Showing papers on "Xanthene published in 2013"

Selective Ruthenium-Catalyzed Three-Component Synthesis of Pyrroles†

Abstract: It's a snap: a novel catalytic three-component coupling reaction using simple and easily available substrates leads to a wide range of substituted pyrroles with high regioselectively (Xantphos=9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene).

Triplet state formation in photoexcited slip-stacked perylene-3,4:9,10-bis(dicarboximide) dimers on a xanthene scaffold.

Abstract: Two covalent perylene-3,4:9,10-bis(dicarboximide) (PDI) dimers in which the PDI molecules are attached to a xanthene (Xan) scaffold in which the long axes of the two π–π stacked PDI molecules are slipped by 4.3 and 7.9 A were prepared. These dimers are designed to mimic J-aggregates and provide insights into the photophysics of triplet state formation in PDI aggregates that target organic electronics. Using ultrafast transient absorption and stimulated Raman spectroscopy, the mechanism of 3*PDI formation was found to depend strongly on a competition between the rate of Xan•+–PDI•– formation involving the spacer group and the rate of excimer-like state formation. Which mechanism is favored depends on the degree of electronic coupling between the two PDI molecules and/or solvent polarity. Singlet exciton fission to produce 3*PDI does not compete kinetically with these processes. The excimer-like state decays relatively slowly with τ = 28 ns to produce 3*PDI, while charge recombination of Xan•+–PDI•– yields ...

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...

Fe3O4 nanoparticles: a highly efficient and easily reusable catalyst for the one-pot synthesis of xanthene derivatives under solvent-free conditions

Abstract: Magnetically separable Fe3O4 nanoparticles supply an environment- ally friendly procedure for the synthesis of 14-aryl-14H-dibenzo(a,j)xanthene and 1,8-dioxooctahydroxanthene derivatives. These compounds were obtained in high yields and short reaction times by the reaction of dimedone and 2-naph- thol with various aromatic aldehydes under solvent-free conditions. The cata- lyst could be easily recovered using an external magnet and reused for six cyc- les with almost consistent activity.

Synthesis, characterization and antimicrobial activity of novel xanthene sulfonamide and carboxamide derivatives

Abstract: Xanthene intermediates 4a and 4b were obtained from the reduction of nitro xanthene derivatives 3a and 3b which were synthesized via condensation of dimedone with m-nitrobenzaldehyde and p-nitrobenzaldehyde, respectively. Then xanthene sulfonamide 6a-n, and xanthene carboxamide derivatives 8a-h were synthesized by reaction of amino xanthene 4a, 4b with sulfonyl chlorides 5a-g and acyl chlorides 7a-d. Structures of the novel amino xanthene compounds and xanthene sulfonamide/carboxamide derivatives were established by their spectral data and elemental analyses. Furthermore, all the synthesized compounds were tested in vitro for their antimicrobial activity. The results were compared with reference standard antibiotics, erythromycin and nystatin. 6c, 6f, 6m and 8b Compounds were found to display most effective antimicrobial activity against a series of bacteria and fungi.

Interfacing Click Chemistry with Automated Oligonucleotide Synthesis for the Preparation of Fluorescent DNA Probes Containing Internal Xanthene and Cyanine Dyes

Abstract: Double-labeled oligonucleotide probes containing fluorophores interacting by energy-transfer mechanisms are essential for modern bioanalysis, molecular diagnostics, and in vivo imaging techniques. Although bright xanthene and cyanine dyes are gaining increased prominence within these fields, little attention has thus far been paid to probes containing these dyes internally attached, a fact which is mainly due to the quite challenging synthesis of such oligonucleotide probes. Herein, by using 2′-O-propargyl uridine phosphoramidite and a series of xanthenes and cyanine azide derivatives, we have for the first time performed solid-phase copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) click labeling during the automated phosphoramidite oligonucleotide synthesis followed by postsynthetic click reactions in solution. We demonstrate that our novel strategy is rapid and efficient for the preparation of novel oligonucleotide probes containing internally positioned xanthene and cyanine dye pairs and thus represents a significant step forward for the preparation of advanced fluorescent oligonucleotide probes. Furthermore, we demonstrate that the novel xanthene and cyanine labeled probes display unusual and very promising photophysical properties resulting from energy-transfer interactions between the fluorophores controlled by nucleic acid assembly. Potential benefits of using these novel fluorescent probes within, for example, molecular diagnostics and fluorescence microscopy include: Considerable Stokes shifts (40–110 nm), quenched fluorescence of single-stranded probes accompanied by up to 7.7-fold light-up effect of emission upon target DNA/RNA binding, remarkable sensitivity to single-nucleotide mismatches, generally high fluorescence brightness values (FB up to 26), and hence low limit of target detection values (LOD down to <5 nM).

A Common Diaryl Ether Intermediate for the Gram‐Scale Synthesis of Oxazine and Xanthene Fluorophores

Abstract: Common ground: copper-catalyzed coupling reactions can be used for the high-yielding preparation of widely used oxazine and xanthene fluorophores from a common diaryl ether intermediate on a gram-scale. This general approach may facilitate the future development of novel fluorophores and probes with unique properties.

A red-emissive aminobenzopyrano-xanthene dye: elucidation of fluorescence emission mechanisms in solution and in the aggregate state

Abstract: We have designed and synthesized a new class of rhodamine dyes with an extended π-conjugated system and named them 3′,3′′-bis(oxospiroisobenzofuran)-3,7-bis(diethylamino)benzopyrano-xanthene (ABPX01) dyes. ABPX01 exhibits fluorescence emission in both dilute solution and the aggregate state, whereas conventional rhodamine dyes show aggregation-induced quenching (AIQ). The chemical species of ABPX01 in solution were determined by spectrophotometric measurements and density functional theory (DFT) calculations to study the relationship among chemical species, color, and fluorescence emission. ABPX01 has various forms: the spirolactone form (ABPX010), which is colorless; and the monocationic form (ABPX01H+) and the dicationic form (ABPX01H22+), which are colored. By orienting a pair of spirolactone benzene moieties differently, the stereoisomers of trans- and cis-ABPX010 were separated and their crystal structures determined. ABPX01H22+ was identified to be a red fluorescent species. Detailed spectroscopic and electron microscopic investigations led to the assumption that the ABPX01H22+ formed ion associates with Cl− as counter anions in HCl aqueous solution, and the nano- and submicrometer-sized colloidal aggregates of ABPX01 hydrochloride exhibit fluorescence emission. To further verify the aggregation-induced emission enhancement (AIEE) mechanism, ABPX01 hydrochloride was synthesized and its fluorescence was similarly checked in the powder state. AIEE in ABPX01 might be attributed to the synergistic combination of the restriction of dye–dye interaction induced dimer formation by sterically hindered ion associates and carboxylic benzene moieties, and the structural rigidity and intermolecular arrangement of the xanthene moiety. We expect that the design strategy of ABPX dyes will be extended to the development of a wide variety of functional organic-dye-based fluorophores (ODFs) with suitable fluorescence-emission controlled mechanisms for many useful applications in new electroluminescent devices.

UV/TiO2 Photocatalytic Degradation of Xanthene Dyes

Abstract: UV/titanium dioxide (TiO2) degradation of two xanthene dyes, erythrosine B (Ery) and eosin Y (Eos), was studied in a photocatalytic reactor. Photocatalysis was able to degrade 98% of Ery and 73% of Eos and led to 65% of chemical oxygen demand removal. Experiments in buffered solutions at different initial pH values reveal the pH dependence of the process, with better results obtained under acidic conditions due to the electrostatic attraction caused by the opposite charges of TiO2 (positive) and of anionic dyes (negative). Batch activity tests under methanogenic conditions showed the high toxicity exerted by the dyes even at low concentrations (~85% with initial concentration of 0.3 mmol L 1 ), but the end products of photocatalytic treatment were much less toxic toward methanogenic bacteria, as detoxification of 85 ± 5% for Eos and 64 ± 7% for Ery were obtained. In contrast, the dyes had no inhibitory effect on the biogeniccarbon biodegradation activity of aerobic biomass, obtained by respirometry. The results demonstrate that photocatalysis combining UV/TiO2 as a pretreatment followed by an anaerobic biological process may be promising for the treatment of wastewaters produced by many industries.

Evaluation of the Photodynamic Activity of Xanthene Dyes on Artemia salina described by Chemometric Approaches

Abstract: The development of drugs for photodynamic therapy (PDT) is an important area of research due to their growing use in medical applications. Therefore, it is important to develop new bioassay methods for PDT photosensitizers that are inexpensive, easy to handle and highly sensitive to environmental conditions. Xanthene dyes (fluorescein, rose bengal B, erythrosine B and eosin Y) with LED light sources were investigated using Artemia salina as a bioindicator of photodynamic activity. In this study, three factors were investigated: (i) photosensitizers concentration, (ii) the LED irradiation time and (iii) the waiting time between the addition of the photosensitizers and the beginning of the irradiation. To analyze the photokilling of A. salina, it was employed a 2 3 full factorial design. The death of A. salina was related to dye structure and the interaction between the irradiation time and the photosensitizers concentration. About 60% of crustaceans death was obtained using rose bengal B, which presentes the highest quantum yield of singlet oxygen due to the number of iodide substituents in the xanthenes ring. The proposed bioassay using A. salina, xanthene dyes and LED irradiation was found suitable for quantitative PDT drug evaluation.

Malachite nanoparticle: A potent surface for the adsorption of xanthene dyes

Abstract: The ability of the Malachite nanoparticles (NPs) for differential adsorption of dye with differential functionality was explored. Fluorescein (with COOH and OH), Rhodamine B (with COOH) and Rhodamine 6G each having same xanthene moiety but differing in their functionality was taken for the study. Fluorescein was adsorbed more followed by other two dyes at pH ∼ 7. Electrostatic interaction was sought to play a major role in the adsorption process. Batch studies were conducted to evaluate the effects of regulating parameters viz. contact time, temperature, adsorbent dosage, and solution pH. Experimental results showed that a steady state was achieved at ∼6 h after which the adsorption seemed constant for all the three dyes. Temperature range of 10–40 °C was taken for the study and the adsorption was found to increase with the temperature. The concentration of dye was varied from 10 to 500 mg L −1 and the maximum adsorption was obtained for Flu with q e value ∼29.54 mg g −1 followed by RB q e value ∼20.74 mg g −1 . R6G was least adsorbed with q e value ∼6.4 mg g −1 . The experimental data found to follow the Langmuir isotherm preferentially and followed second order kinetics. Furthermore effective desorption was carried out using 50% ethanol. Flu was desorbed to ∼99.5% whereas complete extraction of RB and R6G were obtained. The multi-cycle efficiency was also investigated. Overall, the work substantiates the possible use of Malachite NPs as an effective adsorbent for removal of dye from aqueous solution.

A computational study on the energetics and reactivity of some xanthene and thioxanthene derivatives

Abstract: A computational study has been carried out for xanthene and thioxanthene homologous derivatives with keto, hydroxyl, carboxyl, and carboxamide functional groups on position 9, contributing to the understanding of their energetics and reactivity. For that it is presented and compared with the molecular structures, the electrostatic potential energy maps, and the electronic properties of all these heteropolycyclic compounds. The estimation of the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was made only for the thioxanthydrol, thioxanthene-9-carboxylic acid, and thioxanthene-9-carboxamide using the experimental values available in the literature for the homologous compounds containing oxygen.

A green and efficient procedure for one-pot synthesis of xanthenes and acridines using silica boron-sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid

Abstract: Silica boron–sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid have been found to be an efficient heterogeneous catalyst in the synthesis of xanthene and acridine derivatives. The SBSAN-catalyzed reaction between carbonyl compound (aldehyde/ketone/ethyl orthoformate) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) for synthesis of xanthene derivatives is performed under mild conditions with the excellent isolated yield. Also, we can apply a broad scope of carbonyl compounds and amines for efficient synthesis of various acridine derivatives in the presence of SBSAN catalyst. In these multicomponent approaches the SBSAN catalyst can be reused for several times without any treatment in its catalytic activity.

Triarylmethane dye compounds, colored resin composition comprising the same for color filter and color filter using the same

Abstract: PURPOSE: A xanthene-based purple dye compound has excellent solubility to organic solvent, especially to propylene glycol monomethyl ether acetate, and has excellent heat resistance, light-proofness, chemical resistance, and high luminance. CONSTITUTION: A xanthene-based purple dye compound is represented by chemical formula 1. In the chemical formula, X^- is selected from a halogen anion, fluorine complex anion, alkyl sulfate anion, sulfonate anion, and sulfone imide anion; each of R1, R2, R3, and R4 is selected from hydrogen, a substituted or unsubstituted C1-30 alkyl group, a substituted or unsubstituted C2-48 alkenyl group, and a substituted or unsubstituted C6-10 aromatic hydrocarbon; R5 is a substituted or unsubstituted C1-10 saturated hydrocarbon; and R6 is hydrogen or a methyl group.

Reaction of benzoxanthene lignans with peroxyl radicals in polar and non-polar media: cooperative behaviour of OH groups

Abstract: Benzo[kl]xanthene lignans, promising bioactive polyphenols obtained by biomimetic oxidative coupling of caffeic acid derivatives, react efficiently with peroxyl radicals in both polar and non-polar solvents, thanks to the simultaneous presence of guaiacol-like and catechol-like OH-groups.

DABCO Catalyzed Synthesis of Xanthene Derivatives in Aqueous Media.

Abstract: The reaction of 5,5-dimethylcyclohexane-1,3-dione with various heteroarylaldehydes afforded the corresponding heteroaryl substituted xanthene derivatives 1(a–f). The reaction proceeds via the initial Knoevenagel, subsequent Michael, and final heterocyclization reactions using 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalyst in aqueous media. The synthesized heteroaryl substituted xanthenes 1(a–f) reacted with malononitrile to obtain different alkylidenes 2(a–f). Short reaction time, environmentally friendly procedure, avoiding of cumbersome apparatus, and excellent yields are the main advantages of this procedure which makes it more economic than the other conventional methods.

Xanthene and Xanthone Derivatives as G-Quadruplex Stabilizing Ligands

Abstract: Following previous studies on anthraquinone and acridine-based G-quadruplex ligands, here we present a study of similar aromatic cores, with the specific aim of increasing G-quadruplex binding and selectivity with respect to duplex DNA. Synthesized compounds include two and three-side chain xanthone and xanthene derivatives, as well as a dimeric "bridged" form. ESI and FRET measurements suggest that all the studied molecules are good G-quadruplex ligands, both at telomeres and on G-quadruplex forming sequences of oncogene promoters. The dimeric compound and the three-side chain xanthone derivative have been shown to represent the best compounds emerging from the different series of ligands presented here, having also high selectivity for G-quadruplex structures with respect to duplex DNA. Molecular modeling simulations are in broad agreement with the experimental data.

Microwave-induced CAN promoted atom-economic synthesis of 1H-benzo[b]xanthene and 4H-benzo[g]chromene derivatives of N-allyl quinolone and their antimicrobial activity

Abstract: Some new 1H-benzo[b]xanthene and 4H-benzo[g]chromene derivatives of N-allyl quinolone were efficiently synthesized via microwave-induced one-pot three component reaction of N-allyl quinolones, 2-hydroxy-1,4-naphthoquinone and cyclic β-diketones/malononitrile, and iso-propylcyanoacetate in the presence of catalytic amount of ceric ammonium nitrate under solvent-free condition. This methodology allowed us to achieve the desired products in excellent yields in a very short time without the use of solvent. The % atom economy was calculated for all the newly synthesized compounds and found in the range of 92–96 %. Titled derivatives were elucidated by 1H NMR, 13C NMR, FT-IR, elemental analysis, and mass spectral data as well as tested against a panel of pathogenic strains of bacteria and fungi using by microdilution minimum inhibitory concentration method. The structural activity relationship analysis demonstrated that electronic influence and lipophilicity of different groups make much difference in the antimicrobial potency.

Synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[ a ]xanthene-11-ones catalyzed by biodegradable ionic liquid

Abstract: A biodegradable acyclic SO3H-functionalized ionic liquid has been used as a novel catalyst for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones via one-pot multi-component condensation of β-naphthol, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds, under solvent-free conditions, to afford good to excellent yields ranging from 85 to 93 % within 30–60 min. After the reaction the products could be simply separated from the reaction mixture and the catalyst could be recycled and reused several times without noticeable reduction of catalytic activity.

Synthesis and characterization of highly soluble and thermally stable new polyimides based on 3,5-diamino benzoyl amino phenyl-14H-dibenzo[a,j]xanthene

Abstract: A new xanthene-containing diamine monomer was successfully synthesized in four steps by the condensation of β-naphthol and 4-nitrobenzaldehyde in the presence of p-toluenesulfonic acid catalyst, reduction of the nitro intermediate, the nucleophilic substitution reaction of amine compound and 3,5-dinitrobenzoyl chloride, and subsequent reduction of the dinitro compound. The diamine monomer could be obtained in quantitative yield. A series of novel organosoluble aromatic polyimides were prepared by direct polycondensation of synthesized diamine with four tetracarboxylic dianhydrides via a conventional two-step polymerization process. The polymers were obtained in quantitative yields with inherent viscosities of 0.20–0.74 dL/g. Most of the polymers dissolved in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide. The resulting polyimides exhibited good thermal stability; no weight loss was detected before a temperature of 450 °C in nitrogen. Wide-angle X-ray diffraction measurements showed that these polyimides were predominantly amorphous.