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.

Gas-phase action and fluorescence spectroscopy of mass-selected fluorescein monoanions and two derivatives

Abstract: Gaseous fluorescein monoanions are weakly fluorescent; they display a broad fluorescence spectrum and a large Stokes shift. This contrasts with the situation in aqueous solution. One explanation of the intriguing behavior in vacuo is based on internal proton transfer from the pendant carboxyphenyl group to one of the xanthene oxygens in the excited state; another that rotation of the carboxyphenyl group relative to the xanthene leads to a partial charge transfer from one chromophore (xanthene) to the other (carboxyphenyl) when the π orbitals start to overlap. To shed light on the mechanism at play, we synthesized two fluorescein derivatives where the carboxylic acid group is replaced with either an ester or a tertiary amide functionality and explored their gas-phase ion fluorescence using the home-built LUminescence iNstrument in Aarhus (LUNA) setup. Results on the fluorescein methyl ester that has no acidic proton clearly disprove the former explanation: The spectrum remains broad, and the band center (at 605 nm) is shifted even more to the red than that of fluorescein (590 nm). Experiments on the other variant that contains a piperidino amide are also in favor of the second explanation as here the piperidino already causes the dihedral angle between the planes defining the xanthene and the benzene ring to be less than 90° in the ground state (i.e., 63°), according to density functional theory calculations. As a result of the closer similarity between the ground-state and excited-state structures, the fluorescence spectrum is narrower than those of the other two ions, and the band maximum is further to the blue (575 nm). In accordance with a more delocalized ground state of the amide derivative, action spectra associated with photoinduced dissociation recorded at another setup show that the absorption-band maximum for the amide derivative is redshifted compared to that of fluorescein (538 nm vs. 525 nm).

One-Pot Synthesis of Xanthene Derivatives Using Silica Supported (2-(Sulfooxy)ethyl)sulfamic Acid as a Novel and Efficient Catalyst Under Solvent-Free Condition

Abstract: An efficient and simple method for the synthesis of xanthenes derivatives is described via one-pot condensation of various aldehydes and 2-naphthol using (2-(sulfooxy)ethyl)sulfamic acid (SESA) as a novel catalyst. Different types of aromatic aldehydes were used in the reaction and in all cases the products synthesized successfully Use of easily available catalyst, time minimizing, excellent yields, simplicity of the reaction, heterogeneous system, a cleaner reaction and easy work- up are the advantages of the present method.

Preparation method for 9,9-diaryl thiophene xanthene-10,10-dioxide

Abstract: The invention discloses a preparation method for 9,9-diaryl thiophene xanthene-10,10-dioxide, and belongs to the field of fine organic synthesis and organic semiconductor material preparation. The preparation method comprises the following steps: using diphenylsulphone as a starting material and tetrahydro furan as a solvent, conducting ortho metalation reaction on diphenylsulphone under the action of n-butyllithium within a temperature range of -78-0 DEG C to obtain a corresponding aryl lithium salt; allowing the aryl lithium salt to react with an added aryl formic ether ester derivative, and performing hydrolysis to obtain a corresponding tertiary alcohol; dissolving the tertiary alcohol and electron-rich aromatic with an acetate or methylene chloride solution, using Lewis acid as a catalyst, and carrying out friedel-crafts reaction to obtain the 9,9-diaryl thiophene xanthene-10,10-dioxide. The preparation method has the advantages that the reactions are easy to control, the operation is simple, the cost is low, the repeatability is good, the productivity is high, and the product quality is high; an organic modular unit and an organic functional semiconductor can be conveniently made; the 9,9-diaryl thiophene xanthene-10,10-dioxide is used in the fields of organic light emitting diodes, organic transistors, organic laser, and organic nonlinear optics, and the like.