Showing papers on "Xanthene published in 2003"

Rational design principle for modulating fluorescence properties of fluorescein-based probes by photoinduced electron transfer.

Abstract: Fluorescence properties of fluorescein-based probes are shown to be finely controlled by the rate of photoinduced electron transfer from the benzoic acid moiety (electron donor) to the singlet excited state of the xanthene moiety (electron acceptor fluorophore). The occurrence of photoinduced electron transfer is clearly evidenced by transient absorption spectra showing bands due to the radical cation of the electron donor moiety and the radical anion of the xanthene moiety, observed in laser flash photolysis experiments. The photoinduced electron transfer rates and the rates of back electron transfer follow the Marcus parabolic dependence of electron transfer rate on the driving force. Such a dependence provides for the first time a quantitative basis for a rational design principle which has high efficiency in modulating fluorescence properties of fluorescein-based probes.

Photooxidation of eosin Y in the presence of semiconducting oxides

Abstract: The photocatalytic degradation of eosin Y, an anionic xanthene fluorescent dye, has been investigated in aqueous heterogeneous solutions containing TiO 2 P-25 and ZnO as photocatalysts. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the Langmuir–Hinshelwood model. The effect of H 2 O 2 on the reaction rate is ascertained. CO 2 and Br − ions have been identified as mineralization products, while toxicity experiments showed a 85% reduction of the toxicity of an eosin Y solution after 60 min of photocatalytic treatment. The initial photonic efficiency ( ζ ) of decolorization, as well as mineralization under various experimental conditions have been calculated.

Proton-Coupled O−O Activation on a Redox Platform Bearing a Hydrogen-Bonding Scaffold

Abstract: Porphyrin architectures bearing a hydrogen-bonding scaffold have been synthesized The H-bond pendant allows proton-coupled electron transfer (PCET) to be utilized as a vehicle for effecting catalytic O-O bond activation chemistry Suzuki cross-coupling reactions provide a modular synthetic strategy for the attachment of porphyrins to a rigid xanthene or dibenzofuran pillar bearing the H-bond pendant The resulting HPX (hanging porphyrin xanthene) and HPD (hanging porphyrin dibenzofuran) systems permit both the orientation and acid-base properties of the hanging H-bonding group to be controlled Comparative reactivity studies for the catalase-like disproportionation of hydrogen peroxide and the epoxidation of olefins by the HPX and HPD platforms with acid and ester hanging groups reveal that the introduction of a proton-transfer network, properly oriented to a redox-active platform, can orchestrate catalytic O-O bond activation For the catalase and epoxidation reaction types, a marked reactivity enhancement is observed for the xanthene-bridged platform appended with a pendant carboxylic acid group, establishing that this approach can yield superior catalysts to analogues that do not control both proton and electron inventories

Transient Absorption Studies of the Pacman Effect in Spring-Loaded Diiron(III) μ-Oxo Bisporphyrins

Abstract: Picosecond transient absorption spectroscopy of diiron(III) μ-oxo bisporphyrins appended to xanthene, (DPX)Fe2O and (DPXM)Fe2O, and dibenzofuran (DPD)Fe2O have been investigated in order to decipher the effect of a spring-loaded cleft on their photophysics and attendant oxidation photocatalysis. The tension of the cofacial pocket is systematically tuned with the bridge span and meso-substitution opposite to the bridge; the distances of the relaxed cofacial pockets and clamped Fe−O−Fe pockets are known from X-ray crystallography (ΔdM-M(relaxed − clamped) = 4.271 A (DPD), 2.424 A (DPXM), 0.208 A (DPX)). The photophysical and chemical properties of these cofacial platforms are compared to the unbridged diiron(III) μ-oxo analogue, (Etio)2Fe2O. Photon absorption by the diiron(III) μ-oxo chromophore prompts Fe−O−Fe photocleavage to release the spring and present a PFeIVO/PFeII pair (P = porphyrin subunit); net photooxidation is observed when oxygen atom transfer to substrate occurs before the spring can reclamp...

High pressure infrared and nuclear magnetic resonance studies of the rhodium-sulfoxantphos catalysed hydroformylation of 1-octene in ionic liquids

Abstract: The rhodium-sulfoxantphos catalysed hydroformylation of 1-octene in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI·PF6) as a room temperature ionic liquid was monitored in situ by high pressure IR (HP-IR) and NMR (HP-NMR). Similar ee (bis-equatorial) and ea (equatorial-apical) (diphosphine)Rh(CO)2H catalytic species, as observed in organic solvents, are formed in the BMI·PF6 ionic liquid. The ratio of the ee and ea isomers is influenced by both the temperature and syngas pressure. An increase in hydrogen partial pressure has no effect on the activity of the system during the reaction performed in BMI∶PF6, while some hydroformylation systems using xanthene backbone ligands in conventional organic solvents can be sensitive to hydrogen partial pressure.

Dimerization of Xanthene Dyes in Water: Experimental Studies and Molecular Dynamic Simulations

Abstract: 1-D and 2-D NMR experiments and molecular dynamics simulations have been performed to study the dimerization process of two laser dyes namely Rodamine 6G and Pyronine 6G in water. Two possible stacked dimer structures have been evidenced, and the agreement between experimental and theoretical results is very good. The role of dispersive and electrostatic forces in the dimerization mechanism is discussed. This analysis allows us to suggest some chemical modifications on xanthene dyes to prevent such dimerization. On this basis, a new synthesized rhodamine is described which does not exhibit any dimerization phenomenon in a large range of concentrations.

Solute Dependence of Three Pulse Photon Echo Peak Shift Measurements in Methanol Solution

Abstract: Three pulse photon echo peak shift (3PEPS) measurement has recently become a popular method to study solvation and protein dynamics. In this paper, dependence of the 3PEPS signal on probe solute molecules was studied using several xanthene dyes and styryl dye molecules in methanol and compared with pump−probe measurements. For xanthene dyes, the decay was faster when the blue side of the absorption spectrum was excited. This effect is considered to be the result of a limited observation window and vibrational relaxation of the excess energy through higher density of states in the excited state. Nonlinear coupling may be also need to be considered. It seemed that the 3PEPS signal was more sensitive to excited state dynamics rather than to the ground state ones. For styryl dyes, a gradual increase of the peak shift was observed in the picosecond region, which may be the result of photoinduced isomerization.

Xanthene-carboxylic acid esters of tropenol and scopine as m3 antagonists, method for producing the same and use thereof as medicaments

Abstract: The invention relates to novel xanthene-carboxylic acid esters of general formula (1), in which X and the groups A, R, R1, R2, R3, R3', R4 and R4' are defined as per the claims and the description. The invention also relates to a method for producing said esters and to the use thereof as medicaments.

Dye composition comprising at least one particular dissymetrical polycationic direct dye, dyeing process, use and multi-compartment devices

Abstract: A dye composition for dyeing human keratin fibres, such as hair, comprising at least one dissymmetrical polycationic direct dye of formula (I) below: Col 1 -Z-Col 2 (I) wherein: Col 1 and Col 2 , which differ in structure, are chosen from tazo dyes, methine dyes, azomethine dyes, phenothiazine dyes, triarylmethane dyes, xanthene dyes, phenanthridine dyes and phthalocyanin dyes and Z is chosen from linear and branched, saturated, unsaturated and cyclic C 1 -C 20 hydrocarbon-based groups comprising at least one nitrogen atom and bearing at least one cationic charge; and also to processes for dyeing human keratin fibres using the composition, to the use of the at least one dissymmetrical polycationic direct dye of formula (I) as direct dyes, and to multi-compartment devices.

Optical storage media comprising pentacyclic xanthylium dyes

Abstract: The invention relates to an optical recording medium comprising a substrate, a reflecting layer and a recording layer, wherein the recording layer comprises a compound of formula (I),(II),(III); wherein R1, to R13, may be hydrogen or a variety of substituents, but R1, and R11 are not simultaneously hydrogen;Ym- is an inorganic, organic or organometallic anion, or a mixture thereof; Zn+ is a proton or a metal, ammonium or phosphonium cation, or a mixture thereof; m, n and o are each independently of the others an integer from 1 to 3; and p and q are each a number from 0 to 4, the ratio of o, p and q to one another, depending on the charge of the associated sub-structures, being such that there is no excess positive or negative charge in formula (I), (II) or (III). Also claimed are the use of a xanthene perchlorate in the preparation of compounds of formula (I), (II) or (III) having organometallic anions, and the use of lactates in the application of layers of dye to grooved substrates by spin-coating.

Dye composition comprising at least one polycationic direct dye, dyeing processes, uses, and multi-compartment devices

Abstract: Disclosed herein is a dye composition for dyeing human keratin fibers, such as the hair, comprising a direct polycationic dye of formula (I) below: Col-Z-Col (I) in which Col, which may be identical or different, is a noncationic dye chosen from azo dyes, methine dyes, azomethine dyes, phenothiazine dyes, triarylmethene dyes, xanthene dyes, phenanthridine dyes, and phthalocyanin dyes; and Z is chosen from linear and branched, saturated and unsaturated C 1 -C 20 hydrocarbon-based groups comprising at least one nitrogen atom and bearing at least two cationic charges, and also to processes for dyeing human keratin fiber using said composition, to the use of the dyes of formula (I) as direct dyes, and to multi-compartment devices.

A comparative kinetic study on the singlet molecular oxygen-mediated photoxidation of α- and β-chymotrypsins

Abstract: Kinetic aspects of the sensitized photooxidation of alpha- and beta-chymotrypsins have been studied at pH 6 and 8. The sensitization, employing classical O2(1Deltag)-photogenerators, such as xanthene dyes, is a kinetically intricate process because of the presence of ground state dye-protein associations and to the simultaneous participation of superoxide ion and singlet molecular oxygen [O2(1Deltag)]. Both proteins, that possess the same distribution pattern of photooxidizable amino acids, suffer a pure O2(1Deltag)-mediated photodynamic attack, using the carbonylic sensitizer Perinaphthenone. Overall and reactive rate constants for the O2(1Deltag)-quenching (in the order of 108 and 107/M/s, respectively), and rates of oxygen consumption determined by time-resolved, spectroscopic and polarographic methods indicate that alpha- and beta-chymotrypsins are less photooxidizable at pH 6, as a result of an enhancement of the O2(1Deltag)-physical quenching component. In general terms, beta-chymotrypsin exhibits the greater overall proclivity to interact with O2(1Deltag), whereas structural factors, possibly evidenced by a higher exposure of the reactive tryptophan residues, impart an increased photooxidation degree to the proteins at pH 8, specially to the alpha-chymotrypsin.

Recreational water treatment employing singlet oxygen

Abstract: Recreational or process water can be treated by uniformly dissolving in the water a singlet oxygen-generating photosensitizer selected from the group consisting of condensed aromatic compounds, acridine dyes, coumarin dyes, crystal violet, fluorene derivatives, porphyrin derivatives, chlorins, thiazine dyes, thioketones, xanthene dyes, or by uniformly dissolving in the water a singlet oxygen-generating photosensitizer having an absorption maximum less than 659 nm and sufficiently strong coloration so that the presence of the photosensitizer can be visually detected in the water. Exposure of the photosensitizer and ambient or added oxygen to sufficient light or other activating energy causes the generation of singlet oxygen and the destruction or control of microorganisms.

High-performance optical storage media

Abstract: The invention relates to an optical recording medium comprising a substrate, a reflecting layer and a recording layer, wherein the recording layer comprises a compound of formula: (Formula I), (Formula II) or (Formula III); wherein R, to R„ may be hydrogen or a variety of substituents, but R1 and R9 are not simultaneously hydrogen; Ym-- is an inorganic, organic or organometallic anion, or a mixture thereof; Zn+ is a proton or a metal, ammonium or phosphonium cation, or a mixture thereof; m, n and o are each independently of the others an integer from 1 to 3; and p and q are each a number from 0 to 4, the ratio of o, p and q to one another, depending on the charge of the associated sub-structures, being such that there is no excess positive or negative charge in formula (I), (II) or (III). Also claimed are the use of a xanthene perchlorate in the preparation of compounds of formula (I), (II) or (III) having organometallic anions, and the use of lactates in the application of layers of dye of compounds of formula (I), (II) or (III) to grooved substrates by spin-coating.

Xanthonoid glycoside compound with its benzapyrene [a] substituted by hydroxy-propyl and photochemistries synthesizing method

Abstract: A kind of 11-carboxypropyl substituted benzo [a] xanthone compounds is prepared from substituted binaphthol through catalytic reaction under existance of water and copper-amine complex as catalyst toobtain 1-oxy-13c-hydroxy-1,13-dihydro-dibenzo [a,kl] xanthene compound, and optical open-loop synthesizing respectively in water, alcohol, and ammonia (or amine) contained system.

Ultrasound contrast using halogenated xanthenes

Abstract: New contrast agents for ultrasound imaging and methods for use of such agents for imaging of human or animal tissue are described, wherein a primary active component of such medicaments is a halogenated xanthene or halogenated xanthene derivative. Preferably, the halogenated xanthene is Rose Bengal or a functional derivative of Rose Bengal.

Xanthene laser colorants

Abstract: Synthesis of xanthene colorants and their properties in the context of their application as laser dyes are discussed.

New xanthene compound

Abstract: PROBLEM TO BE SOLVED: To provide a new xanthene compound which can give printed products having excellent light fastness without increasing the amount of an additive, and to provide a coloring liquid using the same SOLUTION: This xanthene compound having a structure represented by the general formula (I) [R 1 and R 2 are each independently a 1 to 4C straight chain or branched alkyl; R 3 and R 4 are each independently H, a 1 to 4C straight chain or branched alkyl or a 1 to 4C straight chain or branched alkoxy; M is H, an alkyl metal or NH 4 ] COPYRIGHT: (C)2004,JPO&NCIPI

Film, optical memory material using the same film and method for producing the same film

Abstract: PROBLEM TO BE SOLVED: To prepare a film in which a fluorescent material is dispersed in PMMA, to obtain an optical memory material using the film, and to provide a three-dimensional memory using the optical memory material. SOLUTION: The film is composed of at least PMMA (polymethyl methacrylate), a fluorescent material dispersed in the PMMA and having a xanthene skeleton and a lactone ring and/or a fluorescent material having the xanthene skeleton and a COOR group (R is hydrogen atom or a substituent group) capable of forming an intramolecular lactone ring. The optical memory material is obtained by using the film. The three-dimensional memory is obtained by using the optical memory material. COPYRIGHT: (C)2005,JPO&NCIPI

Light-fast, high-capacity optical storage media

Abstract: The invention relates to an optical recording medium comprising a substrate, a reflecting layer and a recording layer, wherein the recording layer comprises a compound of formula (I),(II),(III); wherein R 1 , to R 13 , may be hydrogen or a variety of substituents, but R 1 , and R 11 are not simultaneously hydrogen;Y m − is an inorganic, organic or organometallic anion, or a mixture thereof; Z n+ is a proton or a metal, ammonium or phosphonium cation, or a mixture thereof; m, n and o are each independently of the others an integer from 1 to 3; and p and q are each a number from 0 to 4, the ratio of o, p and q to one another, depending on the charge of the associated sub-structures, being such that there is no excess positive or negative charge in formula (I), (II) or (III). Also claimed are the use of a xanthene perchlorate in the preparation of compounds of formula (I), (II) or (III) having organometallic anions, and the use of lactates in the application of layers of dye to grooved substrates by spin-coating.

Variation of Xanthene-Based Bidentate Ligands in the Palladium-Catalyzed Arylation of Ureas.

Abstract: A series of xanthene-based bidentate ligands containing various substituents on diphenylphosphino groups were synthesized and tested in the palladium-catalyzed arylation reaction of urea with unactivated aryl bromides. It was found that both steric and electronic properties of the ligands have a pronounced effect on the yields and ratios of the products. Arylation of urea and phenylurea with unactivated aryl bromides in the presence of Pd2dba3·CHCl3/3,5-(CF3)2Xantphos and Cs2CO3 as base in dioxane at 100°C gave the corresponding N,N′-diarylureas in 62–98% yields.