Mutsuo Tanaka

Surface modification of GC and HOPG with diazonium, amine, azide, and olefin derivatives.

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Decisive Factors in the Photoisomerization Behavior of Crowned Spirobenzopyrans: Metal Ion Interaction with Crown Ether and Phenolate Anion Moieties

The influence of metal ion interaction with crowned spirobenzopyrans on the photoisomerization behavior was investigated through the use of various solvents, crowned spirobenzopyrans, and metal ions. Studies on the photoisomerization behavior of crowned spirobenzopyrans in various solvents revealed that solvation of the phenolate anion moiety in the merocyanine form induced photoisomerization back to the spiropyran form, giving rise to negative photochromism. Metal ion interaction with the phenolate anion moiety similarly caused photoisomerization back to the spiropyran form, while that with the crown ether moiety just produced a polar environment and its influence on photoisomerization behavior was dependent on the affinity of the metal ion captured by the crown ether moiety for the phenolate anion. Therefore, photochromic switching of crowned spirobenzopyrans between positive and negative to control the metal ion interaction with the phenolate anion moiety through the crown ether moiety is possible. This finding suggests a molecular design method for crowned spirobenzopyrans showing desired ion-responsive photochromism.

Hydrogenation of carbon dioxide over CuZn-chromate/zeolite composite catalyst: The effects of reaction behavior of alkenes on hydrocarbon synthesis

Abstract The hydrogenation of carbon dioxide was studied using composite catalysts comprised of CuZn-chromate and HY zeolite. These composite catalysts enabled the reaction combining methanol synthesis and methanol-to-gasoline reaction, and achieved the formation of ethylene and propene as the first example of the composite catalysts. The addition of alkaline metals, especially cesium, to CuZn-chromate enhanced the selectivities of those alkenes. The influences of the reaction pressure and the space velocity on the production of alkenes show that alkanes are obtained by the hydrogenation of the corresponding alkenes. The composite catalysts producing alkenes in high selectivity afforded heavier hydrocarbons preferentially. These results indicate that the hydrogenation of alkenes inhibits the carbon homologation of alkenes to result in the predominant formation of the corresponding lighter alkanes. From these observations, it was found that methanol synthesis catalysts used for the composite catalysts are required to be effective for methanol synthesis at high temperature (over 300°C) and to bear the low activity of the hydrogenation of alkenes.

One-step detection of galectins on hybrid monolayer surface with protruding lactoside.

Galectins, or beta-galactoside binding lectins, are detected deep in tumor tissue and are recognized as diagnostic and prognostic markers of cancer and other serious diseases. There is a need to develop a faster, easier, and simpler method for detecting galectins. We have succeeded in forming a mixed self-assembled monolayer (SAM) interface consisting of beta-galactoside terminated alkanethiol (lactoside protuberant dodecanethiol) and tri(ethylene glycol) (TEG) terminated short alkanethiol, which proved to be a superior protein resistant material, to enable us to develop a label-free, one-step, and highly sensitive system for detecting the expected biomarker, galectin. We successfully detected nanomolar level (~ 1 nM) galectin-4 and -8 on a 4% lactoside protrusive surface, even though the affinity between the galectins and lactoside was very weak (KD = 1 x 10(-3)~1 x 10(-6)). The combination of the suppression of background noise by filling with TEG terminated short alkanethiol and control of the ligand ratio in the interface contributed to the highly sensitive detection of galectin. We also detected galectin-4 at subten nanomolar levels even in a solution containing much higher concentrations of serum proteins (1800 times larger than the galectin concentration) without using molecule labeling or an immunological method.

Carbonylation of tert-butyl alcohol over H-zeolites

A high catalytic activity and excellent stability of the vapor phase Koch-type carbonylation of tert-butyl alcohol towards 2,2-dimethylpropanoic acid on a H-ZSM-5 catalyst were achieved with a yield as high as 90% without any threat of deactivation in 120 h.

Hydrogenation of carbon dioxide over Fe-Cu-Na/zeolite composite catalysts : Na migration via solid-solid reaction and its effects on the catalytic activity

Abstract Composite catalysts containing zeolites and Na-rich Fe–Cu Fischer–Tropsch catalysts were studied for the hydrogenation of carbon dioxide at 250°C. Sodium migration from the surface of the F–T catalyst to the zeolite via solid–solid reaction seemed to change the acidity of the zeolite and the reduction degree of the Fe catalyst, which finding was supported by TG and XRD measurements. It was shown that branched and higher hydrocarbons can be obtained in good yields by using composite catalysts containing iron-based catalysts with moderate alkali content and zeolites with suitable acidity.

Design and fabrication of biosensing interface for waveguide-mode sensor.

In order to develop a biosensing system with waveguide-mode sensor, fabrication of a biosensing interface on the silica surface of the sensing chip was carried out using triethoxysilane derivatives with anti-leptin antibody. Triethoxysilane derivatives bearing succinimide ester and oligoethylene glycol moieties were synthesized to immobilize the antibody and to suppress nonspecific adsorption of proteins, respectively. The chip modified with triethoxysilane derivatives bearing oligoethylene glycol moiety suppressed nonspecific adsorption of proteins derived from human serum effectively by rinse with PBS containing surfactant (0.05% Tween 20). On the other hand, it was confirmed that antibody was immobilized on the chip by immersion into antibody solution to show response of antigen-antibody reaction, where the chip was modified with triethoxysilane derivatives bearing succinimide ester moiety. When the interface was fabricated with antibody and a mixture of triethoxysilane derivatives bearing succinimide ester and oligoethylene glycol moieties, the response of antigen-antibody reaction depended on composition of the mixture and enhanced with the increase of ratio for triethoxysilane derivatives bearing succinimide ester moiety reflecting the antibody concentration immobilized on the chip. While introduction of excess triethoxysilane derivatives bearing succinimide ester moiety induced nonspecific adsorption of proteins derived from human serum, the immobilized antibody on the chip kept its activity after 1-month storage in a refrigerator. Taking into consideration those factors, the biosensing interface was fabricated using triethoxysilane derivatives with anti-leptin antibody to examine performance of the waveguide-mode sensor. It was found that the detection limits for human leptin were 50 ng/mL in PBS and 100 ng/mL in human serum. The results demonstrate that the waveguide-mode sensor powered by the biosensing interface fabricated with those triethoxysilane derivatives and antibody has potential to detect several tens of nanograms per milliliter of biomarkers in human serum with an unlabeled detection method.

Chromened t-butylcalix[4]arenes: cooperation effect of chromene and calixarene moieties on photochromism and metal-ion binding ability

Abstract Novel t-butylcalix[4]arenes bearing several chromene molecules were synthesized, and their photochromism and metal-ion binding ability were examined with alkali and alkaline-earth metal ions. While the metal-ion binding ability of the t-butylcalix[4]arene moiety facilitated the photoisomerization of the chromene moiety to a great extent, the chromene moiety influenced the metal-ion binding ability of the t-butylcalix[4]arene moiety through lariat effect. Therefore, the metal-ion that induced the most facilitated photoisomerization of the chromene moiety was shifted drastically from Li+ to Ba2+ with the increase of the incorporated chromene number. Even without metal ions, the interaction among the chromene moieties derived from the cone-conformation of the t-butylcalix[4]arene moiety also facilitated the photoisomerization.

Reaction of pentaarylantimony with acid halide, aldehyde and ketone

Pentaarylantimony (pentaphenylantimony, penta-p-tolylantimony and penta-p-chlorophenylantimony) was found to be a mild arylation reagent. The arylation was chemoselective toward aromatic acid halides to give the corresponding aromatic ketones. No direct addition to ketone and acid anhydride occurred. Arylation reactions of aldehyde or ketone were promoted by the addition of Lewis acid. The nucleophilicities of aromatic antimony compounds depend on the number of antimony-aromatic carbon bonds.

Novel coupling reaction of pentaarylantimony with carbon electrophiles

Abstract The cross-coupling reactions of pentaarylantimony with organic halides and allyl acetate were studied under various conditions of acetonitrile solvent, palladium catalysts and copper iodide. Acetonitrile solvent enabled a nucleophilic coupling reaction with allylic halides, although a radical reaction and an intramolecular ligand coupling have been regarded as general under other conditions. Palladium catalysts were effective for the coupling reaction with allyl acetate. Copper iodide promoted the reaction of organic halides, such as methyl iodide and ethyl bromoacetate. In the latter two cases, the formation of diaryls is a significant side reaction.