Fabrication of Self‐Oscillating Micelles with a Built‐In Oxidizing Agent

Various biological behaviors are fueled by “respiration”, which is an example of catabolism. So far, we have reported various self‐oscillating soft materials exhibiting bioinspired dynamic movements. These autonomous polymer systems are driven by the Belousov–Zhabotinsky (BZ) reaction, which is analogous to the tricarboxylic acid (TCA) cycle that is an integral part of respiration. However, in the BZ reaction, the external addition of an oxidizing agent is necessary to initiate the oxidation process, which is realized by intracellular moieties such as ubiquinone in living systems. Herein, we realized self‐oscillating micelles that are driven without the external addition of an oxidizing agent. This was achieved by embedding the oxidizing source into the structure of the self‐oscillating AB diblock copolymers. This strategy introduces a new function equivalent to intracellular oxidizing moieties, and is useful for the design of completely autonomous bioinspired materials.     

Regulated Single‐Axis Rotations of a Carbonaceous Guest in a van der Waals Complex with an Entropy Cost

In a tight host–guest complex assembled solely by nondirectional van der Waals forces, unique motions of the guest, such as solid‐state inertial rotations, emerge. The regulation of dynamic motions is an important element to be explored for novel functions of such complexes, which may be seemingly difficult to achieve because of the nondirectionality of the assembling forces. A regulated, single‐axis rotation was made possible by choosing an appropriate shape of the guest in the tubular host. Specifically, an ellipsoidal guest was made to stand along a cylinder axis of the host, which consequently resulted in single‐axis rotations of the guest in the solid. The rotational frequency was considerably high for solid‐state rotations but was suppressed to 10 GHz, which was 1/20 of the isotropic rotation of a spherical guest. In‐depth kinetic analyses quantitatively revealed that the entropy cost was a determining factor that regulated the dynamics.     

Quasi-particle structure around a single vortex in high-Tc superconductors

For analyzing the checker-board like modulation of the local density of states (LDOS) around a vortex observed in the slightly overdoped Bi₂Sr₂CaCu₂O_x, we examined the effect of pseudogap state of high-T_c superconductors to the LDOS around the vortex. We first derived the Bogoliubov-de Gennes equation for d-wave superconductivity (d-SC) in the presence of d-spin density wave (d-SDW). Using the Fourier–Bessel expansion, we solved this equation for a single vortex state, numerically. We found that the peak of the bound states around E = 0 becomes small and modulation of the LDOS is observed for larger d-SDW order parameter.     

Novel photodegradation of the antifungal antibiotic pyrrolnitrin in anhydrous and aqueous aprotic solvents

The UV irradiation of pyrrolnitrin (1a), which is an antibiotic clinically useful against dermatophytosis and possesses a unique 2-(pyrrol-3-yl)nitrobenzene moiety in the molecule, in an anhydrous aprotic solvent resulted in the exclusive formation of transient 7,4'-dichlorospiro[1,3-dihydrobenzo(c)isoxazole-3,3'-pyrrolin-2'-one] (2a) via the intramolecular oxidation of the juxtaposed pyrrole ring by the triplet-excited nitro group. The irradiation in an aqueous aprotic solvent, however, allowed the concurrent occurrence of intramolecular cyclization by the singlet-excited nitro group in 1a and the hydroxylation at the 2-position of the pyrrole ring by water to afford 3,7-dichloro-8-hydroxy-8,8a-dihydropyrrolo[2,3-b]indol-2-one (3a), accompanied by the formation of 2a. Elongation of the irradiation time in these photoreactions caused a rapid consumption of the products, 2a and 3a, to give undetermined polar polymeric products. The present results indicate that the photodegradation of 1a is significantly influenced by the presence of water in the reaction media and by the nature of its excited state. Thus, the loss of the antifungal activities by the photosensitive antibiotic 1a was chemically proved.     

Chemoselective transfer hydrodechlorination of aryl chlorides catalyzed by Cp*Rh complexes

An effective Cp*Rh catalyzed transfer hydrodechlorination of aryl chlorides was achieved with high tolerance towards a variety of functional groups using 2-butanol as a hydrogen source.     

Selective sterol-phospholipid associations in fluid bilayers

The nearest-neighbor preferences of three exchangeable lipid monomers (two phospholipids that differ in length, A and B, and a derivative of cholesterol, C) have been quantified in the fluid bilayer state by use of the nearest-neighbor recognition method (Davidson, S. K. M.; Regen, S. L. Chem. Rev. 1997, 97, 1269). Thus, an analysis of the equilibrium dimer distributions has shown that (i) the sterol favors both phospholipids as nearest neighbors relative to other sterol molecules, (ii) that this recognition is selective (i.e., the sterol favors the longer phospholipid as a nearest neighbor over the shorter one, especially when the sterol concentrations in the bilayer is high (e.g., 40 mol %), and (iii) the phospholipids, themselves, are unable to recognize each other. Taken together, these findings indicate that the probable mechanism by which cholesterol induces homoassociation of A and B in analogous bilayers is one in which the sterol "pulls" two or more of the longer phospholipid monomers (B) out of a "sea" of randomly mixed A and B. These findings also lend support for the notion of cholesterol-phospholipid complexation in fluid bilayers. The biological implications of these findings are briefly discussed.     

Single-molecule reaction and characterization by vibrational excitation

Controlled chemical reaction of single trans-2-butene molecules on the Pd(110) surface was realized by dosing tunneling electrons from the tip of a scanning tunneling microscope at 4.7 K. The reaction product was identified as a 1,3-butadiene molecule by inelastic electron tunneling spectroscopy. Threshold voltage for the reaction is approximately 365 mV, which coincides with the vibrational excitation of the C-H stretching mode. The reaction was ascertained to be caused by C-H bond dissociation by multiple vibrational excitations of the C-H stretching mode via inelastic electron tunneling process.     

High-resolution infrared measurements of v1 and force field calculations for thioborine (HBS)

The gas-phase high-resolution spectrum is reported for v₁ of the linear molecule thioborine (HBS) from 2775 cm^?1 to 2720 cm^?1. Band centers and rotational constants are given for the 10⁰0-00⁰0 transitions of H¹¹B³²S, H¹⁰B³²S, H¹¹B³⁴S and H¹⁰B³⁴S and for the 11¹0-01¹0 transitions of H¹¹B³²S and H¹⁰B³²S. A valence force field is determined from measured values of v₁, D_o (the centrifugal distortion) and q (the l-doubling constant). The remaining unobserved vibrational fundamentals are calculated from the force constants.     

ac ionic conductivity of hollandite type compounds from 100 Hz to 37.0 GHz

The frequency- and temperature-dependences of a.c. ionic conductivity of one-dimensional super-ionic conductors K-priderites with a hollandite type structures were investigated from 100 Hz to 37.0 GHz. Four kinds of K-priderite, K_1.6Mg_0.8Ti_7.2O₁₆, (K_1.3, Li_0.1) Mg_0.7Ti_7.3O₁₆, K_1.6Al_1.6Ti_6.4O₁₆ and (K_1.3, Li_0.2) Al_1.5Ti_6.5O₁₆, were studied. An equivalent circuit to combine the data of the complex conductivity at low and high frequencies was proposed. The data of complex conductivity at low frequencies can be analyzed in terms of the moving box model proposed by Beyeler et al. The transport of K⁺ ions at low frequencies is characterized by the cooperative motion of the K⁺ ions with various mobilities and is accompanied with the polarization of the K⁺ ions in the channels. The ion transport across intrinsic barriers at or above microwave frequencies is characterized by the frequency-independent ionic conductivity and is interpreted by the configurational model proposed by Beyeler et al. The height of intrinsic barriers is related to the lattice constants of a crystal.