Photoisomerization mechanism of thioindigo dyes. Thioindigo in nonpolar solvents

Karstens, Ties; Kobs, K.; Memming, R.; Schröppel, F.

doi:10.1016/0009-2614(77)85088-4

Cited by 14 publications

(4 citation statements)

References 9 publications

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“…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%

“…13,26−28 The photochemistry of trans-thioindigo was intensely studied 29 since its high cis−trans photoisomeriza-tion rate makes it a possible dye for optical storage materials. 30 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.…”

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: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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

et al. 2016

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“…The spectral and photophysical properties of the two molecules, however, differ significantly, which in the 1950s led to extensive studies of the excited-state behavior of thioindigo. − More recently, indigo has also become the subject of photophysical investigation. − Because of its intense fluorescence, thioindigo has been explored as a dye for fluorescent solar collectors. , Thioindigos have also been investigated as organic semiconductors and charge generation devices. , Additionally, thioindigo is a photochromic compound, undergoing photoinduced trans–cis isomerization. The photoinduced isomerization has been studied in solution, − monolayers, and thin films , and on solid support . The application of the trans–cis isomerization in liquid crystals , and ion transport has also been investigated.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Photophysics of Thioindigo Diimines and Related Compounds

et al. 2014

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We report the synthesis and comprehensive characterization of diamine and diimine derivatives of the fluorescent compound thioindigo. Diamines 1 were obtained by metal-mediated amine condensation reaction with thioindigo. Oxidation of the products of the coupling reaction provided the diimines 2. X-ray crystal structures, cyclic voltammetry, and spectral and photophysical data of the compounds are presented. X-ray crystal structures demonstrate a planar structure for the diimine derivatives and a twisted conformation for the diamines. The diamine compounds 1 absorb in the UV (λmax 324-328 nm), significantly blue-shifted from the absorption spectrum of thioindigo. Diamines 1 exhibit moderate fluorescence (ΦF = 0.25, 0.045). A transient triplet state is observed in laser flash photolysis (LFP) experiments of 1, with lifetimes 1 order of magnitude longer than those of thioindigo. The diimine compounds 2 absorb at longer wavelengths (λmax 495-510 nm) than the diamines but are still slightly blue-shifted from thioindigo, with molar extinction coefficients 17-70% higher compared to thioindigo. The diimine compounds are not emissive, and LFP studies indicate transient species with microsecond lifetimes. Quenching experiments and transient absorption spectra are consistent with trans-cis isomerization.

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“…I n later publications they have concluded from the quenching of the trans -+ cis isomerization by 0, and flash photolytic nieasurenients that this reaction occurs in the triplet state [4,5,6]. In a recent paper KAR-STICKS et al [7] discount the possibility of a triplet mechanism, and after that GRELL-MANN and HENTZSCHZL [8] presented findings which are assumed to agree with the idea of a corninon triplet state responsible for the trans + cis isomerization.…”

Section: Introductionmentioning

confidence: 96%

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

Haucke

Paetzold

1979

J. Prakt. Chem.

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Spektroskopie und Photochemie indigoider Verbindungen. VI. Direkte trans → cis Photoisomerisierung indigoider Farbstoffe Wir haben die Fluoreszenz und die photochemische trans → cis Isomerisierung einiger indigoider Farbstoffe in flüssigen Lösungen bei 300 K und festen Gläsern bei 77 K, die Temperaturabhängigkeit der Fluoreszenzquantenausbeute und die Löschung der trans → cis Isomerisierung durch Elektronendonatoren in Benzen und Iodbenzen und durch O2 in Benzen untersucht. Diese und andere Ergebnisse werden vorgestellt und diskutiert. Es wird angenommen, daß die direkte trans → cis Photoisomerisierung — zumindest im ersten Schritt — über einen Singulett‐Zustand verläuft.

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Photoisomerization mechanism of thioindigo dyes. Thioindigo in nonpolar solvents

Cited by 14 publications

References 9 publications

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

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

Synthesis and Photophysics of Thioindigo Diimines and Related Compounds

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

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