Statistical nonstationarity of the composition of styrene with methyl methacrylate in the cooligomer

It was found that the composition of cooligomer produced in the styrene(A)–methyl methacrylate(B)–CCl₄(S) system deviates from the statistical steady-state composition predicted from the Mayo-Lewis equation on the low molecular weight side when the molar ratio of [A]/[B] is large. When the molar ratio of [A]/[B] is small, however, it is not obvious whether or not this phenomenon is observed, because the cooligomer of low molecular weight cannot be obtained easily since the chain transfer constant of the poly(methyl methacrylate) radical to CCl₄ is very small in comparison, with that of the polystyryl radical. This behavior is shown to be attributable mainly to the preferential consumption of styrene monomer in the initiation step, based on the structure of the cooligomer, as inferred from the mechanism of the initiation, transfer, and termination, and the stochastic approach in which the cooligomerization process is regarded as a Markov process.     

Multi-electron transfer processes for molecular conversions

Multi-electron transfer plays an important role in many chemical reactions. A collection of examples, both of metal complexes that exhibit one-step, multi-electron transfer process, and of chemical reactions based on a multi-electron transfer system, is presented. Emphasis is placed on the role of multi-electron transfer process in a sense that some molecular conversion systems such as reduction of O₂ and oxidation of H₂O become feasible through multi-electron transfer. As an important example of molecular conversion, oxidative polymerization of sulfur-containing compounds through two-electron transfer, is also reviewed.     

Synthesis of poly(sulfonium cation) as an alkylating reagent

Methyl 4-phenylthiophenyl sulfoxide is polymerized to poly(methyl-4-phenylthiophenylsulfonium) in poly(phosphoric acid) with a yield higher than 90%. The demethylation of poly(sufonium cation) is examined to control the composition ratio of the thiophenylene unit in the polycation. The polycation is soluble in common solvents due to the alternative structure of phenylene sufide and phenylenesulfonium cation and is easily converted to poly(phenylene sulfide) through the demethylation with a nucleophile. The poly(sulfonium cation) can be applicable as an alkylating agent for phenol, aniline and benzoic acid to the corresponding to anisole, N-methyl aniline, N,N-dimethyl aniline and benzoic methyl ester, respectively, with high conversion through the demethylation. These products can be isolated without a complicated purification because poly(phenylene sulfide) is precipitated in the mixture as the side product due to the poor solvent solubility.     

A cluster expansion theory with multireference functions using the unitary ansatz

A cluster expansion theory with multireference functions is developed. The method is applied to the ground state of H₂, the lowest two ¹∑⁺ states of LiH, and the lowest three ¹A₁ states of H₂O. Well-balanced potential curves are obtained for H₂ and LiH. Excitation energies are in good agreement with experiment.     

Helical structures induced by laterally-connected chiral twin molecules

A novel chiral twin material, (R)-bis[5-octyloxy-2-(4-octyloxyphenoxycarbonyl)phenyl] 3-methyladipate, has been prepared, where two mesogenic parts are connected laterally by a spacer possessing a chiral centre. A weaker helical structure, in particular in the chiral smectic C (S*_c) phase, was found to be induced by the laterally-connected twin material than by the analogous terminally-connected twin material. If laterally-connected chiral twin molecules prefer to stay in the smectic layer structure so that the two mesogenic parts exist in the same smectic layer, the twist interaction between adjacent layers cannot be produced by direct correlation of motion and directions of two mesogenic parts. Thus, the helical structure in the S*_c phase induced by laterally-connected chiral twin molecules becomes weak. An analogous laterally-branched 'monomeric' compound, (S)-5-octyloxy-2-(4-octyloxyphenoxycarbonyl)phenyl 3-methyl-pentanoate, has also been prepared, and the induced helical structures compared.     

A graphical symmetric group approach for a spin adapted full configuration interaction: partitioning of a configuration graph into sets of closed-shell and open-shell graphs

We developed a spin adapted full configuration interaction (FCI) method which was expected to be effective for parallel processing. The graphical symmetric group approach (GSGA) was employed, where a configuration graph was partitioned into several sets of closed-shell and open-shell graphs. The configuration state functions (CSFs) bearing the same number of closed-shells and open-shells were assembled in a configuration group. The graphical approach provided a number to identify each CSF in a sequential order within the group. Combination of this partitioning and an intermediate configuration-driven algorithm in calculating the so-called σ vectors allowed us to use symbolic coupling constants. Furthermore, this combination made it easy to implement an efficient algorithm suitable to task-distributed parallel procedure for evaluating σ vectors. A program was written and some test calculations were carried out with high parallel efficiency. The largest size of FCI used 10 million CSFs (20 million determinants).     

Role of polymer ligands in the oxygenation of metal chlorophyllins

In order to obtain information about the characteristics of polymer-(metal chlorophyllins), their redox and oxygenation reactions were studied. Complexes composed of metal chlorophyllins (MChn) and partially quaternized poly(4-vinylpyridine) (QPVP) exhibited an increased stability due to electrostatic interaction between polymer cation and carboxylate anions of side groups in the MChn. The reduction of these polymer complexes by S₂O₄^2- occurred easily with an decrease in their apparent reduction potentials. The resulting low-valence complexes had an ability to absorb molecular oxygen. The oxygenation of these polymer complexes was not completely reversible; however the rate of the irreversible reoxidation was less by a factor of 10¹⁰ for the polymeric complex than that for the monomeric MChn-pyridine complex. The stability of these oxygen complexes is discussed in relation to the hydrophobicity of QPVPs.     

Structural and dynamic properties of colloidal liquids and gases of silica spheres (29 nm in diameter) as studied by the light scattering measurements

Static and dynamic light-scattering measurements are made for colloidal-liquids and -gases of silica spheres (29 nm in diameter) in the exhaustively deionized aqueous suspension and in the presence of sodium chloride. Single broad peak is observed in the light-scattering curve and the liquid-like and gas-like distributions have been observed. Colloidal crystals are not formed at any sphere concentrations. The nearest-neighbored interparticle distances of colloidal liquids, l _obs , agree excellently with the effective diameters of spheres (d _eff ) including the electrical double layers in the effective soft-sphere model and also with the mean intersphere distances, l _o , calculated from the sphere concentration, i.e., l _obs ≈d _eff ≈ l _o . This relation supports the importance of the electrostatic interparticle repulsive interaction. Two dynamic processes have been extracted separately from the time profiles of autocorrelation function of colloidal liquids. Decay curves of colloidal gases are characterized by the single translational diffusion coefficients, which are always lower than the calculation from the Stokes-Einstein equation using true diameter of spheres and increase as ionic concentration increases. These experimental results emphasize the importance of the expanded electrical double layers and the electrostatic intersphere repulsion on the structural and dynamic properties of the colloidal liquids and gases. Electronic Publication