40020-01-7Relevant articles and documents
Photophysical and spectroscopic studies of indigo derivatives in their keto and leuco forms
Seixas De Melo,Moura,Melo
, p. 6975 - 6981 (2004)
A comprehensive spectroscopic and photophysical study of the keto and leuco forms of indigo and three other ring-substituted derivatives in solution was performed. The characterization involves absorption, fluorescence, and triplet-triplet absorption spectra, making it possible to obtain the quantum yields for fluorescence (φF), singlet-triplet intersystem crossing (φISC)> internal conversion (τIC), and lifetimes for fluorescence (τF) and triplet decay (τ T). For the case of the keto forms, pulse radiolysis experiments have revealed the existence of a triplet acceptor (from energy transfer from different donors) for the indigo, purple, and indirubin compounds. It is shown that with the keto form the major deactivation pathway involves internal conversion from the lowest singlet excited state to the ground state whereas with the leuco form there is competition between internal conversion, triplet formation, and fluorescence deactivation processes. Furthermore, leuco forms present much higher Stokes shifts compared with keto ones, suggesting an excited-state geometry different from the ground-state geometry, possibly involving rotational photoisomerization.
Direct electrochemical reduction of indigo
Roessler, Albert,Dossenbach, Otmar,Meyer, Ulrich,Marte, Walter,Rys, Paul
, p. 879 - 882 (2007/10/03)
Increasing ecoefficiency of textile wet processes has become an important topic in our research group. Reducing agents required for the application of vat and sulfur dyes cannot be recycled, and they lead to problematic waste products. Therefore, modern aspects of economical and ecological requirements are not fulfilled. The application of direct electrochemical reduction of indigo as a novel route has been investigated by spectrophotometric and voltammetric experiments in laboratory cells. Experiments yield information about the reaction mechanism and the kinetics, and they show the possibility of this new route for production of water-soluble indigo, which offers tremendous environmental benefits.
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.
