cis-trans Isomerization and Pulsed Laser Studies of Substituted Indigo Dyes

Giuliano, C. R.; Hess, L. D.; Margerum, J. D.

doi:10.1021/ja01005a600

Cited by 61 publications

(39 citation statements)

References 4 publications

(7 reference statements)

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“…[23][24][25] For some indigo derivatives such as thioindigo, however, it has been proposed that triplet states are involved as intermediates in the trans → cis photoisomerization. [15][16][17][18][19][20][21][22] The first-principles investigation of the photochemistry in the triplet manifold should therefore be of interest for these derivatives of indigo.…”

Section: Potential-energy Profiles Of Trans → Cis Photoisomerizationmentioning

confidence: 99%

“…[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%

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Molecular mechanisms of the photostability of indigo

Yamazaki

Sobolewski

Domcke

2011

Phys. Chem. Chem. Phys.

131

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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: Potential-energy Profiles Of Trans → Cis Photoisomerizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular mechanisms of the photostability of indigo

Yamazaki

Sobolewski

Domcke

2011

Phys. Chem. Chem. Phys.

131

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“…Its photostability has been well documented. [43] Upon N-alkylation (9 b, i.e., removal of hydrogen bonding) isomerization becomes an efficient process, [44] presumably by OBF because of the absence of a vinyl CÀH unit necessary for HT (Scheme 12). Scheme 12. However, with a C À H unit on the double bond (at C5 and C16), bilirubin should be able to undergo the volume conserving HT process without immediately disrupting the H-bond network.…”

Section: Other Systemsmentioning

confidence: 99%

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Liu

Hammond²

2001

Chem. Eur. J.

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ALiu and Hammond recently reasoned that the hula-twist (HT), a volume-conserving cis-trans isomerization mechanism, is involved in reactions of confined systems. We now show that HT can be applied to various reported photochemical isomerization of chromophores (small organic systems as well as photoactive bio-pigments). The results, when taken as a whole, argue powerfully that HT is a common supramolecular photoisomerization reaction mechanism.

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“…These derivatives have thermal barriers for cis to trans isomerization high enough to observe the photoisomerization unambiguously by UV/vis and 1 H NMR spectroscopy. Manipulation of the kinetics of the thermal cis to trans isomerization by acidic or basic additives were already reported for N,N’ ‐diacetyl and N,N ’‐dimethyl indigo . Kinetic analysis in THF revealed, that the speed of the thermal cis to trans isomerization of mono‐arylated indigo is highly dependent on the amount of water in the solvent.…”

Section: Introductionmentioning

confidence: 85%

Photoisomerization of Mono‐Arylated Indigo and Water‐Induced Acceleration of Thermal cis‐to‐trans Isomerization

2018

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Substituted indigo derivatives undergo photoisomerization of the central double bond if both nitrogen atoms are functionalized. Indigo itself however does not photoisomerize because of a competing and highly efficient excited‐state proton transfer. In this work, we show that also mono‐arylated indigo undergoes photoisomerization despite still possessing one nitrogen‐bound proton and the likely presence of a competing intramolecular excited‐state proton transfer. The two different isomers exhibit strongly different absorptions and therefore can be distinguished by the naked eye. Different to diaryl‐substituted indigo, thermal decay of the metastable cis isomers of mono‐arylated derivatives can be greatly accelerated by small amounts of water (by more than a factor of 300 for measured half‐lives). Such tunability is of high interest for applications that require quick and autonomous switching‐off of photoresponsive trigger units.

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cis-trans Isomerization and Pulsed Laser Studies of Substituted Indigo Dyes

Cited by 61 publications

References 4 publications

Molecular mechanisms of the photostability of indigo

Molecular mechanisms of the photostability of indigo

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Photoisomerization of Mono‐Arylated Indigo and Water‐Induced Acceleration of Thermal cis‐to‐trans Isomerization

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