Solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration of pyrrole studied by near-infrared/infrared spectroscopy and DFT calculations

Near-infrared (NIR) and IR spectra were measured for pyrrole in CCl(4), CHCl(3), and CH(2)Cl(2) to study solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration. It was found that the wavenumbers of the NH fundamental and its first overtone decrease in the order of CCl(4), CHCl(3), and CH(2)Cl(2), which is the increasing order for of the dielectric constant of the solvents. Their absorption intensities increase in the same order, and the intensity increase is more significant for the fundamental than the overtone. These results for the solvent dependence of the wavenumbers and absorption intensities of NH stretching bands of pyrrole are quite different from those due to the formation of hydrogen bonds. Quantum chemical calculations of the wavenumbers and absorption intensities of NH stretching bands by using the 1D Schr?dinger equation based on the self-consistent reaction field (SCRF)/isodensity surface polarized continuum model (IPCM) suggest that the decreases in the wavenumbers of both the fundamental and the overtone of the NH stretching mode with the increase in the dielectric constant of the solvents arise from the anharmonicity of vibrational potential and their intensity increases come from the gradual increase in the slope of the dipole moment function.     

Synthetic protocol for diarylethenes through Suzuki-Miyaura coupling

The synthesis of a variety of diarylethenes through the Suzuki-Miyaura coupling reaction of 1,2-dichlorohexafluorocyclopentene with arylboronic acids and esters has been developed. Thiophenes with various substituents such as cyano and ester functionalities can be incorporated.     

Second harmonic generation in ferroelectric liquid crystals and their mixtures

Abstract

The second harmonic generation (SHG) in the ferroelectric liquid crystal (FLC) state has been studied as functions of electric field strength, rotating angle, temperature and molecular structure. It has been confirmed that a sharp angularly phase-matching curve of the SHG controlled by an electric field is observed even in the liquid crystal. The temperature dependences of the phase-matched SHG and Maker fringe in the ferroelectric phase have also been studied, and temperature dependences of non-linear optical coefficients obtained. The SHG in several kinds of FLC and dye doped FLC have also been measured, and the enhancement of SHG realized by means of doping the FLC with several kinds of dye.     

Magnitude and direction of the spontaneous polarization of ferroelectric liquid crystals with several bond moments

The magnitude and direction of the spontaneous polarization in most ferroelectric liquid crystals have been confirmed to be determined by the location and magnitude of the bond moment around the chiral carbon and the core. In compounds with several bond moments their relative orientation is very important for obtaining a large spontaneous polarization. Compounds with benzene rings in the core substituted with OH also have a large spontaneous polarization, perhaps due to the formation of hydrogen bonds. Reversal of the direction of the spontaneous polarization with temperature has been found for EFPPOPB. This anomalous behaviour has been explained tentatively in terms of a conformation change due to the existence of a flexible -CH₂- unit between the chiral carbon and the dipole moment.     

Mild Deprotection of Methyl,Benzyl, Methoxymethyl,Methylthiomethyl, Methoxyethoxymethyl,and β-(Trimethylsilyl)-ethoxymethyl Esters with AlCl3-N,N-dimethylaniline

Methyl, benzyl, methoxymethyl, methylthiomethyl, methoxyethoxymethyl, and β-(trimethylsilyl)ethoxymethyl esters could be cleaved readily under mild conditions on treatment with AlCl₃-N,N-dimethylaniline in CH₂Cl₂ to give parent carboxylic acids in high yields.     

Enhanced transdermal delivery of indomethacin-loaded PLGA nanoparticles by iontophoresis

Nanoparticles effectively deliver therapeutic agent by penetrating into the skin. Indomethacin (IM) and coumarin-6 were loaded in PLGA nanoparticles with an average diameter of 100 nm. IM and coumarin-6 were chosen as a model drug and as a fluorescent marker, respectively. The surfaces of the nanoparticles were negatively charged. Permeability of IM-loaded PLGA nanoparticles through rat skin was studied. Higher amount of IM was delivered through skin when IM was loaded in nanoparticles than IM was free molecules. Also, iontophoresis was applied to enhance the permeability of nanoparticles. When iontophoresis with 3 V/cm was applied, permeability of IM was much higher than that obtained by simple diffusion of nanoparticles through skin. The combination of charged nanoparticle system with iontophoresis is useful for effective transdermal delivery of therapeutic agents.     

One-pot asymmetric synthesis of γ-nitroaldehydes from aldehydes and nitroalkanes through a catalytic tandem reaction using an amino acid lithium salt

One-pot asymmetric synthesis of γ-nitroaldehydes from aldehydes and nitroalkanes was achieved by a catalytic tandem reaction using a primary amino acid lithium salt, O-tert-butyldiphenylsilyl l-tyrosine lithium salt, as a catalyst. Various aryl, alkenyl, and alkyl aldehydes were converted into γ-nitroaldehydes via in situ generation of nitroalkenes.     

Generation of carbanions through stibine-metal and bismuthine-metal exchange reactions and its applications to precision synthesis of ω-end-functionalized polymers

Generation of carbanions from organostibines and organobismuthines through heteroatom-metal exchange reactions was examined from synthetic and mechanistic viewpoints. The exchange reaction proceeded spontaneously upon treatment with various organometallic reagents, such as alkyl lithiums, tetraalkyl zincates, and alkyl magnesium halides to afford the corresponding carbanions quantitatively. Due to the high reactivity of these heteroatom compounds, the exchange reactions took place exclusively even in the presence of various polar functional groups, which potentially react with organometallic species. The advantage of this method was exemplified by the end-group transformation of living polymers that bear these heteroatom species at the ω-polymer end, prepared by using organostibine and bismuthine-mediated living radical polymerizations. Various polymers that bear polar functional groups and acidic hydrogen-for example, poly(methyl methacrylate), poly(butyl acrylate), poly(N-isopropyl acrylamide), and poly(2-hydroxyethyl methacrylate)-could be used in the exchange reactions, and subsequent trapping with electrophiles afforded the corresponding polymers with controlled molecular weights, molecular weight distributions, and end-group functionalities. Competition experiments showed that organostibines and organobismuthines were among the most reactive heteroatom compounds towards organometallic reagents and that their high reactivity was responsible for the high chemoselectivity in the exchange reaction.     

Exact formula of the distribution of Schmidt eigenvalues for dynamical formation of entanglement in quantum chaos

The exact formula of the one-level distribution of the Schmidt eigenvalues is obtained for dynamical formation of entanglement in quantum chaos. The formula is based on the random matrix theory of the fixed-trace ensemble, and is derived using the theory of the holonomic system of differential equations. We confirm that the formula describes the universality of the distribution of the Schmidt eigenvalues in quantum chaos.     

Inelastic scattering of cosmic ray muons on iron nuclei and the virtual photon shadowing

Hadronic cascade showers originating from inelastic interactions of cosmic ray muons with iron nuclei have been observed in a calorimeter located between two magnetic spectrometers. The separation of those events from the electromagnetic showers has been successfully done in the ranges of the transferred energy v ≳ 50 GeV and its ratio to muon energy v/E ≳ 0,1, by utilizing the difference of their longitudinal cascade developments. The comparison of the obtained μ-Fe cross section with available μ-, e- and σ-proton data as well as μ-, e- and σ-nucleus data indicates that;

• 1 At v ˜ 100 GeV, the virtual photon cross section on iron nucleus is almost the same as the real photon one, at least Q² ≳ 0.1 GeV²/c², and is about 70% of the cross section on proton times the atomic mass number of iron, i.e. the shadowing effect is clearly seen.
• 2 Up to TeV region, this virtual photon cross section on iron does not increase significantly. contrary to the tendency of the real photon cross section on proton around 100 GeV. This suggests most likely that the shadowing still increases with energy at such high energies.