Dual Emission from Precious Metal-Free Luminophores Consisting of C,H, O,Si, and S/P at Room Temperature

Fluorescence–phosphorescence dual-emissive compounds are valuable tools for ratiometric luminescence sensing. Herein, it is reported that 2,5-bis(phenylsulfonyl)- and 2,5-bis[bis(4-methoxyphenyl)phosphinyl]-1,4-disiloxybenzenes exhibit dual emission with emission peaks that were easily identified without performing time-gated measurement. The disiloxybenzenes in powder simultaneously fluoresced and phosphoresced at 358–374 and 457–470 nm, respectively, under vacuum. The intensity ratios of the phosphorescence/fluorescence maxima of the disiloxybenzenes in powder and in a thin film of poly(methyl methacrylate) were sensitive to temperature and molecular oxygen, respectively. The plots of the relative intensity versus temperature or partial pressure of molecular oxygen were well fitted with calibration curves defined by an exponential approximation with excellent correlation coefficients R² (0.9708–0.9921), demonstrating the high potential of the disiloxybenzenes as precious metal-free probes applicable to ratiometric luminescence sensing.     

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt-TiO2 Nanoparticles with a Double Layer of Photosensitizers

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of Ru^II-photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO₂ nanoparticles with different surface structures, Zr- RuCP⁶ -Zr- RuP⁶ @N wt %Pt-TiO₂, RuCP⁶ -Zr- RuP⁶ @N wt %Pt-TiO₂, and RuCP² -Zr- RuP⁶ @N wt %Pt-TiO₂ (N=0.2, 1, and 5), and evaluated their photocatalytic H₂ evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I⁻ to the photo-oxidized Ru^III PS is comparable, the activity increased in the following order: RuCP² -Zr- RuP⁶ @1 wt %Pt-TiO₂ < RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂ < Zr- RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂. The apparent quantum yield of Zr- RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂ in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr⁴⁺-phosphate groups attracted I⁻ anions to the nanoparticle–solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.     

Indeno[1,2,3,4-pqra]Perylene: A Medium-Sized Aromatic Hydrocarbon Exhibiting Full-Range Visible-Light Absorption

We report the synthesis and properties of indeno[1,2,3,4-pqra]perylene, which was prepared by the fusion of one anthracene unit with one naphthalene unit via three carbon-carbon bonds. The synthetic route through two-fold C−H arylation enabled not only the synthesis of unsubstituted indenoperylene, but also rapid access to its arylated derivatives on the gram scale. Indenoperylene is a medium-sized aromatic hydrocarbon with the composition C₂₄H₁₂ that is isomeric to coronene. Nevertheless, its absorption covers the entire visible region owing to its small HOMO-LUMO gap. Furthermore, indenoperylene exhibits high stability despite the absence of peripheral substituents. We propose that the unique electronic structure of indenoperylene originates from the coexistence of an electron-withdrawing subunit (benzoaceanthrylene) and an electron-donating subunit (perylene). The electronic properties of indenoperylene were modulated via post-functionalization through regioselective bromination. The current research demonstrates that indenoperylene is a promising candidate as a main skeleton for near-infrared-responsive and redox-active materials.     

Reversible and Stepwise Single-Crystal-to-Single-Crystal Transformation of a Platinum(II) Complex with Vapochromic Luminescence

The vapochromic single-crystal-to-single-crystal (SCSC) transformation of a highly luminescent Pt^II complex bearing an N-heterocyclic carbene [Pt(CN)₂(tBu-impy)] (tBu-impyH⁺=1-tert-butyl-3-(2-pyridyl)-1H-imidazolium) is reported. The trihydrate form of the complex, which exhibits blue ³MMLCT emission owing to weak Pt⋅⋅⋅Pt interactions, changed its luminescence color from blue to yellowish-green upon the desorption of water molecules while keeping the high emission quantum yield of more than 0.45. Variable-temperature and continuous in-situ tracking of single-crystal X-ray diffraction measurements revealed that the SCSC transformation proceeds reversibly by the release and reabsorption of water molecules, thereby changing the stacked structure slightly. As a result, the dynamics of vapor-induced SCSC transformation were elucidated: that the anhydrous form returned to the original trihydrate form in a two-step process under a water vapor atmosphere. In addition, the Pt^II complex exhibited a similar SCSC response accompanied by a luminescence color change in the presence of methanol vapor, while being inactive toward ethanol vapor.     

Aerial imaging steganography method for aerial imaging by retro-reflection with dual acrylic ball

Optical Review - This paper proposes a novel steganography method to show an aerial image that is formed with aerial imaging by retro-reflection by use of dual transparent balls made of acrylic...     

Synthesis of thermally stable aromatic poly(spiroorthocarbonate)s having a Cardo or bent structure

Novel poly(spiroorthocarbonate)s [poly(SOC)]s having a Cardo or bent structure were synthesized by polycondensation of several bis‐catechols having fluorene (BCFL), spirobisindane (BCSPI), or spirobischromane (BCSPC) in the structure with 2,2,6,6‐tetrachlorobenzo[1,2‐d:4,5‐d’]bis[1,3]dioxole (4ClBD). Synthesis of poly(SOC)s was confirmed by NMR and IR spectrometry. The poly(SOC)s obtained from BCFL or BCSPC were soluble in common organic solvents. The glass transition temperature of the poly(SOC)s was not detected by differential scanning calorimetry (DSC) in the range of 50–300 °C. The 10 wt % decomposition temperature of the poly(SOC)s was found to be above 400 °C. These results indicated the high thermal stability of the poly(SOC)s. Soluble poly(SOC)s could be possessed to form a film on a glass plate by the spin coat method. The obtained polymer films were 0.2 μm in thickness with 95% light transmission in the optical wavelength range. These results suggested that the Cardo or bent structure may block the packing of the main‐chain of the structure, which improves the solubility of the polymers, increases transparency, and enhances the thermal stability of SOCs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1409‐1416     

Synthesis of Disaccharide Nucleosides by the O‐Glycosylation of Natural Nucleosides with Thioglycoside Donors

Disaccharide nucleosides constitute an important group of naturally‐occurring sugar derivatives. In this study, we report on the synthesis of disaccharide nucleosides by the direct O‐glycosylation of nucleoside acceptors, such as adenosine, guanosine, thymidine, and cytidine, with glycosyl donors. Among the glycosyl donors tested, thioglycosides were found to give the corresponding disaccharide nucleosides in moderate to high chemical yields with the above nucleoside acceptors using p‐toluenesulfenyl chloride (TolSCl) and silver triflate (AgOTf) as promoters. The interaction of these promoters with nucleoside acceptors was examined by ¹H NMR spectroscopic experiments.     

Synthesis of Selectively gem-Difluorinated Molecules; Chiral gem-Difluorocyclopropanes via Chemo-Enzymatic Reaction and gem-Difluorinated Compounds via Radical Reaction

The incorporation of fluorine atoms into an organic compound can alter the chemical reactivity or biological activity of the resulting compound due to the strong electron withdrawing nature of the fluorine atom. We have synthesized many original gem-difluorinated compounds and described the results in four sections. The first section describes the synthesis of optically active-gem-difluorocyclopropanes via the chemo-enzymatic reaction; we applied these compounds to liquid crystalline molecules, then further discovered a potent DNA cleavage activity for the gem-difluorocyclopropane derivatives. The second section describes the synthesis of selectively gem-difluorinated compounds via a radical reaction; we synthesized fluorinated analogues of a sex pheromone of the male African sugarcane borer, Eldana saccharina, and used the compounds as proof for investigating the origin of pheromone molecule recognition on the receptor protein. The third involves the synthesis of 2,2-difluorinated-esters by visible light-driven radical addition of 2,2-difluoroacetate with alkenes or alkynes in the presence of an organic pigment. The last section describes the synthesis of gem-difluorinated compounds via the ring-opening of gem-difluorocyclopropanes. We further developed a novel method of synthesizing gem-difluorohomoallylic alcohols via the ring-opening of gem-difluorocyclopropane and aerobic oxidation by photo-irradiation in the presence of an organic pigment. Since gem-difluorinated compounds that were prepared by the present method have two olefinic moieties with a different reactivity at the terminal position, we accomplished the synthesis of four types of gem-difluorinated cyclic alkenols via the ring-closing-metathesis (RCM) reaction.     

Safety Evaluation of Far-UV-C Irradiation to Epithelial Basal Cells in the Corneal Limbus

Basal cells in the corneal limbus play an important role in the turnover cycle because they are the source of all cells that constitute the corneal epithelium. We examined the penetration depth of ultraviolet (UV) light in the corneal limbus and assessed the safety of Far-UV-C on stem cells in the basal area of the corneal limbus. Rats were irradiated with UV at peaks of 207, 222, 235, 254 and 311 nm while under anesthesia. The UV penetration depth in the rat corneal limbal epithelium was wavelength dependent: 311 nm UV-B and 254 nm UV-C reached the basal cells of the epithelium, and 235 nm radiation reached the middle area; however, 207 and 222 nm UV-C reached only the superficial layer of the epithelium. Porcine cornea, which is similar to the human eye in size and structure, were irradiated with 222 and 254 nm UV-C. As in rats, 222 nm UV-C reached only the superficial layer of the porcine corneal limbal epithelium. These results indicate that Far-UV-C, such as radiation of wavelengths of 207 and 222 nm, could not reach corneal epithelial stem cells, i.e. the cells remained intact. It is unlikely that the turnover of the corneal epithelium is obstructed or disrupted by exposure to Far-UV-C.     

Single Crystalline,Non-stoichiometric Cocrystals of Hydrogen-Bonded Organic Frameworks

Porous frameworks composed of non-stoichiometrically mixed multicomponent molecules attract much attention from a functional viewpoint. However, their designed preparation and precise structural characterization remain challenging. Herein, we demonstrate that cocrystallization of tetrakis(4-carboxyphenyl)hexahydropyrene and pyrene derivatives ( CP-Hp and CP-Py , respectively) yields non-stoichiometric mixed frameworks through networking via hydrogen bonding. The composition ratio of CP-Hp and CP-Py in the framework was determined by single crystalline X-ray crystallographic analysis, indicating that the mixed frameworks were formed over a wide range of composition ratios. Furthermore, microscopic Raman spectroscopy on the single crystal indicates that the components are not uniformly distributed such as ideal solid solution, but are done gradationally or inhomogeneously.