Compressibilities of disordered fluoride pyrochlores NaCdZn2F7 and NaCaMg2F7

The compressibilities of disordered pyrochlores NaCaMg₂F₇ and NaCdZn₂F₇ (both , Z=8) have been studied with X-ray single-crystal and powder diffraction using diamond anvil cells to 6.5 and 9.0 GPa at room temperature, respectively. The compressibility data are fitted with the Murnaghan equations of state. The zero-pressure bulk modulus B₀ and the unit-cell volume at ambient pressure V₀ (for the fixed first pressure derivative of the bulk modulus B′=4.00) are equal to 83(2) GPa and 1107.12(1.33) Å³ for NaCdZn₂F₇ and to 83(5) GPa and 1079.29(2.62) Å³ for NaCaMg₂F₇. Upon decreasing the unit-cell volume, the positional x parameter of the F(2) atom increases in NaCdZn₂F₇ but is constant in NaCaMg₂F₇. In both cases, the (Na,Cd)F₈ and (Na,Ca)F₈ cubes become more regular and are softer than the ZnF₆ and MgF₆ octahedra, respectively. Both materials are structurally stable at least to the respective highest pressures reached in this study. These observations are compared to the high-pressure behavior of oxide pyrochlores.     

Conformational analysis of n-perfluoroalkanes: n-C4F10 and n-C6F14

The vibrational spectra of n-C₄ F₁₀ and n-C₆F₁₄ were investigated in the vapour, liquid and solid phases and the equilibrium conformations of these molecules were determined. Different solid-phase spectra were recorded by changing deposition and/or annealing conditions.     

IR matrix isolation spectra of some perfluoro organic-free radicals Part 1. C2F5

The pentafluoro ethyl radical has been prepared by the pyrolysis of C₂F₅I in a platinum effusion tube at ?650°C and isolated in an argon matrix. By elimination of absorption bands attributable to known fluorine compounds and from relative intensity measurements on the remaining bands, twenty frequencies were assigned C₂F₅ in the spectral range 4000–200 cm^?1. Fourteen of these frequencies were assigned as fundamentals of C₂F₅, with C_s symmetry, and the remainder to combination or overtone modes of the radical.     

Synthesis and molecular structures of heptafluoropropylated fullerenes: C70(n-C3F7)8, C70(n-C3F7)6O, and C70(C3F7)4

Ampoule reactions of C₇₀ with n- and i-C₃F₇I were carried out at 250-310 °C. Two step HPLC separations allowed the isolation of several C₇₀(n-C₃F₇)_4-8 and C₇₀(i-C₃F₇)₄ compounds. Crystal and molecular structures of C₇₀(n-C₃F₇)₈-V, C₇₀(n-C₃F₇)₆O, C₇₀(n-C₃F₇)₄, and three isomers of C₇₀(i-C₃F₇)₄ have been determined by X-ray crystallography using synchrotron radiation. Molecular structures of the new compounds were compared with the known examples and discussed in terms of addition patterns and relative energies of their formation.     

Synthesis and molecular structures of heptafluoroisopropylated fullerenes: C60(i-C3F7)8, C60(i-C3F7)6, and C60(CF3)2(i-C3F7)2

One isomer of C₆₀(i-C₃F₇)₈, three isomers of C₆₀(i-C₃F₇)₆, and the first mixed perfluoroalkylated fullerene, C₆₀(CF₃)₂(i-C₃F₇)₂, have been isolated by HPLC from a mixture prepared by reaction of C₆₀ with heptafluoroisopropyl iodide in a glass ampoule at 260-290 °C. The molecular structures of the four new compounds have been determined by means of X-ray single crystal diffraction partially also by use of synchrotron radiation. Theoretical calculations at the DFT level of theory have been employed to rationalize the energetics of isomers and of C₆₀-R_f binding.     

Structure cristalline de RbSb2F7

The crystal structure of RbSb₂F₇ was determined by single crystal X-ray diffraction methods. The antimony atom coordination is of the AX₆E type, either monocapped octahedral or the distorded 2.2.2.1 arrangement. The anion (Sb₂F₇)^x-_x forms a polymeric layer parallel to the bc plane. There is an Sb-F-Sb bridge intermediate between the symmetric and asymmetric bridges of CsSb₂F₇ and KSb₂F₇ respectively.     

Perfluororganozink-verbindungen: darstellung und eigenschaften von (Rf)2Zn-komplexen (Rf = CF3, C2F5, C3F7, C6F5) [1]

A new method for the preparation of bis(perfluoroorgano) zinc compounds is described: CF₃I and C₆F₅I react with dialkylzinc in the presence of a Lewis base quantitatively to give (CF₃)₂Zn and (C₆F₅)₂Zn complexes, while the analogous reactions with C₂F₅I and iC₃F₇I do not yield the pure compounds. ¹H, ¹⁹F n.m.r, i.r. and Raman spectra are presented.     

Magnetic circular dichroism of Eu(C2H5SO4)3·9H2O due to magnetic dipole transitions

The magnetic circular dichroism (MCD) for the three low-energy absorption bands of the Eu(C₂H₅SO₄)₃·9H₂O crystal has been measured at room temperature. It may be well understood from the MCD as well as from other experimental results that two of these bands, ⁷F₁ → ⁵D₀ and ⁷F₀ → ⁵D₁, are of magnetic dipole origin. However, the MCD of another band at about 18650 cm^?1, ⁷F₁ → ⁵D₁, cannot be interpreted as being only one electric dipole in origin, which has been pointed out by several investigations. The present MCD analysis indicates that although this broad band consists of one electric- and two magnetic-dipole transitions, each of which has a sizeable absorption strength, the MCD spectrum originates exclusively from the two magnetic dipole transitions     

Zur kenntnis von [O2]22+[Ti7F30]2−

[O₂]²⁺₂[Ti₇F₃₀]^2? has been obtained by reaction of TiO₂ with a mixture of fluorine and oxygen (p_F2/O2 ≈ 300–3500 atm., t ≈ 300–450°C) either as colourless powder or in form of colourless, clear needles. From single crystal studies the spacegroup is P$\text{3}$ - C_3i¹ (No. 147) with a = 10.19₂, c = 6.50_o Å, Z = 1. The crystal structure has been refined to R = 0.086 [R_w = 0.058] (748 unique reflexions [F_o > 2σ(F_o)]). From the structure determination [O₂]²⁺₂[Ti₇F₃₀]^2? has isolated columns of partially distorted [TiF₆] octahedra (- column structure) which are connected only quite loosely by (disordered) O₂⁺ cations. ν_O2+ is at 1857 cm^?1, the magnetic moment μ_eff = 2.35 B.M. (295 K) is quite as expected for a ‘spin-only’ case.     

Alignment of acentric MoO3F3 anions in a polar material: (Ag3MoO3F3)(Ag3MoO4)Cl

(Ag₃MoO₃F₃)(Ag₃MoO₄)Cl was synthesized by hydro(solvato)thermal methods and characterized by single-crystal X-ray diffraction (P3m1, No. 156, Z=1, a=7.4488(6)Å, c=5.9190(7) Å). The transparent colorless crystals are comprised of chains of distorted fac-MoO₃F₃³⁻ octahedra and MoO₄²⁻ tetrahedra anions, as suggested by the formulas Ag₃MoO₃F₃ and Ag₃MoO₄⁺, and are connected through Ag⁺ cations in a polar alignment along the c-axis. One Cl⁻ anion per formula unit serves as a charge balance and connects the two types of chains in a staggered fashion, offset by . In MoO₄²⁻, the Mo atom displaces towards a single oxide vertex, and in MoO₃F₃³⁻, the Mo displaces towards the three oxide ligands. The ordered oxide-fluoride ligands on the MoO₃F₃³⁻ anion is important to prevent local inversion centers, while the polar organization is directed by the Cl⁻ anion and interchain dipole-dipole interactions. The dipole moments of MoO₃F₃³⁻ and MoO₄²⁻ align in the negative c-axis direction, to give a polar structure with no cancellation of the individual moments. The direction and magnitude of the dipole moments for MoO₃F₃³⁻ and MoO₄²⁻ were calculated from bond valence analyses and are 6.1 and 1.9 debye (10⁻¹⁸ esu cm) respectively, compared to 4.4 debye for polar NbO₆ octahedra in LiNbO₃, and 4.5 debye for polar TiO₆ octahedra in KTiOPO₄ (KTP).     

P4N4F7O—the isoelectronic counterpart of P4N4F8

TAS⁺ ((Me₂N)₃S⁺) P₄N₄F₇O⁻ (8) was prepared from TAS⁺P₄N₄F₉⁻ via F/O exchange using Me₃SiOSiMe₃. The salt was characterised by X-ray crystallography. The bonding situation in the anion is briefly discussed. The structural properties of the anion are compared with those of the isoelectronic neutral phosphazene P₄N₄F₈.     

Reaction of C60 with KMnF4 : Isolation and characterization of a new isomer of C60F8 and re-evaluation of the structures of C60F7(CF3) and the known isomer of C60F8

The volatile fluorofullerene products of high-temperature reactions of C₆₀ with the ternary manganese(III, IV) fluorides KMnF₄, KMnF₅, A₂MnF₆ (A⁺ = Li⁺, K⁺, Cs⁺), and K₃MnF₆ were monitored as a function of reaction temperature, reaction time, and stoichiometric ratio by in situ Knudsen-cell mass spectrometry. When combined with fluorofullerene product ratios from larger-scale (bulk) screening reactions with the same reagents, an optimized set of conditions was found that yielded the greatest amount of C₆₀F₈ (KMnF₄/C₆₀ mol ratio 28-30, 470 °C, 4-5 h). Two isomers of C₆₀F₈ were purified by HPLC, one of which has not been previously reported. Quantum chemical calculations at the DFT level combined with 1D and 2D ¹⁹F NMR, FTIR, and FT-Raman spectroscopy indicate that the C₆₀F₈ isomer previously reported to be 1,2,3,8,9,12,15,16-C₆₀F₈ is actually 1,2,3,6,9,12,15,18-C₆₀F₈, making it the first high-temperature fluorofullerene with non-contiguous fluorine atoms. The new isomer, which was found to be 1,2,7,8,9,12,13,14-C₆₀F₈, is predicted to be 5.5 kJ mol⁻¹ more stable than 1,2,3,6,9,12,15,18-C₆₀F₈ at the DFT level. In addition, new DFT calculations and spectroscopic data indicate that the compound previously isolated from the high-temperature reaction of C₆₀ and K₂PtF₆ and reported to be 16-CF₃-1,2,3,8,9,12,15-C₆₀F₇ is actually 18-CF₃-1,2,3,6,8,12,15-C₆₀F₇.     

UV photolysis of n-C3F7I. Radiative lifetime of metastable iodine atoms

The photolysis of n-C₃F₇I and C₂F₅I has been studied with a frequency doubled dye laser at fixed frequency in the UV by detection of time resolved resonance fluorescence of the metastable iodine formed. The rate coefficient for quenching of I(²P_{$\text{1}\text{2}$}) by n-C₃F₇I has been obtained as k = (4.6 ± 0.3) × 10^?17 cm³ molecule_?1s_?1. This value is by more than an order of magnitude lower than published values. Further proof is given for the value of the radiative lifetime of the metastable atoms which was obtained recently by this experimental method. This answers questions raised by Husain et al. on this subject in this journal.     

Coordination chemistry of higher oxidation states. 10 [1]. Oxofluoroanions of osmium(VIII) [OsO4F2]2− and [OsO3F3]−

Trioxotrifluoroosmates(VIII) M[OsO₃F₃] (M = Cs, Rb, K) have been prepared by direct combination of OsO₃F₂ and the appropriate alkali fluoride MF. The reaction of OsO₄ with M′F (M′ = Cs, Rb) in aqueous solution produces the tetraoxodifluoroosmates(VIII) M′₂[OsO₄F₂]. On the basis of their vibrational spectra the assignment of a $\text{fac}$ (C_3v) structure to [OsO₃F₃]^? and a $\text{cis}$ (C_2v) to [OsO₄F₂]^2? is proposed. The electronic spectra of the anions have been recorded and are interpreted using the optical electronegativity concept.     

Absorption and fluorescence of Ho3+ IN La2S3·3Ga2S3

Absorption bands of Ho³⁺ in vitreous La₂S₃·3Ga₂S₃ in the range 500 to 2000 nm were assigned. Excitation spectra reveal additional levels ⁵G₆ and ⁵F₃ obscured by the intrinsic absorption of the glass. The Ho³⁺ emission in chalcogenide glasses is more intense than in oxide glasses due to smaller non radiative relaxation as predicted by the theory of multiphonon relaxation.     

Structure cristalline du composé RbEu3F10

Crystals of RbEu₃F₁₀ are cubic with a = 11.844 Å, Z = 8, and three possible space groups, $\text{Fm3m, F}\text{4}\text{3m}$, and F432. The structure has been resolved from three-dimensional X-ray data and refined by the least-squares method. The final R values are, respectively, 0.065 and 0.067 for Fm3m and $\text{F}\text{4}\text{3m}$, and are not significantly different. The rare earth symmetry is C_4v for Fm3m and C_2v for $\text{F}\text{4}\text{3m}$. Consequently, we have used the Eu³⁺ ion in the RbEu₃F₁₀ phase as a structural probe in order to state precisely the symmetry of the lanthanide site and distinguish among the possible space groups.     

Preparation and properties of potassium pentafluorodioxo-tungstate (VI) K3WO2F5 and potassium octafluoropentaoxo-ditungstate (VI) K6W2O5F8

The potassium salts of two new hepta coordinated oxyfluoro anions of tungsten (VI) are reported in this paper. The monomer, K₃WO₂F₅ was obtained from the aqueous solution while the dimer, K₆W₂O₅F₈ was isolated from alcohol. The absorption peak of K₆W₂O₅F₈ at 830 cm^-1 has been attributed to W-O-W link. The W-O-W angle is found to be 155° and the force constant is 4.44 mdyn/A°. The d values obtained from x-ray powder diffraction studies are given.     

Role of B(C6F5)3 in activating the nickel-methyl complex (η-C5H5)Ni(CH3)(PPh3) to initiate the vinyl polymerization of norbornene

The Ni-methyl complex (η⁵-C₅H₅)Ni(CH₃)(PPh₃) (1) reacted with B(C₆F₅)₃ to give an unstable contact ion-pair complex with a μ-methyl bridge between the Ni and B atoms. Formation of the B-CH₃ bond was confirmed by the reaction of this complex with PPh₃ to give [(η⁵-C₅H₅)Ni(PPh₃)₂][B(CH₃)(C₆F₅)₃] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded (η⁵-C₅H₅)Ni(C₆F₅)(PPh₃) which is very stable and does not show any reactions with norbornene with or without added B(C₆F₅)₃. ¹⁹F NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C₆F₅)₃ system has the C₆F₅ end-group. A series of reactions, which includes CH₃/C₆F₅ exchange between the Ni and B centers with concomitant dissociation of PPh₃ to accept coordination of a norbornene monomer, is proposed as the route to active species that can initiate vinyl polymerization of norbornene.     

Analyse des sites de KLu3F10 et BaCaLu2F10 par spectroscopie de l'ion Eu3+

The Eu³⁺ ion is used as a structural probe, in order to state precisely the symmetry at the different cationic sites in the KLu₃F₁₀ and BaCaLu₂F₁₀ compounds. The emission and excitation spectra recorded at 4.4, 77, and 295°K are analyzed and the experimental data for both systems are compared. The energy levels of the Eu³⁺ ion in KLu₃F₁₀ are given. It is shown that Eu³⁺ ions enter three different sites in BaCaLu₂F₁₀. The nature of these sites is discussed.     

Impact of Eu3+ Ions on Physical and Optical Properties of Li2O-Na2O-B2O3 Glass

The lithium sodium borate glasses doped with Eu³⁺ ion are prepared using melt quenching technique, their structural and optical properties have been evaluated. The density of prepared glasses exhibits an inverse behavior to the molar volume ranging from 2.26 g/cm³ to 2.43 g/cm³ and 26.95 cm³ /mol to 26.20 cm³ /mol, respectively. The absence of sharp peaks in XRD patterns confirms the amorphous nature of the prepared glasses. The absorption spectra yield four transitions centered at 391 nm (⁷F₀→⁵L₆), 463 nm (⁷F₀→⁵D₂), 531 nm (⁷F₀→⁵D₁), and 582 nm (⁷F₀→⁵D₀). The most intense red luminescence is observed at 612 nm corresponding to ⁵D₀→⁷F₂ transition under 390 nm laser excitations.