Dynamics and mechanisms of the multiphoton gated photochromic reaction of diarylethene derivatives

The cycloreversion (ring-opening) process of one of the photochromic diarylethene derivatives, bis(2-methyl-5-phenylthiophen-3-yl)perfluorocyclopentene, was investigated by means of picosecond and femtosecond laser photolysis methods. The drastic enhancement of the reaction yield was observed only by the picosecond laser exposure. The excitation intensity effect of the reaction profiles revealed that the successive multiphoton absorption process leading to higher excited states opened the efficient cycloreversion process with a reaction yield of (50 +/- 10)%, while the one-photon absorption directly pumped to a higher excited state did not lead to the efficient cycloreversion reaction. These results indicate that not the energy of the excitation but the character of the electronic state takes an important role in the enhancement of the cycloreversion reaction.     

Development of a homogeneous immunoassay system using protein A fusion fragmented Renilla luciferase

A homogeneous immunoassay system was developed using fragmented Renilla luciferase (Rluc). The B domain of protein A was fused to two Rluc fragments. When complexes between an antibody and fragmented Rluc fusion proteins bind to target molecules, the Rluc fragments come into close proximity and the luminescence activity of fragmented Rluc is restored by complementation. As proof-of-principle, this fragmented Rluc system was used to detect E. coli homogeneously using an anti-E. coli antibody.     

Intermolecular reductive radical addition to 2-(2,2,2-trifluoroethylidene)-1,3-dithiane 1-oxide: experimental and theoretical studies

Tin hydride mediated radical addition of organic halide to 2-(2,2,2-trifluoroethylidene)-1,3-dithiane 1-oxide has been devised. The reaction is equivalent to an unrealizable radical addition to trifluoromethylketene, providing useful α-trifluoromethyl carbonyl equivalents. The trifluoromethyl and the sulfoxide groups of the substrate play key roles for the success of the radical addition, lowering the barrier of the radical addition step and controlling the stereoselectivity of the reaction, which DFT calculations have elucidated.     

Thermodynamic Phase Transition Through Crystal‐to‐Crystal Process of Photochromic 1,2‐Bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene

A photochromic diarylethene, 1,2‐bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene ( 1a ), was found to have two polymorphic crystal forms, α‐ and β‐crystals. From X‐ray crystallographic analysis, the space groups of α‐ and β‐crystals were determined to be P2₁/c and C2/c, respectively. The difference between two crystal forms is ascribed to the orientation of two of four molecules in the unit cell. The thermodynamic phase transition from α‐ to β‐forms occurred via a crystal‐to‐crystal process, as confirmed by differential scanning calorimetry measurements, optical microscopic observations in the reflection mode and under crossed Nicols, and powder X‐ray diffraction measurements. The movement of the molecules in the crystal was evaluated by analyzing the change of face indices before and after the phase transition.     

Synthesis of photochromic diarylethene polymers for a write-by-light/erase-by-heat recording system

A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with functional properties of photocoloration, photostability of the colored state, and thermal erasion by heating was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching above 150 °C in solution and in the solid state as well as the performance of the monomeric diarylethene chromophore. In addition, the colored state has a high photostability under visible room light. The diarylethene homopolymer had a glass transition temperature (T_g) as high as polystyrene. The copolymer of 1a with N-1-adamantylmaleimide exhibited extremely high T_g above 200 °C with keeping the photofunctional performance. Such photochromic polymer and copolymers with high T_g can be potentially applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.     

Introduction of 2-methoxycarbonylallyl end group by copolymerization of methyl α-(phenoxymethyl)acrylate accompanying with addition-fragmentation reaction

Copolymerizations of methyl α-(phenoxymethyl)acrylate (MPMA) with methyl acrylate, methyl methacrylate, styrene, and methyl α-ethylacrylate were carried out. Addition of a polymer radical to MPMA followed by the subsequent fragmentation of poly(MPMA) radical resulted in the 2-methoxycarbonylallyl end group and phenoxy radical in the course of the copolymerization. The extent of the fragmentation determined by ¹H-NMR spectroscopy depends on reactivity of the MPMA radical toward the reference monomers. An increase in the addition rate of the MPMA radical to the reference monomer brought about suppression of the fragmentation. The addition of the MPMA radical to styrene seems to be sufficiently fast to prevent the fragmentation. Since the rate of the fragmentation relative to the propagation was considerably accelerated by raising the temperature to 110°C, MPMA can be used as a novel chain transfer agent to control molecular weight and end group at a temperature above 100°C. © 1993 John Wiley & Sons, Inc.     

Detection of small RNA molecules by a combination of branched rolling circle amplification and bioluminescent pyrophosphate assay

Polyfluorinated compounds (PFCs) are a relatively new and diverse set of compounds analyzed as contaminants in food. Their unique physical-chemical properties dictate the methods used for their analysis. Current analyses of the more volatile PFCs involve gas chromatography–mass spectrometry; liquid chromatography–tandem mass spectrometry is generally used for the less volatile PFCs. Considerations in the analysis of PFCs in foods include contamination from the widespread presence of materials that contain various PFCs, endogenous interfering compounds, and matrix effects. Future opportunities for research on PFCs in food exist, particularly in the areas of biological molecule–PFC interactions and the effects of food processing on these interactions. Future research will be facilitated by the synthesis of a wider variety of analytical standards.     

Single-crystalline photochromism of diarylethenes: reactivity-structure relationship

Photochromic reactivity of diarylethenes in the single-crystalline phase was found to be controlled by the distance between the reactive carbon atoms in the antiparallel conformation.     

Synthetic and analytical studies on colour reagents-X Colour reagents for lithium

Few colour reagents are known for lithium. Of several hundreds of reagents synthesised by the authors and their collaborators, o,ot-dihydroxyazo compounds were found to be the best, especially those with beta-naphthol derivatives as a coupling component. The bluish colour of the reagent turns to red in the presence of lithium.