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, proficient and an elegant synthetic route for the synthesis of spiroxanthene and dibarbiturate derivatives has been developed under the umbrella of green chemistry as discussed by the authors.
23 citations
TL;DR: Bacterial bioluminescence was shown to be most sensitive to heavy halogen atoms involved in molecular structure; hence, it is suitable for construction of sensors to monitor toxicity of halogenated compounds.
Abstract: The paper investigates an application of luminescent bioassays to monitor the toxicity of organic halides. Effects of xanthene dyes (fluorescein, eosin Y, and erythrosin B), used as model compounds, on bioluminescent reactions of firefly Luciola mingrelica, marine bacteria Photobacterium leiognathi, and hydroid polyp Obelia longissima were studied. Dependence of bioluminescence quenching constants on the atomic weight of halogen substituents in dye molecules was demonstrated. Bacterial bioluminescence was shown to be most sensitive to heavy halogen atoms involved in molecular structure; hence, it is suitable for construction of sensors to monitor toxicity of halogenated compounds. Mechanisms of bioluminescence quenching—energy transfer processes, collisional interactions, and enzyme–dye binding—were considered. Changes of bioluminescence (BL) spectra in the presence of the dyes were analyzed. Interactions of the dyes with enzymes were studied using fluorescence characteristics of the dyes in steady-state and time-resolved experiments. The dependences of fluorescence anisotropy of enzyme-bound dyes, the average fluorescence lifetime, and the number of exponential components in fluorescence decay on the atomic weight of halogen substituents were demonstrated. The results are discussed in terms of “dark effect of heavy halogen atom” in the process of enzyme–dye binding; hydrophobic interactions were assumed to be responsible for the effect.
23 citations
TL;DR: In this article, the fluorescence lifetimes of the acid form of rhodamines B in nitrile solvents were measured as a function of temperature, and the non-radiative rate constants were calculated from fluorescence lifetime and quantum yields.
Abstract: The fluorescence lifetimes of the acid form of rhodamines B in nitrile solvents were measured as a function of temperature. Non-radiative rate constants were calculated from the fluorescence lifetimes and quantum yields. Arrhenius plots of the non-radiative rate constants were linear. The value of the non-radiative activation energy was, within experimental error, the same for all the solvents studied and equal to 3.4 ± 0.3 kcal mol −1 . However, at constant temperature, the natural logarithm of the non-radiative rate constant increased linearly with the solvent polarity parameter E T (30). The dependence of the non-radiative rate on solvent polarity can be explained by a model involving a planar—pyramidal change at the xanthene—amine bond. On the basis of this model, a comparison of the non-radiative rate of the dye in alcohols and nitriles shows that the dependence on solvent polarity is due to specific solute—solvent interactions at the amino and carboxyphenyl groups.
23 citations
TL;DR: An efficient method for the synthesis of new substituted 9-arylxanthenes (2a-2u) starting from diarylcarbinol compounds with an arenoxy group (1a-1u) has been developed using the intramolecular Friedel-Crafts reaction as mentioned in this paper.
Abstract: An efficient organocatalytic method for the synthesis of new substituted 9-arylxanthenes (2a–2u) starting from diarylcarbinol compounds with an arenoxy group (1a–1u) has been developed using the intramolecular Friedel–Crafts reaction The substrates were prepared in two steps by Ullmann-type coupling and then Grignard reaction Some organic Bronsted acids were studied as catalysts (3a–3g) in the intramolecular Friedel–Crafts alkylation reaction for the first time N-triflylphosphoramide (3g) provided the synthesis of some novel substituted 9-arylxanthenes with excellent yields at room temperature within 15 minutes
23 citations
TL;DR: Working with silica nanoparticle encapsulated BODIPY and xanthene photosensitizers, it is determined that singlet oxygen spends up to 78% of its lifetime inside the nanocarriers.
23 citations