Resonance Raman scattering with a forbidden but vibronically allowed electronic transition: Excitation profiles of combinations and overtones of copper tetraphenylporphyrin in the Q-band resonance

Resonance Raman scattering with the Q band of CuTPP shows a peculiar intensity pattern; bands due to combinations and overtones are strong, whereas the corresponding fundamentals are very weak. By a quantitative analysis of excitation profiles, this phenomenon has been fully accounted for on the basis of the vibronic theory of Raman intensities. Vibronic coupling parameters between the Q and B states of CuTPP have been obtained.     

A useful procedure for diiodination of carbazoles and subsequent efficient transformation to novel 3,6-bis(triethoxysilyl)carbazoles giving mesoporous materials

Bis(pyridine)iodonium tetrafluoroborate (IPy₂BF₄) was successfully used as a diiodination reagent for carbazole and its derivatives to give 3,6-diiodocarbazoles in excellent yield. Subsequent rhodium-catalyzed disilylation of 3,6-diiodocarbazoles with triethoxysilane gave the corresponding 3,6-bis(triethoxysilyl)carbazoles, which are precursors for sol-gel polymerization, in good yield.     

Visual observation of contact-induced intercrystalline migration of aromatic species adsorbed in zeolites by fluorescence microscopy.

Intercrystalline migration and a migration-assisted chemical reaction of adsorbed aromatic species between zeolite particles in physical contact were visualized by fluorescence microscopy coupled with a particle manipulation technique. The luminescence color characteristics of particular zeolite particles originating from the specific photochemistry of adsorbed species was exploited to follow the migration of the molecules. Two examples are shown that are relevant to the visualization of the time-dependent migration process: A one guest-two sets of zeolite crystals system: chrysene (Chry)-loaded zeolite Na+ -X (the sodium form of zeolite X) crystals were placed in contact with unloaded Tl+ -X (thallium-exchanged X) crystals and allowed to stand at room temperature. Initially, the blue fluorescence of Chry was detected only from the Na+ -X particles, but later, the development of green phosphorescence emission was discernible from the Tl+ -X which suggests that Chry migrated from the Na+ -X to the Tl+ -X crystals. A two guest-species systems: Electron-donating Chry-loaded Na+ -X crystals were placed in contact with electron-accepting 1,2,4,5-tetracyanobenzene (TCNB)-loaded Na+ -X or Na+ -Y crystals. With time, the former system (Chry/Na+ -X and TCNB/Na+ -X) gave rise to the emission of Chry-TCNB charge-transfer complexes resulting mainly from the migration of Chry while the latter system (Chry/Na+ -X and TCNB/Na+ -Y) afforded the same emission resulting largely from the migration of TCNB. The present investigation reveals that there is a certain direction for guest migration depending on the zeolite host and the nature of host-guest or guest-guest interaction.     

Direct Monitoring of Thickness and Refractive Index of Optical Thin Film Deposited on Fiber End-face

We propose a system for depositing thin films on waveguides which enables low-temperature deposition and precise control of the refractive index and film thickness. It is composed of a conventional ion-beam sputtering (IBS) system and a new system for directly monitoring film characteristics during deposition. We controlled refractive indices over a wide range from 1.52 to 1.97 by moving the sputtering targets (SiO₂ and Si₃N₄) in the IBS system. The refractive index or film thickness was in-situ monitored by observing the optical power reflected from the end-face of a monitoring fiber set in the deposition chamber. Antireflection coating films were successfully deposited on a fiber end-face and a laser diode chip facet with low reflectivity from 0.05 to 0.07%. This deposition system is attractive for constructing highly functional optical devices for future photonic networks.     

Exploration of Nano-Saturns: A Spectacular Sphere–Ring Supramolecular System

Saturn-like systems consisting of nanoscale rings and spheres are fascinating motifs in supramolecular chemistry. Several ring molecules are known to include spherical molecules at the center of the cavity via noncovalent attractive interactions. In this Minireview, we generalize the molecular design, the structural features, and the supramolecular chemistry of such “nano-Saturns”, which consist of monocyclic rings and fullerene spheres (mainly C₆₀), on the basis of previous experimental and theoretical studies. Ring molecules are classified into three types (loop, belt, and disk) according to their shapes and possible interactions. Whereas typical belt-shaped rings tend to form tight complexes due to the wide contact area via π–π interactions, flat disk-shaped rings generally form weak complexes due to the narrow contact area mainly via CH–π interactions. In spite of the small association energies, disk-shaped rings are attractive because such rings can mimic the planet Saturn precisely as exemplified by an anthracene cyclic hexamer–C₆₀ complex.     

Uniqueness of the ground state solutions of quasilinear Schrödinger equations

We are concerned with the uniqueness result of positive solutions for a class of quasilinear elliptic equation arising from plasma physics. We convert a quasilinear elliptic equation into a semilinear one and show the unique existence of positive radial solution for original equation under the suitable conditions on the power of nonlinearity and quasilinearity. We also investigate the non-degeneracy of a positive radial solution for a converted semilinear elliptic equation.     

Additive Pummerer reaction of heteroaromatic sulfilimines with carbon nucleophiles

The additive Pummerer reaction of several heteroaromatic sulfilimines has been investigated. The overall process involves the reaction of the sulfilimine with TFAA to produce a transient N-tosyl-N-trifluoroacetyl sulfonium ion. Nucleophilic attack at the adjacent vinyl carbon results in the ejection of the sulfonamide group and the resulting thionium ion loses a proton to give the observed product.     

Direction control of chemical wave propagation in self-oscillating gel array

A chemomechanical actuator utilizing a reaction-diffusion wave across gap junction was constructed toward a novel mircoconveyer by micropatterned self-oscillating gel array. Unidirectional propagation of the chemical wave of the Belousov-Zhabotinsky (BZ) reaction was induced on gel arrays. In the case of using a triangle-shaped gel as an element of the array, the chemical wave propagated from the corner side of the triangle gel to the plane side of the other gel (C-to-P) across the gap junction, whereas it propagated from the plane side to the corner side (P-to-C) in the case of the pentagonal gel array. Numerical analysis based on the Keener-Tyson model was done for understanding the mechanism of unidirectional propagation in triangle and pentagonal gel arrays. The swelling and deswelling changes of the gels followed the unidirectional propagation of the chemical wave.     

Thermotropic Liquid Crystalline Polymers Having Five‐Membered Heterocycles as Mesogens, 7. Synthesis and Photoluminescent Properties of Semi‐Rigid Thermotropic Liquid Crystalline Polyesters Based on a Quaterphenyl Analog of 2,2′‐Bis(1,3,4‐thiadiazole)

New semi‐rigid thermotropic liquid crystalline (LC) polyesters composed of a quaterphenyl analogue of 2,2′‐bis(1,3,4‐thiadiazole) were synthesized by high‐temperature solution polycondensation of a dioxydiundecanol derivative of 5,5′‐diphenyl‐2,2′‐bis(1,3,4‐thiadiazole) with four diacyl chlorides, whose structures were characterized by FT‐IR and ¹³C NMR spectroscopy, as well as elemental analysis. Differential scanning calorimetry (DSC) measurements and texture observations using polarizing microscopy displayed that all the polyesters form stable enantiotropic smectic and/or nematic LC phases. Solution and solid state absorption and fluorescence spectra indicated that the polyesters show absorption maxima arising from the 2,2′‐bis(1,3,4‐thiadiazole) moiety and emit bluish green light, the Stokes shifts being 129 nm in solution and 60–64 nm in the solid state. Band gap energies of the polyesters calculated from the solid state absorption spectra were 2.67–2.82 eV.     

8-Endo selective Friedel-Crafts cyclization of vinyloxiranes with Co2(CO)6-complexed acetylene

An 8-endo selective Friedel-Crafts cyclization of vinyloxirane 8 with Co₂(CO)₆-complexed benzeneacetylene was found to give poly-functional eight-membered cyclic compound 9 in high yields.