Alkynes, alkenes, and thiophenes are found to behave as a directing group for C–H bond activation by a transition-metal catalyst. This collaborative interaction led to the discovery of not only simple intramolecular cyclizations but also carbon–carbon bond formation or annulation reactions with other reactants involving such unsaturated bond-directing groups. This highlight review discusses the recent progress in this sort of novel synthetic tools.
Silica particles coated with proton conductive layers composed of block copolymers were prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization with particles (PwP). The experimental results verified the successful formation of poly(acrylic acid)-b-polystyrene-coated silica particles via RAFT PwP. The new particles can be applied in novel filler in electrolyte membranes for polymer electrolyte fuel cells.
Na10GeP2S12 glass and glass-ceramic were synthesized here for the first time via mechanical milling and subsequent heat treatment. The Na10GeP2S12 phase prepared in this study had a similar crystal structure to the Na10SnP2S12 phase reported previously. The ionic conductivity at room temperature and the activation energy of the Na10GeP2S12 glass-ceramic were 1.2 × 10−5 S cm−1 and 44 kJ mol−1, respectively.
In this study, Ni2Mo3N cube-like particles have been synthesized by a solid-state reaction of metallic molybdenum, nickel chloride hexahydrate, and sodium azide in a sealed autoclave at 750 °C. The structures and morphologies of the obtained product are derived from X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. Furthermore, the thermal stability and oxidation resistance of the obtained product are investigated.
In this work, we developed a red fluorescent turn-off Mg2+ probe with high Mg2+ selectivity. The quenching response to Mg2+ in combination with a green fluorescent turn-on Mg2+ probe enabled a ratiometric imaging of the changes in intracellular Mg2+ concentration. This ratiometric imaging system significantly enhanced the detection sensitivity of intracellular Mg2+ fluctuations in comparison with a conventional ratiometric Mg2+ sensing system, thus leading to a valuable technique for visualizing small change in intracellular Mg2+ concentration.
A simple method for controlling the pore structure and properties of ordered mesoporous silica (OMS) by the physisorption of organic molecules is reported. The paraffin-modified OMSs were characterized by N2 gas and water vapor adsorption isotherms, small-angle X-ray scattering, and infrared spectroscopy. We found that paraffin first adsorbed on the pore surface defects, resulting in a smooth OMS pore surface; thus, the paraffin controlled the pore structure. In addition, the surface hydrophobicity increased with increasing paraffin filling fraction.
The perovskite-type oxynitride SrTaO2N was synthesized from Sr2Ta2O7 and carbon nitride (C3N4) and the formation mechanism was investigated using X-ray diffraction and thermogravimetry combined with mass spectrometry. In this process, ammonia is not required for the nitridation of the oxide. The C3N4 thermally decomposes to gaseous C2N2, which forms SrCN2 and Ta3N5 intermediates on the Sr2Ta2O7. These intermediates then react with the oxide to form SrTaO2N at 800 °C, which is 200 °C lower than the temperature required for the ammonolysis of Sr2Ta2O7. The product was SrTaO2N, having a slight nitrogen deficiency and small particle size because the present C3N4 nitridation was performed at lower temperature than conventional ammonolysis.
We report the reactivity of a new MnI(cyclam) complex (cyclam: 1,4,8,11-tetraazacyclotetradecane) toward O2 and H2O as a model for the photoinhibited species of oxygen-evolving complex (OEC). The reactivity varies according to the number of CO ligands. A MnI dicarbonyl complex, [MnI(cyclam)(CO)2]+ reacts with O2, but not with H2O, to form a bis(μ-oxo)Mn2III,IV complex, though a MnI tricarbonyl complex, [MnI(cyclam)(CO)3]+ does not react with either O2 or H2O. Newly synthesized MnI(cyclam) dicarbonyl complex was characterized by ESI mass spectrometry, UV–vis absorption spectroscopy, IR spectroscopy, and X-ray analysis.
The LiNbO3 (LN)-type oxynitrides, MnTaO2N and (1 − x)MnTaO2N-xMn4Ta2O9 were synthesized under high pressures and at high temperatures. The new LN-type oxynitride, Mn(Mn1/6Ta5/6)O2.5N0.5 (0.75MnTaO2N-0.25Mn4Ta2O9) could be obtained with trace impurities. In this compound, the displacement of B ion (Ta/Mn ion) from the center of the BX6 octahedron was smaller than that in other LN-type oxides containing Ta and/or Mn ions. This indicates that the displacement of Ta/Mn ion was reduced by doping with nitride ion.
An innovative additive, CaO-Al is utilized for the mechanochemical degradation (MCD) of chlorinated persistent organic pollutants (Cl-POPs). The introduction of Al into CaO significantly accelerates the reaction by promoting the release of electrons. The degradation efficiency of hexachlorobenzene (HCBz), 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (P.P′-DDD), and γ-hexachlorocyclohexane (γ-HCH) reaches 99.70, 97.75, and 99.71%, respectively, after 3, 1.5, and 8 h of milling. The stability of these organics in MCD follows the sequence of γ-HCH > HCBz > P.P′-DDD, which is consistent with their degree of unsaturation.
An electrochemiluminescence (ECL) system based on cadmium sulfide quantum dots (CdS QDs) amplified the ECL of nitrogen and sulfur co-doped graphene quantum dots (N,S:GQDs) was established and applied for lead ion (Pb2+) determination. The anodic ECL signal of N,S:GQDs was enhanced greatly by CdS QDs; furthermore, the enhanced ECL signal could be quenched by Pb2+. Based on the quenching effect, a simple method for the selective ECL determination of Pb2+ was proposed.
Reaction of [(η5-C5H4Me)4Fe4(HCCH)(HCC–Br)](PF6) with NEt3 in acetonitrile gave the cyanomethylated product [(η5-C5H4Me)4Fe4(HCCH)(HCC–CH2CN)](PF6), while that in dichloromethane gave the [4Fe–4C]-substituted enamine [(η5-C5H4Me)4Fe4(HCCH)(HCC–CH=CHNEt2)](PF6). A possible mechanism starts from the Lewis acid–base interaction between the cationic [CCH] subunit and NEt3 on the tetrairon core.
In this work, a novel type of tough hydrogel electrolytes (THGEs) has been developed for the application to quantum-dot-sensitized solar cells (QDSSCs). The THGEs doped with polysulfide redox couples show high dimensional stability and moderate ion conductivity. In addition, the THGEs are expected to mitigate the electron recombination at the TiO2–electrolyte interface as well as to increase the physical durability of QDSSCs.
A physical insight regarding poly(tetrafluoroethylene) (PTFE) is revealed herein. The driving force for the oriented growth of materials on aligned PTFE is investigated. The growth has been reported in numerous publications for a wide range of deposited materials on aligned PTFE layers since its discovery in 1991 because it is a promising method for preparing ordered molecular films. MD model simulations demonstrate herein that the shallow charged atomic grooves between adjacent PTFE chains trap typical two linear molecules, thus explaining the remarkable degrees of uniaxial orientation in their deposited thin films on the layers. Charge modifications to the model demonstrate for the first time that the negative charge of its fluorine atoms is crucial for the remarkable degrees. Hence, such an orientation is only possible with PTFE.
Eu-doped Ca2SiO4 ceramics have been newly found to show radio-photoluminescence (RPL). An as-prepared material shows photoluminescence (PL) only due to Eu3+ whereas an additional broad emission due to Eu2+ appears in the red region as a result of RPL after X-ray irradiation. The RPL is attributed to the intravalence conversion of the Eu ion (Eu3+ → Eu2+), and this response can be detected as low as 10 mGy of X-ray dose.
We examined guanine damages caused by photoinduced electron transfer (ET) in biomimetic environments using pyrene-modified oligonucleotides and molecular crowders. As a result, guanine damage induced by ET in full-matched DNA was decreased under viscous crowding conditions. On the other hand, behaviors of mismatched DNA revealed that through-space ET between pyrene moiety and the consecutive guanine site was promoted under molecular-crowding conditions.
Baddeleyite niobium oxynitride (NbON) is a possible low-cost alternative to baddeleyite TaON, which is a well-known oxynitride semiconductor with high photocatalytic activity for visible light. In this study, baddeleyite NbON thin films were epitaxially grown on yittria-stabilized zirconia (YSZ) (100) substrates by using nitrogen-plasma-assisted pulsed laser deposition. Low temperature growth at 500 °C on a thin self-seed layer, which was deposited at 600 °C, was key to obtain baddeleyite NbON with almost stoichiometric chemical composition. X-ray diffraction measurement revealed multiple domain structure of the film with an epitaxial relationship of (100)NbON//(100)YSZ and NbON//YSZ. Band gap of the baddeleyite NbON films was 2.3 eV, which is smaller than that of baddeleyite TaON (2.5 eV). The NbON films showed n-type conduction with rather low mobility of 1.6 × 10−3 cm2 V−1 s−1, which is probably attributable to high defect density and grain boundaries.
Change in the shape of clay microparticles is essential for applications such as adsorption of toxic elements, microencapsulation, and liquid chromatography. To increase the surface area of the hectorite microparticles, doughnut-like morphology with uniform particle size was realized using a hybrid method of spray drying and centrifugal disc atomization. Addition of tetrasodium pyrophosphate to the aqueous hectorite dispersion was critical for the change in shape; this can be explained with reference to changes in the repulsive interparticle interactions.
Micromixing enables highly selective mono addition of aryllithiums to dialdehydes. Because the unchanged formyl group in the products can be used for further transformations, the present approach serves as a powerful method for protecting-group-free synthesis.
Coordination reaction of biphenyl-3,5-diyl bis(tert-butyl nitroxide) and [Gd(hfac)3(H2O)2] gave unexpected complexes containing a novel dimerized ligand via a [3+3] cycloaddition of the benzene rings, as revealed by means of crystallographic analysis. Magnetic study of the product was performed to confirm the diamagnetic nature of the ligand having four nitrone groups.
The Tishchenko reaction is one of the useful methods for ester synthesis. Intra- and intermolecular Tishchenko reactions using metallic zinc are described. A practical Tishchenko reaction using metallic zinc was applied to various benzaldehydes to give products in good to excellent yields (up to 95%). A sequential reaction with Ullmann coupling afforded lactones in high yields from 2-bromobenzaldehyde derivatives.
Stereocomplex (SC) interaction between poly(lactide)s (PLAs) was investigated by atomic force microscopy (AFM). Poly(l,l-lactide) (PLLA) and poly(d,d-lactide) (PDLA) were synthesized and grafted on a gold substrate, respectively. The chemical graft modification on the substrates was confirmed by contact angle measurement. In order to observe the force on stereocomplexation between PLAs, PLLA was also grafted on the tip of an AFM cantilever and moved toward the PLLA or PLDA on the substrate. When the cantilever was retracted from the substrate, a rupture (discrete deflection of the cantilever) was observed on the order of hundreds of piconewtons (pN), which reflects an attractive interaction between PLAs on the substrate and on the AFM tip. Force mapping measurement was then performed on the substrates in order to estimate distribution of the rupture force. The distribution of the rupture force between the PDLA and PLLA shifted to higher values than that between the PLLA and PLLA due to the stereocomplex formation. Conclusively, we firstly indicated that interaction between PLAs would be enhanced about two-fold by forming SC on the PLLA/PLLA interface.
An efficient ipso-thiolation of arylboronic acid esters with thiosulfonates has been achieved under mild and odorless conditions using a copper catalyst. The use of TMEDA and cesium fluoride as the ligand and base, respectively, dramatically facilitated the desired transformation. The method exhibited a broad substrate scope, which allowed for the expeditious synthesis of diverse aryl sulfides from easily available starting materials.
In this study, a sponge filter (SF) was developed from lanthanum-flocculated graphene oxide and chitosan to separate phosphate from aqueous solution. The results showed that the SF could effectively separate phosphate from aqueous solution through a chemical filtration process; the filtrated phosphate was adsorbed in the material. The filtration capacity on phosphate was 13.12 mg g−1, implying that chemical flocculation is suitable for graphene oxide flocculation, and chemical filtration by SF is a promising phosphate contamination removal pathway.
Pure AgX (X = Cl, Br, I) nanomaterials have been synthesized through a simple solvothermal method. Their visible-light-responsive photocatalytic activities have been estimated from the degradation of the organic dye rhodamine B (RhB) and the colorless antibiotic oxytetracycline (OTC). Importantly, the effect of light irradiation on the photostability of AgX (X = Cl, Br, I) during photocatalysis, which has not been previously reported, has been investigated herein.
The cyclic trimer of dibenzofuran linked at the 4,6-positions, named cyclo-4,6-dibenzofuranylene, was synthesized by Ni(0)-mediated reductive coupling of 4,6-dibromodibenzofuran. DFT calculation indicated that the flake-shaped C2 symmetric structure is the most stable conformer and the propeller-shaped D3 symmetric structure is the minor conformer with a higher energy (+19.1 kcal mol−1). The calculated inversion energy of the C2 conformer through a Cs symmetric transition state was +4.1 kcal mol−1, showing rapid fluctuation, which is consistent with the observation of only one set of 1H NMR signals of dibenzofuran of cyclo-4,6-dibenzofuranylene.
A reentrant gel–sol–gel phase transition in organic media is achieved for a single-component, thermoresponsive Co(II)-based coordination polymer bridged by suitably designed lipophilic 1,2,4-triazole ligands. Its green chloroform solution at room temperature turns into a blue gel upon heating, whereas it is transformed to a yellow gel by cooling. These unique thermal phase transitions are reversible and occur all by themselves, which originate from the simultaneous pursuit of entropy-driven changes in coordination structures and enthalpy-driven interactions between the coordination polymers.
Benzoyl-1,2,4-triazole underwent esterification with a primary alcohol in the presence of 4-(N,N-dimethylamino)pyridine (DMAP) catalyst at the rate comparable to benzoyl chloride. The kinetic study concluded that the reaction proceeds in a similar mechanism to carboxylic acid anhydride and is thus sensitive to the steric hindrance of alcohol. As the esterification of benzoyl-1,2,4-triazole did not afford acidic by-product and require an equimolar or more amount of base, it is effective for the protection of acid-sensitive alcohol and polyester synthesis.
A Ni-Y2O3 catalyst containing ruthenium (Ru/Ni-Y2O3) was synthesized and applied to the hydrogenolysis of tetrahydrofurfuryl alcohol (THFA) to produce 1,5-pentanediol (1,5-PeD), which showed superior catalytic performance over that of the Ni-Y2O3 catalyst itself. The optimized ruthenium-containing catalyst, which was prepared by impregnation of 1.0 wt % ruthenium in Ni-Y2O3, showed high catalytic activity for producing 1,5-PeD, giving an 86.5% yield at 93.4% conversion of THFA under 2.0 MPa of H2 at 423 K after 40 h. The formation of Ru-Ni0-Y2O3 boundaries was proposed to accelerate the C–O bond scission of the tetrahydrofuran ring to give 1,5-PeD.
Chondrocyte dedifferentiation during subculture prevents cartilage tissue engineering. The dedifferentiation is generally caused by cell spreading and trypsin treatment. Thus, it is expected that chondrocytes maintain their specific functions when the cells are subcultured on a substrate that can suppress cell spreading and allow the cells to detach without trypsin treatment. Here, we showed that thermoresponsive poly(2-methoxyethyl acrylate) and analogous polymers can be used to suppress cell spreading and detachment without trypsin treatment.
An efficient and improved synthetic route of fluocinolone acetonide with combination of bio-fermentation was developed from 21-acetyloxy-17α-hydroxy-4,9(11)-diene-3,20-dione (1a). Process of the 6α and 9α fluorination steps was studied, and it was observed that the stereoselectivity of 6α fluorination is highly substrate dependent. After an extensive screening on the fluorinating reagents and activation reagents, 6α-F was introduced in 85% yield with 98.9% stereoselectivity. Instead of HF gas, aqueous HF solution was applied in 9α fluorination step to provide the desired product in 89% yield. Starting from 1a, fluocinolone acetonide was prepared in 9 steps with an overall 38.5% yield.