Topic
Xanthene
About: Xanthene is a research topic. Over the lifetime, 2132 publications have been published within this topic receiving 34803 citations. The topic is also known as: Xanthene & dibenzo[a,e]pyran.
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TL;DR: A simple, efficient, and eco-friendly synthetic protocol has been developed for the synthesis of pyranoxanthenes via one pot three-component reaction This reaction is between aromatic aldehyde, 2,2-dimethylchroman-7-ol and 1,3-cyclohexanedione by using molecular iodine in AcOH as a reaction medium under microwave irradiation.
9 citations
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TL;DR: Treatment of either p-tert-butylcalix[4]arene (3), xanthene or 9,10 dihydroanthracene with diphenyl ether in the presence of Nafion-H results in the formation of [9,9]spirobixanthene (5).
9 citations
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TL;DR: The slopes of the linear relationship between the increase in the dipole potential of phospholipid bilayers and the concentration of styrylpyridinium dyes in membrane-bathing solutions were found and the relationships between the change in φd and the chemical structure of modifiers, as well as the charge and spontaneous curvature of lipid monolayers.
Abstract: This paper assesses the magnitude of change in the dipole potential (φd) of membranes caused by the adsorption of modifiers on lipid bilayers of various compositions. We tested flavonoids, muscle relaxants, thyroid hormones, and xanthene and styrylpyridinium dyes in order to assess their dipole-modifying properties. A quantitative description of the modifying action of flavonoids, muscle relaxants, thyroid hormones, and xanthene dyes is shown as the ratio of the maximum change in the bilayer dipole potential upon saturation and the absolute φd value of the unmodified membrane. The slopes of the linear relationship between the increase in the dipole potential of phospholipid bilayers and the concentration of styrylpyridinium dyes in membrane-bathing solutions were found. We described the relationships between the change in φd and the chemical structure of modifiers, as well as the charge and spontaneous curvature of lipid monolayers.
9 citations
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TL;DR: In this paper, the authors measured the fluorescence lifetime of rhodamine B in a series of normal alcohols (C/sub n/H/sub 2n-1/OH, n = 1-6) as a function of temperature.
Abstract: The fluorescence lifetime of rhodamine B in a series of normal alcohols (C/sub n/H/sub 2n-1/OH, n = 1-6) was measured as a function of temperature. The nonradiative rate constants were calculated from the fluorescence lifetimes and quantum yields. Activation energies were obtained from Arrhenius plots of the nonradiative rate constant. The variation of the nonradiative rate constant with solvent polarity and temperature was consistent with a photophysical mechanism that involves equilibrium between the planar and twisted configurations of the diethylamino groups on the xanthene ring of rhodamine B and internal conversion from the twisted configuration. The activation energy is equal to the free energy difference between the twisted and planar configurations. The solvent polarity dependence of the free energy difference and of the rate constant for internal conversion from the twisted configuration determines the variation of the nonradiative rate constant with solvent. When solvent polarity effects are taken into account by using the parameter E/sub T/(30), the nonradiative rate constant shows weak or no dependence on the solvent viscosity.
9 citations
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TL;DR: In this paper, the dyes suitable for the sensitization of the polymerization of acrylonitrile have been determined among various dyes, including xanthene and acridine.
Abstract: Among various dyes, the dyes suitable for the sensitization of the polymerization of acrylonitrile have been determined. Acridine and xanthene dyes have been found to be the most effective. Using acridine yellow, one of the most effective, the dye-sensitized photopolymerization has been investigated in detail; it has been shown that the reaction has several features characteristic of heterogeneous polymerization, e.g., its order is higher than one-and-a-half on monomer concentration. Assuming the initiation process to be a direct interaction between excited dye and monomer, and assuming the unimolecular termination by occlusion of the propagating radicals, the kinetic data has been interpreted.
9 citations