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Fluoride Anions (fluoride + anion)
Selected AbstractsSimple Bisthiocarbonohydrazones as Sensitive, Selective, Colorimetric, and Switch-On Fluorescent Chemosensors for Fluoride AnionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2007Feng Han Abstract Bisthiocarbonohydrazones are found to be a class of sensitive, selective, ratiometric, and colorimetric chemosensors for anions such as fluoride (F,) or acetate (Ac,). The sensitivities, or the binding constants of the sensors with anions, were found to be strongly dependent on the substituents appended on the ,-conjugation framework, the delocalization bridge CHN, the aromatic moiety, and the hetero atom in the CX group (X=O, S) of the sensors. Single-crystal structures and 1H,NMR titration analysis shows that the CHN moiety is a hydrogen-bond donor, and it is proposed that an additional CH,,,F hydrogen bond is formed for the sensors in the presence F,. A sensor bearing anthracenyl groups is demonstrated as a switch-on fluorescent chemosensor for F, and Ac,. The recognition of F, in acetonitrile (MeCN) by a sensor with nitrophenyl substituents is tolerant to MeOH (MeCN/MeOH=10:1, v/v) and water (MeCN/H2O=30:1, v/v); at these solvent ratios the absorption intensity of the sensor,F, complex solution at maximal absorption wavelength was attenuated to half of the original value in pure MeCN. [source] K3TaF8 from laboratory X-ray powder dataACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010ubomír Smr The crystal structure of tripotassium octafluoridotantalate, K3TaF8, determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal,prismatic [TaF7]2, ions. All six atoms in the asymmetric unit are in special positions of the P63mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face-sharing K6 octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK3]2+ running along [001] with isolated [TaF7]2, trigonal prisms in between. The structure of the title compound is different from the reported structure of Na3TaF8 and represents a new structure type. [source] Exploring the Dynamics of Calix[4]pyrrole: Effect of Solvent and Fluorine SubstitutionCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2007Ramón Blas Dr. Abstract Molecular dynamics simulations show that calix[4]pyrrole (CP) and octafluorocalix[4]pyrrole (8F-CP) are extremely flexible molecules. CP mainly adopts the 1,3-alternate conformation in all the solvents, although the percentage of alternative conformations increases in polar solvents, especially those with good hydrogen-bonding acceptor properties. However, in the case of 8F-CP, the cone conformation is the most populated in some solvents. Transitions between conformers are common and fast, and both CP and 8F-CP can adopt the cone conformation needed for optimum interaction with anions more easily than would be predicted on the basis of previous gas-phase calculations. Furthermore, the present studies show that when a fluoride anion is specifically placed initially in close proximity to CP and 8F-CP in their respective 1,3-alternate conformations, an extremely fast change to the cone conformation is observed in both cases. The results suggest that preorganization does not represent a major impediment to anion-binding for either CP or 8F-CP, and that ion-induced conformational changes can follow different mechanisms depending on the solvent and the chemical substituents present on the calix[4]pyrrole beta-pyrrolic positions. [source] How do electrons travel in unusual metallic fluorides of Ag2+?,PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2005Tomasz Jaro Abstract We investigate computationally two representative examples of higher fluorides of Ag(II), namely KAgF3 and AgFBF4. Both compounds formally contain linear (Ag,F)+ chains, in which divalent silver is coordinated additionally by four fluoride anions. For AgFBF4, the equatorial coordination is weak, and leads to metallic conductivity in 1D, as emerges from our band structure calculations. For KAgF3, however, the axial coordination is very strong, and the compound is virtually a 2D metal (i.e. it is mainly the x2,y2 orbitals of Ag that participate in electronic transport in this interesting material). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] K3TaF8 from laboratory X-ray powder dataACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010ubomír Smr The crystal structure of tripotassium octafluoridotantalate, K3TaF8, determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal,prismatic [TaF7]2, ions. All six atoms in the asymmetric unit are in special positions of the P63mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face-sharing K6 octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK3]2+ running along [001] with isolated [TaF7]2, trigonal prisms in between. The structure of the title compound is different from the reported structure of Na3TaF8 and represents a new structure type. [source] Pyrazino[2.3- g]quinoxaline-Bridged Indole-Based Building Blocks: Design, Synthesis, Anion-Binding Properties, and Phosphate-Directed Assembly in the Solid StateCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2010Ting Wang Abstract Strategies for exploring anionic templates to direct sophisticated supramolecular assembly have attracted attention. Herein, a series of new anion receptors 1,3 containing two indole-based binding sites bridged by linking spacer pyrazino[2.3- g]quinoxaline (PQ) have been rationally designed and prepared from the precursors 2,3-diindol-3,-yl quinoxaline (DIQ) and 5,6-dihydrodiindolo[3,2- a:2,,3,- c]phenazine (DIPZ). X-ray analyses showed a self-connected network and dimeric packing through hydrogen bonding and ,,, stacking interaction in the solid state in the structures of 1 and 2, respectively. All three receptors exhibited a series of prominent absorption bands from the expanded ,,system. The indole-based expanded receptors were found to strongly and selectively bind F,, AcO,, and H2PO4, among the tested anions (F,, Cl,, Br,, AcO,, H2PO4,, HSO4,, NO3,, and ClO4,), and operated as efficient colorimetric sensors for naked-eye detection of fluoride anions in DMSO. These tailored building blocks captured two anions located at far-spaced binding sites, and adopted noninterfering anion-binding processes to guarantee the anion-binding affinity, topology, and dimensionality. Solid-state studies elucidated that the neutral 1,3 interacted with the tetrahedral dihydrogen phosphate anion in proper proportions and designed topologies, thus leading to the formation of a series of multidimensional networks by self-assembly in the solid state. The observations showed a well-characterized phosphate-directed assembly of multidimensional metal-free coordination polymers in the solid state, in which the formed phosphate aggregates, including dimer encapsulated in an indole-mediated hydrogen-bonded pocket and an infinite chain, behaved as anionic templates to direct the self-assembly. However, no evidence proved the presence of such phosphate-directed infinite coordination polymers in solution. [source] | ||||||||||