Characterization of Highly Coordinated Allylgermanes: Pivotal Players for Enhanced Nucleophilicity and Stereoselectivity

Allylgermanes with a 4‐, 5‐, and 6‐coordinated germanium center were characterized by X‐ray crystallography. Cationic 6‐coordinated group 14 allylmetals, which were hitherto assumed to be a transition‐state structure of allylations, were successfully isolated. Forming high coordination states significantly enhanced the reactivity of the allylgermanes. In contrast to the 4‐coordinated allylgermanes with low reactivity, the highly coordinated species readily reacted with several aldehydes. Furthermore, the high coordination states exerted a significant effect on the E/Z selectivity of allylation depending on external additives. The coordination structure had a dramatic influence on the electronic and steric environments around the Ge center, enabling the geometrically controlled allylation of aldehydes.     

Effects of physical aging on solubility,diffusivity, and permeability of propane and n-butane in poly(4-methyl-2-pentyne)

The effects of physical aging on the solubility, diffusivity, and permeability of propane and n-butane in a hydrocarbon-based disubstituted polyacetylene, poly(4-methyl-2-pentyne) (PMP), were studied. As the relative pressure of propane and n-butane increased, the solubility of both hydrocarbons increased. Like other glassy polymers, the sorption isotherms for propane and n-butane in all PMP films were concave to the relative pressure axis, indicating dual-mode sorption behavior. The diffusion of propane and n-butane in PMP followed typical Fickian diffusion in a plane sheet. The propane diffusivity in both the unaged and aged films increased with increasing concentration of propane sorbed in the film. The n-butane diffusivity in aged films also increased with increasing n-butane concentration. However, unaged films showed the opposite behavior: the diffusivity decreased with increasing n-butane concentration. These diffusion phenomena are a consequence of the interplay between thermodynamic and mobility factors. The permeabilities of propane and n-butane decreased monotonically with increasing penetrant concentration, similar to the behavior observed in other common glassy polymers. The relaxation of the nonequilibrium excess free volume in PMP films induced the decrease in both solubility and diffusivity. As a result, the permeability of propane and n-butane in PMP decreased upon physical aging. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2407–2418, 2004     

Contiguous relations,Laplace’s methods,and continued fractions for $${}_3F_2(1)$$ 3 F 2 ( 1 )

The Ramanujan Journal - Using Hilbert transforms, we establish two families of sum rules involving Bessel moments, which are integrals associated with Feynman diagrams in two-dimensional quantum...     

Asymptotic spectral analysis of growing regular graphs

We propose the quantum probabilistic techniques to obtain the asymptotic spectral distribution of the adjacency matrix of a growing regular graph. We prove the quantum central limit theorem for the adjacency matrix of a growing regular graph in the vacuum and deformed vacuum states. The condition for the growth is described in terms of simple statistics arising from the stratification of the graph. The asymptotic spectral distribution of the adjacency matrix is obtained from the classical reduction.

     

Novel Synthesis and Structures of Amines and Triazole-Derived Glycoside and Nucleoside Derivatives of Phosphanyl Sugar Analogs

ABSTRACT

3-Methyl-1-phenyl-2-phospholene and 1-phenyl-2-phospholene 1-oxides were converted into 2-bromo-3-hydroxy-3-methyl-1-phenylphospholane and 2-bromo-3-hydroxy-1-phenylphospholane 1-oxide (1-bromo-1,3,4-trideoxy-1,4-C-[(R, S)-phenylphosphinylidene]-glycero-tetrofuranose) by the action of bromine in aqueous medium. The bromo substituent of the phospholane was substituted by treatment with amines or an azide anion to afford novel glycoside derivatives of phosphanyl sugar analogs such as 2-amino-3-hydroxy-1-phenylphospholane (3,4-dideoxy-1,4-C-[(R, S)-phenylphosphinylidene]-glycero-tetrofuranosylamine) and 2-azido-3-hydroxy-3-methyl-1-phenylphospholane 1-oxides with retention of the configuration. The 1,3-dipolar cycloaddition of the 2-azido derivative of the phospholane with alkynes gave 3-hydroxy-3-methyl-1-phenyl-2-(triazol-1′-y1)phospholane 1-oxides as a novel triazole-derived nucleoside of phosphanyl sugar analogs. The structure of the glycoside and nucleoside derivatives of the phosphanyl sugar analogs prepared was deterimined from IR, NMR, and X-ray crystallography analysis.     

Substituent effect on electrophoretic mobility for a series of poly(N-acryloyl-amino acid)s

In this study, the electrophoretic mobilities (μ) for a series of poly(N-acryloyl-amino acid)s were determined by capillary zone electrophoresis to investigate the effect of substituent on the electrophoretic behavior of polyelectrolytes. The μ values determined showed a strong correlation with the molar volume of the corresponding amino acids.     

Contrast viscosity changes upon photoirradiation for mixtures of poly(acrylic acid)-based alpha-cyclodextrin and azobenzene polymers

Polymer-polymer interactions were investigated for mixtures of a poly(acrylic acid) (pAA) carrying azobenzene (pC12Azo) and two kinds of pAA carrying alpha-cyclodextrin (CD), in which CDs are attached to the main chain through the 3- and 6-positions in CD (p3alphaCD and p6alphaCD, respectively), using several techniques, such as viscosity and NMR measurements. Viscosity data exhibited contrast changes upon UV irradiation: thinning (p3alphaCD/pC12Azo) and thickening (p6alphaCD/pC12Azo). NOESY spectra confirmed that the contrast viscosity changes were ascribable to differences in how CD moieties interact with pC12Azo after photoisomerization of azobenzene moieties from trans to cis: dissociation of inclusion complexes (p3alphaCD/pC12Azo) and formation of interlocked complexes (p6alphaCD/pC12Azo).     

Modeling vibrational dephasing and energy relaxation of intramolecular anharmonic modes for multidimensional infrared spectroscopies

Starting from a system-bath Hamiltonian in a molecular coordinate representation, we examine an applicability of a stochastic multilevel model for vibrational dephasing and energy relaxation in multidimensional infrared spectroscopy. We consider an intramolecular anharmonic mode nonlinearly coupled to a colored noise bath at finite temperature. The system-bath interaction is assumed linear plus square in the system coordinate, but linear in the bath coordinates. The square-linear system-bath interaction leads to dephasing due to the frequency fluctuation of system vibration, while the linear-linear interaction contributes to energy relaxation and a part of dephasing arises from anharmonicity. To clarify the role and origin of vibrational dephasing and energy relaxation in the stochastic model, the system part is then transformed into an energy eigenstate representation without using the rotating wave approximation. Two-dimensional (2D) infrared spectra are then calculated by solving a low-temperature corrected quantum Fokker-Planck (LTC-QFP) equation for a colored noise bath and by the stochastic theory. In motional narrowing regime, the spectra from the stochastic model are quite different from those from the LTC-QFP. In spectral diffusion regime, however, the 2D line shapes from the stochastic model resemble those from the LTC-QFP besides the blueshifts caused by the dissipation from the colored noise bath. The preconditions for validity of the stochastic theory for molecular vibrational motion are also discussed.