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X-ray crystallography is an important analytical method for the characterisation of materials in the solid state. During the last decade, it has become important as a tool in the new field of photocrystallography. This combines both crystallography and photochemistry and is used to monitor the formation of light-induced metastable and transient species, so that structural information can be obtained during the change of a material. This is an important area of research as solid state chemistry can display new phenomena and reveal properties that are not possible in solution. Chapter 1 of this thesis commences with a brief introduction to the different methods used to achieve and measure the excitation within crystalline compounds, while Chapter 2 contains an introduction into diffraction methods. In Chapters 3-5 new photocrystallographic studies were performed on two series of compounds. The first one consists of a systematic study on metal complexes with different pyridylethylene ligands. The focus was to align complexes in the solid state so that they can undergo photo induced cycloaddition reactions. These solid state reactions are important as they present “green synthetic chemistry”. The second study involves the photoinduced linkage isomerisation of [Ni(L)2(NO2)2] complexes. Structural characterisation shows that the NO2 ligands change their coordination mode when irradiated with light of different wavelengths. Conditions for the metastable isomerisation were optimised by altering temperature and wavelengths. In Chapters 6 and 7 a systematic study of structural changes in a series of lanthanide complexes and their use as triboluminescence materials, is described. The proposed mechanism of triboluminescence for these complexes is discussed. To summarise, in this thesis, systematic investigations have been carried out in different aspects of crystallography using appropriate series of compounds. The nature of and the conditions required for the change to occur within the solid state have been established. |
