Hideo Tokuhisa

A new synthetic method for rotaxanes via tandem claisen rearrangement, diesterification, and aminolysis

A novel methodology to make rotaxanes via covalent bond formation has been developed. Rotaxanes composed of crownophanes having two phenolic hydroxy groups as a molecular rotor and an axle having diamide moieties were synthesized in moderate yields via three step processes: tandem Claisen rearrangement, intramolecular diesterification, and aminolysis.

Odd–even effect and metal induced structural convergence in self-assembled monolayers of bipyridine derivatives

Scanning tunneling microscopy (STM) observations reveal that bipyridine derivatives which exhibit various two-dimensional structures due to the odd-even chain length effect are converged into a lamellar structure upon metal coordination.

Efficient biosensor interfaces based on space-controlled self-assembled monolayers.

In this paper we demonstrate control over the spacing of surface-modifying probe molecules through the use of labile dendron spacers. During this process, anchor molecules are first adsorbed to a surface, with dendron modifiers attached. Steric interactions of the bulky dendrons control the density of anchor molecules bound to the surface. The dendron branches are subsequently detached from the anchor molecules, and the anchors are chemically modified with probe molecules, resulting in a surface with controlled spacing between probe molecules. Control over this spacing is important when the probe size is small in comparison with the target molecule. This importance is demonstrated for the binding of protein (streptavidin) targets to the probe (biotin) surface. The effect of probe space control on the efficiency of target capture is evaluated by examining the binding of streptavidin to thiolated biotin for a series of mixed monolayers. Surface modification is monitored by Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS). The relative concentration of probe molecules at the surface is measured using X-ray photoelectron spectroscopy (XPS) measurements. Thiolated-biotin surfaces with optimized spacing show an increased capture efficiency for streptavidin relative to surfaces with nonoptimal or no control over probe spacing, as measured by surface plasmon resonance (SPR) spectroscopy. These results are of potential significance for the optimization and fabrication of micro- and nanoarrays used in chemical and biochemical measurements.

Interaction Force of Chitin-Binding Domains onto Chitin Surface

Interaction force of chitin-binding domains (ChBD1 and ChBD2) from a thermostable chitinase onto chitin surface was directly measured by atomic force microscopy (AFM) in a buffer solution. In the force curve measurement, multiple pull-off events were observed for the AFM tips functionalized with either ChBD1 or ChBD2, whereas the AFM tips terminated with nitrilotriacetic acid groups without ChBD showed no interaction peak, suggesting that the detected forces are derived from the binding functions of ChBDs onto the chitin surface. The force curve analyses indicate that the binding force of ChBD2 is stronger than that of ChBD1. This result suggests that ChBD1 and ChBD2 play different roles in adsorption onto chitin surface.

Innovative platform for transmission localized surface plasmon transducers and its application in detecting heavy metal Pd(II).

Transmission localized surface plasmon resonance (T-LSPR) transducers based on the characteristic surface plasmon absorption band of Au island films have become increasingly attractive. The first and main bottleneck hampering the development of T-LSPR sensors is instability, manifested as change in the surface plasmon absorbance band following immersion in organic solvents and aqueous solutions. In this paper, we innovate the platform for T-LSPR transducer by using remarkably stable and highly adhesive Au/Al(2)O(3) nanocomposite film. Isolated Au nanoparticles embedded in dielectric matrix Al(2)O(3) were prepared by a simple one-step radio frequency magnetron cosputtering technique. The obtained nanocomposite film is exceedingly stable during immersion in solvents, drying, and binding of different molecules; it successfully passes the adhesive tape test and sonication treatment. The superior stability and adhesion, obtained without the use of any intermediate adhesion layer or protective overlayer, is attributed to (1) the Au nanoparticles embedment and Al(2)O(3) rim formation during the sputtering process and (2) the resistance of element Al in matrix to the nucleophilic attack by the solvent molecules. Given this success, we believe that the Au/Al(2)O(3) nanocomposite film holds promise as an innovative sensing platform in T-LSPR detection technology, as demonstrated here for the Pd(II) sensing process with excellent sensitivity and low detection limit.

Synthesis of chiral crownophanes via tandem Claisen rearrangement

Abstract A synthetic route for crownophanes containing a chiral binaphthyl unit using tandem Claisen rearrangement is described to demonstr te the versatility of this approach. Molecular recognition by the resulting crownophane for butylurea is also investigated.

Stepwise synthesis of crownophanes having either one or two hydroxy groups via Claisen rearrangement

Abstract Bis(naphthyl)crownophanes having an isobutenyl group and different ring size were synthesized. By control of the reaction temperature and time, both the first-step product having one hydroxyl group and the second-step product having two hydroxy groups can be isolated in high yields.

Photoinduced switching of ionic conductivity by metal ion complexes of vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain

Vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain were synthesized and their photoresponsive ion-conducting behavior was investigated in the presence of sodium perchlorate. Any of the copolymers or the homopolymer of crowned azobenzene can undergo photochemical switching of ionic conductivity in composite films containing an ion-conducting carrier. UV-light-induced isomerization of the azobenzene moiety causes some disorder in the crown ether moiety (an ion-hopping site), in the liquid crystal state of the polymers, thus decreasing ionic conductivity, and this is reversed by subsequent visible-light irradiation. The highest magnitude in the photoinduced ionic-conductivity changes was attained in polymers containing the highest content of crowned azobenzene moiety, owing to the more efficient photoinduced phase transition. The polymers with the highest content of crowned azobenzene moiety also showed the fastest response in photoinduced switching.

Glass-fritless Cu alloy pastes for silicon solar cells recquiring low temperature sintering

This paper describes a novel Cu paste for low temperature sintering, which is necessary to fabricate electrodes on transparent conductive films in hetero-junction solar cell. To this end, glass fritless Cu alloy pastes containing a low melting point alloy were prepared. The pastes were evaluated in terms of printability, contact resistance, line resistance, adhesive property, and oxidation resistance. As a result, it can be concluded that the pastes would be applicable for silicon solar cells requiring low temperature process.

Synthesis of Chiral Crownophanes Having Two Phenolic Groups via Tandem Claisen Rearrangement and Their Chiral Recognition

Asymmetric crownophanes having a chiral binaphthyl unit and two phenolic hydroxyl groups were thermally synthesized from the corresponding macrocyclic ethers via tandem Claisen rearrangement. Circular dichroism (CD) spectroscopic studies and HPLC experiments confirmed that little racemization of these crownophanes occurred during the thermal rearrangement. The association constants for the interaction of the chiral crownophanes with the enantiomers of phenylethylamine, phenylglycinol, and phenylalaninol were determined by a 1H NMR titration method in CD2Cl2. As a result, the 27 membered crownophane has some chiral recognition for phenylglycinol.