Spectroscopy and photochemistry of indigoid compounds. VI. Direct Trans → cis Photoisomerization of Indigoid Dyes

Haucke, G.; Paetzold, R.

doi:10.1002/prac.19793210613

Cited by 22 publications

(25 citation statements)

References 15 publications

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“…Cibalackrot and its synthetic precursor (preCiba) were prepared according to literature methods. 26,27 A brief description of the synthesis and of spectral identification can be found in the Supporting Information (SI).…”

Section: Methodsmentioning

confidence: 99%

“…Its synthesis was described by Engi in 1911 (from the Gesellschaft fuer Chemische Industrie in Basel) 25 and Posner 26 and its basic fluorescent properties studied by Birckner, Hauke and Paetzold. 27,28 More recently, laser flash photolysis and fluorescence results have been presented. 29 Besides these works, only two Japanese patents on it as an electrophotographic photoreceptor 30,31 and an optoelectronic device 31 with high-energy conversion efficiency are found in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

et al. 2006

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Spectral and photophysical properties of the indigo derivative Cibalackrot in keto and reduced (leuco) forms were studied by absorption spectra, fluorescence and pulse radiolysis and compared with the structurally similar indigo. With the keto form of this dye, fluorescence (φ F ) 0.76) and intersystem crossing (φ T ) 0.11) are dominant, whereas with indigo, efficient internal conversion (φ IC ) 0.99) is observed, probably involving proton transfer through intramolecular hydrogen bonds. With Cibalackrot, this pathway is blocked, supporting the above model for indigo. With the reduced form of Cibalackrot, more than 98% of the absorbed quanta are dissipated through S 1 ∼∼f S 0 internal conversion, which contrasts with leuco-indigo, where fluorescence (φ F ) 0.35), internal conversion (φ IC ) 0.53) and intersystem crossing (φ T ) 0.12 5 ) are found to be competitive. In addition, a synthetic precursor of Cibalackrot (preCiba) was also investigated. This has a rigid molecular structure (with a moiety identical to Cibalackrot and the other to indigo), but intra-or intermolecular proton transfer is allowed between adjacent carbonyl and N-H groups. With this precursor in its keto structure the photophysical parameters are generally very close to those of the keto form of indigo, and different from those of Cibalackrot. A more detailed investigation of the time-decay profiles of preCiba in dioxane (and with added water and D 2 O) has shown that these follow biexponential laws with a shorter component of 14-25 ps, which appears associated with a risetime at longer wavelength emissions (and to a positive preexponential at shorter emission wavelengths) and a longer lived (decay) component of 104-130 ps. In the steady-state spectra of preCiba, the variation with temperature reveals a blue shift of the emission maxima, which is interpreted as the presence (simultaneous emission) of two species (keto and enol) in the excited state. Indigo and deuterated indigo are also found to present a similar behavior. The overall data are interpreted as to be due to an excited-state process involving the proton transfer between keto and enol forms. Rate constants with values of 7 × 10 10 s -1 for preCiba and 1.6 × 10 11 s -1 for deuterated indigo were obtained. This inverse isotope effect is justified on the basis of the proposed model for proton-transfer excited-state deactivation.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

et al. 2006

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“…Thus, unlike the thioindigo derivatives for which the bans to cis isomerization could be partly quenched by oxygen (20), compounds 1 t -3 t apparently isomerize solely from the singlet excited state.…”

Section: A Excited State Involved In the Isomerizationmentioning

confidence: 96%

“…It is known that the isomerization of stilbenes results from a singlet excited state (10,16) and that for thioindigo derivatives, molecules which are closely related to the series studied here, it depends on the geometry of the starting material with the trans isomer undergoing a photoisomerization via the triplet excited state (17)(18)(19), while the reverse photochemical reaction occurs from the singlet state (20,21). When the c -, t isomerization of thioindigo derivatives was studied in a toluene-containing solution, the isomerization quantum yield was found to vary with the temperature and to reach a maximum value (ca.…”

Section: A Excited State Involved In the Isomerizationmentioning

confidence: 99%

“…In the case of trans-thioindigo, different mechanisms have been postulated for the rotation process; in the first one, the isomerization occurs from the singlet excited state through the twisted state which subsequently can undergo the intersystem crossing to the triplet excited state (20); in the second one, the planar singlet excited state crosses over to the triplet excited state which then undergoes the internal rotatioil to the twisted form (27).…”

Section: A Excited State Involved In the Isomerizationmentioning

confidence: 99%

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Photoisomerization of N,N′-disubstituted indigos. A search for energy storage

Pouliquen¹,

Wintgens²,

Toscano³

et al. 1984

Can. J. Chem.

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The photochemical behaviour of N,N1-disubstituted indigo dyes has been investigated. The trans to cis and cis to trans photoisomerization quantum yields are found to be of the order of 0.25 or less (down to 0.03). These dyes, which fluoresce only weakly in solution and at room temperature, show a drastic increase in their fluorescence when inserted into a polymer matrix or at 77 K in butyronitrile glass. This has been interpreted in terms of the inhibition of formation of a twisted excited intermediate as well as of the rotation of the substituent on the nitrogen atom. An important electron transfer occurs from the singlet excited state when the indigo dyes are placed in the presence of electron-donating molecules. When irradiating with visible light, the photostationary state is always in favour of the trans isomers. This, and kinetic as well as thermodynamic considerations, excludes these compounds as candidates for solar energy storage.JOSEPH POULIQUEN, VERONIQUE WINTGENS, VICENTE TOSCANO, BRAHIM BEN JAAFAR, SADHANA TRIPATHI, JEAN KOSSANYI et PIERRE VALAT. Can. J. Chem. 62, 2478 (1984.Le comportement des indigos substituks 1-4 a kt6 examink. On trouve que les rendements quantiques de photoisomerisation sont faibles (de l'ordre de, ou infkrieurs 9, 0,20). Ces composks qui fluorescent faiblement en solution et B 20°C, prksentent une augmentation considkrable de leur fluorescence quand ils sont inclus dans un polymkre ou bien lorsque la tempkrature est abaisske B 77 K dans le butyronitrile. Ceci a kt6 interpret6 comme un empschement a la rotation autour de la double liaison centrale, et comme une gene i la rotation du substituant sur l'azote ainsi que de l'inversion de cet atome. L'irradiation en lumi2re blanche est toujours en faveur des isomkres trans. Ceci, ainsi que des considkrations cinktiques et thermodynamiques excluent ces composks pour le stockage de l'tnergie solaire. IntroductionIn the search for new sources of energy, photochemical transformations have been examined as a potential means of obtaining energy-rich stable products. Criteria for efficient photochemical conversion of solar energy are: absorption in the visible or near-ultraviolet region, high quantum efficiencies, large positive ground state enthalpies, and stable photoproducts. In addition, the reactant must be inexpensive and not dangerous.The importance of dyes has been widely recognized in different converting systems related to photobiology (1,2), photoelectrochemistry (3, 4), and photochemistry (5).Photochemical systems mostly involve (Fig. 1) absorption of visible light by a reagent R to produce a high energy content product P which can later release the stored energy while reverting to the starting material. Among the systems reported thus far, one finds intramolecular cycloadditions (the best system investigated seems to be the norbornadiene-quadricyclane one (6) which can store about 26 kcal/mol(7)) and valence isomerization (such as the photochemical transformation of 1-methyl 5-phenyl A-2 pyrazoline into 2-phenylcyclopropylazo...

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25th Anniversary Article: Progress in Chemistry and Applications of Functional Indigos for Organic Electronics

2013

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Indigo and its derivatives are dyes and pigments with a long and distinguished history in organic chemistry. Recently, applications of this 'old' structure as a functional organic building block for organic electronics applications have renewed interest in these molecules and their remarkable chemical and physical properties. Natural-origin indigos have been processed in fully bio-compatible field effect transistors, operating with ambipolar mobilities up to 0.5 cm(2) /Vs and air-stability. The synthetic derivative isoindigo has emerged as one of the most successful building-blocks for semiconducting polymers for plastic solar cells with efficiencies > 5%. Another isomer of indigo, epindolidione, has also been shown to be one of the best reported organic transistor materials in terms of mobility (∼2 cm(2) /Vs) and stability. This progress report aims to review very recent applications of indigoids in organic electronics, but especially to logically bridge together the hereto independent research directions on indigo, isoindigo, and other materials inspired by historical dye chemistry: a field which was the root of the development of modern chemistry in the first place.

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Spectroscopy and photochemistry of indigoid compounds. VI. Direct Trans → cis Photoisomerization of Indigoid Dyes

Cited by 22 publications

References 15 publications

Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

Photoisomerization of N,N′-disubstituted indigos. A search for energy storage

25th Anniversary Article: Progress in Chemistry and Applications of Functional Indigos for Organic Electronics

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