Rhodamines Rhodamine

Rhoda.mines, Rhodamines are commercially the most important arninoxanthenes. If phthalic anhydride is used in place of formaldehyde in the above condensation reaction with y -dialkylarninophenol, a triphenyknethane analogue, 9-phenylxanthene, is produced. Historically, these have been called rhodamines. Rhodamine B (Basic Violet 10, Cl45170) (17) is usually manufactured by the condensation of two moles of y -diethylaminophenol with phthahc anhydride (24). An alternative route is the reaction of diethylamine with fluorescein dichloride [630-88-6] (3,6-dichlorofluoran) (18) under pressure. 

Fig. 8.8. Energy transfer assays are exemplified here by a probe containing a 5 -terminal fluorescein (I) and a probe containing a 3 -end rhodamine. Upon excitation at 490 nm, fluorescein emits radiation (green fluorescence) at 520 nm. While rhodamine can be excited at 520 nm, the nonhybridized probes are not close enough for energy transfer. Probes are designed so that hybridization brings the two labels to optimal proximity. Excitation of fluorescein yields fluorescence which also serves to excite rhodamine. Rhodamine fluorescence can be specifically determined at 575 nm.

Figure 2.2. The above illustration represents the configuration of tip and sample used in FRET/NSOM. The acceptor dye of the FRET pair is rhodamine. Rhodamine was incorporated into a DPPC monolayer at 0.5 mol % and used to coat an NSOM probe lacking any metal. Fluorescein was used as the donor dye in the sample, and was incorporated into two DPPC/0.5 mol % fluorescein layers separated by a spacer of three arachidic acid layers. Light exiting the tip, (blue arrow) excites the donor dye in the sample but does not directly excite the acceptor dye on the tip. When the modified NSOM probe is near the sample, however, energy transfer from the excited donor in the monolayer to the rhodamine acceptor (dark green arrow) on the tip leads to a new emission, shifted to the red (red arrow) of the donor emission (light green arrows). By monitoring rhodamine fluorescence, it is possible to optically probe only those structures within nanometers of the NSOM tip. Reproduced with permission from (Vickery et al. 1999). Copyright 1999 Biophysical Society.

It condenses with resorcinol and amino-phenols to give phthalein and rhodamine dyestuffs respectively. Esters are used in the formation of polyimides. ... 

Figure Bl.22.7. Left resonant seeond-hannonie generation (SHG) speetnimfrom rhodamine 6G. The inset displays the resonant eleetronie transition indueed by tire two-photon absorption proeess at a wavelength of approximately 350 mn. Right spatially resolved image of a laser-ablated hole in a rhodamine 6G dye monolayer on fiised quartz, mapped by reeording the SHG signal as a fiinetion of position in the film [55], SHG ean be used not only for the eharaeterization of eleetronie transitions within a given substanee, but also as a mieroseopy tool.

Figure C 1.5.5. Time-dependent fluorescence signals observed from liquid solutions of rhodamine 6G by confocal fluorescence microscopy. Data were obtained with 514.5 mn excitation and detected tlirough a 540-580 nm...

Figure C 1.5.7. Surface-eiilianced Raman spectra of a single rhodamine 6G particle on silver recorded at 1 s intervals. Over 300 spectra were recorded from this particle before tlie signals disappeared. The nine spectra displayed here were chosen to highlight several as yet unexplained sudden changes in botli frequency and intensity. Reprinted witli pennission from Nie and Emory [ ]. Copyright 1997 American Association for tlie Advancement of Science.

Michaels A M, Nirmal M and Brus L E 1999 Surface enhanced Raman spectroscopy of individual rhodamine 6G molecules on large Ag nanocrystals J. Am. Chem. See. 121 9932-9... 

Bromophenol blue 2, 7 -DichIorofluorescein Eosin, tetrabromofluorescein Fluorescein Potassium rhodizonate, C404(0K)2 Rhodamine 6G Sodium 3-aIizarinsuIfonate Thorin Dissolve 0.1 g of the acid in 200 mL 95% ethanol. Dissolve 0.1 g of the acid in 100 mL 70% ethanol. Use 1 mL for 100 mL of initial solution. See Dichlorofluorescein. Dissolve 0.4 g of the acid in 200 mL 70% ethanol. Use 10 drops. Prepare fresh as required by dissolving 15 mg in 5 mL of water. Use 10 drops for each titration. Dissolve 0.1 g in 200 mL 70% ethanol. Prepare a 0.2% aqueous solution. Use 5 drops per 120 mL endpoint volume. Prepare a 0.025% aqueous solution. Use 5 drops. 

Figure 9.17 illustrates these features in the case of the dye rhodamine B. The maximum of the typically broad Sj — Sq absorption occurs at about 548 nm with a very high value of... 

Figure 9.17 Absorption and fluorescence spectra of rhodamine B in methanol (5 X 10 mol 1 ). The curve marked is for the J 2 absorption (process 8 in Figure 9.18) and that marked 5 for process 1. (Reproduced, with permission, from Dienes, A. and Shank, C. Y, Chapter 4 in Creation and Detection of the Excited State (Ed. W. R. Ware), Vol. 2, p. 154, Marcel Dekker, New York, 1972)...

For uniformity with the stmctures given in the Colourindex 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 triphenylmethane derivatives (eg, (4)), which are mainly phthaleins made from phthaUc anhydride condensations. A third much smaller group of rosamines (9-phenylxanthenes) is prepared from substituted ben2aldehydes. 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 stmcture in general have been considered. For example, the aggregation phenomena of xanthene dyes has been reviewed (3), as has then photochemistry (4), electron transfer (5), triplet absorption spectra (6), and photodegradation (7). For the fluoresceins in particular, spectral properties and photochemistry have been reviewed (8), and the photochemistry of rhodamines has been investigated (9). 

The free base of compound (17) is Rhodamine B base [509-34-2] (Solvent Red 49 Cl 45170 1). The phosphotungstomolybdic acid salt of (17) is Pigment Violet 1 [1326-03-0] Cl45170 2). Pigment Red 173 [12227-77-9] Cl45170 3) is the corresponding aluminum salt. 

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