Double Concave Cesium Encapsulation by Two Charged Sumanenyl Bowls

The controlled reaction of Na and Cs, two alkali metals of different ionic sizes and binding abilities, with sumanene (C₂₁H₁₂) affords a novel type of organometallic sandwich [Cs(C₂₁H₁₁⁻)₂]⁻, which crystallized as a solvent‐separated ion pair with a [Na(18‐crown‐6)(THF)₂]⁺ cation (where THF=tetrahydrofuran). The unprecedented double concave encapsulation of a metal ion by two bowl‐shaped sumanenyl anions in [Cs(C₂₁H₁₁⁻)₂]⁻ was revealed crystallographically. Evaluation of bonding and energetics of the remarkable product was accomplished computationally (B2PLYP‐D/TZVP/ZORA), providing insights into its formation.     

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.     

Rapid Determination of Trifluoromethanesulfonate and p-Toluenesulfonate by Ion-Pair Chromatography Using a Reversed-Phase Silica-Based Monolithic Column: Application to the Analysis of Ionic Liquids

A method of ion-pair chromatography was developed on a reversed-phase silica-based monolithic column for the fast and simultaneous determination of trifluoromethanesulfonate (CF₃SO₃ ⁻) and p-toluenesulfonate (C₇H₇SO₃ ⁻). The analysis was performed using a mobile phase of tetrabutylammonium hydroxide + citric acid + acetonitrile on the Chromolith Speed ROD RP-18e column with direct conductivity detection. The effects of the eluent, column temperature and flow rate on the retention of the anions were investigated. The experimental phenomenon was discussed according to hydrophobic interaction and ion-exchange mechanism in the separation. The optimized chromatographic conditions were selected. The optimized eluent for the separation consisted of 0.2 mmol L⁻¹ tetrabutylammonium hydroxide + 0.10 mmol L⁻¹ citric acid + 9% acetonitrile (pH 5.5). The flow rate was set at 6.0 mL min⁻¹. The column temperature was 25 °C. Under the optimal conditions, the better separation of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ was achieved without any interference by other anions (Cl⁻, Br⁻, I⁻, NO₃ ⁻, SO₄ ²⁻, ClO₃ ⁻, BF₄ ⁻ and PF₆ ⁻). The detection limit (S/N = 3) was 0.28 and 0.71 mg L⁻¹ for CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻, respectively. The method has been applied to the determination of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ in ionic liquids. The spiked recoveries of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ were 101.1 and 100.2%, respectively.

     

O-atom transfer biomimetic oxidation of benzoin in the presence of monooxomolybdenum(IV) thiolate complexes

Novel catalytically active monooxomolybdenum(IV) species containing four thiolate ligands obtainable in solution by NaBH₄ reduction of [Mo^vO(SC₆H₅)₄]⁻, [Mo^vO(Z-cys-Val-OMe)₄]⁻, (Z=benzyloxycarbonyl), or [Mo^vO(S₂C₆H₄)₂]⁻ perform the pyridine-N-oxide oxidation of benzoin in N,N-dimethylformamide at 30 °C. The order of catalytic activity is [Mo^vO(Z-cys-Val-OMe)₄]⁻ > [Mo^vO(S₂C₆H₄)₂]⁻ > [Mo^vO(SC₆H₅)₄]⁻ ([benzoin]/[oxidant]/[catalyst]= 20/20/1), while the oxidation by air under the same catalytic conditions gives a different order, [Mo^vO(Z-cys-Val-OMe)₄]⁻> [Mo^vO(SC₆H₅)₄]⁻ >[Mo^vO(S₂C₆H₄)₂]⁻. During the catalytic cycle in the amine-N-oxide oxidation, two intermediate species, [Mo^IVOL₄]²⁻ and [Mo^VIO₂L₄]²⁻, were detected by ¹H NMR, while in the air oxidation an unidentified Mo(VT) species is involved.     

Conformational properties of simple monocyclic conjugated enediynes

An investigation employing the AM1 semi-empirical SCF MO method to calculate structure optimization and conformational interconversion pathways for Z-cyclonona-3-ene-1,5-diyne (1), Z-cyclodeca-3-ene-l,5-diyne (2), and Z-cycloundeca-3-ene-1, 5-diyne (3) has been undertaken. The plane-symmetrical half-chair conformation of 1 is calculated to be 23.8 kJ mol⁻¹ more stable than the planar C_2v transition-state geometry. Compound 2 has two energy-minimum conformations with the twistboat (C₂) form being 31.1 kJ mol⁻¹ more stable than the twist (C₁) geometry. The calculated energy barrier for interconversion of C₂ and C₁ conformations is 37.4 kJ mol⁻¹. The unsymmetrical twist-boat form of 3 is calculated to be the most stable conformation. The twist-boat geometry can undergo two degenerate processes to achieve a time-averaged symmetry of C_2v.     

Na2Mg(SO3) · 2H2O. Ein neues ternäres Magnesiumsulfit Kristallstruktur,schwingungsspektroskopische und thermoanalytische Untersuchungen

Na₂Mg(SO₃)₂ · 2H₂O. A New Ternary Magnesium Sulfite. Crystal Structure, Thermoanalytical, I.R., and Raman Data Single crystals of the hitherto unknown Na₂Mg(SO₃)₂ · 2 H₂O have been obtained by crystallization from Mg(HSO₃)₂ solutions saturated with NaCl and with the technique of gel crystallization. The crystal structure of the triclinic Na₂Mg(SO₃)₂ · 2 H₂O (P1 , Z = 1, a = 752.4(1), b = 590.3(1), c = 517.8(1) pm, α = 106.25(1), β = 109.80(1), and γ = 101.49(1)°) has been determined using single crystal X-ray diffraction data. The Mg? O distances of the nearly regular MgO₆ octahedra are between 206.6 and 210.5 pm. The MgO₆ octahedra are connected by sulfite bridges forming chains in [001], which are held together by strong hydrogen bridges. The SO₃^2? ions have nearly C_3v symmetry. The results of thermoanalytical and I.R. and Raman spectroscopic measurements are reported and discussed. The O? D stretching modes of HDO molecules in partially deuterated samples show that the water molecules differ strongly from C_2v symmetry.     

IR-Laser Ablation of Potassium Cyanide: A Surprisingly Simple Route to Polynitrogen and Polycarbon Species

Pulsed laser irradiation of solid potassium cyanide (KCN) produces, besides free nitrogen and carbon atoms, the molecular species KN and KC which are potential candidates for interstellar species of potassium. Additionally, N₃, N₃⁻, KN₃, C₃, C₃⁻, and KC₃ are produced and isolated in solid noble gases as well as in solid N₂. Molecular potassium nitrene (KN) reacts with dinitrogen in neon and argon matrices after photochemical excitation (λ=470 nm) forming molecular end-on (C_∞v) and side-on (C_2v) potassium azide isomers. The side-on isomer (C_2v) is thermodynamically favored at the CCSD(T)/ma-def2-TZVP level of theory. It can be obtained from the end-on isomer by UV-irradiation (λ=273 nm).     

Syntheses,Structures, Reactivities,and Basicities of Quinolinyl and Isoquinolinyl Complexes of an Electron Rich Chiral Rhenium Fragment and Their Electrophilic Addition Products

Reactions of Li⁺ [(η⁵-C₅H₅)Re(NO)(PPh₃)]⁻ with 2- and 4-chloroquinoline or 1-chloroisoquinoline give the corresponding σ quinolinyl and isoquinolinyl complexes 3 , 6 , and 8 . With 3 and 8 there is further protonation to yield HCl adducts, but additions of KH give the free bases. Treatment of 3 with HBF₄⋅OEt₂ or H(OEt₂)₂⁺ BAr_f⁻ gives the quinolinium salts [(η⁵-C₅H₅)Re(NO)(PPh₃)(C(NH)C(CH)₄C (CH)(CH))]⁺ X⁻ ( 3-H ⁺ X⁻; X⁻=BF₄⁻/BAr_f⁻, 94–98 %). Addition of CF₃SO₃CH₃ to 3 , 6 , or 8 affords the corresponding N-methyl quinolinium salts. In the case of [(η⁵-C₅H₅)Re(NO)(PPh₃)(C(NCH₃)C(CH)₄C (CH)(CH))]⁺ CF₃SO₃⁻ ( 3-CH₃ ⁺ CF₃SO₃⁻), addition of CH₃Li gives the dihydroquinolinium complex (S_ReR_C,R_ReS_C)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(C(NCH₃)C(CH)₄C (CHCH₃)(CH₂))]⁺ CF₃SO₃⁻ ((S_ReR_C,R_ReS_C)- 5 ⁺ CF₃SO₃⁻, 76 %) in diastereomerically pure form. Crystal structures of 3-H ⁺ BAr_f⁻, 3-CH₃ ⁺ CF₃SO₃⁻, (S_ReR_C, R_ReS_C)- 5 ⁺ Cl⁻, and 6-CH₃ ⁺ CF₃SO₃⁻ show that the quinolinium ligands adopt Re⋅⋅⋅ C conformations that maximize overlap of their acceptor orbitals with the rhenium fragment HOMO, minimize steric interactions with the bulky PPh₃ ligand, and promote various π interactions. NMR experiments establish the Brønsted basicity order 3 > 8 > 6 , with K_a(BH⁺) values >10 orders of magnitude greater than the parent heterocycles, although they remain less active nucleophilic catalysts in the reactions tested. DFT calculations provide additional insights regarding Re⋅⋅⋅ C bonding and conformations, basicities, and the stereochemistry of CH₃Li addition.     

Darstellung und struktur von Cp2ZrX2 und [Cp2Zr(X)(H2O)2]+ X−(X = toluolsulfonat)

Cp₂Zr(C₇H₇SO₃)₂ (C) can be prepared from Cp₂ZrCl₂ and silver toluenesulfonate in acetonitrile. Reaction of C with H₂O gives the ionic 18-electron species [Cp₂Zr(C₇H₇SO₃)(H₂O)₂]⁺ C₇H₇SO₃⁻ (D). The structures of both complexes have been determined by X-ray analyses. The Cp₂Zr units in C and D have the usual bent metallocene structure. The metal-bonded O atoms of the three additional ligands in D lie in a plane bisecting the plane of the Cp ligands, the C₇H₇SO₃ group being symmetrically flanked by the H₂O ligands. The H₂OZrOH₂ angle is 148°. On the other hand, the OZrO angle of 90° in C is relatively small for a Cp₂ZrX₂ compound.     

Isolation and Characterization of a Non‐Rigid Hexamethylbenzene–SO2+ Complex

During our studies towards the preparation of the pentagonal‐pyramidal hexamethylbenzene dication C₆(CH₃)₆²⁺, we isolated the unprecedented dicationic species C₆(CH₃)₆SO²⁺ (AsF₆⁻)₂ from the reaction of hexamethylbenzene with a mixture of anhydrous HF, AsF₅, and liquid SO₂. This compound can be understood as a complex of unknown SO²⁺ with hexamethylbenzene. Herein, we report on its synthesis, molecular structure, and spectroscopic characterization.     

Syntheses,Structural Characterization,Reactivity, and Theoretical Studies on Some Heteroligand Oxoperoxotungstate(VI)

White microcrystalline diamagnetic oxoperoxotungstate(VI) complexes K[WO(O₂)₂F]·H₂O, K₂[WO(O₂)₂(CO₃)]·H₂O, [WO(O₂)(SO₄)(H₂O)₂] have been synthesized from reaction of Na₂WO₄·2H₂O with aqueous HF, solid KHCO₃, aqueous H₂SO₄ (W:F⁻ 1:3; W: CO₃ ^{2 −} 1:1; and W: SO₄ ^{2 −} 1:3), and an excess of 30% H₂O₂ at pH 7.5–8. Precipitation was completed by the addition of precooled acetone. The occurrence of terminal WO and triangular bidentate O₂ ^{2 −}(C _{2 v} ) in the synthesized compounds was ascertained from IR spectra. The IR spectra also suggested that the F⁻ and SO₄ ^{2 −} ions in K[WO(O₂)₂F]·H₂O and [WO(O₂)(SO₄)(H₂O)₂] were bonded to the WO ⁺⁴ center in monodentate manner, while CO₃ ^{2 −} ion in K₂[WO(O₂)₂(CO₃)]·H₂O binds the metal center in bidentate chelating fashion. The complex [WO(O₂)(SO₄)(H₂O)₂] is stable upto 110°C. The water molecule in [WO(O₂)(SO₄)(H₂O)₂] is coordinated to the WO ⁺⁴ center, whereas it occurs as water of crystallization in the corresponding peroxo(fluoro) and peroxo(carbonato) compounds. Mass spectra of the compounds are in good agreement with the molecular formulae of the complexes. K₂[WO(O₂)₂(CO₃)]·H₂O acts as an oxidant for bromide in the aqueous‐phase bromination of organic substrates to the corresponding bromo‐organics, and the complex also oxidizes Hantzsch‐1,4‐dihydropyridine to the corresponding pyridine derivative in excellent yield at room temperature. Density functional theory computation was carried out to compute the frequencies of relevant vibrational modes and electronic properties, and the results are in agreement with the experimentally obtained data.     

Matrix-isolation infrared spectra of oxy(tetraphenylporphyrinato)iron(II) containing CS2 and SO2 as axial ligands

The IR spectra of cocondensation products of Fe(TPP) with CS₂/Ar exhibit the ν(CS₂) of Fe(TPP)(CS₂) at 1522 cm⁻¹ which is 7 cm⁻¹ lower than that of free CS₂. When Fe(TPP) was cocendensed with O₂/CS₂/Ar, the bands characteristic of Fe(TPP)(CS₂)O₂ (ν(CS₂), 1519 cm⁻¹ and ν(O₂), 1190 cm⁻¹) were observed in addition to those of Fe(TPP)(CS₂) and Fe(TPP)O₂ (ν(O₂), 1195 cm⁻¹). These assignments were confirmed by ¹²CS₂/¹³CS₂ isotope shifts and warm-up experiments. A S-bonded structure in which the linear CS₂ molecule is weakly coordinated to the Fe atom has been proposed for these adducts. The IR spectra of cocondensation products of Fe(TPP) with SO₂/Ar exhibit bands characteristic of Fe(TPP)(SO₂) (1342, 1146) and Fe(TPP)(SO₂)₂ (1332 and 1142) in addition to those of SO₂ monomer ((1355*, 1351*) and (1152*, 1148*)), SO₂ dimer (1344, 1151) and SO₂H₂O (1343 and 1150 cm⁻¹). Here, the numbers in brackets indicate the SO₂ stretching frequencies, ν₃ and ν₁, respectively, and the asterisks denote those split by the matrix effect. The cocodensation products of Fe(TPP) with O₂/SO₂/Ar exhibit new bands at 1328 (ν₃), 1142(ν₁) and 1188 cm⁻¹ (ν(O₂)). The O-bonded structure in which the bent SO₂ molecule is coordinated to the Fe atom via the terminal oxygen has been proposed, based on small shifts of the ν₃ and ν₁ vibrations upon coordination.     

Determination of Three Nonsteroidal Anti-Inflammatory Drugs in Human Plasma by LC Coupled with Chemiluminescence Detection

A simple and sensitive method was developed for the determination of three nonsteroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen and fenbufen in human plasma. The method involved in column liquid chromatographic separation and chemilumenescence (CL) detection based on the CL reaction of NSAIDs, potassium permanganate (KMnO₄) and sodium sulfite (Na₂SO₃) in sulfuric acid (H₂SO₄) medium. The chromatographic separation was carried out using a reversed-phase C₁₈ column, which allowed the selective determination of the three medicines in the complicated samples. The special features of the CL detector provided lower LOD for determination than that of existing chromatographic alternatives. The results indicated that the linear ranges were 0.01–10.0 μg mL⁻¹ for ibuprofen, 0.001–1.0 μg mL⁻¹ for naproxen, and 0.01–10.0 μg mL⁻¹ for fenbufen. The limits of detection were 0.5 ng mL⁻¹ for ibuprofen, 0.05 ng mL⁻¹ for naproxen and 0.5 ng mL⁻¹ for fenbufen (S/N = 3). All average recoveries were in the range of 90.0–102.3%. Finally, the method had been satisfactorily applied for the determination of ibuprofen, naproxen and fenbufen in human plasma samples.

     

Jahn—Teller effects in the mindo approximation: structures of the molecular cations of methane and the chloromethanes

The MINDO/3 technique gives geometries for (CH₄)⁺, (CCl₄)⁺ and the intermediate ions (CH_nCl_{4 ? n})⁺ (n = 1, 2, 3) which have symmetries in precise accord with the predictions of the Jahn—Teller effect. The ground state of (CH₄)⁺ has D_2d symmetry, with a C_3v structure ca. 45.6 kJ mol^?1 higher. (CCl₄)⁺ has a C_2v ground state, with a D_2d structure ca. 144 kJ mol^?1 higher: no bound state of C_3v symmetry could be found. (CH₃Cl)⁺ and (CHCl₃)⁺ both have C_s symmetry, and (CH₂Cl₂)⁺ has C_2v symmetry. The analogous fluoro ions are discussed briefly.     

One- and Two-Electron Transfer Oxidation of 1,4-Disilabenzene with Formation of Stable Radical Cations and Dications

Electron-transferable oxidants such as B(C₆F₅)₃/nBuLi, B(C₆F₅)₃/LiB(C₆F₅)₄, B(C₆F₅)₃/LiHBEt₃, Al(C₆F₅)₃/(o-RC₆H₄)AlH₂ (R=N(CMe₂CH₂)₂CH₂), B(C₆F₅)₃/AlEt₃, Al(C₆F₅)₃, Al(C₆F₅)₃/nBuLi, Al(C₆F₅)₃/AlMe₃, (CuC₆F₅)₄, and Ag₂SO₄, respectively were employed for reactions with (L)₂Si₂C₄(SiMe₃)₂(C₂SiMe₃)₂ (L=PhC(NtBu)₂, 1 ). The stable radical cation [ 1 ]^+. was formed and paired with the anions [nBuB(C₆F₅)₃]⁻ (in 2 ), [B(C₆F₅)₄]⁻ (in 3 ), [HB(C₆F₅)₃]⁻ (in 4 ), [EtB(C₆F₅)₃]⁻ (in 5 ), {[(C₆F₅)₃Al]₂(μ-F)]⁻ (in 6 ), [nBuAl(C₆F₅)₃]⁻ (in 7 ), and [Cu(C₆F₅)₂]⁻ (in 8 ), respectively. The stable dication [ 1 ]²⁺ was also generated with the anions [EtB(C₆F₅)₃]⁻ ( 9 ) and [MeAl(C₆F₅)₃]⁻ ( 10 ), respectively. In addition, the neutral compound [(L)₂Si₂C₄(SiMe₃)₂(C₂SiMe₃)₂][μ-O₂S(O)₂] ( 11 ) was obtained. Compounds 2 – 11 are characterized by UV-vis absorption spectroscopy, X-ray crystallography, and elemental analysis. Compounds 2 – 8 are analyzed by EPR spectroscopy and compounds 9 – 11 by NMR spectroscopy. The structure features are discussed on the central Si₂C₄-rings of 1 , [ 1 ]^+., [ 1 ]²⁺, and 11 , respectively.     

Gas‐phase dissociation of ionic liquid aggregates studied by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation

Positive singly charged ionic liquid aggregates [(C_nmim)_m+1(BF₄)_m]⁺ (mim = 3‐methylimidazolium; n = 2, 4, 8 and 10) and [(C₄mim)_m+1(A)_m]⁺ (A = Cl⁻, BF₄⁻, PF₆⁻, CF₃SO₃⁻ and (CF₃SO₂)₂N⁻) were investigated by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation. The electrospray ionisation mass spectra (ESI‐MS) showed the formation of an aggregate with extra stability for m = 4 for all the ionic liquids with the exception of [C₄mim][CF₃SO₃]. ESI‐MS‐MS and breakdown curves of aggregate ions showed that their dissociation occurred by loss of neutral species ([C_nmim][A])_a with a ≥ 1. Variable‐energy collision induced dissociation of each aggregate from m = 1 to m = 8 for all the ionic liquids studied enabled the determination of E_{cm, 1/2} values, whose variation with m showed that the monomers were always kinetically much more stable than the larger aggregates, independently of the nature of cation and anion. The centre‐of‐mass energy values correlate well with literature data on ionic volumes and interaction and hydrogen bond energies. Copyright © 2008 John Wiley & Sons, Ltd.     

Fourier-transform Raman and infrared spectra and normal coordinate analysis of (C6H5)2BiCl and [N(CH3)4]+[(C6H5)2BiCl2]−

The vibrational properties of the diphenylbismuth(III) chloride compounds (C₆H₅)₂BiCl and [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ have been investigated. A comprehensive assignment of the fundamental modes in the measured Fourier-transform Raman and infrared spectra has been carried out. Normal coordinate calculations of these compounds based on new X-ray crystal structure data have been performed to identify the BiCl stretching and bending vibrations of both compounds. For [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ in the solid state, the ν_s(BiCl₂) and ν_as(BiCl₂) occur at 215 cm⁻ (Raman) and 237 cm⁻ (Raman), respectively, in good agreement with the calculated wavenumbers. The force constant calculation yields a BiCl stretching force constant of 0.89 × 10² N m⁻¹.     

Etude vibrationnelle de la phase II des hydrogénodisulfates de triammonium, (NH4)3H(SO4)2 et (ND4)3D(SO4)2

The i.r. and Raman spectra of room temperature phase (phase II) of (NH₄)₃H(SO₄)₂ and (ND₄)₃D(SO₄)₂ as polycrystalline samples and single crystals have been investigated between 4000 and 30 cm⁻¹. An assignment of internal and external modes is given in terms of group frequencies and symmetry types. This crystal contains non-centrosymmetric dimers (SO₄HSO₄)³⁻ where sulphate ions are associated by strong asymmetric OH … O hydrogen bonds; they are characterized by two strong Raman bands at 1078 and 966 cm⁻¹, and a νOH frequency at about 1250 cm⁻¹. The acidic proton is statistically disordered around the crystallographic symmetry centre while all of the NH⁺₄ ions show an important dynamical orientational disorder.     

Calorimetric studies on phase transitions arising from orientational order-disorder of the molecular axes of ferrocene and its derivatives

Heat capacities of the channel inclusion compound, Fe(C₅D₅)₂ · 3(NH₂)₂CS, and two ferrocenium salts, [Fe(C₅H₅)(C₆H₆)]⁺ (PF₆)⁻ and [Fe(C₅H₅)₂]⁺ (PF₆)⁻, have been measured with adiabatic calorimeters between 13 and 393 K. Five phase transitions were found for Fe(C₅D₅)₂ · 3(NH₂)₂CS corresponding to those for Fe(C₅H₅)₂ · 3(NH₂)₂CS. The dominant phase transitions at 145.8 and 160.6 K are responsible for the onset of reorientational order-disorder of the molecular axis of Fe(C₅D₅)₂ in the clathrate cavity. The mass-effect of the guest ferrocene molecule on the phase transitions was not remarkable. The ferrocenium salt, [Fe(C₅H₅)(C₆H₆]⁺(PF₆)⁻, exhibited four phase transitions and two glass transition phenomena at low temperatures while its analog, [Fe(C₅H₅)₂]⁺(PF₆)⁻, brought about only three phase transitions without showing the glass transition. The higher-temperature phase transitions in these two salts have been assigned to the reorientational order-disorder mechanism of the molecular axes of the cations in the pseudo-cavities formed by eight PF⁻₆ anions. For the origin of the lower-temperature phase transitions in these two salts, three possibilities have been discussed. Among them, plausible origin is likely to be an order-disorder change of PF⁻₆ anion in the lattice. An important unsettled problem common to these three compounds is a question whether or not the Fe(C₅D₅)₂ and the cations, [Fe(C₅H₅)(C₆H₆)]⁺ and [Fe(C₅H₅)₂]⁺, are still reorienting around their molecular axes even at the lowest-temperature phase.     

LC Method for Determination of Ginkgolic Acids in Mice Plasma and Its Application to a Pharmacokinetic Study

A sensitive and simple LC method for the quantification of ginkgolic acids in mice plasma has been developed. Following acetonitrile deproteinization, samples were separated on a SinoChrom ODS-AP C₁₈ column. The mobile phase was 3% (v/v) acetic acid water solution–methanol (8:92, v/v) at a flow rate of 1.0 mL min⁻¹. Detection was at 310 nm. Calibration curve was linear over the range of 0.25–50 μg mL⁻¹ with intra- and inter-day precisions (RSD%) of less than 9.5%. The extraction recovery ranged from 87.0 to 90.2% (RSD 2.4–6.4%) for ginkgolic acids. The method was successfully applied to the pharmacokinetic study of ginkgolic acids in mice after oral dosing of 1.0 g kg⁻¹.