Ionic liquids as oxidic media for electron transfer studies

We review the basic ideas underlying the electron free energy level diagrams that have been found useful in considering the thermodynamics of redox processes in molten silicates and related high temperature ionic liquid (IL) solvents, and then show how closely they link to behavior observable in ambient temperature ionic liquids. Much of the information available on redox levels in molten oxides has been gleaned from chemical analysis and spectroscopic species distribution studies, but it is simpler to obtain the data electrochemically. Here, we report some cyclic voltammetry measurements of the Fe(II)∕Fe(III) redox equilibrium in aprotic ionic liquids whose anions provide oxide environments for the redox species that are of different electronic polarizability character from the high temperature solvents, and relate the observations to those of the earlier studies. Quasi-reversible behavior is found in each of the cases studied. As might be expected, the Fe(II)∕Fe(III) equilibrium experiences a more basic environment in an acetate IL than it experiences in any of the common glassforming oxide media, while triflate anions contrast by providing a more acid environment than does the most acid of the molten oxide glassformers studied (an alkali phosphate). The difference can amount to well over 1 V, suggesting the possibility of a "basicity cell" where the same redox couple locates in anode and cathode compartments of the cell, and only the anion environment is different.     

Application of tri- and tetrasubstituted alkene dipeptide mimetics to conformational studies of cyclic RGD peptides

The first application of a combination of novel ψ[(E)-CXCX]-type alkene dipeptide isosteres to conformation studies of cyclic bioactive peptides was carried out (X=H or Me). For exploration of bioactive conformations of Kessler's cyclic RGD peptides, cyclo(-Arg-Gly-Asp-d-Phe-Val-) 1 and cyclo(-Arg-Gly-Asp-d-Phe-N-MeVal-) 2, d-Phe-ψ[(E)-CXCX]-l-Val-type dipeptide isosteres were utilized having di-, tri- and tetrasubstituted alkenes containing the γ-methylated isosteres that have been reported to be potential type II′ β-turn promoters. All of the (E)-alkene pseudopeptides 3-6 exhibited higher antagonistic potency against α_vβ₃ integrin than 1, although potencies were slightly lower than 2. Detailed structural analysis using ¹H NMR spectroscopy revealed that representative type II′ β/γ backbone arrangements proposed for 1, were not observed in peptides 3-6. Rather on the basis of ¹H NMR data, the conformations of peptides 3-6 were estimated to be more analogous to those of the N-methylated peptide 2.     

Study of simulation method of time evolution of atomic and molecular systems by quantum electrodynamics

We discuss a method to follow step‐by‐step time evolution of atomic and molecular systems based on quantum electrodynamics. Our strategy includes expanding the electron field operator by localized wavepackets to define creation and annihilation operators and following the time evolution using the equations of motion of the field operator in the Heisenberg picture. We first derive a time evolution equation for the excitation operator, the product of two creation or annihilation operators, which is necessary for constructing operators of physical quantities such as the electronic charge density operator. We, then, describe our approximation methods to obtain time differential equations of the electronic density matrix, which is defined as the expectation value of the excitation operator. By solving the equations numerically, we show “electron‐positron oscillations,” the fluctuations originated from virtual electron‐positron pair creations and annihilations, appear in the charge density of a hydrogen atom and molecule. We also show that the period of the electron‐positron oscillations becomes shorter by including the self‐energy process, in which the electron emits a photon and then absorbs it again, and it can be interpreted as the increase in the electron mass due to the self‐energy. © 2014 Wiley Periodicals, Inc.     

Synthesis of Calcium Phosphates by Gas-Solid Reaction of CaO-P 2 O 5

Calcium phosphates are useful materials in fertilizer, dentifrice, biomaterials, etc., and have been popularly synthesized by a wet method, a hydrothermal method, a flux method, and a solid-state reaction method. However, there has been no report on synthesis by chemical vapor deposition (CVD) method or gas-phase reaction. In the present study, calcium phosphates were synthesized by gas-solid reaction of CaO solid and P 2 O 5 gas. The CaO/P 2 O 5 ratio of starting materials was changed from 5.06 to 0.64, and the reaction was carried out at 400-1100;C. These calcium phosphates were investigated using X-ray diffractometry (XRD) and scanning electron microscope (SEM). By gas-solid reaction of CaO-P 2 O 5 , g -MET only was synthesized at 400-500;C, g -MET, HA, and g -PYR at 600-700;C, and g -MET, HA, g -PYR, and g -TCP above 800;C. Synthesized calcium phosphates were independent on the CaO/P 2 O 5 ratio of starting materials but dependent on the reaction temperature.     

Convenient synthesis of fully and partially deuterated stereoregular poly(phenylacetylene)s bearing a carboxy pendant and helicity induction on the polymers with chiral amines and its memory

Poly[(4-carboxyphenyl)acetylene] and its derivatives deuterated in the main chain and/or on the phenyl group (poly- 1 's) were conveniently synthesized by the polymerization of 4-ethynylbenzoic acid or its derivative deuterated on the phenyl group in the presence of bases with a water-soluble rhodium complex in water or deuterium oxide. The obtained polymers possesses highly cis–transoidal stereoregular structures according to NMR and Raman spectroscopy. Possible deuterium isotope effects of these partially and fully deuterated poly- 1 's during the helicity induction with chiral amines and its memory assisted by achiral amines were investigated. The thermal cis–trans isomerization of the methyl esters of poly- 1 's was also studied with ¹H NMR spectroscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4711–4722, 2004     

Inverted-sandwich-type and open-lantern-type dinuclear transition metal complexes: theoretical study of chemical bonds by electronic stress tensor

We study the electronic structure of two types of transition metal complexes, the inverted-sandwich-type and open-lantern-type, by the electronic stress tensor. In particular, the bond order $b_\varepsilon$ measured by the energy density which is defined from the electronic stress tensor is studied and compared with the conventional MO-based bond order. We also examine the patterns found in the largest eigenvalue of the stress tensor and corresponding eigenvector field, the ??spindle structure?? and ??pseudo-spindle structure??. As for the inverted-sandwich-type complex, our bond order $b_\varepsilon$ calculation shows that relative strength of the metal-benzene bond among V, Cr, and Mn complexes is V?>?Cr?>?Mn, which is consistent with the MO-based bond order. As for the open-lantern-type complex, we find that our energy density-based bond order can properly describe the relative strength of Cr?CCr and Mo?CMo bonds by the surface integration of the energy density over the ??Lagrange surface?? which can take into account the spatial extent of the orbitals.     

Approximations for nonlinear mappings by the hybrid method in Hilbert spaces

The hybrid method in mathematical programming was introduced by Haugazeau (1968) [1] and he proved a strong convergence theorem for finding a common element of finite nonempty closed convex subsets of a real Hilbert space. Later, Bauschke and Combettes (2001) [2] proposed some condition for a family of mappings (the so-called coherent condition) and established interesting results by the hybrid method. The authors (Nakajo et al., 2009) [10] extended Bauschke and Combettes’s results. In this paper, we introduce a condition weaker than the coherent condition and prove strong convergence theorems which generalize the results of Nakajo et al. (2009) [10]. And we get strong convergence theorems for a family of asymptotically κ-strict pseudo-contractions, a family of Lipschitz and pseudo-contractive mappings and a one-parameter uniformly Lipschitz semigroup of pseudo-contractive mappings.     

From colloidal stability in ionic liquids to advanced soft materials using unique media

Owing to their fascinating properties, ionic liquids (ILs) are now receiving a great deal of attention as alternatives to organic solvents and electrolyte solutions and as synthetic and dispersion media for colloidal systems. Colloidal stability is an essential factor in determining the properties and performance of colloidal systems combined with ILs. The remarkable properties of ILs primarily originate from their highly ionic nature. Although such high ionic strength often causes colloidal aggregation in aqueous and organic suspensions, some colloidal particles can be well suspended in ILs without any stabilizers. In the first part of this article, we focus on recent experiments conducted to investigate the colloidal stability of bare and polymer-grafted silica nanoparticles and on the surface force between silica substrates and ILs. Three different repulsions between colloidal particles (i.e., electrostatic, steric, and solvation forces) are also highlighted, after which a possible interpretation of the results in terms of the stabilization mechanism in ILs both in the presence and in the absence of stabilizers is proposed. The latter part of this article provides an overview of our recent studies on colloidal soft materials with ILs. On the basis of the dispersed states of the silica colloids in ILs, two different soft materials, a colloidal gel and a colloidal glass in ILs, were fabricated. The relationship between their functional properties, such as ionic transport, rheological properties, and optical properties, and the microstructure of the colloidal materials is also described.     

Single-shot two-dimensional spectral interferometry for ultrafast laser-produced plasmas

Coherent white light was used as a light source for spectral interferometry of ultrafast laser-produced plasmas. Using a narrowband filter, two-dimensional images of field ionization in helium were obtained with a 14 fs time resolution.     

Electrochemical Formation of Fe(IV)=O Derived from H2O2 on a Hematite Electrode as an Active Catalytic Site for Selective Hydrocarbon Oxidation Reactions

The high-valence iron species (Fe(IV)=O) in the cytochrome P450 enzyme superfamily is generated via the activation of O₂, and serves as the active center of selective hydrocarbon oxidation reactions. Furthermore, P450 can employ an alternate route to produce Fe(IV)=O, even from H₂O₂ without O₂ activation. Meanwhile, Fe(IV)=O has recently been revealed to be the reactive intermediate during H₂O oxidation to O₂ on hematite electrodes. Herein, we demonstrated the generation of Fe(IV)=O on hematite electrodes during the electrochemical oxidative decomposition of H₂O₂ using in situ UV-visible absorption spectra. The generation of Fe(IV)=O on hematite electrodes from H₂O₂ exhibited 100 mV lower overpotential than that from H₂O. This is because H₂O₂ serves not only as the oxygen source of Fe(IV)=O, but also as the additional oxidant. Finally, we confirmed that the Fe(IV)=O generated on hematite electrodes can serve as the catalytic site for styrene epoxidation reactions.