Highly accelerating effect of lewis acids on ruthenium(II)-catalyzed radical addition reactions

The intramolecular ruthenium(II)-catalyzed radical addition of the trichloroacetyl pendant group to the 2-oxazolone skeleton is greatly enhanced in the presence of catalytic Lewis acids including rare earth metal triflates, thus providing a convenient route to a highly potential chiral synthon for vic-amino alcohols.     

Restricted hydration structures of Rb and Br ions confined in slit-shaped carbon nanospace

Hydration structures of "nanosolutions" around both cation and anion for rubidium bromide confined in nanospaces (pore width = 1.1 nm) of activated carbon fiber were determined with EXAFS measurements and related analysis. The analytical results indicate that the ionic solutions confined in hydrophobic nanospaces tend to form an incomplete dehydration structure, because of the spatial restriction by the nanospace and capturing water molecules in the ordered structure.     

3-Acyl- and 3-alkoxycarbonyl-2-oxazolones and their homopolymers as amino-protecting reagents

3-Acyl- and 3-alkoxycarbonyl-2-oxazolones as well as their homopolymers serve as practically useful N-protecting reagents of amines including α-amino acids.     

Simultaneous Measurement of Refractive Index and Thickness of Transparent Plates by Low Coherence Interferometry

We demonstrate a novel low coherence Michelson interferometer which can provide simultaneous measurement of the refractive index and thickness of transparent plates used as a measured object. Unlike the existing low coherence interferometers reported so far, either an object or a focusing lens aligned on the signal arm is scanned repeatedly by a precise translation stage in synchronization with movement of a reflection mirror on the reference arm. The so-called object or lens scanning method gives us two measured quantities a movement distance of the stage between two light focusing states on the front and rear planes of an object and the corresponding optical path difference. These two measured quantities, result in desirable values of the index and thickness of the object with a short calculation. The measurement accuracy of ≤0.1% is expected for a thickness of more than 1 mm. In the experiment using the object scanning method, the accuracy of 0.3% or less was successfully attained for nearly 1-mm thick plates of fused quartz, sapphire, LiTaO₃ and slide glass.     

Reconstitution of bacterial photosynthetic unit in a lipid bilayer studied by single-molecule spectroscopy at 5 K

As a model of photosynthetic unit (PSU), self-assembled aggregates of pigment-protein complexes from photosynthetic bacteria were prepared in a lipid bilayer by reconstitution of the light-harvesting 2 (LH2) complex and light-harvesting 1-reaction center (LH1-RC) complex through detergent removal of their micelles in the presence of lipids. By performing polarization-controlled fluorescence and fluorescence-excitation spectroscopy on single aggregates at a temperature of 5 K, the composition of individual aggregates was determined and excitation energy transfer (EET) between constituent complexes was observed. LH2 and LH1-RC from a bacterium, Rhodobacter (Rb.) sphaeroides, were found to form a trimeric aggregate in which EET takes place from one LH2 to two LH1-RCs. In contrast, a heterodimer of LH2 and LH1-RC in which EET works was found to assemble from a combination of complexes of different bacterial species, that is, LH2 from Rb. sphaeroides and LH1-RC from Rhodopseudomonas (Rps.) palustris.     

Radiation-Induced Polymerization of n-Butyl and n-Hexyl Methacrylates at High Pressure and Pressure-Volume Behavior of Polymer-Monomer Coexistence System as Polymerized

Radiation-induced polymerization of n-butyl and n-hexyl methacrylates (BMA, HMA) at high pressure (up to 8000 kg/cm²) and pressure-volume (P-V) behavior of the polymer-monomer coexistence systems at various pressures were studied by dilatometric method. The Van't Hoff plot of the rate of polymerizations broke at 3500 and 4500 kg/cm² for BMA and HMA, respectively. (first breaks). The activation volumes were about -24 cm³/mole for both monomers below the pressure giving the first breaks. The pressure dependences on the rate of polymerizations were small in the pressure ranges of the first break pressures to 4500 kg/cm² for BMA and 5500 kg/cm² for HMA (second breaks), and above the second break pressures the rate of polymerizations increased with constant activation volumes with increasing pressure. The P-V isotherms of the coexistence systems polymerized below 3000 kg/cm² were the same as those of the monomers, and the coexistence systems polymerized at 3800 (BMA) and 4200 kg/cm² (HMA) showed solidlike features in the pressure range of 3000 kg/cm² to the polymerization pressures. The coexistence systems polymerized at 5500 (BMA) and 6500 kg/cm² (HMA) showed solidlike features in the range of 4500 kg/cm² to the polymerization pressure and 5500 kg/cm² to the polymerifation pressure, respectively. The pressure of 4500 kg/cm² for BMA and 5500 kg/cm for HMA corresponded to the pressure giving the second break in the Van't Hoff plot. We concluded from these results that the solidlike features were due to a strong interaction between as-polymerized polymer chains and monomer molecules similarly to the case of the PMMA-MMA coexistence system, and that the ester chains of BMA and HMA play an important role in alignment of monomer molecules above 4500 (BMA) and 5500 kg/cm² (HMA).     

Theoretical studies on magnetic atom imaging by use of photoelectron diffraction

We theoretically study possible methods how to obtain imaging of magnetic atoms by use of photoelectron diffraction (PD). We propose a novel method to apply Daimon effect where PD peaks are rotated around forward focusing peaks. In usual circular dichroism, we simply use the difference of the PD intensities for different X-ray circular polarization. In contrast to this dichroism, we rather use the difference of the PD intensities for different circular polarizations but - is used for the – circular polarization only in the data handling. This technique allows us to obtain clear atomic image only of spin polarized atoms, and to distinguish magnetic atoms with up-spins from those with down spins. Some illustrative calculations demonstrate the potential use and also the limitation of this technique.     

Noncovalent Modification of Cycloparaphenylene by Catenane Formation Using an Active Metal Template Strategy**

The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2′-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C−H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions.