Topic
Xanthene
About: Xanthene is a research topic. Over the lifetime, 2132 publications have been published within this topic receiving 34803 citations. The topic is also known as: Xanthene & dibenzo[a,e]pyran.
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TL;DR: In this article, the system of various xanthene dyes in diffusionless weakly polar electron donating solvents was discussed for the system for ultrafast intermolecular electron transfer (ET), which is determined by mutual displacement of the reactants and by the solvent relaxation.
Abstract: Ultrafast intermolecular electron transfer (ET) is discussed for the system of various xanthene dyes in diffusionless weakly polar electron donating solvents. ET was observed by fluorescence quenching dynamics. It gives a non-exponential process in case of dyes in aniline. ET rate is determined by mutual displacement of the reactants and by the solvent relaxation. In case of dyes in N,N-dimethylaniline, ET quenching gives very different dynamics and shows a single exponential decay with a rate constant as fast as 1013 s-1. Ultrafast ET, which is much faster than solvent relaxation time, requires a new mechanism for a cause of ET.and its rate constant may be determined by nuclear motion, rather than controlled by solvent dynamics.
23 citations
TL;DR: The synthesis of regioisomerically pure unsymmetrical xanthene derivatives consisting of three units which can be independently modified to control their physical properties is demonstrated.
23 citations
TL;DR: In this article, infrared multiple photon dissociation (IRMPD) action spectra are reported for the three charged prototropic forms of FL and DCF and compared with computed IR spectra from electronic structure calculations.
Abstract: Fluorescein (FL) and its derivative 2',7'-dichlorofluoroescein (DCF) are well-known fluorescent dyes used in many biological and biochemical applications. Although extensive studies have been carried out to investigate their chemical and photophysical properties in different solvent media, little is known about their intrinsic behaviors in the gas phase. Here, infrared multiple photon dissociation (IRMPD) action spectra are reported for the three charged prototropic forms of FL and DCF and compared with computed IR spectra from electronic structure calculations. In each case, the measured spectra show good agreement with the calculated spectra of the lowest energy computed conformer. Moreover, the major bands of the monoanion IRMPD spectra show striking similarities to those of the dianions and are quite different from those of the cations. These experimental results clearly indicate that the gaseous monoanions are predominantly deprotonated on the xanthene chromophore, rather than the benzoate deprotonation site favored in solution. Investigations such as this, which provide a better understanding of intrinsic properties of ionic dyes, forms a baseline from which to elucidate solvent effects and will aid the rational design of dyes possessing desirable fluorescence properties.
23 citations
TL;DR: In this article, the e.s.r. spectra for the semireduced radicals of fluorescein, eosin Y, and rose bengal B, formed during the photolysis of these dyes in alcohol solutions of various indole derivatives and triethylamine.
Abstract: E.s.r. spectra are reported for the semireduced radicals of fluorescein, eosin Y, and rose bengal B, formed during the photolysis of these dyes in alcohol solutions of various indole derivatives and triethylamine. When indoleacetic acid is used as substrate, the dye radicals exist as the diprotonated monoanion radicals, with OH proton splitting constants varying from 0.12 G (fluorescein) to 1.0 G (rose bengal B). In the presence of tryptamine or triethylamine the intermediate dye radicals exist as the unprotonated radical trianions. The e.s.r. spectrum of the semireduced monoanion radical of rhodamine B was also observed during photolysis of the dye in the presence of triethylamine.
23 citations
TL;DR: In this article, two xanthene-derived photosensitizers were covalently grafted onto the surface of the silanized bacterial cellulose sheets to produce singlet oxygen (1O2) upon illumination.
Abstract: We report on the functionalization of wet bacterial cellulose sheets towards photo-bactericidal materials that produce singlet oxygen (1O2) upon illumination. Pre-modification was carried out by a silane chemistry approach in order to make the cellulosic material accessible to Cu(I)-catalyzed azide-alkyne click chemistry. This way, two xanthene-derived photosensitizers were covalently grafted onto the surface of the silanized bacterial cellulose sheets. The obtained materials and photosensitizers were comprehensively characterized by means of FTIR, NMR, elemental analysis, UV/Vis absorption and fluorescence techniques, including nanosecond laser flash photolysis, for the determination of respective triplet state and singlet oxygen quantum yields. The photomicrobicidal activity was tested under white light illumination against gram-negative as well as gram-positive bacteria, including Escherichia coli, Bacillus subtilis and Staphylococcus aureus, as well as fungi (Candida albicans and Aspergillus brasiliensis). The results show type II photochemical antimicrobial activity against S. aureus and B. subtilis, but no effect against gram-negative bacteria and fungi.
22 citations