Nobuyuki Ichinose

Photo-oxygenation of 1,2-diarylcyclopropanes via electron transfer

Abstract The photo-oxygenation of 1,2-diarylcyclopropanes bearing electron-donating substituents in the presence of 9,10-dicyanoanthracene (DCA) in acetonitrile affords trans- and cis-3,5-diaryl-1,2-dioxolanes in excellent yields. The DCA-sensitized photo-oxygenation of less electron-rich 1,2-diarylcyclopropanes gives various oxidation products in low yields. These photoreactions are greatly accelerated by the addition of certain aromatic hydrocarbons and metal salts, and are completely quenched by the addition of triethylamine and 1,4-diazabicyclo[2.2.2]octane. No photo-oxygenation takes place in non-polar solvents. The electron transfer mechanism is proposed for the photo-oxygenations, in which the cation radicals of 1,2- diarylcyclopropanes are involved as chain carriers.

Laser induced molecular transfer using ablation of a triazeno-polymer

Abstract We report on the laser induced transfer of molecular dopants between thin polymer films. Pulsed UV laser radiation (355 nm) of moderate intensity, is directed through a transparent polymer film and absorbed by a photolabile triazeno-polymer (TP) doped with pyrene at low concentration. The explosive photodecomposition of TP results in the transfer of intact pyrene molecules to a tightly contacted neat polymer film of either poly(ethyl methacrylate) (PEMA) or poly(butyl methacrylate) (PBMA). Fluorometry of the receiving polymer surface indicated that the pyrene emission intensity grows as the laser pulse number increases but reduces with rising laser fluence. Surface examination suggests that most of the transferred dopant is implanted beneath the receiving polymer surface and the efficiency of this process is enhanced with lowering of its glass transition temperature T g . A mechanism is discussed to explain the current experimental results.

Area‐selective formation of an organosilane monolayer on silicon oxide nanopatterns fabricated by scanning probe anodization

An organosilane monolayer was formed from a precursor vapor (trimethylchlorosilane, TMCS) onto the surface of silicon oxide (SiOx) nanopatterns surrounded by hydrogen‐terminated silicon (Si–H). The nanopattern was fabricated with a resolution of 20 nm by scanning probe anodization, that is, localized anodization induced beneath the tip of a scanning probe microscope. The area‐selectivity arises from the difference in the chemical reactivity of the vapor between the SiOx and Si–H surfaces. The TMCS‐coated SiOx patterns showed a resistivity to chemical etching with an aqueous solution of ammonium fluoride and hydrogen peroxide. Lateral force microscopy with an organosilane‐coated probe also indicated the presence of the monolayer on SiOx through a friction force contrast between the monolayer‐coated and uncoated regions.

Electron-transfer mediated photooxygenation of biphenyl and its derivatives in the presence of Mg(ClO4)2

Abstract The 9,10-dicyanoanthracene-sensitized photooxygenation of biphenyl and its derivatives in the presence of Mg(ClO 4 ) 2 in acetonitrile brought about the oxidative cleavage of benzene nucleus to give benzoic acid and its derivatives.

Photochemistry of cyclopropanes, methylenecyclopropanes, and vinylidenecyclopropanes

Abstract This review deals with the recent advances in the photochemistry of cyclopropanes, methylenecyclopropanes, and vinylidenecyclopropanes. cis–trans Photoisomerization of 1,2-diarycyclopropanes via excited singlet and triplet states and radical cations, photochemical polar addition to arylcyclopropanes, and photooxygenation of arylcyclopropanes and methylenecyclopropanes giving cyclic peroxides are described. The new photochemistry of vinylidenecyclopropanes including cis–trans photoisomerization, (3+2) photocycloadditions, and photorearrangements is also discussed.

Laser implantation of photochromic molecules into polymer films: a new approach towards molecular device fabrication

Laser molecular implantation enables us to dope space-selectively a surface layer of a polymer film with intact organic molecules. Thus it is applicable towards building various kinds of devices utilizing functional organic molecules. This paper presents that photochromic molecules can be implanted in polymer surfaces by using 351 nm or 355 nm nanosecond lasers and the implanted molecules can be switched repetitively by the alternate irradiation of UV and visible lights. As an example of the space selectivity, the fabrication of gratings by laser implantation is demonstrated and evaluated from an application view point.

U.v.-irradiation of thin films of polystyrene derivatives : formation of carboxylic group and crosslinking from 4-trimethylsilylmethyl substituent

Abstract Photoirradiation of thin films of poly(4-trimethylsilylmethylstyrene) (PTMSMS), poly(4-methylstyrene) (P4MS), and polystyrene (PS) at 254 nm with a low-pressure Hg lamp in air made the surfaces hydrophilic through oxygenation. The hydrophilicity estimated from the contact angle with water was in the order of PTMSMS ≈ P4MS > PS. Formation of carboxylic acid group on the surface and crosslinking in the bulk were demonstrated for PTMSMS, whereas the photoirradiation of PS and P4MS was accompanied by degradation of the polymer main chain. The chemical behaviour of the polymers reflected selectivities in the cleavage of the benzylic CSi or CH bond of the 4-substituents toward that of the benzylic CH bond on the main chain.

Time-resolved surface scattering imaging of organic liquids under femtosecond KrF laser pulse excitation

Time-resolved surface scattering imaging was performed for liquid benzyl chloride and liquid toluene under femtosecond KrF laser ablation conditions. No scattering image was obtained until 1 ns, while scattering started from 2 ns when the laser fluence exceeded 25 mJ/cm2, and its intensity increased with the passage of time. The higher the laser fluence was, the steeper the increasing slope was. The scattering is due to surface roughness, which is the initial stage of macroscopic morphological changes. Root-mean-square surface roughness was estimated from the scattering intensity by using frosted fused-silica plates as reference samples. The induced surface roughness increases to a few hundred nm in 10 ns.

Effect of hydrogen bonding on laser-induced transfer of 1-pyrenebutyric acid in solid polymers

Abstract Polymer films (poly(alkyl methacrylate) or polystyrene) doped with pyrene or 1-pyrenebutyric acid (source film) were overlaid with a neat poly(butyl methacrylate) (target film) and were irradiated with a KrF excimer laser passing through the target film. Dopant molecules were found to be ejected from the source film and were transferred into the target film. The transferred amount of pyrene was about 20 times larger than that of 1-pyrenebutyric acid for poly(methyl methacrylate). The difference is considered to be caused by intermolecular interactions such as hydrogen bonding between polymer side groups and 1-pyrenebutyric acid.

Implantation of Organic Molecules into Biotissue by Pulsed Laser Irradiation

Zinc tetraphenyl porphyrin (ZnTPP) molecules were implanted into a piece of chicken skin by irradiation with KrF laser pulses. The study of the implanted ZnTPP at the skin surface using a fluorescence microscope indicated that the molecules are space-selectively introduced at the irradiated area.