Exciton dynamics in nanostar dendritic systems using a quantum master equation approach: core monomer effects and possibility of energy transport control

The directional energy transport, i.e. exciton migration, in nanostar dendritic systems composed of two-state monomer units is studied using a quantum master equation approach. We examine the effects of the variation in the excitation energy of the monomer in the core region (core monomer) on the multistep exciton migration from the periphery to the core based on the relaxation factors among exciton states originating in weak exciton-phonon coupling. It turns out that when the core monomer possesses both an excitation energy slightly lower than that of the first generation and a partial exciton overlap with the first generation, more efficient and rapid exciton migration to the core is expected as compared with other core monomer cases with the energy level closer to or much lower than that of the first generation.     

Hydrogen Production from a Methanol–Water Solution Catalyzed by an Anionic Iridium Complex Bearing a Functional Bipyridonate Ligand under Weakly Basic Conditions

An efficient catalytic system for the production of hydrogen from a methanol–water solution has been developed using a new anionic iridium complex bearing a functional bipyridonate ligand as a catalyst. This system can be operated under mild conditions [weakly basic solution (0.046 mol L^?1 NaOH) below 100 °C] without the use of an additional organic solvent. Long‐term continuous hydrogen production from a methanol–water solution catalyzed by the anionic iridium complex was also achieved.     

Versatile In Situ Generated N‐Boc‐Imines: Application to Phase‐Transfer‐Catalyzed Asymmetric Mannich‐Type Reactions

The efficient construction of nitrogen‐containing organic compounds is a major challenge in chemical synthesis. Imines are one of the most important classes of electrophiles for this transformation. However, both the available imines and applicable nucleophiles for them are quite limited given the existing preparative methods. Described herein are imine precursors which generate reactive imines with a wide variety of substituents under mild basic conditions. This approach enables the construction of various nitrogen‐containing molecules which cannot be accessed by the traditional approach. The utility of the novel imine precursor was demonstrated in the asymmetric Mannich‐type reaction under phase‐transfer conditions.     

Third-order nonlinear optical properties of open-shell supermolecular systems composed of acetylene linked phenalenyl radicals

The third-order nonlinear optical (NLO) properties, at the molecular level, the static second hyperpolarizabilities, γ, of supermolecular systems composed of phenalenyl and pyrene rings linked by acetylene units are investigated by employing the long-range corrected spin-unrestricted density functional theory, LC-UBLYP, method. The phenalenyl based superethylene, superallyl, and superbutadiene in their lowest spin states have intermediate diradical characters and exhibit larger γ values than the closed-shell pyrene based superpolyene systems. The introduction of a positive charge into the phenalenyl based superallyl radical changes the sign of γ and enhances its amplitude by a factor of 35. Although such sign inversion is also observed in the allyl radical and cation systems in their ground state equilibrium geometries, the relative amplitude of γ is much different, that is, |γ(regular allyl cation)/γ(regular allyl radical)| = 0.61 versus |γ(phenalenyl based superallyl cation)/γ(phenalenyl based superallyl radical)| = 35. In contrast, the model ethylene, allyl radical/cation, and butadiene systems with stretched carbon-carbon bond lengths (2.0 ?), having intermediate diradical characters, exhibit similar γ features to those of the phenalenyl based superpolyene systems. This exemplifies that the size dependence of γ as well as its sign change by introducing a positive charge on the phenalenyl based superpolyene systems originate from their intermediate diradical characters. In addition, the change from the lowest to the highest π-electron spin states significantly reduces the γ amplitudes of the neutral phenalenyl based superpolyene systems. For phenalenyl based superallyl cation, the sign inversion of γ (from negative to positive) is observed upon switching between the singlet and triplet states, which is predicted to be associated with a modification of the balance between the positive and negative contributions to γ. The present study paves the way toward designing a variety of open-shell NLO supermolecular systems composed of phenalenyl radical building blocks.     

Efficient synthesis of biazoles by aerobic oxidative homocoupling of azoles catalyzed by a copper(I)/2-pyridonate catalytic system

A highly efficient and convenient CuCl/2-pyridonate catalytic system for oxidative homocoupling of azoles affording a biazole product has been developed. With this system, a variety of biazoles have been effectively synthesized in good to excellent yields in the presence of a very small amount of copper catalyst (1.0 mol%). It was feasible to employ air as a green oxidant.     

Metal‐cation‐induced chiroptical switching for poly(phenylacetylene) bearing a macromolecular ionophore as a graft chain

A poly(phenylacetylene) bearing a polycarbohydrate ionophore as a graft chain (copolymer 4 ) was synthesized by the copolymerization of end‐functionalized (1→6)‐2,5‐anhydro‐3,4‐di‐O‐ethyl‐D ‐glucitol with a 4‐ethynylbenzoyl group (macromonomer 2 ) with phenylacetylene. Copolymer 4 showed a split‐type circular dichroism (CD) in the long absorption region of the conjugated polymer backbone (280–500 nm), and the CD pattern varied in response to external stimuli, such as the solvents and temperature. This suggested that 4 had a predominantly one‐handed helical conformation in the polyacetylene backbone. The CD pattern of 4 was completely inverted by the formation of a complex between the macromolecular ionophore units and the selected metal cations, that is, Ba²⁺, Pb²⁺, Sr²⁺, Na⁺, and Li⁺. This suggested that copolymer 4 underwent a helix–helix transition through the host–guest complexation with achiral inorganic metal cations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5855–5863, 2005     

Selection of spectral lines and transition probability data in plasma temperature measurements by photoelectric scanning spectrometry

A strict, comparative investigation of published transition probabilities for thermometric lines and an experimental study of determinations of plasma temperatures were made for improving the accuracy in temperature measurements by the well-known slope method. Four sets of FeI lines which satisfy the requirements for the thermometric lines were selected in the wavelength region of 200–400 nm. A statistical method was used to evaluate degrees of agreement among different sets of transition probabilities. In the experimental study, excitation temperatures of a stabilized arc plasma were determined from relative line-intensities recorded by photoelectric scanning spectrometry. In conclusion, two recommended combinations of lines and transition probability data are presented for the slope temperature measurement. Line pairs used in combination of selected transition probabilities suitable for the two-line method are also given.     

Reaction kinetics of multiphoton excited BCI3 with H2S

In order to investigate unique behaviors in kinetics of the reaction of multiphoton excited BCl₃ with H₂S, two kinds of experiments were performed. The first, parallel beam experiment, gives the activation energy of the primary reaction pathway considerably smaller than the bond strength. The second, focussed beam experiment, shows that the isotope selectivity increase with incident pulse energy. Both results were found different from typical multiphoton dissociation experiments, showing its own characteristics.     

Fuzzy-theoretic and concept-formational approaches to hint-effect experiments in human decision processes

This paper describes the results of hint-effect experiments, and analyses the human decision-making process from fuzzy-theoretic and concept-formational viewpoints. To begin with, we discuss the problem of the decision-making process subject to a specific and newly given information. In other words, the fuzzy-theoretic experiment concerning with some hints in the estimation and decision processes of the card arrangement is conducted. Next, the concept-formational process is analysed clearly by means of the introduction of both the cusp-curved surface in catastrophe theory and fuzziness concept in fuzzy set theory. Finally, we show the hint effect in the estimation and decision processes.     

Preparation of CH3SiO3/2 film from methyltriethoxysilane

An oligomer solution was prepared from methyltriethoxysilane with HNO₃ catalyst. Aluninum acetylacetonate was introudced into the solution to eliminate crystalline precipitates (CH₃SiO_3/2)₈. Self-sustained film was attempted by dropping the solution onto an aqueous solution, into which NaCl was added to elevate the solution density. The film formation greatly depended both on the reaction time and on the supporting solution. The structure of the film thus obtained was investigated by FTIR attenuated total reflectance spectroscopy.