Photoegradation of indigo in dichloromethane solution

Novotná, Petra; Boon, J.J.; Horst, Jerre van der; Pacáková, Věra

doi:10.1111/j.1478-4408.2003.tb00161.x

Cited by 53 publications

(55 citation statements)

References 14 publications

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“…More recently Novotna and co-workers studied the degradation of indigo in dichloromethane solution and isatin appeared as the major degradation product, yet no systematic study of oxygen's influence on the reaction mechanism has been given. [4] With indigo and its derivatives, the role of oxygen is also of primordial importance in the process of textile dyeing. The dyeing process with a vat dye, such as indigo, involves the reduction of the colored form of the dye (insoluble in water) followed by oxidation with atmospheric oxygen.…”

Section: à3mentioning

confidence: 99%

Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their Keto Forms

et al. 2006

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The spectral and photophysical properties of indigo derivatives with di‐, tetra‐, and hexa‐substitution in their neutral (keto) form are investigated in solution. The study comprises absorption and emission spectra, together with quantitative measurements of quantum yields of fluorescence (ϕF) and singlet oxygen formation (ϕΔ) and fluorescence lifetimes. The energy difference between the HOMO and LUMO orbitals is dependent on the degree (number of groups) and relative position of substitution. The ϕF and ϕΔ values were found to be very low ≤10−3. Because of the absence of transient triplet–triplet signal, the intersystem crossing yields (ϕT) were estimated by assuming that all the triplet states formed give rise to singlet oxygen formation, that is, ϕΔ≈ϕT . It was then possible from ϕIC=1−ϕF−ϕT to estimate the S1∼∼→S0 internal conversion yields and thus, with the other data, to determine the rate constants for all decay processes. From these, several conclusions are drawn. Firstly, the radiationless rate constants, kNR , clearly dominate over the radiative rate constants, kF , (and processes). Secondly, the main deactivation channel for the compounds in their keto form is the radiationless S1∼∼→S0 internal conversion process. Finally, although the changes are relatively small, internal conversion yield seems to be independent of the overall pattern of substitution. A more detailed investigation of the decay profiles with collection at the blue and red emission of the fluorescence band of indigo and one di‐substituted indigo reveals the decays to be bi‐exponential and that at longer emission wavelengths these appear to be associated with both rise and decay times indicating that two excited species exist, which is consistent with a keto‐excited form giving rise (by fast proton transfer) to the enol‐form of indigo. Evidence is presented which supports the idea that intramolecular (and possibly some intermolecular) proton transfer can explain the high efficiency of internal conversion in indigo.

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Section: à3mentioning

confidence: 99%

Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their Keto Forms

et al. 2006

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“…Several products were assigned based on previous observations by Novotna et al (2003), who studied photodegradation of indigo dye in dichloromethane solution. They proposed the mechanism shown in Fig.…”

Section: Properties Of Indole Soamentioning

confidence: 99%

“…Multiple unresolved questions remain. For example, formation of tryptanthrin was very slow in experiments by Novotna et al (2003), and it is not at clear how this compound could form in just a few hours of photooxidation in the chamber. Furthermore, it is not clear which processes occur in the gaseous phase vs. the particle phase.…”

Section: Properties Of Indole Soamentioning

confidence: 99%

Secondary organic aerosol from atmospheric photooxidation of indole

et al. 2017

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Abstract. Indole is a heterocyclic compound emitted by various plant species under stressed conditions or during flowering events. The formation, optical properties, and chemical composition of secondary organic aerosol (SOA) formed by low-NO x photooxidation of indole were investigated. The SOA yield (1.3 ± 0.3) was estimated from measuring the particle mass concentration with a scanning mobility particle sizer (SMPS) and correcting it for wall loss effects. The high value of the SOA mass yield suggests that most oxidized indole products eventually end up in the particle phase. The SOA particles were collected on filters and analysed offline with UV-vis spectrophotometry to measure the mass absorption coefficient (MAC) of the bulk sample. The samples were visibly brown and had MAC values of ∼ 2 m 2 g −1 at λ = 300 nm and ∼ 0.5 m 2 g −1 at λ = 400 nm, comparable to strongly absorbing brown carbon emitted from biomass burning. The chemical composition of SOA was examined with several mass spectrometry methods. Direct analysis in real-time mass spectrometry (DART-MS) and nanospray desorption electrospray high-resolution mass spectrometry (nano-DESI-HRMS) were both used to provide information about the overall distribution of SOA compounds. High-performance liquid chromatography, coupled to photodiode array spectrophotometry and high-resolution mass spectrometry (HPLC-PDA-HRMS), was used to identify chromophoric compounds that are responsible for the brown colour of SOA. Indole derivatives, such as tryptanthrin, indirubin, indigo dye, and indoxyl red, were found to contribute significantly to the visible absorption spectrum of indole SOA. The potential effect of indole SOA on air quality was explored with an airshed model, which found elevated concentrations of indole SOA during the afternoon hours contributing considerably to the total organic aerosol under selected scenarios. Because of its high MAC values, indole SOA can contribute to decreased visibility and poor air quality.

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“…The voltammetric analyses consistently indicate a purity less than that indicated by the spectrophotometric method. The latter method is known to be affected by the state of aggregation of the indigo in the solvent [6], and it has been suggested [36] that impurities in natural indigo reduce the size of indigo aggregates in solvents. Thus when pure synthetic indigo (larger aggregates) is used as a standard, the determinations of the impure natural indigo samples (finer aggregates) will overestimate the real indigo content.…”

Section: Determination Of Indigo Content In Plant-derived Indigos At mentioning

confidence: 99%

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

et al. 2008

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Electrochemical determination of redox active dye species is demonstrated in indigo samples contaminated with high levels of organic and inorganic impurities. The use of a hydrodynamic electrode system based on a vibrating probe (250 Hz, 200 lm lateral amplitude) allows time-independent diffusion controlled signals to be enhanced and reliable concentration data to be obtained under steady state conditions at relatively fast scan rates up to 4 V s -1 . In this work the indigo content of a complex plant-derived indigo sample (dye content typically 30%) is determined after indigo is reduced by addition of glucose in aqueous 0.2 M NaOH. The soluble leuco-indigo is measured by its oxidation response at a vibrating electrode. The vibrating electrode, which consisted of a laterally vibrating 500 lm diameter gold disc, is calibrated with Fe(CN) 6 3-/4-in 0.1 M KCl and employed for indigo determination at 55, 65, and 75°C in 0.2 M NaOH. Determinations of the indigo content of 25 different samples of plant-derived indigo are compared with those obtained by conventional spectrophotometry. This comparison suggests a significant improvement by the electrochemical method, which appears to be less sensitive to impurities.

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Photoegradation of indigo in dichloromethane solution

Cited by 53 publications

References 14 publications

Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their Keto Forms

Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their Keto Forms

Secondary organic aerosol from atmospheric photooxidation of indole

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

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