Solvothennal and hydrothennal synthesis is widely applied in the generation of . metastable crystalline phases, and is used in this work to prepare a range of novel antimony-sulphide and rare-earth oxy-anion compounds in' the presence of linear, branched and macrocycle amines. The new crystalline phases were characterised using single-crystal X-ray diffraction, elemental analysis, diffuse reflectance spectroscopy and SQUID magnetometry. Transition-metals included in the reactions resulted in the fonnation of both binary antimony-sulphide and ternary transition-metal-antimony-sulphide structures. Binary phases include [Fe(en)3]Sb2Ss.0.55H20, [Fe(en)3hSb4Sg, [T(dien)2]Sb6SIO.xH20 (T= Ni, Co), [Co(en)3]SbgS13 and tNi(en)3]Sb12S19, where discrete [Sb2Sst units, SbS2chains, Sb6SI0 6- and SbgS13 2- layers and a three-dimensional Sbl2Slt framework are charge balanced by transition-I.l1etal-amine complexes. The ternary phases synthesised using tris(2-aminoethyl)amine (tren) and diethylenetriamine (dien) include [Cr(tren)]Sb4S7 chains with [Cr(tren)f+ pendent complexes, and [T(dien)hSblgS30[ T(dien)2] (T= Mn, Fe, Co), in which complex antimony-sulphide chains are bridged via dimeric [T2S2] units to fonn novel layers. The transition-metal ions all exhibit paramagnet~c behaviour and the band gaps of the phases were found to increase from 1.79(4) to 2.46(1) eV with increasing framework density. The first examples of hydrothennal antimony-sulphide reactions using a macrocycle, cyclam, as the structure directing agent resulted in the synthesis of novel , layered and three-dimensional phases of[cyclarnH2]Sb6SIO and [cyclamH2]Sb4S7. By including transition-metal salts in the reaction mixture, it was possible to incorporate transition-metal ions within the macrocyclic rings in [Ni(cyclam)]Sb4S7 and [Co(cyclam)]x[cyclarnH2]J_xSb4S7, where the C02+ occupancy varies between O.08<x<O.74. This unexpected result reveals that metalated and nonrnetalated cyclam rings are present within this crystal structure. The first examples of lanthanide-carbonate frameworks were prepared from aqueous ethylenediamin~ (en) solutions. During the synthesis of [Lll4(C03)6(H20)2].en.H20 (Ln= Dy-Lu, Y), the oxalic acid starting reagent decomposes completely in the presence of sulphur to form carbonate ions which link the lanthanide ions into new three-dimensional structures. Free ethylenediamine and water molecules were located in the one-dimensional channels that run through the structure. Magnetic analysis of the lanthanide-carbonate series revealed paramagnetic behaviour, with the exception of [Er4(C03)6(H20)2].en.HiO, which exhibited a competing ferrimagnetic interaction, which results in ordering below 9.85 K and a saturated magnetic moment achieved at 10,000 G.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:486686 |
| Date | January 2007 |
| Creators | Lees, Rachel Jane Elizabeth |
| Publisher | Heriot-Watt University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10399/2087 |
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