Browsing by Author "Nadeem, MA"

Now showing 1 - 8 of 8
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    2D cobalt based coordination polymer constructed from benzimidazole and acetate ion exhibiting spin-canted antiferromagnetism
    (Royal Society of Chemistry, 2010-05-07) Arai, L; Nadeem, MA; Bhadbhade, MM; Stride, JA
    A coordination polymer, [CoII(bIM)(acetate)] (bIM = benzimidazole) was synthesized using a solvothermal method; the complex has a two dimensional non-interpenetrated network structure and exhibits a spin-canted antiferromagnetic behaviour at low temperature and a high coercive field. © 2010, Royal Society of Chemistry
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    Controlled synthesis of isomorphous coordination polymers via in situ ligand transformation reaction: crystal structure, thermal and magnetic properties
    (American Chemical Society, 2010-09) Nadeem, MA; Bhadbhade, MM; Bircher, R; Stride, JA
    A series of isomorphous [M2(ip)2(L)2]n (M = Co, Ni; ip = isophthalate; L = 4,4′-dipyridyl and pyrazine) coordination polymers was synthesized via in situ ligand transformation reactions, in which 1,2,3-benzene tricarboxylic acid (1,2,3-btcH3) undergoes decarboxylation to isophthalate (ip), which was found to be highly dependent on the reaction temperature. The polymers crystallize in the same crystal triclinic system P. The magnetic properties were investigated by a Quantum Design physical property measurement system (PPMS); all four compounds feature almost isostructural M(II) dimers having ferromagnetic (FM) interactions. The interdimer interactions mediated by two different carboxylate groups of ip are weak, while there is no significant magnetic exchange via the 4,4′-dipyridyl ligands along the chain direction. However, substitution with pyrazine leads to antiferromagnetic exchange of nearest neighbor dimers. © 2010, American Chemical Society
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    A flexible copper based microporous metal-organic framework displaying selective adsorption of hydrogen over nitrogen
    (Royal Society of Chemistry, 2011-04-01) Nadeem, MA; Thornton, AW; Hill, MR; Stride, JA
    A microporous metal-organic framework [Cu-3(ipO)(2)(pyz)(2)](n), (ipO = 2-hydroxyisophthalic acid, pyz = pyrazine) was synthesized via an in situ. ligand transformation reaction. The microporous framework displays helical arrays of ipo ligands holding the Cu atoms in 2D sheets, whilst the coordination of pyz molecules acts to arrange these sheets into a microporous 3D structure. Remarkable selective sorption behaviour (>5) for H-2 over N-2 is observed and explained with molecular dynamics simulations.© 2011, Royal Society of Chemistry.
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    Four new coordination polymers constructed from benzene tricarboxylic acid: synthesis, crystal structure, thermal and magnetic properties
    (Royal Society of Chemistry, 2010-11-07) Nadeem, MA; Bhadbhade, MM; Stride, JA
    The use of 1,3,5-benzene tricarboxylic acid (H3btc) as an organic linker has allowed us to achieve the rational design of two pairs of isostructural coordination polymers having molecular formulae [M2(btc)(F)]n (M(II) = Mn (1), Co (2)) and [M3(btc)(Hbtc)(OH)(H2O)11]n (M(II) = Fe (3), Co (4)) where btc and Hbtc represent the fully and doubly de-protonated tricarboxylates respectively. These compounds were synthesized using hydrothermal methods and characterized by thermal analysis and variable temperature magnetic measurements. The X-ray analysis reveals that compounds 1 and 2 crystallize in the monoclinic space group C2/c while compounds 3 and 4 crystallize in the monoclinic space group C2. Compounds 1 and 2 feature fluoride bridged 1D metal chains linked together via carboxylate groups of btc, whilst compounds 3 and 4 consist of 1D zigzag chains having strong hydrogen bonds with neighbouring chains. Variable temperature magnetic measurements show an overall antiferromagnetic behaviour for compounds 1, 2 and 4, with no indication of magnetic ordering phenomena in the temperature range from 300–2 K. As 3 and 4 are isostructural, we assume that the magnetic properties are similar. © 2010, Royal Society of Chemistry
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    Magneto-structural correlations of a three-dimensional Mn based metal-organic framework
    (Royal Society of Chemistry, 2010-05-14) Nadeem, MA; Craig, DJ; Bircher, R; Stride, JA
    A 3D metal–organic framework, [Na{Mn3(Hbtc)2(btc)}·5H2O]n ( 1) (H3btc = 1,3,5-benzene tricarboxylic acid), was synthesized under hydrothermal conditions. The structure of 1 was established by single crystal X-ray diffraction analysis; 1 crystallizes in the monoclinic space group P2/c, a = 9.753(3) Å, b = 12.751(2) Å, c = 14.174(4) Å, = 109.41(1)°. The complex 1 is isostructural to previously reported MIL-45 and consists of one dimensional wave like chains of carboxylate bridged hexa-coordinated Mn(II) ions. Variable temperature magnetic susceptibility measurements revealed dominant antiferromagnetic exchange interactions and the intra-chain exchange constants J1 = -2.4 cm-1 and J2 = -0.6 cm-1 compare well with literature values for similar materials. Inter-chain interactions are expected to be very small in this compound and there is no indication of magnetic ordering phenomena in the temperature range from 300–2 K. © 2010, Royal Society of Chemistry
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    Neutron scattering studies of magnetic coordination polymers
    (Australian Institute of Physics, 2012-02-01) Mole, RA; Montero, LF; Nadeem, MA; Peterson, VK; Piltz, RO; Stride, JA
    Porous coordination polymers have been the subject of intense study over the past ten years. The key feature of these materials is a robust framework that remains in tact upon desolvation – the potential uses of these materials range from gas storage to catalysis. The current work focuses on the magnetic behaviour of these frameworks; given the nature of the structures are often low dimensional and low density magnetic topologies and the possibility exists to incorporate frustration, the magnetic properties are often of interest in there own right. If these magnetic properties could be linked to the small changes in structure associated with desolvation, the potential exists for using these materials as magnetic sensors. The material which I will focus on in this contribution, Co3(OH)2(C4O4)2.3H2O, shows an unusual three phase magnetic behaviour due to a combination of single ion effects and magnetic frustration, of particular interest is a novel spin idle phase.1 Recently we have moved on from looking at this spin idle phase and have started to probe the incommensurate phase that proceeds it. Further we have started to study the effect of hydration on the magnetic behaviour. Previous work 2 has shown that there is a large effect on dehydration – with it being hypothesized that a switch from antiferromagnetic to ferromagnetic behaviour is observed. Our recent work has shown that although there is a very clear effect – it is due to small changes in the coordination sphere of the magnetic ion and not the hydrogen bonding pathway as previously suggested. The work has made use of a combination of both single crystal and powder neutron diffraction.
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    Switchable magnetism: neutron diffraction studies of the desolvated coordination polymer Co-3(OH)(2)(C4O4)(2)
    (American Chemical Society, 2013-11-13) Mole, RA; Nadeem, MA; Stride, JA; Peterson, VK; Wood, PT
    We report the magnetic structure of the two magnetically ordered phases of Co3(OH)2(C4O4)2, a coordination polymer that consists of a triangular framework decorated with anisotropic Co(II) ions. Neutron diffraction experiments allow us to confirm that the magnetic behavior changes upon dehydration and reveal the complex phase behavior of this system, relative to the hydrated compound Co3(OH)2(C4O4)2·3H2O. One phase is shown to display spin idle behavior, where only a fraction of the moments order at intermediate temperatures, while at the lowest temperatures the system orders fully, in this case with a net magnetic moment. This novel magnetic behavior is discussed within the framework of a simple Hamiltonian and representational analysis and rationalizes this multiphase behavior by considering the combination of frustration and anisotropy. The change in behavior on dehydration is also rationalized with respect to the changes in the single-ion anisotropy of the cobalt. © 2013, American Chemical Society.
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    Three isolated structural motifs in one crystal: penetration of two 1D chains through large cavities within 2D polymeric sheets
    (Royal Society of Chemistry, 2010-05) Nadeem, MA; Bhadbhade, MM; Bircher, R; Stride, JA
    An unprecedented architecture comprising of three isolated coordination polymers within the same crystalline structure has been obtained, in which two independent infinite one dimensional polymer chains, Cu(bpy)(H2O), fill the voids generated by a third, two dimensional, host framework, Cu3(Hbtc)(btc)(bpy)2. © 2010, Royal Society of Chemistry