Showing papers on "Xanthene published in 2018"

Fur-Imine-Functionalized Graphene Oxide-Immobilized Copper Oxide Nanoparticle Catalyst for the Synthesis of Xanthene Derivatives.

Abstract: Fur-imine-functionalized graphene oxide-immobilized copper oxide nanoparticles (Cu(II)-Fur-APTES/GO) are synthesized and found to be a cost-effective, efficient, and reusable heterogeneous nanocatalyst for the preparation of pharmaceutically important xanthene derivatives under greener solvent conditions. Cu(II)-Fur-APTES/GO exhibits excellent result in the synthesis of xanthenes with reduced reaction time (25−50 min) and higher yields (up to 95%) and has a simple procedure, ease of product separation, and no byproducts. Moreover, the nanocatalyst has a Cu loading of 13.5 at. % over functionalized GO which is far superior than the already known metal-based heterogeneous catalysts. The newly synthesized catalyst has been characterized by various physiochemical techniques such as X-ray photoelectron spectroscopy, X-ray diffraction, energy-dispersive X-ray, Raman spectroscopy for structural characterization, field emission scanning electron microscopy and high-resolution transmission electron microscopy for ...

[4 + 2] Cyclization of para-Quinone Methide Derivatives with Alkynes

Abstract: The first cyclization of para-quinone methide derivatives with alkynes was established by utilizing the [4 + 2] reaction of ortho-hydroxyphenyl-substituted para-quinone methides with ynones or benzyne, which efficiently constructed the scaffolds of chromene and xanthene in high yields (up to 88%). This protocol has not only fulfilled the task of developing cyclization reactions of para-quinone methide derivatives but also provided an efficient method for constructing chromene and xanthene scaffolds.

Synthesis of sulfamic acid supported on Cr-MIL-101 as a heterogeneous acid catalyst and efficient adsorbent for methyl orange dye

Abstract: Typical highly porous metal–organic framework (MOFs) materials based on chromium benzenedicarboxylates (Cr-BDC) were prepared through a one-pot hydrothermal synthesis, and were then modified by loading the appropriate ratio of sulfamic acid (SA) using a simple impregnation technique. Pure and modified MIL-101 was characterized by XRD, TEM, SEM and FT-IR measurements. TEM and SEM measurements confirmed that the MIL-101 particles preserved their regular octahedral structure after loading with different weight contents of sulfamic acid. The total number of acid sites and Bronsted to Lewis acid sites ratio (B/L) were examined using potentiometric titration and pyridine adsorption. The acid strength and surface acidity of SA/MIL-101 gradually increased after the modification of Cr-MIL-101 by sulfamic acid crystals up to 55 wt%, then decreased again. The catalytic performance of the solid catalysts was confirmed in the synthesis of 14-phenyl-14H-dibenzo [a,j] xanthene and 7-hydroxy-4-methyl coumarin. In the two reactions, the sample with 55% sulfamic acid loaded on MIL-101 displayed the highest catalytic activity and acidity. The adsorption behaviors of sulfamic acid loaded on MIL-101 materials for methyl orange (MO) as an anionic dye were studied, and were exceptionally suitable for the Langmuir adsorption isotherm. All loaded adsorbents showed high adsorption capacity for methyl orange at 25 °C. The results indicate that the adsorption capacity was modified by changing the amount of sulfamic acid loaded on MIL-101.

DDQ-mediated direct C(sp3)–H phosphorylation of xanthene derivatives

Abstract: A convenient and efficient C(sp3)–H phosphorylation has been achieved via the metal-free DDQ-mediated cross-dehydrogenative coupling between diarylphosphine oxides and xanthene derivatives at room temperature. This transformation provides a direct synthetic route to the construction of C(sp3)–P bonds with good functional group compatibility, leading to the formation of alkylphosphonates in up to 96% yield.

Precise Control of Thermal and Redox Properties of Organic Hole-Transport Materials

Abstract: We report design principles of the thermal and redox properties of synthetically accessible spiro-based hole transport materials (HTMs) and show the relevance of these findings to high-performance perovskite solar cells (PSCs). The chemical modification of an asymmetric spiro[fluorene-9,9'-xanthene] core is amenable to selective placement of redox active triphenylamine (TPA) units. We therefore leveraged computational techniques to investigate five HTMs bearing TPA groups judiciously positioned about this asymmetric spiro core. It was determined that TPA groups positioned about the conjugated fluorene moiety increase the free energy change for hole-extraction from the perovskite layer, while TPAs about the xanthene unit govern the Tg values. The synergistic effects of these characteristics resulted in an HTM characterized by both a low reduction potential (≈0.7 V vs. NHE) and a high Tg value (>125 °C) to yield a device power conversion efficiency (PCE) of 20.8 % in a PSC.

Electrochemical synthesis of AuPt nanoflowers in deep eutectic solvent at low temperature and their application in organic electro-oxidation

Abstract: Deep eutectic solvents (DESs), called a new generation of green solvents, have broad applied in synthesis of nanomaterials due to their remarkable physicochemical properties In this work, we used a unique strategy (adding moderate water (10%) to DES) to effectively prepare nanomaterials Flower-like AuPt alloy nanoparticles were successfully synthesized using one-step electrochemical reduction method at a low potential of −030 V (vs Pt) and a low temperature of 30 °C In this process, the DES acted as solvent and shape-directing agent More importantly, we used the electrode modified with the as-prepared nanomaterials as the anode to the electrochemical oxidation synthesis The glassy carbon electrode modified with the AuPt nanoflowers was directly employed to the electro-oxidation of xanthene (XT) to xanthone (XO) under a constant low potential of 080 V (vs Ag/AgCl) and room temperature, with a high yield of XO Moreover, the synthesis process was milder and more environment-friendly than conventional organic syntheses This new strategy would have a promising application in electroorganic synthesis fields

Natural phosphate-supported Cu( ii ), an efficient and recyclable catalyst for the synthesis of xanthene and 1,4-disubstituted-1,2,3-triazole derivatives

Abstract: Cu(NO3)2 supported on natural phosphate, Cu(II)/NP, was prepared by co-precipitation and applied as a heterogeneous catalyst for synthesizing xanthenes (2–3 h, 85–97%) through Knoevenagel–Michael cascade reaction of aromatic aldehydes with 1,3-cyclic diketones in ethanol under refluxing conditions. It was further used for regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles (1–25 min, 95–99%) via a three-component reaction between organic halides, aromatic alkynes and sodium azide in methanol at room temperature. The proposed catalyst, Cu(II)/NP, was characterized using X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and inductively coupled plasma analyses. Compared to other reports in literature, the reactions took place through a simple co-precipitation, having short reaction time ( 85%), and high recyclability of catalyst (>5 times) without significant decrease in the inherent property and selectivity of catalyst. The proposed protocols provided significant economic and environmental advantages.

Pamoic acid esters and their xanthene derivatives: Flourimetric detection of nitroaromatic compounds and non-linear optical properties

Abstract: In this study, four pamoic acid esters and a dibenzoxanthene derivative of pamoic acid ester were prepared and characterized by the analytical and spectroscopic methods Molecular structure of the synthesized compounds were determined by single crystal X-ray diffraction studies. Absorpsion and emission behaviours of the compounds were investigated in detail. Fluorescent detection of nitro aromatic compounds [nitro benzen (NB), 4-nitrophenol (4-NP) and 2,4-dinitrophenol(2,4-DNP)] by the synthesized compounds was examined. Sensing cabability to NACs, fluorescent titration experiments were performed and compound (2) exhibit the highest sensitivity against NB with a quenching constant (Ksv) of 1.03 × 107 M−1. Finally, non-linear optic properties of the compounds was investiagated by computational

Copper(i) and silver(i) complexes of 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene: photophysical properties and structural rigidity under pressure.

Abstract: The heteroleptic complexes [Cu(tBu-xantphos)(bpy)][PF6] and [Ag(tBu-xantphos)(bpy)][PF6], where tBu-xantphos = 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene and bpy = 2,2′-bipyridine have been synthesized and their photophysical properties investigated. Single crystal X-ray diffraction studies of the compounds under ambient and increased pressure are presented; increase in pressure results in little structural perturbation. For the copper(I) complexes, the effects of changing the N^N ligand from bpy to 6-methyl-2,2′-bipyridine (6-Mebpy), 6-bromo-2,2′-bipyridine (6-Brbpy), and 4,4′-di(tert-butyl)-2,2′-bipyridine (4,4′-tBu2bpy) were also investigated. Emissions from the copper(I) complexes are weak, both in solution and the solid state and this is attributed to vibrational quenching effects of the tert-butyl substituents of the tBu-xantphos ligands.

Cobalt(II)–Salen Complexes for Photocatalytic Hydrogen Production in Noble Metal-Free Molecular Systems

Abstract: Developing cost-effective hydrogen-production systems is always appealing in order to satisfy the future energy request. Here, two Co(II)–salen complexes 1 and 2 were firstly introduced into homogeneous photocatalytic hydrogen-evolution systems. Based on these two cobalt complexes, we developed noble-metal-free hydrogen production systems using xanthene dyes [such as Disodium salts of Eosin Y (EY2−), Rose Bengal (RB2−) and Fluorescein (Fl2−)] as photosensitizers and trimethylamine (TEA) as sacrificial donor. Complex 1 presented the best catalytic performance for hydrogen production with a TON of 319 based on catalyst within 9 h irradiation, which is superior to other cobalt complexes in noble-metal-free systems. UV–Vis spectra studies demonstrate that EY2− suffered quick decomposition, especially under the presence of complex 1, which should be responsible for hydrogen-production deactivation. The thermodynamically favorable photo-induced electron transfer from 3*EY2− to complex 1 was supported by investigations involving fluorescence quenching and cyclic voltammetry studies. However, the immediate color change (within seconds) as the hydrogen production systems exposed under the irradiation indicates that EY2− firstly suffered dehalogenation which functions as the real active dyes.

Chromium-based metallosurfactants: synthesis, physicochemical characterization and probing of their interactions with xanthene dyes

Abstract: Surfactants are known to enhance the photophysical properties of dyes. In this work, a photophysical study of xanthene dyes in micellar media of single and double alkyl chain cationic chromium-based metallosurfactants has been carried out. For this study, two chromium complexes, i.e. hexadecyltrimethyl ammonium chromium trichlorate and bishexadecyltrimethyl ammonium chromium tetrachlorate, were synthesized and characterized using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and nuclear magnetic resonance. Conductivity and surface tension methods were employed to assess the role of the metal ion (which is present as part of the counter-ion) in the self-aggregation behavior of as-synthesized metallosurfactants. Furthermore, the interaction of two chromium metallosurfactants was investigated with xanthene dyes (fluorescein and eosin yellow), wherein binding constants were evaluated using fluorescence and UV-vis spectroscopy. Due to the difference in the structure of the dyes, fluorescein shows a higher binding value than eosin yellow. This may be due to the steric crowding of eosin yellow due to an additional substituent that causes difficulty in the interaction of the apolar group of the dye with the hydrophilic region of the chromium complexes. The solubilization loci of both the dyes were estimated where fluorescein being hydrophobic occupied the hydrophobic core of the metallomicelles and eosin yellow was present in the outer polar Stern region. The double alkyl chain chromium metallosurfactant, being more hydrophobic, exhibits strong binding towards fluorescein and eosin yellow in comparison to the single alkyl chain chromium metallosurfactant. Moreover, chromium metallosurfactants enhance the solubilization and fluorescence quantum yield of the dyes.

Antioxidant, Antimicrobial and Antiproliferative Activities of Synthesized 2,2,5,5-Tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1 H -xanthene-1,8(2 H )-dione Derivatives

Abstract: Ten biologically active 2,2,5,5-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione derivatives were synthesized and their structures were confirmed by IR, 1H and 13C NMR spectroscopy and mass spectrometry. Synthesized compounds were scanned for their antioxidant, antimicrobial and antiproliferative activity. Antibacterial activity was tested by the diffusion and dilution method against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, while antifungal activity was tested against Candida albicans and Saccharomyces cerevisiae. Antiproliferative activity was tested against HeLa (cervical carcinoma), SW620 (colorectal adenocarcinoma, metastatic), hepatocellular carcinoma (HEpG2), lung carcinoma cells (A549) and mouse embryo fibroblast cell line (3T3). The best antioxidant activity showed compound 2 with two hydroxy groups substituted on phenyl ring in positions 2' and 3'. The best antimicrobial activity of all synthesized compounds showed compound 8, while the best antiproliferative activity showed compound 6. Results signify the importance of xanthene-1,8-dione derivatives as potential antioxidant and antiproliferative agents.

Lactic Acid: A New Application as an Efficient Catalyst for the Green One-Pot Synthesis of 2-Hydroxy-12-aryl-8, 9, 10, 12-Tetrahydrobenzo[a]xanthene-11-one and 12-Aryl-8,9,10,12-Tetrahydrobenzo[a]xanthen-11-one Analogs

Abstract: An efficient and benign protocol leading to the synthesis of benzoxanthene derivatives using a multi-component reaction consisting of aromatic aldehydes, dimedone and 2,7-dihydroxynaphthalene or β-naphthol in the presence of lactic acid as an efficient, inexpensive and green catalyst under solvent-free conditions is reported. Operational simplicity, good yields, short reaction time, moderate and eco-friendly conditions, and no need for column chromatography make this present methodology more innovative than existing ones.

A Comparative Study on the Photophysics and Photochemistry of Xanthene Dyes in the Presence of Polyamidoamine (PAMAM) Dendrimers.

Abstract: The photophysical and photochemical properties of the xanthene dyes Eosin Y, Erythrosin B, and Rose Bengal are evaluated in the presence of amino-terminated polyamidoamine (PAMAM) dendrimers of relatively high generation (G3-G5) in alkaline aqueous solution. UV/Vis absorption and fluorescence spectra of the dyes show bathochromic shifts, which correlate with the size of the dendrimer. Binding constants (Kbind ) are calculated from absorption data. The resulting high Kbind values indicate strong interactions between both molecules. Triplet-triplet absorption spectra of the dyes are recorded by laser flash photolysis, and a decrease in the triplet lifetimes is observed in the presence of dendrimers. At the same time, an increase in the absorption of the semireduced form of the dyes is observed. Rate constants for triplet quenching (3 kq ) and radical quantum yields (ΦR ) are obtained. The results are explained by a very efficient electron-transfer process from PAMAM to xanthene dyes for all of the dye/dendrimer couples that are evaluated.