- Investigation of KYF4: Yb, Er // KYF4 nanocrystals - Mechanism of the KYF4 formation
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This paper presents our investigation of the formation mechanism of cubic phase Yb3+ and Er 3+ doped nanoscale KYF4. We generated Yb, Er doped KYF4 nanoparticles, modified with undoped KYF4 following
- Sch?fer,Ptacek,Hickmann,Prinz,Neumann,Haase
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- Phase transitions in K3AlF6
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Phase transitions in the elpasolite-type K3AlF6 complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures T1=132°C, T2=153°C and T3=306°C. The α-K3AlF6 phase is stable below T1 and crystallizes in a monoclinic unit cell with a=18.8588(2)A, b=34.0278(2)A, c=18.9231(1)A, β=90.453(1)° (a=2ac-cc, b=4bc, c=ac+2cc; ac, bc, cc - the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T1 and T2. The γ polymorph is stable in the T2a=36.1229(6)A, b=17.1114(3)A, c=12.0502(3)A (a=3ac-3cc, b=2bc, c=a c+cc) at 250 °C and space group Fddd. Above T 3 the cubic δ polymorph forms with ac=8.5786(4)A at 400 °C and space group Fm3m. The similarity between the K 3AlF6 and K3MoO3F3 compounds is discussed.
- Abakumov, Artem M.,Rossell, Marta D.,Alekseeva, Anastasiya M.,Vassiliev, Sergey Yu.,Mudrezova, Svetlana N.,Van Tendeloo, Gustaaf,Antipov, Evgeny V.
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- Two anhydrous salts of tetrafluoroterephthalic acid (H2tF-BDC): K2tF-BDC and Rb2tF-BDC
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Two new anhydrous salts of tetrafluoroterephthalic acid (H 2tF-BDC), namely K2tF-BDC (1) and Rb2tF-BDC (2), were synthesized and structurally characterized. The crystal structure of 1 (I2/m, Z = 2) was solved and refined from X-ray single crystal data. K + (CN = 8) is coordinated by six oxygen atoms of five different tF-BDC2- linkers and two fluorine atoms of two of these linkers, which connect the KO6F2 polyhedra to a 3D network. The crystal structure of 2 (P1, Z = 1) was refined from X-ray powder diffraction data. It crystallizes in a structure type already known from Tl 2tF-BDC. Rb+ (CN = 8) is also coordinated by six oxygen and two fluorine atoms. But six tF-BDC2- linkers are involved in the coordination. Again, a 3D network is formed. Both compounds can be obtained as single-phase samples. They are not porous and stable in air. The thermal stability was investigated by DTA/TG measurements. The decomposition starts at approx. 200°C (1) and 230°C (2). Their good solubility in water makes them interesting starting materials for the synthesis of new MOFs with the perfluorinated linker tF-BDC2-. Copyright
- Werker, Melanie,Dolfus, Benedikt,Ruschewitz, Uwe
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- Measurement of absolute rate data for the reaction of atomic potassium, K(4 2S1/2), with CF3Cl, CF2Cl2, CFCl3, CF3Br and SF6 as a function of temperature by time-resolved atomic resonance absorption spectroscopy at λ = 404 nm [k(5 2PJ) ← K(4 2S1/2)]
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We present a kinetic study of the reactions of atomic potassium in its electronic ground state, K(42S1/2), with the molecules CF3Cl, CF2Cl2, CFCl3, CF3Br and SF6. Atomic potassium was generated by pulsed irradiation of potassium halide vapour at elevated temperatures and monitored in the 'single-shot mode' by time-resolved atomic resonance absorption using the Rydberg doublet at λ = 404 nm [K(5 2PJ) ← K(4 2S1/2)]. Absolute rate constants for reaction with these molecules were determined as a function of temperature yielding the following Arrhenius parameters (errors 1σ): A/10-10 cm3 molecules-1 s-1 E/kJ mol-1 CF3Cl 1.1±0.5 13.8±2.5 CF2Cl2 2.1±0.6 5.5±0.5 CFCl3 ca. 1 ca. 0 CF3Br 3.9±0.4 12.3±0.6 SF6 8.4±1.33 12.3±0.9 CF4 exhibited anomalous kinetic behaviour. These results represent the first kinetic measurements, relative or absolute, for these fundamental reactions of atomic potassium. This new set of absolute rate data are compared with analogous results reported hitherto for atomic sodium, Na(3 2S1/2), both alkali-metal atoms exhibiting rapid reactions characterised by small energy barriers and being highly exothermic in character.
- Husain, David,Lee, Yook Heng
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- Exploration on anion ordering, optical properties and electronic structure in K3WO3F3 elpasolite
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Room-temperature modification of potassium oxyfluorotungstate, G2-K 3WO3F3, has been prepared by low-temperature chemical route and single crystal growth. Wide optical transparency range of 0.39.4 μm and forbidden band gap Eg=4.32 eV have been obtained for G2-K3WO3F3 crystal. Meanwhile, its electronic structure has been calculated with the first-principles calculations. The good agreement between the theorectical and experimental results have been achieved. Furthermore, G2-K3WO3F3 is predicted to possess the relatively large nonlinear optical coefficients. 2012 Elsevier Inc.
- Atuchin,Isaenko,Kesler,Lin,Molokeev,Yelisseyev,Zhurkov
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- Wet chemical synthesis of LiBaF3 phosphor
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LiBaF3 has great potential applications as X-ray storage phosphor, slow neutron imaging, scintillator, vacuum ultraviolet (VUV) optical lithography, etc. Conventionally, LiBaF3 is prepared by solid state reaction between the constituent fluorides. However, the preparation of phase pure material and especially single crystals is rather tricky due to incongruent melting. For the first time, a wet chemical preparation of rare earth activated LiBaF3 is described here. As precipitated powders containing Ce 3+ or Tb3+ exhibited characteristic luminescence. For observing Eu2+ emission, it was necessary to heat the powders in a reductive atmosphere. It is suggested that phosphors prepared by this method may prove useful in applications like OSL, X-ray imaging, etc. which do not require large single crystals.
- Singh, Vartika S.,Joshi,Moharil
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- The mild hydrothermal synthesis of complex fluorides of AZnF3 (A = Na, K)
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The complex fluorides of AZnF3 (A = Na, K), which are isostructural with perovskite phases were obtained by the method of hydrothermal synthesis at 160-220 °C. Compared with traditional high-temperature solid-state method, the products were pure and contained lower amount of oxygen.
- Li, Hong,Jia, Zhihong,Shi, Chunshan
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- A novel 18F labelled imidazo-oxazolopyridine derivative as β-amyloid imaging agent: Synthesis and preliminary evaluation
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Visualization of β-amyloid plaques in brain is pivotal for the diagnosis of Alzheimer’s disease. In the present study, we have designed, synthesized and evaluated an imidazo-oxazolopyridine derivative, 2-[2-(4-fluorophenyl)imidazo[1,2-a]pyridine-6- yl]oxa
- Singh, Shivani,Singh, Sweta,Tiwari, Anjani Kumar,Sharma, Rakesh Kumar,Mathur, Rashi,Kaul, Ankur
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- Molecular Beam Study of Steric Effects in the Reaction K + HF (v = 1, j = 2) -> KF + H
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HF molecules were optically aligned by use of linearly polarized infrared radiation generated by a color center laser tuned to the R1(l) line of HF.The state-specific integral cross section of the reaction K + HF (v = 1, j = 2) -> KF + H was measured for the two different preparations of the approach geometry which result when the plane of polarization is positioned either parallel (?) or perpendicular (?) to the most probable relative velocity of the reagents.At a translational energy of Etr = 0.46 eV the resulting relative difference of the cross sections (? - ?)/?(? = 1/2(? + ?)) amounts to 17 +/- 5percent.This steric effect decreases with rising Etr and reaches zero near 1.2 eV.The data strongly suggest that the reaction occurs via a collinear transition state.
- Hoffmeister, Manfred,Schleysing, Ruediger,Loesch, Hansjuergen
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- The crystal structure of α-K3AIF6: Elpasolites and double perovskites with broken corner-sharing connectivity of the octahedral framework
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The crystal structure of α-K3AIF6 was solved and refined from a combination of powder X-ray and neutron diffraction data (a = 18.8385(3)A, c = 33.9644(6)A, S.G. /41 Z= 80, R P(X-ray) = 0.037, Rp(neutr
- Abakumov, Artem M.,King, Graham,Laurinavichute, Veronika K.,Rozova, Marina G.,Woodward, Patrick M.,Antipov, Evgeny V.
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- A metabolically stable PET tracer for imaging synaptic vesicle protein 2A: synthesis and preclinical characterization of [18F]SDM-16
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Purpose: To quantify the synaptic vesicle glycoprotein 2A (SV2A) changes in the whole central nervous system (CNS) under pathophysiological conditions, a high affinity SV2A PET radiotracer with improved in vivo stability is desirable to minimize the potential confounding effect of radiometabolites. The aim of this study was to develop such a PET tracer based on the molecular scaffold of UCB-A, and evaluate its pharmacokinetics, in vivo stability, specific binding, and nonspecific binding signals in nonhuman primate brains, in comparison with [11C]UCB-A, [11C]UCB-J, and [18F]SynVesT-1. Methods: The racemic SDM-16 (4-(3,5-difluorophenyl)-1-((2-methyl-1H-imidazol-1-yl)methyl)pyrrolidin-2-one) and its two enantiomers were synthesized and assayed for in vitro binding affinities to human SV2A. We synthesized the enantiopure [18F]SDM-16 using the corresponding enantiopure arylstannane precursor. Nonhuman primate brain PET scans were performed on FOCUS 220 scanners. Arterial blood was drawn for the measurement of plasma free fraction (fP), radiometabolite analysis, and construction of the plasma input function. Regional time-activity curves (TACs) were fitted with the one-tissue compartment (1TC) model to obtain the volume of distribution (VT). Nondisplaceable binding potential (BPND) was calculated using either the nondisplaceable volume of distribution (VND) or the centrum semiovale (CS) as the reference region. Results: SDM-16 was synthesized in 3 steps with 44% overall yield and has the highest affinity (Ki = 0.9?nM) to human SV2A among all reported SV2A ligands. [18F]SDM-16 was prepared in about 20% decay-corrected radiochemical yield within 90?min, with greater than 99% radiochemical and enantiomeric purity. This radiotracer displayed high specific binding in monkey brains and was metabolically more stable than the other SV2A PET tracers. The fP of [18F]SDM-16 was 69%, which was higher than those of [11C]UCB-J (46%), [18F]SynVesT-1 (43%), [18F]SynVesT-2 (41%), and [18F]UCB-H (43%). The TACs were well described with the 1TC. The averaged test–retest variability (TRV) was 7 ± 3%, and averaged absolute TRV (aTRV) was 14 ± 7% for the analyzed brain regions. Conclusion: We have successfully synthesized a novel SV2A PET tracer [18F]SDM-16, which has the highest SV2A binding affinity and metabolical stability among published SV2A PET tracers. The [18F]SDM-16 brain PET images showed superb contrast between gray matter and white matter. Moreover, [18F]SDM-16 showed high specific and reversible binding in the NHP brains, allowing for the reliable and sensitive quantification of SV2A, and has potential applications in the visualization and quantification of SV2A beyond the brain.
- Zheng, Chao,Holden, Daniel,Zheng, Ming-Qiang,Pracitto, Richard,Wilcox, Kyle C.,Lindemann, Marcel,Felchner, Zachary,Zhang, Li,Tong, Jie,Fowles, Krista,Finnema, Sjoerd J.,Nabulsi, Nabeel,Carson, Richard E.,Huang, Yiyun,Cai, Zhengxin
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p. 1482 - 1496
(2021/11/16)
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- NHC-Copper Mediated Ligand-Directed Radiofluorination of Aryl Halides
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[18F]-labeled aryl fluorides are widely used as radiotracers for positron emission tomography (PET) imaging. Aryl halides (ArX) are particularly attractive precursors to these radiotracers, as they are readily available, inexpensive, and stable. However, to date, the direct preparation of [18F]-aryl fluorides from aryl halides remains limited to SNAr reactions between highly activated ArX substrates and K18F. This report describes an aryl halide radiofluorination reaction in which the C(sp2)-18F bond is formed via a copper-mediated pathway. Copper N-heterocyclic carbene complexes serve as mediators for this transformation, using aryl halide substrates with directing groups at the ortho position. This reaction is applied to the radiofluorination of electronically diverse aryl halide derivatives, including the bioactive molecules vismodegib and PH089.
- Sharninghausen, Liam S.,Brooks, Allen F.,Winton, Wade P.,Makaravage, Katarina J.,Scott, Peter J. H.,Sanford, Melanie S.
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supporting information
p. 7362 - 7367
(2020/08/19)
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- Compositions, methods, and systems for the synthesis and use of imaging agents
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The present invention generally relates to novel synthetic methods, systems, kits, salts, and precursors useful in medical imaging. In some embodiments, the present invention provides compositions comprising an imaging agent precursor, which may be formed using the synthetic methods described herein. An imaging agent may be converted to an imaging agent using the methods described herein. In some cases, the imaging agent is enriched in 18F. In some cases, an imaging agent including salt forms (e.g., ascorbate salt) may be used to image an area of interest in a subject, including, but not limited to, the heart, cardiovascular system, cardiac vessels, brain, and other organs.
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(2016/08/17)
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- Synthesis of [18F]Arenes via the Copper-Mediated [18F]Fluorination of Boronic Acids
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A copper-mediated radiofluorination of aryl- and vinylboronic acids with K18F is described. This method exhibits high functional group tolerance and is effective for the radiofluorination of a range of electron-deficient, -neutral, and -rich aryl-, heteroaryl-, and vinylboronic acids. This method has been applied to the synthesis of [18F]FPEB, a PET radiotracer for quantifying metabotropic glutamate 5 receptors.
- Mossine, Andrew V.,Brooks, Allen F.,Makaravage, Katarina J.,Miller, Jason M.,Ichiishi, Naoko,Sanford, Melanie S.,Scott, Peter J. H.
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supporting information
p. 5780 - 5783
(2015/12/11)
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- Simple preparation of new [18F]F-labeled synthetic amino acid derivatives with two click reactions in one-pot and SPE purification
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New [18F]fluorinated 1,2,3-triazolyl amino acid derivatives were efficiently prepared from Huisgen 1,3-dipolar cycloaddition reactions, well known as click reaction. We developed two simultaneous click reactions in one-pot with a simple solid-p
- Yook, Cheol-Min,Lee, Sang Ju,Oh, Seung Jun,Ha, Hyun-Joon,Lee, Jong Jin
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p. 317 - 326
(2015/08/03)
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- Standard enthalpy of formation of nickel trifluoride by isothermal calorimetry
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The change in enthalpy in reactions of NiF3(s) with water and aqueous solution of potassium hydroxide are measured in the isothermal calorimetry mode at 298.15 K. The standard enthalpy of formation ΔfH° of nickel trifluoride was foun
- Solov'ev,Korunov,Zubkov,Firer
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p. 516 - 518
(2012/07/14)
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- POTASSIUM FLUORIDE DISPERSION SOLUTION, AND PROCESS FOR PRODUCTION OF FLUORINATED ORGANIC COMPOUND USING THE SAME
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A potassium fluoride dispersion essentially consisting of potassium fluoride and an aprotic organic solvent having a boiling point higher than that of methanol, which is obtainable by mixing a mixture containing potassium fluoride and 5 to 50 parts by weight of methanol per 1 part by weight of potassium fluoride with the aprotic organic solvent followed by concentrating the obtained mixture, and a process for producing a fluorine-containing organic compound comprising contacting an organic compound having at least one group capable of being substituted nucleophilically with a fluorine atom with the potassium fluoride dispersion.
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(2009/04/25)
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- Optically active uniform potassium and lithium rare earth fluoride nanocrystals derived from metal trifluroacetate precursors
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This paper reports the first systematical synthesis of near-monodisperse potassium and lithium rare earth (RE) fluoride (K(Li)REF4) nanocrystals with diverse shapes (cubic KLaF4 and KCeF4 wormlike nanowires, nanocubes and
- Du, Ya-Ping,Zhang, Ya-Wen,Sun, Ling-Dong,Yan, Chun-Hua
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p. 8574 - 8581
(2011/01/06)
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- Radiolabelling
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Compounds of the formula (I) are disclosed: [in-line-formulae]18F—(CHR)n(CH2)mCHO ??(I)[/in-line-formulae] in which n and m are independently 0 and 1 with at least one of n and m being 1, and R (if present) is a hydrogen atom or a methyl group, subject to the proviso that if n is 1 and R is methyl then m is 0. Synthesis of the compounds is described together with their use in radiolabelling reactions, e.g. for the radiolabelling of peptides to facilitate detection by Positron Emission Tomography (PET) imaging. The preferred compound is [18F]Fluoroacetaldehyde.
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Page/Page column 4
(2008/12/08)
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- Microfluidic Chemical Reaction Circuits
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New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.
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Page/Page column 27; 28; 30
(2008/12/08)
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- LIGANDS FOR CARDIAC BETA1 ADRENOCEPTOR FOR IMAGING CONGESTIVE HEART FAILURE
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Novel β1 adrenoreceptor ligands that find use as imaging agents within nuclear medicine applications (e.g., PET imaging and SPECT imaging) are provided. Methods of imaging, including methods of imaging congestive heart failure, are also provide
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Page/Page column 45-46
(2008/12/07)
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- POTASSIUM PERFLUOROALKANESULFONATES AND PROCESS FOR PRODUCTION THEREOF
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A process for the production of potassium perfluoroalkane- sulfonates which comprises the electrolytic fluorination step of electrofluorinating an alkanesulfonyl halide in anhydrous hydrofluoric acid to obtain a gas containing a perfluoro- alkanesulfonyl fluoride as the main component. The process may further comprise the gas absorption step of reacting the gas with an aqueous solution of potassium hydroxide to form a solution containing a potassium perfluoroalkanesulfonate, the purification step of removing contaminant potassium fluoride, potassium hydroxide and potassium sulfate from the solution, and the concentration/recovery step of subjecting the purified aqueous solution to concentration and drying. In the electrolytic fluorination, the formation of by-products can be inhibited by keeping the proton concentration of the electrolytic solution within the range of 150 to 1500ppm.
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(2008/06/13)
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- RADIO-LABELED ISOXAZOLE DERIVATIVES USEFUL FOR THE LABELING AND DIAGNOSTIC OF HSP90 FUNCTIONALITY
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A radio-labeled isoxazole derivative of formula I, wherein R1 represents H, N-{11C]alkyl-piperazinyl, N-[11C]alkyl-piperazinyl-alkyl, N-[3H]alkyl- piperazinyl, N-methyl-piperazinyl or N-[3H]alkyl-pipe
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(2008/06/13)
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- Solubilities of lanthanum oxide in fluoride melts: Part I. Solubility in M3AlF6 (M = Li, Na, K)
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Solubility of lanthanum oxide was measured by thermal analysis. The solubility in alkali cryolites is rather high, because of chemical reactions between lanthanum oxide and cryolites. In Li3AlF6-La 2O3, alumina
- Ambrová,Jurisová
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p. 105 - 108
(2008/10/09)
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- NOVEL ORGANIC COMPOUND AND METHOD FOR PRODUCING RADIOACTIVE HALOGEN-LABELED ORGANIC COMPOUND USING THE SAME
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It is intended to provide a precursor compound to be labeled for selectively producing syn-1-amino-3-cyclobutanecarboxylic acid substituted with a radioactive halogen and a method for producing syn-1-amino-3-cyclobutanecarboxylic acid substituted with a r
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Page/Page column 12-13; 1/1
(2008/06/13)
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- Bifunctional perfluoroaryl boranes: Synthesis and coordination chemistry with neutral lewis base donors
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A practical synthetic route for the preparation of the known bifunctional perfluoroaryldiborane C6F4-1,2-[B(C6F 5)2]2,1, and the new diborane C 6F4-1,2-[B(C12F8)]2, 2, that circumvents the use of toxic mercury reagents has been developed. Key intermediates and 2 have been fully characterized in solution and the solid state. Solution and structural investigations of their MeCN and THF adducts have shown that 2 is a superior Lewis acid to 1, primarily owing to the reduction in steric pressure afforded by the planar 9-borafluorene rings in 2 versus the freely rotating set of pentafluorophenyl rings in 1. The two compounds bind Lewis bases via differing coordination modes, as demonstrated by the solid-state structures of the Lewis base adducts 1·MeCN, 2·THF, and 2·MeCN. Solution studies suggest that bis Lewis base adducts are also accessible; the structures of two examples (1·(MeCN)2 and 2·(THF)2) have been determined, and their role in the dynamic solution behavior of these systems is discussed.
- Chase, Preston A.,Henderson, Lee D.,Piers, Warren E.,Parvez, Masood,Clegg, William,Elsegood, Mark R. J.
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p. 349 - 357
(2008/10/09)
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- Vaporization products of transition-metal and rare-earth complex fluorides studied by high-temperature mass spectrometry
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Gaseous products of the thermal decomposition of Ni(IV), Tb(IV), Mn(IV), and Pt(IV) complex fluorides were studied by high-temperature mass spectrometry. The results demonstrate that the decomposition of potassium hexafluoronickelate and potassium heptafl
- Leskiv,Abramov,Oleinik,Kepman,Sukhoverkhov,Mazej,Rau,Chilingarov,Sidorov
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p. 1327 - 1333
(2008/10/09)
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- Decomposition products of KF · H2O2 studied by X-ray powder diffraction
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The composition of decomposition products of KF · H 2O2 is studied by X-ray diffraction analysis. It is shown that, on heating to 140°C under polythermal conditions, the peroxo solvate decomposes to form anhydrous potassium fluoride. The decomposition is accompanied by the appearance of extra reflections, which are presumably due to products of partial KF hydrolysis. Upon prolonged storage (for 3 or 4 years) of the peroxo solvate at 20°C or upon its decomposition at 80°C under isothermal conditions, potassium fluoride is isolated as a new previously unknown crystalline phase. Copyright
- Titova,Nikol'skaya,Buyanov,Pudova
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p. 639 - 641
(2008/10/09)
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- METHODS FOR PREPARING PERFLUORINATED [18 F]-RADIOLABELLED NITROIMIDAZOLE DERIVATIVES FOR CELLULAR HYPOXIA DETECTION
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The present invention relates to chemical synthesis of radiolabelled perfluorinated bioactive compounds. More particularly, the present invention relates to radiolabelled compounds to be used as indicators for tissue hypoxia. More particularly, the present invention relates to the synthesis and the use of [18F] labelled perfluorinated nitroimidazole compounds having an incorporation of [18F] atoms characterized by a specific radioactivity of the compound comprised between 1 and 30 Ci/mmol, preferably between 1 and 20 Ci/mmol, preferably 1 and 10 Ci/mmol. More particularly to [18F] labelled EF3 or [18F] labelled EF5. The present invention also relates to a method for the detection of tissue hypoxia in a patient comprising introducing an [18F] labelled nitroimidazole compound into said patient, imaging tissue hypoxia in said patient, and, quantifying tissue hypoxia in said patient.
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Page/Page column 8-9
(2010/02/13)
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- RADIOLABELED CANNABINOID-1 RECEPTOR MODULATORS
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The present invention relates to particular radiolabeled Cannabinoid-1 (CB1) receptor modulators, and methods of using these modulators for labeling and diagnostic imaging of Cannabinoid-1 receptors in mammals, particularly humans. In addition, intermediates useful for the synthesis of the radiolabeled Cannabinoid-1 receptor modulators are also disclosed, as well as the processes for synthesizing the radiolabeled Cannabinoid-1 receptor modulators. Still further, formulations of the radiolabeled Cannabinoid-1 receptor compounds are described.
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Page/Page column 31
(2010/02/10)
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- COX-2-targeted imaging agents
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The presently disclosed subject matter provides a method for synthesizing a radiological imaging agent by reacting a COX-2-selective ligand with a compound comprising a detectable group, wherein the COX-2-selective ligand is a derivative of a non-steroidal anti-inflammatory drug (NSAID) comprising an ester moiety or a secondary amide moiety. Also provided are compositions that are synthesized using the method, as well as methods of using the compositions of the presently disclosed subject matter.
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Page/Page column 25
(2008/06/13)
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- Reaction of sodium and potassium carbonates with ammonium hydrogen fluoride
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Reactions of sodium and potassium carbonates with ammonium hydrogen difluoride were studied, and the temperatures of formation of alkali metal (Li, Na, K) fluorides were compared.
- Makarov,Tikhomirova,Rakitin,Kalinnikov
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p. 380 - 383
(2007/10/03)
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- Localization of Eu3+ in KGd1.9Eu0.1F7 and KGd1.9Eu0.1F6.97O0.015 by site-selective excitation and time-resolved spectroscopy
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This paper reports site-selective excitation (or observation) and time-resolved spectroscopy of the host matrices KGd2F7 and KGd2F6.97O0.015 doped by Eu3+. The crystal structure of KGd2F7 derives from that of the fluorite-type, by an ordering of the cations and anions. The luminescence spectra and site-selective excitation in the 5D0→7F0 region, have allowed to identify several distributions of discrete sites for the Eu3+ ions, in which two sites are characterized by unusual spectra which are attributed to Eu-O bonds. Another kind of site, characteristic of fluorinated surroundings close to the centrosymmetry, exhibits a very long lifetime (6.8 ms) of the 5D0 level. Although the accurate structures of these compounds are not yet known, they are very close to that of KGd2.77F9.32 previously solved and the spectroscopic results are in agreement with the number and the symmetries of the rare earth crystallographic sites.
- Pierrard,Gredin,Dupont,De Kozak,Piriou
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- The crystal structure of Kx(MgxIn1-x)F3 (x = 0.38): A new magnéli-bronze type fluoride
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Kx(MgxIn1-x)F3 (x = 0.38) is monoclinic, pseudo tetragonal: a = 12.781(2) ?, b = 12.787(2) ?, c = 7.930(1) ?, β = 90,00(1)°, Z = 20. The crystal structure was solved in the space group P21/a (No. 14), subgroup of the tetragonal space group P4/mbm (No. 127), from X-ray single crystal data using 4302 unique reflections (1770 with Fo/σ(Fo) > 4). The final observed R factor is 0.053. Kx(MgxIn1-x)F3 has the Magnéli-bronze structural type, which consists in a tridimensional framework of mixed [(MgxIn1-x)F6] octahedra linked together by corners. The potassium ions are mainly located in large almost fully occupied 15-coordinated sites and in practically empty 12-coordinated cavities.
- Caramanian, Armen,Dupont, Nathalie,Gredin, Patrick,De Kozak, Ariel
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p. 933 - 938
(2008/10/08)
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- Effect of reactant structure on the solid state reaction between KHF2 and oxides of iron and vanadium
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Fluoro and oxyfluoro complexes of iron and vanadium were prepared using KHF2 and their thermal behavior was studied using TG/DTA techniques. All the three oxides of iron reacted with the cubic phase of KHF2, giving identical products, namely (NH4)3FeF6·1.5H2O irrespective of oxidation state of iron. KHF2 in its tetragonal, as well as cubic phases reacts with vanadium oxide depending on the molar ratio of the reactants. A possible pathway for the thermal degradation is given for the above complexes and the residues obtained were identified.
- Adhyapak-Thosar,Rao
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p. 105 - 111
(2008/10/09)
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- Vibrational Spectra and Structural Aspects of Fluorosulfites
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The Raman and infrared spectra of the fluorosulfites of K+, Rb+, Cs+, NH4+, and Me4N+ have been examined. Previous assignment of the fundamental vibrations is revised, and an ab initio study of the SO2F- anion is presented. For the pyramidal anion of symmetry Cs, distances of r(S-O) = 1.458 ? and r(S-F) = 1.698 ? have been calculated. The heat of formation of Me4NSO2F (-14.0 kcal/mol) was derived from the dissociation pressure of the salt. In addition, the lattice energy of Me4NF (159.2 kcal/mol) was calculated from a thermochemical cycle. The thermochemical data are discussed in terms of reactivity of the fluorides and stability of the fluorosulfites.
- Kornath, Andreas,Neumann, Frank,Ludwig, Ralf
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p. 5570 - 5573
(2008/10/09)
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- The [PO2F2?2AsF5]- anion, an example of a stable, oxygen-bridged, 1:2 donor-acceptor polynuclear anion
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KPO2F2 reacts at room temperature with excess AsF5 in a 1:2 mol ratio. The resulting stable white product was characterized by vibrational and multinuclear NMR spectroscopy in the solid state and SO2 solution, respectively. It is shown that AsF5 neither displaces PO2F from KPO2F2, nor generates PO2+AsF6-, but forms a stable, oxygen-bridged polynuclear [PO2F2?2AsF5]- anion. When pyrolyzed, this anion undergoes a stepwise decomposition to KAsF6, POF3 and AsOF3, followed by the decomposition of KAsF6 to KF and AsF5. While [PO2F2?2AsF5]- is stable in SO2 solution, it decomposes in CD3CN solution to the known CD3CN?AsF5 adduct and [PO2F2?AsF5]- anion. The inability of AsF5 to displace PO2F from its salts confirms that the latter is a very strong Lewis acid which is comparable in strength to AsF5. With PF5 the KPO2F2 salt forms at -78°C the 1:2 adduct K[PO2F2?2PF5], which on warm-up to room temperature loses 1 mol of PF5 to give the 1:1 adduct, K[PO2F2?PF5]. The 1:1 adduct is marginally stable at room temperature and undergoes slow POF3 evolution. An improved synthesis of POF3 from PF5 and P4O10 is reported. Gauthier-Villars.
- Christe,Gnann,Wagner,Wilson
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p. 865 - 877
(2008/10/08)
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- The Kinetics and Mechanism of Hexafluorophosphate Ion Hydrolysis in the Presence of Li(1+) Ions
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The kinetics of alkaline hydrolysis of the hexafluorophosphate ion in the presence of Li(1+) ions is studied in the temperature range 423-483 K.The observed rate constants, catalysis constants, and the activation pa rameters for the hydrolysis process are calculated. It is established that, under the experimental conditions, the energy requirements for the disintegration of the hydrate shells of PF6(1-) and Li(1+) are close to the effect of the weakening of the P-F bond under the influence of Li(1+)ions.
- Plakhotnik, V. N.,Sukhaya, E. M.
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- The Solid-Phase Reaction between Neodymium Cuprate and Potassium Fluorocuprate
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The solid-phase reaction between neodymium cuprate and potassium fluorocuprate is studied using isothermal annealings, and differential thermal(DTA) and X-ray powder diffraction analyses. The K2CuF4-Nd2CuO4 sectionis not quasi-binary. The mixed neodymium, potassium, and copper oxofluoride (which is a NdOF-based solid solution), having a fluorite-like structure, and a solid solution, having the Nd2CuO4 structure, are found.
- Fadeeva, E. E.,Ardashnikova, E. I.,Popovkin, B. A.
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p. 1058 - 1060
(2008/10/08)
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- Low-temperature precursor synthesis of crystalline nickel disulfide
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Pure, crystalline nickel disulfide is synthesized within seconds from the solid-state reaction between potassium hexafluoronickelate(IV) and sodium pentasulflde hydrate at ～65°C. The nickel disulfide product is isolated by simply washing away the byproduct salts. The reaction is influenced by the hydration and the sulfur content of the sulfiding agent and by the transition-metal precursor. Increasing the hydration of the sodium pentasulfide or lowering the oxidation state of the nickel in potassium hexafluoronickelate from Ni(IV) to Ni(III) favors a less crystalline product. Reactions containing sulfiding agents with lower sulfur content, such as sodium monosulfide or sodium disulfide, produce mixtures of nickel monosulfide and nickel disulfide. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry results are presented.
- Bonneau, Philippe R.,Shibao, Robert K.,Kaner, Richard B.
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p. 2511 - 2514
(2008/10/08)
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- Alkali-metal Heptafluorodiarsenates(III): their Preparation and the Crystal Structure of the Potassium Salt
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Heptafluorodiarsenates(III), MAs2F7 (M=K, Rb, or Cs), have been prepared by the dissolution of the alkalimetal fluoride in arsenic trifluoride and crystallisation from the solvent at room temperature.Loss of arsenic trifluoride and formation of the tetrafluoroarsenate(III) occurs on heating to 100 deg C under vacuum.The structure of the potassium salt has been determined by the heavy-atom method from 799 reflections, and refined by full-matrix least-squares methods to R 0.070.Crystals are monoclinic, space group P21/c, with a=10.99(1), b=7.39(1), c=8.75(1) Angstroem, and β=110.8(2)o.The structure consists of potassium ions, tetrafluoroarsenate(III) ions, and arsenic trifluoride molecules, with some interaction between anions and molecules to form a complex chain arrangement.
- Edwards, Anthony J.,Patel, Shantubai N.
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p. 1630 - 1632
(2007/10/02)
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- Some chemistry of difluoraminocarbonyl fluoride, NF2CFO. The preparation of perfluorourea, (NF2)2CO, and difluoraminocarbonyl chloride, NF2C(O)Cl. New preparations for NF2OCF3 and NF2<
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Reactions of NF2CFO with CF3OF or with Al2Cl6 and HCl yield NF2OCF3 or NF2C(O)Cl, respectively. The reactions of NF2CFO with KF and CsF to give KOCF2NF
- Fraser, George W.,Shreeve, Jean'ne M.
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p. 1711 - 1715
(2008/10/08)
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- Complexes of xenon oxide tetrafluoride
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Xenon oxide tetrafluoride bears a strong resemblance to the halogen fluorides both in physical properties and chemical behavior. A number of physical properties of XeOF4 have been measured. Xenon oxide tetrafluoride is a clear, colorless liquid freezing at -46.2°. Its electrical conductivity at 24° is 1.03 × 10-5 ohm-1 cm.-1 and its dielectric constant is 24.6 at 24°. It is miscible with anhydrous HF, but its conductivity is not enhanced in such a solution. The addition of CsF or RbF to XeOF4 increases its conductivity markedly. Xenon oxide tetrafluoride forms a series of addition compounds with the heavier alkali fluorides. The following complexes have been isolated: CsF·XeOF4, 3RbF-2XeOF4 and 3KF·-XeOF4. No reaction occurs with NaF. Thermogravimetric studies show that a number of intermediates are formed before final decomposition to the alkali fluorides. Xenon oxide tetrafluoride reacts with SbF5 to form a complex of composition XeOF4· 2SbF5. A reaction also occurs with AsF5 at -78°, but the complex is unstable at room temperature.
- Selig, Henry
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p. 183 - 186
(2008/10/08)
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