Picosecond absorption spectroscopy of the fluorescent state of trans-thioindigo

Krysanov, S.A.; Алфимов, М. В.

doi:10.1016/0047-2670(83)87005-1

Cited by 2 publications

(3 citation statements)

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“…The excited state dynamics of such a dye involve photoisomerization and a triplet excited state. The transient bands at 440 and 610 nm were, however, both assigned to a singlet → singlet transitions from the trans isomer . Thus, based on the previous result for thioindigo and indigo carmine, the band at 640 nm observed in the TA spectra of indigo is assigned to a singlet → singlet transition.…”

Section: Resultssupporting

confidence: 50%

“…Indigo transient species were previously studied by time-resolved fluorescence , and also by TA; however, the literature only reports the band at 455 nm, which corresponds to the S 1 → S n electronic transition . Regarding the band at 640 nm, TA studies with indigo carmine (a sulfonated indigo derivative) also detected two absorption bands (465 and 645 nm in DMF) both assigned to singlet → singlet absorption by comparison with picosecond spectroscopy data for trans -thioindigo. ,− The photochemistry of trans -thioindigo was intensely studied since its high cis–trans photoisomerization rate makes it a possible dye for optical storage materials . The excited state dynamics of such a dye involve photoisomerization and a triplet excited state.…”

Section: Resultsmentioning

confidence: 99%

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Time-Resolved Spectroscopy of Indigo and of a Maya Blue Simulant

et al. 2016

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Maya Blue is a puzzling pigment found in objects produced by the ancient Maya civilization. It is a combination of indigo and palygorskite, and it is well-known for the high chemical and photochemical stability of the dye promoted by the clay confined environment. This pigment has survived over 1500 years, and it was first thought to be purely inorganic. The reasons for such stability have been investigated over the past years, and it may involve hydrogen bonds, complexation, and oxidation to dehydroindigo. However, these theories are not completely understood, and more evidence about indigo/palygorskite interactions must be obtained. In this study indigo and a Maya Blue simulant pigment were, for the first time, studied by transient absorption (TA) and time-resolved infrared (TRIR) spectroscopy. From such analysis it was possible to investigate the electronic excited states of indigo and the photochemistry behavior of the dye when interacting with the palygorskite. Concerning the TRIR measurements, the shifts of the C O and N−H vibrations indicate that hydrogen bonds are formed involving the dye and the coordinated water molecules present in the clay. Furthermore, a red shift is observed in the absorption of electronic ground state (50 nm) and also in the electronic excited state (27 nm) of Maya Blue simulant, suggesting that the excited states are stabilized by the clay. Indigo in DMSO solution presents a lifetime of ca. 120 ps while in the clay it becomes much shorter, ca. 3 ps. The shorter lifetime and also the red shift observed in the TA results suggest a stabilization of the first electronic excited state, which promotes a more efficient energy relaxation through conical intersection and, as a consequence, a faster excited state decay. Such factors can be important for the Maya Blue photostability, as they are also believed to be responsible for the high photostability of DNA and melanin.

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Section: Resultssupporting

confidence: 50%

Section: Resultsmentioning

confidence: 99%

Time-Resolved Spectroscopy of Indigo and of a Maya Blue Simulant

et al. 2016

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“…It has been found that the S 1 lifetimes of indigo as well as of its ringsubstituted compounds, such as indigo carmine (5,5'-indigodisulfonic acid disodium salt) or Tyrian purple (6,6'-dibromoindigo), are of the order of several tens or hundreds of picoseconds in the natural keto form. 23,24,[26][27][28][29][30] The excited-state lifetime of indigo is much shorter than the S 1 lifetimes of the leuco (reduced) form of indigo, 23,31 dehydroindigo (the oxidized form of indigo), 32 as well as other derivatives, such as thioindigo, 13,20,27,33 which are of the order of nanoseconds. These findings suggest that particularly efficient radiationless decay mechanisms exist in indigo which are responsible for its exceptional photostability.…”

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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Picosecond absorption spectroscopy of the fluorescent state of trans-thioindigo

Cited by 2 publications

References 10 publications

Time-Resolved Spectroscopy of Indigo and of a Maya Blue Simulant

Time-Resolved Spectroscopy of Indigo and of a Maya Blue Simulant

Molecular mechanisms of the photostability of indigo

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