Solvothermal synthesis and characterisation of novel Gallium-sulphide compounds
Abstract
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.