The importance of the phthalocyanine molecule has generated interest in diverse fields such as thin films, polymer chemistry, liquid crystals, catalysts and numerable electrical, electronic and biological applications together with traditional applications such as dyes and pigments. These laboratories have, to date, concentrated on the synthesis of functionalised phthalocyanine moieties with properties which can be designed for specific applications and, as a result, a battery of materials has been produced at a rate that far exceeded the rate at which the compounds could be fully characterised. The work presented in this thesis is concerned with the study of a range of materials, already available in the group, with a view to providing information on the behavio L'r of Pcs in various molecular assemblies to develop them for specific applications. Chapter 2 is concerned with thin Pc films. The study concentrates on the thermotropic behaviour of some liquid crystalline Pes fonnulated as spin coated, Langmuir-Blodgett, smeared and sublimed films . Chapter 3 contains an account of photochemical stability studies carried out on a series of octaalkyl Pc both in solution and in the solid phase. The role of the central species, substituents and solvent (if applicable) is explored and the results of a series of experiments designed to probe the mechanistic features of the photochemistry are also presented. The development and characterisation of a series of zinc phthalocyanines as potential photosensitisers for use in the photodynamic therapy (PDT) of cancer is covered in chapter 4. The author has carried out photophysical measurements on some octaaJkyl zinc phthalocyanines and comparisons have been made, where appropriate, with other materials currently considered to be promising drug candidates for use in PDT. During the course of this research interesting aggregation and liquid crystal properties were observed for certain zinc and metal-free derivatives. Chapter 5 details how UVVis and IH-NMR. techniques were used to probe these intriguing effects a little further.