Effects of interaction between the chelate rings and π‐conjugated systems in fused salphen complexes on UV‐Vis‐NIR spectra

Dinuclear (Zn₂, Ni₂, and NiZn) complexes of fused salphen with acene‐type annelation were synthesized from 3,7‐diformyl‐2,6‐dihydroxynaphthalene. The spectroscopic properties of these complexes were compared with those of their constitutional isomers with phene‐type annelation. The acene‐type complexes exhibited a characteristic absorption band in the near‐infrared region that showed a noticeable solvent effect. Time‐dependent density functional theory calculations suggested that the absorption arose from a π → π* transition localized at the naphthalene ring, which was perturbed by the adjoining chelate rings. Effects of the connection topology in the fused salphen complexes are discussed by comparison with those of polycyclic aromatic hydrocarbons.     

High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect. Pulse compression down to 19 fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7x10(-9) in a few picoseconds interval prior to the main laser pulse.     

Simple multilevel halftoning excelled in gradation reproducibility

A simple multilevel halftoning method, which is based on the conventional error diffusion method and realizes halftoning excelled in the distribution of dots, is proposed. The proposed method consists of three steps, e.g., the image decomposition, the generation of binary halftone images by the error diffusion, and the synthesis of a multilevel halftone image, and each step does not require a complicated algorithm. The effectiveness of the proposed method is indicated by applying it to three- and four-level halftoning of gray-tone and natural images.     

Halogen-substituent effect on the spectroscopic properties of 2-phenyl-6-dimethylaminobenzothiazoles

6-Dimethylamino-2-phenylbenzothiazole (1-H) is a push-pull benzothiazole fluorophore mimicking the firefly oxyluciferin structure. We newly prepared 7-chloro and 7-bromo derivatives of 1-H and its 4-acetyl derivative (2-H), and their spectroscopic and photophysical properties were investigated. The halogenated derivatives showed the blue-shifted electronic absorption maxima and fluorescence emission maxima compared to 1-H and 2-H, resulted from the deformations of the NMe₂ groups and the electron withdrawing properties of the halogen groups. In addition, the halogen substitutions accelerate intersystem crossing by heavy atom effect, resulting in a decrease in fluorescence quantum yields. Interestingly, however, the halogenated derivatives of 2-H still showed moderate fluorescence quantum yields. The halogenation effect is one of the guides to design push-pull benzothiazole fluorophores for tuning fluorescence properties.     

Enhanced activity and modified substrate-favoritism of Burkholderia cepacia lipase by the treatment with a pyridinium alkyl-PEG sulfate ionic liquid

Three types of pyridinium salts, i.e., 1-ethylpyridin-1-ium cetyl-PEG₁₀ sulfate (PY_ET), 1-butylpyridin-1-ium cetyl-PEG₁₀ sulfate (PY_BU), and 1-(3-methoxypropyl)pyridin-1-ium cetyl-PEG₁₀ sulfate (PY_MP), have been prepared and evaluated for their activation property of Burkholderia cepacia lipase by comparison to the control IL-coated enzymes, 1-butyl-2,3-dimethylimidazolium cetyl-PEG₁₀ sulfate-coated lipase PS (IL1-PS). Among the tested pyridinium salt-coated lipases, the PY_ET-coated lipase PS (PY_ET-PS) exhibited the best results; the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, 1-(pyridin-4-yl)ethanol, or 4-phenylbut-3-en-2-ol proceeded faster than those of the IL1-PS-catalyzed reaction while maintaining an excellent enantioselectivity (E?>?200). This improved efficiency was found to be dependent on the increased K_cat value.     

Eremophilane,bakkane, secoeremophilane,and secobakkane sesquiterpenoids from Ligularia virgaurea collected in China

Secobakkane B (C-6/C-7 cleaved secobakkane type aldehyde), secovirgaurenols B and C (C-8/C-9 cleaved secoeremophilane type), a 1β,10β-epoxyfuranoeremophilane, two 1β,10β-epoxyeremophilanolides, and fukinospirolide C (bakkane-type lactone), as well as 33 known compounds were isolated from three samples of Ligularia virgaurea collected in China. Two of the three analyzed samples were grouped in the neoadenostylone (N) type, and the rest, a mixture of the 6-hydroxyeuryopsyn (H) and cacalol (C) types, out of five chemotypes found in this species.     

Self-encapsulation of homogeneous catalyst species into polymer gel leading to a facile and efficient separation system of amine products in the Ru-catalyzed reduction of carboxamides with polymethylhydrosiloxane (PMHS)

A practical procedure for production of amines is offered by the ruthenium-catalyzed reduction of carboxamides with polymethylhydrosiloxane, in which encapsulation of the catalyst species into the formed insoluble siloxane resins contributes to the separation of both metallic and siloxane residues from the product.     

Effects of polarization of 1.4 microm femtosecond laser pulses on the formation and fragmentation of naphthalene molecular ions compared at the same effective ionization intensity

Naphthalene was ionized with 130 fs pulses of different polarizations at 1.4 microm. In contrast to the results of ionization by 0.8 microm pulses, fragmentation was dramatically suppressed and naphthalene molecular ions of up to 3+ were produced. The use of this simple model of ionization and large electron kinetic energy enabled us to study the electron-recollision-induced fragmentation and/or double ionization more precisely. The failure of the theoretical prediction of ion yield for the case of naphthalene prevented us from judging the electron recollision solely by a comparison with theoretical curves. Therefore, the effects of laser polarization on the ratios between differently charged states and between molecular and total ions were compared at the same effective (peak) intensity instead of average intensity. Comparison under the same effective intensity enabled us to identify the effects of ellipticity clearly. Evidence of the electron recollision was found in the doubly charged molecular ion formation but not in the fragmentation. The single-electron recollision event was not sufficient to induce fragmentation because of its low energy transfer efficiency. We concluded that the fragmentation originated in the unstable nature of the highly charged molecular ion itself and in the Coulomb explosion in the case of naphthalene.     

Comb-shaped poly(ethylene glycol)-modified subtilisin Carlsberg is soluble and highly active in ionic liquids

Subtilisin Carlsberg conjugated with comb-shaped poly(ethylene glycol) was solubilized in common ionic liquids without adding water, and exhibited higher transesterification activity in an ionic liquid, [Emim][Tf2N], than in organic solvents commonly used for enzymatic biotransformation.     

Structure-activity relationship studies on CXCR4 antagonists having cyclic pentapeptide scaffolds

Structure-activity relationship studies on CXCR4 antagonists, which were previously found by using cyclic pentapeptide libraries, were performed to optimize side-chain functional groups, involving conformationally constrained analogues. In addition, a new lead of cyclic pentapeptides with the introduction of a novel pharmacophore was developed.