School of Chemistry - Theses
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ItemSynthetic and structural investigations of coordination polymers and oligomers( 2011)Novel oligomeric species and coordination polymers have been synthesised and characterised using single crystal X-ray diffraction methods. The electrochemical, magnetic and gas sorption properties of some of these compounds have also been investigated. Chapter 2 describes the preparation and characterisation of coordination complexes containing the di-anionic 2,5-dihydroxybenzoquinone and chloranilate ligands, which have been produced by in situ generation of dhbq2- or can2- from 1,2,4,5-tetrahydroxybenzene or 3,6-dichloro-1,2,4,5-tetrahydroxybenzene, respectively. A one-dimensional polymer of composition Zn(dhbq)(H2O)2⋅4H2O was prepared, and the dehydrated solid has been shown to sorb approximately 0.9 mol of H2 per mol of Zn(dhbq) at 87 K. The ability of the solid to sorb CO2, CH4 and N2 has also been investigated. Several two-dimensional polymers with (6,3) topology have been synthesised. The electrochemical properties of one of these compounds, (PMePh3)2Cd2(dhbq)3, have been studied using solid-state cyclic voltammetry. Also, several examples of 3D Zn-dhbq and Mn-can coordination polymers of (10,3)a topology have been prepared. In several other compounds, the nature of the added counter cation salt was found to affect the connectivity of the resulting network. Chapter 3 contains the details of investigations into 9-substituted-2,3,7- trihydroxyfluor-6-ones. The crystal structures of various salts of the mono-cations of the 9-methyl-, 9-(4-pyridyl)-, 9-(3,4-dihydroxyphenyl)-, and 9-phenyl- fluorones are described, in addition to that of a protonated and reduced bis-fluorone of composition (C13H8O5)(C6H4)(C13H9O5)+. The tri-anion of the 9-phenyl fluorone (Z3-) was used to produce a series of [4+4] metallocycles of composition [(MO2)4Z4]4-. The packing of these metallocycles is reasonably uniform in the presence of the polyaromatic cations PMePh3+, PBzPh3+, Ph3PNPPh3+, AsPh4+ or PPh4+, and in most cases a polyaromatic cation is located in the centre of the square metallocycles. Mass spectrometry experiments show that the metallocycles remain intact in the gas phase. The topology of the 3D metal-tpt networks was found to depend heavily on both the connectivity of the metal centre and on the relative rotation of the three- connecting tpt ligands. For example, tetrahedral CuI centres in combination with the trigonal tpt ligands produced a boracite network of composition [CuI3(tpt)4]3+, although tetrahedral ZnII centres in combination with tpt produced a network with C3N4 topology in Zn3(tpt)4(ClO4)6.Three different networks that contain square planar four-connecting CuII centres were produced - twisted boracite networks of composition CuII3(tpt)4(PF6)6 and CuII3(tpt)4(SiF6)3; a Pt3O4-like network in the compound CuII3(tpt)4(SiF6)3(H2O)2; and a network that occurs in the compound CuII3(tpt)4(ClO4)6, which bears a resemblance to the PtS net. A series of hydrated linear polymers containing the bridging mucate or saccharate dianions in combination with either 2,2`-bipyridine (bipy) or 1,10- phenanthroline (phen) form the basis of Chapter 5. The polymers of composition M(sacc)(phen) (M = Mn, Co or Zn) and M(muc)(phen) (M = Mn or Cd) were found to be essentially isostructural, despite the differing chirality of the mucate and saccharate ligands. Similar chains are also present within Cu(sacc)(bipy), although the CuII centres have square planar coordination environments. Interestingly, the compounds M(sacc)(bipy) (M = Ni or Zn) contain two distinct types of M(sacc)(bipy) chain - one containing only Δ metal centres, the other containing only Λ metal centres. In all compounds discussed in this chapter, both inter-chain hydrogen bonding interactions and π-stacking of the aromatic bipy or phen ligands play important structure-directing roles. The CO2 sorption properties of the representative compounds Co(sacc)(phen) and Cu(muc)(phen) were investigated. Reaction of Cu(NO3)2, 1,10-phenanthroline and potassium hydrogen saccharate in methanol was found to produce two similar yet distinct clusters, both of composition CuII21(sacc)6(phen)12(NO3)12 (the 'Diabolecules'). Structural details of these two clusters are presented in Chapter 6. In both Diabolecule clusters, the saccharate ligand is present in an unprecedented penta-anionic protonation state. Face-to-face aromatic interactions between the phen ligands are an important feature of the packing of both types of cluster. Mass spectrometry experiments show that the cubic cluster remains intact in the gas phase.