Showing papers on "Xanthene published in 2016"

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.

Environmentally Robust Rhodamine Reporters for Probe-based Cellular Detection of the Cancer-linked Oxidoreductase hNQO1

Abstract: We successfully synthesized a fluorescent probe capable of detecting the cancer-associated NAD(P)H:quinoneoxidoreductase isozyme-1 within human cells, based on results from an investigation of the stability of various rhodamines and seminaphthorhodamines toward the biological reductant NADH, present at ∼100–200 μM within cells. While rhodamines are generally known for their chemical stability, we observe that NADH causes significant and sometimes rapid modification of numerous rhodamine analogues, including those oftentimes used in imaging applications. Results from mechanistic studies lead us to rule out a radical-based reduction pathway, suggesting rhodamine reduction by NADH proceeds by a hydride transfer process to yield the reduced leuco form of the rhodamine and oxidized NAD+. A relationship between the structural features of the rhodamines and their reactivity with NADH is observed. Rhodamines with increased alkylation on the N3- and N6-nitrogens, as well as the xanthene core, react the least with ...

Deep-Red and Near-Infrared Xanthene Dyes for Rapid Live Cell Imaging

Abstract: In this work, two xanthene dyes (H-hNR and TF-hNR) have been synthesized by a convenient and efficient method. These two dyes exhibited deep-red and near-infrared emissions, high fluorescence quantum yields, and good photostability. Their structure–optical properties were investigated by X-ray crystal structure analysis and density functional theory calculations. Live cell imaging data revealed that H-hNR and TF-hNR could rapidly stain both A549 and HeLa cells with low concentrations. The excellent photophysical and imaging properties render them as promising candidates for use in live cell imaging.

Detection of gas-phase explosive analytes using fluorescent spectroscopy of thin films of xanthene dyes

Abstract: A sensing system for explosives is demonstrated. The sensor is based on a layered structure of approximately a monolayer of a fluorophore deposited onto a few hundred nm of a transparent polymer, supported by a glass slide. The fluorophores are inexpensive xanthene laser dyes, which have high quantum yields, and the polymers are commodity materials polymethylmethacrylate and polyvinylidene difluoride. The different fluorophore/polymer combinations give different emission responses to analytes, including both signal quenching and enhancement. The pattern of responses can be used to identify the analyte. The common explosives TNT, PETN, RDX, HMX, and TATP as gas phase species can all be uniquely identified at room temperature using only the natural vapor pressure of the explosive to deliver sample to the sensor.

Nanostructured Polymeric Micelles Carrying Xanthene Dyes for Photodynamic Evaluation.

Abstract: It was evaluated the properties of the xanthene dyes Erythrosin B, Eosin Y and theirs Methyl, Butyl and Decyl ester derivatives as possible photosensitizers (PS) for photodynamic treatments. The more hydrophobic dyes self-aggregate in water/ethanol solutions above 70% water (vol/vol) in the mixture. In buffered water, these PS were encapsulated in Pluronic polymeric surfactants of P-123 and F-127 by two methodologies: direct addition and the thin-film solid dispersion methods. The thin-film solid method provided formulations with higher stabilities besides effective encapsulation of the PS as monomers. Size measurements demonstrated that Pluronic forms self-assembled micelles with uniform size, which present slightly negative surface potential and a spherical form detected by TEM microscopy. The ester length modulates xanthene localization in the micelle, which is deeper with the increase in the alkyl chain. Moreover, some PS are distributed into two populations: one on the corona micelle interface shell (PEO layer) and the other into the core (PPO region). Although all PS formulations show high singlet oxygen quantum yield, promising results were obtained for Erythrosin B esters with the hydrophobic P-123, which ensures their potential as drug for clinical photodynamic applications.

A chemosensor for Al3+ ions in aqueous ethanol media: photophysical and live cell imaging studies

Abstract: A novel fluorescent chemosensor L has been designed and synthesized based on the rhodamine-B moiety. The dye L exhibits selective fluorescence enhancement towards the Al3+ ion over other biologically relevant metal ions in aqueous ethanolic media (EtOH–H2O, 2 : 3, v/v). The structure of the probe L has been established by 1H and 13C-NMR spectroscopy, single crystal X-ray diffraction, ESI-mass spectrometry and elemental analysis. The cleavage of the spirolactam bond of the rhodamine moiety induced by the Al3+ ion generates the delocalized xanthene fluorophore that is responsible for the emission enhancement of the probe L. The recognition behavior of the receptor L has been investigated experimentally with supports from theoretical DFT studies. Furthermore, the efficacy of L in cell imaging studies is also probed by confocal microscopy.

Choline chloride and itaconic acid-based deep eutectic solvent as an efficient and reusable medium for the preparation of 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones

Abstract: Choline chloride and itaconic acid-based deep eutectic solvent has been identified as an effective catalyst and reaction medium for synthesis of 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones by condensation of 2-hydroxynaphthalene-1,4-dione with various aldehydes. The reaction conditions are mild and environmentally friendly.

Palladium–copper catalyzed C(sp3)–C(sp2) bond C–H activation cross-coupling reaction: selective arylation to synthesize 9-aryl-9H-xanthene and 9,9-diaryl-xanthene derivatives

Abstract: A novel cooperatively catalyzed C(sp3)–C(sp2) bond C–H activation cross-coupling reaction has been developed. A series of 9-aryl-9H-xanthenes and 9,9-diaryl-xanthenes were selectively synthesized in moderate to good yields by controlling the reaction time and temperature.

Fe2+ supported on hydroxyapatite-core–shell-γ-Fe2O3 nanoparticles: Efficient and recyclable green catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives

Abstract: In this work, Fe2+ supported on hydroxyapatite-core–shell-γ-Fe2O3 nanoparticles (γ-Fe2O3–HAp-Fe2+ NPs) has been prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and vibrating sample magnetometry spectra. Then, γ-Fe2O3–HAp-Fe2+ NPs were used as an efficient, reusable and heterogeneous nanocatalyst for one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes via the one-pot condensation reaction of arylaldehydes and 2-naphthol under solvent-free conditions in good to excellent yields. This procedure has a lot of advantages such as very easy reaction conditions, simplicity in operation, short reaction time, high yield, and green aspects by avoiding toxic conventional catalysts and solvents. Additionally, γ-Fe2O3–HAp-Fe2+ NPs were easily recycled from the reaction mixture and were reused seven times without any loss in activity.

Chitosan and imide-functional Fe3O4 nanoparticles to prepare new xanthene based poly(ether-imide) nanocomposites

Abstract: In this work a new series of multifunctional nanocomposites were synthesized based on a soluble poly(ether-imide). The poly(ether-imide) was successfully synthesized via direct polycondensation reaction. A methyl rich diamine containing xanthene group as a new monomer was synthesized and used for polymerization. The xanthene based poly(ether-imide) was characterized using size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR). Fe3O4 nanoparticles were imide-functionalized by a dianhydride, chitosan and phenylalanine. The functional Fe3O4 nanoparticles were incorporated into the new synthesized poly(ether-imide). Effects of the functionalized Fe3O4 nanoparticles on the thermal and combustion properties of the corresponding nanocomposites were investigated. Thermogravimetric analysis (TGA) results indicated that the thermal stability and char yields of the nanocomposites were enhanced compared to the neat poly(ether-imide). Microscale combustion calorimetry (MCC) revealed that the synthesized poly(ether-imide) had low flammability. The incorporation of functional Fe3O4 nanoparticles could further improve the combustion properties of poly(ether-imide). The high interaction between poly(ether-imide) and functional Fe3O4, the presence of an imide group and high hydroxyl content of the functional Fe3O4 nanoparticles seem to be responsible for the improvement of the thermal and combustion properties. Furthermore, the presence of methyl, ether and bulky xanthene groups in the polyimide backbone decreased the glass transition temperature (Tg) and increased the solubility in organic solvents. These properties will be useful for processing and new applications of poly(ether-imide).

A red fluorophore comprising a borinate-containing xanthene analogue as a polyol sensor

Abstract: A xanthene derivative containing a borinate moiety emitted red fluorescence with a high quantum yield. The interaction between the borinate and a sugar molecule induced a fluorescence change based on the change in the HOMO–LUMO gap. The response was pH-resistant in a wide range. In addition, catechol quenched through photoinduced electron transfer. The red fluorescence and polyol binding ability of dyes will pave the way for new biological applications of chemical sensors.

One-pot solvent-free synthesis of 1,8-dioxo-octahydroxanthene derivatives using sulfonic acid-functionalized LUS-1 and their antimicrobial activities

Abstract: An efficient acidic functionalization of mesoporous silica LUS-1 (Laval University silica) was carried out by grafting and oxidation of (3-mercaptopropyl)trimethoxysilane The functionalized LUS-1 was characterized by different methods such as TGA, XRD, BET and SEM methods and its catalytic activity for one-pot synthesis of xanthene derivatives via the three-component condensation reaction of aromatic aldehydes and dimedone has been reported The short reaction time, excellent yields, simple work-up procedure, and environmentally friendly conditions are particular advantages of this method Antibacterial and antifungal activities of synthesized compounds were measured against gram-positive and gram-negative bacteria and fungus Only compound 9-(2,4-dichlorophenyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione (3h) showed activity against Bacillus subtilis

Nano-Fe3O4 -encapsulated silica particles bearing sulfonic acid groups as a magnetically separable catalyst for the green and efficient synthesis of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives

Abstract: In this research, an efficient and environmentally friendly ("green") method for one-pot synthesis of xanthene derivatives was developed in the presence of Fe3O4@SiO2–SO3H nanoparticles. The functionalization of silica-coated Fe3O4 magnetite nanoparticles (Fe3O4@SiO2) using chlorosulfonic acid was afforded by nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid (Fe3O4@SiO2–SO3H) that could be applied as a reusable and efficient heterogeneous nanocatalyst. The multicomponent reactions of 2-hydroxy-1,4-naphthoquinone, β-naphthol and aldehydes were carried out under reflux conditions to obtain some 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives. Being a simple procedure with environmental benignness, excellent yields, short reaction times, simple purification and facile catalyst separation are the advantages of this protocol. Fe3O4@SiO2–SO3H was readily recovered using an external magnet and could be reused several times without significant loss of reactivity. The catalyst was fully characterized by vibrating sample magnetometry (VSM), Fourier transform-infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, energy dispersive X-ray spectroscopy (EDAX) and transmission electron microscopy (TEM).

Metal free synthesis of tetrahydrobenzo[a]xanthenes using orange peel as a natural and low cost efficient heterogeneous catalyst

Abstract: In this work, a facile, efficient and metal free catalytic system has been developed for the synthesis of tetrahydrobenzo[a]xanthene derivatives via a one-pot three-component condensation of various aldehydes, 2-naphthol, and dimedone. For the first time, the orange peel as a green, acidic, and low cost natural catalyst with high porosity and high efficiency was used in tetrahydrobenzo[a]xanthenes synthesis procedure. This environmental-friendly novel catalytic system led to the desired products in high to excellent yields under solvent free conditions at 120 °C.

Visible Light‐Driven Hydrogen Evolution from Aqueous Solution in a Noble‐Metal‐Free System Catalyzed by a Cobalt Phthalocyanine

Abstract: Solar-driven hydrogen evolution from water has emerged as an important methodology for the storage of renewable energy in chemical bonds. Efficient photochemical splitting of water requires the highly active and low-cost hydrogen-evolving catalysts, which remains a significant challenge. After screening a series of metallophthalocyanines (MPcs), the macrocyclic cobalt phthalocyanine (CoPc) is found to be an active catalyst for visible light-driven H2 production under basic conditions (pH=12.0) in water/ethanol mixed solvent when employed with xanthene dyes as the photosensitizers (PSs) and triethylamine (TEA) as the sacrificial electron donor. The noble-metal-free system gives the highest TON of 2650 with respect to the catalyst, corresponding to a TOF of ca. 810 h−1. By means of UV/vis and fluorescent spectroscopy as well as computational studies and electrochemistry, a possible catalytic mechanism of the hydrogen-generating reaction involving organo hydrides not cobalt hydrides was proposed. To the best of our knowledge, this is the first example of utilizing a cobalt phthalocyanine as molecular catalyst for the photogeneration of hydrogen from water.

Distribution of Xanthene Dyes in DPPC Vesicles: Rationally Accounting for Drug Partitioning Using a Membrane Model

Abstract: The correct selection of a dye that has effective action as a photosensitizer is a primary concern for successful therapeutic outcomes. The effectiveness of the photodynamic agent is related to both the targeting of cell membranes and the photochemical yield of the chosen dye. The distributions of xanthene derivatives Eosin Y, Erythrosin B, and Rose Bengal B in vesicles of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in both liquid-crystalline and gel phases were investigated by fluorescence spectroscopy. Binding constants, fluorescence anisotropy, fluorescence quenching, fluorescence quantum yield, and fluorescence resonance energy transfer at physiological pH conditions were determined. To Erythrosin B and Eosin Y, the iodide quenching rate constant was shown to involve a sphere of action mechanism driven by a specific interaction between Erythrosin B and Eosin Y molecules and the choline head-group of the phospholipid; in contrast, Rose Bengal B was located deep in the membrane and this mechanism was not present. The dyes can be ordered by their penetration depth in the membrane, and this order was found to be Eosin Y < Erythrosin B < Rose Bengal B. These results demonstrate a rational approach for the screening of more active agents for photodynamic therapy based on the affinity between the xanthene derivatives and DPPC vesicles.

Synthesis of a new iron–sulfur cluster compound and its photocatalytic H2 evolution activity through visible light irradiation

Abstract: A new iron–sulfur cluster compound, namely [(μ-BNT)Fe2(CO)6] (A; BNT = (R)-1,1′-binaphthalene-2,2′-dithiol), was synthesized by self-assembly of BNT with [Fe3(CO)12] and characterized using 1H NMR, 13C NMR, infrared spectra and elemental analysis. The H2 evolution activity of A was evaluated in a constructed homogeneous photocatalytic system by combining A as catalyst, xanthene dyes as photosensitizer and triethylamine as sacrificial reagent, to give efficient H2 generation under visible-light irradiation (λ > 420 nm). The maximum H2 evolution of 404 turnovers (versus catalyst) was recorded under optimal conditions in CH3CN–H2O (1:1, v/v) after 4 h irradiation. The mechanism of H2 evolution is briefly discussed using fluorescence spectra and electrochemical analysis. Copyright © 2016 John Wiley & Sons, Ltd.

One-pot synthesis of xanthene derivatives catalyzed by Fe(III) tetranitrophthalocyanine immobilized on activated carbon

Abstract: Xanthene derivatives were synthesized by a multicomponent one-pot reaction of aromatic aldehydes, β-naphthol, and 5,5-dimethylcyclohexane-1,3-dione or 1,3-cyclohexanedione upon efficient and eco-friendly catalysis of Fe(III) tetranitrophthalocyanine immobilized on activated carbon in ethanol. The method tolerated a variety of functional groups and the process was carried out under mild conditions to give high yield of products (85–91%) in 30 min. The catalyst can be recycled without any loss in catalytic activity.

Excited States of Xanthene Analogues: Photofragmentation and Calculations by CC2 and Time-Dependent Density Functional Theory.

Abstract: Action spectroscopy has emerged as an analytical tool to probe excited states in the gas phase. Although comparison of gas-phase absorption properties with quantum-chemical calculations is, in principle, straightforward, popular methods often fail to describe many molecules of interest—such as xanthene analogues. We, therefore, face their nano- and picosecond laser-induced photofragmentation with excited-state computations by using the CC2 method and time-dependent density functional theory (TDDFT). Whereas the extracted absorption maxima agree with CC2 predictions, the TDDFT excitation energies are blueshifted. Lowering the amount of Hartree–Fock exchange in the DFT functional can reduce this shift but at the cost of changing the nature of the excited state. Additional bandwidth observed in the photofragmentation spectra is rationalized in terms of multiphoton processes. Observed fragmentation from higher-lying excited states conforms to intense excited-to-excited state transitions calculated with CC2. The CC2 method is thus suitable for the comparison with photofragmentation in xanthene analogues.

Design and synthesis of a rhodol isomer and its derivatives with high selectivity and sensitivity for sensing Hg2+ and F− in aqueous media

Abstract: Because of their high extinction coefficients, high quantum yields, and reasonable water solubility, xanthene dyes have played crucial roles in the field of molecular imaging as fluorescent tracers. In this work, a novel hydroxyl regioisomeric rhodol 1 has been designed and synthesized. Both absorption and fluorescence data in water revealed that the rhodol isomer 1 can generate stable optical signals in the pH range 4–10. The maximum absorbance wavelength (ca. 540 nm) of 1 meets perfectly the discrete excitation of the laser at 539 nm, and the emission maximum wavelength (ca. 590 nm) is largely red shifted compared to that of the rhodol fluorophore (ca. 540 nm). Meanwhile, the dye could be easily designed to form chemodosimeters or probes by modification of the carboxyl group or the hydroxyl group. The hydrazide derivative and the silyl ether derivative of the dye in aqueous media exhibited excellent selectivity and sensitivity toward Hg2+ and F−, respectively. Thus, the excellent optical properties and chemical properties of this dye allow it to be designed as a fluorescent tracer for biological applications.

Ruthenium anchored on multi-walled carbon nanotubes: an efficient and reusable catalyst for the synthesis of xanthenes

Abstract: A novel and highly efficient ruthenium-based catalyst was synthesized by immobilizing Ru(CO)4 onto functionalized multi-walled carbon nanotubes. The catalyst was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, diffuse reflectance UV–Vis spectrophotometry, inductively coupled plasma and elemental analysis. This heterogeneous catalyst was successfully applied in the multi-component synthesis of various xanthene derivatives in good to excellent yields (28 samples, up to 96 % yield) under reflux condition and ultrasonic irradiation. The prepared catalyst was recovered four times without appreciable loss of activity.

New synthetic strategies for xanthene-dye-appended cyclodextrins

Abstract: Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). By using 6-monoamino-β-cyclodextrin and commercially available inexpensive dyes, we prepared rhodamine- and fluorescein-appended cyclodextrins. The compounds were characterized by NMR and IR spectroscopy and MS spectrometry, their UV–vis spectra were recorded at various pH, and their purity was determined by capillary electrophoresis. Two potential models for the supramolecular assembly of the xanthene-dye-appended cyclodextrins were developed based on the set of data collected by the extensive NMR characterization.