Thermochromism in an organic crystal based on the coexistence of sigma- and pi-dimers

Transition-metal complexes and organic radical molecules can be used to make electric conductors and ferromagnets, the optical properties of which can be controlled by changing temperature and are used as molecular switches and sensors. Whereas a number of organic radicals in solution show temperature-dependent optical properties, such behaviour in crystalline forms is more rare. Here, we show a fully reversible continuous thermochromism with a unique mechanism in purely organic crystals of diazaphenalenyl radical. This behaviour is based on changes in the diazaphenalenyl dimers coexisting in the crystal. From the X-ray crystal structure analyses and temperature-dependent visible spectra, we conclude the presence of a thermal equilibrium between sigma-bonded and pi-bonded dimers, which are separated by 2.62(6) kcal mol(-1). This conclusion is supported by room-temperature electron spin resonance spectra of the solid, which showed signals that are attributable to a thermally accessible triplet state of the pi-dimer structure. This proves the coexistence of two dimers of different bonding natures in the crystal, causing it to demonstrate thermometer-like behaviour.     

Synthesis of ultrahigh molecular weight phenolic polymers by enzymatic polymerization in the presence of amphiphilic triblock copolymer in water

An enzymatic oxidative polymerization of phenols was investigated in the presence of poly(ethylene glycol) (PEG)-poly(propylene glycol) (PPG)-poly(ethylene glycol) (PEG) triblock copolymer (Pluronic) in water. The formation of micellar aggregate of phenol and Pluronic by hydrogen bonding interaction in an aqueous solution was verified by DLS measurement. The PEG content of Pluronic greatly affected the polymerization behaviors. Using Pluronic with high PEG content improved the regioselectivity of the polymerization of phenol to give the polymer mainly consisting of phenylene unit. The polymerization in the presence of Pluronic F68 (EG₇₆-PG₂₉-EG₇₆) produced the phenolic polymer with ultrahigh molecular weight (M_w > 10⁶). From other phenols, high molecular weight polymers were also obtained. In addition, the FT-IR, DSC, and XRD analyses exhibited the formation of miscible complex between the phenolic polymer and Pluronic by hydrogen bonding interaction.     

Optical resolution of n-butyl d- and l-lactates using immobilized lipase catalyst

n-Butyl d- and l-lactates (BuDLa and BuLLa) were incubated with immobilized lipase. ¹H-NMR showed that BuDLa reacted to oligomers, while BuLLa did not react. A mixture containing 90.4% of BuLLa and 9.6% of BuDLa was incubated with the enzyme for 72 h, then distilled. The purity of BuLLa increased to 98.6%.     

Failure of pseudo-periodic surrogates

A surrogate test is a method for determining the properties of time-series data. Some methods have been proposed to generate surrogate data that can be used to determine whether a pseudo-periodic time series has deterministic properties beyond pseudo-periodicity. Luo’s method is one such method. In this article, Luo’s method and the problems associated with it are discussed. In this method, surrogate datasets are produced by adding the time-shifted data to the original data. Consequently, the pseudo-periodicity of the time series is presumably preserved, but the fine structure related to the deterministic properties is destroyed. Luo’s method gives correct results for many data. However, it generates incorrect results for certain time series, for example, the time series of the Rössler chaotic attractor and phase-shifted sinusoidal waves. To overcome this problem, we propose an alternative method based on the Poincaré section.     

Flow-induced vibrations in closed side branch pipes and their attenuation methods

Some problems due to flow-induced vibrations related to closed side branch pipes have been observed in thermal and nuclear power plants. Fluctuating pressure generated in the main pipes was unusually, acoustically excited in closed side branch pipes, and intense vibrations were caused at pipes and components. For example, flow-excited acoustic resonance in closed side branches of stub pipes of safety relief valves caused the failure of steam dryers in the United States Quad City Unit 2 nuclear power plant. Furthermore, there was a possibility that residual air or gas in a closed side branch pipe unexpectedly caused severe vibrations of low frequency in the feed water piping system. We have investigated the root cause and influence of air on severe vibrations. Intense fluctuating pressure was often caused by water hammer due to valve closure and it became larger in the closed side branch pipes. We showed that an additional side branch with an orifice was very effective to suppress the flow-induced acoustic resonance. Design methods of the orifice to attenuate fluctuating pressure generated by water hammer were presented considering Mach number, the pressure loss coefficient of orifice and the intensity of particle velocity. Moreover, suitability of the characteristic curve method was confirmed for evaluation of the attenuation effect of an orifice on fluctuating pressure generated by water hammer. Finally, we considered some flow-induced vibration problems related to closed side branch pipes and their attenuation methods.     

纯铬钝化膜的电化学性能

本文用交流阻抗技术,通过对钝化铬在中性H₃BO₃+Na₂B₄O₇溶液中添加了K₃Fe₂(CN)₆/K₄Fe(CN)₆氧化还原对溶液中的极化性能及交流阻抗特性的研究,讨论了铬的钝化膜的电路模型。     

Physicochemical Property of Huaishan (Rhizoma Dioscorea) and Matai (Eleocharis dulcis) Starches

The physicochemical properties of starch, the main component in tuberous root of Huaishan (Rhizoma Dioscorea) and corm of Matai (Eleocharis dulcis) was investigated and compared with those of a Japanese yam, “Yamanoimo” starch, and potato starch. Mean particle sizes of Huaishan and Matai starches were 24 ± 5 μm and 12 ± 5 μm, respectively. X-Ray diffraction pattern suggests that Huaishan starch was B-type or C-type just close to B-type and Matai starch was A-type or C-type just close to A-type. Apparently, the intermediate component (IntCom) of Huaishan starch, which was obtained by fractionation of the starch into amylose and amylopectin, may still contain amylose and amylopectin. IntCom of Matai starch has an intermediate nature between amylose and amylopectin. It is concluded that the amylopectin molecules of Huaishan starch contain a larger amount of longer branch-ed chains and those of Matai starch contain a larger amount of shorter branched chains. Amylograms of Matai and Huaishan starches suggest that the gelatinized starches are difficult to retrograde. Digestibility of Huaishan starch by an α-amylase was the highest among the tested starches.     

[{W(O)(O2)2(H2O)}2(μ‐O)]2–‐Catalyzed Epoxidation of Allylic Alcohols in Water with High Selectivity and Utilization of Hydrogen Peroxide

A dinuclear peroxotungstate, K₂[{W(O)(O₂)₂(H₂O)}₂(μ‐O)]⋅2 H₂O, exhibits high catalytic performance for the epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide at 305 K in water solvent. The effectiveness of this system is evidenced by high chemo‐, regio‐, and diastereoselectivity, and stereospecificity for the epoxidation of allylic alcohols. Furthermore, products/catalyst separation can be easily carried out by simple extraction and the catalyst recovered can be reused with the maintenance of the catalytic performance.