SiBr4--prediction and determination of crystal structures.

For SiBr4 no crystal structures have been reported yet. In this work the crystal structures of SiBr4 were predicted by global lattice-energy minimizations using force-field methods. Over an energy range of 5 kJ mol(-1) above the global minimum ten possible structures were found. Two of these structures were experimentally determined from X-ray synchrotron powder diffraction data: The low-temperature beta phase crystallizes in P2(1)/c, the high-temperature alpha phase in Pa3. Temperature-dependant X-ray powder diffraction shows that the phase transition occurs at 168 K.

Carbon nanotube wiring of electrodes for high-rate lithium batteries using an imidazolium-based ionic liquid precursor as dispersant and binder: a case study on iron fluoride nanoparticles.

To meet the energy and power demands of lithium-based batteries, numerous nanostructured and -decorated material prototypes have been proposed. In particular for insulating electrodes, a decrease of grain size coupled with wiring by a conductive phase is quite effective in improving the electroactivity. In this work, we report a novel electron-wiring method using single-wall carbon nanotubes in an imidazolium-based ionic liquid precursor, which enables them to be well disentangled and dispersed, even unzipped. As a case study, in situ formed iron fluoride nanoparticles (∼10 nm) are collected into micrometer-sized aggregates after wiring of merely 5 wt % carbon nanotubes in weight. These composite materials act as cathodes and exhibit a remarkable improvement of capacity and rate performances (e.g., 220 mAh/g at 0.1C and 80 mAh/g at 10C) due to the construction of mixed conductive networks. Therein, the ionic liquid remainder also serves as an in situ binder to generate a nanographene-coated fluoride, which can even run well without the addition of extra conductive carbon and binder. This nanotechnological procedure based on an ionic liquid succeeds without applying high temperature and pressure and is a significant step forward in developing high-power lithium batteries.

Silver(I) pyrophosphonates: structural, photoluminescent and thermal expansion studies.

The solvothermal reactions of silver(I) salts with mono-organophosphonic acids, i.e. 3-thienylphosphonic acid (3-TPA), phenylphosphonic acid (PPA), α-naphthylphosphonic acid (α-NPA) and cyclohexylphosphonic acid (CPA), yield four new silver(I) pyrophosphonates, namely: [Ag(2)(ptp)] (1), [Ag(2)(ppp)] (2), [Ag(3)(CH(3)CN)(pnp)(pnpH)] (3), and [Ag(3)(pcp)(pcpH)] (4) [ptp(2-) = pyro-3-thienylphosphonate, ppp(2-) = pyrophenylphosphonate, pnp(2-) = pyro-α-naphthylphosphonate, pcp(2-) = pyrocyclohexylphosphoante]. In all cases, the pyrophosphonate ligands are generated in situ from their relative mono-organophosphonic acids, mediated by silver(I) ions. Single crystal structural determinations reveal that compounds 1 and 2 display two-dimensional layer architectures, while 3 and 4 show one-dimensional chain structures. Structure 1 can be best described as a layer made up of Ag(4)O(P)(6) clusters linked by O-P-O units and AgAg contacts, with the organic groups grafted on the two sides of the inorganic layer. A similar layer structure is found in 2 except that the AgAg interactions are absent. Compound 3 shows a chain structure where the silver ions are bridged by the phosphonate oxygen atoms forming an infinite Ag-O(P) chain which is decorated by the pyrophosphonate ligand and CH(3)CN. Compound 4 has another type of chain structure made up of Ag-O(P) with extensive Ag···Ag argentophilic interactions. Solid state photoluminescent properties and thermal expansion behaviors are also investigated.

Metal phosphonates based on bis(benzimidazol-2-ylmethyl)imino methylenephosphonate: from discrete dimer to two-dimensional network containing metallomacrocycles.

Hydrothermal reactions of bis(benzimidazol-2-ylmethyl)imino(methylenephosphonic acid) {[(C(7)H(5)N(2))CH(2)]2NCH(2)PO(3)H(2), bbimpH2} with metal salts result in four new compounds, namely, Mn2{[(C(7)H(5)N(2))CH2]2NCH(2)PO(3)}2(H2O)2.2H2O (1), Cd2{[(C(7)H(5)N(2))CH2]2NCH(2)PO(3)}2.2H2O (2), Fe2{[(C(7)H(5)N(2))CH2]2NCH(2)PO(3)}2.H2O (3), and CuI(2){[(C(7)H(5)N(2))CH2]2NCH(2)P(OH)O2}2 (4). Compounds 1 and 2 have dinuclear structures in which two {MN(3)O(3)} octahedra are linked through edge sharing. In compound 3, a chain structure is observed where the {FeN(3)O(2)} trigonal bipyramids are linked by {CPO(3)} tetrahedra through corner-sharing. The structure of compound 4 is unique. The monovalent Cu(I) ions are connected by the imidazole nitrogen atoms from the bbimp(2-) ligands forming a 16-member metallomacrocycle. These metallomacrocycles are further connected by the phosphonate oxygen atoms, leading to a two-dimensional net containing 16- and 32-member rings. Magnetic studies of 1 and 3 reveal that weak ferromagnetic interactions are mediated between magnetic centers in compound 1, while antiferromagnetic interactions were observed in compound 3.