Photoinduced Coupling Research Articles

Novel photo‐induced coupling reactions of 9‐fluorenylidene‐malononitrile or 1,1‐diphenyl‐2,2‐dicyanoethylene with 10‐methyl‐9,10‐dihydroacridine. A study on the photophysics of the reaction

Abstract9‐Fluorenylidenemalononitrile (FDCN) or 1, 1‐diphenyl‐2,2‐dicyanoethylene (DPCN) reacted with 10‐methyl‐9,10‐dihydroacridine (AcrH2) under irradiation (λ 320 nm) to give couping products. In order to gain further insight into the mechanism of the photo‐induced reaction, the photophysics of the reactions of FDCN or DPCN with AcrH2 have been investigated by using UV‐vis spectroscopy, fluorescence spectroscopy, excitation spectroscopy and time‐resolved fluorescence spectroscopy, respectively. The results show that FDCN or DPCN interacts with AcrH2 in the ground states to form a charge transfer complex, which further reacts to give the coupling product upon. irradiation.

Novel photo-induced coupling reaction of 9-fluorenylidenemalononitrile with 10-methyl-9,10-dihydroacridine.

9-Fluorenylidenemalononitrile reacts with 10-methyl-9,10-dihydroacridine in deaerated acetonitrile under irradiation with lambda > 320 nm to give a coupling product 9-dicyanomethyl-9-(10'-methyl-9'-acridinyl)fluorene, characterized by X-ray crystallographic, MS and NMR analyses.

Enzymatic Synthesis of Neoglycopeptide Building Blocks

A transglutaminase-catalyzed transacylation is the major step in a practical, regioselective synthesis of N-linked spacer-modified glycopeptide analogues. The process requires minimal modification of the saccharide during the N-glycosylation, photoinduced coupling of cysteamine, and final enzymatic reaction (see scheme).

Photoinduced coupling and adsorption of caffeic acid on silver surface studied by surface-enhanced Raman spectroscopy

The effect of light on the caffeic acid (CA) oxidative coupling is studied in aqueous solution and on silver by surface-enhanced Raman spectroscopy (SERS). CA can polymerize in aqueous solution or on a metal surface through an oxidative mechanism involving the formation of the corresponding quinone giving rise to characteristic Raman features in each case. We show here that the effect of light in relation to this oxidative coupling is crucial taking place mainly in the solution bulk. The products derived from such polymerization can then adsorb on the silver surface employed for SERS measurements, thus allowing its detection by Raman spectroscopy. The influence of irradiation time and the wavelength of the light employed for the photoinduced coupling was investigated.

ChemInform Abstract: Photoinduced Coupling of Acetylenes and Quinone in the Solid State as Preorganized Donor—Acceptor Pairs.

AbstractChemInform 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.

Paterno−Büchi Coupling of (Diaryl)acetylenes and Quinone via Photoinduced Electron Transfer

Photoinduced coupling of an acetylene with a quinone in two wavelength regions (λDB and λCT) can be regioselective to yield a single quinone methide adduct when various diarylacetylenes (DA) and 2,6-dichlorobenzoquinone (DB) are used. Thus, the direct photoexcitation of DB at λDB = 355 nm or the specific activation of the 1:1 electron donor−acceptor complex [DA,DB] at λCT = 532 nm both lead to the transient ion-radical pair [DA•+,DB•-], which is established by time-resolved (ps,ns) spectroscopy. Competition between back electron transfer (kBET) and ion-radical pair collapse (kC) to the distonic adduct DA-DB, as described in Schemes 1 and 2, limits the quantum yields for both photochemical processes in Table 4. The biradical nature of the distonic adduct in Scheme 3 accommodates the various facets of acetylene reactivity and unique regioselectivity to yield the same quinone methide by both actinic processes. In a more general context, the electron-transfer mechanism established by the charge-transfer excit...

Photoinduced non-oxidative coupling of methane over silica-alumina and alumina around room temperature

Around room temperature, photoinduced coupling of methane proceeds without any oxidant molecules on silica-alumina and alumina evacuated at 1073 K; many coupling products in the gaseous phase are obtained from silica-alumina, while most of products on alumina are obtained only through thermal desorption.

Image formation of alkyl‐pendent aromatic polyimide by photocoupling with aromatic ketones

AbstractPositive and negative photostructures are formed after the polyimide (PI) of 4,4′‐biphthalic anhydride (BPA) and 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane (DADMDPM), PI(BPA/DADMDPM) is doped with Michler′s ketone (MK) and benzophenone (BP), respectively, and is subjected to UV light (400 ± 50 nm) irradiation and solvent development. The principle of positive feature formation is based on the photocoupling of MK with PI, which increases PI solubility and thus enables a positive pattern to be developed. The phenomenon of negative photopatterning results from intermacromolecular H‐bonding between the carbonyl group of the imide ring and the hydroxy group which is formed in the photoinduced coupling reaction between BP and PI. Lithographic evaluation shows that the MK‐doped positive‐acting PI film cannot form useful patterns because UV wavelengths are strongly absorbed by MK, which limits the depth of photocoupling in the film. On the other hand, 2‐μm‐wide lines can be resolved in the BP‐doped negative‐acting 0.6‐μm‐thick PI film.

THE PHOTOCHEMISTRY OF IODO, METHYL AND THIOMETHYL SUBSTITUTED ARYL AZIDES IN TOLUENE SOLUTION AND FROZEN POLYCRYSTALS

The photolysis of para-methyl and para-thiomethylphenylazide at 77 K produces the corresponding triplet nitrenes which can be detected by electron paramagnetic resonance (EPR) spectroscopy. Photolysis of these azides in frozen toluene at 77 K leads to insertion of the nitrene into a benzylic C-H bond of the matrix in modest yields. Photolysis of iodinated aryl azides under these conditions does not produce triplet nitrenes that can be detected by EPR spectroscopy. In contrast to the para-methyl and para-thiomethyl substituted phenyl nitrenes, photo-induced coupling of iodo-substituted phenyl nitrenes to toluene proceeds in very poor yield.

Photoinduced coupling reaction of benzotriazole with aromatic hydrocarbons sensitized by 9,10-dicyanoanthracene (DCA)via an electron-transfer mechanism. A simple synthesis of 1-arylbenzotriazole

The photoinduced coupling reaction of benzotriazole with aromatic hydrocarbons (anisole, biphenyl and naphthalene) is sensitized by 9,10-dicyanoanthracene (DCA) to give 1-arylbenzotriazoles in moderate yields via an electron-transfer mechanism.

ChemInform Abstract: CIDNP Study on Porphyrin‐Photosensitized Reactions with Phenol and Quinone. Dimerization of 4‐Methoxyphenol and Cross Coupling of Benzoquinone to Porphyrins Covalently Linked with Phenol Group.

AbstractPhotoreaction of 5,10,15,20‐tetraphenylporphyrin (TPP) with phenol (Ia) gives rise to the triplet pair of radical ions TPP·‐ + (Ia)·+.

Effect of the Phase Transition on the Photochemical Reactions in Lipid Bilayer Membranes

Abstract The effect of phase transition on the photochemical reactions in liposome system containing amphiphilic dye is studied. The fluorescence intensity of the amphiphilic cyanine dye with two long alkyl chains, N, N'-distearylthiacarbocyanine bromide, which is incorporated into bilayer liposome, is considerably modified by the fluid-solid phase transition of the lipid bilayer, while the fluorescence of the cyanine dye with one long alkyl chain, N-stearyl-N'-methylthiacarbocyanine bromide, was not affected by the phase transition. These results were interpreted in terms of the suppression of the twisting motion of the chromophores around the bridging bond in the excited singlet state. Factors affecting the photoinduced coupling of redox reactions across bilayer membrane, i.e. reduction of Fe(CN)3- 6 in outside aqueous phase of liposome and oxidation of potassium ascorbate in inside solution, are also studied using chlorophyll a incorporating liposome. It is found that phase transition exerts the influe...

Photoinduced reactions. 101. Photoinduced coupling reaction of 5-bromouridine to tryptophan derivatives

Photoinduced reactions. 101. Photoinduced coupling reaction of 5-bromouridine to tryptophan derivatives