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.

Determination of S * -T Transition Probabilities of Some Xanthene and Thiazine Dyes on the Basis of T-Energy Transfer. II. Results in the Aqueous Solution

Abstract: Intersystem crossing probability \varphiSTA for fluorescein, eosin, erythrosin, methylene blue and thionine in the aqueous solution of pH 7.2 (only for fluorescein 0.05N NaOH solution) has been determined by comparing the quantum yield of the nonsensitized (Φ) and the sensitized photo-reduction (ΦS) on the basis of the relationsΦ=\varphiSTAβA ΦS=\varphiSTDβγA,where βA is the fraction of triplet dye molecules that undergo reduction, \varphiSTA and \varphiSTD are respectively for acceptor (dye) and donor (sensitizer), and γ is the energy transfer efficiency. This was assumed as unity. ATU and EDTA were used as a reducing agent. 1,5-Naphthalenedisulfonic acid and 1-anthracenesulfonic acid were used as sensitizers. The above relations and assumption have been found to hold satisfactorily. The \varphiSTD values for two sensitizers were determined using erythrosin as a reference substances for which \varphiSTA was assumed to be unity. \varphiSTD obtained was 0.88 for 1,5-naphthalenedisulfonic acid, and 0.82 for...

A diversity-oriented rhodamine library for wide-spectrum bactericidal agents with low inducible resistance against resistant pathogens

Abstract: Antimicrobial resistance is a public health emergency and warrants coordinated global efforts. Challenge is that no alternative molecular platform has been identified for discovery of abundant antimicrobial hit compounds. Xanthene libraries have been screened for bioactive compounds. However, the potentially accessible chemistry space of xanthene dyes is limited by the existing xanthene synthesis. Herein we report a mild one-step synthesis, which permits late-stage introduction of a xanthene moiety onto i.e. natural products, pharmaceuticals, and bioactive compounds and construction of a focused library of rhodamine dyes exhibiting facile functional, topographical and stereochemical diversity. In vitro screening yields 37 analogs with mid-to-high bactericidal activity against WHO priority drug-resistant pathogens. These findings suggest that synthetic dye libraries exhibiting high structural diversity is a feasible chemical space combating antibacterial resistance, to complement the natural sources.

Fluorescence and electronic action spectroscopy of mass-selected gas-phase fluorescein, 2',7'-dichlorofluorescein, and 2',7'-difluorofluorescein ions.

Abstract: 2′,7′-Dichloro- and 2′,7′-difluorofluoresceins are superior alternatives to underivatized fluorescein. Although several studies characterizing their condensed-phase photophysical properties have been reported, little is known about their intrinsic characteristics. Here, the gas-phase properties of three charge states of each fluorescein are characterized using a quadrupole ion trap mass spectrometer which has been modified for spectroscopy. Electronic action spectra, constructed by monitoring the extent of photodissociation as a function of excitation wavelength, indicate that the gaseous dianions and cations resemble their solution-phase counterparts. In contrast, a large shift in the electronic action spectra of the monoanions indicates the presence of a different tautomer in the gas phase than that present in solution. The gaseous monoanion is deprotonated on the xanthene ring, rather than being deprotonated on the pendant group as found in soluion. The dianions and cations do not emit detectable fluor...

Spiro[fluorene-9,90-xanthene]-basedhole transporting materials for efficient perovskite solar cells with enhancedstability

Abstract: Four spiro[fluorene-9,9′-xanthene] (SFX)-based hole transporting materials (HTMs) functionalized with four-armed arylamine moieties located at different positions are designed and synthesized. These compounds exhibit highest occupied molecular orbital (HOMO) energy levels of −4.9 to −5.1 eV and a hole mobility of 2.2 to 15 × 10−5 cm2 V−1 s−1 after doping. Perovskite solar cells (PSCs) based on a methylammonium lead iodide (MAPbI3) active layer using one of these HTMs (mp-SFX-2PA) exhibit power conversion efficiencies (PCEs) of up to 16.8%, which is higher than that of the control devices based on benchmark spiro-OMeTAD under the same conditions (15.5%). PSCs based on mp-SFX-2PA exhibit better stability (retain 90% of their initial PCEs after 2000 h storage in an ambient atmosphere) than the control devices based on spiro-OMeTAD (retain only 28% of their initial PCEs). mp-SFX-2PA based devices employing a mixed formamidinium lead iodide (FAPbI3)/methylammonium lead bromine (MAPbBr3) perovskite layer exhibit an improved PCE of 17.7%. The effects of arylamines and their location positions on device performance are discussed.