Supramolecular Crowding Can Avoid Oxygen Quenching of Photon Upconversion in Water

A common challenge in chemistry that deals with photoexcited states is to avoid oxygen quenching. This is crucial for hot research fields such as photon upconversion (UC), in which oxygen-sensitive triplet excited states play pivotal roles. However, methods to avoid oxygen quenching in aqueous media are far more limited despite eagerly anticipated catalytic and biological applications. This work introduces a simple strategy to achieve air-stable triplet–triplet annihilation (TTA)-based UC in water, namely, supramolecular crowding. Amphiphilic cationic acceptor molecules and anions with long alkyl chains co-assemble in water in which hydrophobic donor molecules are molecularly dispersed. Despite the common notion that oxygen molecules diffuse readily across hydrophobic domains in water, more than 80 % of the TTA-UC emission of the obtained hydrophobic co-assemblies is maintained in air-saturated water. This work demonstrates the new promising potential of supramolecular chemistry for photophysical and photochemical functions with oxygen-sensitive species.     

The first topologically controlled synthesis of doubly bridged beta-cyclodextrin dimers

Reaction 6(A),6(B)-di(O-tosyl)-beta-cyclodextrin with Na(2)S in DMF gave the cis-dimer of beta-cyclodextrin in 21% isolated yield while the trans-dimer was not detected.     

Shear-thickening flow of suspensions of carbon nanofibers in aqueous PVA solutions

The suspensions of carbon nanofibers in aqueous poly(vinyl alcohol) solutions were prepared in the presence of spherical carbon black particles, and the steady-shear viscosity and dynamic viscoelasticity were measured for complex suspensions. Although the single suspensions of carbon black are highly stable, the flocculation of carbon nanofibers is promoted by the addition of carbon black particles. The complex suspensions show remarkable shear thickening in the steady-flow and strain hardening in oscillatory shear with large amplitude. The nonlinear responses strongly depend on the carbon black concentration, whereas the dynamic viscoelasticity at low strains in the linear ranges is not significantly influenced. As the highly elastic effects arise from the long-range motion of particles, the possible mechanism may be the orientation of nanofibers in strong shear fields. The suspensions show the time-dependent behavior of viscosity when the time-scale of measurements is shorter than that of structural recovery to the isotropic states.     

Structure of anislactone A; a new skeletal type of sesquiterpene from the pericarps of Illicium anisatum

A novel sesquiterpene lactone was isolated from the pericarps of Illicium anisatum, a well known toxic plant in Japan, and its structure was established from spectral data and X-ray crystallographic analysis.     

Ellagitannins and lignan glycosides from Balanophora japonica (Balanophoraceae)

Three new ellagitannins named balanophotannins A-C having a 1,1'-(3,3',4,4'-tetrahydroxy)dibenzofurandicarboxyl group in their molecules and four known lignan glycosides were isolated from the extracts of fresh aboveground and underground parts of a medicinal parasitic plant Balanophora japonica (Balanophoraceae). Their structures were elucidated on the basis of spectral and chemical evidence. Chemotaxonomic significance of the known lignan glycosides in Balanophora japonica was discussed.     

Observation of the acceleration of a single bunch by using the induction device in the KEK proton synchrotron

A single rf bunch in the KEK proton synchrotron was accelerated with an induction acceleration method from the injection energy of 500 MeV to 5 GeV.     

Meson loop effect on high density chiral phase transition

We test the stability of the mean field solution in the Nambu-Jona-Lasinio model in a semi-quantitative manner. For stable solutions with respect to both the σ and π directions, we investigate effects of the mesonic loop corrections of 1/N _c , which correspond to the next-to-leading order in the 1/N _c expansion, on the high density chiral phase transition. The corrections weaken the first order phase transition and shift the critical chemical potential to a lower value. At N _c = 3, however, instability of the mean field effective potential prevents us from determining the minimum of the corrected one.      

Synthesis and Synthetic Application of alpha-Formylvinylphosphonates. Facile Synthesis of Phosphono-Substituted Heterocyclic Compounds

The beta-ethoxy-alpha-phosphonovinyl anion, generated from beta-(ethoxy)vinylphosphonate 1 and LDA, reacted with aldehydes and ketones or phenyl isocyanate to give the corresponding allylic alcohols 2a-m or 1,3-diphenyl-5-phosphonouracil 4 in good or moderate yields. Treatment of the alcohols 2a-d,g,h,j with trifluoroacetic acid led to alpha-formylvinylphosphonates 5a-d,g,h,j in excellent yields. Synthetic application of the alpha-formylvinylphosphonates 5a-d,g,h to phosphono-substituted heterocyclic compounds was studied.