Chemical Bonding in Polarised Push–Pull Ethylenes

1,1‐Diamino‐2,2‐bis(triflyl)ethylenes with both twisted and planar structures around the partial “C=C” bond were synthesised. Bonding properties in these compounds were analysed by an experimental approach using high‐resolution X‐ray diffraction data treated with X‐ray wavefunction refinement (XWR). In the twisted compound, a dominant contribution of the charge‐separated resonance structure was revealed. On the contrary, the nearly planar compound still showed π‐bonding character, however, with a considerable contribution of the charge‐separated resonance structure.     

N-Doping of Polyaromatic Capsules: Small Cavity Modification Leads to Large Change in Host–Guest Interactions

To gain insight into the host functions of a nanocavity encircled by both polyaromatic panels and heteroatoms, nitrogen-doped polyaromatic capsules were successfully synthesized from metal ions and pyridine-embedded, bent anthracene-based ligands. The new capsules display unique host–guest interactions in the isolated cavities, which are distinct from those of the undoped analogues. Besides the inclusion of Ag⁺ ions, the large absorption change of fullerene C₆₀ and altered emission of a BODIPY dimer are observed upon encapsulation by the present hosts. Moreover, the N-doped capsule exhibits specific binding ability toward progesterone and methyltestosterone, known as a natural female and synthetic male hormone, respectively, in water.     

Adsorption kinetics of carcinogens to DNA liquid crystalline gel beads

Adsorption behaviors of acridine orange (AO) and biphenyl (BP) to DNA liquid crystalline gel (LCG) beads in aqueous dispersing solution have been studied theoretically and experimentally. A theoretical consideration based on nonequilibrium thermodynamics predicted that the time course of the adsorption process is expressed with a scaled equation, and a scaled number of adsorbed carcinogen molecules ? is expressed with the square root of a scaled immersion time t, ? proportional, variant square root t at early stage, whereas it is expressed with a power law function 1 - ? proportional, variant (te - t)3/2 for ?0 > 1 and an exponential equation ?0 - ? proportional, variant e-t/alpha tau0 for ?0 > 1 at later stages of adsorption. Here, ?0 is the ratio of the initial number of carcinogen molecules in the dispersing solution to the number of the sites of adsorption of carcinogen molecules in the beads, te is the scaled equilibrium time of adsorption, tau0 is a time constant for adsorption, and alpha is a constant. Observed adsorption processes for AO were well expressed by the predicted ones, and the fitting parameters ?0 and tau0 increased with increasing cobalt chloride concentration CCo used for preparation of the beads, and both saturated above CCo > or = 400 mM for the adsorption of AO, whereas the adsorption processes for BP were expressed with the square root function. These results indicate that (1) the adsorption process at early stage is explained by diffusion-limited binding of the carcinogen molecules to DNA beads, and the time range of the early stage depends on the solubility (the solubility of AO in water is high whereas that of BP is low); and (2) the process at later stages depends on the balance of the numbers of adsorption sites and carcinogen molecules.     

Melting and swelling behaviors of UV-irradiated gelatin gel microcapsules

Gelatin gel microcapsules with a narrow size distribution have been prepared for the use of regenerative therapy by means of SPG (Shirasu porous glass) emulsification and UV-induced cross linking, and the melting and swelling behaviors of the gel membrane of the microcapsules were observed. The gel melting temperature was proportional to the 2/3 power of UV irradiation time t for tor=1 h. The average cross-sectional area of the microcapsules that remains insoluble normalized by that at 25 degrees C monotonically increased with temperature for tor=1 h. Repeated quenching of the gel microcapsules between two temperatures (25 and 40 degrees C) induced a reversible size change, which was attributed to the helix-coil transition of collagen molecules locally. From a theoretical consideration of gel particles, the observed gel melting behavior was explained well, and the scaled volume of the microcapsules was expressed as a function of scaled temperature with four fitting parameters for t相似文献   

Möbius function and characteristic monomials for combinatorial enumeration

After the definitions of amplified representations and number-theoretical vectors, the markaracter table of a cyclic subgroup is converted into the corresponding Q-conjugacy character table. The conversion is shown to necessitate an interconversion matrix that contains M?bius functions as elements. Since the interconversion matrix gives characteristic monomials for cyclic groups, all the powers appearing in each of the characteristic monomials are shown to be integers. Characteristic monomials for finite groups are then built up by starting from those of cyclic groups. This procedure clarifies the fact that all the powers appearing in each characteristic monomial for finite groups are integers. The relationship between characteristic monomial tables and unit-subduced-cycle-index tables is discussed with respect to their application to isomer enumeration. Received: 15 July 1998 / Accepted: 16 December 1998 / Published online: 16 March 1999     

Circular dichroism of optically active poly(dialkylsilane) aggregates in microcapsules

Poly[n-hexyl-(S)-3-methylpentylsilane] aggregates confined in microcapsules to keep the aggregation number and ranging in average polymer mass m(p) in a microcapsule from 2 x 10(-)(16) to 2 x 10(-)(14) g were studied by circular dichroism measurements in ethanol (a nonsolvent) and tetrahydrofuran (an associative solvent at low temperature) at various temperatures. The weight-average molecular weight M(w) and the polydispersity index (the ratio of M(w) to the number-average molecular weight) of the polysilane sample were 6.6 x 10(4) and 1.07, respectively, and the average number of polymer molecules in each capsule was estimated to be 1.9 x 10(3) for m(p) = 2 x 10(-)(16) g and 1.7 x 10(5) for m(p) = 2 x 10(-)(14) g. The size of each aggregate did not affect the optical activity because the circular dichroism thus obtained was proportional to m(p) under the same conditions in the investigated m(p) range; on the other hand, the peak height of the circular dichroism in tetrahydrofuran had a significant hysteresis between 0 and 25 degrees C. Moreover, the circular dichroism appreciably reflected the prepared method, that is, the temperature and solvent; in other words, the aggregates memorized the initial conditions in their stacking structures.     

Importance of the proligand-promolecule model in stereochemistry. I. The unit-subduced-cycle-index (USCI) approach to geometric features of prismane derivatives

Among the four methods of the unit-subduced-cycle-index (USCI) approach (Fujita in Symmetry and Combinatorial Enumeration in Chemistry. Springer, Berlin, Heidelberg, 1991), the fixed-point-matrix (FPM) method and the partial-cycle-index (PCI) method have been applied to the combinatorial enumeration of prismane derivatives. These enumeration processes are based on the proligand-promolecule model, which enables us to take account of achiral and chiral proligands. Prochirality in a geometric meaning has been discussed in general by emphasizing the presence of enantiospheric orbits in enumerated prismane derivatives. An enantiospheric orbit accommodating chiral proligands (along with achiral ones) has been shown to exhibit prochirality by using various prismane derivatives as examples. On the other hand, the scope of pseudoasymmetry has been extended to cover such a rigid skeleton as prismane in addition to a usual pseudoasymmetric center as a single atom, where the proligand-promolecule model plays an essential role.