Conformational Control of a Polyether-Linked Porphyrin Dimer Induced by Complexation with a Sodium Cation

Abstract

A porphyrin dimer with a polyether linkage was newly synthesized and its conformational change triggered by complexation with an sodium cation was examined. It was confirmed by ¹H NMR titration experiments that the dimer bearing a pentaoxyehtylene linkage (1b) was effectively formed a 1:1 complex with a sodium perchlorate. A detailed investigation of the CIS values for the protons confirmed that the complex of 1b?Na⁺ adopts a slipped face-to-face conformation.     

Self-Modulation of Scattering Intensity from a Silica Sphere Coated with a Sol-Gel Film Doped with J-Aggregates

A micrometer-sized nonlinear optical resonator constituted of a silica microsphere coated with J-aggregates has been fabricated by the sol-gel process. We determined the scattering light spectrum and discuss the application of the observed effect for the realization of an optical switching element. Optical evaluation of the sphere has been performed in the attenuated-total-reflection (ATR) configuration. We excited a whispering gallery mode and measured the nonlinear ATR signal dependence on excitation intensity. The experimental result agrees very well with the simulation results obtained using the Mie theory and the finite-difference time-domain method taking into account optical Kerr nonlinearity. The permittivity of the film of J-aggregates was measured by ATR method at several wavelengths and the value at the desired wavelength was determined by extrapolation using the Lorentz function.     

Formation of transient pairs of F and H centers at next nearest neighbor sites in alkali chloride crystals studied by the time delayed double excitation spectroscopy in picosecond range

Abstract

By making use of the time delayed double excitation spectroscopy, transient absorption spectra just after the excitation of self-trapped excitons (STE) from the lowest triplet state to higher excited states have been observed to find the transient F-H center pair [F-H]. Absorption bands due to transient [F-H] appeared as a doublet peaking at 2.70eV and 2.86eV (NaCl), at 2.25eV and 2.38eV (KCl) and at 1.97eV and 2.09eV (RbCl) at 108ps after the excitation. The ratio of peak heights between bands at low and high energy sides was 2:1 in all crystals. The results were tentatively understood by a recent theory for the STE by Song et al. (1987).     

An optical waveguide bend with enhanced curvature and the optimization of its structure

We have investigated a waveguide bend having enhanced curvature with reduced loss. The waveguide width is made wider toward the inner side of the bend. The numerical analysis, by means of the beam propagation method, showed that the loss of the proposed bend is lower than that of an abrupt bend or a smooth bend of constant curvature. For a typical waveguide, we have optimized the structure of the bend and achieved one order of loss reduction in comparison with an abrupt bend of the same angle.     

Determination of cadmium and bismuth in high-purity zinc metal by inductively coupled plasma mass spectrometry with on-line matrix separation

Traces of cadmium and bismuth in high-purity zinc metal were determined by inductively coupled plasma mass spectrometry (ICP-MS) in combination with flow injection (FI) on-line matrix separation (FI-ICP-MS). The anion-exchange separation method of the potassium iodide (KI) system was applied to the separation of the analytes from the matrix zinc. The analytes, cadmium and bismuth, were adsorbed on the anion-exchange (BIO. RAD AG1-X8) mini-column (1.0 mm i.d.x 100 mm bed length), while the matrix zinc can be completely removed from the anion-exchange resin. The analytes were eluted by 2 mol/l HNO(3) and directly introduced into the ICP-MS. The detection limits (D.L.) obtained by using a single injection (350 microl) were 0.81 and 0.075 ng g(-1) for cadmium and bismuth, respectively. In the case of multi-injection concentration onto the anion-exchange mini-column (five injections 350 microl each), the detection limits could be improved to 0.16 and 0.014 ng g(-1) for cadmium and bismuth, respectively. The reproducibilities of the single injection and the multi-injection method were satisfactory with a relative standard deviation of less than 5% (at the 10 and 1 ng ml(-1) level for the single injection and the multi-injection method, respectively). The method was successfully applied to the determination of trace impurities in four samples of high-purity zinc metal (7 nines grade) and three standard reference materials of high-purity unalloyed zinc samples (from NIST).     

Interaction between dyes and polyelectrolytes. I. Effect of polyelectrolytes on the reaction of methylene blue with 1-benzyl-1,4-dihydronicotinamide

The effect of polyelectrolytes on the reaction of methylene blue with 1-benzyl-1,4-dihydronicotinamide was investigated. An accelerating effect was observed on addition of sodium polystyrenesulfonate of poly(potassium p-styrenesulfonate). On the other hand, deceleration was observed on addition of potassium polyvinylsulfate. No appreciable effect was observed when sodium p-toluenesulfonate or potassium chloride was used as an electrolyte. An obvious color change was observed when methylene blue is bound to these anionic polyelectrolytes. Some correlations with spectral change of methylene blue and acceleration or deceleration effect are discussed.     

Binding the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate,by polycations that contain apolar pendant groups: Equilibrium dialysis and fluorescence measurements

The thermodynamic parameters for the interaction of the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate (TNS), and polycations that contain a piperidinium cation and various nonpolar pendant groups were calculated. Binding is exothermic and involves a positive entropy gain. The contribution of the entropy term to the free energy change tends to increase with increasing hydrophobicity of the polymers. The intensity of the fluorescence of TNS is enhanced when the probe binds to the polycations. The nature and phenomena of hydrophobic fluorescent probe binding with the polymers are discussed.     

INTRACELLULAR DICHROIC ORIENTATION OF THE BLUE LIGHT-ABSORBING PIGMENT AND THE BLUE-ABSORPTION BAND OF THE RED-ABSORBING FORM OF PHYTOCHROME RESPONSIBLE FOR PHOTOTROPISM OF THE FERN Adiantum PROTONEMATA

The intracellular localization and orientation of the receptors for the blue light-induced phototropism in the fern Adianrum protonemata, phytochrome and the blue light-absorbing pigment, were investigated by combining the techniques of cell centrifugation and of microbeam irradiation with linearly polarized light. The phototropic response was induced in the cells even after they had been centrifuged basipetally to spin down the endoplasm from the apical region. When a polarized blue microbeam was given to a flank of the apical region of the protonema, the phototropic response after compensation of phytochrome effect by far-red light was most effectively induced when the polarization plane was parallel to the long axis of the cell. If protonemata were pre-irradiated with blue and far-red light, the phototropic response was mediated through phytochrome alone. If such pre-irradiated protonemata were similarly irradiated with a polarized blue microbeam, polarized light vibrating parallel to the cell axis was again most effective in inducing the response. These results indicate that both the blue light-absorbing pigment and the phytochrome responsible for the blue light-induced phototropism in Adiantum are confined to the plasma membrane and/or the ectoplasm and that the transition moments of their blue-absorption bands are nearly parallel to the cell surface.     

Cation binding properties of poly(crown ethers) with photodimerizable groups

Polymers that have crown ether groups as cation binding sites and cinnamic acid ester groups as photodimerizable groups were prepared by the cationic polymerizations of 2-vinyloxyethyl 4′-(2,3-benzo-1,4,7,10,13-pentaoxa-2-cyclopentadecene)acrylate and 2-vinyloxyethyl 4′-(2,3-benzo-1,4,7,10,13,16-hexaoxa-2-cyclooctadecene)acrylate. When irradiated with ultraviolet (UV) light the cinnamic acid ester groups of the polymers caused dimerization in dilute solution without the formation of insoluble materials. The irradiation was carried out in a dioxane solution and an aqueous solution in the presence and absence of salts. The effect of phototransformation of polymers on the cation binding properties was investigated by a method of picrate salts extraction. The binding ability of the phototransformed polymers for alkali and alkaline earth metal cations was higher than that of the native polymer. Furthermore the cation binding ability of the phototransformed polymers was less sensitive to temperature than that of the native polymer. The effect of the degree of photodimerization of the polymers and the concentration of KCl that exists during irradiation on the cation binding ability was also investigated.