High spin rotational bands in 65Zn

The nucleus ₃₀ ⁶⁵ Zn was studied using the ⁵²Cr(¹⁶O, 2pn)⁶⁵Zn reaction at a beam energy of 65 MeV. The level scheme is extended up to an excitation energy of 10.57 MeV for spin-parity (41/2?) with several newly observed transitions placed in it.     

[ReIII(thiourea-S)6]Cl3 · 4 H2O and [ReIII(N-methylthiourea-S)6]Cl3 as Precursors to other ReIII Complexes: a Kinetic Study in Aqueous Media. Crystal Structure of [ReIII(N-methylthiourea-S)6](PF6)3 · H2O

Capability of [Re^III(tu-S)₆]Cl₃, where tu = thiourea, as a precursor to other Re^III complexes by ligand substitution in aqueous medium is studied. For the decomposition of [Re(tu-S)₆]Cl₃, experiments suggest pseudo first order kinetics and observed rate constants vary from 1.3 × 10^–2 to 9.6 × 10^–2 min^–1 in the pH range 2.80–5.04. Experiments in presence of incoming ligand (ethylendiaminetetraacetic acid or diethylentriaminepentaacetic acid) show that ligand substitution is significantly slower than decomposition of the precursor, even when pH and temperature are modified. Similar results were obtained working with [Re^III(Metu-S)₆]Cl₃, where Metu = N-methylthiourea. Molecular structure of [Re^III(Metu-S)₆](PF₆)₃ · H₂O was determined by single crystal X-ray diffractometry. The coordination polyhedron around the Re ion is a distorted octahedron. The six methylthiourea ligands are bonded to the metal through the sulfur atoms [bond lengths range from 2.409(2) to 2.451(2) Å].     

Density, refractive index, interfacial tension, and viscosity of ionic liquids [EMIM][EtSO4], [EMIM][NTf2], [EMIM][N(CN)2], and [OMA][NTf2] in dependence on temperature at atmospheric pressure

The density, refractive index, interfacial tension, and viscosity of ionic liquids (ILs) [EMIM][EtSO 4] (1-ethyl-3-methylimidazolium ethylsulfate), [EMIM][NTf 2] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), [EMIM][N(CN) 2] (1-ethyl-3-methylimidazolium dicyanimide), and [OMA][NTf 2] (trioctylmethylammonium bis(trifluoromethylsulfonyl)imide) were studied in dependence on temperature at atmospheric pressure both by conventional techniques and by surface light scattering (SLS). A vibrating tube densimeter was used for the measurement of density at temperatures from (273.15 to 363.15) K and the results have an expanded uncertainty ( k = 2) of +/-0.02%. Using an Abbe refractometer, the refractive index was measured for temperatures between (283.15 and 313.15) K with an expanded uncertainty ( k = 2) of about +/-0.0005. The interfacial tension was obtained from the pendant drop technique at a temperature of 293.15 K with an expanded uncertainty ( k = 2) of +/-1%. For higher and lower temperatures, the interfacial tension was estimated by an adequate prediction scheme based on the datum at 293.15 K and the temperature dependence of density. For the ILs studied within this work, at a first order approximation, the quantity directly accessible by the SLS technique was the ratio of surface tension to dynamic viscosity. By combining the experimental results of the SLS technique with density and interfacial tension from conventional techniques, the dynamic viscosity could be obtained for temperatures between (273.15 and 333.15) K with an estimated expanded uncertainty ( k = 2) of less than +/-3%. The measured density, refractive index, and viscosity are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with but always smaller than the expanded uncertainties ( k = 2). Besides a comparison with the literature, the influence of structural variations on the thermophysical properties of the ILs is discussed in detail. The viscosities mostly agree with values reported in the literature within the combined estimated expanded uncertainties ( k = 2) of the measurements while our density and interfacial tension data differ by more than +/-1% and +/-5%.     

Effect of the spin-orbit interaction on the thermodynamic properties of crystals: specific heat of bismuth

We discuss measurements and ab initio calculations of the specific heat for crystalline bismuth, strictly speaking, a semimetal but in the temperature region accessible to us (T>2 K) acting as a semiconductor. We extend experimental data available in the literature and notice that the ab initio calculations without spin-orbit interaction exhibit a maximum at approximately 8 K, about 20% lower than the measured one. Inclusion of spin-orbit interaction decreases the discrepancy markedly: the maximum of C(T) is now only 7% larger than the measured one. Exact agreement is obtained if the strength of the spin-orbit Hamiltonian is reduced by a factor of approximately 0.9. We also discuss the dependence of the lattice parameter and the cohesive energy on spin-orbit interaction.     

Superconductivity in heavy alkaline-Earth intercalated graphites

We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC(6), by susceptibility and specific heat (C(p)) measurements. In comparison with CaC(6), we found that the anisotropy of the upper critical fields for SrC(6) is much reduced. The C(p) anomaly at T(c) is smaller than the BCS prediction, indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower T(c) of SrC(6) as compared to CaC(6) can be understood in terms of "negative" pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC(6) down to 0.3 K.     

A novel series of rhenium-bipyrimidine complexes: synthesis, crystal structure and electrochemical properties

Four novel rhenium complexes of formula [ReCl(4)(bpym)] (1), [ReBr(4)(bpym)] (2) PPh(4)[ReCl(4)(bpym)] (3) and NBu(4)[ReBr(4)(bpym)] (4) (bpym = 2,2'-bipyrimidine, PPh(4) = tetraphenylphosphonium cation and NBu(4) = tetrabutylammonium cation), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of [ReX(4)(bpym)] molecules held together by van der Waals forces. In both complexes the Re(iv) central atom is surrounded by four halide anions and two nitrogen atoms of a bpym bidentate ligand in a distorted octahedral environment. The structures of 3 and 4 consist of [ReX(4)(bpym)](-) anions and PPh(4)(+) () or NBu(4)(+) (4) cations. The coordination sphere of the Re(iii) metal ion is the same as in 1 and 2, respectively. However, whereas the Re-X bonds are longer the Re-N bonds are shorter than in 1 and 2. This fact reveals that the bpym ligand forms a stronger bond with Re(iii) than with Re(iv) resulting in a stabilisation of the lower oxidation state. [ReX(4)(bpym)] complexes are easily reduced, chemically and electrochemically, to the corresponding [ReX(4)(bpym)](-) anions. A voltammetric study shows that the electron transference is a reversible process characterized by formal redox potentials of +0.19 V (1) and +0.32 V (2) vs. NHE, in acetonitrile as solvent.