Effect of Edge Functionalization on the Bottom-Up Synthesis of Nano-Graphenes

We demonstrate the effect of edge functionalization on the on-surface Ullmann coupling of nano-carbon materials. Unlike 10,10′-Dibromo-9,9′-bianthryl (DBBA), which is widely known to form anthracene polymers and armchair-edge graphene nanoribbons on Au(111), newly-developed precursor named 5-bromo-11(10-bromoanthracene-9-yl)anthra[2,3-b : 7,6-b′]dithiophene (BABAT) with isomers, which has similar structure as DBBA with one anthracene substituted with anthradithiophene, was found to make intramolecular C−C bonding instead of long anthracene polymers after annealing at 200 °C on Au(111). The mechanism was investigated using first-principle density functional theory, which revealed that on-surface polymerization is not kinetically preferred in case of BABAT. The reaction rate of intramolecular C−C bonding of BABAT is ∼206 times faster than that of DBBA. The intramolecular C−C bonding in DBBA biradicals, on the other hand, do not take place because of faster reverse reaction. By referring to electron density of BABAT biradicals, it was concluded that thiophene functionalization modifies distribution of electron density in BABAT radicals and facilitates electrophilic addition, leading to intramolecular C−C bonding after 200 °C annealing. These results indicate that the design of radical moiety is particularly important in the on-surface Ullmann-type coupling.     

Selective Synthesis of Primary Anilines from NH3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface

Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH₃ and cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N‐cyclohexylidene‐anilines), followed by hydrogenation to produce N‐cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N‐cyclohexylidene‐anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH₃ and cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.     

Phase-detected Brillouin optical correlation-domain reflectometry

Optical Review - Optical fiber sensing techniques based on Brillouin scattering have been extensively studied for structural health monitoring owing to their capability of distributed strain and...     

Semicrystalline poly(vinyl ether)s with high and phototunable glass transition temperature: application for thermally stable and reworkable adhesives

The photoinduced solid–liquid phase transition of azobenzene-based polymers is an attractive method to synthesize stimuli-responsive functional materials. As the structure–property relationships of such materials are not fully understood, a new class of polymer backbone, that is, poly(vinyl ether) (PVE), was studied for the development of azobenzene-based polymers with high thermal stability. For this purpose, a series of azobenzene-based PVEs with different monomer structures were synthesized using a Lewis acid catalyst-based cationic polymerization method. Typical PVEs are viscous polymers with low glass-transition temperatures (T_g's). The flexibility of the polymer backbone improves with the use of alkylene spacers, changing the order of alignment of the mesogenic azobenzene moieties attached to the backbone, leading to high T_g's of the azobenzene-based PVEs. One of the synthesized PVEs shows a high glass-transition temperature of 94 °C, which is 14 °C higher compared to that of the corresponding polymethacrylate. Furthermore, the PVE exhibits photoinduced solid–liquid phase transition from the semicrystalline state. This phase transition material, with its high thermal stability, has the potential for broader applications, such as for the phototuning of adhesion. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 568–577     

HPLC determination of acetaminophen in saliva based on precolumn fluorescence derivatization with 12-(3,5-dichloro-2,4,6-triazinyl)benzo[d]benzo[1',2'-6,5]isoindolo[1,2-b][1,3]thiazolidine.

A high-performance liquid-chromatographic method for the determination of acetaminophen in saliva has been developed. This method is based on the precolumn derivatization of acetaminophen with 12-(3,5-dichloro-2,4,6-triazinyl)benzo[d]benzo[1',2'-6,5]isoindolo[1,2-b][1,3]thiazolidine, a new fluorescence derivatization reagent for phenolic compounds. The resulting derivative of acetaminophen is separated by isocratic elution on a reversed-phase column, and is fluorometrically detected at an emission wavelength of 560 nm with an excitation wavelength of 540 nm. The detection limit (signal-to-noise ratio = 3) was 0.1 microg/mL in saliva. The proposed method permits a highly sensitive and simple determination of acetaminophen in a small amount of saliva without any sample purification.     

In situ photochemical conversion from cinnamoyl-functionalized liquid-crystalline monomers to liquid-crystalline dimers

Liquid-crystalline (LC) monomers, which were functionalized with a cinnamoyl group on their extremity, were synthesized and irradiated with UV light in their LC phases. In the presence of a triplet sensitizer, most LC monomers were converted into the corresponding dimers, which were produced by the cycloaddition reaction of the cinnamoyl group. The photodimerization reaction could proceed while the LC phases were maintained, because the dimers showed LC phases whose temperature ranges were wider than those of the corresponding monomers. A ¹H NMR study of the LC dimers indicated that the cyclobutane unit dominantly had an anti-head-to-head configuration, that is, δ-truxinate. As the LC monomers, which had a phenyl biphenyl-4-carboxylate moiety as a mesogen, showed smectic A phases and the corresponding dimers also exhibited smectic A phases, we estimated the smectic layer distances by X-ray diffraction analysis and found that the dimers adopted the structure in which the two mesogens aligned laterally and existed in the same smectic layer in the LC phases.     

Liquid-phase Reductive Deposition as Novel Preparation Method for Highly Dispersive Nickel Catalysts

We have been developing the selective deposition method onto TiO₂ nanoparticles, named as the liquid-phase selective-deposition method, where TiO₂ plays a role of formation center of Ni nanoparticles as well as protection from the aggregative growth of the particles. The concept of this method is to well disperse and stabilize Ni nanoparticles on TiO₂ surface by specific adsorption of Ni precursory complexes and then heterogeneous nucleation on the adsorption sites. The particle size was decreased with increasing the amount of Zn added, thus the catalytically active Ni surface area was increased. The selective deposition onto TiO₂ surface and addition of Zn to the nanoparticle promoted the catalytic activity of Ni–Zn nanoparticle, e.g. the catalytic activity of Ni–Zn/TiO₂ was ca. 10 times higher than that of the unsupported Ni nanoparticles. Ni in the nanocomposite was assigned as metallic, although their surface was oxidized under the atmospheric condition, but Zn and B were deposited as their oxide.     

ESR and ENDOR studies on a 5-O-membered crown ether bearing a triphenylmethyl moiety

A new 5-O-membered crown ether spin-labelled with a triphenylmethyl group was prepared. The intramolecular unpaired π-electron delocalization was investigated by ENDOR. The ENDOR of the crown methylene group adjacent to the aromatic ring revealed non-equivalence in the magnitude of the proton hyperfine splittings. Based on the temperature-dependent ENDOR line separation, the activation energy of the conformational change of the methylene protons was estimated. Upon metal chelation into the crown ring the dissociation of the dimer to the monomer radical was greatly affected, and an increase in the activation energy of the vibrating methylene protons was detected.     

Mass spectrometric studies of lithium-containing oxides at high temperature

The sublimation and vaporization of various lithium containing oxides have been studied by high temperature mass spectrometry. The installed Knudsen cell apparatus gave some useful information about the vapor species, appearance potentials, partial pressures and heats of reactions involved. The investigated oxides are Li₂O, Li₂O-Al₂O₃, Li₂O-MoO₂ and Li₂O-SiO₂ systems. This paper mainly presents the most recent data for the Li₂O-SiO₂ system. A relationship for the decomposition reaction of ortho-Li₄SiO₄ was deduced. The heat of the reaction was determined by the third law method.The activity of the Li₂O component in the double oxides was estimated from the partial pressures of the vapor species. γ-LiAlO₂ and meta-Li₂SiO₃ showed fairly low activities in comparison with Li₂O oxide. The activity coefficients decreased with the Li₂O mole fraction in the lithium compounds.The heats of formation and atomization of LiO and Li₂O gaseous species were determined.