Steric effect on the formation of columnar phases in β-diketonate copper(II) complexes

A systematic study of the mesomorphic properties of three series of copper(II) complexes based on β-diketonate ligands containing branched side chains is reported. These disc-like compounds have four, six and eight flexible alkoxy side chains appended to the central core, in which two or four side chains were substituted by bulkier secondary alkoxy groups: 1-methylbutyloxy R ' = C₅(2°) or 1-methylheptyloxy R ' = C₈(2°). The mesomorphic results indicated that at least eight side chains are required to form stable columnar mesophases; other compounds with four or six side chains are not mesogenic regardless of the combination of the carbon length on the alkoxy or secondary alkoxy groups of the side chains. The compounds 3 with shorter R ' = C₅(2°) side chains were all non-mesogenic regardless of the carbon length of three alkoxy side chains (R = C₈, C₁₀, C₁₂) used. However, when the longer 1-methylheptyloxy side chain R ' = C₈(2°) was substituted, the compounds 3b-3e with various alkoxy groups (R = C₆, C₇, C₈, C₁₀, C₁₂) exhibited columnar phases. The mesophases were characterized and identified as columnar hexagonal phases (Col_h), as expected, by thermal analysis and optical polarized microscopy. The presence of the introduced secondary alkoxy groups apparently appeared to influence the formation of columnar phases. The clearing points were relatively lower than other similar copper(II) compounds not substituted by secondary alkoxy side chains.     

Study on complex formation equilibria of tervalent lanthanons with fluorinated β-ketoesters in aqueous dioxane medium

Summary The thermodynamic stepwise formation constants (log ^T K _n) of nine tervalent lanthanons (La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Er³⁺ and Lu³⁺) with three fluorinated -ketoesters (methyltrifluroacetoacetate, ethyltrifluoroacetoacetate, and ethylpentafluoropropionylacetate) have been evaluated potentiometrically in a 50% dioxane-water mixture at 25 and 35 ± 0.01 °C. The values of log ^T K _n do not follow a linearity when plotted againstZ/r and invariably obey the sequence: La³⁺ < Nd³⁺ < Pr³⁺ < Sm³⁺ < Gd³⁺ < Eu³⁺ < Dy³⁺ Er³⁺ Lu³⁺ in all instances. The standard thermodynamic parameters (G ₁ ⁰ , H ₁ ⁰ , S ₁ ⁰ ) associated with log ^T K _n have also been calculated. The validity of the chosen equilibrium model was examined by an error analysis usingS _min values (sum of the squared residuals), scatter plots, and slopes and intercepts of Abrahams-Kave type normal probability plots.

---

Komplexbildungsgleichgewichte von dreiwertigen Lanthanoiden mit fluorierten -Ketoestern in wäßrigem Dioxanmedium

Zusammenfassung Es wurden die thermodynamischen stufenweisen Komplexbildungskonstanten (log ^T K _n) von 9 dreiwertigen Lanthanoiden (La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Er³⁺ und Lu³⁺) mit drei fluorierten -Ketoestern (Methyltrifluoracetoacetat, Ethyltrifluoracetoacetat und Ethylpentafluopropionylacetat) in 50% Dioxan-Wasser bei 25 und 35±0.01 °C potentiometrisch bestimmt. Die Werte für log ^T K _n ergeben keine lineare Abhängigkeit gegenüberZ/r, sie gehorchen stets der Reihenfolge: La³⁺ < Nd³⁺ < Pr³⁺ < Sm³⁺ < Gd³⁺ < Eu³⁺ < Dy³⁺ Er³⁺ Lu³⁺. Die thermodynamischen Standardparameter G ₁ ⁰ , H ₁ ⁰ und S ₁ ⁰ wurden ebenfalls berechnet. Die Gültigkeit des gewählten Gleichgewichtsmodells wurde unter Verwendung der Summe der Quadratreste (S _min), von Streukurven und Steigung/Ordinatenabschnitt der Normalwahrscheinlichkeitsdarstellung nach Abrahams-Kave untersucht.

     

Study on the inclusion compound of β-cyclodextrin with (η5-cyclopentadienyl)tricarbonylmanganese(0)

The supramolecular inclusion compound of β-cyclodextrin (β-CD, host) with (η5-cyclopentadienyl)tricarbonylmanganese [MnCp(CO)3, guest] was obtained in a crystalline state. The host-guest compound is thermally stable and do not liberate the guest on heating at 100$ in vacuum. It was characteried by elemental analysis,1H NMR, differential scanning thermal (DSC) analysis and TLC. Continueous variation plot by NMR method shows that β-CD formed 1:1 inclusion compound with MnCp(CO)3. On the basis of 1H NMR spectra and the model building with Corey Pauling Koltum (CPK) models, the most probable inclusion mode is proposed.     

Study on formation of poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber

In this paper, the crystallization behavior, thermal degradation properties, rheological behavior and the spinnability of poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber were studied. Experimental results indicated that the spherulite growth rate of PHBV was very slow and its size was very large. PHBV began to degrade above 170°C. The flowing curve indicated that the processing temperature and the residential time had important effects on PHBV melts. When the equipment of melting spinning was improved and processing conditions were strictly controlled, the mechanical properties of the PHBV filament can comply with the requirements of the American Pharmacopoeia. __________ Translated from Journal of Donghua University (Natural Science Edition), 2007, 33(4): 425–430     

Study on the Vortex of the Qinghai-Xizang (Tibet) Plateau in Summer

In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is shallow and thermal originated from a strong heat source near the surface of the west of the Plateau. Then moving eastward , it develops and becomes stronger and thicker with larger upward vertical velocity, and causes great precipitation in the middle Plateau. But at this time the heat source in the vortex becomes weaker, and even the heat sink occurs near the surface. Consequently, it disappears in a cold trough with a strong heat sink in the east of the Plateau. The heat source (sink) is mainly determined by the vertical eddy flux convergence (divergence) of the sensible heat caused by the cumulus convection and turbu-lance. Both the nonuniform heating (cooling) at the surface and the convergence (divergence) of the eddy kinetic energy coact and play an important role in the genesis (di     

Study on the Structure of Supramolecular Inclusion Complex of β-Cyclodextrin with Retinoic Acid

The importance of Vitamin A for human health has been stressed in resent studies1, meanwhile its derivative so-called retinoic acid (RA) has been widely used as pharmaceutical to treat several types of skin disease and cancer2,3. However the application of retinoic acid is restrained for its poor water solubility, unstability and side effect on the human body.Cyclodextrins (CDs) are macrocyclic oligosaccharides built up from 6, 7, or 8 glucopyranose units called (, (, and (-CD, respectively…     

Study of the Supramolecular Inclusion of β-Cyclodextrin with Andrographolide

An inclusion complex of -cyclodextrin with andrographolide (Andro) was prepared by using a convenient new method of microwave irradiation. The structure of the inclusion complex was determined by UV and IR analyses as well as ¹H NMR, ¹³C NMR and two dimensional NOE spectroscopic measurements. The results indicated that the possible stoichiometry of complex formation is 1:1 (guest:host ratio) and the two isomeric 1:1 inclusion complexes are present simultaneously in solution. Thermal studies proved the thermal stability of the inclusion complex.     

The reactions of phosphorus(III) halides with β-diketiminato ligands

Reactions of the lithium or sodium salt, [HC(CMeNDipp)₂]M (Dipp = 2,6-diisopropylbenzene, M = Li or Na), with PBr₃ or PCl₃ affords a series of phosphenium cations that were characterized in the solid state by X-ray crystallography. Solid-state analysis reveals that for compounds 1 and 2, C–H activation of the ligand occurs and the phosphorus is bound to a nitrogen and carbon atom of the ligand. Compound 3 exhibits the more traditional nitrogen chelation of the ligand to the phosphorus atom.     

Cycloaddition reactions of sulfonylisothiocyanates with β,β-disubstituted enamines

Sulfonylisothiocyanates 1 and β,β-dimethylenamines 2 react to yield the dipoles 3. In nonpolar solvents an equilibrium exists between 3 and the thietanes 4. The free activation enthalpy for the ring closure 3→4 was obtained from the temperature dependent NMR spectra in liquid sulfur dioxide. Protonation of 3 with perchloric acid leads to the salts 8 which, as indicated by ΔG^≠-values obtained from NMR spectra, are also capable of ring closure.     

[3+3] Cyclization reactions of β-nitroenamines and β-enaminonitriles with α,β-unsaturated carboxylic acid chlorides

New indolizidines, quinolizidines, and octahydro-pyrido[1,2-a]azepines of lactam type were synthesized from 2-nitromethylene-pyrrolidine, -piperidine, and -hexahydroazepine, respectively, by [3+3] cyclizations with α,β-unsaturated carboxylic acid chlorides. In the case of quinolizidines, a double bond migration was observed, and explained in terms of amidity percentage. Cyanomethylene-pyrrolidine gave indolizidines of lactam type, while transformations of 1-cyanomethylene-tetrahydoisoquinoline resulted in lactams as well as ketones, when simple open-chain acid chlorides or cinnamoyl chloride were used, respectively.     

Yields of O2(b1Σ) from reactions of HO2

A discharge-flow apparatus with resonance fluorescence and chemiluminescence detection has been used to monitor O₂(b ¹σ) production from several reactions of the HO₂ radical at 300 K and 1-torr total pressure. O₂(b), HO₂, and OH were observed when F atoms were added to H₂O₂ in the gas phase. Signal strengths of O₂(b) were proportional to initial concentrations of H₂O₂ and HO₂. These observations were analyzed by using a simple three step mechanism and a more complete computer simulation with 22 reaction steps. The results indicate that the F + HO₂ reaction yields O₂(b) with an efficiency of (3.6 ± 1.4) × 10^?3. By monitoring [O₂(b)] and [HO₂] upon addition of an excess second reactant to HO₂, O₂(b) yields from the reactions of HO₂ with O, Cl, D, H, and OH were found to be <1 × 10^?2, <5 × 10^?4, <2 × 10^?3, <8 × 10^?3, and <1 × 10^?3, respectively. Yields of O₂(b) from the HO₂ ± HO₂ reaction were found to be less than 3 × 10^?2.     

A useful synthesis of α,β-bis(methylseleno)alkanes and α,δ-bis(methylseleno)alk-2-enes by the reactions of alkenes and 1,3-dienes with B(SeMe)3-Lewis acid

Reactions of tris(methylsenleno)borane-SnCl₄ with alkenes 1a–g gave α,β-bis(methylseleno)alkanes 2a –g, stereospecifically, and reactions with 1,3-dienes 1i–k afforded α,β-bis(methylseleno)alk-2-enes 2i–k , regioselectively.