The Ideal Ionic Liquid Salt Bridge for the Direct Determination of Gibbs Energies of Transfer of Single Ions,Part I: The Concept

Described is a procedure for the thermodynamically rigorous, experimental determination of the Gibbs energy of transfer of single ions between solvents. The method is based on potential difference measurements between two electrochemical half cells with different solvents connected by an ideal ionic liquid salt bridge (ILSB). Discussed are the specific requirements for the IL with regard to the procedure, thus ensuring that the liquid junction potentials (LJP) at both ends of the ILSB are mostly canceled. The remaining parts of the LJPs can be determined by separate electromotive force measurements. No extra‐thermodynamic assumptions are necessary for this procedure. The accuracy of the measurements depends, amongst others, on the ideality of the IL used, as shown in our companion paper Part II.     

Phosphaniminate von Alkalimetallen: Die Kristallstrukturen von [KNPCy3]4, [KNPCy3]4·2OPCy3, [CsNPCy3]4·4OPCy3 und [Li4(NPPh3)(OSiMe2NPPh3)3(DME)]

The alkalimetal phosphoraneiminates [KNPCy₃]₄, ( 1 ) [KNPCy₃]₄·2OPCy₃ ( 2 ) and [CsNPCy₃]₄·4OPCy₃ ( 3 ) (Cy = cyclohexyl) which are obtainable by the reaction of pottassium amide or cesium amide with Cy₃PI₂ or Cy₃PBr₂ in liquid ammonia, as well as the lithium derivative [Li₄(NPPh₃)(OSiMe₂NPPh₃)₃(DME)] ( 4 ) have been characterized by crystal structure determinations. 4 has been formed by the insertion reaction of silicon greaze (‐OSiMe₂)n into the LiN bonds of [LiNPPh₃]₆ in DME solution (DME = 1, 2‐dimethoxyethane). 1 : Space group P&1macr;, Z = 2, lattice dimensions at 193 K: a = 1389.8(1); b = 1408.1(1); c = 2205.2(2) pm; α = 78.952(10)?; β = 81.215(10)?; γ = 66.232(8)?; R1 = 0.0418. 2 : Space group Pbcn, Z = 4, lattice constants at 193 K: a = 2943.6(2); b = 2048.2(1); c = 1893.8(1) pm; R1 = 0.0428. 3 : Space group Cmc2₁, Z = 4, lattice dimensions at 193 K: a = 2881.6(2); b = 2990.2(2); c = 1883.7(2) pm; R1 = 0.0586. 4 ·1/2DME: Space group R&3macr;c, Z = 12, lattice dimensions at 193 K: a = b = 1583.5(1); c = 11755.3(5) pm; R1 = 0.0495. All complexes have heterocubane structures. In 1‐3 they are formed by four alkali metal atoms and by the nitrogen atoms of the (μ₃‐NPCy₃^‐) groups, whereas 4 forms a "heteroleptic" Li₄NO₃ heterocubane.     

Size Matters! On the Way to Ionic Liquid Systems without Ion Pairing

Several, partly new, ionic liquids (ILs) containing imidazolium and ammonium cations as well as the medium‐sized [NTf₂]^? (0.230 nm³; Tf=CF₃SO₃^?) and the large [Al(hfip)₄]^? (0.581 nm³; hfip=OC(H)(CF₃)₂) anions were synthesized and characterized. Their temperature‐dependent viscosities and conductivities between 25 and 80 °C showed typical Vogel–Fulcher–Tammann (VFT) behavior. Ion‐specific self‐diffusion constants were measured at room temperature by pulsed‐gradient stimulated‐echo (PGSTE) NMR experiments. In general, self‐diffusion constants of both cations and anions in [Al(hfip)₄]^?‐based ILs were higher than in [NTf₂]^?‐based ILs. Ionicities were calculated from self‐diffusion constants and measured bulk conductivities, and showed that [Al(hfip)₄]^?‐based ILs yield higher ionicities than their [NTf₂]^? analogues, the former of which reach values of virtually 100 % in some cases.From these observations it was concluded that [Al(hfip)₄]^?‐based ILs come close to systems without any interactions, and this hypothesis is underlined with a Hirshfeld analysis. Additionally, a robust, modified Marcus theory quantitatively accounted for the differences between the two anions and yielded a minimum of the activation energy for ion movement at an anion diameter of slightly greater than 1 nm, which fits almost perfectly the size of [Al(hfip)₄]^?. Shallow Coulomb potential wells are responsible for the high mobility of ILs with such anions.     

Oxidizing Elemental Platinum with Oleum under Harsh Conditions: The Unique Tris(disulfato)platinate(IV) [Pt(S2O7)3]2− Anion

For the first time, direct oxidation of elemental platinum by a mineral acid to its tetravalent state was observed in course of the reaction of platinum with oleum (65 % SO₃) in the presence of barium carbonate. The reaction has been carried out in torch‐sealed glass ampoules at 160 °C and gave yellow single crystals of Ba[Pt(S₂O₇)₃](H₂SO₄)_0.5(H₂S₂O₇)_0.5 (triclinic, P$\bar 1$ , Z=2, a=992.05(2), b=1069.07(3), c=1114.22(3) pm, α=69.49(7), β=72.96(2), γ=72.93(1)°, V=1033.95(5) ų). The structure of Ba[Pt(S₂O₇)₃](H₂SO₄)_0.5(H₂S₂O₇)_0.5 exhibits the unique tris‐(disulfato)‐platinate anion [Pt(S₂O₇)₃]^2? with three chelating disulfate groups coordinated to the platinum atom. Charge balance is achieved by the Ba²⁺ ions, which are coordinated by (S₂O₇)^2? groups from the platinate complex and by disordered sulfuric acids and disulfuric acid molecules. Thermal decomposition of the bulk material revealed elemental platinum and barium sulfate as decomposition residual.     

Lines tangent to

We show that for there are complex common tangent lines to general spheres in and that there is a choice of spheres with all common tangents real.

     

Three-body problem in a dilute bose-Einstein condensate

We derive the explicit three-body contact potential for a dilute condensed Bose gas from microscopic theory. The three-body coupling constant exhibits the general form predicted by Wu [Phys. Rev. 115, 1390 (1959)]] and is determined in terms of the amplitudes of two- and three-body collisions in vacuum. In the present form, the coupling constant becomes accessible to quantitative studies which should provide the crucial link between few-body collisions and the stability of condensates with attractive two-body forces.