Showing papers on "Xanthene published in 1992"

Laser flash photolysis studies of novel xanthene dye derivatives

Abstract: The transient phenomena in a laser flash photolysis study of a new series of xanthene dyes in ethanol solution at room temperature are described. The difference between the triplet- and ground-state absorption spectra of tetrabromohydrofluorescein (TBHF) or tetraiodohydrofluorescein (TIHF) shows peaks around 360 and 580 nm. Tetrabromohydrocyanofluorescein (TBHCF) and tetraiodohydrocyanofluorescein (TIHCF) demonstrate triplet-triplet absorption with peaks around 340 and 460 nm. The corresponding anion radicals D .- , which are produced by electron-transfer reactions from aromatic amina, have absorption maxima at 410 nm

Manganese(III)-mediated carbon-carbon bond formation in the reaction of xanthenes with active methylene compounds

Abstract: Oxidation of xanthenes with manganese(III) acetate in the presence of active methylene compounds such as 1,3-dicarbonyl compounds, malononitrile derivatives, acetone, and nitromethane selectively gives 9-substitued xanthene derivatives in good yields. A similar oxidation of thioxanthene also yields 2-(9-thioxanthenyl)-1,3-dicarbonyl compounds in 57-91% yields. The obtained 2-(9-xanthenyl)-1,3-dicarbonyl compounds are readily converted to 2-(9-xanthenylidene)-1,3-dicarbonyl derivatives using manganese(III) complexes or 2,3-dichloro 5,6-dicyano-1,4-benzoquinone

Effect of solvent on nonradiative processes in xanthene dyes: Pyronin B in alcohols and alcohol-water mixtures

Abstract: The fluorescence lifetime τ f and quantum yield O f of pyronin B in water, n-alcohols, and alcohol-water mixtures were measured as a function of temperature. The nonradiative rate constant k nr was calculated from τ f and O f . At 25 o C, k nr was equal to (4.1±0.2)×10 8 s -1 in water and ranged from (1.3±0.3)×10 8 to (3.9±0.4)×10 8 s -1 in alcohols and from (3.6±0.7)×10 8 to (6.0±0.5)×10 8 s -1 in mixtures

Electronic absorption and fluorescence spectra of xanthene dyes in polymers

Abstract: The electronic absorption and fluorescence spectra of fluorescein, fluorescein disodium, erythrosine B and rose bengal in different polymers (poly(vinyl alcohol), poly(vinyl acetate) and polyethylene glycol 600) were studied. It has been noted that fluorescein displays very complex dissociation and ionization equilibria in polymers, depending on the polymer—dye interactions. Its fluorescence emission may be assigned to the neutral zwitterion form in aprotic polymers and solvents. The photophysical properties of fluorescein disodium, erythrosine B and rose bengal are strongly dependent on the polymer—dye interactions and on the internal heavy atom effect. These results are very similar to those obtained for liquid solvents.

Merbromin (mercurochrome) and other xanthene dyes: Quantum yields of triplet sensitizer generation and singlet oxygen formation in alcoholic solutions

Abstract: Absorption, fluorescence and phosphorescence maxima, singlet and triplet energies, and quantum yields of fluorescence φ F and intersystem crossing φ T of highly purified disodium salts of fluorescein dyes in alcoholic solutions are reported. The method of φ T determination by “external heavy atom enhanced photo-oxygenation” is described. Oxygen exerts no measurable effect on the short-lived excited singlet states but quenches the triplet states quantitatively in O 2 -saturated solutions, mainly by energy transfer yielding singlet oxygen, 1 O 2 ( 1 Δ g ). By increasing the number and atomic weight of halogen substituents in the fluorescein molecule, the quantum yields of triplet formation φ T and 1 O 2 generation φ Δ are enhanced, whereas the efficiency S Δ , with which interactions of the triplet excited dye with 3 O 2 yield singlet oxygen, seems to decrease. Within experimental error, φ F +φ T is equal to unity for the xanthene dianions. For the cationic sensitizer rhodamine B, however, this sum equals about 0.7, indicating that deactivation of the singlet excited state by internal conversion plays an appreciable role. Merbromin, a HgOH-substituted dibromofluorescein used world-wide as an inexpensive antiseptic (mercuchrome TM , mercurochrome TM ), shows quantum yields of 0.16±0.04 for triplet formation and 0.14±0.02 for 1 O 2 generation in alcoholic solution. Why mercury does not exhibit the expected internal heavy atom effect on the intersystem crossing process, remains to be elucidated.

Effect of solvent polarity on non-radiative processes in xanthene dyes: the acid form of rhodamine B in nitrile solvents

Abstract: The fluorescence lifetimes of the acid form of rhodamines B in nitrile solvents were measured as a function of temperature. Non-radiative rate constants were calculated from the fluorescence lifetimes and quantum yields. Arrhenius plots of the non-radiative rate constants were linear. The value of the non-radiative activation energy was, within experimental error, the same for all the solvents studied and equal to 3.4 ± 0.3 kcal mol −1 . However, at constant temperature, the natural logarithm of the non-radiative rate constant increased linearly with the solvent polarity parameter E T (30). The dependence of the non-radiative rate on solvent polarity can be explained by a model involving a planar—pyramidal change at the xanthene—amine bond. On the basis of this model, a comparison of the non-radiative rate of the dye in alcohols and nitriles shows that the dependence on solvent polarity is due to specific solute—solvent interactions at the amino and carboxyphenyl groups.

Oxidation of the α-tocopherol model compound 2,2,5,7,8-pentamethyl-6-chromanol in the presence of alcohols

Abstract: Oxidation of the vitamin E model compound, 2,2,5,7,8-pentamethyl-6-chromanol (1b) byt-butyl hydroperoxide in chloroform has been studied in the presence of ethanol, heptanol and cholesterol. In the absence of an alcohol, the major products were the spirodimer (13b) and spirotrimer (14b) of 1b, together with 1H,2,3-dihydro-3,3,5,6,9,10,11a(R)-heptamethyl-7a(S)-(3-hydroxy-3-methylbutyl)-pyrano[2,3-a] xanthene 8(7aH), 11(11aH) dione (6b). In the presence of ethanol, heptanol and cholesterol, the major products were 5-ethoxymethyl-2,2,7,8-tetramethyl-6-chromanol (16b), 5-heptoxymethyl-2,2,7,8-tetramethyl-6-chromanol (17) and 5-cholesteroxymethyl-2,2,7,8-tetramethyl-6-chromanol (18). However, when water was present in a homogeneous reaction, the most rapidly formed product was 2-(3-hydroxy-3-methylbutyl)-3,5,6-trimethyl-1,4-benzoquinone (5b). Compounds 13b, 14b, 16b, 17 and 18 are formedvia a quinone methide intermediate, and compound 5b is formedvia a phenoxylium ion. The phenoxylium species appears to be the preferred intermediate when water is present, whereas the quinone methide species is prefered in the absence of water.

Xanthene Dye-Sensitized Electron Transfer to Methylviologen in Aqueous Organic Solution. Effects of Organic Solvents and Heavy Atoms in the Dyes

Abstract: Electron transfer from the triplet state of xanthene dyes (F1In2− and F1Brn2−, n = 2, 3, and 4) to methylviologen (MV2+) was investigated with a laser flash photolysis technique. Efficiency for the charge separation in aqueous organic solution to give free radical ions, F1In−• or F1Brn−• and MV+•, increased almost linearly with increasing mole fraction of added organic solvents such as acetonitrile, acetone, dioxane, ethanol, methanol, and DMSO in the decreasing order of efficiency. The effect of organic solvents on dissociation of radical ion pairs tends to increase with decrease of their hydrogen-accepting property expressed by Taft’s β value. Halogen-atom substitution in F1In2− and F1Brn2− reduced the MV+ yield, and this heavy-atom effect is associated with increase in the rate of recombination of triplet radical ion pairs accompanying spin inversion.

Determination of the exchange integral by the low-field CIDNP in intramolecular hydrogen abstraction reaction of polymethylene-linked xanthone and xanthene

Abstract: The intramolecular hydrogen abstraction reaction in a series of polymethylene-linked xanthone and xanthene systems is investigated from the viewpoint of the magnetic field effect of the low-field chemically induced dynamic nuclear polarization (CIDNP) spectra. The magnetic field effect can be successfully simulated with the stochastic Liouville equation, and the effective exchange integral J between the two terminal radicals is determined from the peak of the magnetic field dependence. The effective J values thus determined are much larger than those obtained by the CIDEP method

Effects of Electrostatic and π—π Interactions on the Stabilities of Xanthene Dye—4,4′-Bipyridinium Complexes: Structural Design of a Geared Supramolecular Machine

Abstract: Xanthene dyes and substituted 4,4′-bipyridinium salts form well defined 1:1 complexes in solution and in the crystalline state. Electrostatic, charge-transfer, and π-π interactions are the driving forces for the formation of these complexes. Electrostatic interactions contribute 1.1–1.3 kcal/mol per ion pair, and interring interactions, i.e., charge transfer and π-π interactions, contribute 6.2–6.3 kcal mol−1 to the complexes' stabilization. Application of a bis-bipyridinium host results in enhanced binding of eosin Y, 1, due to increased π-π and donor-acceptor interactions and complementary electrostatic attractions. The binding properties of the bipyridinium moiety to eosin Y is controlled by its functionalization with a photochromic azobenzene unit. The association constants of 8-trans and 8-cis to eosin Y, 1, are 3000 M−1 and 38000 M−1, respectively. This difference in the association constants of the diad isomers to 1 allows the photo-controlled reversibly-geared association and dissociation of the diad to and from eosin Y in the supramolecular assembly.

Xanthene dyes for ink jet printing

Abstract: A compound of Formula (1): ##STR1## wherein: X1 is a sulpho or carboxy group; each X2 independently is a substituent; m has a value of from 0 to 2; Y1 and Y2 are each independently alkyl or halo; and Z is a carboxy group. The above compounds may be used as colorants for ink jet printing inks either alone or as a mixture with a second magenta compound.

Dye-set for polysaccharide-containing ink-jet printing inks

Abstract: A set of dyes is provided for use in vehicles employing high molecular weight saccharides. The dye-set comprises about 1 to 4% xanthene magenta, about 0.9 to 2% of a mixture of Acid Yellow 23 and Direct Yellow 86, and about 0.75 to 2.5 of Acid Blue 9 or a mixture of Acid Blue 9 and a copper phthalocyanine dye containing not more than about 25% copper phthalocyanine. The particular dye-set evidences the following properties: good crusting resistance, good stability, the proper viscosity, the proper surface tension, recognizable secondaries, high color saturation, little color-to-color bleed, rapid drytime, no negative reaction with the vehicle, be highly soluble in the vehicle, consumer-safe, and low strike-through.

Luminescent/paramagnetic probes for detecting order in biological assemblies: transformation of luminescent probes into pi-radicals by photochemical reduction.

Abstract: The spectroscopic methods of fluorescence polarization and electron paramagnetic resonance (EPR) are used to study order and orientation of extrinsically labeled protein elements of ordered biological systems. These methods generate complementary information about the order of the system, but a consistent quantitative interpretation of the related data is complicated because the signals arise from different donors. We introduce a new method that allows us to detect both signals from the same donor. Unsubstituted xanthene dyes (eosin, erythrosin, and fluorescein) were irradiated by laser light at their absorption maximum in the presence of different reducing agents. Due to photochemical reduction, the quinoidal structure of the xanthene ring is transformed into a semiquinone, and a pi-radical is formed having a characteristic EPR signal of an unpaired electron spin with proton hyperfine interactions. A strong EPR signal is observed from the dye in solution or when specifically attached to a protein following irradiation in the presence of dithiothreitol or cysteine. We applied this technique to the study of skeletal muscle fibers. The fluorescent dye (iodoacetamido)fluorescein was covalently attached to the reactive thiol of the myosin molecule in muscle fibers. Fluorescence polarization and EPR spectroscopy were performed on the labeled fibers in rigor. Both signals indicate a highly ordered system characteristic of cross-bridges bound to actin. Our use of the same signal donor for fluorescence and EPR studies of probe order is a promising new technique for the study of order in protein elements of biological assemblies.

Dye-set for ink-jet printing inks

Abstract: of EP0526012A set of dyes is provided for use in vehicles employing high molecular weight saccharides. The dye-set comprises about 1 to 4% xanthene magenta, about 0.9 to 2% of a mixture of Acid Yellow 23 and Direct Yellow 86, and about 0.75 to 2.5 of Acid Blue 9 or a mixture of Acid Blue 9 and a copper phthalocyanine dye containing not more than about 25% copper phthalocyanine. The particular dye-set evidences the following properties: good crusting resistance, good stability, the proper viscosity, the proper surface tension, recognizable secondaries, high color saturation, little color-to-color bleed, rapid drytime, no negative reaction with the vehicle, be highly soluble in the vehicle, consumer-safe, and low strike-through.

Triplet sensitization of anthracene photodimerization in γ-cyclodextrin

Abstract: The anthracene derivatives which formed a 2:1 inclusion complex with γ-cyclodextrin (γ-CyD) underwent photodimerization with a high quantum yield (approximately 0.5) in both solution and solid state. The photosensitization of this supramolecular system in solution was carried out successfully using xanthene dyes, such as eosin Y, erythrosin and rose bengal, as triplet sensitizers. The photodimerization is described in terms of the hostassisted photoreaction.

Anionic xanthene derivatives and their use in inks

Abstract: A compound of Formula (1): wherein: X¹ is a sulpho or carboxy group; each X² independently is a substituent; m has a value of from 0 to 2; Y¹ and Y² are each independently alkyl or halo; and Z is a carboxy group. The above compounds may be used as colorants for ink jet printing inks either alone or as a mixture with a second magenta compound.

Polyimides based on a 9-aryl-9(perfluoroalkyl)-xanthene-2,3,6,7-dianhydride or 9,9'-bis(perfluoro-alkyl)xanthene-2,3,6,7-dianhydride and benzidine derivatives

Abstract: Polyimide compositions, films, and electronic devices using polyimides, based on 9-aryl-9(perfluoroalkyl)xanthene-2,3,6,7-dianhydride or 9,9'-bis(perfluoroalkyl)xanthene-2,3,6,7-dianhydride and benzidine derivatives. These polyimides offer a combination of low linear coefficient of thermal expansion, low dielectric constant, and low water absorption.

Sulfonated xanthene filter dyes, and photographic products and processes employing these dyes

Abstract: Xanthene derivatives having cations of the formula: in which X is an -SO2-N(R6)-COR7 or -SO2-N(R6)-CO2(CH2)2Y grouping, wherein R6 is an alkyl group containing not more than about 6 carbon atoms, R7 is an alkyl or aryl group containing not more than about 10 carbon atoms and Y is an electron-withdrawing group; Z is a hydrogen atom or an -SO2-N(R1)-R2-NR3R4R5 grouping; R1 is hydrogen or an alkyl group containing not more than about 6 carbon atoms; R2 is an alkylene group containing from 2 to about 10 carbon atoms; R3 and R4 are each independently an alkyl group containing not more than about 6 carbon atoms, and R5 is a hydrogen atom or an alkyl group containing not more than about 6 carbon atoms, are useful as light-screening dyes in photographic products and processes.

Reactive dyes containing a chloro or fluorotriazine group

Abstract: Reactive dyes of the formula ##STR1## are particularly suitable for dyeing or printing cellulosic fibre materials by the exhaust method or by continuous processes and give, with a high color yield, dyeings and prints with good fastness properties, in which D is the radical of a monoazo, polyazo, metal complex azo, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthone, nitroaryl, naphthoquinone, pyrenequinone or perylenetetracarbimide dye; R is hydrogen or alkyl having 1 to 4 carbon atoms, which can be substituted by hydroxyl, cyano, carboxyl, sulfo or sulfato; X is fluorine or chlorine; B is a substituted or unsubstituted aliphatic or aromatic bridge member; Y is a substituted or unsubstituted aliphatic, aromatic, araliphatic or heterocyclic radical, which is free from reactive groups; R 2 is hydrogen or alkyl having 1 to 4 carbon atoms, which can be substituted by halogen, hydroxyl, cyano, C 1 -C 4 alkoxy, C 1 -C 4 alkoxycarbonyl, carboxyl, carbamoyl, sulfamoyl, sulfo or sulfato; and R 1 , independently of R 2 , has the same meaning as R 2 or is a radical of the formula ##STR2## in which B, Y and R 2 are as defined under formula (1), independently of these meanings.

Bifunctional reactive dyes containing vinylsulfone/pyrimidine groups

Abstract: Metal-free dyes of the formula and metal complexes thereof in which Fb is a radical of a dye of the monoazo or polyazo, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, xanthene, thioxanthone, naphthoquinone, stilbene or triphenylmethane series, B or B' is a direct bond or bridge member on a ring C atom of an aromatic-carbocyclic ring or on a ring C or N atom of an aromatic-heterocyclic ring in Fb, X is CH=CH2 or CH2CH2-Y, in which Y is a radical which can be eliminated by alkali R is H or C1-C4-alkyl, which can optionally be substituted, Z is a fibre-reactive radical of the formula in which M is H, C1-C4-alkyl, C1-C4-thioalkyl, F or CF3, are particularly suitable for dyeing and printing natural and synthetic materials containing OH or amide groups.

9,9-bis(perfluoroalkyl)xanthene, 9-aryl-9- perfluoroalkylxanthene,and monomer and polymer derived from them

Abstract: Disclosed are rigid fluorinated monomers, their preparation, and polymers derived therefrom based on two novel tricyclic xanthene core systems, 9,9-bis-(perfluoroalkyl)xanthene (I) and 9-phenyl-9-perfluoroalkylxanthene (II) The monomers have utility in the preparation of advanced high-performance polymers, particularly polyimides