The Relation between the Absorption Spectra and the Chemical Constitution of Dyes XXII. cis-trans Isomerism in Thioindigo Dyes<sup>1</sup>

Wyman, George M.; Brode, Wallace R.

doi:10.1021/ja01148a023

Cited by 95 publications

(31 citation statements)

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“…The photostability of indigo was attributed originally to the lack of trans – cis photoisomerization 7. In contrast, indigo derivatives like thioindigo ( 2 ) readily isomerize about the central double bond8 and, unlike indigo, show strong fluorescence 9. It was proposed that the trans isomer of indigo is stabilized by hydrogen bonds formed between the NH and CO groups connecting the two halves of the molecule 7.…”

Section: Photoisomerization Of Indigo Dyes In Different Solvents[a]mentioning

confidence: 99%

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

et al. 2013

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The photochemical properties of indigo, a widely used industrial dye, has attracted both experimentalists and theoreticians from the beginning. Especially the high photostability of indigo has been the subject of intensive research. Recently, it was proposed that after photoexcitation an intramolecular proton transfer followed by a nonradiative relaxation to the ground state promote photostability. In indigo the hydrogen bond and the proton transfer occur between the opposing hemiindigo parts. Here, we provide experimental and theoretical evidence that a hydrogen transfer within one hemiindigo or hemithioindigo part is sufficient to attain photostability. This concept can serve as an interesting strategy towards new photostable dyes for the visible part of the spectrum.

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Section: Photoisomerization Of Indigo Dyes In Different Solvents[a]mentioning

confidence: 99%

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

et al. 2013

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“…5,6 For indigo derivatives in which the intramolecular hydrogen bonds are missing, on the other hand, the cis isomer is readily generated by photoexcitation. [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.…”

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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“…The spatialc ontrol exerted by azobenzenes, however,i sl imited by the low barriers of rotation aroundt he CÀNs ingleb onds, which contribute to aw ide distribution of geometries particularly for the cis isomer [8] and similar limitationsa pply to most other available water-soluble photochromic compounds, fore xample,f ulgimides. [9] In contrast, superior spatial controli so ffered by thioindigos (Scheme 1a), the photochemistry andp hotophysics of which have been studied in great depth particularly in the 1970s by the groups of Wyman, [10][11][12][13] Lüttke, [14,15] and Paetzold, [16,17] but which have received less attention in the last decades. [18] Thioindigos interconvert betweenthe trans and the metastable cis isomer by an ear1 808 rotationa round the central double bond.…”

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confidence: 99%

Reversible Spatial Control in Aqueous Media by Visible Light: A Thioindigo Photoswitch that is Soluble and Operates Efficiently in Water

Koeppe

Römpp

2018

Chemistry A European J

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Aiming to extend the scope of indigoid photoswitches to polar protic environments, we have synthesized a sulfonated thioindigo derivative highly soluble in water. Studies by UV/Vis absorption, fluorescence, and NMR spectroscopy indicate that, despite aggregation effects at micromolar concentrations, the novel dye offers satisfactory performance in aqueous solution in the absence of solvation aides. Enrichment of the metastable cis isomer by irradiation may exceed 65 % and its half-life at room temperature may exceed several hours. Degradation after 20 yellow and blue light irradiation cycles within 2 hours is less than 2 %. Performance can be expected to further improve in future molecular designs if the tendency towards self-association is further reduced. Crucially, photoisomerization of indigoids is not necessarily inhibited by water and, thus, the superior spatial control offered by this class of molecular switches may be of great benefit also in biological systems.

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The Relation between the Absorption Spectra and the Chemical Constitution of Dyes XXII. cis-trans Isomerism in Thioindigo Dyes¹

Cited by 95 publications

References 0 publications

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

Molecular mechanisms of the photostability of indigo

Reversible Spatial Control in Aqueous Media by Visible Light: A Thioindigo Photoswitch that is Soluble and Operates Efficiently in Water

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The Relation between the Absorption Spectra and the Chemical Constitution of Dyes XXII. cis-trans Isomerism in Thioindigo Dyes1

Cited by 95 publications

References 0 publications

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

Photostability of 4,4′‐Dihydroxythioindigo, a Mimetic of Indigo

Molecular mechanisms of the photostability of indigo

Reversible Spatial Control in Aqueous Media by Visible Light: A Thioindigo Photoswitch that is Soluble and Operates Efficiently in Water

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The Relation between the Absorption Spectra and the Chemical Constitution of Dyes XXII. cis-trans Isomerism in Thioindigo Dyes¹