Rare examples of P–C reductive elimination at a Ru(II) center to form phosphonium salts have been developed. A five-membered phospharuthenacycle derived from P(1-Naph)Ph2 and [(η6-C6Me6)RuCl2]2 is converted to η4-phosphaphenalenium complexes [(η6-C6Me6)Ru(η4-phosphaphenalenium)][BArF4] via alkyne insertion followed by P–C reductive elimination. This reaction sequence including P–C reductive elimination is applicable to various dialkyl and diarylalkynes, although the η4-phosphaphenalenium complexes with electron-rich aryl groups are not stable enough to be isolated. The reaction of the η4-phosphaphenalenium complexes with I2, CO or CuCl2 resulted in the liberation of the phosphaphenalenium salts. In contrast to the highly distorted phosphacycle in the Ru complex, the phosphaphenalenium cations have nearly planar π-conjugated structure, and their BArF4 salts display green to yellow and blue to green fluorescence in solution and in the solid state, respectively, depending on the substituents on the phenalene skeleton. Because of the cationic character of the phosphacycle as well as their large counteranion, π–π stacking of the phosphacycles in the crystalline state is effectively suppressed, leading to emission with shorter wavelength in the solid state than in solution. Electronic structures of phosphaphenalenium ions as well as effects of substituents were investigated by TD-DFT calculations.
Seebeck coefficients (Se) of supramolecular thermocells harnessing four kinds of cyclodextrins as host molecules were investigated. Theoretical analysis revealed that association enthalpy between the hosts and triiodide has a major influence on the Seebeck coefficients of the thermocells. Thermodynamic parameters of host–guest associations were evaluated by isothermal titration calorimetry, which is in good agreement with the theoretically estimated values from thermocell measurements. This result provides a guideline to estimate Seebeck coefficient of supramolecular thermocells and to determine the thermodynamic parameters.
(Yb1−xCox)2O3−δ catalysts with cubic (C-type) rare-earth sesquioxide structure were synthesized by a co-precipitation method. The introduction of Co2+/3+ ions into the Yb2O3 lattice resulted in an improved catalytic activity for N2O decomposition, due to the enhanced redox properties and increased amount of active sites. Among the prepared catalysts, (Yb0.90Co0.10)2O3−δ exhibited the highest activity for the decomposition of N2O, which was completely converted to N2 and O2 at 500 °C. Moreover, (Yb0.90Co0.10)2O3−δ also showed high durability in the presence of H2O, O2, or CO2.
The lithium-richest phase in the binary Li-Tt system (Tt = Si, Ge, Sn, and Pb) has a stoichiometry of Li17Tt4. In the beginning of this paper, the structural complexity of Li17Tt4 is gradually stripped away using the concept of the M26 cluster found in γ-brass structures and a Tt-centered polyhedral representation. By means of the first-principles electronic structure calculations, which are followed by the analyses of the electron localization function (ELF), Bader charges, and spin density, we observe non-nuclear maxima of the ELF, electron density, and spin density. Since the electron densities off the atoms are confined in crystalline voids, separated from each other, and behaving as an anion, Li17Tt4 can be identified as a potential zero-dimensional electride. This finding agrees with a simple Zintl picture, which suggests a valence electron count of [(Li+)17(Tt4−)4·e−]. Detailed analyses on the band structures, the projected density of states, and crystal orbitals at the Γ point in the reciprocal space hint at the potential of forming a bond between the non-nuclear electron density and the neighboring atoms. Signatures of bonding and anti-bonding orbital interactions can be witnessed.
Fluorescent pyrone derivatives were extracted from the pyrolitic product of citric acid confined in supermicroporous silicas (SMPSs). We utilized the tiny spaces of SMPSs to produce fluorescent molecules as small fragments of carbogenic dots. We characterized their optical properties and investigated their structual information. The obtained molecule was determined as a pyrone derivative. The isolated product showed similar optical properties to those of reported carbogenic dots. Therefore, we suggest that the pyrone structure is the key fragment structure of carbogenic dots.
To ensure high enantiopurity of the product, enantio-differentiating hydrogenation of methyl acetoacetate over a (R,R)-tartaric acid-modified Raney nickel catalyst is normally performed under elevated H2-pressure (∼10 MPa). In this study, higher enantioselectivity than previously reported for methyl acetoacetate was achieved (92% ee) under low H2-pressure of 0.42 MPa. Effects of reaction conditions on the enantioselectivity and hydrogenation rate were investigated using a low-pressure reaction system (<0.5 MPa of H2). It was found that impurities in the solvent greatly reduce the enantioselectivity of MAA. The low-pressure reaction system enabled a satisfactory kinetic approach. The reaction rate was well described by Langmuir-Hinshelwood formalism, verifying the previous assumption that the addition of adsorbed hydrogen to the substrate interacting with surface tartrate is a rate-determining step.
Fullerenes are attractive spherical aromatic molecules with good electron acceptor capabilities and good utility as an n-type organic semiconductor. By using a fullerene-amine addition reaction, it was possible to fabricate ultrathin-film assemblies of fullerene on the surface of substrates, which were confirmed by photoelectric conversion applications. Addition reactions between fullerenes and primary aliphatic diamines can also occur to form insoluble adduct particles consisting of fullerenes and diamines. In one example, C60-ethylenediamine adduct particles can be solubilized by addition of alkylacid chloride to residual amino groups of the adducts. Spin-coated or dip-coated thin-films of C60-ethylenediamine adducts from their solutions are useful as n-type organic semiconductors which was confirmed with solar cell application. In this account, the history of the fabrication and application of fullerene thin-film assemblies and fullerene-diamine adducts using the fullerene-amine addition reaction is introduced and summarized from the early studies to more recent developments.
The properties of water phase in reversed micelle formed by (CF3CONH(CH2)2N+(CH3)2(CH2)15CH3 Br− (C1F)) were investigated. The polarity and pH of water phase in reversed micelle were studied by dye probe method using porphyrin derivatives and alizarin red S. The mobility of water phase was studied by 1H NMR spectroscopy measuring the longitudinal relaxation time (T1) of water in the reversed micelle, and by near infrared (NIR) spectroscopy measuring absorption due to OH vibration. The effects of the w value (w = [water]/[C1F]) change on the polarity, pH, and mobility of water were examined. These measurements supported the biphase structure model of water in the reversed micelle. According to the analysis of polarity, the free water phase was estimated to be less polar than boundary water phase. The pH of water around the probe molecule in the reversed micelle was acidic and was not affected by the change of the w value. NIR spectroscopy of the reversed micelle indicated that OH vibration was much affected by the size of the water pool in the reversed micelle. The shift of absorption λmax due to OH vibration can be explained by the strong interaction between water and the ammonium group of the surfactant molecule.
Li1.6Mn1.6−xCrxO4 was synthesized by hydrothermal reaction followed by acid leaching to form lithium ion sieve. The structure, morphology and composition were examined using X-ray diffraction, SEM and EDS. The influences of Cr doping content and hydrothermal temperature on Li+ adsorption capacity and manganese dissolution ratio were investigated. The result indicates that Cr is incorporated into the spinel structure with cell contraction when x ≤ 0.08. Li1.6Mn1.6−xCrxO4 shows Li+ adsorption capacity of 31.67 mg/g and Mn dissolution ratio of 2.1% when x is 0.016 at 270 °C. After 20 cycles in salt lake brine, the Mn dissolution ratio and Li adsorption capacity is 0.35% and 25.5 mg/g, respectively. The Cr-doped ion-sieve shows improved adsorption capacity, retention and structural stability compared with the undoped lithium ion-sieve. The adsorption process for the Cr-doped ion-sieve follows a pseudo-second-order kinetic model.
Tetraarylanthraquinodimethane derivatives 1 with butterfly-shaped folded structures and the corresponding dications 12+ with twisted conformations can undergo interconversion upon two-electron transfer, which is accompanied by a drastic color change. While reversible electrochromic behavior occurs in solution, electron donors 1 exhibit fluorescence only in the solid state. The emission color changed upon grinding as-synthesized samples of 1, and the original emission color was recovered by a dissolving-drying process. Such mechanofluorochromic behavior can be accounted for by the results of powder X-ray diffraction (PXRD), for which as-synthesized crystalline sample was transformed into an amorphous state after grinding. Thus, the title electron donors 1 provided two-way chromic systems exhibiting electrochromism in solution as well as mechanofluorochromism in a solid state.
A new lipophilic spin-trapping flow-injection electron spin resonance (LFI-ESR) system was developed for quantitative detection of DMPO spin-adduct of alkoxyl radical (RO•), which was produced by thermal decomposition of an azo-initiator (AIBN) in ethyl acetate at 70 °C. The 50% and 75% inhibition dose (ID50 and ID75) of a series of lipophilic antioxidants, such as tocopherol derivatives (αToc, βToc, γToc, δToc, Toc, αTocM, βTocM, γTocM, TocM, TRX, and 7TocM), a lipophilic phenol (BHT), and unsaturated fatty acids (Ole, Lin, and Lic), were determined by monitoring the ESR signal intensity of the DMPO spin-adducts of RO• radical (DMPO/OR). On the basis of the observed ID50 and ID75 values, the lipophilic alkoxyl radical eliminating capacities (L-AREC) of these lipophilic antioxidants were determined using TRX as a standard. The evaluated L-AREC values are directly connected to the second order rate constants for the RO• radical induced hydrogen atom abstractions from the hydroxyl groups of the phenolic antioxidants, as well as from the allylic methylene groups of unsaturated fatty acids. The L-AREC values estimated by LFI-ESR method are concluded to be a practical and reliable indicator that reflect the inhibiting abilities of lipophilic antioxidants towards the radical chain reaction involved in the autoxidation processes of unsaturated fatty acids.
Liquid-crystalline compounds consisting of mesogenic cores linked to cyclic carbonates through flexible spacers have been developed. These liquid crystals form complexes with lithium salts and self-assemble into nanostructures with well-defined ion pathways. It is found that the type and length of the intramolecular spacer affects the liquid crystallinity and ion conductivity of the materials. Mesogenic compounds based on alkylene-based spacers show odd-even effects on the liquid-crystalline properties of the compounds. The liquid crystals based on spacers with an even number of carbon atoms show liquid crystallinity in wider temperature ranges and higher ion conductivities as compared to the liquid crystals based on spacers with an odd number of carbon atoms. On the other hand, liquid crystals based on polar oligooxyethylene spacers are observed to show liquid-crystallinity in wider temperature ranges and higher ion conductivities as compared to the alkylene-based liquid crystals. The liquid crystals with more polar and more flexible spacers, that is, oligooxyethylene groups show higher ion conductivities than those of the liquid crystal with alkylene spacers. This enhanced behavior may be due to the increase in the fluidity of the ionic pathways. These findings may provide us with new designs of self-assembled ion conductors.
We focus on enhancement of the sterilizing property of ultraviolet irradiation and the change in the sterilizing property of ozonated water and sodium hypochlorite due to ultraviolet irradiation. As a result, the effect due to ultraviolet irradiation was not observed in ozonated water. On the other hand, the sterilizing power of sodium hypochlorite was greatly improved by ultraviolet irradiation.
Controlled drug release holds promise to revolutionize medicine, particularly if short-term and long-term release can be combined in a single system. We present here a new pulsatile release system, in which the pulses were achieved using 3D scaffolds of poly(L-lactic acid), PLLA. From a morphological characterization of the scaffold’s surfaces, before and after releasing experiments at distinct pHs, we infer that release is governed by electrostatic interactions and the fractal geometry of the scaffolds. Furthermore, the scaffold can present short-term (within hours) or long-term (several days long) releasing profiles by varying the pH, which opens the way for unprecedented drug release control.
In this account, we provide an overview of synthetic methods for accessing fluoroalkylated compounds via electrophilic fluoroalkylation, especially of alkenes, focusing mainly on our own studies directed towards the discovery of drugs and agrochemicals. First, we describe trifluoromethylations with Togni reagent 1 in the presence of catalysts or electron-donating additives, providing access to a wide range of fluoroalkylated molecules. We then cover fluoroalkylations using fluorinated acid anhydrides. We recently showed that these acid anhydrides enable alkene fluoroalkylation via the in-situ formation of diacyl peroxide, with or without the aid of copper catalysts, affording various fluoroalkyl group-containing molecules in a practical manner. We also present some examples of structural diversification of the products, illustrating their synthetic utility as building blocks, which could be widely applicable, for example, in the construction of fluoroalkylated compound libraries.
Single crystal Co(H2O)2Ni(CN)4·4H2O has been successfully synthesized by a slow diffusion method using trisodium citrate dihydrate for controlling the nucleation rate and the crystal growth. The single crystal X-ray diffraction results show the obtained crystals with a two-dimensional orthorhombic unit cell, assembled from cationic Co ions and anionic [Ni(CN)4]2− units connected by bridging cyanide groups.