Showing papers on "Xanthene published in 2001"

Emission from the Charge Transfer State of Xanthene Dye-Sensitized TiO2 Nanoparticles: A New Approach to Determining Back Electron Transfer Rate and Verifying the Marcus Inverted Regime

Abstract: Electron injection and back electron transfer dynamics of xanthene dyes adsorbed on TiO2 nanoparticles have been studied by picosecond transient absorption and time-resolved fluorescence spectroscopy. When the xanthene dyes are adsorbed on the TiO2 surface, a good fraction of the dye molecules forms charge transfer (CT) complex with the TiO2 nanoparticle. On excitation of the above system, electron transfer from dye molecule to nanoparticle takes place. Electron injection has been observed by direct detection of electron in the conduction band of nanoparticle and bleach of the dye as detected by picosecond transient absorption spectroscopy. The corresponding dynamics have been determined by monitoring the recovery kinetics of the bleach of the dye in the visible region. Electron injection in the above systems can take place in two different ways: (1) through the excited state of the dye and (2) through direct injection to the conduction band on excitation of the charge transfer complex. For the charge tr...

Atropisomers of asymmetric xanthene fluorescent dyes and methods of dna sequencing and fragment analysis

Abstract: Atropisomeric energy-transfer dye compounds are disclosed. A variety of molecular biology applications utilize atropisomeric xanthene fluorescent dyes as labels for substrates such as nucleotides, nucleosides, polynucleotides, polypeptides and carbohydrates. Methods include DNA sequencing, DNA fragment analysis, PCR, SNP analysis, oligonucleotide ligation, amplification, minisequencing, and primer extension.

Assay of Xanthene Dyes in Lipsticks by Inverse Supercritical Fluid Extraction and HPLC

Abstract: An inverse supercritical fluid extraction (SFE) procedure has been developed for the efficient isolation of six of the most common xanthene dyes (fluorescein; 4′,5′-dibromofluorescein; 2′,4′,5′,7′-tetrabromofluorescein; 2′,4′,5′,7′-tetrabromo-4,5,6,7-tetrachlorofluorescein; 4′,5′-diiodofluorescein and 2′,4′,5′,7′-tetraiodofluorescein) from lipstick matrices. A rapid high-performance liquid chromatographic method is also presented for the separation of the six dyes on a cyanopropyl-bonded silica column eluted with acetonitrile-methanol-acetate buffer. Extraction of the lipstick with supercritical CO2 at 350 atm and 40°C for 10 min exclusively removed the matrix components, whereas the xanthene colorants remained in the extraction vessel. After treatment with CO2, the target analytes were quantitatively recovered (>96.8%) by dispersion of the sample in ethanol under sonication. The inverse SFE method was compared with conventional liquid-liquid extraction on commercial lipstick products. The two methods produced comparable recoveries. However, inverse SFE was superior in terms of precision and speed of analysis and gave cleaner extracts.

Intramolecular Ar−O−Ar Bond Formation in Calixarenes

Abstract: The formal dehydration of two vicinal phenol moieties of p-tert-butylcalix[6]arene was achieved in two steps by mild oxidation of the calixarene followed by treatment of the resulting monospirodienone derivative (9c) with an ionic hydrogenation mixture (Et3SiH/CF3COOH). Reaction of 9c yielded the unsubstituted xanthenocalix[6]arene 11d, while treatment of the monospirodienone derivative of a spherand-type calixarene (13) with Et3SiH/CF3COOH afforded the dibenzofuran derivative 15. The formation of the latter product indicates that, at least for 13, the rings forming the Ar−O−Ar bond in the product are not those connected by the spiro bond in the starting material. Methylation of the phenolic hydroxyl groups of 11d with methyl p-toluenesulfonate/K2CO3 or dimethyl sulfate/base afforded its dimethyl and tetramethyl ether derivatives. The parent xanthone calix[6]arene derivative 17b was prepared by O-methylation of the phenol groups followed by CrO3 oxidation of the xanthene methylene group and deprotection o...

Luminescence Properties of Nitro Derivatives of Fluorescein

Abstract: The fluorescence quantum yields of nitro-substituted Fluoresceins depends on their structure, degree of protonation, solvent nature, aggregative state, and temperature. A scheme is proposed for the energy levels in the molecules of these compounds, which involves closely located S 1 ( *) and T(n *) states and their possible inversion. Studies of luminescence properties of nitroaromatic compounds involve some problems associated with both a weak (as a rule) luminescence intensity and interpretation of the results which are influences by a variety of chemical and physical factors (1 4). Of particular importance are extent of the -system and contribution of n * levels to electronically excited levels of charge-transfer states. Derivatives of Fluores- cein (I) and Eosin (II), having a nitro group in the xanthene core (compounds III VII) (5), seem to be convenient models for estimation of the effect of the above factors on the general phototransformation pattern. Available data on the influence of the nitro group on luminescence properties in the series of xanthene dyes refer only to Eosine B (VI) and are fragmentary (efficiency of population of T 1 states) and contradictory (6, 7). X X A 2 Y 2 A 1 Y 1

The role of the triplet state on the photobleaching processes of xanthene dyes in a poly(vinyl alcohol) matrix

Abstract: This work presents the results for the temperature dependence of the photobleaching reactions of Fluorescein and Rose Bengal dissolved in poly(vinyl alcohol) in the presence of diethylenetriamine, potassium dichromate and 2-aminoethanethiol hydrochloride. These samples were subjected to a continuous irradiation with a 150 W mercury high pressure arc lamp at a wavelength coincident with the maximum of the dye absorption. The photobleaching processes were described by a double exponential and a mono-exponential function for Fluorescein and Rose Bengal, respectively. Apparent activation energies were calculated using the Arrhenius plots and these values were strongly affected by the presence of additives. Different additives are employed in the studies of the photobleaching reactions of Fluorescein and Rose Bengal in poly(vinyl alcohol) matrices: (a) diethylenetriamine is a quencher of all excited states; (b) potassium dichromate is an electron acceptor complexed with the polymer chains and inhibited the photobleaching; (c) 2-aminoethanethiol hydrochloride is an efficient quencher of the triplet state. The role of these additives upon the photoreaction is discussed.

Xanthen-9-ylidene protecting groups in glycerol chemistry

Abstract: The preparation of racemic, (S)- and (R)-1,2-O-(xanthen-9-ylidene)glycerol 17a, 20a and 23a and racemic, (S)- and (R)-1,2-O-(2,7-dimethylxanthen-9-ylidene)glycerol 17b, 20b and 23b is reported. The racemic derivatives 17a and 17b are converted into their stearate esters, which are then treated with dichloroacetic acid and pyrrole under mild conditions to give racemic 1-O-stearoylglycerol 25 in good yield. The xanthen-9-ylidene and 2,7-dimethylxanthen-9-ylidene residues are incorporated into 9,9-di(pyrrol-2-yl)xanthene 36 and 2,7-dimethyl-9,9-di(pyrrol-2-yl)xanthene 37. These by-products are easily removed by treatment with iron(III) chloride in diethyl ether solution. What are believed to be enantiomerically pure (R)- and (S)-1-O-stearoylglycerol 28 and 5 are similarly prepared in good yields from (S)- and (R)-1,2-O-(xanthen-9-ylidene)glycerol 20a and 23a.

Two rhodamine derivatives: 9-[2-(ethoxycarbonyl)phenyl]-3,6-bis-(ethylamino)-2,7-dimethylxanthylium chloride monohydrate and 3,6-diamino-9-[2-(methoxycarbonyl)-phenyl]xanthylium chloride trihydrate.

Abstract: The title compounds, C28H31N2O3+·Cl−·H2O (common name rhod­amine-6g), (I), and C21H17N2O3+·Cl−·3H2O (common name rhod­amine-123), (II), both have planar xanthene skeletons with a formal +1 charge on the amino N atoms delocalized through the π-electron system so that the N—Csp2 bond distances indicate significant double-bond character. The substituted planar phenyl groups make angles of 63.29 (8) and 87.96 (11)° with the xanthene planes in (I) and (II), respectively. In both mol­ecules, the carbonyl bond vectors point toward the xanthene rings. The ethyl­amine groups in (I) are oriented similarly with their CH2–CH3 bond vectors pointing nearly perpendicular to the xanthene plane. The chloride ions and water mol­ecules are disordered in both structures. In (I), the chloride ion and water mol­ecule are disordered between two sites. One water and chloride alternately occupy the same site with occupancy factors of 0.5. The other 0.5-chloride and 0.5-water occupy two distinct positions separated by 0.747 (8) A. In (II), the chloride ion is disordered between three sites and one of the waters is disordered about two other sites. Both crystal structures are stabilized by hydrogen bonds involving the chloride ions, amino groups and water mol­ecules, as well as by π–π stacking between xanthene planes.

Colorimetric and Fluorimetric analysis of carbohydrates

Abstract: Methods are disclosed for the simple, rapid, and selective colorimetric detection of carbohydrates, including fructose, glucose, sialic acid, and oligosaccharides. There is no need for any prior hydrolysis or other chemical modification or of the analytes. Resorcinarenes, xanthene dyes, and related compounds, formally produced by the reaction of 2 equivalents of resorcinol and a suitable electrophilic condensation partner, are used as chromophores or fluorophores for the detection of sugars and other carbohydrates.

Migration of the electronic excitation energy in langmuir – blodgett films of xanthene dyes

Abstract: The concentration and temperature dependencies of the photophysical properties of three new amphiphilic xanthene dyes in the Langmuir-Blodgett (LB) films have been studied. The mechanisms of excitation-energy relaxation were discussed in terms of the excitons migration among energetically disordered monomers and the energy trapping by molecular aggregates. The experimental results were analyzed in view of carried out molecular mechanics and MO calcuations. Triplet states of eosin in the LB films were investigated. The observed nonexponential decay kinetics of delayed fluorescence (DF) and phosphorescence were analyzed in the framework of an annihilation model for both exchange and multipolar interactions.

金属イオン {m}-有機試薬 {r} 反応を用いる光分析法

Abstract: Firstly, the syntheses of various organic reagents {R} containing such xanthene derivatives as O-hydroxyhydro-quinonephthalein (QnPh), and 3,4,5,6-tetrahydroxyfluoran (gallein, Gall) were studied. Secondarily, the coexisting effects of surfactant (cationic-, anionic-, amphoteric- and nonionic-surfactants alone or combination) on the coloring or fluorescence reactions between various {R} such as xanthene derivatives, aromatic amines and various metal ions {M} such as bismuth (III), tin (IV), iron (III), molybdenum (VI), uranium (VI), cobalt (II), aluminum (III), etc. were systematically investigated. Thirdly, numerous simple and sensitive photometric analyses (spectrophotometry and fluorophotometry) for various {M} and organic compounds {Org} such as biological samples, and pharmaceutical preparations by formation reactions of {R-M} binary or {(R-M)-Org} ternary complexes were established in the coexistence of surfactant alone or combination.

Methods of making magenta colorants for ink systems

Abstract: Novel addition products of isocyanates with oxyalkylene-substituted aminophenol compounds as intermediates for the production of urethane-substituted xanthene colorants, particularly triphenylmethane derivatives such as rhodamines, are provided. The xanthene colorants exhibit improved wax and/or oil solubility and high purity. The urethane-substituted xanthene colorant features very good wax and/or oil solubility, and is believed to be relatively nontoxic. A method for producing this novel colorant is also provided.

Enhanced Chemiluminescence of Bis(2,4,6-trichlorophenyl) Oxalate–Hydrogen Peroxide–Dyestuff System in the Presence of Polymer Particles

Abstract: Chemiluminescence property of bis(2,4,6-trichlorophenyl) oxalate–hydrogen peroxide–dyestuff system was examined in the presence of polymer particles. The chemiluminescence of the system was enhanced through an interaction between xanthene dyestuffs and polymer particles. For example, when using erythrosine B, the chemiluminescence intensity in the presence of the particles was about 20 times larger than that in the absence of them. It was clarified from preliminary experiments that the enhanced chemiluminescence with the particles was useful for the determination of H2O2 and dyestuff-labeled D-glucose.

Reactive dyestuffs their preparation and their use

Abstract: Novel reactive dyes of the formula have been found in which D is the radical of an organic dye from the monoazo, polyazo, metal complex azo, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthone or nitroaryl series, and the remaining substituents have the meanings given in the description; and also a process for their preparation, and their use for the dyeing of fibre materials containing OH and NH groups.

Within ink systems

Abstract: Novel addition products of isocyanates with oxyalkylene-substituted aminophenol compounds as intermediates for the production of urethane-substituted xanthene colorants, particularly triphenylmethane derivatives such as rhodamines, are provided. The xanthene colorants exhibit improved wax and/or oil solubility and high purity. The urethane-substituted xanthene colorant features very good wax and/or oil solubility, and is believed to be relatively nontoxic. A method for producing this novel colorant is also provided.

Water soluble ink, and ink jet recording device using it

Abstract: PROBLEM TO BE SOLVED: To provide a water soluble ink which is excellent in water resistance, light resistance as well as in chroma by most suitably combining a direct dye and an acid dye, and to provide an ink jet recording device using this water soluble ink. SOLUTION: The blue ink shall contain a xanthene-based Magenta dye, C.I.Direct Red 227 and a copper phthalocyanine-based cyanine dye as an cyanine dye in the range of a weight ratio of the xanthene-based Magenta dye to the copper phthalocyanine-based cyanine dye of 1:11 to 1:50. The red ink shall contain a xanthene-based Magenta dye, C.I.Direct Red 227 and a yellow dye in the range of a weight ratio of the xanthene-based Magenta dye to the C.I. Direct Red 227 of 1:2 to 1:4.