Photo-induced morphological winding and unwinding motion of nanoscrolls composed of niobate nanosheets with a polyfluoroalkyl azobenzene derivative.

Photo-responsive nanoscrolls can be successfully fabricated by mixing a polyfluoroalkyl azobenzene derivative and a niobate nanosheet, which is exfoliated from potassium hexaniobate. In this study, we have found that the photo-responsive nanoscroll shows a morphological motion of winding and unwinding, which is basically due to the nanosheet sliding within the nanoscroll, by efficient photo-isomerization reactions of the intercalated azobenzene in addition to the interlayer distance change of the nanoscrolls. The relative nanosheet sliding of the nanoscroll is estimated to be ca.

Direct detection of key reaction intermediates in photochemical CO2 reduction sensitized by a rhenium bipyridine complex.

Photochemical CO2 reduction sensitized by rhenium-bipyridyl complexes has been studied through multiple approaches during the past several decades. However, a key reaction intermediate, the CO2-coordinated Re-bipyridyl complex, which should govern the activity of CO2 reduction in the photocatalytic cycle, has never been detected in a direct way. In this study on photoreduction of CO2 catalyzed by the 4,4'-dimethyl-2,2'-bipyridine (dmbpy) complex, [Re(dmbpy)(CO)3Cl] (1), we successfully detect the solvent-coordinated Re complex [Re(dmbpy)(CO)3DMF] (2) as the light-absorbing species to drive photoreduction of CO2.

An artificial muscle model unit based on inorganic nanosheet sliding by photochemical reaction.

From the viewpoint of developing photoresponsive supramolecular systems in microenvironments to exhibit more sophisticated photo-functions even at the macroscopic level, inorganic/organic hybrid compounds based on clay or niobate nanosheets as the microenvironments were prepared, characterized, and examined for their photoreactions. We show here a novel type of artificial muscle model unit having much similarity with that in natural muscle fibrils. Upon photoirradiation, the organic/inorganic hybrid nanosheets reversibly slide horizontally on a giant scale, and the interlayer spaces in the layered hybrid structure shrink and expand vertically.

Size-matching effect on inorganic nanosheets: control of distance, alignment, and orientation of molecular adsorption as a bottom-up methodology for nanomaterials.

We have been investigating complexes composed of nanolayered materials with anionic charges such as clay nanosheets and dye molecules such as cationic porphyrins. It was found that the structure of dye assembly on the layered materials can be effectively controlled by the use of electrostatic host-guest interaction. The intermolecular distance, the molecular orientation angle, the segregation/integration behavior, and the immobilization strength of the dyes can be controlled in the clay-dye complexes.

How is the water molecule activated on metalloporphyrins? Oxygenation of substrates induced through one-photon/two-electron conversion in artificial photosynthesis by visible light.

The reaction mechanism of the highly efficient (phi = 0.60), selective photochemical epoxidation of alkenes sensitized by CO-coordinated tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(II) (Ru(II)TMP(CO)), with water acting both as an electron and oxygen atom donor, was investigated. The steady-state light irradiation of the reaction mixture indicated the formation of the Ru(II)TMP (CO) cation radical under neutral conditions, which was effectively trapped by an hydroxide ion to regenerate the starting sensitizer.

Controlling the microadsorption structure of porphyrin dye assembly on clay surfaces using the "size-matching rule" for constructing an efficient energy transfer system.

The microadsorption structure of two kinds of porphyrin molecules on an anionic clay surface was investigated by photochemical energy transfer reaction. Three procedures were examined for the preparation of the clay/porphyrin complexes: (i) coadsorption (CA) method, (ii) sequential adsorption (SA) method, and (iii) independent adsorption (IA) method as described in the text. Efficient and moderate energy transfer reactions were observed in the CA and SA complexes, respectively.

A photoactivated artificial muscle model unit: reversible, photoinduced sliding of nanosheets.

A novel photoactivated artificial muscle model unit is reported. Here we show that organic/inorganic hybrid nanosheets reversibly slide horizontally on a giant scale and the interlayer spaces in the layered hybrid structure shrink and expand vertically by photoirradiation. The sliding movement of the system on a giant scale is the first example of an artificial muscle model unit having much similarity with that in natural muscle fibrils.

Efficient excited energy transfer reaction in clay/porphyrin complex toward an artificial light-harvesting system.

The quantitative excited energy transfer reaction between cationic porphyrins on an anionic clay surface was successfully achieved. The efficiency reached up to ca. 100% owing to the "Size-Matching Rule" as described in the text.

Novel methodology to control the adsorption structure of cationic porphyrins on the clay surface using the "size-matching rule".

Saponite-type clays that have different cation exchange capacities were successfully synthesized by hydrothermal synthesis. The structure and properties were analyzed by X-ray diffraction, X-ray fluorescence, (27)Al NMR, FT-IR, thermogravimetric and differential thermal analysis, atomic force microscopy, and cation exchange capacity measurement. The intercharge distances on the synthetic saponite (SS) surfaces were calculated to be 0.

Two distinct amyloid beta-protein (Abeta) assembly pathways leading to oligomers and fibrils identified by combined fluorescence correlation spectroscopy, morphology, and toxicity analyses.

Nonfibrillar assemblies of amyloid β-protein (Aβ) are considered to play primary roles in Alzheimer disease (AD). Elucidating the assembly pathways of these specific aggregates is essential for understanding disease pathogenesis and developing knowledge-based therapies. However, these assemblies cannot be monitored in vivo, and there has been no reliable in vitro monitoring method at low protein concentration.

The water oxidation bottleneck in artificial photosynthesis: how can we get through it? An alternative route involving a two-electron process.

The state-of-the-art of research on artificial photosynthesis is briefly reviewed. Insights into how Nature takes electrons from water, the photon-flux density of sunlight, the time scale for the arrival of the next photon (electron-hole) at the oxygen-evolving complex, how Nature solves the photon-flux-density problem, and how we can get through the bottleneck of water oxidation are discussed. An alternate route for a two-electron process induced by one-photon excitation is postulated for getting through the bottleneck of water oxidation.

Key reaction intermediates of the photochemical oxygenation of alkene sensitized by Ru(II)-porphyrin with water by visible light.

Two key reaction intermediates in the photochemical oxygenation of alkene sensitized by carbonyl-coordinated ruthenium(ii)-porphyrin complex, with water acting both as an electron and oxygen atom donor, are postulated. Under the low concentration of hydroxide ion (<2 x 10(-3) M) added to the reaction mixture of tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(ii) (Ru(II)TMP(CO)), K(4)PtCl(6) as a sacrificial electron acceptor, and cyclohexene as a substrate in aqueous acetonitrile, the major reaction product was cyclohexaneoxide ("Epoxide"), while it drastically decreased along with an increase of 2-cyclohexenol ("Alcohol") by increasing the amount of hydroxide ion (>2 x 10(-3) M). The tendency was more obvious in the case of tetrasodium tetra(4-sulfonate)phenylporphyrinatoruthenium(ii) (Ru(II)TSPP(CO)) in aqueous solution.

Unique solvatochromism of a membrane composed of a cationic porphyrin-clay complex.

A novel optically transparent membrane composed of porphyrin-clay mineral complexes was developed. Reversible solvatochromism behavior of the membrane was successfully observed, due to an orientation change of porphyrin in the clay interlayer space. The lambda(max) value of porphyrin was 423 nm in acetone, while it was 464 nm in hexane.

Syntheses, characterization, and catalytic ability in alkane oxygenation of chloro(dimethyl sulfoxide)ruthenium(II) complexes with tris(2-pyridylmethyl)amine and its derivatives.

New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)3-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl2(Me2SO)4] resulted in a mixture of trans and cis isomers of the chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complexes containing a TPA or a BPG, whereas a trans(Cl,N(amino)) isomer was selectively obtained for 5-(MeOCO)3-TPA and TQA. The trans and cis isomers of the [RuCl(TPA)(Me2SO)]+ complex were easily separated by fractional recrystallization.

Photoassisted oxygenation of alkane catalyzed by ruthenium complexes using 2,6-dichloropyridine N-oxide under visible light irradiation.

The chloro(Me(2)SO)ruthenium(II) complexes with tris(2-pyridylmethyl)amine or its derivative catalyses the selective, stereospecific, and photoregulative alkane oxidation in the presence of 2,6-dichloropyridine N-oxide under visible light irradiation.

[Bis[(S)-2-(4-tert-butyl-4,5-dihydrooxazol-2-yl)phenyl]phenylphoshine-kappa(2)N,P](1,3-dimethyl-pi-allyl-kappa(3)C)palladium(II) hexafluorophosphate and (S)(P)-[bis[(S)-2-(4-tert-butyl-4,5-dihydrooxazol-2-yl)phenyl]phenylphosphine-kappa(2)N,P]dichloropalladium(II).

In the structures of the title compounds, [Pd(C(5)H(9))(C(32)H(37)N(2)O(2)P)]PF(6) and [PdCl(2)(C(32)H(37)N(2)O(2)P)], the bis(dihydrooxazolyl)phosphine ligand is N,P-bidentate, with S chirality on the P atom. In the allyl complex, the pi-allyl ligand ligates in a syn-syn-kappa(3)C manner.