An approach to the synthesis of naphtho[b]furans from allyl bromonaphthyl ethers employing sequential photoinduced radical cyclization and dehydrohalogenation reactions

A simple method has been developed for the efficient synthesis of naphtho[b]furans from allyl bromonaphthyl ethers. The approach utilizes a novel photochemical process involving sequential radical cyclization and dehydrohalogenation. Because light is a readily available, environmentally friendly reagent that produces no by-products, the new process serves as a green synthetic method.     

Visible light activated catalytic effect of iron containing soda-lime silicate glass characterized by 57Fe-Mössbauer spectroscopy

A relationship between local structure and visible light activated catalytic effect of iron containing soda lime silicate glass with the composition of 15Na₂O·15CaO·xFe₂O₃·(70-x)SiO₂, x = 5–50 mass %, abbreviated as NCFSx was investigated by means of ⁵⁷Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD), small angle X-ray scattering (SAXS), electrospray ionization mass spectrometry (ESI–MS) and ultraviolet–visible light absorption spectroscopy (UV–Vis). Mössbauer spectra of NCFSx glass with ‘x’ being equal to or larger than 30 after isothermal annealing at 1,000 °C for 100 min consisted of a paramagnetic doublet and a magnetic sextet. The former had isomer shift (δ) of 0.24 mm s^?1 and quadrupole splitting (Δ) of 0.99 mm s^?1 due to distorted Fe^IIIO₄ tetrahedra, and the latter had δ of 0.36 mm s^?1 and internal magnetic field (H _int) of 51.8 T due to hematite (α-Fe₂O₃). The absorption area (A) of α-Fe₂O₃ varied from 47.2 to 75.9, 93.1, 64.8 and 47.9 % with ‘x’ from 30 to 35, 40, 45 and 50, indicating that the amount of precipitated α-Fe₂O₃ varied with the Fe₂O₃ content of NCFSx glass. The precipitation of α-Fe₂O₃ was also confirmed by XRD study of annealed NCFS glass with ‘x’ larger than 30. A relaxed sexted with δ, H _int and Γ of 0.34 mm s^?1 and 37.9 T and 1.32 mm s^?1 was observed from the Mössbauer spectra of annealed NCFSx glass with ‘x’ of 45 and 50, implying that the precipitation of non-stoichiometric iron hydroxide oxide with the composition of Fe_1.833(OH)_0.5O_2.5 having the similar structure of α-Fe₂O₃ and α-FeOOH. A remarkable decrease in the concentration of methylene blue (MB) from 10 to 0.0 μmol L^?1 with the first-order rate constant (k) of 2.87 × 10^?2 h^?1 was observed for 10-day leaching test using annealed NCFS50 glass under visible light irradiation. ESI–MS study indicated that existence of fragments with m/z value of 129, 117 and 207 etc. originating from MB having m/z of 284. This result evidently showed that the MB concentration decreased due to visible light induced decomposition caused by the visible light activated catalytic effect of α-Fe₂O₃ and/or Fe_1.833(OH)_0.5O_2.5 precipitated in soda-lime silicate glass matrix.     

Oblique detonation waves stabilized in rectangular-cross-section bent tubes

Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through rectangular-cross-section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the rectangular-cross-section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the rectangular-cross-section bent tubes was the curvature radius of the inside wall of the rectangular-cross-section bent tube equivalent to 14–40 times the cell width.     

Quantitative Effect of Reducing Body Thickness on Visualizing Murine Deep Abdominal Lymph Nodes by In Vivo Fluorescence Reflectance Imaging

Scattering and absorption in the tissues are major problems for in vivo imaging based on a fluorescence reflectance imaging technique. We evaluated the quantitative relationship between body thickness and fluorescent signals from a deep abdominal source in intact mice. Mice were injected with quantum dots (peak emission, 800 nm) into the right rear footpad, and fluorescent signals from the iliac lymph node located deeply in the abdomen were assessed by fluorescence reflectance imaging. Stepwise compression of the mouse abdomen to reduce the body thickness was attained using a homemade simple device. The iliac node signals were weak and diffuse without compression but became stronger and more localized with decreasing body thickness. Using excitation light of approximately 710 nm wavelength, the lymph node/background contrast increased about 16 times with a 4 mm reduction in body thickness. Contrast enhancement was more evident using shorter wavelength excitation light. Overlying tissues profoundly affect signals from a deep source in fluorescence reflectance imaging. Our simple compression method may contribute to quantitatively assessing deep fluorescent sources.     

Very fast magic angle spinning (1)H-(14)N 2D solid-state NMR: sub-micro-liter sample data collection in a few minutes

Substantial resolution and sensitivity enhancements of solid-state (1)H detected (14)N HMQC NMR spectra at very fast MAS rates up to 80 kHz, in a 1mm MAS rotor, are presented. Very fast MAS enhances the (1)H transverse relaxation time and efficiently decouples the (1)H-(14)N interactions, both effects leading to resolution enhancement. The micro-coil contributes to the sensitivity increase via strong (14)N rf fields and high sensitivity per unit volume. (1)H-(14)N HMQC 2D spectra of glycine and glycyl-L-alanine at 70 kHz MAS at 11.7 T are observed in a few minutes with a sample volume of 0.8 μL.     

Common origin of the circular-dichroism pattern in angle-resolved photoemission spectroscopy of SrTiO3 and Cu(x)Bi2Se3

Circular dichroism in the angular distribution of photoelectrons from SrTiO(3):Nb and Cu(x)Bi(2)Se(3) is investigated by 7-eV laser angle-resolved photoemission spectroscopy. In addition to the well-known node that occurs in the circular dichroism pattern when the incidence plane matches the mirror plane of the crystal, we show that another type of node occurs when the mirror plane of the crystal is vertical to the incidence plane and the electronic state is two-dimensional. The flower-shaped circular dichroism patterns in the angular distribution occurring around the Fermi level of SrTiO(3):Nb and around the Dirac point of Cu(x)Bi(2)Se(3) are explained on equal footings. We point out that the penetration depth of the topological states of Cu(x)Bi(2)Se(3) depends on momentum.     

A stable dialkylphosphinyl radical

Dialkylphosphinyl radical 1 was synthesized as thermally stable yellow crystals and found to be monomeric both in solution and in the solid state. EPR spectrum showed that the spin density of 1 is mainly localized on the 3p orbital of the dicoordinated phosphorus atom. A distinct absorption band due to the electronic transition from nonbonding electron pair orbital to singly occupied 3p orbital on the phosphorus atom of 1 was observed at 445 nm in solution. Phosphinyl radical 1 underwent facile reaction with carbon tetrachloride, hydrogen abstraction, and a unique reaction with a persistent radical, galvinoxyl, giving a cyclic phosphaalkene and a silylether.     

Highly efficient, organocatalytic aerobic alcohol oxidation

5-Fluoro-2-azaadamantane N-oxyl (5-F-AZADO) realizes a simple, organocatalytic aerobic alcohol oxidation system that has a wide scope under mild conditions at ambient pressure and temperature and is weakly acidic and halogen- and transition-metal-free. The oxoammonium nitrate (5-F-AZADO(+)NO(3)(-)) works as a bifunctional catalyst of 5-F-AZADO and NO(x) that enables the catalytic aerobic oxidation of alcohols by itself (a metal-salt-free system).     

Liberating Efimov Physics from Three Dimensions

When two particles attract via a resonant short-range interaction, three particles always form an infinite tower of bound states characterized by a discrete scaling symmetry. It has been considered that this Efimov effect exists only in three dimensions. Here we review how the Efimov physics can be liberated from three dimensions by considering two-body and three-body interactions in mixed dimensions and four-body interaction in one dimension. In such new systems, intriguing phenomena appear, such as confinement-induced Efimov effect, Bose?CFermi crossover in Efimov spectrum, and formation of interlayer Efimov trimers. Some of them are observable in ultracold atom experiments and we believe that this study significantly broadens our horizons of universal Efimov physics.     

Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π‐conjugated hexaphyrins with absorption and emission capabilities in the third near‐infrared region (NIR‐III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis‐Pd^II and bis‐Pt^II complexes of hexaphyrin via N‐confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long‐wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis‐Pt^II complex, t ‐Pt₂‐3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t ‐Pt₂‐3 potentially useful as a NIR‐III PA contrast agent. The rigid bis‐Pd^II complexes, t ‐Pd₂‐3 and c ‐Pd₂‐3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR‐III‐emissive and photoacoustic‐response capabilities.