Microelectrochemical studies of atom transfer and chain transfer catalysts
The purpose of the work described in this thesis was to measure standard electrode potentials and rate constants for various systems, based around cobalt and copper centred catalysts. The intention was to increase understanding of these two different types of complexes, with the knowledge described herein aiding in catalyst and system design. Two main techniques have been used, those of UME voltammetry and SECM. The UME measurements proved technically simple and were used to provide information on redox kinetics and coupled solution reactions. Conversely, the SECM experiments were more complex to perform but allow more complicated systems to be studied. The results obtained in Chapter 3 provide further information about the properties of [Cu] ATP catalysts. Enhanced information could be obtained with better knowledge of the values ofE1I2 or F!., but the work has shown that in organic solvents even simple parameters are difficult to obtain due to complexities such as ion pairing. The theme of Chapter 4; the reaction of [CUll] with Cu o had previously been unexamined. This reaction has been characterised and provides new information of the processes involved in adding Cu o to ATP reaction mixtures. A computer simulation was applied that described the theoretical behaviour of an oxidative etching event. A good fit was obtained between experiment and theory at large values of d/a and at short times. The potentials of a number of [CuI]/[CUIl ]and [Cul]/[CUO] redox couples have been measured in order to understand the substrate potential response during the SECM etching process. The rate of reaction of a number of different [COl] with E2mB has been measured in a range of solvents, as described in Chapter 5. The solvent was seen to have a great effect on the behaviour of each system, stabilising the formation of R[Colll ], such that two reduction processes became evident where mma was the solvent. Such [Co] species are commonly used as C - C bond forming reagents and therefore knowledge of their behaviour in certain solvents is invaluable. Additionally the [Colt E2mB system may be used as an initiator/catalyst system for polymerisation reactions, either in homogeneous or emulsion solutions.