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.

Molecular polarisability. The conformations as solutes of phenoxathiin, xanthene, and thioxanthene

Abstract: The molar Kerr constants, dipole moments, refractivities, etc., are reported for phenoxathiin, xanthene, and thioxanthene examined as solutes in carbon tetrachloride and in benzene. The experimental data are analysed to indicate that the solute molecules have nonplanar, folded conformations defined by dihedral angles, Φ, of 138°(±6°), 160°(±6°), and 135°(±8°), respectively.

9-(4-Methoxy-phen-yl)-3,3,6,6-tetra-methyl-3,4,6,7-tetra-hydro-2H-xanthene-1,8(5H,9H)-dione.

Abstract: In the mol­ecule of the title compound, C24H28O4, the three six-membered rings of the xanthene system are not planar, having envelope, boat and envelope conformations. In the crystal structure, C—H⋯O hydrogen bonds link the mol­ecules, generating centrosymmetric R22(12), R44(28) and R22(16) ring motifs and forming a three-dimensional network.

High‐optical transparency and low‐dielectric constant of new organosoluble polyamides containing trifluoromethyl and xanthene groups

Abstract: A series of fluorinated polyamides was prepared directly by low-temperature polycondensation of a new cardo diacid chloride, 9,9-bis[4-(4-chloroformylphenoxy)phenyl]xanthene (BCPX), with various diamines containing trifluoromethyl substituents in N,N-dimethylacetamide (DMAc). Almost all polyamides showed excellent solubility in amide-type solvents such as DMAc and could also be dissolved in pyridine, m-cresol, and tetrahydrofuran. These polymers had inherent viscosities between 0.77 and 1.31 dL g−1, and their weight-average molecular weights and number-average molecular weights were in the range of 69,000–102,000 and 41,000–59,000, respectively. The resulting polymers showed glass transition temperatures between 240–258°C and 10% weight loss temperatures ranging from 484°C to 517°C and 410°C to 456°C in nitrogen and air, respectively, and char yields at 800°C in nitrogen higher than 55%. All polymers were amorphous and could be cast into transparent, light-colored, and flexible films with tensile strengths of 81–100 MPa, elongations at break of 8–12%, and tensile modulus of 1.6–2.1 GPa. These polymers had low-dielectric constants of 3.34–3.65 (100 kHz), low-moisture absorption in the range of 0.76–1.91%, and high transparency with an ultraviolet–visible absorption cut-off wavelength in the 322–340 nm range. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

One-Pot Synthesis of New Symmetric and Asymmetric Xanthene Dyes.

Abstract: Symmetric and asymmetric xanthene dyes have been prepared by a convenient one-step procedure from aldehyde and diol or m-aminophenol precursors using concentrated phosphoric acid as a solvent. This protocol provides access to water-soluble dyes with large Stoke's shifts and far-red fluorescence emission. These compounds are envisioned as components of fluorescence-based sensors for a variety of imaging applications.

ESR Study on Fluorescein Semiquinone Radical

Abstract: The ESR spectrum of the fluorescein semiquinone radical (dianion form) produced by illumination of an alkaline aqueous solution of uranine and leuco-uranine at pH between 11 and 14 was observed and its hfs constants were determined by comparing the spectrum with those of the mono- and trianion forms of fluorescein semiquinone and those of eosm semiquinone reported by Leaver. Six protons in the xanthene ring were found to be comprised of three pairs of magnetically equivalent protons, which suggests a certain dynamic mechanism to average the coupling constants. From a temperature dependence of the line width, protonation to the –O− group followed by deprotonation from the –OH group was proposed as a plausible mechanism.