Supramolecular assemblies of two piperazine metal-organic bismuth(III) derivatives: a new precursor for the preparation of bismuth(III) oxide bromide nano-structures

Two BiBr₃ supramolecular complexes, [Bi(2-bpmp)Br_2.06Cl_0.94] (1) and [Bi(4-H₂bpmp)Br_4.29Cl_0.71]·H₂O (2) {2-bpmp = N,N′-bis(2-pyridylmethyl)piperazine and 4-bpmp = N,N′-bis(4-pyridylmethyl)piperazine}, were prepared by reaction of bismuth(III) chloride and potassium bromide with two nitrogen donor ligands under thermal gradient conditions using the branched tube method. Compounds 1 and 2 were structurally characterized by single-crystal X-ray diffraction. In monomeric 1, bismuth is coordinated by two pyridyl and piperazine nitrogens of 2-bpmp, and by three halides. Compound 2 is also monomeric but is bonded to only one pyridyl nitrogen. In both compounds, extensive hydrogen-bonding interactions lead to supramolecular networks; in 2, the hydrogen bonds are augmented by π–π stacking interactions. Thermal stabilities of both compounds were studied by thermal gravimetric and differential thermal analyses. Thermal decomposition of nanosized 1 and 2 in air produced BiOBr nanoparticles.     

Lead(II) complexes of 2,2′-diamino-4,4′-bithiazole (DABTZ) including crystal structure of a novel 1D chain polymer, [PB(DABTZ)(μ-SCN)(μ-NO3)] n

Three new 2,2′-diamino-4,4′-bithiazole (DABTZ) lead(II) complexes were synthesized and characterized by elemental analyses, IR-, ¹H-NMR-, and ¹³C-NMR-spectroscopy. The single crystal X-ray structural analysis of [Pb(DABTZ)(μ-SCN)(μ-NO₃)] _n shows the complex to be a 1D chain polymer as a result of sequential thiocyanate and nitrate bridging. The Pb atoms are seven-coordinated by two nitrogen atoms of the 2,2′-diamino-4,4′-bithiazole, three nitrate and two thiocyanate ligands. The arrangement of the 2,2′-diamino-4,4′-bithiazole, nitrate and thiocyanate ligands does not suggest a gap in the coordination around the Pb^II ion, caused by a stereo-active lone pair of electrons on lead(II) where the coordination around the lead atoms is the less common holodirected.     

Synthesis,structure and properties of aquabis(2,4′-bipyridine)di(propionato-O)copper(II)

The title complex has been synthesized and characterized by elemental and thermal analysis, IR and electronic spectroscopy, conductivity studies and X-ray crystallography. In the crystal, the complex has two-fold symmetry and the copper atom adopts square pyramidal coordination. Bond valences for Cu were computed. Cu–O_(propionate) bonds are slightly stronger than the Cu–N bonds, and the Cu–O_(water) bond is distinctly weaker. Molecules are linked by O–H···O hydrogen bonds to form infinite hydrogen-bonded chains along the y axis.     

Pseudo-Anosov Flows and Incompressible Tori

We study incompressible tori in 3-manifolds supporting pseudo-Anosov flows and more generally ZZ subgroups of the fundamental group of such a manifold. If no element in this subgroup can be represented by a closed orbit of the pseudo-Anosov flow, we prove that the flow is topologically conjugate to a suspension of an Anosov diffeomorphism of the torus. In particular it is non singular and is an Anosov flow. It follows that either a pseudo-Anosov flow is topologically conjugate to a suspension Anosov flow, or any immersed incompressible torus can be realized as a free homotopy from a closed orbit of the flow to itself. The key tool is an analysis of group actions on non-Hausdorff trees, also known as R-order trees – we produce an invariant axis in the free action case. An application of these results is the following: suppose the manifold has an R-covered foliation transverse to a pseudo-Anosov flow. If the flow is not an R-covered Anosov flow, then it follows that the manifold is atoroidal.