Photoinduced Transformation Research Articles

ChemInform Abstract: Photoinduced Molecular Transformations. Part 121. New Short Step General Synthesis of Isobenzofuran-1(3H)-ones (Phthalides) Based on a Single or Double β-Scission of Alkoxyl Radicals Generated from 1- Ethylbenzocyclobuten-1-ols and fr

ChemInform Abstract: Photoinduced Molecular Transformations. Part 121. New Short Step General Synthesis of Isobenzofuran-1(3H)-ones (Phthalides) Based on a Single or Double β-Scission of Alkoxyl Radicals Generated from 1- Ethylbenzocyclobuten-1-ols and fr

ChemInform Abstract: Photoinduced Molecular Transformations. Part 124. A New Route to . gamma.-Substituted γ-Lactones and δ-Substituted δ- Lactones Based on the Regioselective β-Scission of Alkoxyl Radicals Generated from Transannular Hemiacetals.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Photoinduced Molecular Transformations. Part 123. One-Step Synthesis of 1H-Benz(f)indole-4,9-diones by a New Regioselective Photoaddition of 2-Amino-1,4-naphthoquinone with Various Alkenes and Its Application to One-Step Synthesis of

ChemInform Abstract: Photoinduced Molecular Transformations. Part 123. One-Step Synthesis of 1H-Benz(f)indole-4,9-diones by a New Regioselective Photoaddition of 2-Amino-1,4-naphthoquinone with Various Alkenes and Its Application to One-Step Synthesis of

ChemInform Abstract: Photoinduced Molecular Transformations. Part 131. Synthesis of 18- Norsteroids, Deoxofukujusonorone and the Related Steroids, Based on a Selective β-Scission of Alkoxyl Radicals as the Key Step.

A new transformation of steroids into 18-norsteroids under mild conditions is described. The key step was a regioselective β-scission of the alkoxyl radicals generated by photolysis of the hypoiodite of 18-hydroxy-18,20α-epoxy steroids, prepared by photolysis of steroidal 20α-ol nitrites followed by deoximation of the resulting 18-hydroxyimino-20α-hydroxy steroid with sodium nitrite and acetic acid. 3β-Hydroxypregn-5-en-20-one (pregnenolone) was thus transformed into 3β-hydroxy-18-norpregna-5,13-dien-20-one (12-deoxofukujusonorone) in 10 steps.

ChemInform Abstract: Photoinduced Molecular Transformations. Part 133. New Photoinduced Deconjugation of Steroidal α,β-Unsaturated Cyclic Ketone Oxime into the β,γ-Unsaturated Isomer Involving Stereospecific Proton Transfer.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Photoinduced Molecular Transformations. Part 132. A Two-Step Intramolecular Transposition of the 17β-Acetyl Group of Pregnan- 20-one to C-18 Through the Formation of Cyclobutanols by the Reaction of the Excited Carbonyl, Followed by a

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Photoinduced Morphology Switching of Polymer Nanoaggregates in Aqueous Solution

A novel photosensitive C-PNIPAAm comprising hydrophilic PNIPAAm conjugated with a relatively short but very hydrophobic coumarin part was designed and prepared using a coumarin-containing disulfide derivative (C-S-S-C) as transfer agent in the presence of Bu(3)P and water. It was found that C-PNIPAAm can form polymer micelles in aqueous solution. And the micellar morphology in aqueous solution can be photoswitched into hollow spheres according to the photodimerization of coumarin end groups upon 365 nm irradiation and reform the micellar morphology after the subsequent photoscission of dimers upon 254 nm. This instant morphology changing phenomenon was successfully monitored by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. TEM observations showed the small spherical shape of micelles with diameter at 30-50 nm before photo-cross-linking, the big vesicles with diameter at 200-350 nm after photo-cross-linking, and the small micelles with diameter at 30-50 nm after the subsequent photo-de-cross-linking in the first irradiation cycle. The reason for this significant morphology switching can be attributed to the reversible photoinduced amphiphilic structure transformation between the telechelic "hydrophobic end-hydrophilic chain" structure and the ABA type of "hydrophilic chain-hydrophobic center-hydrophilic chain" one upon alternating irradiation.

Molecular adlayer and photo-induced structural transformation of a diarylethene derivative on Au(1 1 1) investigated with scanning tunneling microscopy

The self-assembly and photo-induced structural transformation of a diarylethene derivative 1,2-bis(3,5-dimethyl dithioene [3,2- b:2′,3′- d]thiophene-2-yl) perfluorocyclopentene (BDDTP) have been investigated by cyclic voltammetry and electrochemical scanning tunneling microscopy (EC-STM) on a Au(1 1 1) substrate. BDDTP was found to form two ordered adlayer structures on Au(1 1 1) surface. STM observation revealed that the original ordered structures transformed into disordered adlayers after ex situ and in situ ultraviolet (UV) irradiation. Such a dramatic difference in the self-assembly behavior of BDDTP before and after UV irradiation results from the conformational transformation induced by photo-irradiation and the associated molecule–substrate interaction change. The result provides useful information to understand the self-assembly behavior and photochromic reaction of diarylethenes compounds on solid supports.

Nonlinear Optical Properties of Flavylium Salts: A Quantum Chemical Study

Ab initio calculations have been carried out to unravel the relationships between the structure and the first hyperpolarizability in flavylium derivatives, with the aim to design efficient second-order nonlinear optical (NLO) switching compounds. Large contrasts of the first hyperpolarizability have been obtained along the pH-controlled and photoinduced transformations for specific combinations of chemical substituents in the 4'- and 7-positions, which demonstrates that these multistate systems should behave as highly efficient molecular NLO switches.

Photoinduced Phase Transformations in Boron Nitride: New Polytypic Forms of sp3-Bonded (6H- and 30H-) BN

New sp3-bonded polytypic forms of boron nitride (BN), namely, 6H-BN and 30H-BN, were prepared by plasma-assisted chemical vapor deposition (CVD) with an excimer laser at 193 nm being irradiated on the growing film surface. Only the 6H-BN was formed by postdeposition laser irradiation (PDL) of sp2-bonded BN precursor films prepared by plain plasma-assisted CVD. The PDL demonstrated direct photoinduced phase transformation from sp2-bonded BN into denser sp3-bonded BN here. Typical lattice constants a and c for 6H-BN determined by X-ray diffraction were 2.501 A and 12.45 A, respectively, while those for 30H-BN were 2.538 A and 62.61 A, respectively. The polytypic structures were analyzed in terms of “hexagonality” H and “close-packing” index D, and the “metastability” ΔE estimated by the first principles calculations. Linear relationships were found among the H, D, and ΔE for the polytypes of BN, AlN, and SiC, whose behavior proved to depend on the degree of ionicity in their iono-covalent bonds. The growth ...

ChemInform Abstract: Photoinduced One-Pot Transformation of 2-Phenyl-4-ethylidene-5(4H)-oxazolone and Allylic Alcohols to γ,δ-Unsaturated N-Benzoyl Amides.

Abstract Photolysis of 2-Phenyl-4-ethylidene-5(4H)-oxazolones in the presence of allylic alcohols resulted in a novel one-pot transformation to γ,δ-unsaturated N-benzoyl amides via decarbonylation, nucleophilic addition of allylic alcohols, photoinduced hydrogen transfer and the Claisen rearrangement.

ChemInform Abstract: Photoacid and Photobase Generators: Prospects and Their Use in the Development of Polymeric Photosensitive Systems

This article describes the recent progress in the preparation of a set of compounds which can generate acids or bases upon irradiation of light. These compounds are called photoacid generators and photobase generators, respectively. Photoacid generators can be divided into two groups according to their characteristics; i.e., ionic- and non-ionic compounds. Photobase generators are fewer than photoacid generators. These compounds are widely used in the field of polymeric photosensitive systems such as photoinitiated polymerization, photoinduced crosslinking of polymers and oligomers, photoinduced degradation of polymers, and photoinduced transformation of functional groups in polymer chains. In particular, this article focuses on the applications of photoacid and photobase generators to promote the development of photoresist and UV curing materials.

Real-time scaling of micro-objects by multiplexed holographic recording on photo-thermoplastic structure

The processes of micro-object hologram real-time recording on a photo-thermo-plastic carrier based on a chalcogenide glassy semiconductor As–Se–S–Sn system were studied. The possibility to measure micro-object dimensions using an interference fringe pattern was shown. Double-exposure hologram recording by use of photo-induced structural transformation processes in a photo-semiconductor and photo-thermoplastic recording process was investigated.

ChemInform Abstract: Novel Azacrown Ether-Containing Spiro[indoline-2,3′-naphthoxazines]: Design, Synthesis, and Cation-Dependent Photochromism.

Novel spironaphthoxazine compounds with an aza-15-crown-5 ether fragment at position 5′ or 9′ of the naphthalene ring were synthesised. Spectrokinetic measurements showed the occurrence of two competing formation processes for complexation with alkaline earth or rare earth metal cations. A comparative study of the prepared compounds demonstrated the role of molecular design and the metal cation nature in the cation-dependent photoinduced transformation of spiro[indoline-naphthoxazines].

Photoinduced transformations of Acid Violet 7 and Acid Green 25 in the presence of TiO 2 suspension

An azo dye (Acid Violet 7) and an anthraquinone dye (Acid Green 25) were degraded in aqueous solution using titanium dioxide as photocatalyst. Their fate was studied through dyes decomposition, identification of the main and secondary transformation products and assessment of mineralization. Carbon complete mineralization was achieved in both cases together with the total conversion of the sulphonic groups into sulphate ions; nitrogen was recovered as nitrate and ammonium ions. The transformation intermediate products were identified by means of HPLC/MS and GC/MS techniques. Acid Violet 7 transformation involved the detachment of sulphonic group, hydroxylation, and detachment of the amino acetic moiety, with the formation of hydroxyl naphthalene. Conversely, Acid Green 25 transformation proceeded through the formation of 19 initial compounds and involved the detachment of one (or two) sulphonic groups and/or hydroxylation, followed by the detachment of the benzenic ring.

Photo-induced transformations of Hg(II) species in the presence of Nitzschia hantzschiana, ferric ion, and humic acid

Effects of algae Nitzschia hantzschiana, Fe(III) ions, humic acid, and pH on the photochemical reduction of Hg(II) using the irradiation of metal halide lamps (λ ≥ 365 nm, 250 W) were investigated. The photoreduction rate of Hg(II) was found to increase with increasing concentrations of algae, Fe(III) ions, and humic acid. Alteration of pH value affected the photoreduction of Hg(II) in aqueous solution with or without algae. The photoreduction rate of Hg(II) decreased with increasing initial Hg(II) concentration in aqueous solution in the presence of algae. The photochemical kinetics of initial Hg(II) and algae concentrations on the photoreduction of Hg(II) were studied at pH 7.0. The study on the total Hg mass balance in terms of photochemical process revealed that more than 42% of Hg(II) from the algal suspension was reduced to volatile metallic Hg under the conditions investigated.

Fluorescence patterning in films of a photoswitchable BODIPY–spiropyran dyad

A BODIPY-spiropyran dyad was embedded within poly(methyl methacrylate) films spin-coated on glass slides. Visible illumination of the resulting materials excites selectively the BODIPY fragment, which then deactivates radiatively by emitting light in the form of fluorescence. Ultraviolet irradiation promotes the isomerization of the spiropyran component to the corresponding merocyanine. This photoinduced transformation activates electron and energy transfer pathways from the fluorescent to the photochromic fragment. Consistently, the BODIPY fluorescence is effectively suppressed within the photogenerated isomer. As a result, ultraviolet illumination with a laser, producing a doughnut-shaped spot on the sample, confines the fluorescent species within the doughnut hole. This behavior is an essential requisite for the implementation of super-resolution imaging schemes based on fluorescence photodeactivation. Thus, the operating principles governing the photochemical and photophysical response of this molecular switch can ultimately lead to the development of innovative probes for fluorescence nanoscopy.

Facile Fabrication of Efficient Organic CMOS Circuits

Organic electronic circuits based on a combination of n- and p-type transistors (so-called CMOS circuits) are attractive, since they promise the realization of a manifold of versatile and low-cost electronic devices. Here, we report a novel photoinduced transformation method, which allows for a particularly straightforward fabrication of highly functional organic CMOS circuits. A solution-deposited single-layer film, comprising a mixture of the n-type semiconductor [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) and the p-type semiconductor poly-3-hexylthiophene (P3HT) in a 3:1 mass ratio, was utilized as the common active material in an array of transistors. Selected film areas were exposed to laser light, with the result that the irradiated PCBM monomers were photochemically transformed into a low-solubility and high-mobility dimeric state. Thereafter, the entire film was developed via immersion into a developer solution, which selectively removed the nonexposed, and monomeric, PCBM component. The end result was that the transistors in the exposed film areas are n-type, as dimeric PCBM is the majority component in the active material, while the transistors in the nonexposed film areas are p-type, as P3HT is the sole remaining material. We demonstrate the merit of the method by utilizing the resulting combination of n-type and p-type transistors for the realization of CMOS inverters with a high gain of approximately 35.

Harvesting the Strain Installed by a Paternò−Büchi Step in a Synthetically Useful Way: High-Yielding Photoprotolytic Oxametathesis in Polycyclic Systems

High-yielding one-pot photoinduced transformation of readily available endoaroyl and heteroaroyl Diels-Alder adducts into novel polycyclic aldehydes or their hemiacetals, decorated by carbo- and heterocyclic pendants, is described.

Oxygen‐assisted photoinduced structural transformation in amorphous Ge–S films

AbstractWe report our results of continuous illumination of Ge46S54 chalcogenide glass films with bandgap light in air. The outcome of this process is the formation of Ge–S backbone depleted in germanium. We relate this to consumption of some of the germanium available in the initial material due to the occurrence of a photoinduced oxidation. This is proved using energy dispersion spectroscopy which shows the presence of 17.68 at.% oxygen in the glass post‐radiation. Raman spectra demonstrate that the initial material shows breathing modes, characteristic for Ge46S54 glass. After prolonged illumination Raman spectra reveal structure characteristic for the composition of the Ge–S backbone close to Ge33S67. The oxide forms a film on the surface and this changes the surface relief, studied by atomic force microscopy, but the oxidation is not surface‐limited. The oxidation process in these glasses is discussed and the higher priority of germanium oxidation compared to the oxidation of sulphur is stated.