Synthesis of a photo-responsive single-walled nanoscroll and its photo-reactivity in a nano-layered microenvironment.

A photo-responsive nanoscroll composed of niobate nanosheets and a polyfluoroalkyl azobenzene derivative (C3F-Azo-C6H) is one of the most interesting layered materials because the reversible winding and unwinding motion could be efficiently induced by photo-irradiations. Previously, we have studied a double-walled nanoscroll (DWNS) of niobate that could be synthesized by the intercalation of a cationic polyfluorinated surfactant only into the interlayer I of the layered niobate among the two interlayers, I and II. In this study, we have successfully synthesized another novel photo-responsive single-walled nanoscroll (SWNS) of niobate by a stepwise guest-guest ion-exchange method. All niobate nanosheets that were exfoliated at both interlayers I and II were efficiently converted to nanoscrolls by the intercalation of C3F-Azo-C6H. The synthetic yield has been quantitatively estimated. Though the photo-isomerization reaction of C3F-Azo-C6H was induced in the SWNS, its photo-reactivity was the lowest when compared with those of the nanosheet-stacked film and the DWNS. The photo-reactivity of C3F-Azo-C6H decreased in the order of DWNS > nanosheet-stacked film > SWNS. The different flexibility of the layered miroenvironment might influence the photo-reactivity of C3F-Azo-C6H in the niobate hybrid. The SWNS exhibited a reversible expansion and shrinkage of its interlayer spaces upon photo-irradiation, while the winding and unwinding motion was not observed, contrary to the DWNS. The direction of the expansion and shrinkage of the interlayer of the SWNS was opposite to those of the nanosheet-stacked film and the DWNS. Based on the experimental results, the tilt angle of C3F-Azo-C6H against the nanosheet surface and the matching structures of the top and bottom surfaces of the nanosheet could be the probable key factors that control the photo-reactivity of C3F-Azo-C6H in the layered microenvironment; the morphological changes of the nano hybrids was also discussed.

Concentration-dependent luminescence of ionic liquids containing trialkyl(pentafluorocyclotriphosphazenyl)ammonium moieties.

Room-temperature ionic liquid compounds (CpzNR3(+)X(-)) consisting of trialkyl(pentafluorocyclotriphosphazenyl)ammonium (CpzNR3(+)) and anions (X(-)) such as chloride and bis(trifluoromethylsulfonyl)imide (TFSI(-)) emitted blue luminescence under an excitation of 360 nm. The luminescent quantum yields (Φem) of CpzNR3(+)X(-) were determined to be 0.012-0.044 in methanol solution at 360 nm excitation. The excitation spectra and luminescent lifetime (τ) measurements indicated the existence of two luminescent species. The appearance of luminescence from the pentafluorocyclotriphosphazenyl (Cpz) chromophore at longer wavelengths and the dependence of the luminescent intensity upon the concentration of CpzNR3(+)X(-) revealed that the observed luminescence was attributed to the J-aggregates of the Cpz chromophore. The formation of these aggregates was also evidenced by the concentration-dependent (1)H-NMR chemical shift. The J-aggregates involved both luminescent aggregates of smaller sizes with shorter τ (1.0 ns) and those of larger sizes with longer τ (5.0 ns). The Φem of the aggregates with larger sizes were enhanced with increasing CpzNR3(+)X(-) concentration. Thus, the luminescence stemming from the luminescent aggregates can be reasonably explained by the "aggregation-induced enhanced emission" (AIEE) mechanism.

Solvent dynamics regulated electron transfer in S(2)-excited Sb and Ge tetraphenylporphyrins with an electron donor substituent at the meso-position.

Electron and energy transfer processes from higher excited states are attractive for efficient photoenergy utilization because energy dissipating internal conversion processes can be avoided. In the present study, charge separation processes in meso-substituted Sb- and Ge tetraphenylporphyrins (TPPs) were investigated by means of laser spectroscopy. For both Sb- and GeTPPs, S2- and S1-fluorescence emissions were confirmed. Sb- and GeTPPs containing a meso-substituent with a higher electron donor-ability exhibited charge separation from the S2 state, and this was confirmed by transient absorption spectroscopy and a fluorescence up-conversion method. Charge separation was faster for SbTPP with a donor at the meso position than for SbTPP bearing a donor as an axial ligand. The faster charge separation of the present TPPs was attributed to a larger electronic coupling due to a larger HOMO electron density at the meso-carbon of the porphyrin ring. In addition, the charge separation processes in the present meso-substituted TPPs occurred under the adiabatic condition. Contribution of the intramolecular exciplex to the relaxation process was also indicated for the S1 state of GeTPPs.

Water-solubilization of alkyloxo(methoxo)porphyrinatoantimony bromides.

In order to develop water-soluble porphyrins, alkyloxo(methoxo)porphyrinatoantimony bromides (alkyl = hexyl (1a), decyl (1b), dodecyl (1c), tetradecyl (1d), octadecyl (1e)) were prepared. 1 had more than 1 mmol dm(-3) of solubility in water. From the dependence of the half-width of the bands in the absorption spectra and surface tension on the concentration of 1, it was estimated that 1b-d were present as aggregates in concentrations higher than 10 micromol dm(-3). From the NMR analysis in D(2)O, it was deduced that the alkyloxo ligands of 1 were arranged alternately in the aggregates. The diameter of the aggregates of 1 in water was determined to be around 100 nm by the dynamic light scattering method. Since the solubilities of di(methoxo)tetraphenylporphyrinatoantimony bromide and 5-(4'-decyloxyphenyl)-10,15,20-triphenylporphyrinato(dimethoxo)antimony(v) bromide were low, it was calculated that the long alkyl axial ligands were requisite for the high solubility in water.

Acceleration effect of the forensic luminol reaction induced by visible light irradiation of whole human blood aqueous solutions.

The first quantitative study on the effect of visible light irradiation on the luminol reaction, used forensically, was conducted using whole human blood aqueous solutions (hemolytic state) and an LED lamp. Whole human blood aqueous solutions under an air atmosphere were irradiated with visible light, resulting in the maximum chemiluminescence (CL) intensity (@ 440 nm) increasing about 1.7-fold due to acceleration of the luminol reaction rate. No acceleration effect was observed under an argon (Ar) atmosphere, or under an air atmosphere in the presence of sodium azide (NaN3; a scavenger of singlet oxygen (1O2)). Furthermore, no conversion from Fe(II) hemoglobin to Fe(III) hemoglobin (methemoglobin) was observed in the absorption spectrum following irradiation. We suggest that these effects are due to easier approach of the luminol reagents to heme following damage of the globin protein around the heme, or damage to the red blood cell membrane, induced by 1O2 generated by an excited state of heme.

Intramolecular electron transfer from axial ligand to S2-excited Sb-tetraphenylporphyrin.

The S(2) state properties of Sb-tetraphenylporphyrin (SbTPP) derivatives were investigated using subpicosecond spectroscopic methods. The S(2) fluorescence of various SbTPP derivatives was observed for the first time. It was revealed that the S(2) fluorescence lifetime changed depending on the donor-ability of the ligand because of the contribution of the charge separation to the S(2) excited SbTPP, which was confirmed by transient absorption spectroscopy.

Guanine-specific DNA damage photosensitized by the dihydroxo(tetraphenylporphyrinato)antimony(V) complex.

The dihydroxo(tetraphenylporphyrinato)antimony(V) complex (SbTPP) demonstrates bactericidal activity under visible-light irradiation. This phototoxic effect could be caused by photodamage to biomolecules, but the mechanism has not been well understood. In this study, to clarify the mechanism of phototoxicity by SbTPP, DNA damage photosensitized by SbTPP was examined using [(32)P]-5'-end-labeled DNA fragments. SbTPP induced markedly severe photodamage to single-stranded rather than to double-stranded DNA. Photo-irradiated SbTPP frequently caused DNA cleavage at the guanine residue of single-stranded DNA after Escherichia coli formamidopyrimidine-DNA glycosylase or piperidine treatment. HPLC measurement confirmed the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), an oxidation product of 2'-deoxyguanosine, and showed that the content of 8-oxodG in single-stranded DNA is larger than that in double-stranded DNA. The effects of scavengers of reactive oxygen species on DNA damage suggested the involvement of singlet oxygen. These results have shown that the mechanism via singlet oxygen formation mainly contributes to the phototoxicity of SbTPP. On the other hand, SbTPP induced DNA damage specifically at the underlined G of 5'-GG, 5'-GGG, and 5'-GGGG in double-stranded DNA. The sequence-specificity of DNA damage is quite similar to that induced by the type I photosensitizers, suggesting that photo-induced electron transfer slightly participates in the phototoxicity of SbTPP. In conclusion, SbTPP induces DNA photodamage via singlet oxygen formation and photo-induced electron transfer. A similar mechanism can damage other biomacromolecules, such as protein and the phospholipid membrane. The damage to biomacromolecules via these mechanisms may participate in the phototoxicity of SbTPP.

Ethanol production from non-pretreated napiergrass through a simultaneous saccharification and fermentation process followed by a pentose fermentation with Escherichia coli KO11.

Efficient ethanol production from lignocellulosic napiergrass (Pennisetum purpureum Schumach) was examined by the combination of the simultaneous saccharification and fermentation (SSF) with commercial cellulase and Saccharomyces cerevisiae NBRC 2044 and subsequent pentose fermentation (PF) by Escherichia coli KO11. Under the optimized conditions, the combination of the SSF and PF processes resulted in the production of 144 mg g(-1) of ethanol from the non-pretreated napiergrass powder. The ethanol yield was 44.2% of the theoretical yield based on the hexose (37.5 g) and pentose (26.5 g) derived from 100 g of dry powdered napiergrass.

Quantitative analysis for a color-change of humidity indicator by microscopic absorption spectrometry.

A sensitive and easily distinguishable cobalt-free humidity indicator of porphyrin-silica gel-MgCl(2) composite was prepared from pH-induced spectra changeable tetraarylporphyrin, silica gel (SiO(2)), and MgCl(2). The pH change arose from proton release under dry conditions, and proton capture under humid conditions by a reversible reaction between MgCl(2) and a silanol group of SiO(2). A pink-orange porphyrin-Si(OH)(2)-MgCl(2) composite was dried to give a green protonated porphyrin-SiO(2)Mg composite. The optimized concentrations of MgCl(2) to make the concentrations of protonated porphyrin maximum under dry conditions were determined by absorption spectrometry of the green composite using a confocal laser scanning microscope as a microscopic spectrometer. Moreover, the green composite was prepared by heating dichloro(tetraarylporphyrinato)phosphorus chloride with MgCl(2) and SiO(2). The humidity-sensitivity of the green composite was evaluated by the absorption spectra under controlled humidity. A distinguishable color change of the green composite took place below 30% of relative humidity.

Electron transfer from axial ligand to S1- and S2-excited phosphorus tetraphenylporphyrin.

Photoinduced processes of a series of phosphorus tetraphenylporphyrin (PTPP) derivatives ([PTPP-(NHC6H4X)2]+Cl-, X = OCH3, CH3, H, Cl, CF3, and CN) have been investigated by using femtosecond laser flash photolysis mainly. PTPP with OH as an axial ligand showed S2 fluorescence upon excitation of the Soret band. The S2 fluorescence lifetime was estimated to be 1.5 ps. On the other hand, both S2 and S1 fluorescence bands of PTPP-(NHC6H4X)2 were difficult to observe, indicating the existence of an additional deactivation process such as charge separation (CS). From MO calculation and cyclic voltammetry, PTPP and the axial ligand are expected to act as an acceptor and a donor, respectively, upon excitation of PTPP. CS via the S2 state was confirmed during the femtosecond laser flash photolysis by observing the transient absorption of radical anion of PTPP. Furthermore, CS via the S1 state of PTPP was also observed. The CS rate via the S1 state was faster than that from the S2 state. The free energy dependence of the electron-transfer rates was discussed on the basis of Marcus theory.

Redox-photosensitized aminations of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia.

1,2,4-Triphenylbenzene and 2,2'-methylenedioxy-1,1'-binaphthalene successfully photosensitized the aminations of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia and primary amines in the presence of m- or p-dicyanobenzene, which gave the 4-amino-1,2-benzocycloalkenes, 3-amino-1-arylpropanes, and 7-amino-5-(p-cyanophenyl)bicyclo[2.2.1]hept-2-ene, respectively. A key pathway for the photosensitized amination is the hole transfer from the cation radicals of the sensitizers that were generated by photoinduced electron transfer to the electron acceptors to the substrates. Therefore, it was found that the relationships in oxidation potentials between the sensitizers and the substrates and the positive charge distribution of the cation radicals of the substrates were important factors for the efficient amination.