Xanthene dyes structures

Fig. 6 General structure of xanthene dyes containing fluorescein, eosin, and rhodamine...

A different strategy for measuring protease activity is based on the property of xanthene dyes to form H-type dimers (see Sect. 6.2.3) when they are in close proximity. These dimers are accompanied with a characteristic quenching of their fluorescence and, particularly for rhodamines, with a blue shift in the absorption spectrum [121, 122]. The probe D-NorFES-D designed to measure activity of elastase in HL-60 cells consists of an undecapeptide derivatized with one tetramethylrhodamine dye on each side. The sequence contains proline residues to create a bent structure and bring the two fluoro-phores in close proximity. Intact D-NorFES-D shows 90% of its fluorescence quenched plus a blue shift of the absorption spectrum. After addition of the serine protease elastase, an increase in the fluorescence and a bathochromic shift of the absorption spectrum is observed, resulting in an increase in the emission ratio [80],... 

Structurally related to the triarylmethanes is the xanthene chromogen (1.30), in which two of the aryl nuclei are linked by an oxygen atom to form a pyrone ring. Similar terminal groupings (amino, hydroxy, or both) are usually present. Xanthene dyes have mainly... 

Dye component with the general structure 124 (see p. 559) (Xanthene dyes)... 

Recently, several novel xanthene dye derivatives with H and CN groups at the 9 position have been synthesized [373]. Their general structure is 9, with... 

For uniformity with the structures given in the Colourlndex the ammonium radical (9) is used for the amino-substituted xanthenes and the keto form for the hydroxy derivatives. The xanthene dyes may be classified into two main groups diphenylmethane derivatives, called pyronines, and triphenyknethane derivatives (eg, (4)), which are mainly phthaleins made from phthalic anhydride condensations. A third much smaller group of rosamines (9-phenylxanthenes) is prepared from substituted benzaldehydes. The phthaleins may be further subdivided into the following fluoresceins (hydroxy-substituted) rhodamines (amino-substituted), eg, (6) and mixed hydroxy/amino-substituted. 

The physical properties of the xanthene type dye structure in general have been considered. For example, the aggregation phenomena of xanthene... 

Reactive xanthene dyes with p-hydroxyethylsulfonyl groups, as exemplified by structure (29), provide brilliant shades and excellent washfastness on cotton (40). The sulfurein derivative (29) is synthesized by condensing 3-aminophenol- 3-hydroxyethylsulfone with... 

The formation of donor-acceptor complexes between bipyridinium salts (electron acceptors) and xanthene dyes (electron donors) (e.g., eosin. Rose Bengal) has been studied extensively. Crystal structures of these complexes have been identified, and the structural features of the donor-acceptor complexes in solutions have been characterized using NMR spectroscopy. The xanthene dye/bipyridinium donor-acceptor complexes are stabilized by... 

CAS 81-88-9. C28H31C1N203. A basic, red fluorescent dye, structurally related to xanthene. 

A number of dyes are derived from the xanthene structure (xanthene dyes) such as fluorescein 26, eosin 27 and pyronine G 28 ... 

Phthalide derivatives are of major importance in the dye industry, particularly in the area of recording material color formers. Pressure-sensitive carbonless copy paper and thermal recording paper are typical applications. Five principal structural classes have been developed extensively the xanthene dyes (fluorans (208)), 3,3-diarylphthalides (209), spirofluorenes (210), 3,3-bis(di-arylethylene)phthalides (211), and 3-substituted phthalides <84Mi 208-03>. Some of these structures are common to many familiar acid/base indicators, dyes, biological stains, or laser dyes such as fluorescein (212) and phenolphthalein (213) ,... 

In most cases, the present of CDs will enhance the luminescence. However, CDs can also selectively quench the luminescence of some compoimds. A study of the effect of /3-CD on the fluorescence of xanthene dyes, coumarins and pyromethene-difluoroboron complexes in aqueous solution shows that fi-CD enhances the fluorescence of 7-hydroxycoumarin and coumarins, but quenches the fluorescence of the 7-hydroxy-4-methylcoumarins [73]. This behavior of CDs provides a new approach to multicomponent fluorometric analysis and indicates that CDs can be used for differentiating the structures of similar compounds such as the positional isomers by the selective incorporation of the analyte. 

The ring structure is present in a class of xanthene dyes. 

Bradley and Davidson pointed out that for any particular aromatic ketone, the efficiency of photoinitiation is determined by the structure of the ketone and by the molecular geometry of the a-aminoalkyl radical produced. On the other hand, Paczkowski et al, suggested that the initial electron-transfer reaction from aromatic amines to the excited state of xanthene dyes, used in their study, is responsible for the variation of the photoinitiation efficiency. 

The structure of the polymer produced from titanocene dichloride and the xanthene dye Erythrosine B is given as 2. 

Xanthene dyes can be either acidic or basic. Acid xanthenes are known to exist in two tautomeric forms. The phenolic type, or fluorans, are free-acid structures such as D C Orange No. 10 (23b) and D C Red No. 21 (23c). Most have poor water solubility. In contrast to these, the quinoids or xanthenes are usually the highly water-soluble sodium salt counterparts of the fluorans such as D C Orange No. 11 (24) and D C Red No. 22 (27a). 

The most important xanthenes are the imino derivatives known as rhodamines, exemplified by rhodamine B (Cl Basic Violet 10) (3.23a), A. 543 nm and 552 nm and rhodamine 6G (Cl Basic Red 1) (3.23b), /L 530 and X 557 nm (Figure 3.11). These are intensively fluorescent dyes with quantum yields close to unity. Rhodamine 6G especially has found wide apphcation in dayhght fluorescent pigments (see section 3.5.2) and this ring structure has been much modified for use in many other outlets, especially as laser dyes (see section 3.5.3) and in biomedical applications (see section 3.5.6). 

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