX [4s3p1d] basis set for Cl atoms. The parameters of the effective r _g configuration of the monomer molecules corresponding to the temperature of the experiment were calculated. The difference between the calculated equilibrium r _e(Ln-Cl) and temperature-averaged r _g(Ln-Cl) distances was found to be 0.001–0.002 Å and did not exceed the error of the r _g(Ln-Cl) parameter determined in the electron diffraction experiment. The experimental parameters of the r _g structure were shown to be consistent with the idea about the planar equilibrium geometrical configuration of ErCl₃ and YbCl₃ molecules.     

Structure and energetics of β-diketonates. XVI. Molecular structure and vibrational spectrum of zinc acetylacetonate according to gas-phase electron diffraction and quantum-chemical calculations

The molecular structure of zinc acetylacetonate was studied in a simultaneous electron diffraction and mass spectrometric experiment at 376(7) K and by quantum-chemical calculations. The Zn(acac)₂ molecule has a structure of D _2d symmetry with the chelate rings lying in mutually perpendicular planes. The main geometrical parameters of the molecule are r _h1(Zn-O) = 1.942(4) Å, r _h1(C-O) = 1.279(3) Å, r _h1(C-C_r) = 1.398(3) Å, r _h1(C-C _m ) = 1.504(5) Å, ∠(O-Zn-O) = 93.2(7)°, ∠(Zn-O-C) = 125.9(7)°, ∠(C-C_r-C) = 125.8(14)°, ∠(O-C-C _m ) = 115.2(9)°. The effective rotation angle of methyl groups is close to 30°, which is indicative of the free rotation of these groups. The vibration frequencies were obtained by quantumchemical calculations, and the IR spectrum of the Zn(acac)₂ molecule was interpreted.     

Synthesis of Block Copolymers of Styrene with <Emphasis Type="Italic">D</Emphasis>,<Emphasis Type="Italic">L</Emphasis>-Lactide by the Sequential Controlled Cationic Polymerization and Ring-Opening Anionic Polymerization

The cationic polymerization of styrene initiated by the system 2-chloro-2-phenylpropane–TiCl₄–pyridine is studied in a mixture CH₂Cl₂–n-hexane at a temperature of –80°С. It is shown that under these conditions polymerization occurs via the living mechanism at [monomer]: [initiator] ≤ 100. The method of preparing polystyrenes with terminal primary hydroxyl groups (M_n = 4000–10000 g/mol) by the sequential controlled cationic polymerization of styrene and the in situ alkylation of 4-phenoxy-1-butanol by polystyrene macrocations is proposed. The resulting functionalized polystyrenes are used as macroinitiators of anionic-coordination ring-opening polymerization of D,L-lactide in the presence of tin bis(2-ethyl hexanoate) [Sn(Oct)₂] in toluene at 80°С. Copolymers polystyrene-block-poly(D,L-lactide) with the controlled length of the poly(D,L-lactide) block (M_n = 10000–17000 g/mol) and a relatively low molecular-weight distribution (M_w/M_n = 1.6–1.8) are synthesized. Formation of the block copolymers is confirmed by ¹Н NMR spectroscopy, gel-permeation chromatography, and atomic force microscopy.     

Ensemble evaluation of polydisperse nanocellulose dimensions: rheology,electron microscopy,X-ray scattering and turbidimetry

Six types of CNCs with different sizes were prepared from tunicins by sulfuric acid hydrolysis and subsequent sonication in water. The size distributions of CNCs were comprehensively evaluated by turbidimetry, small angle X-ray scattering, and microscopy to predict their intrinsic viscosities. Experimental intrinsic viscosities [η] of the CNC dispersions were evaluated by shear viscosity measurement, and then compared with their theoretical [η] values based on theories for rotational motions of rigid rods. The experimental [η] values for the straight CNCs were in good agreement with their theoretical [η] values, irrespective of the size and distributions. On the other hand, the experimental [η] value of the kinked CNC was higher than the theoretical [η] value, in agreement with a theoretical calculation giving higher intrinsic viscosities for bent fibers.     

The thermodynamic properties of the [(Me<Subscript>3</Subscript>Si)<Subscript>7</Subscript>C<Subscript>60</Subscript>]<Subscript>2</Subscript> fullerene complex

The temperature dependence of the heat capacity C _p ^o of the [(Me₃Si)₇C₆₀]₂ fullerene complex was measured for the first time using precision adiabatic vacuum calorimetry over the temperature range 6.7–340 K and high-accuracy differential scanning calorimetry at 320–635 K. For the most part, the error in the C _p ^o values was about ±0.5%. An irreversible endothermic effect caused by the splitting of the dimeric bond between fullerene fragments and the thermal decomposition of the complex was observed at 448–570 K. The thermodynamic characteristics of this transformation were calculated and analyzed. Multifractal analysis of the low-temperature (T < 50 K) heat capacity was performed, and conclusions were drawn concerning the character of the heterodynamicity of the structure. The experimental data obtained were used to calculate the standard thermodynamic functions C _p ^o (T), H ^o (T) ? H ^o (0), S ^o (T) ? S ^o (0), and G ^o (T) ? H ^o (0) over the temperature range from T → 0 to 445 K and estimate the standard entropy of formation of the compound from simple substances at 298.15 K. The standard thermodynamic properties of [(Me₃Si)₇C₆₀]₂ are compared with those of the (C₆₀)₂ dimer, the [(η⁶-Ph₂)₂Cr]⁺[C₆₀]^?? fulleride, and the initial C₆₀ fullerene.     

Viscosities and Surface Tensions of Phenetole with <Emphasis Type="Italic">N</Emphasis>-Methyl-2-pyrrolidone, <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide and Tetrahydrofuran Binary Systems at Three Temperatures

Viscosities, η, and surface tensions, σ, of binary systems of phenetole (ethoxy benzene or ethyl phenyl ether) with N-methyl-2-pyrrolidone, N,N-dimethylformamide or with tetrahydrofuran were measured over the entire mole fraction range and at (298, 303 and 308) K. The experimental data was used to compute the deviations in viscosity, Δη, and surface tension, Δσ. Values of the excess Gibbs energy of activation G*^E, surface entropy S _σ and surface enthalpy H _σ were calculated. Viscosity data of the binary systems were calculated using the Grunberg and Nissan and the three-body and four-body McAllister correlations. The Redlich–Kister method was used for evaluation of coefficients and standard deviations for Δη, Δσ and G*^E. The results were interpreted in terms of the probable effect of molecular interactions between components as well as polarity.     

OES and GC/MS Study of RF Plasma of Xylenes

The radio-frequency discharge of xylene isomers was monitored with optical emission spectroscopy (OES). It was found that the meta isomer showed relatively stronger excimer to monomer intensity ratio than the other two isomers. OES also indicates the formation of xylyl (methylbenzyl) radicals. The reaction products of low pressure xylene plasmas were analyzed by gas-chromatography mass spectrometry (GC/MS). It showed that the main composition of the reaction products was 1,2-di-p-tolylethane (DPTE), regardless the types of xylene isomers used. It is known that o- and m-xylyl radicals can undergo rearrangement and convert to p-xylyl radicals. Similar to the cases in benzene and toluene plasmas, the recombination reaction between two p-xylyl radicals is believed to be responsible for the formation of DPTE. Density functional theory calculations suggest that the direct conversion of xylene excimers to DPTE is unlikely.     

Heat capacity and thermodynamic functions of ferrocenemethanol

The heat capacity (C _{p, m}) of ferrocenemethanol (FM) C₅H₅FeC₅H₄CH₂OH have been measured by the low-temperature adiabatic calorimetry method in the range 6–371 K. The triple point temperature, the enthalpy of fusion, and the purity of the substance under consideration have been determined. The ideal gas thermodynamic functions of FM—absolute entropy S _m(g) ⁰ and change in the enthalpy Δ ₀ ^T H _m at 298.15 K—have been derived from the heat capacity data and the known values of the saturation vapor pressure and enthalpy of sublimation. The ideal gas thermodynamic functions C _{p, m} ⁰ and S _m(g) ⁰ and the enthalpy of formation of FM have been calculated by the empirical difference method at T = 298.15 K. The experimental and calculated values of the thermodynamic functions are consistent within error limits, which proves their reliability.