Solvothermal synthesis and characterisation of novel Gallium-sulphide compounds
Romero Perez, Maria Lucia
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In this thesis, novel supertetrahedral gallium-sulphide compounds were synthesised under solvothermal conditions. Three-dimensional frameworks, which are analogous to previously reported structures, along with a large number of new hybrid supertetrahedral compounds were produced. Inorganic three-dimensional structures were obtained using dimethylamine as a template/solvent. In total, four different inorganic frameworks were prepared. They consist of double interpenetrated diamond lattices, containing diverse building units. The first two are formed of [Ga10S20]10- and [Ga10S19O]10- respectively, while the other two consist of alternating clusters of [M4Ga16S35]14- (M= Zn or Co) and [Ga10S20]10-. To date, only one type of hybrid gallium-sulphide supertetrahedral cluster with stoichiometry [Ga4S6L4] (L= Ncoordinated amine) has been described in the literature. The hybrid gallium-sulphide supertetrahedral structures, reported in Chapter 4, are based on clusters of general stoichiometry [Ga10S16L4]2-. It is shown that the combination of mono and polydentate pyridine ligands leads to formation of multi-functionalised clusters. These multifunctionalised clusters are connected through the ligands, building extended structures. In most cases, the structures are formed by interpenetrated elements such as quadruplestranted helical nano-tubes. These nano-tubes are extremely rare and consist of organically functionalised supertetrahedra connected through 1,2-di(4-pyridyl)ethylene, [C2H8N]2[Ga10S16(N2C12H12)(NC2H7)2]. In addition, the structure is noncentrosymmetric and a chiral solid. Other extended structures consist of twodimensional covalent organic-inorganic networks such as [C7H10N]2[Ga10S16(NC7H9) (N2C12H10)3/2], containing layers with a honey-comb topology. Also, [C5H6N]3 [Ga10S16 (OH)(N2C13H14)] is formed by supertetrahedral composite layers consist of a corrugated two-dimensional network with a (4, 4) topology. Structures containing other building blocks have also been produced. These contain one-dimensional chains which are based on edge-sharing GaS4 tetrahedra along with a two-dimensional structure consisting of neutral hybrid layers of [(C6H14N2)4Ga6S9]. The materials have been characterised by powder and single crystal X-ray diffraction, elemental analysis, thermogravimetry and FTIR. The optical properties have been studied using UV-Vis Diffuse Reflectance Spectroscopy. Ion-exchange experiments and BET surface area/pore size distribution analysis have been carried out to determine the ion-exchange capacity for the three-dimensional structure.