Showing papers on "Xanthene published in 2010"
TL;DR: Data suggest a reaction pathway involving reductive quenching of the triplet excited state of the PS giving the reduced PS(-) that then transfers an electron to the Co catalyst, necessary for effective bimolecular electron transfer.
Abstract: Rhodamine photosensitizers (PSs) substituting S or Se for O in the xanthene ring give turnover numbers (TONs) as high as 9000 for the generation of hydrogen via the reduction of water using [CoIII(dmgH)2(py)Cl] (where dmgH = dimethylglyoximate and py = pyridine) as the catalyst and triethanolamine as the sacrificial electron donor. The turnover frequencies were 0, 1700, and 5500 mol H2/mol PS/h for O, S, and Se derivatives, respectively (ΦH2 = 0%, 12.2%, and 32.8%, respectively), which correlates well with relative triplet yields estimated from quantum yields for singlet oxygen generation. Phosphorescence from the excited PS was quenched by the sacrificial electron donor. Fluorescence lifetimes were similar for the O- and S-containing rhodamines (∼2.6 ns) and shorter for the Se analog (∼0.1 ns). These data suggest a reaction pathway involving reductive quenching of the triplet excited state of the PS giving the reduced PS− that then transfers an electron to the Co catalyst. The longer-lived triplet state ...
298 citations
TL;DR: This reaction is remarkable, as it does not involve any redox-active catalyst or reagent commonly used for C H bond activation and thus holds great potential for the design of sustainable syntheses with simple and cheap reagents and low levels of waste.
Abstract: Activated benzylic CH2-groups in xanthene (I) or dihydroacridines (IV) undergo acid-catalyzed oxidative coupling towards carbonyl compounds.
169 citations
TL;DR: The synthesis and characterization of a novel class of caged compounds—rhodamine NN dyes, which have a 2-diazoketone caging group incorporated into a spiro-9H-xanthene fragment, which enable new imaging protocols based on the stepwise activation and detection of several fluorescent markers.
Abstract: Caged (that is, masked) fluorescent dyes are maintained in their nonfluorescent state by the incorporation of a photochemical labile group. The photosensitive masking group or “molecular cage” can be cleaved-off by irradiation with nearUV light, thereby rendering the dye fluorescent. Caged fluorescent dyes are of enormous interest for biological imaging because they may be used, for example, for the analysis of protein dynamics, multicolor fluorescence microscopy, and far-field optical nanoscopy. o-Nitrobenzyl groups are often used as masking groups; however, the use of these dyes is limited because of their rather complex synthesis and the unwanted by-products liberated by photolysis. Herein we report on the synthesis and characterization of a novel class of caged compounds—rhodamine NN dyes, which have a 2-diazoketone (COCNN) caging group incorporated into a spiro-9H-xanthene fragment (compounds 3 and 9-R in Schemes 1 and 3, respectively). This very simple and small caging group is the core element of a new class of masked rhodamines that have remarkable properties. The rhodamine NN dyes can be easily prepared and conjugated with biomolecules, they undergo rapid uncaging under standard irradiation conditions (with wavelengths 420 nm) with formation of highly fluorescent rhodamine derivatives, and they can be used in aqueous buffers, as well as in various embedding media utilized in imaging applications. In microscopy, these novel rhodamines may be used as labels alone or in combination with conventional fluorescent dyes and switchable rhodamine spiroamides. In the latter case, they enable new imaging protocols based on the stepwise activation and detection of several fluorescent markers. The combination of the new rhodamine NN derivative (9-R) with the photochromic spiroamide of rhodamine S and a normal (uncaged) N,N,N’,N’-tetramethylrhodamine resulted in a monochoromatic multilabel imaging scheme with low cross-talk, despite using three fluorophores with very similar absorption and emission spectra. Rhodamines are very photostable and bright fluorescent dyes which can readily be chemically modified and caged. Coumarines and fluorescein have also been used as caged fluorescent dyes. As a photocleavable unit, most of these caged compounds contain a 2-nitrobenzyl group or a derivative with an alkyl or a carboxy group in the a position to the phenyl ring (at the CH2 group) and/or one or two methoxy groups in the aromatic ring. Compounds with a free carboxy group are required for bioconjugation. However, the synthesis of caged rhodamines with a free (“second”) carboxy group is difficult and their yield is low. The 2-nitrobenzyl group and its substitutes are bulky and generate toxic, colored, and highly reactive 2-nitrosobenzaldehyde or 2-nitrosobenzophenone derivatives upon photolysis. These compounds or their oligomers are expected to be poisonous to living cells, and they are also colored and interfere with optical measurements. Other modern caging groups with the required absorption in the near-UV region are also bulky, rather lipophilic, and the procedures for their synthesis and introduction are often complex. For example, 2-(N,N-dimethylamino)-5-nitrophenol was reported to give photocleavable phenyl esters. 7-Diethylamino-4-(hydroxymethyl)-2H-chromen-2-one is known to form esters which can be cleaved easily by irradiation at 412 nm. Derivatives of 8-bromo-7-hydroxyquinoline and 6-bromo-7-hydroxycoumarines have also been proposed as light-sensitive protecting groups. The photolysis of these caged compounds generates light-absorbing by-products. We set out to prepare masked fluorescent dyes without bulky caging groups. A very small 2-diazoketone fragment would be an ideal caging group, provided that it is still possible to integrate this group into the colorless form of a fluorescent dye and then restore the fluorescent state by photolysis. Rhodamines are ideal for this purpose, because they contain a carboxy group, which is known to form colorless and nonfluorescent lactones or lactams with the spiro-9H-xanthene fragment. Furthermore, this carboxy group may be transformed into a 2-diazoketone residue. For the practical realization of this caging strategy, we used rhodamine B as a model compound and performed the reaction of diazomethane with its acid chloride 1. The yellow crystalline diazoketone 3 was obtained in high yield (Scheme 1). In the course of the facile caging reaction, the positively charged C9 atom of the xanthene fragment attacks the negatively charged carbon atom of the diazomethane residue in the intermediate 2. The simultaneous abstraction of a proton furnishes the stable five-membered ring. [*] Dr. V. N. Belov, Dr. C. A. Wurm, Dr. V. P. Boyarskiy, Dr. S. Jakobs, Prof. Dr. S. W. Hell Department of NanoBiophotonics Max Planck Institute for Biophysical Chemistry Am Fassberg 11, 37077 G ttingen (Germany) Fax: (+49)551-201-2506 E-mail: vbelov@gwdg.de cwurm@gwdg.de shell@gwdg.de Homepage: http://www.mpibpc.gwdg.de/abteilungen/200/
153 citations
TL;DR: The new photostable rhodamine dyes represented by the compounds 1 a-r and 3-5 are proposed as efficient fluorescent markers with unique combination of structural features and are able to pass the plasma membrane of living cells, introducing them as potential labels for recent live-cell-tag approaches.
Abstract: New photostable rhodamine dyes represented by the compounds 1 a–r and 3–5 are proposed as efficient fluorescent markers with unique combination of structural features. Unlike rhodamines with monoalkylated nitrogen atoms, N′,N-bis(2,2,2-trifluoroethyl) derivatives 1 e, 1 i, 1 j, 3-H and 5 were found to undergo sulfonation of the xanthene fragment at the positions 4′ and 5′. Two fluorine atoms were introduced into the positions 2′ and 7′ of the 3′,6′-diaminoxanthene fragment in compounds 1 a–d, 1 i–l and 1 m–r. The new rhodamine dyes may be excited with λ=488 or 514 nm light; most of them emit light at λ=512–554 nm (compounds 1 q and 1r at λ=576 and 589 nm in methanol, respectively) and have high fluorescence quantum yields in solution (up to 98 %), relatively long excited-state lifetimes (>3 ns) and are resistant against photobleaching, especially at high laser intensities, as is usually applied in confocal microscopy. Sulfonation of the xanthene fragment with 30 % SO3 in H2SO4 is compatible with the secondary amide bond (rhodamine-CON(Me)CH2CH2COOH) formed with MeNHCH2CH2COOCH3 to providing the sterically unhindered carboxylic group required for further (bio)conjugation reactions. After creating the amino reactive sites, the modified derivatives may be used as fluorescent markers and labels for (bio)molecules in optical microscopy and nanoscopy with very-high light intensities. Further, the new rhodamine dyes are able to pass the plasma membrane of living cells, introducing them as potential labels for recent live-cell-tag approaches. We exemplify the excellent performance of the fluorinated rhodamines in optical microscopy by fluorescence correlation spectroscopy (FCS) and stimulated emission depletion (STED) nanoscopy experiments.
109 citations
TL;DR: Silica-bonded S-sulfonic acid (SBSSA) has been found to be an efficient catalyst for the synthesis of 1,8-dioxo-decahydroacridines and 1, 8-Dioxo -octahydroxanthenes in excellent yields as mentioned in this paper.
70 citations
TL;DR: In this article, a spiro(fluorene-9,9′-xanthene) skeleton bis(ether amine) monomer was prepared through a simple acid-catalyzed condensation reaction of 9-fluorenone with resorcinol to form the spiro framework through an sp3 carbon atom.
65 citations
TL;DR: It is found that the heavy atom effect alone cannot explain the experimental results, asΦf for chlorinated dyes exceeds that of fluorescein and close to unity, and the sum of Φf and Φisc for brominated and iodinated xanthene dyes is remarkably less than unity.
Abstract: The fluorescence quantum yield (Ff), fluorescence lifetime (sf), intersystem crossing quantum yield (Fisc) and redox potentials of seven halogenated fluoresceins in their dianion forms were measured and compared in methanol to get a deep insight into the effect of halogeno atoms on their photophysics It is found that the heavy atom effect alone cannot explain the experimental results, as (1) Ff for chlorinated dyes exceeds that of fluorescein and close to unity, (2) the sum of Ff and Fisc for brominated and iodinated xanthene dyes is remarkably less than unity The observations can be rationalized by the involvement of intramolecular photoinduced electron transfer, in which the benzoate acts as the electron donor while the xanthene moiety is the acceptor The more negative reduction potential of excited singlet state for chlorinated fluoresceins results in their much smaller ket, and hence higher Ff
60 citations
TL;DR: Anthracene-stacked oligomers and a polymer were synthesized using a xanthene skeleton as the scaffold, and their structures and properties were fully characterized.
55 citations
TL;DR: An efficient iron-catalyzed, microwave-promoted cascade benzylation-cyclization of phenols is reported and both 9-aryl and 9-alkyl xanthene derivatives in good to high yields using FeCl(3) as the catalyst under MW irradiation conditions.
47 citations
TL;DR: Mangiferin, isomangifer in, and homomangifierin, the xanthone C-glycosides with a wide spectrum of pharmacological effects, were synthesized concisely, featuring a C- glycosylation of a xanthene derivative with perbenzylglucopyranosyl N-phenyltrifluoroacetimidate.
Abstract: Mangiferin, isomangiferin, and homomangiferin, the xanthone C-glycosides with a wide spectrum of pharmacological effects, were synthesized concisely, featuring a C-glycosylation of a xanthene derivative with perbenzylglucopyranosyl N-phenyltrifluoroacetimidate.
45 citations
TL;DR: Six aza[60]fullerene monoadducts were synthesized by the thermal reaction between the azafullerenyl radical C(59)N* and 9-alkyl-substituted fluorenes, 9,10-dihydroanthracene, or xanthene.
Abstract: Six aza[60]fullerene monoadducts were synthesized by the thermal reaction between the azafullerene radical C59N• and 9-alkyl-substituted fluorenes, 9,10-dihydroanthracene, or xanthene. Unlike fluorenes, dihydroanthracene, and xanthene, the structurally related substituted diphenylmethanes, ethylbenzene, cumene, 1,2-diphenylethane, 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene, 10,11-dihydro-5H-dibenzo[a,d]cycloheptene, 9-methylanthracene, and 9-benzylanthracene do not lead to the isolation of azafullerene monoadducts. Moreover, 1,2-dichlorobenzene, the most commonly utilized solvent for azafullerene reactions, reacts slowly with the azafullerenyl radical C59N• affording the corresponding aza[60]fullerene monoadduct.
TL;DR: In this article, the reaction of P,S-chelating diphosphane ligands [bis(2-diphenylphosphanylphenyl)ether monosulfide] with [Ru(CO) 2 Cl 2 ] n in a 1:1 molar ratio affords two new ruthenium(II) complexes.
Abstract: The reaction of P,S-chelating diphosphane ligands [bis(2-diphenylphosphanylphenyl)ether monosulfide] (a) and [9,9-dimethyl-4,5-bis(diphenylphosphanyl)xanthene monosulfide] (b) with [Ru(CO) 2 Cl 2 ] n in a 1:1 molar ratio affords two new ruthenium(II) complexes of the type [Ru(CO) 2 Cl 2 (P∩S)] (1a, 1b), where P∩S = a, b. The compounds are characterized by elemental analyses, mass spectrometry, thermal studies, and IR and NMR spectroscopy, together with single-crystal X-ray structure determination of bis(2-diphenylphosphanylphenyl)ether (DPEphos), a, 1a, and 1b. The ruthenium atom in both 1a and 1b occupies the center of a slightly distorted octahedral environment formed by a P atom, an S atom, two Cl atoms, and two CO groups. The crystal structures of a and 1a highlights an interesting feature, in which the P(2)-P(1)-S(1) spatial angle (ca. 174.7°) in free ligand a is reduced to around 46° upon complexation, which indicates a very high flexibility of the angle. Complex 1a also exhibits some hemilabile behavior in solution because of its flexible ligand backbone, while ligand b in complex 1b remains rigid in solution. Complexes 1a and 1b are thermally stable up to about 300 °C and show high catalytic activities in the transfer hydrogenation of aldehydes and ketones to the corresponding alcohols. The highest conversion (about 99 %) with the corresponding TOF value of about 1000 h -1 was obtained for 1a in the case of benzaldehyde. The catalytic efficiency of 1a is found to be much higher than 1b, which might result from the hemilabile behavior of ligand a.
TL;DR: In this paper, various xanthenes have been synthesized by the condensation of β -naphthol, 2-hydroxynaphthalene-1,4-dione or dimedone with various aldehydes in the presence of trifluoroacetic acid as catalyst in 1,1,3,3- N, N, N, n, N ', N', N '', N ''-tetramethylguanidinium trifloroacetate (TMGT) ionic liquid within
TL;DR: In this article, a simple and facile synthesis of 14-aryl-14 H -dibenzo[a, i ]xanthene-8,13-dione derivatives was accomplished by the one-pot condensation of β-naphthol, aldehydes, and 2-hydroxy-1,4-Naphthoquinone under solvent-free conditions in the presence of the heterogeneous catalyst, silica chloride.
TL;DR: In this paper, high-soluble fluorescent fluorescein and rhodamine dyes were synthesized through amidification of their carboxylic acid functionality with original di- or tri-sulfonated amino linkers derived from taurine or α-Sulfo-β-alanine.
TL;DR: The o-R19H(+) was found to have the largest Stokes shift in the gas phase (around 10 nm), suggesting that an intramolecular relaxation operates in the excited electronic state for this isomer.
Abstract: Visible light absorption and fluorescence of three positional isomers of protonated Rhodamine 19 (o-, m- and p-R19H(+)) were studied in solution and in the gas phase. In solution, strong solvatochromic effects lead to spectral shifts between rhodamine isomers. In contrast, in the gas phase, these species were found to exhibit very similar fluorescence, while pronounced differences were observed in the absorption spectra. The o-R19H(+) was found to have the largest Stokes shift in the gas phase (around 10 nm), suggesting that an intramolecular relaxation operates in the excited electronic state for this isomer. Several mechanisms for this relaxation are proposed, such as the change of the dihedral angle between the carboxyphenyl group and the xanthene chromophore or that between the carboxylic group and the phenyl ring.
TL;DR: In this article, the condensation of β-naphthol with aromatic aldehydes and 2-hydroxynaphthalene-1,4-dione in presence of silica supported perchloric acid under solvent-free media to afford the corresponding 14-aryl-14H-dibenzo[a,i]xanthene-8,13-diones in excellent yields and short reaction times is described.
Abstract: The condensation of β-naphthol with aromatic aldehydes and 2-hydroxynaphthalene-1,4-dione in presence of silica supported perchloric acid under solvent-free media to afford the corresponding 14-aryl-14H-dibenzo[a,i]xanthene-8,13-diones in excellent yields and short reaction times is described. The reaction work-up is very simple and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions.
TL;DR: X-Ray crystal structure analysis confirmed that both cyclic and acyclic complexes have two cofacially oriented salen-type manganese(III) units in a complex cation, showing an Mn...Mn distance of ca.
Abstract: Dimanganese(III) complexes of salen-type ligands anchored by 9,9-dimethylxanthene-4,5-diyl spacers were synthesized. Two types of structures, cyclic and acyclic forms, are presented. The 2 + 2 Schiff-base condensation of 5,5′-(9,9-dimethylxanthene-4,5-diyl)bis(salicylaldehyde) and 1,2-diaminobenzene gave a macrocyclic ligand, from which a cyclic dimanganese(III) complex was synthesized. A similar dimanganese(III) complex with stereogenic centers was synthesized by the metal-assisted condensation reaction using (1R,2R)-1,2-diaminocyclohexane. Acyclic dimanganese(III) complexes anchored by one xanthene spacer were obtained by metal-assisted stepwise condensation reactions using the xanthene-bridged bis(salicylaldehyde), (1R,2R)-1,2-diaminocyclohexane monohydrochloride, and salicylaldehydes. X-Ray crystal structure analysis confirmed that both cyclic and acyclic complexes have two cofacially oriented salen-type manganese(III) units in a complex cation, showing an Mn⋯Mn distance of ca. 5.1 A. Asymmetric oxidation of sulfides was performed by using the chiral dimeric complexes as catalysts, which showed enantiomeric excesses ranging from 5 to 19%. The addition of 4-(dimethylamino)pyridine to the reaction system improved the enantioselectivity up to 39% ee. This effect was not observed for the corresponding mononuclear catalyst.
TL;DR: In this paper, the effects of substituting one of the methylene groups in the 9,10-dihydroanthracene by ether or ketone functional groups yielding xanthene and anthrone species, respectively, were determined from direct comparison of the standard (p° ǫ = 0.1/1/MPa) molar enthalpies of formation in the gaseous phase.
TL;DR: Three xanthene dyes with different anchoring Groups were employed to electrodeposit ZnO/dye hybrid thin films to study the effect of anchoring groups on the electrochemical self-assembly (ESA) of hybrid thin Films.
Abstract: Three xanthene dyes with different anchoring groups, eosin Y (EY), dicarboxy-eosin Y (CEY) and sulfonated eosin Y (SEY) were employed to electrodeposit ZnO/dye hybrid thin films to study the effect of anchoring groups on the electrochemical self-assembly (ESA) of hybrid thin films The adsorption stabilities of the dyes in oxidized form were in the order, CEY >> EY > SEY, as evaluated by Langmuir isothermal adsorption experiments The reduction potential of dyes, the dependence on Zn(2+) concentration that reflects stabilities of complexes between reduced dyes and Zn(2+) ion, and the diffusion coefficients of dyes were determined by electrochemical measurements These properties of the dyes were considered as the key parameters to dominate ESA of hybrid thin films which were actually prepared with these dyes by potentiostatic electrolysis at -08 and -10 V (vs SCE) representing ESA with dyes in oxidized and reduced forms, respectively, and were analyzed for their chemical composition and structural features
TL;DR: In this paper, uniformly applied ensemble spectroscopic studies are presented, including 1H NMR, UV-Vis, and fluorescence titration experiments of aqueous cucurbit[7]uril complexes with the monocationic xanthene dyes rhodamine 6G (Rh6G), rhB, rhBBE and pyronin Y (PyY).
Abstract: Improvements in optical properties of organic xanthene fluorophores through molecular encapsulation in cucurbit[7]uril (CB7) should enable better molecular probes and devices to be designed. Although the interactions of several dyes with CB7 have been studied, the data have often been incomplete. Uniformly applied ensemble spectroscopic studies are presented herein, including 1H NMR, UV–Vis, and fluorescence titration experiments of aqueous CB7 complexes with the monocationic xanthene dyes rhodamine 6G (Rh6G, 1), rhodamine B (RhB, 2), rhodamine B benzyl ester (RhBBE, 3), pyronin B (PyB, 4) and pyronin Y (PyY, 5). All of these cationic xanthene dyes formed 1:1 complexes with cucurbit[7]uril as evidenced by NMR data and Job’s plots of fluorescence changes upon addition of CB7. Non-linear regression analysis of the fluorescence titration curves gave precise Ka’s for RhB, RhBBE and PyB between 1.1 × 105 M−1 and 9.1 × 106 M−1. The fluorescence emission intensity of Rh6G was lowered 0.8-fold in the presence of CB7 while the other dyes examined showed an increase between 1.3 and 4.7-fold. NMR titration experiments from 0 to 2.0 equivalents of CB7 per equivalent of xanthene gave in only some cases very clear evidence of inclusion complexation. Non-specific adsorption of these xanthene dyes onto borosilicate glass was very pronounced and could be inhibited by dye inclusion into CB7. Pyronin B-Cucurbit[7]uril complex
TL;DR: A simple yet highly sensitive diastereoselective fluorescent assay was developed, which can differentiate diastsereomeric 1,2-aminoalcohols such as ephedrine, pseudoephedine, and methylephedrine using commercially available xanthene dyes.
Abstract: A simple yet highly sensitive diastereoselective fluorescent assay was developed, which can differentiate diastereomeric 1,2-aminoalcohols such as ephedrine, pseudoephedrine, and methylephedrine using commercially available xanthene dyes. The assay is based on the rhodamine B lactone–zwitterion equilibrium, which is highly sensitive to the presence and structure of 1,2-aminoalcohols. This is in contrast to the majority of rhodamine sensors, which are based on the pH sensitive carboxylate–lactone equilibrium. A model is proposed in which the diastereoselectivity arises from the differences in the strength of an intermolecular lone pair-π interaction within the analyte–rhodamine zwitterion complex. An assay was developed based on this sensing mechanism in which the structure and concentration of a 1,2-aminoalcohol solution can be determined using a mixture of rhodamine B and fluorescein. The selectivity and accuracy of this two-dye system was then demonstrated by the ability to measure the diastereomeric excess of samples of methylephedrine with 98% accuracy.
TL;DR: In this paper, a three-component one-pot synthesis of 12-aryl-12H-benzo, 6,7,8,10-tetrahydro-7,7-dimethyl-9H-[1,3]dioxolo[4,5-b]xanthen-9-ones by three component reaction of 3,4-methylenedioxyphenol, aldehydes, and dimedone was achieved.
Abstract: Three-component one-pot synthesis of some novel 12-aryl-12H-benzo[i][1,3]dioxolo[4,5-b]xanthene-6,11-diones involving treatment of 3,4-methylenedioxyphenol, aldehydes, and 2-hydroxy-1,4-naphthoquinone in presence of HClO4–SiO2 was achieved, and this reaction was extended to preparation of 10-aryl-6,7,8,10-tetrahydro-7,7-dimethyl-9H-[1,3]dioxolo[4,5-b]xanthen-9-ones by three-component reaction of 3,4-methylenedioxyphenol, aldehydes, and dimedone.
TL;DR: This compound was isolated from the aerial parts of Blumea riparia (Bl.) DC.
TL;DR: In this article, a diamine monomer, 9,9-bis[4-(4-aminophenoxy)phenyl]xanthene (BAPX), was synthesized via a two-step process consisting of an aromatic nucleophilic substitution reaction of readily available 4-chloronitrobenzene with 9, 9-bis(4-hydroxyphenyl)xanthee in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C.
Abstract: In order to obtain polyamides with enhanced solubility and processability, as well as good mechanical and thermal properties, several novel polyamides containing sulfone-ether linkages and xanthene cardo groups based on a new diamine monomer, 9,9-bis[4-(4-aminophenoxy)phenyl]xanthene (BAPX), were investigated. The BAPX monomer was synthesized via a two-step process consisting of an aromatic nucleophilic substitution reaction of readily available 4-chloronitrobenzene with 9,9-bis(4-hydroxyphenyl)xanthene in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Four novel aromatic polyamides containing sulfone-ether linkages and xanthene cardo groups with inherent viscosities between 0.98 and 1.22 dL g−1 were prepared by low-temperature polycondensation of BAPX with 4,4′-sulfonyldibenzoyl chloride, 4,4′-[sulfonyl-bis(4-phenyleneoxy)]dibenzoyl chloride, 3,3′-[sulfonyl-bis(4-phenyleneoxy)]dibenzoyl chloride and 4,4′-[sulfonyl-bis(2,6-dimethyl-1,4-phenyleneoxy)]dibenzoyl chloride in N,N-dimethylacetamide (DMAc) solution containing pyridine. All these new polyamides were amorphous and readily soluble in various polar solvents such as DMAc and N-methylpyrrolidone. These polymers showed relatively high glass transition temperatures in the range 238–298 °C, almost no weight loss up to 450 °C in air or nitrogen atmosphere, decomposition temperatures at 10% weight loss ranging from 472 to 523 °C and 465 to 512 °C in nitrogen and air, respectively, and char yields at 800 °C in nitrogen higher than 50 wt%. Transparent, flexible and tough films of these polymers cast from DMAc solution exhibited tensile strengths ranging from 78 to 87 MPa, elongations at break from 9 to 13% and initial moduli from 1.7 to 2.2 GPa. Primary characterization of these novel polyamides shows that they might serve as new candidates for processable high-performance polymeric materials. Copyright © 2010 Society of Chemical Industry
TL;DR: In recent years, xanthenes and benzoxanthens have been of great interest because they have been found to possess useful biological activities such as anti-inflammatory, 1 antiviral, 2 and antibact...
TL;DR: In this article, the authors synthesized xanthenes substituted with two different donor ligand units, N-heterocyclic carbene (NHC) and oxazoline, by the sequential coupling reaction.
TL;DR: The combination of two benzimidazole moieties with a spacer formed by a leucine unit and a xanthene skeleton provides an efficient receptor for neutral guests with oxygen atoms such as sulfoxides, ketones, or alcohols.
TL;DR: The computed results reveal that the combined role of electron attractor groups and conformational degrees of freedom contributes to a more favorable level alignment at the interface and to the desired increase of the intramolecular reorganization energies.
Abstract: We present a computational study on the electrical bistability behavior of four xanthene derivatives based on sodium fluorescein. Intra- and intermolecular charge transfer parameters are computed and employed to rationalize the efficiencies experimentally determined for resistive memory devices based on these organic materials. Charge injection at the electrode/organic interface in the presence of pristine and reduced molecular species is estimated by comparing the electron affinities of xanthene derivatives with the work function of commonly employed electrodes, and bulk charge transport is modeled assuming a charge hopping regime. It is shown that the OFF state is injection limited and that the efficiency of the bistability phenomenon is governed by sizeable intramolecular reorganization energies associated with electron transfer. The computed results reveal that the combined role of electron attractor groups and conformational degrees of freedom contributes to a more favorable level alignment at the interface and to the desired increase of the intramolecular reorganization energies. These optimal conditions are fulfilled for Rose Bengal. It is expected that the interrelated role of molecular parameters, conformational degrees of freedom and electron attractor character of substituents disclosed by this study might be used to formulate general structure-property relationships for the design of new, more efficient restive memory devices based on molecular semiconductors.
TL;DR: The photo-physical properties of Xanthene dyes: Basic Rhodamine Yellow (BRY), Rhodamine590perchlorate (R590p), SulforhodamineB (SRB) doped in tetramethylorthosilicate (TMOS) and poly-methylmethacrylate (PMMA) are observed in this article.