Theoretical Mechanistic Insights into Ground- and Excited-State Approaches to Modifying Reactivity

Abstract

In this thesis, theoretical chemistry methods have been employed to study the reactivity of different polymeric processes, with the different processes of interest touching on catalysis, photochemistry, and photocatalysis. As necessary, computational methods and procedures were assessed and benchmarked for appropriateness and, when possible, calculated results and conclusions were set in context against experimental data. The main findings of this work are as follows.

Multi-component anthraquinone-based systems were studied for their visible light photoinitiating ability. Experimental and theoretical approaches were used to determine the effectiveness of photoinitiation, and to elucidate the photoinitiation mechanisms and rationalise the difference in reactivity between substitution patterns. Excited state redox processes were found to take place, with the substitution patterns greatly affecting the radical cation and anion stabilities, relative to their excited states.

Electric fields were applied to Norrish Type I photoinitiators, and compared with more established methods of altering photochemical behaviour. It was found that electric fields, introduced with charged functional groups, was a flexibile approach to altering several important properties of these systems.

Photonitroxide-mediated polymerisation were studied using anthraquinone-functionalised alkoxyamines, and theoretical and experimental methods were employed again. Here, quantum chemistry shows that mesolytic cleavage, akin to what is observed upon electrochemical oxidation of alkoxyamines, dominates, rather than the homolytic cleavage required for nitroxide-mediated polymerisation. The benefit, however, is the potential facile access to generally hard-to-activate carbocations.

Finally, the catalysis of a radical co-polymerisation and hydrolysis of a biologically relevant molecule in a micellar environment were investigated, demonstrating their respective effectiveness and rationalising the source of the catalytic action.