Xanthenes compounds

The formation of the xanthene also offers an explanation for the reports " " " that contact with air must be avoided during the resin s synthesis and curing, if a graphitizable material is to be obtained. Oxidation sensitivity is entirely consistent with a xanthene compound being the key intermediate, since they can be readily oxidized to form a xanthene-9 -one" . 

Anionic dyes are selected from the group consisting of nitroso compounds, nitro compounds, azo compounds, stilbenes, triaryl-methane compounds, xanthene compounds, quinoline compoimds, thiazole compounds, azine compounds, oxazine compoimds, thi-azine compounds, aminoketone compounds, anthraquinone compounds, indigoid compounds and phthalocyanine compoimds. 

Cationic dyes include the basic dyes and some of the mordant dyes that are designed to bind acidic sites on a substrate, such as fibers. Useful t5q>es of such dyes include the azo compounds, diphenylmethane compounds, triarylmethanes, xanthene compounds, acridine compounds, quinoline compounds, methine or polymethine compounds, thiazole compounds, indamine or in-dophenyl compounds, azine compounds, oxazine compounds, and thiazine compounds. 

Xanthene Compounds. Ghosh et al. have quantified the excited state(s) injection and direct molecule-to-particle dynamics of several xanthene compounds (fluorescein, eosin Y, erythrosine B and rose bengal) adsorbed to TiOa nanoparticles (Ramakrishna, 2001). The strong electronic coupling thought necessary for the ultrafast electron injection was previously observed by time-resolved resonance Raman spectroscopy, for eosin Y bonded to a Ti02 surface (Rossetti, 1984). A mechanistic scheme for interfacial electron transfer... 

Figure 21-11. Mechanistic scheme for electron injection from the xanthene compounds to Ti02 nanoparticles, showing both excited state electron injection (Iiet) and direct injection from the charge transfer complex (hi>ex). Charge recombination of electron from Ti02 to the cation radical was proposed to be radiative, hi/. ...

University of Kansas Research Foundation, Xanthene compounds and dyestuffs and means of producing the same. GB 846674,1960. 

In general, the xanthenes are synthesized by the reaction of two moles of a nucleophilic / -substituted phenol (10) with an electrophilic carbonyl compound (11), the reaction occurring most readily with an acid catalyst at temperatures of 100—200°C. 

Fig. 5. Reflection spectra of magenta dye developers (—) a xanthene (1) and (--) a metallized azo (Fig. 4b) compound. The lower blue absorption of the...

Acid Dyes. These water-soluble anionic dyes ate appHed to nylon, wool, sUk, and modified acryHcs. They ate also used to some extent for paper, leather, food, and cosmetics. The original members of this class aU had one or mote sulfonic or catboxyHc acid groups in thein molecules. This characteristic probably gave the class its name. Chemically, the acid dyes consist of azo (including preformed metal complexes), anthraquiaone, and ttiaryHnethane compounds with a few azHie, xanthene, ketone imine, nitro, nitroso, and quHiophthalone compounds. 

While unmodified xanthene ligands (compound a in Figure 5.2-4) show highly preferential solubility in the organic phase in the biphasic l-octene/[BMIM][PFg] mixture even at room temperature, the application of the guanidinium-modified xanthene ligand (compound b in Figure 5.2-4) resulted in excellent immobilization of the Rh-catalyst in the ionic liquid. 

Fluoran compound used as leuco dye needs to have substituent(s) on the xanthene moiety to develop color, though fluoran 1 itself is prepared as a by-product in the synthesis of phenolphthalein from phenol and phthalic anhydride. 

Commercial PCB mixtures frequently contain impurities that may contribute to the 2,3,7,8-TCDD toxic equivalency factor. These impurities may include other PCBs, dioxins, dibenzofurans, naphthalenes, diphenyl ethers and toluenes, phenoxy and biphenyl anisoles, xanthenes, xanthones, anthracenes, and fluorenes (Jones etal. 1993). PCB concentrations in avian tissues sometimes correlate positively with DDE concentrations (Mora et al. 1993). Eggs of peregrine falcons (Falco peregrinus) from California, for example, contained measurable quantities of various organochlorine compounds, including dioxins, dibenzofurans, mirex, hexachlorobenzene, and / ,//-DDE at 7.1 to 26.0 mg/kg FW PCB 126 accounted for 83% of the 2,3,7,8-TCDD equivalents, but its interaction with other detectable organochlorine compounds is largely unknown (Jarman et al. 1993). 

As a group, these typically pink compounds are derived from the xanthene structure (131) ... 

In this respect, Johansson 1 reported that ro is the same (within experimental accuracy) for fluorophores belonging to the same family, e.g. perylene and per-ylenyl compounds (0.369 + 0.002), or xanthene derivatives such as rhodamine... 

Until recently there were comparatively few reports of fluorescence lifetime studies of dye molecules in the near-IR, but this situation has changed rapidly. The fluorescence lifetimes of near-IR emitting dyes such as carbocyanines, porphyrins, oxazines, and xanthenes, are usually in the nanosecond region, consistent with the high oscillator strength of the Si-So transition in such compounds. 

The solution phase synthesis of peptides often results in mixtures of labelled, unlabelled compounds along with other impurities and requires extensive purification. A route using a solid phase approach [polyethylene glycol-poly-styrene PEG-PS derivatised with a xanthen-2-oxovalerate (XAL) linker] was recently developed [193] (Scheme 44). 

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