Azomethine Dyes Research Articles

Effect of the solvent on reduction of azomethine dyes with ketyl radicals and recombination of ketyl radicals

The rate constants of transfer of a hydrogen atom from ketyl radicals to azomethine dyes (kH) and the rate constants of recombination of ketyl radicals (2kr) in different solvents were measured by the method of pulsed photolysis. The dependences of kH and 2kr on the polarity of the solvent are V-shaped: kH and 2kr are maximum in weakly solvating solvents and in water and are minimum in nucleophilic solvents of medium polarity. This is due to the fact that nucleophilic solvation decreases and electrophilic solvation increases the reactivity of the ketyl radicals.

Kinetic isotope effect in the transfer of a hydrogen atom from a ketyl radical to an azomethine dye

1. The kinetic isotope effect in the transfer of a hydrogen atom from a ketyl radical to an azomethine dye in alcohol solvents reaches 4.2, which points to a considerable weakening of the O-H bond of the ketyl radical in the transition state. The kinetic isotope effect is reduced when the Hammett σ-constant of the substituent on the ketyl radical decreases and is almost independent of the structure of the dye. 2. The kinetic isotope effect in toluene and in water is considerably lower than in alcohols (1.6–1.7) which is evidence of the asymmetry and nonlinearity of the transition state in the hydrogen transfer reaction.

Fading of Colour Photographic Dyes III-Isolation and Identification of Reductive Fading Products of 1-phenyl-3-methyl-4-aza-(p-diethylaminophenyl)-2-pyrazoline-4,5-dione by Bisulphite

In order to confirm the fading reaction mechanisms of magenta azomethine dyes in the presence of bisulphite and thiosulphate ions, a faded material was synthesized from viewpoint of organic chemistry. Then identification was made on the compound by means of elemental and spectroscopic analyses. The colourless compound prepared was proven to be an adduct of dye and bisulphite ion hydrated with one molecule of water, and to be identical with the faded product observed in situ by Miyagawa et al according to spectroscopic analysis. Kinetic and thermodynamic parameters of the formation of the colourless compound are also provided in this paper to confirm the above result.

On the Dark Stability of the Magenta Azomethine Dye Image Obtained from Two-Equivalent Pyrazolone Couplers

Dark stability of the magenta dye image obtained from 2-equivalent 3-acylamino-5-pyrazolone couplers was investigated from the viewpoint of the reaction of the magenta dye with the residual coupler.A correlation was found between the reaction rate and the pKa values of the starting 3acylamino-5-pyrazolone couplers, i.e., the couplers with the lowest pKa values showed the least reactivity. This observation suggests that the reaction proceeds via an ionic reaction mechanism rather than by a radical reaction mechanism.The use of couplers with low pKas for colour negative film makes it possible to remove formaldehyde from the stabilizing bath in colour negative processing.

Photochemistry of Pyrazolotriazole Azomethine Dyes

AbstractSinglet and triplet state properties of pyrazolotriazole azomethine dyes have been examined using absorption, fluorescence, and flash photolysis techniques. Second derivative absorption spectroscopy and emission polarization studies suggest that the visible absorption band of these compounds is a single electronic transition and that the structure seen in non-polar solvents is vibronic. Room temperature emission is very weak, with quantum yields of ca. 1x 10-4 Triplet state energies of ca. 100-118 kJ mol-1 have been obtained from energy transfer studies and a lower limit of 10 ns has been estimated for the triplet state lifetime.

Untersuchungen zur Reaktion von Pyrazolon‐Azomethin‐Farbstoffen mit 2‐Pyrazolin‐5‐on‐Derivaten

Investigations on the Reaction of Pyrazolone Azomethine Dyes with 2‐Pyrazolin‐5‐one‐DerivativesThe reaction between pyrazolone azomethine dyes 1 and different 2‐pyrazolin‐5‐ones 2 was investigated. Among the reaction products compounds 5 {3,3′3″‐trimethyl‐1,1′1″‐triphenyl‐[4,4′4″‐tri‐(2‐pyrazolin‐5‐on)]} was isolated, which hitherto was unknown as a product of this reaction. A new reaction pathway is proposed.

Fotosensibilisierte Ausbleichung von Azomethinfarbstoffen

Fotosensitized Fading of Azomethine DyesThe quantum yields of photofading of the azomethine dyes 1a—h were determined in the presence of the sensitizers benzophenone (B), michler's ketone (MK) and anthracen (A), in isopropanol and benzene. In isopropanol, excluding oxygen, the leuco dyes 5 are formed by benzophenone in high quantum yield (Φ = 0.4). Photofading also takes place using Michler's ketone (Φ ≅ 3 · 10−3) and anthracene (Φ ≅ 1 · 10−4), but 5 was not found. With benzophenone (Φ ≅ 7 · 10−3), Micher's ketone (Φ ≅ 1 · 10−3) and anthracene (Φ ≅ 1 · 10−4) as sensitizers the chromophore of 1a—h were destroyed, when oxygen was present. The photofading with benzophenone and Michler's ketone is a result of radicalic processes.Radical scavangers 8 and 9, therefore, give a strong decrease of the quantum yield of photofading. The photofading in benzene corresponds to the results in isopropanol considering the lower potential of this solvent for photoreduction processes.

Study of the mechanism of the photoreduction of azomethine dyes sensitized by carbonyl compounds

1. The process of transfer of hydrogen from ketyl radicals to azomethine dyes proceeds through a transition state (or intermediate complex) with charge transfer from ketyl radicals to the dyes. 2. Azomethine dyes — derivatives of anilides of acylacetic acids — are far less active in the reaction with ketyl radicals than pyrazolone dyes. 3. The reducing activity of the radicals with respect to azomethine dyes decreases in the series: ketyl of acetone > ketyl of acetophenone > ketyl of benzophenone > neutral semiquinone radicals.

Azomethinfarbstoffe ‐ Sensibilisatoren, Löscher und Reaktionspartner für Singulettsauerstoff

Azomethine Dyes — Sensitizers, Quenchers and Reaction Partner for Singlet OxygenAzomethine dyes show photofading in photographic materials, possibly due to oxidation by singlet oxygen. The azomethine dyes 1a–h, 2a–h, 3c, d, f are inefficient photosensitizers of singlet oxygen formation. In tetrachloromethane the quantum yield ϕ1O2 is in the range between 8 · 10−4 and 4 · 10−3.Contrary to the literature we found that azomethine dyes react with 1O2 (kr). The reaction constants were measured by a competetive technique using 9, 10‐diphenyl anthracene and methylene blue as 1O2 sensitizer. The values of kr show that the reaction of the dyes with 1O2 can not be ignored. Besides this reaction, 1O2 is also quenched by the dyes (kq). The values of kq point to quenching of 1O2 by the tertiary amino group of the dyes via a CT‐mechanism. This study shows that in photofading of azomethine dyes the oxydation by 1O2 must be taken into consideration.

Spektralverhalten von Pyrazolin‐5‐on‐Azomethinfarbstoffen – Quantenchemische Beschreibung der Substituenteneinflüsse

Absorption Behaviour of Pyrazoline‐5‐one Azomethine Dyes – Quantumchemical Description of the Influence of SubstituentsThe VIS absorption of the pyrazoline‐5‐one azomethine dyes 1a–h is measured in dependence of the substituents of the amino group.HMO calculations confirm that the „x‐ and y‐bands”︁ have a strong charge transfer character. The absorptions in the visible region correspond to a transition from the HOMO mainly localized at the amino‐substituted phenyl to the complex acceptor 4‐imino‐pyrazoline‐5‐one (“x‐band”) or to the pyrazoline‐5‐one fragment (“y‐band”). The calculated transition energies correlate with the values νmax of the x‐band (r = 0.993). There is also a linear correlation between the square of the LCAO‐MO coefficients in position 7 and 6 of the dye and εmax (r = 0.978).

Fading Mechanism of Azomethine Dyes for Image Formation in Color Photography: Reaction Mechanism of Photo-fading of Model Dyes with Benzophenone in Ethanol

Fading Mechanism of Azomethine Dyes for Image Formation in Color Photography: Reaction Mechanism of Photo-fading of Model Dyes with Benzophenone in Ethanol

Kinetics and Mechanism of the Reaction between 4,4'-Aryl- methyIidene-Bis-2-Pyrazoline-5-Ones and Quinonediimines

AbstractThe second order rate constants of the dye formation from 4,4'-arylmelhylidene-bis-2-pyrazoline-5-ones B with quinone-diimine QDI are determined. From the dependence of the rate constants on the substituents in the arylmethylidene bridge and in the pyrazoline-5-one ring as well as from the dependence on the ionic strength it follows that the leuco dye formation LD is the ratedetermining step of dye formation. The azomethine dye D and the 4-arylmethylidene-2-pyrazoline-5-one S are formed from the leuco dye i.D with the same rate. 4-Arylmethylidene-2-pyrazoline-5-one S hydrolyzes under the coupling conditions in a pseudo first order reaction. The comparatively slow hydrolysis of S limits further dye formation.

Oxidative Kupplung von 5‐Amino‐pyrazolen mit p‐Phenylendiaminen

Oxidative Coupling of 5‐Aminopyrazoles with p‐PhenylenediaminesBy oxidative coupling of 5‐amino‐3‐methyl‐1‐phenyl‐pyrazole 4 with N,N‐diethyl‐p‐phenylenediamine the 4‐(4‐N,N‐diethylamino‐phenylimino)‐3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐imin 5 is formed. 5 is oxidized very easily to the 1H‐pyrazolo[3,4‐b]quinoxaline 6a. The Z/E‐isomerism of the azomethine dye is investigated by dynamic n.m.r.‐spectroscopy. 1H‐Pyrazolo[3,4‐b]quinoxalines (6a–d) are also formed by reaction of 1,3‐disubstituted 5‐aminopyrazoles with p‐nitroso‐dialkylanilines.

Synthese von 1,2,4‐Benzotriazin‐3‐ylessigsäureestern und‐amiden

Synthesis of 1,2,4‐Benzotriazine‐3‐acetates and ‐acetamidesSubstituted 1,2,4‐benzotriazine‐3‐acetates 6 are prepared by the reduction of (2‐nitrophenyl)hydrazonoethers 4 or (2‐nitrophenyl)amidrazones 5. The 1,2,4‐benzotriazin‐3‐ylacet‐anilid 9g forms a yellow azomethine dye 10 by oxidative coupling with N,N‐diethyl‐p‐phenylenediamine.

Photoreduction of azomethine and indoaniline dyes sensitized by benzophenone

1. The highly efficient photodecomposition of azomethine and indoaniline dyes occurs in the presence of benzophenone as a result of their reduction of ketyl radicals formed in the system. 2. The intermediate in the reduction of these dyes, AH radical, participates in the acid-base equilibrium and loses a proton in alkaline media.

Oxidative Kupplung CH‐acider Verbindungen mit p‐Phenylendiaminen. III [1]. Reaktivität 4‐substituierter 3‐Methyl‐1‐phenyl‐pyrazolin‐5‐one gegenüber N,N‐Diethylchinondiimin

Oxidative Coupling of CH‐acid Compounds with p‐Phenylene Diamines. III. Reactivity of 4‐Substituted 3‐Methyl‐1‐phenyl‐pyrazolin‐5‐ones with N,N‐Diethyl‐quinone‐(1,4)‐diimineSubstitution products 2–28 of 3‐methyl‐1‐phenyl‐pyrazolin‐5‐one 1, with a wide variety of substituents in the 4‐position, were synthesized. Most of these compounds react with N,N‐diethyl‐quinone‐(1,4)‐diimine by elimination of the substituent giving the same azomethine dye as that formed by oxidative coupling of the 4‐unsubstituted compound. A study of the influence of side reactions by measurement of dye yields has been undertaken.

ChemInform Abstract: AZOMETHINE AND MEROCYANINE DYES BASED ON 3‐ARYLBENZO(F)QUINOLINIUM SALTS AND THEIR SPECTRAL AND ELECTROPHOTOGRAPHIC PROPERTIES

AbstractDie Lepidinderivate (I) reagieren mit 1‐Nitroso‐2‐naphthol (II) zu Azomethinen (III).

Azomethine and merocyanine dyes based on 3-arylbenzo[f]quinolinium salts and their spectral and electrophotographic properties

Azomethine dyes were obtained by reaction of 1-methyl- and 1,2-dimethyl-3-arylbenzo[f]quinolinium methiodides with 1-nitroso-2-naphthol. Merocyanine dyes were isolated by the action of KOH on 2-hydroxy-5,6-benzostyryl derivatives of 3-arylbenzo[f]quinolinium salts. The absorption spectra of the dyes in ethanol and chloroform are presented, and it is shown that, as compared with the spectra of the merocyanines, there is a bathochromic shift of the absorption bands in the spectra of the azomethine dyes. The azomethine and merocyanine dyes have solvatochromic properties and display photosensitivity in the UV and visible regions when they are introduced into a polymer matrix.

Excited-state multiplicity for the direct photochemical isomerization of azomethine dyes

Excited-state multiplicity for the direct photochemical isomerization of azomethine dyes

A model for the triplet state photochemical isomerization of azomethine dyes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA model for the triplet state photochemical isomerization of azomethine dyesWilliam G. HerkstroeterCite this: J. Am. Chem. Soc. 1976, 98, 2, 330–336Publication Date (Print):January 1, 1976Publication History Published online1 May 2002Published inissue 1 January 1976https://doi.org/10.1021/ja00418a003RIGHTS & PERMISSIONSArticle Views131Altmetric-Citations33LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (793 KB) Get e-Alerts Get e-Alerts