Photoreduction of trans-4-R-4′-nitrostilbenes with R: OMe, H and NO2 by di- and trialkylamines in polar media

Görner, Helmut

doi:10.1039/b108192f

Cited by 24 publications

(23 citation statements)

References 39 publications

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“…According to Görner and Döpp [19][20][21][22], the nitro groups in these dyes are photoreduced to nitroso groups as the first step and to amino groups as the second step. The coloured products, dyes with nitroso groups, are accumulated as AS progresses, indicating that no further AS of azo compounds with the nitroso groups may occur.…”

Section: Resultsmentioning

confidence: 99%

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Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Okada

Hihara²,

Morita

2009

Coloration Technology

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The photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on nylon fabric was analysed using the Kubelka–Munk (K/S) spectra of fabrics exposed to a carbon arc in air. The exposure of dyed fabric through ultraviolet and coloured filters, which do not shield the main absorption band, showed a large decrease in the initial rate (KPA) of fading. Compared with the KPA values without filters, the values using filters were half as large for dyes without the nitro groups and a quarter as large for dyes with the nitro groups. The KPA values may be qualitatively explained by the sum of azo scission (decrease of K/S value at λmax) and the conversion of nitro groups to nitroso groups. These phenomena occur, respectively, via thermal disproportionation reactions between hydrazinyl radicals (from the azo group) and the reaction between hydrazinyl and N‐centred nitrosyl hydroxide radicals (from the nitro group). The azo scission is promoted by N‐centred nitrosyl hydroxide radicals via the latter reactions.

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Section: Resultsmentioning

confidence: 99%

“…Görner and Döpp [19][20][21][22] recently reported the photoreduction of nitro groups in aromatic compounds and showed that the nitro groups are converted into nitroso groups in the first step and into amino groups in the second step. The photoreduction of nitro groups in general has been extensively studied [23,24].…”

Section: Introductionmentioning

confidence: 99%

Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Okada

Hihara²,

Morita

2009

Coloration Technology

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“…[11] The lifetimes range from 10 ± 14 ms in ethanol to 60 ± 90 ms in dichloromethane. [11,39] For selective production of . The quantum F D in toluene was obtained from q D values using optically matched solutions (A 308 0.8) and acridine as reference F ref D 0.71.…”

Section: Methodsmentioning

confidence: 99%

Time-Resolved Spectroscopy of Sulfur- and Carboxy-Substituted N-Alkylphthalimides

Görner¹,

Griesbeck²,

Heinrich³

et al. 2001

Chem. Eur. J.

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The photophysical and photochemical properties of N-phthaloylmethionine (1), S-methyl-N-phthaloylcysteine methyl ester (2) and N-phthaloyltranexamic acid (3) were studied by time-resolved UV/Vis spectroscopy, using laser pulses at 248 or 308 nm. The quantum yield of fluorescence is low (F f`1 0 À2 ) for 1 ± 3 in fluid and glassy media, whereas that of phosphorescence is large (0.3 ± 0.5) in ethanol at À 196 8C. The triplet properties were examined in several solvents, at room temperature and below. The spectra and decay kinetics are similar, but the population of the p,p* triplet state, as measured by T ± T absorption, is much lower for 1 and 2 than for 3 or N-methyltrimellitimide (5') at ambient temperatures. The quantum yield (F D ) of singlet molecular oxygen O 2 ( 1 D g ) formation is substantial for 3 and 5' in several air-or oxygen-saturated solvents at room temperature, but small for 2 and 1. The quantum yield of decomposition is substantial (0.2 ± 0.5) for 3 and small (`0.05) for 2 and 1. It is postulated that photoinduced charge separation in the spectroscopically undetectable 3 n,p* state may account for the cyclization products of 1 and 2. In aqueous solution, this also applies for 3, whereas in organic solvents cyclization involves mainly the lower lying 3 p,p* state. Triplet acetone, acetophenone and xanthone are quenched by 1 ± 3 in acetonitrile; the rate constant is close to the diffusion-controlled limit, but smaller for benzophenone. While the energy transfer from the triplet ketone occurs for 3, a major contribution of electron transfer to the N-phthalimide derivative is suggested for 1 and 2, where the radical anion of benzophenone or 4-carboxybenzophenone is observed in alkaline aqueous solution.

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“…The azo dyes with NDH groups are then dehydrated into azo dyes with nitroso groups. (According to Görner and co-workers [21][22][23][24], the nitro groups in aromatic compounds are converted into nitroso groups in the first step of photoreduction and into amino groups in the second step via further photo-excitation. )…”

Section: Reaction Of (No 2 H) As H-acceptor With (Mhn) As H-donor To mentioning

confidence: 99%

Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric^†

Okada

Hihara

Hirose³

et al. 2010

Coloration Technology

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The initial rates of photofading for 30 disperse azo dyes on nylon fabric upon exposure to a carbon arc in air have been analysed by formulating a kinetic equation that describes azo scission via the disproportionation reactions and intramolecular H‐transfer by two kinds of hydrazinyl radicals and the conversion of a nitro group to a nitroso group via the disproportionation reaction of nitrosyl hydroxide radicals. The five reaction rate constants are discussed in terms of the heats of reaction by calculating the heats of formation for the reactants, intermediates and products of each reaction using the PM5 method. Phenylazo‐ and thiazoleazo‐N,N‐substituted anilines and phenylazo‐pyridones exhibited large rate constants of multiple terms, while phenylazo‐phenols had the highest light fastness and very small rate constants for the disproportionation reactions of hydrazinyl radicals. Photofading on nylon fabric was primarily controlled by the thermal reactions of photo‐induced monohydrogenated dye radicals, which occurred via one or two primary multiple routes.

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Photoreduction of trans-4-R-4′-nitrostilbenes with R: OMe, H and NO2 by di- and trialkylamines in polar media

Cited by 24 publications

References 39 publications

Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Time-Resolved Spectroscopy of Sulfur- and Carboxy-Substituted N-Alkylphthalimides

Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric^†

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Photoreduction of trans-4-R-4′-nitrostilbenes with R: OMe, H and NO2 by di- and trialkylamines in polar media

Cited by 24 publications

References 39 publications

Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

Time-Resolved Spectroscopy of Sulfur- and Carboxy-Substituted N-Alkylphthalimides

Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric†

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Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric^†