Laser flash studies of thioindigo and indigo dyes. Evidence for a trans configuration of the triplet state

Görner, Helmut; Schulte‐Frohlinde, D.

doi:10.1016/0009-2614(79)85035-6

Cited by 41 publications

(22 citation statements)

References 14 publications

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“…[5][6][7][8][9][10][11][12][13][14] For these indigo derivatives, it has been proposed that triplet states are involved as intermediates in the trans → cis photoisomerization process. [15][16][17][18][19][20][21][22] Indigo itself, however, exhibits a very low quantum yield of intersystem crossing. [23][24][25] Another experimental observation related to the photostability of indigo is the extremely short lifetime of the lowest excited singlet state.…”

Section: Introductionmentioning

confidence: 99%

Molecular mechanisms of the photostability of indigo

Yamazaki

Sobolewski

Domcke

2011

Phys. Chem. Chem. Phys.

135

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The photophysics of indigo as well as of bispyrroleindigo, the basic chromophore of indigo, has been investigated with ab initio electronic-structure calculations. Vertical electronic excitation energies and excited-state potential-energy profiles have been calculated with the CASSCF, CASPT2 and CC2 methods. The calculations reveal that indigo and bispyrroleindigo undergo intramolecular single-proton transfer between adjacent N-H and C=O groups in the (1)ππ* excited state. The nearly barrierless proton transfer provides the pathway for a very efficient deactivation of the (1)ππ* state via a conical intersection with the ground state. While a low-lying S(1)-S(0) conical intersection exists also after double-proton transfer, the latter reaction path exhibits a much higher barrier. The reaction path for trans→cis photoisomerization via the twisting of the central C=C bond has been investigated for bispyrroleindigo. It has been found that the twisting of the central C=C bond is unlikely to play a role in the photochemistry of indigo, because of a large potential-energy barrier and a rather high energy of the S(1)-S(0) conical intersection of the twisted structure. These findings indicate that the exceptional photostability of indigo is the result of rapid internal conversion via intramolecular single-proton transfer, combined with the absence of a low-barrier reaction path for the generation of the cis isomer via trans→cis photoisomerization.

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Section: Introductionmentioning

confidence: 99%

Molecular mechanisms of the photostability of indigo

Yamazaki

Sobolewski

Domcke

2011

Phys. Chem. Chem. Phys.

135

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“…For thioindigo a fluorescence quantum yield Φ F = 0.7 has been reported at room temperature [2]. In solution the decay to the triplet and isomerization to the cis form compete with fluorescence [3][4][5]. Isomerization and thermally activated radiationless decay should be less important in the rigid matrix at liquid helium temperature, and hence an increase of the fluorescence quantum yield is expected.…”

Section: Applicationsmentioning

confidence: 95%

Design and Performance of a Miniature Cryostat for Emission Measurements in Liquid Helium

Jasny¹,

Slenczka²,

Dick³

2001

Zeitschrift Für Physikalische Chemie

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“…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%

“…N O characterization of the triplet of the trans isomers could be obtained, even by laser flash photolysis using a ruby laser, although the T-T absorption spectra of 1 t has already been found (27). Indeed.…”

Section: A Excited State Involved In the Isomerizationmentioning

confidence: 99%

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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Laser flash studies of thioindigo and indigo dyes. Evidence for a trans configuration of the triplet state

Cited by 41 publications

References 14 publications

Molecular mechanisms of the photostability of indigo

Molecular mechanisms of the photostability of indigo

Design and Performance of a Miniature Cryostat for Emission Measurements in Liquid Helium

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

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