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    Öğe
    Hydrothermal synthesis, structural investigation, and magnetic properties of 2-D layered lanthanide (Ln = Pr, Eu, Gd, Tb, and Er) coordination polymers possessing infinite 1-D nanosized cavities
    (Taylor & Francis Ltd, 2015) Sharif, Shahzad; Sahin, Onur; Khan, Bushra; Khan, Islam Ullah
    Five 2-D Ln(III) coordination polymers, [Ln(PDA)(PDAH)](n) (PDA=2,6-pyridinedicarboxylate), have been obtained under mild hydrothermal condition. In each coordination polymer, PDA is tetradentate and pentadentate, while lanthanides have coordination number eight to generate trigonal prismatic, triangular face bicapped LnO(6)N(2) geometry having 9 triangular and 2 square faces. Two different types of bridging oxygens are responsible to grow the 2-D coordination polymers providing open channels possessing infinite 1-D nanosized cavities. Adjacent 2-D chains are further extended to a 3-D hydrogen-bonded layered network through intermolecular - interactions and C-HO hydrogen bonds. Four lanthanides are arranged roughly at the vertices of a square and bridged by eight carboxylates leading to the overall tetrahedral shape of the secondary building units. The abnormal behavior of lanthanide contraction for the atomic radii of europium can be attributed to overlapping of electron clouds. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions. Thermal decomposition analysis reveals that the coordination polymers have significant thermal stability. The coordination polymers are further characterized using elemental analysis and FT-IR spectroscopy.
  • [ X ]
    Öğe
    Synthesis, crystal structure and magnetic properties of an octanuclear cerium(III) complex of pyridine-2,6-dicarboxylate
    (Walter De Gruyter Gmbh, 2019) Sharif, Shahzad; Khan, Islam Ullah; Sahin, Onur; Jabeen, Nadia; Ahmad, Saeed; Khan, Bushra
    An octanuclear compound of cerium(III), [Ce-8(Pydc)(10)(HPydc)(4)center dot 22H(2)O]center dot 11H(2)O (1) (Pydc = pyridine-2,6-dicarboxylate anion) was prepared under mild solvothermal conditions and its crystal structure was determined by single-crystal X-ray diffraction. Three kinds of coordination environments are observed, which include: [Ce(Pydc)(3)], [Ce(Pydc)(H2O)(4)(O,O)], and [Ce(H2O)(7) (O,O)]. Each cerium atom in 1 is nine-coordinated but two different geometries are found. The Ce1 and Ce2 atoms exhibit a nearly tricapped trigonal prismatic CeN3O8 geometry, while Ce3 and Ce4 possess CeNO8 and CeO9 coordination polyhedra, which approximate to slightly distorted mono-capped square antiprisms having 12 triangular faces. The Pydc ligands adopt tri-, tetra-, and penta-coordination modes through tridentate chelating and, mu(2) and mu(3)-bridging modes, respectively. The clusters are joined by O-II center dot center dot center dot O hydrogen bonds to generate 3D supramolecular network. Magnetic susceptibility measurements for 1 indicate that the chi(m) values obey the Curie-Weiss law. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions between the cerium(III) ions.