Single‐Crystal‐like Nanoporous Spinel Oxides: A Strategy for Synthesis of Nanoporous Metal Oxides Utilizing Metal‐Cyanide Hybrid Coordination Polymers

Development of a new method to synthesize nanoporous metal oxides with highly crystallized frameworks is of great interest because of their wide use in practical applications. Here we demonstrate a thermal decomposition of metal‐cyanide hybrid coordination polymers (CPs) to prepare nanoporous metal oxides. During the thermal treatment, the organic units (carbon and nitrogen) are completely removed, and only metal contents are retained to prepare nanoporous metal oxides. The original nanocube shapes are well‐retained even after the thermal treatment. When both Fe and Co atoms are contained in the precursors, nanoporous Fe?Co oxide with a highly oriented crystalline framework is obtained. On the other hand, when nanoporous Co oxide and Fe oxide are obtained from Co‐ and Fe‐contacting precursors, their frameworks are amorphous and/or poorly crystallized. Single‐crystal‐like nanoporous Fe?Co oxide shows a stable magnetic property at room temperature compared to poly‐crystalline metal oxides. We further extend this concept to prepare nanoporous metal oxides with hollow interiors. Core‐shell heterostructures consisting of different metal‐cyanide hybrid CPs are prepared first. Then the cores are dissolved by chemical etching using a hydrochloric acid solution (i.e., the cores are used as sacrificial templates), leading to the formation of hollow interiors in the nanocubes. These hollow nanocubes are also successfully converted to nanoporous metal oxides with hollow interiors by thermal treatment. The present approach is entirely different from the surfactant‐templating approaches that traditionally have been utilized for the preparation of mesoporous metal oxides. We believe the present work proves a new way to synthesize nanoporous metal oxides with controlled crystalline frameworks and architectures.     

Chemo‐ and Enantioselective Oxidative α‐Azidation of Carbonyl Compounds

We report high‐performance I⁺/H₂O₂ catalysis for the oxidative or decarboxylative oxidative α‐azidation of carbonyl compounds by using sodium azide under biphasic neutral phase‐transfer conditions. To induce higher reactivity especially for the α‐azidation of 1,3‐dicarbonyl compounds, we designed a structurally compact isoindoline‐derived quaternary ammonium iodide catalyst bearing electron‐withdrawing groups. The nonproductive decomposition pathways of I⁺/H₂O₂ catalysis could be suppressed by the use of a catalytic amount of a radical‐trapping agent. This oxidative coupling tolerates a variety of functional groups and could be readily applied to the late‐stage α‐azidation of structurally diverse complex molecules. Moreover, we achieved the enantioselective α‐azidation of 1,3‐dicarbonyl compounds as the first successful example of enantioselective intermolecular oxidative coupling with a chiral hypoiodite catalyst.     

Supramolecular polymer gels from polystyrene bearing cyclic amidine Group and acrylic acid/n‐butyl acrylate copolymers

We have prepared supramolecular polymer gels by mixing solutions of a polystyrene bearing cyclic amidine pendant groups (Poly‐A) and copolymers of acrylic acid and n‐butyl acrylate (Poly‐C), followed by evaporation. FT‐IR analysis indicated that the gels were formed through three‐dimensional network of the amidinium‐carboxylate salt bridge. DSC study showed that the Poly‐A and the Poly‐C were miscible when the salt bridge content was high. On the other hand, the mixtures with small salt bridge content showed phase separation. Dynamic shear measurements showed that the gel prepared from Poly‐A and Poly‐C with acrylic acid unit content of 15% had G' higher than G″ over a temperature range of ?22 °C to 32 °C, in which the G' value reached almost 1 MPa. The gel had a crossover point of G' and G″ at 32 °C, very close to room temperature, which suggested facile processability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 765–770     

Theory of ferromagnetism in Ca(1-x)La(x)B(6)

Novel ferromagnetism in Ca(1-x)La(x)B(6) is studied in terms of the Ginzburg-Landau theory for excitonic-order parameters, taking into account symmetry of the wave functions. We found that the minima of the free energy break both inversion and time-reversal symmetries, while the product of these two remains preserved. This explains various novelties of the ferromagnetism and predicts a number of magnetic properties, including the magnetoelectric effect, which can be tested experimentally.     

Excitation migration among inhomogeneously broadened levels of Eu3+ ions

Excitation migration between ⁵D₀ states of Eu³⁺ ions in Ca(PO₃)₂ glass is studied by using the technique of the selective excitation of the inhomogeneously broadened ⁵D₀ levels. In time-resolved emission spectra for ⁵D₀→⁷F₁ transition after the pulse excitation due to ⁷F₀→⁵D₀ transition by the use of a tunable dye laser at 77°K, a subpeak is observed to appear and to grow in intensity with increasing delay time, besides the main peak excited directly by the excitation light. The observed facts are explained by considering the phonon-assisted energy transfer between ⁵D₀ states involving an acoustic phonon. From the analysis of the results, the probability of the excitation migration due to the phonon-assisted process is estimated to be ≌ 10 A ms^-1. From the theoretical consideration, the rate of the linewidth change and the probability of the excitation migration due to the resonant transfer process are obtained. These results indicate that the phonon-assisted process is more dominant than the resonant process for the excitation migration in the system studied.     

Interfaces of correlated electron systems: proposed mechanism for colossal electroresistance

Mott's metal-insulator transition at an interface due to band bending is studied by the density matrix renormalization group approach. We show that the result can be recovered by a simple modification of the conventional Poisson's equation approach used in semiconductor heterojunctions. A novel mechanism of colossal electroresistance is proposed, which incorporates the hysteretic behavior of the transition in higher dimensions.     

Skeletal reorganization of enynes into 1-vinylcycloalkenes in ionic liquids

The skeletal reorganization of enynes catalyzed by transition metal chlorides, such as PtCl(2), [RuCl(2)(CO)(3)](2), [RhCl(CO)(2)](2), and AuCl(3), in ionic liquids proceeds under milder conditions (at lower reaction temperatures and for shorter reaction times) than those needed for ordinary solvents. The products produced by the skeletal reorganization of enynes were easily removed from the catalyst by a simple extraction with Et(2)O or distillation. The PtCl(2) can be reused up to five times.     

A new ketone synthesis by palladium-catalyzed cross-coupling reactions of esters with organoboron compounds

[reaction: see text] The palladium-catalyzed coupling reaction of 2-pyridyl esters with organoboron compounds is described. The reaction is compatible with various functional groups and proceeds under mild reaction conditions. The coordination of the nitrogen atom to Pd is a key step for efficient reaction.