The concept of treating chiral α- and β-alkoxy aldehydes with bicoordinate Lewis acids such as TiCl4, SnCl4, or MgBr2 followed by the addition of carbon nucleophiles for achieving chelation control with 1,2- and 1,3-asymmetric induction, respectively, was introduced three decades ago and has since evolved into a general method. In the case of enol silanes, the chelation-controlled Mukaiyama aldol reaction is involved, which has been used in recent natural products syntheses.
Flexizymes are a family of aminoacylation ribozymes devised by in vitro selection in our research group. They charge a wide variety of nonproteinogenic amino acids onto virtually any kind of tRNAs, enabling us to reprogram the genetic code in a custom-made cell-free translation system. This genetic code reprogramming method was integrated with a mRNA display method, which not only expresses nonstandard peptides such as macrocyclic peptides but also selects ligands specifically binding to target proteins. This system is referred to as random nonstandard peptide integrated discovery (RaPID) system, which has yielded inhibitors against disease-related target proteins. In this review, we summarize the evolutionary history and recent applications of the flexizymes and RaPID system.
Flexizymes are a family of aminoacylation ribozymes devised by in vitro selection in our research group. They charge a wide variety of nonproteinogenic amino acids onto virtually any kinds of tRNAs, enabling us to reprogram the genetic code in a custom-made cell-free translation system. This genetic code reprogramming method was integrated with a mRNA display method, which not only express nonstandard peptides such as macrocyclic peptides but also select ligands specifically binding to target proteins. This system is referred to as random nonstandard peptide integrated discovery (RaPID) system, which has yielded inhibitors against disease-related target proteins. In this review, we summarize the evolutionary history and recent applications of the flexizymes and RaPID system.
CsoR/RcnR transcriptional repressors adopt a disc-shaped, all α-helical dimer of dimers tetrameric architecture, with a four-helix bundle the key structural feature of the dimer. Individual members of this large family of repressors coordinate Cu(I) or Ni(II)/Co(II) or perform cysteine sulfur chemistry in mitigating the effects of metal or metabolite toxicity, respectively. Here we highlight recent insights into the functional diversity of this fascinating family of repressors.
Molecular displacement in an alternating chain of donors and acceptors triggers ferroelectric switching of large electric polarization with a low electric field in some charge-transfer complexes. While the displacement of a point charge (i.e., static charge) provides a good picture of the polarization for spin-Peierls-type transition in an ionic complex of tetrathiafulvalene (TTF) and p-bromanil (BA), it completely fails to explain both the magnitude and direction of the observed spontaneous polarization in the neutral-ionic transition of TTF–p-chloranil (CA). The most spectacular behavior is that the TTF cations are displaced toward the anode and the CA anions toward the cathode. Recent experimental and theoretical research has highlighted the strong effects of dynamic electrons traveling in the intermolecular space of TTF–CA. The new “electronic ferroelectricity” mechanism can also be envisioned as a powerful guide for guaranteeing high-performance dielectric and related electronic functionalities, especially for organic molecular systems.
While the displacement of a static charge provides a good picture of the ferroelectric polarization for the spin-Peierls-type transition in an ionic complex of tetrathiafulvalene (TTF) and p-bromanil (BA), it completely fails to explain both the magnitude and direction of the observed spontaneous polarization in the neutral–ionic transition of TTF–p-chloranil (CA). Recent experimental and theoretical research has highlighted the strong effects of dynamical electrons traveling in the intermolecular space of TTF–CA.
Materials fabrication with nanoscale structural precision based on bottom-up-type self-assembly has become more important in various current disciplines in chemistry including materials chemistry, organic chemistry, physical chemistry, analytical chemistry, biochemistry, colloid and surface chemistry, and supramolecular chemistry. Although the design of new materials based on nanoscale self-assembly is anticipated as a key concept, preparing complete three-dimensional structures at nanoscale precision remains a difficult target using current technologies. Rather, dimension-reduced approaches such as layering of two-dimensional nanostructures into precisely controlled lamellar nanomaterials are currently achievable. In particular, layer-by-layer (LbL) assembly is known as a highly versatile method for fabrication of controlled layered structures from various kinds of component materials using very simple, inexpensive, and rapid procedures. Therefore, fabrication of multilayer films through the LbL deposition process has attracted growing interest from various research communities. The high versatility and flexibility of LbL assembly is continuously creating new concepts, new materials, new procedures, and new applications. In this highlight review, we focus on nanoarchitectonics by LbL assembly. After an initial introduction on the invention and a brief history of the LbL assembly technique, innovations and the evolution of the technique are described based mainly on recent examples, which are categorized into two sections: (i) developments in methodology (technical, material, and phenomenological aspects with expansion of concept) and (ii) progress in applications (physical, chemical/biochemical, and biomedical applications).
In this highlight review, we focus on nanoarchitectonics combined with LbL assembly. Following an introduction of the invention and a brief history of the LbL assembly, innovations and evolution of the LbL assembly technique are described based on recent examples. These examples are categorized into two sections: (i) development in methodology (technical, material, and phenomenological aspects with expansion of concept) and (ii) progress in application (physical, chemical, biochemical, and biomedical applications).
MMX-Type quasi-one-dimensional iodide-bridged diplatinum complexes (MMX chains) provide various electronic states and attractive physical properties. In this review, we summarize the recent progress in MMX chains consisting of pyrophosphite (pop) ligands. The MMX chains with binary countercations, which have short Pt–I–Pt distance and robust frameworks, form a new electronic state. They show reversible dehydration–rehydration accompanied by the change of electronic states and electrical conductivity. Relatively high electrical conductivity in the MMX chains with binary countercations enables us to investigate the negative differential resistance (NDR) and electrochemical characteristics in the solid state for the first time in MMX chains.
MMX-type quasi-one-dimensional iodide-bridged diplatinum complexes (MMX chains) provide various electronic states and attractive physical properties. In this review, we summarize the recent progress in MMX chains consisting of pyrophosphite (pop) ligands. The MMX chains with binary countercations, which have short Pt–I–Pt distance and robust frameworks, form a new electronic state and show the water-vapor-induced reversible switching of electronic states and electrical conductivity. Their relatively high electrical conductivity enables us to investigate the nonlinear conduction and electrochemical characteristics in the solid state for the first time in MMX chains.
A visible-light-responsive nitrogen-doped solid-acid photocatalyst HNb3O8-N is investigated via solid-state high-resolution NMR spectroscopy. The 1H magic-angle-spinning (MAS) spectrum observed under an ultrahigh field of 21.8 T is found drastically different from that of the precursor catalyst HNb3O8. The 1H signals of HNb3O8-N are assigned with the help of 1H–93Nb and 1H–15N two-dimensional heteronuclear correlation (HETCOR) spectroscopy. It is clarified that H3O+ ions contained in HNb3O8 change into H2O and H+, the latter of which protonates NbO6 octrahedra. Deduced from the 1H chemical shift for the nitrogen-adjacent protons, three microstructure models for HNb3O8-N, involving the proton-exchange model, are proposed.
MnCo2O4@reduced graphene oxide (MnCo2O4@RGO) was prepared via a one-step hydrothermal route. X-ray diffraction and transmission electron microscopy showed that MnCo2O4 nanoparticles with an average size of 12 nm were homogeneously dispersed on reduced graphene oxide sheets. Electrochemical experiments on MnCo2O4@RGO showed that the nanocomposite exhibited high specific capacitance of 334 F g−1 at a large current density of 1 A g−1. Even after 2000 charge–discharge cycles, 98% of the initial specific capacitance was retained, a property which will prove valuable for practical applications such as supercapacitors.
Low-temperature X-ray analyses on several pseudopolymorphs (solvate crystals) revealed that the C1–C2 bond length of the highly congested title molecule can adopt quite different values [1.700(6)–1.739(6) Å]. Such an unusual observation indicates that the ultralong covalent bond is endowed with “expandability,” thus the prestrained bond can be elongated or shortened very easily accompanied by only a minute change in energy, which can be compensated by intermolecular perturbation in the crystal.
The oxidation of 9-p-tolylcarbazole by iron(III) perchlorate in acetonitrile produces oligo(9,9′-di-p-tolyl-3,3′-bicarbazyl), partially doped with perchlorate. To the chloroform solution of the oligomers, we added metals to produce hybrid solutions. The hybrid films, prepared by applying the solutions onto a glass plate, exhibited good transparencies (90% or above in the visible region) and electrical conductivities of 4.1 × 10−3 S cm−1.
The chitosan derivatives bearing different 4-chlorophenylcarbamate–urea structures were synthesized under different reaction conditions, and their chiral recognition abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). These CSPs coated on silica gel exhibited different recognition ability depending on their structures and could be used with a few prohibited solvents as the eluent, which efficiently improved the resolution for some racemates.
A selenium-substituted phosphaalkene, (Me3Si)2C=PSeTrp (1, Trp: 9-triptycyl), was synthesized by two methods, substitution reaction of (Me3Si)2C=PCl (3) with TrpSeLi, and treatment of TsiP(Cl)SeTrp (4, Tsi: C(SiMe3)3) with a catalytic amount of AlCl3. The newly obtained phosphaalkene was characterized in detail.
Nickel catalyzes the three-component coupling reaction of dimethylzinc, enyne, and carbonyls to provide tetrasubstituted allenyl alcohols. Diethylzinc and diphenylzinc can participate in similar coupling reactions to provide the corresponding allenyl alcohols in reasonable yields.
Transparent and superhydrophobic films of wax-gourd-like biomimetic Co3O4 microfibers were successfully fabricated on glass slides and ITO using a feasible and controllable hydrothermal method, which involved calcination at high temperature. It was demonstrated that the roughness of the as-prepared microfibers could realize not only superhydrophobicity but also preferable transmittance. The transmittance of the Co3O4 microfiber films after chemical modification with thiol reached up to 88.2%, with a contact angle of 165° and a sliding angle as low as 8°.
A novel method to disperse single-walled carbon nanotubes (SWNTs) in water using self-aggregating peptides was demonstrated. SWNT dispersion was performed by the addition of water to solid mixtures of SWNTs and the peptides, in addition to subsequent sonication processes. Spectroscopic and microscopic analyses revealed that our method successfully disentangled and dispersed larger amounts of SWNTs with better dispersion stability as compared to conventional methods.
Novel ethynylated anthracene bisimide (ABI) derivatives were synthesized by Sonogashira and Stille couplings, and the electronic spectra of the new compounds were compared with those of molecules with related structures. The absorption spectrum and the electrochemical data of the ABI with a 9-anthrylethynyl group suggested weak electronic interactions between the donor anthracene unit and the acceptor ABI unit.
Novel organic ionic plastic crystals containing cyclic perfluorosulfonylamide anions were synthesized by anion metathesis between a cyano-functionalized quaternary ammonium halide and Li[N(SO2CF2)2CF2] (LiCPFSA). The structure of [N(CH3)2(CH2CN)2][CPFSA] was disclosed by single-crystal X-ray diffraction study. This is the first report on the crystal structure of cyclic perfluorosulfonylamide anion.
Nanocrystalline Bi2Te3 (nanospheres with diameters of 50–500 nm, urchin-like nanorods with diameters ranging from 5 to 15 nm and lengths ranging from 40 to 100 nm) has been successfully synthesized by a microwave–solvothermal method using TeO2, Bi(NO3)3·5H2O, and HNO3 in a solvent of poly(ethylene glycol) (PEG-400). Compared with other reaction systems, less reagents and reductant-free conditions were important factors to simplify the reaction process.
A highly regular dendrite pattern surface was fabricated using a dot-pattern zinc sheet by electrodeposition. The relationship between pretreatment conditions and morphology of the dendrite pattern was investigated. The dendrite growth position could be controlled with high regularity depending on the height of the relief structure formed by electrodeposition.
Arynes were efficiently generated from readily available ortho-sulfinylaryl triflates by the treatment with phenylmagnesium bromide in tetrahydrofuran at −78 °C. Aryne generation was initiated by a rapid sulfoxide–metal exchange reaction, followed by the immediate elimination of the ortho-OTf group. Various arynophiles efficiently reacted with arynes generated by this method within 10 min, providing the corresponding adducts in high yields.
Effect on stability of liquid crystal (LC) alignment due to formation of polymer clusters on alignment films produced from the copolymer of 1,3,5-triacryloyloxyadamantane and 4,4′-diacryloyloxybiphenyl was investigated with morphology analysis. Experimental results revealed that the stability of the LC alignment was increased because the polymer clusters effectively held the LC molecules adjacent to the polymer clusters.
The MnO2 nanorod–Au nanoparticle composites that exhibit superior supercapacitance and long-term durability have been fabricated using a two-step procedure. The role of Au nanoparticles is not only to improve the electrical conductivity but also to enhance the structural stability. The composites have a specific capacitance of 406.8 F g−1 at a scan rate of 50 mV s−1, which is almost five times that of the pure MnO2 nanorods. The composites have 91.3% capacitance retention over 2000 charge–discharge cycles at 5 A g−1, which is much better than the capacitance retention of pure MnO2 nanorods (74.6%).
We prepared high quality and single- or bilayer graphene by Si sublimation method from 4H-SiC. The exciton relaxation dynamics of CdTe quantum dots (QDs) on epitaxial graphene was analyzed by picosecond single-photon timing spectroscopy, and the fast component was estimated to be 49 ps. This lifetime is in good agreement with the values calculated from Persson–Lang model (59 ps) and Swathi–Sebastian model (36 ps) of energy transfer, suggesting that the dominant process is energy transfer from CdTe QDs to graphene.
Geopolymer foam materials could function as adsorbents for cesium ions. Geopolymer foams showing cesium adsorption were prepared by condensing a mixture of metakaolin and alkali solution at 100 °C in the presence of silica from rice husk powder, and they showed effective adsorption of cesium.
Laser-induced desorption and ionization (LDI) of gold ions (Aun+: n = 1–3) were observed from gold nanorods in a liver tissue section (thickness: 10 µm). Larger amounts of gold nanorods produced stronger mass signals. Organic molecules in the tissue were not detected and did not inhibit the LDI processes of the gold nanorods in the tissue. Because of the selective LDI processes of the gold nanorods, the distribution of gold in the liver was successfully determined by imaging mass spectrometry.
A series of novel 1-(4-phenylthiazol-2-yl)-1,4-dihydrothiochroman[4,3-c]pyrazole have been prepared by a three-component reaction of thiochromanone-3-carbaldehyde, phenacyl bromide, and thiosemicarbazide. The reaction was in one-pot and did not require any additional catalyst with moderate yields. This method provided several advantages such as environment friendliness and simple work-up procedure. The compounds were assayed for antifungal activity and some of the new compounds can be further utilized as lead compounds.
A highly enantioselective fluorination of β-ketoesters catalyzed by chiral sodium phosphate is achieved. In this process, the simultaneous formation of sodium enolate and sodium phosphate under basic conditions is the key to achieving excellent selectivity. Indanone derivatives as well as benzofuranone derivatives could be employed in this reaction to afford the fluorinated adducts in good yields with good to excellent enantioselectivities.
The surface stability of metal nanoparticles was enhanced by adsorption of layered silicate (so-called “clay”) on metal nanocubes whose surface was protected by a surfactant. The strong adsorption of the layered silicate to the metal nanocubes via the surfactant eliminated the need for using excess surfactant for metal nanoparticle dispersion. Furthermore, the surface of the negatively charged hybrids was demonstrated to be modifiable with cationic molecules.
Herein, we have compared the behavior of ZnO and TiO2 in the photocatalytic oxidation of glycerol through detection of the main products. ZnO showed higher selectivity for the products where the carbon chain was preserved, such as glyceraldehyde (GAD) and dihydroxyacetone (DHA). TiO2 generated more products from the cleavage of the glycerol molecule, such as formaldehyde (FORM) and glycolaldehyde (GCOL). ZnO yielded about 16 times more GAD and 2.5 times more DHA than did TiO2.