Showing papers on "Xanthene published in 2002"

Performance and photostability of xanthene and pyrromethene laser dyes in sol-gel phases

Abstract: The photostability of rhodamine 6G, rhodamine 610 and pyrromethene 567 in solutions, wet-gel and dried sol-gel host media has been determined. A method for the synthesis of xerogel monoliths has been modified to reduce the preparation time for the doped sol-gel samples, and high optical quality sol-gel samples doped with laser dyes have been prepared. A high efficiency and photostability is observed for xanthene laser dyes in wet and dried sol-gel phases but not for a pyrromethene laser dye.

Electrochiroptical response of a hexaarylethane derivative with a helical π-skeleton: drastic UV–Vis and CD spectral changes upon electrolysis of 4′,5′-dibromodispiro[xanthene-9,9′(9′H,10′H)-phenanthrene-10′,9″-xanthene]

Abstract: Upon two-electron oxidation of the title electron donor 1a, the elongated central C9–C10 bond [1.656(5) A (X-ray)] is cleaved to give the biphenyl-2,2′-diyl bis(xanthenylium) dye 2a2+, which regenerates the colorless dispiro compound 1a by two-electron reduction. The presence of isosbestic points in the UV–Vis spectra during the electrochemical oxidation of 1a to 2a2+ indicates the negligible steady-state concentration of the intermediate cation radical. Interconversion between optically resolved 1a and 2a2+ is accompanied by drastic changes in the CD spectra again with several isosbestic points, and racemization of (P)- and (M)-1a and (S)- and (R)-2a2+ does not occur at ambient conditions. This redox pair represents a new motif for the multi-output response system, where the electrochemical input is transduced into two independent spectral outputs.

Porphyrin Architectures Bearing Functionalized Xanthene Spacers

Abstract: A modular synthetic strategy for the construction of cofacial porphyrin architectures bearing hydrogen-bond synthons on a xanthene platform is presented. The convergent approach is based on a xanthene aldehyde-ester building block that is easily obtainable on a multigram scale with minimal purification. Treatment of this xanthene derivative with a variety of aryl aldehydes and pyrrole under standard Lindsey conditions affords a family of meso-substituted porphyrins bearing a single functionalized xanthene spacer. Direct modification of the hydrogen-bond synthon after macrocyclization proceeds smoothly to furnish porphyrin systems with a variety of cofacial functionalities (e.g., carboxylic acid, ester, amide). Porphyrins bearing two trans-functionalized xanthene spacers are prepared by the MacDonald [2 + 2] condensation of the xanthene aldehyde-ester with readily available 5-aryl-substituted dipyrromethanes such as 5-mesityldipyrromethane to afford the pure alpha,alpha- and alpha,beta-porphyrin atropisomers after chromatographic separation. The versatility of this synthetic method offers intriguing opportunities for the use of these and related templates for the study of proton-coupled activation of small molecules.

Visible light-sensitized semiconductor photocatalytic degradation of 2,4-dichlorophenol

Abstract: Sensitized-photocatalytic decomposition of 2,4-dichlorophenol (2,4-DCP) using xanthene dyes as photosensitizer on TiO2 particles under visible light irradiation was studied. 2,4-DCP can be decomposed efficiently by this method and the decomposition efficiency of 2,4-DCP decreases in the following order: eosin Y ≈ rose bengal > erythrosine B > rhodamine B.

1H and 13C NMR Detection of the Carbocations or Zwitterions from Rhodamine B Base, a Fluoran-Based Black Color Former, Trityl Benzoate, and Methoxy-Substituted Trityl Chlorides in the Presence of Alkali Metal or Alkaline Earth Metal Perchlorates in Acetonitrile Solution

Abstract: The cleavage of C–O bonds in two fluoran-based dyes by the addition of alkali metal (M+ = Li+, Na+) and alkaline earth metal (M2+ = Mg2+, Ba2+) perchlorates in acetonitrile solution was examined by means of UV-visible absorption and 1H and 13C NMR spectroscopy at room temperature. Although the 1H NMR signals of the xanthene part of Rhodamine B base (3′,6′-bis(diethylamino)fluoran) were shifted toward lower fields, those of the isobenzofuran (or the benzoate) part were not shifted much upon the addition of M+ and M2+. The appearance of 13C signals at 163.6 and 162.4 ppm (vs TMS) in the presence of Li+ and Ba2+, respectively, confirmed the formation of the zwitterions from Rhodamine B base. The assignments of the 1H and 13C signals were performed by the HMBC method. The colored zwitterion of a practical black color former, 2′-anilino-6′-dibutylamino-3′-methylspiro[3H-isobenzofuran-1, 9′-(9H)xanthene]-3-one, was produced by the addition of M+ and M2+. The 13C NMR signals at 162.2 and 159.8 ppm in the presenc...

Structural Investigation and Preparation of 14-alkyl- 14H-dibenzo(a,j)xanthenes revised

Abstract: at low temperatures. However, we foundthat xanthene derivatives have been producedinstead. Further investigations showed that unhin-dered aliphatic aldehydes react with 2-naphthol togive xanthene derivatives. In the case of isobutyral-dehyde (2-methylpropanal) no reaction wasobserved with 2-naphthol. Preparation of alkyl oraryl derivatives of xanthene at relatively high tem-peratures shows that these are thermodynamicallystable compounds. The main question, whichremains, is that why at low temperatures the reac-tion with aromatic aldehydes stops at methanebi-snaphthol derivatives and hindered aliphaticaldehydes does not proceed at all. Probably, stabil-ity of the carbocation and the bulkiness of the alde-hydes are two key factors governing the reactionfate. In the case of aromatic aldehydes the carboca-tion is very stable and has the opportunity to reactwith another molecule of 2-naphthol, but its Rgroup is too bulky to permit the dehydration step toproceed. The carbocation formed from an aldehydesuch as 2-methylpropanal suffers from both itsmuch less stability and the bulkiness of R.CALCULATIONSTo have some idea of molecular shapes, wereverted to semi-empirical calculations. Molecularorbital calculations were performed by MMX-forcefield implemented in PCMODEL, and AMl calcu-lations were run using MOPAC6.0 program.

Synthesis of 3,4-dioxocularine and aristocularine alkaloids in a convergent route from aryloxy-phenyl acetamides involving oxalyl chloride-Lewis Acid

Abstract: Double cyclization of aryloxy-phenyl acetamides is promoted by oxalyl chloride/stannyl chloride and gives 3,4-dioxocularine and aristocularine alkaloids. Rearrangement of the dibenzoxepine ring prior to the second cyclization produces xanthene derivatives. The synthesized cularinoids exhibit significant activity against various tumoral cell lines.

Resonance Rayleigh Scattering for the Determination of Berberine in Tablet Form with some Acidic Xanthene Fluorescent Dyes

Abstract: A simple determination method of berberine with a limit of determination at the nanogram level is proposed under the use of a common spectrofluorometer to detect the intensity of resonance Rayleigh scattering (RRS). In aqueous solution at pH 4–5, berberine reacts with acidic xanthene fluorescent dyes such as eosine Y, erythrosine, ethyl eosin, phloxin and Rose Bengal to form an ion-associate. This results in a significant enhancement of RRS intensity and the appearance of new RRS spectra. The characteristics of RRS spectra of the ion-associates and the optimum conditions of these reactions have been investigated. The intensity of RRS is directly proportional to the concentration of berberine in the range of 0–5.0 × 10−6 mol/L. The procedures described have a very high sensitivity and the detection limits for berberine are 14–215 ng/ml, and the sensitivity order is eosine Y > erythrosine > ethyl eosin > > phloxin > rose Bengal. The results of analysis for synthetic samples were in good agreement with the desired values, and the ones for tablets were identical with those obtained with the procedure described in the Chinese Pharmacopoeia.

Solubility of Xanthene in Organic Nonelectrolyte Solvents: Comparison of Observed Versus Predicted Values Based Upon Mobile Order Theory

Abstract: Experimental solubilities are reported at 25.0°C for xanthene dissolved in 34 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, cyano and t -butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 27 solvents for which predictions could be made computations show that Mobile order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 71.4%.

Calculation of Partition Coefficients of Organic Reagents in Micellar Thin-Layer Chromatography

Abstract: Equilibrium partition processes were quantitatively estimated for acidic reagents of the xanthene and triphenylmethane series in the system water–surfactant micelle–stationary phase. An anionic surfactant (sodium dodecyl sulfate) was used as the micelle-forming compound. Partition coefficients were calculated, and the preferential solubilization of reagents in surfactant micelles was demonstrated. Energies of reagent transfer to sodium dodecyl sulfate micelles and their adsorption energies at the stationary phase were calculated.

Intermediates for selectively soluble magenta colorants

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.

Synthesis and Photophysical Properties of New Fluorinated Benzo[c]xanthene Dyes as Intracellular pH Indicators.

Abstract: Two new fluorinated benzo[c]xanthene dyes were synthesized by reaction of fluorinated 1,6-dihydroxynaphthalenes with 2,4- (and 2,5)-dicarboxy-3′-dimethylamino-2′-hydroxybenzophenone. The two critical fluorinated 1,6-dihydroxynaphthalene intermediates were prepared via a regioselective route. The fluorinated benzo[c]xanthene dyes exhibit desired lower pKa values (6.4 and 7.2, respectively) than their parent compound (pKa=7.5) while the pH-dependent dual-emission characteristics are well retained. Their cell-permeable esters have been prepared for intracellular applications.

Novel magenta colorants for use 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.

A New Route to Benzo[b]xanthene-6,11,12-trione Derivatives Based on the Photoinduced o-Hydroxy-benzoylation of 1,4-Naphthoquinone

Abstract: A two-step procedure for the synthesis of the title xanthenequinone derivatives is described. The procedure involves the photoinduced acylation of 1,4-naphthoquinone with 2-hydroxybenzaldehydes, followed by treatment withAg 2 O.

Photopolymerization of Butyl Methacrylate in the Presence of Nanoparticles of ZnO, Sensitized to Visible Light with Xanthene Dyes

Abstract: The photopolymerization of butyl methacrylate in isopropanol with participation of nanoparticles of wide-gap semiconductor ZnO has been studied. The possibility of sensitizing ZnO nanoparticles to visible light with a series of halogenated fluoresceins has been established. The rate of photoinitiation of polymerization in the systems studied is principally determined by the rate of electron transfer from the photoexcited molecule of the sensitizer into the conduction zone of the semiconductor nanoparticles.

Substrates colored with novel magenta colorants

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.

Oxygen Transfer from Sulfoxides: Oxidation of Alkylarenes Catalyzed by a Polyoxomolybdate, [PMo12O40]3-.

Abstract: The polyoxomolydate of the Keggin structure, PMo12O403-, catalyzes, under anaerobic conditions, oxygen transfer from sulfoxides to alkylarenes such as xanthene and diphenylmethane to yield xanthen-9-one and benzophenone, respectively. With use of 17O and 18O labeled phenylmethylsulfoxide it was shown that the sulfoxide is complexed by the polyoxometalate and the oxygen is transferred from the sulfoxide to the alkylarene. There is a good correlation between the reaction rate and the heterolytic benzylic C−H bond energy indicating a hydride transfer reaction from the alkylarene to the polyoxometalate−sulfoxide complex. In the case of triphenylmethane the resulting carbocation reacts to yield 9-phenylfluorene as the major product. The reaction kinetics supports such a reaction pathway.

Heat sensitive recording body

Abstract: PROBLEM TO BE SOLVED: To provide a heat sensitive recording body, which is excellent in color developing properties, is favorable in the storage stability of an image obtained by recording and the lowering of a recoding density of which is small even due to the environmental change before recording. SOLUTION: In the heat sensitive recording body having at least a heat sensitive recording layer including a colorless or a light-colored leucocompound, a developer coloring the leucocompound under heat and a coloring accelerator on a support, a 4,4'-dihydroxy diphenyl sulfon is employed as the developer, 6'-[ethyl(3-methyl butyl)amino]-3'-methyl-2'-(phenyl amino)-spiro[isobenzo furan-1(3H),9'-(9H)xanthene]-3-on and 4-anilino-3-methyl-6-dibutyl amino fluorane are employed as the leucocompound, di(P-methyl benzyl) oxalate and aliphatic amide are employed as the coloring accelerator under the condition that 5 to 20% of the total solid of the heat sensitive recording layer is occupied by the aliphatic amide.