矢貝 史樹

Photophysical properties of meridional (mer) and facial (fac) isomers of eight iridium(III) trischelete complexes composed of combination of two ligands, 2-(p-tolyl)pyridine and 2-phenylpyrazole, were investigated. Characteristics of heteroleptic complexes were compared to the homoleptic complexes. Phosphorescence radiation process is rationally explained by inter-ligand energy transfer, however, mer → fac isomerization showed different behavior indicating participation of another excited state. © 2006 Elsevier B.V. All rights reserved.

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.

The absorption and fluorescence properties of a barbiturate-type donor-pi-acceptor (D-pi-A.) merocyanine dye are controlled by complexation with dimeric melamine receptors featuring different tether lengths.

Binary organogels were prepared from coaggregates of azobenzene-tethered melamine dimer and cyanurate/barbiturates. In the gels of hydrocarbon liquids, the coaggregates formed heavily entangled nanofibers, morphologies of which are dramatically different from the previously reported coaggregates based on flexible dodecamethylene-tethered melamine dimers. In the present systems, the rigidity of the azobenzene tether may induce regular packing of molecules. In addition, UV-vis and IR spectroscopic measurements provided unequivocal evidence for the contribution of the central amide groups and the azobenzene chromophores in the tether moiety upon forming well-defined nanofibers by hydrogen-bonding and face-to-face (H-type) pi-pi stacking interactions, respectively. As a result of tight molecular packing in the self-assembled nanofibers, the azobenzene moiety in the gel state showed remarkable resistance to trans -> cis isomerization upon irradiation with UV light.

Hydrogen-bonded disk-shaped aggregates (rosettes) composed of azobenzene-appended melamine and barbiturate or cyanurate are investigated in view of their hierarchical organization and photoresponsive behavior by (1)H NMR and UV/vis spectroscopies, dynamic light scattering, and gelation behavior in aliphatic solvents and liquid crystalline behavior in bulk state. In the bulk state the rosette possessing a sterically bulky tridodecyloxyphenyl substituent in the barbiturate component stacks in an offset arrangement to form a rectangular columnar mesophase, whereas in aliphatic solvents it does not hierarchically organize into higher-order columnar aggregates. This drawback is improved by exchanging the barbiturate component into a more sterically nondemanding N-dodecylcyanurate component. The resulting new rosette stacks in a face-to-face arrangement to form a hexagonal columnar mesophase in the bulk state and hierarchically organizes into elongated fibrous aggregates in cyclohexane, which eventually leads to the formation of organogel. Dynamic light scattering and UV-vis experiments upon UV-irradiation of the columnar aggregates in cyclohexane revealed that the dissociation and the reformation of columnar aggregates can be controlled by the trans-cis isomerization of the azobenzene moiety. Molecular modeling indicates that the rosette possessing cis-azobenzene side chains loses its planarity. Using this photoinduced morphological change of the rosette, photoresponsive organogel is created by the use of a disk-shaped supramolecule the first time.

Binary hydrogen-bonded supramolecular polymers composed of a dimeric melamine (bis(melamine)) and barbiturate-type merocyanine dyes are prepared in aliphatic solvents. Macroscopic structure and rheological behavior of the supramolecular polymers are investigated by scanning electron microscopic observation and dynamic rheological measurement. Despite conformational flexibility in the bis(melamine) component, supramolecular polymers exhibit well-defined one-dimensional fibrous or two-dimensional sheetlike macroscopic structures, which are dependent on the blended merocyanine dyes. UV-vis studies of the supramolecular polymerization in dilute solutions imply that the merocyanine dyes exist as selfaggregated state upon supramolecular polymerization with the bis(melamine) component. This observation strongly suggests the presence of secondary structures of the quasi-one-dimensional flexible supramolecular polymers.

The incorporation of photoswitching molecules into molecular building blocks creates the possibility of photoresponsive self-assemblies in which the self-assembled architecture or self-assembling process can be controlled by external light stimulus. Among the photoswitching molecules, azobenzene has been used most widely by virtue of the large photoinduced changes in its molecular geometry and physical properties. This article reviews how azobenzene can be effectively used to construct the self-assemblies in which supramolecular structure and formation/dissociation can be altered by light.

The sensitizing abilities of near infrared (near IR)-absorbing ionic (D1) and non-ionic (D2 and D3) cyanine dyes in a photoinduced radical polymerization system were evaluated. The solubility in an organic solvent of non-ionic cyanine dyes is much higher than that of an ionic cyanine dye. The photoinduced radical polymerization system consists of a sensitizing dye (D1-D3), 2,4,6-tris(trichloromethyl)-s-triazine (TCT, as a radical genetrator), and a poly-functional acrylate monomer (DPHA) in the binder polymer. All dyes showed a sensitizing ability in the photoinduced radical polymerization systems by near IR light. Non-ionic cyanine dyes, D2 and D3, showed a higher sensitizing ability than D1. From the IR and UV-vis studies, it was revealed that the high sensitizing ability of D2 and D3 is a result of an interaction between the dye and TCT in the polymer matrices, promoting the electron-transfer from the dyes to the TCT. (C) 2004 Elsevier B.V. All rights reserved.

Photoluminescence (PL) and Electroluminescence (EL) abilities of 9,10-bis(silylethynyl)antheacene were investigated. Fluorescence quantum yield of these compounds increased drastically and reached nearly unity by the substitution of silylethynyl groups for 9, 10-position of anthracene. EL devices made of 9,10-bis triphyenylsilylethynyl) anthracene showed greenish yellow EL, and the use of PEDOT/PSS and Alq imoroves the oerformance of the device. © 2005 TAPJ. 3

The behavior of the 3-alkylidene-1-pyrazoline radical cations generated by photoinduced electron transfer reactions was examined. The nitrogen-retained radical cations have been detected using laser flash photolysis. The photochemical products indicate that EIZ isomerization, intramolecular cyclization, and solvent addition (acetonitrile) occurred. (C) 2004 Elsevier Ltd. All rights reserved.

糖尿病診療の場で頻繁に測定されるグルコース濃度を,血清を用いて赤外吸収スペクトルにより定量した.ATRサンプルホルダーの形状の工夫,減圧乾燥による測定時間の短縮,2次微分によるグルコース由来の吸収スペクトルの特定,総タンパク質濃度の影響の考慮などの改善により,赤外吸収スペクトルから血液中のグルコース濃度を定量できる可能性が示唆された

Magic angle spinning NMR spectroscopy has been used to investigate the self-organization of bacteriochlorophylls in chlorosomal light-harvesting antennae. Two model cadmium chlorins were studied that were uniformly 13C and 15N enriched in the ring moieties. The chlorin models differ from the natural BChl c in the central metal and the 3-, 12-, 17-, and 20-side chains. One model system has the farnesyl tail replaced by a methyl, whereas the other has a stearyl tail. The 13Cd MAS NMR signals indicate a five-coordination of the Cd metal. In particular, the combined NMR data show a HO⋯Cd coordination, very similar to the HO⋯Mg coordination in the natural system. Anomalously large 1H ring-current shifts of up to 10 ppm reveal a dense orderly stacking of the molecules in planar layers, for which a correlation length of at least 24 Åwas defined from long-range ring-current shift calculations. In addition, our model structures confirm and validate the essential role of the [31R] and [3-S] stereoisomers in the formation of the chlorosomal antennae, as tubular structures are not formed without this chirality. The 3D arrangement of the layers is revealed by intermolecular 13C-13C correlations obtained from CP3 CHHC experiments. With the tail truncated to methyl, a microcrystalline solid is formed with favorable interactions between the planar sheets in a head-to-tail orientation. The stearyl tails lead to a considerably disordered aggregate consisting of both syn and anti layers similar to the chlorosomes, as indicated by a doubling of the N-D signal. These results reveal a balance between relatively strong local interactions and contributions to the free energy of the system associated with a longer length scale. This leads to a robust chlorosome structure, stable against thermodynamic noise, and allows for fine-tuning of the structure.

Azobenzene-appended melamine M2 and barbiturate B2, both possessing bulky tridodecyloxyphenyl (TDP) wedge(s), were designed and synthesized to establish a photoresponsive hydrogen-bonded supramolecular assembly. The geometrical isomer EE-M2 bearing two E-azobenzene moieties easily complexed with 1132, affording a remarkably stable cyclic hexamer EE-M2(3)(.)B2(3) (rosette) in chloroform, toluene, and methyleyelohexane, as confirmed by size exclusion chromatography, dynamic light scattering, H-1 NMR, and UV-vis studies. The E-->Z photoisomerization of the azobenzene moieties upon irradiation with UV light was significantly suppressed in the rosette because of the steric crowding of the TDP wedges (total of nine TDP wedges in a rosette), whereas irradiation of the monomeric EE-M2 resulted in facile transformation into ZZ-M2 bearing two Z-azobenzene moieties. H-1 NMR studies of the complexation of the initially photogenerated ZZ-M2 with B2 revealed that it is hard for ZZ-M2 to form a rosette with B2 because of the intermolecular steric interaction between the TDP wedges. The photoregulatable complexation efficiency of M2 allowed us to accomplish the phototriggered formation of the rosette by irradiation of a monomeric mixture of ZZ-M2 and B2 using visible light.

Bismelamine supramolecular synthon featuring a flexible methylene tether shows excellent gelation ability in organic solvents on binding with amphiphilic cyanurate or barbiturates. Physical properties of the resulting gel can be facilely tunable by changing the cyanurate/barbiturate components.

The photophysical properties of a series of α,ω -diaryloligosilanes: (9-anthryl)-(SiMe ) -(1-naphthyl) (1-4, and 6), n=1, 2, 3, 4, and 6, were investigated. For n≥2, the intramolecular exciplex emission was observed in cyclohexane. For the stationary and the time-resolved fluorescence (TR-FL) measurements, the excitation of the naphthyl moiety showed a very efficient intramolecular energy transfer to the anthryl moiety, thus only fluorescence from the anthryl moiety was observed. In the case of 4 and 6, a charge-transfer (CT) emission was observed in acetonitrile. Then TR-FL of 6 revealed that the intramolecular-energy transfer from the naphthyl to anthryl moieties is faster than the CT. © 2004 Elsevier B.V. All rights reserved. 2 n

A series of self-complementary N,N'-disubstituted 4,6-diaminopyrimidin-2(1H)-ones self-assemble in organic solvents to form a robust and linear supramolecular polymer network via DDA-AAD hydrogen-bonding.

Photochemical characterization is reported for the mer-stereoisomer of fac-tris[2-(4′,6′-difluorophenyl)pyridine]iridium(III) (2), which has attracted attention as a electrophosphorescent material. The mer-2 has a much smaller emission-quantum yield and a shorter emission lifetime than those of the fac-isomer. The relation of the photophysical properties of mer-2 and one-way photoisomerization to fac-2 is discussed.

UV-irradiation of hydrogen-bonded assembly between trans-azobenzene-incorporated melamine and barbiturate in chloroform drastically suppressed transformation from soluble cyclic rosette into insoluble tape-like polymers.

Zinc chlorins were prepared from chlorophyll-a. Visible spectra in benzene showed that synthetic zinc chlorins complexed with pyridine as an axial ligand to form the monopyridine adducts. The equilibrium constants for the complexation were dependent upon the chlorin structure: substitution of electron-withdrawing groups at the peripheral position enhanced the coordinated ability of the central zinc. H-1 NMR spectra in benzene-d(6) also indicated that single pyridine coordinated to the central zinc. Comparison of the equilibrium constant in a zinc chlorin with those of the corresponding zinc bacteriochlorin (7,8-dihydrochlorin) and porphyrin (17,18-dedihydrochlorin) led to an increase in the saturation and flexibility of the tetrapyrrole pi-plane ligands making the central zinc more axial-ligated. All the zinc tetrapyrroles in benzene complexed with pyridine to form 5-coordinated (I:1) complexes, not 6-coordinated bis-adducts. The observed equilibrium constants were consistent with the energy changes of the complexation calculated from molecular modeling. (C) 1998 Elsevier Science Ltd. All rights reserved.