Recent progress of luminescent metal complexes with photochromic units

Photo-responsive molecules have been studied extensively because of their light irradiation abilities that enable modulation of certain physical and chemical properties in emerging molecular electronic and photonic devices. For advanced photonic applications, photochromic metal complexes that have photochromic units as the photo-responsive ligand are highly desirable, as they allow improvement of the photochromic properties and their photo-switching functionality. This article focuses on recent progress in luminescent metal complexes with photochromic units. Luminescence-switching properties of photochromic metal complexes depend on characteristic electronic transitions. The electronic transitions of photochromic metal complexes can be divided into three categories: (1) π–π* transition of the ligand, (2) metal to ligand charge transfer (MLCT) in transition-metal complex, and (3) f–f transition in lanthanide complex. Luminescence modulation using various metal complexes with photochromic units has been studied extensively in recent years, and various applications for future molecular switching devices are expected in the field of advanced photonics. Based on the literature and our studies on luminescent metal complexes with photochromic units, we report on the recent progress of luminescent metal complexes with photochromic units.     

Dual mode bioreactions on polymer nanoparticles covered with phosphorylcholine group

We investigated the preparation of polymer nanoparticles covered with phosphorylcholine (PC) groups and the immobilization of proteins in order to observe dual mode bioreactions on the nanoparticles. For the surface modification on the nanoparticles, a water-soluble amphiphilic phospholipid polymer with PC groups as a hydrophilic moiety was synthesized. In this polymer, an active ester group, which can immobilize proteins, was introduced. Using the phospholipid polymer as a solubilizer, poly(L-lactic acid) nanoparticles were prepared from its methylene chloride solution in an aqueous medium by the solvent evaporation method. The diameter of the nanoparticles was ca. 200 nm and the surface was covered with the PC groups and active ester groups. Proteins could immobilize on the nanoparticles under mild conditions by the reaction between the active ester group and amino group in the proteins. Both an antibody and enzyme were immobilized on the nanoparticles and bioreactions such as the antigen/antibody reaction and enzymatic reaction were observed. When an antigen was added to the suspension of the nanoparticles, aggregation of the nanoparticles occurred and then they precipitated. Also, the enzymatic reaction proceeded well when the enzyme substrate was added to the suspension. Based on these results, we provided polymer nanoparticles functionalized with both the antibody and enzyme, and the dual mode bioreactions could occur. We concluded that the novel polymer nanoparticles could be used for nano-/micro-scaled diagnostic and medical treatment systems.     

Chain ordering of Stratum corneum lipids investigated by EPR slow-tumbling simulation

We investigated the chain ordering of the lipid bilayer of Stratum corneum (SC) using an electron paramagnetic resonance (EPR) spin probe method in conjunction with slow-tumbling simulation. The ordering of SC lipids was evaluated by analysis of the signals of 5-doxylstearic acid (5-DSA) spin probe incorporated into the lamellar lipids. The result obtained with the conventional method of calculating the order parameter using hyperfine values was 0.80. The value of the order parameter obtained by spectral simulation was 0.73. It was found that the conventional method of calculating the chain ordering using hyperfine values could not differentiate subtle EPR spectral changes. However, EPR slow-tumbling simulation can differentiate such subtle spectral changes. Thus, the present EPR investigation suggests that simulation provides more detail about the structure of the lipid bilayer than the conventional method.     

Maskless microfabrication of thermosensitive gels using a microscope and application to a controlled release microchip

Here we show a simple and convenient method to prepare micropatterned gels by the use of a microscope, without large-scale or special-order experimental setup. UV light focused by an objective lens was locally irradiated to a pre-gel solution in a microchannel. This method would be useful for preparing microgels at target positions in microchips. A controlled drug-release microchip has actually been fabricated by utilizing this local photo-irradiation method, and pulsatile drug release in response to temperature changes was demonstrated.     

Development of isomerization and cycloisomerization with use of a ruthenium hydride with N-heterocyclic carbene and its application to the synthesis of heterocycles

A pure ruthenium hydride complex with N-heterocyclic carbene (NHC) ligand was efficiently generated from the reaction of a second-generation Grubbs ruthenium catalyst with vinyloxytrimethylsilane and unambiguously characterized. This ruthenium hydride complex showed high catalytic activity for the selective isomerization of terminal olefin and for the cycloisomerization of 1,6-dienes. These reactions of N-allyl-o-vinylaniline lead to novel synthetic methods for heterocycles such as indoles and 3-methylene-2,3-dihydroindoles, which are useful synthons for bioactive natural products. These procedures address an important issue in diversity-oriented synthesis.     

Time evolution of electron wave-packets in modulated superlattices and at their boundaries

Time evolution of an electron wave-packet moving perpendicular to a superlattice surface is calculated by numerically solving the Schrödinger differential equation. Reflections and penetrations of the wave-packets at the superlattice surface are shown. Low transmission efficiency is observed when the potential discontinuity between two component semiconductors of the superlattice is large, even though the electron impinging energy is in the allowed mini-band of the superlattice. An “anti-reflection coating” which removes this reflection is discussed. The effect of layer-thickness fluctuation on the electron scattering is also simulated by this method. It is found that a fluctuation model of no correlation with neighboring layers produce a scattering rate which strongly depends on the random number sequence used to generate the fluctuation.     

On the anomalous temperature dependence of ferroelectric Sc*. liquid crystals

A biaxial elastic model for the temperature dependence of S_c* helical pitch is proposed on the basis of a phenomenological theory of S_c* liquid crystals accompanied by a biaxial molecular ordering playing an important role for the anomalous behaviour of the helical pitch near the S_c*-S_A transition point. In the S_c*. phase of p-(n-decyloxybenzylidene)-p-amino-(2-methylbuthyl)-cinnamate (DOBAMBC), a qualitative agreement with the observed helical pitch is found by choosing a few material parameters concerned with a biaxial elasticity and an anisotropy of the elastic constants.     

Total synthesis of (+)-tryptoquivaline

We report the first total synthesis of (+)-tryptoquivaline 1a and of a key precursor, 2,3-dialkylquinazolinone 13b.