Br NQR relaxation and successive phase transitions of CH3NH3HgBr3

The measurement of ⁸¹Br NQR in CH₃NH₃HgBr₃ has been carried out in the temperature range between 80 and 300 K using a pulse NQR method. The temperature dependence of ⁸¹Br NQR frequencies in CH₃NH₃HgBr₃ has revealed that it undergoes three characteristic successive phase transitions at T?=?123, 184 and 239 K. The phase transition temperature at T?=?239 K is the second-order type, whereas those at T?=?184 and 123 K are the first-order nature of the phase transitions. Each phase transition seems to be closely related to the motions of methyl ammonium cation as a partial or whole. The enhancement of 1/T ₁ at T?=?239 K indicates the onset of the molecular motion of the cation as a whole with increasing temperatures.     

127I NQR and 1H NMR studies of 4-aminopyridinium tetraiodoantimonate(III); molecular motion and phase transition

The crystals of 4-NH₂PyHSbI₄ (Py = C₅H₄N) have been investigated by means of ¹²⁷I NQR, ¹H NMR T ₁ and DTA. The crystals can exist in two modifications of β and α(I) at room temperatures. The α(I)-phase is a metastable state which is obtained when the stable β form is heated. The α(I)-phase undergoes a first-order type phase transition of α(I) $\leftrightarrow \alpha $ (II) at 272 K (on heating), while the β-phase is stable down to 77 K. Four and two ¹²⁷I (m = ±1/2 $\leftrightarrow \pm $ 3/2) NQR lines have been found for the β- and α(II)-phases, respectively. One half of them is assignable to the terminal I atom(s) and the other to the bridging I atom(s) in each phase. All the resonance lines of the α(II)-phase underwent a disappearance above ca. 240 K and no resonance line was observed in the α(I)-phase. The second moment M ₂ value of ¹H NMR spectra with 8 G² at 290 K shows that the 4-NH₂PyH^?+? cations reside in the rigid lattice in the β-phase. In contrast, in the α(I)-phase the cation rotates about an axis more symmetric than pseudo threefold axis. The activation energy of 21 kJ mol^???1 was estimated for the reorientational motion in the α(I)-phase from the ¹H NMR T ₁ measurements. The nature of phase transitions in the 4-NH₂PyHSbI₄ is discussed in comparison with that in 4-NH₂PyHSbBr₄.     

Synthesis of Highly Insulated Molecular Wires by Polymerization of Organic-Soluble Symmetrical Linked Inclusion Complex Monomers

Summary: We developed a new method for synthesizing an organic-soluble permethylated cyclodextrin-based insulated molecular wire (IMW); this method involves the polymerization of a symmetrical linked inclusion complex as a monomer. This monomer was synthesized by dimerization of linked inclusion complexes at the terminal alkynyl groups by Glaser coupling. The polyrotaxane thus obtained is highly soluble in a variety of organic solvents and has a high covering ratio, regioregularity, and photoluminescence efficiency.     

Pd/C-catalyzed chemoselective hydrogenation in the presence of diphenylsulfide

[Structure: see text] A Pd/C-catalyzed chemoselective hydrogenation using diphenylsulfide as a catalyst poison has been developed. This methodology selectively hydrogenates olefin and acetylene functionalities without hydrogenolysis of aromatic carbonyls and halogens, benzyl esters, and N-Cbz protective groups.     

Stereo-dynamical ion-pair formation in collisions of highly-charged ions with argon dimers

Multiple ionization process of a rare gas dimer BC collided with a slow highly charged ion A^q+ is investigated with the three-center Coulombic over-barrier model previously developed by the present authors. To reveal stereodynamical effects, we calculate asymmetric ion-pair formation cross sections σ(Q_B,Q_C) as a function of the orientation angle. We introduce a pair of atomic impact parameters b_B and b_C with which we distinguish the near and far sites. Furthermore, we distinguish the forward and backward emitted ions produced as a result of Coulomb explosion. Partial screening effects are also considered.     

-bases for cohomology of local systems on hyperplane complements

We study cohomology with coefficients in a rank one local system on the complement of an arrangement of hyperplanes . The cohomology plays an important role for the theory of generalized hypergeometric functions. We combine several known results to construct explicit bases of logarithmic forms for the only non-vanishing cohomology group, under some nonresonance conditions on the local system, for any arrangement . The bases are determined by a linear ordering of the hyperplanes, and are indexed by certain ``no-broken-circuits" bases of . The basic forms depend on the local system, but any two bases constructed in this way are related by a matrix of integer constants which depend only on the linear orders and not on the local system. In certain special cases we show the existence of bases of monomial logarithmic forms.

     

Copper-mediated C-H bond arylation of arenes with arylboronic acids

A new copper-mediated cross-coupling of arenes and arylboronic acids is described. Under the influence of Cu(OCOCF 3) 2, the C-H bond arylation of electron-rich arenes with arylboronic acids takes place to afford a range of biaryls in good yields. The reaction is selective for cross-coupling; no homocoupling product arising from arenes or arylboronic acids is detected. Multiple C-H bond arylation is possible with indoles and pyrroles furnishing interesting extended pi-systems.     

On-site manipulation of single chromosomal DNA molecules by using optically driven microstructures

We report a novel method for manipulation of single giant DNA molecules under a video microscope. Using optically driven microstructures, we manipulated chromosomal DNA of length in the order of millimetres, extended by electroosmotic flow without DNA breakage in aqueous solution: we picked up DNA, using microfabricated hooks and wound it around microfabricated bobbins.     

Enantioselective synthesis of phomallenic acid C, an inhibitor of FAS II pathway

Enantioselective synthesis of phomallenic acid C, an inhibitor of bacterial FAS II pathway, was successful. Allenyldiyne structure was constructed by a direct anti-S_N2′ coupling of propargyl mesylate with diynylindium in the presence of palladium catalyst. Enantiomeric purity was determined by Ohrui-Akasaka method to be 83%ee.     

Block copolymer micelles with dye loaded on their shells or cores

We prepared reversible micelles with dye loaded on the shells or cores by ion exchange. A poly(4-styrylmethyl triphenylphosphonium chloride)-block-polystyrene diblock copolymer prepared from poly(4-vinylbenzylchloride)-block-polystyrene and triphenylphosphine was reacted with methyl orange in a mixed solvent of benzene and acetonitrile to produce poly[4-styrylmethyl triphenylphosphonium 4-(4-dimethylamino)phenylazobenzenesulfonate]-block-polystyrene. The loading of the methyl orange on the micellar shells or cores was dependent on the composition of the mixed solvents. Dynamic light scattering demonstrated that the loading of the dye on the cores significantly expanded the micelles when compared to that on the shells. The loading of the dye on the cores shifted the UV wavelength of the methyl orange, whereas that on the shells produced no changes in the UV wavelength. Transmission electron microscopy confirmed the formation of the spherical micelles.