Calculations of Isoelectronic Series of He Using Noninteger n‐Slater Type Orbitals in Single and Double Zeta Approximations

Using integer and noninteger n-Slater type orbitals in single- and double-zeta approximations, the Hartree-Fock-Roothaan calculations were performed for the ground states of first ten cationic members of the isoelectronic series of He atom. All the noninteger parameters and orbital exponents were fully optimized. In the case of noninteger n-Slater type orbitals in double zeta basis sets, the results of calculations obtained are more close to the numerical Hatree-Fock values and the average deviations of our ground state energies do not exceed 2×10^－6 hartrees of their numerical results.     

Influence of the remanent polarisation on the liquid crystal alignment in composite films of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and a cyanobiphenyl-based liquid crystal

Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4?-n-hexylbiphenyl (6CB) or 4-cyano-4?-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We measured the macroscopic alignment of the liquid crystal molecules in the thickness direction by means of Infrared Transition-Moment Orientational Analysis. Electrical poling at 100 V/µm caused an increased order parameter up to 0.15. After subsequent annealing above the nematic-to-isotropic phase-transition temperature, the order parameter was reduced to 0.02. Nevertheless, the order parameter was still higher than for non-poled film indicating a slight orientation in thickness direction. Both values are lower than those expected from model calculations. In agreement with dielectric measurements, we attribute this result to the shielding effect of mobile charge carriers within the liquid crystal inclusions.     

Perfluoroalkyl(dithiocarbamato) tellurium(II) compounds

[NMe(4)][R(f)Te(SC(S)NR(2))(2)] derivatives are selectively formed by the oxidation of [NMe(4)]TeR(f) (R(f) = CF(3), C(2)F(5)) with [R(2)NC(S)S](2) (NR(2) = NEt(2), NBz(2), N(CH(2))(4)) in almost quantitative yields. An alternative route to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR(2)](2) (NR(2) = NEt(2), NBz(2)) with equimolar amounts of Me(3)SiR(f) and [NMe(4)]F. Some of the derivatives were recrystallized with bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods exhibit the structural feature of a distorted pentagonal planar environment (resembling "butterflies") around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral derivatives, R(f)TeSC(S)NR(2), upon treatment with Ag[BF(4)]. In solution they equilibrate with Te(2)(R(f))(2) and [R(2)NC(S)S](2) and finally are transformed into Te(R(f))(2), Te[SC(S)NR(2)](2), and Te[SC(S)NR(2)](4), respectively. All compounds are fully characterized by NMR spectroscopic methods ((1)H, (13)C, (19)F, (125)Te). Additionally, synthesis and characterization of the hitherto unknown derivative [NMe(4)]TeC(2)F(5) are described.     

Synthesis, crystal structure and magnetic properties of novel heterobimetallic malonate-bridged MIIReIV complexes (M = Mn, Fe, Co and Ni)

Five novel ReIV-MII bimetallic complexes of formula [ReCl4(mu-mal)M(dmphen)2].MeCN [M = Co (1), Fe (2) and Ni (3)], [ReCl4(mu-mal)Ni(dmphen)(MeCN)2(H2O)].(MeCN)0.5(H2O)0.5 (4), and [ReCl4(mu-mal)Mn(dmphen)(H2O)2].dmphen.MeCN.H2O (5) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized, and the structures of 1, 2, 4, and 5 determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of neutral [ReCl4(mu-mal)M(dmphen)2] dinuclear units where the metal ions are linked through a malonate ligand which adopts simultaneously the bidentate (at ReIV) and monodentate (at MII) coordination modes. The bridging carboxylate-malonate group in them exhibits the anti-syn conformation. The rhenium atom is six-coordinated with four chloro atoms and two carboxylate-oxygens from a bidentate malonate group in a distorted octahedral environment. The M atom is five-coordinated being surrounded by four nitrogen atoms of two bidentate dmphen ligands and one oxygen atom of the malonato ligand. There are also ReIV(mu-mal)NiII dinuclear units in 4 with the same type of bridge, but the nickel atom is six-coordinated with one bidentate dmphen, two molecules of acetonitrile and one water molecule as peripheral ligands. Compound 5 is a neutral chain compound with regular alternating rhenium(IV) and manganese(II) ions. The [ReCl4(mal)]2- units in each chain act as bismonodenate ligands through two carboxylate-oxygen atoms toward [Mn(dmphen)(H2O)2]2+ entities. Variable-temperature magnetic measurements of 1-5 in the temperature range 2.0-300 K show the occurrence of weak antiferromagnetic interactions which are rationalized on the basis of the structural knowledge and simple orbital considerations. Very noticeable is compound 5, a ferrimagnetic chain with regular alternating ReIV and MnII cations.     

New layered germanide halides RE2GeX2 (RE = Y, Gd; X = Br, I)

The title compounds were synthesized from RE, REX3, and Ge under an Ar atmosphere at 1200-1370 K. Y2GeI2 and Gd2GeI2 crystallize in space group Rm with lattice constants a = 4.2135(3) and 4.2527(1) A and c = 31.480(2) and 31.657(1) A, respectively. Gd2GeBr2 crystallizes in two modifications, the 1T-type (space group Pm1; a = 4.1668(2) A, c = 9.8173(6) A) and the 3R-type (space group Rm; a = 4.1442(9) A, c = 29.487(7) A). The structural motifs of RE2GeX2 compounds are Ge-centered slightly distorted RE6 octahedra connected via their common edges and extending in the a and b directions. The resulting close-packed double layers are separated by halogen atoms. The electrical resistivity measurements revealed semiconductor behavior for Y2GeI2 and Gd2GeI2 and a metal-semiconductor transition for 1T-Gd2GeBr2. Magnetic susceptibility and heat capacity measurements show long-range magnetic ordering for Gd2GeI2 and 1T-Gd2GeBr2 at approximately 15 and approximately 13 K, respectively.     

Struktur,Verzwillingung und Eigenschaften von Ce4Br3C4

Structure, Twinning, and Properties of Ce₄Br₃C₄ The new compound Ce₄Br₃C₄ can be prepared from Ce metal, CeBr₃ and C (3 : 3 : 2) at 1020 °C. It crystallizes in P 1 with a = 422.7(1) pm, b = 1103.4(3) pm, c = 1126.8(2) pm, α = 77.15(3)°, β = 90.13(2)° and γ = 84.42(3)°. The crystals are characteristically twinned, the twin law being (1 0 0, ¹/₂ –1 0, 0 0 –1). The crystal structure contains puckered layers of edge sharing Ce₆C₂ octahedra. The mean C–C distance in the C₂ units is 133(5) pm. Ce₄Br₃C₄ has at room temperature a specific resistivity of 100 mΩ cm and an effective magnetic moment of 2.55(3) μ_B (Ce³⁺).     

The closo-Cluster Triad: B9X9, [B9X9]· –, and [B9X9]2– with Tricapped Trigonal Prisms (X = Cl,Br, I). Syntheses,Crystal and Electronic Structures

Halogenation of nido-B₁₀H₁₄ with C₂H₂Cl₄, C₂Cl₆, Br₂, or I₂, produces by cluster degradation the (2 n)-closo-clusters B₉X₉ (X = Cl, Br, I). The synthesis of salts of the perhalogenated radical anions of the type (2 n + 1)-closo-[B₉X₉]^{· –} and of the corresponding dianions (2 n + 2)-closo-[B₉X₉]^2– from neutral B₉X₉ is described [n is the number of cluster atoms; (2 n), (2 n + 1), and (2 n + 2) is the number of cluster electrons]. Molecular and crystal structures of B₉Cl₉, B₉Br₉, [(C₆H₅)₄P][B₉Br₉] · CH₂Cl₂, and [(C₄H₉)₄N]₂[B₉Br₉] · CH₂Cl₂ have been determined via X-ray diffraction. All three oxidation states of the cluster retain the tricapped trigonal prism. The reduction of the clusters B₉X₉ was shown by cyclic voltammetry in CH₂Cl₂ to proceed via two successive one-electron reversible steps, separated by at least 0.4 V. The paramagnetic radical anions [B₉X₉]^{· –} (X = Cl, Br) were further characterized by magnetic susceptibility measurements of [Cp₂Fe][B₉X₉] and [Cp₂Co][B₉X₉], respectively. The EPR spectra of [B₉X₉]^{· –} (X = Cl, Br, I) in glassy frozen CH₂Cl₂ solutions showed increasing g anisotropy for the heavier halogen derivatives, illustrating significant halogen participation at the singly occupied MO. The ¹¹B NMR spectra of CD₂Cl₂ solutions of the neutral clusters B₉X₉ exhibit only one sharp resonance, indicating that the boron atoms are highly fluxional in solution. In contrast, two different boron resonances as expected for a rigid tricapped trigonal prism are clearly observed for the [B₉X₉]^2– dianions in solutions and for solid B₉Br₉ in the ¹¹B MAS NMR spectra. Temperature dependent ¹¹B MAS NMR experiments on B₉Br₉ and [B₉Br₉]^2– in the solid state show a reversible coalescence of the two resonances at higher temperature. ¹¹B MAS NMR spectra and DTA measurements of [B₉Br₉]^2– showed a phase transition.     

Comparative atomistic and coarse-grained study of water: What do we lose by coarse-graining?

We employ the inverse Boltzmann method to coarse-grain three commonly used three-site water models (TIP3P, SPC and SPC/E) where one molecule is replaced with one coarse-grained particle with isotropic two-body interactions only. The shape of the coarse-grained potentials is dominated by the ratio of two lengths, which can be rationalized by the geometric constraints of the water clusters. It is shown that for simple two-body potentials either the radial distribution function or the geometrical packing can be optimized. In a similar way, as needed for multiscale methods, either the pressure or the compressibility can be fitted to the all atom liquid. In total, a speed-up by a factor of about 50 in computational time can be reached by this coarse-graining procedure.