6537-68-4Relevant academic research and scientific papers
Excited-state isomerization of leuco indigo
Rondao,Seixas De Melo,Melo,Parola
, p. 2826 - 2832 (2012)
The photoreaction of indigo and two other derivatives in its reduced (leuco) form was investigated by absorption and fluorescence (steady-state and time-resolved) techniques. The fluorescence quantum yield (φF) dependence with the UV irradiation time was found to increase up to a value of φF ≈ 0.2-0.3 (after 16 min) for indigo and φF = 0.2 (at ～150 min) for its derivative 4,4′-dibutoxy-7,7′- dimethoxy-5,5′-dinitroindigo (DBMNI). With a model compound, where rotation around the central C-C bond is blocked, the φF value was found constant with the UV irradiation time. Time-resolved fluorescence revealed that initially the decays are fitted with a biexponential law (with 0.12 and 2.17 ns), ending with an almost monoexponential decay (～2.17 ns). Quantum yields for the isomerization photoreaction (φR) were also obtained for indigo and DBMNI with values of 0.9 and 0.007, respectively. The results are rationalized in terms of a photoisomerization (conversion) reaction occurring in the first excited singlet state of trans to cis forms of leuco indigo.
Anthraquinone catalysis in the glucose-driven reduction of indigo to leuco-indigo
Vuorema, Anne,John, Philip,Keskitalo, Marjo,Mahon, Mary F.,Kulandainathan, M. Anbu,Marken, Frank
, p. 1816 - 1824 (2009)
Anthraquinone immobilised onto the surface of indigo microcrystals enhances the reductive dissolution of indigo to leuco-indigo. Indigo reduction is driven by glucose in aqueous NaOH and a vibrating gold disc electrode is employed to monitor the increasing leuco-indigo concentration with time. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular "wedge effect" during co-intercalation of Na+ and anthraquinone into the layered indigo crystal structure. The glucose-driven indigo reduction, which is ineffective in 0.1 M NaOH at 65°C, becomes facile and goes to completion in the presence of anthraquinone catalyst. Electron microscopy of indigo crystals before and after reductive dissolution confirms a delamination mechanism initiated at the edges of the plate-like indigo crystals. Catalysis occurs when the anthraquinone-indigo mixture reaches a molar ratio of 1:400 (at 65°C; corresponding to 3 μM anthraquinone) with excess of anthraquinone having virtually no effect. A strong temperature effect (with a composite EA≈ 120 kJ mol-1) is observed for the reductive dissolution in the presence of anthraquinone. The molar ratio and temperature effects are both consistent with the heterogeneous nature of the anthraquinone catalysis in the aqueous reaction mixture.
5,5′-alkylsubsituted indigo for solution-processed optoelectronic devices
Watanabe, Motonori,Uemura, Naoki,Ida, Shintaro,Hagiwara, Hidehisa,Goto, Kenta,Ishihara, Tatsumi
, p. 4280 - 4287 (2016/07/06)
A series of alkylated indigos were synthesized. Alkylated indigos were characterized by NMR, mass spectrometry, absorption spectra, cyclic voltammetry, and density functional theory (DFT) calculations. Propyl and butyl group substituted indigo was most soluble in chloroform and 1,2-dicrolobenzene, and these solubility were 65–89 times increased as compared to the parent indigo. DFT calculations suggested that the presence of the alkyl chains at the 5.5′-position increases the energy of the highest occupied molecular orbital, while reducing the energy of the lowest unoccupied molecular orbital. This theoretical finding was in good agreement with the experimental results. Crystal structures obtained by X-ray diffraction showed one-dimensional pi–pi stacking. Alkylated molecules were converted to leuco structure, and these structures were then converted to the corresponding indigos in the film state. After deposition of the films on TiO2/FTO substrate, oxidative photocurrents were observed.
NMR spectroscopic study of the Murex trunculus dyeing process
Hoffman, Rina C.,Zilber, Reut C.,Hoffman, Roy E.
scheme or table, p. 892 - 895 (2011/09/16)
It is widely accepted that indigo dyes derived from Murex trunculus were used to produce the biblical dyes tekhelet and argaman. We describe a method of following the debromination of natural leucoindigos and their binding to wool using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation. Binding to the wool is shown to occur prior to oxidation. NMR allows the dyeing process to be followed. This, in principle, could be used to correct problems during dyeing that would increase the reliability of the process. Copyright
Maya Blue as a nanostructured polyfunctional hybrid organic-inorganic material: The need to change paradigms
Domenech, Antonio,Domenech-Carbo, Maria Teresa,Sanchez Del Rio, Manuel,Vazquez De Agredos Pascual, Maria Luisa,Lima, Enrique
scheme or table, p. 2371 - 2379 (2010/03/04)
Maya Blue, an ancient nanostructured organic-inorganic hybrid material resulting from the attachment of indigo, a natural dye, to a phyllosilicate clay, palygorskite, has received considerable attention of late. Despite intensive research, several aspects
Synthesis of N,N'-Diacylindigotins (N,N'-Diacyl-2,2'-bi-indolinylidene-3,3'-diones) via an Oxidative Oxygen-to-Nitrogen Acyl Shift of O,O'-Diacyl-leucoingigos(3,3'-Diacyloxy-2,2'-bi-indolyls)
Setsune, Jun-ichiro,Wakemoto, Hirofumi,Matsueda, Taizo,Matsuura, Toshikazu,Tajima, Hideaki,et al.
, p. 2305 - 2310 (2007/10/02)
O,O'-Diacyl-leucoindigos (3f-j), which were readily obtained by the reaction of leucoindigo disodium salt (4) with acyl chlorides, underwent rapid oxidation by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to fenerate the indigo chromophore with concomitant shift of the acyl groups intramolecularly from oxygen to nitrogen.A number of N,N'-diacylindigotins with functionalized acyl groups were prepared by this method and the direct N-acylation method .A large bathochromic shift of the visible absorption band in the cis form of N,N'-diacylindigotins with bulky acyl groups (2c), (2d), and (2j) was observed which suggested that the electronic structure of the indigo chromophore is perturbed by the steric constraint of the N-acyl groups.
