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Find video protocols related to scientific articles indexed in Pubmed.
[Beta-1 adrenoceptor blockade decreases the firing rate to painful stimuli in spinal wide-dynamic range neurons in rats].
Rev Med Inst Mex Seguro Soc
PUBLISHED: 10-11-2014
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It is known that epinephrine/norepinephrine inhibit acute pain transmission. However, the role of ß-adrenoceptors is not clear. Thus, we analyzed if beta-1 and/or beta-2 adrenoceptors can modulate acute pain transmission by performing in vivo single unit recordings during painful and non-painful peripheral stimulation in rats.
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Contrasting ion-association behaviour of Ta and Nb polyoxometalates.
Dalton Trans
PUBLISHED: 09-06-2014
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Small-angle X-ray scattering (SAXS) studies of aqueous [Ta6O19](8-) compared to prior studies of aqueous [Nb6O19](8-) reveals key differences in behaviour, which is likely at the root of the difficultly in developing polyoxotantalate chemistry. Specifically, where contact ion-pairing dominates between [Nb6O19](8-) and its counterions, solvent-separated ion-pairing between [Ta6O19](8-) and its counterions has been unveiled in the current study.
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Nitrogen-rich multinuclear ferrocenophanes as multichannel chemosensor molecules for transition and heavy-metal cations.
Sensors (Basel)
PUBLISHED: 08-07-2014
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[m.n] Multinuclear ferrocenophanes prepared by aza-Wittig reaction of bisiminophosphoranes derived from 1,1'-diazidoferrocene and isophthaladelhyde or 2,5-diformylthiophene, behave as efficient electrochemical and chromogenic chemosensor molecules for Zn2+, Pb2+, and Hg2+ metal cations. Whereas the OSWV of receptor 3, bearing two m-phenylene units in the bridges, display one oxidation peak, receptor 4 incorporating two thiophene rings in the bridges, exhibits two well-separated oxidation peaks. In both receptors only the addition of Zn2+, Pb2+, and Hg2+ metal cations induced a remarkable anodic shift of ferrocene/ferrocenium redox couple. Likewise, in the absorption spectra of these receptors the low energy band is red-shifted by ?? = 165 - 209 nm, and these changes promoted a significant color changes which could be used for the naked eye detection of these metal cations. The coordination modes for two representative cases were unveiled by DFT calculations that show an unsual coordination in the [42Pb]2+ complex with the Pb2+ cation in a distorted cubic N4S4 donor cage.
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Open bis(triazolium) structural motifs as a benchmark to study combined hydrogen- and halogen-bonding interactions in oxoanion recognition processes.
J. Org. Chem.
PUBLISHED: 07-23-2014
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We have designed a series of triazolium-pyrene-based dyads to probe their potential as fluorescent chemosensors for anion recognition through combinations of hydrogen and halogen bonding. Cooperation between the two distinct noncovalent interactions leads to an unusual effect on receptor affinity, as a result of fundamental differences in the interactions of halogen and hydrogen bond donor groups with anions. Absorption, emission spectrophotometries and proton and phosphorus NMR spectroscopies indicate that the two interactions act in concert to achieve the selective binding of the hydrogen pyrophosphate anion, a conclusion supported by computational studies. Hence, as clearly demonstrated with respective halogen- and hydrogen-bonding triazolium receptors, the integration of a halogen atom into the anion receptor at the expense of one hydrogen-bonding receptor greatly influences the anion recognition affinity of the receptor. The association constant values of the halogen-bonding complexes are larger than the hydrogen-bonding counterpart. Thus, halogen bonding has been exploited for the selective fluorescent sensing of hydrogen pyrophosphate anion. Halogen bonding has been demonstrated to increase the strength of hydrogen pyrophosphate binding, as compared to the hydrogen-bonded analogue. Grimme's PBE-D functional, which adequately reproduces the pyrene stacking energies, has been successfully applied to model the affinity for anions, especially hydrogen pyrophosphate, of the new receptors.
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Anion binding studies on receptors derived from the indolo[2,3-a]carbazole scaffold having different binding cavity sizes.
Sensors (Basel)
PUBLISHED: 07-04-2014
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The indolo[2,3-a]carbazole scaffold is a fused polyheteroaromatic system bearing two NH groups which suitably converge as hydrogen bond donor sites for the recognition of anions. A simple derivatisation of the indolocarbazole system at positions 1 and 10 with different functional groups, namely alcohols and amides, has contributed to modulate the anion binding selectivity and sensibility. A particularly good response has been obtained for the benzoate anion.
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Pre-analytical errors management in the clinical laboratory: a five-year study.
Biochem Med (Zagreb)
PUBLISHED: 04-27-2014
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This study describes quality indicators for the pre-analytical process, grouping errors according to patient risk as critical or major, and assesses their evaluation over a five-year period.
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The ferrocene-pyrylium dyad as a selective colorimetric chemodosimeter for the toxic cyanide and hydrogen sulfide anions in water.
Org. Biomol. Chem.
PUBLISHED: 03-20-2014
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The ferrocene-pyrylium dyad behaves as a selective redox and colorimetric chemodosimeter for CN(-) and HS(-) anions, exhibiting a clear perturbation in the redox potential of the ferrocene unit and in the absorption band, in the presence of these anions.
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Low pH electrolytic water splitting using earth-abundant metastable catalysts that self-assemble in situ.
J. Am. Chem. Soc.
PUBLISHED: 02-18-2014
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Typical catalysts for the electrolysis of water at low pH are based on precious metals (Pt for the cathode and IrO2 or RuO2 for the anode). However, these metals are rare and expensive, and hence lower cost and more abundant catalysts are needed if electrolytically produced hydrogen is to become more widely available. Herein, we show that electrode-film formation from aqueous solutions of first row transition metal ions at pH 1.6 can be induced under the action of an appropriate cell bias and that in the case of cobalt voltages across the cell in excess of 2 V lead to the formation of a pair of catalysts that show functional stability for oxygen evolution and proton reduction for over 24 h. We show that these films are metastable and that if the circuit is opened, they redissolve into the electrolyte bath with concomitant O2 and H2 evolution, such that the overall Faradaic efficiency for charge into the system versus amounts of gases obtained approaches unity for both O2 and H2. This work highlights the ability of first row transition metals to mediate heterogeneous electrolytic water splitting in acidic media by exploiting, rather than trying to avoid, the natural propensity of the catalysts to dissolve at the low pHs used. This in turn we hope will encourage others to examine the promise of metastable electrocatalysts based on abundant elements for a range of reactions for which they have traditionally been overlooked on account of their perceived instability under the prevailing conditions.
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Discovery of anion-? interactions in the recognition mechanism of inorganic anions by 1,2,3-triazolium rings.
Chem. Commun. (Camb.)
PUBLISHED: 02-15-2014
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A bis(triazolium)-based receptor designed for anion recognition is presented. NMR spectroscopic data indicate that one triazolium ring is acting as a hydrogen bond donor, whereas the second triazolium ring behaves as an anion-? receptor. The simultaneous presence of two noncovalent interactions allows us to achieve a highly selective binding of the hydrogenpyrophosphate anion.
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Assembly and core transformation properties of two tetrahedral clusters: [Fe(III)13P8W60O227(OH)15(H2O)2]30- and [Fe(III)13P8W60O224(OH)12(PO4)4]33-.
Dalton Trans
PUBLISHED: 02-12-2014
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Two nanosized 2.6 nm Fe(III) substituted polyoxotungstates [Fe(III)13P8W60O227(OH)15(H2O)2](30-) (1) and [Fe(III)13P8W60O224(OH)12(PO4)4](33-) (2) are presented herein. Both clusters are synthesized from the reactions of trilacunary polyoxotungstate precursor [?-P2W15O56](12-) and FeCl3 under strict pH control at atmospheric pressure. The compounds are fully characterised in the solid state (FTIR and single-crystal XRD, elemental and thermogravimetric analyses), solution (cyclic voltammetry and UV-Vis spectroscopy) and in the gas phase (ESI-MS). An {Fe(III)13} core is present in both clusters which can be described as Archimedean solids (truncated tetrahedron, 1; elongated cuboctahedron, 2). 1 shows iron delivery properties coupled to a K(+)-triggered transformation of the {Fe13} core to a {K?Fe12} core in solution. Cyclic voltammetry shows the presence of independent W- and Fe-centred redox processes that support the stability of the clusters in solution. ESI-MS analyses confirm further the stability of 1 and 2 in the gas phase.
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Age-dependent defective TGF-beta1 signaling in patients undergoing coronary artery bypass grafting.
J Cardiothorac Surg
PUBLISHED: 02-04-2014
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Transforming growth factor beta (TGF-?1) is a pleiotropic cytokine, which is deregulated in atherosclerosis; however the role of age in this process is unknown. We aimed to assess whether TGF-?1 signaling is affected by age.
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High-Resolution Imaging of Intravascular Atherogenic Inflammation in Live Mice.
Circ. Res.
PUBLISHED: 12-23-2013
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The inflammatory processes that initiate and propagate atherosclerosis remain poorly understood, largely because defining the intravascular behavior of immune cells has been technically challenging. Respiratory and pulsatile movements have hampered in vivo visualization of leukocyte accumulation in athero-prone arteries at resolutions achieved in other tissues.
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Bis(carbazolyl)ureas as selective receptors for the recognition of hydrogenpyrophosphate in aqueous media.
J. Org. Chem.
PUBLISHED: 09-20-2013
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Recognition properties of the novel bis(carbazole) tris-ureidic-based receptors 1 and 2 toward different anions have been studied by (1)H NMR and absorption and emission spectroscopy, as well as by DFT calculations. Receptor 1, in which the two urea-functionalized arms are decorated with p-nitrophenyl rings, behaves as a highly selective chromogenic molecular probe for hydrogenpyrophosphate anion in a competitive medium (acetonitrile/water, 70/30). Receptor 2, bearing two urea arms decorated with photoactive pyrenyl rings, acts as a highly selective fluorescent molecular probe for hydrogenpyrophosphate anion in either acetonitrile or an aqueous mixture (acetonitrile/water, 85/15). Receptor 2 exhibits a dual monomer-excimer emission spectrum and undergoes a remarked ratiometry in acetonitrile in the presence of hydrogenpyrophosphate: the excimer band disappears, whereas the monomer band is slightly increased. However, in the aqueous mixture, a strong increase of the excimer emission band was observed, while the monomer emission bands remained almost unaffected. The resulting binding modes and spectroscopic features are explained by suitable structures of model complexes for both receptors. In such complexes, a peripheral cooperative effect was found, alleviating the excess of negative charge in the guest toward the outer surface of the host, as well as the required enlargement on its internal cavity.
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A densely decorated disubstituted ferrocene as an ion-pair recognition receptor.
Chem. Commun. (Camb.)
PUBLISHED: 09-12-2013
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A functionalized 1,1-disubstituted ferrocene acts as an electro-optical ion-pair receptor for Mg(2+), Ca(2+), Cd(2+), and Zn(2+) cations in the presence of a co-bound H2PO4(-) anion, through perturbation of the redox potential of the ferrocene unit, enhancement of the fluorescence and a noticeable colour change.
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Exploring the assembly of supramolecular polyoxometalate triangular morphologies with Johnson solid cores: [(Mn(II)(H2O)3)2(K?{?-GeW10Mn(II)2O38}3)]19-.
Inorg Chem
PUBLISHED: 07-26-2013
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A new polyoxometalate (POM) cluster compound is presented which incorporates a trimeric assembly of Keggin-type germanotungstate fragments trapping a Johnson-type solid {Mn8} core. The mixed K-Li salt of the polyanion [(Mn(II)(H2O)3)2(K?{?-GeW10Mn(II)2O38}3)](19-) was characterized in the solid state and solution. The correlation of the assembly processes and the observed architecture of the "trinity" family of POMs is discussed.
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Ferrocenylbenzobisimidazoles for recognition of anions and cations.
Inorg Chem
PUBLISHED: 06-19-2013
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The preparation of 2,7-disubstituted benzobisimidazoles decorated with substituents displaying different electrooptical properties is described. The presence of redox, chromogenic, and fluorescent groups at the heteroaromatic core, which acts as ditopic binding site, made these receptors potential candidates as multichannel probes for ions. The triad 4 behaves as a selective redox and fluorescent chemosensor for HSO4(-) and Hg(2+) ions, whereas receptor 5 acts as a redox and chromogenic chemosensor molecule for AcO(-) and SO4(2-) anions. The change in the absorption spectra is accompanied by a color change from yellow to orange, while sensing of Zn(2+), Hg(2+), and Pb(2+) cations is carried out only by electrochemical techniques. Receptor 6 exhibits a remarkable cathodic shift of the oxidation wave only in the presence of AcO(-), H2PO4(-), and HP2O7(3-) anions, whereas addition of Pb(2+) induces an anodic shift. A new low energy band in the absorption spectra, which is responsible for the color change from colorless to pale yellow, and an important increase of the monomer emission band is observed only in the presence of H2PO4(-), and HP2O7(3-) anions. The most salient feature of the receptor 6 is its ability to act as a multichannel (redox, chromogenic, and fluorescent) chemodosimeter for Cu(2+), and Hg(2+) metal cations.
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Snake venomics of Lachesis muta rhombeata and genus-wide antivenomics assessment of the paraspecific immunoreactivity of two antivenoms evidence the high compositional and immunological conservation across Lachesis.
J Proteomics
PUBLISHED: 04-15-2013
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We report the proteomic analysis of the Atlantic bushmaster, Lachesis muta rhombeata, from Brazil. Along with previous characterization of the venom proteomes of L. stenophrys (Costa Rica), L. melanocephala (Costa Rica), L. acrochorda (Colombia), and L. muta muta (Bolivia), the present study provides the first overview of the composition and distribution of venom proteins across this wide-ranging genus, and highlights the remarkable similar compositional and pharmacological profiles across Lachesis venoms. The paraspecificity of two antivenoms, produced at Instituto Vital Brazil (Brazil) and Instituto Clodomiro Picado (Costa Rica) using different conspecific taxa in the immunization mixtures, was assessed using genus-wide comparative antivenomics. This study confirms that the proteomic similarity among Lachesis sp. venoms is mirrored in their high immunological conservation across the genus. The clinical and therapeutic consequences of genus-wide venomics and antivenomics investigations of Lachesis venoms are discussed.
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Modified mesoporous silica nanoparticles as a reusable, selective chromogenic sensor for mercury(II) recognition.
Dalton Trans
PUBLISHED: 01-18-2013
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A new tripodal receptor and a novel dyed mesoporous material are presented. The presence of thioureas conjugated with azobenzene chromophores enables the selective colorimetric detection of mercury(II) cations in THF through a remarkable colour change from yellow to deep purple.
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Mono- and dinuclear osmium N,N-di- and tetraphenylbipyridyls and extended bipyridyls. Synthesis, structure and electrochemistry.
Dalton Trans
PUBLISHED: 01-04-2013
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The efficient synthesis of mono- and dinuclear Os(IV) bipyridyl complexes is reported. These compounds show a two-step oxidation process leading to notable structural changes, which are reflected in their emission properties. During the second oxidation process a tetracation with a hydride-dihydrogen structure (instead of a trihydride) is formed. This results in a significant bathochromic shift of the emission band, accompanied by a moderate increase in intensity.
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The use and misuse of photosynthesis in the quest for novel methods to harness solar energy to make fuel.
Philos Trans A Math Phys Eng Sci
PUBLISHED: 01-01-2013
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This short review will illustrate that photosynthesis can provide a real contribution towards our sustain- able, green fuel requirements in the future. However, it is argued that the focus on biofuels is misplaced and that, in the longer term, investment in artificial photosynthesis will prove much more beneficial.
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A bisferrocene-benzobisimidazole triad as a multichannel ditopic receptor for selective sensing of hydrogen sulfate and mercury ions.
Org. Lett.
PUBLISHED: 11-11-2011
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The bisferrocene-benzobisimidazole triad behaves as a selective redox and fluorescent chemosensor for HSO(4)(-) and Hg(2+) ions, exhibiting an easily detectable signal change in both the redox potential of the ferrocene/ferrocinium redox couple and in the emission band which is red-shifted (?? = 10-13 nm) and enhanced in intensity (Chelation Enhanced Fluorescence, CHEF = 486-225) upon complexation with these ions, in EtOH solutions.
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Aldimines generated from aza-Wittig reaction between bis(iminophosphoranes) derived from 1,1-diazidoferrocene and aromatic or heteroaromatic aldehydes: electrochemical and optical behaviour towards metal cations.
Dalton Trans
PUBLISHED: 10-11-2011
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Aldimine 4 bearing a 2-quinolyl group was prepared by aza-Wittig reaction between the triphenyliminophosphorane derived from the 1,1-diazidoferrocene and 2-formylquinoline. However, aldimine 5, bearing a pyrene ring, was prepared using the most reactive tributyliminophosphorane derivative and the corresponding 1-formylpyrene. On the other hand, formation of aldimine 8 involves a tandem process, Staudinger reaction/intramolecular aza-Wittig reaction, by using directly 1,1-diazidoferrocene and 2-(diphenylphosphonyl)benzaldehyde. Aldimine 4 behaves as chemosensor molecule for Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) cations through two different channels: electrochemical (?E(1/2) = 222-361 mV) and chromogenic (?? = 122-153 nm), which can be used for the "naked eye" detection of these metal cations. Aldimine 5 behaves as a highly selective redox (in CH(3)CN) and fluorescent (in CH(3)Cl-DMF) probe for Hg(2+) metal cations even in the presence of a large excess of the other metal cations tested. Aldimine 8 displays electrochemical affinity (?E(1/2) = 60-288 mV) to Li(+), Ca(2+), Mg(2+), Zn(2+) and Pb(2+) metal cations, with the phosphorus oxide functionality as a binding site. From the (1)H NMR titration data as well as DFT calculations, different tentative binding modes have been established, for these structurally related ferrocenyl derivatives.
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Increased gene dosage of the Ink4/Arf locus does not attenuate atherosclerosis development in hypercholesterolaemic mice.
Atherosclerosis
PUBLISHED: 09-09-2011
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Human genome-wide association studies have identified genetic variants in the chromosome 9p21 region that confer increased risk of coronary artery disease and other age-related diseases. These variants are located in a block of high linkage disequilibrium with the neighboring Ink4/Arf tumor-suppressor locus (also named CDKN2A/CDKN2B). Since previous studies suggest an atheroprotective role of the Ink4/Arf locus, here we assessed whether gain-of-function of the encoded genes can be exploited therapeutically to reduce atherosclerosis.
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Deficient p27 phosphorylation at serine 10 increases macrophage foam cell formation and aggravates atherosclerosis through a proliferation-independent mechanism.
Arterioscler. Thromb. Vasc. Biol.
PUBLISHED: 09-01-2011
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Genetic ablation of the growth suppressor p27(Kip1) (p27) in the mouse aggravates atherosclerosis coinciding with enhanced arterial cell proliferation. However, it is unknown whether molecular mechanisms that limit p27s protective function contribute to atherosclerosis development and whether p27 exerts proliferation-independent activities in the arterial wall. This study aims to provide insight into both questions by investigating the role in atherosclerosis of p27 phosphorylation at serine 10 (p27-phospho-Ser10), a major posttranslational modification of this protein.
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Synthesis, structural charaterization, and electrochemical and optical properties of ferrocene-triazole-pyridine triads.
Inorg Chem
PUBLISHED: 08-10-2011
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The synthesis and electrochemical, optical, and cation-sensing properties of the ferrocene-triazole-pyridine triads 3 and 5 are presented. Azidoferrocene 1 and 1,1-diazidoferrocene 4 underwent the "click" reaction with 2-ethynylpyridine to give the triads 3 and 5 in 81% and 68% yield, respectively. Electrochemical studies carried out in CH(3)CN in the presence of increasing amounts of Zn(2+), Ni(2+), Cd(2+), Hg(2+), and Pb(2+) metal cations, showed that the wave corresponding to the ferrocene/ferrocenium redox couple is anodically shifted by 70-130 mV for triad 3 and 167-214 mV for triad 5. The maximum shift of the ferrocene oxidation wave was found for 5 in the presence of Zn(2+). In addition, the low-energy band of the absorption spectra of 3 and 5 are red-shifted (?? = 5-10 nm) upon complexation with these metal cations. The crystal structures of compounds 3 and 5 and the complex [3(2)·Zn](2+) have been determined by single-crystal X-ray methods. (1)H NMR studies as well as density functional theory calculations have been carried out to get information about the binding sites that are involved in the complexation process.
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A simple but effective dual redox and fluorescent ion pair receptor based on a ferrocene-imidazopyrene dyad.
Org. Lett.
PUBLISHED: 03-16-2011
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The ferrocene-imidazopyrene dyad, bearing the imidazole ring as the only receptor site, acts as a redox and optical molecular sensor for ion pairs, exhibiting an easily detectable signal change in the redox potential of the ferrocene/ferrocinium redox couple and in the emission spectrum. Perturbation of the emission spectrum follows the order Pb(2+) > Hg(2+) > Zn(2+) for cations and H(2)PO(4)(-) > AcO(-) for anions.
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Unprecedented 1,3-diaza[3]ferrocenophane scaffold as molecular probe for anions.
Inorg Chem
PUBLISHED: 02-14-2011
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The guanidine unit in the guise of 2-aminoimidazole in the new structural motif 2-arylamino-1,3-diaza[3]ferrocenophane 4 acts as a binding site for anions. The electrochemical behavior of this compound has been studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) and was found to exhibit a quasi reversible oxidation peak, associated to the Fe(II)/Fe(III) redox couple (Ep = 440 mV), and a non-reversible oxidation wave (Ep = 817 mV), probably associated to the oxidation of the C?N unit present in the guanidine bridge. Recognition of AcO(-), PhCO(2)(-), F(-), Cl(-), and Br(-) anions by the free receptor and the less basic anions Br(-), Cl(-), and NO(3)(-) by its monoprotonated form takes place by unusual redox-ratiometric measurements and spectroscopic ((1)H NMR and UV-vis) changes.
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Ferrocene-based heteroditopic receptors displaying high selectivity toward lead and mercury metal cations through different channels.
J. Org. Chem.
PUBLISHED: 01-13-2011
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The synthesis and electrochemical, optical, and ion-sensing properties of ferrocene-imidazophenazine dyads are presented. Dyad 4 behaves as a highly selective chemosensor molecule for Pb(2+) cations in CH(3)-CN/H(2)O (9:1). The emission spectrum (?(exc) = 317 nm) undergoes an important chelation-enhanced fluorescence effect (CHEF = 47) in the presence of Pb(2+) cations, a new low-energy band appeared at 502 nm, in its UV/vis spectrun, and the oxidation redox peak is anodically shifted (?E(1/2) = 230 mV). The presence of Hg(2+) cations also induced a perturbation of the redox potencial although in less extension than those found with Pb(2+) cations. Dyad 7, bearing two fused pyridine rings, has shown its ability for sensing Hg(2+) cations selectively through three channels: electrochemical, optical, and fluorescent; the oxidation redox peak is anodically shifted (?E(1/2) = 200 mV), a new low-energy band of the absorption spectrum appeared at 485 nm, and the emission spectrum (?(exc) = 340 nm) is red-shifted by 32 nm accompanied by a remarkable chelation-enhanced fluorescent effect (CHEF = 165). Linear sweep voltammetry revealed that Cu(2+) cations induced oxidation of the ferrocene unit in both dyads. (1)H NMR studies have been carried out to obtain information about the molecular sites which are involved in the binding process.
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[The impact of detecting endothelial dysfunction in atherosclerosis: Role of positron emission tomography (PET).]
Arch Cardiol Mex
PUBLISHED: 12-15-2010
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The endothelium plays an important role in the regulation of the intracellular fluid, vascular permeability, and modulation of vascular focal tone and angiogenesis. Endothelial dysfunction is manifested by the loss of the endothelium ability to modulate physiology changes in its vascular bed, and actually it is considered a prognostic marker of coronary artery disease. The relevance of assessing endothelial dysfunction relies in that it has been observed in different pathologies like DM, dyslipidemia, hypertension, tabaquism and in immunologic diseases like antiphospholipid syndrome and systemic lupus. PET is a non invasive method that allows the absolute quantification of myocardial blood flow during rest, stress and adrenergic stimulation, which allows to asses endothelial function. Therefore PET is a useful diagnostic technique to identify patients with endothelial dysfunction, and in the assessment of its response to administered therapy, allowing an optimal control and prevention of secondary adverse events of these diseases.
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Selective picomolar detection of mercury(II) using optical sensors.
Chem. Commun. (Camb.)
PUBLISHED: 12-03-2010
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The rational design of a mercury(II) ligand consisting in a 1-(4-oxyphenyl)-4(1-pyrenyl)-2,3-diaza-1,3-butadiene receptor unit, optimizes the sensitivity and reliability of a SPR sensor by the formation of a well packed SAM over the gold surface. SPR analysis allows detecting mercury(II) concentrations in aqueous systems in the picomolar range, meliorating on three orders of magnitude the EU mercury(II) detection limit in drinkable water.
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A new building block for anion supramolecular chemistry. Study of carbazolocarbazole as anion receptor.
Org. Biomol. Chem.
PUBLISHED: 09-16-2010
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A novel carbazolocarbazole system has been evaluated as an anion receptor in DMF solution. A good affinity has been detected for oxoanions. The anion binding studies have been contrasted by different experimental techniques.
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Ferrocene-based multichannel molecular chemosensors with high selectivity and sensitivity for Pb(II) and Hg(II) metal cations.
Dalton Trans
PUBLISHED: 08-11-2010
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The synthesis, electrochemical, optical and cation-sensing properties of ferrocene-imidazoquinoxaline dyads 6, are presented. Dyad 6a behaves as a highly selective redox, chromogenic and fluorescent chemosensor molecule for Pb(2+) cations in CH(3)CN solutions; the oxidation redox peak is anodically shifted (DeltaE(1/2) = 110 mV); in the absorption spectrum a new low-energy band appeared at lambda = 463 nm, and the emission band is red-shifted (Deltalambda = 31 nm) along with an important chelation-enhanced fluorescence factor (CHEF = 276), upon complexation with this metal cation. The dyad 6b, bearing two additional pyridine rings as substituents, has shown its ability for sensing Hg(2+) cations through three different channels: the oxidation peak is anodically higher shifted (DeltaE(1/2) = 300 mV), a new low-energy band appears in the absorption spectrum at lambda = 483 nm, and the emission band was also red-shifted (Deltalambda = 28 nm) and underwent an important chelation-enhanced fluorescent factor (CHEF = 227). The changes in their absorption spectra are accompanied by color changes from yellow to orange which allow their potential use for the "naked eye" detection of these metal cations. Linear sweep voltammetry revealed that Cu(2+) cations induced oxidation of the ferrocene unit in both dyads, which is accompanied by an important increase of the emission band.
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Synthesis and characterization of new carbazolocarbazoles: toward pi-extended N-fused heteroacenes.
Org. Lett.
PUBLISHED: 06-17-2010
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A regiospecific route has been developed for the synthesis of carbazolo[1,2-a]carbazole. The synthetic strategy is based on the use of appropriately tetrasubstituted naphthalene. Optical and electrochemical characterization of the fused heteroaromatic system reveals that this optically transparent heteroacene, with a low-lying HOMO, might be used as an organic material.
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A multifaceted ferrocene-benzobisimidazole derivative: fluorogenic probe for Pb(2+) and Zn(2+) cations and unconventional fluorescence behaviour towards Cu(2+) metal cations.
Dalton Trans
PUBLISHED: 05-17-2010
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The ferrocene-benzobisimidazole derivative shows high affinity for Pb(2+) and Zn(2+) metal cations over a range of other metal cations examined. In the presence of Pb(2+) the emission spectrum is red-shifted by 13 nm with an important chelation-enhanced fluorescence effect (CHEF) CHEF = 55. The presence of Zn(2+) cations also induced a perturbation of the emission spectrum although to a lesser extent than that found for Pb(2+) cations (CHEF = 37). Upon complexation with Cu(2+) cations, not only is the emission band red-shifted (Deltalambda = 67 nm) with a noticeable CHEF = 20, but also the maximum of such fluorescence emission exhibits a concomitant shift towards higher wavelengths when the excitation wavelength is gradually shifted to the red-edge of the absorption band (red-edge effect).
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Conformationally modulated intramolecular electron transfer process in a diaza[2,2]ferrocenophane.
Inorg Chem
PUBLISHED: 03-10-2010
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A novel conformationally modulated Intramolecular Electron Transfer (IET) phenomenon has been observed due to the cyclic structure of the diaza[2.2]ferrocenophane 3. The corresponding mixed-valence compound of 3, prepared by electrochemical or chemical partial oxidation, interestingly shows the appearance of two absorption bands in the near infrared (NIR) spectral region. These bands are attributable to two intervalence charge-transfer transitions associated to two atropoisomers exhibiting different energy for the IET process. A solvent and temperature control over the atropoisomeric equilibrium have also been observed. The experimental data and conclusions about both the conformational and the electronic properties of compound 3 are also supported by density functional theory calculations.
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Unexpected transalkylation on 3-alkyl-2-alkylthio-1,3,4-thiadiazolium-5-thiolates: a computational and experimental mechanistic study.
Org. Biomol. Chem.
PUBLISHED: 02-01-2010
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5-Alkylthio-3-methyl-2-thioxo-1,3,4-thiadiazolines have been obtained on heating alkyl 1-methyl-1-hydrazinecarbodithioates with CS(2). A DFT-based computational mechanistic study suggests an initial pseudopericyclic [1,4]H shift as a key step, as well as the intermediacy of the otherwise expected isomers 2-alkylthio-3-methyl-1,3,4-thiadiazolium-5-thiolates, from which the final products are formed by stepwise S,S-transalkylation.
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A selective redox and chromogenic probe for Hg(II) in aqueous environment based on a ferrocene-azaquinoxaline dyad.
Inorg Chem
PUBLISHED: 11-21-2009
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A new chemosensor molecule 4 based on a ferrocene-azaquinoxaline dyad effectively recognizes Hg(2+) in an aqueous environment as well as Pb(2+) and Zn(2+) metal cations in CH(3)CN solution through three different channels. Upon recognition, an anodic shift of the ferrocene/ferrocenium oxidation peaks and a progressive red shift (Deltalambda = 112-40 nm) of the low energy band, in their absorption spectra, is produced. These changes in the absorption spectra are accompanied by color changes from orange to deep green, for Hg(2+), and to purple in the cases of Pb(2+) and Zn(2+). Remarkably, the redox and colorimetric responses toward Hg(2+) are preserved in the presence of water (CH(3)CN/H(2)O, 3/7). The emission spectrum of 4 in CH(3)CN (lambda(exc) = 270 nm) undergoes important chelation enhancement of fluorescence (CHEF) in the presence of Hg(2+) (CHEF = 204), Pb(2+) (CHEF = 90), and Zn(2+) (CHEF = 184) metal cations. Along with the spectroscopic data, the combined (1)H NMR data of the complexes and the theoretical calculation suggest the proposed bridging coordination modes.
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A new open benzodipyrrole-based chemosensor for hydrogenpyrophosphate anion in aqueous environment.
Chem. Commun. (Camb.)
PUBLISHED: 11-06-2009
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Benzodipyrrolic derivatives have been synthesised and evaluated as neutral receptors for anions, in a mixed acetone-water media.
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Heteroditopic ligands based on ferrocenyl benzimidazoles fused to an additional diaza heterocyclic ring system.
Dalton Trans
PUBLISHED: 09-25-2009
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The synthesis of ferrocene-based heteroditopic receptors in which the ferrocene moiety is attached to an imidazo[4,5-e]benzothiadiazole or imidazo[4,5-f]quinoxaline is reported. These nitrogen-rich ferrocene derivatives show remarkable ion-sensing properties because of the presence of the redox active ferrocene unit and the polyazaheteroaromatic ring systems which act as a dual binding site for anions and metal cations. They display an anodic shift of the oxidation wave (DeltaE(1/2) = 67-200 mV) upon complexation with metal cations and a strong cathodic shift (DeltaE(1/2) = -82 to -100 mV) in the presence of F(-) and HP(2)O(7)(3-) anions. For the Zn(2+), Cd(2+), Hg(2+) and Pb(2+) metal cations tested, the change in the absorption spectra is accompanied by a dramatic colour change which allows the potential for "naked eye" detection.
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A click-generated triazole tethered ferrocene-pyrene dyad for dual-mode recognition of the pyrophosphate anion.
Org. Lett.
PUBLISHED: 07-04-2009
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The ferrocene-pyrene dyad 3 is able to selectively sense the pyrophosphate anion. The anion recognition was evaluated using electrochemistry, (1)H NMR, as well as fluorescence spectroscopy. The binding event can be inferred from either the redox-shift (DeltaE(1/2) = -100 mV) or the emission intensity ratio of the pyrene monomer to the excimer emission bands in both the neutral and oxidized forms of the receptor upon complexation.
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Imidazole-annelated ferrocene derivatives as highly selective and sensitive multichannel chemical probes for Pb(II) cations.
J. Org. Chem.
PUBLISHED: 06-03-2009
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New ferrocenyl-containing imidazopyridine and imidazophenazine receptors 2-5 show high selective affinity for Pb(II) ions over a range of other metal ions examined through different channels. Imidazopyridine-ferrocene dyad 2 behaves as a highly selective redox, chromogenic, and fluorescent chemosensor molecule for Pb(2+) cations: the oxidation redox peak is anodically shifted (DeltaE(1/2) = 150 mV), and the low energy band of the absorption spectrum is red-shifted (Deltalambda = 44 nm) upon complexation with this metal cation. This change in the absorption spectrum is accompanied by a color change from colorless to orange, which allows the potential for "naked eye" detection. The emission spectrum undergoes an important chelation-enhanced fluorescence (CHEF) effect (CHEF = 620), with an unprecedented detection limit of 2.7 microg L(-1). The presence of Zn(2+) cations also induced a perturbation of the redox potential, absorption, and emission spectra although in less extension than those found with Pb(2+) cations. Imidazophenazine-ferrocene dyad 3 has also shown its ability for sensing Pb(2+) cations through redox (DeltaE(1/2) = 120 mV), absorption (Deltalambda = 23 nm), and emission (CHEF = 133) channels, whereas the presence of Zn(2+) only has a little effect on the emission spectrum (CHEF = 74). The electrochemical changes observed in the two-armed ferrocenes 4 and 5 upon complexation show that the potential shift is higher for Zn(2+) ions (DeltaE(1/2) = 190-170 mV) than for Pb(2+) ions (DeltaE(1/2) = 180-110 mV), which is in clear contrast to those observed for the monoarmed ferrocenes 2 and 3. The recognition properties of the two-armed imidazopyridine-ferrocene triad 4 are quite similar to those exhibited by the parent monosubstituted receptor 2, and the most salient features are a strong perturbation of the redox wave (DeltaE(1/2) = 180 mV), a dramatic increasing of the fluorescent quantum yield (Phi(complex)/Phi(ligand) = 890) in the presence of Pb(2+), while the optical responses toward Zn(2+) cations were silent. The two-armed imidazophenazine-ferrocene triad 5 senses Pb(2+) cations through perturbation of the oxidation potential of the Fe(II)/Fe(III) redox couple (DeltaE(1/2) = 110 mV), important blue shift (Deltalambda = 160 nm) of the high energy band in the absorption spectrum, and a remarkable increase of the emission band (CHEF = 220), whereas smaller changes were observed in the presence of Zn(2+) cations. (1)H NMR studies as well as DFT calculations have been carried out to get information about which molecular sites are involved in the binding event.
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[Factors associated with Clostridium difficile disease in a tertiary-care medical institution in Mexico: a case-control study].
Rev. Invest. Clin.
PUBLISHED: 03-02-2009
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Clostridium difficile-associated disease (CDAD) has been clearly associated with the use of broad-spectrum antibiotics worldwide. However, information about CDAD is scarce in Mexico and Latin America.
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A redox-fluorescent molecular switch based on a heterobimetallic Ir(iii) complex with a ferrocenyl azaheterocycle as ancillary ligand.
Dalton Trans
PUBLISHED: 02-20-2009
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The synthesis, electronic and spectroelectrochemical studies of a cyclometalated heteroleptic Ir(iii) complex containing a redox active ferrocenyl imidazophenanthroline ancillary ligand, is presented. Depending on the oxidation state of the ferrocene, controlled by external electrochemical stimuli, the emission fluorescence intensity of this bistable heterometallic complex can be modulated.
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A multiresponsive two-arm ferrocene-based chemosensor molecule for selective detection of mercury.
Dalton Trans
PUBLISHED: 01-30-2009
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The preparation, electrochemical, electronic, and cation sensing properties of an indole-ferrocene-indole triad, are presented. A salient feature of this new structural motif is that the redox-active organometallic fragment is linked to the indole rings by unsaturated nitrogen functionalities. Triad behaves as a highly selective dual-redox and chromogenic chemosensor molecule for Hg(2+) cations: the oxidation redox peak is anodically shifted (DeltaE(1/2) = 210 mV), and the low energy band of the absorption spectrum is red-shifted (Deltalambda = 120 mm), upon complexation with this metal cation. This change in the absorption spectrum is accompanied by a dramatic colour change from orange to green which allows the potential for "naked eye" detection. (1)H NMR as well as DFT calculations have been carried out to get information about the molecular sites which are involved in bonding.
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Mononuclear ferrocenophane structural motifs with two thiourea arms acting as a dual binding site for anions and cations.
Inorg Chem
PUBLISHED: 01-24-2009
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The synthesis of a new type of mononuclear ferrocenophane-based thiourea, in which the ferrocene moiety is simultaneously attached to two thiourea groups directly from 1,1-bis(isothiocyanato)ferrocene, is reported. These nitrogen-rich structural motifs show remarkable ion-sensing properties because of the presence of the redox active ferrocene unit and the thiourea bridges, which unexpectedly act as a dual binding site for anions and metal ions. They display a selective downfield shift of the thiourea protons and a remarkable cathodic shift of the ferrocene/ferrocenium redox couple with F(-), AcO(-), H(2)PO(4)(-), and HP(2)O(7)(3-) anions, whereas the selective recognition of Hg(2+) metal cations is achieved either by electrochemical or by spectral measurements. The preferred binding modes are proposed for the most representative complexes by means of density functional theory based theoretical calculations showing the Janus-like faces of the receptor.
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PDMS based photonic lab-on-a-chip for the selective optical detection of heavy metal ions.
Analyst
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The selective absorbance detection of mercury(II) (Hg(2+)) and lead(II) (Pb(2+)) ions using ferrocene-based colorimetric ligands and miniaturized multiple internal reflection (MIR) systems implemented in a low-cost photonic lab on a chip (PhLoC) is reported. The detection principle is based on the formation of selective stable complexes between the heavy metal ion and the corresponding ligand. This interaction modulates the ligand spectrum by giving rise to new absorbance bands or wavelength shifting of the existing ones. A comparative study for the detection of Hg(2+) was carried out with two MIR-based PhLoC systems showing optical path lengths (OPLs) of 0.64 cm and 1.42 cm as well as a standard cuvette (1.00 cm OPL). Acetonitrile solutions containing the corresponding ligand and increasing concentrations of the heavy metal ion were pumped inside the systems and the absorbance in the visible region of the spectra was recorded. The optical behaviour of all the tested systems followed the expected Beer-Lambert law. Thus, the best results were achieved with the one with the longest OPL, which showed a linear behaviour in a concentration range of 1 ?M-90 ?M Hg(2+), a sensitivity of 5.6 × 10(-3) A.U. ?M(-1) and a LOD of 2.59 ?M (0.49 ppm), this being 1.7 times lower than that recorded with a standard cuvette, and using a sample/reagent volume around 190 times smaller. This microsystem was also applied for the detection of Pb(2+) and a linear behaviour in a concentration range of 3-100 ?M was obtained, and a sensitivity of 9.59 × 10(-4) A.U. ?M(-1) and a LOD of 4.19 ?M (0.868 ppm) were achieved. Such a simple analytical tool could be implemented in portable instruments for automatic in-field measurements and, considering the minute sample and reagent volume required, would enable the deployment of high throughput environmental analysis of these pollutants and other related hazardous species.
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Ion pair recognition receptor based on an unsymmetrically 1,1-disubstituted ferrocene-triazole derivative.
J. Org. Chem.
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The ferrocene-triazole derivative 4, available from 1,1-bis(diazido)ferrocene by sequential functionalization through click-type chemistry and the Staudinger reaction, is elaborated as a lab-on-a-molecule for the selective sensing of HP(2)O(7)(3-) and Hg(2+). Receptor 4 behaves as a ratiometric fluorescent probe for HP(2)O(7)(3-) with a good selectivity over other anions, whereas in the presence of Hg(2+) it modifies the fluorescent emission of the pyrene unit, acting as a selective on-off fluorescent sensor for Hg(2+) with a low detection limit. The most salient feature of compound 4 is its behavior as an excellent electrooptical ion pair recognition receptor able to simultaneously recognize Pb(2+) cations in the presence of HP(2)O(7)(3-) anion through multichannel perturbations of the redox potential of the ferrocene unit, the emission spectrum, and a noticeable color change from yellow to green.
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Rational design of a fluorescent receptor for the recognition of anthrax biomarker dipicolinate.
Analyst
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A new carbazole-2,7-dicarboxamide derivative has been synthesised and has been proved to effectively bind the dipicolinate anion, which is commonly used as an anthrax biomarker. The fluorescent response from this synthetic receptor offers a selective colour change in an organic-aqueous environment that is of valuable analytical use.
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Indolocarbazole-based ligands for ladder-type four-coordinate boron complexes.
Org. Lett.
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A novel class of ?-conjugated systems, which combine the indolo[3,2-b]carbazole unit with the formation of four-coordinate boron complexes, is presented. The resulting conjugated compounds have a double-laddered structure that provides interesting optical and electrochemical properties. The wide absorption range, covering most of the visible spectrum, along with the narrowing of the HOMO-LUMO energy gap, due to the presence of diphenylboryl centers, reinforces the potential of these molecules within the area of organic electronics.
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Multichannel HSO4- recognition promoted by a bound cation within a ferrocene-based ion pair receptor.
Chem. Commun. (Camb.)
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A ferrocene-based ion pair receptor is shown only to recognise HSO(4)(-) anions in the presence of a cobound Pb(2+) or Zn(2+) cation guest species through a perturbation of the redox potential of the ferrocene unit and a remarkable enhancement of the fluorescence.
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A ferrocenyl-guanidine derivative as a highly selective electrochemical and colorimetric chemosensor molecule for acetate anions.
Dalton Trans
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A highly preorganized chemosensor molecule 1 based on a ferrocenyl-guanidine decorated with a chromogenic aryl azo moiety recognizes the acetate anion in acetonitrile solution. At first, receptor 1 underwent two-step oxidation events. Initially, oxidation of 1 occurs at the Fe(II) centre (E(p) = 440 mV) to form a ferrocenium species, followed by fast electron transfer from the guanidine moiety of the receptor to the Fe(III) centre with concomitant generation of an Fe(II) species with a radical cation centred at the nitrogen atom. In the second step, the radical cation species formed should undergo electrochemical oxidation at higher potential (E(p) = 830 mV). This assumption is supported by spectroelectrochemical studies. A remarkable cathodic shift (182 mV) of the ferrocene/ferrocenium oxidation peak (E(p) = 440 mV) and a progressive red-shift (?? = 30 nm) of the low energy band are observed in its absorption spectrum upon complexation of receptor 1 with the acetate anion. This change in the absorption spectrum is accompanied by a colour change from yellow to orange, which can be used for the "naked-eye" detection of this anion. Its monoprotonated form is able to selectively sense the less basic Cl(-), Br(-), NO(3)(-), and HSO(4)(-) anions: the oxidation redox peak at E(p) = 865 mV is cathodically shifted (107-182 mV).
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Highly selective mercury(II) cations detection in mixed-aqueous media by a ferrocene-based fluorescent receptor.
Dalton Trans
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A new chemosensor molecule 3 based on a ferrocene-imidazophenanthrophenazine dyad effectively recognizes Hg(2+) in an aqueous environment through three different channels. Upon recognition, an anodic shift of the ferrocene-ferrocenium oxidation potential (?E(1/2) = 240 mV) and a progressive red shift (?? = 17 nm) of the low energy band in its absorption spectrum is produced. The emission spectrum of 3 in an aqueous environment, CH(3)CN-EtOH-H(2)O (65:25:10), and conducted at pH = 7.4 (20 × 10(-3) M HEPES) (? = 0.003), is perturbed after addition of Hg(2+) cations and an intense and structureless red shift emission band at 494 nm (?? = 92 nm) appeared along with an increase of the intensity of the emission band (CHEF = 77), the quantum yield (? = 0.054) resulted in a 18-fold increase. The combined (1)H NMR data of the complex and the theoretical calculations suggest the proposed bridging coordination mode.
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Imidazole derivatives: a comprehensive survey of their recognition properties.
Org. Biomol. Chem.
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Due to its amphoteric nature the imidazole ring can function as selective and effective anion and/or cation and even neutral organic molecules receptor system. As a result, the design of new multichannel imidazole-based receptors capable of recognizing different types of analytes is strongly demanded. This review summarizes the most recent and relevant advances in this area.
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Combined study of anion recognition by a carbazole-based neutral tripodal receptor in a competitive environment.
Org. Biomol. Chem.
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Anion recognition studies have been carried out on a series of neutral synthetic receptors in which carbazole-2-carboxamide has been used as building block. Different ligands which include one to three carbazole units in their structure have been prepared. Binding experiments have been performed under competitive conditions in DMSO and DMSO-water solutions. The tripodal receptor offered a better host-guest association due to the synergistic effect of a well arranged set of hydrogen bonds. A selective response towards the biologically important pyrophosphate anion has been achieved. This selectivity is enhanced when studies are carried out with an increasing water content, which gets as high as 20% (v/v) in NMR experiments. The significance of this result lies in the use of a neutral receptor which exclusively interacts with the anionic guest through hydrogen bonding. The influence of multiple equilibria in the studied system has been analysed. Several techniques ((1)H NMR, (31)P NMR, mass spectrometry, diffusion-NMR, ITC, absorption and emission spectroscopy) have been employed to get a better understanding of the different processes taking place in solution for the evaluated receptors.
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Ferrocene-based multichannel ion-pair recognition receptors.
Dalton Trans
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Ferrocenylimidazoles and unsymmetrically 1,1-disubstituted ferrocenes, bearing a triazole ring directly linked to the redox unit, behave as efficient ion-pair recognition receptors.
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