Chapter one presents a detailed literature survey on dithienylcyclopentene switches, describing their synthesis, properties and applications. The photochromic and electrochromic effects of functionalising such switching units with metal complexes, is then discussed. Finally, an introduction to cobalt carbonyl complexes is given, with an outline of the photochemical and electrochemical properties of such carbonyl complexes, as described in the literature. Chapter two describes the synthetic procedures employed to prepare a number of dithienyl-perhydro- and perfluoro-cyclopentene switches, substituted with thienyl and ferrocenyl moieties. The methods used to generate their corresponding Co2(CO)6 and Co2(CO)4dppm complexes are also described. 1H, 13C, 19F and 31P NMR techniques were employed to analyse the resulting products. Elemental analysis and infra-red spectroscopy were also utilised, where applicable, to further characterise the final pure compounds and the results are detailed in this chapter. Chapter three describes the photochemical properties found for the thienyl-based dithienylcyclopentene switches and their corresponding cobalt carbonyl complexes. The photochromic properties of the thienyl-based switches were monitored in the UVvis absorption spectra and the 1H NMR spectra. Their thermal stability, fatigue resistance and fluorescent properties were also investigated. Furthermore, the effects of incorporating cobalt carbonyl moieties onto these thienyl-based switches, on their photocyclisation processes, are reported in this chapter. Chapter four reports the photochromic behaviour of the ferrocenyl-based dithienylcyclopentene switches, as observed in the UV-vis and 1H NMR. Investigations into the thermal stability, fatigue resistance and fluorescent properties of these switches were carried out. The effects on the photochromic properties of the ferrocenyl-based switches, following the introduction of Co2(CO)6 and Co2(CO)4dppm moieties, are also described in this chapter. Chapter five focuses on the electrochemical properties of the thienyl-based dithienylcyclopentene switches. Electrochemically induced cyclisation/ cycloreversion processes were investigated through cyclic voltammetry and UV-vis spectroelectrochemistry techniques. Similar experiments were carried out for the cobalt carbonyl derivatives in order to examine the effects of the presence of the metal carbonyls on the oxidative ring-closing/opening abilities of the thienyl-based switches. The effects of the oxidation processes on the cobalt carbonyl centres were also studied by monitoring the changes of the carbonyl stretches in the infra-red spectra. Chapter six details the electrochemical behaviour of the ferrocenyl-based dithienylcyclopentene switches. The oxidative and reductive processes of these switches were monitored in the cyclic voltammograms and UV-vis spectra of these switches in order to investigate if ring-opening/closing can be induced by electrochemical means. Their Co2(CO)6 and Co2(CO)4dppm complexes were also subjected to similar experiments in order to determine the effects of introducing such metal carbonyl complexes on the electrochemical switching behaviour of these ferrocenyl-based switches. IR spectroelectrochemical techniques were employed to examine the effects of oxidation processes on the cobalt carbonyl centres. Chapter seven presents an overall conclusion of the results obtained, with an emphasis on a comparison between the effects of the thiophene substituents and the ferrocene units, and the prospects of future work in this area is discussed. All publications are presented in the appendix.